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KEYS: encrypted: use constant-time HMAC comparison

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MACs should, in general, be compared using crypto_memneq() to prevent
timing attacks.

Cc: Mimi Zohar <zohar@linux.vnet.ibm.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>
This commit is contained in:
Eric Biggers 2017-06-08 14:48:32 +01:00 committed by James Morris
parent 64d107d3ac
commit 0f534e4a13
1 changed files with 3 additions and 2 deletions
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5
security/keys/encrypted-keys/encrypted.c
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@ -30,6 +30,7 @@
#include <linux/scatterlist.h>
#include <linux/ctype.h>
#include <crypto/aes.h>
#include <crypto/algapi.h>
#include <crypto/hash.h>
#include <crypto/sha.h>
#include <crypto/skcipher.h>
@ -534,8 +535,8 @@ static int datablob_hmac_verify(struct encrypted_key_payload *epayload,
ret = calc_hmac(digest, derived_key, sizeof derived_key, p, len);
if (ret < 0)
goto out;
ret = memcmp(digest, epayload->format + epayload->datablob_len,
sizeof digest);
ret = crypto_memneq(digest, epayload->format + epayload->datablob_len,
sizeof(digest));
if (ret) {
ret = -EINVAL;
dump_hmac("datablob",