1 /* $NetBSD: auth2.c,v 1.29 2023/12/20 17:15:20 christos Exp $ */ 2 /* $OpenBSD: auth2.c,v 1.168 2023/12/18 14:45:49 djm Exp $ */ 3 4 /* 5 * Copyright (c) 2000 Markus Friedl. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 26 */ 27 28 #include "includes.h" 29 __RCSID("$NetBSD: auth2.c,v 1.29 2023/12/20 17:15:20 christos Exp $"); 30 31 #include <sys/types.h> 32 #include <sys/stat.h> 33 #include <sys/uio.h> 34 35 #include <fcntl.h> 36 #include <limits.h> 37 #include <pwd.h> 38 #include <stdarg.h> 39 #include <string.h> 40 #include <unistd.h> 41 #include <time.h> 42 43 #include "stdlib.h" 44 #include "atomicio.h" 45 #include "xmalloc.h" 46 #include "ssh2.h" 47 #include "packet.h" 48 #include "log.h" 49 #include "sshbuf.h" 50 #include "misc.h" 51 #include "servconf.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 #include "kex.h" 68 69 /* import */ 70 extern ServerOptions options; 71 extern struct sshbuf *loginmsg; 72 73 /* methods */ 74 75 extern Authmethod method_none; 76 extern Authmethod method_pubkey; 77 extern Authmethod method_passwd; 78 extern Authmethod method_kbdint; 79 extern Authmethod method_hostbased; 80 #ifdef KRB5 81 extern Authmethod method_kerberos; 82 #endif 83 #ifdef GSSAPI 84 extern Authmethod method_gssapi; 85 #endif 86 87 static int log_flag = 0; 88 89 Authmethod *authmethods[] = { 90 &method_none, 91 &method_pubkey, 92 #ifdef GSSAPI 93 &method_gssapi, 94 #endif 95 &method_passwd, 96 &method_kbdint, 97 &method_hostbased, 98 #ifdef KRB5 99 &method_kerberos, 100 #endif 101 NULL 102 }; 103 104 /* protocol */ 105 106 static int input_service_request(int, u_int32_t, struct ssh *); 107 static int input_userauth_request(int, u_int32_t, struct ssh *); 108 109 /* helper */ 110 static Authmethod *authmethod_byname(const char *); 111 static Authmethod *authmethod_lookup(Authctxt *, const char *); 112 static char *authmethods_get(Authctxt *authctxt); 113 114 #define MATCH_NONE 0 /* method or submethod mismatch */ 115 #define MATCH_METHOD 1 /* method matches (no submethod specified) */ 116 #define MATCH_BOTH 2 /* method and submethod match */ 117 #define MATCH_PARTIAL 3 /* method matches, submethod can't be checked */ 118 static int list_starts_with(const char *, const char *, const char *); 119 120 char * 121 auth2_read_banner(void) 122 { 123 struct stat st; 124 char *banner = NULL; 125 size_t len, n; 126 int fd; 127 128 if ((fd = open(options.banner, O_RDONLY)) == -1) 129 return (NULL); 130 if (fstat(fd, &st) == -1) { 131 close(fd); 132 return (NULL); 133 } 134 if (st.st_size <= 0 || st.st_size > 1*1024*1024) { 135 close(fd); 136 return (NULL); 137 } 138 139 len = (size_t)st.st_size; /* truncate */ 140 banner = xmalloc(len + 1); 141 n = atomicio(read, fd, banner, len); 142 close(fd); 143 144 if (n != len) { 145 free(banner); 146 return (NULL); 147 } 148 banner[n] = '\0'; 149 150 return (banner); 151 } 152 153 static void 154 userauth_send_banner(struct ssh *ssh, const char *msg) 155 { 156 int r; 157 158 if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_BANNER)) != 0 || 159 (r = sshpkt_put_cstring(ssh, msg)) != 0 || 160 (r = sshpkt_put_cstring(ssh, "")) != 0 || /* language, unused */ 161 (r = sshpkt_send(ssh)) != 0) 162 fatal_fr(r, "send packet"); 163 debug("%s: sent", __func__); 164 } 165 166 static void 167 userauth_banner(struct ssh *ssh) 168 { 169 char *banner = NULL; 170 171 if (options.banner == NULL) 172 return; 173 174 if ((banner = PRIVSEP(auth2_read_banner())) == NULL) 175 goto done; 176 userauth_send_banner(ssh, banner); 