linux-kernel - [PATCH 4.2.y-ckt 079/305] crypto: talitos - Fix timing leak in ESP ICV verification

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Message-Id: <1452902519-2754-80-git-send-email-kamal@canonical.com>
Date:	Fri, 15 Jan 2016 15:58:13 -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 079/305] crypto: talitos - Fix timing leak in ESP ICV verification

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 79960943fdc114fd4583c9ab164b5c89da7aa601 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>
[ kamal: backport to 4.2-stable: context ]
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 drivers/crypto/talitos.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/crypto/talitos.c b/drivers/crypto/talitos.c
index 83aca95..95606c1 100644
--- a/drivers/crypto/talitos.c
+++ b/drivers/crypto/talitos.c
@@ -1025,7 +1025,7 @@ static void ipsec_esp_decrypt_swauth_done(struct device *dev,
 			icvdata = &edesc->link_tbl[0];
 
 		sg = sg_last(req->dst, edesc->dst_nents ? : 1);
-		err = memcmp(icvdata, (char *)sg_virt(sg) + sg->length -
+		err = crypto_memneq(icvdata, (char *)sg_virt(sg) + sg->length -
 			     ctx->authsize, ctx->authsize) ? -EBADMSG : 0;
 	}
 
-- 
1.9.1