linux-kernel - [PATCH 3.18 14/60] Bluetooth: use constant time memory comparison for secret values

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Date:   Tue, 25 Jul 2017 12:16:05 -0700
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, "Jason A. Donenfeld" <Jason@...c4.com>,
        Marcel Holtmann <marcel@...tmann.org>
Subject: [PATCH 3.18 14/60] Bluetooth: use constant time memory comparison for secret values

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

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

From: Jason A. Donenfeld <Jason@...c4.com>

commit 329d82309824ff1082dc4a91a5bbed8c3bec1580 upstream.

This file is filled with complex cryptography. Thus, the comparisons of
MACs and secret keys and curve points and so forth should not add timing
attacks, which could either result in a direct forgery, or, given the
complexity, some other type of attack.

Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
Signed-off-by: Marcel Holtmann <marcel@...tmann.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 net/bluetooth/smp.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/net/bluetooth/smp.c
+++ b/net/bluetooth/smp.c
@@ -22,6 +22,7 @@
 
 #include <linux/crypto.h>
 #include <linux/scatterlist.h>
+#include <crypto/algapi.h>
 #include <crypto/b128ops.h>
 
 #include <net/bluetooth/bluetooth.h>
@@ -163,7 +164,7 @@ bool smp_irk_matches(struct hci_dev *hde
 	if (err)
 		return false;
 
-	return !memcmp(bdaddr->b, hash, 3);
+	return !crypto_memneq(bdaddr->b, hash, 3);
 }
 
 int smp_generate_rpa(struct hci_dev *hdev, u8 irk[16], bdaddr_t *rpa)
@@ -584,7 +585,7 @@ static u8 smp_random(struct smp_chan *sm
 	if (ret)
 		return SMP_UNSPECIFIED;
 
-	if (memcmp(smp->pcnf, confirm, sizeof(smp->pcnf)) != 0) {
+	if (crypto_memneq(smp->pcnf, confirm, sizeof(smp->pcnf))) {
 		BT_ERR("Pairing failed (confirmation values mismatch)");
 		return SMP_CONFIRM_FAILED;
 	}