1 /* $OpenBSD: auth2-pubkey.c,v 1.55 2016/01/27 00:53:12 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 27 #include <sys/types.h> 28 #include <sys/stat.h> 29 #include <sys/wait.h> 30 31 #include <errno.h> 32 #include <fcntl.h> 33 #include <paths.h> 34 #include <pwd.h> 35 #include <signal.h> 36 #include <stdio.h> 37 #include <stdarg.h> 38 #include <string.h> 39 #include <time.h> 40 #include <unistd.h> 41 #include <limits.h> 42 43 #include "xmalloc.h" 44 #include "ssh.h" 45 #include "ssh2.h" 46 #include "packet.h" 47 #include "buffer.h" 48 #include "log.h" 49 #include "misc.h" 50 #include "servconf.h" 51 #include "compat.h" 52 #include "key.h" 53 #include "hostfile.h" 54 #include "auth.h" 55 #include "pathnames.h" 56 #include "uidswap.h" 57 #include "auth-options.h" 58 #include "canohost.h" 59 #ifdef GSSAPI 60 #include "ssh-gss.h" 61 #endif 62 #include "monitor_wrap.h" 63 #include "authfile.h" 64 #include "match.h" 65 #include "ssherr.h" 66 #include "channels.h" /* XXX for session.h */ 67 #include "session.h" /* XXX for child_set_env(); refactor? */ 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, *fp = NULL; 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("%s: disabled because of invalid user", __func__); 87 return 0; 88 } 89 have_sig = packet_get_char(); 90 if (datafellows & SSH_BUG_PKAUTH) { 91 debug2("%s: SSH_BUG_PKAUTH", __func__); 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("%s: unsupported public key algorithm: %s", 107 __func__, pkalg); 108 goto done; 109 } 110 key = key_from_blob(pkblob, blen); 111 if (key == NULL) { 112 error("%s: cannot decode key: %s", __func__, pkalg); 113 goto done; 114 } 115 if (key->type != pktype) { 116 error("%s: type mismatch for decoded key " 117 "(received %d, expected %d)", __func__, 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 fp = sshkey_fingerprint(key, options.fingerprint_hash, SSH_FP_DEFAULT); 127 if (auth2_userkey_already_used(authctxt, key)) { 128 logit("refusing previously-used %s key", key_type(key)); 129 goto done; 130 } 131 if (match_pattern_list(sshkey_ssh_name(key), 132 options.pubkey_key_types, 0) != 1) { 133 logit("%s: key type %s not in PubkeyAcceptedKeyTypes", 134 __func__, sshkey_ssh_name(key)); 135 goto done; 136 } 137 138 if (have_sig) { 139 debug3("%s: have signature for %s %s", 140 __func__, sshkey_type(key), fp); 141 sig = packet_get_string(&slen); 142 packet_check_eom(); 143 buffer_init(&b); 144 if (datafellows & SSH_OLD_SESSIONID) { 145 buffer_append(&b, session_id2, session_id2_len); 146 } else { 147 buffer_put_string(&b, session_id2, session_id2_len); 148 } 149 /* reconstruct packet */ 150 buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST); 151 xasprintf(&userstyle, "%s%s%s", authctxt->user, 152 authctxt->style ? ":" : "", 153 authctxt->style ? authctxt->style : ""); 154 buffer_put_cstring(&b, userstyle); 155 free(userstyle); 156 buffer_put_cstring(&b, 157 datafellows & SSH_BUG_PKSERVICE ? 158 "ssh-userauth" : 159 authctxt->service); 160 if (datafellows & SSH_BUG_PKAUTH) { 161 buffer_put_char(&b, have_sig); 162 } else { 163 buffer_put_cstring(&b, "publickey"); 164 buffer_put_char(&b, have_sig); 165 buffer_put_cstring(&b, pkalg); 166 } 167 buffer_put_string(&b, pkblob, blen); 168 #ifdef DEBUG_PK 169 buffer_dump(&b); 170 #endif 171 pubkey_auth_info(authctxt, key, NULL); 172 173 /* test for correct signature */ 174 authenticated = 0; 175 if (PRIVSEP(user_key_allowed(authctxt->pw, key, 1)) && 176 PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b), 177 buffer_len(&b))) == 1) { 178 authenticated = 1; 179 /* Record the successful key to prevent reuse */ 180 auth2_record_userkey(authctxt, key); 181 key = NULL; /* Don't