Annotation of src/usr.bin/ssh/kexgexc.c, Revision 1.27
1.27 ! jsing 1: /* $OpenBSD: kexgexc.c,v 1.26 2017/12/18 02:25:15 djm Exp $ */
1.1 markus 2: /*
3: * Copyright (c) 2000 Niels Provos. All rights reserved.
4: * Copyright (c) 2001 Markus Friedl. All rights reserved.
5: *
6: * Redistribution and use in source and binary forms, with or without
7: * modification, are permitted provided that the following conditions
8: * are met:
9: * 1. Redistributions of source code must retain the above copyright
10: * notice, this list of conditions and the following disclaimer.
11: * 2. Redistributions in binary form must reproduce the above copyright
12: * notice, this list of conditions and the following disclaimer in the
13: * documentation and/or other materials provided with the distribution.
14: *
15: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16: * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18: * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19: * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20: * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21: * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22: * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24: * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25: */
26:
1.9 deraadt 27: #include <sys/types.h>
1.12 djm 28:
29: #include <openssl/dh.h>
1.7 stevesk 30:
1.8 stevesk 31: #include <stdio.h>
1.7 stevesk 32: #include <string.h>
1.9 deraadt 33: #include <signal.h>
1.1 markus 34:
1.19 markus 35: #include "sshkey.h"
1.9 deraadt 36: #include "cipher.h"
1.19 markus 37: #include "digest.h"
1.1 markus 38: #include "kex.h"
39: #include "log.h"
40: #include "packet.h"
41: #include "dh.h"
42: #include "ssh2.h"
43: #include "compat.h"
1.19 markus 44: #include "dispatch.h"
45: #include "ssherr.h"
46: #include "sshbuf.h"
1.23 deraadt 47: #include "misc.h"
1.1 markus 48:
1.25 markus 49: static int input_kex_dh_gex_group(int, u_int32_t, struct ssh *);
50: static int input_kex_dh_gex_reply(int, u_int32_t, struct ssh *);
1.19 markus 51:
52: int
53: kexgex_client(struct ssh *ssh)
1.1 markus 54: {
1.19 markus 55: struct kex *kex = ssh->kex;
56: int r;
57: u_int nbits;
1.1 markus 58:
1.16 dtucker 59: nbits = dh_estimate(kex->dh_need * 8);
1.1 markus 60:
1.19 markus 61: kex->min = DH_GRP_MIN;
62: kex->max = DH_GRP_MAX;
63: kex->nbits = nbits;
1.22 dtucker 64: if (datafellows & SSH_BUG_DHGEX_LARGE)
1.23 deraadt 65: kex->nbits = MINIMUM(kex->nbits, 4096);
1.21 djm 66: /* New GEX request */
67: if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_REQUEST)) != 0 ||
68: (r = sshpkt_put_u32(ssh, kex->min)) != 0 ||
69: (r = sshpkt_put_u32(ssh, kex->nbits)) != 0 ||
70: (r = sshpkt_put_u32(ssh, kex->max)) != 0 ||
71: (r = sshpkt_send(ssh)) != 0)
72: goto out;
73: debug("SSH2_MSG_KEX_DH_GEX_REQUEST(%u<%u<%u) sent",
74: kex->min, kex->nbits, kex->max);
1.1 markus 75: #ifdef DEBUG_KEXDH
76: fprintf(stderr, "\nmin = %d, nbits = %d, max = %d\n",
1.19 markus 77: kex->min, kex->nbits, kex->max);
1.1 markus 78: #endif
