1 /* $NetBSD: auth2-pubkey.c,v 1.14 2016/03/11 01:55:00 christos Exp $ */ 2 /* $OpenBSD: auth2-pubkey.c,v 1.55 2016/01/27 00:53:12 djm Exp $ */ 3 4 /* 5 * Copyright (c) 2000 Markus Friedl. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 26 */ 27 28 #include "includes.h" 29 __RCSID("$NetBSD: auth2-pubkey.c,v 1.14 2016/03/11 01:55:00 christos Exp $"); 30 #include <sys/types.h> 31 #include <sys/stat.h> 32 #include <sys/wait.h> 33 34 #include <errno.h> 35 #include <fcntl.h> 36 #include <paths.h> 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 #include "digest.h" 69 70 #ifdef WITH_LDAP_PUBKEY 71 #include "ldapauth.h" 72 #endif 73 74 #include "ssherr.h" 75 #include "channels.h" /* XXX for session.h */ 76 #include "session.h" /* XXX for child_set_env(); refactor? */ 77 78 /* import */ 79 extern ServerOptions options; 80 extern u_char *session_id2; 81 extern u_int session_id2_len; 82 83 static int 84 userauth_pubkey(Authctxt *authctxt) 85 { 86 Buffer b; 87 Key *key = NULL; 88 char *pkalg, *userstyle, *fp = NULL; 89 u_char *pkblob, *sig; 90 u_int alen, blen, slen; 91 int have_sig, pktype; 92 int authenticated = 0; 93 94 if (!authctxt->valid) { 95 debug2("%s: disabled because of invalid user", __func__); 96 return 0; 97 } 98 have_sig = packet_get_char(); 99 if (datafellows & SSH_BUG_PKAUTH) { 100 debug2("%s: SSH_BUG_PKAUTH", __func__); 101 /* no explicit pkalg given */ 102 pkblob = packet_get_string(&blen); 103 buffer_init(&b); 104 buffer_append(&b, pkblob, blen); 105 /* so we have to extract the pkalg from the pkblob */ 106 pkalg = buffer_get_string(&b, &alen); 107 buffer_free(&b); 108 } else { 109 pkalg = packet_get_string(&alen); 110 pkblob = packet_get_string(&blen); 111 } 112 pktype = key_type_from_name(pkalg); 113 if (pktype == KEY_UNSPEC) { 114 /* this is perfectly legal */ 115 logit("%s: unsupported public key algorithm: %s", 116 __func__, pkalg); 117 goto done; 118 } 119 key = key_from_blob(pkblob, blen); 120 if (key == NULL) { 121 error("%s: cannot decode key: %s", __func__, pkalg); 122 goto done; 123 } 124 if (key->type != pktype) { 125 error("%s: type mismatch for decoded key " 126 "(received %d, expected %d)", __func__, key->type, pktype); 127 goto done; 128 } 129 if (key_type_plain(key->type) == KEY_RSA && 130 (datafellows & SSH_BUG_RSASIGMD5) != 0) { 131 logit("Refusing RSA key because client uses unsafe " 132 "signature scheme"); 133 goto done; 134 } 135 fp = sshkey_fingerprint(key, options.fingerprint_hash, SSH_FP_DEFAULT); 136 if (auth2_userkey_already_used(authctxt, key)) { 137 logit("refusing previously-used %s key", key_type(key)); 138 goto done; 139 } 140 if (match_pattern_list(sshkey_ssh_name(key), 141 options.pubkey_key_types, 0) != 1) { 142 logit("%s: key type %s not in PubkeyAcceptedKeyTypes", 143 __func__, sshkey_ssh_name(key)); 144 goto done; 145 } 146 147 if (have_sig) { 148 debug3("%s: have signature for %s %s", 149 __func__, sshkey_type(key), fp); 150 sig = packet_get_string(&slen); 151 packet_check_eom(); 152 buffer_init(&b); 153 if (datafellows & SSH_OLD_SESSIONID) { 154 buffer_append(&b, session_id2, session_id2_len); 155 } else { 156 buffer_put_string(&b, session_id2, session_id2_len); 157 } 158 /* reconstruct packet */ 159 buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST); 160 xasprintf(&userstyle, "%s%s%s", authctxt->user, 161 authctxt->style ? ":" : "", 162 authctxt->style ? authctxt->style : ""); 163 buffer_put_cstring(&b, userstyle); 164 free(userstyle); 165 buffer_put_cstring(&b, 166 datafellows & SSH_BUG_PKSERVICE ? 