crypto/openssh/auth-options.c

   1 /* $OpenBSD: auth-options.c,v 1.68 2015/07/03 03:43:18 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
  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 (strncasecmp(opts, cp, strlen(cp)) == 0) {
 213                         char *s;
 214                         struct envstring *new_envstring;
 215
 216                         opts += strlen(cp);
 217                         s = xmalloc(strlen(opts) + 1);
 218                         i = 0;
 219                         while (*opts) {
 220                                 if (*opts == '"')
 221                                         break;
 222                                 if (*opts == '\\' && opts[1] == '"') {
 223                                         opts += 2;
 224                                         s[i++] = '"';
 225                                         continue;
 226                                 }
 227                                 s[i++] = *opts++;
 228                         }
 229                         if (!*opts) {
 230                                 debug("%.100s, line %lu: missing end quote",
 231                                     file, linenum);
 232                                 auth_debug_add("%.100s, line %lu: missing end quote",
 233                                     file, linenum);
 234                                 free(s);
 235                                 goto bad_option;
 236                         }
 237                         s[i] = '\0';
 238                         opts++;
 239                         if (options.permit_user_env) {
 240                                 auth_debug_add("Adding to environment: "
 241                                     "%.900s", s);
 242                                 debug("Adding to environment: %.900s", s);
 243                                 new_envstring = xcalloc(1,
 244                                     sizeof(*new_envstring));
 245                                 new_envstring->s = s;
 246                                 new_envstring->next = custom_environment;
 247                                 custom_environment = new_envstring;
 248                                 s = NULL;
 249                         }
 250                         free(s);
 251                         goto next_option;
 252                 }
 253                 cp = "from=\"";
 254                 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
 255                         const char *remote_ip = get_remote_ipaddr();
 256                         const char *remote_host = get_canonical_hostname(
 257                             options.use_dns);
 258                         char *patterns = xmalloc(strlen(opts) + 1);
 259
 260                         opts += strlen(cp);
 261                         i = 0;
 262                         while (*opts) {
 263                                 if (*opts == '"')
 264                                         break;
 265                                 if (*opts == '\\' && opts[1] == '"') {
 266                                         opts += 2;
 267                                         patterns[i++] = '"';
 268                                         continue;
 269                                 }
 270                                 patterns[i++] = *opts++;
 271                         }
 272                         if (!*opts) {
 273                                 debug("%.100s, line %lu: missing end quote",
 274                                     file, linenum);
 275                                 auth_debug_add("%.100s, line %lu: missing end quote",
 276                                     file, linenum);
 277                                 free(patterns);
 278                                 goto bad_option;
 279                         }
 280                         patterns[i] = '\0';
 281                         opts++;
 282                         switch (match_host_and_ip(remote_host, remote_ip,
 283                             patterns)) {
 284                         case 1:
 285                                 free(patterns);
 286                                 /* Host name matches. */
 287                                 goto next_option;
 288                         case -1:
 289                                 debug("%.100s, line %lu: invalid criteria",
 290                                     file, linenum);
 291                                 auth_debug_add("%.100s, line %lu: "
 292                                     "invalid criteria", file, linenum);
 293                                 /* FALLTHROUGH */
 294                         case 0:
 295                                 free(patterns);
 296                                 logit("Authentication tried for %.100s with "
 297                                     "correct key but not from a permitted "
 298                                     "host (host=%.200s, ip=%.200s).",
 299                                     pw->pw_name, remote_host, remote_ip);
 300                                 auth_debug_add("Your host '%.200s' is not "
 301                                     "permitted to use this key for login.",
 302                                     remote_host);
 303                                 break;
 304                         }
