[PATCH 1/9] crypto,fs: Separate out hkdf_extract() and hkdf_expand()

[PATCH 1/9] crypto,fs: Separate out hkdf_extract() and hkdf_expand()

[Hannes Reinecke]

Separate out the HKDF functions into a separate file to make them
available to other callers.

Signed-off-by: Hannes Reinecke <hare@kernel.org>
Cc: Eric Biggers <ebiggers@kernel.org>
Cc: linux-crypto@vger.kernel.org
---
 crypto/Makefile       |   1 +
 crypto/hkdf.c         | 112 ++++++++++++++++++++++++++++++++++++++++++
 fs/crypto/hkdf.c      |  68 ++++---------------------
 include/crypto/hkdf.h |  18 +++++++
 4 files changed, 140 insertions(+), 59 deletions(-)
 create mode 100644 crypto/hkdf.c
 create mode 100644 include/crypto/hkdf.h

diff --git a/crypto/Makefile b/crypto/Makefile
index edbbaa3ffef5..b77fc360f0ff 100644
--- a/crypto/Makefile
+++ b/crypto/Makefile
@@ -29,6 +29,7 @@ obj-$(CONFIG_CRYPTO_ECHAINIV) += echainiv.o
 
 crypto_hash-y += ahash.o
 crypto_hash-y += shash.o
+crypto_hash-y += hkdf.o
 obj-$(CONFIG_CRYPTO_HASH2) += crypto_hash.o
 
 obj-$(CONFIG_CRYPTO_AKCIPHER2) += akcipher.o
diff --git a/crypto/hkdf.c b/crypto/hkdf.c
new file mode 100644
index 000000000000..22e343851c0b
--- /dev/null
+++ b/crypto/hkdf.c
@@ -0,0 +1,112 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Implementation of HKDF ("HMAC-based Extract-and-Expand Key Derivation
+ * Function"), aka RFC 5869.  See also the original paper (Krawczyk 2010):
+ * "Cryptographic Extraction and Key Derivation: The HKDF Scheme".
+ *
+ * This is used to derive keys from the fscrypt master keys.
+ *
+ * Copyright 2019 Google LLC
+ */
+
+#include <crypto/hash.h>
+#include <crypto/sha2.h>
+#include <crypto/hkdf.h>
+
+/*
+ * HKDF consists of two steps:
+ *
+ * 1. HKDF-Extract: extract a pseudorandom key of length HKDF_HASHLEN bytes from
+ *    the input keying material and optional salt.
+ * 2. HKDF-Expand: expand the pseudorandom key into output keying material of
+ *    any length, parameterized by an application-specific info string.
+ *
+ */
+
+/* HKDF-Extract (RFC 5869 section 2.2), unsalted */
+int hkdf_extract(struct crypto_shash *hmac_tfm, const u8 *ikm,
+		 unsigned int ikmlen, u8 *prk)
+{
+	unsigned int prklen = crypto_shash_digestsize(hmac_tfm);
+	u8 *default_salt;
+	int err;
+
+	default_salt = kzalloc(prklen, GFP_KERNEL);
+	if (!default_salt)
+		return -ENOMEM;
+	err = crypto_shash_setkey(hmac_tfm, default_salt, prklen);
+	if (!err)
+		err = crypto_shash_tfm_digest(hmac_tfm, ikm, ikmlen, prk);
+
+	kfree(default_salt);
+	return err;
+}
+EXPORT_SYMBOL_GPL(hkdf_extract);
+
+/*
+ * HKDF-Expand (RFC 5869 section 2.3).
+ * This expands the pseudorandom key, which was already keyed into @hmac_tfm,
+ * into @okmlen bytes of output keying material parameterized by the
+ * application-specific @info of length @infolen bytes.
+ * This is thread-safe and may be called by multiple threads in parallel.
+ */
+int hkdf_expand(struct crypto_shash *hmac_tfm,
+		const u8 *info, unsigned int infolen,
+		u8 *okm, unsigned int okmlen)
+{
+	SHASH_DESC_ON_STACK(desc, hmac_tfm);
+	unsigned int i, hashlen = crypto_shash_digestsize(hmac_tfm);
+	int err;
+	const u8 *prev = NULL;
+	u8 counter = 1;
+	u8 *tmp;
+
+	if (WARN_ON(okmlen > 255 * hashlen))
+		return -EINVAL;
+
+	tmp = kzalloc(hashlen, GFP_KERNEL);
+	if (!tmp)
+		return -ENOMEM;
+
+	desc->tfm = hmac_tfm;
+
+	for (i = 0; i < okmlen; i += hashlen) {
+
+		err = crypto_shash_init(desc);
+		if (err)
+			goto out;
+
+		if (prev) {
+			err = crypto_shash_update(desc, prev, hashlen);
+			if (err)
+				goto out;
+		}
+
+		err = crypto_shash_update(desc, info, infolen);
+		if (err)
+			goto out;
+
+		BUILD_BUG_ON(sizeof(counter) != 1);
+		if (okmlen - i < hashlen) {
+			err = crypto_shash_finup(desc, &counter, 1, tmp);
+			if (err)
+				goto out;
+			memcpy(&okm[i], tmp, okmlen - i);
+			memzero_explicit(tmp, sizeof(tmp));
+		} else {
+			err = crypto_shash_finup(desc, &counter, 1, &okm[i]);
+			if (err)
+				goto out;
+		}
+		counter++;
+		prev = &okm[i];
+	}
+	err = 0;
+out:
+	if (unlikely(err))
+		memzero_explicit(okm, okmlen); /* so caller doesn't need to */
+	shash_desc_zero(desc);
+	kfree(tmp);
+	return err;
+}
+EXPORT_SYMBOL_GPL(hkdf_expand);
diff --git a/fs/crypto/hkdf.c b/fs/crypto/hkdf.c
index 5a384dad2c72..9c2f9aca9412 100644
--- a/fs/crypto/hkdf.c
+++ b/fs/crypto/hkdf.c
@@ -11,6 +11,7 @@
 
 #include <crypto/hash.h>
 #include <crypto/sha2.h>
+#include <crypto/hkdf.h>
 
 #include "fscrypt_private.h"
 
@@ -44,20 +45,6 @@
  * there's no way to persist a random salt per master key from kernel mode.
  */
 
-/* HKDF-Extract (RFC 5869 section 2.2), unsalted */
-static int hkdf_extract(struct crypto_shash *hmac_tfm, const u8 *ikm,
-			unsigned int ikmlen, u8 prk[HKDF_HASHLEN])
-{
-	static const u8 default_salt[HKDF_HASHLEN];
-	int err;
-
-	err = crypto_shash_setkey(hmac_tfm, default_salt, HKDF_HASHLEN);
-	if (err)
-		return err;
-
-	return crypto_shash_tfm_digest(hmac_tfm, ikm, ikmlen, prk);
-}
-
 /*
  * Compute HKDF-Extract using the given master key as the input keying material,
  * and prepare an HMAC transform object keyed by the resulting pseudorandom key.
@@ -118,61 +105,24 @@ int fscrypt_hkdf_expand(const struct fscrypt_hkdf *hkdf, u8 context,
 			u8 *okm, unsigned int okmlen)
 {
 	SHASH_DESC_ON_STACK(desc, hkdf->hmac_tfm);
-	u8 prefix[9];
-	unsigned int i;
+	u8 *prefix;
 	int err;
-	const u8 *prev = NULL;
-	u8 counter = 1;
-	u8 tmp[HKDF_HASHLEN];
 
 	if (WARN_ON_ONCE(okmlen > 255 * HKDF_HASHLEN))
 		return -EINVAL;
 
+	prefix = kzalloc(okmlen + 9, GFP_KERNEL);
+	if (!prefix)
+		return -ENOMEM;
 	desc->tfm = hkdf->hmac_tfm;
 
 	memcpy(prefix, "fscrypt\0", 8);
 	prefix[8] = context;
+	memcpy(prefix + 9, info, infolen);
 
-	for (i = 0; i < okmlen; i += HKDF_HASHLEN) {
-
-		err = crypto_shash_init(desc);
-		if (err)
-			goto out;
-
-		if (prev) {
-			err = crypto_shash_update(desc, prev, HKDF_HASHLEN);
-			if (err)
-				goto out;
-		}
-
-		err = crypto_shash_update(desc, prefix, sizeof(prefix));
-		if (err)
-			goto out;
-
-		err = crypto_shash_update(desc, info, infolen);
-		if (err)
-			goto out;
-
-		BUILD_BUG_ON(sizeof(counter) != 1);
-		if (okmlen - i < HKDF_HASHLEN) {
-			err = crypto_shash_finup(desc, &counter, 1, tmp);
-			if (err)
-				goto out;
-			memcpy(&okm[i], tmp, okmlen - i);
-			memzero_explicit(tmp, sizeof(tmp));
-		} else {
-			err = crypto_shash_finup(desc, &counter, 1, &okm[i]);
-			if (err)
-				goto out;
-		}
-		counter++;
-		prev = &okm[i];
-	}
-	err = 0;
-out:
-	if (unlikely(err))
-		memzero_explicit(okm, okmlen); /* so caller doesn't need to */
-	shash_desc_zero(desc);
+	err = hkdf_expand(hkdf->hmac_tfm, prefix, infolen + 8,
+			  okm, okmlen);
+	kfree(prefix);
 	return err;
 }
 
diff --git a/include/crypto/hkdf.h b/include/crypto/hkdf.h
new file mode 100644
index 000000000000..bf06c080d7ed
--- /dev/null
+++ b/include/crypto/hkdf.h
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * HKDF: HMAC-based Key Derivation Function (HKDF), RFC 5869
+ *
+ * Extracted from fs/crypto/hkdf.c, which has
+ * Copyright 2019 Google LLC
+ */
+
+#ifndef _CRYPTO_HKDF_H
+#define _CRYPTO_HKDF_H
+
+int hkdf_extract(struct crypto_shash *hmac_tfm, const u8 *ikm,
+		 unsigned int ikmlen, u8 *prk);
+int hkdf_expand(struct crypto_shash *hmac_tfm,
+		const u8 *info, unsigned int infolen,
+		u8 *okm, unsigned int okmlen);
+
+#endif
-- 
2.35.3

Re: [PATCH 1/9] crypto,fs: Separate out hkdf_extract() and hkdf_expand()

[Eric Biggers]

On Mon, Jul 22, 2024 at 04:21:14PM +0200, Hannes Reinecke wrote:
> diff --git a/crypto/Makefile b/crypto/Makefile
> index edbbaa3ffef5..b77fc360f0ff 100644
> --- a/crypto/Makefile
> +++ b/crypto/Makefile
> @@ -29,6 +29,7 @@ obj-$(CONFIG_CRYPTO_ECHAINIV) += echainiv.o
>  
>  crypto_hash-y += ahash.o
>  crypto_hash-y += shash.o
> +crypto_hash-y += hkdf.o
>  obj-$(CONFIG_CRYPTO_HASH2) += crypto_hash.o

This should go under a kconfig option CONFIG_CRYPTO_HKDF that is selected by the
users that need it.  That way the code will be built only when needed.

Including a self-test would also be desirable.

> diff --git a/crypto/hkdf.c b/crypto/hkdf.c
> new file mode 100644
> index 000000000000..22e343851c0b
> --- /dev/null
> +++ b/crypto/hkdf.c
> @@ -0,0 +1,112 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Implementation of HKDF ("HMAC-based Extract-and-Expand Key Derivation
> + * Function"), aka RFC 5869.  See also the original paper (Krawczyk 2010):
> + * "Cryptographic Extraction and Key Derivation: The HKDF Scheme".
> + *
> + * This is used to derive keys from the fscrypt master keys.

This is no longer in fs/crypto/, so the part about fscrypt should be removed.

> +/*
> + * HKDF consists of two steps:
> + *
> + * 1. HKDF-Extract: extract a pseudorandom key of length HKDF_HASHLEN bytes from
> + *    the input keying material and optional salt.

It doesn't make sense to refer to HKDF_HASHLEN here since it is specific to
fs/crypto/.

> +/* HKDF-Extract (RFC 5869 section 2.2), unsalted */
> +int hkdf_extract(struct crypto_shash *hmac_tfm, const u8 *ikm,
> +		 unsigned int ikmlen, u8 *prk)

Needs kerneldoc now that this is a library interface.

> +{
> +	unsigned int prklen = crypto_shash_digestsize(hmac_tfm);
> +	u8 *default_salt;
> +	int err;
> +
> +	default_salt = kzalloc(prklen, GFP_KERNEL);
> +	if (!default_salt)
> +		return -ENOMEM;

Now that this is a library interface, it should take the salt as a parameter,
and the users who want the default salt should explicitly specify that.  If we
only provide support for unsalted use, that might inadventently discourage the
use of a salt in future code.  As the function is named hkdf_extract(), people
might also overlook that it's unsalted and doesn't actually match the RFC's
definition of HKDF-Extract.

The use of kzalloc here is also inefficient, as the maximum length of a digest
is known (HKDF_HASHLEN in fs/crypto/ case, HASH_MAX_DIGESTSIZE in general).

> +	err = crypto_shash_setkey(hmac_tfm, default_salt, prklen);
> +	if (!err)
> +		err = crypto_shash_tfm_digest(hmac_tfm, ikm, ikmlen, prk);
> +
> +	kfree(default_salt);
> +	return err;
> +}
> +EXPORT_SYMBOL_GPL(hkdf_extract);
> +
> +/*
> + * HKDF-Expand (RFC 5869 section 2.3).
> + * This expands the pseudorandom key, which was already keyed into @hmac_tfm,
> + * into @okmlen bytes of output keying material parameterized by the
> + * application-specific @info of length @infolen bytes.
> + * This is thread-safe and may be called by multiple threads in parallel.
> + */
> +int hkdf_expand(struct crypto_shash *hmac_tfm,
> +		const u8 *info, unsigned int infolen,
> +		u8 *okm, unsigned int okmlen)

Needs kerneldoc now that this is a library interface.

> diff --git a/fs/crypto/hkdf.c b/fs/crypto/hkdf.c
> index 5a384dad2c72..9c2f9aca9412 100644
> --- a/fs/crypto/hkdf.c
> +++ b/fs/crypto/hkdf.c
>// SPDX-License-Identifier: GPL-2.0
>/*
> * Implementation of HKDF ("HMAC-based Extract-and-Expand Key Derivation
> * Function"), aka RFC 5869.  See also the original paper (Krawczyk 2010):
> * "Cryptographic Extraction and Key Derivation: The HKDF Scheme".
> *
> * This is used to derive keys from the fscrypt master keys.
> *
> * Copyright 2019 Google LLC
> */

The above file comment should be adjusted now that this file doesn't contain the
actual HKDF implementation.

> @@ -118,61 +105,24 @@ int fscrypt_hkdf_expand(const struct fscrypt_hkdf *hkdf, u8 context,
>  			u8 *okm, unsigned int okmlen)
>  {
>  	SHASH_DESC_ON_STACK(desc, hkdf->hmac_tfm);
> -	u8 prefix[9];
> -	unsigned int i;
> +	u8 *prefix;
>  	int err;
> -	const u8 *prev = NULL;
> -	u8 counter = 1;
> -	u8 tmp[HKDF_HASHLEN];
>  
>  	if (WARN_ON_ONCE(okmlen > 255 * HKDF_HASHLEN))
>  		return -EINVAL;
>  
> +	prefix = kzalloc(okmlen + 9, GFP_KERNEL);
> +	if (!prefix)
> +		return -ENOMEM;
>  	desc->tfm = hkdf->hmac_tfm;
>  
>  	memcpy(prefix, "fscrypt\0", 8);
>  	prefix[8] = context;
> +	memcpy(prefix + 9, info, infolen);

This makes the variable called 'prefix' no longer be the prefix, but rather the
full info string.  A better name for it would be 'full_info'.

Also, it's being allocated with the wrong length.  It should be 9 + infolen.

> +	err = hkdf_expand(hkdf->hmac_tfm, prefix, infolen + 8,
> +			  okm, okmlen);
> +	kfree(prefix);

kfree_sensitive()

> diff --git a/include/crypto/hkdf.h b/include/crypto/hkdf.h
> new file mode 100644
> index 000000000000..bf06c080d7ed
> --- /dev/null
> +++ b/include/crypto/hkdf.h
> @@ -0,0 +1,18 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +/*
> + * HKDF: HMAC-based Key Derivation Function (HKDF), RFC 5869
> + *
> + * Extracted from fs/crypto/hkdf.c, which has
> + * Copyright 2019 Google LLC
> + */

If this is keeping the copyright of fs/crypto/hkdf.c, the license needs to stay
the same (GPL-2.0, not GPL-2.0-or-later).

- Eric

Re: [PATCH 1/9] crypto,fs: Separate out hkdf_extract() and hkdf_expand()

[Hannes Reinecke]

On 7/23/24 03:36, Eric Biggers wrote:
> On Mon, Jul 22, 2024 at 04:21:14PM +0200, Hannes Reinecke wrote:
>> diff --git a/crypto/Makefile b/crypto/Makefile
>> index edbbaa3ffef5..b77fc360f0ff 100644
>> --- a/crypto/Makefile
>> +++ b/crypto/Makefile
>> @@ -29,6 +29,7 @@ obj-$(CONFIG_CRYPTO_ECHAINIV) += echainiv.o
>>   
>>   crypto_hash-y += ahash.o
>>   crypto_hash-y += shash.o
>> +crypto_hash-y += hkdf.o
>>   obj-$(CONFIG_CRYPTO_HASH2) += crypto_hash.o
> 
> This should go under a kconfig option CONFIG_CRYPTO_HKDF that is selected by the
> users that need it.  That way the code will be built only when needed.
> 
Okay.

> Including a self-test would also be desirable.
> 
First time for me, but ok.

>> diff --git a/crypto/hkdf.c b/crypto/hkdf.c
>> new file mode 100644
>> index 000000000000..22e343851c0b
>> --- /dev/null
>> +++ b/crypto/hkdf.c
>> @@ -0,0 +1,112 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Implementation of HKDF ("HMAC-based Extract-and-Expand Key Derivation
>> + * Function"), aka RFC 5869.  See also the original paper (Krawczyk 2010):
>> + * "Cryptographic Extraction and Key Derivation: The HKDF Scheme".
>> + *
>> + * This is used to derive keys from the fscrypt master keys.
> 
> This is no longer in fs/crypto/, so the part about fscrypt should be removed.
> 
Will be removing this line.

>> +/*
>> + * HKDF consists of two steps:
>> + *
>> + * 1. HKDF-Extract: extract a pseudorandom key of length HKDF_HASHLEN bytes from
>> + *    the input keying material and optional salt.
> 
> It doesn't make sense to refer to HKDF_HASHLEN here since it is specific to
> fs/crypto/.
> 
Ok.

>> +/* HKDF-Extract (RFC 5869 section 2.2), unsalted */
>> +int hkdf_extract(struct crypto_shash *hmac_tfm, const u8 *ikm,
>> +		 unsigned int ikmlen, u8 *prk)
> 
> Needs kerneldoc now that this is a library interface.
> 
Indeed, will be updating the comment.

>> +{
>> +	unsigned int prklen = crypto_shash_digestsize(hmac_tfm);
>> +	u8 *default_salt;
>> +	int err;
>> +
>> +	default_salt = kzalloc(prklen, GFP_KERNEL);
>> +	if (!default_salt)
>> +		return -ENOMEM;
> 
> Now that this is a library interface, it should take the salt as a parameter,
> and the users who want the default salt should explicitly specify that.  If we
> only provide support for unsalted use, that might inadventently discourage the
> use of a salt in future code.  As the function is named hkdf_extract(), people
> might also overlook that it's unsalted and doesn't actually match the RFC's
> definition of HKDF-Extract.
> 
> The use of kzalloc here is also inefficient, as the maximum length of a digest
> is known (HKDF_HASHLEN in fs/crypto/ case, HASH_MAX_DIGESTSIZE in general).
> 
I was trying to keep the changes to the actual code to a minimum, so I 
didn't modify the calling sequence of the original code.
But sure, passing in the 'salt' as a parameter is sensible.

>> +	err = crypto_shash_setkey(hmac_tfm, default_salt, prklen);
>> +	if (!err)
>> +		err = crypto_shash_tfm_digest(hmac_tfm, ikm, ikmlen, prk);
>> +
>> +	kfree(default_salt);
>> +	return err;
>> +}
>> +EXPORT_SYMBOL_GPL(hkdf_extract);
>> +
>> +/*
>> + * HKDF-Expand (RFC 5869 section 2.3).
>> + * This expands the pseudorandom key, which was already keyed into @hmac_tfm,
>> + * into @okmlen bytes of output keying material parameterized by the
>> + * application-specific @info of length @infolen bytes.
>> + * This is thread-safe and may be called by multiple threads in parallel.
>> + */
>> +int hkdf_expand(struct crypto_shash *hmac_tfm,
>> +		const u8 *info, unsigned int infolen,
>> +		u8 *okm, unsigned int okmlen)
> 
> Needs kerneldoc now that this is a library interface.
> 
Ok.

>> diff --git a/fs/crypto/hkdf.c b/fs/crypto/hkdf.c
>> index 5a384dad2c72..9c2f9aca9412 100644
>> --- a/fs/crypto/hkdf.c
>> +++ b/fs/crypto/hkdf.c
>> // SPDX-License-Identifier: GPL-2.0
>> /*
>> * Implementation of HKDF ("HMAC-based Extract-and-Expand Key Derivation
>> * Function"), aka RFC 5869.  See also the original paper (Krawczyk 2010):
>> * "Cryptographic Extraction and Key Derivation: The HKDF Scheme".
>> *
>> * This is used to derive keys from the fscrypt master keys.
>> *
>> * Copyright 2019 Google LLC
>> */
> 
> The above file comment should be adjusted now that this file doesn't contain the
> actual HKDF implementation.
> 
Ok.

>> @@ -118,61 +105,24 @@ int fscrypt_hkdf_expand(const struct fscrypt_hkdf *hkdf, u8 context,
>>   			u8 *okm, unsigned int okmlen)
>>   {
>>   	SHASH_DESC_ON_STACK(desc, hkdf->hmac_tfm);
>> -	u8 prefix[9];
>> -	unsigned int i;
>> +	u8 *prefix;
>>   	int err;
>> -	const u8 *prev = NULL;
>> -	u8 counter = 1;
>> -	u8 tmp[HKDF_HASHLEN];
>>   
>>   	if (WARN_ON_ONCE(okmlen > 255 * HKDF_HASHLEN))
>>   		return -EINVAL;
>>   
>> +	prefix = kzalloc(okmlen + 9, GFP_KERNEL);
>> +	if (!prefix)
>> +		return -ENOMEM;
>>   	desc->tfm = hkdf->hmac_tfm;
>>   
>>   	memcpy(prefix, "fscrypt\0", 8);
>>   	prefix[8] = context;
>> +	memcpy(prefix + 9, info, infolen);
> 
> This makes the variable called 'prefix' no longer be the prefix, but rather the
> full info string.  A better name for it would be 'full_info'.
> 
> Also, it's being allocated with the wrong length.  It should be 9 + infolen.
> 
Will fix it up.

>> +	err = hkdf_expand(hkdf->hmac_tfm, prefix, infolen + 8,
>> +			  okm, okmlen);
>> +	kfree(prefix);
> 
> kfree_sensitive()
> 
>> diff --git a/include/crypto/hkdf.h b/include/crypto/hkdf.h
>> new file mode 100644
>> index 000000000000..bf06c080d7ed
>> --- /dev/null
>> +++ b/include/crypto/hkdf.h
>> @@ -0,0 +1,18 @@
>> +/* SPDX-License-Identifier: GPL-2.0-or-later */
>> +/*
>> + * HKDF: HMAC-based Key Derivation Function (HKDF), RFC 5869
>> + *
>> + * Extracted from fs/crypto/hkdf.c, which has
>> + * Copyright 2019 Google LLC
>> + */
> 
> If this is keeping the copyright of fs/crypto/hkdf.c, the license needs to stay
> the same (GPL-2.0, not GPL-2.0-or-later).
> 
Will be modifying it.

Thanks a lot for your review!

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@suse.de                                +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich

[PATCH 1/9] crypto,fs: Separate out hkdf_extract() and hkdf_expand()

[Hannes Reinecke]

Separate out the HKDF functions into a separate module to
to make them available to other callers.
And add a testsuite to the module with test vectors
from RFC 5869 to ensure the integrity of the algorithm.

Signed-off-by: Hannes Reinecke <hare@kernel.org>
Cc: Eric Biggers <ebiggers@kernel.org>
Cc: linux-crypto@vger.kernel.org
---
 crypto/Kconfig        |   4 +
 crypto/Makefile       |   1 +
 crypto/hkdf.c         | 404 ++++++++++++++++++++++++++++++++++++++++++
 fs/crypto/Kconfig     |   1 +
 fs/crypto/hkdf.c      |  87 ++-------
 include/crypto/hkdf.h |  34 ++++
 6 files changed, 459 insertions(+), 72 deletions(-)
 create mode 100644 crypto/hkdf.c
 create mode 100644 include/crypto/hkdf.h

diff --git a/crypto/Kconfig b/crypto/Kconfig
index 72e2decb8c6a..fe596b3ab063 100644
--- a/crypto/Kconfig
+++ b/crypto/Kconfig
@@ -141,6 +141,10 @@ config CRYPTO_ACOMP
 	select CRYPTO_ALGAPI
 	select CRYPTO_ACOMP2
 