167 "ssh-userauth" : 168 authctxt->service); 169 if (datafellows & SSH_BUG_PKAUTH) { 170 buffer_put_char(&b, have_sig); 171 } else { 172 buffer_put_cstring(&b, "publickey"); 173 buffer_put_char(&b, have_sig); 174 buffer_put_cstring(&b, pkalg); 175 } 176 buffer_put_string(&b, pkblob, blen); 177 #ifdef DEBUG_PK 178 buffer_dump(&b); 179 #endif 180 pubkey_auth_info(authctxt, key, NULL); 181 182 /* test for correct signature */ 183 authenticated = 0; 184 if (PRIVSEP(user_key_allowed(authctxt->pw, key, 1)) && 185 PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b), 186 buffer_len(&b))) == 1) { 187 authenticated = 1; 188 /* Record the successful key to prevent reuse */ 189 auth2_record_userkey(authctxt, key); 190 key = NULL; /* Don't free below */ 191 } 192 buffer_free(&b); 193 free(sig); 194 } else { 195 debug("%s: test whether pkalg/pkblob are acceptable for %s %s", 196 __func__, sshkey_type(key), fp); 197 packet_check_eom(); 198 199 /* XXX fake reply and always send PK_OK ? */ 200 /* 201 * XXX this allows testing whether a user is allowed 202 * to login: if you happen to have a valid pubkey this 203 * message is sent. the message is NEVER sent at all 204 * if a user is not allowed to login. is this an 205 * issue? -markus 206 */ 207 if (PRIVSEP(user_key_allowed(authctxt->pw, key, 0))) { 208 packet_start(SSH2_MSG_USERAUTH_PK_OK); 209 packet_put_string(pkalg, alen); 210 packet_put_string(pkblob, blen); 211 packet_send(); 212 packet_write_wait(); 213 authctxt->postponed = 1; 214 } 215 } 216 if (authenticated != 1) 217 auth_clear_options(); 218 done: 219 debug2("%s: authenticated %d pkalg %s", __func__, authenticated, pkalg); 220 if (key != NULL) 221 key_free(key); 222 free(pkalg); 223 free(pkblob); 224 free(fp); 225 return authenticated; 226 } 227 228 void 229 pubkey_auth_info(Authctxt *authctxt, const Key *key, const char *fmt, ...) 230 { 231 char *fp, *extra; 232 va_list ap; 233 int i; 234 235 extra = NULL; 236 if (fmt != NULL) { 237 va_start(ap, fmt); 238 i = vasprintf(&extra, fmt, ap); 239 va_end(ap); 240 if (i < 0 || extra == NULL) 241 fatal("%s: vasprintf failed", __func__); 242 } 243 244 if (key_is_cert(key)) { 245 fp = sshkey_fingerprint(key->cert->signature_key, 246 options.fingerprint_hash, SSH_FP_DEFAULT); 247 auth_info(authctxt, "%s ID %s (serial %llu) CA %s %s%s%s", 248 key_type(key), key->cert->key_id, 249 (unsigned long long)key->cert->serial, 250 key_type(key->cert->signature_key), 251 fp == NULL ? "(null)" : fp, 252 extra == NULL ? "" : ", ", extra == NULL ? "" : extra); 253 free(fp); 254 } else { 255 fp = sshkey_fingerprint(key, options.fingerprint_hash, 256 SSH_FP_DEFAULT); 257 auth_info(authctxt, "%s %s%s%s", key_type(key), 258 fp == NULL ? "(null)" : fp, 259 extra == NULL ? "" : ", ", extra == NULL ? "" : extra); 260 free(fp); 261 } 262 free(extra); 263 } 264 265 /* 266 * Splits 's' into an argument vector. Handles quoted string and basic 267 * escape characters (\\, \", \'). Caller must free the argument vector 268 * and its members. 269 */ 270 static int 271 split_argv(const char *s, int *argcp, char ***argvp) 272 { 273 int r = SSH_ERR_INTERNAL_ERROR; 274 int argc = 0, quote, i, j; 275 char *arg, **argv = xcalloc(1, sizeof(*argv)); 276 277 *argvp = NULL; 278 *argcp = 0; 279 280 for (i = 0; s[i] != '\0'; i++) { 281 /* Skip leading whitespace */ 282 if (s[i] == ' ' || s[i] == '\t') 283 continue; 284 285 /* Start of a token */ 286 quote = 0; 287 if (s[i] == '\\' && 288 (s[i + 1] == '\'' || s[i + 1] == '\"' || s[i + 1] == '\\')) 289 i++; 290 else if (s[i] == '\'' || s[i] == '"') 291 quote = s[i++]; 292 293 argv = xreallocarray(argv, (argc + 2), sizeof(*argv)); 294 arg = argv[argc++] = xcalloc(1, strlen(s + i) + 1); 295 argv[argc] = NULL; 296 297 /* Copy the token in, removing escapes */ 298 for (j = 0; s[i] != '\0'; i++) { 299 if (s[i] == '\\') { 300 if (s[i + 1] == '\'' || 301 s[i + 1] == '\"' || 302 s[i + 1] == '\\') { 303 i++; /* Skip '\' */ 304 arg[j++] = s[i]; 305 } else { 306 /* Unrecognised escape */ 307 arg[j++] = s[i]; 308 } 309 } else if (quote == 0 && (s[i] == ' ' || s[i] == '\t')) 310 break; /* done */ 311 else if (quote != 0 && s[i] == quote) 312 break; /* done */ 313 else 314 arg[j++] = s[i]; 315 } 316 if (s[i] == '\0') { 317 if (quote != 0) { 318 /* Ran out of string looking for close quote */ 319 r = SSH_ERR_INVALID_FORMAT; 320 goto out; 321 } 322 break; 323 } 324 } 325 /* Success */ 326 *argcp = argc; 327 *argvp = argv; 328 argc = 0; 329 argv = NULL; 330 r = 0; 331 out: 332 if (argc != 0 && argv != NULL) { 333 for (i = 0; i < argc; i++) 334 free(argv[i]); 335 free(argv); 336 } 337 return r; 338 } 339 340 /* 341 * Reassemble an argument vector into a string, quoting and escaping as 342 * necessary. Caller must free returned string. 