diff options
| -rw-r--r-- | mac.c | 23 | ||||
| -rw-r--r-- | mac.h | 4 | ||||
| -rw-r--r-- | packet.c | 35 |
3 files changed, 41 insertions, 21 deletions
@@ -1,4 +1,4 @@ -/* $OpenBSD: mac.c,v 1.32 2015/01/15 18:32:54 naddy Exp $ */ +/* $OpenBSD: mac.c,v 1.33 2016/07/08 03:44:42 djm Exp $ */ /* * Copyright (c) 2001 Markus Friedl. All rights reserved. * @@ -167,7 +167,8 @@ mac_init(struct sshmac *mac) } int -mac_compute(struct sshmac *mac, u_int32_t seqno, const u_char *data, int datalen, +mac_compute(struct sshmac *mac, u_int32_t seqno, + const u_char *data, int datalen, u_char *digest, size_t dlen) { static union { @@ -211,6 +212,24 @@ mac_compute(struct sshmac *mac, u_int32_t seqno, const u_char *data, int datalen return 0; } +int +mac_check(struct sshmac *mac, u_int32_t seqno, + const u_char *data, size_t dlen, + const u_char *theirmac, size_t mlen) +{ + u_char ourmac[SSH_DIGEST_MAX_LENGTH]; + int r; + + if (mac->mac_len > mlen) + return SSH_ERR_INVALID_ARGUMENT; + if ((r = mac_compute(mac, seqno, data, dlen, + ourmac, sizeof(ourmac))) != 0) + return r; + if (timingsafe_bcmp(ourmac, theirmac, mac->mac_len) != 0) + return SSH_ERR_MAC_INVALID; + return 0; +} + void mac_clear(struct sshmac *mac) { @@ -1,4 +1,4 @@ -/* $OpenBSD: mac.h,v 1.9 2015/01/13 19:31:40 markus Exp $ */ +/* $OpenBSD: mac.h,v 1.10 2016/07/08 03:44:42 djm Exp $ */ /* * Copyright (c) 2001 Markus Friedl. All rights reserved. * @@ -46,6 +46,8 @@ int mac_setup(struct sshmac *, char *); int mac_init(struct sshmac *); int mac_compute(struct sshmac *, u_int32_t, const u_char *, int, u_char *, size_t); +int mac_check(struct sshmac *, u_int32_t, const u_char *, size_t, + const u_char *, size_t); void mac_clear(struct sshmac *); #endif /* SSHMAC_H */ @@ -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; |