+config CRYPTO_HKDF
+	tristate
+	select CRYPTO_HASH2
+
 config CRYPTO_MANAGER
 	tristate "Cryptographic algorithm manager"
 	select CRYPTO_MANAGER2
diff --git a/crypto/Makefile b/crypto/Makefile
index 4c99e5d376f6..5ec5b994d9ae 100644
--- a/crypto/Makefile
+++ b/crypto/Makefile
@@ -34,6 +34,7 @@ obj-$(CONFIG_CRYPTO_HASH2) += crypto_hash.o
 obj-$(CONFIG_CRYPTO_AKCIPHER2) += akcipher.o
 obj-$(CONFIG_CRYPTO_SIG2) += sig.o
 obj-$(CONFIG_CRYPTO_KPP2) += kpp.o
+obj-$(CONFIG_CRYPTO_HKDF) += hkdf.o
 
 dh_generic-y := dh.o
 dh_generic-y += dh_helper.o
diff --git a/crypto/hkdf.c b/crypto/hkdf.c
new file mode 100644
index 000000000000..67d55fc3e180
--- /dev/null
+++ b/crypto/hkdf.c
@@ -0,0 +1,404 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Implementation of HKDF ("HMAC-based Extract-and-Expand Key Derivation
+ * Function"), aka RFC 5869.  See also the original paper (Krawczyk 2010):
+ * "Cryptographic Extraction and Key Derivation: The HKDF Scheme".
+ *
+ * Copyright 2019 Google LLC
+ */
+
+#include <crypto/internal/hash.h>
+#include <crypto/sha2.h>
+#include <crypto/hkdf.h>
+#include <linux/module.h>
+
+/*
+ * HKDF consists of two steps:
+ *
+ * 1. HKDF-Extract: extract a pseudorandom key from the input keying material
+ *    and optional salt.
+ * 2. HKDF-Expand: expand the pseudorandom key into output keying material of
+ *    any length, parameterized by an application-specific info string.
+ *
+ */
+
+/**
+ * hkdf_extract - HKDF-Extract (RFC 5869 section 2.2)
+ * @hmac_tfm: hash context
+ * @ikm: input keying material
+ * @ikmlen: length of @ikm
+ * @salt: input salt value
+ * @saltlen: length of @salt
+ * @prk: resulting pseudorandom key
+ *
+ * Extracts a pseudorandom key @prk from the input keying material
+ * @ikm with length @ikmlen and salt @salt with length @saltlen.
+ * The length of @prk is given by the digest size of @hmac_tfm.
+ * For an 'unsalted' version of HKDF-Extract @salt should be set
+ * to all zeroes and @saltlen should be set to the length of @prk.
+ *
+ * Returns 0 on success with the pseudorandom key stored in @prk,
+ * otherwise a negative error.
+ */
+int hkdf_extract(struct crypto_shash *hmac_tfm, const u8 *ikm,
+		 unsigned int ikmlen, const u8 *salt, unsigned int saltlen,
+		 u8 *prk)
+{
+	int err;
+
+	err = crypto_shash_setkey(hmac_tfm, salt, saltlen);
+	if (!err)
+		err = crypto_shash_tfm_digest(hmac_tfm, ikm, ikmlen, prk);
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(hkdf_extract);
+
+/*
+ * hkdf_expand - HKDF-Expand (RFC 5869 section 2.3)
+ * @hmac_tfm: hash context keyed with pseudorandom key
+ * @info: application-specific information
+ * @infolen: length of @info
+ * @okm: output keying material
+ *
+ * This expands the pseudorandom key, which was already keyed into @hmac_tfm,
+ * into @okmlen bytes of output keying material parameterized by the
+ * application-specific @info of length @infolen bytes.
+ * This is thread-safe and may be called by multiple threads in parallel.
+ *
+ * Returns 0 on success with output keying material stored in @okm,
+ * negative error number otherwise.
+ */
+int hkdf_expand(struct crypto_shash *hmac_tfm,
+		const u8 *info, unsigned int infolen,
+		u8 *okm, unsigned int okmlen)
+{
+	SHASH_DESC_ON_STACK(desc, hmac_tfm);
+	unsigned int i, hashlen = crypto_shash_digestsize(hmac_tfm);
+	int err;
+	const u8 *prev = NULL;
+	u8 counter = 1;
+	u8 *tmp;
+
+	if (WARN_ON(okmlen > 255 * hashlen))
+		return -EINVAL;
+
+	tmp = kzalloc(hashlen, GFP_KERNEL);
+	if (!tmp)
+		return -ENOMEM;
+
+	desc->tfm = hmac_tfm;
+
+	for (i = 0; i < okmlen; i += hashlen) {
+
+		err = crypto_shash_init(desc);
+		if (err)
+			goto out;
+
+		if (prev) {
+			err = crypto_shash_update(desc, prev, hashlen);
+			if (err)
+				goto out;
+		}
+
+		if (info && infolen) {
+			err = crypto_shash_update(desc, info, infolen);
+			if (err)
+				goto out;
+		}
+
+		BUILD_BUG_ON(sizeof(counter) != 1);
+		if (okmlen - i < hashlen) {
+			err = crypto_shash_finup(desc, &counter, 1, tmp);
+			if (err)
+				goto out;
+			memcpy(&okm[i], tmp, okmlen - i);
+			memzero_explicit(tmp, sizeof(tmp));
+		} else {
+			err = crypto_shash_finup(desc, &counter, 1, &okm[i]);
+			if (err)
+				goto out;
+		}
+		counter++;
+		prev = &okm[i];
+	}
+	err = 0;
+out:
+	if (unlikely(err))
+		memzero_explicit(okm, okmlen); /* so caller doesn't need to */
+	shash_desc_zero(desc);
+	kfree(tmp);
+	return err;
+}
+EXPORT_SYMBOL_GPL(hkdf_expand);
+
+struct hkdf_testvec {
+	const char *test;
+	const unsigned char *ikm;
+	const unsigned char *salt;
+	const unsigned char *info;
+	const unsigned char *prk;
+	const unsigned char *okm;
+	unsigned short ikm_size;
+	unsigned short salt_size;
+	unsigned short info_size;
+	unsigned short prk_size;
+	unsigned short okm_size;
+};
+
+/*
+ * HKDF test vectors from RFC5869
+ */
+static const struct hkdf_testvec hkdf_sha256_tv[] = {
+	{
+		.test = "basic hdkf test",
+		.ikm  = "\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b"
+			"\x0b\x0b\x0b\x0b\x0b\x0b",
+		.ikm_size = 22,
+		.salt = "\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c",
+		.salt_size = 13,
+		.info = "\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9",
+		.info_size = 10,
+		.prk = "\x07\x77\x09\x36\x2c\x2e\x32\xdf\x0d\xdc\x3f\x0d\xc4\x7b\xba\x63"
+			"\x90\xb6\xc7\x3b\xb5\x0f\x9c\x31\x22\xec\x84\x4a\xd7\xc2\xb3\xe5",
+		.prk_size = 32,
+		.okm  = "\x3c\xb2\x5f\x25\xfa\xac\xd5\x7a\x90\x43\x4f\x64\xd0\x36\x2f\x2a"
+			"\x2d\x2d\x0a\x90\xcf\x1a\x5a\x4c\x5d\xb0\x2d\x56\xec\xc4\xc5\xbf"
+			"\x34\x00\x72\x08\xd5\xb8\x87\x18\x58\x65",
+		.okm_size = 42,
+	}, {
+		.test = "hkdf test with long input",
+		.ikm  = "\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f"
+			"\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f"
+			"\x20\x21\x22\x23\x24\x25\x26\x27\x28\x29\x2a\x2b\x2c\x2d\x2e\x2f"
+			"\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x3a\x3b\x3c\x3d\x3e\x3f"
+			"\x40\x41\x42\x43\x44\x45\x46\x47\x48\x49\x4a\x4b\x4c\x4d\x4e\x4f",
+		.ikm_size = 80,
+		.salt = "\x60\x61\x62\x63\x64\x65\x66\x67\x68\x69\x6a\x6b\x6c\x6d\x6e\x6f"
+			"\x70\x71\x72\x73\x74\x75\x76\x77,\x78\x79\x7a\x7b\x7c\x7d\x7e\x7f"
+			"\x80\x81\x82\x83\x84\x85\x86\x87\x88\x89\x8a\x8b\x8c\x8d\x8e\x8f"
+			"\x90\x91\x92\x93\x94\x95\x96\x97\x98\x99\x9a\x9b\x9c\x9d\x9e\x9f"
+			"\xa0\xa1\xa2\xa3\xa4\xa5\xa6\xa7\xa8\xa9\xaa\xab\xac\xad\xae\xaf",
+		.salt_size = 80,
+		.info = "\xb0\xb1\xb2\xb3\xb4\xb5\xb6\xb7\xb8\xb9\xba\xbb\xbc\xbd\xbe\xbf"
+			"\xc0\xc1\xc2\xc3\xc4\xc5\xc6\xc7\xc8\xc9\xca\xcb\xcc\xcd\xce\xcf"
+			"\xd0\xd1\xd2\xd3\xd4\xd5\xd6\xd7\xd8\xd9\xda\xdb\xdc\xdd\xde\xdf"
+			"\xe0\xe1\xe2\xe3\xe4\xe5\xe6\xe7\xe8\xe9\xea\xeb\xec\xed\xee\xef"
+			"\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9\xfa\xfb\xfc\xfd\xfe\xff",
+		.info_size = 80,
+		.prk = "\x06\xa6\xb8\x8c\x58\x53\x36\x1a\x06\x10\x4c\x9c\xeb\x35\xb4\x5c"
+			"\xef\x76\x00\x14\x90\x46\x71\x01\x4a\x19\x3f\x40\xc1\x5f\xc2\x44",
+		.prk_size = 32,
+		.okm = "\xb1\x1e\x39\x8d\xc8\x03\x27\xa1\xc8\xe7\xf7\x8c\x59\x6a\x49\x34"
+			"\x4f\x01\x2e\xda\x2d\x4e\xfa\xd8\xa0\x50\xcc\x4c\x19\xaf\xa9\x7c"
+			"\x59\x04\x5a\x99\xca\xc7\x82\x72\x71\xcb\x41\xc6\x5e\x59\x0e\x09"
+			"\xda\x32\x75\x60\x0c\x2f\x09\xb8\x36\x77\x93\xa9\xac\xa3\xdb\x71"
+			"\xcc\x30\xc5\x81\x79\xec\x3e\x87\xc1\x4c\x01\xd5\xc1\xf3\x43\x4f"
+			"\x1d\x87",
+		.okm_size = 82,
+	}, {
+		.test = "hkdf test with zero salt and info",
+		.ikm  = "\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b"
+			"\x0b\x0b\x0b\x0b\x0b\x0b",
+		.ikm_size = 22,
+		.salt = NULL,
+		.salt_size = 0,
+		.info = NULL,
+		.info_size = 0,
+		.prk = "\0x19\xef\x24\xa3\x2c\x71\x7b\x16\x7f\x33\xa9\x1d\x6f\x64\x8b\xdf"
+			"\x96\x59\x67\x76\xaf\xdb\x63\x77\xac\x43\x4c\x1c\x29\x3c\xcb\x04",
+		.prk_size = 32,
+		.okm = "\x8d\xa4\xe7\x75\xa5\x63\xc1\x8f\x71\x5f\x80\x2a\x06\x3c\x5a\x31"
+			"\xb8\xa1\x1f\x5c\x5e\xe1\x87\x9e\xc3\x45\x4e\x5f\x3c\x73\x8d\x2d"
+			"\x9d\x20\x13\x95\xfa\xa4\xb6\x1a\x96\xc8",
+		.okm_size = 42,
+	}
+};
+
+static const struct hkdf_testvec hkdf_sha1_tv[] = {
+	{
+		.test = "basic hkdf test",
+		.ikm  = "\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b",
+		.ikm_size = 11,
+		.salt = "\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c",
+		.salt_size = 13,
+		.info = "\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9",
+		.info_size = 10,
+		.prk  = "\x9b\x6c\x18\xc4\x32\xa7\xbf\x8f\x0e\x71\xc8\xeb\x88\xf4\xb3\x0b"
+			"\xaa\x2b\xa2\x43",
+		.prk_size = 20,
+		.okm  = "\x08\x5a\x01\xea\x1b\x10\xf3\x69\x33\x06\x8b\x56\xef\xa5\xad\x81"
+			"\xa4\xf1\x4b\x82\x2f\x5b\x09\x15\x68\xa9\xcd\xd4\xf1\x55\xfd\xa2"
+			"\xc2\x2e\x42\x24\x78\xd3\x05\xf3\xf8\x96",
+		.okm_size = 42,
+	}, {
+		.test = "hkdf test with long input",
+		.ikm = "\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f"
+			"\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f"
+			"\x20\x21\x22\x23\x24\x25\x26\x27\x28\x29\x2a\x2b\x2c\x2d\x2e\x2f"
+			"\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x3a\x3b\x3c\x3d\x3e\x3f"
+			"\x40\x41\x42\x43\x44\x45\x46\x47\x48\x49\x4a\x4b\x4c\x4d\x4e\x4f",
+		.ikm_size = 80,
+		.salt = "\x60\x61\x62\x63\x64\x65\x66\x67\x68\x69\x6a\x6b\x6c\x6d\x6e\x6f"
+			"\x70\x71\x72\x73\x74\x75\x76\x77\x78\x79\x7a\x7b\x7c\x7d\x7e\x7f"
+			"\x80\x81\x82\x83\x84\x85\x86\x87\x88\x89\x8a\x8b\x8c\x8d\x8e\x8f"
+			"\x90\x91\x92\x93\x94\x95\x96\x97\x98\x99\x9a\x9b\x9c\x9d\x9e\x9f"
+			"\xa0\xa1\xa2\xa3\xa4\xa5\xa6\xa7\xa8\xa9\xaa\xab\xac\xad\xae\xaf",
+		.salt_size = 80,
+		.info = "\xb0\xb1\xb2\xb3\xb4\xb5\xb6\xb7\xb8\xb9\xba\xbb\xbc\xbd\xbe\xbf"
+			"\xc0\xc1\xc2\xc3\xc4\xc5\xc6\xc7\xc8\xc9\xca\xcb\xcc\xcd\xce\xcf"
+			"\xd0\xd1\xd2\xd3\xd4\xd5\xd6\xd7\xd8\xd9\xda\xdb\xdc\xdd\xde\xdf"
+			"\xe0\xe1\xe2\xe3\xe4\xe5\xe6\xe7\xe8\xe9\xea\xeb\xec\xed\xee\xef"
+			"\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9\xfa\xfb\xfc\xfd\xfe\xff",
+		.info_size = 80,
+		.prk  = "\x8a\xda\xe0\x9a\x2a\x30\x70\x59\x47\x8d\x30\x9b\x26\xc4\x11\x5a"
+			"\x22\x4c\xfa\xf6",
+		.prk_size = 20,
+		.okm = "\x0b\xd7\x70\xa7\x4d\x11\x60\xf7\xc9\xf1\x2c\xd5\x91\x2a\x06\xeb"
+			"\xff\x6a\xdc\xae\x89\x9d\x92\x19\x1f\xe4\x30\x56\x73\xba\x2f\xfe"
+			"\x8f\xa3\xf1\xa4\xe5\xad\x79\xf3\xf3\x34\xb3\xb2\x02\xb2\x17\x3c"
+			"\x48\x6e\xa3\x7c\xe3\xd3\x97\xed\x03\x4c\x7f\x9d\xfe\xb1\x5c\x5e"
+			"\x92\x73\x36\xd0\x44\x1f\x4c\x43\x00\xe2\xcf\xf0\xd0\x90\x0b\x52"
+			"\xd3\xb4",
+		.okm_size = 82,
+	}, {
+		.test = "hkdf test with zero salt and info",
+		.ikm = "\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b"
+			"\x0b\x0b\x0b\x0b\x0b\x0b",
+		.ikm_size = 22,
+		.salt = NULL,
+		.salt_size = 0,
+		.info = NULL,
+		.info_size = 0,
+		.prk = "\xda\x8c\x8a\x73\xc7\xfa\x77\x28\x8e\xc6\xf5\xe7\xc2\x97\x78\x6a"
+			"\xa0\xd3\x2d\x01",
+		.prk_size = 20,
+		.okm = "\x0a\xc1\xaf\x70\x02\xb3\xd7\x61\xd1\xe5\x52\x98\xda\x9d\x05\x06"
+			"\xb9\xae\x52\x05\x72\x20\xa3\x06\xe0\x7b\x6b\x87\xe8\xdf\x21\xd0"
+			"\xea\x00\x03\x3d\xe0\x39\x84\xd3\x49\x18",
+		.okm_size = 42,
+	}, {
+		.test = "unsalted hkdf test with zero info",
+		.ikm = "\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c"
+			"\x0c\x0c\x0c\x0c\x0c\x0c",
+		.ikm_size = 22,
+		.salt = "\0x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"
+			"\x00\x00\x00\x00",
+		.salt_size = 20,
+		.info = NULL,
+		.info_size = 0,
+		.prk = "\x2a\xdc\xca\xda\x18\x77\x9e\x7c\x20\x77\xad\x2e\xb1\x9d\x3f\x3e"
+			"\x73\x13\x85\xdd",
+		.prk_size = 20,
+		.okm = "\x2c\x91\x11\x72\x04\xd7\x45\xf3\x50\x0d\x63\x6a\x62\xf6\x4f\x0a"
+			"\xb3\xba\xe5\x48\xaa\x53\xd4\x23\xb0\xd1\xf2\x7e\xbb\xa6\xf5\xe5"
+			"\x67\x3a\x08\x1d\x70\xcc\xe7\xac\xfc\x48",
+		.okm_size = 42,
+	}
+};
+
+static int hkdf_test(const char *shash, const struct hkdf_testvec *tv)
+{	struct crypto_shash *tfm = NULL;
+	u8 *prk = NULL, *okm = NULL;
+	unsigned int prk_size;
+	const char *driver;
+	int err;
+
+	tfm = crypto_alloc_shash(shash, 0, 0);
+	if (IS_ERR(tfm)) {
+		pr_err("%s(%s): failed to allocate transform: %ld\n",
+		       tv->test, shash, PTR_ERR(tfm));
+		return PTR_ERR(tfm);
+	}
+	driver = crypto_shash_driver_name(tfm);
+
+	prk_size = crypto_shash_digestsize(tfm);
+	prk = kzalloc(prk_size, GFP_KERNEL);
+	if (!prk) {
+		err = -ENOMEM;
+		goto out_free_shash;
+	}
+
+	if (tv->prk_size != prk_size) {
+		pr_err("%s(%s): prk size mismatch (vec %u, digest %u\n",
+		       tv->test, driver, tv->prk_size, prk_size);
+		err = -EINVAL;
+		goto out_free_prk;
+	}
+
+	err = hkdf_extract(tfm, tv->ikm, tv->ikm_size,
+			   tv->salt, tv->salt_size, prk);
+	if (err) {
+		pr_err("%s(%s): hkdf_extract failed with %d\n",
+		       tv->test, driver, err);
+		goto out_free_prk;
+	}
+
+	if (memcmp(prk, tv->prk, tv->prk_size)) {
+		pr_err("%s(%s): hkdf_extract prk mismatch\n",
+		       tv->test, driver);
+		err = -EINVAL;
+		goto out_free_prk;
+	}
+
+	okm = kzalloc(tv->okm_size, GFP_KERNEL);
+	if (!okm) {
+		err = -ENOMEM;
+		goto out_free_prk;
+	}
+
+	err = crypto_shash_setkey(tfm, tv->prk, tv->prk_size);
+	if (err) {
+		pr_err("%s(%s): failed to hash key to PRK, error %d\n",
+		       tv->test, driver, err);
+		goto out_free_okm;
+	}
+
+	err = hkdf_expand(tfm, tv->info, tv->info_size,
+			  okm, tv->okm_size);
+	if (err) {
+		pr_err("%s(%s): hkdf_expand() failed with %d\n",
+		       tv->test, driver, err);
+	} else if (memcmp(okm, tv->okm, tv->okm_size)) {
+		pr_err("%s(%s): hkdf_expand() okm mismatch\n",
+		       tv->test, driver);
+		print_hex_dump(KERN_ERR, "okm: ", DUMP_PREFIX_NONE, 16, 1, okm, tv->okm_size, false);
+		err = -EINVAL;
+	}
+out_free_okm:
+	kfree(okm);
+out_free_prk:
+	kfree(prk);
+out_free_shash:
+	crypto_free_shash(tfm);
+	return err;
+}
+
+static int __init crypto_hkdf_module_init(void)
+{
+	int ret = 0, i;
+
+	if (IS_ENABLED(CONFIG_CRYPTO_MANAGER_DISABLE_TESTS))
+		return 0;
+
+	for (i = 0; i < ARRAY_SIZE(hkdf_sha256_tv); i++) {
+		ret = hkdf_test("hmac(sha256)", &hkdf_sha256_tv[i]);
+		if (ret)
+			return ret;
+	}
+	for (i = 0; i < ARRAY_SIZE(hkdf_sha1_tv); i++) {
+		ret = hkdf_test("hmac(sha1)", &hkdf_sha1_tv[i]);
+		if (ret)
+			return ret;
+	}
+	return 0;
+}
+
+static void __exit crypto_hkdf_module_exit(void) {}
+
+module_init(crypto_hkdf_module_init);
+module_exit(crypto_hkdf_module_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Hashed-Key derivation functions");
+MODULE_ALIAS_CRYPTO("hkdf");
diff --git a/fs/crypto/Kconfig b/fs/crypto/Kconfig
index 5aff5934baa1..0ea56f588a4a 100644
--- a/fs/crypto/Kconfig
+++ b/fs/crypto/Kconfig
@@ -3,6 +3,7 @@ config FS_ENCRYPTION
 	bool "FS Encryption (Per-file encryption)"
 	select CRYPTO
 	select CRYPTO_HASH
+	select CRYPTO_HKDF
 	select CRYPTO_SKCIPHER
 	select CRYPTO_LIB_SHA256
 	select KEYS
diff --git a/fs/crypto/hkdf.c b/fs/crypto/hkdf.c
index 5a384dad2c72..4f1d331bee9f 100644
--- a/fs/crypto/hkdf.c
+++ b/fs/crypto/hkdf.c
@@ -1,9 +1,5 @@
 // SPDX-License-Identifier: GPL-2.0
 /*
- * Implementation of HKDF ("HMAC-based Extract-and-Expand Key Derivation
- * Function"), aka RFC 5869.  See also the original paper (Krawczyk 2010):
- * "Cryptographic Extraction and Key Derivation: The HKDF Scheme".
- *
  * This is used to derive keys from the fscrypt master keys.
  *
  * Copyright 2019 Google LLC
@@ -11,6 +7,7 @@
 
 #include <crypto/hash.h>
 #include <crypto/sha2.h>
+#include <crypto/hkdf.h>
 
 #include "fscrypt_private.h"
 
@@ -44,20 +41,6 @@
  * there's no way to persist a random salt per master key from kernel mode.
  */
 
-/* HKDF-Extract (RFC 5869 section 2.2), unsalted */
-static int hkdf_extract(struct crypto_shash *hmac_tfm, const u8 *ikm,
-			unsigned int ikmlen, u8 prk[HKDF_HASHLEN])
-{
-	static const u8 default_salt[HKDF_HASHLEN];
-	int err;
-
-	err = crypto_shash_setkey(hmac_tfm, default_salt, HKDF_HASHLEN);
-	if (err)
-		return err;
-
-	return crypto_shash_tfm_digest(hmac_tfm, ikm, ikmlen, prk);
-}
-
 /*
  * Compute HKDF-Extract using the given master key as the input keying material,
  * and prepare an HMAC transform object keyed by the resulting pseudorandom key.
@@ -69,6 +52,7 @@ int fscrypt_init_hkdf(struct fscrypt_hkdf *hkdf, const u8 *master_key,
 		      unsigned int master_key_size)
 {
 	struct crypto_shash *hmac_tfm;
+	static const u8 default_salt[HKDF_HASHLEN];
 	u8 prk[HKDF_HASHLEN];
 	int err;
 
@@ -79,12 +63,8 @@ int fscrypt_init_hkdf(struct fscrypt_hkdf *hkdf, const u8 *master_key,
 		return PTR_ERR(hmac_tfm);
 	}
 
-	if (WARN_ON_ONCE(crypto_shash_digestsize(hmac_tfm) != sizeof(prk))) {
-		err = -EINVAL;
-		goto err_free_tfm;
-	}
-
-	err = hkdf_extract(hmac_tfm, master_key, master_key_size, prk);
+	err = hkdf_extract(hmac_tfm, master_key, master_key_size,
+			   default_salt, HKDF_HASHLEN, prk);
 	if (err)
 		goto err_free_tfm;
 
@@ -118,61 +98,24 @@ int fscrypt_hkdf_expand(const struct fscrypt_hkdf *hkdf, u8 context,
 			u8 *okm, unsigned int okmlen)
 {
 	SHASH_DESC_ON_STACK(desc, hkdf->hmac_tfm);
-	u8 prefix[9];
-	unsigned int i;
+	u8 *full_info;
 	int err;
-	const u8 *prev = NULL;
-	u8 counter = 1;
-	u8 tmp[HKDF_HASHLEN];
 
 	if (WARN_ON_ONCE(okmlen > 255 * HKDF_HASHLEN))
 		return -EINVAL;
 
+	full_info = kzalloc(infolen + 9, GFP_KERNEL);
+	if (!full_info)
+		return -ENOMEM;
 	desc->tfm = hkdf->hmac_tfm;
 
-	memcpy(prefix, "fscrypt\0", 8);
-	prefix[8] = context;
-
-	for (i = 0; i < okmlen; i += HKDF_HASHLEN) {
-
-		err = crypto_shash_init(desc);
-		if (err)
-			goto out;
-
-		if (prev) {
-			err = crypto_shash_update(desc, prev, HKDF_HASHLEN);
-			if (err)
-				goto out;
-		}
-
-		err = crypto_shash_update(desc, prefix, sizeof(prefix));
-		if (err)
-			goto out;
-
-		err = crypto_shash_update(desc, info, infolen);
-		if (err)
-			goto out;
-
-		BUILD_BUG_ON(sizeof(counter) != 1);
-		if (okmlen - i < HKDF_HASHLEN) {
-			err = crypto_shash_finup(desc, &counter, 1, tmp);
-			if (err)
-				goto out;
-			memcpy(&okm[i], tmp, okmlen - i);
-			memzero_explicit(tmp, sizeof(tmp));
-		} else {
-			err = crypto_shash_finup(desc, &counter, 1, &okm[i]);
-			if (err)
-				goto out;
-		}
-		counter++;
-		prev = &okm[i];
-	}
-	err = 0;
-out:
-	if (unlikely(err))
-		memzero_explicit(okm, okmlen); /* so caller doesn't need to */
-	shash_desc_zero(desc);
+	memcpy(full_info, "fscrypt\0", 8);
+	full_info[8] = context;
+	memcpy(full_info + 9, info, infolen);
+
+	err = hkdf_expand(hkdf->hmac_tfm, full_info, infolen + 8,
+			  okm, okmlen);
+	kfree_sensitive(full_info);
 	return err;
 }
 
diff --git a/include/crypto/hkdf.h b/include/crypto/hkdf.h
new file mode 100644
index 000000000000..ee3e7d21a5fe
--- /dev/null
+++ b/include/crypto/hkdf.h
@@ -0,0 +1,34 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * HKDF: HMAC-based Key Derivation Function (HKDF), RFC 5869
+ *
+ * Extracted from fs/crypto/hkdf.c, which has
+ * Copyright 2019 Google LLC
+ */
+
+#ifndef _CRYPTO_HKDF_H
+#define _CRYPTO_HKDF_H
+
+#ifdef CONFIG_CRYPTO_HKDF
+int hkdf_extract(struct crypto_shash *hmac_tfm, const u8 *ikm,
+		 unsigned int ikmlen, const u8 *salt, unsigned int saltlen,
+		 u8 *prk);
+int hkdf_expand(struct crypto_shash *hmac_tfm,
+		const u8 *info, unsigned int infolen,
+		u8 *okm, unsigned int okmlen);
+#else
+static inline int hkdf_extract(struct crypto_shash *hmac_tfm,
+			       const u8 *ikm, unsigned int ikmlen,
+			       const u8 *salt, unsigned int saltlen,
+			       u8 *prk)
+{
+	return -ENOTSUP;
+}
+static inline int hkdf_expand(struct crypto_shash *hmac_tfm,
+			      const u8 *info, unsigned int infolen,
+			      u8 *okm, unsigned int okmlen)
+{
+	return -ENOTSUP;
+}
+#endif
+#endif
-- 
2.35.3

Re: [PATCH 1/9] crypto,fs: Separate out hkdf_extract() and hkdf_expand()

[Eric Biggers]

On Tue, Aug 13, 2024 at 01:15:04PM +0200, Hannes Reinecke wrote:
> Separate out the HKDF functions into a separate module to
> to make them available to other callers.
> And add a testsuite to the module with test vectors
> from RFC 5869 to ensure the integrity of the algorithm.

integrity => correctness

> diff --git a/crypto/hkdf.c b/crypto/hkdf.c
> new file mode 100644
> index 000000000000..67d55fc3e180
> --- /dev/null
> +++ b/crypto/hkdf.c
[...]
> +/**
> + * hkdf_extract - HKDF-Extract (RFC 5869 section 2.2)
> + * @hmac_tfm: hash context

Should document hmac_tfm properly.  Maybe something like:

@hmac_tfm: an HMAC transform using the hash function desired for HKDF.  The
           caller is responsible for setting the @prk afterwards.

> + * @ikm: input keying material
> + * @ikmlen: length of @ikm
> + * @salt: input salt value
> + * @saltlen: length of @salt
> + * @prk: resulting pseudorandom key
> + *
> + * Extracts a pseudorandom key @prk from the input keying material
> + * @ikm with length @ikmlen and salt @salt with length @saltlen.
> + * The length of @prk is given by the digest size of @hmac_tfm.
> + * For an 'unsalted' version of HKDF-Extract @salt should be set
> + * to all zeroes and @saltlen should be set to the length of @prk.

should => must (both times above)

> + * otherwise a negative error.

negative errno value (not just any negative error)

> +/*
> + * hkdf_expand - HKDF-Expand (RFC 5869 section 2.3)

Needs to be /** to make it a kerneldoc comment

> + * @hmac_tfm: hash context keyed with pseudorandom key
> + * @info: application-specific information
> + * @infolen: length of @info
> + * @okm: output keying material

Missing documentation for @okmlen parameter

> + *
> + * This expands the pseudorandom key, which was already keyed into @hmac_tfm,
> + * into @okmlen bytes of output keying material parameterized by the
> + * application-specific @info of length @infolen bytes.
> + * This is thread-safe and may be called by multiple threads in parallel.
> + *
> + * Returns 0 on success with output keying material stored in @okm,
> + * negative error number otherwise.
> + */
> +int hkdf_expand(struct crypto_shash *hmac_tfm,
> +		const u8 *info, unsigned int infolen,
> +		u8 *okm, unsigned int okmlen)
> +{
> +	SHASH_DESC_ON_STACK(desc, hmac_tfm);
> +	unsigned int i, hashlen = crypto_shash_digestsize(hmac_tfm);
> +	int err;
> +	const u8 *prev = NULL;
> +	u8 counter = 1;
> +	u8 *tmp;
> +
> +	if (WARN_ON(okmlen > 255 * hashlen))
> +		return -EINVAL;
> +
> +	tmp = kzalloc(hashlen, GFP_KERNEL);
> +	if (!tmp)
> +		return -ENOMEM;

tmp can be allocated on the stack since it has maximum length
HASH_MAX_DIGESTSIZE.

Also, either way, it needs to be zeroized at the end of the function.

> +	desc->tfm = hmac_tfm;
> +
> +	for (i = 0; i < okmlen; i += hashlen) {
> +
> +		err = crypto_shash_init(desc);
> +		if (err)
> +			goto out;
> +
> +		if (prev) {
> +			err = crypto_shash_update(desc, prev, hashlen);
> +			if (err)
> +				goto out;
> +		}
> +
> +		if (info && infolen) {

'if (infolen)' instead of 'if (info && infolen)'.  The latter is a bad practice
because it can hide bugs.

> +struct hkdf_testvec {
> +	const char *test;
> +	const unsigned char *ikm;
> +	const unsigned char *salt;
> +	const unsigned char *info;
> +	const unsigned char *prk;
> +	const unsigned char *okm;
> +	unsigned short ikm_size;
> +	unsigned short salt_size;
> +	unsigned short info_size;
> +	unsigned short prk_size;
> +	unsigned short okm_size;
> +};

u8 and u16 instead of unsigned char and unsigned short, please.

> +static int hkdf_test(const char *shash, const struct hkdf_testvec *tv)
> +{	struct crypto_shash *tfm = NULL;
> +	u8 *prk = NULL, *okm = NULL;
> +	unsigned int prk_size;
> +	const char *driver;
> +	int err;
> +
> +	tfm = crypto_alloc_shash(shash, 0, 0);
> +	if (IS_ERR(tfm)) {
> +		pr_err("%s(%s): failed to allocate transform: %ld\n",
> +		       tv->test, shash, PTR_ERR(tfm));
> +		return PTR_ERR(tfm);
> +	}
> +	driver = crypto_shash_driver_name(tfm);
> +
> +	prk_size = crypto_shash_digestsize(tfm);
> +	prk = kzalloc(prk_size, GFP_KERNEL);
> +	if (!prk) {
> +		err = -ENOMEM;
> +		goto out_free_shash;
> +	}
> +
> +	if (tv->prk_size != prk_size) {
> +		pr_err("%s(%s): prk size mismatch (vec %u, digest %u\n",
> +		       tv->test, driver, tv->prk_size, prk_size);
> +		err = -EINVAL;
> +		goto out_free_prk;
> +	}

Since freeing NULL is a no-op, this function only really needs one label.

