sshconnect2.c revision 69588
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 * 13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 14 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 15 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 16 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 17 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 18 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 19 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 20 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 21 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 22 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 23 */ 24 25#include "includes.h" 26RCSID("$OpenBSD: sshconnect2.c,v 1.27 2000/10/19 16:45:16 provos Exp $"); 27 28#include <openssl/bn.h> 29#include <openssl/rsa.h> 30#include <openssl/dsa.h> 31#include <openssl/md5.h> 32#include <openssl/dh.h> 33#include <openssl/hmac.h> 34 35#include "ssh.h" 36#include "xmalloc.h" 37#include "rsa.h" 38#include "buffer.h" 39#include "packet.h" 40#include "uidswap.h" 41#include "compat.h" 42#include "readconf.h" 43#include "bufaux.h" 44#include "ssh2.h" 45#include "kex.h" 46#include "myproposal.h" 47#include "key.h" 48#include "dsa.h" 49#include "sshconnect.h" 50#include "authfile.h" 51#include "cli.h" 52#include "dispatch.h" 53#include "authfd.h" 54 55void ssh_dh1_client(Kex *, char *, struct sockaddr *, Buffer *, Buffer *); 56void ssh_dhgex_client(Kex *, char *, struct sockaddr *, Buffer *, Buffer *); 57 58/* import */ 59extern char *client_version_string; 60extern char *server_version_string; 61extern Options options; 62 63/* 64 * SSH2 key exchange 65 */ 66 67unsigned char *session_id2 = NULL; 68int session_id2_len = 0; 69 70void 71ssh_kex2(char *host, struct sockaddr *hostaddr) 72{ 73 int i, plen; 74 Kex *kex; 75 Buffer *client_kexinit, *server_kexinit; 76 char *sprop[PROPOSAL_MAX]; 77 78 if (options.ciphers == NULL) { 79 if (options.cipher == SSH_CIPHER_3DES) { 80 options.ciphers = "3des-cbc"; 81 } else if (options.cipher == SSH_CIPHER_BLOWFISH) { 82 options.ciphers = "blowfish-cbc"; 83 } else if (options.cipher == SSH_CIPHER_DES) { 84 fatal("cipher DES not supported for protocol version 2"); 85 } 86 } 87 if (options.ciphers != NULL) { 88 myproposal[PROPOSAL_ENC_ALGS_CTOS] = 89 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers; 90 } 91 if (options.compression) { 92 myproposal[PROPOSAL_COMP_ALGS_CTOS] = "zlib"; 93 myproposal[PROPOSAL_COMP_ALGS_STOC] = "zlib"; 94 } else { 95 myproposal[PROPOSAL_COMP_ALGS_CTOS] = "none"; 96 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none"; 97 } 98 99 /* buffers with raw kexinit messages */ 100 server_kexinit = xmalloc(sizeof(*server_kexinit)); 101 buffer_init(server_kexinit); 102 client_kexinit = kex_init(myproposal); 103 104 /* algorithm negotiation */ 105 kex_exchange_kexinit(client_kexinit, server_kexinit, sprop); 106 kex = kex_choose_conf(myproposal, sprop, 0); 107 for (i = 0; i < PROPOSAL_MAX; i++) 108 xfree(sprop[i]); 109 110 /* server authentication and session key agreement */ 111 switch(kex->kex_type) { 112 case DH_GRP1_SHA1: 113 ssh_dh1_client(kex, host, hostaddr, 114 client_kexinit, server_kexinit); 115 break; 116 case DH_GEX_SHA1: 117 ssh_dhgex_client(kex, host, hostaddr, client_kexinit, 118 server_kexinit); 119 break; 120 default: 121 fatal("Unsupported key exchange %d", kex->kex_type); 122 } 123 124 buffer_free(client_kexinit); 125 buffer_free(server_kexinit); 126 xfree(client_kexinit); 127 xfree(server_kexinit); 128 129 debug("Wait SSH2_MSG_NEWKEYS."); 130 packet_read_expect(&plen, SSH2_MSG_NEWKEYS); 131 packet_done(); 132 debug("GOT