177 178 done: 179 free(banner); 180 } 181 182 /* 183 * loop until authctxt->success == TRUE 184 */ 185 void 186 do_authentication2(struct ssh *ssh) 187 { 188 Authctxt *authctxt = ssh->authctxt; 189 190 ssh_dispatch_init(ssh, &dispatch_protocol_error); 191 if (ssh->kex->ext_info_c) 192 ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &kex_input_ext_info); 193 ssh_dispatch_set(ssh, SSH2_MSG_SERVICE_REQUEST, &input_service_request); 194 ssh_dispatch_run_fatal(ssh, DISPATCH_BLOCK, &authctxt->success); 195 ssh->authctxt = NULL; 196 } 197 198 static int 199 input_service_request(int type, u_int32_t seq, struct ssh *ssh) 200 { 201 Authctxt *authctxt = ssh->authctxt; 202 char *service = NULL; 203 int r, acceptit = 0; 204 205 if ((r = sshpkt_get_cstring(ssh, &service, NULL)) != 0 || 206 (r = sshpkt_get_end(ssh)) != 0) 207 goto out; 208 209 if (authctxt == NULL) 210 fatal("input_service_request: no authctxt"); 211 212 if (strcmp(service, "ssh-userauth") == 0) { 213 if (!authctxt->success) { 214 acceptit = 1; 215 /* now we can handle user-auth requests */ 216 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_REQUEST, 217 &input_userauth_request); 218 } 219 } 220 /* XXX all other service requests are denied */ 221 222 if (acceptit) { 223 if ((r = sshpkt_start(ssh, SSH2_MSG_SERVICE_ACCEPT)) != 0 || 224 (r = sshpkt_put_cstring(ssh, service)) != 0 || 225 (r = sshpkt_send(ssh)) != 0 || 226 (r = ssh_packet_write_wait(ssh)) < 0) 227 goto out; 228 } else { 229 debug("bad service request %s", service); 230 ssh_packet_disconnect(ssh, "bad service request %s", service); 231 } 232 ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &dispatch_protocol_error); 233 r = 0; 234 out: 235 free(service); 236 return r; 237 } 238 239 #define MIN_FAIL_DELAY_SECONDS 0.005 240 #define MAX_FAIL_DELAY_SECONDS 5.0 241 static double 242 user_specific_delay(const char *user) 243 { 244 char b[512]; 245 size_t len = ssh_digest_bytes(SSH_DIGEST_SHA512); 246 u_char *hash = xmalloc(len); 247 double delay; 248 249 (void)snprintf(b, sizeof b, "%llu%s", 250 (unsigned long long)options.timing_secret, user); 251 if (ssh_digest_memory(SSH_DIGEST_SHA512, b, strlen(b), hash, len) != 0) 252 fatal_f("ssh_digest_memory"); 253 /* 0-4.2 ms of delay */ 254 delay = (double)PEEK_U32(hash) / 1000 / 1000 / 1000 / 1000; 255 freezero(hash, len); 256 debug3_f("user specific delay %0.3lfms", delay/1000); 257 return MIN_FAIL_DELAY_SECONDS + delay; 258 } 259 260 static void 261 ensure_minimum_time_since(double start, double seconds) 262 { 263 struct timespec ts; 264 double elapsed = monotime_double() - start, req = seconds, remain; 265 266 if (elapsed > MAX_FAIL_DELAY_SECONDS) { 267 debug3_f("elapsed %0.3lfms exceeded the max delay " 268 "requested %0.3lfms)", elapsed*1000, req*1000); 269 return; 270 } 271 272 /* if we've already passed the requested time, scale up */ 273 while ((remain = seconds - elapsed) < 0.0) 274 seconds *= 2; 275 276 ts.tv_sec = remain; 277 ts.tv_nsec = (remain - ts.tv_sec) * 1000000000; 278 debug3_f("elapsed %0.3lfms, delaying %0.3lfms (requested %0.3lfms)", 279 elapsed*1000, remain*1000, req*1000); 280 nanosleep(&ts, NULL); 281 } 282 283 static int 284 input_userauth_request(int type, u_int32_t seq, struct ssh *ssh) 285 { 286 Authctxt *authctxt = ssh->authctxt; 287 Authmethod *m = NULL; 288 char *user = NULL, *service = NULL, *method = NULL, *style = NULL; 289 int r, authenticated = 0; 290 double tstart = monotime_double(); 291 292 if (authctxt == NULL) 293 