1.19 markus 79: ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_GROUP,
80: &input_kex_dh_gex_group);
81: r = 0;
82: out:
83: return r;
84: }
1.1 markus 85:
1.19 markus 86: static int
1.25 markus 87: input_kex_dh_gex_group(int type, u_int32_t seq, struct ssh *ssh)
1.19 markus 88: {
89: struct kex *kex = ssh->kex;
90: BIGNUM *p = NULL, *g = NULL;
91: int r, bits;
1.1 markus 92:
1.19 markus 93: debug("got SSH2_MSG_KEX_DH_GEX_GROUP");
1.1 markus 94:
1.19 markus 95: if ((p = BN_new()) == NULL ||
96: (g = BN_new()) == NULL) {
97: r = SSH_ERR_ALLOC_FAIL;
98: goto out;
99: }
100: if ((r = sshpkt_get_bignum2(ssh, p)) != 0 ||
101: (r = sshpkt_get_bignum2(ssh, g)) != 0 ||
102: (r = sshpkt_get_end(ssh)) != 0)
103: goto out;
104: if ((bits = BN_num_bits(p)) < 0 ||
105: (u_int)bits < kex->min || (u_int)bits > kex->max) {
106: r = SSH_ERR_DH_GEX_OUT_OF_RANGE;
107: goto out;
108: }
109: if ((kex->dh = dh_new_group(g, p)) == NULL) {
110: r = SSH_ERR_ALLOC_FAIL;
111: goto out;
112: }
113: p = g = NULL; /* belong to kex->dh now */
1.1 markus 114:
1.19 markus 115: /* generate and send 'e', client DH public key */
116: if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0 ||
117: (r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_INIT)) != 0 ||
118: (r = sshpkt_put_bignum2(ssh, kex->dh->pub_key)) != 0 ||
119: (r = sshpkt_send(ssh)) != 0)
120: goto out;
121: debug("SSH2_MSG_KEX_DH_GEX_INIT sent");
1.1 markus 122: #ifdef DEBUG_KEXDH
1.19 markus 123: DHparams_print_fp(stderr, kex->dh);
1.1 markus 124: fprintf(stderr, "pub= ");
1.19 markus 125: BN_print_fp(stderr, kex->dh->pub_key);
1.1 markus 126: fprintf(stderr, "\n");
127: #endif
1.19 markus 128: ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_GROUP, NULL);
129: ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_REPLY, &input_kex_dh_gex_reply);
130: r = 0;
131: out:
1.27 ! jsing 132: BN_clear_free(p);
! 133: BN_clear_free(g);
1.19 markus 134: return r;
135: }
1.1 markus 136:
1.19 markus 137: static int
1.25 markus 138: input_kex_dh_gex_reply(int type, u_int32_t seq, struct ssh *ssh)
1.19 markus 139: {
140: struct kex *kex = ssh->kex;
141: BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
142: struct sshkey *server_host_key = NULL;
143: u_char *kbuf = NULL, *signature = NULL, *server_host_key_blob = NULL;
144: u_char hash[SSH_DIGEST_MAX_LENGTH];
145: size_t klen = 0, slen, sbloblen, hashlen;
146: int kout, r;
147:
148: debug("got SSH2_MSG_KEX_DH_GEX_REPLY");
149: if (kex->verify_host_key == NULL) {
150: r = SSH_ERR_INVALID_ARGUMENT;
151: goto out;
152: }
1.1 markus 153: /* key, cert */
1.19 markus 154: if ((r = sshpkt_get_string(ssh, &server_host_key_blob,
155: &sbloblen)) != 0 ||
156: (r = sshkey_from_blob(server_host_key_blob, sbloblen,
157: &server_host_key)) != 0)
158: goto out;
1.20 djm 159: if (server_host_key->type != kex->hostkey_type ||
160: (kex->hostkey_type == KEY_ECDSA &&
161: server_host_key->ecdsa_nid != kex->hostkey_nid)) {
1.19 markus 162: r = SSH_ERR_KEY_TYPE_MISMATCH;
163: goto out;
164: }
165: if (kex->verify_host_key(server_host_key, ssh) == -1) {
