1 /* $OpenBSD: auth2.c,v 1.168 2023/12/18 14:45:49 djm Exp $ */ 2 /* 3 * Copyright (c) 2000 Markus Friedl. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24 */ 25 26 #include "includes.h" 27 28 #include <sys/types.h> 29 #include <sys/stat.h> 30 #include <sys/uio.h> 31 32 #include <fcntl.h> 33 #include <limits.h> 34 #include <pwd.h> 35 #include <stdarg.h> 36 #include <string.h> 37 #include <unistd.h> 38 #include <time.h> 39 40 #include "stdlib.h" 41 #include "atomicio.h" 42 #include "xmalloc.h" 43 #include "ssh2.h" 44 #include "packet.h" 45 #include "log.h" 46 #include "sshbuf.h" 47 #include "misc.h" 48 #include "servconf.h" 49 #include "sshkey.h" 50 #include "hostfile.h" 51 #include "auth.h" 52 #include "dispatch.h" 53 #include "pathnames.h" 54 #include "ssherr.h" 55 #include "blacklist_client.h" 56 #ifdef GSSAPI 57 #include "ssh-gss.h" 58 #endif 59 #include "monitor_wrap.h" 60 #include "digest.h" 61 #include "kex.h" 62 63 /* import */ 64 extern ServerOptions options; 65 extern struct sshbuf *loginmsg; 66 67 /* methods */ 68 69 extern Authmethod method_none; 70 extern Authmethod method_pubkey; 71 extern Authmethod method_passwd; 72 extern Authmethod method_kbdint; 73 extern Authmethod method_hostbased; 74 #ifdef GSSAPI 75 extern Authmethod method_gssapi; 76 #endif 77 78 Authmethod *authmethods[] = { 79 &method_none, 80 &method_pubkey, 81 #ifdef GSSAPI 82 &method_gssapi, 83 #endif 84 &method_passwd, 85 &method_kbdint, 86 &method_hostbased, 87 NULL 88 }; 89 90 /* protocol */ 91 92 static int input_service_request(int, u_int32_t, struct ssh *); 93 static int input_userauth_request(int, u_int32_t, struct ssh *); 94 95 /* helper */ 96 static Authmethod *authmethod_byname(const char *); 97 static Authmethod *authmethod_lookup(Authctxt *, const char *); 98 static char *authmethods_get(Authctxt *authctxt); 99 100 #define MATCH_NONE 0 /* method or submethod mismatch */ 101 #define MATCH_METHOD 1 /* method matches (no submethod specified) */ 102 #define MATCH_BOTH 2 /* method and submethod match */ 103 #define MATCH_PARTIAL 3 /* method matches, submethod can't be checked */ 104 static int list_starts_with(const char *, const char *, const char *); 105 106 char * 107 auth2_read_banner(void) 108 { 109 struct stat st; 110 char *banner = NULL; 111 size_t len, n; 112 int fd; 113 114 if ((fd = open(options.banner, O_RDONLY)) == -1) 115 return (NULL); 116 if (fstat(fd, &st) == -1) { 117 close(fd); 118 return (NULL); 119 } 120 if (st.st_size <= 0 || st.st_size > 1*1024*1024) { 121 close(fd); 122 return (NULL); 123 } 124 125 len = (size_t)st.st_size; /* truncate */ 126 banner = xmalloc(len + 1); 127 n = atomicio(read, fd, banner, len); 128 close(fd); 129 130 if (n != len) { 131 free(banner); 132 return (NULL); 133 } 134 banner[n] = '\0'; 135 136 return (banner); 137 } 138 139 static void 140 userauth_send_banner(struct ssh *ssh, const char *msg) 141 { 142 int r; 143 144 if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_BANNER)) != 0 || 145 (r = sshpkt_put_cstring(ssh, msg)) != 0 || 146 (r = sshpkt_put_cstring(ssh, "")) != 0 || /* language, unused */ 147 (r = sshpkt_send(ssh)) != 0) 148 fatal_fr(r, "send packet"); 149 debug("%s: sent", __func__); 150 } 151 152 static void 153 userauth_banner(struct ssh *ssh) 154 { 155 char *banner = NULL; 156 157 if (options.banner == NULL) 158 return; 159 160 if ((banner = PRIVSEP(auth2_read_banner())) == NULL) 161 goto done; 162 userauth_send_banner(ssh, banner); 163 164 done: 165 free(banner); 166 } 167 168 /* 169 * loop until