 305                         /* deny access */
 306                         return 0;
 307                 }
 308                 cp = "permitopen=\"";
 309                 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
 310                         char *host, *p;
 311                         int port;
 312                         char *patterns = xmalloc(strlen(opts) + 1);
 313
 314                         opts += strlen(cp);
 315                         i = 0;
 316                         while (*opts) {
 317                                 if (*opts == '"')
 318                                         break;
 319                                 if (*opts == '\\' && opts[1] == '"') {
 320                                         opts += 2;
 321                                         patterns[i++] = '"';
 322                                         continue;
 323                                 }
 324                                 patterns[i++] = *opts++;
 325                         }
 326                         if (!*opts) {
 327                                 debug("%.100s, line %lu: missing end quote",
 328                                     file, linenum);
 329                                 auth_debug_add("%.100s, line %lu: missing "
 330                                     "end quote", file, linenum);
 331                                 free(patterns);
 332                                 goto bad_option;
 333                         }
 334                         patterns[i] = '\0';
 335                         opts++;
 336                         p = patterns;
 337                         /* XXX - add streamlocal support */
 338                         host = hpdelim(&p);
 339                         if (host == NULL || strlen(host) >= NI_MAXHOST) {
 340                                 debug("%.100s, line %lu: Bad permitopen "
 341                                     "specification <%.100s>", file, linenum,
 342                                     patterns);
 343                                 auth_debug_add("%.100s, line %lu: "
 344                                     "Bad permitopen specification", file,
 345                                     linenum);
 346                                 free(patterns);
 347                                 goto bad_option;
 348                         }
 349                         host = cleanhostname(host);
 350                         if (p == NULL || (port = permitopen_port(p)) < 0) {
 351                                 debug("%.100s, line %lu: Bad permitopen port "
 352                                     "<%.100s>", file, linenum, p ? p : "");
 353                                 auth_debug_add("%.100s, line %lu: "
 354                                     "Bad permitopen port", file, linenum);
 355                                 free(patterns);
 356                                 goto bad_option;
 357                         }
 358                         if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0)
 359                                 channel_add_permitted_opens(host, port);
 360                         free(patterns);
 361                         goto next_option;
 362                 }
 363                 cp = "tunnel=\"";
 364                 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
 365                         char *tun = NULL;
 366                         opts += strlen(cp);
 367                         tun = xmalloc(strlen(opts) + 1);
 368                         i = 0;
 369                         while (*opts) {
 370                                 if (*opts == '"')
 371                                         break;
 372                                 tun[i++] = *opts++;
 373                         }
 374                         if (!*opts) {
 375                                 debug("%.100s, line %lu: missing end quote",
 376                                     file, linenum);
 377                                 auth_debug_add("%.100s, line %lu: missing end quote",
 378                                     file, linenum);
 379                                 free(tun);
 380                                 forced_tun_device = -1;
 381                                 goto bad_option;
 382                         }
 383                         tun[i] = '\0';
 384                         forced_tun_device = a2tun(tun, NULL);
 385                         free(tun);
 386                         if (forced_tun_device == SSH_TUNID_ERR) {
 387                                 debug("%.100s, line %lu: invalid tun device",
 388                                     file, linenum);
 389                                 auth_debug_add("%.100s, line %lu: invalid tun device",
 390                                     file, linenum);
 391                                 forced_tun_device = -1;
 392                                 goto bad_option;
 393                         }
 394                         auth_debug_add("Forced tun device: %d", forced_tun_device);
 395                         opts++;
 396                         goto next_option;
 397                 }
 398 next_option:
 399                 /*
 400                  * Skip the comma, and move to the next option
 401                  * (or break out if there are no more).
