crypto: nx - Fix timing leak in GCM and CCM decryption

Using non-constant time memcmp() makes the verification of the authentication
tag in the decrypt path vulnerable to timing attacks. Fix this by using
crypto_memneq() instead.

Cc: stable@vger.kernel.org
Signed-off-by: David Gstir <david@sigma-star.at>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Author: iokill

drivers/crypto/nx/nx-aes-ccm.c

@@ -409,7 +409,7 @@ static int ccm_nx_decrypt(struct aead_request   *req,
 		processed += to_process;
 	} while (processed < nbytes);
 
-	rc = memcmp(csbcpb->cpb.aes_ccm.out_pat_or_mac, priv->oauth_tag,
+	rc = crypto_memneq(csbcpb->cpb.aes_ccm.out_pat_or_mac, priv->oauth_tag,
 		    authsize) ? -EBADMSG : 0;
 out:
 	spin_unlock_irqrestore(&nx_ctx->lock, irq_flags);

drivers/crypto/nx/nx-aes-gcm.c

@@ -21,6 +21,7 @@
 
 #include <crypto/internal/aead.h>
 #include <crypto/aes.h>
+#include <crypto/algapi.h>
 #include <crypto/scatterwalk.h>
 #include <linux/module.h>
 #include <linux/types.h>
@@ -418,7 +419,7 @@ static int gcm_aes_nx_crypt(struct aead_request *req, int enc,
 			itag, req->src, req->assoclen + nbytes,
 			crypto_aead_authsize(crypto_aead_reqtfm(req)),
 			SCATTERWALK_FROM_SG);
-		rc = memcmp(itag, otag,
+		rc = crypto_memneq(itag, otag,
 			    crypto_aead_authsize(crypto_aead_reqtfm(req))) ?
 		     -EBADMSG : 0;
 	}