authctxt->success == TRUE 170 */ 171 void 172 do_authentication2(struct ssh *ssh) 173 { 174 Authctxt *authctxt = ssh->authctxt; 175 176 ssh_dispatch_init(ssh, &dispatch_protocol_error); 177 if (ssh->kex->ext_info_c) 178 ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &kex_input_ext_info); 179 ssh_dispatch_set(ssh, SSH2_MSG_SERVICE_REQUEST, &input_service_request); 180 ssh_dispatch_run_fatal(ssh, DISPATCH_BLOCK, &authctxt->success); 181 ssh->authctxt = NULL; 182 } 183 184 static int 185 input_service_request(int type, u_int32_t seq, struct ssh *ssh) 186 { 187 Authctxt *authctxt = ssh->authctxt; 188 char *service = NULL; 189 int r, acceptit = 0; 190 191 if ((r = sshpkt_get_cstring(ssh, &service, NULL)) != 0 || 192 (r = sshpkt_get_end(ssh)) != 0) 193 goto out; 194 195 if (authctxt == NULL) 196 fatal("input_service_request: no authctxt"); 197 198 if (strcmp(service, "ssh-userauth") == 0) { 199 if (!authctxt->success) { 200 acceptit = 1; 201 /* now we can handle user-auth requests */ 202 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_REQUEST, 203 &input_userauth_request); 204 } 205 } 206 /* XXX all other service requests are denied */ 207 208 if (acceptit) { 209 if ((r = sshpkt_start(ssh, SSH2_MSG_SERVICE_ACCEPT)) != 0 || 210 (r = sshpkt_put_cstring(ssh, service)) != 0 || 211 (r = sshpkt_send(ssh)) != 0 || 212 (r = ssh_packet_write_wait(ssh)) != 0) 213 goto out; 214 } else { 215 debug("bad service request %s", service); 216 ssh_packet_disconnect(ssh, "bad service request %s", service); 217 } 218 ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &dispatch_protocol_error); 219 r = 0; 220 out: 221 free(service); 222 return r; 223 } 224 225 #define MIN_FAIL_DELAY_SECONDS 0.005 226 #define MAX_FAIL_DELAY_SECONDS 5.0 227 static double 228 user_specific_delay(const char *user) 229 { 230 char b[512]; 231 size_t len = ssh_digest_bytes(SSH_DIGEST_SHA512); 232 u_char *hash = xmalloc(len); 233 double delay; 234 235 (void)snprintf(b, sizeof b, "%llu%s", 236 (unsigned long long)options.timing_secret, user); 237 if (ssh_digest_memory(SSH_DIGEST_SHA512, b, strlen(b), hash, len) != 0) 238 fatal_f("ssh_digest_memory"); 239 /* 0-4.2 ms of delay */ 240 delay = (double)PEEK_U32(hash) / 1000 / 1000 / 1000 / 1000; 241 freezero(hash, len); 242 debug3_f("user specific delay %0.3lfms", delay/1000); 243 return MIN_FAIL_DELAY_SECONDS + delay; 244 } 245 246 static void 247 ensure_minimum_time_since(double start, double seconds) 248 { 249 struct timespec ts; 250 double elapsed = monotime_double() - start, req = seconds, remain; 251 252 if (elapsed > MAX_FAIL_DELAY_SECONDS) { 253 debug3_f("elapsed %0.3lfms exceeded the max delay " 254 "requested %0.3lfms)", elapsed*1000, req*1000); 255 return; 256 } 257 258 /* if we've already passed the requested time, scale up */ 259 while ((remain = seconds - elapsed) < 0.0) 260 seconds *= 2; 261 262 ts.tv_sec = remain; 263 ts.tv_nsec = (remain - ts.tv_sec) * 1000000000; 264 debug3_f("elapsed %0.3lfms, delaying %0.3lfms (requested %0.3lfms)", 265 elapsed*1000, remain*1000, req*1000); 266 nanosleep(&ts, NULL); 267 } 268 269 static int 270 input_userauth_request(int type, u_int32_t seq, struct ssh *ssh) 271 { 272 Authctxt *authctxt = ssh->authctxt; 273 Authmethod *m = NULL; 274 char *user = NULL, *service = NULL, *method = NULL, *style = NULL; 275 int r, authenticated = 0; 276 double tstart = monotime_double(); 277 278 if (authctxt == NULL) 279 fatal("input_userauth_request: no authctxt"); 280 281 if ((r = sshpkt_get_cstring(ssh, &user, NULL)) != 