auth-options.c

   1 /* $OpenBSD: auth-options.c,v 1.54 2010/12/24 21:41:48 djm Exp $ */
   2 /*
   3  * Author: Tatu Ylonen <ylo@cs.hut.fi>
   4  * Copyright (c) 1995 Tatu Ylonen <ylo@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 #include "xmalloc.h"
  25 #include "match.h"
  26 #include "log.h"
  27 #include "canohost.h"
  28 #include "buffer.h"
  29 #include "channels.h"
  30 #include "servconf.h"
  31 #include "misc.h"
  32 #include "key.h"
  33 #include "auth-options.h"
  34 #include "hostfile.h"
  35 #include "auth.h"
  36 #ifdef GSSAPI
  37 #include "ssh-gss.h"
  38 #endif
  39 #include "monitor_wrap.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 /* Throttle log messages. */
  62 int logged_from_hostip = 0;
  63 int logged_cert_hostip = 0;
  64
  65 extern ServerOptions options;
  66
  67 void
  68 auth_start_parse_options(void)
  69 {
  70         logged_from_hostip = 0;
  71         logged_cert_hostip = 0;
  72 }
  73
  74 void
  75 auth_clear_options(void)
  76 {
  77         no_agent_forwarding_flag = 0;
  78         no_port_forwarding_flag = 0;
  79         no_pty_flag = 0;
  80         no_x11_forwarding_flag = 0;
  81         no_user_rc = 0;
  82         key_is_cert_authority = 0;
  83         while (custom_environment) {
  84                 struct envstring *ce = custom_environment;
  85                 custom_environment = ce->next;
  86                 xfree(ce->s);
  87                 xfree(ce);
  88         }
  89         if (forced_command) {
  90                 xfree(forced_command);
  91                 forced_command = NULL;
  92         }
  93         if (authorized_principals) {
  94                 xfree(authorized_principals);
  95                 authorized_principals = NULL;
  96         }
  97         forced_tun_device = -1;
  98         channel_clear_permitted_opens();
  99 }
 100
 101 /*
 102  * return 1 if access is granted, 0 if not.
 103  * side effect: sets key option flags
 104  */
 105 int
 106 auth_parse_options(struct passwd *pw, char *opts, char *file, u_long linenum)
 107 {
 108         const char *cp;
 109         int i;
 110
 111         /* reset options */
 112         auth_clear_options();
 113
 114         if (!opts)
 115                 return 1;
 116
 117         while (*opts && *opts != ' ' && *opts != '\t') {
 118                 cp = "cert-authority";
 119                 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
 120                         key_is_cert_authority = 1;
 121                         opts += strlen(cp);
 122                         goto next_option;
 123                 }
 124                 cp = "no-port-forwarding";
 125                 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
 126                         auth_debug_add("Port forwarding disabled.");
 127                         no_port_forwarding_flag = 1;
 128                         opts += strlen(cp);
 129                         goto next_option;
 130                 }
 131                 cp = "no-agent-forwarding";
 132                 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
 133                         auth_debug_add("Agent forwarding disabled.");
 134                         no_agent_forwarding_flag = 1;
 135                         opts += strlen(cp);
 136                         goto next_option;
 137                 }
 138                 cp = "no-X11-forwarding";
 139                 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
 140                         auth_debug_add("X11 forwarding disabled.");
 141                         no_x11_forwarding_flag = 1;
 142                         opts += strlen(cp);
 143                         goto next_option;
 144                 }
 145                 cp = "no-pty";
 146                 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
 147                         auth_debug_add("Pty allocation disabled.");
 148                         no_pty_flag = 1;
 149                         opts += strlen(cp);
 150                         goto next_option;
 151                 }
 152                 cp = "no-user-rc";
 153                 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
 154                         auth_debug_add("User rc file execution disabled.");
 155                         no_user_rc = 1;
 156                         opts += strlen(cp);
 157                         goto next_option;
 158                 }
 159                 cp = "command=\"";
 160                 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
 161                         opts += strlen(cp);
 162                         if (forced_command != NULL)
 163                                 xfree(forced_command);
 164                         forced_command = xmalloc(strlen(opts) + 1);
 165                         i = 0;
 166                         while (*opts) {
 167                                 if (*opts == '"')
 168                                         break;
 169                                 if (*opts == '\\' && opts[1] == '"') {
 170                                         opts += 2;
 171                                         forced_command[i++] = '"';
 172                                         continue;
 173                                 }
 174                                 forced_command[i++] = *opts++;
 175                         }
 176                         if (!*opts) {
 177                                 debug("%.100s, line %lu: missing end quote",
 178                                     file, linenum);
 179                                 auth_debug_add("%.100s, line %lu: missing end quote",