fatal("input_userauth_request: no authctxt"); 294 295 if ((r = sshpkt_get_cstring(ssh, &user, NULL)) != 0 || 296 (r = sshpkt_get_cstring(ssh, &service, NULL)) != 0 || 297 (r = sshpkt_get_cstring(ssh, &method, NULL)) != 0) 298 goto out; 299 debug("userauth-request for user %s service %s method %s", user, service, method); 300 if (!log_flag) { 301 logit("SSH: Server;Ltype: Authname;Remote: %s-%d;Name: %s", 302 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), user); 303 log_flag = 1; 304 } 305 debug("attempt %d failures %d", authctxt->attempt, authctxt->failures); 306 307 if ((style = strchr(user, ':')) != NULL) 308 *style++ = 0; 309 310 if (authctxt->attempt >= 1024) 311 auth_maxtries_exceeded(ssh); 312 if (authctxt->attempt++ == 0) { 313 /* setup auth context */ 314 authctxt->pw = PRIVSEP(getpwnamallow(ssh, user)); 315 authctxt->user = xstrdup(user); 316 if (authctxt->pw && strcmp(service, "ssh-connection")==0) { 317 authctxt->valid = 1; 318 debug2_f("setting up authctxt for %s", user); 319 } else { 320 authctxt->valid = 0; 321 /* Invalid user, fake password information */ 322 authctxt->pw = fakepw(); 323 pfilter_notify(1); 324 } 325 #ifdef USE_PAM 326 if (options.use_pam) 327 PRIVSEP(start_pam(ssh)); 328 #endif 329 ssh_packet_set_log_preamble(ssh, "%suser %s", 330 authctxt->valid ? "authenticating " : "invalid ", user); 331 setproctitle("%s%s", authctxt->valid ? user : "unknown", 332 use_privsep ? " [net]" : ""); 333 authctxt->service = xstrdup(service); 334 authctxt->style = style ? xstrdup(style) : NULL; 335 if (use_privsep) 336 mm_inform_authserv(service, style); 337 userauth_banner(ssh); 338 if ((r = kex_server_update_ext_info(ssh)) != 0) 339 fatal_fr(r, "kex_server_update_ext_info failed"); 340 if (auth2_setup_methods_lists(authctxt) != 0) 341 ssh_packet_disconnect(ssh, 342 "no authentication methods enabled"); 343 } else if (strcmp(user, authctxt->user) != 0 || 344 strcmp(service, authctxt->service) != 0) { 345 ssh_packet_disconnect(ssh, "Change of username or service " 346 "not allowed: (%s,%s) -> (%s,%s)", 347 authctxt->user, authctxt->service, user, service); 348 } 349 /* reset state */ 350 auth2_challenge_stop(ssh); 351 352 #ifdef GSSAPI 353 /* XXX move to auth2_gssapi_stop() */ 354 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 355 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); 356 #endif 357 358 auth2_authctxt_reset_info(authctxt); 359 authctxt->postponed = 0; 360 authctxt->server_caused_failure = 0; 361 362 /* try to authenticate user */ 363 m = authmethod_lookup(authctxt, method); 364 if (m != NULL && authctxt->failures < options.max_authtries) { 365 debug2("input_userauth_request: try method %s", method); 366 authenticated = m->userauth(ssh, method); 367 } 368 if (!authctxt->authenticated && strcmp(method, "none") != 0) 369 ensure_minimum_time_since(tstart, 370 user_specific_delay(authctxt->user)); 371 userauth_finish(ssh, authenticated, method, NULL); 372 r = 0; 373 out: 374 free(service); 375 free(user); 376 free(method); 377 return r; 378 } 379 380 void 381 userauth_finish(struct ssh *ssh, int authenticated, const char *packet_method, 382 const char *submethod) 383 { 384 Authctxt *authctxt = ssh->authctxt; 385 Authmethod *m = NULL; 386 const char *method = packet_method; 387 char *methods; 388 int r, partial = 0; 389 390 if (authenticated) { 391 if (!authctxt->valid) { 392 fatal("INTERNAL ERROR: authenticated invalid user %s", 393 authctxt->user); 394 } 395 if (authctxt->postponed) 396 fatal("INTERNAL ERROR: authenticated