> +	err = crypto_shash_setkey(tfm, tv->prk, tv->prk_size);
> +	if (err) {
> +		pr_err("%s(%s): failed to hash key to PRK, error %d\n",
> +		       tv->test, driver, err);

Not sure what "failed to hash key to PRK" means here.  It failed to set the PRK,
so a better error message might be "failed to set PRK".

> +static int __init crypto_hkdf_module_init(void)
> +{
> +	int ret = 0, i;
> +
> +	if (IS_ENABLED(CONFIG_CRYPTO_MANAGER_DISABLE_TESTS))
> +		return 0;
> +
> +	for (i = 0; i < ARRAY_SIZE(hkdf_sha256_tv); i++) {
> +		ret = hkdf_test("hmac(sha256)", &hkdf_sha256_tv[i]);
> +		if (ret)
> +			return ret;
> +	}
> +	for (i = 0; i < ARRAY_SIZE(hkdf_sha1_tv); i++) {
> +		ret = hkdf_test("hmac(sha1)", &hkdf_sha1_tv[i]);
> +		if (ret)
> +			return ret;
> +	}

It's surprising that there are tests for sha1 which is obsolete, but none for
sha512 which is what is actually being used.

In any case, nothing guarantees that sha256 and sha1 are available here, as they
aren't selected by CRYPTO_HKDF.  They would need to be selected, at least if
CRYPTO_MANAGER_DISABLE_TESTS=n, or else the tests would need to be skipped if
the underlying hash algorithm is not available in the crypto API.

> +MODULE_DESCRIPTION("Hashed-Key derivation functions");

This may be a misunderstanding about what HKDF stands for.

How about: MODULE_DESCRIPTION("HMAC-based Key Derivation Function (HKDF)");


> diff --git a/fs/crypto/hkdf.c b/fs/crypto/hkdf.c
> index 5a384dad2c72..4f1d331bee9f 100644
> --- a/fs/crypto/hkdf.c
> +++ b/fs/crypto/hkdf.c
[...]
> @@ -79,12 +63,8 @@ int fscrypt_init_hkdf(struct fscrypt_hkdf *hkdf, const u8 *master_key,
>  		return PTR_ERR(hmac_tfm);
>  	}
>  
> -	if (WARN_ON_ONCE(crypto_shash_digestsize(hmac_tfm) != sizeof(prk))) {
> -		err = -EINVAL;
> -		goto err_free_tfm;
> -	}

Why is this WARN_ON_ONCE being removed?  It doesn't seem to be replaced by
anything.

> -
> -	err = hkdf_extract(hmac_tfm, master_key, master_key_size, prk);
> +	err = hkdf_extract(hmac_tfm, master_key, master_key_size,
> +			   default_salt, HKDF_HASHLEN, prk);
>  	if (err)
>  		goto err_free_tfm;
>  
> @@ -118,61 +98,24 @@ int fscrypt_hkdf_expand(const struct fscrypt_hkdf *hkdf, u8 context,
>  			u8 *okm, unsigned int okmlen)
>  {
>  	SHASH_DESC_ON_STACK(desc, hkdf->hmac_tfm);
> -	u8 prefix[9];
> -	unsigned int i;
> +	u8 *full_info;
>  	int err;
> -	const u8 *prev = NULL;
> -	u8 counter = 1;
> -	u8 tmp[HKDF_HASHLEN];
>  
>  	if (WARN_ON_ONCE(okmlen > 255 * HKDF_HASHLEN))
>  		return -EINVAL;

... but this WARN_ON_ONCE is no longer needed since hkdf_expand() does it.

>  
> +	full_info = kzalloc(infolen + 9, GFP_KERNEL);
> +	if (!full_info)
> +		return -ENOMEM;
>  	desc->tfm = hkdf->hmac_tfm;
>  
> -	memcpy(prefix, "fscrypt\0", 8);
> -	prefix[8] = context;
> -
> -	for (i = 0; i < okmlen; i += HKDF_HASHLEN) {
> -
> -		err = crypto_shash_init(desc);
> -		if (err)
> -			goto out;
> -
> -		if (prev) {
> -			err = crypto_shash_update(desc, prev, HKDF_HASHLEN);
> -			if (err)
> -				goto out;
> -		}
> -
> -		err = crypto_shash_update(desc, prefix, sizeof(prefix));
> -		if (err)
> -			goto out;
> -
> -		err = crypto_shash_update(desc, info, infolen);
> -		if (err)
> -			goto out;
> -
> -		BUILD_BUG_ON(sizeof(counter) != 1);
> -		if (okmlen - i < HKDF_HASHLEN) {
> -			err = crypto_shash_finup(desc, &counter, 1, tmp);
> -			if (err)
> -				goto out;
> -			memcpy(&okm[i], tmp, okmlen - i);
> -			memzero_explicit(tmp, sizeof(tmp));
> -		} else {
> -			err = crypto_shash_finup(desc, &counter, 1, &okm[i]);
> -			if (err)
> -				goto out;
> -		}
> -		counter++;
> -		prev = &okm[i];
> -	}
> -	err = 0;
> -out:
> -	if (unlikely(err))
> -		memzero_explicit(okm, okmlen); /* so caller doesn't need to */
> -	shash_desc_zero(desc);
> +	memcpy(full_info, "fscrypt\0", 8);
> +	full_info[8] = context;
> +	memcpy(full_info + 9, info, infolen);
> +
> +	err = hkdf_expand(hkdf->hmac_tfm, full_info, infolen + 8,
> +			  okm, okmlen);
> +	kfree_sensitive(full_info);
>  	return err;

infolen + 9, not infolen + 8.  Otherwise this patch breaks fscrypt.

> diff --git a/include/crypto/hkdf.h b/include/crypto/hkdf.h
> new file mode 100644
> index 000000000000..ee3e7d21a5fe
> --- /dev/null
> +++ b/include/crypto/hkdf.h
> @@ -0,0 +1,34 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * HKDF: HMAC-based Key Derivation Function (HKDF), RFC 5869
> + *
> + * Extracted from fs/crypto/hkdf.c, which has
> + * Copyright 2019 Google LLC
> + */
> +
> +#ifndef _CRYPTO_HKDF_H
> +#define _CRYPTO_HKDF_H
> +
> +#ifdef CONFIG_CRYPTO_HKDF
> +int hkdf_extract(struct crypto_shash *hmac_tfm, const u8 *ikm,
> +		 unsigned int ikmlen, const u8 *salt, unsigned int saltlen,
> +		 u8 *prk);
> +int hkdf_expand(struct crypto_shash *hmac_tfm,
> +		const u8 *info, unsigned int infolen,
> +		u8 *okm, unsigned int okmlen);
> +#else
> +static inline int hkdf_extract(struct crypto_shash *hmac_tfm,
> +			       const u8 *ikm, unsigned int ikmlen,
> +			       const u8 *salt, unsigned int saltlen,
> +			       u8 *prk)
> +{
> +	return -ENOTSUP;
> +}
> +static inline int hkdf_expand(struct crypto_shash *hmac_tfm,
> +			      const u8 *info, unsigned int infolen,
> +			      u8 *okm, unsigned int okmlen)
> +{
> +	return -ENOTSUP;
> +}
> +#endif
> +#endif

This header is missing <crypto/hash.h> which it depends on.

Also the !CONFIG_CRYPTO_HKDF stubs are unnecessary and should not be included.

- Eric

Re: [PATCH 1/9] crypto,fs: Separate out hkdf_extract() and hkdf_expand()

[Hannes Reinecke]

On 8/27/24 19:52, Eric Biggers wrote:
> On Tue, Aug 13, 2024 at 01:15:04PM +0200, Hannes Reinecke wrote:
>> Separate out the HKDF functions into a separate module to
>> to make them available to other callers.
>> And add a testsuite to the module with test vectors
>> from RFC 5869 to ensure the integrity of the algorithm.
[ .. ]
>> +	desc->tfm = hmac_tfm;
>> +
>> +	for (i = 0; i < okmlen; i += hashlen) {
>> +
>> +		err = crypto_shash_init(desc);
>> +		if (err)
>> +			goto out;
>> +
>> +		if (prev) {
>> +			err = crypto_shash_update(desc, prev, hashlen);
>> +			if (err)
>> +				goto out;
>> +		}
>> +
>> +		if (info && infolen) {
> 
> 'if (infolen)' instead of 'if (info && infolen)'.  The latter is a bad practice
> because it can hide bugs.
> 
Do I need to set a 'WARN_ON(!info)' (or something) in this case? Or are 
the '->update' callbacks expected to handle it themselves?

[ .. ]
>> diff --git a/include/crypto/hkdf.h b/include/crypto/hkdf.h
>> new file mode 100644
>> index 000000000000..ee3e7d21a5fe
>> --- /dev/null
>> +++ b/include/crypto/hkdf.h
>> @@ -0,0 +1,34 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +/*
>> + * HKDF: HMAC-based Key Derivation Function (HKDF), RFC 5869
>> + *
>> + * Extracted from fs/crypto/hkdf.c, which has
>> + * Copyright 2019 Google LLC
>> + */
>> +
>> +#ifndef _CRYPTO_HKDF_H
>> +#define _CRYPTO_HKDF_H
>> +
>> +#ifdef CONFIG_CRYPTO_HKDF
>> +int hkdf_extract(struct crypto_shash *hmac_tfm, const u8 *ikm,
>> +		 unsigned int ikmlen, const u8 *salt, unsigned int saltlen,
>> +		 u8 *prk);
>> +int hkdf_expand(struct crypto_shash *hmac_tfm,
>> +		const u8 *info, unsigned int infolen,
>> +		u8 *okm, unsigned int okmlen);
>> +#else
>> +static inline int hkdf_extract(struct crypto_shash *hmac_tfm,
>> +			       const u8 *ikm, unsigned int ikmlen,
>> +			       const u8 *salt, unsigned int saltlen,
>> +			       u8 *prk)
>> +{
>> +	return -ENOTSUP;
>> +}
>> +static inline int hkdf_expand(struct crypto_shash *hmac_tfm,
>> +			      const u8 *info, unsigned int infolen,
>> +			      u8 *okm, unsigned int okmlen)
>> +{
>> +	return -ENOTSUP;
>> +}
>> +#endif
>> +#endif
> 
> This header is missing <crypto/hash.h> which it depends on.
> 
> Also the !CONFIG_CRYPTO_HKDF stubs are unnecessary and should not be included.
> 
But that would mean that every call to '#include <crypto/hkdf.h>' would 
need to be encapsulated by 'CONFIG_CRYPTO_HKDF' (or the file itself is
conditionally compiled on that symbol).
Is that the direction you want to head?

Thanks for the review!

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@suse.de                                +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich

Re: [PATCH 1/9] crypto,fs: Separate out hkdf_extract() and hkdf_expand()

[Eric Biggers]

On Thu, Aug 29, 2024 at 12:39:33PM +0200, Hannes Reinecke wrote:
> On 8/27/24 19:52, Eric Biggers wrote:
> > On Tue, Aug 13, 2024 at 01:15:04PM +0200, Hannes Reinecke wrote:
> > > Separate out the HKDF functions into a separate module to
> > > to make them available to other callers.
> > > And add a testsuite to the module with test vectors
> > > from RFC 5869 to ensure the integrity of the algorithm.
> [ .. ]
> > > +	desc->tfm = hmac_tfm;
> > > +
> > > +	for (i = 0; i < okmlen; i += hashlen) {
> > > +
> > > +		err = crypto_shash_init(desc);
> > > +		if (err)
> > > +			goto out;
> > > +
> > > +		if (prev) {
> > > +			err = crypto_shash_update(desc, prev, hashlen);
> > > +			if (err)
> > > +				goto out;
> > > +		}
> > > +
> > > +		if (info && infolen) {
> > 
> > 'if (infolen)' instead of 'if (info && infolen)'.  The latter is a bad practice
> > because it can hide bugs.
> > 
> Do I need to set a 'WARN_ON(!info)' (or something) in this case? Or are the
> '->update' callbacks expected to handle it themselves?

No, if someone does pass NULL with a nonzero length there will be a crash.  But
the same will happen with another invalid pointer that is not NULL.  It's just a
bad practice to insert random NULL checks like this because it can hide bugs.
Really a call like info=NULL, infolen=10 is ambiguous --- you've made it
silently override infolen to 0 but how do you know the caller wanted that?

> > > +#ifdef CONFIG_CRYPTO_HKDF
> > > +int hkdf_extract(struct crypto_shash *hmac_tfm, const u8 *ikm,
> > > +		 unsigned int ikmlen, const u8 *salt, unsigned int saltlen,
> > > +		 u8 *prk);
> > > +int hkdf_expand(struct crypto_shash *hmac_tfm,
> > > +		const u8 *info, unsigned int infolen,
> > > +		u8 *okm, unsigned int okmlen);
> > > +#else
> > > +static inline int hkdf_extract(struct crypto_shash *hmac_tfm,
> > > +			       const u8 *ikm, unsigned int ikmlen,
> > > +			       const u8 *salt, unsigned int saltlen,
> > > +			       u8 *prk)
> > > +{
> > > +	return -ENOTSUP;
> > > +}
> > > +static inline int hkdf_expand(struct crypto_shash *hmac_tfm,
> > > +			      const u8 *info, unsigned int infolen,
> > > +			      u8 *okm, unsigned int okmlen)
> > > +{
> > > +	return -ENOTSUP;
> > > +}
> > > +#endif
> > > +#endif
> > 
> > This header is missing <crypto/hash.h> which it depends on.
> > 
> > Also the !CONFIG_CRYPTO_HKDF stubs are unnecessary and should not be included.
> > 
> But that would mean that every call to '#include <crypto/hkdf.h>' would need
> to be encapsulated by 'CONFIG_CRYPTO_HKDF' (or the file itself is
> conditionally compiled on that symbol).

No, it doesn't mean that.  As long as the functions are not called when
!CONFIG_CRYPTO_HKDF, it doesn't hurt to have declarations of them.

- Eric

Re: [PATCH 1/9] crypto,fs: Separate out hkdf_extract() and hkdf_expand()

[Hannes Reinecke]

On 8/29/24 23:54, Eric Biggers wrote:
> On Thu, Aug 29, 2024 at 12:39:33PM +0200, Hannes Reinecke wrote:
>> On 8/27/24 19:52, Eric Biggers wrote:
>>> On Tue, Aug 13, 2024 at 01:15:04PM +0200, Hannes Reinecke wrote:
>>>> Separate out the HKDF functions into a separate module to
>>>> to make them available to other callers.
>>>> And add a testsuite to the module with test vectors
>>>> from RFC 5869 to ensure the integrity of the algorithm.
>> [ .. ]
>>>> +	desc->tfm = hmac_tfm;
>>>> +
>>>> +	for (i = 0; i < okmlen; i += hashlen) {
>>>> +
>>>> +		err = crypto_shash_init(desc);
>>>> +		if (err)
>>>> +			goto out;
>>>> +
>>>> +		if (prev) {
>>>> +			err = crypto_shash_update(desc, prev, hashlen);
>>>> +			if (err)
>>>> +				goto out;
>>>> +		}
>>>> +
>>>> +		if (info && infolen) {
>>>
>>> 'if (infolen)' instead of 'if (info && infolen)'.  The latter is a bad practice
>>> because it can hide bugs.
>>>
>> Do I need to set a 'WARN_ON(!info)' (or something) in this case? Or are the
>> '->update' callbacks expected to handle it themselves?
> 
> No, if someone does pass NULL with a nonzero length there will be a crash.  But
> the same will happen with another invalid pointer that is not NULL.  It's just a
> bad practice to insert random NULL checks like this because it can hide bugs.
> Really a call like info=NULL, infolen=10 is ambiguous --- you've made it
> silently override infolen to 0 but how do you know the caller wanted that?
> 
Just wanted to clarify; different maintainers have different styles ...

>>>> +#ifdef CONFIG_CRYPTO_HKDF
>>>> +int hkdf_extract(struct crypto_shash *hmac_tfm, const u8 *ikm,
>>>> +		 unsigned int ikmlen, const u8 *salt, unsigned int saltlen,
>>>> +		 u8 *prk);
>>>> +int hkdf_expand(struct crypto_shash *hmac_tfm,
>>>> +		const u8 *info, unsigned int infolen,
>>>> +		u8 *okm, unsigned int okmlen);
>>>> +#else
>>>> +static inline int hkdf_extract(struct crypto_shash *hmac_tfm,
>>>> +			       const u8 *ikm, unsigned int ikmlen,
>>>> +			       const u8 *salt, unsigned int saltlen,
>>>> +			       u8 *prk)
>>>> +{
>>>> +	return -ENOTSUP;
>>>> +}
>>>> +static inline int hkdf_expand(struct crypto_shash *hmac_tfm,
>>>> +			      const u8 *info, unsigned int infolen,
>>>> +			      u8 *okm, unsigned int okmlen)
>>>> +{
>>>> +	return -ENOTSUP;
>>>> +}
>>>> +#endif
>>>> +#endif
>>>
>>> This header is missing <crypto/hash.h> which it depends on.
>>>
>>> Also the !CONFIG_CRYPTO_HKDF stubs are unnecessary and should not be included.
>>>
>> But that would mean that every call to '#include <crypto/hkdf.h>' would need
>> to be encapsulated by 'CONFIG_CRYPTO_HKDF' (or the file itself is
>> conditionally compiled on that symbol).
> 
> No, it doesn't mean that.  As long as the functions are not called when
> !CONFIG_CRYPTO_HKDF, it doesn't hurt to have declarations of them.
> 
Guess that is correct. Will be reposting the series.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@suse.de                                +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich

[PATCHv10 0/9] nvme: implement secure concatenation

[Hannes Reinecke]

From: Hannes Reinecke <hare@suse.de>

Hi all,

here's my attempt to implement secure concatenation for NVMe-of TCP
as outlined in TP8018.
The original (v5) patchset had been split in two, the first part of
which has already been merged with nvme-6.11, and this is the second part
which actually implements secure concatenation.

Secure concatenation means that a TLS PSK is generated from the key
material negotiated by the DH-HMAC-CHAP protocol, and the TLS PSK
is then used for a subsequent TLS connection.
The difference between the original definition of secure concatenation
and the method outlined in TP8018 is that with TP8018 the connection
is reset after DH-HMAC-CHAP negotiation, and a new connection is setup
with the generated TLS PSK.

To implement that Sagi came up with the idea to directly reset the
admin queue once the DH-CHAP negotiation has completed; that way
it will be transparent to the upper layers and we don't have to
worry about exposing queues which should not be used.

A blktest submission is in
https://github.com/osandov/blktests/pull/147
in case anyone want to run their own tests.

As usual, comments and reviews are welcome.

Patchset can be found at
git.kernel.org:/pub/scm/linux/kernel/git/hare/nvme.git
branch secure-concat.v10

Changes to v9:
- Include reviews from Eric Biggers
- Fixup secure concatenation after reset
- Rebased to nvme-6.12

Changes to v8:
- Include reviews from Eric Biggers
- Make hkdf a proper module
- Add testcases for hkdf

Changes to v7:
- Add patch to display nvme target TLS status in debugfs
- Include reviews from Sagi

Changes to v6:
- Rebase to nvme-6.11

Changes to v5:
- Include reviews from Sagi
- Split patchset in two parts

Changes to v4:
- Rework reset admin queue functionality based on an idea
  from Sagi (thanks!)
    - kbuild robot fixes
      - Fixup dhchap negotiation with non-empty C2 value

Changes to v3:
- Include reviews from Sagi
- Do not start I/O queues after DH-HMAC-CHAP negotiation
- Use bool to indicate TLS has been enabled on a queue
- Add 'tls_keyring' sysfs attribute
- Add 'tls_configured_key' sysfs attribute

Changes to v2:
- Fixup reset after dhchap negotiation
- Disable namespace scanning on I/O queues after
  dhchap negotiation
          - Reworked TLS key handling (again)

Changes to the original submission:
- Sanitize TLS key handling
- Fixup modconfig compilation

Hannes Reinecke (9):
  crypto,fs: Separate out hkdf_extract() and hkdf_expand()
  nvme: add nvme_auth_generate_psk()
  nvme: add nvme_auth_generate_digest()
  nvme: add nvme_auth_derive_tls_psk()
  nvme-keyring: add nvme_tls_psk_refresh()
  nvme-tcp: request secure channel concatenation
  nvme-fabrics: reset admin connection for secure concatenation
  nvmet-tcp: support secure channel concatenation
  nvmet: add tls_concat and tls_key debugfs entries

 crypto/Kconfig                         |   6 +
 crypto/Makefile                        |   1 +
 crypto/hkdf.c                          | 402 +++++++++++++++++++++++++
 drivers/nvme/common/Kconfig            |   1 +
 drivers/nvme/common/auth.c             | 344 +++++++++++++++++++++
 drivers/nvme/common/keyring.c          |  64 ++++
 drivers/nvme/host/auth.c               | 108 ++++++-
 drivers/nvme/host/fabrics.c            |  34 ++-
 drivers/nvme/host/fabrics.h            |   3 +
 drivers/nvme/host/nvme.h               |   2 +
 drivers/nvme/host/sysfs.c              |   4 +-
 drivers/nvme/host/tcp.c                |  56 +++-
 drivers/nvme/target/auth.c             |  72 ++++-
 drivers/nvme/target/debugfs.c          |  27 ++
 drivers/nvme/target/fabrics-cmd-auth.c |  49 ++-
 drivers/nvme/target/fabrics-cmd.c      |  33 +-
 drivers/nvme/target/nvmet.h            |  38 ++-
 drivers/nvme/target/tcp.c              |  23 +-
 fs/crypto/Kconfig                      |   1 +
 fs/crypto/hkdf.c                       |  85 +-----
 include/crypto/hkdf.h                  |  18 ++
 include/linux/nvme-auth.h              |   7 +
 include/linux/nvme-keyring.h           |   9 +
 include/linux/nvme.h                   |   7 +
 24 files changed, 1287 insertions(+), 107 deletions(-)
 create mode 100644 crypto/hkdf.c
 create mode 100644 include/crypto/hkdf.h

-- 
2.35.3

[PATCH 1/9] crypto,fs: Separate out hkdf_extract() and hkdf_expand()

[Hannes Reinecke]

Separate out the HKDF functions into a separate module to
to make them available to other callers.
And add a testsuite to the module with test vectors
from RFC 5869 to ensure the integrity of the algorithm.

Signed-off-by: Hannes Reinecke <hare@kernel.org>
Cc: Eric Biggers <ebiggers@kernel.org>
Cc: linux-crypto@vger.kernel.org
---
 crypto/Kconfig        |   6 +
 crypto/Makefile       |   1 +
 crypto/hkdf.c         | 402 ++++++++++++++++++++++++++++++++++++++++++
 fs/crypto/Kconfig     |   1 +
 fs/crypto/hkdf.c      |  85 ++-------
 include/crypto/hkdf.h |  18 ++
 6 files changed, 443 insertions(+), 70 deletions(-)
 create mode 100644 crypto/hkdf.c
 create mode 100644 include/crypto/hkdf.h

diff --git a/crypto/Kconfig b/crypto/Kconfig
index a779cab668c2..bdcee33085b6 100644
--- a/crypto/Kconfig
+++ b/crypto/Kconfig
@@ -141,6 +141,12 @@ config CRYPTO_ACOMP
 	select CRYPTO_ALGAPI
 	select CRYPTO_ACOMP2
 
+config CRYPTO_HKDF
+	tristate
+	select CRYPTO_SHA1 if !CONFIG_CRYPTO_MANAGER_DISABLE_TESTS
+	select CRYPTO_SHA256 if !CONFIG_CRYPTO_MANAGER_DISABLE_TESTS
+	select CRYPTO_HASH2
+
 config CRYPTO_MANAGER
 	tristate "Cryptographic algorithm manager"
 	select CRYPTO_MANAGER2
diff --git a/crypto/Makefile b/crypto/Makefile
index 4c99e5d376f6..5ec5b994d9ae 100644
--- a/crypto/Makefile
+++ b/crypto/Makefile
@@ -34,6 +34,7 @@ obj-$(CONFIG_CRYPTO_HASH2) += crypto_hash.o
 obj-$(CONFIG_CRYPTO_AKCIPHER2) += akcipher.o
 obj-$(CONFIG_CRYPTO_SIG2) += sig.o
 obj-$(CONFIG_CRYPTO_KPP2) += kpp.o
+obj-$(CONFIG_CRYPTO_HKDF) += hkdf.o
 