 180                                     file, linenum);
 181                                 xfree(forced_command);
 182                                 forced_command = NULL;
 183                                 goto bad_option;
 184                         }
 185                         forced_command[i] = '\0';
 186                         auth_debug_add("Forced command.");
 187                         opts++;
 188                         goto next_option;
 189                 }
 190                 cp = "principals=\"";
 191                 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
 192                         opts += strlen(cp);
 193                         if (authorized_principals != NULL)
 194                                 xfree(authorized_principals);
 195                         authorized_principals = xmalloc(strlen(opts) + 1);
 196                         i = 0;
 197                         while (*opts) {
 198                                 if (*opts == '"')
 199                                         break;
 200                                 if (*opts == '\\' && opts[1] == '"') {
 201                                         opts += 2;
 202                                         authorized_principals[i++] = '"';
 203                                         continue;
 204                                 }
 205                                 authorized_principals[i++] = *opts++;
 206                         }
 207                         if (!*opts) {
 208                                 debug("%.100s, line %lu: missing end quote",
 209                                     file, linenum);
 210                                 auth_debug_add("%.100s, line %lu: missing end quote",
 211                                     file, linenum);
 212                                 xfree(authorized_principals);
 213                                 authorized_principals = NULL;
 214                                 goto bad_option;
 215                         }
 216                         authorized_principals[i] = '\0';
 217                         auth_debug_add("principals: %.900s",
 218                             authorized_principals);
 219                         opts++;
 220                         goto next_option;
 221                 }
 222                 cp = "environment=\"";
 223                 if (options.permit_user_env &&
 224                     strncasecmp(opts, cp, strlen(cp)) == 0) {
 225                         char *s;
 226                         struct envstring *new_envstring;
 227
 228                         opts += strlen(cp);
 229                         s = xmalloc(strlen(opts) + 1);
 230                         i = 0;
 231                         while (*opts) {
 232                                 if (*opts == '"')
 233                                         break;
 234                                 if (*opts == '\\' && opts[1] == '"') {
 235                                         opts += 2;
 236                                         s[i++] = '"';
 237                                         continue;
 238                                 }
 239                                 s[i++] = *opts++;
 240                         }
 241                         if (!*opts) {
 242                                 debug("%.100s, line %lu: missing end quote",
 243                                     file, linenum);
 244                                 auth_debug_add("%.100s, line %lu: missing end quote",
 245                                     file, linenum);
 246                                 xfree(s);
 247                                 goto bad_option;
 248                         }
 249                         s[i] = '\0';
 250                         auth_debug_add("Adding to environment: %.900s", s);
 251                         debug("Adding to environment: %.900s", s);
 252                         opts++;
 253                         new_envstring = xmalloc(sizeof(struct envstring));
 254                         new_envstring->s = s;
 255                         new_envstring->next = custom_environment;
 256                         custom_environment = new_envstring;
 257                         goto next_option;
 258                 }
 259                 cp = "from=\"";
 260                 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
 261                         const char *remote_ip = get_remote_ipaddr();
 262                         const char *remote_host = get_canonical_hostname(
 263                             options.use_dns);
 264                         char *patterns = xmalloc(strlen(opts) + 1);
 265
 266                         opts += strlen(cp);
 267                         i = 0;
 268                         while (*opts) {
 269                                 if (*opts == '"')
 270                                         break;
 271                                 if (*opts == '\\' && opts[1] == '"') {
 272                                         opts += 2;
 273                                         patterns[i++] = '"';
 274                                         continue;
 275                                 }
 276                                 patterns[i++] = *opts++;
 277                         }
 278                         if (!*opts) {
 279                                 debug("%.100s, line %lu: missing end quote",
 280                                     file, linenum);
 281                                 auth_debug_add("%.100s, line %lu: missing end quote",
 282                                     file, linenum);