free below */ 182 } 183 buffer_free(&b); 184 free(sig); 185 } else { 186 debug("%s: test whether pkalg/pkblob are acceptable for %s %s", 187 __func__, sshkey_type(key), fp); 188 packet_check_eom(); 189 190 /* XXX fake reply and always send PK_OK ? */ 191 /* 192 * XXX this allows testing whether a user is allowed 193 * to login: if you happen to have a valid pubkey this 194 * message is sent. the message is NEVER sent at all 195 * if a user is not allowed to login. is this an 196 * issue? -markus 197 */ 198 if (PRIVSEP(user_key_allowed(authctxt->pw, key, 0))) { 199 packet_start(SSH2_MSG_USERAUTH_PK_OK); 200 packet_put_string(pkalg, alen); 201 packet_put_string(pkblob, blen); 202 packet_send(); 203 packet_write_wait(); 204 authctxt->postponed = 1; 205 } 206 } 207 if (authenticated != 1) 208 auth_clear_options(); 209 done: 210 debug2("%s: authenticated %d pkalg %s", __func__, authenticated, pkalg); 211 if (key != NULL) 212 key_free(key); 213 free(pkalg); 214 free(pkblob); 215 free(fp); 216 return authenticated; 217 } 218 219 void 220 pubkey_auth_info(Authctxt *authctxt, const Key *key, const char *fmt, ...) 221 { 222 char *fp, *extra; 223 va_list ap; 224 int i; 225 226 extra = NULL; 227 if (fmt != NULL) { 228 va_start(ap, fmt); 229 i = vasprintf(&extra, fmt, ap); 230 va_end(ap); 231 if (i < 0 || extra == NULL) 232 fatal("%s: vasprintf failed", __func__); 233 } 234 235 if (key_is_cert(key)) { 236 fp = sshkey_fingerprint(key->cert->signature_key, 237 options.fingerprint_hash, SSH_FP_DEFAULT); 238 auth_info(authctxt, "%s ID %s (serial %llu) CA %s %s%s%s", 239 key_type(key), key->cert->key_id, 240 (unsigned long long)key->cert->serial, 241 key_type(key->cert->signature_key), 242 fp == NULL ? "(null)" : fp, 243 extra == NULL ? "" : ", ", extra == NULL ? "" : extra); 244 free(fp); 245 } else { 246 fp = sshkey_fingerprint(key, options.fingerprint_hash, 247 SSH_FP_DEFAULT); 248 auth_info(authctxt, "%s %s%s%s", key_type(key), 249 fp == NULL ? "(null)" : fp, 250 extra == NULL ? "" : ", ", extra == NULL ? "" : extra); 251 free(fp); 252 } 253 free(extra); 254 } 255 256 /* 257 * Splits 's' into an argument vector. Handles quoted string and basic 258 * escape characters (\\, \", \'). Caller must free the argument vector 259 * and its members. 260 */ 261 static int 262 split_argv(const char *s, int *argcp, char ***argvp) 263 { 264 int r = SSH_ERR_INTERNAL_ERROR; 265 int argc = 0, quote, i, j; 266 char *arg, **argv = xcalloc(1, sizeof(*argv)); 267 268 *argvp = NULL; 269 *argcp = 0; 270 271 for (i = 0; s[i] != '\0'; i++) { 272 /* Skip leading whitespace */ 273 if (s[i] == ' ' || s[i] == '\t') 274 continue; 275 276 /* Start of a token */ 277 quote = 0; 278 if (s[i] == '\\' && 279 (s[i + 1] == '\'' || s[i + 1] == '\"' || s[i + 1] == '\\')) 280 i++; 281 else if (s[i] == '\'' || s[i] == '"') 282 quote = s[i++]; 283 284 argv = xreallocarray(argv, (argc + 2), sizeof(*argv)); 285 arg = argv[argc++] = xcalloc(1, strlen(s + i) + 1); 286 argv[argc] = NULL; 287 288 /* Copy the token in, removing escapes */ 289 for (j = 0; s[i] != '\0'; i++) { 290 if (s[i] == '\\') { 291 if (s[i + 1] == '\'' || 292 s[i + 1] == '\"' || 293 s[i + 1] == '\\') { 294 i++; /* Skip '\' */ 295 arg[j++] = s[i]; 296 } else { 297 /* Unrecognised escape */ 298 arg[j++] = s[i]; 299 } 300 } else if (quote == 0 && (s[i] == ' ' || s[i] == '\t')) 301 break; /* done */ 302 else if (quote != 0 && s[i] == quote) 303 break; /* done */ 304 else 305 arg[j++] = s[i]; 306 } 307 if (s[i] == '\0') { 308 if (quote != 0) { 309 /* Ran out of string looking for close quote */ 310 r = SSH_ERR_INVALID_FORMAT; 311 goto out; 312 } 313 break; 314 } 315 } 316 /* Success */ 317 *argcp = argc; 318 *argvp = argv; 319 argc = 0; 320 argv = NULL; 321 r = 0; 322 out: 323 if (argc != 0 && argv != NULL) { 324 for (i = 0; i < argc; i++) 325 free(argv[i]); 326 free(argv); 327 } 328 return r; 329 } 330 331 /* 332 * Reassemble an argument vector into a string, quoting and escaping as 333 * necessary. Caller must free returned string. 