1 /* $NetBSD: auth2.c,v 1.26 2022/10/18 06:46:51 kre Exp $ */ 2 /* $OpenBSD: auth2.c,v 1.164 2022/02/23 11:18:13 djm Exp $ */ 3 /* 4 * Copyright (c) 2000 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 __RCSID("$NetBSD: auth2.c,v 1.26 2022/10/18 06:46:51 kre Exp $"); 29 30 #include <sys/types.h> 31 #include <sys/stat.h> 32 #include <sys/uio.h> 33 34 #include <fcntl.h> 35 #include <limits.h> 36 #include <pwd.h> 37 #include <stdarg.h> 38 #include <string.h> 39 #include <unistd.h> 40 #include <time.h> 41 42 #include "stdlib.h" 43 #include "atomicio.h" 44 #include "xmalloc.h" 45 #include "ssh2.h" 46 #include "packet.h" 47 #include "log.h" 48 #include "sshbuf.h" 49 #include "misc.h" 50 #include "servconf.h" 51 #include "compat.h" 52 #include "sshkey.h" 53 #include "hostfile.h" 54 #include "auth.h" 55 #include "dispatch.h" 56 #include "pathnames.h" 57 #include "canohost.h" 58 #include "pfilter.h" 59 60 #ifdef GSSAPI 61 #include "ssh-gss.h" 62 #endif 63 64 #include "monitor_wrap.h" 65 #include "ssherr.h" 66 #include "digest.h" 67 68 /* import */ 69 extern ServerOptions options; 70 extern struct sshbuf *loginmsg; 71 72 /* methods */ 73 74 extern Authmethod method_none; 75 extern Authmethod method_pubkey; 76 extern Authmethod method_passwd; 77 extern Authmethod method_kbdint; 78 extern Authmethod method_hostbased; 79 #ifdef KRB5 80 extern Authmethod method_kerberos; 81 #endif 82 #ifdef GSSAPI 83 extern Authmethod method_gssapi; 84 #endif 85 86 static int log_flag = 0; 87 88 Authmethod *authmethods[] = { 89 &method_none, 90 &method_pubkey, 91 #ifdef GSSAPI 92 &method_gssapi, 93 #endif 94 &method_passwd, 95 &method_kbdint, 96 &method_hostbased, 97 #ifdef KRB5 98 &method_kerberos, 99 #endif 100 NULL 101 }; 102 103 /* protocol */ 104 105 static int input_service_request(int, u_int32_t, struct ssh *); 106 static int input_userauth_request(int, u_int32_t, struct ssh *); 107 108 /* helper */ 109 static Authmethod *authmethod_byname(const char *); 110 static Authmethod *authmethod_lookup(Authctxt *, const char *); 111 static char *authmethods_get(Authctxt *authctxt); 112 113 #define MATCH_NONE 0 /* method or submethod mismatch */ 114 #define MATCH_METHOD 1 /* method matches (no submethod specified) */ 115 #define MATCH_BOTH 2 /* method and submethod match */ 116 #define MATCH_PARTIAL 3 /* method matches, submethod can't be checked */ 117 static int list_starts_with(const char *, const char *, const char *); 118 119 char * 120 auth2_read_banner(void) 121 { 122 struct stat st; 123 char *banner = NULL; 124 size_t len, n; 125 int fd; 126 127 if ((fd = open(options.banner, O_RDONLY)) == -1) 128 return (NULL); 129 if (fstat(fd, &st) == -1) { 130 close(fd); 131 return (NULL); 132 } 133 if (st.st_size <= 0 || st.st_size > 1*1024*1024) { 134 close(fd); 135 return (NULL); 136 } 137 138 len = (size_t)st.st_size; /* truncate */ 139 banner = xmalloc(len + 1); 140 n = atomicio(read, fd, banner, len); 141 close(fd); 142 143 if (n != len) { 144 free(banner); 145 return (NULL); 146 } 147 banner[n] = '\0'; 148 149 return (banner); 150 } 151 152 static void 153 userauth_send_banner(struct ssh *ssh, const char *msg) 154 { 155 int r; 156 157 if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_BANNER)) != 0 || 158 (r = sshpkt_put_cstring(ssh, msg)) != 0 || 159 (r = sshpkt_put_cstring(ssh, "")) != 0 || /* language, unused */ 160 (r = sshpkt_send(ssh)) != 0) 161 fatal_fr(r, "send packet"); 162 debug("%s: sent", __func__); 163 } 164 165 static