crypto/openssh/auth2-pubkey.c

   1 /* $OpenBSD: auth2-pubkey.c,v 1.119 2023/07/27 22:25:17 djm Exp $ */
   2 /*
   3  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
   4  * Copyright (c) 2010 Damien Miller.  All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  * 1. Redistributions of source code must retain the above copyright
  10  *    notice, this list of conditions and the following disclaimer.
  11  * 2. Redistributions in binary form must reproduce the above copyright
  12  *    notice, this list of conditions and the following disclaimer in the
  13  *    documentation and/or other materials provided with the distribution.
  14  *
  15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  16  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  17  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  18  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  19  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  20  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  24  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  25  */
  26
  27 #include "includes.h"
  28
  29 #include <sys/types.h>
  30
  31 #include <stdlib.h>
  32 #include <errno.h>
  33 #ifdef HAVE_PATHS_H
  34 # include <paths.h>
  35 #endif
  36 #include <pwd.h>
  37 #include <signal.h>
  38 #include <stdio.h>
  39 #include <stdarg.h>
  40 #include <string.h>
  41 #include <time.h>
  42 #include <unistd.h>
  43 #include <limits.h>
  44
  45 #include "xmalloc.h"
  46 #include "ssh.h"
  47 #include "ssh2.h"
  48 #include "packet.h"
  49 #include "kex.h"
  50 #include "sshbuf.h"
  51 #include "log.h"
  52 #include "misc.h"
  53 #include "servconf.h"
  54 #include "compat.h"
  55 #include "sshkey.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 #include "ssherr.h"
  69 #include "channels.h" /* XXX for session.h */
  70 #include "session.h" /* XXX for child_set_env(); refactor? */
  71 #include "sk-api.h"
  72
  73 /* import */
  74 extern ServerOptions options;
  75
  76 static char *
  77 format_key(const struct sshkey *key)
  78 {
  79         char *ret, *fp = sshkey_fingerprint(key,
  80             options.fingerprint_hash, SSH_FP_DEFAULT);
  81
  82         xasprintf(&ret, "%s %s", sshkey_type(key), fp);
  83         free(fp);
  84         return ret;
  85 }
  86
  87 static int
  88 userauth_pubkey(struct ssh *ssh, const char *method)
  89 {
  90         Authctxt *authctxt = ssh->authctxt;
  91         struct passwd *pw = authctxt->pw;
  92         struct sshbuf *b = NULL;
  93         struct sshkey *key = NULL, *hostkey = NULL;
  94         char *pkalg = NULL, *userstyle = NULL, *key_s = NULL, *ca_s = NULL;
  95         u_char *pkblob = NULL, *sig = NULL, have_sig;
  96         size_t blen, slen;
  97         int hostbound, r, pktype;
  98         int req_presence = 0, req_verify = 0, authenticated = 0;
  99         struct sshauthopt *authopts = NULL;
 100         struct sshkey_sig_details *sig_details = NULL;
 101
 102         hostbound = strcmp(method, "publickey-hostbound-v00@openssh.com") == 0;
 103
 104         if ((r = sshpkt_get_u8(ssh, &have_sig)) != 0 ||
 105             (r = sshpkt_get_cstring(ssh, &pkalg, NULL)) != 0 ||
 106             (r = sshpkt_get_string(ssh, &pkblob, &blen)) != 0)
 107                 fatal_fr(r, "parse %s packet", method);
 108
 109         /* hostbound auth includes the hostkey offered at initial KEX */
 110         if (hostbound) {
 111                 if ((r = sshpkt_getb_froms(ssh, &b)) != 0 ||
 112                     (r = sshkey_fromb(b, &hostkey)) != 0)
 113                         fatal_fr(r, "parse %s hostkey", method);
 114                 if (ssh->kex->initial_hostkey == NULL)
 115                         fatal_f("internal error: initial hostkey not recorded");
 116                 if (!sshkey_equal(hostkey, ssh->kex->initial_hostkey))
 117                         fatal_f("%s packet contained wrong host key", method);
 118                 sshbuf_free(b);
 119                 b = NULL;
 120         }
 121
 122         if (log_level_get() >= SYSLOG_LEVEL_DEBUG2) {