0 || 282 (r = sshpkt_get_cstring(ssh, &service, NULL)) != 0 || 283 (r = sshpkt_get_cstring(ssh, &method, NULL)) != 0) 284 goto out; 285 debug("userauth-request for user %s service %s method %s", user, service, method); 286 debug("attempt %d failures %d", authctxt->attempt, authctxt->failures); 287 288 if ((style = strchr(user, ':')) != NULL) 289 *style++ = 0; 290 291 if (authctxt->attempt >= 1024) 292 auth_maxtries_exceeded(ssh); 293 if (authctxt->attempt++ == 0) { 294 /* setup auth context */ 295 authctxt->pw = PRIVSEP(getpwnamallow(ssh, user)); 296 authctxt->user = xstrdup(user); 297 if (authctxt->pw && strcmp(service, "ssh-connection")==0) { 298 authctxt->valid = 1; 299 debug2_f("setting up authctxt for %s", user); 300 } else { 301 authctxt->valid = 0; 302 /* Invalid user, fake password information */ 303 authctxt->pw = fakepw(); 304 #ifdef SSH_AUDIT_EVENTS 305 PRIVSEP(audit_event(ssh, SSH_INVALID_USER)); 306 #endif 307 } 308 #ifdef USE_PAM 309 if (options.use_pam) 310 PRIVSEP(start_pam(ssh)); 311 #endif 312 ssh_packet_set_log_preamble(ssh, "%suser %s", 313 authctxt->valid ? "authenticating " : "invalid ", user); 314 setproctitle("%s%s", authctxt->valid ? user : "unknown", 315 use_privsep ? " [net]" : ""); 316 authctxt->service = xstrdup(service); 317 authctxt->style = style ? xstrdup(style) : NULL; 318 if (use_privsep) 319 mm_inform_authserv(service, style); 320 userauth_banner(ssh); 321 if ((r = kex_server_update_ext_info(ssh)) != 0) 322 fatal_fr(r, "kex_server_update_ext_info failed"); 323 if (auth2_setup_methods_lists(authctxt) != 0) 324 ssh_packet_disconnect(ssh, 325 "no authentication methods enabled"); 326 } else if (strcmp(user, authctxt->user) != 0 || 327 strcmp(service, authctxt->service) != 0) { 328 ssh_packet_disconnect(ssh, "Change of username or service " 329 "not allowed: (%s,%s) -> (%s,%s)", 330 authctxt->user, authctxt->service, user, service); 331 } 332 /* reset state */ 333 auth2_challenge_stop(ssh); 334 335 #ifdef GSSAPI 336 /* XXX move to auth2_gssapi_stop() */ 337 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 338 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); 339 #endif 340 341 auth2_authctxt_reset_info(authctxt); 342 authctxt->postponed = 0; 343 authctxt->server_caused_failure = 0; 344 345 /* try to authenticate user */ 346 m = authmethod_lookup(authctxt, method); 347 if (m != NULL && authctxt->failures < options.max_authtries) { 348 debug2("input_userauth_request: try method %s", method); 349 authenticated = m->userauth(ssh, method); 350 } 351 if (!authctxt->authenticated && strcmp(method, "none") != 0) 352 ensure_minimum_time_since(tstart, 353 user_specific_delay(authctxt->user)); 354 userauth_finish(ssh, authenticated, method, NULL); 355 r = 0; 356 out: 357 free(service); 358 free(user); 359 free(method); 360 return r; 361 } 362 363 void 364 userauth_finish(struct ssh *ssh, int authenticated, const char *packet_method, 365 const char *submethod) 366 { 367 Authctxt *authctxt = ssh->authctxt; 368 Authmethod *m = NULL; 369 const char *method = packet_method; 370 char *methods; 371 int r, partial = 0; 372 373 if (authenticated) { 374 if (!authctxt->valid) { 375 fatal("INTERNAL ERROR: authenticated invalid user %s", 376 authctxt->user); 377 } 378 if (authctxt->postponed) 379 fatal("INTERNAL ERROR: authenticated and postponed"); 380 /* prefer primary authmethod name to possible synonym */ 381 if ((m = authmethod_byname(method)) == NULL) 382 fatal("INTERNAL ERROR: bad method %s", method); 383 method = m->name; 