crypto/openssh/auth2-pubkey.c

   1 /* $OpenBSD: auth2-pubkey.c,v 1.41 2014/07/15 15:54:14 millert 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/wait.h>
  31
  32 #include <errno.h>
  33 #include <fcntl.h>
  34 #ifdef HAVE_PATHS_H
  35 # include <paths.h>
  36 #endif
  37 #include <pwd.h>
  38 #include <signal.h>
  39 #include <stdio.h>
  40 #include <stdarg.h>
  41 #include <string.h>
  42 #include <time.h>
  43 #include <unistd.h>
  44
  45 #include "xmalloc.h"
  46 #include "ssh.h"
  47 #include "ssh2.h"
  48 #include "packet.h"
  49 #include "buffer.h"
  50 #include "log.h"
  51 #include "misc.h"
  52 #include "servconf.h"
  53 #include "compat.h"
  54 #include "key.h"
  55 #include "hostfile.h"
  56 #include "authfile.h"
  57 #include "auth.h"
  58 #include "pathnames.h"
  59 #include "uidswap.h"
  60 #include "auth-options.h"
  61 #include "canohost.h"
  62 #ifdef GSSAPI
  63 #include "ssh-gss.h"
  64 #endif
  65 #include "monitor_wrap.h"
  66 #include "authfile.h"
  67 #include "match.h"
  68
  69 /* import */
  70 extern ServerOptions options;
  71 extern u_char *session_id2;
  72 extern u_int session_id2_len;
  73
  74 static int
  75 userauth_pubkey(Authctxt *authctxt)
  76 {
  77         Buffer b;
  78         Key *key = NULL;
  79         char *pkalg, *userstyle;
  80         u_char *pkblob, *sig;
  81         u_int alen, blen, slen;
  82         int have_sig, pktype;
  83         int authenticated = 0;
  84
  85         if (!authctxt->valid) {
  86                 debug2("userauth_pubkey: disabled because of invalid user");
  87                 return 0;
  88         }
  89         have_sig = packet_get_char();
  90         if (datafellows & SSH_BUG_PKAUTH) {
  91                 debug2("userauth_pubkey: SSH_BUG_PKAUTH");
  92                 /* no explicit pkalg given */
  93                 pkblob = packet_get_string(&blen);
  94                 buffer_init(&b);
  95                 buffer_append(&b, pkblob, blen);
  96                 /* so we have to extract the pkalg from the pkblob */
  97                 pkalg = buffer_get_string(&b, &alen);
  98                 buffer_free(&b);
  99         } else {
 100                 pkalg = packet_get_string(&alen);
 101                 pkblob = packet_get_string(&blen);
 102         }
 103         pktype = key_type_from_name(pkalg);
 104         if (pktype == KEY_UNSPEC) {
 105                 /* this is perfectly legal */
 106                 logit("userauth_pubkey: unsupported public key algorithm: %s",
 107                     pkalg);
 108                 goto done;
 109         }
 110         key = key_from_blob(pkblob, blen);
 111         if (key == NULL) {
 112                 error("userauth_pubkey: cannot decode key: %s", pkalg);
 113                 goto done;
 114         }
 115         if (key->type != pktype) {
 116                 error("userauth_pubkey: type mismatch for decoded key "
 117                     "(received %d, expected %d)", key->type, pktype);
 118                 goto done;
 119         }
 120         if (key_type_plain(key->type) == KEY_RSA &&
 121             (datafellows & SSH_BUG_RSASIGMD5) != 0) {
 122                 logit("Refusing RSA key because client uses unsafe "
 123                     "signature scheme");
 124                 goto done;
 125         }
 126         if (have_sig) {
 127                 sig = packet_get_string(&slen);
 128                 packet_check_eom();
 129                 buffer_init(&b);
 130                 if (datafellows & SSH_OLD_SESSIONID) {
 131                         buffer_append(&b, session_id2, session_id2_len);
 132                 } else {
 133                         buffer_put_string(&b, session_id2, session_id2_len);
 134                 }
 135                 /* reconstruct packet */
 136                 buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
 137                 xasprintf(&userstyle, "%s%s%s", authctxt->user,
 138                     authctxt->style ? ":" : "",
 139                     authctxt->style ? authctxt->style : "");
 140                 buffer_put_cstring(&b, userstyle);
 141                 free(userstyle);
 142                 buffer_put_cstring(&b,
 143                     datafellows & SSH_BUG_PKSERVICE ?