334 */ 335 static char * 336 assemble_argv(int argc, char **argv) 337 { 338 int i, j, ws, r; 339 char c, *ret; 340 struct sshbuf *buf, *arg; 341 342 if ((buf = sshbuf_new()) == NULL || (arg = sshbuf_new()) == NULL) 343 fatal("%s: sshbuf_new failed", __func__); 344 345 for (i = 0; i < argc; i++) { 346 ws = 0; 347 sshbuf_reset(arg); 348 for (j = 0; argv[i][j] != '\0'; j++) { 349 r = 0; 350 c = argv[i][j]; 351 switch (c) { 352 case ' ': 353 case '\t': 354 ws = 1; 355 r = sshbuf_put_u8(arg, c); 356 break; 357 case '\\': 358 case '\'': 359 case '"': 360 if ((r = sshbuf_put_u8(arg, '\\')) != 0) 361 break; 362 /* FALLTHROUGH */ 363 default: 364 r = sshbuf_put_u8(arg, c); 365 break; 366 } 367 if (r != 0) 368 fatal("%s: sshbuf_put_u8: %s", 369 __func__, ssh_err(r)); 370 } 371 if ((i != 0 && (r = sshbuf_put_u8(buf, ' ')) != 0) || 372 (ws != 0 && (r = sshbuf_put_u8(buf, '"')) != 0) || 373 (r = sshbuf_putb(buf, arg)) != 0 || 374 (ws != 0 && (r = sshbuf_put_u8(buf, '"')) != 0)) 375 fatal("%s: buffer error: %s", __func__, ssh_err(r)); 376 } 377 if ((ret = malloc(sshbuf_len(buf) + 1)) == NULL) 378 fatal("%s: malloc failed", __func__); 379 memcpy(ret, sshbuf_ptr(buf), sshbuf_len(buf)); 380 ret[sshbuf_len(buf)] = '\0'; 381 sshbuf_free(buf); 382 sshbuf_free(arg); 383 return ret; 384 } 385 386 /* 387 * Runs command in a subprocess. Returns pid on success and a FILE* to the 388 * subprocess' stdout or 0 on failure. 389 * NB. "command" is only used for logging. 390 */ 391 static pid_t 392 subprocess(const char *tag, struct passwd *pw, const char *command, 393 int ac, char **av, FILE **child) 394 { 395 FILE *f; 396 struct stat st; 397 int devnull, p[2], i; 398 pid_t pid; 399 char *cp, errmsg[512]; 400 u_int envsize; 401 char **child_env; 402 403 *child = NULL; 404 405 debug3("%s: %s command \"%s\" running as %s", __func__, 406 tag, command, pw->pw_name); 407 408 /* Verify the path exists and is safe-ish to execute */ 409 if (*av[0] != '/') { 410 error("%s path is not absolute", tag); 411 return 0; 412 } 413 temporarily_use_uid(pw); 414 if (stat(av[0], &st) < 0) { 415 error("Could not stat %s \"%s\": %s", tag, 416 av[0], strerror(errno)); 417 restore_uid(); 418 return 0; 419 } 420 if (auth_secure_path(av[0], &st, NULL, 0, 421 errmsg, sizeof(errmsg)) != 0) { 422 error("Unsafe %s \"%s\": %s", tag, av[0], errmsg); 423 restore_uid(); 424 return 0; 425 } 426 427 /* 428 * Run the command; stderr is left in place, stdout is the 429 * authorized_keys output. 430 */ 431 if (pipe(p) != 0) { 432 error("%s: pipe: %s", tag, strerror(errno)); 433 restore_uid(); 434 return 0; 435 } 436 437 /* 438 * Don't want to call this in the child, where it can fatal() and 439 * run cleanup_exit() code. 440 */ 441 restore_uid(); 442 443 switch ((pid = fork())) { 444 case -1: /* error */ 445 error("%s: fork: %s", tag, strerror(errno)); 446 close(p[0]); 447 close(p[1]); 448 return 0; 449 case 0: /* child */ 450 /* Prepare a minimal environment for the child. */ 451 envsize = 5; 452 child_env = xcalloc(sizeof(*child_env), envsize); 453 child_set_env(&child_env, &envsize, "PATH", _PATH_STDPATH); 454 child_set_env(&child_env, &envsize, "USER", pw->pw_name); 455 child_set_env(&child_env, &envsize, "LOGNAME", pw->pw_name); 456 child_set_env(&child_env, &envsize, "HOME", pw->pw_dir); 457 if ((cp = getenv("LANG")) != NULL) 458 child_set_env(&child_env, &envsize, "LANG", cp); 