auth-options.c

   1 /* $OpenBSD: auth-options.c,v 1.48 2010/03/07 11:57:13 dtucker 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 "auth-options.h"
  31 #include "servconf.h"
  32 #include "misc.h"
  33 #include "key.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 extern ServerOptions options;
  59
  60 void
  61 auth_clear_options(void)
  62 {
  63         no_agent_forwarding_flag = 0;
  64         no_port_forwarding_flag = 0;
  65         no_pty_flag = 0;
  66         no_x11_forwarding_flag = 0;
  67         no_user_rc = 0;
  68         key_is_cert_authority = 0;
  69         while (custom_environment) {
  70                 struct envstring *ce = custom_environment;
  71                 custom_environment = ce->next;
  72                 xfree(ce->s);
  73                 xfree(ce);
  74         }
  75         if (forced_command) {
  76                 xfree(forced_command);
  77                 forced_command = NULL;
  78         }
  79         forced_tun_device = -1;
  80         channel_clear_permitted_opens();
  81 }
  82
  83 /*
  84  * return 1 if access is granted, 0 if not.
  85  * side effect: sets key option flags
  86  */
  87 int
  88 auth_parse_options(struct passwd *pw, char *opts, char *file, u_long linenum)
  89 {
  90         const char *cp;
  91         int i;
  92
  93         /* reset options */
  94         auth_clear_options();
  95
  96         if (!opts)
  97                 return 1;
  98
  99         while (*opts && *opts != ' ' && *opts != '\t') {
 100                 cp = "cert-authority";
 101                 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
 102                         key_is_cert_authority = 1;
 103                         opts += strlen(cp);
 104                         goto next_option;
 105                 }
 106                 cp = "no-port-forwarding";
 107                 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
 108                         auth_debug_add("Port forwarding disabled.");
 109                         no_port_forwarding_flag = 1;
 110                         opts += strlen(cp);
 111                         goto next_option;
 112                 }
 113                 cp = "no-agent-forwarding";
 114                 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
 115                         auth_debug_add("Agent forwarding disabled.");
 116                         no_agent_forwarding_flag = 1;
 117                         opts += strlen(cp);
 118                         goto next_option;
 119                 }
 120                 cp = "no-X11-forwarding";
 121                 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
 122                         auth_debug_add("X11 forwarding disabled.");
 123                         no_x11_forwarding_flag = 1;
 124                         opts += strlen(cp);
 125                         goto next_option;
 126                 }
 127                 cp = "no-pty";
 128                 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
 129                         auth_debug_add("Pty allocation disabled.");
 130                         no_pty_flag = 1;
 131                         opts += strlen(cp);
 132                         goto next_option;
 133                 }
 134                 cp = "no-user-rc";
 135                 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
 136                         auth_debug_add("User rc file execution disabled.");
 137                         no_user_rc = 1;
 138                         opts += strlen(cp);
 139                         goto next_option;
 140                 }
 141                 cp = "command=\"";
 142                 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
 143                         opts += strlen(cp);
 144                         forced_command = xmalloc(strlen(opts) + 1);
 145                         i = 0;
 146                         while (*opts) {
 147                                 if (*opts == '"')
 148                                         break;
 149                                 if (*opts == '\\' && opts[1] == '"') {
 150                                         opts += 2;
 151                                         forced_command[i++] = '"';
 152                                         continue;
 153                                 }
 154                                 forced_command[i++] = *opts++;
 155                         }
 156                         if (!*opts) {
 157                                 debug("%.100s, line %lu: missing end quote",
 158                                     file, linenum);
 159                                 auth_debug_add("%.100s, line %lu: missing end quote",
 160                                     file, linenum);
 161                                 xfree(forced_command);
 162                                 forced_command = NULL;
 163                                 goto bad_option;
 164                         }
 165                         forced_command[i] = '\0';
 166                         auth_debug_add("Forced command: %.900s", forced_command);
 167                         opts++;
 168                         goto next_option;
 169                 }
 170                 cp = "environment=\"";
 171                 if (options.permit_user_env &&
 172                     strncasecmp(opts, cp, strlen(cp)) == 0) {
 173                         char *s;
 174                         struct envstring *new_envstring;
 175
 176                         opts += strlen(cp);
 177                         s = xmalloc(strlen(opts) + 1);
 178                         i = 0;
 179                         while (*opts) {
 180                                 if (*opts == '"')
 181                                         break;
 182                                 if (*opts == '\\' && opts[1] == '"') {