void 166 userauth_banner(struct ssh *ssh) 167 { 168 char *banner = NULL; 169 170 if (options.banner == NULL) 171 return; 172 173 if ((banner = PRIVSEP(auth2_read_banner())) == NULL) 174 goto done; 175 userauth_send_banner(ssh, banner); 176 177 done: 178 free(banner); 179 } 180 181 /* 182 * loop until authctxt->success == TRUE 183 */ 184 void 185 do_authentication2(struct ssh *ssh) 186 { 187 Authctxt *authctxt = ssh->authctxt; 188 189 ssh_dispatch_init(ssh, &dispatch_protocol_error); 190 ssh_dispatch_set(ssh, SSH2_MSG_SERVICE_REQUEST, &input_service_request); 191 ssh_dispatch_run_fatal(ssh, DISPATCH_BLOCK, &authctxt->success); 192 ssh->authctxt = NULL; 193 } 194 195 /*ARGSUSED*/ 196 static int 197 input_service_request(int type, u_int32_t seq, struct ssh *ssh) 198 { 199 Authctxt *authctxt = ssh->authctxt; 200 char *service = NULL; 201 int r, acceptit = 0; 202 203 if ((r = sshpkt_get_cstring(ssh, &service, NULL)) != 0 || 204 (r = sshpkt_get_end(ssh)) != 0) 205 goto out; 206 207 if (authctxt == NULL) 208 fatal("input_service_request: no authctxt"); 209 210 if (strcmp(service, "ssh-userauth") == 0) { 211 if (!authctxt->success) { 212 acceptit = 1; 213 /* now we can handle user-auth requests */ 214 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_REQUEST, 215 &input_userauth_request); 216 } 217 } 218 /* XXX all other service requests are denied */ 219 220 if (acceptit) { 221 if ((r = sshpkt_start(ssh, SSH2_MSG_SERVICE_ACCEPT)) != 0 || 222 (r = sshpkt_put_cstring(ssh, service)) != 0 || 223 (r = sshpkt_send(ssh)) != 0 || 224 (r = ssh_packet_write_wait(ssh)) < 0) 225 goto out; 226 } else { 227 debug("bad service request %s", service); 228 ssh_packet_disconnect(ssh, "bad service request %s", service); 229 } 230 r = 0; 231 out: 232 free(service); 233 return r; 234 } 235 236 #define MIN_FAIL_DELAY_SECONDS 0.005 237 static double 238 user_specific_delay(const char *user) 239 { 240 char b[512]; 241 size_t len = ssh_digest_bytes(SSH_DIGEST_SHA512); 242 u_char *hash = xmalloc(len); 243 double delay; 244 245 (void)snprintf(b, sizeof b, "%llu%s", 246 (unsigned long long)options.timing_secret, user); 247 if (ssh_digest_memory(SSH_DIGEST_SHA512, b, strlen(b), hash, len) != 0) 248 fatal_f("ssh_digest_memory"); 249 /* 0-4.2 ms of delay */ 250 delay = (double)PEEK_U32(hash) / 1000 / 1000 / 1000 / 1000; 251 freezero(hash, len); 252 debug3_f("user specific delay %0.3lfms", delay/1000); 253 return MIN_FAIL_DELAY_SECONDS + delay; 254 } 255 256 static void 257 ensure_minimum_time_since(double start, double seconds) 258 { 259 struct timespec ts; 260 double elapsed = monotime_double() - start, req = seconds, remain; 261 262 /* if we've already passed the requested time, scale up */ 263 while ((remain = seconds - elapsed) < 0.0) 264 seconds *= 2; 265 266 ts.tv_sec = remain; 267 ts.tv_nsec = (remain - ts.tv_sec) * 1000000000; 268 debug3_f("elapsed %0.3lfms, delaying %0.3lfms (requested %0.3lfms)", 269 elapsed*1000, remain*1000, req*1000); 270 nanosleep(&ts, NULL); 271 } 272 273 /*ARGSUSED*/ 274 static int 275 input_userauth_request(int type, u_int32_t seq, struct ssh *ssh) 276 { 277 Authctxt *authctxt = ssh->authctxt; 278 Authmethod *m = NULL; 279 char *user = NULL, *service = NULL, *method = NULL, *style = NULL; 280 int r, authenticated = 0; 281 double tstart = monotime_double(); 282 283 if (authctxt == NULL) 284 fatal("input_userauth_request: no authctxt"); 285 286 if ((r = sshpkt_get_cstring(ssh, &user, NULL)) != 0 || 287 (r = sshpkt_get_cstring(ssh, &service, NULL)) != 0 || 288 (r = sshpkt_get_cstring(ssh, &method, NULL)) != 0) 289 goto out; 290 debug("userauth-request for user %s service %s method %s", user, service, method); 291 if (!log_flag) { 292 logit("SSH: Server;Ltype: Authname;Remote: %s-%d;Name: %s", 293 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), user); 294 log_flag = 1; 295 } 296 debug("attempt %d failures %d", authctxt->attempt, authctxt->failures); 297 298 if ((style = strchr(user, ':')) != NULL) 299 *style++ = 0; 300 301 if (authctxt->attempt >= 1024) 302 auth_maxtries_exceeded(ssh); 303 if (authctxt->attempt++ == 0) { 304 /* setup auth context */ 305 authctxt->pw = PRIVSEP(getpwnamallow(ssh, user)); 306 authctxt->user = xstrdup(user); 307 if (authctxt->pw && strcmp(service, "ssh-connection")==0) { 308 authctxt->valid = 1; 309 debug2_f("setting up authctxt for %s", user); 310 } else { 311 authctxt->valid = 0; 312 /* Invalid user, fake password information */ 313 authctxt->pw = fakepw(); 314 pfilter_notify(1); 315 } 316 #ifdef USE_PAM 317 if (options.use_pam) 318 PRIVSEP(start_pam(ssh)); 319 #endif 320 ssh_packet_set_log_preamble(ssh, "%suser %s", 321 authctxt->valid ? "authenticating " : "invalid ", user); 322 setproctitle("%s%s", authctxt->valid ? user : "unknown", 323 use_privsep ? " [net]" : ""); 324 authctxt->service = xstrdup(service); 325 authctxt->style = style ? xstrdup(style) : NULL; 326 if (use_privsep) 327 mm_inform_authserv(service, style); 328 userauth_banner(ssh); 329 if (auth2_setup_methods_lists(authctxt) != 0) 330 ssh_packet_disconnect(ssh, 331 "no authentication methods enabled"); 332 } else if (strcmp(user, authctxt->user) != 0 || 333 strcmp(service, authctxt->service) != 0) { 334 ssh_packet_disconnect(ssh, "Change of username or service " 335 "not allowed: (%s,%s) -> (%s,%s)", 336 authctxt->user, authctxt->service, user, service); 337 } 338 /* reset state */ 339 auth2_challenge_stop(ssh); 340 341 #ifdef GSSAPI 342 /* XXX move to auth2_gssapi_stop() */ 343 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 344 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); 345 #endif 346 347 auth2_authctxt_reset_info(authctxt); 348 authctxt->postponed = 0; 349 authctxt->server_caused_failure = 0; 350 351 /* try to authenticate user */ 352 m = authmethod_lookup(authctxt, method); 353 if (m != NULL && authctxt->failures < options.max_authtries) { 354 debug2("input_userauth_request: try method %s", method); 355 authenticated = m->userauth(ssh, method); 356 } 357 if (!authctxt->authenticated) 358 ensure_minimum_time_since(tstart, 359 user_specific_delay(authctxt->user)); 360 userauth_finish(ssh, authenticated, method, NULL); 361 r = 0; 362 out: 363 free(service); 364 free(user); 365 free(method); 366 return r; 367 } 368 369 void 370 userauth_finish(struct ssh *ssh, int authenticated, const char *packet_method, 371 const char *submethod) 372 { 373 Authctxt *authctxt = ssh->authctxt; 374 Authmethod *m = NULL; 375 const char *method = packet_method; 376 char *methods; 377 int r, partial = 0; 378 379 if (authenticated) { 380 if (!authctxt->valid) { 381 fatal("INTERNAL ERROR: authenticated invalid user %s", 382 authctxt->user); 383 } 384 if (authctxt->postponed) 385 fatal("INTERNAL ERROR: authenticated and postponed"); 386 /* prefer primary authmethod name to possible synonym */ 387 if ((m = authmethod_byname(method)) == NULL) 388 fatal("INTERNAL ERROR: bad method %s", method); 389 method = m->name; 390 } 391 392 /* Special handling for root */ 393 if (authenticated && authctxt->pw->pw_uid == 0 && 394 !auth_root_allowed(ssh, method)) { 395 authenticated = 0; 396 #ifdef SSH_AUDIT_EVENTS 397 PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED)); 398 #endif 399 } 400 401 #ifdef USE_PAM 402 if (options.use_pam && authenticated) { 403 if (!PRIVSEP(do_pam_account())) { 404 /* if PAM returned a message, send it to the user */ 405 if (sshbuf_len(loginmsg) > 0) { 406 if ((r = sshbuf_put(loginmsg, "\0", 1)) != 0) 407 fatal("%s: buffer error: %s", 408 __func__, ssh_err(r)); 409 userauth_send_banner(ssh, 410 (const char *)sshbuf_ptr(loginmsg)); 411 if ((r = ssh_packet_write_wait(ssh)) < 0) { 412 sshpkt_fatal(ssh, r, 413 "%s: send PAM banner", __func__); 414 } 415 } 416 fatal("Access denied for user %s by PAM account " 417 "configuration", authctxt->user); 418 } 419 } 420 #endif 421 422 if (authenticated && options.num_auth_methods != 0) { 423 if (!auth2_update_methods_lists(authctxt, method, submethod)) { 424 authenticated = 0; 425 partial = 1; 426 } 427 } 428 429 /* Log before sending the reply */ 430 auth_log(ssh, authenticated, partial, method, submethod); 431 432 /* Update information exposed to session */ 433 if (authenticated || partial) 434 auth2_update_session_info(authctxt, method, submethod); 435 436 if (authctxt->postponed) 437 return; 438 439 if (authenticated == 1) { 440 /* turn off userauth */ 441 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_REQUEST, 442 &dispatch_protocol_ignore); 443 if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_SUCCESS)) != 0 || 444 (r = sshpkt_send(ssh)) != 0 || 445 (r = ssh_packet_write_wait(ssh)) < 0) 446 fatal_fr(r, "send success packet"); 447 /* now we can break out */ 448 authctxt->success = 1; 449 ssh_packet_set_log_preamble(ssh, "user %s", authctxt->user); 450 } else { 451 /* Allow initial try of "none" auth without failure penalty */ 452 if (!partial && !authctxt->server_caused_failure && 453 (authctxt->attempt > 1 || strcmp(method, "none") != 0)) { 454 authctxt->failures++; 455 pfilter_notify(1); 456 } 457 if (authctxt->failures >= options.max_authtries) 458 auth_maxtries_exceeded(ssh); 459 methods = authmethods_get(authctxt); 460 debug3_f("failure partial=%d next methods=\"%s\"", 461 partial, methods); 462 if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_FAILURE)) != 0 || 463 (r = sshpkt_put_cstring(ssh, methods)) != 0 || 464 (r = sshpkt_put_u8(ssh, partial)) != 0 || 465 (r = sshpkt_send(ssh)) != 0 || 466 (r = ssh_packet_write_wait(ssh)) < 0) 467 fatal_fr(r, "send failure packet"); 468 free(methods); 469 } 470 } 471 472 /* 473 * Checks whether method is allowed by at least one AuthenticationMethods 474 * methods list. Returns 1 if allowed, or no methods lists configured. 475 * 0 otherwise. 476 */ 477 int 478 auth2_method_allowed(Authctxt *authctxt, const char *method, 479 const char *submethod) 480 { 481 u_int i; 482 483 /* 484 * NB. authctxt->num_auth_methods might be zero as a result of 485 * auth2_setup_methods_lists(), so check the configuration. 