auth-options.c

   1 /* $OpenBSD: auth-options.c,v 1.53 2010/08/31 09:58:37 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 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                 xfree(ce->s);
  76                 xfree(ce);
  77         }
  78         if (forced_command) {
  79                 xfree(forced_command);
  80                 forced_command = NULL;
  81         }
  82         if (authorized_principals) {
  83                 xfree(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                                 xfree(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                                 xfree(forced_command);
 171                                 forced_command = NULL;
 172                                 goto bad_option;
 173                         }
 174                         forced_command[i] = '\0';
 175                         auth_debug_add("Forced command: %.900s", 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                                 xfree(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                                 xfree(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                                 xfree(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 = xmalloc(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                                 xfree(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                                 xfree(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                                 xfree(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                                 xfree(patterns);
 327                                 goto bad_option;
 328                         }
 329                         patterns[i] = '\0';
 330                         opts++;
 331                         p = patterns;
 332                         host = hpdelim(&p);
 333                         if (host == NULL || strlen(host) >= NI_MAXHOST) {
 334                                 debug("%.100s, line %lu: Bad permitopen "
 335                                     "specification <%.100s>", file, linenum,
 336                                     patterns);
 337                                 auth_debug_add("%.100s, line %lu: "
 338                                     "Bad permitopen specification", file,
 339                                     linenum);
 340                                 xfree(patterns);
 341                                 goto bad_option;
 342                         }
 343                         host = cleanhostname(host);
 344                         if (p == NULL || (port = a2port(p)) <= 0) {
 345                                 debug("%.100s, line %lu: Bad permitopen port "
 346                                     "<%.100s>", file, linenum, p ? p : "");
 347                                 auth_debug_add("%.100s, line %lu: "
 348                                     "Bad permitopen port", file, linenum);
 349                                 xfree(patterns);
 350                                 goto bad_option;
 351                         }
 352                         if (options.allow_tcp_forwarding)
 353                                 channel_add_permitted_opens(host, port);
 354                         xfree(patterns);
 355                         goto next_option;
 356                 }
 357                 cp = "tunnel=\"";
 358                 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
 359                         char *tun = NULL;
 360                         opts += strlen(cp);
 361                         tun = xmalloc(strlen(opts) + 1);
 362                         i = 0;
 363                         while (*opts) {
 364                                 if (*opts == '"')
 365                                         break;
 366                                 tun[i++] = *opts++;
 367                         }
 368                         if (!*opts) {
 369                                 debug("%.100s, line %lu: missing end quote",
 370                                     file, linenum);
 371                                 auth_debug_add("%.100s, line %lu: missing end quote",
 372                                     file, linenum);
 373                                 xfree(tun);
 374                                 forced_tun_device = -1;
 375                                 goto bad_option;
 376                         }
 377                         tun[i] = '\0';
 378                         forced_tun_device = a2tun(tun, NULL);
 379                         xfree(tun);
 380                         if (forced_tun_device == SSH_TUNID_ERR) {
 381                                 debug("%.100s, line %lu: invalid tun device",
 382                                     file, linenum);
 383                                 auth_debug_add("%.100s, line %lu: invalid tun device",
 384                                     file, linenum);
 385                                 forced_tun_device = -1;
 386                                 goto bad_option;
 387                         }
 388                         auth_debug_add("Forced tun device: %d", forced_tun_device);
 389                         opts++;
 390                         goto next_option;
 391                 }
 392 next_option:
 393                 /*
 394                  * Skip the comma, and move to the next option
 395                  * (or break out if there are no more).