459 460 for (i = 0; i < NSIG; i++) 461 signal(i, SIG_DFL); 462 463 if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1) { 464 error("%s: open %s: %s", tag, _PATH_DEVNULL, 465 strerror(errno)); 466 _exit(1); 467 } 468 /* Keep stderr around a while longer to catch errors */ 469 if (dup2(devnull, STDIN_FILENO) == -1 || 470 dup2(p[1], STDOUT_FILENO) == -1) { 471 error("%s: dup2: %s", tag, strerror(errno)); 472 _exit(1); 473 } 474 closefrom(STDERR_FILENO + 1); 475 476 /* Don't use permanently_set_uid() here to avoid fatal() */ 477 if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) != 0) { 478 error("%s: setresgid %u: %s", tag, (u_int)pw->pw_gid, 479 strerror(errno)); 480 _exit(1); 481 } 482 if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) != 0) { 483 error("%s: setresuid %u: %s", tag, (u_int)pw->pw_uid, 484 strerror(errno)); 485 _exit(1); 486 } 487 /* stdin is pointed to /dev/null at this point */ 488 if (dup2(STDIN_FILENO, STDERR_FILENO) == -1) { 489 error("%s: dup2: %s", tag, strerror(errno)); 490 _exit(1); 491 } 492 493 execve(av[0], av, child_env); 494 error("%s exec \"%s\": %s", tag, command, strerror(errno)); 495 _exit(127); 496 default: /* parent */ 497 break; 498 } 499 500 close(p[1]); 501 if ((f = fdopen(p[0], "r")) == NULL) { 502 error("%s: fdopen: %s", tag, strerror(errno)); 503 close(p[0]); 504 /* Don't leave zombie child */ 505 kill(pid, SIGTERM); 506 while (waitpid(pid, NULL, 0) == -1 && errno == EINTR) 507 ; 508 return 0; 509 } 510 /* Success */ 511 debug3("%s: %s pid %ld", __func__, tag, (long)pid); 512 *child = f; 513 return pid; 514 } 515 516 /* Returns 0 if pid exited cleanly, non-zero otherwise */ 517 static int 518 exited_cleanly(pid_t pid, const char *tag, const char *cmd) 519 { 520 int status; 521 522 while (waitpid(pid, &status, 0) == -1) { 523 if (errno != EINTR) { 524 error("%s: waitpid: %s", tag, strerror(errno)); 525 return -1; 526 } 527 } 528 if (WIFSIGNALED(status)) { 529 error("%s %s exited on signal %d", tag, cmd, WTERMSIG(status)); 530 return -1; 531 } else if (WEXITSTATUS(status) != 0) { 532 error("%s %s failed, status %d", tag, cmd, WEXITSTATUS(status)); 533 return -1; 534 } 535 return 0; 536 } 537 538 static int 539 match_principals_option(const char *principal_list, struct sshkey_cert *cert) 540 { 541 char *result; 542 u_int i; 543 544 /* XXX percent_expand() sequences for authorized_principals? */ 545 546 for (i = 0; i < cert->nprincipals; i++) { 547 if ((result = match_list(cert->principals[i], 548 principal_list, NULL)) != NULL) { 549 debug3("matched principal from key options \"%.100s\"", 550 result); 551 free(result); 552 return 1; 553 } 554 } 555 return 0; 556 } 557 558 static int 559 process_principals(FILE *f, char *file, struct passwd *pw, 560 struct sshkey_cert *cert) 561 { 562 char line[SSH_MAX_PUBKEY_BYTES], *cp, *ep, *line_opts; 563 u_long linenum = 0; 564 u_int i; 565 566 while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) { 567 /* Skip leading whitespace. */ 568 for (cp = line; *cp == ' ' || *cp == '\t'; cp++) 569 ; 570 /* Skip blank and comment lines. */ 571 if ((ep = strchr(cp, '#')) != NULL) 572 *ep = '\0'; 573 if (!*cp || *cp == '\n') 574 continue; 575 /* Trim trailing whitespace. */ 576 ep = cp + strlen(cp) - 1; 577 while (ep > cp && (*ep == '\n' || *ep == ' ' || *ep == '\t')) 578 *ep-- = '\0'; 579 /* 580 * If the line has internal whitespace then assume it has 581 * key options. 