384 } 385 386 /* Special handling for root */ 387 if (authenticated && authctxt->pw->pw_uid == 0 && 388 !auth_root_allowed(ssh, method)) { 389 authenticated = 0; 390 #ifdef SSH_AUDIT_EVENTS 391 PRIVSEP(audit_event(ssh, SSH_LOGIN_ROOT_DENIED)); 392 #endif 393 } 394 395 if (authenticated && options.num_auth_methods != 0) { 396 if (!auth2_update_methods_lists(authctxt, method, submethod)) { 397 authenticated = 0; 398 partial = 1; 399 } 400 } 401 402 /* Log before sending the reply */ 403 auth_log(ssh, authenticated, partial, method, submethod); 404 405 /* Update information exposed to session */ 406 if (authenticated || partial) 407 auth2_update_session_info(authctxt, method, submethod); 408 409 if (authctxt->postponed) 410 return; 411 412 #ifdef USE_PAM 413 if (options.use_pam && authenticated) { 414 int r, success = PRIVSEP(do_pam_account()); 415 416 /* If PAM returned a message, send it to the user. */ 417 if (sshbuf_len(loginmsg) > 0) { 418 if ((r = sshbuf_put(loginmsg, "\0", 1)) != 0) 419 fatal("%s: buffer error: %s", 420 __func__, ssh_err(r)); 421 userauth_send_banner(ssh, sshbuf_ptr(loginmsg)); 422 if ((r = ssh_packet_write_wait(ssh)) != 0) { 423 sshpkt_fatal(ssh, r, 424 "%s: send PAM banner", __func__); 425 } 426 } 427 if (!success) { 428 fatal("Access denied for user %s by PAM account " 429 "configuration", authctxt->user); 430 } 431 } 432 #endif 433 434 if (authenticated == 1) { 435 /* turn off userauth */ 436 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_REQUEST, 437 &dispatch_protocol_ignore); 438 if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_SUCCESS)) != 0 || 439 (r = sshpkt_send(ssh)) != 0 || 440 (r = ssh_packet_write_wait(ssh)) != 0) 441 fatal_fr(r, "send success packet"); 442 /* now we can break out */ 443 authctxt->success = 1; 444 ssh_packet_set_log_preamble(ssh, "user %s", authctxt->user); 445 } else { 446 /* Allow initial try of "none" auth without failure penalty */ 447 if (!partial && !authctxt->server_caused_failure && 448 (authctxt->attempt > 1 || strcmp(method, "none") != 0)) { 449 authctxt->failures++; 450 BLACKLIST_NOTIFY(ssh, BLACKLIST_AUTH_FAIL, "ssh"); 451 } 452 if (authctxt->failures >= options.max_authtries) { 453 #ifdef SSH_AUDIT_EVENTS 454 PRIVSEP(audit_event(ssh, SSH_LOGIN_EXCEED_MAXTRIES)); 455 #endif 456 auth_maxtries_exceeded(ssh); 457 } 458 methods = authmethods_get(authctxt); 459 debug3_f("failure partial=%d next methods=\"%s\"", 460 partial, methods); 461 if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_FAILURE)) != 0 || 462 (r = sshpkt_put_cstring(ssh, methods)) != 0 || 463 (r = sshpkt_put_u8(ssh, partial)) != 0 || 464 (r = sshpkt_send(ssh)) != 0 || 465 (r = ssh_packet_write_wait(ssh)) != 0) 466 fatal_fr(r, "send failure packet"); 467 free(methods); 468 } 469 } 470 471 /* 472 * Checks whether method is allowed by at least one AuthenticationMethods 473 * methods list. Returns 1 if allowed, or no methods lists configured. 474 * 0 otherwise. 475 */ 476 int 477 auth2_method_allowed(Authctxt *authctxt, const char *method, 478 const char *submethod) 479 { 480 u_int i; 481 482 /* 483 * NB. authctxt->num_auth_methods might be zero as a result of 484 * auth2_setup_methods_lists(), so check the configuration. 