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: d00a1c72f7f4 ("keys: add new trusted key-type")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
---
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;
}
--
2.50.1