and postponed"); 397 /* prefer primary authmethod name to possible synonym */ 398 if ((m = authmethod_byname(method)) == NULL) 399 fatal("INTERNAL ERROR: bad method %s", method); 400 method = m->name; 401 } 402 403 /* Special handling for root */ 404 if (authenticated && authctxt->pw->pw_uid == 0 && 405 !auth_root_allowed(ssh, method)) { 406 authenticated = 0; 407 #ifdef SSH_AUDIT_EVENTS 408 PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED)); 409 #endif 410 } 411 412 #ifdef USE_PAM 413 if (options.use_pam && authenticated) { 414 if (!PRIVSEP(do_pam_account())) { 415 /* if PAM returned a message, send it to the user */ 416 if (sshbuf_len(loginmsg) > 0) { 417 if ((r = sshbuf_put(loginmsg, "\0", 1)) != 0) 418 fatal("%s: buffer error: %s", 419 __func__, ssh_err(r)); 420 userauth_send_banner(ssh, 421 (const char *)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 fatal("Access denied for user %s by PAM account " 428 "configuration", authctxt->user); 429 } 430 } 431 #endif 432 433 if (authenticated && options.num_auth_methods != 0) { 434 if (!auth2_update_methods_lists(authctxt, method, submethod)) { 435 authenticated = 0; 436 partial = 1; 437 } 438 } 439 440 /* Log before sending the reply */ 441 auth_log(ssh, authenticated, partial, method, submethod); 442 443 /* Update information exposed to session */ 444 if (authenticated || partial) 445 auth2_update_session_info(authctxt, method, submethod); 446 447 if (authctxt->postponed) 448 return; 449 450 if (authenticated == 1) { 451 /* turn off userauth */ 452 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_REQUEST, 453 &dispatch_protocol_ignore); 454 if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_SUCCESS)) != 0 || 455 (r = sshpkt_send(ssh)) != 0 || 456 (r = ssh_packet_write_wait(ssh)) < 0) 457 fatal_fr(r, "send success packet"); 458 /* now we can break out */ 459 authctxt->success = 1; 460 ssh_packet_set_log_preamble(ssh, "user %s", authctxt->user); 461 } else { 462 /* Allow initial try of "none" auth without failure penalty */ 463 if (!partial && !authctxt->server_caused_failure && 464 (authctxt->attempt > 1 || strcmp(method, "none") != 0)) { 465 authctxt->failures++; 466 pfilter_notify(1); 467 } 468 if (authctxt->failures >= options.max_authtries) 469 auth_maxtries_exceeded(ssh); 470 methods = authmethods_get(authctxt); 471 debug3_f("failure partial=%d next methods=\"%s\"", 472 partial, methods); 473 if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_FAILURE)) != 0 || 474 (r = sshpkt_put_cstring(ssh, methods)) != 0 || 475 (r = sshpkt_put_u8(ssh, partial)) != 0 || 476 (r = sshpkt_send(ssh)) != 0 || 477 (r = ssh_packet_write_wait(ssh)) < 0) 478 fatal_fr(r, "send failure packet"); 479 free(methods); 480 } 481 } 482 483 /* 484 * Checks whether method is allowed by at least one AuthenticationMethods 485 * methods list. Returns 1 if allowed, or no methods lists configured. 486 * 0 otherwise. 487 */ 488 int 489 auth2_method_allowed(Authctxt *authctxt, const char *method, 490 const char *submethod) 491 { 492 u_int i; 493 494 /* 495 * NB. authctxt->num_auth_methods might be zero as a result of 496 * auth2_setup_methods_lists(), so check the configuration. 