SSH2_MSG_NEWKEYS."); 133 134 debug("send SSH2_MSG_NEWKEYS."); 135 packet_start(SSH2_MSG_NEWKEYS); 136 packet_send(); 137 packet_write_wait(); 138 debug("done: send SSH2_MSG_NEWKEYS."); 139 140#ifdef DEBUG_KEXDH 141 /* send 1st encrypted/maced/compressed message */ 142 packet_start(SSH2_MSG_IGNORE); 143 packet_put_cstring("markus"); 144 packet_send(); 145 packet_write_wait(); 146#endif 147 debug("done: KEX2."); 148} 149 150/* diffie-hellman-group1-sha1 */ 151 152void 153ssh_dh1_client(Kex *kex, char *host, struct sockaddr *hostaddr, 154 Buffer *client_kexinit, Buffer *server_kexinit) 155{ 156#ifdef DEBUG_KEXDH 157 int i; 158#endif 159 int plen, dlen; 160 unsigned int klen, kout; 161 char *signature = NULL; 162 unsigned int slen; 163 char *server_host_key_blob = NULL; 164 Key *server_host_key; 165 unsigned int sbloblen; 166 DH *dh; 167 BIGNUM *dh_server_pub = 0; 168 BIGNUM *shared_secret = 0; 169 unsigned char *kbuf; 170 unsigned char *hash; 171 172 debug("Sending SSH2_MSG_KEXDH_INIT."); 173 /* generate and send 'e', client DH public key */ 174 dh = dh_new_group1(); 175 packet_start(SSH2_MSG_KEXDH_INIT); 176 packet_put_bignum2(dh->pub_key); 177 packet_send(); 178 packet_write_wait(); 179 180#ifdef DEBUG_KEXDH 181 fprintf(stderr, "\np= "); 182 BN_print_fp(stderr, dh->p); 183 fprintf(stderr, "\ng= "); 184 BN_print_fp(stderr, dh->g); 185 fprintf(stderr, "\npub= "); 186 BN_print_fp(stderr, dh->pub_key); 187 fprintf(stderr, "\n"); 188 DHparams_print_fp(stderr, dh); 189#endif 190 191 debug("Wait SSH2_MSG_KEXDH_REPLY."); 192 193 packet_read_expect(&plen, SSH2_MSG_KEXDH_REPLY); 194 195 debug("Got SSH2_MSG_KEXDH_REPLY."); 196 197 /* key, cert */ 198 server_host_key_blob = packet_get_string(&sbloblen); 199 server_host_key = dsa_key_from_blob(server_host_key_blob, sbloblen); 200 if (server_host_key == NULL) 201 fatal("cannot decode server_host_key_blob"); 202 203 check_host_key(host, hostaddr, server_host_key, 204 options.user_hostfile2, options.system_hostfile2); 205 206 /* DH paramter f, server public DH key */ 207 dh_server_pub = BN_new(); 208 if (dh_server_pub == NULL) 209 fatal("dh_server_pub == NULL"); 210 packet_get_bignum2(dh_server_pub, &dlen); 211 212#ifdef DEBUG_KEXDH 213 fprintf(stderr, "\ndh_server_pub= "); 214 BN_print_fp(stderr, dh_server_pub); 215 fprintf(stderr, "\n"); 216 debug("bits %d", BN_num_bits(dh_server_pub)); 217#endif 218 219 /* signed H */ 220 signature = packet_get_string(&slen); 221 packet_done(); 222 223 if (!dh_pub_is_valid(dh, dh_server_pub)) 224 packet_disconnect("bad server public DH value"); 225 226 klen = DH_size(dh); 227 kbuf = xmalloc(klen); 228 kout = DH_compute_key(kbuf, dh_server_pub, dh); 229#ifdef DEBUG_KEXDH 230 debug("shared secret: len %d/%d", klen, kout); 231 fprintf(stderr, "shared secret == "); 232 for (i = 0; i< kout; i++) 233 fprintf(stderr, "%02x", (kbuf[i])&0xff); 234 fprintf(stderr, "\n"); 235#endif 236 shared_secret = BN_new(); 237 238 BN_bin2bn(kbuf, kout, shared_secret); 239 memset(kbuf, 0, klen); 240 xfree(kbuf); 241 242 /* calc and verify H */ 243 hash = kex_hash( 244 client_version_string, 245 server_version_string, 246 buffer_ptr(client_kexinit), buffer_len(client_kexinit), 247 buffer_ptr(server_kexinit), buffer_len(server_kexinit), 248 server_host_key_blob, sbloblen, 249 dh->pub_key, 250 dh_server_pub, 251 shared_secret 252 ); 253 xfree(server_host_key_blob); 254 DH_free(dh); 255#ifdef DEBUG_KEXDH 256 fprintf(stderr, "hash == "); 257 for (i = 0; i< 20; i++) 258 fprintf(stderr, "%02x", (hash[i])&0xff); 259 fprintf(stderr, "\n"); 260#endif 261 if (dsa_verify(server_host_key, (unsigned char *)signature, slen, hash, 20) != 1) 262 