 144                     "ssh-userauth" :
 145                     authctxt->service);
 146                 if (datafellows & SSH_BUG_PKAUTH) {
 147                         buffer_put_char(&b, have_sig);
 148                 } else {
 149                         buffer_put_cstring(&b, "publickey");
 150                         buffer_put_char(&b, have_sig);
 151                         buffer_put_cstring(&b, pkalg);
 152                 }
 153                 buffer_put_string(&b, pkblob, blen);
 154 #ifdef DEBUG_PK
 155                 buffer_dump(&b);
 156 #endif
 157                 pubkey_auth_info(authctxt, key, NULL);
 158
 159                 /* test for correct signature */
 160                 authenticated = 0;
 161                 if (PRIVSEP(user_key_allowed(authctxt->pw, key)) &&
 162                     PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
 163                     buffer_len(&b))) == 1)
 164                         authenticated = 1;
 165                 buffer_free(&b);
 166                 free(sig);
 167         } else {
 168                 debug("test whether pkalg/pkblob are acceptable");
 169                 packet_check_eom();
 170
 171                 /* XXX fake reply and always send PK_OK ? */
 172                 /*
 173                  * XXX this allows testing whether a user is allowed
 174                  * to login: if you happen to have a valid pubkey this
 175                  * message is sent. the message is NEVER sent at all
 176                  * if a user is not allowed to login. is this an
 177                  * issue? -markus
 178                  */
 179                 if (PRIVSEP(user_key_allowed(authctxt->pw, key))) {
 180                         packet_start(SSH2_MSG_USERAUTH_PK_OK);
 181                         packet_put_string(pkalg, alen);
 182                         packet_put_string(pkblob, blen);
 183                         packet_send();
 184                         packet_write_wait();
 185                         authctxt->postponed = 1;
 186                 }
 187         }
 188         if (authenticated != 1)
 189                 auth_clear_options();
 190 done:
 191         debug2("userauth_pubkey: authenticated %d pkalg %s", authenticated, pkalg);
 192         if (key != NULL)
 193                 key_free(key);
 194         free(pkalg);
 195         free(pkblob);
 196         return authenticated;
 197 }
 198
 199 void
 200 pubkey_auth_info(Authctxt *authctxt, const Key *key, const char *fmt, ...)
 201 {
 202         char *fp, *extra;
 203         va_list ap;
 204         int i;
 205
 206         extra = NULL;
 207         if (fmt != NULL) {
 208                 va_start(ap, fmt);
 209                 i = vasprintf(&extra, fmt, ap);
 210                 va_end(ap);
 211                 if (i < 0 || extra == NULL)
 212                         fatal("%s: vasprintf failed", __func__);
 213         }
 214
 215         if (key_is_cert(key)) {
 216                 fp = key_fingerprint(key->cert->signature_key,
 217                     SSH_FP_MD5, SSH_FP_HEX);
 218                 auth_info(authctxt, "%s ID %s (serial %llu) CA %s %s%s%s",
 219                     key_type(key), key->cert->key_id,
 220                     (unsigned long long)key->cert->serial,
 221                     key_type(key->cert->signature_key), fp,
 222                     extra == NULL ? "" : ", ", extra == NULL ? "" : extra);
 223                 free(fp);
 224         } else {
 225                 fp = key_fingerprint(key, SSH_FP_MD5, SSH_FP_HEX);
 226                 auth_info(authctxt, "%s %s%s%s", key_type(key), fp,
 227                     extra == NULL ? "" : ", ", extra == NULL ? "" : extra);
 228                 free(fp);
 229         }
 230         free(extra);
 231 }
 232
 233 static int
 234 match_principals_option(const char *principal_list, struct sshkey_cert *cert)
 235 {
 236         char *result;
 237         u_int i;
 238
 239         /* XXX percent_expand() sequences for authorized_principals? */
 240
 241         for (i = 0; i < cert->nprincipals; i++) {
 242                 if ((result = match_list(cert->principals[i],
 243                     principal_list, NULL)) != NULL) {
 244                         debug3("matched principal from key options \"%.100s\"",
 245                             result);
 246                         free(result);
 247                         return 1;
 248                 }
 249         }
 250         return 0;
 251 }
 252
 253 static int
 254 match_principals_file(char *file, struct passwd *pw, struct sshkey_cert *cert)
 255 {
 256         FILE *f;
 257         char line[SSH_MAX_PUBKEY_BYTES], *cp, *ep, *line_opts;
 258         u_long linenum = 0;
 259         u_int i;
 260
 261         temporarily_use_uid(pw);
 262         debug("trying authorized principals file %s", file);
 263         if ((f = auth_openprincipals(file, pw, options.strict_modes)) == NULL) {
 264                 restore_uid();
 265                 return 0;
 266         }
 267         while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) {
 268                 /* Skip leading whitespace. */
 269                 for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