 402                  */
 403                 if (!*opts)
 404                         fatal("Bugs in auth-options.c option processing.");
 405                 if (*opts == ' ' || *opts == '\t')
 406                         break;          /* End of options. */
 407                 if (*opts != ',')
 408                         goto bad_option;
 409                 opts++;
 410                 /* Process the next option. */
 411         }
 412
 413         /* grant access */
 414         return 1;
 415
 416 bad_option:
 417         logit("Bad options in %.100s file, line %lu: %.50s",
 418             file, linenum, opts);
 419         auth_debug_add("Bad options in %.100s file, line %lu: %.50s",
 420             file, linenum, opts);
 421
 422         /* deny access */
 423         return 0;
 424 }
 425
 426 #define OPTIONS_CRITICAL        1
 427 #define OPTIONS_EXTENSIONS      2
 428 static int
 429 parse_option_list(struct sshbuf *oblob, struct passwd *pw,
 430     u_int which, int crit,
 431     int *cert_no_port_forwarding_flag,
 432     int *cert_no_agent_forwarding_flag,
 433     int *cert_no_x11_forwarding_flag,
 434     int *cert_no_pty_flag,
 435     int *cert_no_user_rc,
 436     char **cert_forced_command,
 437     int *cert_source_address_done)
 438 {
 439         char *command, *allowed;
 440         const char *remote_ip;
 441         char *name = NULL;
 442         struct sshbuf *c = NULL, *data = NULL;
 443         int r, ret = -1, result, found;
 444
 445         if ((c = sshbuf_fromb(oblob)) == NULL) {
 446                 error("%s: sshbuf_fromb failed", __func__);
 447                 goto out;
 448         }
 449
 450         while (sshbuf_len(c) > 0) {
 451                 sshbuf_free(data);
 452                 data = NULL;
 453                 if ((r = sshbuf_get_cstring(c, &name, NULL)) != 0 ||
 454                     (r = sshbuf_froms(c, &data)) != 0) {
 455                         error("Unable to parse certificate options: %s",
 456                             ssh_err(r));
 457                         goto out;
 458                 }
 459                 debug3("found certificate option \"%.100s\" len %zu",
 460                     name, sshbuf_len(data));
 461                 found = 0;
 462                 if ((which & OPTIONS_EXTENSIONS) != 0) {
 463                         if (strcmp(name, "permit-X11-forwarding") == 0) {
 464                                 *cert_no_x11_forwarding_flag = 0;
 465                                 found = 1;
 466                         } else if (strcmp(name,
 467                             "permit-agent-forwarding") == 0) {
 468                                 *cert_no_agent_forwarding_flag = 0;
 469                                 found = 1;
 470                         } else if (strcmp(name,
 471                             "permit-port-forwarding") == 0) {
 472                                 *cert_no_port_forwarding_flag = 0;
 473                                 found = 1;
 474                         } else if (strcmp(name, "permit-pty") == 0) {
 475                                 *cert_no_pty_flag = 0;
 476                                 found = 1;
 477                         } else if (strcmp(name, "permit-user-rc") == 0) {
 478                                 *cert_no_user_rc = 0;
 479                                 found = 1;
 480                         }
 481                 }
 482                 if (!found && (which & OPTIONS_CRITICAL) != 0) {
 483                         if (strcmp(name, "force-command") == 0) {
 484                                 if ((r = sshbuf_get_cstring(data, &command,
 485                                     NULL)) != 0) {
 486                                         error("Unable to parse \"%s\" "
 487                                             "section: %s", name, ssh_err(r));
 488                                         goto out;
 489                                 }
 490                                 if (*cert_forced_command != NULL) {
 491                                         error("Certificate has multiple "
 492                                             "force-command options");
 493                                         free(command);
 494                                         goto out;
 495                                 }
 496                                 *cert_forced_command = command;
 497                                 found = 1;
 498                         }
 499                         if (strcmp(name, "source-address") == 0) {
 500                                 if ((r = sshbuf_get_cstring(data, &allowed,
 501                                     NULL)) != 0) {
 502                                         error("Unable to parse \"%s\" "
 503                                             "section: %s", name, ssh_err(r));
 504                                         goto out;
 505                                 }
 506                                 if ((*cert_source_address_done)++) {
 507                                         error("Certificate has multiple "
 508                                             "source-address options");