343 */ 344 static char * 345 assemble_argv(int argc, char **argv) 346 { 347 int i, j, ws, r; 348 char c, *ret; 349 struct sshbuf *buf, *arg; 350 351 if ((buf = sshbuf_new()) == NULL || (arg = sshbuf_new()) == NULL) 352 fatal("%s: sshbuf_new failed", __func__); 353 354 for (i = 0; i < argc; i++) { 355 ws = 0; 356 sshbuf_reset(arg); 357 for (j = 0; argv[i][j] != '\0'; j++) { 358 r = 0; 359 c = argv[i][j]; 360 switch (c) { 361 case ' ': 362 case '\t': 363 ws = 1; 364 r = sshbuf_put_u8(arg, c); 365 break; 366 case '\\': 367 case '\'': 368 case '"': 369 if ((r = sshbuf_put_u8(arg, '\\')) != 0) 370 break; 371 /* FALLTHROUGH */ 372 default: 373 r = sshbuf_put_u8(arg, c); 374 break; 375 } 376 if (r != 0) 377 fatal("%s: sshbuf_put_u8: %s", 378 __func__, ssh_err(r)); 379 } 380 if ((i != 0 && (r = sshbuf_put_u8(buf, ' ')) != 0) || 381 (ws != 0 && (r = sshbuf_put_u8(buf, '"')) != 0) || 382 (r = sshbuf_putb(buf, arg)) != 0 || 383 (ws != 0 && (r = sshbuf_put_u8(buf, '"')) != 0)) 384 fatal("%s: buffer error: %s", __func__, ssh_err(r)); 385 } 386 if ((ret = malloc(sshbuf_len(buf) + 1)) == NULL) 387 fatal("%s: malloc failed", __func__); 388 memcpy(ret, sshbuf_ptr(buf), sshbuf_len(buf)); 389 ret[sshbuf_len(buf)] = '\0'; 390 sshbuf_free(buf); 391 sshbuf_free(arg); 392 return ret; 393 } 394 395 /* 396 * Runs command in a subprocess. Returns pid on success and a FILE* to the 397 * subprocess' stdout or 0 on failure. 398 * NB. "command" is only used for logging. 399 */ 400 static pid_t 401 subprocess(const char *tag, struct passwd *pw, const char *command, 402 int ac, char **av, FILE **child) 403 { 404 FILE *f; 405 struct stat st; 406 int devnull, p[2], i; 407 pid_t pid; 408 char *cp, errmsg[512]; 409 u_int envsize; 410 char **child_env; 411 412 *child = NULL; 413 414 debug3("%s: %s command \"%s\" running as %s", __func__, 415 tag, command, pw->pw_name); 416 417 /* Verify the path exists and is safe-ish to execute */ 418 if (*av[0] != '/') { 419 error("%s path is not absolute", tag); 420 return 0; 421 } 422 temporarily_use_uid(pw); 423 if (stat(av[0], &st) < 0) { 424 error("Could not stat %s \"%s\": %s", tag, 425 av[0], strerror(errno)); 426 restore_uid(); 427 return 0; 428 } 429 if (auth_secure_path(av[0], &st, NULL, 0, 430 errmsg, sizeof(errmsg)) != 0) { 431 error("Unsafe %s \"%s\": %s", tag, av[0], errmsg); 432 restore_uid(); 433 return 0; 434 } 435 436 /* 437 * Run the command; stderr is left in place, stdout is the 438 * authorized_keys output. 439 */ 440 if (pipe(p) != 0) { 441 error("%s: pipe: %s", tag, strerror(errno)); 442 restore_uid(); 443 return 0; 444 } 445 446 /* 447 * Don't want to call this in the child, where it can fatal() and 448 * run cleanup_exit() code. 449 */ 450 restore_uid(); 451 452 switch ((pid = fork())) { 453 case -1: /* error */ 454 error("%s: fork: %s", tag, strerror(errno)); 455 close(p[0]); 456 close(p[1]); 457 return 0; 458 case 0: /* child */ 459 /* Prepare a minimal environment for the child. */ 460 envsize = 5; 461 child_env = xcalloc(sizeof(*child_env), envsize); 462 child_set_env(&child_env, &envsize, "PATH", _PATH_STDPATH); 463 child_set_env(&child_env, &envsize, "USER", pw->pw_name); 464 child_set_env(&child_env, &envsize, "LOGNAME", pw->pw_name); 465 child_set_env(&child_env, &envsize, "HOME", pw->pw_dir); 466 if ((cp = getenv("LANG")) != NULL) 467 child_set_env(&child_env, &envsize, "LANG", cp); 468 469 for (i = 0; i < NSIG; i++) 470 signal(i, SIG_DFL); 471 472 if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1) { 473 error("%s: open %s: %s", tag, _PATH_DEVNULL, 474 strerror(errno)); 475 _exit(1); 476 } 477 /* Keep stderr around a while longer to catch errors */ 478 if (dup2(devnull, STDIN_FILENO) == -1 || 479 dup2(p[1], STDOUT_FILENO) == -1) { 480 error("%s: dup2: %s", tag, strerror(errno)); 481 _exit(1); 482 } 483 if (closefrom(STDERR_FILENO + 1) == -1) { 484 error("closefrom: %s", strerror(errno)); 485 _exit(1); 486 } 487 488 /* Don't use permanently_set_uid() here to avoid fatal() */ 489 if (setgid(pw->pw_gid) == -1) { 490 error("setgid %u: %s", (u_int)pw->pw_gid, 491 strerror(errno)); 492 _exit(1); 493 } 494 if (setuid(pw->pw_uid) == -1) { 495 error("setuid %u: %s", (u_int)pw->pw_uid, 496 strerror(errno)); 497 _exit(1); 498 } 499 /* stdin is pointed to /dev/null at this point */ 500 if (dup2(STDIN_FILENO, STDERR_FILENO) == -1) { 501 error("%s: dup2: %s", tag, strerror(errno)); 502 _exit(1); 503 } 504 505 execve(av[0], av, child_env); 506 error("%s exec \"%s\": %s", tag, command, strerror(errno)); 507 _exit(127); 508 default: /* parent */ 509 break; 510 } 511 512 close(p[1]); 513 if ((f = fdopen(p[0], "r")) == NULL) { 514 error("%s: fdopen: %s", tag, strerror(errno)); 515 close(p[0]); 516 /* Don't leave zombie child */ 517 kill(pid, SIGTERM); 518 while (waitpid(pid, NULL, 0) == -1 && errno == EINTR) 519 ; 520 return 0; 521 } 522 /* Success */ 523 debug3("%s: %s pid %ld", __func__, tag, (long)pid); 524 *child = f; 525 return pid; 526 } 527 528 /* Returns 0 if pid exited cleanly, non-zero otherwise */ 529 static int 530 exited_cleanly(pid_t pid, const char *tag, const char *cmd) 531 { 532 int status; 533 534 while (waitpid(pid, &status, 0) == -1) { 535 if (errno != EINTR) { 536 error("%s: waitpid: %s", tag, strerror(errno)); 537 return -1; 538 } 539 } 540 if (WIFSIGNALED(status)) { 541 error("%s %s exited on signal %d", tag, cmd, WTERMSIG(status)); 542 return -1; 543 } else if (WEXITSTATUS(status) != 0) { 544 error("%s %s failed, status %d", tag, cmd, WEXITSTATUS(status)); 545 return -1; 546 } 547 return 0; 548 } 549 550 static int 551 match_principals_option(const char *principal_list, struct sshkey_cert *cert) 552 { 553 char *result; 554 u_int i; 555 556 /* XXX percent_expand() sequences for authorized_principals? */ 557 558 for (i = 0; i < cert->nprincipals; i++) { 559 if ((result = match_list(cert->principals[i], 560 principal_list, NULL)) != NULL) { 561 debug3("matched principal from key options \"%.100s\"", 562 result); 563 free(result); 564 return 1; 565 } 566 } 567 return 0; 568 } 569 570 static int 571 process_principals(FILE *f, char *file, struct passwd *pw, 572 struct sshkey_cert *cert) 573 { 574 char line[SSH_MAX_PUBKEY_BYTES], *cp, *ep, *line_opts; 575 u_long linenum = 0; 576 u_int i; 577 578 while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) { 579 /* Skip leading whitespace. */ 580 for (cp = line; *cp == ' ' || *cp == '\t'; cp++) 581 ; 582 /* Skip blank and comment lines. */ 583 if ((ep = strchr(cp, '#')) != NULL) 584 *ep = '\0'; 585 if (!*cp || *cp == '\n') 586 continue; 587 /* Trim trailing whitespace. */ 588 ep = cp + strlen(cp) - 1; 589 while (ep > cp && (*ep == '\n' || *ep == ' ' || *ep == '\t')) 590 *ep-- = '\0'; 591 /* 592 * If the line has internal whitespace then assume it has 593 * key options. 594 */ 595 line_opts = NULL; 596 if ((ep = strrchr(cp, ' ')) != NULL || 597 (ep = strrchr(cp, '\t')) != NULL) { 598 for (; *ep == ' ' || *ep == '\t'; ep++) 599 ; 600 line_opts = cp; 601 cp = ep; 602 } 603 for (i = 0; i < cert->nprincipals; i++) { 604 if (strcmp(cp, cert->principals[i]) == 0) { 605 debug3("%s:%lu: matched principal \"%.100s\"", 606 file == NULL ? "(command)" : file, 607 linenum, cert->principals[i]); 608 if (auth_parse_options(pw, line_opts, 609 file, linenum) != 1) 610 continue; 611 return 1; 612 } 613 } 614 } 615 return 0; 616 } 617 618 static int 619 match_principals_file(char *file, struct passwd *pw, struct sshkey_cert *cert) 620 { 621 FILE *f; 622 int success; 623 624 temporarily_use_uid(pw); 625 debug("trying authorized principals file %s", file); 626 if ((f = auth_openprincipals(file, pw, options.strict_modes)) == NULL) { 627 restore_uid(); 628 return 0; 629 } 630 success = process_principals(f, file, pw, cert); 631 fclose(f); 632 restore_uid(); 633 return success; 634 } 635 636 /* 637 * Checks whether principal is allowed in output of command. 638 * returns 1 if the principal is allowed or 0 otherwise. 