Damien Miller | eba71ba | 2000-04-29 23:57:08 +1000 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (c) 2000 Markus Friedl. All rights reserved. |
| 3 | * |
| 4 | * Redistribution and use in source and binary forms, with or without |
| 5 | * modification, are permitted provided that the following conditions |
| 6 | * are met: |
| 7 | * 1. Redistributions of source code must retain the above copyright |
| 8 | * notice, this list of conditions and the following disclaimer. |
| 9 | * 2. Redistributions in binary form must reproduce the above copyright |
| 10 | * notice, this list of conditions and the following disclaimer in the |
| 11 | * documentation and/or other materials provided with the distribution. |
| 12 | * 3. All advertising materials mentioning features or use of this software |
| 13 | * must display the following acknowledgement: |
| 14 | * This product includes software developed by Markus Friedl. |
| 15 | * 4. The name of the author may not be used to endorse or promote products |
| 16 | * derived from this software without specific prior written permission. |
| 17 | * |
| 18 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
| 19 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
| 20 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
| 21 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
| 22 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
| 23 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| 24 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| 25 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| 26 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
| 27 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| 28 | */ |
| 29 | |
| 30 | #include "includes.h" |
Damien Miller | 6d48871 | 2000-05-08 13:44:52 +1000 | [diff] [blame] | 31 | RCSID("$OpenBSD: sshconnect2.c,v 1.8 2000/05/07 18:23:32 markus Exp $"); |
Damien Miller | eba71ba | 2000-04-29 23:57:08 +1000 | [diff] [blame] | 32 | |
| 33 | #include <openssl/bn.h> |
| 34 | #include <openssl/rsa.h> |
| 35 | #include <openssl/dsa.h> |
| 36 | #include <openssl/md5.h> |
| 37 | #include <openssl/dh.h> |
| 38 | #include <openssl/hmac.h> |
| 39 | |
| 40 | #include "ssh.h" |
| 41 | #include "xmalloc.h" |
| 42 | #include "rsa.h" |
| 43 | #include "buffer.h" |
| 44 | #include "packet.h" |
| 45 | #include "cipher.h" |
| 46 | #include "uidswap.h" |
| 47 | #include "compat.h" |
| 48 | #include "readconf.h" |
| 49 | #include "bufaux.h" |
| 50 | #include "ssh2.h" |
| 51 | #include "kex.h" |
| 52 | #include "myproposal.h" |
| 53 | #include "key.h" |
| 54 | #include "dsa.h" |
| 55 | #include "sshconnect.h" |
| 56 | #include "authfile.h" |
| 57 | |
| 58 | /* import */ |
| 59 | extern char *client_version_string; |
| 60 | extern char *server_version_string; |
| 61 | extern Options options; |
| 62 | |
| 63 | /* |
| 64 | * SSH2 key exchange |
| 65 | */ |
| 66 | |
| 67 | unsigned char *session_id2 = NULL; |
| 68 | int session_id2_len = 0; |
| 69 | |
| 70 | void |
| 71 | ssh_kex2(char *host, struct sockaddr *hostaddr) |
| 72 | { |
| 73 | Kex *kex; |
| 74 | char *cprop[PROPOSAL_MAX]; |
| 75 | char *sprop[PROPOSAL_MAX]; |
| 76 | Buffer *client_kexinit; |
| 77 | Buffer *server_kexinit; |
| 78 | int payload_len, dlen; |
| 79 | unsigned int klen, kout; |
| 80 | char *ptr; |
| 81 | char *signature = NULL; |
| 82 | unsigned int slen; |
| 83 | char *server_host_key_blob = NULL; |
| 84 | Key *server_host_key; |
| 85 | unsigned int sbloblen; |