 123                 char *keystring;
 124                 struct sshbuf *pkbuf;
 125
 126                 if ((pkbuf = sshbuf_from(pkblob, blen)) == NULL)
 127                         fatal_f("sshbuf_from failed");
 128                 if ((keystring = sshbuf_dtob64_string(pkbuf, 0)) == NULL)
 129                         fatal_f("sshbuf_dtob64 failed");
 130                 debug2_f("%s user %s %s public key %s %s",
 131                     authctxt->valid ? "valid" : "invalid", authctxt->user,
 132                     have_sig ? "attempting" : "querying", pkalg, keystring);
 133                 sshbuf_free(pkbuf);
 134                 free(keystring);
 135         }
 136
 137         pktype = sshkey_type_from_name(pkalg);
 138         if (pktype == KEY_UNSPEC) {
 139                 /* this is perfectly legal */
 140                 verbose_f("unsupported public key algorithm: %s", pkalg);
 141                 goto done;
 142         }
 143         if ((r = sshkey_from_blob(pkblob, blen, &key)) != 0) {
 144                 error_fr(r, "parse key");
 145                 goto done;
 146         }
 147         if (key == NULL) {
 148                 error_f("cannot decode key: %s", pkalg);
 149                 goto done;
 150         }
 151         if (key->type != pktype) {
 152                 error_f("type mismatch for decoded key "
 153                     "(received %d, expected %d)", key->type, pktype);
 154                 goto done;
 155         }
 156         if (auth2_key_already_used(authctxt, key)) {
 157                 logit("refusing previously-used %s key", sshkey_type(key));
 158                 goto done;
 159         }
 160         if (match_pattern_list(pkalg, options.pubkey_accepted_algos, 0) != 1) {
 161                 logit_f("signature algorithm %s not in "
 162                     "PubkeyAcceptedAlgorithms", pkalg);
 163                 goto done;
 164         }
 165         if ((r = sshkey_check_cert_sigtype(key,
 166             options.ca_sign_algorithms)) != 0) {
 167                 logit_fr(r, "certificate signature algorithm %s",
 168                     (key->cert == NULL || key->cert->signature_type == NULL) ?
 169                     "(null)" : key->cert->signature_type);
 170                 goto done;
 171         }
 172         if ((r = sshkey_check_rsa_length(key,
 173             options.required_rsa_size)) != 0) {
 174                 logit_r(r, "refusing %s key", sshkey_type(key));
 175                 goto done;
 176         }
 177         key_s = format_key(key);
 178         if (sshkey_is_cert(key))
 179                 ca_s = format_key(key->cert->signature_key);
 180
 181         if (have_sig) {
 182                 debug3_f("%s have %s signature for %s%s%s",
 183                     method, pkalg, key_s,
 184                     ca_s == NULL ? "" : " CA ", ca_s == NULL ? "" : ca_s);
 185                 if ((r = sshpkt_get_string(ssh, &sig, &slen)) != 0 ||
 186                     (r = sshpkt_get_end(ssh)) != 0)
 187                         fatal_fr(r, "parse signature packet");
 188                 if ((b = sshbuf_new()) == NULL)
 189                         fatal_f("sshbuf_new failed");
 190                 if (ssh->compat & SSH_OLD_SESSIONID) {
 191                         if ((r = sshbuf_putb(b, ssh->kex->session_id)) != 0)
 192                                 fatal_fr(r, "put old session id");
 193                 } else {
 194                         if ((r = sshbuf_put_stringb(b,
 195                             ssh->kex->session_id)) != 0)
 196                                 fatal_fr(r, "put session id");
 197                 }
 198                 if (!authctxt->valid || authctxt->user == NULL) {
 199                         debug2_f("disabled because of invalid user");
 200                         goto done;
 201                 }
 202                 /* reconstruct packet */
 203                 xasprintf(&userstyle, "%s%s%s", authctxt->user,
 204                     authctxt->style ? ":" : "",
 205                     authctxt->style ? authctxt->style : "");