497 */ 498 if (options.num_auth_methods == 0) 499 return 1; 500 for (i = 0; i < authctxt->num_auth_methods; i++) { 501 if (list_starts_with(authctxt->auth_methods[i], method, 502 submethod) != MATCH_NONE) 503 return 1; 504 } 505 return 0; 506 } 507 508 static char * 509 authmethods_get(Authctxt *authctxt) 510 { 511 struct sshbuf *b; 512 char *list; 513 int i, r; 514 515 if ((b = sshbuf_new()) == NULL) 516 fatal_f("sshbuf_new failed"); 517 for (i = 0; authmethods[i] != NULL; i++) { 518 if (strcmp(authmethods[i]->name, "none") == 0) 519 continue; 520 if (authmethods[i]->enabled == NULL || 521 *(authmethods[i]->enabled) == 0) 522 continue; 523 if (!auth2_method_allowed(authctxt, authmethods[i]->name, 524 NULL)) 525 continue; 526 if ((r = sshbuf_putf(b, "%s%s", sshbuf_len(b) ? "," : "", 527 authmethods[i]->name)) != 0) 528 fatal_fr(r, "buffer error"); 529 } 530 if ((list = sshbuf_dup_string(b)) == NULL) 531 fatal_f("sshbuf_dup_string failed"); 532 sshbuf_free(b); 533 return list; 534 } 535 536 static Authmethod * 537 authmethod_byname(const char *name) 538 { 539 int i; 540 541 if (name == NULL) 542 fatal_f("NULL authentication method name"); 543 for (i = 0; authmethods[i] != NULL; i++) { 544 if (strcmp(name, authmethods[i]->name) == 0 || 545 (authmethods[i]->synonym != NULL && 546 strcmp(name, authmethods[i]->synonym) == 0)) 547 return authmethods[i]; 548 } 549 debug_f("unrecognized authentication method name: %s", name); 550 return NULL; 551 } 552 553 static Authmethod * 554 authmethod_lookup(Authctxt *authctxt, const char *name) 555 { 556 Authmethod *method; 557 558 if ((method = authmethod_byname(name)) == NULL) 559 return NULL; 560 561 if (method->enabled == NULL || *(method->enabled) == 0) { 562 debug3_f("method %s not enabled", name); 563 return NULL; 564 } 565 if (!auth2_method_allowed(authctxt, method->name, NULL)) { 566 debug3_f("method %s not allowed " 567 "by AuthenticationMethods", name); 568 return NULL; 569 } 570 return method; 571 } 572 573 /* 574 * Check a comma-separated list of methods for validity. Is need_enable is 575 * non-zero, then also require that the methods are enabled. 576 * Returns 0 on success or -1 if the methods list is invalid. 577 */ 578 int 579 auth2_methods_valid(const char *_methods, int need_enable) 580 { 581 char *methods, *omethods, *method, *p; 582 u_int i, found; 583 int ret = -1; 584 585 if (*_methods == '\0') { 586 error("empty authentication method list"); 587 return -1; 588 } 589 omethods = methods = xstrdup(_methods); 590 while ((method = strsep(&methods, ",")) != NULL) { 591 for (found = i = 0; !found && authmethods[i] != NULL; i++) { 592 if ((p = strchr(method, ':')) != NULL) 593 *p = '\0'; 594 if (strcmp(method, authmethods[i]->name) != 0) 595 continue; 596 if (need_enable) { 597 if (authmethods[i]->enabled == NULL || 598 *(authmethods[i]->enabled) == 0) { 599 error("Disabled method \"%s\" in " 600 "AuthenticationMethods list \"%s\"", 601 method, _methods); 602 goto out; 603 } 604 } 605 found = 1; 606 break; 607 } 608 if (!found) { 609 error("Unknown authentication method \"%s\" in list", 610 method); 611 goto out; 612 } 613 } 614 ret = 0; 615 out: 616 free(omethods); 617 return ret; 618 } 619 620 /* 621 * Prune the AuthenticationMethods supplied in the configuration, removing 622 * any methods lists that include disabled methods. Note that this might 623 * leave authctxt->num_auth_methods == 0, even when multiple required auth 624 * has been requested. For this reason, all tests for whether multiple is 625 * enabled should consult options.num_auth_methods directly. 626 */ 627 int 628 auth2_setup_methods_lists(Authctxt *authctxt) 629 { 630 u_int i; 631 632 /* First, normalise away the "any" pseudo-method */ 633 if (options.num_auth_methods == 1 && 634 strcmp(options.auth_methods[0], "any") == 0) { 635 free(options.auth_methods[0]); 636 options.auth_methods[0] = NULL; 637 options.num_auth_methods = 0; 638 } 639 640 if (options.num_auth_methods == 0) 641 return 0; 642 debug3_f("checking methods"); 643 authctxt->auth_methods = xcalloc(options.num_auth_methods, 644 sizeof(*authctxt->auth_methods)); 645 authctxt->num_auth_methods = 0; 646 for (i = 0; i < options.num_auth_methods; i++) { 647 if (auth2_methods_valid(options.auth_methods[i], 1) != 0) { 648 logit("Authentication methods list \"%s\" contains " 649 "disabled method, skipping", 650 options.auth_methods[i]); 651 continue; 652 } 653 debug("authentication methods list %d: %s", 654 authctxt->num_auth_methods, options.auth_methods[i]); 655 authctxt->auth_methods[authctxt->num_auth_methods++] = 656 xstrdup(options.auth_methods[i]); 657 } 658 if (authctxt->num_auth_methods == 0) { 659 error("No AuthenticationMethods left after eliminating " 660 "disabled methods"); 661 return -1; 662 } 663 return 0; 664 } 665 666 static int 667 list_starts_with(const char *methods, const char *method, 668 const char *submethod) 669 { 670 size_t l = strlen(method); 671 int match; 672 const char *p; 673 674 if (strncmp(methods, method, l) != 0) 675 return MATCH_NONE; 676 p = methods + l; 677 match = MATCH_METHOD; 678 if (*p == ':') { 679 if (!submethod) 680 return MATCH_PARTIAL; 681 l = strlen(submethod); 682 p += 1; 683 if (strncmp(submethod, p, l)) 684 return MATCH_NONE; 685 p += l; 686 match = MATCH_BOTH; 687 } 688 if (*p != ',' && *p != '\0') 689 return MATCH_NONE; 690 return match; 691 } 692 693 /* 694 * Remove method from the start of a comma-separated list of methods. 695 * Returns 0 if the list of methods did not start with that method or 1 696 * if it did. 697 */ 698 static int 699 remove_method(char **methods, const char *method, const char *submethod) 700 { 701 char *omethods = *methods, *p; 702 size_t l = strlen(method); 703 int match; 704 705 match = list_starts_with(omethods, method, submethod); 706 if (match != MATCH_METHOD && match != MATCH_BOTH) 707 return 0; 708 p = omethods + l; 709 if (submethod && match == MATCH_BOTH) 710 p += 1 + strlen(submethod); /* include colon */ 711 if (*p == ',') 712 p++; 713 *methods = xstrdup(p); 714 free(omethods); 715 return 1; 716 } 717 718 /* 719 * Called after successful authentication. Will remove the successful method 720 * from the start of each list in which it occurs. If it was the last method 721 * in any list, then authentication is deemed successful. 722 * Returns 1 if the method completed any authentication list or 0 otherwise. 723 */ 724 int 725 auth2_update_methods_lists(Authctxt *authctxt, const char *method, 726 const char *submethod) 727 { 728 u_int i, found = 0; 729 730 debug3_f("updating methods list after \"%s\"", method); 731 for (i = 0; i < authctxt->num_auth_methods; i++) { 732 if (!remove_method(&(authctxt->auth_methods[i]), method, 733 submethod)) 734 continue; 735 found = 1; 736 if (*authctxt->auth_methods[i] == '\0') { 737 debug2("authentication methods list %d complete", i); 738 return 1; 739 } 740 debug3("authentication methods list %d remaining: \"%s\"", 741 i, authctxt->auth_methods[i]); 742 } 743 /* This should not happen, but would be bad if it did */ 744 if (!found) 745 fatal_f("method not in AuthenticationMethods"); 746 return 0; 747 } 748 749 /* Reset method-specific information */ 750 void auth2_authctxt_reset_info(Authctxt *authctxt) 751 { 752 sshkey_free(authctxt->auth_method_key); 753 free(authctxt->auth_method_info); 754 authctxt->auth_method_key = NULL; 755 authctxt->auth_method_info = NULL; 756 } 757 758 /* Record auth method-specific information for logs */ 759 void 760 auth2_record_info(Authctxt *authctxt, const char *fmt, ...) 