485 */ 486 if (options.num_auth_methods == 0) 487 return 1; 488 for (i = 0; i < authctxt->num_auth_methods; i++) { 489 if (list_starts_with(authctxt->auth_methods[i], method, 490 submethod) != MATCH_NONE) 491 return 1; 492 } 493 return 0; 494 } 495 496 static char * 497 authmethods_get(Authctxt *authctxt) 498 { 499 struct sshbuf *b; 500 char *list; 501 int i, r; 502 503 if ((b = sshbuf_new()) == NULL) 504 fatal_f("sshbuf_new failed"); 505 for (i = 0; authmethods[i] != NULL; i++) { 506 if (strcmp(authmethods[i]->name, "none") == 0) 507 continue; 508 if (authmethods[i]->enabled == NULL || 509 *(authmethods[i]->enabled) == 0) 510 continue; 511 if (!auth2_method_allowed(authctxt, authmethods[i]->name, 512 NULL)) 513 continue; 514 if ((r = sshbuf_putf(b, "%s%s", sshbuf_len(b) ? "," : "", 515 authmethods[i]->name)) != 0) 516 fatal_fr(r, "buffer error"); 517 } 518 if ((list = sshbuf_dup_string(b)) == NULL) 519 fatal_f("sshbuf_dup_string failed"); 520 sshbuf_free(b); 521 return list; 522 } 523 524 static Authmethod * 525 authmethod_byname(const char *name) 526 { 527 int i; 528 529 if (name == NULL) 530 fatal_f("NULL authentication method name"); 531 for (i = 0; authmethods[i] != NULL; i++) { 532 if (strcmp(name, authmethods[i]->name) == 0 || 533 (authmethods[i]->synonym != NULL && 534 strcmp(name, authmethods[i]->synonym) == 0)) 535 return authmethods[i]; 536 } 537 debug_f("unrecognized authentication method name: %s", name); 538 return NULL; 539 } 540 541 static Authmethod * 542 authmethod_lookup(Authctxt *authctxt, const char *name) 543 { 544 Authmethod *method; 545 546 if ((method = authmethod_byname(name)) == NULL) 547 return NULL; 548 549 if (method->enabled == NULL || *(method->enabled) == 0) { 550 debug3_f("method %s not enabled", name); 551 return NULL; 552 } 553 if (!auth2_method_allowed(authctxt, method->name, NULL)) { 554 debug3_f("method %s not allowed " 555 "by AuthenticationMethods", name); 556 return NULL; 557 } 558 return method; 559 } 560 561 /* 562 * Check a comma-separated list of methods for validity. Is need_enable is 563 * non-zero, then also require that the methods are enabled. 564 * Returns 0 on success or -1 if the methods list is invalid. 565 */ 566 int 567 auth2_methods_valid(const char *_methods, int need_enable) 568 { 569 char *methods, *omethods, *method, *p; 570 u_int i, found; 571 int ret = -1; 572 573 if (*_methods == '\0') { 574 error("empty authentication method list"); 575 return -1; 576 } 577 omethods = methods = xstrdup(_methods); 578 while ((method = strsep(&methods, ",")) != NULL) { 579 for (found = i = 0; !found && authmethods[i] != NULL; i++) { 580 if ((p = strchr(method, ':')) != NULL) 581 *p = '\0'; 582 if (strcmp(method, authmethods[i]->name) != 0) 583 continue; 584 if (need_enable) { 585 if (authmethods[i]->enabled == NULL || 586 *(authmethods[i]->enabled) == 0) { 587 error("Disabled method \"%s\" in " 588 "AuthenticationMethods list \"%s\"", 589 method, _methods); 590 goto out; 591 } 592 } 593 found = 1; 594 break; 595 } 596 if (!found) { 597 error("Unknown authentication method \"%s\" in list", 598 method); 599 goto out; 600 } 601 } 602 ret = 0; 603 out: 604 free(omethods); 605 return ret; 606 } 607 608 /* 609 * Prune the AuthenticationMethods supplied in the configuration, removing 610 * any methods lists that include disabled methods. Note that this might 611 * leave authctxt->num_auth_methods == 0, even when multiple required auth 612 * has been requested. For this reason, all tests for whether multiple is 613 * enabled should consult options.num_auth_methods directly. 