| 86 | DH *dh; |
| 87 | BIGNUM *dh_server_pub = 0; |
| 88 | BIGNUM *shared_secret = 0; |
| 89 | int i; |
| 90 | unsigned char *kbuf; |
| 91 | unsigned char *hash; |
| 92 | |
| 93 | /* KEXINIT */ |
| 94 | |
| 95 | debug("Sending KEX init."); |
| 96 | if (options.ciphers != NULL) { |
| 97 | myproposal[PROPOSAL_ENC_ALGS_CTOS] = |
| 98 | myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers; |
| 99 | } else if ( |
| 100 | options.cipher == SSH_CIPHER_ARCFOUR || |
| 101 | options.cipher == SSH_CIPHER_3DES_CBC || |
| 102 | options.cipher == SSH_CIPHER_CAST128_CBC || |
| 103 | options.cipher == SSH_CIPHER_BLOWFISH_CBC) { |
| 104 | myproposal[PROPOSAL_ENC_ALGS_CTOS] = |
| 105 | myproposal[PROPOSAL_ENC_ALGS_STOC] = cipher_name(options.cipher); |
| 106 | } |
| 107 | if (options.compression) { |
| 108 | myproposal[PROPOSAL_COMP_ALGS_CTOS] = "zlib"; |
| 109 | myproposal[PROPOSAL_COMP_ALGS_STOC] = "zlib"; |
| 110 | } else { |
| 111 | myproposal[PROPOSAL_COMP_ALGS_CTOS] = "none"; |
| 112 | myproposal[PROPOSAL_COMP_ALGS_STOC] = "none"; |
| 113 | } |
| 114 | for (i = 0; i < PROPOSAL_MAX; i++) |
| 115 | cprop[i] = xstrdup(myproposal[i]); |
| 116 | |
| 117 | client_kexinit = kex_init(cprop); |
| 118 | packet_start(SSH2_MSG_KEXINIT); |
| 119 | packet_put_raw(buffer_ptr(client_kexinit), buffer_len(client_kexinit)); |
| 120 | packet_send(); |
| 121 | packet_write_wait(); |
| 122 | |
| 123 | debug("done"); |
| 124 | |
| 125 | packet_read_expect(&payload_len, SSH2_MSG_KEXINIT); |
| 126 | |
| 127 | /* save payload for session_id */ |
| 128 | server_kexinit = xmalloc(sizeof(*server_kexinit)); |
| 129 | buffer_init(server_kexinit); |
| 130 | ptr = packet_get_raw(&payload_len); |
| 131 | buffer_append(server_kexinit, ptr, payload_len); |
| 132 | |
| 133 | /* skip cookie */ |
| 134 | for (i = 0; i < 16; i++) |
| 135 | (void) packet_get_char(); |
| 136 | /* kex init proposal strings */ |
| 137 | for (i = 0; i < PROPOSAL_MAX; i++) { |
| 138 | sprop[i] = packet_get_string(NULL); |
| 139 | debug("got kexinit string: %s", sprop[i]); |
| 140 | } |
| 141 | i = (int) packet_get_char(); |
| 142 | debug("first kex follow == %d", i); |
| 143 | i = packet_get_int(); |
| 144 | debug("reserved == %d", i); |
| 145 | packet_done(); |
| 146 | |
| 147 | debug("done read kexinit"); |
| 148 | kex = kex_choose_conf(cprop, sprop, 0); |
| 149 | |
| 150 | /* KEXDH */ |
| 151 | |
| 152 | debug("Sending SSH2_MSG_KEXDH_INIT."); |
| 153 | |
| 154 | /* generate and send 'e', client DH public key */ |
| 155 | dh = dh_new_group1(); |
| 156 | packet_start(SSH2_MSG_KEXDH_INIT); |
| 157 | packet_put_bignum2(dh->pub_key); |
| 158 | packet_send(); |
| 159 | packet_write_wait(); |
| 160 | |
| 161 | #ifdef DEBUG_KEXDH |
| 162 | fprintf(stderr, "\np= "); |
| 163 | bignum_print(dh->p); |
| 164 | fprintf(stderr, "\ng= "); |
| 165 | bignum_print(dh->g); |
| 166 | fprintf(stderr, "\npub= "); |
| 167 | bignum_print(dh->pub_key); |
| 168 | fprintf(stderr, "\n"); |
| 169 | DHparams_print_fp(stderr, dh); |
| 170 | #endif |
| 171 | |
| 172 | debug("Wait SSH2_MSG_KEXDH_REPLY."); |
| 173 | |
| 174 | packet_read_expect(&payload_len, SSH2_MSG_KEXDH_REPLY); |
| 175 | |
| 176 | debug("Got SSH2_MSG_KEXDH_REPLY."); |
| 177 | |
| 178 | /* key, cert */ |
| 179 | server_host_key_blob = packet_get_string(&sbloblen); |
| 180 | server_host_key = dsa_key_from_blob(server_host_key_blob, sbloblen); |
| 181 | if (server_host_key == NULL) |
| 182 | fatal("cannot decode server_host_key_blob"); |