 396                  */
 397                 if (!*opts)
 398                         fatal("Bugs in auth-options.c option processing.");
 399                 if (*opts == ' ' || *opts == '\t')
 400                         break;          /* End of options. */
 401                 if (*opts != ',')
 402                         goto bad_option;
 403                 opts++;
 404                 /* Process the next option. */
 405         }
 406
 407         /* grant access */
 408         return 1;
 409
 410 bad_option:
 411         logit("Bad options in %.100s file, line %lu: %.50s",
 412             file, linenum, opts);
 413         auth_debug_add("Bad options in %.100s file, line %lu: %.50s",
 414             file, linenum, opts);
 415
 416         /* deny access */
 417         return 0;
 418 }
 419
 420 #define OPTIONS_CRITICAL        1
 421 #define OPTIONS_EXTENSIONS      2
 422 static int
 423 parse_option_list(u_char *optblob, size_t optblob_len, struct passwd *pw,
 424     u_int which, int crit,
 425     int *cert_no_port_forwarding_flag,
 426     int *cert_no_agent_forwarding_flag,
 427     int *cert_no_x11_forwarding_flag,
 428     int *cert_no_pty_flag,
 429     int *cert_no_user_rc,
 430     char **cert_forced_command,
 431     int *cert_source_address_done)
 432 {
 433         char *command, *allowed;
 434         const char *remote_ip;
 435         u_char *name = NULL, *data_blob = NULL;
 436         u_int nlen, dlen, clen;
 437         Buffer c, data;
 438         int ret = -1, found;
 439
 440         buffer_init(&data);
 441
 442         /* Make copy to avoid altering original */
 443         buffer_init(&c);
 444         buffer_append(&c, optblob, optblob_len);
 445
 446         while (buffer_len(&c) > 0) {
 447                 if ((name = buffer_get_cstring_ret(&c, &nlen)) == NULL ||
 448                     (data_blob = buffer_get_string_ret(&c, &dlen)) == NULL) {
 449                         error("Certificate options corrupt");
 450                         goto out;
 451                 }
 452                 buffer_append(&data, data_blob, dlen);
 453                 debug3("found certificate option \"%.100s\" len %u",
 454                     name, dlen);
 455                 if (strlen(name) != nlen) {
 456                         error("Certificate constraint name contains \\0");
 457                         goto out;
 458                 }
 459                 found = 0;
 460                 if ((which & OPTIONS_EXTENSIONS) != 0) {
 461                         if (strcmp(name, "permit-X11-forwarding") == 0) {
 462                                 *cert_no_x11_forwarding_flag = 0;
 463                                 found = 1;
 464                         } else if (strcmp(name,
 465                             "permit-agent-forwarding") == 0) {
 466                                 *cert_no_agent_forwarding_flag = 0;
 467                                 found = 1;
 468                         } else if (strcmp(name,
 469                             "permit-port-forwarding") == 0) {
 470                                 *cert_no_port_forwarding_flag = 0;
 471                                 found = 1;
 472                         } else if (strcmp(name, "permit-pty") == 0) {
 473                                 *cert_no_pty_flag = 0;
 474                                 found = 1;
 475                         } else if (strcmp(name, "permit-user-rc") == 0) {
 476                                 *cert_no_user_rc = 0;
 477                                 found = 1;
 478                         }
 479                 }
 480                 if (!found && (which & OPTIONS_CRITICAL) != 0) {
 481                         if (strcmp(name, "force-command") == 0) {
 482                                 if ((command = buffer_get_cstring_ret(&data,
 483                                     &clen)) == NULL) {
 484                                         error("Certificate constraint \"%s\" "
 485                                             "corrupt", name);
 486                                         goto out;
 487                                 }
 488                                 if (strlen(command) != clen) {
 489                                         error("force-command constraint "
 490                                             "contains \\0");
 491                                         goto out;
 492                                 }
 493                                 if (*cert_forced_command != NULL) {
 494                                         error("Certificate has multiple "
 495                                             "force-command options");
 496                                         xfree(command);
 497                                         goto out;
 498                                 }
 499                                 *cert_forced_command = command;
 500                                 found = 1;
 501                         }
 502                         if (strcmp(name, "source-address") == 0) {
 503                                 if ((allowed = buffer_get_cstring_ret(&data,
 504                                     &clen)) == NULL) {
 505                                         error("Certificate constraint "
 506                                             "\"%s\" corrupt", name);
 507                                         goto out;
 508                                 }
 509                                 if (strlen(allowed) != clen) {
 510                                         error("source-address constraint "
 511                                             "contains \\0");
 512                                         goto out;
 513                                 }
 514                                 if ((*cert_source_address_done)++) {
 515                                         error("Certificate has multiple "
 516                                             "source-address options");
 517                                         xfree(allowed);
 518                                         goto out;
 519                                 }
