auth2-pubkey.c

   1 /* $OpenBSD: auth2-pubkey.c,v 1.47 2015/02/17 00:14:05 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/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 #include <limits.h>
  45
  46 #include "xmalloc.h"
  47 #include "ssh.h"
  48 #include "ssh2.h"
  49 #include "packet.h"
  50 #include "buffer.h"
  51 #include "log.h"
  52 #include "misc.h"
  53 #include "servconf.h"
  54 #include "compat.h"
  55 #include "key.h"
  56 #include "hostfile.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 (auth2_userkey_already_used(authctxt, key)) {
 127                 logit("refusing previously-used %s key", key_type(key));
 128                 goto done;
 129         }
 130         if (match_pattern_list(sshkey_ssh_name(key), options.pubkey_key_types,
 131             strlen(options.pubkey_key_types), 0) != 1) {
 132                 logit("%s: key type %s not in PubkeyAcceptedKeyTypes",
 133                     __func__, sshkey_ssh_name(key));
 134                 goto done;
 135         }
 136
 137         if (have_sig) {
 138                 sig = packet_get_string(&slen);
 139                 packet_check_eom();
 140                 buffer_init(&b);
 141                 if (datafellows & SSH_OLD_SESSIONID) {
 142                         buffer_append(&b, session_id2, session_id2_len);
 143                 } else {
 144                         buffer_put_string(&b, session_id2, session_id2_len);
 145                 }
 146                 /* reconstruct packet */
 147                 buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
 148                 xasprintf(&userstyle, "%s%s%s", authctxt->user,
 149                     authctxt->style ? ":" : "",
 150                     authctxt->style ? authctxt->style : "");
 151                 buffer_put_cstring(&b, userstyle);
 152                 free(userstyle);
 153                 buffer_put_cstring(&b,
 154                     datafellows & SSH_BUG_PKSERVICE ?
 155                     "ssh-userauth" :
 156                     authctxt->service);
 157                 if (datafellows & SSH_BUG_PKAUTH) {
 158                         buffer_put_char(&b, have_sig);
 159                 } else {
 160                         buffer_put_cstring(&b, "publickey");
 161                         buffer_put_char(&b, have_sig);
 162                         buffer_put_cstring(&b, pkalg);
 163                 }
 164                 buffer_put_string(&b, pkblob, blen);
 165 #ifdef DEBUG_PK
 166                 buffer_dump(&b);
 167 #endif
 168                 pubkey_auth_info(authctxt, key, NULL);
 169
 170                 /* test for correct signature */
 171                 authenticated = 0;
 172                 if (PRIVSEP(user_key_allowed(authctxt->pw, key)) &&
 173                     PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
 174                     buffer_len(&b))) == 1) {
 175                         authenticated = 1;
 176                         /* Record the successful key to prevent reuse */
 177                         auth2_record_userkey(authctxt, key);
 178                         key = NULL; /* Don't free below */
 179                 }
 180                 buffer_free(&b);
 181                 free(sig);
 182         } else {
 183                 debug("test whether pkalg/pkblob are acceptable");
 184                 packet_check_eom();
 185
 186                 /* XXX fake reply and always send PK_OK ? */
 187                 /*
 188                  * XXX this allows testing whether a user is allowed
 189                  * to login: if you happen to have a valid pubkey this
 190                  * message is sent. the message is NEVER sent at all
 191                  * if a user is not allowed to login. is this an
 192                  * issue? -markus
 193                  */
 194                 if (PRIVSEP(user_key_allowed(authctxt->pw, key))) {
 195                         packet_start(SSH2_MSG_USERAUTH_PK_OK);
 196                         packet_put_string(pkalg, alen);
 197                         packet_put_string(pkblob, blen);
 198                         packet_send();
 199                         packet_write_wait();
 200                         authctxt->postponed = 1;
 201                 }
 202         }
 203         if (authenticated != 1)
 204                 auth_clear_options();
 205 done:
 206         debug2("userauth_pubkey: authenticated %d pkalg %s", authenticated, pkalg);
 207         if (key != NULL)
 208                 key_free(key);
 209         free(pkalg);
 210         free(pkblob);
 211         return authenticated;
 212 }
 213
 214 void
 215 pubkey_auth_info(Authctxt *authctxt, const Key *key, const char *fmt, ...)