| 183 | |
| 184 | check_host_key(host, hostaddr, server_host_key, |
| 185 | options.user_hostfile2, options.system_hostfile2); |
| 186 | |
| 187 | /* DH paramter f, server public DH key */ |
| 188 | dh_server_pub = BN_new(); |
| 189 | if (dh_server_pub == NULL) |
| 190 | fatal("dh_server_pub == NULL"); |
| 191 | packet_get_bignum2(dh_server_pub, &dlen); |
| 192 | |
| 193 | #ifdef DEBUG_KEXDH |
| 194 | fprintf(stderr, "\ndh_server_pub= "); |
| 195 | bignum_print(dh_server_pub); |
| 196 | fprintf(stderr, "\n"); |
| 197 | debug("bits %d", BN_num_bits(dh_server_pub)); |
| 198 | #endif |
| 199 | |
| 200 | /* signed H */ |
| 201 | signature = packet_get_string(&slen); |
| 202 | packet_done(); |
| 203 | |
| 204 | if (!dh_pub_is_valid(dh, dh_server_pub)) |
| 205 | packet_disconnect("bad server public DH value"); |
| 206 | |
| 207 | klen = DH_size(dh); |
| 208 | kbuf = xmalloc(klen); |
| 209 | kout = DH_compute_key(kbuf, dh_server_pub, dh); |
| 210 | #ifdef DEBUG_KEXDH |
| 211 | debug("shared secret: len %d/%d", klen, kout); |
| 212 | fprintf(stderr, "shared secret == "); |
| 213 | for (i = 0; i< kout; i++) |
| 214 | fprintf(stderr, "%02x", (kbuf[i])&0xff); |
| 215 | fprintf(stderr, "\n"); |
| 216 | #endif |
| 217 | shared_secret = BN_new(); |
| 218 | |
| 219 | BN_bin2bn(kbuf, kout, shared_secret); |
| 220 | memset(kbuf, 0, klen); |
| 221 | xfree(kbuf); |
| 222 | |
| 223 | /* calc and verify H */ |
| 224 | hash = kex_hash( |
| 225 | client_version_string, |
| 226 | server_version_string, |
| 227 | buffer_ptr(client_kexinit), buffer_len(client_kexinit), |
| 228 | buffer_ptr(server_kexinit), buffer_len(server_kexinit), |
| 229 | server_host_key_blob, sbloblen, |
| 230 | dh->pub_key, |
| 231 | dh_server_pub, |
| 232 | shared_secret |
| 233 | ); |
| 234 | xfree(server_host_key_blob); |
| 235 | buffer_free(client_kexinit); |
| 236 | buffer_free(server_kexinit); |
| 237 | xfree(client_kexinit); |
| 238 | xfree(server_kexinit); |
| 239 | #ifdef DEBUG_KEXDH |
| 240 | fprintf(stderr, "hash == "); |
| 241 | for (i = 0; i< 20; i++) |
| 242 | fprintf(stderr, "%02x", (hash[i])&0xff); |
| 243 | fprintf(stderr, "\n"); |
| 244 | #endif |
| 245 | if (dsa_verify(server_host_key, (unsigned char *)signature, slen, hash, 20) != 1) |
| 246 | fatal("dsa_verify failed for server_host_key"); |
| 247 | key_free(server_host_key); |
| 248 | |
| 249 | kex_derive_keys(kex, hash, shared_secret); |
| 250 | packet_set_kex(kex); |
| 251 | |
| 252 | /* have keys, free DH */ |
| 253 | DH_free(dh); |
| 254 | |
| 255 | /* save session id */ |
| 256 | session_id2_len = 20; |
| 257 | session_id2 = xmalloc(session_id2_len); |
| 258 | memcpy(session_id2, hash, session_id2_len); |
| 259 | |
| 260 | debug("Wait SSH2_MSG_NEWKEYS."); |
| 261 | packet_read_expect(&payload_len, SSH2_MSG_NEWKEYS); |
| 262 | packet_done(); |
| 263 | debug("GOT SSH2_MSG_NEWKEYS."); |
| 264 | |
| 265 | debug("send SSH2_MSG_NEWKEYS."); |
| 266 | packet_start(SSH2_MSG_NEWKEYS); |
| 267 | packet_send(); |
| 268 | packet_write_wait(); |
| 269 | debug("done: send SSH2_MSG_NEWKEYS."); |
| 270 | |
| 271 | #ifdef DEBUG_KEXDH |
| 272 | /* send 1st encrypted/maced/compressed message */ |
| 273 | packet_start(SSH2_MSG_IGNORE); |
| 274 | packet_put_cstring("markus"); |
| 275 | packet_send(); |
| 276 | packet_write_wait(); |
| 277 | #endif |
| 278 | debug("done: KEX2."); |
| 279 | } |
| 280 | /* |
| 281 | * Authenticate user |
| 282 | */ |
| 283 | int |