 dh_generic-y := dh.o
 dh_generic-y += dh_helper.o
diff --git a/crypto/hkdf.c b/crypto/hkdf.c
new file mode 100644
index 000000000000..26dc84f441ed
--- /dev/null
+++ b/crypto/hkdf.c
@@ -0,0 +1,402 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Implementation of HKDF ("HMAC-based Extract-and-Expand Key Derivation
+ * Function"), aka RFC 5869.  See also the original paper (Krawczyk 2010):
+ * "Cryptographic Extraction and Key Derivation: The HKDF Scheme".
+ *
+ * Copyright 2019 Google LLC
+ */
+
+#include <crypto/internal/hash.h>
+#include <crypto/sha2.h>
+#include <crypto/hkdf.h>
+#include <linux/module.h>
+
+/*
+ * HKDF consists of two steps:
+ *
+ * 1. HKDF-Extract: extract a pseudorandom key from the input keying material
+ *    and optional salt.
+ * 2. HKDF-Expand: expand the pseudorandom key into output keying material of
+ *    any length, parameterized by an application-specific info string.
+ *
+ */
+
+/**
+ * hkdf_extract - HKDF-Extract (RFC 5869 section 2.2)
+ * @hmac_tfm: an HMAC transform using the hash function desired for HKDF.  The
+ *            caller is responsible for setting the @prk afterwards.
+ * @ikm: input keying material
+ * @ikmlen: length of @ikm
+ * @salt: input salt value
+ * @saltlen: length of @salt
+ * @prk: resulting pseudorandom key
+ *
+ * Extracts a pseudorandom key @prk from the input keying material
+ * @ikm with length @ikmlen and salt @salt with length @saltlen.
+ * The length of @prk is given by the digest size of @hmac_tfm.
+ * For an 'unsalted' version of HKDF-Extract @salt must be set
+ * to all zeroes and @saltlen must be set to the length of @prk.
+ *
+ * Returns 0 on success with the pseudorandom key stored in @prk,
+ * or a negative errno value otherwise.
+ */
+int hkdf_extract(struct crypto_shash *hmac_tfm, const u8 *ikm,
+		 unsigned int ikmlen, const u8 *salt, unsigned int saltlen,
+		 u8 *prk)
+{
+	int err;
+
+	err = crypto_shash_setkey(hmac_tfm, salt, saltlen);
+	if (!err)
+		err = crypto_shash_tfm_digest(hmac_tfm, ikm, ikmlen, prk);
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(hkdf_extract);
+
+/**
+ * hkdf_expand - HKDF-Expand (RFC 5869 section 2.3)
+ * @hmac_tfm: hash context keyed with pseudorandom key
+ * @info: application-specific information
+ * @infolen: length of @info
+ * @okm: output keying material
+ * @okmlen: length of @okm
+ *
+ * This expands the pseudorandom key, which was already keyed into @hmac_tfm,
+ * into @okmlen bytes of output keying material parameterized by the
+ * application-specific @info of length @infolen bytes.
+ * This is thread-safe and may be called by multiple threads in parallel.
+ *
+ * Returns 0 on success with output keying material stored in @okm,
+ * or a negative errno value otherwise.
+ */
+int hkdf_expand(struct crypto_shash *hmac_tfm,
+		const u8 *info, unsigned int infolen,
+		u8 *okm, unsigned int okmlen)
+{
+	SHASH_DESC_ON_STACK(desc, hmac_tfm);
+	unsigned int i, hashlen = crypto_shash_digestsize(hmac_tfm);
+	int err;
+	const u8 *prev = NULL;
+	u8 counter = 1;
+	u8 tmp[HASH_MAX_DIGESTSIZE];
+
+	if (WARN_ON(okmlen > 255 * hashlen ||
+		    hashlen > HASH_MAX_DIGESTSIZE))
+		return -EINVAL;
+
+	memzero_explicit(tmp, HASH_MAX_DIGESTSIZE);
+
+	desc->tfm = hmac_tfm;
+
+	for (i = 0; i < okmlen; i += hashlen) {
+		err = crypto_shash_init(desc);
+		if (err)
+			goto out;
+
+		if (prev) {
+			err = crypto_shash_update(desc, prev, hashlen);
+			if (err)
+				goto out;
+		}
+
+		if (infolen) {
+			err = crypto_shash_update(desc, info, infolen);
+			if (err)
+				goto out;
+		}
+
+		BUILD_BUG_ON(sizeof(counter) != 1);
+		if (okmlen - i < hashlen) {
+			err = crypto_shash_finup(desc, &counter, 1, tmp);
+			if (err)
+				goto out;
+			memcpy(&okm[i], tmp, okmlen - i);
+			memzero_explicit(tmp, sizeof(tmp));
+		} else {
+			err = crypto_shash_finup(desc, &counter, 1, &okm[i]);
+			if (err)
+				goto out;
+		}
+		counter++;
+		prev = &okm[i];
+	}
+	err = 0;
+out:
+	if (unlikely(err))
+		memzero_explicit(okm, okmlen); /* so caller doesn't need to */
+	shash_desc_zero(desc);
+	memzero_explicit(tmp, HASH_MAX_DIGESTSIZE);
+	return err;
+}
+EXPORT_SYMBOL_GPL(hkdf_expand);
+
+struct hkdf_testvec {
+	const char *test;
+	const u8 *ikm;
+	const u8 *salt;
+	const u8 *info;
+	const u8 *prk;
+	const u8 *okm;
+	u16 ikm_size;
+	u16 salt_size;
+	u16 info_size;
+	u16 prk_size;
+	u16 okm_size;
+};
+
+/*
+ * HKDF test vectors from RFC5869
+ */
+static const struct hkdf_testvec hkdf_sha256_tv[] = {
+	{
+		.test = "basic hdkf test",
+		.ikm  = "\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b"
+			"\x0b\x0b\x0b\x0b\x0b\x0b",
+		.ikm_size = 22,
+		.salt = "\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c",
+		.salt_size = 13,
+		.info = "\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9",
+		.info_size = 10,
+		.prk = "\x07\x77\x09\x36\x2c\x2e\x32\xdf\x0d\xdc\x3f\x0d\xc4\x7b\xba\x63"
+			"\x90\xb6\xc7\x3b\xb5\x0f\x9c\x31\x22\xec\x84\x4a\xd7\xc2\xb3\xe5",
+		.prk_size = 32,
+		.okm  = "\x3c\xb2\x5f\x25\xfa\xac\xd5\x7a\x90\x43\x4f\x64\xd0\x36\x2f\x2a"
+			"\x2d\x2d\x0a\x90\xcf\x1a\x5a\x4c\x5d\xb0\x2d\x56\xec\xc4\xc5\xbf"
+			"\x34\x00\x72\x08\xd5\xb8\x87\x18\x58\x65",
+		.okm_size = 42,
+	}, {
+		.test = "hkdf test with long input",
+		.ikm  = "\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f"
+			"\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f"
+			"\x20\x21\x22\x23\x24\x25\x26\x27\x28\x29\x2a\x2b\x2c\x2d\x2e\x2f"
+			"\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x3a\x3b\x3c\x3d\x3e\x3f"
+			"\x40\x41\x42\x43\x44\x45\x46\x47\x48\x49\x4a\x4b\x4c\x4d\x4e\x4f",
+		.ikm_size = 80,
+		.salt = "\x60\x61\x62\x63\x64\x65\x66\x67\x68\x69\x6a\x6b\x6c\x6d\x6e\x6f"
+			"\x70\x71\x72\x73\x74\x75\x76\x77,\x78\x79\x7a\x7b\x7c\x7d\x7e\x7f"
+			"\x80\x81\x82\x83\x84\x85\x86\x87\x88\x89\x8a\x8b\x8c\x8d\x8e\x8f"
+			"\x90\x91\x92\x93\x94\x95\x96\x97\x98\x99\x9a\x9b\x9c\x9d\x9e\x9f"
+			"\xa0\xa1\xa2\xa3\xa4\xa5\xa6\xa7\xa8\xa9\xaa\xab\xac\xad\xae\xaf",
+		.salt_size = 80,
+		.info = "\xb0\xb1\xb2\xb3\xb4\xb5\xb6\xb7\xb8\xb9\xba\xbb\xbc\xbd\xbe\xbf"
+			"\xc0\xc1\xc2\xc3\xc4\xc5\xc6\xc7\xc8\xc9\xca\xcb\xcc\xcd\xce\xcf"
+			"\xd0\xd1\xd2\xd3\xd4\xd5\xd6\xd7\xd8\xd9\xda\xdb\xdc\xdd\xde\xdf"
+			"\xe0\xe1\xe2\xe3\xe4\xe5\xe6\xe7\xe8\xe9\xea\xeb\xec\xed\xee\xef"
+			"\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9\xfa\xfb\xfc\xfd\xfe\xff",
+		.info_size = 80,
+		.prk = "\x06\xa6\xb8\x8c\x58\x53\x36\x1a\x06\x10\x4c\x9c\xeb\x35\xb4\x5c"
+			"\xef\x76\x00\x14\x90\x46\x71\x01\x4a\x19\x3f\x40\xc1\x5f\xc2\x44",
+		.prk_size = 32,
+		.okm = "\xb1\x1e\x39\x8d\xc8\x03\x27\xa1\xc8\xe7\xf7\x8c\x59\x6a\x49\x34"
+			"\x4f\x01\x2e\xda\x2d\x4e\xfa\xd8\xa0\x50\xcc\x4c\x19\xaf\xa9\x7c"
+			"\x59\x04\x5a\x99\xca\xc7\x82\x72\x71\xcb\x41\xc6\x5e\x59\x0e\x09"
+			"\xda\x32\x75\x60\x0c\x2f\x09\xb8\x36\x77\x93\xa9\xac\xa3\xdb\x71"
+			"\xcc\x30\xc5\x81\x79\xec\x3e\x87\xc1\x4c\x01\xd5\xc1\xf3\x43\x4f"
+			"\x1d\x87",
+		.okm_size = 82,
+	}, {
+		.test = "hkdf test with zero salt and info",
+		.ikm  = "\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b"
+			"\x0b\x0b\x0b\x0b\x0b\x0b",
+		.ikm_size = 22,
+		.salt = NULL,
+		.salt_size = 0,
+		.info = NULL,
+		.info_size = 0,
+		.prk = "\0x19\xef\x24\xa3\x2c\x71\x7b\x16\x7f\x33\xa9\x1d\x6f\x64\x8b\xdf"
+			"\x96\x59\x67\x76\xaf\xdb\x63\x77\xac\x43\x4c\x1c\x29\x3c\xcb\x04",
+		.prk_size = 32,
+		.okm = "\x8d\xa4\xe7\x75\xa5\x63\xc1\x8f\x71\x5f\x80\x2a\x06\x3c\x5a\x31"
+			"\xb8\xa1\x1f\x5c\x5e\xe1\x87\x9e\xc3\x45\x4e\x5f\x3c\x73\x8d\x2d"
+			"\x9d\x20\x13\x95\xfa\xa4\xb6\x1a\x96\xc8",
+		.okm_size = 42,
+	}
+};
+
+static const struct hkdf_testvec hkdf_sha1_tv[] = {
+	{
+		.test = "basic hkdf test",
+		.ikm  = "\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b",
+		.ikm_size = 11,
+		.salt = "\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c",
+		.salt_size = 13,
+		.info = "\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9",
+		.info_size = 10,
+		.prk  = "\x9b\x6c\x18\xc4\x32\xa7\xbf\x8f\x0e\x71\xc8\xeb\x88\xf4\xb3\x0b"
+			"\xaa\x2b\xa2\x43",
+		.prk_size = 20,
+		.okm  = "\x08\x5a\x01\xea\x1b\x10\xf3\x69\x33\x06\x8b\x56\xef\xa5\xad\x81"
+			"\xa4\xf1\x4b\x82\x2f\x5b\x09\x15\x68\xa9\xcd\xd4\xf1\x55\xfd\xa2"
+			"\xc2\x2e\x42\x24\x78\xd3\x05\xf3\xf8\x96",
+		.okm_size = 42,
+	}, {
+		.test = "hkdf test with long input",
+		.ikm = "\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f"
+			"\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f"
+			"\x20\x21\x22\x23\x24\x25\x26\x27\x28\x29\x2a\x2b\x2c\x2d\x2e\x2f"
+			"\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x3a\x3b\x3c\x3d\x3e\x3f"
+			"\x40\x41\x42\x43\x44\x45\x46\x47\x48\x49\x4a\x4b\x4c\x4d\x4e\x4f",
+		.ikm_size = 80,
+		.salt = "\x60\x61\x62\x63\x64\x65\x66\x67\x68\x69\x6a\x6b\x6c\x6d\x6e\x6f"
+			"\x70\x71\x72\x73\x74\x75\x76\x77\x78\x79\x7a\x7b\x7c\x7d\x7e\x7f"
+			"\x80\x81\x82\x83\x84\x85\x86\x87\x88\x89\x8a\x8b\x8c\x8d\x8e\x8f"
+			"\x90\x91\x92\x93\x94\x95\x96\x97\x98\x99\x9a\x9b\x9c\x9d\x9e\x9f"
+			"\xa0\xa1\xa2\xa3\xa4\xa5\xa6\xa7\xa8\xa9\xaa\xab\xac\xad\xae\xaf",
+		.salt_size = 80,
+		.info = "\xb0\xb1\xb2\xb3\xb4\xb5\xb6\xb7\xb8\xb9\xba\xbb\xbc\xbd\xbe\xbf"
+			"\xc0\xc1\xc2\xc3\xc4\xc5\xc6\xc7\xc8\xc9\xca\xcb\xcc\xcd\xce\xcf"
+			"\xd0\xd1\xd2\xd3\xd4\xd5\xd6\xd7\xd8\xd9\xda\xdb\xdc\xdd\xde\xdf"
+			"\xe0\xe1\xe2\xe3\xe4\xe5\xe6\xe7\xe8\xe9\xea\xeb\xec\xed\xee\xef"
+			"\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9\xfa\xfb\xfc\xfd\xfe\xff",
+		.info_size = 80,
+		.prk  = "\x8a\xda\xe0\x9a\x2a\x30\x70\x59\x47\x8d\x30\x9b\x26\xc4\x11\x5a"
+			"\x22\x4c\xfa\xf6",
+		.prk_size = 20,
+		.okm = "\x0b\xd7\x70\xa7\x4d\x11\x60\xf7\xc9\xf1\x2c\xd5\x91\x2a\x06\xeb"
+			"\xff\x6a\xdc\xae\x89\x9d\x92\x19\x1f\xe4\x30\x56\x73\xba\x2f\xfe"
+			"\x8f\xa3\xf1\xa4\xe5\xad\x79\xf3\xf3\x34\xb3\xb2\x02\xb2\x17\x3c"
+			"\x48\x6e\xa3\x7c\xe3\xd3\x97\xed\x03\x4c\x7f\x9d\xfe\xb1\x5c\x5e"
+			"\x92\x73\x36\xd0\x44\x1f\x4c\x43\x00\xe2\xcf\xf0\xd0\x90\x0b\x52"
+			"\xd3\xb4",
+		.okm_size = 82,
+	}, {
+		.test = "hkdf test with zero salt and info",
+		.ikm = "\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b"
+			"\x0b\x0b\x0b\x0b\x0b\x0b",
+		.ikm_size = 22,
+		.salt = NULL,
+		.salt_size = 0,
+		.info = NULL,
+		.info_size = 0,
+		.prk = "\xda\x8c\x8a\x73\xc7\xfa\x77\x28\x8e\xc6\xf5\xe7\xc2\x97\x78\x6a"
+			"\xa0\xd3\x2d\x01",
+		.prk_size = 20,
+		.okm = "\x0a\xc1\xaf\x70\x02\xb3\xd7\x61\xd1\xe5\x52\x98\xda\x9d\x05\x06"
+			"\xb9\xae\x52\x05\x72\x20\xa3\x06\xe0\x7b\x6b\x87\xe8\xdf\x21\xd0"
+			"\xea\x00\x03\x3d\xe0\x39\x84\xd3\x49\x18",
+		.okm_size = 42,
+	}, {
+		.test = "unsalted hkdf test with zero info",
+		.ikm = "\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c"
+			"\x0c\x0c\x0c\x0c\x0c\x0c",
+		.ikm_size = 22,
+		.salt = "\0x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"
+			"\x00\x00\x00\x00",
+		.salt_size = 20,
+		.info = NULL,
+		.info_size = 0,
+		.prk = "\x2a\xdc\xca\xda\x18\x77\x9e\x7c\x20\x77\xad\x2e\xb1\x9d\x3f\x3e"
+			"\x73\x13\x85\xdd",
+		.prk_size = 20,
+		.okm = "\x2c\x91\x11\x72\x04\xd7\x45\xf3\x50\x0d\x63\x6a\x62\xf6\x4f\x0a"
+			"\xb3\xba\xe5\x48\xaa\x53\xd4\x23\xb0\xd1\xf2\x7e\xbb\xa6\xf5\xe5"
+			"\x67\x3a\x08\x1d\x70\xcc\xe7\xac\xfc\x48",
+		.okm_size = 42,
+	}
+};
+
+static int hkdf_test(const char *shash, const struct hkdf_testvec *tv)
+{	struct crypto_shash *tfm = NULL;
+	u8 *prk = NULL, *okm = NULL;
+	unsigned int prk_size;
+	const char *driver;
+	int err;
+
+	tfm = crypto_alloc_shash(shash, 0, 0);
+	if (IS_ERR(tfm)) {
+		pr_err("%s(%s): failed to allocate transform: %ld\n",
+		       tv->test, shash, PTR_ERR(tfm));
+		return PTR_ERR(tfm);
+	}
+	driver = crypto_shash_driver_name(tfm);
+
+	prk_size = crypto_shash_digestsize(tfm);
+	prk = kzalloc(prk_size, GFP_KERNEL);
+	if (!prk) {
+		err = -ENOMEM;
+		goto out_free;
+	}
+
+	if (tv->prk_size != prk_size) {
+		pr_err("%s(%s): prk size mismatch (vec %u, digest %u\n",
+		       tv->test, driver, tv->prk_size, prk_size);
+		err = -EINVAL;
+		goto out_free;
+	}
+
+	err = hkdf_extract(tfm, tv->ikm, tv->ikm_size,
+			   tv->salt, tv->salt_size, prk);
+	if (err) {
+		pr_err("%s(%s): hkdf_extract failed with %d\n",
+		       tv->test, driver, err);
+		goto out_free;
+	}
+
+	if (memcmp(prk, tv->prk, tv->prk_size)) {
+		pr_err("%s(%s): hkdf_extract prk mismatch\n",
+		       tv->test, driver);
+		err = -EINVAL;
+		goto out_free;
+	}
+
+	okm = kzalloc(tv->okm_size, GFP_KERNEL);
+	if (!okm) {
+		err = -ENOMEM;
+		goto out_free;
+	}
+
+	err = crypto_shash_setkey(tfm, tv->prk, tv->prk_size);
+	if (err) {
+		pr_err("%s(%s): failed to set prk, error %d\n",
+		       tv->test, driver, err);
+		goto out_free;
+	}
+
+	err = hkdf_expand(tfm, tv->info, tv->info_size,
+			  okm, tv->okm_size);
+	if (err) {
+		pr_err("%s(%s): hkdf_expand() failed with %d\n",
+		       tv->test, driver, err);
+	} else if (memcmp(okm, tv->okm, tv->okm_size)) {
+		pr_err("%s(%s): hkdf_expand() okm mismatch\n",
+		       tv->test, driver);
+		print_hex_dump(KERN_ERR, "okm: ", DUMP_PREFIX_NONE, 16, 1, okm, tv->okm_size, false);
+		err = -EINVAL;
+	}
+out_free:
+	kfree(okm);
+	kfree(prk);
+	crypto_free_shash(tfm);
+	return err;
+}
+
+static int __init crypto_hkdf_module_init(void)
+{
+	int ret = 0, i;
+
+	if (IS_ENABLED(CONFIG_CRYPTO_MANAGER_DISABLE_TESTS))
+		return 0;
+
+	for (i = 0; i < ARRAY_SIZE(hkdf_sha256_tv); i++) {
+		ret = hkdf_test("hmac(sha256)", &hkdf_sha256_tv[i]);
+		if (ret)
+			return ret;
+	}
+	for (i = 0; i < ARRAY_SIZE(hkdf_sha1_tv); i++) {
+		ret = hkdf_test("hmac(sha1)", &hkdf_sha1_tv[i]);
+		if (ret)
+			return ret;
+	}
+	return 0;
+}
+
+static void __exit crypto_hkdf_module_exit(void) {}
+
+module_init(crypto_hkdf_module_init);
+module_exit(crypto_hkdf_module_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("HMAC-based Key Derivation Function (HKDF)");
+MODULE_ALIAS_CRYPTO("hkdf");
diff --git a/fs/crypto/Kconfig b/fs/crypto/Kconfig
index 5aff5934baa1..0ea56f588a4a 100644
--- a/fs/crypto/Kconfig
+++ b/fs/crypto/Kconfig
@@ -3,6 +3,7 @@ config FS_ENCRYPTION
 	bool "FS Encryption (Per-file encryption)"
 	select CRYPTO
 	select CRYPTO_HASH
+	select CRYPTO_HKDF
 	select CRYPTO_SKCIPHER
 	select CRYPTO_LIB_SHA256
 	select KEYS
diff --git a/fs/crypto/hkdf.c b/fs/crypto/hkdf.c
index 5a384dad2c72..855a0f4b7318 100644
--- a/fs/crypto/hkdf.c
+++ b/fs/crypto/hkdf.c
@@ -1,9 +1,5 @@
 // SPDX-License-Identifier: GPL-2.0
 /*
- * Implementation of HKDF ("HMAC-based Extract-and-Expand Key Derivation
- * Function"), aka RFC 5869.  See also the original paper (Krawczyk 2010):
- * "Cryptographic Extraction and Key Derivation: The HKDF Scheme".
- *
  * This is used to derive keys from the fscrypt master keys.
  *
  * Copyright 2019 Google LLC
@@ -11,6 +7,7 @@
 
 #include <crypto/hash.h>
 #include <crypto/sha2.h>
+#include <crypto/hkdf.h>
 
 #include "fscrypt_private.h"
 
@@ -44,20 +41,6 @@
  * there's no way to persist a random salt per master key from kernel mode.
  */
 
-/* HKDF-Extract (RFC 5869 section 2.2), unsalted */
-static int hkdf_extract(struct crypto_shash *hmac_tfm, const u8 *ikm,
-			unsigned int ikmlen, u8 prk[HKDF_HASHLEN])
-{
-	static const u8 default_salt[HKDF_HASHLEN];
-	int err;
-
-	err = crypto_shash_setkey(hmac_tfm, default_salt, HKDF_HASHLEN);
-	if (err)
-		return err;
-
-	return crypto_shash_tfm_digest(hmac_tfm, ikm, ikmlen, prk);
-}
-
 /*
  * Compute HKDF-Extract using the given master key as the input keying material,
  * and prepare an HMAC transform object keyed by the resulting pseudorandom key.
@@ -69,6 +52,7 @@ int fscrypt_init_hkdf(struct fscrypt_hkdf *hkdf, const u8 *master_key,
 		      unsigned int master_key_size)
 {
 	struct crypto_shash *hmac_tfm;
+	static const u8 default_salt[HKDF_HASHLEN];
 	u8 prk[HKDF_HASHLEN];
 	int err;
 
@@ -84,7 +68,8 @@ int fscrypt_init_hkdf(struct fscrypt_hkdf *hkdf, const u8 *master_key,
 		goto err_free_tfm;
 	}
 
-	err = hkdf_extract(hmac_tfm, master_key, master_key_size, prk);
+	err = hkdf_extract(hmac_tfm, master_key, master_key_size,
+			   default_salt, HKDF_HASHLEN, prk);
 	if (err)
 		goto err_free_tfm;
 
@@ -118,61 +103,21 @@ int fscrypt_hkdf_expand(const struct fscrypt_hkdf *hkdf, u8 context,
 			u8 *okm, unsigned int okmlen)
 {
 	SHASH_DESC_ON_STACK(desc, hkdf->hmac_tfm);
-	u8 prefix[9];
-	unsigned int i;
+	u8 *full_info;
 	int err;
-	const u8 *prev = NULL;
-	u8 counter = 1;
-	u8 tmp[HKDF_HASHLEN];
-
-	if (WARN_ON_ONCE(okmlen > 255 * HKDF_HASHLEN))
-		return -EINVAL;
 
+	full_info = kzalloc(infolen + 9, GFP_KERNEL);
+	if (!full_info)
+		return -ENOMEM;
 	desc->tfm = hkdf->hmac_tfm;
 
-	memcpy(prefix, "fscrypt\0", 8);
-	prefix[8] = context;
-
-	for (i = 0; i < okmlen; i += HKDF_HASHLEN) {
-
-		err = crypto_shash_init(desc);
-		if (err)
-			goto out;
-
-		if (prev) {
-			err = crypto_shash_update(desc, prev, HKDF_HASHLEN);
-			if (err)
-				goto out;
-		}
-
-		err = crypto_shash_update(desc, prefix, sizeof(prefix));
-		if (err)
-			goto out;
-
-		err = crypto_shash_update(desc, info, infolen);
-		if (err)
-			goto out;
-
-		BUILD_BUG_ON(sizeof(counter) != 1);
-		if (okmlen - i < HKDF_HASHLEN) {
-			err = crypto_shash_finup(desc, &counter, 1, tmp);
-			if (err)
-				goto out;
-			memcpy(&okm[i], tmp, okmlen - i);
-			memzero_explicit(tmp, sizeof(tmp));
-		} else {
-			err = crypto_shash_finup(desc, &counter, 1, &okm[i]);
-			if (err)
-				goto out;
-		}
-		counter++;
-		prev = &okm[i];
-	}
-	err = 0;
-out:
-	if (unlikely(err))
-		memzero_explicit(okm, okmlen); /* so caller doesn't need to */
-	shash_desc_zero(desc);
+	memcpy(full_info, "fscrypt\0", 8);
+	full_info[8] = context;
+	memcpy(full_info + 9, info, infolen);
+
+	err = hkdf_expand(hkdf->hmac_tfm, full_info, infolen + 9,
+			  okm, okmlen);
+	kfree_sensitive(full_info);
 	return err;
 }
 
diff --git a/include/crypto/hkdf.h b/include/crypto/hkdf.h
new file mode 100644
index 000000000000..c1f23a32a6b6
--- /dev/null
+++ b/include/crypto/hkdf.h
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * HKDF: HMAC-based Key Derivation Function (HKDF), RFC 5869
+ *
+ * Extracted from fs/crypto/hkdf.c, which has
+ * Copyright 2019 Google LLC
+ */
+
+#ifndef _CRYPTO_HKDF_H
+#define _CRYPTO_HKDF_H
+
+int hkdf_extract(struct crypto_shash *hmac_tfm, const u8 *ikm,
+		 unsigned int ikmlen, const u8 *salt, unsigned int saltlen,
+		 u8 *prk);
+int hkdf_expand(struct crypto_shash *hmac_tfm,
+		const u8 *info, unsigned int infolen,
+		u8 *okm, unsigned int okmlen);
+#endif
-- 
2.35.3

[PATCH 2/9] nvme: add nvme_auth_generate_psk()

[Hannes Reinecke]

Add a function to generate a NVMe PSK from the shared credentials
negotiated by DH-HMAC-CHAP.

Signed-off-by: Hannes Reinecke <hare@kernel.org>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
---
 drivers/nvme/common/auth.c | 98 ++++++++++++++++++++++++++++++++++++++
 include/linux/nvme-auth.h  |  3 ++
 2 files changed, 101 insertions(+)

diff --git a/drivers/nvme/common/auth.c b/drivers/nvme/common/auth.c
index a3455f1d67fa..8448bd195ff1 100644
--- a/drivers/nvme/common/auth.c
+++ b/drivers/nvme/common/auth.c
@@ -11,6 +11,7 @@
 #include <asm/unaligned.h>
 #include <crypto/hash.h>
 #include <crypto/dh.h>
+#include <crypto/hkdf.h>
 #include <linux/nvme.h>
 #include <linux/nvme-auth.h>
 
@@ -471,5 +472,102 @@ int nvme_auth_generate_key(u8 *secret, struct nvme_dhchap_key **ret_key)
 }
 EXPORT_SYMBOL_GPL(nvme_auth_generate_key);
 
+/**
+ * nvme_auth_generate_psk - Generate a PSK for TLS
+ * @hmac_id: Hash function identifier
+ * @skey: Session key
+ * @skey_len: Length of @skey
+ * @c1: Value of challenge C1
+ * @c2: Value of challenge C2
+ * @hash_len: Hash length of the hash algorithm
+ * @ret_psk: Pointer too the resulting generated PSK
+ * @ret_len: length of @ret_psk
+ *
+ * Generate a PSK for TLS as specified in NVMe base specification, section 8.13.5.9:
+ *    Generated PSK for TLS
+ *
+ * The generated PSK for TLS shall be computed applying the HMAC function using the
+ * hash function H( ) selected by the HashID parameter in the DH-HMAC-CHAP_Challenge
+ * message with the session key KS as key to the concatenation of the two challenges
+ * C1 and C2 (i.e., generated PSK = HMAC(KS, C1 || C2)).
+ *
+ * Returns 0 on success with a valid generated PSK pointer in @ret_psk and the length
+ * of @ret_psk in @ret_len, or a negative error number otherwise.
+ */
+int nvme_auth_generate_psk(u8 hmac_id, u8 *skey, size_t skey_len,
+		u8 *c1, u8 *c2, size_t hash_len, u8 **ret_psk,size_t *ret_len)
+{
+	struct crypto_shash *tfm;
+	struct shash_desc *shash;
+	u8 *psk;
+	const char *hmac_name;
+	int ret, psk_len;
+
+	if (!c1 || !c2) {
+		pr_warn("%s: invalid parameter\n", __func__);
+		return -EINVAL;
+	}
+
+	hmac_name = nvme_auth_hmac_name(hmac_id);
+	if (!hmac_name) {
+		pr_warn("%s: invalid hash algoritm %d\n",
+			__func__, hmac_id);
+		return -EINVAL;
+	}
+
+	tfm = crypto_alloc_shash(hmac_name, 0, 0);
+	if (IS_ERR(tfm))
+		return PTR_ERR(tfm);
+
+	psk_len = crypto_shash_digestsize(tfm);
+	psk = kzalloc(psk_len, GFP_KERNEL);
+	if (!psk) {
+		ret = -ENOMEM;
+		goto out_free_tfm;
+	}
+
+	shash = kmalloc(sizeof(struct shash_desc) +
+			crypto_shash_descsize(tfm),
+			GFP_KERNEL);
+	if (!shash) {
+		ret = -ENOMEM;
+		goto out_free_psk;
+	}
+
+	shash->tfm = tfm;
+	ret = crypto_shash_setkey(tfm, skey, skey_len);
+	if (ret)
+		goto out_free_shash;
+
+	ret = crypto_shash_init(shash);
+	if (ret)
+		goto out_free_shash;
+
+	ret = crypto_shash_update(shash, c1, hash_len);
+	if (ret)
+		goto out_free_shash;
+
+	ret = crypto_shash_update(shash, c2, hash_len);
+	if (ret)
+		goto out_free_shash;
+
+	ret = crypto_shash_final(shash, psk);
+	if (!ret) {
+		*ret_psk = psk;
+		*ret_len = psk_len;
+	}
+
+out_free_shash:
+	kfree_sensitive(shash);
+out_free_psk:
+	if (ret)
+		kfree_sensitive(psk);
+out_free_tfm:
+	crypto_free_shash(tfm);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(nvme_auth_generate_psk);
+
 MODULE_DESCRIPTION("NVMe Authentication framework");
 MODULE_LICENSE("GPL v2");
diff --git a/include/linux/nvme-auth.h b/include/linux/nvme-auth.h
index c1d0bc5d9624..b13884b04dfd 100644
--- a/include/linux/nvme-auth.h
+++ b/include/linux/nvme-auth.h
@@ -40,5 +40,8 @@ int nvme_auth_gen_pubkey(struct crypto_kpp *dh_tfm,
 int nvme_auth_gen_shared_secret(struct crypto_kpp *dh_tfm,
 				u8 *ctrl_key, size_t ctrl_key_len,
 				u8 *sess_key, size_t sess_key_len);
+int nvme_auth_generate_psk(u8 hmac_id, u8 *skey, size_t skey_len,
+			   u8 *c1, u8 *c2, size_t hash_len,
+			   u8 **ret_psk, size_t *ret_len);
 
 #endif /* _NVME_AUTH_H */
-- 
2.35.3

[PATCH 3/9] nvme: add nvme_auth_generate_digest()

[Hannes Reinecke]

Add a function to calculate the PSK digest as specified in TP8018.