 206                 if ((r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
 207                     (r = sshbuf_put_cstring(b, userstyle)) != 0 ||
 208                     (r = sshbuf_put_cstring(b, authctxt->service)) != 0 ||
 209                     (r = sshbuf_put_cstring(b, method)) != 0 ||
 210                     (r = sshbuf_put_u8(b, have_sig)) != 0 ||
 211                     (r = sshbuf_put_cstring(b, pkalg)) != 0 ||
 212                     (r = sshbuf_put_string(b, pkblob, blen)) != 0)
 213                         fatal_fr(r, "reconstruct %s packet", method);
 214                 if (hostbound &&
 215                     (r = sshkey_puts(ssh->kex->initial_hostkey, b)) != 0)
 216                         fatal_fr(r, "reconstruct %s packet", method);
 217 #ifdef DEBUG_PK
 218                 sshbuf_dump(b, stderr);
 219 #endif
 220                 /* test for correct signature */
 221                 authenticated = 0;
 222                 if (PRIVSEP(user_key_allowed(ssh, pw, key, 1, &authopts)) &&
 223                     PRIVSEP(sshkey_verify(key, sig, slen,
 224                     sshbuf_ptr(b), sshbuf_len(b),
 225                     (ssh->compat & SSH_BUG_SIGTYPE) == 0 ? pkalg : NULL,
 226                     ssh->compat, &sig_details)) == 0) {
 227                         authenticated = 1;
 228                 }
 229                 if (authenticated == 1 && sig_details != NULL) {
 230                         auth2_record_info(authctxt, "signature count = %u",
 231                             sig_details->sk_counter);
 232                         debug_f("sk_counter = %u, sk_flags = 0x%02x",
 233                             sig_details->sk_counter, sig_details->sk_flags);
 234                         req_presence = (options.pubkey_auth_options &
 235                             PUBKEYAUTH_TOUCH_REQUIRED) ||
 236                             !authopts->no_require_user_presence;
 237                         if (req_presence && (sig_details->sk_flags &
 238                             SSH_SK_USER_PRESENCE_REQD) == 0) {
 239                                 error("public key %s signature for %s%s from "
 240                                     "%.128s port %d rejected: user presence "
 241                                     "(authenticator touch) requirement "
 242                                     "not met ", key_s,
 243                                     authctxt->valid ? "" : "invalid user ",
 244                                     authctxt->user, ssh_remote_ipaddr(ssh),
 245                                     ssh_remote_port(ssh));
 246                                 authenticated = 0;
 247                                 goto done;
 248                         }
 249                         req_verify = (options.pubkey_auth_options &
 250                             PUBKEYAUTH_VERIFY_REQUIRED) ||
 251                             authopts->require_verify;
 252                         if (req_verify && (sig_details->sk_flags &
 253                             SSH_SK_USER_VERIFICATION_REQD) == 0) {
 254                                 error("public key %s signature for %s%s from "
 255                                     "%.128s port %d rejected: user "
 256                                     "verification requirement not met ", key_s,
 257                                     authctxt->valid ? "" : "invalid user ",
 258                                     authctxt->user, ssh_remote_ipaddr(ssh),
 259                                     ssh_remote_port(ssh));
 260                                 authenticated = 0;
 261                                 goto done;
 262                         }
 263                 }
 264                 auth2_record_key(authctxt, authenticated, key);
 265         } else {
 266                 debug_f("%s test pkalg %s pkblob %s%s%s", method, pkalg, key_s,
 267                     ca_s == NULL ? "" : " CA ", ca_s == NULL ? "" : ca_s);
 268
 269                 if ((r = sshpkt_get_end(ssh)) != 0)
 270                         fatal_fr(r, "parse packet");
 271
