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/* $OpenBSD: kexgexc.c,v 1.25 2017/05/30 14:23:52 markus Exp $ */ |
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/* |
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* Copyright (c) 2000 Niels Provos. All rights reserved. |
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* Copyright (c) 2001 Markus Friedl. All rights reserved. |
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* |
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* Redistribution and use in source and binary forms, with or without |
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* modification, are permitted provided that the following conditions |
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* are met: |
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* 1. Redistributions of source code must retain the above copyright |
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* notice, this list of conditions and the following disclaimer. |
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* 2. Redistributions in binary form must reproduce the above copyright |
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* notice, this list of conditions and the following disclaimer in the |
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* documentation and/or other materials provided with the distribution. |
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* |
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
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*/ |
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#include <sys/types.h> |
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#include <openssl/dh.h> |
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#include <stdio.h> |
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#include <string.h> |
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#include <signal.h> |
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#include "sshkey.h" |
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#include "cipher.h" |
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#include "digest.h" |
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#include "kex.h" |
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#include "log.h" |
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#include "packet.h" |
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#include "dh.h" |
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#include "ssh2.h" |
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#include "compat.h" |
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#include "dispatch.h" |
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#include "ssherr.h" |
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#include "sshbuf.h" |
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#include "misc.h" |
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static int input_kex_dh_gex_group(int, u_int32_t, struct ssh *); |
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static int input_kex_dh_gex_reply(int, u_int32_t, struct ssh *); |
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int |
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kexgex_client(struct ssh *ssh) |
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{ |
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struct kex *kex = ssh->kex; |
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int r; |
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u_int nbits; |
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nbits = dh_estimate(kex->dh_need * 8); |
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kex->min = DH_GRP_MIN; |
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kex->max = DH_GRP_MAX; |
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kex->nbits = nbits; |
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if (datafellows & SSH_BUG_DHGEX_LARGE) |
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kex->nbits = MINIMUM(kex->nbits, 4096); |
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/* New GEX request */ |
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if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_REQUEST)) != 0 || |
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(r = sshpkt_put_u32(ssh, kex->min)) != 0 || |
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(r = sshpkt_put_u32(ssh, kex->nbits)) != 0 || |
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(r = sshpkt_put_u32(ssh, kex->max)) != 0 || |
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(r = sshpkt_send(ssh)) != 0) |
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goto out; |
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debug("SSH2_MSG_KEX_DH_GEX_REQUEST(%u<%u<%u) sent", |
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kex->min, kex->nbits, kex->max); |
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#ifdef DEBUG_KEXDH |
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fprintf(stderr, "\nmin = %d, nbits = %d, max = %d\n", |
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kex->min, kex->nbits, kex->max); |
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#endif |
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ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_GROUP, |
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&input_kex_dh_gex_group); |
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r = 0; |
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out: |
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return r; |
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} |
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static int |
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input_kex_dh_gex_group(int type, u_int32_t seq, struct ssh *ssh) |
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{ |
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struct kex *kex = ssh->kex; |
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BIGNUM *p = NULL, *g = NULL; |
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int r, bits; |
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debug("got SSH2_MSG_KEX_DH_GEX_GROUP"); |
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if ((p = BN_new()) == NULL || |
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(g = BN_new()) == NULL) { |
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r = SSH_ERR_ALLOC_FAIL; |
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goto out; |
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} |
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if ((r = sshpkt_get_bignum2(ssh, p)) != 0 || |
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(r = sshpkt_get_bignum2(ssh, g)) != 0 || |
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(r = sshpkt_get_end(ssh)) != 0) |
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goto out; |
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if ((bits = BN_num_bits(p)) < 0 || |
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(u_int)bits < kex->min || (u_int)bits > kex->max) { |
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r = SSH_ERR_DH_GEX_OUT_OF_RANGE; |
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goto out; |
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} |
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if ((kex->dh = dh_new_group(g, p)) == NULL) { |
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r = SSH_ERR_ALLOC_FAIL; |
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goto out; |
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} |
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p = g = NULL; /* belong to kex->dh now */ |
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/* generate and send 'e', client DH public key */ |
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if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0 || |
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(r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_INIT)) != 0 || |
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(r = sshpkt_put_bignum2(ssh, kex->dh->pub_key)) != 0 || |
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(r = sshpkt_send(ssh)) != 0) |
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goto out; |
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debug("SSH2_MSG_KEX_DH_GEX_INIT sent"); |
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#ifdef DEBUG_KEXDH |
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DHparams_print_fp(stderr, kex->dh); |
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fprintf(stderr, "pub= "); |
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BN_print_fp(stderr, kex->dh->pub_key); |
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fprintf(stderr, "\n"); |
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#endif |
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ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_GROUP, NULL); |
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ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_REPLY, &input_kex_dh_gex_reply); |
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r = 0; |
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out: |
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if (p) |
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BN_clear_free(p); |
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if (g) |
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BN_clear_free(g); |