582 */ 583 line_opts = NULL; 584 if ((ep = strrchr(cp, ' ')) != NULL || 585 (ep = strrchr(cp, '\t')) != NULL) { 586 for (; *ep == ' ' || *ep == '\t'; ep++) 587 ; 588 line_opts = cp; 589 cp = ep; 590 } 591 for (i = 0; i < cert->nprincipals; i++) { 592 if (strcmp(cp, cert->principals[i]) == 0) { 593 debug3("%s:%lu: matched principal \"%.100s\"", 594 file == NULL ? "(command)" : file, 595 linenum, cert->principals[i]); 596 if (auth_parse_options(pw, line_opts, 597 file, linenum) != 1) 598 continue; 599 return 1; 600 } 601 } 602 } 603 return 0; 604 } 605 606 static int 607 match_principals_file(char *file, struct passwd *pw, struct sshkey_cert *cert) 608 { 609 FILE *f; 610 int success; 611 612 temporarily_use_uid(pw); 613 debug("trying authorized principals file %s", file); 614 if ((f = auth_openprincipals(file, pw, options.strict_modes)) == NULL) { 615 restore_uid(); 616 return 0; 617 } 618 success = process_principals(f, file, pw, cert); 619 fclose(f); 620 restore_uid(); 621 return success; 622 } 623 624 /* 625 * Checks whether principal is allowed in output of command. 626 * returns 1 if the principal is allowed or 0 otherwise. 627 */ 628 static int 629 match_principals_command(struct passwd *user_pw, struct sshkey_cert *cert) 630 { 631 FILE *f = NULL; 632 int ok, found_principal = 0; 633 struct passwd *pw; 634 int i, ac = 0, uid_swapped = 0; 635 pid_t pid; 636 char *tmp, *username = NULL, *command = NULL, **av = NULL; 637 void (*osigchld)(int); 638 639 if (options.authorized_principals_command == NULL) 640 return 0; 641 if (options.authorized_principals_command_user == NULL) { 642 error("No user for AuthorizedPrincipalsCommand specified, " 643 "skipping"); 644 return 0; 645 } 646 647 /* 648 * NB. all returns later this function should go via "out" to 649 * ensure the original SIGCHLD handler is restored properly. 650 */ 651 osigchld = signal(SIGCHLD, SIG_DFL); 652 653 /* Prepare and verify the user for the command */ 654 username = percent_expand(options.authorized_principals_command_user, 655 "u", user_pw->pw_name, (char *)NULL); 656 pw = getpwnam(username); 657 if (pw == NULL) { 658 error("AuthorizedPrincipalsCommandUser \"%s\" not found: %s", 659 username, strerror(errno)); 660 goto out; 661 } 662 663 /* Turn the command into an argument vector */ 664 if (split_argv(options.authorized_principals_command, &ac, &av) != 0) { 665 error("AuthorizedPrincipalsCommand \"%s\" contains " 666 "invalid quotes", command); 667 goto out; 668 } 669 if (ac == 0) { 670 error("AuthorizedPrincipalsCommand \"%s\" yielded no arguments", 671 command); 672 goto out; 673 } 674 for (i = 1; i < ac; i++) { 675 tmp = percent_expand(av[i], 676 "u", user_pw->pw_name, 677 "h", user_pw->pw_dir, 678 (char *)NULL); 679 if (tmp == NULL) 680 fatal("%s: percent_expand failed", __func__); 681 free(av[i]); 682 av[i] = tmp; 683 } 684 /* Prepare a printable command for logs, etc. */ 685 command = assemble_argv(ac, av); 686 687 if ((pid = subprocess("AuthorizedPrincipalsCommand", pw, command, 688 ac, av, &f)) == 0) 689 goto out; 690 691 uid_swapped = 1; 692 temporarily_use_uid(pw); 693 694 ok = process_principals(f, NULL, pw, cert); 695 696 if (exited_cleanly(pid, "AuthorizedPrincipalsCommand", command) != 0) 697 goto out; 698 699 /* Read completed successfully */ 700 found_principal = ok; 701 out: 702 if (f != NULL) 703 fclose(f); 704 signal(SIGCHLD, osigchld); 705 for (i = 0; i < ac; i++) 706 free(av[i]); 707 free(av); 708 if (uid_swapped) 709 restore_uid(); 710 free(command); 711 free(username); 712 return found_principal; 713 } 714 /* 715 * Checks whether key is allowed in authorized_keys-format file, 716 * returns 1 if the key is allowed or 0 otherwise. 