 272                 if (!authctxt->valid || authctxt->user == NULL) {
 273                         debug2_f("disabled because of invalid user");
 274                         goto done;
 275                 }
 276                 /* XXX fake reply and always send PK_OK ? */
 277                 /*
 278                  * XXX this allows testing whether a user is allowed
 279                  * to login: if you happen to have a valid pubkey this
 280                  * message is sent. the message is NEVER sent at all
 281                  * if a user is not allowed to login. is this an
 282                  * issue? -markus
 283                  */
 284                 if (PRIVSEP(user_key_allowed(ssh, pw, key, 0, NULL))) {
 285                         if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_PK_OK))
 286                             != 0 ||
 287                             (r = sshpkt_put_cstring(ssh, pkalg)) != 0 ||
 288                             (r = sshpkt_put_string(ssh, pkblob, blen)) != 0 ||
 289                             (r = sshpkt_send(ssh)) != 0 ||
 290                             (r = ssh_packet_write_wait(ssh)) != 0)
 291                                 fatal_fr(r, "send packet");
 292                         authctxt->postponed = 1;
 293                 }
 294         }
 295 done:
 296         if (authenticated == 1 && auth_activate_options(ssh, authopts) != 0) {
 297                 debug_f("key options inconsistent with existing");
 298                 authenticated = 0;
 299         }
 300         debug2_f("authenticated %d pkalg %s", authenticated, pkalg);
 301
 302         sshbuf_free(b);
 303         sshauthopt_free(authopts);
 304         sshkey_free(key);
 305         sshkey_free(hostkey);
 306         free(userstyle);
 307         free(pkalg);
 308         free(pkblob);
 309         free(key_s);
 310         free(ca_s);
 311         free(sig);
 312         sshkey_sig_details_free(sig_details);
 313         return authenticated;
 314 }
 315
 316 static int
 317 match_principals_file(struct passwd *pw, char *file,
 318     struct sshkey_cert *cert, struct sshauthopt **authoptsp)
 319 {
 320         FILE *f;
 321         int success;
 322
 323         if (authoptsp != NULL)
 324                 *authoptsp = NULL;
 325
 326         temporarily_use_uid(pw);
 327         debug("trying authorized principals file %s", file);
 328         if ((f = auth_openprincipals(file, pw, options.strict_modes)) == NULL) {
 329                 restore_uid();
 330                 return 0;
 331         }
 332         success = auth_process_principals(f, file, cert, authoptsp);
 333         fclose(f);
 334         restore_uid();
 335         return success;
 336 }
 337
 338 /*
 339  * Checks whether principal is allowed in output of command.
 340  * returns 1 if the principal is allowed or 0 otherwise.
 341  */
 342 static int
 343 match_principals_command(struct passwd *user_pw, const struct sshkey *key,
 344     const char *conn_id, const char *rdomain, struct sshauthopt **authoptsp)
 345 {
 346         struct passwd *runas_pw = NULL;
 347         const struct sshkey_cert *cert = key->cert;
 348         FILE *f = NULL;
 349         int r, ok, found_principal = 0;
 350         int i, ac = 0, uid_swapped = 0;
 351         pid_t pid;
 352         char *tmp, *username = NULL, *command = NULL, **av = NULL;
 353         char *ca_fp = NULL, *key_fp = NULL, *catext = NULL, *keytext = NULL;
 354         char serial_s[32], uidstr[32];
 355         void (*osigchld)(int);
 356
 357         if (authoptsp != NULL)
 358                 *authoptsp = NULL;
 359         if (options.authorized_principals_command == NULL)
 360                 return 0;
 361         if (options.authorized_principals_command_user == NULL) {
 362                 error("No user for AuthorizedPrincipalsCommand specified, "
 363                     "skipping");
 364                 return 0;
 365         }
 366
 367         /*
 368          * NB. all returns later this function should go via "out" to
 369          * ensure the original SIGCHLD handler is restored properly.