fatal("dsa_verify failed for server_host_key"); 263 key_free(server_host_key); 264 265 kex_derive_keys(kex, hash, shared_secret); 266 packet_set_kex(kex); 267 268 /* save session id */ 269 session_id2_len = 20; 270 session_id2 = xmalloc(session_id2_len); 271 memcpy(session_id2, hash, session_id2_len); 272} 273 274/* diffie-hellman-group-exchange-sha1 */ 275 276/* 277 * Estimates the group order for a Diffie-Hellman group that has an 278 * attack complexity approximately the same as O(2**bits). Estimate 279 * with: O(exp(1.9223 * (ln q)^(1/3) (ln ln q)^(2/3))) 280 */ 281 282int 283dh_estimate(int bits) 284{ 285 286 if (bits < 64) 287 return (512); /* O(2**63) */ 288 if (bits < 128) 289 return (1024); /* O(2**86) */ 290 if (bits < 192) 291 return (2048); /* O(2**116) */ 292 return (4096); /* O(2**156) */ 293} 294 295void 296ssh_dhgex_client(Kex *kex, char *host, struct sockaddr *hostaddr, 297 Buffer *client_kexinit, Buffer *server_kexinit) 298{ 299#ifdef DEBUG_KEXDH 300 int i; 301#endif 302 int plen, dlen; 303 unsigned int klen, kout; 304 char *signature = NULL; 305 unsigned int slen, nbits; 306 char *server_host_key_blob = NULL; 307 Key *server_host_key; 308 unsigned int sbloblen; 309 DH *dh; 310 BIGNUM *dh_server_pub = 0; 311 BIGNUM *shared_secret = 0; 312 BIGNUM *p = 0, *g = 0; 313 unsigned char *kbuf; 314 unsigned char *hash; 315 316 nbits = dh_estimate(kex->enc[MODE_OUT].cipher->key_len * 8); 317 318 debug("Sending SSH2_MSG_KEX_DH_GEX_REQUEST."); 319 packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST); 320 packet_put_int(nbits); 321 packet_send(); 322 packet_write_wait(); 323 324#ifdef DEBUG_KEXDH 325 fprintf(stderr, "\nnbits = %d", nbits); 326#endif 327 328 debug("Wait SSH2_MSG_KEX_DH_GEX_GROUP."); 329 330 packet_read_expect(&plen, SSH2_MSG_KEX_DH_GEX_GROUP); 331 332 debug("Got SSH2_MSG_KEX_DH_GEX_GROUP."); 333 334 if ((p = BN_new()) == NULL) 335 fatal("BN_new"); 336 packet_get_bignum2(p, &dlen); 337 if ((g = BN_new()) == NULL) 338 fatal("BN_new"); 339 packet_get_bignum2(g, &dlen); 340 if ((dh = dh_new_group(g, p)) == NULL) 341 fatal("dh_new_group"); 342 343#ifdef DEBUG_KEXDH 344 fprintf(stderr, "\np= "); 345 BN_print_fp(stderr, dh->p); 346 fprintf(stderr, "\ng= "); 347 BN_print_fp(stderr, dh->g); 348 fprintf(stderr, "\npub= "); 349 BN_print_fp(stderr, dh->pub_key); 350 fprintf(stderr, "\n"); 351 DHparams_print_fp(stderr, dh); 352#endif 353 354 debug("Sending SSH2_MSG_KEX_DH_GEX_INIT."); 355 /* generate and send 'e', client DH public key */ 356 packet_start(SSH2_MSG_KEX_DH_GEX_INIT); 357 packet_put_bignum2(dh->pub_key); 358 packet_send(); 359 packet_write_wait(); 360 361 debug("Wait SSH2_MSG_KEX_DH_GEX_REPLY."); 362 363 packet_read_expect(&plen, SSH2_MSG_KEX_DH_GEX_REPLY); 364 365 debug("Got SSH2_MSG_KEXDH_REPLY."); 366 367 /* key, cert */ 368 server_host_key_blob = packet_get_string(&sbloblen); 369 server_host_key = dsa_key_from_blob(server_host_key_blob, sbloblen); 370 if (server_host_key == NULL) 371 fatal("cannot decode server_host_key_blob"); 372 373 check_host_key(host, hostaddr, server_host_key, 374 options.user_hostfile2, options.system_hostfile2); 375 376 /* DH paramter f, server public DH key */ 377 dh_server_pub = BN_new(); 378 if (dh_server_pub == NULL) 379 fatal("dh_server_pub == NULL"); 380 packet_get_bignum2(dh_server_pub, &dlen); 381 382#ifdef DEBUG_KEXDH 383 fprintf(stderr, "\ndh_server_pub= "); 384 BN_print_fp(stderr, dh_server_pub); 385 fprintf(stderr, "\n"); 386 debug("bits %d", BN_num_bits(dh_server_pub)); 387#endif 388 389 /* signed H */ 390 signature = packet_get_string(&slen); 391 packet_done(); 392 393 if (!dh_pub_is_valid(dh, dh_server_pub)) 