166: r = SSH_ERR_SIGNATURE_INVALID;
167: goto out;
168: }
1.6 miod 169: /* DH parameter f, server public DH key */
1.19 markus 170: if ((dh_server_pub = BN_new()) == NULL) {
171: r = SSH_ERR_ALLOC_FAIL;
172: goto out;
173: }
174: /* signed H */
175: if ((r = sshpkt_get_bignum2(ssh, dh_server_pub)) != 0 ||
176: (r = sshpkt_get_string(ssh, &signature, &slen)) != 0 ||
177: (r = sshpkt_get_end(ssh)) != 0)
178: goto out;
1.1 markus 179: #ifdef DEBUG_KEXDH
180: fprintf(stderr, "dh_server_pub= ");
181: BN_print_fp(stderr, dh_server_pub);
182: fprintf(stderr, "\n");
183: debug("bits %d", BN_num_bits(dh_server_pub));
184: #endif
1.19 markus 185: if (!dh_pub_is_valid(kex->dh, dh_server_pub)) {
186: sshpkt_disconnect(ssh, "bad server public DH value");
187: r = SSH_ERR_MESSAGE_INCOMPLETE;
188: goto out;
189: }
1.1 markus 190:
1.19 markus 191: klen = DH_size(kex->dh);
192: if ((kbuf = malloc(klen)) == NULL ||
193: (shared_secret = BN_new()) == NULL) {
194: r = SSH_ERR_ALLOC_FAIL;
195: goto out;
196: }
197: if ((kout = DH_compute_key(kbuf, dh_server_pub, kex->dh)) < 0 ||
198: BN_bin2bn(kbuf, kout, shared_secret) == NULL) {
199: r = SSH_ERR_LIBCRYPTO_ERROR;
200: goto out;
201: }
1.1 markus 202: #ifdef DEBUG_KEXDH
203: dump_digest("shared secret", kbuf, kout);
204: #endif
1.19 markus 205: if (ssh->compat & SSH_OLD_DHGEX)
206: kex->min = kex->max = -1;
1.1 markus 207:
208: /* calc and verify H */
1.19 markus 209: hashlen = sizeof(hash);
210: if ((r = kexgex_hash(
1.14 djm 211: kex->hash_alg,
1.1 markus 212: kex->client_version_string,
213: kex->server_version_string,
1.19 markus 214: sshbuf_ptr(kex->my), sshbuf_len(kex->my),
215: sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
1.1 markus 216: server_host_key_blob, sbloblen,
1.19 markus 217: kex->min, kex->nbits, kex->max,
218: kex->dh->p, kex->dh->g,
219: kex->dh->pub_key,
1.1 markus 220: dh_server_pub,
1.3 djm 221: shared_secret,
1.19 markus 222: hash, &hashlen)) != 0)
223: goto out;
1.3 djm 224:
1.19 markus 225: if ((r = sshkey_verify(server_host_key, signature, slen, hash,
1.26 djm 226: hashlen, kex->hostkey_alg, ssh->compat)) != 0)
1.19 markus 227: goto out;
1.1 markus 228:
229: /* save session id */
230: if (kex->session_id == NULL) {
1.3 djm 231: kex->session_id_len = hashlen;
1.19 markus 232: kex->session_id = malloc(kex->session_id_len);
233: if (kex->session_id == NULL) {
234: r = SSH_ERR_ALLOC_FAIL;
235: goto out;
236: }
1.1 markus 237: memcpy(kex->session_id, hash, kex->session_id_len);
238: }
239:
1.19 markus 240: if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0)
241: r = kex_send_newkeys(ssh);
242: out:
243: explicit_bzero(hash, sizeof(hash));
244: DH_free(kex->dh);
245: kex->dh = NULL;
1.27 ! jsing 246: BN_clear_free(dh_server_pub);
1.19 markus 247: if (kbuf) {
248: explicit_bzero(kbuf, klen);
249: free(kbuf);
250: }
1.27 ! jsing 251: BN_clear_free(shared_secret);
1.19 markus 252: sshkey_free(server_host_key);
253: free(server_host_key_blob);
254: free(signature);
255: return r;
1.1 markus 256: }
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