 183                                         opts += 2;
 184                                         s[i++] = '"';
 185                                         continue;
 186                                 }
 187                                 s[i++] = *opts++;
 188                         }
 189                         if (!*opts) {
 190                                 debug("%.100s, line %lu: missing end quote",
 191                                     file, linenum);
 192                                 auth_debug_add("%.100s, line %lu: missing end quote",
 193                                     file, linenum);
 194                                 xfree(s);
 195                                 goto bad_option;
 196                         }
 197                         s[i] = '\0';
 198                         auth_debug_add("Adding to environment: %.900s", s);
 199                         debug("Adding to environment: %.900s", s);
 200                         opts++;
 201                         new_envstring = xmalloc(sizeof(struct envstring));
 202                         new_envstring->s = s;
 203                         new_envstring->next = custom_environment;
 204                         custom_environment = new_envstring;
 205                         goto next_option;
 206                 }
 207                 cp = "from=\"";
 208                 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
 209                         const char *remote_ip = get_remote_ipaddr();
 210                         const char *remote_host = get_canonical_hostname(
 211                             options.use_dns);
 212                         char *patterns = xmalloc(strlen(opts) + 1);
 213
 214                         opts += strlen(cp);
 215                         i = 0;
 216                         while (*opts) {
 217                                 if (*opts == '"')
 218                                         break;
 219                                 if (*opts == '\\' && opts[1] == '"') {
 220                                         opts += 2;
 221                                         patterns[i++] = '"';
 222                                         continue;
 223                                 }
 224                                 patterns[i++] = *opts++;
 225                         }
 226                         if (!*opts) {
 227                                 debug("%.100s, line %lu: missing end quote",
 228                                     file, linenum);
 229                                 auth_debug_add("%.100s, line %lu: missing end quote",
 230                                     file, linenum);
 231                                 xfree(patterns);
 232                                 goto bad_option;
 233                         }
 234                         patterns[i] = '\0';
 235                         opts++;
 236                         switch (match_host_and_ip(remote_host, remote_ip,
 237                             patterns)) {
 238                         case 1:
 239                                 xfree(patterns);
 240                                 /* Host name matches. */
 241                                 goto next_option;
 242                         case -1:
 243                                 debug("%.100s, line %lu: invalid criteria",
 244                                     file, linenum);
 245                                 auth_debug_add("%.100s, line %lu: "
 246                                     "invalid criteria", file, linenum);
 247                                 /* FALLTHROUGH */
 248                         case 0:
 249                                 xfree(patterns);
 250                                 logit("Authentication tried for %.100s with "
 251                                     "correct key but not from a permitted "
 252                                     "host (host=%.200s, ip=%.200s).",
 253                                     pw->pw_name, remote_host, remote_ip);
 254                                 auth_debug_add("Your host '%.200s' is not "
 255                                     "permitted to use this key for login.",
 256                                     remote_host);
 257                                 break;
 258                         }
 259                         /* deny access */
 260                         return 0;
 261                 }
 262                 cp = "permitopen=\"";
 263                 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
 264                         char *host, *p;
 265                         int port;
 266                         char *patterns = xmalloc(strlen(opts) + 1);
 267
 268                         opts += strlen(cp);
 269                         i = 0;
 270                         while (*opts) {
 271                                 if (*opts == '"')
 272                                         break;
 273                                 if (*opts == '\\' && opts[1] == '"') {
 274                                         opts += 2;
 275                                         patterns[i++] = '"';
 276                                         continue;
 277                                 }
 278                                 patterns[i++] = *opts++;
 279                         }
 280                         if (!*opts) {
 281                                 debug("%.100s, line %lu: missing end quote",
 282                                     file, linenum);
 283                                 auth_debug_add("%.100s, line %lu: missing "
 284                                     "end quote", file, linenum);
 285                                 xfree(patterns);
 286                                 goto bad_option;
 287                         }
 288                         patterns[i] = '\0';
