Emeric Vigier | 2f62582 | 2012-08-06 11:09:52 -0400 | [diff] [blame] | 1 | /* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- |
| 2 | * selinux.c SELinux security checks for D-Bus |
| 3 | * |
| 4 | * Author: Matthew Rickard <mjricka@epoch.ncsc.mil> |
| 5 | * |
| 6 | * Licensed under the Academic Free License version 2.1 |
| 7 | * |
| 8 | * This program is free software; you can redistribute it and/or modify |
| 9 | * it under the terms of the GNU General Public License as published by |
| 10 | * the Free Software Foundation; either version 2 of the License, or |
| 11 | * (at your option) any later version. |
| 12 | * |
| 13 | * This program is distributed in the hope that it will be useful, |
| 14 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 15 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 16 | * GNU General Public License for more details. |
| 17 | * |
| 18 | * You should have received a copy of the GNU General Public License |
| 19 | * along with this program; if not, write to the Free Software |
| 20 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
| 21 | * |
| 22 | */ |
| 23 | |
| 24 | #include <config.h> |
| 25 | #include <dbus/dbus-internals.h> |
| 26 | #include <dbus/dbus-string.h> |
| 27 | #ifndef DBUS_WIN |
| 28 | #include <dbus/dbus-userdb.h> |
| 29 | #endif |
| 30 | #include "selinux.h" |
| 31 | #include "services.h" |
| 32 | #include "policy.h" |
| 33 | #include "utils.h" |
| 34 | #include "config-parser.h" |
| 35 | |
| 36 | #ifdef HAVE_ERRNO_H |
| 37 | #include <errno.h> |
| 38 | #endif |
| 39 | #ifdef HAVE_SELINUX |
| 40 | #include <sys/types.h> |
| 41 | #include <unistd.h> |
| 42 | #include <limits.h> |
| 43 | #include <pthread.h> |
| 44 | #include <syslog.h> |
| 45 | #include <selinux/selinux.h> |
| 46 | #include <selinux/avc.h> |
| 47 | #include <selinux/av_permissions.h> |
| 48 | #include <selinux/flask.h> |
| 49 | #include <signal.h> |
| 50 | #include <stdarg.h> |
| 51 | #include <stdio.h> |
| 52 | #include <grp.h> |
| 53 | #endif /* HAVE_SELINUX */ |
| 54 | #ifdef HAVE_LIBAUDIT |
| 55 | #include <cap-ng.h> |
| 56 | #include <libaudit.h> |
| 57 | #endif /* HAVE_LIBAUDIT */ |
| 58 | |
| 59 | #define BUS_SID_FROM_SELINUX(sid) ((BusSELinuxID*) (sid)) |
| 60 | #define SELINUX_SID_FROM_BUS(sid) ((security_id_t) (sid)) |
| 61 | |
| 62 | #ifdef HAVE_SELINUX |
| 63 | /* Store the value telling us if SELinux is enabled in the kernel. */ |
| 64 | static dbus_bool_t selinux_enabled = FALSE; |
| 65 | |
| 66 | /* Store an avc_entry_ref to speed AVC decisions. */ |
| 67 | static struct avc_entry_ref aeref; |
| 68 | |
| 69 | /* Store the SID of the bus itself to use as the default. */ |
| 70 | static security_id_t bus_sid = SECSID_WILD; |
| 71 | |
| 72 | /* Thread to listen for SELinux status changes via netlink. */ |
| 73 | static pthread_t avc_notify_thread; |
| 74 | |
| 75 | /* Prototypes for AVC callback functions. */ |
| 76 | static void log_callback (const char *fmt, ...); |
| 77 | static void log_audit_callback (void *data, security_class_t class, char *buf, size_t bufleft); |
| 78 | static void *avc_create_thread (void (*run) (void)); |
| 79 | static void avc_stop_thread (void *thread); |
| 80 | static void *avc_alloc_lock (void); |
| 81 | static void avc_get_lock (void *lock); |
| 82 | static void avc_release_lock (void *lock); |
| 83 | static void avc_free_lock (void *lock); |
| 84 | |
| 85 | /* AVC callback structures for use in avc_init. */ |
| 86 | static const struct avc_memory_callback mem_cb = |
| 87 | { |
| 88 | .func_malloc = dbus_malloc, |
| 89 | .func_free = dbus_free |
| 90 | }; |
| 91 | static const struct avc_log_callback log_cb = |
| 92 | { |
| 93 | .func_log = log_callback, |
| 94 | .func_audit = log_audit_callback |
| 95 | }; |
| 96 | static const struct avc_thread_callback thread_cb = |
| 97 | { |