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return r; |
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} |
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static int |
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input_kex_dh_gex_reply(int type, u_int32_t seq, struct ssh *ssh) |
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{ |
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struct kex *kex = ssh->kex; |
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BIGNUM *dh_server_pub = NULL, *shared_secret = NULL; |
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struct sshkey *server_host_key = NULL; |
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u_char *kbuf = NULL, *signature = NULL, *server_host_key_blob = NULL; |
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u_char hash[SSH_DIGEST_MAX_LENGTH]; |
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size_t klen = 0, slen, sbloblen, hashlen; |
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int kout, r; |
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debug("got SSH2_MSG_KEX_DH_GEX_REPLY"); |
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if (kex->verify_host_key == NULL) { |
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r = SSH_ERR_INVALID_ARGUMENT; |
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goto out; |
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} |
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/* key, cert */ |
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if ((r = sshpkt_get_string(ssh, &server_host_key_blob, |
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&sbloblen)) != 0 || |
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(r = sshkey_from_blob(server_host_key_blob, sbloblen, |
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&server_host_key)) != 0) |
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goto out; |
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if (server_host_key->type != kex->hostkey_type || |
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(kex->hostkey_type == KEY_ECDSA && |
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server_host_key->ecdsa_nid != kex->hostkey_nid)) { |
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r = SSH_ERR_KEY_TYPE_MISMATCH; |
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goto out; |
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} |
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if (kex->verify_host_key(server_host_key, ssh) == -1) { |
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r = SSH_ERR_SIGNATURE_INVALID; |
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goto out; |
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} |
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/* DH parameter f, server public DH key */ |
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if ((dh_server_pub = BN_new()) == NULL) { |
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r = SSH_ERR_ALLOC_FAIL; |
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goto out; |
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} |
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/* signed H */ |
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if ((r = sshpkt_get_bignum2(ssh, dh_server_pub)) != 0 || |
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(r = sshpkt_get_string(ssh, &signature, &slen)) != 0 || |
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(r = sshpkt_get_end(ssh)) != 0) |
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goto out; |
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#ifdef DEBUG_KEXDH |
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fprintf(stderr, "dh_server_pub= "); |
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BN_print_fp(stderr, dh_server_pub); |
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fprintf(stderr, "\n"); |
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debug("bits %d", BN_num_bits(dh_server_pub)); |
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#endif |
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if (!dh_pub_is_valid(kex->dh, dh_server_pub)) { |
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sshpkt_disconnect(ssh, "bad server public DH value"); |
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r = SSH_ERR_MESSAGE_INCOMPLETE; |
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goto out; |
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} |
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klen = DH_size(kex->dh); |
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if ((kbuf = malloc(klen)) == NULL || |
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(shared_secret = BN_new()) == NULL) { |
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r = SSH_ERR_ALLOC_FAIL; |
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goto out; |
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} |
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if ((kout = DH_compute_key(kbuf, dh_server_pub, kex->dh)) < 0 || |
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BN_bin2bn(kbuf, kout, shared_secret) == NULL) { |
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r = SSH_ERR_LIBCRYPTO_ERROR; |
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goto out; |
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} |
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#ifdef DEBUG_KEXDH |
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dump_digest("shared secret", kbuf, kout); |
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#endif |
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if (ssh->compat & SSH_OLD_DHGEX) |
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kex->min = kex->max = -1; |
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/* calc and verify H */ |
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hashlen = sizeof(hash); |
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if ((r = kexgex_hash( |
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kex->hash_alg, |
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kex->client_version_string, |
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kex->server_version_string, |
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sshbuf_ptr(kex->my), sshbuf_len(kex->my), |
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sshbuf_ptr(kex->peer), sshbuf_len(kex->peer), |
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server_host_key_blob, sbloblen, |
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kex->min, kex->nbits, kex->max, |
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kex->dh->p, kex->dh->g, |
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kex->dh->pub_key, |
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dh_server_pub, |
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shared_secret, |
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hash, &hashlen)) != 0) |
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goto out; |
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if ((r = sshkey_verify(server_host_key, signature, slen, hash, |
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hashlen, ssh->compat)) != 0) |
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goto out; |
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/* save session id */ |
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if (kex->session_id == NULL) { |
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kex->session_id_len = hashlen; |
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kex->session_id = malloc(kex->session_id_len); |
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if (kex->session_id == NULL) { |
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r = SSH_ERR_ALLOC_FAIL; |
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goto out; |
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} |
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memcpy(kex->session_id, hash, kex->session_id_len); |
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} |
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if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0) |
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r = kex_send_newkeys(ssh); |
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out: |
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explicit_bzero(hash, sizeof(hash)); |
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DH_free(kex->dh); |
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kex->dh = NULL; |
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if (dh_server_pub) |
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BN_clear_free(dh_server_pub); |
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if (kbuf) { |
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explicit_bzero(kbuf, klen); |
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free(kbuf); |
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} |
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if (shared_secret) |
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BN_clear_free(shared_secret); |
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sshkey_free(server_host_key); |
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free(server_host_key_blob); |
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free(signature); |
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return r; |
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} |