717 */ 718 static int 719 check_authkeys_file(FILE *f, char *file, Key* key, struct passwd *pw) 720 { 721 char line[SSH_MAX_PUBKEY_BYTES]; 722 const char *reason; 723 int found_key = 0; 724 u_long linenum = 0; 725 Key *found; 726 char *fp; 727 728 found_key = 0; 729 730 found = NULL; 731 while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) { 732 char *cp, *key_options = NULL; 733 if (found != NULL) 734 key_free(found); 735 found = key_new(key_is_cert(key) ? KEY_UNSPEC : key->type); 736 auth_clear_options(); 737 738 /* Skip leading whitespace, empty and comment lines. */ 739 for (cp = line; *cp == ' ' || *cp == '\t'; cp++) 740 ; 741 if (!*cp || *cp == '\n' || *cp == '#') 742 continue; 743 744 if (key_read(found, &cp) != 1) { 745 /* no key? check if there are options for this key */ 746 int quoted = 0; 747 debug2("user_key_allowed: check options: '%s'", cp); 748 key_options = cp; 749 for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) { 750 if (*cp == '\\' && cp[1] == '"') 751 cp++; /* Skip both */ 752 else if (*cp == '"') 753 quoted = !quoted; 754 } 755 /* Skip remaining whitespace. */ 756 for (; *cp == ' ' || *cp == '\t'; cp++) 757 ; 758 if (key_read(found, &cp) != 1) { 759 debug2("user_key_allowed: advance: '%s'", cp); 760 /* still no key? advance to next line*/ 761 continue; 762 } 763 } 764 if (key_is_cert(key)) { 765 if (!key_equal(found, key->cert->signature_key)) 766 continue; 767 if (auth_parse_options(pw, key_options, file, 768 linenum) != 1) 769 continue; 770 if (!key_is_cert_authority) 771 continue; 772 if ((fp = sshkey_fingerprint(found, 773 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) 774 continue; 775 debug("matching CA found: file %s, line %lu, %s %s", 776 file, linenum, key_type(found), fp); 777 /* 778 * If the user has specified a list of principals as 779 * a key option, then prefer that list to matching 780 * their username in the certificate principals list. 781 */ 782 if (authorized_principals != NULL && 783 !match_principals_option(authorized_principals, 784 key->cert)) { 785 reason = "Certificate does not contain an " 786 "authorized principal"; 787 fail_reason: 788 free(fp); 789 error("%s", reason); 790 auth_debug_add("%s", reason); 791 continue; 792 } 793 if (key_cert_check_authority(key, 0, 0, 794 authorized_principals == NULL ? pw->pw_name : NULL, 795 &reason) != 0) 796 goto fail_reason; 797 if (auth_cert_options(key, pw) != 0) { 798 free(fp); 799 continue; 800 } 801 verbose("Accepted certificate ID \"%s\" (serial %llu) " 802 "signed by %s CA %s via %s", key->cert->key_id, 803 (unsigned long long)key->cert->serial, 804 key_type(found), fp, file); 805 free(fp); 806 found_key = 1; 807 break; 808 } else if (key_equal(found, key)) { 809 if (auth_parse_options(pw, key_options, file, 810 linenum) != 1) 811 continue; 812 if (key_is_cert_authority) 813 continue; 814 if ((fp = sshkey_fingerprint(found, 815 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) 816 continue; 817 debug("matching key found: file %s, line %lu %s %s", 818 file, linenum, key_type(found), fp); 819 free(fp); 820 found_key = 1; 821 break; 822 } 823 } 824 if (found != NULL) 825 key_free(found); 826 if (!found_key) 827 debug2("key not found"); 828 return found_key; 829 } 830 831 /* Authenticate a certificate key against TrustedUserCAKeys */ 832 static int 833 user_cert_trusted_ca(struct passwd *pw, Key *key) 834 { 835 char *ca_fp, *principals_file = NULL; 836 const char *reason; 837 int ret = 0, found_principal = 0, use_authorized_principals; 838 839 if (!key_is_cert(key) || options.trusted_user_ca_keys == NULL) 840 return 0; 841 842 if ((ca_fp = sshkey_fingerprint(key->cert->signature_key, 843 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) 844 return 0; 845 846 if (sshkey_in_file(key->cert->signature_key, 847 options.trusted_user_ca_keys, 1, 0) != 0) { 848 debug2("%s: CA %s %s is not listed in %s", __func__, 849 key_type(key->cert->signature_key), ca_fp, 850 options.trusted_user_ca_keys); 851 goto out; 852 } 853 /* 854 * If AuthorizedPrincipals is in use, then compare the certificate 855 * principals against the names in that file rather than matching 856 * against the username. 