486 */ 487 if (options.num_auth_methods == 0) 488 return 1; 489 for (i = 0; i < authctxt->num_auth_methods; i++) { 490 if (list_starts_with(authctxt->auth_methods[i], method, 491 submethod) != MATCH_NONE) 492 return 1; 493 } 494 return 0; 495 } 496 497 static char * 498 authmethods_get(Authctxt *authctxt) 499 { 500 struct sshbuf *b; 501 char *list; 502 int i, r; 503 504 if ((b = sshbuf_new()) == NULL) 505 fatal_f("sshbuf_new failed"); 506 for (i = 0; authmethods[i] != NULL; i++) { 507 if (strcmp(authmethods[i]->name, "none") == 0) 508 continue; 509 if (authmethods[i]->enabled == NULL || 510 *(authmethods[i]->enabled) == 0) 511 continue; 512 if (!auth2_method_allowed(authctxt, authmethods[i]->name, 513 NULL)) 514 continue; 515 if ((r = sshbuf_putf(b, "%s%s", sshbuf_len(b) ? "," : "", 516 authmethods[i]->name)) != 0) 517 fatal_fr(r, "buffer error"); 518 } 519 if ((list = sshbuf_dup_string(b)) == NULL) 520 fatal_f("sshbuf_dup_string failed"); 521 sshbuf_free(b); 522 return list; 523 } 524 525 static Authmethod * 526 authmethod_byname(const char *name) 527 { 528 int i; 529 530 if (name == NULL) 531 fatal_f("NULL authentication method name"); 532 for (i = 0; authmethods[i] != NULL; i++) { 533 if (strcmp(name, authmethods[i]->name) == 0 || 534 (authmethods[i]->synonym != NULL && 535 strcmp(name, authmethods[i]->synonym) == 0)) 536 return authmethods[i]; 537 } 538 debug_f("unrecognized authentication method name: %s", name); 539 return NULL; 540 } 541 542 static Authmethod * 543 authmethod_lookup(Authctxt *authctxt, const char *name) 544 { 545 Authmethod *method; 546 547 if ((method = authmethod_byname(name)) == NULL) 548 return NULL; 549 550 if (method->enabled == NULL || *(method->enabled) == 0) { 551 debug3_f("method %s not enabled", name); 552 return NULL; 553 } 554 if (!auth2_method_allowed(authctxt, method->name, NULL)) { 555 debug3_f("method %s not allowed " 556 "by AuthenticationMethods", name); 557 return NULL; 558 } 559 return method; 560 } 561 562 /* 563 * Check a comma-separated list of methods for validity. Is need_enable is 564 * non-zero, then also require that the methods are enabled. 565 * Returns 0 on success or -1 if the methods list is invalid. 566 */ 567 int 568 auth2_methods_valid(const char *_methods, int need_enable) 569 { 570 char *methods, *omethods, *method, *p; 571 u_int i, found; 572 int ret = -1; 573 574 if (*_methods == '\0') { 575 error("empty authentication method list"); 576 return -1; 577 } 578 omethods = methods = xstrdup(_methods); 579 while ((method = strsep(&methods, ",")) != NULL) { 580 for (found = i = 0; !found && authmethods[i] != NULL; i++) { 581 if ((p = strchr(method, ':')) != NULL) 582 *p = '\0'; 583 if (strcmp(method, authmethods[i]->name) != 0) 584 continue; 585 if (need_enable) { 586 if (authmethods[i]->enabled == NULL || 587 *(authmethods[i]->enabled) == 0) { 588 error("Disabled method \"%s\" in " 589 "AuthenticationMethods list \"%s\"", 590 method, _methods); 591 goto out; 592 } 593 } 594 found = 1; 595 break; 596 } 597 if (!found) { 598 error("Unknown authentication method \"%s\" in list", 599 method); 600 goto out; 601 } 602 } 603 ret = 0; 604 out: 605 free(omethods); 606 return ret; 607 } 608 609 /* 610 * Prune the AuthenticationMethods supplied in the configuration, removing 611 * any methods lists that include disabled methods. Note that this might 612 * leave authctxt->num_auth_methods == 0, even when multiple required auth 613 * has been requested. For this reason, all tests for whether multiple is 614 * enabled should consult options.num_auth_methods directly. 