 283                                 xfree(patterns);
 284                                 goto bad_option;
 285                         }
 286                         patterns[i] = '\0';
 287                         opts++;
 288                         switch (match_host_and_ip(remote_host, remote_ip,
 289                             patterns)) {
 290                         case 1:
 291                                 xfree(patterns);
 292                                 /* Host name matches. */
 293                                 goto next_option;
 294                         case -1:
 295                                 debug("%.100s, line %lu: invalid criteria",
 296                                     file, linenum);
 297                                 auth_debug_add("%.100s, line %lu: "
 298                                     "invalid criteria", file, linenum);
 299                                 /* FALLTHROUGH */
 300                         case 0:
 301                                 xfree(patterns);
 302                                 if (!logged_from_hostip) {
 303                                         logit("Authentication tried for %.100s with "
 304                                             "correct key but not from a permitted "
 305                                             "host (host=%.200s, ip=%.200s).",
 306                                             pw->pw_name, remote_host, remote_ip);
 307                                         logged_from_hostip = 1;
 308                                 }
 309                                 auth_debug_add("Your host '%.200s' is not "
 310                                     "permitted to use this key for login.",
 311                                     remote_host);
 312                                 break;
 313                         }
 314                         /* deny access */
 315                         return 0;
 316                 }
 317                 cp = "permitopen=\"";
 318                 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
 319                         char *host, *p;
 320                         int port;
 321                         char *patterns = xmalloc(strlen(opts) + 1);
 322
 323                         opts += strlen(cp);
 324                         i = 0;
 325                         while (*opts) {
 326                                 if (*opts == '"')
 327                                         break;
 328                                 if (*opts == '\\' && opts[1] == '"') {
 329                                         opts += 2;
 330                                         patterns[i++] = '"';
 331                                         continue;
 332                                 }
 333                                 patterns[i++] = *opts++;
 334                         }
 335                         if (!*opts) {
 336                                 debug("%.100s, line %lu: missing end quote",
 337                                     file, linenum);
 338                                 auth_debug_add("%.100s, line %lu: missing "
 339                                     "end quote", file, linenum);
 340                                 xfree(patterns);
 341                                 goto bad_option;
 342                         }
 343                         patterns[i] = '\0';
 344                         opts++;
 345                         p = patterns;
 346                         host = hpdelim(&p);
 347                         if (host == NULL || strlen(host) >= NI_MAXHOST) {
 348                                 debug("%.100s, line %lu: Bad permitopen "
 349                                     "specification <%.100s>", file, linenum,
 350                                     patterns);
 351                                 auth_debug_add("%.100s, line %lu: "
 352                                     "Bad permitopen specification", file,
 353                                     linenum);
 354                                 xfree(patterns);
 355                                 goto bad_option;
 356                         }
 357                         host = cleanhostname(host);
 358                         if (p == NULL || (port = a2port(p)) <= 0) {
 359                                 debug("%.100s, line %lu: Bad permitopen port "
 360                                     "<%.100s>", file, linenum, p ? p : "");
 361                                 auth_debug_add("%.100s, line %lu: "
 362                                     "Bad permitopen port", file, linenum);
 363                                 xfree(patterns);
 364                                 goto bad_option;
 365                         }
 366                         if (options.allow_tcp_forwarding)
 367                                 channel_add_permitted_opens(host, port);
 368                         xfree(patterns);
 369                         goto next_option;
 370                 }
 371                 cp = "tunnel=\"";
 372                 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
 373                         char *tun = NULL;
 374                         opts += strlen(cp);
 375                         tun = xmalloc(strlen(opts) + 1);
 376                         i = 0;
 377                         while (*opts) {
 378                                 if (*opts == '"')
 379                                         break;
 380                                 tun[i++] = *opts++;
 381                         }
 382                         if (!*opts) {