857 */ 858 if ((principals_file = authorized_principals_file(pw)) != NULL) { 859 if (match_principals_file(principals_file, pw, key->cert)) 860 found_principal = 1; 861 } 862 /* Try querying command if specified */ 863 if (!found_principal && match_principals_command(pw, key->cert)) 864 found_principal = 1; 865 /* If principals file or command is specified, then require a match */ 866 use_authorized_principals = principals_file != NULL || 867 options.authorized_principals_command != NULL; 868 if (!found_principal && use_authorized_principals) { 869 reason = "Certificate does not contain an authorized principal"; 870 fail_reason: 871 error("%s", reason); 872 auth_debug_add("%s", reason); 873 goto out; 874 } 875 if (key_cert_check_authority(key, 0, 1, 876 use_authorized_principals ? NULL : pw->pw_name, &reason) != 0) 877 goto fail_reason; 878 if (auth_cert_options(key, pw) != 0) 879 goto out; 880 881 verbose("Accepted certificate ID \"%s\" (serial %llu) signed by " 882 "%s CA %s via %s", key->cert->key_id, 883 (unsigned long long)key->cert->serial, 884 key_type(key->cert->signature_key), ca_fp, 885 options.trusted_user_ca_keys); 886 ret = 1; 887 888 out: 889 free(principals_file); 890 free(ca_fp); 891 return ret; 892 } 893 894 /* 895 * Checks whether key is allowed in file. 896 * returns 1 if the key is allowed or 0 otherwise. 897 */ 898 static int 899 user_key_allowed2(struct passwd *pw, Key *key, char *file) 900 { 901 FILE *f; 902 int found_key = 0; 903 904 /* Temporarily use the user's uid. */ 905 temporarily_use_uid(pw); 906 907 debug("trying public key file %s", file); 908 if ((f = auth_openkeyfile(file, pw, options.strict_modes)) != NULL) { 909 found_key = check_authkeys_file(f, file, key, pw); 910 fclose(f); 911 } 912 913 restore_uid(); 914 return found_key; 915 } 916 917 /* 918 * Checks whether key is allowed in output of command. 919 * returns 1 if the key is allowed or 0 otherwise. 920 */ 921 static int 922 user_key_command_allowed2(struct passwd *user_pw, Key *key) 923 { 924 FILE *f = NULL; 925 int r, ok, found_key = 0; 926 struct passwd *pw; 927 int i, uid_swapped = 0, ac = 0; 928 pid_t pid; 929 char *username = NULL, *key_fp = NULL, *keytext = NULL; 930 char *tmp, *command = NULL, **av = NULL; 931 void (*osigchld)(int); 932 933 if (options.authorized_keys_command == NULL) 934 return 0; 935 if (options.authorized_keys_command_user == NULL) { 936 error("No user for AuthorizedKeysCommand specified, skipping"); 937 return 0; 938 } 939 940 /* 941 * NB. all returns later this function should go via "out" to 942 * ensure the original SIGCHLD handler is restored properly. 943 */ 944 osigchld = signal(SIGCHLD, SIG_DFL); 945 946 /* Prepare and verify the user for the command */ 947 username = percent_expand(options.authorized_keys_command_user, 948 "u", user_pw->pw_name, (char *)NULL); 949 pw = getpwnam(username); 950 if (pw == NULL) { 951 error("AuthorizedKeysCommandUser \"%s\" not found: %s", 952 username, strerror(errno)); 953 goto out; 954 } 955 956 /* Prepare AuthorizedKeysCommand */ 957 if ((key_fp = sshkey_fingerprint(key, options.fingerprint_hash, 958 SSH_FP_DEFAULT)) == NULL) { 959 error("%s: sshkey_fingerprint failed", __func__); 960 goto out; 961 } 962 if ((r = sshkey_to_base64(key, &keytext)) != 0) { 963 error("%s: sshkey_to_base64 failed: %s", __func__, ssh_err(r)); 964 goto out; 965 } 966 967 /* Turn the command into an argument vector */ 968 if (split_argv(options.authorized_keys_command, &ac, &av) != 