639 */ 640 static int 641 match_principals_command(struct passwd *user_pw, struct sshkey_cert *cert) 642 { 643 FILE *f = NULL; 644 int ok, found_principal = 0; 645 struct passwd *pw; 646 int i, ac = 0, uid_swapped = 0; 647 pid_t pid; 648 char *tmp, *username = NULL, *command = NULL, **av = NULL; 649 void (*osigchld)(int); 650 651 if (options.authorized_principals_command == NULL) 652 return 0; 653 if (options.authorized_principals_command_user == NULL) { 654 error("No user for AuthorizedPrincipalsCommand specified, " 655 "skipping"); 656 return 0; 657 } 658 659 /* 660 * NB. all returns later this function should go via "out" to 661 * ensure the original SIGCHLD handler is restored properly. 662 */ 663 osigchld = signal(SIGCHLD, SIG_DFL); 664 665 /* Prepare and verify the user for the command */ 666 username = percent_expand(options.authorized_principals_command_user, 667 "u", user_pw->pw_name, (char *)NULL); 668 pw = getpwnam(username); 669 if (pw == NULL) { 670 error("AuthorizedPrincipalsCommandUser \"%s\" not found: %s", 671 username, strerror(errno)); 672 goto out; 673 } 674 675 /* Turn the command into an argument vector */ 676 if (split_argv(options.authorized_principals_command, &ac, &av) != 0) { 677 error("AuthorizedPrincipalsCommand \"%s\" contains " 678 "invalid quotes", command); 679 goto out; 680 } 681 if (ac == 0) { 682 error("AuthorizedPrincipalsCommand \"%s\" yielded no arguments", 683 command); 684 goto out; 685 } 686 for (i = 1; i < ac; i++) { 687 tmp = percent_expand(av[i], 688 "u", user_pw->pw_name, 689 "h", user_pw->pw_dir, 690 (char *)NULL); 691 if (tmp == NULL) 692 fatal("%s: percent_expand failed", __func__); 693 free(av[i]); 694 av[i] = tmp; 695 } 696 /* Prepare a printable command for logs, etc. */ 697 command = assemble_argv(ac, av); 698 699 if ((pid = subprocess("AuthorizedPrincipalsCommand", pw, command, 700 ac, av, &f)) == 0) 701 goto out; 702 703 uid_swapped = 1; 704 temporarily_use_uid(pw); 705 706 ok = process_principals(f, NULL, pw, cert); 707 708 if (exited_cleanly(pid, "AuthorizedPrincipalsCommand", command) != 0) 709 goto out; 710 711 /* Read completed successfully */ 712 found_principal = ok; 713 out: 714 if (f != NULL) 715 fclose(f); 716 signal(SIGCHLD, osigchld); 717 for (i = 0; i < ac; i++) 718 free(av[i]); 719 free(av); 720 if (uid_swapped) 721 restore_uid(); 722 free(command); 723 free(username); 724 return found_principal; 725 } 726 /* 727 * Checks whether key is allowed in authorized_keys-format file, 728 * returns 1 if the key is allowed or 0 otherwise. 729 */ 730 static int 731 check_authkeys_file(FILE *f, char *file, Key* key, struct passwd *pw) 732 { 733 char line[SSH_MAX_PUBKEY_BYTES]; 734 const char *reason; 735 int found_key = 0; 736 u_long linenum = 0; 737 Key *found; 738 char *fp; 739 #ifdef WITH_LDAP_PUBKEY 740 ldap_key_t * k; 741 unsigned int i = 0; 742 #endif 743 744 #ifdef WITH_LDAP_PUBKEY 745 found_key = 0; 746 /* allocate a new key type */ 747 found = key_new(key->type); 748 749 /* first check if the options is enabled, then try.. */ 750 if (options.lpk.on) { 751 debug("[LDAP] trying LDAP first uid=%s",pw->pw_name); 752 if (ldap_ismember(&options.lpk, pw->pw_name) > 0) { 753 if ((k = ldap_getuserkey(&options.lpk, pw->pw_name)) != NULL) { 754 /* Skip leading whitespace, empty and comment lines. */ 755 for (i = 0 ; i < k->num ; i++) { 756 /* dont forget if multiple keys to reset options */ 757 char *cp, *xoptions = NULL; 758 759 for (cp = (char *)k->keys[i]->bv_val; *cp == ' ' || *cp == '\t'; cp++) 760 ; 761 if (!