394 packet_disconnect("bad server public DH value"); 395 396 klen = DH_size(dh); 397 kbuf = xmalloc(klen); 398 kout = DH_compute_key(kbuf, dh_server_pub, dh); 399#ifdef DEBUG_KEXDH 400 debug("shared secret: len %d/%d", klen, kout); 401 fprintf(stderr, "shared secret == "); 402 for (i = 0; i< kout; i++) 403 fprintf(stderr, "%02x", (kbuf[i])&0xff); 404 fprintf(stderr, "\n"); 405#endif 406 shared_secret = BN_new(); 407 408 BN_bin2bn(kbuf, kout, shared_secret); 409 memset(kbuf, 0, klen); 410 xfree(kbuf); 411 412 /* calc and verify H */ 413 hash = kex_hash_gex( 414 client_version_string, 415 server_version_string, 416 buffer_ptr(client_kexinit), buffer_len(client_kexinit), 417 buffer_ptr(server_kexinit), buffer_len(server_kexinit), 418 server_host_key_blob, sbloblen, 419 nbits, dh->p, dh->g, 420 dh->pub_key, 421 dh_server_pub, 422 shared_secret 423 ); 424 xfree(server_host_key_blob); 425 DH_free(dh); 426#ifdef DEBUG_KEXDH 427 fprintf(stderr, "hash == "); 428 for (i = 0; i< 20; i++) 429 fprintf(stderr, "%02x", (hash[i])&0xff); 430 fprintf(stderr, "\n"); 431#endif 432 if (dsa_verify(server_host_key, (unsigned char *)signature, slen, hash, 20) != 1) 433 fatal("dsa_verify failed for server_host_key"); 434 key_free(server_host_key); 435 436 kex_derive_keys(kex, hash, shared_secret); 437 packet_set_kex(kex); 438 439 /* save session id */ 440 session_id2_len = 20; 441 session_id2 = xmalloc(session_id2_len); 442 memcpy(session_id2, hash, session_id2_len); 443} 444 445/* 446 * Authenticate user 447 */ 448 449typedef struct Authctxt Authctxt; 450typedef struct Authmethod Authmethod; 451 452typedef int sign_cb_fn( 453 Authctxt *authctxt, Key *key, 454 unsigned char **sigp, int *lenp, unsigned char *data, int datalen); 455 456struct Authctxt { 457 const char *server_user; 458 const char *host; 459 const char *service; 460 AuthenticationConnection *agent; 461 Authmethod *method; 462 int success; 463}; 464struct Authmethod { 465 char *name; /* string to compare against server's list */ 466 int (*userauth)(Authctxt *authctxt); 467 int *enabled; /* flag in option struct that enables method */ 468 int *batch_flag; /* flag in option struct that disables method */ 469}; 470 471void input_userauth_success(int type, int plen, void *ctxt); 472void input_userauth_failure(int type, int plen, void *ctxt); 473void input_userauth_error(int type, int plen, void *ctxt); 474void input_userauth_info_req(int type, int plen, void *ctxt); 475 476int userauth_none(Authctxt *authctxt); 477int userauth_pubkey(Authctxt *authctxt); 478int userauth_passwd(Authctxt *authctxt); 479int userauth_kbdint(Authctxt *authctxt); 480 481void authmethod_clear(); 482Authmethod *authmethod_get(char *authlist); 483Authmethod *authmethod_lookup(const char *name); 484 485Authmethod authmethods[] = { 486 {"publickey", 487 userauth_pubkey, 488 &options.dsa_authentication, 489 NULL}, 490 {"password", 491 userauth_passwd, 492 &options.password_authentication, 493 &options.batch_mode}, 494 {"keyboard-interactive", 495 userauth_kbdint, 496 &options.kbd_interactive_authentication, 497 &options.batch_mode}, 498 {"none", 499 userauth_none, 500 NULL, 501 NULL}, 502 {NULL, NULL, NULL, NULL} 503}; 504 505void 506ssh_userauth2(const char *server_user, char *host) 507{ 508 Authctxt authctxt; 509 int type; 510 int plen; 511 512 debug("send SSH2_MSG_SERVICE_REQUEST"); 513 packet_start(SSH2_MSG_SERVICE_REQUEST); 514 packet_put_cstring("ssh-userauth"); 515 packet_send(); 516 packet_write_wait(); 517 type = packet_read(&plen); 518 if (type != SSH2_MSG_SERVICE_ACCEPT) { 519 fatal("denied SSH2_MSG_SERVICE_ACCEPT: %d", type); 520 } 521 if (packet_remaining() > 