Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 1 | /* $OpenBSD: kexgexs.c,v 1.24 2015/01/26 06:10:03 djm Exp $ */ |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 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 | |
| 27 | #include "includes.h" |
| 28 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 29 | #ifdef WITH_OPENSSL |
| 30 | |
| 31 | #include <sys/param.h> /* MIN MAX */ |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 32 | |
| 33 | #include <stdarg.h> |
| 34 | #include <stdio.h> |
| 35 | #include <string.h> |
| 36 | #include <signal.h> |
| 37 | |
| 38 | #include <openssl/dh.h> |
| 39 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 40 | #include "sshkey.h" |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 41 | #include "cipher.h" |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 42 | #include "digest.h" |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 43 | #include "kex.h" |
| 44 | #include "log.h" |
| 45 | #include "packet.h" |
| 46 | #include "dh.h" |
| 47 | #include "ssh2.h" |
| 48 | #include "compat.h" |
| 49 | #ifdef GSSAPI |
| 50 | #include "ssh-gss.h" |
| 51 | #endif |
| 52 | #include "monitor_wrap.h" |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 53 | #include "dispatch.h" |
| 54 | #include "ssherr.h" |
| 55 | #include "sshbuf.h" |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 56 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 57 | static int input_kex_dh_gex_request(int, u_int32_t, void *); |
| 58 | static int input_kex_dh_gex_init(int, u_int32_t, void *); |
| 59 | |
| 60 | int |
| 61 | kexgex_server(struct ssh *ssh) |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 62 | { |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 63 | ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_REQUEST_OLD, |
| 64 | &input_kex_dh_gex_request); |
| 65 | ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_REQUEST, |
| 66 | &input_kex_dh_gex_request); |
| 67 | debug("expecting SSH2_MSG_KEX_DH_GEX_REQUEST"); |
| 68 | return 0; |
| 69 | } |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 70 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 71 | static int |
| 72 | input_kex_dh_gex_request(int type, u_int32_t seq, void *ctxt) |
| 73 | { |
| 74 | struct ssh *ssh = ctxt; |
| 75 | struct kex *kex = ssh->kex; |
| 76 | int r; |
| 77 | u_int min = 0, max = 0, nbits = 0; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 78 | |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 79 | switch (type) { |
| 80 | case SSH2_MSG_KEX_DH_GEX_REQUEST: |
| 81 | debug("SSH2_MSG_KEX_DH_GEX_REQUEST received"); |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 82 | if ((r = sshpkt_get_u32(ssh, &min)) != 0 || |
| 83 | (r = sshpkt_get_u32(ssh, &nbits)) != 0 || |
| 84 | (r = sshpkt_get_u32(ssh, &max)) != 0 || |
| 85 | (r = sshpkt_get_end(ssh)) != 0) |
| 86 | goto out; |
| 87 | kex->nbits = nbits; |
| 88 | kex->min = min; |
| 89 | kex->max = max; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 90 | min = MAX(DH_GRP_MIN, min); |
| 91 | max = MIN(DH_GRP_MAX, max); |
| 92 | nbits = MAX(DH_GRP_MIN, nbits); |
| 93 | nbits = MIN(DH_GRP_MAX, nbits); |
| 94 | break; |
| 95 | case SSH2_MSG_KEX_DH_GEX_REQUEST_OLD: |
| 96 | debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD received"); |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 97 | if ((r = sshpkt_get_u32(ssh, &nbits)) != 0 || |
| 98 | (r = sshpkt_get_end(ssh)) != 0) |
| 99 | goto out; |
| 100 | kex->nbits = nbits; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 101 | /* unused for old GEX */ |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 102 | kex->min = min = DH_GRP_MIN; |
| 103 | kex->max = max = DH_GRP_MAX; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 104 | break; |
| 105 | default: |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 106 | r = SSH_ERR_INVALID_ARGUMENT; |
| 107 | goto out; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 108 | } |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 109 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 110 | if (kex->max < kex->min || kex->nbits < kex->min || |