614 */ 615 int 616 auth2_setup_methods_lists(Authctxt *authctxt) 617 { 618 u_int i; 619 620 /* First, normalise away the "any" pseudo-method */ 621 if (options.num_auth_methods == 1 && 622 strcmp(options.auth_methods[0], "any") == 0) { 623 free(options.auth_methods[0]); 624 options.auth_methods[0] = NULL; 625 options.num_auth_methods = 0; 626 } 627 628 if (options.num_auth_methods == 0) 629 return 0; 630 debug3_f("checking methods"); 631 authctxt->auth_methods = xcalloc(options.num_auth_methods, 632 sizeof(*authctxt->auth_methods)); 633 authctxt->num_auth_methods = 0; 634 for (i = 0; i < options.num_auth_methods; i++) { 635 if (auth2_methods_valid(options.auth_methods[i], 1) != 0) { 636 logit("Authentication methods list \"%s\" contains " 637 "disabled method, skipping", 638 options.auth_methods[i]); 639 continue; 640 } 641 debug("authentication methods list %d: %s", 642 authctxt->num_auth_methods, options.auth_methods[i]); 643 authctxt->auth_methods[authctxt->num_auth_methods++] = 644 xstrdup(options.auth_methods[i]); 645 } 646 if (authctxt->num_auth_methods == 0) { 647 error("No AuthenticationMethods left after eliminating " 648 "disabled methods"); 649 return -1; 650 } 651 return 0; 652 } 653 654 static int 655 list_starts_with(const char *methods, const char *method, 656 const char *submethod) 657 { 658 size_t l = strlen(method); 659 int match; 660 const char *p; 661 662 if (strncmp(methods, method, l) != 0) 663 return MATCH_NONE; 664 p = methods + l; 665 match = MATCH_METHOD; 666 if (*p == ':') { 667 if (!submethod) 668 return MATCH_PARTIAL; 669 l = strlen(submethod); 670 p += 1; 671 if (strncmp(submethod, p, l)) 672 return MATCH_NONE; 673 p += l; 674 match = MATCH_BOTH; 675 } 676 if (*p != ',' && *p != '\0') 677 return MATCH_NONE; 678 return match; 679 } 680 681 /* 682 * Remove method from the start of a comma-separated list of methods. 683 * Returns 0 if the list of methods did not start with that method or 1 684 * if it did. 685 */ 686 static int 687 remove_method(char **methods, const char *method, const char *submethod) 688 { 689 char *omethods = *methods, *p; 690 size_t l = strlen(method); 691 int match; 692 693 match = list_starts_with(omethods, method, submethod); 694 if (match != MATCH_METHOD && match != MATCH_BOTH) 695 return 0; 696 p = omethods + l; 697 if (submethod && match == MATCH_BOTH) 698 p += 1 + strlen(submethod); /* include colon */ 699 if (*p == ',') 700 p++; 701 *methods = xstrdup(p); 702 free(omethods); 703 return 1; 704 } 705 706 /* 707 * Called after successful authentication. Will remove the successful method 708 * from the start of each list in which it occurs. If it was the last method 709 * in any list, then authentication is deemed successful. 710 * Returns 1 if the method completed any authentication list or 0 otherwise. 711 */ 712 int 713 auth2_update_methods_lists(Authctxt *authctxt, const char *method, 714 const char *submethod) 715 { 716 u_int i, found = 0; 717 718 debug3_f("updating methods list after \"%s\"", method); 719 for (i = 0; i < authctxt->num_auth_methods; i++) { 720 if (!remove_method(&(authctxt->auth_methods[i]), method, 721 submethod)) 722 continue; 723 found = 1; 724 if (*authctxt->auth_methods[i] == '\0') { 725 debug2("authentication methods list %d complete", i); 726 return 1; 727 } 728 debug3("authentication methods list %d remaining: \"%s\"", 729 i, authctxt->auth_methods[i]); 730 } 731 /* This should not happen, but would be bad if it did */ 732 if (!found) 733 fatal_f("method not in AuthenticationMethods"); 734 return 0; 735 } 736 737 /* Reset method-specific information */ 738 void auth2_authctxt_reset_info(Authctxt *authctxt) 739 { 740 sshkey_free(authctxt->auth_method_key); 741 free(authctxt->auth_method_info); 742 authctxt->auth_method_key = NULL; 743 authctxt->auth_method_info = NULL; 744 } 745 746 /* Record auth method-specific information for logs */ 747 void 748 auth2_record_info(Authctxt *authctxt, const char *fmt, ...) 