linux-kernel - [PATCH 4.3 006/200] crypto: nx - Fix timing leak in GCM and CCM decryption

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Date:	Sun, 14 Feb 2016 14:20:13 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, David Gstir <david@...ma-star.at>,
	Herbert Xu <herbert@...dor.apana.org.au>
Subject: [PATCH 4.3 006/200] crypto: nx - Fix timing leak in GCM and CCM decryption

4.3-stable review patch.  If anyone has any objections, please let me know.

------------------

From: David Gstir <david@...ma-star.at>

commit cb8affb55c7e64816f3effcd9b2fc3268c016fac upstream.

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.

Signed-off-by: David Gstir <david@...ma-star.at>
Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/crypto/nx/nx-aes-ccm.c |    2 +-
 drivers/crypto/nx/nx-aes-gcm.c |    3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

--- a/drivers/crypto/nx/nx-aes-ccm.c
+++ b/drivers/crypto/nx/nx-aes-ccm.c
@@ -409,7 +409,7 @@ static int ccm_nx_decrypt(struct aead_re
 		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);
--- a/drivers/crypto/nx/nx-aes-gcm.c
+++ b/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 @@ mac:
 			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;
 	}