[PATCH 2/6] net/ipv6: use constant time memory comparison for mac

[Jason A. Donenfeld]

Otherwise, we enable a MAC forgery via timing attack.

Signed-off-by: Jason A. Donenfeld <ja...@zx2c4.com>
Cc: "David S. Miller" <da...@davemloft.net>
Cc: net...@vger.kernel.org
Cc: sta...@vger.kernel.org
---
 net/ipv6/seg6_hmac.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/ipv6/seg6_hmac.c b/net/ipv6/seg6_hmac.c
index f950cb53d5e3..54213c83b44e 100644
--- a/net/ipv6/seg6_hmac.c
+++ b/net/ipv6/seg6_hmac.c
@@ -38,6 +38,7 @@
 #include <net/xfrm.h>
 
 #include <linux/cryptohash.h>
+#include <crypto/algapi.h>
 #include <crypto/hash.h>
 #include <crypto/sha.h>
 #include <net/seg6.h>
@@ -274,7 +275,7 @@ bool seg6_hmac_validate_skb(struct sk_buff *skb)
        if (seg6_hmac_compute(hinfo, srh, &ipv6_hdr(skb)->saddr, hmac_output))
                return false;
 
-       if (memcmp(hmac_output, tlv->hmac, SEG6_HMAC_FIELD_LEN) != 0)
+       if (crypto_memneq(hmac_output, tlv->hmac, SEG6_HMAC_FIELD_LEN))
                return false;
 
        return true;
-- 
2.13.1