749 { 750 va_list ap; 751 int i; 752 753 free(authctxt->auth_method_info); 754 authctxt->auth_method_info = NULL; 755 756 va_start(ap, fmt); 757 i = vasprintf(&authctxt->auth_method_info, fmt, ap); 758 va_end(ap); 759 760 if (i == -1) 761 fatal_f("vasprintf failed"); 762 } 763 764 /* 765 * Records a public key used in authentication. This is used for logging 766 * and to ensure that the same key is not subsequently accepted again for 767 * multiple authentication. 768 */ 769 void 770 auth2_record_key(Authctxt *authctxt, int authenticated, 771 const struct sshkey *key) 772 { 773 struct sshkey **tmp, *dup; 774 int r; 775 776 if ((r = sshkey_from_private(key, &dup)) != 0) 777 fatal_fr(r, "copy key"); 778 sshkey_free(authctxt->auth_method_key); 779 authctxt->auth_method_key = dup; 780 781 if (!authenticated) 782 return; 783 784 /* If authenticated, make sure we don't accept this key again */ 785 if ((r = sshkey_from_private(key, &dup)) != 0) 786 fatal_fr(r, "copy key"); 787 if (authctxt->nprev_keys >= INT_MAX || 788 (tmp = recallocarray(authctxt->prev_keys, authctxt->nprev_keys, 789 authctxt->nprev_keys + 1, sizeof(*authctxt->prev_keys))) == NULL) 790 fatal_f("reallocarray failed"); 791 authctxt->prev_keys = tmp; 792 authctxt->prev_keys[authctxt->nprev_keys] = dup; 793 authctxt->nprev_keys++; 794 795 } 796 797 /* Checks whether a key has already been previously used for authentication */ 798 int 799 auth2_key_already_used(Authctxt *authctxt, const struct sshkey *key) 800 { 801 u_int i; 802 char *fp; 803 804 for (i = 0; i < authctxt->nprev_keys; i++) { 805 if (sshkey_equal_public(key, authctxt->prev_keys[i])) { 806 fp = sshkey_fingerprint(authctxt->prev_keys[i], 807 options.fingerprint_hash, SSH_FP_DEFAULT); 808 debug3_f("key already used: %s %s", 809 sshkey_type(authctxt->prev_keys[i]), 810 fp == NULL ? "UNKNOWN" : fp); 811 free(fp); 812 return 1; 813 } 814 } 815 return 0; 816 } 817 818 /* 819 * Updates authctxt->session_info with details of authentication. Should be 820 * whenever an authentication method succeeds. 821 */ 822 void 823 auth2_update_session_info(Authctxt *authctxt, const char *method, 824 const char *submethod) 825 { 826 int r; 827 828 if (authctxt->session_info == NULL) { 829 if ((authctxt->session_info = sshbuf_new()) == NULL) 830 fatal_f("sshbuf_new"); 831 } 832 833 /* Append method[/submethod] */ 834 if ((r = sshbuf_putf(authctxt->session_info, "%s%s%s", 835 method, submethod == NULL ? "" : "/", 836 submethod == NULL ? "" : submethod)) != 0) 837 fatal_fr(r, "append method"); 838 839 /* Append key if present */ 840 if (authctxt->auth_method_key != NULL) { 841 if ((r = sshbuf_put_u8(authctxt->session_info, ' ')) != 0 || 842 (r = sshkey_format_text(authctxt->auth_method_key, 843 authctxt->session_info)) != 0) 844 fatal_fr(r, "append key"); 845 } 846 847 if (authctxt->auth_method_info != NULL) { 848 /* Ensure no ambiguity here */ 849 if (strchr(authctxt->auth_method_info, '\n') != NULL) 850 fatal_f("auth_method_info contains \\n"); 851 if ((r = sshbuf_put_u8(authctxt->session_info, ' ')) != 0 || 852 (r = sshbuf_putf(authctxt->session_info, "%s", 853 authctxt->auth_method_info)) != 0) { 854 fatal_fr(r, "append method info"); 855 } 856 } 857 if ((r = sshbuf_put_u8(authctxt->session_info, '\n')) != 0) 858 fatal_fr(r, "append"); 859 } 860 861