* [PATCH 1/3] KEYS: trusted_tpm1: Compare HMAC values in constant time
[not found] <20250731212354.105044-1-ebiggers@kernel.org>
@ 2025-07-31 21:23 ` Eric Biggers
2025-08-05 13:44 ` Jarkko Sakkinen
0 siblings, 1 reply; 5+ messages in thread
From: Eric Biggers @ 2025-07-31 21:23 UTC (permalink / raw)
To: James Bottomley, Jarkko Sakkinen, Mimi Zohar, keyrings
Cc: David Howells, linux-integrity, linux-crypto, linux-kernel,
Eric Biggers, stable
To prevent timing attacks, HMAC value comparison needs to be constant
time. Replace the memcmp() with the correct function, crypto_memneq().
Fixes: d00a1c72f7f4 ("keys: add new trusted key-type")
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
---
security/keys/trusted-keys/trusted_tpm1.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c
index 89c9798d18007..e73f2c6c817a0 100644
--- a/security/keys/trusted-keys/trusted_tpm1.c
+++ b/security/keys/trusted-keys/trusted_tpm1.c
@@ -5,10 +5,11 @@
*
* See Documentation/security/keys/trusted-encrypted.rst
*/
#include <crypto/hash_info.h>
+#include <crypto/utils.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/parser.h>
#include <linux/string.h>
#include <linux/err.h>
@@ -239,11 +240,11 @@ int TSS_checkhmac1(unsigned char *buffer,
TPM_NONCE_SIZE, enonce, TPM_NONCE_SIZE, ononce,
1, continueflag, 0, 0);
if (ret < 0)
goto out;
- if (memcmp(testhmac, authdata, SHA1_DIGEST_SIZE))
+ if (crypto_memneq(testhmac, authdata, SHA1_DIGEST_SIZE))
ret = -EINVAL;
out:
kfree_sensitive(sdesc);
return ret;
}
@@ -332,20 +333,20 @@ static int TSS_checkhmac2(unsigned char *buffer,
ret = TSS_rawhmac(testhmac1, key1, keylen1, SHA1_DIGEST_SIZE,
paramdigest, TPM_NONCE_SIZE, enonce1,
TPM_NONCE_SIZE, ononce, 1, continueflag1, 0, 0);
if (ret < 0)
goto out;
- if (memcmp(testhmac1, authdata1, SHA1_DIGEST_SIZE)) {
+ if (crypto_memneq(testhmac1, authdata1, SHA1_DIGEST_SIZE)) {
ret = -EINVAL;
goto out;
}
ret = TSS_rawhmac(testhmac2, key2, keylen2, SHA1_DIGEST_SIZE,
paramdigest, TPM_NONCE_SIZE, enonce2,
TPM_NONCE_SIZE, ononce, 1, continueflag2, 0, 0);
if (ret < 0)
goto out;
- if (memcmp(testhmac2, authdata2, SHA1_DIGEST_SIZE))
+ if (crypto_memneq(testhmac2, authdata2, SHA1_DIGEST_SIZE))
ret = -EINVAL;
out:
kfree_sensitive(sdesc);
return ret;
}
base-commit: d6084bb815c453de27af8071a23163a711586a6c
--
2.50.1
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH 1/3] KEYS: trusted_tpm1: Compare HMAC values in constant time
2025-07-31 21:23 ` [PATCH 1/3] KEYS: trusted_tpm1: Compare HMAC values in constant time Eric Biggers
@ 2025-08-05 13:44 ` Jarkko Sakkinen
2025-08-05 17:32 ` Eric Biggers
0 siblings, 1 reply; 5+ messages in thread
From: Jarkko Sakkinen @ 2025-08-05 13:44 UTC (permalink / raw)
To: Eric Biggers
Cc: James Bottomley, Mimi Zohar, keyrings, David Howells,
linux-integrity, linux-crypto, linux-kernel, stable
On Thu, Jul 31, 2025 at 02:23:52PM -0700, Eric Biggers wrote:
> To prevent timing attacks, HMAC value comparison needs to be constant
> time. Replace the memcmp() with the correct function, crypto_memneq().
