1 /* $OpenBSD: auth-options.c,v 1.65 2015/01/14 10:30:34 markus Exp $ */ 2 /* 3 * Author: Tatu Ylonen <ylo (at) cs.hut.fi> 4 * Copyright (c) 1995 Tatu Ylonen <ylo (at) cs.hut.fi>, Espoo, Finland 5 * All rights reserved 6 * As far as I am concerned, the code I have written for this software 7 * can be used freely for any purpose. Any derived versions of this 8 * software must be clearly marked as such, and if the derived work is 9 * incompatible with the protocol description in the RFC file, it must be 10 * called by a name other than "ssh" or "Secure Shell". 11 */ 12 13 #include "includes.h" 14 15 #include <sys/types.h> 16 17 #include <netdb.h> 18 #include <pwd.h> 19 #include <string.h> 20 #include <stdio.h> 21 #include <stdarg.h> 22 23 #include "openbsd-compat/sys-queue.h" 24 25 #include "key.h" /* XXX for typedef */ 26 #include "buffer.h" /* XXX for typedef */ 27 #include "xmalloc.h" 28 #include "match.h" 29 #include "ssherr.h" 30 #include "log.h" 31 #include "canohost.h" 32 #include "sshbuf.h" 33 #include "misc.h" 34 #include "channels.h" 35 #include "servconf.h" 36 #include "sshkey.h" 37 #include "auth-options.h" 38 #include "hostfile.h" 39 #include "auth.h" 40 41 /* Flags set authorized_keys flags */ 42 int no_port_forwarding_flag = 0; 43 int no_agent_forwarding_flag = 0; 44 int no_x11_forwarding_flag = 0; 45 int no_pty_flag = 0; 46 int no_user_rc = 0; 47 int key_is_cert_authority = 0; 48 49 /* "command=" option. */ 50 char *forced_command = NULL; 51 52 /* "environment=" options. */ 53 struct envstring *custom_environment = NULL; 54 55 /* "tunnel=" option. */ 56 int forced_tun_device = -1; 57 58 /* "principals=" option. */ 59 char *authorized_principals = NULL; 60 61 extern ServerOptions options; 62 63 void 64 auth_clear_options(void) 65 { 66 no_agent_forwarding_flag = 0; 67 no_port_forwarding_flag = 0; 68 no_pty_flag = 0; 69 no_x11_forwarding_flag = 0; 70 no_user_rc = 0; 71 key_is_cert_authority = 0; 72 while (custom_environment) { 73 struct envstring *ce = custom_environment; 74 custom_environment = ce->next; 75 free(ce->s); 76 free(ce); 77 } 78 if (forced_command) { 79 free(forced_command); 80 forced_command = NULL; 81 } 82 if (authorized_principals) { 83 free(authorized_principals); 84 authorized_principals = NULL; 85 } 86 forced_tun_device = -1; 87 channel_clear_permitted_opens(); 88 } 89 90 /* 91 * return 1 if access is granted, 0 if not. 92 * side effect: sets key option flags 93 */ 94 int 95 auth_parse_options(struct passwd *pw, char *opts, char *file, u_long linenum) 96 { 97 const char *cp; 98 int i; 99 100 /* reset options */ 101 auth_clear_options(); 102 103 if (!opts) 104 return 1; 105 106 while (*opts && *opts != ' ' && *opts != '\t') { 107 cp = "cert-authority"; 108 if (strncasecmp(opts, cp, strlen(cp)) == 0) { 109 key_is_cert_authority = 1; 110 opts += strlen(cp); 111 goto next_option; 112 } 113 cp = "no-port-forwarding"; 114 if (strncasecmp(opts, cp, strlen(cp)) == 0) { 115 auth_debug_add("Port forwarding disabled."); 116 no_port_forwarding_flag = 1; 117 opts += strlen(cp); 118 goto next_option; 119 } 120 cp = "no-agent-forwarding"; 121 if (strncasecmp(opts, cp, strlen(cp)) == 0) { 122 auth_debug_add("Agent forwarding disabled."); 123 no_agent_forwarding_flag = 1; 124 opts += strlen(cp); 125 goto next_option; 126 } 127 cp = "no-X11-forwarding"; 128 if (strncasecmp(opts, cp, strlen(cp)) == 0) { 129 auth_debug_add("X11 forwarding disabled."); 130 no_x11_forwarding_flag = 1; 131 opts += strlen(cp); 132 goto next_option; 133 } 134 cp = "no-pty"; 135 if (strncasecmp(opts, cp, strlen(cp)) == 0) { 136 auth_debug_add("Pty allocation disabled."); 137 no_pty_flag = 1; 138 opts += strlen(cp); 139 goto next_option; 140 } 141 cp = "no-user-rc"; 142 if (strncasecmp(opts, cp, strlen(cp)) == 0) { 143 auth_debug_add("User rc file execution disabled."); 144 no_user_rc = 1; 145 opts += strlen(cp); 146 goto next_option; 147 } 148 cp = "command=\""; 149 if (strncasecmp(opts, cp, strlen(cp)) == 0) { 150 opts += strlen(cp); 151 if (forced_command != NULL) 152 free(forced_command); 153 forced_command = xmalloc(strlen(opts) + 1); 154 i = 0; 155 while (*opts) { 156 if (*opts == '"') 157 break; 158 if (*opts == '\\' && opts[1] == '"') { 159 opts += 2; 160 forced_command[i++] = '"'; 161 continue; 162 } 163 forced_command[i++] = *opts++; 164 } 165 if (!*opts) { 166 debug("%.100s, line %lu: missing end quote", 167 file, linenum); 168 auth_debug_add("%.100s, line %lu: missing end quote", 169 file, linenum); 170 free(forced_command); 171 forced_command = NULL; 172 goto bad_option; 173 } 174 forced_command[i] = '\0'; 175 auth_debug_add("Forced command."); 176 opts++; 177 goto next_option; 178 } 179 cp = "principals=\""; 180 if (strncasecmp(opts, cp, strlen(cp)) == 0) { 181 opts += strlen(cp); 182 if (authorized_principals != NULL) 183 free(authorized_principals); 184 authorized_principals = xmalloc(strlen(opts) + 1); 185 i = 0; 186 while (*opts) { 187 if (*opts == '"') 188 break; 189 if (*opts == '\\' && opts[1] == '"') { 190 opts += 2; 191 authorized_principals[i++] = '"'; 192 continue; 193 } 194 authorized_principals[i++] = *opts++; 195 } 196 if (!*opts) { 197 debug("%.100s, line %lu: missing end quote", 198 file, linenum); 199 auth_debug_add("%.100s, line %lu: missing end quote", 200 file, linenum); 201 free(authorized_principals); 202 authorized_principals = NULL; 203 goto bad_option; 204 } 205 authorized_principals[i] = '\0'; 206 auth_debug_add("principals: %.900s", 207 authorized_principals); 208 opts++; 209 goto next_option; 210 } 211 cp = "environment=\""; 212 if (options.permit_user_env && 213 strncasecmp(opts, cp, strlen(cp)) == 0) { 214 char *s; 215 struct envstring *new_envstring; 216 217 opts += strlen(cp); 218 s = xmalloc(strlen(opts) + 1); 219 i = 0; 220 while (*opts) { 221 if (*opts == '"') 222 break; 223 if (*opts == '\\' && opts[1] == '"') { 224 opts += 2; 225 s[i++] = '"'; 226 continue; 227 } 228 s[i++] = *opts++; 229 } 230 if (!*opts) { 231 debug("%.100s, line %lu: missing end quote", 232 file, linenum); 233 auth_debug_add("%.100s, line %lu: missing end quote", 234 file, linenum); 235 free(s); 236 goto bad_option; 237 } 238 s[i] = '\0'; 239 auth_debug_add("Adding to environment: %.900s", s); 240 debug("Adding to environment: %.900s", s); 241 opts++; 242 new_envstring = xcalloc(1, sizeof(struct envstring)); 243 new_envstring->s = s; 244 new_envstring->next = custom_environment; 245 custom_environment = new_envstring; 246 goto next_option; 247 } 248 cp = "from=\""; 249 if (strncasecmp(opts, cp, strlen(cp)) == 0) { 250 const char *remote_ip = get_remote_ipaddr(); 251 const char *remote_host = get_canonical_hostname( 252 options.use_dns); 253 char *patterns = xmalloc(strlen(opts) + 1); 254 255 opts += strlen(cp); 256 i = 0; 257 while (*opts) { 258 if (*opts == '"') 259 break; 260 if (*opts == '\\' && opts[1] == '"') { 261 opts += 2; 262 patterns[i++] = '"'; 263 continue; 264 } 265 patterns[i++] = *opts++; 266 } 267 if (!