| 284 | ssh2_try_passwd(const char *server_user, const char *host, const char *service) |
| 285 | { |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 286 | static int attempt = 0; |
Damien Miller | eba71ba | 2000-04-29 23:57:08 +1000 | [diff] [blame] | 287 | char prompt[80]; |
| 288 | char *password; |
| 289 | |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 290 | if (attempt++ > options.number_of_password_prompts) |
| 291 | return 0; |
| 292 | |
Damien Miller | eba71ba | 2000-04-29 23:57:08 +1000 | [diff] [blame] | 293 | snprintf(prompt, sizeof(prompt), "%.30s@%.40s's password: ", |
| 294 | server_user, host); |
| 295 | password = read_passphrase(prompt, 0); |
| 296 | packet_start(SSH2_MSG_USERAUTH_REQUEST); |
| 297 | packet_put_cstring(server_user); |
| 298 | packet_put_cstring(service); |
| 299 | packet_put_cstring("password"); |
| 300 | packet_put_char(0); |
| 301 | packet_put_cstring(password); |
| 302 | memset(password, 0, strlen(password)); |
| 303 | xfree(password); |
| 304 | packet_send(); |
| 305 | packet_write_wait(); |
| 306 | return 1; |
| 307 | } |
| 308 | |
| 309 | int |
| 310 | ssh2_try_pubkey(char *filename, |
| 311 | const char *server_user, const char *host, const char *service) |
| 312 | { |
| 313 | Buffer b; |
| 314 | Key *k; |
| 315 | unsigned char *blob, *signature; |
| 316 | int bloblen, slen; |
Damien Miller | 6f83b8e | 2000-05-02 09:23:45 +1000 | [diff] [blame] | 317 | struct stat st; |
Damien Miller | eba71ba | 2000-04-29 23:57:08 +1000 | [diff] [blame] | 318 | |
Damien Miller | 6f83b8e | 2000-05-02 09:23:45 +1000 | [diff] [blame] | 319 | if (stat(filename, &st) != 0) { |
| 320 | debug("key does not exist: %s", filename); |
| 321 | return 0; |
| 322 | } |
Damien Miller | eba71ba | 2000-04-29 23:57:08 +1000 | [diff] [blame] | 323 | debug("try pubkey: %s", filename); |
| 324 | |
| 325 | k = key_new(KEY_DSA); |
| 326 | if (!load_private_key(filename, "", k, NULL)) { |
| 327 | int success = 0; |
| 328 | char *passphrase; |
| 329 | char prompt[300]; |
Damien Miller | 6f83b8e | 2000-05-02 09:23:45 +1000 | [diff] [blame] | 330 | snprintf(prompt, sizeof prompt, |
Damien Miller | eba71ba | 2000-04-29 23:57:08 +1000 | [diff] [blame] | 331 | "Enter passphrase for DSA key '%.100s': ", |
Damien Miller | 6f83b8e | 2000-05-02 09:23:45 +1000 | [diff] [blame] | 332 | filename); |
Damien Miller | eba71ba | 2000-04-29 23:57:08 +1000 | [diff] [blame] | 333 | passphrase = read_passphrase(prompt, 0); |
| 334 | success = load_private_key(filename, passphrase, k, NULL); |
| 335 | memset(passphrase, 0, strlen(passphrase)); |
| 336 | xfree(passphrase); |
| 337 | if (!success) |
| 338 | return 0; |
| 339 | } |
| 340 | dsa_make_key_blob(k, &blob, &bloblen); |
| 341 | |
| 342 | /* data to be signed */ |
| 343 | buffer_init(&b); |
| 344 | buffer_append(&b, session_id2, session_id2_len); |
| 345 | buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST); |
| 346 | buffer_put_cstring(&b, server_user); |
| 347 | buffer_put_cstring(&b, service); |
| 348 | buffer_put_cstring(&b, "publickey"); |
| 349 | buffer_put_char(&b, 1); |
| 350 | buffer_put_cstring(&b, KEX_DSS); |
| 351 | buffer_put_string(&b, blob, bloblen); |
| 352 | xfree(blob); |
| 353 | |
| 354 | /* generate signature */ |
| 355 | dsa_sign(k, &signature, &slen, buffer_ptr(&b), buffer_len(&b)); |
| 356 | key_free(k); |
| 357 | #ifdef DEBUG_DSS |
| 358 | buffer_dump(&b); |
| 359 | #endif |
| 360 | /* append signature */ |
| 361 | buffer_put_string(&b, signature, slen); |