Signed-off-by: Hannes Reinecke <hare@kernel.org>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
---
 drivers/nvme/common/auth.c | 137 +++++++++++++++++++++++++++++++++++++
 include/linux/nvme-auth.h  |   2 +
 2 files changed, 139 insertions(+)

diff --git a/drivers/nvme/common/auth.c b/drivers/nvme/common/auth.c
index 8448bd195ff1..d04d966fd19c 100644
--- a/drivers/nvme/common/auth.c
+++ b/drivers/nvme/common/auth.c
@@ -569,5 +569,142 @@ int nvme_auth_generate_psk(u8 hmac_id, u8 *skey, size_t skey_len,
 }
 EXPORT_SYMBOL_GPL(nvme_auth_generate_psk);
 
+/**
+ * nvme_auth_generate_digest - Generate TLS PSK digest
+ * @hmac_id: Hash function identifier
+ * @psk: Generated input PSK
+ * @psk_len: Lenght of @psk
+ * @subsysnqn: NQN of the subsystem
+ * @hostnqn: NQN of the host
+ * @ret_digest: Pointer to the returned digest
+ *
+ * Generate a TLS PSK digest as specified in TP8018 Section 3.6.1.3:
+ *   TLS PSK and PSK identity Derivation
+ *
+ * The PSK digest shall be computed by encoding in Base64 (refer to RFC 4648)
+ * the result of the application of the HMAC function using the hash function
+ * specified in item 4 above (ie the hash function of the cipher suite associated
+ * with the PSK identity) with the PSK as HMAC key to the concatenation of:
+ * - the NQN of the host (i.e., NQNh) not including the null terminator;
+ * - a space character;
+ * - the NQN of the NVM subsystem (i.e., NQNc) not including the null terminator;
+ * - a space character; and
+ * - the seventeen ASCII characters "NVMe-over-Fabrics"
+ * (i.e., <PSK digest> = Base64(HMAC(PSK, NQNh || " " || NQNc || " " || "NVMe-over-Fabrics"))).
+ * The length of the PSK digest depends on the hash function used to compute
+ * it as follows:
+ * - If the SHA-256 hash function is used, the resulting PSK digest is 44 characters long; or
+ * - If the SHA-384 hash function is used, the resulting PSK digest is 64 characters long.
+ *
+ * Returns 0 on success with a valid digest pointer in @ret_digest, or a negative
+ * error number on failure.
+ */
+int nvme_auth_generate_digest(u8 hmac_id, u8 *psk, size_t psk_len,
+		char *subsysnqn, char *hostnqn, u8 **ret_digest)
+{
+	struct crypto_shash *tfm;
+	struct shash_desc *shash;
+	u8 *digest, *hmac;
+	const char *hmac_name;
+	size_t digest_len, hmac_len;
+	int ret;
+
+	if (WARN_ON(!subsysnqn || !hostnqn))
+		return -EINVAL;
+
+	hmac_name = nvme_auth_hmac_name(hmac_id);
+	if (!hmac_name) {
+		pr_warn("%s: invalid hash algoritm %d\n",
+			__func__, hmac_id);
+		return -EINVAL;
+	}
+
+	switch (nvme_auth_hmac_hash_len(hmac_id)) {
+	case 32:
+		hmac_len = 44;
+		break;
+	case 48:
+		hmac_len = 64;
+		break;
+	default:
+		pr_warn("%s: invalid hash algorithm '%s'\n",
+			__func__, hmac_name);
+		return -EINVAL;
+	}
+
+	hmac = kzalloc(hmac_len + 1, GFP_KERNEL);
+	if (!hmac)
+		return -ENOMEM;
+
+	tfm = crypto_alloc_shash(hmac_name, 0, 0);
+	if (IS_ERR(tfm)) {
+		ret = PTR_ERR(tfm);
+		goto out_free_hmac;
+	}
+
+	digest_len = crypto_shash_digestsize(tfm);
+	digest = kzalloc(digest_len, GFP_KERNEL);
+	if (!digest) {
+		ret = -ENOMEM;
+		goto out_free_tfm;
+	}
+
+	shash = kmalloc(sizeof(struct shash_desc) +
+			crypto_shash_descsize(tfm),
+			GFP_KERNEL);
+	if (!shash) {
+		ret = -ENOMEM;
+		goto out_free_digest;
+	}
+
+	shash->tfm = tfm;
+	ret = crypto_shash_setkey(tfm, psk, psk_len);
+	if (ret)
+		goto out_free_shash;
+
+	ret = crypto_shash_init(shash);
+	if (ret)
+		goto out_free_shash;
+
+	ret = crypto_shash_update(shash, hostnqn, strlen(hostnqn));
+	if (ret)
+		goto out_free_shash;
+
+	ret = crypto_shash_update(shash, " ", 1);
+	if (ret)
+		goto out_free_shash;
+
+	ret = crypto_shash_update(shash, subsysnqn, strlen(subsysnqn));
+	if (ret)
+		goto out_free_shash;
+
+	ret = crypto_shash_update(shash, " NVMe-over-Fabrics", 18);
+	if (ret)
+		goto out_free_shash;
+
+	ret = crypto_shash_final(shash, digest);
+	if (ret)
+		goto out_free_shash;
+
+	ret = base64_encode(digest, digest_len, hmac);
+	if (ret < hmac_len)
+		ret = -ENOKEY;
+	*ret_digest = hmac;
+	ret = 0;
+
+out_free_shash:
+	kfree_sensitive(shash);
+out_free_digest:
+	kfree_sensitive(digest);
+out_free_tfm:
+	crypto_free_shash(tfm);
+out_free_hmac:
+	if (ret)
+		kfree_sensitive(hmac);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(nvme_auth_generate_digest);
+
 MODULE_DESCRIPTION("NVMe Authentication framework");
 MODULE_LICENSE("GPL v2");
diff --git a/include/linux/nvme-auth.h b/include/linux/nvme-auth.h
index b13884b04dfd..998f06bf10fd 100644
--- a/include/linux/nvme-auth.h
+++ b/include/linux/nvme-auth.h
@@ -43,5 +43,7 @@ int nvme_auth_gen_shared_secret(struct crypto_kpp *dh_tfm,
 int nvme_auth_generate_psk(u8 hmac_id, u8 *skey, size_t skey_len,
 			   u8 *c1, u8 *c2, size_t hash_len,
 			   u8 **ret_psk, size_t *ret_len);
+int nvme_auth_generate_digest(u8 hmac_id, u8 *psk, size_t psk_len,
+		char *subsysnqn, char *hostnqn, u8 **ret_digest);
 
 #endif /* _NVME_AUTH_H */
-- 
2.35.3

[PATCH 4/9] nvme: add nvme_auth_derive_tls_psk()

[Hannes Reinecke]

Add a function to derive the TLS PSK as specified TP8018.

Signed-off-by: Hannes Reinecke <hare@kernel.org>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
---
 drivers/nvme/common/Kconfig |   1 +
 drivers/nvme/common/auth.c  | 109 ++++++++++++++++++++++++++++++++++++
 include/linux/nvme-auth.h   |   2 +
 3 files changed, 112 insertions(+)

diff --git a/drivers/nvme/common/Kconfig b/drivers/nvme/common/Kconfig
index 244432e0b73d..da963e4f3f1f 100644
--- a/drivers/nvme/common/Kconfig
+++ b/drivers/nvme/common/Kconfig
@@ -12,3 +12,4 @@ config NVME_AUTH
 	select CRYPTO_SHA512
 	select CRYPTO_DH
 	select CRYPTO_DH_RFC7919_GROUPS
+	select CRYPTO_HKDF
diff --git a/drivers/nvme/common/auth.c b/drivers/nvme/common/auth.c
index d04d966fd19c..b0ee24f90683 100644
--- a/drivers/nvme/common/auth.c
+++ b/drivers/nvme/common/auth.c
@@ -15,6 +15,8 @@
 #include <linux/nvme.h>
 #include <linux/nvme-auth.h>
 
+#define HKDF_MAX_HASHLEN 64
+
 static u32 nvme_dhchap_seqnum;
 static DEFINE_MUTEX(nvme_dhchap_mutex);
 
@@ -706,5 +708,112 @@ int nvme_auth_generate_digest(u8 hmac_id, u8 *psk, size_t psk_len,
 }
 EXPORT_SYMBOL_GPL(nvme_auth_generate_digest);
 
+/**
+ * nvme_auth_derive_tls_psk - Derive TLS PSK
+ * @hmac_id: Hash function identifier
+ * @psk: generated input PSK
+ * @psk_len: size of @psk
+ * @psk_digest: TLS PSK digest
+ * @ret_psk: Pointer to the resulting TLS PSK
+ *
+ * Derive a TLS PSK as specified in TP8018 Section 3.6.1.3:
+ *   TLS PSK and PSK identity Derivation
+ *
+ * The TLS PSK shall be derived as follows from an input PSK
+ * (i.e., either a retained PSK or a generated PSK) and a PSK
+ * identity using the HKDF-Extract and HKDF-Expand-Label operations
+ * (refer to RFC 5869 and RFC 8446) where the hash function is the
+ * one specified by the hash specifier of the PSK identity:
+ * 1. PRK = HKDF-Extract(0, Input PSK); and
+ * 2. TLS PSK = HKDF-Expand-Label(PRK, "nvme-tls-psk", PskIdentityContext, L),
+ * where PskIdentityContext is the hash identifier indicated in
+ * the PSK identity concatenated to a space character and to the
+ * Base64 PSK digest (i.e., "<hash> <PSK digest>") and L is the
+ * output size in bytes of the hash function (i.e., 32 for SHA-256
+ * and 48 for SHA-384).
+ *
+ * Returns 0 on success with a valid psk pointer in @ret_psk or a negative
+ * error number otherwise.
+ */
+int nvme_auth_derive_tls_psk(int hmac_id, u8 *psk, size_t psk_len,
+		u8 *psk_digest, u8 **ret_psk)
+{
+	struct crypto_shash *hmac_tfm;
+	const char *hmac_name;
+	const char *psk_prefix = "tls13 nvme-tls-psk";
+	static const char default_salt[HKDF_MAX_HASHLEN];
+	size_t info_len, prk_len;
+	char *info;
+	unsigned char *prk, *tls_key;
+	int ret;
+
+	hmac_name = nvme_auth_hmac_name(hmac_id);
+	if (!hmac_name) {
+		pr_warn("%s: invalid hash algoritm %d\n",
+			__func__, hmac_id);
+		return -EINVAL;
+	}
+	if (hmac_id == NVME_AUTH_HASH_SHA512) {
+		pr_warn("%s: unsupported hash algorithm %s\n",
+			__func__, hmac_name);
+		return -EINVAL;
+	}
+
+	hmac_tfm = crypto_alloc_shash(hmac_name, 0, 0);
+	if (IS_ERR(hmac_tfm))
+		return PTR_ERR(hmac_tfm);
+
+	prk_len = crypto_shash_digestsize(hmac_tfm);
+	prk = kzalloc(prk_len, GFP_KERNEL);
+	if (!prk) {
+		ret = -ENOMEM;
+		goto out_free_shash;
+	}
+
+	if (WARN_ON(prk_len > HKDF_MAX_HASHLEN)) {
+		ret = -EINVAL;
+		goto out_free_prk;
+	}
+	ret = hkdf_extract(hmac_tfm, psk, psk_len,
+			   default_salt, prk_len, prk);
+	if (ret)
+		goto out_free_prk;
+
+	ret = crypto_shash_setkey(hmac_tfm, prk, prk_len);
+	if (ret)
+		goto out_free_prk;
+
+	info_len = strlen(psk_digest) + strlen(psk_prefix) + 5;
+	info = kzalloc(info_len, GFP_KERNEL);
+	if (!info)
+		goto out_free_prk;
+
+	put_unaligned_be16(psk_len, info);
+	memcpy(info + 2, psk_prefix, strlen(psk_prefix));
+	sprintf(info + 2 + strlen(psk_prefix), "%02d %s", hmac_id, psk_digest);
+
+	tls_key = kzalloc(psk_len, GFP_KERNEL);
+	if (!tls_key) {
+		ret = -ENOMEM;
+		goto out_free_info;
+	}
+	ret = hkdf_expand(hmac_tfm, info, strlen(info), tls_key, psk_len);
+	if (ret) {
+		kfree(tls_key);
+		goto out_free_info;
+	}
+	*ret_psk = tls_key;
+
+out_free_info:
+	kfree(info);
+out_free_prk:
+	kfree(prk);
+out_free_shash:
+	crypto_free_shash(hmac_tfm);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(nvme_auth_derive_tls_psk);
+
 MODULE_DESCRIPTION("NVMe Authentication framework");
 MODULE_LICENSE("GPL v2");
diff --git a/include/linux/nvme-auth.h b/include/linux/nvme-auth.h
index 998f06bf10fd..60e069a6757f 100644
--- a/include/linux/nvme-auth.h
+++ b/include/linux/nvme-auth.h
@@ -45,5 +45,7 @@ int nvme_auth_generate_psk(u8 hmac_id, u8 *skey, size_t skey_len,
 			   u8 **ret_psk, size_t *ret_len);
 int nvme_auth_generate_digest(u8 hmac_id, u8 *psk, size_t psk_len,
 		char *subsysnqn, char *hostnqn, u8 **ret_digest);
+int nvme_auth_derive_tls_psk(int hmac_id, u8 *psk, size_t psk_len,
+		u8 *psk_digest, u8 **ret_psk);
 
 #endif /* _NVME_AUTH_H */
-- 
2.35.3

[PATCH 5/9] nvme-keyring: add nvme_tls_psk_refresh()

[Hannes Reinecke]

Add a function to refresh a generated PSK in the specified keyring.

Signed-off-by: Hannes Reinecke <hare@kernel.org>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
---
 drivers/nvme/common/keyring.c | 64 +++++++++++++++++++++++++++++++++++
 include/linux/nvme-keyring.h  |  9 +++++
 2 files changed, 73 insertions(+)

diff --git a/drivers/nvme/common/keyring.c b/drivers/nvme/common/keyring.c
index ed5167f942d8..8cb253fcd586 100644
--- a/drivers/nvme/common/keyring.c
+++ b/drivers/nvme/common/keyring.c
@@ -124,6 +124,70 @@ static struct key *nvme_tls_psk_lookup(struct key *keyring,
 	return key_ref_to_ptr(keyref);
 }
 
+/**
+ * nvme_tls_psk_refresh - Refresh TLS PSK
+ * @keyring: Keyring holding the TLS PSK
+ * @hostnqn: Host NQN to use
+ * @subnqn: Subsystem NQN to use
+ * @hmac_id: Hash function identifier
+ * @data: TLS PSK key material
+ * @data_len: Length of @data
+ * @digest: TLS PSK digest
+ *
+ * Refresh a generated version 1 TLS PSK with the identity generated
+ * from @hmac_id, @hostnqn, @subnqn, and @digest in the keyring given
+ * by @keyring.
+ *
+ * Returns the updated key success or an error pointer otherwise.
+ */
+struct key *nvme_tls_psk_refresh(struct key *keyring,
+		const char *hostnqn, const char *subnqn, u8 hmac_id,
+		u8 *data, size_t data_len, const char *digest)
+{
+	key_perm_t keyperm =
+		KEY_POS_SEARCH | KEY_POS_VIEW | KEY_POS_READ |
+		KEY_POS_WRITE | KEY_POS_LINK | KEY_POS_SETATTR |
+		KEY_USR_SEARCH | KEY_USR_VIEW | KEY_USR_READ;
+	char *identity;
+	key_ref_t keyref;
+	key_serial_t keyring_id;
+	struct key *key;
+
+	if (!hostnqn || !subnqn || !data || !data_len)
+		return ERR_PTR(-EINVAL);
+
+	identity = kasprintf(GFP_KERNEL, "NVMe1G%02d %s %s %s",
+		 hmac_id, hostnqn, subnqn, digest);
+	if (!identity)
+		return ERR_PTR(-ENOMEM);
+
+	if (!keyring)
+		keyring = nvme_keyring;
+	keyring_id = key_serial(keyring);
+	pr_debug("keyring %x refresh tls psk '%s'\n",
+		 keyring_id, identity);
+	keyref = key_create_or_update(make_key_ref(keyring, true),
+				"psk", identity, data, data_len,
+				keyperm, KEY_ALLOC_NOT_IN_QUOTA |
+				      KEY_ALLOC_BUILT_IN |
+				      KEY_ALLOC_BYPASS_RESTRICTION);
+	if (IS_ERR(keyref)) {
+		pr_debug("refresh tls psk '%s' failed, error %ld\n",
+			 identity, PTR_ERR(keyref));
+		kfree(identity);
+		return ERR_PTR(-ENOKEY);
+	}
+	kfree(identity);
+	/*
+	 * Set the default timeout to 1 hour
+	 * as suggested in TP8018.
+	 */
+	key = key_ref_to_ptr(keyref);
+	key_set_timeout(key, 3600);
+	return key;
+}
+EXPORT_SYMBOL_GPL(nvme_tls_psk_refresh);
+
 /*
  * NVMe PSK priority list
  *
diff --git a/include/linux/nvme-keyring.h b/include/linux/nvme-keyring.h
index 19d2b256180f..351a02b1bbc3 100644
--- a/include/linux/nvme-keyring.h
+++ b/include/linux/nvme-keyring.h
@@ -8,6 +8,9 @@
 
 #if IS_ENABLED(CONFIG_NVME_KEYRING)
 
+struct key *nvme_tls_psk_refresh(struct key *keyring,
+		const char *hostnqn, const char *subnqn, u8 hmac_id,
+		u8 *data, size_t data_len, const char *digest);
 key_serial_t nvme_tls_psk_default(struct key *keyring,
 		const char *hostnqn, const char *subnqn);
 
@@ -15,6 +18,12 @@ key_serial_t nvme_keyring_id(void);
 struct key *nvme_tls_key_lookup(key_serial_t key_id);
 #else
 
+static struct key *nvme_tls_psk_refresh(struct key *keyring,
+		const char *hostnqn, char *subnqn, u8 hmac_id,
+		u8 *data, size_t data_len, const char *digest)
+{
+	return ERR_PTR(-ENOTSUPP);
+}
 static inline key_serial_t nvme_tls_psk_default(struct key *keyring,
 		const char *hostnqn, const char *subnqn)
 {
-- 
2.35.3

[PATCH 6/9] nvme-tcp: request secure channel concatenation

[Hannes Reinecke]

Add a fabrics option 'concat' to request secure channel concatenation.
When secure channel concatenation is enabled a 'generated PSK' is inserted
into the keyring such that it's available after reset.

Signed-off-by: Hannes Reinecke <hare@kernel.org>
---
 drivers/nvme/host/auth.c    | 108 +++++++++++++++++++++++++++++++++++-
 drivers/nvme/host/fabrics.c |  34 +++++++++++-
 drivers/nvme/host/fabrics.h |   3 +
 drivers/nvme/host/nvme.h    |   2 +
 drivers/nvme/host/sysfs.c   |   4 +-
 drivers/nvme/host/tcp.c     |  47 ++++++++++++++--
 include/linux/nvme.h        |   7 +++
 7 files changed, 191 insertions(+), 14 deletions(-)

diff --git a/drivers/nvme/host/auth.c b/drivers/nvme/host/auth.c
index 371e14f0a203..d2fdaefd236f 100644
--- a/drivers/nvme/host/auth.c
+++ b/drivers/nvme/host/auth.c
@@ -12,6 +12,7 @@
 #include "nvme.h"
 #include "fabrics.h"
 #include <linux/nvme-auth.h>
+#include <linux/nvme-keyring.h>
 
 #define CHAP_BUF_SIZE 4096
 static struct kmem_cache *nvme_chap_buf_cache;
@@ -131,7 +132,12 @@ static int nvme_auth_set_dhchap_negotiate_data(struct nvme_ctrl *ctrl,
 	data->auth_type = NVME_AUTH_COMMON_MESSAGES;
 	data->auth_id = NVME_AUTH_DHCHAP_MESSAGE_NEGOTIATE;
 	data->t_id = cpu_to_le16(chap->transaction);
-	data->sc_c = 0; /* No secure channel concatenation */
+	if (!ctrl->opts->concat || chap->qid != 0)
+		data->sc_c = NVME_AUTH_SECP_NOSC;
+	else if (ctrl->opts->tls_key)
+		data->sc_c = NVME_AUTH_SECP_REPLACETLSPSK;
+	else
+		data->sc_c = NVME_AUTH_SECP_NEWTLSPSK;
 	data->napd = 1;
 	data->auth_protocol[0].dhchap.authid = NVME_AUTH_DHCHAP_AUTH_ID;
 	data->auth_protocol[0].dhchap.halen = 3;
@@ -311,8 +317,9 @@ static int nvme_auth_set_dhchap_reply_data(struct nvme_ctrl *ctrl,
 	data->hl = chap->hash_len;
 	data->dhvlen = cpu_to_le16(chap->host_key_len);
 	memcpy(data->rval, chap->response, chap->hash_len);
-	if (ctrl->ctrl_key) {
+	if (ctrl->ctrl_key)
 		chap->bi_directional = true;
+	if (ctrl->ctrl_key || ctrl->opts->concat) {
 		get_random_bytes(chap->c2, chap->hash_len);
 		data->cvalid = 1;
 		memcpy(data->rval + chap->hash_len, chap->c2,
@@ -322,7 +329,10 @@ static int nvme_auth_set_dhchap_reply_data(struct nvme_ctrl *ctrl,
 	} else {
 		memset(chap->c2, 0, chap->hash_len);
 	}
-	chap->s2 = nvme_auth_get_seqnum();
+	if (ctrl->opts->concat)
+		chap->s2 = 0;
+	else
+		chap->s2 = nvme_auth_get_seqnum();
 	data->seqnum = cpu_to_le32(chap->s2);
 	if (chap->host_key_len) {
 		dev_dbg(ctrl->device, "%s: qid %d host public key %*ph\n",
@@ -677,6 +687,84 @@ static void nvme_auth_free_dhchap(struct nvme_dhchap_queue_context *chap)
 		crypto_free_kpp(chap->dh_tfm);
 }
 
+void nvme_auth_revoke_tls_key(struct nvme_ctrl *ctrl)
+{
+	dev_dbg(ctrl->device, "Wipe generated TLS PSK %08x\n",
+		key_serial(ctrl->opts->tls_key));
+	key_revoke(ctrl->opts->tls_key);
+	key_put(ctrl->opts->tls_key);
+	ctrl->opts->tls_key = NULL;
+}
+EXPORT_SYMBOL_GPL(nvme_auth_revoke_tls_key);
+
+static int nvme_auth_secure_concat(struct nvme_ctrl *ctrl,
+				   struct nvme_dhchap_queue_context *chap)
+{
+	u8 *psk, *digest, *tls_psk;
+	struct key *tls_key;
+	size_t psk_len;
+	int ret = 0;
+
+	if (!chap->sess_key) {
+		dev_warn(ctrl->device,
+			 "%s: qid %d no session key negotiated\n",
+			 __func__, chap->qid);
+		return -ENOKEY;
+	}
+
+	ret = nvme_auth_generate_psk(chap->hash_id, chap->sess_key,
+				     chap->sess_key_len,
+				     chap->c1, chap->c2,
+				     chap->hash_len, &psk, &psk_len);
+	if (ret) {
+		dev_warn(ctrl->device,
+			 "%s: qid %d failed to generate PSK, error %d\n",
+			 __func__, chap->qid, ret);
+		return ret;
+	}
+	dev_dbg(ctrl->device,
+		  "%s: generated psk %*ph\n", __func__, (int)psk_len, psk);
+
+	ret = nvme_auth_generate_digest(chap->hash_id, psk, psk_len,
+					ctrl->opts->subsysnqn,
+					ctrl->opts->host->nqn, &digest);
+	if (ret) {
+		dev_warn(ctrl->device,
+			 "%s: qid %d failed to generate digest, error %d\n",
+			 __func__, chap->qid, ret);
+		goto out_free_psk;
+	};
+	dev_dbg(ctrl->device, "%s: generated digest %s\n",
+		 __func__, digest);
+	ret = nvme_auth_derive_tls_psk(chap->hash_id, psk, psk_len, digest, &tls_psk);
+	if (ret) {
+		dev_warn(ctrl->device,
+			 "%s: qid %d failed to derive TLS psk, error %d\n",
+			 __func__, chap->qid, ret);
+		goto out_free_digest;
+	};
+
+	tls_key = nvme_tls_psk_refresh(ctrl->opts->keyring, ctrl->opts->host->nqn,
+				       ctrl->opts->subsysnqn, chap->hash_id,
+				       tls_psk, psk_len, digest);
+	if (IS_ERR(tls_key)) {
+		ret = PTR_ERR(tls_key);
+		dev_warn(ctrl->device,
+			 "%s: qid %d failed to insert generated key, error %d\n",
+			 __func__, chap->qid, ret);
+		tls_key = NULL;
+		kfree_sensitive(tls_psk);
+	}
+	if (ctrl->opts->tls_key)
+		nvme_auth_revoke_tls_key(ctrl);
+	ctrl->opts->tls_key = tls_key;
+out_free_digest:
+	kfree_sensitive(digest);
+out_free_psk:
+	kfree_sensitive(psk);
+	return ret;
+}
+
 static void nvme_queue_auth_work(struct work_struct *work)
 {
 	struct nvme_dhchap_queue_context *chap =
@@ -833,6 +921,14 @@ static void nvme_queue_auth_work(struct work_struct *work)
 	}
 	if (!ret) {
 		chap->error = 0;
+		/* Secure concatenation can only be enabled on the admin queue */
+		if (!chap->qid && ctrl->opts->concat &&
+		    (ret = nvme_auth_secure_concat(ctrl, chap))) {
+			dev_warn(ctrl->device,
+				 "%s: qid %d failed to enable secure concatenation\n",
+				 __func__, chap->qid);
+			chap->error = ret;
+		}
 		return;
 	}
 
@@ -912,6 +1008,12 @@ static void nvme_ctrl_auth_work(struct work_struct *work)
 			 "qid 0: authentication failed\n");
 		return;
 	}
+	/*
+	 * Only run authentication on the admin queue for
+	 * secure concatenation
+	 */
+	if (ctrl->opts->concat)
+		return;
 
 	for (q = 1; q < ctrl->queue_count; q++) {
 		ret = nvme_auth_negotiate(ctrl, q);
diff --git a/drivers/nvme/host/fabrics.c b/drivers/nvme/host/fabrics.c
index 432efcbf9e2f..93e9041b9657 100644
--- a/drivers/nvme/host/fabrics.c
+++ b/drivers/nvme/host/fabrics.c
@@ -472,8 +472,9 @@ int nvmf_connect_admin_queue(struct nvme_ctrl *ctrl)
 	result = le32_to_cpu(res.u32);
 	ctrl->cntlid = result & 0xFFFF;
 	if (result & (NVME_CONNECT_AUTHREQ_ATR | NVME_CONNECT_AUTHREQ_ASCR)) {
-		/* Secure concatenation is not implemented */
-		if (result & NVME_CONNECT_AUTHREQ_ASCR) {
+		/* Check for secure concatenation */
+		if ((result & NVME_CONNECT_AUTHREQ_ASCR) &&
+		    !ctrl->opts->concat) {
 			dev_warn(ctrl->device,
 				 "qid 0: secure concatenation is not supported\n");
 			ret = -EOPNOTSUPP;
@@ -550,7 +551,7 @@ int nvmf_connect_io_queue(struct nvme_ctrl *ctrl, u16 qid)
 		/* Secure concatenation is not implemented */
 		if (result & NVME_CONNECT_AUTHREQ_ASCR) {
 			dev_warn(ctrl->device,
-				 "qid 0: secure concatenation is not supported\n");
+				 "qid %d: secure concatenation is not supported\n", qid);
 			ret = -EOPNOTSUPP;
 			goto out_free_data;
 		}
@@ -706,6 +707,7 @@ static const match_table_t opt_tokens = {
 #endif
 #ifdef CONFIG_NVME_TCP_TLS
 	{ NVMF_OPT_TLS,			"tls"			},
+	{ NVMF_OPT_CONCAT,		"concat"		},
 #endif
 	{ NVMF_OPT_ERR,			NULL			}
 };
@@ -735,6 +737,7 @@ static int nvmf_parse_options(struct nvmf_ctrl_options *opts,
 	opts->tls = false;
 	opts->tls_key = NULL;
 	opts->keyring = NULL;
+	opts->concat = false;
 
 	options = o = kstrdup(buf, GFP_KERNEL);
 	if (!options)
@@ -1053,6 +1056,14 @@ static int nvmf_parse_options(struct nvmf_ctrl_options *opts,
 			}
 			opts->tls = true;
 			break;
+		case NVMF_OPT_CONCAT:
+			if (!IS_ENABLED(CONFIG_NVME_TCP_TLS)) {
+				pr_err("TLS is not supported\n");
+				ret = -EINVAL;
+				goto out;
+			}
+			opts->concat = true;
+			break;
 		default:
 			pr_warn("unknown parameter or missing value '%s' in ctrl creation request\n",
 				p);
@@ -1079,6 +1090,23 @@ static int nvmf_parse_options(struct nvmf_ctrl_options *opts,
 			pr_warn("failfast tmo (%d) larger than controller loss tmo (%d)\n",
 				opts->fast_io_fail_tmo, ctrl_loss_tmo);
 	}
+	if (opts->concat) {
+		if (opts->tls) {
+			pr_err("Secure concatenation over TLS is not supported\n");
+			ret = -EINVAL;
+			goto out;
+		}
+		if (opts->tls_key) {
+			pr_err("Cannot specify a TLS key for secure concatenation\n");
+			ret = -EINVAL;
+			goto out;
+		}
+		if (!opts->dhchap_secret) {
+			pr_err("Need to enable DH-CHAP for secure concatenation\n");
+			ret = -EINVAL;
+			goto out;
+		}
+	}
 
 	opts->host = nvmf_host_add(hostnqn, &hostid);
 	if (IS_ERR(opts->host)) {
diff --git a/drivers/nvme/host/fabrics.h b/drivers/nvme/host/fabrics.h
index 21d75dc4a3a0..9cf5b020adba 100644
--- a/drivers/nvme/host/fabrics.h
+++ b/drivers/nvme/host/fabrics.h
@@ -66,6 +66,7 @@ enum {
 	NVMF_OPT_TLS		= 1 << 25,
 	NVMF_OPT_KEYRING	= 1 << 26,
 	NVMF_OPT_TLS_KEY	= 1 << 27,
+	NVMF_OPT_CONCAT		= 1 << 28,
 };
 
 /**
@@ -101,6 +102,7 @@ enum {
  * @keyring:    Keyring to use for key lookups
  * @tls_key:    TLS key for encrypted connections (TCP)
  * @tls:        Start TLS encrypted connections (TCP)
+ * @concat:     Enabled Secure channel concatenation (TCP)
  * @disable_sqflow: disable controller sq flow control
  * @hdr_digest: generate/verify header digest (TCP)
  * @data_digest: generate/verify data digest (TCP)
@@ -130,6 +132,7 @@ struct nvmf_ctrl_options {
 	struct key		*keyring;
 	struct key		*tls_key;
 	bool			tls;
+	bool			concat;
 	bool			disable_sqflow;
 	bool			hdr_digest;
 	bool			data_digest;
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 313a4f978a2c..4c735b88b434 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -1132,6 +1132,7 @@ void nvme_auth_stop(struct nvme_ctrl *ctrl);
 int nvme_auth_negotiate(struct nvme_ctrl *ctrl, int qid);
 int nvme_auth_wait(struct nvme_ctrl *ctrl, int qid);
 void nvme_auth_free(struct nvme_ctrl *ctrl);
+void nvme_auth_revoke_tls_key(struct nvme_ctrl *ctrl);
 #else
 static inline int nvme_auth_init_ctrl(struct nvme_ctrl *ctrl)
 {
@@ -1154,6 +1155,7 @@ static inline int nvme_auth_wait(struct nvme_ctrl *ctrl, int qid)
 	return -EPROTONOSUPPORT;
 }
 static inline void nvme_auth_free(struct nvme_ctrl *ctrl) {};
+static void nvme_auth_revoke_tls_key(struct nvme_ctrl *ctrl) {};
 #endif
 
 u32 nvme_command_effects(struct nvme_ctrl *ctrl, struct nvme_ns *ns,
diff --git a/drivers/nvme/host/sysfs.c b/drivers/nvme/host/sysfs.c
index b68a9e5f1ea3..efb35eef1915 100644
--- a/drivers/nvme/host/sysfs.c
+++ b/drivers/nvme/host/sysfs.c
@@ -780,10 +780,10 @@ static umode_t nvme_tls_attrs_are_visible(struct kobject *kobj,
 		return 0;
 
 	if (a == &dev_attr_tls_key.attr &&
-	    !ctrl->opts->tls)
+	    !ctrl->opts->tls && !ctrl->opts->concat)
 		return 0;
 	if (a == &dev_attr_tls_configured_key.attr &&
-	    !ctrl->opts->tls_key)
+	    (!ctrl->opts->tls_key || ctrl->opts->concat))
 		return 0;
 	if (a == &dev_attr_tls_keyring.attr &&
 	    !ctrl->opts->keyring)
diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
index 3e416af2659f..b8a3461b617c 100644
--- a/drivers/nvme/host/tcp.c
+++ b/drivers/nvme/host/tcp.c
@@ -233,7 +233,7 @@ static inline bool nvme_tcp_tls_configured(struct nvme_ctrl *ctrl)
 	if (!IS_ENABLED(CONFIG_NVME_TCP_TLS))
 		return 0;
 