| 98 | .func_create_thread = avc_create_thread, |
| 99 | .func_stop_thread = avc_stop_thread |
| 100 | }; |
| 101 | static const struct avc_lock_callback lock_cb = |
| 102 | { |
| 103 | .func_alloc_lock = avc_alloc_lock, |
| 104 | .func_get_lock = avc_get_lock, |
| 105 | .func_release_lock = avc_release_lock, |
| 106 | .func_free_lock = avc_free_lock |
| 107 | }; |
| 108 | #endif /* HAVE_SELINUX */ |
| 109 | |
| 110 | /** |
| 111 | * Log callback to log denial messages from the AVC. |
| 112 | * This is used in avc_init. Logs to both standard |
| 113 | * error and syslogd. |
| 114 | * |
| 115 | * @param fmt the format string |
| 116 | * @param variable argument list |
| 117 | */ |
| 118 | #ifdef HAVE_SELINUX |
| 119 | |
| 120 | #ifdef HAVE_LIBAUDIT |
| 121 | static int audit_fd = -1; |
| 122 | #endif |
| 123 | |
| 124 | void |
| 125 | bus_selinux_audit_init(void) |
| 126 | { |
| 127 | #ifdef HAVE_LIBAUDIT |
| 128 | audit_fd = audit_open (); |
| 129 | |
| 130 | if (audit_fd < 0) |
| 131 | { |
| 132 | /* If kernel doesn't support audit, bail out */ |
| 133 | if (errno == EINVAL || errno == EPROTONOSUPPORT || errno == EAFNOSUPPORT) |
| 134 | return; |
| 135 | /* If user bus, bail out */ |
| 136 | if (errno == EPERM && getuid() != 0) |
| 137 | return; |
| 138 | _dbus_warn ("Failed opening connection to the audit subsystem"); |
| 139 | } |
| 140 | #endif /* HAVE_LIBAUDIT */ |
| 141 | } |
| 142 | |
| 143 | static void |
| 144 | log_callback (const char *fmt, ...) |
| 145 | { |
| 146 | va_list ap; |
| 147 | |
| 148 | va_start(ap, fmt); |
| 149 | |
| 150 | #ifdef HAVE_LIBAUDIT |
| 151 | if (audit_fd >= 0) |
| 152 | { |
| 153 | capng_get_caps_process(); |
| 154 | if (capng_have_capability(CAPNG_EFFECTIVE, CAP_AUDIT_WRITE)) |
| 155 | { |
| 156 | char buf[PATH_MAX*2]; |
| 157 | |
| 158 | /* FIXME: need to change this to show real user */ |
| 159 | vsnprintf(buf, sizeof(buf), fmt, ap); |
| 160 | audit_log_user_avc_message(audit_fd, AUDIT_USER_AVC, buf, NULL, NULL, |
| 161 | NULL, getuid()); |
| 162 | return; |
| 163 | } |
| 164 | } |
| 165 | #endif /* HAVE_LIBAUDIT */ |
| 166 | |
| 167 | vsyslog (LOG_INFO, fmt, ap); |
| 168 | va_end(ap); |
| 169 | } |
| 170 | |
| 171 | /** |
| 172 | * On a policy reload we need to reparse the SELinux configuration file, since |
| 173 | * this could have changed. Send a SIGHUP to reload all configs. |
| 174 | */ |
| 175 | static int |
| 176 | policy_reload_callback (u_int32_t event, security_id_t ssid, |
| 177 | security_id_t tsid, security_class_t tclass, |
| 178 | access_vector_t perms, access_vector_t *out_retained) |
| 179 | { |
| 180 | if (event == AVC_CALLBACK_RESET) |
| 181 | return raise (SIGHUP); |
| 182 | |
| 183 | return 0; |
| 184 | } |
| 185 | |
| 186 | /** |
| 187 | * Log any auxiliary data |
| 188 | */ |
| 189 | static void |
| 190 | log_audit_callback (void *data, security_class_t class, char *buf, size_t bufleft) |
| 191 | { |
| 192 | DBusString *audmsg = data; |
| 193 | |
| 194 | if (bufleft > (size_t) _dbus_string_get_length(audmsg)) |
| 195 | { |
| 196 | _dbus_string_copy_to_buffer_with_nul (audmsg, buf, bufleft); |
| 197 | } |
| 198 | else |
| 199 | { |
| 200 | DBusString s; |
| 201 | |
| 202 | _dbus_string_init_const(&s, "Buffer too small for audit message"); |
| 203 | |
| 204 | if (bufleft > (size_t) _dbus_string_get_length(&s)) |
| 205 | _dbus_string_copy_to_buffer_with_nul (&s, buf, bufleft); |
| 206 | } |
| 207 | } |
| 208 | |
| 209 | /** |
| 210 | * Create thread to notify the AVC of enforcing and policy reload |
| 211 | * changes via netlink. |
| 212 | * |
| 213 | * @param run the thread run function |
| 214 | * @return pointer to the thread |
| 215 | */ |
| 216 | static void * |
| 217 | avc_create_thread (void (*run) (void)) |
| 218 | { |
| 219 | int rc; |
| 220 | |
| 221 | rc = pthread_create (&avc_notify_thread, NULL, (void *(*) (void *)) run, NULL); |