*cp || *cp == '\n' || *cp == '#') 762 continue; 763 764 if (key_read(found, &cp) != 1) { 765 /* no key? check if there are options for this key */ 766 int quoted = 0; 767 debug2("[LDAP] user_key_allowed: check options: '%s'", cp); 768 xoptions = cp; 769 for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) { 770 if (*cp == '\\' && cp[1] == '"') 771 cp++; /* Skip both */ 772 else if (*cp == '"') 773 quoted = !quoted; 774 } 775 /* Skip remaining whitespace. */ 776 for (; *cp == ' ' || *cp == '\t'; cp++) 777 ; 778 if (key_read(found, &cp) != 1) { 779 debug2("[LDAP] user_key_allowed: advance: '%s'", cp); 780 /* still no key? advance to next line*/ 781 continue; 782 } 783 } 784 785 if (key_equal(found, key) && 786 auth_parse_options(pw, xoptions, file, linenum) == 1) { 787 found_key = 1; 788 debug("[LDAP] matching key found"); 789 fp = sshkey_fingerprint(found, SSH_FP_HASH_DEFAULT, SSH_FP_HEX); 790 verbose("[LDAP] Found matching %s key: %s", key_type(found), fp); 791 792 /* restoring memory */ 793 ldap_keys_free(k); 794 free(fp); 795 restore_uid(); 796 key_free(found); 797 return found_key; 798 break; 799 } 800 }/* end of LDAP for() */ 801 } else { 802 logit("[LDAP] no keys found for '%s'!", pw->pw_name); 803 } 804 } else { 805 logit("[LDAP] '%s' is not in '%s'", pw->pw_name, options.lpk.sgroup); 806 } 807 } 808 #endif 809 debug("trying public key file %s", file); 810 f = auth_openkeyfile(file, pw, options.strict_modes); 811 812 if (!f) { 813 restore_uid(); 814 return 0; 815 } 816 817 found_key = 0; 818 819 found = NULL; 820 while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) { 821 char *cp, *key_options = NULL; 822 if (found != NULL) 823 key_free(found); 824 found = key_new(key_is_cert(key) ? KEY_UNSPEC : key->type); 825 auth_clear_options(); 826 827 /* Skip leading whitespace, empty and comment lines. */ 828 for (cp = line; *cp == ' ' || *cp == '\t'; cp++) 829 ; 830 if (!*cp || *cp == '\n' || *cp == '#') 831 continue; 832 833 if (key_read(found, &cp) != 1) { 834 /* no key? check if there are options for this key */ 835 int quoted = 0; 836 debug2("user_key_allowed: check options: '%s'", cp); 837 key_options = cp; 838 for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) { 839 if (*cp == '\\' && cp[1] == '"') 840 cp++; /* Skip both */ 841 else if (*cp == '"') 842 quoted = !quoted; 843 } 844 /* Skip remaining whitespace. */ 845 for (; *cp == ' ' || *cp == '\t'; cp++) 846 ; 847 if (key_read(found, &cp) != 1) { 848 debug2("user_key_allowed: advance: '%s'", cp); 849 /* still no key? advance to next line*/ 850 continue; 851 } 852 } 853 if (key_is_cert(key)) { 854 if (!key_equal(found, key->cert->signature_key)) 855 continue; 856 if (auth_parse_options(pw, key_options, file, 857 linenum) != 1) 858 continue; 859 if (!key_is_cert_authority) 860 continue; 861 if ((fp = sshkey_fingerprint(found, 862 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) 863 continue; 864 debug("matching CA found: file %s, line %lu, %s %s", 865 file, linenum, key_type(found), fp); 866 /* 867 * If the user has specified a list of principals as 868 * a key option, then prefer that list to matching 869 * their username in the certificate principals list. 870 */ 871 if (authorized_principals != NULL && 872 !match_principals_option(authorized_principals, 873 key->cert)) { 874 reason = "Certificate does not contain an " 875 "authorized principal"; 876 fail_reason: 877 free(fp); 878 error("%s", reason); 879 auth_debug_add("%s", reason); 880 continue; 881 } 882 if (key_cert_check_authority(key, 0, 0, 883 authorized_principals == NULL ? pw->pw_name : NULL, 884 &reason) != 0) 885 goto fail_reason; 886 if (auth_cert_options(key, pw) != 0) { 887 free(fp); 888 continue; 889 } 890 verbose("Accepted certificate ID \"%s\" (serial %llu) " 891 "signed by %s CA %s via %s", key->cert->key_id, 892 (unsigned long long)key->cert->serial, 893 key_type(found), fp, file); 894 free(fp); 895 found_key = 1; 896 break; 897 } else if (key_equal(found, key)) { 898 if (auth_parse_options(pw, key_options, file, 899 linenum) != 1) 900 continue; 901 if (key_is_cert_authority) 902 continue; 903 if ((fp = sshkey_fingerprint(found, 904 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) 905 continue; 906 debug("matching key found: file %s, line %lu %s %s", 907 file, linenum, key_type(found), fp); 908 free(fp); 909 found_key = 1; 910 break; 911 } 912 } 913 if (found != NULL) 914 key_free(found); 915 if (!found_key) 916 debug2("key not found"); 917 return found_key; 918 } 919 920 /* Authenticate a certificate key against TrustedUserCAKeys */ 921 static