 270                         ;
 271                 /* Skip blank and comment lines. */
 272                 if ((ep = strchr(cp, '#')) != NULL)
 273                         *ep = '\0';
 274                 if (!*cp || *cp == '\n')
 275                         continue;
 276                 /* Trim trailing whitespace. */
 277                 ep = cp + strlen(cp) - 1;
 278                 while (ep > cp && (*ep == '\n' || *ep == ' ' || *ep == '\t'))
 279                         *ep-- = '\0';
 280                 /*
 281                  * If the line has internal whitespace then assume it has
 282                  * key options.
 283                  */
 284                 line_opts = NULL;
 285                 if ((ep = strrchr(cp, ' ')) != NULL ||
 286                     (ep = strrchr(cp, '\t')) != NULL) {
 287                         for (; *ep == ' ' || *ep == '\t'; ep++)
 288                                 ;
 289                         line_opts = cp;
 290                         cp = ep;
 291                 }
 292                 for (i = 0; i < cert->nprincipals; i++) {
 293                         if (strcmp(cp, cert->principals[i]) == 0) {
 294                                 debug3("matched principal \"%.100s\" "
 295                                     "from file \"%s\" on line %lu",
 296                                     cert->principals[i], file, linenum);
 297                                 if (auth_parse_options(pw, line_opts,
 298                                     file, linenum) != 1)
 299                                         continue;
 300                                 fclose(f);
 301                                 restore_uid();
 302                                 return 1;
 303                         }
 304                 }
 305         }
 306         fclose(f);
 307         restore_uid();
 308         return 0;
 309 }
 310
 311 /*
 312  * Checks whether key is allowed in authorized_keys-format file,
 313  * returns 1 if the key is allowed or 0 otherwise.
 314  */
 315 static int
 316 check_authkeys_file(FILE *f, char *file, Key* key, struct passwd *pw)
 317 {
 318         char line[SSH_MAX_PUBKEY_BYTES];
 319         const char *reason;
 320         int found_key = 0;
 321         u_long linenum = 0;
 322         Key *found;
 323         char *fp;
 324
 325         found_key = 0;
 326
 327         found = NULL;
 328         while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) {
 329                 char *cp, *key_options = NULL;
 330                 if (found != NULL)
 331                         key_free(found);
 332                 found = key_new(key_is_cert(key) ? KEY_UNSPEC : key->type);
 333                 auth_clear_options();
 334
 335                 /* Skip leading whitespace, empty and comment lines. */
 336                 for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
 337                         ;
 338                 if (!*cp || *cp == '\n' || *cp == '#')
 339                         continue;
 340
 341                 if (key_read(found, &cp) != 1) {
 342                         /* no key?  check if there are options for this key */
 343                         int quoted = 0;
 344                         debug2("user_key_allowed: check options: '%s'", cp);
 345                         key_options = cp;
 346                         for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) {
 347                                 if (*cp == '\\' && cp[1] == '"')
 348                                         cp++;   /* Skip both */
 349                                 else if (*cp == '"')
 350                                         quoted = !quoted;
 351                         }
 352                         /* Skip remaining whitespace. */
 353                         for (; *cp == ' ' || *cp == '\t'; cp++)
 354                                 ;
 355                         if (key_read(found, &cp) != 1) {
 356                                 debug2("user_key_allowed: advance: '%s'", cp);
 357                                 /* still no key?  advance to next line*/
 358                                 continue;
 359                         }
 360                 }
 361                 if (key_is_cert(key)) {
 362                         if (!key_equal(found, key->cert->signature_key))
 363                                 continue;
 364                         if (auth_parse_options(pw, key_options, file,
 365                             linenum) != 1)
 366                                 continue;
 367                         if (!key_is_cert_authority)
 368                                 continue;
 369                         fp = key_fingerprint(found, SSH_FP_MD5,
 370                             SSH_FP_HEX);
 371                         debug("matching CA found: file %s, line %lu, %s %s",
 372                             file, linenum, key_type(found), fp);
 373                         /*
 374                          * If the user has specified a list of principals as
 375                          * a key option, then prefer that list to matching
 376                          * their username in the certificate principals list.