-	return ctrl->opts->tls;
+	return ctrl->opts->tls || ctrl->opts->concat;
 }
 
 static inline struct blk_mq_tags *nvme_tcp_tagset(struct nvme_tcp_queue *queue)
@@ -1948,7 +1948,7 @@ static int nvme_tcp_alloc_admin_queue(struct nvme_ctrl *ctrl)
 	if (nvme_tcp_tls_configured(ctrl)) {
 		if (ctrl->opts->tls_key)
 			pskid = key_serial(ctrl->opts->tls_key);
-		else {
+		else if (ctrl->opts->tls) {
 			pskid = nvme_tls_psk_default(ctrl->opts->keyring,
 						      ctrl->opts->host->nqn,
 						      ctrl->opts->subsysnqn);
@@ -1978,9 +1978,25 @@ static int __nvme_tcp_alloc_io_queues(struct nvme_ctrl *ctrl)
 {
 	int i, ret;
 
-	if (nvme_tcp_tls_configured(ctrl) && !ctrl->tls_pskid) {
-		dev_err(ctrl->device, "no PSK negotiated\n");
-		return -ENOKEY;
+	if (nvme_tcp_tls_configured(ctrl)) {
+		if (ctrl->opts->concat) {
+			/*
+			 * The generated PSK is stored in the
+			 * fabric options
+			 */
+			if (!ctrl->opts->tls_key) {
+				dev_err(ctrl->device, "no PSK generated\n");
+				return -ENOKEY;
+			}
+			if (ctrl->tls_pskid &&
+			    ctrl->tls_pskid != key_serial(ctrl->opts->tls_key)) {
+				dev_err(ctrl->device, "Stale PSK id %08x\n", ctrl->tls_pskid);
+				ctrl->tls_pskid = 0;
+			}
+		} else if (!ctrl->tls_pskid) {
+			dev_err(ctrl->device, "no PSK negotiated\n");
+			return -ENOKEY;
+		}
 	}
 
 	for (i = 1; i < ctrl->queue_count; i++) {
@@ -2211,6 +2227,21 @@ static void nvme_tcp_reconnect_or_remove(struct nvme_ctrl *ctrl,
 	}
 }
 
+/*
+ * The TLS key needs to be revoked when:
+ * - concatenation is enabled and
+ *   -> This is a generated key and only valid for this session
+ * - the generated key is present in ctrl->tls_key and
+ *   -> authentication has completed and the key has been generated
+ * - tls has been enabled
+ *   -> otherwise we are about to reset the admin queue after authentication
+ *      to enable TLS with the generated key
+ */
+static bool nvme_tcp_key_revoke_needed(struct nvme_ctrl *ctrl)
+{
+	return ctrl->opts->concat && ctrl->opts->tls_key && ctrl->tls_pskid;
+}
+
 static int nvme_tcp_setup_ctrl(struct nvme_ctrl *ctrl, bool new)
 {
 	struct nvmf_ctrl_options *opts = ctrl->opts;
@@ -2314,6 +2345,8 @@ static void nvme_tcp_error_recovery_work(struct work_struct *work)
 				struct nvme_tcp_ctrl, err_work);
 	struct nvme_ctrl *ctrl = &tcp_ctrl->ctrl;
 
+	if (nvme_tcp_key_revoke_needed(ctrl))
+		nvme_auth_revoke_tls_key(ctrl);
 	nvme_stop_keep_alive(ctrl);
 	flush_work(&ctrl->async_event_work);
 	nvme_tcp_teardown_io_queues(ctrl, false);
@@ -2354,6 +2387,8 @@ static void nvme_reset_ctrl_work(struct work_struct *work)
 		container_of(work, struct nvme_ctrl, reset_work);
 	int ret;
 
+	if (nvme_tcp_key_revoke_needed(ctrl))
+		nvme_auth_revoke_tls_key(ctrl);
 	nvme_stop_ctrl(ctrl);
 	nvme_tcp_teardown_ctrl(ctrl, false);
 
@@ -2849,7 +2884,7 @@ static struct nvmf_transport_ops nvme_tcp_transport = {
 			  NVMF_OPT_HDR_DIGEST | NVMF_OPT_DATA_DIGEST |
 			  NVMF_OPT_NR_WRITE_QUEUES | NVMF_OPT_NR_POLL_QUEUES |
 			  NVMF_OPT_TOS | NVMF_OPT_HOST_IFACE | NVMF_OPT_TLS |
-			  NVMF_OPT_KEYRING | NVMF_OPT_TLS_KEY,
+			  NVMF_OPT_KEYRING | NVMF_OPT_TLS_KEY | NVMF_OPT_CONCAT,
 	.create_ctrl	= nvme_tcp_create_ctrl,
 };
 
diff --git a/include/linux/nvme.h b/include/linux/nvme.h
index b58d9405d65e..fe8858d19813 100644
--- a/include/linux/nvme.h
+++ b/include/linux/nvme.h
@@ -1678,6 +1678,13 @@ enum {
 	NVME_AUTH_DHGROUP_INVALID	= 0xff,
 };
 
+enum {
+	NVME_AUTH_SECP_NOSC		= 0x00,
+	NVME_AUTH_SECP_SC		= 0x01,
+	NVME_AUTH_SECP_NEWTLSPSK	= 0x02,
+	NVME_AUTH_SECP_REPLACETLSPSK	= 0x03,
+};
+
 union nvmf_auth_protocol {
 	struct nvmf_auth_dhchap_protocol_descriptor dhchap;
 };
-- 
2.35.3

[PATCH 7/9] nvme-fabrics: reset admin connection for secure concatenation

[Hannes Reinecke]

When secure concatenation is requested the connection needs to be
reset to enable TLS encryption on the new cnnection.
That implies that the original connection used for the DH-CHAP
negotiation really shouldn't be used, and we should reset as soon
as the DH-CHAP negotiation has succeeded on the admin queue.

Based on an idea from Sagi.

Signed-off-by: Hannes Reinecke <hare@kernel.org>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
---
 drivers/nvme/host/tcp.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
index b8a3461b617c..04f0ac57855e 100644
--- a/drivers/nvme/host/tcp.c
+++ b/drivers/nvme/host/tcp.c
@@ -2251,6 +2251,15 @@ static int nvme_tcp_setup_ctrl(struct nvme_ctrl *ctrl, bool new)
 	if (ret)
 		return ret;
 
+	if (ctrl->opts && ctrl->opts->concat && !ctrl->tls_pskid) {
+		dev_dbg(ctrl->device, "restart admin queue for secure concatenation\n");
+		nvme_stop_keep_alive(ctrl);
+		nvme_tcp_teardown_admin_queue(ctrl, false);
+		ret = nvme_tcp_configure_admin_queue(ctrl, false);
+		if (ret)
+			return ret;
+	}
+
 	if (ctrl->icdoff) {
 		ret = -EOPNOTSUPP;
 		dev_err(ctrl->device, "icdoff is not supported!\n");
-- 
2.35.3

[PATCH 8/9] nvmet-tcp: support secure channel concatenation

[Hannes Reinecke]

Evaluate the SC_C flag during DH-CHAP-HMAC negotiation and insert
the generated PSK once negotiation has finished.

Signed-off-by: Hannes Reinecke <hare@kernel.org>
---
 drivers/nvme/target/auth.c             | 72 +++++++++++++++++++++++++-
 drivers/nvme/target/fabrics-cmd-auth.c | 49 +++++++++++++++---
 drivers/nvme/target/fabrics-cmd.c      | 33 +++++++++---
 drivers/nvme/target/nvmet.h            | 38 +++++++++++---
 drivers/nvme/target/tcp.c              | 23 +++++++-
 5 files changed, 192 insertions(+), 23 deletions(-)

diff --git a/drivers/nvme/target/auth.c b/drivers/nvme/target/auth.c
index 7897d02c681d..7470ac020db6 100644
--- a/drivers/nvme/target/auth.c
+++ b/drivers/nvme/target/auth.c
@@ -15,6 +15,7 @@
 #include <linux/ctype.h>
 #include <linux/random.h>
 #include <linux/nvme-auth.h>
+#include <linux/nvme-keyring.h>
 #include <asm/unaligned.h>
 
 #include "nvmet.h"
@@ -138,7 +139,7 @@ int nvmet_setup_dhgroup(struct nvmet_ctrl *ctrl, u8 dhgroup_id)
 	return ret;
 }
 
-u8 nvmet_setup_auth(struct nvmet_ctrl *ctrl)
+u8 nvmet_setup_auth(struct nvmet_ctrl *ctrl, struct nvmet_req *req)
 {
 	int ret = 0;
 	struct nvmet_host_link *p;
@@ -164,6 +165,11 @@ u8 nvmet_setup_auth(struct nvmet_ctrl *ctrl)
 		goto out_unlock;
 	}
 
+	if (nvmet_queue_tls_keyid(req->sq)) {
+		pr_debug("host %s tls enabled\n", ctrl->hostnqn);
+		goto out_unlock;
+	}
+
 	ret = nvmet_setup_dhgroup(ctrl, host->dhchap_dhgroup_id);
 	if (ret < 0) {
 		pr_warn("Failed to setup DH group");
@@ -232,6 +238,9 @@ u8 nvmet_setup_auth(struct nvmet_ctrl *ctrl)
 void nvmet_auth_sq_free(struct nvmet_sq *sq)
 {
 	cancel_delayed_work(&sq->auth_expired_work);
+#ifdef CONFIG_NVME_TARGET_TCP_TLS
+	sq->tls_key = 0;
+#endif
 	kfree(sq->dhchap_c1);
 	sq->dhchap_c1 = NULL;
 	kfree(sq->dhchap_c2);
@@ -260,6 +269,12 @@ void nvmet_destroy_auth(struct nvmet_ctrl *ctrl)
 		nvme_auth_free_key(ctrl->ctrl_key);
 		ctrl->ctrl_key = NULL;
 	}
+#ifdef CONFIG_NVME_TARGET_TCP_TLS
+	if (ctrl->tls_key) {
+		key_put(ctrl->tls_key);
+		ctrl->tls_key = NULL;
+	}
+#endif
 }
 
 bool nvmet_check_auth_status(struct nvmet_req *req)
@@ -541,3 +556,58 @@ int nvmet_auth_ctrl_sesskey(struct nvmet_req *req,
 
 	return ret;
 }
+
+void nvmet_auth_insert_psk(struct nvmet_sq *sq)
+{
+	int hash_len = nvme_auth_hmac_hash_len(sq->ctrl->shash_id);
+	u8 *psk, *digest, *tls_psk;
+	size_t psk_len;
+	int ret;
+#ifdef CONFIG_NVME_TARGET_TCP_TLS
+	struct key *tls_key = NULL;
+#endif
+
+	ret = nvme_auth_generate_psk(sq->ctrl->shash_id,
+				     sq->dhchap_skey,
+				     sq->dhchap_skey_len,
+				     sq->dhchap_c1, sq->dhchap_c2,
+				     hash_len, &psk, &psk_len);
+	if (ret) {
+		pr_warn("%s: ctrl %d qid %d failed to generate PSK, error %d\n",
+			__func__, sq->ctrl->cntlid, sq->qid, ret);
+		return;
+	}
+	ret = nvme_auth_generate_digest(sq->ctrl->shash_id, psk, psk_len,
+					sq->ctrl->subsysnqn,
+					sq->ctrl->hostnqn, &digest);
+	if (ret) {
+		pr_warn("%s: ctrl %d qid %d failed to generate digest, error %d\n",
+			__func__, sq->ctrl->cntlid, sq->qid, ret);
+		goto out_free_psk;
+	}
+	ret = nvme_auth_derive_tls_psk(sq->ctrl->shash_id, psk, psk_len,
+				       digest, &tls_psk);
+	if (ret) {
+		pr_warn("%s: ctrl %d qid %d failed to derive TLS PSK, error %d\n",
+			__func__, sq->ctrl->cntlid, sq->qid, ret);
+		goto out_free_digest;
+	}
+#ifdef CONFIG_NVME_TARGET_TCP_TLS
+	tls_key = nvme_tls_psk_refresh(NULL, sq->ctrl->hostnqn, sq->ctrl->subsysnqn,
+				       sq->ctrl->shash_id, tls_psk, psk_len, digest);
+	if (IS_ERR(tls_key)) {
+		pr_warn("%s: ctrl %d qid %d failed to refresh key, error %ld\n",
+			__func__, sq->ctrl->cntlid, sq->qid, PTR_ERR(tls_key));
+		tls_key = NULL;
+		kfree_sensitive(tls_psk);
+	}
+	if (sq->ctrl->tls_key)
+		key_put(sq->ctrl->tls_key);
+	sq->ctrl->tls_key = tls_key;
+#endif
+
+out_free_digest:
+	kfree_sensitive(digest);
+out_free_psk:
+	kfree_sensitive(psk);
+}
diff --git a/drivers/nvme/target/fabrics-cmd-auth.c b/drivers/nvme/target/fabrics-cmd-auth.c
index 3f2857c17d95..cf4b38c0e7bd 100644
--- a/drivers/nvme/target/fabrics-cmd-auth.c
+++ b/drivers/nvme/target/fabrics-cmd-auth.c
@@ -43,8 +43,26 @@ static u8 nvmet_auth_negotiate(struct nvmet_req *req, void *d)
 		 data->auth_protocol[0].dhchap.halen,
 		 data->auth_protocol[0].dhchap.dhlen);
 	req->sq->dhchap_tid = le16_to_cpu(data->t_id);
-	if (data->sc_c)
-		return NVME_AUTH_DHCHAP_FAILURE_CONCAT_MISMATCH;
+	if (data->sc_c != NVME_AUTH_SECP_NOSC) {
+		if (!IS_ENABLED(CONFIG_NVME_TARGET_TCP_TLS))
+			return NVME_AUTH_DHCHAP_FAILURE_CONCAT_MISMATCH;
+		/* Secure concatenation can only be enabled on the admin queue */
+		if (req->sq->qid)
+			return NVME_AUTH_DHCHAP_FAILURE_CONCAT_MISMATCH;
+		switch (data->sc_c) {
+		case NVME_AUTH_SECP_NEWTLSPSK:
+			if (nvmet_queue_tls_keyid(req->sq))
+				return NVME_AUTH_DHCHAP_FAILURE_CONCAT_MISMATCH;
+			break;
+		case NVME_AUTH_SECP_REPLACETLSPSK:
+			if (!nvmet_queue_tls_keyid(req->sq))
+				return NVME_AUTH_DHCHAP_FAILURE_CONCAT_MISMATCH;
+			break;
+		default:
+			return NVME_AUTH_DHCHAP_FAILURE_CONCAT_MISMATCH;
+		}
+		ctrl->concat = true;
+	}
 
 	if (data->napd != 1)
 		return NVME_AUTH_DHCHAP_FAILURE_HASH_UNUSABLE;
@@ -103,6 +121,13 @@ static u8 nvmet_auth_negotiate(struct nvmet_req *req, void *d)
 			 nvme_auth_dhgroup_name(fallback_dhgid));
 		ctrl->dh_gid = fallback_dhgid;
 	}
+	if (ctrl->dh_gid == NVME_AUTH_DHGROUP_NULL &&
+	    ctrl->concat) {
+		pr_debug("%s: ctrl %d qid %d: NULL DH group invalid "
+			 "for secure channel concatenation\n", __func__,
+			 ctrl->cntlid, req->sq->qid);
+		return NVME_AUTH_DHCHAP_FAILURE_CONCAT_MISMATCH;
+	}
 	pr_debug("%s: ctrl %d qid %d: selected DH group %s (%d)\n",
 		 __func__, ctrl->cntlid, req->sq->qid,
 		 nvme_auth_dhgroup_name(ctrl->dh_gid), ctrl->dh_gid);
@@ -154,6 +179,12 @@ static u8 nvmet_auth_reply(struct nvmet_req *req, void *d)
 	kfree(response);
 	pr_debug("%s: ctrl %d qid %d host authenticated\n",
 		 __func__, ctrl->cntlid, req->sq->qid);
+	if (!data->cvalid && ctrl->concat) {
+		pr_debug("%s: ctrl %d qid %d invalid challenge\n",
+			 __func__, ctrl->cntlid, req->sq->qid);
+		return NVME_AUTH_DHCHAP_FAILURE_FAILED;
+	}
+	req->sq->dhchap_s2 = le32_to_cpu(data->seqnum);
 	if (data->cvalid) {
 		req->sq->dhchap_c2 = kmemdup(data->rval + data->hl, data->hl,
 					     GFP_KERNEL);
@@ -163,11 +194,15 @@ static u8 nvmet_auth_reply(struct nvmet_req *req, void *d)
 		pr_debug("%s: ctrl %d qid %d challenge %*ph\n",
 			 __func__, ctrl->cntlid, req->sq->qid, data->hl,
 			 req->sq->dhchap_c2);
-	} else {
+	}
+	if (req->sq->dhchap_s2 == 0) {
+		if (ctrl->concat)
+			nvmet_auth_insert_psk(req->sq);
 		req->sq->authenticated = true;
+		kfree(req->sq->dhchap_c2);
 		req->sq->dhchap_c2 = NULL;
-	}
-	req->sq->dhchap_s2 = le32_to_cpu(data->seqnum);
+	} else if (!data->cvalid)
+		req->sq->authenticated = true;
 
 	return 0;
 }
@@ -241,7 +276,7 @@ void nvmet_execute_auth_send(struct nvmet_req *req)
 			pr_debug("%s: ctrl %d qid %d reset negotiation\n",
 				 __func__, ctrl->cntlid, req->sq->qid);
 			if (!req->sq->qid) {
-				dhchap_status = nvmet_setup_auth(ctrl);
+				dhchap_status = nvmet_setup_auth(ctrl, req);
 				if (dhchap_status) {
 					pr_err("ctrl %d qid 0 failed to setup re-authentication\n",
 					       ctrl->cntlid);
@@ -298,6 +333,8 @@ void nvmet_execute_auth_send(struct nvmet_req *req)
 		}
 		goto done_kfree;
 	case NVME_AUTH_DHCHAP_MESSAGE_SUCCESS2:
+		if (ctrl->concat)
+			nvmet_auth_insert_psk(req->sq);
 		req->sq->authenticated = true;
 		pr_debug("%s: ctrl %d qid %d ctrl authenticated\n",
 			 __func__, ctrl->cntlid, req->sq->qid);
diff --git a/drivers/nvme/target/fabrics-cmd.c b/drivers/nvme/target/fabrics-cmd.c
index c4b2eddd5666..9a1256deee51 100644
--- a/drivers/nvme/target/fabrics-cmd.c
+++ b/drivers/nvme/target/fabrics-cmd.c
@@ -199,10 +199,26 @@ static u16 nvmet_install_queue(struct nvmet_ctrl *ctrl, struct nvmet_req *req)
 	return ret;
 }
 
-static u32 nvmet_connect_result(struct nvmet_ctrl *ctrl)
+static u32 nvmet_connect_result(struct nvmet_ctrl *ctrl, struct nvmet_req *req)
 {
+	bool needs_auth = nvmet_has_auth(ctrl, req);
+	key_serial_t keyid = nvmet_queue_tls_keyid(req->sq);
+
+	/* Do not authenticate I/O queues for secure concatenation */
+	if (ctrl->concat && req->sq->qid)
+		needs_auth = false;
+
+	if (keyid)
+		pr_debug("%s: ctrl %d qid %d should %sauthenticate, tls psk %08x\n",
+			 __func__, ctrl->cntlid, req->sq->qid,
+			 needs_auth ? "" : "not ", keyid);
+	else
+		pr_debug("%s: ctrl %d qid %d should %sauthenticate%s\n",
+			 __func__, ctrl->cntlid, req->sq->qid,
+			 needs_auth ? "" : "not ",
+			 ctrl->concat ? ", secure concatenation" : "");
 	return (u32)ctrl->cntlid |
-		(nvmet_has_auth(ctrl) ? NVME_CONNECT_AUTHREQ_ATR : 0);
+		(needs_auth ? NVME_CONNECT_AUTHREQ_ATR : 0);
 }
 
 static void nvmet_execute_admin_connect(struct nvmet_req *req)
@@ -251,7 +267,7 @@ static void nvmet_execute_admin_connect(struct nvmet_req *req)
 
 	uuid_copy(&ctrl->hostid, &d->hostid);
 
-	dhchap_status = nvmet_setup_auth(ctrl);
+	dhchap_status = nvmet_setup_auth(ctrl, req);
 	if (dhchap_status) {
 		pr_err("Failed to setup authentication, dhchap status %u\n",
 		       dhchap_status);
@@ -269,12 +285,13 @@ static void nvmet_execute_admin_connect(struct nvmet_req *req)
 		goto out;
 	}
 
-	pr_info("creating %s controller %d for subsystem %s for NQN %s%s%s.\n",
+	pr_info("creating %s controller %d for subsystem %s for NQN %s%s%s%s.\n",
 		nvmet_is_disc_subsys(ctrl->subsys) ? "discovery" : "nvm",
 		ctrl->cntlid, ctrl->subsys->subsysnqn, ctrl->hostnqn,
-		ctrl->pi_support ? " T10-PI is enabled" : "",
-		nvmet_has_auth(ctrl) ? " with DH-HMAC-CHAP" : "");
-	req->cqe->result.u32 = cpu_to_le32(nvmet_connect_result(ctrl));
+		ctrl->pi_support ? ", T10-PI" : "",
+		nvmet_has_auth(ctrl, req) ? ", DH-HMAC-CHAP" : "",
+		nvmet_queue_tls_keyid(req->sq) ? ", TLS" : "");
+	req->cqe->result.u32 = cpu_to_le32(nvmet_connect_result(ctrl, req));
 out:
 	kfree(d);
 complete:
@@ -330,7 +347,7 @@ static void nvmet_execute_io_connect(struct nvmet_req *req)
 		goto out_ctrl_put;
 
 	pr_debug("adding queue %d to ctrl %d.\n", qid, ctrl->cntlid);
-	req->cqe->result.u32 = cpu_to_le32(nvmet_connect_result(ctrl));
+	req->cqe->result.u32 = cpu_to_le32(nvmet_connect_result(ctrl, req));
 out:
 	kfree(d);
 complete:
diff --git a/drivers/nvme/target/nvmet.h b/drivers/nvme/target/nvmet.h
index 190f55e6d753..c2e17201c757 100644
--- a/drivers/nvme/target/nvmet.h
+++ b/drivers/nvme/target/nvmet.h
@@ -121,6 +121,9 @@ struct nvmet_sq {
 	u32			dhchap_s2;
 	u8			*dhchap_skey;
 	int			dhchap_skey_len;
+#endif
+#ifdef CONFIG_NVME_TARGET_TCP_TLS
+	struct key		*tls_key;
 #endif
 	struct completion	free_done;
 	struct completion	confirm_done;
@@ -237,6 +240,7 @@ struct nvmet_ctrl {
 	u64			err_counter;
 	struct nvme_error_slot	slots[NVMET_ERROR_LOG_SLOTS];
 	bool			pi_support;
+	bool			concat;
 #ifdef CONFIG_NVME_TARGET_AUTH
 	struct nvme_dhchap_key	*host_key;
 	struct nvme_dhchap_key	*ctrl_key;
@@ -246,6 +250,9 @@ struct nvmet_ctrl {
 	u8			*dh_key;
 	size_t			dh_keysize;
 #endif
+#ifdef CONFIG_NVME_TARGET_TCP_TLS
+	struct key		*tls_key;
+#endif
 };
 
 struct nvmet_subsys {
@@ -716,13 +723,29 @@ static inline void nvmet_req_bio_put(struct nvmet_req *req, struct bio *bio)
 		bio_put(bio);
 }
 
+#ifdef CONFIG_NVME_TARGET_TCP_TLS
+static inline key_serial_t nvmet_queue_tls_keyid(struct nvmet_sq *sq)
+{
+	return sq->tls_key ? key_serial(sq->tls_key) : 0;
+}
+static inline void nvmet_sq_put_tls_key(struct nvmet_sq *sq)
+{
+	if (sq->tls_key) {
+		key_put(sq->tls_key);
+		sq->tls_key = NULL;
+	}
+}
+#else
+static inline key_serial_t nvmet_queue_tls_keyid(struct nvmet_sq *sq) { return 0; }
+static inline void nvmet_sq_put_tls_key(struct nvmet_sq *sq) {}
+#endif
 #ifdef CONFIG_NVME_TARGET_AUTH
 void nvmet_execute_auth_send(struct nvmet_req *req);
 void nvmet_execute_auth_receive(struct nvmet_req *req);
 int nvmet_auth_set_key(struct nvmet_host *host, const char *secret,
 		       bool set_ctrl);
 int nvmet_auth_set_host_hash(struct nvmet_host *host, const char *hash);
-u8 nvmet_setup_auth(struct nvmet_ctrl *ctrl);
+u8 nvmet_setup_auth(struct nvmet_ctrl *ctrl, struct nvmet_req *req);
 void nvmet_auth_sq_init(struct nvmet_sq *sq);
 void nvmet_destroy_auth(struct nvmet_ctrl *ctrl);
 void nvmet_auth_sq_free(struct nvmet_sq *sq);
@@ -732,16 +755,18 @@ int nvmet_auth_host_hash(struct nvmet_req *req, u8 *response,
 			 unsigned int hash_len);
 int nvmet_auth_ctrl_hash(struct nvmet_req *req, u8 *response,
 			 unsigned int hash_len);
-static inline bool nvmet_has_auth(struct nvmet_ctrl *ctrl)
+static inline bool nvmet_has_auth(struct nvmet_ctrl *ctrl, struct nvmet_req *req)
 {
-	return ctrl->host_key != NULL;
+	return ctrl->host_key != NULL && !nvmet_queue_tls_keyid(req->sq);
 }
 int nvmet_auth_ctrl_exponential(struct nvmet_req *req,
 				u8 *buf, int buf_size);
 int nvmet_auth_ctrl_sesskey(struct nvmet_req *req,
 			    u8 *buf, int buf_size);
+void nvmet_auth_insert_psk(struct nvmet_sq *sq);
 #else
-static inline u8 nvmet_setup_auth(struct nvmet_ctrl *ctrl)
+static inline u8 nvmet_setup_auth(struct nvmet_ctrl *ctrl,
+				  struct nvmet_req *req)
 {
 	return 0;
 }
@@ -754,11 +779,12 @@ static inline bool nvmet_check_auth_status(struct nvmet_req *req)
 {
 	return true;
 }
-static inline bool nvmet_has_auth(struct nvmet_ctrl *ctrl)
+static inline bool nvmet_has_auth(struct nvmet_ctrl *ctrl,
+				  struct nvmet_req *req)
 {
 	return false;
 }
 static inline const char *nvmet_dhchap_dhgroup_name(u8 dhgid) { return NULL; }
+static inline void nvmet_auth_insert_psk(struct nvmet_sq *sq) {};
 #endif
-
 #endif /* _NVMET_H */
diff --git a/drivers/nvme/target/tcp.c b/drivers/nvme/target/tcp.c
index 7c51c2a8c109..671600b5c64b 100644
--- a/drivers/nvme/target/tcp.c
+++ b/drivers/nvme/target/tcp.c
@@ -1073,10 +1073,11 @@ static int nvmet_tcp_done_recv_pdu(struct nvmet_tcp_queue *queue)
 
 	if (unlikely(!nvmet_req_init(req, &queue->nvme_cq,
 			&queue->nvme_sq, &nvmet_tcp_ops))) {
-		pr_err("failed cmd %p id %d opcode %d, data_len: %d\n",
+		pr_err("failed cmd %p id %d opcode %d, data_len: %d, status: %04x\n",
 			req->cmd, req->cmd->common.command_id,
 			req->cmd->common.opcode,
-			le32_to_cpu(req->cmd->common.dptr.sgl.length));
+		       le32_to_cpu(req->cmd->common.dptr.sgl.length),
+		       le16_to_cpu(req->cqe->status));
 
 		nvmet_tcp_handle_req_failure(queue, queue->cmd, req);
 		return 0;
@@ -1602,6 +1603,7 @@ static void nvmet_tcp_release_queue_work(struct work_struct *w)
 	/* stop accepting incoming data */
 	queue->rcv_state = NVMET_TCP_RECV_ERR;
 
+	nvmet_sq_put_tls_key(&queue->nvme_sq);
 	nvmet_tcp_uninit_data_in_cmds(queue);
 	nvmet_sq_destroy(&queue->nvme_sq);
 	cancel_work_sync(&queue->io_work);
@@ -1807,6 +1809,23 @@ static void nvmet_tcp_tls_handshake_done(void *data, int status,
 	spin_unlock_bh(&queue->state_lock);
 
 	cancel_delayed_work_sync(&queue->tls_handshake_tmo_work);
+
+	if (!status) {
+		struct key *tls_key = nvme_tls_key_lookup(peerid);
+
+		if (IS_ERR(tls_key)) {
+			pr_warn("%s: queue %d failed to lookup key %x\n",
+				__func__, queue->idx, peerid);
+			spin_lock_bh(&queue->state_lock);
+			queue->state = NVMET_TCP_Q_FAILED;
+			spin_unlock_bh(&queue->state_lock);
+			status = PTR_ERR(tls_key);
+		} else {
+			pr_debug("%s: queue %d using TLS PSK %x\n",
+				 __func__, queue->idx, peerid);
+			queue->nvme_sq.tls_key = tls_key;
+		}
+	}
 	if (status)
 		nvmet_tcp_schedule_release_queue(queue);
 	else
-- 
2.35.3

[PATCH 9/9] nvmet: add tls_concat and tls_key debugfs entries

[Hannes Reinecke]

Add debugfs entries to display the 'concat' and 'tls_key' controller
attributes.