 216 {
 217         char *fp, *extra;
 218         va_list ap;
 219         int i;
 220
 221         extra = NULL;
 222         if (fmt != NULL) {
 223                 va_start(ap, fmt);
 224                 i = vasprintf(&extra, fmt, ap);
 225                 va_end(ap);
 226                 if (i < 0 || extra == NULL)
 227                         fatal("%s: vasprintf failed", __func__);
 228         }
 229
 230         if (key_is_cert(key)) {
 231                 fp = sshkey_fingerprint(key->cert->signature_key,
 232                     options.fingerprint_hash, SSH_FP_DEFAULT);
 233                 auth_info(authctxt, "%s ID %s (serial %llu) CA %s %s%s%s",
 234                     key_type(key), key->cert->key_id,
 235                     (unsigned long long)key->cert->serial,
 236                     key_type(key->cert->signature_key),
 237                     fp == NULL ? "(null)" : fp,
 238                     extra == NULL ? "" : ", ", extra == NULL ? "" : extra);
 239                 free(fp);
 240         } else {
 241                 fp = sshkey_fingerprint(key, options.fingerprint_hash,
 242                     SSH_FP_DEFAULT);
 243                 auth_info(authctxt, "%s %s%s%s", key_type(key),
 244                     fp == NULL ? "(null)" : fp,
 245                     extra == NULL ? "" : ", ", extra == NULL ? "" : extra);
 246                 free(fp);
 247         }
 248         free(extra);
 249 }
 250
 251 static int
 252 match_principals_option(const char *principal_list, struct sshkey_cert *cert)
 253 {
 254         char *result;
 255         u_int i;
 256
 257         /* XXX percent_expand() sequences for authorized_principals? */
 258
 259         for (i = 0; i < cert->nprincipals; i++) {
 260                 if ((result = match_list(cert->principals[i],
 261                     principal_list, NULL)) != NULL) {
 262                         debug3("matched principal from key options \"%.100s\"",
 263                             result);
 264                         free(result);
 265                         return 1;
 266                 }
 267         }
 268         return 0;
 269 }
 270
 271 static int
 272 match_principals_file(char *file, struct passwd *pw, struct sshkey_cert *cert)
 273 {
 274         FILE *f;
 275         char line[SSH_MAX_PUBKEY_BYTES], *cp, *ep, *line_opts;
 276         u_long linenum = 0;
 277         u_int i;
 278
 279         temporarily_use_uid(pw);
 280         debug("trying authorized principals file %s", file);
 281         if ((f = auth_openprincipals(file, pw, options.strict_modes)) == NULL) {
 282                 restore_uid();
 283                 return 0;
 284         }
 285         while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) {
 286                 /* Skip leading whitespace. */
 287                 for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
 288                         ;
 289                 /* Skip blank and comment lines. */
 290                 if ((ep = strchr(cp, '#')) != NULL)
 291                         *ep = '\0';
 292                 if (!*cp || *cp == '\n')
 293                         continue;
 294                 /* Trim trailing whitespace. */
 295                 ep = cp + strlen(cp) - 1;
 296                 while (ep > cp && (*ep == '\n' || *ep == ' ' || *ep == '\t'))
 297                         *ep-- = '\0';
 298                 /*
 299                  * If the line has internal whitespace then assume it has
 300                  * key options.