 370          */
 371         osigchld = ssh_signal(SIGCHLD, SIG_DFL);
 372
 373         /* Prepare and verify the user for the command */
 374         username = percent_expand(options.authorized_principals_command_user,
 375             "u", user_pw->pw_name, (char *)NULL);
 376         runas_pw = getpwnam(username);
 377         if (runas_pw == NULL) {
 378                 error("AuthorizedPrincipalsCommandUser \"%s\" not found: %s",
 379                     username, strerror(errno));
 380                 goto out;
 381         }
 382
 383         /* Turn the command into an argument vector */
 384         if (argv_split(options.authorized_principals_command,
 385             &ac, &av, 0) != 0) {
 386                 error("AuthorizedPrincipalsCommand \"%s\" contains "
 387                     "invalid quotes", options.authorized_principals_command);
 388                 goto out;
 389         }
 390         if (ac == 0) {
 391                 error("AuthorizedPrincipalsCommand \"%s\" yielded no arguments",
 392                     options.authorized_principals_command);
 393                 goto out;
 394         }
 395         if ((ca_fp = sshkey_fingerprint(cert->signature_key,
 396             options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
 397                 error_f("sshkey_fingerprint failed");
 398                 goto out;
 399         }
 400         if ((key_fp = sshkey_fingerprint(key,
 401             options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
 402                 error_f("sshkey_fingerprint failed");
 403                 goto out;
 404         }
 405         if ((r = sshkey_to_base64(cert->signature_key, &catext)) != 0) {
 406                 error_fr(r, "sshkey_to_base64 failed");
 407                 goto out;
 408         }
 409         if ((r = sshkey_to_base64(key, &keytext)) != 0) {
 410                 error_fr(r, "sshkey_to_base64 failed");
 411                 goto out;
 412         }
 413         snprintf(serial_s, sizeof(serial_s), "%llu",
 414             (unsigned long long)cert->serial);
 415         snprintf(uidstr, sizeof(uidstr), "%llu",
 416             (unsigned long long)user_pw->pw_uid);
 417         for (i = 1; i < ac; i++) {
 418                 tmp = percent_expand(av[i],
 419                     "C", conn_id,
 420                     "D", rdomain,
 421                     "U", uidstr,
 422                     "u", user_pw->pw_name,
 423                     "h", user_pw->pw_dir,
 424                     "t", sshkey_ssh_name(key),
 425                     "T", sshkey_ssh_name(cert->signature_key),
 426                     "f", key_fp,
 427                     "F", ca_fp,
 428                     "k", keytext,
 429                     "K", catext,
 430                     "i", cert->key_id,
 431                     "s", serial_s,
 432                     (char *)NULL);
 433                 if (tmp == NULL)
 434                         fatal_f("percent_expand failed");
 435                 free(av[i]);
 436                 av[i] = tmp;
 437         }
 438         /* Prepare a printable command for logs, etc. */
 439         command = argv_assemble(ac, av);
 440
 441         if ((pid = subprocess("AuthorizedPrincipalsCommand", command,
 442             ac, av, &f,
 443             SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD,
 444             runas_pw, temporarily_use_uid, restore_uid)) == 0)
 445                 goto out;
 446
 447         uid_swapped = 1;
 448         temporarily_use_uid(runas_pw);
 449
 450         ok = auth_process_principals(f, "(command)", cert, authoptsp);
 451
 452         fclose(f);
 453         f = NULL;
 454
 455         if (exited_cleanly(pid, "AuthorizedPrincipalsCommand", command, 0) != 0)
 456                 goto out;
 457
 458         /* Read completed successfully */
 459         found_principal = ok;
 460  out:
 461         if (f != NULL)
 462                 fclose(f);
 463         ssh_signal(SIGCHLD, osigchld);
 464         for (i = 0; i < ac; i++)
 465                 free(av[i]);
 466         free(av);
 467         if (uid_swapped)
 468                 restore_uid();
 469         free(command);
 470         free(username);
 471         free(ca_fp);
 472         free(key_fp);
 473         free(catext);
 474         free(keytext);
 475         return found_principal;
 476 }
 477
 478 /* Authenticate a certificate key against TrustedUserCAKeys */
 479 static int
 480 user_cert_trusted_ca(struct passwd *pw, struct sshkey *key,
 481     const char *remote_ip, const char *remote_host,
 482     const char *conn_id, const char *rdomain, struct sshauthopt **authoptsp)
 483 {
 484         char *ca_fp, *principals_file = NULL;
 485         const char *reason;
 486         struct sshauthopt *principals_opts = NULL, *cert_opts = NULL;
 487         struct sshauthopt *final_opts = NULL;
 488         int r, ret = 0, found_principal = 0, use_authorized_principals;
 489
 490         if (authoptsp != NULL)
 491                 *authoptsp = NULL;
 492
 493         if (!sshkey_is_cert(key) || options.trusted_user_ca_keys == NULL)
 494                 return 0;
 495
 496         if ((ca_fp = sshkey_fingerprint(key->cert->signature_key,
 497             options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
 498                 return 0;
 499
 500         if ((r = sshkey_in_file(key->cert->signature_key,
 501             options.trusted_user_ca_keys, 1, 0)) != 0) {
 502                 debug2_fr(r, "CA %s %s is not listed in %s",
 503                     sshkey_type(key->cert->signature_key), ca_fp,
 504                     options.trusted_user_ca_keys);
 505                 goto out;
 506         }
 507         /*
 508          * If AuthorizedPrincipals is in use, then compare the certificate
 509          * principals against the names in that file rather than matching
 510          * against the username.