 289                         opts++;
 290                         p = patterns;
 291                         host = hpdelim(&p);
 292                         if (host == NULL || strlen(host) >= NI_MAXHOST) {
 293                                 debug("%.100s, line %lu: Bad permitopen "
 294                                     "specification <%.100s>", file, linenum,
 295                                     patterns);
 296                                 auth_debug_add("%.100s, line %lu: "
 297                                     "Bad permitopen specification", file,
 298                                     linenum);
 299                                 xfree(patterns);
 300                                 goto bad_option;
 301                         }
 302                         host = cleanhostname(host);
 303                         if (p == NULL || (port = a2port(p)) <= 0) {
 304                                 debug("%.100s, line %lu: Bad permitopen port "
 305                                     "<%.100s>", file, linenum, p ? p : "");
 306                                 auth_debug_add("%.100s, line %lu: "
 307                                     "Bad permitopen port", file, linenum);
 308                                 xfree(patterns);
 309                                 goto bad_option;
 310                         }
 311                         if (options.allow_tcp_forwarding)
 312                                 channel_add_permitted_opens(host, port);
 313                         xfree(patterns);
 314                         goto next_option;
 315                 }
 316                 cp = "tunnel=\"";
 317                 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
 318                         char *tun = NULL;
 319                         opts += strlen(cp);
 320                         tun = xmalloc(strlen(opts) + 1);
 321                         i = 0;
 322                         while (*opts) {
 323                                 if (*opts == '"')
 324                                         break;
 325                                 tun[i++] = *opts++;
 326                         }
 327                         if (!*opts) {
 328                                 debug("%.100s, line %lu: missing end quote",
 329                                     file, linenum);
 330                                 auth_debug_add("%.100s, line %lu: missing end quote",
 331                                     file, linenum);
 332                                 xfree(tun);
 333                                 forced_tun_device = -1;
 334                                 goto bad_option;
 335                         }
 336                         tun[i] = '\0';
 337                         forced_tun_device = a2tun(tun, NULL);
 338                         xfree(tun);
 339                         if (forced_tun_device == SSH_TUNID_ERR) {
 340                                 debug("%.100s, line %lu: invalid tun device",
 341                                     file, linenum);
 342                                 auth_debug_add("%.100s, line %lu: invalid tun device",
 343                                     file, linenum);
 344                                 forced_tun_device = -1;
 345                                 goto bad_option;
 346                         }
 347                         auth_debug_add("Forced tun device: %d", forced_tun_device);
 348                         opts++;
 349                         goto next_option;
 350                 }
 351 next_option:
 352                 /*
 353                  * Skip the comma, and move to the next option
 354                  * (or break out if there are no more).
 355                  */
 356                 if (!*opts)
 357                         fatal("Bugs in auth-options.c option processing.");
 358                 if (*opts == ' ' || *opts == '\t')
 359                         break;          /* End of options. */
 360                 if (*opts != ',')
 361                         goto bad_option;
 362                 opts++;
 363                 /* Process the next option. */
 364         }
 365
 366         /* grant access */
 367         return 1;
 368
 369 bad_option:
 370         logit("Bad options in %.100s file, line %lu: %.50s",
 371             file, linenum, opts);
 372         auth_debug_add("Bad options in %.100s file, line %lu: %.50s",
 373             file, linenum, opts);
 374
 375         /* deny access */
 376         return 0;
 377 }
 378
 379 /*
 380  * Set options from certificate constraints. These supersede user key options
 381  * so this must be called after auth_parse_options().
 382  */
 383 int
 384 auth_cert_constraints(Buffer *c_orig, struct passwd *pw)
 385 {
 386         u_char *name = NULL, *data_blob = NULL;
 387         u_int nlen, dlen, clen;
 388         Buffer c, data;
 389         int ret = -1;
 390
 391         int cert_no_port_forwarding_flag = 1;
 392         int cert_no_agent_forwarding_flag = 1;
 393         int cert_no_x11_forwarding_flag = 1;
 394         int cert_no_pty_flag = 1;
 395         int cert_no_user_rc = 1;
 396         char *cert_forced_command = NULL;
 397         int cert_source_address_done = 0;
 398
 399         buffer_init(&data);
 400
 401         /* Make copy to avoid altering original */
 402         buffer_init(&c);
 403         buffer_append(&c, buffer_ptr(c_orig), buffer_len(c_orig));
 404
 405         while (buffer_len(&c) > 0) {
 406                 if ((name = buffer_get_string_ret(&c, &nlen)) == NULL ||
 407                     (data_blob = buffer_get_string_ret(&c, &dlen)) == NULL) {
 408                         error("Certificate constraints corrupt");
 409                         goto out;
 410                 }
 411                 buffer_append(&data, data_blob, dlen);