Signed-off-by: Hannes Reinecke <hare@kernel.org>
---
 drivers/nvme/target/debugfs.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/drivers/nvme/target/debugfs.c b/drivers/nvme/target/debugfs.c
index 220c7391fc19..e4300eb95101 100644
--- a/drivers/nvme/target/debugfs.c
+++ b/drivers/nvme/target/debugfs.c
@@ -132,6 +132,27 @@ static int nvmet_ctrl_host_traddr_show(struct seq_file *m, void *p)
 }
 NVMET_DEBUGFS_ATTR(nvmet_ctrl_host_traddr);
 
+#ifdef CONFIG_NVME_TARGET_TCP_TLS
+static int nvmet_ctrl_tls_key_show(struct seq_file *m, void *p)
+{
+	struct nvmet_ctrl *ctrl = m->private;
+	key_serial_t keyid = nvmet_queue_tls_keyid(ctrl->sqs[0]);
+
+	seq_printf(m, "%08x\n", keyid);
+	return 0;
+}
+NVMET_DEBUGFS_ATTR(nvmet_ctrl_tls_key);
+
+static int nvmet_ctrl_tls_concat_show(struct seq_file *m, void *p)
+{
+	struct nvmet_ctrl *ctrl = m->private;
+
+	seq_printf(m, "%d\n", ctrl->concat);
+	return 0;
+}
+NVMET_DEBUGFS_ATTR(nvmet_ctrl_tls_concat);
+#endif
+
 int nvmet_debugfs_ctrl_setup(struct nvmet_ctrl *ctrl)
 {
 	char name[32];
@@ -157,6 +178,12 @@ int nvmet_debugfs_ctrl_setup(struct nvmet_ctrl *ctrl)
 			    &nvmet_ctrl_state_fops);
 	debugfs_create_file("host_traddr", S_IRUSR, ctrl->debugfs_dir, ctrl,
 			    &nvmet_ctrl_host_traddr_fops);
+#ifdef CONFIG_NVME_TARGET_TCP_TLS
+	debugfs_create_file("tls_concat", S_IRUSR, ctrl->debugfs_dir, ctrl,
+			    &nvmet_ctrl_tls_concat_fops);
+	debugfs_create_file("tls_key", S_IRUSR, ctrl->debugfs_dir, ctrl,
+			    &nvmet_ctrl_tls_key_fops);
+#endif
 	return 0;
 }
 
-- 
2.35.3

Re: [PATCH 1/9] crypto,fs: Separate out hkdf_extract() and hkdf_expand()

[Eric Biggers]

On Fri, Oct 11, 2024 at 05:54:22PM +0200, Hannes Reinecke wrote:
> Separate out the HKDF functions into a separate module to
> to make them available to other callers.
> And add a testsuite to the module with test vectors
> from RFC 5869 to ensure the integrity of the algorithm.

integrity => correctness

> +config CRYPTO_HKDF
> +	tristate
> +	select CRYPTO_SHA1 if !CONFIG_CRYPTO_MANAGER_DISABLE_TESTS
> +	select CRYPTO_SHA256 if !CONFIG_CRYPTO_MANAGER_DISABLE_TESTS
> +	select CRYPTO_HASH2

Any thoughts on including SHA512 tests instead of SHA1, given that SHA1 is
obsolete and should not be used?

> +int hkdf_expand(struct crypto_shash *hmac_tfm,
> +		const u8 *info, unsigned int infolen,
> +		u8 *okm, unsigned int okmlen)
> +{
> +	SHASH_DESC_ON_STACK(desc, hmac_tfm);
> +	unsigned int i, hashlen = crypto_shash_digestsize(hmac_tfm);
> +	int err;
> +	const u8 *prev = NULL;
> +	u8 counter = 1;
> +	u8 tmp[HASH_MAX_DIGESTSIZE];
> +
> +	if (WARN_ON(okmlen > 255 * hashlen ||
> +		    hashlen > HASH_MAX_DIGESTSIZE))
> +		return -EINVAL;

The crypto API guarantees HASH_MAX_DIGESTSIZE, so checking that again is not
very useful.

> +
> +	memzero_explicit(tmp, HASH_MAX_DIGESTSIZE);

The zeroization above is unnecessary.  If it's done anyway, it is just an
initialization, so it should use an initializer '= {}' instead of
memzero_explicit() which is intended for "destruction".

> +MODULE_ALIAS_CRYPTO("hkdf");

This alias does not make sense and is unnecessary.  These are library functions
that are not exposed by name through the crypto API, so there is no need to wire
them up to the module autoloading accordingly.

> diff --git a/include/crypto/hkdf.h b/include/crypto/hkdf.h
> new file mode 100644
> index 000000000000..c1f23a32a6b6
> --- /dev/null
> +++ b/include/crypto/hkdf.h
> @@ -0,0 +1,18 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * HKDF: HMAC-based Key Derivation Function (HKDF), RFC 5869
> + *
> + * Extracted from fs/crypto/hkdf.c, which has
> + * Copyright 2019 Google LLC
> + */
> +
> +#ifndef _CRYPTO_HKDF_H
> +#define _CRYPTO_HKDF_H
> +
> +int hkdf_extract(struct crypto_shash *hmac_tfm, const u8 *ikm,
> +		 unsigned int ikmlen, const u8 *salt, unsigned int saltlen,
> +		 u8 *prk);
> +int hkdf_expand(struct crypto_shash *hmac_tfm,
> +		const u8 *info, unsigned int infolen,
> +		u8 *okm, unsigned int okmlen);
> +#endif

This needs to include <crypto/hash.h>.

Otherwise there will be errors if someone includes this as their first header.

- Eric

Re: [PATCH 1/9] crypto,fs: Separate out hkdf_extract() and hkdf_expand()

[Hannes Reinecke]

On 10/14/24 21:38, Eric Biggers wrote:
> On Fri, Oct 11, 2024 at 05:54:22PM +0200, Hannes Reinecke wrote:
>> Separate out the HKDF functions into a separate module to
>> to make them available to other callers.
>> And add a testsuite to the module with test vectors
>> from RFC 5869 to ensure the integrity of the algorithm.
> 
> integrity => correctness
> 
Okay.

>> +config CRYPTO_HKDF
>> +	tristate
>> +	select CRYPTO_SHA1 if !CONFIG_CRYPTO_MANAGER_DISABLE_TESTS
>> +	select CRYPTO_SHA256 if !CONFIG_CRYPTO_MANAGER_DISABLE_TESTS
>> +	select CRYPTO_HASH2
> 
> Any thoughts on including SHA512 tests instead of SHA1, given that SHA1 is
> obsolete and should not be used?
> 
Hmm. The original implementation did use SHA1, so I used that.
But sure I can look into changing that.

>> +int hkdf_expand(struct crypto_shash *hmac_tfm,
>> +		const u8 *info, unsigned int infolen,
>> +		u8 *okm, unsigned int okmlen)
>> +{
>> +	SHASH_DESC_ON_STACK(desc, hmac_tfm);
>> +	unsigned int i, hashlen = crypto_shash_digestsize(hmac_tfm);
>> +	int err;
>> +	const u8 *prev = NULL;
>> +	u8 counter = 1;
>> +	u8 tmp[HASH_MAX_DIGESTSIZE];
>> +
>> +	if (WARN_ON(okmlen > 255 * hashlen ||
>> +		    hashlen > HASH_MAX_DIGESTSIZE))
>> +		return -EINVAL;
> 
> The crypto API guarantees HASH_MAX_DIGESTSIZE, so checking that again is not
> very useful.
> 
Okay, will be removing that check.

>> +
>> +	memzero_explicit(tmp, HASH_MAX_DIGESTSIZE);
> 
> The zeroization above is unnecessary.  If it's done anyway, it is just an
> initialization, so it should use an initializer '= {}' instead of
> memzero_explicit() which is intended for "destruction".
> 
Ok.

>> +MODULE_ALIAS_CRYPTO("hkdf");
> 
> This alias does not make sense and is unnecessary.  These are library functions
> that are not exposed by name through the crypto API, so there is no need to wire
> them up to the module autoloading accordingly.
> 
Ok.

>> diff --git a/include/crypto/hkdf.h b/include/crypto/hkdf.h
>> new file mode 100644
>> index 000000000000..c1f23a32a6b6
>> --- /dev/null
>> +++ b/include/crypto/hkdf.h
>> @@ -0,0 +1,18 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +/*
>> + * HKDF: HMAC-based Key Derivation Function (HKDF), RFC 5869
>> + *
>> + * Extracted from fs/crypto/hkdf.c, which has
>> + * Copyright 2019 Google LLC
>> + */
>> +
>> +#ifndef _CRYPTO_HKDF_H
>> +#define _CRYPTO_HKDF_H
>> +
>> +int hkdf_extract(struct crypto_shash *hmac_tfm, const u8 *ikm,
>> +		 unsigned int ikmlen, const u8 *salt, unsigned int saltlen,
>> +		 u8 *prk);
>> +int hkdf_expand(struct crypto_shash *hmac_tfm,
>> +		const u8 *info, unsigned int infolen,
>> +		u8 *okm, unsigned int okmlen);
>> +#endif
> 
> This needs to include <crypto/hash.h>.
> 
> Otherwise there will be errors if someone includes this as their first header.
> 
Will do.

Thanks for the review!

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@suse.de                                +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich

Re: [PATCH 1/9] crypto,fs: Separate out hkdf_extract() and hkdf_expand()

[Eric Biggers]

On Tue, Oct 15, 2024 at 05:05:40PM +0200, Hannes Reinecke wrote:
> On 10/14/24 21:38, Eric Biggers wrote:
> > On Fri, Oct 11, 2024 at 05:54:22PM +0200, Hannes Reinecke wrote:
> > > Separate out the HKDF functions into a separate module to
> > > to make them available to other callers.
> > > And add a testsuite to the module with test vectors
> > > from RFC 5869 to ensure the integrity of the algorithm.
> > 
> > integrity => correctness
> > 
> Okay.
> 
> > > +config CRYPTO_HKDF
> > > +	tristate
> > > +	select CRYPTO_SHA1 if !CONFIG_CRYPTO_MANAGER_DISABLE_TESTS
> > > +	select CRYPTO_SHA256 if !CONFIG_CRYPTO_MANAGER_DISABLE_TESTS
> > > +	select CRYPTO_HASH2
> > 
> > Any thoughts on including SHA512 tests instead of SHA1, given that SHA1 is
> > obsolete and should not be used?
> > 
> Hmm. The original implementation did use SHA1, so I used that.
> But sure I can look into changing that.

If you're talking about fs/crypto/hkdf.c which is where you're borrowing the
code from, that uses SHA512.

- Eric

Re: [PATCH 1/9] crypto,fs: Separate out hkdf_extract() and hkdf_expand()

[Hannes Reinecke]

On 10/15/24 17:41, Eric Biggers wrote:
> On Tue, Oct 15, 2024 at 05:05:40PM +0200, Hannes Reinecke wrote:
>> On 10/14/24 21:38, Eric Biggers wrote:
>>> On Fri, Oct 11, 2024 at 05:54:22PM +0200, Hannes Reinecke wrote:
>>>> Separate out the HKDF functions into a separate module to
>>>> to make them available to other callers.
>>>> And add a testsuite to the module with test vectors
>>>> from RFC 5869 to ensure the integrity of the algorithm.
>>>
>>> integrity => correctness
>>>
>> Okay.
>>
>>>> +config CRYPTO_HKDF
>>>> +	tristate
>>>> +	select CRYPTO_SHA1 if !CONFIG_CRYPTO_MANAGER_DISABLE_TESTS
>>>> +	select CRYPTO_SHA256 if !CONFIG_CRYPTO_MANAGER_DISABLE_TESTS
>>>> +	select CRYPTO_HASH2
>>>
>>> Any thoughts on including SHA512 tests instead of SHA1, given that SHA1 is
>>> obsolete and should not be used?
>>>
>> Hmm. The original implementation did use SHA1, so I used that.
>> But sure I can look into changing that.
> 
> If you're talking about fs/crypto/hkdf.c which is where you're borrowing the
> code from, that uses SHA512.
> 
Actually, I was talking about the test vectors themselves. RFC 5869 only 
gives test vectors for SHA1 and SHA256, so that's what I've used.
I've found additional test vectors for the other functions at
https://github.com/brycx/Test-Vector-Generation/blob/master/HKDF/hkdf-hmac-sha2-test-vectors.md
so I'll be using them for adding tests for SHA384 and SHA512 (TLS on 
NVMe-over-TCP is using SHA384, too) and delete the SHA1 ones.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@suse.de                                +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich

Re: [PATCH 1/9] crypto,fs: Separate out hkdf_extract() and hkdf_expand()

[Eric Biggers]

On Wed, Oct 16, 2024 at 08:40:54AM +0200, Hannes Reinecke wrote:
> On 10/15/24 17:41, Eric Biggers wrote:
> > On Tue, Oct 15, 2024 at 05:05:40PM +0200, Hannes Reinecke wrote:
> > > On 10/14/24 21:38, Eric Biggers wrote:
> > > > On Fri, Oct 11, 2024 at 05:54:22PM +0200, Hannes Reinecke wrote:
> > > > > Separate out the HKDF functions into a separate module to
> > > > > to make them available to other callers.
> > > > > And add a testsuite to the module with test vectors
> > > > > from RFC 5869 to ensure the integrity of the algorithm.
> > > > 
> > > > integrity => correctness
> > > > 
> > > Okay.
> > > 
> > > > > +config CRYPTO_HKDF
> > > > > +	tristate
> > > > > +	select CRYPTO_SHA1 if !CONFIG_CRYPTO_MANAGER_DISABLE_TESTS
> > > > > +	select CRYPTO_SHA256 if !CONFIG_CRYPTO_MANAGER_DISABLE_TESTS
> > > > > +	select CRYPTO_HASH2
> > > > 
> > > > Any thoughts on including SHA512 tests instead of SHA1, given that SHA1 is
> > > > obsolete and should not be used?
> > > > 
> > > Hmm. The original implementation did use SHA1, so I used that.
> > > But sure I can look into changing that.
> > 
> > If you're talking about fs/crypto/hkdf.c which is where you're borrowing the
> > code from, that uses SHA512.
> > 
> Actually, I was talking about the test vectors themselves. RFC 5869 only
> gives test vectors for SHA1 and SHA256, so that's what I've used.
> I've found additional test vectors for the other functions at
> https://github.com/brycx/Test-Vector-Generation/blob/master/HKDF/hkdf-hmac-sha2-test-vectors.md
> so I'll be using them for adding tests for SHA384 and SHA512 (TLS on
> NVMe-over-TCP is using SHA384, too) and delete the SHA1 ones.

Right, it's an old spec, so that's why it has SHA1.  Using SHA512 test vectors
from elsewhere, or generating your own test vectors using a known-good
implementation, would be fine though.

- Eric

[PATCH 1/9] crypto,fs: Separate out hkdf_extract() and hkdf_expand()

[Hannes Reinecke]

Separate out the HKDF functions into a separate module to to make them
available to other callers. And add a testsuite to the module with
test vectors from RFC 5869 (and additional vectors for SHA384 and
SHA512) to ensure the correctness of the algorithm.

Signed-off-by: Hannes Reinecke <hare@kernel.org>
Cc: Eric Biggers <ebiggers@kernel.org>
Cc: linux-crypto@vger.kernel.org
---
 crypto/Kconfig        |   6 +
 crypto/Makefile       |   1 +
 crypto/hkdf.c         | 573 ++++++++++++++++++++++++++++++++++++++++++
 fs/crypto/Kconfig     |   1 +
 fs/crypto/hkdf.c      |  85 ++-----
 include/crypto/hkdf.h |  20 ++
 6 files changed, 616 insertions(+), 70 deletions(-)
 create mode 100644 crypto/hkdf.c
 create mode 100644 include/crypto/hkdf.h

diff --git a/crypto/Kconfig b/crypto/Kconfig
index a779cab668c2..03656e7b55bb 100644
--- a/crypto/Kconfig
+++ b/crypto/Kconfig
@@ -141,6 +141,12 @@ config CRYPTO_ACOMP
 	select CRYPTO_ALGAPI
 	select CRYPTO_ACOMP2
 
+config CRYPTO_HKDF
+	tristate
+	select CRYPTO_SHA256 if !CONFIG_CRYPTO_MANAGER_DISABLE_TESTS
+	select CRYPTO_SHA512 if !CONFIG_CRYPTO_MANAGER_DISABLE_TESTS
+	select CRYPTO_HASH2
+
 config CRYPTO_MANAGER
 	tristate "Cryptographic algorithm manager"
 	select CRYPTO_MANAGER2
diff --git a/crypto/Makefile b/crypto/Makefile
index 4c99e5d376f6..5ec5b994d9ae 100644
--- a/crypto/Makefile
+++ b/crypto/Makefile
@@ -34,6 +34,7 @@ obj-$(CONFIG_CRYPTO_HASH2) += crypto_hash.o
 obj-$(CONFIG_CRYPTO_AKCIPHER2) += akcipher.o
 obj-$(CONFIG_CRYPTO_SIG2) += sig.o
 obj-$(CONFIG_CRYPTO_KPP2) += kpp.o
+obj-$(CONFIG_CRYPTO_HKDF) += hkdf.o
 