 511          */
 512         if ((principals_file = authorized_principals_file(pw)) != NULL) {
 513                 if (match_principals_file(pw, principals_file,
 514                     key->cert, &principals_opts))
 515                         found_principal = 1;
 516         }
 517         /* Try querying command if specified */
 518         if (!found_principal && match_principals_command(pw, key,
 519             conn_id, rdomain, &principals_opts))
 520                 found_principal = 1;
 521         /* If principals file or command is specified, then require a match */
 522         use_authorized_principals = principals_file != NULL ||
 523             options.authorized_principals_command != NULL;
 524         if (!found_principal && use_authorized_principals) {
 525                 reason = "Certificate does not contain an authorized principal";
 526                 goto fail_reason;
 527         }
 528         if (use_authorized_principals && principals_opts == NULL)
 529                 fatal_f("internal error: missing principals_opts");
 530         if (sshkey_cert_check_authority_now(key, 0, 1, 0,
 531             use_authorized_principals ? NULL : pw->pw_name, &reason) != 0)
 532                 goto fail_reason;
 533
 534         /* Check authority from options in key and from principals file/cmd */
 535         if ((cert_opts = sshauthopt_from_cert(key)) == NULL) {
 536                 reason = "Invalid certificate options";
 537                 goto fail_reason;
 538         }
 539         if (auth_authorise_keyopts(pw, cert_opts, 0,
 540             remote_ip, remote_host, "cert") != 0) {
 541                 reason = "Refused by certificate options";
 542                 goto fail_reason;
 543         }
 544         if (principals_opts == NULL) {
 545                 final_opts = cert_opts;
 546                 cert_opts = NULL;
 547         } else {
 548                 if (auth_authorise_keyopts(pw, principals_opts, 0,
 549                     remote_ip, remote_host, "principals") != 0) {
 550                         reason = "Refused by certificate principals options";
 551                         goto fail_reason;
 552                 }
 553                 if ((final_opts = sshauthopt_merge(principals_opts,
 554                     cert_opts, &reason)) == NULL) {
 555  fail_reason:
 556                         error("%s", reason);
 557                         auth_debug_add("%s", reason);
 558                         goto out;
 559                 }
 560         }
 561
 562         /* Success */
 563         verbose("Accepted certificate ID \"%s\" (serial %llu) signed by "
 564             "%s CA %s via %s", key->cert->key_id,
 565             (unsigned long long)key->cert->serial,
 566             sshkey_type(key->cert->signature_key), ca_fp,
 567             options.trusted_user_ca_keys);
 568         if (authoptsp != NULL) {
 569                 *authoptsp = final_opts;
 570                 final_opts = NULL;
 571         }
 572         ret = 1;
 573  out:
 574         sshauthopt_free(principals_opts);
 575         sshauthopt_free(cert_opts);
 576         sshauthopt_free(final_opts);
 577         free(principals_file);
 578         free(ca_fp);
 579         return ret;
 580 }
 581
 582 /*
 583  * Checks whether key is allowed in file.
 584  * returns 1 if the key is allowed or 0 otherwise.
 585  */
 586 static int
 587 user_key_allowed2(struct passwd *pw, struct sshkey *key,
 588     char *file, const char *remote_ip, const char *remote_host,
 589     struct sshauthopt **authoptsp)
 590 {
 591         FILE *f;
 592         int found_key = 0;
 593
 594         if (authoptsp != NULL)
 595                 *authoptsp = NULL;
 596
 597         /* Temporarily use the user's uid. */
 598         temporarily_use_uid(pw);
 599
 600         debug("trying public key file %s", file);
 601         if ((f = auth_openkeyfile(file, pw, options.strict_modes)) != NULL) {
 602                 found_key = auth_check_authkeys_file(pw, f, file,
 603                     key, remote_ip, remote_host, authoptsp);
 604                 fclose(f);
 605         }
 606
 607         restore_uid();
 608         return found_key;
 609 }
 610
 611 /*
 612  * Checks whether key is allowed in output of command.