 509                                         free(allowed);
 510                                         goto out;
 511                                 }
 512                                 remote_ip = get_remote_ipaddr();
 513                                 result = addr_match_cidr_list(remote_ip,
 514                                     allowed);
 515                                 free(allowed);
 516                                 switch (result) {
 517                                 case 1:
 518                                         /* accepted */
 519                                         break;
 520                                 case 0:
 521                                         /* no match */
 522                                         logit("Authentication tried for %.100s "
 523                                             "with valid certificate but not "
 524                                             "from a permitted host "
 525                                             "(ip=%.200s).", pw->pw_name,
 526                                             remote_ip);
 527                                         auth_debug_add("Your address '%.200s' "
 528                                             "is not permitted to use this "
 529                                             "certificate for login.",
 530                                             remote_ip);
 531                                         goto out;
 532                                 case -1:
 533                                 default:
 534                                         error("Certificate source-address "
 535                                             "contents invalid");
 536                                         goto out;
 537                                 }
 538                                 found = 1;
 539                         }
 540                 }
 541
 542                 if (!found) {
 543                         if (crit) {
 544                                 error("Certificate critical option \"%s\" "
 545                                     "is not supported", name);
 546                                 goto out;
 547                         } else {
 548                                 logit("Certificate extension \"%s\" "
 549                                     "is not supported", name);
 550                         }
 551                 } else if (sshbuf_len(data) != 0) {
 552                         error("Certificate option \"%s\" corrupt "
 553                             "(extra data)", name);
 554                         goto out;
 555                 }
 556                 free(name);
 557                 name = NULL;
 558         }
 559         /* successfully parsed all options */
 560         ret = 0;
 561
 562  out:
 563         if (ret != 0 &&
 564             cert_forced_command != NULL &&
 565             *cert_forced_command != NULL) {
 566                 free(*cert_forced_command);
 567                 *cert_forced_command = NULL;
 568         }
 569         if (name != NULL)
 570                 free(name);
 571         sshbuf_free(data);
 572         sshbuf_free(c);
 573         return ret;
 574 }
 575
 576 /*
 577  * Set options from critical certificate options. These supersede user key
 578  * options so this must be called after auth_parse_options().
 579  */
 580 int
 581 auth_cert_options(struct sshkey *k, struct passwd *pw)
 582 {
 583         int cert_no_port_forwarding_flag = 1;
 584         int cert_no_agent_forwarding_flag = 1;
 585         int cert_no_x11_forwarding_flag = 1;
 586         int cert_no_pty_flag = 1;
 587         int cert_no_user_rc = 1;
 588         char *cert_forced_command = NULL;
 589         int cert_source_address_done = 0;
 590
 591         /* Separate options and extensions for v01 certs */
 592         if (parse_option_list(k->cert->critical, pw,
 593             OPTIONS_CRITICAL, 1, NULL, NULL, NULL, NULL, NULL,
 594             &cert_forced_command,
 595             &cert_source_address_done) == -1)
 596                 return -1;
 597         if (parse_option_list(k->cert->extensions, pw,
 598             OPTIONS_EXTENSIONS, 0,
 599             &cert_no_port_forwarding_flag,
 600             &cert_no_agent_forwarding_flag,
 601             &cert_no_x11_forwarding_flag,
 602             &cert_no_pty_flag,
 603             &cert_no_user_rc,
 604             NULL, NULL) == -1)
 605                 return -1;
 606
 607         no_port_forwarding_flag |= cert_no_port_forwarding_flag;
 608         no_agent_forwarding_flag |= cert_no_agent_forwarding_flag;
 609         no_x11_forwarding_flag |= cert_no_x11_forwarding_flag;
 610         no_pty_flag |= cert_no_pty_flag;
 611         no_user_rc |= cert_no_user_rc;
 612         /* CA-specified forced command supersedes key option */
 613         if (cert_forced_command != NULL) {
 614                 if (forced_command != NULL)
 615                         free(forced_command);
 616                 forced_command = cert_forced_command;
 617         }
 618         return 0;
 619 }
 620