int 922 user_cert_trusted_ca(struct passwd *pw, Key *key) 923 { 924 char *ca_fp, *principals_file = NULL; 925 const char *reason; 926 int ret = 0, found_principal = 0, use_authorized_principals; 927 928 if (!key_is_cert(key) || options.trusted_user_ca_keys == NULL) 929 return 0; 930 931 if ((ca_fp = sshkey_fingerprint(key->cert->signature_key, 932 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) 933 return 0; 934 935 if (sshkey_in_file(key->cert->signature_key, 936 options.trusted_user_ca_keys, 1, 0) != 0) { 937 debug2("%s: CA %s %s is not listed in %s", __func__, 938 key_type(key->cert->signature_key), ca_fp, 939 options.trusted_user_ca_keys); 940 goto out; 941 } 942 /* 943 * If AuthorizedPrincipals is in use, then compare the certificate 944 * principals against the names in that file rather than matching 945 * against the username. 946 */ 947 if ((principals_file = authorized_principals_file(pw)) != NULL) { 948 if (match_principals_file(principals_file, pw, key->cert)) 949 found_principal = 1; 950 } 951 /* Try querying command if specified */ 952 if (!found_principal && match_principals_command(pw, key->cert)) 953 found_principal = 1; 954 /* If principals file or command is specified, then require a match */ 955 use_authorized_principals = principals_file != NULL || 956 options.authorized_principals_command != NULL; 957 if (!found_principal && use_authorized_principals) { 958 reason = "Certificate does not contain an authorized principal"; 959 fail_reason: 960 error("%s", reason); 961 auth_debug_add("%s", reason); 962 goto out; 963 } 964 if (key_cert_check_authority(key, 0, 1, 965 use_authorized_principals ? NULL : pw->pw_name, &reason) != 0) 966 goto fail_reason; 967 if (auth_cert_options(key, pw) != 0) 968 goto out; 969 970 verbose("Accepted certificate ID \"%s\" (serial %llu) signed by " 971 "%s CA %s via %s", key->cert->key_id, 972 (unsigned long long)key->cert->serial, 973 key_type(key->cert->signature_key), ca_fp, 974 options.trusted_user_ca_keys); 975 ret = 1; 976 977 out: 978 free(principals_file); 979 free(ca_fp); 980 return ret; 981 } 982 983 /* 984 * Checks whether key is allowed in file. 985 * returns 1 if the key is allowed or 0 otherwise. 986 */ 987 static int 988 user_key_allowed2(struct passwd *pw, Key *key, char *file) 989 { 990 FILE *f; 991 int found_key = 0; 992 993 /* Temporarily use the user's uid. */ 994 temporarily_use_uid(pw); 995 996 debug("trying public key file %s", file); 997 if ((f = auth_openkeyfile(file, pw, options.strict_modes)) != NULL) { 998 found_key = check_authkeys_file(f, file, key, pw); 999 fclose(f); 1000 } 1001 1002 restore_uid(); 1003 return found_key; 1004 } 1005 1006 /* 1007 * Checks whether key is allowed in output of command. 1008 * returns 1 if the key is allowed or 0 otherwise. 1009 */ 1010 static int 1011 user_key_command_allowed2(struct passwd *user_pw, Key *key) 1012 { 1013 FILE *f = NULL; 1014 int r, ok, found_key = 0; 1015 struct passwd *pw; 1016 int i, uid_swapped = 0, ac = 0; 1017 pid_t pid; 1018 char *username = NULL, *key_fp = NULL, *keytext = NULL; 1019 char *tmp, *command = NULL, **av = NULL; 1020 void (*osigchld)(int); 1021 1022 if (options.authorized_keys_command == NULL) 1023 return 0; 1024 if (options.authorized_keys_command_user == NULL) { 1025 error("No user for AuthorizedKeysCommand specified, skipping"); 1026 return 0; 1027 } 1028 1029 /* 1030 * NB. all returns later this function should go via "out" to 1031 * ensure the original SIGCHLD handler is restored properly. 