*opts) { 268 debug("%.100s, line %lu: missing end quote", 269 file, linenum); 270 auth_debug_add("%.100s, line %lu: missing end quote", 271 file, linenum); 272 free(patterns); 273 goto bad_option; 274 } 275 patterns[i] = '\0'; 276 opts++; 277 switch (match_host_and_ip(remote_host, remote_ip, 278 patterns)) { 279 case 1: 280 free(patterns); 281 /* Host name matches. */ 282 goto next_option; 283 case -1: 284 debug("%.100s, line %lu: invalid criteria", 285 file, linenum); 286 auth_debug_add("%.100s, line %lu: " 287 "invalid criteria", file, linenum); 288 /* FALLTHROUGH */ 289 case 0: 290 free(patterns); 291 logit("Authentication tried for %.100s with " 292 "correct key but not from a permitted " 293 "host (host=%.200s, ip=%.200s).", 294 pw->pw_name, remote_host, remote_ip); 295 auth_debug_add("Your host '%.200s' is not " 296 "permitted to use this key for login.", 297 remote_host); 298 break; 299 } 300 /* deny access */ 301 return 0; 302 } 303 cp = "permitopen=\""; 304 if (strncasecmp(opts, cp, strlen(cp)) == 0) { 305 char *host, *p; 306 int port; 307 char *patterns = xmalloc(strlen(opts) + 1); 308 309 opts += strlen(cp); 310 i = 0; 311 while (*opts) { 312 if (*opts == '"') 313 break; 314 if (*opts == '\\' && opts[1] == '"') { 315 opts += 2; 316 patterns[i++] = '"'; 317 continue; 318 } 319 patterns[i++] = *opts++; 320 } 321 if (!*opts) { 322 debug("%.100s, line %lu: missing end quote", 323 file, linenum); 324 auth_debug_add("%.100s, line %lu: missing " 325 "end quote", file, linenum); 326 free(patterns); 327 goto bad_option; 328 } 329 patterns[i] = '\0'; 330 opts++; 331 p = patterns; 332 /* XXX - add streamlocal support */ 333 host = hpdelim(&p); 334 if (host == NULL || strlen(host) >= NI_MAXHOST) { 335 debug("%.100s, line %lu: Bad permitopen " 336 "specification <%.100s>", file, linenum, 337 patterns); 338 auth_debug_add("%.100s, line %lu: " 339 "Bad permitopen specification", file, 340 linenum); 341 free(patterns); 342 goto bad_option; 343 } 344 host = cleanhostname(host); 345 if (p == NULL || (port = permitopen_port(p)) < 0) { 346 debug("%.100s, line %lu: Bad permitopen port " 347 "<%.100s>", file, linenum, p ? p : ""); 348 auth_debug_add("%.100s, line %lu: " 349 "Bad permitopen port", file, linenum); 350 free(patterns); 351 goto bad_option; 352 } 353 if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0) 354 channel_add_permitted_opens(host, port); 355 free(patterns); 356 goto next_option; 357 } 358 cp = "tunnel=\""; 359 if (strncasecmp(opts, cp, strlen(cp)) == 0) { 360 char *tun = NULL; 361 opts += strlen(cp); 362 tun = xmalloc(strlen(opts) + 1); 363 i = 0; 364 while (*opts) { 365 if (*opts == '"') 366 break; 367 tun[i++] = *opts++; 368 } 369 if (!