 613  * returns 1 if the key is allowed or 0 otherwise.
 614  */
 615 static int
 616 user_key_command_allowed2(struct passwd *user_pw, struct sshkey *key,
 617     const char *remote_ip, const char *remote_host,
 618     const char *conn_id, const char *rdomain, struct sshauthopt **authoptsp)
 619 {
 620         struct passwd *runas_pw = NULL;
 621         FILE *f = NULL;
 622         int r, ok, found_key = 0;
 623         int i, uid_swapped = 0, ac = 0;
 624         pid_t pid;
 625         char *username = NULL, *key_fp = NULL, *keytext = NULL;
 626         char uidstr[32], *tmp, *command = NULL, **av = NULL;
 627         void (*osigchld)(int);
 628
 629         if (authoptsp != NULL)
 630                 *authoptsp = NULL;
 631         if (options.authorized_keys_command == NULL)
 632                 return 0;
 633         if (options.authorized_keys_command_user == NULL) {
 634                 error("No user for AuthorizedKeysCommand specified, skipping");
 635                 return 0;
 636         }
 637
 638         /*
 639          * NB. all returns later this function should go via "out" to
 640          * ensure the original SIGCHLD handler is restored properly.
 641          */
 642         osigchld = ssh_signal(SIGCHLD, SIG_DFL);
 643
 644         /* Prepare and verify the user for the command */
 645         username = percent_expand(options.authorized_keys_command_user,
 646             "u", user_pw->pw_name, (char *)NULL);
 647         runas_pw = getpwnam(username);
 648         if (runas_pw == NULL) {
 649                 error("AuthorizedKeysCommandUser \"%s\" not found: %s",
 650                     username, strerror(errno));
 651                 goto out;
 652         }
 653
 654         /* Prepare AuthorizedKeysCommand */
 655         if ((key_fp = sshkey_fingerprint(key, options.fingerprint_hash,
 656             SSH_FP_DEFAULT)) == NULL) {
 657                 error_f("sshkey_fingerprint failed");
 658                 goto out;
 659         }
 660         if ((r = sshkey_to_base64(key, &keytext)) != 0) {
 661                 error_fr(r, "sshkey_to_base64 failed");
 662                 goto out;
 663         }
 664
 665         /* Turn the command into an argument vector */
 666         if (argv_split(options.authorized_keys_command, &ac, &av, 0) != 0) {
 667                 error("AuthorizedKeysCommand \"%s\" contains invalid quotes",
 668                     options.authorized_keys_command);
 669                 goto out;
 670         }
 671         if (ac == 0) {
 672                 error("AuthorizedKeysCommand \"%s\" yielded no arguments",
 673                     options.authorized_keys_command);
 674                 goto out;
 675         }
 676         snprintf(uidstr, sizeof(uidstr), "%llu",
 677             (unsigned long long)user_pw->pw_uid);
 678         for (i = 1; i < ac; i++) {
 679                 tmp = percent_expand(av[i],
 680                     "C", conn_id,
 681                     "D", rdomain,
 682                     "U", uidstr,
 683                     "u", user_pw->pw_name,
 684                     "h", user_pw->pw_dir,
 685                     "t", sshkey_ssh_name(key),
 686                     "f", key_fp,
 687                     "k", keytext,
 688                     (char *)NULL);
 689                 if (tmp == NULL)
 690                         fatal_f("percent_expand failed");
 691                 free(av[i]);
 692                 av[i] = tmp;
 693         }
 694         /* Prepare a printable command for logs, etc. */
 695         command = argv_assemble(ac, av);
 696
 697         /*
 698          * If AuthorizedKeysCommand was run without arguments
 699          * then fall back to the old behaviour of passing the
 700          * target username as a single argument.