0) { 522 char *reply = packet_get_string(&plen); 523 debug("service_accept: %s", reply); 524 xfree(reply); 525 packet_done(); 526 } else { 527 debug("buggy server: service_accept w/o service"); 528 } 529 packet_done(); 530 debug("got SSH2_MSG_SERVICE_ACCEPT"); 531 532 /* setup authentication context */ 533 authctxt.agent = ssh_get_authentication_connection(); 534 authctxt.server_user = server_user; 535 authctxt.host = host; 536 authctxt.service = "ssh-connection"; /* service name */ 537 authctxt.success = 0; 538 authctxt.method = authmethod_lookup("none"); 539 if (authctxt.method == NULL) 540 fatal("ssh_userauth2: internal error: cannot send userauth none request"); 541 authmethod_clear(); 542 543 /* initial userauth request */ 544 userauth_none(&authctxt); 545 546 dispatch_init(&input_userauth_error); 547 dispatch_set(SSH2_MSG_USERAUTH_SUCCESS, &input_userauth_success); 548 dispatch_set(SSH2_MSG_USERAUTH_FAILURE, &input_userauth_failure); 549 dispatch_run(DISPATCH_BLOCK, &authctxt.success, &authctxt); /* loop until success */ 550 551 if (authctxt.agent != NULL) 552 ssh_close_authentication_connection(authctxt.agent); 553 554 debug("ssh-userauth2 successfull: method %s", authctxt.method->name); 555} 556void 557input_userauth_error(int type, int plen, void *ctxt) 558{ 559 fatal("input_userauth_error: bad message during authentication"); 560} 561void 562input_userauth_success(int type, int plen, void *ctxt) 563{ 564 Authctxt *authctxt = ctxt; 565 if (authctxt == NULL) 566 fatal("input_userauth_success: no authentication context"); 567 authctxt->success = 1; /* break out */ 568} 569void 570input_userauth_failure(int type, int plen, void *ctxt) 571{ 572 Authmethod *method = NULL; 573 Authctxt *authctxt = ctxt; 574 char *authlist = NULL; 575 int partial; 576 577 if (authctxt == NULL) 578 fatal("input_userauth_failure: no authentication context"); 579 580 authlist = packet_get_string(NULL); 581 partial = packet_get_char(); 582 packet_done(); 583 584 if (partial != 0) 585 debug("partial success"); 586 debug("authentications that can continue: %s", authlist); 587 588 for (;;) { 589 method = authmethod_get(authlist); 590 if (method == NULL) 591 fatal("Unable to find an authentication method"); 592 authctxt->method = method; 593 if (method->userauth(authctxt) != 0) { 594 debug2("we sent a %s packet, wait for reply", method->name); 595 break; 596 } else { 597 debug2("we did not send a packet, disable method"); 598 method->enabled = NULL; 599 } 600 } 601 xfree(authlist); 602} 603 604int 605userauth_none(Authctxt *authctxt) 606{ 607 /* initial userauth request */ 608 packet_start(SSH2_MSG_USERAUTH_REQUEST); 609 packet_put_cstring(authctxt->server_user); 610 packet_put_cstring(authctxt->service); 611 packet_put_cstring(authctxt->method->name); 612 packet_send(); 613 packet_write_wait(); 614 return 1; 615} 616 617int 618userauth_passwd(Authctxt *authctxt) 619{ 620 static int attempt = 0; 621 char prompt[80]; 622 char *password; 623 624 if (attempt++ >= options.number_of_password_prompts) 625 return 0; 626 627 if(attempt != 1) 628 error("Permission denied, please try again."); 629 630 snprintf(prompt, sizeof(prompt), "%.30s@%.40s's password: ", 631 authctxt->server_user, authctxt->host); 632 password = read_passphrase(prompt, 0); 633 packet_start(SSH2_MSG_USERAUTH_REQUEST); 634 packet_put_cstring(authctxt->server_user); 635 packet_put_cstring(authctxt->service); 636 packet_put_cstring(authctxt->method->name); 637 packet_put_char(0); 638 packet_put_cstring(password); 639 memset(password, 0, strlen(password)); 640 xfree(password); 641 packet_send(); 642 packet_write_wait(); 643 return 