1 files changed, 17 insertions, 18 deletions

diff --git a/packet.c b/packet.c
index 48111bb15..9839c94dd 100644
--- a/packet.c
+++ b/packet.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: packet.c,v 1.230 2016/03/07 19:02:43 djm Exp $ */
+/* $OpenBSD: packet.c,v 1.231 2016/07/08 03:44:42 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -1690,7 +1690,7 @@ ssh_packet_read_poll2(struct ssh *ssh, u_char *typep, u_int32_t *seqnr_p)
 {
         struct session_state *state = ssh->state;
         u_int padlen, need;
-        u_char *cp, macbuf[SSH_DIGEST_MAX_LENGTH];
+        u_char *cp;
         u_int maclen, aadlen = 0, authlen = 0, block_size;
         struct sshenc *enc   = NULL;
         struct sshmac *mac   = NULL;
@@ -1790,17 +1790,21 @@ ssh_packet_read_poll2(struct ssh *ssh, u_char *typep, u_int32_t *seqnr_p)
          * 'maclen' bytes of message authentication code.
          */
         if (sshbuf_len(state->input) < aadlen + need + authlen + maclen)
-                return 0;
+                return 0; /* packet is incomplete */
 #ifdef PACKET_DEBUG
         fprintf(stderr, "read_poll enc/full: ");
         sshbuf_dump(state->input, stderr);
 #endif
-        /* EtM: compute mac over encrypted input */
+        /* EtM: check mac over encrypted input */
         if (mac && mac->enabled && mac->etm) {
-                if ((r = mac_compute(mac, state->p_read.seqnr,
+                if ((r = mac_check(mac, state->p_read.seqnr,
                     sshbuf_ptr(state->input), aadlen + need,
-                    macbuf, sizeof(macbuf))) != 0)
+                    sshbuf_ptr(state->input) + aadlen + need + authlen,
+                    maclen)) != 0) {
+                        if (r == SSH_ERR_MAC_INVALID)
+                                logit("Corrupted MAC on input.");
                         goto out;
+                }
         }
         if ((r = sshbuf_reserve(state->incoming_packet, aadlen + need,
             &cp)) != 0)
@@ -1810,26 +1814,21 @@ ssh_packet_read_poll2(struct ssh *ssh, u_char *typep, u_int32_t *seqnr_p)
                 goto out;
         if ((r = sshbuf_consume(state->input, aadlen + need + authlen)) != 0)
                 goto out;
-        /*
-         * compute MAC over seqnr and packet,
-         * increment sequence number for incoming packet
-         */
         if (mac && mac->enabled) {
-                if (!mac->etm)
-                        if ((r = mac_compute(mac, state->p_read.seqnr,
-                            sshbuf_ptr(state->incoming_packet),
-                            sshbuf_len(state->incoming_packet),
-                            macbuf, sizeof(macbuf))) != 0)
+                /* Not EtM: check MAC over cleartext */
+                if (!mac->etm && (r = mac_check(mac, state->p_read.seqnr,
+                    sshbuf_ptr(state->incoming_packet),
+                    sshbuf_len(state->incoming_packet),
+                    sshbuf_ptr(state->input), maclen)) != 0) {
+                        if (r != SSH_ERR_MAC_INVALID)
                                 goto out;
-                if (timingsafe_bcmp(macbuf, sshbuf_ptr(state->input),
-                    mac->mac_len) != 0) {
                         logit("Corrupted MAC on input.");
                         if (need > PACKET_MAX_SIZE)
                                 return SSH_ERR_INTERNAL_ERROR;
                         return ssh_packet_start_discard(ssh, enc, mac,
                             state->packlen, PACKET_MAX_SIZE - need);
                 }
-
+                /* Remove MAC from input buffer */
                 DBG(debug("MAC #%d ok", state->p_read.seqnr));
                 if ((r = sshbuf_consume(state->input, mac->mac_len)) != 0)
                         goto out;