*opts) { 370 debug("%.100s, line %lu: missing end quote", 371 file, linenum); 372 auth_debug_add("%.100s, line %lu: missing end quote", 373 file, linenum); 374 free(tun); 375 forced_tun_device = -1; 376 goto bad_option; 377 } 378 tun[i] = '\0'; 379 forced_tun_device = a2tun(tun, NULL); 380 free(tun); 381 if (forced_tun_device == SSH_TUNID_ERR) { 382 debug("%.100s, line %lu: invalid tun device", 383 file, linenum); 384 auth_debug_add("%.100s, line %lu: invalid tun device", 385 file, linenum); 386 forced_tun_device = -1; 387 goto bad_option; 388 } 389 auth_debug_add("Forced tun device: %d", forced_tun_device); 390 opts++; 391 goto next_option; 392 } 393 next_option: 394 /* 395 * Skip the comma, and move to the next option 396 * (or break out if there are no more). 397 */ 398 if (!*opts) 399 fatal("Bugs in auth-options.c option processing."); 400 if (*opts == ' ' || *opts == '\t') 401 break; /* End of options. */ 402 if (*opts != ',') 403 goto bad_option; 404 opts++; 405 /* Process the next option. */ 406 } 407 408 /* grant access */ 409 return 1; 410 411 bad_option: 412 logit("Bad options in %.100s file, line %lu: %.50s", 413 file, linenum, opts); 414 auth_debug_add("Bad options in %.100s file, line %lu: %.50s", 415 file, linenum, opts); 416 417 /* deny access */ 418 return 0; 419 } 420 421 #define OPTIONS_CRITICAL 1 422 #define OPTIONS_EXTENSIONS 2 423 static int 424 parse_option_list(struct sshbuf *oblob, struct passwd *pw, 425 u_int which, int crit, 426 int *cert_no_port_forwarding_flag, 427 int *cert_no_agent_forwarding_flag, 428 int *cert_no_x11_forwarding_flag, 429 int *cert_no_pty_flag, 430 int *cert_no_user_rc, 431 char **cert_forced_command, 432 int *cert_source_address_done) 433 { 434 char *command, *allowed; 435 const char *remote_ip; 436 char *name = NULL; 437 struct sshbuf *c = NULL, *data = NULL; 438 int r, ret = -1, result, found; 439 440 if ((c = sshbuf_fromb(oblob)) == NULL) { 441 error("%s: sshbuf_fromb failed", __func__); 442 goto out; 443 } 444 445 while (sshbuf_len(c) > 0) { 446 sshbuf_free(data); 447 data = NULL; 448 if ((r = sshbuf_get_cstring(c, &name, NULL)) != 0 || 449 (r = sshbuf_froms(c, &data)) != 0) { 450 error("Unable to parse certificate options: %s", 451 ssh_err(r)); 452 goto out; 453 } 454 debug3("found certificate option \"%.100s\" len %zu", 455 name, sshbuf_len(data)); 456 found = 0; 457 if ((which & OPTIONS_EXTENSIONS) != 0) { 458 if (strcmp(name, "permit-X11-forwarding") == 0) { 459 *cert_no_x11_forwarding_flag = 0; 460 found = 1; 461 } else if (strcmp(name, 462 "permit-agent-forwarding") == 0) { 463 *cert_no_agent_forwarding_flag = 0; 464 found = 1; 465 } else if (strcmp(name, 466 "permit-port-forwarding") == 0) { 467 *cert_no_port_forwarding_flag = 0; 468 found = 1; 469 } else if (strcmp(name, "permit-pty") == 0) { 470 *cert_no_pty_flag = 0; 471 found = 1; 472 } else if (strcmp(name, "permit-user-rc") == 0) { 473 *cert_no_user_rc = 0; 474 found = 1; 475 } 476 } 477 if (!found && (which & OPTIONS_CRITICAL) != 0) { 478 if (strcmp(name, "force-command") == 0) { 479 if ((r = sshbuf_get_cstring(data, &command, 480 NULL)) != 0) { 481 error("Unable to parse \"%s\" " 482 "section: %s", name, ssh_err(r)); 483 goto out; 484 } 485 if (*cert_forced_command != NULL) { 486 error("Certificate has multiple " 487 "force-command options"); 488 free(command); 489 goto out; 490 } 491 *cert_forced_command = command; 492 found = 1; 493 } 494 if (strcmp(name, "source-address") == 0) { 495 if ((r = sshbuf_get_cstring(data, &allowed, 496 NULL)) != 0) { 497 error("Unable to parse \"%s\" " 498 "section: %s", name, ssh_err(r)); 499 goto out; 500 } 501 if ((*cert_source_address_done)++) { 502 error("Certificate has multiple " 503 "source-address options"); 