 701          */
 702         if (ac == 1) {
 703                 av = xreallocarray(av, ac + 2, sizeof(*av));
 704                 av[1] = xstrdup(user_pw->pw_name);
 705                 av[2] = NULL;
 706                 /* Fix up command too, since it is used in log messages */
 707                 free(command);
 708                 xasprintf(&command, "%s %s", av[0], av[1]);
 709         }
 710
 711         if ((pid = subprocess("AuthorizedKeysCommand", command,
 712             ac, av, &f,
 713             SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD,
 714             runas_pw, temporarily_use_uid, restore_uid)) == 0)
 715                 goto out;
 716
 717         uid_swapped = 1;
 718         temporarily_use_uid(runas_pw);
 719
 720         ok = auth_check_authkeys_file(user_pw, f,
 721             options.authorized_keys_command, key, remote_ip,
 722             remote_host, authoptsp);
 723
 724         fclose(f);
 725         f = NULL;
 726
 727         if (exited_cleanly(pid, "AuthorizedKeysCommand", command, 0) != 0)
 728                 goto out;
 729
 730         /* Read completed successfully */
 731         found_key = ok;
 732  out:
 733         if (f != NULL)
 734                 fclose(f);
 735         ssh_signal(SIGCHLD, osigchld);
 736         for (i = 0; i < ac; i++)
 737                 free(av[i]);
 738         free(av);
 739         if (uid_swapped)
 740                 restore_uid();
 741         free(command);
 742         free(username);
 743         free(key_fp);
 744         free(keytext);
 745         return found_key;
 746 }
 747
 748 /*
 749  * Check whether key authenticates and authorises the user.
 750  */
 751 int
 752 user_key_allowed(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
 753     int auth_attempt, struct sshauthopt **authoptsp)
 754 {
 755         u_int success = 0, i;
 756         char *file, *conn_id;
 757         struct sshauthopt *opts = NULL;
 758         const char *rdomain, *remote_ip, *remote_host;
 759
 760         if (authoptsp != NULL)
 761                 *authoptsp = NULL;
 762
 763         if (auth_key_is_revoked(key))
 764                 return 0;
 765         if (sshkey_is_cert(key) &&
 766             auth_key_is_revoked(key->cert->signature_key))
 767                 return 0;
 768
 769         if ((rdomain = ssh_packet_rdomain_in(ssh)) == NULL)
 770                 rdomain = "";
 771         remote_ip = ssh_remote_ipaddr(ssh);
 772         remote_host = auth_get_canonical_hostname(ssh, options.use_dns);
 773         xasprintf(&conn_id, "%s %d %s %d",
 774             ssh_local_ipaddr(ssh), ssh_local_port(ssh),
 775             remote_ip, ssh_remote_port(ssh));
 776
 777         for (i = 0; !success && i < options.num_authkeys_files; i++) {
 778                 if (strcasecmp(options.authorized_keys_files[i], "none") == 0)
 779                         continue;
 780                 file = expand_authorized_keys(
 781                     options.authorized_keys_files[i], pw);
 782                 success = user_key_allowed2(pw, key, file,
 783                     remote_ip, remote_host, &opts);
 784                 free(file);
 785                 if (!success) {
 786                         sshauthopt_free(opts);
 787                         opts = NULL;
 788                 }
 789         }
 790         if (success)
 791                 goto out;
 792
 793         if ((success = user_cert_trusted_ca(pw, key, remote_ip, remote_host,
 794             conn_id, rdomain, &opts)) != 0)
 795                 goto out;
 796         sshauthopt_free(opts);
 797         opts = NULL;
 798
 799         if ((success = user_key_command_allowed2(pw, key, remote_ip,
 800             remote_host, conn_id, rdomain, &opts)) != 0)
 801                 goto out;
 802         sshauthopt_free(opts);
 803         opts = NULL;
 804
 805  out:
 806         free(conn_id);
 807         if (success && authoptsp != NULL) {
 808                 *authoptsp = opts;
 809                 opts = NULL;
 810         }
 811         sshauthopt_free(opts);
 812         return success;
 813 }
 814
 815 Authmethod method_pubkey = {
 816         "publickey",
 817         "publickey-hostbound-v00@openssh.com",
 818         userauth_pubkey,
 819         &options.pubkey_authentication
 820 };