| 111 | kex->max < kex->nbits) { |
| 112 | r = SSH_ERR_DH_GEX_OUT_OF_RANGE; |
| 113 | goto out; |
| 114 | } |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 115 | |
| 116 | /* Contact privileged parent */ |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 117 | kex->dh = PRIVSEP(choose_dh(min, nbits, max)); |
| 118 | if (kex->dh == NULL) { |
| 119 | sshpkt_disconnect(ssh, "no matching DH grp found"); |
| 120 | r = SSH_ERR_ALLOC_FAIL; |
| 121 | goto out; |
| 122 | } |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 123 | debug("SSH2_MSG_KEX_DH_GEX_GROUP sent"); |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 124 | if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_GROUP)) != 0 || |
| 125 | (r = sshpkt_put_bignum2(ssh, kex->dh->p)) != 0 || |
| 126 | (r = sshpkt_put_bignum2(ssh, kex->dh->g)) != 0 || |
| 127 | (r = sshpkt_send(ssh)) != 0) |
| 128 | goto out; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 129 | |
| 130 | /* Compute our exchange value in parallel with the client */ |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 131 | if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0) |
| 132 | goto out; |
| 133 | |
| 134 | /* old KEX does not use min/max in kexgex_hash() */ |
| 135 | if (type == SSH2_MSG_KEX_DH_GEX_REQUEST_OLD) |
| 136 | kex->min = kex->max = -1; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 137 | |
| 138 | debug("expecting SSH2_MSG_KEX_DH_GEX_INIT"); |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 139 | ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_INIT, &input_kex_dh_gex_init); |
| 140 | r = 0; |
| 141 | out: |
| 142 | return r; |
| 143 | } |
| 144 | |
| 145 | static int |
| 146 | input_kex_dh_gex_init(int type, u_int32_t seq, void *ctxt) |
| 147 | { |
| 148 | struct ssh *ssh = ctxt; |
| 149 | struct kex *kex = ssh->kex; |
| 150 | BIGNUM *shared_secret = NULL, *dh_client_pub = NULL; |
| 151 | struct sshkey *server_host_public, *server_host_private; |
| 152 | u_char *kbuf = NULL, *signature = NULL, *server_host_key_blob = NULL; |
| 153 | u_char hash[SSH_DIGEST_MAX_LENGTH]; |
| 154 | size_t sbloblen, slen; |
| 155 | size_t klen = 0, hashlen; |
| 156 | int kout, r; |
| 157 | |
| 158 | if (kex->load_host_public_key == NULL || |
| 159 | kex->load_host_private_key == NULL) { |
| 160 | r = SSH_ERR_INVALID_ARGUMENT; |
| 161 | goto out; |
| 162 | } |
| 163 | server_host_public = kex->load_host_public_key(kex->hostkey_type, |
| 164 | kex->hostkey_nid, ssh); |
| 165 | server_host_private = kex->load_host_private_key(kex->hostkey_type, |
| 166 | kex->hostkey_nid, ssh); |
| 167 | if (server_host_public == NULL) { |
| 168 | r = SSH_ERR_NO_HOSTKEY_LOADED; |
| 169 | goto out; |
| 170 | } |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 171 | |
| 172 | /* key, cert */ |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 173 | if ((dh_client_pub = BN_new()) == NULL) { |
| 174 | r = SSH_ERR_ALLOC_FAIL; |
| 175 | goto out; |
| 176 | } |
| 177 | if ((r = sshpkt_get_bignum2(ssh, dh_client_pub)) != 0 || |
| 178 | (r = sshpkt_get_end(ssh)) != 0) |
| 179 | goto out; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 180 | |
| 181 | #ifdef DEBUG_KEXDH |
| 182 | fprintf(stderr, "dh_client_pub= "); |
| 183 | BN_print_fp(stderr, dh_client_pub); |
| 184 | fprintf(stderr, "\n"); |
| 185 | debug("bits %d", BN_num_bits(dh_client_pub)); |
| 186 | #endif |
| 187 | |
| 188 | #ifdef DEBUG_KEXDH |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 189 | DHparams_print_fp(stderr, kex->dh); |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 190 | fprintf(stderr, "pub= "); |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 191 | BN_print_fp(stderr, kex->dh->pub_key); |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 192 | fprintf(stderr, "\n"); |
| 193 | #endif |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 194 | if (!dh_pub_is_valid(kex->dh, dh_client_pub)) { |
| 195 | sshpkt_disconnect(ssh, "bad client public DH value"); |