 377                          */
 378                         if (authorized_principals != NULL &&
 379                             !match_principals_option(authorized_principals,
 380                             key->cert)) {
 381                                 reason = "Certificate does not contain an "
 382                                     "authorized principal";
 383  fail_reason:
 384                                 free(fp);
 385                                 error("%s", reason);
 386                                 auth_debug_add("%s", reason);
 387                                 continue;
 388                         }
 389                         if (key_cert_check_authority(key, 0, 0,
 390                             authorized_principals == NULL ? pw->pw_name : NULL,
 391                             &reason) != 0)
 392                                 goto fail_reason;
 393                         if (auth_cert_options(key, pw) != 0) {
 394                                 free(fp);
 395                                 continue;
 396                         }
 397                         verbose("Accepted certificate ID \"%s\" "
 398                             "signed by %s CA %s via %s", key->cert->key_id,
 399                             key_type(found), fp, file);
 400                         free(fp);
 401                         found_key = 1;
 402                         break;
 403                 } else if (key_equal(found, key)) {
 404                         if (auth_parse_options(pw, key_options, file,
 405                             linenum) != 1)
 406                                 continue;
 407                         if (key_is_cert_authority)
 408                                 continue;
 409                         found_key = 1;
 410                         fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
 411                         debug("matching key found: file %s, line %lu %s %s",
 412                             file, linenum, key_type(found), fp);
 413                         free(fp);
 414                         break;
 415                 }
 416         }
 417         if (found != NULL)
 418                 key_free(found);
 419         if (!found_key)
 420                 debug2("key not found");
 421         return found_key;
 422 }
 423
 424 /* Authenticate a certificate key against TrustedUserCAKeys */
 425 static int
 426 user_cert_trusted_ca(struct passwd *pw, Key *key)
 427 {
 428         char *ca_fp, *principals_file = NULL;
 429         const char *reason;
 430         int ret = 0;
 431
 432         if (!key_is_cert(key) || options.trusted_user_ca_keys == NULL)
 433                 return 0;
 434
 435         ca_fp = key_fingerprint(key->cert->signature_key,
 436             SSH_FP_MD5, SSH_FP_HEX);
 437
 438         if (key_in_file(key->cert->signature_key,
 439             options.trusted_user_ca_keys, 1) != 1) {
 440                 debug2("%s: CA %s %s is not listed in %s", __func__,
 441                     key_type(key->cert->signature_key), ca_fp,
 442                     options.trusted_user_ca_keys);
 443                 goto out;
 444         }
 445         /*
 446          * If AuthorizedPrincipals is in use, then compare the certificate
 447          * principals against the names in that file rather than matching
 448          * against the username.
 449          */
 450         if ((principals_file = authorized_principals_file(pw)) != NULL) {
 451                 if (!match_principals_file(principals_file, pw, key->cert)) {
 452                         reason = "Certificate does not contain an "
 453                             "authorized principal";
 454  fail_reason:
 455                         error("%s", reason);
 456                         auth_debug_add("%s", reason);
 457                         goto out;
 458                 }
 459         }
 460         if (key_cert_check_authority(key, 0, 1,
 461             principals_file == NULL ? pw->pw_name : NULL, &reason) != 0)
 462                 goto fail_reason;
 463         if (auth_cert_options(key, pw) != 0)
 464                 goto out;
 465
 466         verbose("Accepted certificate ID \"%s\" signed by %s CA %s via %s",
 467             key->cert->key_id, key_type(key->cert->signature_key), ca_fp,
 468             options.trusted_user_ca_keys);
 469         ret = 1;
 470
 471  out:
 472         free(principals_file);
 473         free(ca_fp);
 474         return ret;
 475 }
 476
 477 /*
 478  * Checks whether key is allowed in file.
