From 41d131e9000a5e1bb02a6867ac4ee974073fff8c Mon Sep 17 00:00:00 2001 From: Dirkjan Bussink Date: Wed, 23 Apr 2014 17:27:10 -0700 Subject: [PATCH 1/6] Use constant time comparison function for HMAC comparison Signed-off-by: Jon Simons --- src/packet_crypt.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/src/packet_crypt.c b/src/packet_crypt.c index c30264e5..59a6dcc5 100644 --- a/src/packet_crypt.c +++ b/src/packet_crypt.c @@ -188,6 +188,16 @@ unsigned char *ssh_packet_encrypt(ssh_session session, void *data, uint32_t len) return crypto->hmacbuf; } +static int secure_memcmp(const void *s1, const void *s2, size_t n) { + int rc = 0; + const unsigned char *p1 = s1; + const unsigned char *p2 = s2; + for(; n > 0; --n) { + rc |= *p1++ ^ *p2++; + } + return (rc != 0); +} + /** * @internal * @@ -234,7 +244,7 @@ int ssh_packet_hmac_verify(ssh_session session, ssh_print_hexa("Computed mac",hmacbuf,len); ssh_print_hexa("seq",(unsigned char *)&seq,sizeof(uint32_t)); #endif - if (memcmp(mac, hmacbuf, len) == 0) { + if (secure_memcmp(mac, hmacbuf, len) == 0) { return 0; } -- 2.11.0