1; 644} 645 646int 647sign_and_send_pubkey(Authctxt *authctxt, Key *k, sign_cb_fn *sign_callback) 648{ 649 Buffer b; 650 unsigned char *blob, *signature; 651 int bloblen, slen; 652 int skip = 0; 653 int ret = -1; 654 int have_sig = 1; 655 656 dsa_make_key_blob(k, &blob, &bloblen); 657 658 /* data to be signed */ 659 buffer_init(&b); 660 if (datafellows & SSH_OLD_SESSIONID) { 661 buffer_append(&b, session_id2, session_id2_len); 662 skip = session_id2_len; 663 } else { 664 buffer_put_string(&b, session_id2, session_id2_len); 665 skip = buffer_len(&b); 666 } 667 buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST); 668 buffer_put_cstring(&b, authctxt->server_user); 669 buffer_put_cstring(&b, 670 datafellows & SSH_BUG_PUBKEYAUTH ? 671 "ssh-userauth" : 672 authctxt->service); 673 buffer_put_cstring(&b, authctxt->method->name); 674 buffer_put_char(&b, have_sig); 675 buffer_put_cstring(&b, KEX_DSS); 676 buffer_put_string(&b, blob, bloblen); 677 678 /* generate signature */ 679 ret = (*sign_callback)(authctxt, k, &signature, &slen, buffer_ptr(&b), buffer_len(&b)); 680 if (ret == -1) { 681 xfree(blob); 682 buffer_free(&b); 683 return 0; 684 } 685#ifdef DEBUG_DSS 686 buffer_dump(&b); 687#endif 688 if (datafellows & SSH_BUG_PUBKEYAUTH) { 689 buffer_clear(&b); 690 buffer_append(&b, session_id2, session_id2_len); 691 buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST); 692 buffer_put_cstring(&b, authctxt->server_user); 693 buffer_put_cstring(&b, authctxt->service); 694 buffer_put_cstring(&b, authctxt->method->name); 695 buffer_put_char(&b, have_sig); 696 buffer_put_cstring(&b, KEX_DSS); 697 buffer_put_string(&b, blob, bloblen); 698 } 699 xfree(blob); 700 /* append signature */ 701 buffer_put_string(&b, signature, slen); 702 xfree(signature); 703 704 /* skip session id and packet type */ 705 if (buffer_len(&b) < skip + 1) 706 fatal("userauth_pubkey: internal error"); 707 buffer_consume(&b, skip + 1); 708 709 /* put remaining data from buffer into packet */ 710 packet_start(SSH2_MSG_USERAUTH_REQUEST); 711 packet_put_raw(buffer_ptr(&b), buffer_len(&b)); 712 buffer_free(&b); 713 714 /* send */ 715 packet_send(); 716 packet_write_wait(); 717 718 return 1; 719} 720 721/* sign callback */ 722int dsa_sign_cb(Authctxt *authctxt, Key *key, unsigned char **sigp, int *lenp, 723 unsigned char *data, int datalen) 724{ 725 return dsa_sign(key, sigp, lenp, data, datalen); 726} 727 728int 729userauth_pubkey_identity(Authctxt *authctxt, char *filename) 730{ 731 Key *k; 732 int i, ret, try_next; 733 struct stat st; 734 735 if (stat(filename, &st) != 0) { 736 debug("key does not exist: %s", filename); 737 return 0; 738 } 739 debug("try pubkey: %s", filename); 740 741 k = key_new(KEY_DSA); 742 if (!load_private_key(filename, "", k, NULL)) { 743 int success = 0; 744 char *passphrase; 745 char prompt[300]; 746 snprintf(prompt, sizeof prompt, 747 "Enter passphrase for %s key '%.100s': ", 748 key_type(k), filename); 749 for (i = 0; i < options.number_of_password_prompts; i++) { 750 passphrase = read_passphrase(prompt, 0); 751 if (strcmp(passphrase, "") != 0) { 752 success = load_private_key(filename, passphrase, k, NULL); 753 try_next = 0; 754 } else { 755 debug2("no passphrase given, try next key"); 756 try_next = 1; 757 } 758 memset(passphrase, 0, strlen(passphrase)); 759 xfree(passphrase); 760 if (success || try_next) 761 break; 762 debug2("bad passphrase given, try again..."); 763 } 764 if (!success) { 765 key_free(k); 766 return 0; 767 } 768 } 769 ret = sign_and_send_pubkey(authctxt, k, dsa_sign_cb); 770 key_free(k); 771 return ret; 772} 773 774/* sign callback */ 775int agent_sign_cb(Authctxt *authctxt, Key *key, unsigned char **sigp, int *lenp, 776 unsigned char *data, int datalen) 777{ 778 return ssh_agent_sign(authctxt->agent, key, sigp, lenp, data, datalen); 779} 780 781int 782userauth_pubkey_agent(Authctxt *authctxt) 783{ 784 static int called = 0; 785 char *comment; 786 Key *k; 787 int ret; 788 789 if (called == 0) { 790 k = ssh_get_first_identity(authctxt->agent, &comment, 2); 791 called = 1; 792 } else { 793 k = ssh_get_next_identity(authctxt->agent, &comment, 2); 794 } 795 if (k == NULL) { 796 debug2("no more DSA keys from agent"); 797 return 0; 798 } 799 debug("trying DSA agent key %s", comment); 800 xfree(comment); 801 ret = sign_and_send_pubkey(authctxt, k, agent_sign_cb); 802 key_free(k); 803 return ret; 804} 805 806int 807userauth_pubkey(Authctxt *authctxt) 808{ 809 static int idx = 0; 810 int sent = 0; 811 812 if (authctxt->agent != NULL) 813 sent = userauth_pubkey_agent(authctxt); 814 while (sent == 0 && idx < options.num_identity_files2) 815 sent = userauth_pubkey_identity(authctxt, options.identity_files2[idx++]); 816 return sent; 817} 818 819/* 820 * Send userauth request message specifying keyboard-interactive method. 821 */ 822int 823userauth_kbdint(Authctxt *authctxt) 824{ 825 static int attempt = 0; 826 827 if (attempt++ >= options.number_of_password_prompts) 828 return 0; 829 830 debug2("userauth_kbdint"); 831 packet_start(SSH2_MSG_USERAUTH_REQUEST); 832 packet_put_cstring(authctxt->server_user); 833 packet_put_cstring(authctxt->service); 834 packet_put_cstring(authctxt->method->name); 835 packet_put_cstring(""); /* lang */ 836 packet_put_cstring(options.kbd_interactive_devices ? 837 options.kbd_interactive_devices : ""); 838 packet_send(); 839 packet_write_wait(); 840 841 dispatch_set(SSH2_MSG_USERAUTH_INFO_REQUEST, &input_userauth_info_req); 842 return 1; 843} 844 845/* 846 * parse SSH2_MSG_USERAUTH_INFO_REQUEST, prompt user and send 847 * SSH2_MSG_USERAUTH_INFO_RESPONSE 848 */ 849void 850input_userauth_info_req(int type, int plen, void *ctxt) 851{ 852 Authctxt *authctxt = ctxt; 853 char *name = NULL; 854 char *inst = NULL; 855 char *lang = NULL; 856 char *prompt = NULL; 857 char *response = NULL; 858 unsigned int num_prompts, i; 859 int echo = 0; 860 861 debug2("input_userauth_info_req"); 862 863 if (authctxt == NULL) 864 fatal("input_userauth_info_req: no authentication context"); 865 866 name = packet_get_string(NULL); 867 inst = packet_get_string(NULL); 868 lang = packet_get_string(NULL); 869 870 if (strlen(name) > 0) 871 cli_mesg(name); 872 xfree(name); 873 874 if (strlen(inst) > 0) 875 cli_mesg(inst); 876 xfree(inst); 877 xfree(lang); /* unused */ 878 879 num_prompts = packet_get_int(); 880 /* 881 * Begin to build info response packet based on prompts requested. 882 * We commit to providing the correct number of responses, so if 883 * further on we run into a problem that prevents this, we have to 884 * be sure and clean this up and send a correct error response. 885 */ 886 packet_start(SSH2_MSG_USERAUTH_INFO_RESPONSE); 887 packet_put_int(num_prompts); 888 889 for (i = 0; i < num_prompts; i++) { 890 prompt = packet_get_string(NULL); 891 echo = packet_get_char(); 892 893 response = cli_prompt(prompt, echo); 894 895 packet_put_cstring(response); 896 memset(response, 0, strlen(response)); 897 xfree(response); 898 xfree(prompt); 899 } 900 packet_done(); /* done with parsing incoming message. */ 901 902 packet_send(); 903 packet_write_wait(); 904} 905 906/* find auth method */ 907 908#define DELIM "," 909 910static char *def_authlist = "publickey,password"; 911static char *authlist_current = NULL; /* clean copy used for comparison */ 912static char *authname_current = NULL; /* last used auth method */ 913static char *authlist_working = NULL; /* copy that gets modified by strtok_r() */ 914static char *authlist_state = NULL; /* state variable for strtok_r() */ 915 916/* 917 * Before starting to use a new authentication method list sent by the 918 * server, reset internal variables. This should also be called when 919 * finished processing server list to free resources. 