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KEYS: trusted_tpm1: Compare HMAC values in constant time

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commit eed0e3d305 upstream.

To prevent timing attacks, HMAC value comparison needs to be constant
time.  Replace the memcmp() with the correct function, crypto_memneq().

[For the Fixes commit I used the commit that introduced the memcmp().
It predates the introduction of crypto_memneq(), but it was still a bug
at the time even though a helper function didn't exist yet.]

Fixes: d00a1c72f7 ("keys: add new trusted key-type")
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Eric Biggers 2025-08-09 10:19:39 -07:00 committed by Greg Kroah-Hartman
parent 6796412dec
commit 7ac82e0710
1 changed files with 4 additions and 3 deletions
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7
security/keys/trusted-keys/trusted_tpm1.c
View File

@ -7,6 +7,7 @@
*/
#include <crypto/hash_info.h>
#include <crypto/utils.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/parser.h>
@ -241,7 +242,7 @@ int TSS_checkhmac1(unsigned char *buffer,
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);
@ -334,7 +335,7 @@ static int TSS_checkhmac2(unsigned char *buffer,
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;
}
@ -343,7 +344,7 @@ static int TSS_checkhmac2(unsigned char *buffer,
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);