| 196 | r = SSH_ERR_MESSAGE_INCOMPLETE; |
| 197 | goto out; |
| 198 | } |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 199 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 200 | klen = DH_size(kex->dh); |
| 201 | if ((kbuf = malloc(klen)) == NULL || |
| 202 | (shared_secret = BN_new()) == NULL) { |
| 203 | r = SSH_ERR_ALLOC_FAIL; |
| 204 | goto out; |
| 205 | } |
| 206 | if ((kout = DH_compute_key(kbuf, dh_client_pub, kex->dh)) < 0 || |
| 207 | BN_bin2bn(kbuf, kout, shared_secret) == NULL) { |
| 208 | r = SSH_ERR_LIBCRYPTO_ERROR; |
| 209 | goto out; |
| 210 | } |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 211 | #ifdef DEBUG_KEXDH |
| 212 | dump_digest("shared secret", kbuf, kout); |
| 213 | #endif |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 214 | if ((r = sshkey_to_blob(server_host_public, &server_host_key_blob, |
| 215 | &sbloblen)) != 0) |
| 216 | goto out; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 217 | /* calc H */ |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 218 | hashlen = sizeof(hash); |
| 219 | if ((r = kexgex_hash( |
| 220 | kex->hash_alg, |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 221 | kex->client_version_string, |
| 222 | kex->server_version_string, |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 223 | sshbuf_ptr(kex->peer), sshbuf_len(kex->peer), |
| 224 | sshbuf_ptr(kex->my), sshbuf_len(kex->my), |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 225 | server_host_key_blob, sbloblen, |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 226 | kex->min, kex->nbits, kex->max, |
| 227 | kex->dh->p, kex->dh->g, |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 228 | dh_client_pub, |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 229 | kex->dh->pub_key, |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 230 | shared_secret, |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 231 | hash, &hashlen)) != 0) |
| 232 | goto out; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 233 | |
| 234 | /* save session id := H */ |
| 235 | if (kex->session_id == NULL) { |
| 236 | kex->session_id_len = hashlen; |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 237 | kex->session_id = malloc(kex->session_id_len); |
| 238 | if (kex->session_id == NULL) { |
| 239 | r = SSH_ERR_ALLOC_FAIL; |
| 240 | goto out; |
| 241 | } |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 242 | memcpy(kex->session_id, hash, kex->session_id_len); |
| 243 | } |
| 244 | |
| 245 | /* sign H */ |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 246 | if ((r = kex->sign(server_host_private, server_host_public, |
| 247 | &signature, &slen, hash, hashlen, ssh->compat)) < 0) |
| 248 | goto out; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 249 | |
| 250 | /* destroy_sensitive_data(); */ |
| 251 | |
| 252 | /* send server hostkey, DH pubkey 'f' and singed H */ |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 253 | if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_REPLY)) != 0 || |
| 254 | (r = sshpkt_put_string(ssh, server_host_key_blob, sbloblen)) != 0 || |
| 255 | (r = sshpkt_put_bignum2(ssh, kex->dh->pub_key)) != 0 || /* f */ |
| 256 | (r = sshpkt_put_string(ssh, signature, slen)) != 0 || |
| 257 | (r = sshpkt_send(ssh)) != 0) |
| 258 | goto out; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 259 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 260 | if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0) |
| 261 | r = kex_send_newkeys(ssh); |
| 262 | out: |
| 263 | DH_free(kex->dh); |
| 264 | kex->dh = NULL; |
| 265 | if (dh_client_pub) |
| 266 | BN_clear_free(dh_client_pub); |
| 267 | if (kbuf) { |
| 268 | explicit_bzero(kbuf, klen); |
| 269 | free(kbuf); |
| 270 | } |
| 271 | if (shared_secret) |
| 272 | BN_clear_free(shared_secret); |
| 273 | free(server_host_key_blob); |
| 274 | free(signature); |
| 275 | return r; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 276 | } |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 277 | #endif /* WITH_OPENSSL */ |