 301                  */
 302                 line_opts = NULL;
 303                 if ((ep = strrchr(cp, ' ')) != NULL ||
 304                     (ep = strrchr(cp, '\t')) != NULL) {
 305                         for (; *ep == ' ' || *ep == '\t'; ep++)
 306                                 ;
 307                         line_opts = cp;
 308                         cp = ep;
 309                 }
 310                 for (i = 0; i < cert->nprincipals; i++) {
 311                         if (strcmp(cp, cert->principals[i]) == 0) {
 312                                 debug3("matched principal \"%.100s\" "
 313                                     "from file \"%s\" on line %lu",
 314                                     cert->principals[i], file, linenum);
 315                                 if (auth_parse_options(pw, line_opts,
 316                                     file, linenum) != 1)
 317                                         continue;
 318                                 fclose(f);
 319                                 restore_uid();
 320                                 return 1;
 321                         }
 322                 }
 323         }
 324         fclose(f);
 325         restore_uid();
 326         return 0;
 327 }
 328
 329 /*
 330  * Checks whether key is allowed in authorized_keys-format file,
 331  * returns 1 if the key is allowed or 0 otherwise.
 332  */
 333 static int
 334 check_authkeys_file(FILE *f, char *file, Key* key, struct passwd *pw)
 335 {
 336         char line[SSH_MAX_PUBKEY_BYTES];
 337         const char *reason;
 338         int found_key = 0;
 339         u_long linenum = 0;
 340         Key *found;
 341         char *fp;
 342
 343         found_key = 0;
 344
 345         found = NULL;
 346         while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) {
 347                 char *cp, *key_options = NULL;
 348                 if (found != NULL)
 349                         key_free(found);
 350                 found = key_new(key_is_cert(key) ? KEY_UNSPEC : key->type);
 351                 auth_clear_options();
 352
 353                 /* Skip leading whitespace, empty and comment lines. */
 354                 for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
 355                         ;
 356                 if (!*cp || *cp == '\n' || *cp == '#')
 357                         continue;
 358
 359                 if (key_read(found, &cp) != 1) {
 360                         /* no key?  check if there are options for this key */
 361                         int quoted = 0;
 362                         debug2("user_key_allowed: check options: '%s'", cp);
 363                         key_options = cp;
 364                         for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) {
 365                                 if (*cp == '\\' && cp[1] == '"')
 366                                         cp++;   /* Skip both */
 367                                 else if (*cp == '"')
 368                                         quoted = !quoted;
 369                         }
 370                         /* Skip remaining whitespace. */
 371                         for (; *cp == ' ' || *cp == '\t'; cp++)
 372                                 ;
 373                         if (key_read(found, &cp) != 1) {
 374                                 debug2("user_key_allowed: advance: '%s'", cp);
 375                                 /* still no key?  advance to next line*/
 376                                 continue;
 377                         }
 378                 }
 379                 if (key_is_cert(key)) {
 380                         if (!key_equal(found, key->cert->signature_key))
 381                                 continue;
 382                         if (auth_parse_options(pw, key_options, file,
 383                             linenum) != 1)
 384                                 continue;
 385                         if (!key_is_cert_authority)
 386                                 continue;
 387                         if ((fp = sshkey_fingerprint(found,
 388                             options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
 389                                 continue;
 390                         debug("matching CA found: file %s, line %lu, %s %s",
 391                             file, linenum, key_type(found), fp);
 392                         /*
 393                          * If the user has specified a list of principals as
 394                          * a key option, then prefer that list to matching
 395                          * their username in the certificate principals list.