>
> Fixes: d00a1c72f7f4 ("keys: add new trusted key-type")
> Cc: stable@vger.kernel.org
> Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Was crypto_memneq() available at the time?
> ---
> security/keys/trusted-keys/trusted_tpm1.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c
> index 89c9798d18007..e73f2c6c817a0 100644
> --- a/security/keys/trusted-keys/trusted_tpm1.c
> +++ b/security/keys/trusted-keys/trusted_tpm1.c
> @@ -5,10 +5,11 @@
> *
> * See Documentation/security/keys/trusted-encrypted.rst
> */
>
> #include <crypto/hash_info.h>
> +#include <crypto/utils.h>
> #include <linux/init.h>
> #include <linux/slab.h>
> #include <linux/parser.h>
> #include <linux/string.h>
> #include <linux/err.h>
> @@ -239,11 +240,11 @@ int TSS_checkhmac1(unsigned char *buffer,
> TPM_NONCE_SIZE, enonce, TPM_NONCE_SIZE, ononce,
> 1, continueflag, 0, 0);
> if (ret < 0)
> goto out;
>
> - if (memcmp(testhmac, authdata, SHA1_DIGEST_SIZE))
> + if (crypto_memneq(testhmac, authdata, SHA1_DIGEST_SIZE))
> ret = -EINVAL;
> out:
> kfree_sensitive(sdesc);
> return ret;
> }
> @@ -332,20 +333,20 @@ static int TSS_checkhmac2(unsigned char *buffer,
> ret = TSS_rawhmac(testhmac1, key1, keylen1, SHA1_DIGEST_SIZE,
> paramdigest, TPM_NONCE_SIZE, enonce1,
> TPM_NONCE_SIZE, ononce, 1, continueflag1, 0, 0);
> if (ret < 0)
> goto out;
> - if (memcmp(testhmac1, authdata1, SHA1_DIGEST_SIZE)) {
> + if (crypto_memneq(testhmac1, authdata1, SHA1_DIGEST_SIZE)) {
> ret = -EINVAL;
> goto out;
> }
> ret = TSS_rawhmac(testhmac2, key2, keylen2, SHA1_DIGEST_SIZE,
> paramdigest, TPM_NONCE_SIZE, enonce2,
> TPM_NONCE_SIZE, ononce, 1, continueflag2, 0, 0);
> if (ret < 0)
> goto out;
> - if (memcmp(testhmac2, authdata2, SHA1_DIGEST_SIZE))
> + if (crypto_memneq(testhmac2, authdata2, SHA1_DIGEST_SIZE))
> ret = -EINVAL;
> out:
> kfree_sensitive(sdesc);
> return ret;
> }
>
> base-commit: d6084bb815c453de27af8071a23163a711586a6c
> --
> 2.50.1
>
BR, Jarkko
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH 1/3] KEYS: trusted_tpm1: Compare HMAC values in constant time
2025-08-05 13:44 ` Jarkko Sakkinen
@ 2025-08-05 17:32 ` Eric Biggers
2025-08-09 10:37 ` Jarkko Sakkinen
0 siblings, 1 reply; 5+ messages in thread
From: Eric Biggers @ 2025-08-05 17:32 UTC (permalink / raw)
To: Jarkko Sakkinen
Cc: James Bottomley, Mimi Zohar, keyrings, David Howells,
linux-integrity, linux-crypto, linux-kernel, stable
On Tue, Aug 05, 2025 at 04:44:27PM +0300, Jarkko Sakkinen wrote:
> On Thu, Jul 31, 2025 at 02:23:52PM -0700, Eric Biggers wrote:
> > To prevent timing attacks, HMAC value comparison needs to be constant
> > time. Replace the memcmp() with the correct function, crypto_memneq().
> >
> > Fixes: d00a1c72f7f4 ("keys: add new trusted key-type")
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Eric Biggers <ebiggers@kernel.org>
>
> Was crypto_memneq() available at the time?
