Annotation of src/usr.bin/ssh/kexgexc.c, Revision 1.24
1.24 ! djm 1: /* $OpenBSD: kexgexc.c,v 1.23 2016/09/12 01:22:38 deraadt 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:
1.19 markus 49: static int input_kex_dh_gex_group(int, u_int32_t, void *);
50: static int input_kex_dh_gex_reply(int, u_int32_t, void *);
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
87: input_kex_dh_gex_group(int type, u_int32_t seq, void *ctxt)
88: {
89: struct ssh *ssh = ctxt;
90: struct kex *kex = ssh->kex;
91: BIGNUM *p = NULL, *g = NULL;
92: int r, bits;
1.1 markus 93:
1.19 markus 94: debug("got SSH2_MSG_KEX_DH_GEX_GROUP");
1.1 markus 95:
1.19 markus 96: if ((p = BN_new()) == NULL ||
97: (g = BN_new()) == NULL) {
98: r = SSH_ERR_ALLOC_FAIL;
99: goto out;
100: }
101: if ((r = sshpkt_get_bignum2(ssh, p)) != 0 ||
102: (r = sshpkt_get_bignum2(ssh, g)) != 0 ||
103: (r = sshpkt_get_end(ssh)) != 0)
104: goto out;
105: if ((bits = BN_num_bits(p)) < 0 ||
106: (u_int)bits < kex->min || (u_int)bits > kex->max) {
107: r = SSH_ERR_DH_GEX_OUT_OF_RANGE;
108: goto out;
109: }
110: if ((kex->dh = dh_new_group(g, p)) == NULL) {
111: r = SSH_ERR_ALLOC_FAIL;
112: goto out;
113: }
114: p = g = NULL; /* belong to kex->dh now */
1.1 markus 115:
1.19 markus 116: /* generate and send 'e', client DH public key */
117: if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0 ||
118: (r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_INIT)) != 0 ||
119: (r = sshpkt_put_bignum2(ssh, kex->dh->pub_key)) != 0 ||
120: (r = sshpkt_send(ssh)) != 0)
121: goto out;
122: debug("SSH2_MSG_KEX_DH_GEX_INIT sent");
1.1 markus 123: #ifdef DEBUG_KEXDH
1.19 markus 124: DHparams_print_fp(stderr, kex->dh);
1.1 markus 125: fprintf(stderr, "pub= ");
1.19 markus 126: BN_print_fp(stderr, kex->dh->pub_key);
1.1 markus 127: fprintf(stderr, "\n");
128: #endif
1.19 markus 129: ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_GROUP, NULL);
130: ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_REPLY, &input_kex_dh_gex_reply);
131: r = 0;
132: out:
133: if (p)
134: BN_clear_free(p);
135: if (g)
136: BN_clear_free(g);
137: return r;
138: }
1.1 markus 139:
1.19 markus 140: static int
141: input_kex_dh_gex_reply(int type, u_int32_t seq, void *ctxt)
142: {
143: struct ssh *ssh = ctxt;
144: struct kex *kex = ssh->kex;
145: BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
146: struct sshkey *server_host_key = NULL;
147: u_char *kbuf = NULL, *signature = NULL, *server_host_key_blob = NULL;
148: u_char hash[SSH_DIGEST_MAX_LENGTH];
149: size_t klen = 0, slen, sbloblen, hashlen;
150: int kout, r;
151:
152: debug("got SSH2_MSG_KEX_DH_GEX_REPLY");
153: if (kex->verify_host_key == NULL) {
154: r = SSH_ERR_INVALID_ARGUMENT;
155: goto out;
156: }
1.1 markus 157: /* key, cert */
1.19 markus 158: if ((r = sshpkt_get_string(ssh, &server_host_key_blob,
159: &sbloblen)) != 0 ||
160: (r = sshkey_from_blob(server_host_key_blob, sbloblen,
161: &server_host_key)) != 0)
162: goto out;
1.20 djm 163: if (server_host_key->type != kex->hostkey_type ||
164: (kex->hostkey_type == KEY_ECDSA &&
165: server_host_key->ecdsa_nid != kex->hostkey_nid)) {