 396                          */
 397                         if (authorized_principals != NULL &&
 398                             !match_principals_option(authorized_principals,
 399                             key->cert)) {
 400                                 reason = "Certificate does not contain an "
 401                                     "authorized principal";
 402  fail_reason:
 403                                 free(fp);
 404                                 error("%s", reason);
 405                                 auth_debug_add("%s", reason);
 406                                 continue;
 407                         }
 408                         if (key_cert_check_authority(key, 0, 0,
 409                             authorized_principals == NULL ? pw->pw_name : NULL,
 410                             &reason) != 0)
 411                                 goto fail_reason;
 412                         if (auth_cert_options(key, pw) != 0) {
 413                                 free(fp);
 414                                 continue;
 415                         }
 416                         verbose("Accepted certificate ID \"%s\" "
 417                             "signed by %s CA %s via %s", key->cert->key_id,
 418                             key_type(found), fp, file);
 419                         free(fp);
 420                         found_key = 1;
 421                         break;
 422                 } else if (key_equal(found, key)) {
 423                         if (auth_parse_options(pw, key_options, file,
 424                             linenum) != 1)
 425                                 continue;
 426                         if (key_is_cert_authority)
 427                                 continue;
 428                         if ((fp = sshkey_fingerprint(found,
 429                             options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
 430                                 continue;
 431                         debug("matching key found: file %s, line %lu %s %s",
 432                             file, linenum, key_type(found), fp);
 433                         free(fp);
 434                         found_key = 1;
 435                         break;
 436                 }
 437         }
 438         if (found != NULL)
 439                 key_free(found);
 440         if (!found_key)
 441                 debug2("key not found");
 442         return found_key;
 443 }
 444
 445 /* Authenticate a certificate key against TrustedUserCAKeys */
 446 static int
 447 user_cert_trusted_ca(struct passwd *pw, Key *key)
 448 {
 449         char *ca_fp, *principals_file = NULL;
 450         const char *reason;
 451         int ret = 0;
 452
 453         if (!key_is_cert(key) || options.trusted_user_ca_keys == NULL)
 454                 return 0;
 455
 456         if ((ca_fp = sshkey_fingerprint(key->cert->signature_key,
 457             options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
 458                 return 0;
 459
 460         if (sshkey_in_file(key->cert->signature_key,
 461             options.trusted_user_ca_keys, 1, 0) != 0) {
 462                 debug2("%s: CA %s %s is not listed in %s", __func__,
 463                     key_type(key->cert->signature_key), ca_fp,
 464                     options.trusted_user_ca_keys);
 465                 goto out;
 466         }
 467         /*
 468          * If AuthorizedPrincipals is in use, then compare the certificate
 469          * principals against the names in that file rather than matching
 470          * against the username.
 471          */
 472         if ((principals_file = authorized_principals_file(pw)) != NULL) {
 473                 if (!match_principals_file(principals_file, pw, key->cert)) {
 474                         reason = "Certificate does not contain an "
 475                             "authorized principal";
 476  fail_reason:
 477                         error("%s", reason);
 478                         auth_debug_add("%s", reason);
 479                         goto out;
 480                 }
 481         }
 482         if (key_cert_check_authority(key, 0, 1,
 483             principals_file == NULL ? pw->pw_name : NULL, &reason) != 0)
 484                 goto fail_reason;
 485         if (auth_cert_options(key, pw) != 0)
 486                 goto out;
 487
 488         verbose("Accepted certificate ID \"%s\" signed by %s CA %s via %s",
 489             key->cert->key_id, key_type(key->cert->signature_key), ca_fp,
 490             options.trusted_user_ca_keys);
 491         ret = 1;
 492
 493  out:
 494         free(principals_file);
 495         free(ca_fp);
 496         return ret;
 497 }
 498
 499 /*
 500  * Checks whether key is allowed in file.
 501  * returns 1 if the key is allowed or 0 otherwise.
 502  */
 503 static int
 504 user_key_allowed2(struct passwd *pw, Key *key, char *file)
 505 {
 506         FILE *f;
 507         int found_key = 0;
 508
 509         /* Temporarily use the user's uid. */
 510         temporarily_use_uid(pw);
 511
 512         debug("trying public key file %s", file);
 513         if ((f = auth_openkeyfile(file, pw, options.strict_modes)) != NULL) {
 514                 found_key = check_authkeys_file(f, file, key, pw);
 515                 fclose(f);
 516         }
 517
 518         restore_uid();
 519         return found_key;
 520 }
 521
 522 /*
 523  * Checks whether key is allowed in output of command.
 524  * returns 1 if the key is allowed or 0 otherwise.