615 */ 616 int 617 auth2_setup_methods_lists(Authctxt *authctxt) 618 { 619 u_int i; 620 621 /* First, normalise away the "any" pseudo-method */ 622 if (options.num_auth_methods == 1 && 623 strcmp(options.auth_methods[0], "any") == 0) { 624 free(options.auth_methods[0]); 625 options.auth_methods[0] = NULL; 626 options.num_auth_methods = 0; 627 } 628 629 if (options.num_auth_methods == 0) 630 return 0; 631 debug3_f("checking methods"); 632 authctxt->auth_methods = xcalloc(options.num_auth_methods, 633 sizeof(*authctxt->auth_methods)); 634 authctxt->num_auth_methods = 0; 635 for (i = 0; i < options.num_auth_methods; i++) { 636 if (auth2_methods_valid(options.auth_methods[i], 1) != 0) { 637 logit("Authentication methods list \"%s\" contains " 638 "disabled method, skipping", 639 options.auth_methods[i]); 640 continue; 641 } 642 debug("authentication methods list %d: %s", 643 authctxt->num_auth_methods, options.auth_methods[i]); 644 authctxt->auth_methods[authctxt->num_auth_methods++] = 645 xstrdup(options.auth_methods[i]); 646 } 647 if (authctxt->num_auth_methods == 0) { 648 error("No AuthenticationMethods left after eliminating " 649 "disabled methods"); 650 return -1; 651 } 652 return 0; 653 } 654 655 static int 656 list_starts_with(const char *methods, const char *method, 657 const char *submethod) 658 { 659 size_t l = strlen(method); 660 int match; 661 const char *p; 662 663 if (strncmp(methods, method, l) != 0) 664 return MATCH_NONE; 665 p = methods + l; 666 match = MATCH_METHOD; 667 if (*p == ':') { 668 if (!submethod) 669 return MATCH_PARTIAL; 670 l = strlen(submethod); 671 p += 1; 672 if (strncmp(submethod, p, l)) 673 return MATCH_NONE; 674 p += l; 675 match = MATCH_BOTH; 676 } 677 if (*p != ',' && *p != '\0') 678 return MATCH_NONE; 679 return match; 680 } 681 682 /* 683 * Remove method from the start of a comma-separated list of methods. 684 * Returns 0 if the list of methods did not start with that method or 1 685 * if it did. 686 */ 687 static int 688 remove_method(char **methods, const char *method, const char *submethod) 689 { 690 char *omethods = *methods, *p; 691 size_t l = strlen(method); 692 int match; 693 694 match = list_starts_with(omethods, method, submethod); 695 if (match != MATCH_METHOD && match != MATCH_BOTH) 696 return 0; 697 p = omethods + l; 698 if (submethod && match == MATCH_BOTH) 699 p += 1 + strlen(submethod); /* include colon */ 700 if (*p == ',') 701 p++; 702 *methods = xstrdup(p); 703 free(omethods); 704 return 1; 705 } 706 707 /* 708 * Called after successful authentication. Will remove the successful method 709 * from the start of each list in which it occurs. If it was the last method 710 * in any list, then authentication is deemed successful. 711 * Returns 1 if the method completed any authentication list or 0 otherwise. 712 */ 713 int 714 auth2_update_methods_lists(Authctxt *authctxt, const char *method, 715 const char *submethod) 716 { 717 u_int i, found = 0; 718 719 debug3_f("updating methods list after \"%s\"", method); 720 for (i = 0; i < authctxt->num_auth_methods; i++) { 721 if (!remove_method(&(authctxt->auth_methods[i]), method, 722 submethod)) 723 continue; 724 found = 1; 725 if (*authctxt->auth_methods[i] == '\0') { 726 debug2("authentication methods list %d complete", i); 727 return 1; 728 } 729 debug3("authentication methods list %d remaining: \"%s\"", 730 i, authctxt->auth_methods[i]); 731 } 732 /* This should not happen, but would be bad if it did */ 733 if (!found) 734 fatal_f("method not in AuthenticationMethods"); 735 return 0; 736 } 737 738 /* Reset method-specific information */ 739 void auth2_authctxt_reset_info(Authctxt *authctxt) 740 { 741 sshkey_free(authctxt->auth_method_key); 742 free(authctxt->auth_method_info); 743 authctxt->auth_method_key = NULL; 744 authctxt->auth_method_info = NULL; 745 } 746 747 /* Record auth method-specific information for logs */ 748 void 749 auth2_record_info(Authctxt *authctxt, const char *fmt, ...) 