 383                                 debug("%.100s, line %lu: missing end quote",
 384                                     file, linenum);
 385                                 auth_debug_add("%.100s, line %lu: missing end quote",
 386                                     file, linenum);
 387                                 xfree(tun);
 388                                 forced_tun_device = -1;
 389                                 goto bad_option;
 390                         }
 391                         tun[i] = '\0';
 392                         forced_tun_device = a2tun(tun, NULL);
 393                         xfree(tun);
 394                         if (forced_tun_device == SSH_TUNID_ERR) {
 395                                 debug("%.100s, line %lu: invalid tun device",
 396                                     file, linenum);
 397                                 auth_debug_add("%.100s, line %lu: invalid tun device",
 398                                     file, linenum);
 399                                 forced_tun_device = -1;
 400                                 goto bad_option;
 401                         }
 402                         auth_debug_add("Forced tun device: %d", forced_tun_device);
 403                         opts++;
 404                         goto next_option;
 405                 }
 406 next_option:
 407                 /*
 408                  * Skip the comma, and move to the next option
 409                  * (or break out if there are no more).
 410                  */
 411                 if (!*opts)
 412                         fatal("Bugs in auth-options.c option processing.");
 413                 if (*opts == ' ' || *opts == '\t')
 414                         break;          /* End of options. */
 415                 if (*opts != ',')
 416                         goto bad_option;
 417                 opts++;
 418                 /* Process the next option. */
 419         }
 420
 421         /* grant access */
 422         return 1;
 423
 424 bad_option:
 425         logit("Bad options in %.100s file, line %lu: %.50s",
 426             file, linenum, opts);
 427         auth_debug_add("Bad options in %.100s file, line %lu: %.50s",
 428             file, linenum, opts);
 429
 430         /* deny access */
 431         return 0;
 432 }
 433
 434 #define OPTIONS_CRITICAL        1
 435 #define OPTIONS_EXTENSIONS      2
 436 static int
 437 parse_option_list(u_char *optblob, size_t optblob_len, struct passwd *pw,
 438     u_int which, int crit,
 439     int *cert_no_port_forwarding_flag,
 440     int *cert_no_agent_forwarding_flag,
 441     int *cert_no_x11_forwarding_flag,
 442     int *cert_no_pty_flag,
 443     int *cert_no_user_rc,
 444     char **cert_forced_command,
 445     int *cert_source_address_done)
 446 {
 447         char *command, *allowed;
 448         const char *remote_ip;
 449         u_char *name = NULL, *data_blob = NULL;
 450         u_int nlen, dlen, clen;
 451         Buffer c, data;
 452         int ret = -1, found;
 453
 454         buffer_init(&data);
 455
 456         /* Make copy to avoid altering original */
 457         buffer_init(&c);
 458         buffer_append(&c, optblob, optblob_len);
 459
 460         while (buffer_len(&c) > 0) {
 461                 if ((name = buffer_get_cstring_ret(&c, &nlen)) == NULL ||
 462                     (data_blob = buffer_get_string_ret(&c, &dlen)) == NULL) {
 463                         error("Certificate options corrupt");
 464                         goto out;
 465                 }
 466                 buffer_append(&data, data_blob, dlen);
 467                 debug3("found certificate option \"%.100s\" len %u",
 468                     name, dlen);
 469                 if (strlen(name) != nlen) {
 470                         error("Certificate constraint name contains \\0");
 471                         goto out;
 472                 }
 473                 found = 0;
 474                 if ((which & OPTIONS_EXTENSIONS) != 0) {
 475                         if (strcmp(name, "permit-X11-forwarding") == 0) {
 476                                 *cert_no_x11_forwarding_flag = 0;
 477                                 found = 1;
 478                         } else if (strcmp(name,
 479                             "permit-agent-forwarding") == 0) {
 480                                 *cert_no_agent_forwarding_flag = 0;
 481                                 found = 1;
 482                         } else if (strcmp(name,
 483                             "permit-port-forwarding") == 0) {
 484                                 *cert_no_port_forwarding_flag = 0;
 485                                 found = 1;
 486                         } else if (strcmp(name, "permit-pty") == 0) {
 487                                 *cert_no_pty_flag = 0;
 488                                 found = 1;
 489                         } else if (strcmp(name, "permit-user-rc") == 0) {
 490                                 *cert_no_user_rc = 0;
 491                                 found = 1;
 492                         }
 493                 }
 494                 if (!found && (which & OPTIONS_CRITICAL) != 0) {
 495                         if (strcmp(name, "force-command") == 0) {
 496                                 if ((command = buffer_get_cstring_ret(&data,
 497                                     &clen)) == NULL) {
 498                                         error("Certificate constraint \"%s\" "
 499                                             "corrupt", name);
 500                                         goto out;
 501                                 }