 412                 debug3("found certificate constraint \"%.100s\" len %u",
 413                     name, dlen);
 414                 if (strlen(name) != nlen) {
 415                         error("Certificate constraint name contains \\0");
 416                         goto out;
 417                 }
 418                 if (strcmp(name, "permit-X11-forwarding") == 0)
 419                         cert_no_x11_forwarding_flag = 0;
 420                 else if (strcmp(name, "permit-agent-forwarding") == 0)
 421                         cert_no_agent_forwarding_flag = 0;
 422                 else if (strcmp(name, "permit-port-forwarding") == 0)
 423                         cert_no_port_forwarding_flag = 0;
 424                 else if (strcmp(name, "permit-pty") == 0)
 425                         cert_no_pty_flag = 0;
 426                 else if (strcmp(name, "permit-user-rc") == 0)
 427                         cert_no_user_rc = 0;
 428                 else if (strcmp(name, "force-command") == 0) {
 429                         char *command = buffer_get_string_ret(&data, &clen);
 430
 431                         if (command == NULL) {
 432                                 error("Certificate constraint \"%s\" corrupt",
 433                                     name);
 434                                 goto out;
 435                         }
 436                         if (strlen(command) != clen) {
 437                                 error("force-command constrain contains \\0");
 438                                 goto out;
 439                         }
 440                         if (cert_forced_command != NULL) {
 441                                 error("Certificate has multiple "
 442                                     "force-command constraints");
 443                                 xfree(command);
 444                                 goto out;
 445                         }
 446                         cert_forced_command = command;
 447                 } else if (strcmp(name, "source-address") == 0) {
 448                         char *allowed = buffer_get_string_ret(&data, &clen);
 449                         const char *remote_ip = get_remote_ipaddr();
 450
 451                         if (allowed == NULL) {
 452                                 error("Certificate constraint \"%s\" corrupt",
 453                                     name);
 454                                 goto out;
 455                         }
 456                         if (strlen(allowed) != clen) {
 457                                 error("source-address constrain contains \\0");
 458                                 goto out;
 459                         }
 460                         if (cert_source_address_done++) {
 461                                 error("Certificate has multiple "
 462                                     "source-address constraints");
 463                                 xfree(allowed);
 464                                 goto out;
 465                         }
 466                         switch (addr_match_cidr_list(remote_ip, allowed)) {
 467                         case 1:
 468                                 /* accepted */
 469                                 xfree(allowed);
 470                                 break;
 471                         case 0:
 472                                 /* no match */
 473                                 logit("Authentication tried for %.100s with "
 474                                     "valid certificate but not from a "
 475                                     "permitted host (ip=%.200s).",
 476                                     pw->pw_name, remote_ip);
 477                                 auth_debug_add("Your address '%.200s' is not "
 478                                     "permitted to use this certificate for "
 479                                     "login.", remote_ip);
 480                                 xfree(allowed);
 481                                 goto out;
 482                         case -1:
 483                                 error("Certificate source-address contents "
 484                                     "invalid");
 485                                 xfree(allowed);
 486                                 goto out;
 487                         }
 488                 } else {
 489                         error("Certificate constraint \"%s\" is not supported",
 490                             name);
 491                         goto out;
 492                 }
 493
 494                 if (buffer_len(&data) != 0) {
 495                         error("Certificate constraint \"%s\" corrupt "
 496                             "(extra data)", name);
 497                         goto out;
 498                 }
 499                 buffer_clear(&data);
 500                 xfree(name);
 501                 xfree(data_blob);
 502                 name = data_blob = NULL;
 503         }
 504
 505         /* successfully parsed all constraints */
 506         ret = 0;
 507
 508         no_port_forwarding_flag |= cert_no_port_forwarding_flag;
 509         no_agent_forwarding_flag |= cert_no_agent_forwarding_flag;
 510         no_x11_forwarding_flag |= cert_no_x11_forwarding_flag;
 511         no_pty_flag |= cert_no_pty_flag;
 512         no_user_rc |= cert_no_user_rc;
 513         /* CA-specified forced command supersedes key option */
 514         if (cert_forced_command != NULL) {
 515                 if (forced_command != NULL)
 516                         xfree(forced_command);
 517                 forced_command = cert_forced_command;
 518         }
 519
 520  out:
 521         if (name != NULL)
 522                 xfree(name);
 523         if (data_blob != NULL)
 524                 xfree(data_blob);
 525         buffer_free(&data);
 526         buffer_free(&c);
 527         return ret;
 528 }
 529