linux-kernel - [PATCH 4.2.y-ckt 078/305] crypto: nx - Fix timing leak in GCM and CCM decryption

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Date:	Fri, 15 Jan 2016 15:58:12 -0800
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	David Gstir <david@...ma-star.at>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 4.2.y-ckt 078/305] crypto: nx - Fix timing leak in GCM and CCM decryption

4.2.8-ckt2 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

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: Kamal Mostafa <kamal@...onical.com>
---
 drivers/crypto/nx/nx-aes-ccm.c | 2 +-
 drivers/crypto/nx/nx-aes-gcm.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/crypto/nx/nx-aes-ccm.c b/drivers/crypto/nx/nx-aes-ccm.c
index e4311ce..a1d0848 100644
--- a/drivers/crypto/nx/nx-aes-ccm.c
+++ b/drivers/crypto/nx/nx-aes-ccm.c
@@ -412,7 +412,7 @@ 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);
diff --git a/drivers/crypto/nx/nx-aes-gcm.c b/drivers/crypto/nx/nx-aes-gcm.c
index 92c993f..1c478bc 100644
--- a/drivers/crypto/nx/nx-aes-gcm.c
+++ b/drivers/crypto/nx/nx-aes-gcm.c
@@ -414,7 +414,7 @@ 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;
 	}
-- 
1.9.1