[PATCH v2] crypto: rsa-pkcs1pad: export rsa1_asn_lookup()

[PATCH v2] crypto: rsa-pkcs1pad: export rsa1_asn_lookup()

[Jarkko Sakkinen]

ASN.1 template is required for TPM2 asymmetric keys, as it needs to be
piggy-packed with the input data before applying TPM2_RSA_Decrypt. This
patch prepares crypto subsystem for the addition of those keys.

Later rsa_lookup_asn1() can be enabled in crypto/asymmetric_keys/Kconfig
by:

	depends on CRYPTO_RSA >= <TPM2 asymmetric keys>

Cc: James Prestwood <prestwoj@gmail.com>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
v2:
- Fix typo in the kdoc.
- Export also the template struct.
---
 crypto/rsa-pkcs1pad.c         | 16 ++++++++++------
 include/crypto/rsa-pkcs1pad.h | 20 ++++++++++++++++++++
 2 files changed, 30 insertions(+), 6 deletions(-)
 create mode 100644 include/crypto/rsa-pkcs1pad.h

diff --git a/crypto/rsa-pkcs1pad.c b/crypto/rsa-pkcs1pad.c
index cd501195f34a..ea162ccf28ec 100644
--- a/crypto/rsa-pkcs1pad.c
+++ b/crypto/rsa-pkcs1pad.c
@@ -7,6 +7,7 @@
 
 #include <crypto/algapi.h>
 #include <crypto/akcipher.h>
+#include <crypto/rsa-pkcs1pad.h>
 #include <crypto/internal/akcipher.h>
 #include <crypto/internal/rsa.h>
 #include <linux/err.h>
@@ -79,11 +80,7 @@ static const u8 rsa_digest_info_sha3_512[] = {
 	0x05, 0x00, 0x04, 0x40
 };
 
-static const struct rsa_asn1_template {
-	const char	*name;
-	const u8	*data;
-	size_t		size;
-} rsa_asn1_templates[] = {
+const struct rsa_asn1_template rsa_asn1_templates[] = {
 #define _(X) { #X, rsa_digest_info_##X, sizeof(rsa_digest_info_##X) }
 	_(md5),
 	_(sha1),
@@ -101,7 +98,13 @@ static const struct rsa_asn1_template {
 	{ NULL }
 };
 
-static const struct rsa_asn1_template *rsa_lookup_asn1(const char *name)
+/**
+ * rsa_lookup_asn1() - Lookup the ASN.1 digest info given the hash
+ * name:	hash algorithm name
+ *
+ * Returns the ASN.1 digest info on success, and NULL on failure.
+ */
+const struct rsa_asn1_template *rsa_lookup_asn1(const char *name)
 {
 	const struct rsa_asn1_template *p;
 
@@ -110,6 +113,7 @@ static const struct rsa_asn1_template *rsa_lookup_asn1(const char *name)
 			return p;
 	return NULL;
 }
+EXPORT_SYMBOL_GPL(rsa_lookup_asn1);
 
 struct pkcs1pad_ctx {
 	struct crypto_akcipher *child;
diff --git a/include/crypto/rsa-pkcs1pad.h b/include/crypto/rsa-pkcs1pad.h
new file mode 100644
index 000000000000..32c7453ff644
--- /dev/null
+++ b/include/crypto/rsa-pkcs1pad.h
@@ -0,0 +1,20 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * RSA padding templates.
+ */
+
+#ifndef _CRYPTO_RSA_PKCS1PAD_H
+#define _CRYPTO_RSA_PKCS1PAD_H
+
+/*
+ * Hash algorithm name to ASN.1 template mapping.
+ */
+struct rsa_asn1_template {
+	const char *name;
+	const u8 *data;
+	size_t size;
+};
+
+const struct rsa_asn1_template *rsa_lookup_asn1(const char *name);
+
+#endif /* _CRYPTO_RSA_PKCS1PAD_H */
-- 
2.45.0

Re: [PATCH v2] crypto: rsa-pkcs1pad: export rsa1_asn_lookup()

[Herbert Xu]

On Wed, May 15, 2024 at 06:02:10PM +0300, Jarkko Sakkinen wrote:
> ASN.1 template is required for TPM2 asymmetric keys, as it needs to be
> piggy-packed with the input data before applying TPM2_RSA_Decrypt. This
> patch prepares crypto subsystem for the addition of those keys.
> 
> Later rsa_lookup_asn1() can be enabled in crypto/asymmetric_keys/Kconfig
> by:
> 
> 	depends on CRYPTO_RSA >= <TPM2 asymmetric keys>
> 
> Cc: James Prestwood <prestwoj@gmail.com>
> Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
> ---
> v2:
> - Fix typo in the kdoc.
> - Export also the template struct.
> ---
>  crypto/rsa-pkcs1pad.c         | 16 ++++++++++------
>  include/crypto/rsa-pkcs1pad.h | 20 ++++++++++++++++++++
>  2 files changed, 30 insertions(+), 6 deletions(-)
>  create mode 100644 include/crypto/rsa-pkcs1pad.h

Please provide a link to the patch that will make use of this.

Thanks,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: [PATCH v2] crypto: rsa-pkcs1pad: export rsa1_asn_lookup()

[Jarkko Sakkinen]

On Thu May 16, 2024 at 7:14 AM EEST, Herbert Xu wrote:
> On Wed, May 15, 2024 at 06:02:10PM +0300, Jarkko Sakkinen wrote:
> > ASN.1 template is required for TPM2 asymmetric keys, as it needs to be
> > piggy-packed with the input data before applying TPM2_RSA_Decrypt. This
> > patch prepares crypto subsystem for the addition of those keys.
> > 
> > Later rsa_lookup_asn1() can be enabled in crypto/asymmetric_keys/Kconfig
> > by:
> > 
> > 	depends on CRYPTO_RSA >= <TPM2 asymmetric keys>
> > 
> > Cc: James Prestwood <prestwoj@gmail.com>
> > Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
> > ---
> > v2:
> > - Fix typo in the kdoc.
> > - Export also the template struct.
> > ---
> >  crypto/rsa-pkcs1pad.c         | 16 ++++++++++------
> >  include/crypto/rsa-pkcs1pad.h | 20 ++++++++++++++++++++
> >  2 files changed, 30 insertions(+), 6 deletions(-)
> >  create mode 100644 include/crypto/rsa-pkcs1pad.h
>
> Please provide a link to the patch that will make use of this.

OK, fair enough. Will be part of the full patch set.

Overally I can say that this will be used to make textbook RSA
to a proper RSA signature ASN.1 and appropriate padding. I.e.
breath new life to this patch, which has duplicate code:

https://lore.kernel.org/all/20200518172704.29608-18-prestwoj@gmail.com/

TPM2_RSA_Decrypt is exactly textbook RSA so it partially needs
the code from kernel's RSA implementation.

BR, Jarkko