 525  */
 526 static int
 527 user_key_command_allowed2(struct passwd *user_pw, Key *key)
 528 {
 529         FILE *f;
 530         int ok, found_key = 0;
 531         struct passwd *pw;
 532         struct stat st;
 533         int status, devnull, p[2], i;
 534         pid_t pid;
 535         char *username, errmsg[512];
 536
 537         if (options.authorized_keys_command == NULL ||
 538             options.authorized_keys_command[0] != '/')
 539                 return 0;
 540
 541         if (options.authorized_keys_command_user == NULL) {
 542                 error("No user for AuthorizedKeysCommand specified, skipping");
 543                 return 0;
 544         }
 545
 546         username = percent_expand(options.authorized_keys_command_user,
 547             "u", user_pw->pw_name, (char *)NULL);
 548         pw = getpwnam(username);
 549         if (pw == NULL) {
 550                 error("AuthorizedKeysCommandUser \"%s\" not found: %s",
 551                     username, strerror(errno));
 552                 free(username);
 553                 return 0;
 554         }
 555         free(username);
 556
 557         temporarily_use_uid(pw);
 558
 559         if (stat(options.authorized_keys_command, &st) < 0) {
 560                 error("Could not stat AuthorizedKeysCommand \"%s\": %s",
 561                     options.authorized_keys_command, strerror(errno));
 562                 goto out;
 563         }
 564         if (auth_secure_path(options.authorized_keys_command, &st, NULL, 0,
 565             errmsg, sizeof(errmsg)) != 0) {
 566                 error("Unsafe AuthorizedKeysCommand: %s", errmsg);
 567                 goto out;
 568         }
 569
 570         if (pipe(p) != 0) {
 571                 error("%s: pipe: %s", __func__, strerror(errno));
 572                 goto out;
 573         }
 574
 575         debug3("Running AuthorizedKeysCommand: \"%s %s\" as \"%s\"",
 576             options.authorized_keys_command, user_pw->pw_name, pw->pw_name);
 577
 578         /*
 579          * Don't want to call this in the child, where it can fatal() and
 580          * run cleanup_exit() code.
 581          */
 582         restore_uid();
 583
 584         switch ((pid = fork())) {
 585         case -1: /* error */
 586                 error("%s: fork: %s", __func__, strerror(errno));
 587                 close(p[0]);
 588                 close(p[1]);
 589                 return 0;
 590         case 0: /* child */
 591                 for (i = 0; i < NSIG; i++)
 592                         signal(i, SIG_DFL);
 593
 594                 if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1) {
 595                         error("%s: open %s: %s", __func__, _PATH_DEVNULL,
 596                             strerror(errno));
 597                         _exit(1);
 598                 }
 599                 /* Keep stderr around a while longer to catch errors */
 600                 if (dup2(devnull, STDIN_FILENO) == -1 ||
 601                     dup2(p[1], STDOUT_FILENO) == -1) {
 602                         error("%s: dup2: %s", __func__, strerror(errno));
 603                         _exit(1);
 604                 }
 605                 closefrom(STDERR_FILENO + 1);
 606
 607                 /* Don't use permanently_set_uid() here to avoid fatal() */
 608                 if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) != 0) {
 609                         error("setresgid %u: %s", (u_int)pw->pw_gid,
 610                             strerror(errno));
 611                         _exit(1);
 612                 }
 613                 if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) != 0) {
 614                         error("setresuid %u: %s", (u_int)pw->pw_uid,
 615                             strerror(errno));
 616                         _exit(1);
 617                 }
 618                 /* stdin is pointed to /dev/null at this point */
 619                 if (dup2(STDIN_FILENO, STDERR_FILENO) == -1) {
 620                         error("%s: dup2: %s", __func__, strerror(errno));
 621                         _exit(1);
 622                 }
 623