 502                                 if (strlen(command) != clen) {
 503                                         error("force-command constraint "
 504                                             "contains \\0");
 505                                         goto out;
 506                                 }
 507                                 if (*cert_forced_command != NULL) {
 508                                         error("Certificate has multiple "
 509                                             "force-command options");
 510                                         xfree(command);
 511                                         goto out;
 512                                 }
 513                                 *cert_forced_command = command;
 514                                 found = 1;
 515                         }
 516                         if (strcmp(name, "source-address") == 0) {
 517                                 if ((allowed = buffer_get_cstring_ret(&data,
 518                                     &clen)) == NULL) {
 519                                         error("Certificate constraint "
 520                                             "\"%s\" corrupt", name);
 521                                         goto out;
 522                                 }
 523                                 if (strlen(allowed) != clen) {
 524                                         error("source-address constraint "
 525                                             "contains \\0");
 526                                         goto out;
 527                                 }
 528                                 if ((*cert_source_address_done)++) {
 529                                         error("Certificate has multiple "
 530                                             "source-address options");
 531                                         xfree(allowed);
 532                                         goto out;
 533                                 }
 534                                 remote_ip = get_remote_ipaddr();
 535                                 switch (addr_match_cidr_list(remote_ip,
 536                                     allowed)) {
 537                                 case 1:
 538                                         /* accepted */
 539                                         xfree(allowed);
 540                                         break;
 541                                 case 0:
 542                                         /* no match */
 543                                         if (!logged_cert_hostip) {
 544                                                 logit("Authentication tried for %.100s "
 545                                                     "with valid certificate but not "
 546                                                     "from a permitted host "
 547                                                     "(ip=%.200s).", pw->pw_name,
 548                                                     remote_ip);
 549                                                 logged_cert_hostip = 1;
 550                                         }
 551                                         auth_debug_add("Your address '%.200s' "
 552                                             "is not permitted to use this "
 553                                             "certificate for login.",
 554                                             remote_ip);
 555                                         xfree(allowed);
 556                                         goto out;
 557                                 case -1:
 558                                         error("Certificate source-address "
 559                                             "contents invalid");
 560                                         xfree(allowed);
 561                                         goto out;
 562                                 }
 563                                 found = 1;
 564                         }
 565                 }
 566
 567                 if (!found) {
 568                         if (crit) {
 569                                 error("Certificate critical option \"%s\" "
 570                                     "is not supported", name);
 571                                 goto out;
 572                         } else {
 573                                 logit("Certificate extension \"%s\" "
 574                                     "is not supported", name);
 575                         }
 576                 } else if (buffer_len(&data) != 0) {
 577                         error("Certificate option \"%s\" corrupt "
 578                             "(extra data)", name);
 579                         goto out;
 580                 }
 581                 buffer_clear(&data);
 582                 xfree(name);
 583                 xfree(data_blob);
 584                 name = data_blob = NULL;
 585         }
 586         /* successfully parsed all options */
 587         ret = 0;
 588
 589  out:
 590         if (ret != 0 &&
 591             cert_forced_command != NULL &&
 592             *cert_forced_command != NULL) {
 593                 xfree(*cert_forced_command);
 594                 *cert_forced_command = NULL;
 595         }
 596         if (name != NULL)
 597                 xfree(name);
 598         if (data_blob != NULL)
 599                 xfree(data_blob);
 600         buffer_free(&data);
 601         buffer_free(&c);
 602         return ret;
 603 }
 604
 605 /*
 606  * Set options from critical certificate options. These supersede user key
 607  * options so this must be called after auth_parse_options().