No. The Fixes commit is still correct, though, as it's the commit that
introduced the memcmp(). Technically it was still a bug at that time,
even if there wasn't a helper function available yet.
- Eric
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH 1/3] KEYS: trusted_tpm1: Compare HMAC values in constant time
2025-08-05 17:32 ` Eric Biggers
@ 2025-08-09 10:37 ` Jarkko Sakkinen
2025-08-09 17:21 ` Eric Biggers
0 siblings, 1 reply; 5+ messages in thread
From: Jarkko Sakkinen @ 2025-08-09 10:37 UTC (permalink / raw)
To: Eric Biggers
Cc: James Bottomley, Mimi Zohar, keyrings, David Howells,
linux-integrity, linux-crypto, linux-kernel, stable
On Tue, Aug 05, 2025 at 10:32:27AM -0700, Eric Biggers wrote:
> On Tue, Aug 05, 2025 at 04:44:27PM +0300, Jarkko Sakkinen wrote:
> > On Thu, Jul 31, 2025 at 02:23:52PM -0700, Eric Biggers wrote:
> > > To prevent timing attacks, HMAC value comparison needs to be constant
> > > time. Replace the memcmp() with the correct function, crypto_memneq().
> > >
> > > Fixes: d00a1c72f7f4 ("keys: add new trusted key-type")
> > > Cc: stable@vger.kernel.org
> > > Signed-off-by: Eric Biggers <ebiggers@kernel.org>
> >
> > Was crypto_memneq() available at the time?
>
> No. The Fixes commit is still correct, though, as it's the commit that
> introduced the memcmp(). Technically it was still a bug at that time,
> even if there wasn't a helper function available yet.
Add a remark to the commit message.
>
> - Eric
BR, Jarkko
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH 1/3] KEYS: trusted_tpm1: Compare HMAC values in constant time
2025-08-09 10:37 ` Jarkko Sakkinen
@ 2025-08-09 17:21 ` Eric Biggers
0 siblings, 0 replies; 5+ messages in thread
From: Eric Biggers @ 2025-08-09 17:21 UTC (permalink / raw)
To: Jarkko Sakkinen
Cc: James Bottomley, Mimi Zohar, keyrings, David Howells,
linux-integrity, linux-crypto, linux-kernel, stable
On Sat, Aug 09, 2025 at 01:37:49PM +0300, Jarkko Sakkinen wrote:
> On Tue, Aug 05, 2025 at 10:32:27AM -0700, Eric Biggers wrote:
> > On Tue, Aug 05, 2025 at 04:44:27PM +0300, Jarkko Sakkinen wrote:
> > > On Thu, Jul 31, 2025 at 02:23:52PM -0700, Eric Biggers wrote:
> > > > To prevent timing attacks, HMAC value comparison needs to be constant
> > > > time. Replace the memcmp() with the correct function, crypto_memneq().
> > > >
> > > > Fixes: d00a1c72f7f4 ("keys: add new trusted key-type")
> > > > Cc: stable@vger.kernel.org
> > > > Signed-off-by: Eric Biggers <ebiggers@kernel.org>
> > >
> > > Was crypto_memneq() available at the time?
> >
> > No. The Fixes commit is still correct, though, as it's the commit that
> > introduced the memcmp(). Technically it was still a bug at that time,
> > even if there wasn't a helper function available yet.
>
> Add a remark to the commit message.
I don't know what the point is (both commits are over a decade old), but
sure I did that in v2.
- Eric
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2025-08-09 17:21 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
[not found] <20250731212354.105044-1-ebiggers@kernel.org>
2025-07-31 21:23 ` [PATCH 1/3] KEYS: trusted_tpm1: Compare HMAC values in constant time Eric Biggers
2025-08-05 13:44 ` Jarkko Sakkinen
2025-08-05 17:32 ` Eric Biggers
2025-08-09 10:37 ` Jarkko Sakkinen
2025-08-09 17:21 ` Eric Biggers
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox