crypto/openssh/auth2.c

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