 520                                 remote_ip = get_remote_ipaddr();
 521                                 switch (addr_match_cidr_list(remote_ip,
 522                                     allowed)) {
 523                                 case 1:
 524                                         /* accepted */
 525                                         xfree(allowed);
 526                                         break;
 527                                 case 0:
 528                                         /* no match */
 529                                         logit("Authentication tried for %.100s "
 530                                             "with valid certificate but not "
 531                                             "from a permitted host "
 532                                             "(ip=%.200s).", pw->pw_name,
 533                                             remote_ip);
 534                                         auth_debug_add("Your address '%.200s' "
 535                                             "is not permitted to use this "
 536                                             "certificate for login.",
 537                                             remote_ip);
 538                                         xfree(allowed);
 539                                         goto out;
 540                                 case -1:
 541                                         error("Certificate source-address "
 542                                             "contents invalid");
 543                                         xfree(allowed);
 544                                         goto out;
 545                                 }
 546                                 found = 1;
 547                         }
 548                 }
 549
 550                 if (!found) {
 551                         if (crit) {
 552                                 error("Certificate critical option \"%s\" "
 553                                     "is not supported", name);
 554                                 goto out;
 555                         } else {
 556                                 logit("Certificate extension \"%s\" "
 557                                     "is not supported", name);
 558                         }
 559                 } else if (buffer_len(&data) != 0) {
 560                         error("Certificate option \"%s\" corrupt "
 561                             "(extra data)", name);
 562                         goto out;
 563                 }
 564                 buffer_clear(&data);
 565                 xfree(name);
 566                 xfree(data_blob);
 567                 name = data_blob = NULL;
 568         }
 569         /* successfully parsed all options */
 570         ret = 0;
 571
 572  out:
 573         if (ret != 0 &&
 574             cert_forced_command != NULL &&
 575             *cert_forced_command != NULL) {
 576                 xfree(*cert_forced_command);
 577                 *cert_forced_command = NULL;
 578         }
 579         if (name != NULL)
 580                 xfree(name);
 581         if (data_blob != NULL)
 582                 xfree(data_blob);
 583         buffer_free(&data);
 584         buffer_free(&c);
 585         return ret;
 586 }
 587
 588 /*
 589  * Set options from critical certificate options. These supersede user key
 590  * options so this must be called after auth_parse_options().
 591  */
 592 int
 593 auth_cert_options(Key *k, struct passwd *pw)
 594 {
 595         int cert_no_port_forwarding_flag = 1;
 596         int cert_no_agent_forwarding_flag = 1;
 597         int cert_no_x11_forwarding_flag = 1;
 598         int cert_no_pty_flag = 1;
 599         int cert_no_user_rc = 1;
 600         char *cert_forced_command = NULL;
 601         int cert_source_address_done = 0;
 602
 603         if (key_cert_is_legacy(k)) {
 604                 /* All options are in the one field for v00 certs */
 605                 if (parse_option_list(buffer_ptr(&k->cert->critical),
 606                     buffer_len(&k->cert->critical), pw,
 607                     OPTIONS_CRITICAL|OPTIONS_EXTENSIONS, 1,
 608                     &cert_no_port_forwarding_flag,
 609                     &cert_no_agent_forwarding_flag,
 610                     &cert_no_x11_forwarding_flag,
 611                     &cert_no_pty_flag,
 612                     &cert_no_user_rc,
 613                     &cert_forced_command,
 614                     &cert_source_address_done) == -1)
 615                         return -1;
 616         } else {
 617                 /* Separate options and extensions for v01 certs */
 618                 if (parse_option_list(buffer_ptr(&k->cert->critical),
 619                     buffer_len(&k->cert->critical), pw,
 620                     OPTIONS_CRITICAL, 1, NULL, NULL, NULL, NULL, NULL,
 621                     &cert_forced_command,
 622                     &cert_source_address_done) == -1)
 623                         return -1;
 624                 if (parse_option_list(buffer_ptr(&k->cert->extensions),
 625                     buffer_len(&k->cert->extensions), pw,
 626                     OPTIONS_EXTENSIONS, 1,
 627                     &cert_no_port_forwarding_flag,
 628                     &cert_no_agent_forwarding_flag,
 629                     &cert_no_x11_forwarding_flag,
 630                     &cert_no_pty_flag,
 631                     &cert_no_user_rc,
 632                     NULL, NULL) == -1)
 633                         return -1;
 634         }
 635
 636         no_port_forwarding_flag |= cert_no_port_forwarding_flag;
 637         no_agent_forwarding_flag |= cert_no_agent_forwarding_flag;
 638         no_x11_forwarding_flag |= cert_no_x11_forwarding_flag;
 639         no_pty_flag |= cert_no_pty_flag;
 640         no_user_rc |= cert_no_user_rc;
 641         /* CA-specified forced command supersedes key option */
 642         if (cert_forced_command != NULL) {
 643                 if (forced_command != NULL)
 644                         xfree(forced_command);
 645                 forced_command = cert_forced_command;
 646         }
 647         return 0;
 648 }
 649