 608  */
 609 int
 610 auth_cert_options(Key *k, struct passwd *pw)
 611 {
 612         int cert_no_port_forwarding_flag = 1;
 613         int cert_no_agent_forwarding_flag = 1;
 614         int cert_no_x11_forwarding_flag = 1;
 615         int cert_no_pty_flag = 1;
 616         int cert_no_user_rc = 1;
 617         char *cert_forced_command = NULL;
 618         int cert_source_address_done = 0;
 619
 620         if (key_cert_is_legacy(k)) {
 621                 /* All options are in the one field for v00 certs */
 622                 if (parse_option_list(buffer_ptr(&k->cert->critical),
 623                     buffer_len(&k->cert->critical), pw,
 624                     OPTIONS_CRITICAL|OPTIONS_EXTENSIONS, 1,
 625                     &cert_no_port_forwarding_flag,
 626                     &cert_no_agent_forwarding_flag,
 627                     &cert_no_x11_forwarding_flag,
 628                     &cert_no_pty_flag,
 629                     &cert_no_user_rc,
 630                     &cert_forced_command,
 631                     &cert_source_address_done) == -1)
 632                         return -1;
 633         } else {
 634                 /* Separate options and extensions for v01 certs */
 635                 if (parse_option_list(buffer_ptr(&k->cert->critical),
 636                     buffer_len(&k->cert->critical), pw,
 637                     OPTIONS_CRITICAL, 1, NULL, NULL, NULL, NULL, NULL,
 638                     &cert_forced_command,
 639                     &cert_source_address_done) == -1)
 640                         return -1;
 641                 if (parse_option_list(buffer_ptr(&k->cert->extensions),
 642                     buffer_len(&k->cert->extensions), pw,
 643                     OPTIONS_EXTENSIONS, 1,
 644                     &cert_no_port_forwarding_flag,
 645                     &cert_no_agent_forwarding_flag,
 646                     &cert_no_x11_forwarding_flag,
 647                     &cert_no_pty_flag,
 648                     &cert_no_user_rc,
 649                     NULL, NULL) == -1)
 650                         return -1;
 651         }
 652
 653         no_port_forwarding_flag |= cert_no_port_forwarding_flag;
 654         no_agent_forwarding_flag |= cert_no_agent_forwarding_flag;
 655         no_x11_forwarding_flag |= cert_no_x11_forwarding_flag;
 656         no_pty_flag |= cert_no_pty_flag;
 657         no_user_rc |= cert_no_user_rc;
 658         /* CA-specified forced command supersedes key option */
 659         if (cert_forced_command != NULL) {
 660                 if (forced_command != NULL)
 661                         xfree(forced_command);
 662                 forced_command = cert_forced_command;
 663         }
 664         return 0;
 665 }
 666