750 { 751 va_list ap; 752 int i; 753 754 free(authctxt->auth_method_info); 755 authctxt->auth_method_info = NULL; 756 757 va_start(ap, fmt); 758 i = vasprintf(&authctxt->auth_method_info, fmt, ap); 759 va_end(ap); 760 761 if (i == -1) 762 fatal_f("vasprintf failed"); 763 } 764 765 /* 766 * Records a public key used in authentication. This is used for logging 767 * and to ensure that the same key is not subsequently accepted again for 768 * multiple authentication. 769 */ 770 void 771 auth2_record_key(Authctxt *authctxt, int authenticated, 772 const struct sshkey *key) 773 { 774 struct sshkey **tmp, *dup; 775 int r; 776 777 if ((r = sshkey_from_private(key, &dup)) != 0) 778 fatal_fr(r, "copy key"); 779 sshkey_free(authctxt->auth_method_key); 780 authctxt->auth_method_key = dup; 781 782 if (!authenticated) 783 return; 784 785 /* If authenticated, make sure we don't accept this key again */ 786 if ((r = sshkey_from_private(key, &dup)) != 0) 787 fatal_fr(r, "copy key"); 788 if (authctxt->nprev_keys >= INT_MAX || 789 (tmp = recallocarray(authctxt->prev_keys, authctxt->nprev_keys, 790 authctxt->nprev_keys + 1, sizeof(*authctxt->prev_keys))) == NULL) 791 fatal_f("reallocarray failed"); 792 authctxt->prev_keys = tmp; 793 authctxt->prev_keys[authctxt->nprev_keys] = dup; 794 authctxt->nprev_keys++; 795 796 } 797 798 /* Checks whether a key has already been previously used for authentication */ 799 int 800 auth2_key_already_used(Authctxt *authctxt, const struct sshkey *key) 801 { 802 u_int i; 803 char *fp; 804 805 for (i = 0; i < authctxt->nprev_keys; i++) { 806 if (sshkey_equal_public(key, authctxt->prev_keys[i])) { 807 fp = sshkey_fingerprint(authctxt->prev_keys[i], 808 options.fingerprint_hash, SSH_FP_DEFAULT); 809 debug3_f("key already used: %s %s", 810 sshkey_type(authctxt->prev_keys[i]), 811 fp == NULL ? "UNKNOWN" : fp); 812 free(fp); 813 return 1; 814 } 815 } 816 return 0; 817 } 818 819 /* 820 * Updates authctxt->session_info with details of authentication. Should be 821 * whenever an authentication method succeeds. 822 */ 823 void 824 auth2_update_session_info(Authctxt *authctxt, const char *method, 825 const char *submethod) 826 { 827 int r; 828 829 if (authctxt->session_info == NULL) { 830 if ((authctxt->session_info = sshbuf_new()) == NULL) 831 fatal_f("sshbuf_new"); 832 } 833 834 /* Append method[/submethod] */ 835 if ((r = sshbuf_putf(authctxt->session_info, "%s%s%s", 836 method, submethod == NULL ? "" : "/", 837 submethod == NULL ? "" : submethod)) != 0) 838 fatal_fr(r, "append method"); 839 840 /* Append key if present */ 841 if (authctxt->auth_method_key != NULL) { 842 if ((r = sshbuf_put_u8(authctxt->session_info, ' ')) != 0 || 843 (r = sshkey_format_text(authctxt->auth_method_key, 844 authctxt->session_info)) != 0) 845 fatal_fr(r, "append key"); 846 } 847 848 if (authctxt->auth_method_info != NULL) { 849 /* Ensure no ambiguity here */ 850 if (strchr(authctxt->auth_method_info, '\n') != NULL) 851 fatal_f("auth_method_info contains \\n"); 852 if ((r = sshbuf_put_u8(authctxt->session_info, ' ')) != 0 || 853 (r = sshbuf_putf(authctxt->session_info, "%s", 854 authctxt->auth_method_info)) != 0) { 855 fatal_fr(r, "append method info"); 856 } 857 } 858 if ((r = sshbuf_put_u8(authctxt->session_info, '\n')) != 0) 859 fatal_fr(r, "append"); 860 } 861 862