| 362 | xfree(signature); |
| 363 | |
| 364 | /* skip session id and packet type */ |
| 365 | if (buffer_len(&b) < session_id2_len + 1) |
| 366 | fatal("ssh2_try_pubkey: internal error"); |
| 367 | buffer_consume(&b, session_id2_len + 1); |
| 368 | |
| 369 | /* put remaining data from buffer into packet */ |
| 370 | packet_start(SSH2_MSG_USERAUTH_REQUEST); |
| 371 | packet_put_raw(buffer_ptr(&b), buffer_len(&b)); |
| 372 | buffer_free(&b); |
| 373 | |
| 374 | /* send */ |
| 375 | packet_send(); |
| 376 | packet_write_wait(); |
| 377 | return 1; |
| 378 | } |
| 379 | |
| 380 | void |
| 381 | ssh_userauth2(const char *server_user, char *host) |
| 382 | { |
| 383 | int type; |
| 384 | int plen; |
| 385 | int sent; |
| 386 | unsigned int dlen; |
| 387 | int partial; |
| 388 | int i = 0; |
| 389 | char *auths; |
| 390 | char *service = "ssh-connection"; /* service name */ |
| 391 | |
| 392 | debug("send SSH2_MSG_SERVICE_REQUEST"); |
| 393 | packet_start(SSH2_MSG_SERVICE_REQUEST); |
| 394 | packet_put_cstring("ssh-userauth"); |
| 395 | packet_send(); |
| 396 | packet_write_wait(); |
| 397 | |
| 398 | type = packet_read(&plen); |
| 399 | if (type != SSH2_MSG_SERVICE_ACCEPT) { |
| 400 | fatal("denied SSH2_MSG_SERVICE_ACCEPT: %d", type); |
| 401 | } |
| 402 | if (packet_remaining() > 0) { |
| 403 | char *reply = packet_get_string(&plen); |
| 404 | debug("service_accept: %s", reply); |
| 405 | xfree(reply); |
| 406 | } else { |
| 407 | /* payload empty for ssh-2.0.13 ?? */ |
Damien Miller | 6d48871 | 2000-05-08 13:44:52 +1000 | [diff] [blame] | 408 | debug("buggy server: service_accept w/o service"); |
Damien Miller | eba71ba | 2000-04-29 23:57:08 +1000 | [diff] [blame] | 409 | } |
| 410 | packet_done(); |
| 411 | debug("got SSH2_MSG_SERVICE_ACCEPT"); |
| 412 | |
| 413 | /* INITIAL request for auth */ |
| 414 | packet_start(SSH2_MSG_USERAUTH_REQUEST); |
| 415 | packet_put_cstring(server_user); |
| 416 | packet_put_cstring(service); |
| 417 | packet_put_cstring("none"); |
| 418 | packet_send(); |
| 419 | packet_write_wait(); |
| 420 | |
| 421 | for (;;) { |
| 422 | sent = 0; |
| 423 | type = packet_read(&plen); |
| 424 | if (type == SSH2_MSG_USERAUTH_SUCCESS) |
| 425 | break; |
| 426 | if (type != SSH2_MSG_USERAUTH_FAILURE) |
| 427 | fatal("access denied: %d", type); |
| 428 | /* SSH2_MSG_USERAUTH_FAILURE means: try again */ |
| 429 | auths = packet_get_string(&dlen); |
| 430 | debug("authentications that can continue: %s", auths); |
| 431 | partial = packet_get_char(); |
| 432 | packet_done(); |
| 433 | if (partial) |
| 434 | debug("partial success"); |
Damien Miller | e247cc4 | 2000-05-07 12:03:14 +1000 | [diff] [blame] | 435 | if (options.dsa_authentication && |
Damien Miller | eba71ba | 2000-04-29 23:57:08 +1000 | [diff] [blame] | 436 | strstr(auths, "publickey") != NULL) { |
| 437 | while (i < options.num_identity_files2) { |
| 438 | sent = ssh2_try_pubkey( |
| 439 | options.identity_files2[i++], |
| 440 | server_user, host, service); |
| 441 | if (sent) |
| 442 | break; |
| 443 | } |
| 444 | } |
| 445 | if (!sent) { |
| 446 | if (options.password_authentication && |
| 447 | !options.batch_mode && |
| 448 | strstr(auths, "password") != NULL) { |
| 449 | sent = ssh2_try_passwd(server_user, host, service); |
| 450 | } |
| 451 | } |
| 452 | if (!sent) |
| 453 | fatal("Permission denied (%s).", auths); |
| 454 | xfree(auths); |
| 455 | } |
| 456 | packet_done(); |
| 457 | debug("ssh-userauth2 successfull"); |
| 458 | } |