 479  * returns 1 if the key is allowed or 0 otherwise.
 480  */
 481 static int
 482 user_key_allowed2(struct passwd *pw, Key *key, char *file)
 483 {
 484         FILE *f;
 485         int found_key = 0;
 486
 487         /* Temporarily use the user's uid. */
 488         temporarily_use_uid(pw);
 489
 490         debug("trying public key file %s", file);
 491         if ((f = auth_openkeyfile(file, pw, options.strict_modes)) != NULL) {
 492                 found_key = check_authkeys_file(f, file, key, pw);
 493                 fclose(f);
 494         }
 495
 496         restore_uid();
 497         return found_key;
 498 }
 499
 500 /*
 501  * Checks whether key is allowed in output of command.
 502  * returns 1 if the key is allowed or 0 otherwise.
 503  */
 504 static int
 505 user_key_command_allowed2(struct passwd *user_pw, Key *key)
 506 {
 507         FILE *f;
 508         int ok, found_key = 0;
 509         struct passwd *pw;
 510         struct stat st;
 511         int status, devnull, p[2], i;
 512         pid_t pid;
 513         char *username, errmsg[512];
 514
 515         if (options.authorized_keys_command == NULL ||
 516             options.authorized_keys_command[0] != '/')
 517                 return 0;
 518
 519         if (options.authorized_keys_command_user == NULL) {
 520                 error("No user for AuthorizedKeysCommand specified, skipping");
 521                 return 0;
 522         }
 523
 524         username = percent_expand(options.authorized_keys_command_user,
 525             "u", user_pw->pw_name, (char *)NULL);
 526         pw = getpwnam(username);
 527         if (pw == NULL) {
 528                 error("AuthorizedKeysCommandUser \"%s\" not found: %s",
 529                     username, strerror(errno));
 530                 free(username);
 531                 return 0;
 532         }
 533         free(username);
 534
 535         temporarily_use_uid(pw);
 536
 537         if (stat(options.authorized_keys_command, &st) < 0) {
 538                 error("Could not stat AuthorizedKeysCommand \"%s\": %s",
 539                     options.authorized_keys_command, strerror(errno));
 540                 goto out;
 541         }
 542         if (auth_secure_path(options.authorized_keys_command, &st, NULL, 0,
 543             errmsg, sizeof(errmsg)) != 0) {
 544                 error("Unsafe AuthorizedKeysCommand: %s", errmsg);
 545                 goto out;
 546         }
 547
 548         if (pipe(p) != 0) {
 549                 error("%s: pipe: %s", __func__, strerror(errno));
 550                 goto out;
 551         }
 552
 553         debug3("Running AuthorizedKeysCommand: \"%s %s\" as \"%s\"",
 554             options.authorized_keys_command, user_pw->pw_name, pw->pw_name);
 555
 556         /*
 557          * Don't want to call this in the child, where it can fatal() and
 558          * run cleanup_exit() code.