504 free(allowed); 505 goto out; 506 } 507 remote_ip = get_remote_ipaddr(); 508 result = addr_match_cidr_list(remote_ip, 509 allowed); 510 free(allowed); 511 switch (result) { 512 case 1: 513 /* accepted */ 514 break; 515 case 0: 516 /* no match */ 517 logit("Authentication tried for %.100s " 518 "with valid certificate but not " 519 "from a permitted host " 520 "(ip=%.200s).", pw->pw_name, 521 remote_ip); 522 auth_debug_add("Your address '%.200s' " 523 "is not permitted to use this " 524 "certificate for login.", 525 remote_ip); 526 goto out; 527 case -1: 528 default: 529 error("Certificate source-address " 530 "contents invalid"); 531 goto out; 532 } 533 found = 1; 534 } 535 } 536 537 if (!found) { 538 if (crit) { 539 error("Certificate critical option \"%s\" " 540 "is not supported", name); 541 goto out; 542 } else { 543 logit("Certificate extension \"%s\" " 544 "is not supported", name); 545 } 546 } else if (sshbuf_len(data) != 0) { 547 error("Certificate option \"%s\" corrupt " 548 "(extra data)", name); 549 goto out; 550 } 551 free(name); 552 name = NULL; 553 } 554 /* successfully parsed all options */ 555 ret = 0; 556 557 out: 558 if (ret != 0 && 559 cert_forced_command != NULL && 560 *cert_forced_command != NULL) { 561 free(*cert_forced_command); 562 *cert_forced_command = NULL; 563 } 564 if (name != NULL) 565 free(name); 566 sshbuf_free(data); 567 sshbuf_free(c); 568 return ret; 569 } 570 571 /* 572 * Set options from critical certificate options. These supersede user key 573 * options so this must be called after auth_parse_options(). 574 */ 575 int 576 auth_cert_options(struct sshkey *k, struct passwd *pw) 577 { 578 int cert_no_port_forwarding_flag = 1; 579 int cert_no_agent_forwarding_flag = 1; 580 int cert_no_x11_forwarding_flag = 1; 581 int cert_no_pty_flag = 1; 582 int cert_no_user_rc = 1; 583 char *cert_forced_command = NULL; 584 int cert_source_address_done = 0; 585 586 if (sshkey_cert_is_legacy(k)) { 587 /* All options are in the one field for v00 certs */ 588 if (parse_option_list(k->cert->critical, pw, 589 OPTIONS_CRITICAL|OPTIONS_EXTENSIONS, 1, 590 &cert_no_port_forwarding_flag, 591 &cert_no_agent_forwarding_flag, 592 &cert_no_x11_forwarding_flag, 593 &cert_no_pty_flag, 594 &cert_no_user_rc, 595 &cert_forced_command, 596 &cert_source_address_done) == -1) 597 return -1; 598 } else { 599 /* Separate options and extensions for v01 certs */ 600 if (parse_option_list(k->cert->critical, pw, 601 OPTIONS_CRITICAL, 1, NULL, NULL, NULL, NULL, NULL, 602 &cert_forced_command, 603 &cert_source_address_done) == -1) 604 return -1; 605 if (parse_option_list(k->cert->extensions, pw, 606 OPTIONS_EXTENSIONS, 1, 607 &cert_no_port_forwarding_flag, 608 &cert_no_agent_forwarding_flag, 609 &cert_no_x11_forwarding_flag, 610 &cert_no_pty_flag, 611 &cert_no_user_rc, 612 NULL, NULL) == -1) 613 return -1; 614 } 615 616 no_port_forwarding_flag |= cert_no_port_forwarding_flag; 617 no_agent_forwarding_flag |= cert_no_agent_forwarding_flag; 618 no_x11_forwarding_flag |= cert_no_x11_forwarding_flag; 619 no_pty_flag |= cert_no_pty_flag; 620 no_user_rc |= cert_no_user_rc; 621 /* CA-specified forced command supersedes key option */ 622 if (cert_forced_command != NULL) { 623 if (forced_command != NULL) 624 free(forced_command); 625 forced_command = cert_forced_command; 626 } 627 return 0; 628 } 629 630