1032 */ 1033 osigchld = signal(SIGCHLD, SIG_DFL); 1034 1035 /* Prepare and verify the user for the command */ 1036 username = percent_expand(options.authorized_keys_command_user, 1037 "u", user_pw->pw_name, (char *)NULL); 1038 pw = getpwnam(username); 1039 if (pw == NULL) { 1040 error("AuthorizedKeysCommandUser \"%s\" not found: %s", 1041 username, strerror(errno)); 1042 goto out; 1043 } 1044 1045 /* Prepare AuthorizedKeysCommand */ 1046 if ((key_fp = sshkey_fingerprint(key, options.fingerprint_hash, 1047 SSH_FP_DEFAULT)) == NULL) { 1048 error("%s: sshkey_fingerprint failed", __func__); 1049 goto out; 1050 } 1051 if ((r = sshkey_to_base64(key, &keytext)) != 0) { 1052 error("%s: sshkey_to_base64 failed: %s", __func__, ssh_err(r)); 1053 goto out; 1054 } 1055 1056 /* Turn the command into an argument vector */ 1057 if (split_argv(options.authorized_keys_command, &ac, &av) != 0) { 1058 error("AuthorizedKeysCommand \"%s\" contains invalid quotes", 1059 command); 1060 goto out; 1061 } 1062 if (ac == 0) { 1063 error("AuthorizedKeysCommand \"%s\" yielded no arguments", 1064 command); 1065 goto out; 1066 } 1067 for (i = 1; i < ac; i++) { 1068 tmp = percent_expand(av[i], 1069 "u", user_pw->pw_name, 1070 "h", user_pw->pw_dir, 1071 "t", sshkey_ssh_name(key), 1072 "f", key_fp, 1073 "k", keytext, 1074 (char *)NULL); 1075 if (tmp == NULL) 1076 fatal("%s: percent_expand failed", __func__); 1077 free(av[i]); 1078 av[i] = tmp; 1079 } 1080 /* Prepare a printable command for logs, etc. */ 1081 command = assemble_argv(ac, av); 1082 1083 /* 1084 * If AuthorizedKeysCommand was run without arguments 1085 * then fall back to the old behaviour of passing the 1086 * target username as a single argument. 1087 */ 1088 if (ac == 1) { 1089 av = xreallocarray(av, ac + 2, sizeof(*av)); 1090 av[1] = xstrdup(user_pw->pw_name); 1091 av[2] = NULL; 1092 /* Fix up command too, since it is used in log messages */ 1093 free(command); 1094 xasprintf(&command, "%s %s", av[0], av[1]); 1095 } 1096 1097 if ((pid = subprocess("AuthorizedKeysCommand", pw, command, 1098 ac, av, &f)) == 0) 1099 goto out; 1100 1101 uid_swapped = 1; 1102 temporarily_use_uid(pw); 1103 1104 ok = check_authkeys_file(f, options.authorized_keys_command, key, pw); 1105 1106 if (exited_cleanly(pid, "AuthorizedKeysCommand", command) != 0) 1107 goto out; 1108 1109 /* Read completed successfully */ 1110 found_key = ok; 1111 out: 1112 if (f != NULL) 1113 fclose(f); 1114 signal(SIGCHLD, osigchld); 1115 for (i = 0; i < ac; i++) 1116 free(av[i]); 1117 free(av); 1118 if (uid_swapped) 1119 restore_uid(); 1120 free(command); 1121 free(username); 1122 free(key_fp); 1123 free(keytext); 1124 return found_key; 1125 } 1126 1127 /* 1128 * Check whether key authenticates and authorises the user. 1129 */ 1130 int 1131 user_key_allowed(struct passwd *pw, Key *key, int auth_attempt) 1132 { 1133 u_int success, i; 1134 char *file; 1135 1136 if (auth_key_is_revoked(key)) 1137 return 0; 1138 if (key_is_cert(key) && auth_key_is_revoked(key->cert->signature_key)) 1139 return 0; 1140 1141 success = user_cert_trusted_ca(pw, key); 1142 if (success) 1143 return success; 1144 1145 success = user_key_command_allowed2(pw, key); 1146 if (success > 0) 1147 return success; 1148 1149 for (i = 0; !success && i < options.num_authkeys_files; i++) { 1150 1151 if (strcasecmp(options.authorized_keys_files[i], "none") == 0) 1152 continue; 1153 file = expand_authorized_keys( 1154 options.authorized_keys_files[i], pw); 1155 1156 success = user_key_allowed2(pw, key, file); 1157 free(file); 1158 } 1159 1160 return success; 1161 } 1162 1163 /* Records a public key in the list of previously-successful keys */ 1164 void 1165 auth2_record_userkey(Authctxt *authctxt, struct sshkey *key) 1166 { 1167 struct sshkey **tmp; 1168 1169 if (authctxt->nprev_userkeys >= INT_MAX || 1170 (tmp = reallocarray(authctxt->prev_userkeys, 1171 authctxt->nprev_userkeys + 1, sizeof(*tmp))) == NULL) 1172 fatal("%s: reallocarray failed", __func__); 1173 authctxt->prev_userkeys = tmp; 1174 authctxt->prev_userkeys[authctxt->nprev_userkeys] = key; 1175 authctxt->nprev_userkeys++; 1176 } 1177 1178 /* Checks whether a key has already been used successfully for authentication */ 1179 int 1180 auth2_userkey_already_used(Authctxt *authctxt, struct sshkey *key) 1181 { 1182 u_int i; 1183 1184 for (i = 0; i < authctxt->nprev_userkeys; i++) { 1185 if (sshkey_equal_public(key, authctxt->prev_userkeys[i])) { 1186 return 1; 1187 } 1188 } 1189 return 0; 1190 } 1191 1192 Authmethod method_pubkey = { 1193 "publickey", 1194 userauth_pubkey, 1195 &options.pubkey_authentication 1196 }; 1197