761 { 762 va_list ap; 763 int i; 764 765 free(authctxt->auth_method_info); 766 authctxt->auth_method_info = NULL; 767 768 va_start(ap, fmt); 769 i = vasprintf(&authctxt->auth_method_info, fmt, ap); 770 va_end(ap); 771 772 if (i == -1) 773 fatal_f("vasprintf failed"); 774 } 775 776 /* 777 * Records a public key used in authentication. This is used for logging 778 * and to ensure that the same key is not subsequently accepted again for 779 * multiple authentication. 780 */ 781 void 782 auth2_record_key(Authctxt *authctxt, int authenticated, 783 const struct sshkey *key) 784 { 785 struct sshkey **tmp, *dup; 786 int r; 787 788 if ((r = sshkey_from_private(key, &dup)) != 0) 789 fatal_fr(r, "copy key"); 790 sshkey_free(authctxt->auth_method_key); 791 authctxt->auth_method_key = dup; 792 793 if (!authenticated) 794 return; 795 796 /* If authenticated, make sure we don't accept this key again */ 797 if ((r = sshkey_from_private(key, &dup)) != 0) 798 fatal_fr(r, "copy key"); 799 if (authctxt->nprev_keys >= INT_MAX || 800 (tmp = recallocarray(authctxt->prev_keys, authctxt->nprev_keys, 801 authctxt->nprev_keys + 1, sizeof(*authctxt->prev_keys))) == NULL) 802 fatal_f("reallocarray failed"); 803 authctxt->prev_keys = tmp; 804 authctxt->prev_keys[authctxt->nprev_keys] = dup; 805 authctxt->nprev_keys++; 806 807 } 808 809 /* Checks whether a key has already been previously used for authentication */ 810 int 811 auth2_key_already_used(Authctxt *authctxt, const struct sshkey *key) 812 { 813 u_int i; 814 char *fp; 815 816 for (i = 0; i < authctxt->nprev_keys; i++) { 817 if (sshkey_equal_public(key, authctxt->prev_keys[i])) { 818 fp = sshkey_fingerprint(authctxt->prev_keys[i], 819 options.fingerprint_hash, SSH_FP_DEFAULT); 820 debug3_f("key already used: %s %s", 821 sshkey_type(authctxt->prev_keys[i]), 822 fp == NULL ? "UNKNOWN" : fp); 823 free(fp); 824 return 1; 825 } 826 } 827 return 0; 828 } 829 830 /* 831 * Updates authctxt->session_info with details of authentication. Should be 832 * whenever an authentication method succeeds. 833 */ 834 void 835 auth2_update_session_info(Authctxt *authctxt, const char *method, 836 const char *submethod) 837 { 838 int r; 839 840 if (authctxt->session_info == NULL) { 841 if ((authctxt->session_info = sshbuf_new()) == NULL) 842 fatal_f("sshbuf_new"); 843 } 844 845 /* Append method[/submethod] */ 846 if ((r = sshbuf_putf(authctxt->session_info, "%s%s%s", 847 method, submethod == NULL ? "" : "/", 848 submethod == NULL ? "" : submethod)) != 0) 849 fatal_fr(r, "append method"); 850 851 /* Append key if present */ 852 if (authctxt->auth_method_key != NULL) { 853 if ((r = sshbuf_put_u8(authctxt->session_info, ' ')) != 0 || 854 (r = sshkey_format_text(authctxt->auth_method_key, 855 authctxt->session_info)) != 0) 856 fatal_fr(r, "append key"); 857 } 858 859 if (authctxt->auth_method_info != NULL) { 860 /* Ensure no ambiguity here */ 861 if (strchr(authctxt->auth_method_info, '\n') != NULL) 862 fatal_f("auth_method_info contains \\n"); 863 if ((r = sshbuf_put_u8(authctxt->session_info, ' ')) != 0 || 864 (r = sshbuf_putf(authctxt->session_info, "%s", 865 authctxt->auth_method_info)) != 0) { 866 fatal_fr(r, "append method info"); 867 } 868 } 869 if ((r = sshbuf_put_u8(authctxt->session_info, '\n')) != 0) 870 fatal_fr(r, "append"); 871 } 872 873