 559          */
 560         restore_uid();
 561
 562         switch ((pid = fork())) {
 563         case -1: /* error */
 564                 error("%s: fork: %s", __func__, strerror(errno));
 565                 close(p[0]);
 566                 close(p[1]);
 567                 return 0;
 568         case 0: /* child */
 569                 for (i = 0; i < NSIG; i++)
 570                         signal(i, SIG_DFL);
 571
 572                 if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1) {
 573                         error("%s: open %s: %s", __func__, _PATH_DEVNULL,
 574                             strerror(errno));
 575                         _exit(1);
 576                 }
 577                 /* Keep stderr around a while longer to catch errors */
 578                 if (dup2(devnull, STDIN_FILENO) == -1 ||
 579                     dup2(p[1], STDOUT_FILENO) == -1) {
 580                         error("%s: dup2: %s", __func__, strerror(errno));
 581                         _exit(1);
 582                 }
 583                 closefrom(STDERR_FILENO + 1);
 584
 585                 /* Don't use permanently_set_uid() here to avoid fatal() */
 586                 if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) != 0) {
 587                         error("setresgid %u: %s", (u_int)pw->pw_gid,
 588                             strerror(errno));
 589                         _exit(1);
 590                 }
 591                 if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) != 0) {
 592                         error("setresuid %u: %s", (u_int)pw->pw_uid,
 593                             strerror(errno));
 594                         _exit(1);
 595                 }
 596                 /* stdin is pointed to /dev/null at this point */
 597                 if (dup2(STDIN_FILENO, STDERR_FILENO) == -1) {
 598                         error("%s: dup2: %s", __func__, strerror(errno));
 599                         _exit(1);
 600                 }
 601
 602                 execl(options.authorized_keys_command,
 603                     options.authorized_keys_command, user_pw->pw_name, NULL);
 604
 605                 error("AuthorizedKeysCommand %s exec failed: %s",
 606                     options.authorized_keys_command, strerror(errno));
 607                 _exit(127);
 608         default: /* parent */
 609                 break;
 610         }
 611
 612         temporarily_use_uid(pw);
 613
 614         close(p[1]);
 615         if ((f = fdopen(p[0], "r")) == NULL) {
 616                 error("%s: fdopen: %s", __func__, strerror(errno));
 617                 close(p[0]);
 618                 /* Don't leave zombie child */
 619                 kill(pid, SIGTERM);
 620                 while (waitpid(pid, NULL, 0) == -1 && errno == EINTR)
 621                         ;
 622                 goto out;
 623         }
 624         ok = check_authkeys_file(f, options.authorized_keys_command, key, pw);
 625         fclose(f);
 626
 627         while (waitpid(pid, &status, 0) == -1) {
 628                 if (errno != EINTR) {
 629                         error("%s: waitpid: %s", __func__, strerror(errno));
 630                         goto out;
 631                 }
 632         }
 633         if (WIFSIGNALED(status)) {
 634                 error("AuthorizedKeysCommand %s exited on signal %d",
 635                     options.authorized_keys_command, WTERMSIG(status));
 636                 goto out;
 637         } else if (WEXITSTATUS(status) != 0) {
 638                 error("AuthorizedKeysCommand %s returned status %d",
 639                     options.authorized_keys_command, WEXITSTATUS(status));
 640                 goto out;
 641         }
 642         found_key = ok;
 643  out:
 644         restore_uid();
 645         return found_key;
 646 }
 647
 648 /*
 649  * Check whether key authenticates and authorises the user.
 650  */
 651 int
 652 user_key_allowed(struct passwd *pw, Key *key)
 653 {
 654         char *fp;
 655         u_int success, i;
 656         char *file;
 657
 658         if (blacklisted_key(key)) {
 659                 fp = key_fingerprint(key, SSH_FP_MD5, SSH_FP_HEX);
 660                 if (options.permit_blacklisted_keys)
 661                         logit("Public key %s blacklisted (see "
 662                             "ssh-vulnkey(1)); continuing anyway", fp);
 663                 else
 664                         logit("Public key %s blacklisted (see "
 665                             "ssh-vulnkey(1))", fp);
 666                 xfree(fp);
 667                 if (!options.permit_blacklisted_keys)
 668                         return 0;
 669         }
 670
 671         if (auth_key_is_revoked(key))
 672                 return 0;
 673         if (key_is_cert(key) && auth_key_is_revoked(key->cert->signature_key))
 674                 return 0;
 675
 676         success = user_cert_trusted_ca(pw, key);
 677         if (success)
 678                 return success;
 679
 680         success = user_key_command_allowed2(pw, key);
 681         if (success > 0)
 682                 return success;
 683
 684         for (i = 0; !success && i < options.num_authkeys_files; i++) {
 685
 686                 if (strcasecmp(options.authorized_keys_files[i], "none") == 0)
 687                         continue;
 688                 file = expand_authorized_keys(
 689                     options.authorized_keys_files[i], pw);
 690
 691                 success = user_key_allowed2(pw, key, file);
 692                 free(file);
 693         }
 694
 695         return success;
 696 }
 697
 698 Authmethod method_pubkey = {
 699         "publickey",
 700         userauth_pubkey,
 701         &options.pubkey_authentication
 702 };