 dh_generic-y := dh.o
 dh_generic-y += dh_helper.o
diff --git a/crypto/hkdf.c b/crypto/hkdf.c
new file mode 100644
index 000000000000..2434c5c42545
--- /dev/null
+++ b/crypto/hkdf.c
@@ -0,0 +1,573 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Implementation of HKDF ("HMAC-based Extract-and-Expand Key Derivation
+ * Function"), aka RFC 5869.  See also the original paper (Krawczyk 2010):
+ * "Cryptographic Extraction and Key Derivation: The HKDF Scheme".
+ *
+ * Copyright 2019 Google LLC
+ */
+
+#include <crypto/internal/hash.h>
+#include <crypto/sha2.h>
+#include <crypto/hkdf.h>
+#include <linux/module.h>
+
+/*
+ * HKDF consists of two steps:
+ *
+ * 1. HKDF-Extract: extract a pseudorandom key from the input keying material
+ *    and optional salt.
+ * 2. HKDF-Expand: expand the pseudorandom key into output keying material of
+ *    any length, parameterized by an application-specific info string.
+ *
+ */
+
+/**
+ * hkdf_extract - HKDF-Extract (RFC 5869 section 2.2)
+ * @hmac_tfm: an HMAC transform using the hash function desired for HKDF.  The
+ *            caller is responsible for setting the @prk afterwards.
+ * @ikm: input keying material
+ * @ikmlen: length of @ikm
+ * @salt: input salt value
+ * @saltlen: length of @salt
+ * @prk: resulting pseudorandom key
+ *
+ * Extracts a pseudorandom key @prk from the input keying material
+ * @ikm with length @ikmlen and salt @salt with length @saltlen.
+ * The length of @prk is given by the digest size of @hmac_tfm.
+ * For an 'unsalted' version of HKDF-Extract @salt must be set
+ * to all zeroes and @saltlen must be set to the length of @prk.
+ *
+ * Returns 0 on success with the pseudorandom key stored in @prk,
+ * or a negative errno value otherwise.
+ */
+int hkdf_extract(struct crypto_shash *hmac_tfm, const u8 *ikm,
+		 unsigned int ikmlen, const u8 *salt, unsigned int saltlen,
+		 u8 *prk)
+{
+	int err;
+
+	err = crypto_shash_setkey(hmac_tfm, salt, saltlen);
+	if (!err)
+		err = crypto_shash_tfm_digest(hmac_tfm, ikm, ikmlen, prk);
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(hkdf_extract);
+
+/**
+ * hkdf_expand - HKDF-Expand (RFC 5869 section 2.3)
+ * @hmac_tfm: hash context keyed with pseudorandom key
+ * @info: application-specific information
+ * @infolen: length of @info
+ * @okm: output keying material
+ * @okmlen: length of @okm
+ *
+ * This expands the pseudorandom key, which was already keyed into @hmac_tfm,
+ * into @okmlen bytes of output keying material parameterized by the
+ * application-specific @info of length @infolen bytes.
+ * This is thread-safe and may be called by multiple threads in parallel.
+ *
+ * Returns 0 on success with output keying material stored in @okm,
+ * or a negative errno value otherwise.
+ */
+int hkdf_expand(struct crypto_shash *hmac_tfm,
+		const u8 *info, unsigned int infolen,
+		u8 *okm, unsigned int okmlen)
+{
+	SHASH_DESC_ON_STACK(desc, hmac_tfm);
+	unsigned int i, hashlen = crypto_shash_digestsize(hmac_tfm);
+	int err;
+	const u8 *prev = NULL;
+	u8 counter = 1;
+	u8 tmp[HASH_MAX_DIGESTSIZE] = {};
+
+	if (WARN_ON(okmlen > 255 * hashlen))
+		return -EINVAL;
+
+	desc->tfm = hmac_tfm;
+
+	for (i = 0; i < okmlen; i += hashlen) {
+		err = crypto_shash_init(desc);
+		if (err)
+			goto out;
+
+		if (prev) {
+			err = crypto_shash_update(desc, prev, hashlen);
+			if (err)
+				goto out;
+		}
+
+		if (infolen) {
+			err = crypto_shash_update(desc, info, infolen);
+			if (err)
+				goto out;
+		}
+
+		BUILD_BUG_ON(sizeof(counter) != 1);
+		if (okmlen - i < hashlen) {
+			err = crypto_shash_finup(desc, &counter, 1, tmp);
+			if (err)
+				goto out;
+			memcpy(&okm[i], tmp, okmlen - i);
+			memzero_explicit(tmp, sizeof(tmp));
+		} else {
+			err = crypto_shash_finup(desc, &counter, 1, &okm[i]);
+			if (err)
+				goto out;
+		}
+		counter++;
+		prev = &okm[i];
+	}
+	err = 0;
+out:
+	if (unlikely(err))
+		memzero_explicit(okm, okmlen); /* so caller doesn't need to */
+	shash_desc_zero(desc);
+	memzero_explicit(tmp, HASH_MAX_DIGESTSIZE);
+	return err;
+}
+EXPORT_SYMBOL_GPL(hkdf_expand);
+
+struct hkdf_testvec {
+	const char *test;
+	const u8 *ikm;
+	const u8 *salt;
+	const u8 *info;
+	const u8 *prk;
+	const u8 *okm;
+	u16 ikm_size;
+	u16 salt_size;
+	u16 info_size;
+	u16 prk_size;
+	u16 okm_size;
+};
+
+/*
+ * HKDF test vectors from RFC5869
+ *
+ * Additional HKDF test vectors from
+ * https://github.com/brycx/Test-Vector-Generation/blob/master/HKDF/hkdf-hmac-sha2-test-vectors.md
+ */
+static const struct hkdf_testvec hkdf_sha256_tv[] = {
+	{
+		.test = "basic hdkf test",
+		.ikm  = "\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b"
+			"\x0b\x0b\x0b\x0b\x0b\x0b",
+		.ikm_size = 22,
+		.salt = "\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c",
+		.salt_size = 13,
+		.info = "\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9",
+		.info_size = 10,
+		.prk = "\x07\x77\x09\x36\x2c\x2e\x32\xdf\x0d\xdc\x3f\x0d\xc4\x7b\xba\x63"
+			"\x90\xb6\xc7\x3b\xb5\x0f\x9c\x31\x22\xec\x84\x4a\xd7\xc2\xb3\xe5",
+		.prk_size = 32,
+		.okm  = "\x3c\xb2\x5f\x25\xfa\xac\xd5\x7a\x90\x43\x4f\x64\xd0\x36\x2f\x2a"
+			"\x2d\x2d\x0a\x90\xcf\x1a\x5a\x4c\x5d\xb0\x2d\x56\xec\xc4\xc5\xbf"
+			"\x34\x00\x72\x08\xd5\xb8\x87\x18\x58\x65",
+		.okm_size = 42,
+	}, {
+		.test = "hkdf test with long input",
+		.ikm  = "\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f"
+			"\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f"
+			"\x20\x21\x22\x23\x24\x25\x26\x27\x28\x29\x2a\x2b\x2c\x2d\x2e\x2f"
+			"\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x3a\x3b\x3c\x3d\x3e\x3f"
+			"\x40\x41\x42\x43\x44\x45\x46\x47\x48\x49\x4a\x4b\x4c\x4d\x4e\x4f",
+		.ikm_size = 80,
+		.salt = "\x60\x61\x62\x63\x64\x65\x66\x67\x68\x69\x6a\x6b\x6c\x6d\x6e\x6f"
+			"\x70\x71\x72\x73\x74\x75\x76\x77\x78\x79\x7a\x7b\x7c\x7d\x7e\x7f"
+			"\x80\x81\x82\x83\x84\x85\x86\x87\x88\x89\x8a\x8b\x8c\x8d\x8e\x8f"
+			"\x90\x91\x92\x93\x94\x95\x96\x97\x98\x99\x9a\x9b\x9c\x9d\x9e\x9f"
+			"\xa0\xa1\xa2\xa3\xa4\xa5\xa6\xa7\xa8\xa9\xaa\xab\xac\xad\xae\xaf",
+		.salt_size = 80,
+		.info = "\xb0\xb1\xb2\xb3\xb4\xb5\xb6\xb7\xb8\xb9\xba\xbb\xbc\xbd\xbe\xbf"
+			"\xc0\xc1\xc2\xc3\xc4\xc5\xc6\xc7\xc8\xc9\xca\xcb\xcc\xcd\xce\xcf"
+			"\xd0\xd1\xd2\xd3\xd4\xd5\xd6\xd7\xd8\xd9\xda\xdb\xdc\xdd\xde\xdf"
+			"\xe0\xe1\xe2\xe3\xe4\xe5\xe6\xe7\xe8\xe9\xea\xeb\xec\xed\xee\xef"
+			"\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9\xfa\xfb\xfc\xfd\xfe\xff",
+		.info_size = 80,
+		.prk  = "\x06\xa6\xb8\x8c\x58\x53\x36\x1a\x06\x10\x4c\x9c\xeb\x35\xb4\x5c"
+			"\xef\x76\x00\x14\x90\x46\x71\x01\x4a\x19\x3f\x40\xc1\x5f\xc2\x44",
+		.prk_size = 32,
+		.okm  = "\xb1\x1e\x39\x8d\xc8\x03\x27\xa1\xc8\xe7\xf7\x8c\x59\x6a\x49\x34"
+			"\x4f\x01\x2e\xda\x2d\x4e\xfa\xd8\xa0\x50\xcc\x4c\x19\xaf\xa9\x7c"
+			"\x59\x04\x5a\x99\xca\xc7\x82\x72\x71\xcb\x41\xc6\x5e\x59\x0e\x09"
+			"\xda\x32\x75\x60\x0c\x2f\x09\xb8\x36\x77\x93\xa9\xac\xa3\xdb\x71"
+			"\xcc\x30\xc5\x81\x79\xec\x3e\x87\xc1\x4c\x01\xd5\xc1\xf3\x43\x4f"
+			"\x1d\x87",
+		.okm_size = 82,
+	}, {
+		.test = "hkdf test with zero salt and info",
+		.ikm  = "\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b"
+			"\x0b\x0b\x0b\x0b\x0b\x0b",
+		.ikm_size = 22,
+		.salt = NULL,
+		.salt_size = 0,
+		.info = NULL,
+		.info_size = 0,
+		.prk  = "\x19\xef\x24\xa3\x2c\x71\x7b\x16\x7f\x33\xa9\x1d\x6f\x64\x8b\xdf"
+			"\x96\x59\x67\x76\xaf\xdb\x63\x77\xac\x43\x4c\x1c\x29\x3c\xcb\x04",
+		.prk_size = 32,
+		.okm  = "\x8d\xa4\xe7\x75\xa5\x63\xc1\x8f\x71\x5f\x80\x2a\x06\x3c\x5a\x31"
+			"\xb8\xa1\x1f\x5c\x5e\xe1\x87\x9e\xc3\x45\x4e\x5f\x3c\x73\x8d\x2d"
+			"\x9d\x20\x13\x95\xfa\xa4\xb6\x1a\x96\xc8",
+		.okm_size = 42,
+	}, {
+		.test = "hkdf test with short input",
+		.ikm  = "\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b",
+		.ikm_size = 11,
+		.salt = "\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c",
+		.salt_size = 13,
+		.info = "\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9",
+		.info_size = 10,
+		.prk  = "\x82\x65\xf6\x9d\x7f\xf7\xe5\x01\x37\x93\x01\x5c\xa0\xef\x92\x0c"
+			"\xb1\x68\x21\x99\xc8\xbc\x3a\x00\xda\x0c\xab\x47\xb7\xb0\x0f\xdf",
+		.prk_size = 32,
+		.okm  = "\x58\xdc\xe1\x0d\x58\x01\xcd\xfd\xa8\x31\x72\x6b\xfe\xbc\xb7\x43"
+			"\xd1\x4a\x7e\xe8\x3a\xa0\x57\xa9\x3d\x59\xb0\xa1\x31\x7f\xf0\x9d"
+			"\x10\x5c\xce\xcf\x53\x56\x92\xb1\x4d\xd5",
+		.okm_size = 42,
+	}, {
+		.test = "unsalted hkdf test with zero info",
+		.ikm  = "\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c"
+			"\x0c\x0c\x0c\x0c\x0c\x0c",
+		.ikm_size = 22,
+		.salt = "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"
+			"\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00",
+		.salt_size = 32,
+		.info = NULL,
+		.info_size = 0,
+		.prk  = "\xaa\x84\x1e\x1f\x35\x74\xf3\x2d\x13\xfb\xa8\x00\x5f\xcd\x9b\x8d"
+			"\x77\x67\x82\xa5\xdf\xa1\x92\x38\x92\xfd\x8b\x63\x5d\x3a\x89\xdf",
+		.prk_size = 32,
+		.okm  = "\x59\x68\x99\x17\x9a\xb1\xbc\x00\xa7\xc0\x37\x86\xff\x43\xee\x53"
+			"\x50\x04\xbe\x2b\xb9\xbe\x68\xbc\x14\x06\x63\x6f\x54\xbd\x33\x8a"
+			"\x66\xa2\x37\xba\x2a\xcb\xce\xe3\xc9\xa7",
+		.okm_size = 42,
+	}
+};
+
+static const struct hkdf_testvec hkdf_sha384_tv[] = {
+	{
+		.test = "basic hkdf test",
+		.ikm  = "\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b"
+			"\x0b\x0b\x0b\x0b\x0b\x0b",
+		.ikm_size = 22,
+		.salt = "\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c",
+		.salt_size = 13,
+		.info = "\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9",
+		.info_size = 10,
+		.prk  = "\x70\x4b\x39\x99\x07\x79\xce\x1d\xc5\x48\x05\x2c\x7d\xc3\x9f\x30"
+			"\x35\x70\xdd\x13\xfb\x39\xf7\xac\xc5\x64\x68\x0b\xef\x80\xe8\xde"
+			"\xc7\x0e\xe9\xa7\xe1\xf3\xe2\x93\xef\x68\xec\xeb\x07\x2a\x5a\xde",
+		.prk_size = 48,
+		.okm  = "\x9b\x50\x97\xa8\x60\x38\xb8\x05\x30\x90\x76\xa4\x4b\x3a\x9f\x38"
+			"\x06\x3e\x25\xb5\x16\xdc\xbf\x36\x9f\x39\x4c\xfa\xb4\x36\x85\xf7"
+			"\x48\xb6\x45\x77\x63\xe4\xf0\x20\x4f\xc5",
+		.okm_size = 42,
+	}, {
+		.test = "hkdf test with long input",
+		.ikm  = "\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f"
+			"\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f"
+			"\x20\x21\x22\x23\x24\x25\x26\x27\x28\x29\x2a\x2b\x2c\x2d\x2e\x2f"
+			"\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x3a\x3b\x3c\x3d\x3e\x3f"
+			"\x40\x41\x42\x43\x44\x45\x46\x47\x48\x49\x4a\x4b\x4c\x4d\x4e\x4f",
+		.ikm_size = 80,
+		.salt = "\x60\x61\x62\x63\x64\x65\x66\x67\x68\x69\x6a\x6b\x6c\x6d\x6e\x6f"
+			"\x70\x71\x72\x73\x74\x75\x76\x77\x78\x79\x7a\x7b\x7c\x7d\x7e\x7f"
+			"\x80\x81\x82\x83\x84\x85\x86\x87\x88\x89\x8a\x8b\x8c\x8d\x8e\x8f"
+			"\x90\x91\x92\x93\x94\x95\x96\x97\x98\x99\x9a\x9b\x9c\x9d\x9e\x9f"
+			"\xa0\xa1\xa2\xa3\xa4\xa5\xa6\xa7\xa8\xa9\xaa\xab\xac\xad\xae\xaf",
+		.salt_size = 80,
+		.info = "\xb0\xb1\xb2\xb3\xb4\xb5\xb6\xb7\xb8\xb9\xba\xbb\xbc\xbd\xbe\xbf"
+			"\xc0\xc1\xc2\xc3\xc4\xc5\xc6\xc7\xc8\xc9\xca\xcb\xcc\xcd\xce\xcf"
+			"\xd0\xd1\xd2\xd3\xd4\xd5\xd6\xd7\xd8\xd9\xda\xdb\xdc\xdd\xde\xdf"
+			"\xe0\xe1\xe2\xe3\xe4\xe5\xe6\xe7\xe8\xe9\xea\xeb\xec\xed\xee\xef"
+			"\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9\xfa\xfb\xfc\xfd\xfe\xff",
+		.info_size = 80,
+		.prk  = "\xb3\x19\xf6\x83\x1d\xff\x93\x14\xef\xb6\x43\xba\xa2\x92\x63\xb3"
+			"\x0e\x4a\x8d\x77\x9f\xe3\x1e\x9c\x90\x1e\xfd\x7d\xe7\x37\xc8\x5b"
+			"\x62\xe6\x76\xd4\xdc\x87\xb0\x89\x5c\x6a\x7d\xc9\x7b\x52\xce\xbb",
+		.prk_size = 48,
+		.okm  = "\x48\x4c\xa0\x52\xb8\xcc\x72\x4f\xd1\xc4\xec\x64\xd5\x7b\x4e\x81"
+			"\x8c\x7e\x25\xa8\xe0\xf4\x56\x9e\xd7\x2a\x6a\x05\xfe\x06\x49\xee"
+			"\xbf\x69\xf8\xd5\xc8\x32\x85\x6b\xf4\xe4\xfb\xc1\x79\x67\xd5\x49"
+			"\x75\x32\x4a\x94\x98\x7f\x7f\x41\x83\x58\x17\xd8\x99\x4f\xdb\xd6"
+			"\xf4\xc0\x9c\x55\x00\xdc\xa2\x4a\x56\x22\x2f\xea\x53\xd8\x96\x7a"
+			"\x8b\x2e",
+		.okm_size = 82,
+	}, {
+		.test = "hkdf test with zero salt and info",
+		.ikm  = "\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b"
+			"\x0b\x0b\x0b\x0b\x0b\x0b",
+		.ikm_size = 22,
+		.salt = NULL,
+		.salt_size = 0,
+		.info = NULL,
+		.info_size = 0,
+		.prk  = "\x10\xe4\x0c\xf0\x72\xa4\xc5\x62\x6e\x43\xdd\x22\xc1\xcf\x72\x7d"
+			"\x4b\xb1\x40\x97\x5c\x9a\xd0\xcb\xc8\xe4\x5b\x40\x06\x8f\x8f\x0b"
+			"\xa5\x7c\xdb\x59\x8a\xf9\xdf\xa6\x96\x3a\x96\x89\x9a\xf0\x47\xe5",
+		.prk_size = 48,
+		.okm  = "\xc8\xc9\x6e\x71\x0f\x89\xb0\xd7\x99\x0b\xca\x68\xbc\xde\xc8\xcf"
+			"\x85\x40\x62\xe5\x4c\x73\xa7\xab\xc7\x43\xfa\xde\x9b\x24\x2d\xaa"
+			"\xcc\x1c\xea\x56\x70\x41\x5b\x52\x84\x9c",
+		.okm_size = 42,
+	}, {
+		.test = "hkdf test with short input",
+		.ikm  = "\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b",
+		.ikm_size = 11,
+		.salt = "\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c",
+		.salt_size = 13,
+		.info = "\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9",
+		.info_size = 10,
+		.prk  = "\x6d\x31\x69\x98\x28\x79\x80\x88\xb3\x59\xda\xd5\x0b\x8f\x01\xb0"
+			"\x15\xf1\x7a\xa3\xbd\x4e\x27\xa6\xe9\xf8\x73\xb7\x15\x85\xca\x6a"
+			"\x00\xd1\xf0\x82\x12\x8a\xdb\x3c\xf0\x53\x0b\x57\xc0\xf9\xac\x72",
+		.prk_size = 48,
+		.okm  = "\xfb\x7e\x67\x43\xeb\x42\xcd\xe9\x6f\x1b\x70\x77\x89\x52\xab\x75"
+			"\x48\xca\xfe\x53\x24\x9f\x7f\xfe\x14\x97\xa1\x63\x5b\x20\x1f\xf1"
+			"\x85\xb9\x3e\x95\x19\x92\xd8\x58\xf1\x1a",
+		.okm_size = 42,
+	}, {
+		.test = "unsalted hkdf test with zero info",
+		.ikm  = "\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c"
+			"\x0c\x0c\x0c\x0c\x0c\x0c",
+		.ikm_size = 22,
+		.salt = "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"
+			"\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"
+			"\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00",
+		.salt_size = 48,
+		.info = NULL,
+		.info_size = 0,
+		.prk  = "\x9d\x2d\xa5\x06\x6f\x05\xd1\x6c\x59\xfe\xdf\x6c\x5f\x32\xc7\x5e"
+			"\xda\x9a\x47\xa7\x9c\x93\x6a\xa4\x4c\xb7\x63\xa8\xe2\x2f\xfb\xfc"
+			"\xd8\xfe\x55\x43\x58\x53\x47\x21\x90\x39\xd1\x68\x28\x36\x33\xf5",
+		.prk_size = 48,
+		.okm  = "\x6a\xd7\xc7\x26\xc8\x40\x09\x54\x6a\x76\xe0\x54\x5d\xf2\x66\x78"
+			"\x7e\x2b\x2c\xd6\xca\x43\x73\xa1\xf3\x14\x50\xa7\xbd\xf9\x48\x2b"
+			"\xfa\xb8\x11\xf5\x54\x20\x0e\xad\x8f\x53",
+		.okm_size = 42,
+	}
+};
+
+static const struct hkdf_testvec hkdf_sha512_tv[] = {
+	{
+		.test = "basic hkdf test",
+		.ikm  = "\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b"
+			"\x0b\x0b\x0b\x0b\x0b\x0b",
+		.ikm_size = 22,
+		.salt = "\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c",
+		.salt_size = 13,
+		.info = "\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9",
+		.info_size = 10,
+		.prk  = "\x66\x57\x99\x82\x37\x37\xde\xd0\x4a\x88\xe4\x7e\x54\xa5\x89\x0b"
+			"\xb2\xc3\xd2\x47\xc7\xa4\x25\x4a\x8e\x61\x35\x07\x23\x59\x0a\x26"
+			"\xc3\x62\x38\x12\x7d\x86\x61\xb8\x8c\xf8\x0e\xf8\x02\xd5\x7e\x2f"
+			"\x7c\xeb\xcf\x1e\x00\xe0\x83\x84\x8b\xe1\x99\x29\xc6\x1b\x42\x37",
+		.prk_size = 64,
+		.okm  = "\x83\x23\x90\x08\x6c\xda\x71\xfb\x47\x62\x5b\xb5\xce\xb1\x68\xe4"
+			"\xc8\xe2\x6a\x1a\x16\xed\x34\xd9\xfc\x7f\xe9\x2c\x14\x81\x57\x93"
+			"\x38\xda\x36\x2c\xb8\xd9\xf9\x25\xd7\xcb",
+		.okm_size = 42,
+	}, {
+		.test = "hkdf test with long input",
+		.ikm  = "\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f"
+			"\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f"
+			"\x20\x21\x22\x23\x24\x25\x26\x27\x28\x29\x2a\x2b\x2c\x2d\x2e\x2f"
+			"\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x3a\x3b\x3c\x3d\x3e\x3f"
+			"\x40\x41\x42\x43\x44\x45\x46\x47\x48\x49\x4a\x4b\x4c\x4d\x4e\x4f",
+		.ikm_size = 80,
+		.salt = "\x60\x61\x62\x63\x64\x65\x66\x67\x68\x69\x6a\x6b\x6c\x6d\x6e\x6f"
+			"\x70\x71\x72\x73\x74\x75\x76\x77\x78\x79\x7a\x7b\x7c\x7d\x7e\x7f"
+			"\x80\x81\x82\x83\x84\x85\x86\x87\x88\x89\x8a\x8b\x8c\x8d\x8e\x8f"
+			"\x90\x91\x92\x93\x94\x95\x96\x97\x98\x99\x9a\x9b\x9c\x9d\x9e\x9f"
+			"\xa0\xa1\xa2\xa3\xa4\xa5\xa6\xa7\xa8\xa9\xaa\xab\xac\xad\xae\xaf",
+		.salt_size = 80,
+		.info = "\xb0\xb1\xb2\xb3\xb4\xb5\xb6\xb7\xb8\xb9\xba\xbb\xbc\xbd\xbe\xbf"
+			"\xc0\xc1\xc2\xc3\xc4\xc5\xc6\xc7\xc8\xc9\xca\xcb\xcc\xcd\xce\xcf"
+			"\xd0\xd1\xd2\xd3\xd4\xd5\xd6\xd7\xd8\xd9\xda\xdb\xdc\xdd\xde\xdf"
+			"\xe0\xe1\xe2\xe3\xe4\xe5\xe6\xe7\xe8\xe9\xea\xeb\xec\xed\xee\xef"
+			"\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9\xfa\xfb\xfc\xfd\xfe\xff",
+		.info_size = 80,
+		.prk  = "\x35\x67\x25\x42\x90\x7d\x4e\x14\x2c\x00\xe8\x44\x99\xe7\x4e\x1d"
+			"\xe0\x8b\xe8\x65\x35\xf9\x24\xe0\x22\x80\x4a\xd7\x75\xdd\xe2\x7e"
+			"\xc8\x6c\xd1\xe5\xb7\xd1\x78\xc7\x44\x89\xbd\xbe\xb3\x07\x12\xbe"
+			"\xb8\x2d\x4f\x97\x41\x6c\x5a\x94\xea\x81\xeb\xdf\x3e\x62\x9e\x4a",
+		.prk_size = 64,
+		.okm  = "\xce\x6c\x97\x19\x28\x05\xb3\x46\xe6\x16\x1e\x82\x1e\xd1\x65\x67"
+			"\x3b\x84\xf4\x00\xa2\xb5\x14\xb2\xfe\x23\xd8\x4c\xd1\x89\xdd\xf1"
+			"\xb6\x95\xb4\x8c\xbd\x1c\x83\x88\x44\x11\x37\xb3\xce\x28\xf1\x6a"
+			"\xa6\x4b\xa3\x3b\xa4\x66\xb2\x4d\xf6\xcf\xcb\x02\x1e\xcf\xf2\x35"
+			"\xf6\xa2\x05\x6c\xe3\xaf\x1d\xe4\x4d\x57\x20\x97\xa8\x50\x5d\x9e"
+			"\x7a\x93",
+		.okm_size = 82,
+	}, {
+		.test = "hkdf test with zero salt and info",
+		.ikm  = "\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b"
+			"\x0b\x0b\x0b\x0b\x0b\x0b",
+		.ikm_size = 22,
+		.salt = NULL,
+		.salt_size = 0,
+		.info = NULL,
+		.info_size = 0,
+		.prk  = "\xfd\x20\x0c\x49\x87\xac\x49\x13\x13\xbd\x4a\x2a\x13\x28\x71\x21"
+			"\x24\x72\x39\xe1\x1c\x9e\xf8\x28\x02\x04\x4b\x66\xef\x35\x7e\x5b"
+			"\x19\x44\x98\xd0\x68\x26\x11\x38\x23\x48\x57\x2a\x7b\x16\x11\xde"
+			"\x54\x76\x40\x94\x28\x63\x20\x57\x8a\x86\x3f\x36\x56\x2b\x0d\xf6",
+		.prk_size = 64,
+		.okm  = "\xf5\xfa\x02\xb1\x82\x98\xa7\x2a\x8c\x23\x89\x8a\x87\x03\x47\x2c"
+			"\x6e\xb1\x79\xdc\x20\x4c\x03\x42\x5c\x97\x0e\x3b\x16\x4b\xf9\x0f"
+			"\xff\x22\xd0\x48\x36\xd0\xe2\x34\x3b\xac",
+		.okm_size = 42,
+	}, {
+		.test = "hkdf test with short input",
+		.ikm  = "\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b\x0b",
+		.ikm_size = 11,
+		.salt = "\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c",
+		.salt_size = 13,
+		.info = "\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9",
+		.info_size = 10,
+		.prk  = "\x67\x40\x9c\x9c\xac\x28\xb5\x2e\xe9\xfa\xd9\x1c\x2f\xda\x99\x9f"
+			"\x7c\xa2\x2e\x34\x34\xf0\xae\x77\x28\x63\x83\x65\x68\xad\x6a\x7f"
+			"\x10\xcf\x11\x3b\xfd\xdd\x56\x01\x29\xa5\x94\xa8\xf5\x23\x85\xc2"
+			"\xd6\x61\xd7\x85\xd2\x9c\xe9\x3a\x11\x40\x0c\x92\x06\x83\x18\x1d",
+		.prk_size = 64,
+		.okm  = "\x74\x13\xe8\x99\x7e\x02\x06\x10\xfb\xf6\x82\x3f\x2c\xe1\x4b\xff"
+			"\x01\x87\x5d\xb1\xca\x55\xf6\x8c\xfc\xf3\x95\x4d\xc8\xaf\xf5\x35"
+			"\x59\xbd\x5e\x30\x28\xb0\x80\xf7\xc0\x68",
+		.okm_size = 42,
+	}, {
+		.test = "unsalted hkdf test with zero info",
+		.ikm  = "\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c\x0c"
+			"\x0c\x0c\x0c\x0c\x0c\x0c",
+		.ikm_size = 22,
+		.salt = "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"
+			"\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"
+			"\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"
+			"\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00",
+		.salt_size = 64,
+		.info = NULL,
+		.info_size = 0,
+		.prk  = "\x53\x46\xb3\x76\xbf\x3a\xa9\xf8\x4f\x8f\x6e\xd5\xb1\xc4\xf4\x89"
+			"\x17\x2e\x24\x4d\xac\x30\x3d\x12\xf6\x8e\xcc\x76\x6e\xa6\x00\xaa"
+			"\x88\x49\x5e\x7f\xb6\x05\x80\x31\x22\xfa\x13\x69\x24\xa8\x40\xb1"
+			"\xf0\x71\x9d\x2d\x5f\x68\xe2\x9b\x24\x22\x99\xd7\x58\xed\x68\x0c",
+		.prk_size = 64,
+		.okm  = "\x14\x07\xd4\x60\x13\xd9\x8b\xc6\xde\xce\xfc\xfe\xe5\x5f\x0f\x90"
+			"\xb0\xc7\xf6\x3d\x68\xeb\x1a\x80\xea\xf0\x7e\x95\x3c\xfc\x0a\x3a"
+			"\x52\x40\xa1\x55\xd6\xe4\xda\xa9\x65\xbb",
+		.okm_size = 42,
+	}
+};
+
+static int hkdf_test(const char *shash, const struct hkdf_testvec *tv)
+{	struct crypto_shash *tfm = NULL;
+	u8 *prk = NULL, *okm = NULL;
+	unsigned int prk_size;
+	const char *driver;
+	int err;
+
+	tfm = crypto_alloc_shash(shash, 0, 0);
+	if (IS_ERR(tfm)) {
+		pr_err("%s(%s): failed to allocate transform: %ld\n",
+		       tv->test, shash, PTR_ERR(tfm));
+		return PTR_ERR(tfm);
+	}
+	driver = crypto_shash_driver_name(tfm);
+
+	prk_size = crypto_shash_digestsize(tfm);
+	prk = kzalloc(prk_size, GFP_KERNEL);
+	if (!prk) {
+		err = -ENOMEM;
+		goto out_free;
+	}
+
+	if (tv->prk_size != prk_size) {
+		pr_err("%s(%s): prk size mismatch (vec %u, digest %u\n",
+		       tv->test, driver, tv->prk_size, prk_size);
+		err = -EINVAL;
+		goto out_free;
+	}
+
+	err = hkdf_extract(tfm, tv->ikm, tv->ikm_size,
+			   tv->salt, tv->salt_size, prk);
+	if (err) {
+		pr_err("%s(%s): hkdf_extract failed with %d\n",
+		       tv->test, driver, err);
+		goto out_free;
+	}
+
+	if (memcmp(prk, tv->prk, tv->prk_size)) {
+		pr_err("%s(%s): hkdf_extract prk mismatch\n",
+		       tv->test, driver);
+		print_hex_dump(KERN_ERR, "prk: ", DUMP_PREFIX_NONE,
+			       16, 1, prk, tv->prk_size, false);
+		err = -EINVAL;
+		goto out_free;
+	}
+
+	okm = kzalloc(tv->okm_size, GFP_KERNEL);
+	if (!okm) {
+		err = -ENOMEM;
+		goto out_free;
+	}
+
+	err = crypto_shash_setkey(tfm, tv->prk, tv->prk_size);
+	if (err) {
+		pr_err("%s(%s): failed to set prk, error %d\n",
+		       tv->test, driver, err);
+		goto out_free;
+	}
+
+	err = hkdf_expand(tfm, tv->info, tv->info_size,
+			  okm, tv->okm_size);
+	if (err) {
+		pr_err("%s(%s): hkdf_expand() failed with %d\n",
+		       tv->test, driver, err);
+	} else if (memcmp(okm, tv->okm, tv->okm_size)) {
+		pr_err("%s(%s): hkdf_expand() okm mismatch\n",
+		       tv->test, driver);
+		print_hex_dump(KERN_ERR, "okm: ", DUMP_PREFIX_NONE,
+			       16, 1, okm, tv->okm_size, false);
+		err = -EINVAL;
+	}
+out_free:
+	kfree(okm);
+	kfree(prk);
+	crypto_free_shash(tfm);
+	return err;
+}
+
+static int __init crypto_hkdf_module_init(void)
+{
+	int ret = 0, i;
+
+	if (IS_ENABLED(CONFIG_CRYPTO_MANAGER_DISABLE_TESTS))
+		return 0;
+
+	for (i = 0; i < ARRAY_SIZE(hkdf_sha256_tv); i++) {
+		ret = hkdf_test("hmac(sha256)", &hkdf_sha256_tv[i]);
+		if (ret)
+			return ret;
+	}
+	for (i = 0; i < ARRAY_SIZE(hkdf_sha384_tv); i++) {
+		ret = hkdf_test("hmac(sha384)", &hkdf_sha384_tv[i]);
+		if (ret)
+			return ret;
+	}
+	for (i = 0; i < ARRAY_SIZE(hkdf_sha512_tv); i++) {
+		ret = hkdf_test("hmac(sha512)", &hkdf_sha512_tv[i]);
+		if (ret)
+			return ret;
+	}
+	return 0;
+}
+
+static void __exit crypto_hkdf_module_exit(void) {}
+
+module_init(crypto_hkdf_module_init);
+module_exit(crypto_hkdf_module_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("HMAC-based Key Derivation Function (HKDF)");
diff --git a/fs/crypto/Kconfig b/fs/crypto/Kconfig
index 5aff5934baa1..0ea56f588a4a 100644
--- a/fs/crypto/Kconfig
+++ b/fs/crypto/Kconfig
@@ -3,6 +3,7 @@ config FS_ENCRYPTION
 	bool "FS Encryption (Per-file encryption)"
 	select CRYPTO
 	select CRYPTO_HASH
+	select CRYPTO_HKDF
 	select CRYPTO_SKCIPHER
 	select CRYPTO_LIB_SHA256
 	select KEYS
diff --git a/fs/crypto/hkdf.c b/fs/crypto/hkdf.c
index 5a384dad2c72..855a0f4b7318 100644
--- a/fs/crypto/hkdf.c
+++ b/fs/crypto/hkdf.c
@@ -1,9 +1,5 @@
 // SPDX-License-Identifier: GPL-2.0
 /*
- * Implementation of HKDF ("HMAC-based Extract-and-Expand Key Derivation
- * Function"), aka RFC 5869.  See also the original paper (Krawczyk 2010):
- * "Cryptographic Extraction and Key Derivation: The HKDF Scheme".
- *
  * This is used to derive keys from the fscrypt master keys.
  *
  * Copyright 2019 Google LLC
@@ -11,6 +7,7 @@
 
 #include <crypto/hash.h>
 #include <crypto/sha2.h>
+#include <crypto/hkdf.h>
 
 #include "fscrypt_private.h"
 
@@ -44,20 +41,6 @@
  * there's no way to persist a random salt per master key from kernel mode.
  */
 
-/* HKDF-Extract (RFC 5869 section 2.2), unsalted */
-static int hkdf_extract(struct crypto_shash *hmac_tfm, const u8 *ikm,
-			unsigned int ikmlen, u8 prk[HKDF_HASHLEN])
-{
-	static const u8 default_salt[HKDF_HASHLEN];
-	int err;
-
-	err = crypto_shash_setkey(hmac_tfm, default_salt, HKDF_HASHLEN);
-	if (err)
-		return err;
-
-	return crypto_shash_tfm_digest(hmac_tfm, ikm, ikmlen, prk);
-}
-
 /*
  * Compute HKDF-Extract using the given master key as the input keying material,
  * and prepare an HMAC transform object keyed by the resulting pseudorandom key.
@@ -69,6 +52,7 @@ int fscrypt_init_hkdf(struct fscrypt_hkdf *hkdf, const u8 *master_key,
 		      unsigned int master_key_size)
 {
 	struct crypto_shash *hmac_tfm;
+	static const u8 default_salt[HKDF_HASHLEN];
 	u8 prk[HKDF_HASHLEN];
 	int err;
 
@@ -84,7 +68,8 @@ int fscrypt_init_hkdf(struct fscrypt_hkdf *hkdf, const u8 *master_key,
 		goto err_free_tfm;
 	}
 
-	err = hkdf_extract(hmac_tfm, master_key, master_key_size, prk);
+	err = hkdf_extract(hmac_tfm, master_key, master_key_size,
+			   default_salt, HKDF_HASHLEN, prk);
 	if (err)
 		goto err_free_tfm;
 
@@ -118,61 +103,21 @@ int fscrypt_hkdf_expand(const struct fscrypt_hkdf *hkdf, u8 context,
 			u8 *okm, unsigned int okmlen)
 {
 	SHASH_DESC_ON_STACK(desc, hkdf->hmac_tfm);
-	u8 prefix[9];
-	unsigned int i;
+	u8 *full_info;
 	int err;
-	const u8 *prev = NULL;
-	u8 counter = 1;
-	u8 tmp[HKDF_HASHLEN];
-
-	if (WARN_ON_ONCE(okmlen > 255 * HKDF_HASHLEN))
-		return -EINVAL;
 
+	full_info = kzalloc(infolen + 9, GFP_KERNEL);
+	if (!full_info)
+		return -ENOMEM;
 	desc->tfm = hkdf->hmac_tfm;
 
-	memcpy(prefix, "fscrypt\0", 8);
-	prefix[8] = context;
-
-	for (i = 0; i < okmlen; i += HKDF_HASHLEN) {
-
-		err = crypto_shash_init(desc);
-		if (err)
-			goto out;
-
-		if (prev) {
-			err = crypto_shash_update(desc, prev, HKDF_HASHLEN);
-			if (err)
-				goto out;
-		}
-
-		err = crypto_shash_update(desc, prefix, sizeof(prefix));
-		if (err)
-			goto out;
-
-		err = crypto_shash_update(desc, info, infolen);
-		if (err)
-			goto out;
-
-		BUILD_BUG_ON(sizeof(counter) != 1);
-		if (okmlen - i < HKDF_HASHLEN) {
-			err = crypto_shash_finup(desc, &counter, 1, tmp);
-			if (err)
-				goto out;
-			memcpy(&okm[i], tmp, okmlen - i);
-			memzero_explicit(tmp, sizeof(tmp));
-		} else {
-			err = crypto_shash_finup(desc, &counter, 1, &okm[i]);
-			if (err)
-				goto out;
-		}
-		counter++;
-		prev = &okm[i];
-	}
-	err = 0;
-out:
-	if (unlikely(err))
-		memzero_explicit(okm, okmlen); /* so caller doesn't need to */
-	shash_desc_zero(desc);
+	memcpy(full_info, "fscrypt\0", 8);
+	full_info[8] = context;
+	memcpy(full_info + 9, info, infolen);
+
+	err = hkdf_expand(hkdf->hmac_tfm, full_info, infolen + 9,
+			  okm, okmlen);
+	kfree_sensitive(full_info);
 	return err;
 }
 
diff --git a/include/crypto/hkdf.h b/include/crypto/hkdf.h
new file mode 100644
index 000000000000..6a9678f508f5
--- /dev/null
+++ b/include/crypto/hkdf.h
@@ -0,0 +1,20 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * HKDF: HMAC-based Key Derivation Function (HKDF), RFC 5869
+ *
+ * Extracted from fs/crypto/hkdf.c, which has
+ * Copyright 2019 Google LLC
+ */
+
+#ifndef _CRYPTO_HKDF_H
+#define _CRYPTO_HKDF_H
+
+#include <crypto/hash.h>
+
+int hkdf_extract(struct crypto_shash *hmac_tfm, const u8 *ikm,
+		 unsigned int ikmlen, const u8 *salt, unsigned int saltlen,
+		 u8 *prk);
+int hkdf_expand(struct crypto_shash *hmac_tfm,
+		const u8 *info, unsigned int infolen,
+		u8 *okm, unsigned int okmlen);
+#endif
-- 
2.35.3