 624                 execl(options.authorized_keys_command,
 625                     options.authorized_keys_command, user_pw->pw_name, NULL);
 626
 627                 error("AuthorizedKeysCommand %s exec failed: %s",
 628                     options.authorized_keys_command, strerror(errno));
 629                 _exit(127);
 630         default: /* parent */
 631                 break;
 632         }
 633
 634         temporarily_use_uid(pw);
 635
 636         close(p[1]);
 637         if ((f = fdopen(p[0], "r")) == NULL) {
 638                 error("%s: fdopen: %s", __func__, strerror(errno));
 639                 close(p[0]);
 640                 /* Don't leave zombie child */
 641                 kill(pid, SIGTERM);
 642                 while (waitpid(pid, NULL, 0) == -1 && errno == EINTR)
 643                         ;
 644                 goto out;
 645         }
 646         ok = check_authkeys_file(f, options.authorized_keys_command, key, pw);
 647         fclose(f);
 648
 649         while (waitpid(pid, &status, 0) == -1) {
 650                 if (errno != EINTR) {
 651                         error("%s: waitpid: %s", __func__, strerror(errno));
 652                         goto out;
 653                 }
 654         }
 655         if (WIFSIGNALED(status)) {
 656                 error("AuthorizedKeysCommand %s exited on signal %d",
 657                     options.authorized_keys_command, WTERMSIG(status));
 658                 goto out;
 659         } else if (WEXITSTATUS(status) != 0) {
 660                 error("AuthorizedKeysCommand %s returned status %d",
 661                     options.authorized_keys_command, WEXITSTATUS(status));
 662                 goto out;
 663         }
 664         found_key = ok;
 665  out:
 666         restore_uid();
 667         return found_key;
 668 }
 669
 670 /*
 671  * Check whether key authenticates and authorises the user.
 672  */
 673 int
 674 user_key_allowed(struct passwd *pw, Key *key)
 675 {
 676         u_int success, i;
 677         char *file;
 678
 679         if (auth_key_is_revoked(key))
 680                 return 0;
 681         if (key_is_cert(key) && auth_key_is_revoked(key->cert->signature_key))
 682                 return 0;
 683
 684         success = user_cert_trusted_ca(pw, key);
 685         if (success)
 686                 return success;
 687
 688         success = user_key_command_allowed2(pw, key);
 689         if (success > 0)
 690                 return success;
 691
 692         for (i = 0; !success && i < options.num_authkeys_files; i++) {
 693
 694                 if (strcasecmp(options.authorized_keys_files[i], "none") == 0)
 695                         continue;
 696                 file = expand_authorized_keys(
 697                     options.authorized_keys_files[i], pw);
 698
 699                 success = user_key_allowed2(pw, key, file);
 700                 free(file);
 701         }
 702
 703         return success;
 704 }
 705
 706 /* Records a public key in the list of previously-successful keys */
 707 void
 708 auth2_record_userkey(Authctxt *authctxt, struct sshkey *key)
 709 {
 710         struct sshkey **tmp;
 711
 712         if (authctxt->nprev_userkeys >= INT_MAX ||
 713             (tmp = reallocarray(authctxt->prev_userkeys,
 714             authctxt->nprev_userkeys + 1, sizeof(*tmp))) == NULL)
 715                 fatal("%s: reallocarray failed", __func__);
 716         authctxt->prev_userkeys = tmp;
 717         authctxt->prev_userkeys[authctxt->nprev_userkeys] = key;
 718         authctxt->nprev_userkeys++;
 719 }
 720
 721 /* Checks whether a key has already been used successfully for authentication */
 722 int
 723 auth2_userkey_already_used(Authctxt *authctxt, struct sshkey *key)
 724 {
 725         u_int i;
 726
 727         for (i = 0; i < authctxt->nprev_userkeys; i++) {
 728                 if (sshkey_equal_public(key, authctxt->prev_userkeys[i])) {
 729                         return 1;
 730                 }
 731         }
 732         return 0;
 733 }
 734
 735 Authmethod method_pubkey = {
 736         "publickey",
 737         userauth_pubkey,
 738         &options.pubkey_authentication
 739 };