0) { 969 error("AuthorizedKeysCommand \"%s\" contains invalid quotes", 970 command); 971 goto out; 972 } 973 if (ac == 0) { 974 error("AuthorizedKeysCommand \"%s\" yielded no arguments", 975 command); 976 goto out; 977 } 978 for (i = 1; i < ac; i++) { 979 tmp = percent_expand(av[i], 980 "u", user_pw->pw_name, 981 "h", user_pw->pw_dir, 982 "t", sshkey_ssh_name(key), 983 "f", key_fp, 984 "k", keytext, 985 (char *)NULL); 986 if (tmp == NULL) 987 fatal("%s: percent_expand failed", __func__); 988 free(av[i]); 989 av[i] = tmp; 990 } 991 /* Prepare a printable command for logs, etc. */ 992 command = assemble_argv(ac, av); 993 994 /* 995 * If AuthorizedKeysCommand was run without arguments 996 * then fall back to the old behaviour of passing the 997 * target username as a single argument. 998 */ 999 if (ac == 1) { 1000 av = xreallocarray(av, ac + 2, sizeof(*av)); 1001 av[1] = xstrdup(user_pw->pw_name); 1002 av[2] = NULL; 1003 /* Fix up command too, since it is used in log messages */ 1004 free(command); 1005 xasprintf(&command, "%s %s", av[0], av[1]); 1006 } 1007 1008 if ((pid = subprocess("AuthorizedKeysCommand", pw, command, 1009 ac, av, &f)) == 0) 1010 goto out; 1011 1012 uid_swapped = 1; 1013 temporarily_use_uid(pw); 1014 1015 ok = check_authkeys_file(f, options.authorized_keys_command, key, pw); 1016 1017 if (exited_cleanly(pid, "AuthorizedKeysCommand", command) != 0) 1018 goto out; 1019 1020 /* Read completed successfully */ 1021 found_key = ok; 1022 out: 1023 if (f != NULL) 1024 fclose(f); 1025 signal(SIGCHLD, osigchld); 1026 for (i = 0; i < ac; i++) 1027 free(av[i]); 1028 free(av); 1029 if (uid_swapped) 1030 restore_uid(); 1031 free(command); 1032 free(username); 1033 free(key_fp); 1034 free(keytext); 1035 return found_key; 1036 } 1037 1038 /* 1039 * Check whether key authenticates and authorises the user. 1040 */ 1041 int 1042 user_key_allowed(struct passwd *pw, Key *key, int auth_attempt) 1043 { 1044 u_int success, i; 1045 char *file; 1046 1047 if (auth_key_is_revoked(key)) 1048 return 0; 1049 if (key_is_cert(key) && auth_key_is_revoked(key->cert->signature_key)) 1050 return 0; 1051 1052 success = user_cert_trusted_ca(pw, key); 1053 if (success) 1054 return success; 1055 1056 success = user_key_command_allowed2(pw, key); 1057 if (success > 0) 1058 return success; 1059 1060 for (i = 0; !success && i < options.num_authkeys_files; i++) { 1061 1062 if (strcasecmp(options.authorized_keys_files[i], "none") == 0) 1063 continue; 1064 file = expand_authorized_keys( 1065 options.authorized_keys_files[i], pw); 1066 1067 success = user_key_allowed2(pw, key, file); 1068 free(file); 1069 } 1070 1071 return success; 1072 } 1073 1074 /* Records a public key in the list of previously-successful keys */ 1075 void 1076 auth2_record_userkey(Authctxt *authctxt, struct sshkey *key) 1077 { 1078 struct sshkey **tmp; 1079 1080 if (authctxt->nprev_userkeys >= INT_MAX || 1081 (tmp = reallocarray(authctxt->prev_userkeys, 1082 authctxt->nprev_userkeys + 1, sizeof(*tmp))) == NULL) 1083 fatal("%s: reallocarray failed", __func__); 1084 authctxt->prev_userkeys = tmp; 1085 authctxt->prev_userkeys[authctxt->nprev_userkeys] = key; 1086 authctxt->nprev_userkeys++; 1087 } 1088 1089 /* Checks whether a key has already been used successfully for authentication */ 1090 int 1091 auth2_userkey_already_used(Authctxt *authctxt, struct sshkey *key) 1092 { 1093 u_int i; 1094 1095 for (i = 0; i < authctxt->nprev_userkeys; i++) { 1096 if (sshkey_equal_public(key, authctxt->prev_userkeys[i])) { 1097 return 1; 1098 } 1099 } 1100 return 0; 1101 } 1102 1103 Authmethod method_pubkey = { 1104 "publickey", 1105 userauth_pubkey, 1106 &options.pubkey_authentication 1107 }; 1108