1.19 markus 166: r = SSH_ERR_KEY_TYPE_MISMATCH;
167: goto out;
168: }
169: if (kex->verify_host_key(server_host_key, ssh) == -1) {
170: r = SSH_ERR_SIGNATURE_INVALID;
171: goto out;
172: }
1.6 miod 173: /* DH parameter f, server public DH key */
1.19 markus 174: if ((dh_server_pub = BN_new()) == NULL) {
175: r = SSH_ERR_ALLOC_FAIL;
176: goto out;
177: }
178: /* signed H */
179: if ((r = sshpkt_get_bignum2(ssh, dh_server_pub)) != 0 ||
180: (r = sshpkt_get_string(ssh, &signature, &slen)) != 0 ||
181: (r = sshpkt_get_end(ssh)) != 0)
182: goto out;
1.1 markus 183: #ifdef DEBUG_KEXDH
184: fprintf(stderr, "dh_server_pub= ");
185: BN_print_fp(stderr, dh_server_pub);
186: fprintf(stderr, "\n");
187: debug("bits %d", BN_num_bits(dh_server_pub));
188: #endif
1.19 markus 189: if (!dh_pub_is_valid(kex->dh, dh_server_pub)) {
190: sshpkt_disconnect(ssh, "bad server public DH value");
191: r = SSH_ERR_MESSAGE_INCOMPLETE;
192: goto out;
193: }
1.1 markus 194:
1.19 markus 195: klen = DH_size(kex->dh);
196: if ((kbuf = malloc(klen)) == NULL ||
197: (shared_secret = BN_new()) == NULL) {
198: r = SSH_ERR_ALLOC_FAIL;
199: goto out;
200: }
201: if ((kout = DH_compute_key(kbuf, dh_server_pub, kex->dh)) < 0 ||
202: BN_bin2bn(kbuf, kout, shared_secret) == NULL) {
203: r = SSH_ERR_LIBCRYPTO_ERROR;
204: goto out;
205: }
1.1 markus 206: #ifdef DEBUG_KEXDH
207: dump_digest("shared secret", kbuf, kout);
208: #endif
1.19 markus 209: if (ssh->compat & SSH_OLD_DHGEX)
210: kex->min = kex->max = -1;
1.1 markus 211:
212: /* calc and verify H */
1.19 markus 213: hashlen = sizeof(hash);
214: if ((r = kexgex_hash(
1.14 djm 215: kex->hash_alg,
1.1 markus 216: kex->client_version_string,
217: kex->server_version_string,
1.19 markus 218: sshbuf_ptr(kex->my), sshbuf_len(kex->my),
219: sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
1.1 markus 220: server_host_key_blob, sbloblen,
1.19 markus 221: kex->min, kex->nbits, kex->max,
222: kex->dh->p, kex->dh->g,
223: kex->dh->pub_key,
1.1 markus 224: dh_server_pub,
1.3 djm 225: shared_secret,
1.19 markus 226: hash, &hashlen)) != 0)
227: goto out;
1.3 djm 228:
1.19 markus 229: if ((r = sshkey_verify(server_host_key, signature, slen, hash,
230: hashlen, ssh->compat)) != 0)
231: goto out;
1.1 markus 232:
233: /* save session id */
234: if (kex->session_id == NULL) {
1.3 djm 235: kex->session_id_len = hashlen;
1.19 markus 236: kex->session_id = malloc(kex->session_id_len);
237: if (kex->session_id == NULL) {
238: r = SSH_ERR_ALLOC_FAIL;
239: goto out;
240: }
1.1 markus 241: memcpy(kex->session_id, hash, kex->session_id_len);
242: }
243:
1.19 markus 244: if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0)
245: r = kex_send_newkeys(ssh);
246: out:
247: explicit_bzero(hash, sizeof(hash));
248: DH_free(kex->dh);
249: kex->dh = NULL;
250: if (dh_server_pub)
251: BN_clear_free(dh_server_pub);
252: if (kbuf) {
253: explicit_bzero(kbuf, klen);
254: free(kbuf);
255: }
256: if (shared_secret)
257: BN_clear_free(shared_secret);
258: sshkey_free(server_host_key);
259: free(server_host_key_blob);
260: free(signature);
261: return r;
1.1 markus 262: }
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