crypto: ccree - use crypto_memneq() to compare AEAD tag

[PATCH] crypto: ccree - use crypto_memneq() to compare AEAD tag

Posted by David C.C.M. Gall 1 month, 2 weeks ago

cc_aead_complete() compares the computed MAC against the received ICV
with memcmp(), which short-circuits on the first differing byte and
leaks tag-match length via timing. Use crypto_memneq() instead.

Assisted-by: gregkh_clanker_t1000
Signed-off-by: David C.C.M. Gall <david.ccm.gall@googlemail.com>
---
 drivers/crypto/ccree/cc_aead.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/crypto/ccree/cc_aead.c b/drivers/crypto/ccree/cc_aead.c
index 088c4603047f..d57a98f89e53 100644
--- a/drivers/crypto/ccree/cc_aead.c
+++ b/drivers/crypto/ccree/cc_aead.c
@@ -226,8 +226,8 @@ static void cc_aead_complete(struct device *dev, void *cc_req, int err)
 		goto done;
 
 	if (areq_ctx->gen_ctx.op_type == DRV_CRYPTO_DIRECTION_DECRYPT) {
-		if (memcmp(areq_ctx->mac_buf, areq_ctx->icv_virt_addr,
-			   ctx->authsize) != 0) {
+		if (crypto_memneq(areq_ctx->mac_buf, areq_ctx->icv_virt_addr,
+				  ctx->authsize)) {
 			dev_dbg(dev, "Payload authentication failure, (auth-size=%d, cipher=%d)\n",
 				ctx->authsize, ctx->cipher_mode);
 			/* In case of payload authentication failure, MUST NOT
-- 
2.43.0

Re: [PATCH] crypto: ccree - use crypto_memneq() to compare AEAD tag

Posted by Herbert Xu 3 weeks, 3 days ago

On Sat, Aug 15, 2026 at 07:09:58PM +0200, David C.C.M. Gall wrote:
> cc_aead_complete() compares the computed MAC against the received ICV
> with memcmp(), which short-circuits on the first differing byte and
> leaks tag-match length via timing. Use crypto_memneq() instead.
> 
> Assisted-by: gregkh_clanker_t1000
> Signed-off-by: David C.C.M. Gall <david.ccm.gall@googlemail.com>
> ---
>  drivers/crypto/ccree/cc_aead.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

Patch applied.  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