920 */ 921void 922authmethod_clear() 923{ 924 if (authlist_current != NULL) { 925 xfree(authlist_current); 926 authlist_current = NULL; 927 } 928 if (authlist_working != NULL) { 929 xfree(authlist_working); 930 authlist_working = NULL; 931 } 932 if (authname_current != NULL) { 933 xfree(authname_current); 934 authlist_state = NULL; 935 } 936 if (authlist_state != NULL) 937 authlist_state = NULL; 938 return; 939} 940 941/* 942 * given auth method name, if configurable options permit this method fill 943 * in auth_ident field and return true, otherwise return false. 944 */ 945int 946authmethod_is_enabled(Authmethod *method) 947{ 948 if (method == NULL) 949 return 0; 950 /* return false if options indicate this method is disabled */ 951 if (method->enabled == NULL || *method->enabled == 0) 952 return 0; 953 /* return false if batch mode is enabled but method needs interactive mode */ 954 if (method->batch_flag != NULL && *method->batch_flag != 0) 955 return 0; 956 return 1; 957} 958 959Authmethod * 960authmethod_lookup(const char *name) 961{ 962 Authmethod *method = NULL; 963 if (name != NULL) 964 for (method = authmethods; method->name != NULL; method++) 965 if (strcmp(name, method->name) == 0) 966 return method; 967 debug2("Unrecognized authentication method name: %s", name ? name : "NULL"); 968 return NULL; 969} 970 971/* 972 * Given the authentication method list sent by the server, return the 973 * next method we should try. If the server initially sends a nil list, 974 * use a built-in default list. If the server sends a nil list after 975 * previously sending a valid list, continue using the list originally 976 * sent. 977 */ 978 979Authmethod * 980authmethod_get(char *authlist) 981{ 982 char *name = NULL, *authname_old; 983 Authmethod *method = NULL; 984 985 /* Use a suitable default if we're passed a nil list. */ 986 if (authlist == NULL || strlen(authlist) == 0) 987 authlist = def_authlist; 988 989 if (authlist_current == NULL || strcmp(authlist, authlist_current) != 0) { 990 /* start over if passed a different list */ 991 debug3("start over, passed a different list"); 992 authmethod_clear(); 993 authlist_current = xstrdup(authlist); 994 authlist_working = xstrdup(authlist); 995 name = strtok_r(authlist_working, DELIM, &authlist_state); 996 } else { 997 /* 998 * try to use previously used authentication method 999 * or continue to use previously passed list 1000 */ 1001 name = (authname_current != NULL) ? 1002 authname_current : strtok_r(NULL, DELIM, &authlist_state); 1003 } 1004 1005 while (name != NULL) { 1006 debug3("authmethod_lookup %s", name); 1007 method = authmethod_lookup(name); 1008 if (method != NULL && authmethod_is_enabled(method)) { 1009 debug3("authmethod_is_enabled %s", name); 1010 break; 1011 } 1012 name = strtok_r(NULL, DELIM, &authlist_state); 1013 method = NULL; 1014 } 1015 1016 authname_old = authname_current; 1017 if (method != NULL) { 1018 debug("next auth method to try is %s", name); 1019 authname_current = xstrdup(name); 1020 } else { 1021 debug("no more auth methods to try"); 1022 authname_current = NULL; 1023 } 1024 1025 if (authname_old != NULL) 1026 xfree(authname_old); 1027 1028 return (method); 1029} 1030