| 222 | if (rc != 0) |
| 223 | { |
| 224 | _dbus_warn ("Failed to start AVC thread: %s\n", _dbus_strerror (rc)); |
| 225 | exit (1); |
| 226 | } |
| 227 | return &avc_notify_thread; |
| 228 | } |
| 229 | |
| 230 | /* Stop AVC netlink thread. */ |
| 231 | static void |
| 232 | avc_stop_thread (void *thread) |
| 233 | { |
| 234 | pthread_cancel (*(pthread_t *) thread); |
| 235 | } |
| 236 | |
| 237 | /* Allocate a new AVC lock. */ |
| 238 | static void * |
| 239 | avc_alloc_lock (void) |
| 240 | { |
| 241 | pthread_mutex_t *avc_mutex; |
| 242 | |
| 243 | avc_mutex = dbus_new (pthread_mutex_t, 1); |
| 244 | if (avc_mutex == NULL) |
| 245 | { |
| 246 | _dbus_warn ("Could not create mutex: %s\n", _dbus_strerror (errno)); |
| 247 | exit (1); |
| 248 | } |
| 249 | pthread_mutex_init (avc_mutex, NULL); |
| 250 | |
| 251 | return avc_mutex; |
| 252 | } |
| 253 | |
| 254 | /* Acquire an AVC lock. */ |
| 255 | static void |
| 256 | avc_get_lock (void *lock) |
| 257 | { |
| 258 | pthread_mutex_lock (lock); |
| 259 | } |
| 260 | |
| 261 | /* Release an AVC lock. */ |
| 262 | static void |
| 263 | avc_release_lock (void *lock) |
| 264 | { |
| 265 | pthread_mutex_unlock (lock); |
| 266 | } |
| 267 | |
| 268 | /* Free an AVC lock. */ |
| 269 | static void |
| 270 | avc_free_lock (void *lock) |
| 271 | { |
| 272 | pthread_mutex_destroy (lock); |
| 273 | dbus_free (lock); |
| 274 | } |
| 275 | #endif /* HAVE_SELINUX */ |
| 276 | |
| 277 | /** |
| 278 | * Return whether or not SELinux is enabled; must be |
| 279 | * called after bus_selinux_init. |
| 280 | */ |
| 281 | dbus_bool_t |
| 282 | bus_selinux_enabled (void) |
| 283 | { |
| 284 | #ifdef HAVE_SELINUX |
| 285 | return selinux_enabled; |
| 286 | #else |
| 287 | return FALSE; |
| 288 | #endif /* HAVE_SELINUX */ |
| 289 | } |
| 290 | |
| 291 | /** |
| 292 | * Do early initialization; determine whether SELinux is enabled. |
| 293 | */ |
| 294 | dbus_bool_t |
| 295 | bus_selinux_pre_init (void) |
| 296 | { |
| 297 | #ifdef HAVE_SELINUX |
| 298 | int r; |
| 299 | _dbus_assert (bus_sid == SECSID_WILD); |
| 300 | |
| 301 | /* Determine if we are running an SELinux kernel. */ |
| 302 | r = is_selinux_enabled (); |
| 303 | if (r < 0) |
| 304 | { |
| 305 | _dbus_warn ("Could not tell if SELinux is enabled: %s\n", |
| 306 | _dbus_strerror (errno)); |
| 307 | return FALSE; |
| 308 | } |
| 309 | |
| 310 | selinux_enabled = r != 0; |
| 311 | return TRUE; |
| 312 | #else |
| 313 | return TRUE; |
| 314 | #endif |
| 315 | } |
| 316 | |
| 317 | /** |
| 318 | * Initialize the user space access vector cache (AVC) for D-Bus and set up |
| 319 | * logging callbacks. |
| 320 | */ |
| 321 | dbus_bool_t |
| 322 | bus_selinux_full_init (void) |
| 323 | { |
| 324 | #ifdef HAVE_SELINUX |
| 325 | char *bus_context; |
| 326 | |
| 327 | _dbus_assert (bus_sid == SECSID_WILD); |
| 328 | |
| 329 | if (!selinux_enabled) |
| 330 | { |
| 331 | _dbus_verbose ("SELinux not enabled in this kernel.\n"); |
| 332 | return TRUE; |
| 333 | } |
| 334 | |
| 335 | _dbus_verbose ("SELinux is enabled in this kernel.\n"); |
| 336 | |
| 337 | avc_entry_ref_init (&aeref); |
| 338 | if (avc_init ("avc", &mem_cb, &log_cb, &thread_cb, &lock_cb) < 0) |
| 339 | { |
| 340 | _dbus_warn ("Failed to start Access Vector Cache (AVC).\n"); |
| 341 | return FALSE; |
| 342 | } |
| 343 | else |
| 344 | { |
| 345 | openlog ("dbus", LOG_PERROR, LOG_USER); |
| 346 | _dbus_verbose ("Access Vector Cache (AVC) started.\n"); |
| 347 | } |
| 348 | |
| 349 | if (avc_add_callback (policy_reload_callback, AVC_CALLBACK_RESET, |
| 350 | NULL, NULL, 0, 0) < 0) |
| 351 | { |
| 352 | _dbus_warn ("Failed to add policy reload callback: %s\n", |
| 353 | _dbus_strerror (errno)); |
| 354 | avc_destroy (); |
| 355 | return FALSE; |
| 356 | } |
| 357 | |
| 358 | bus_context = NULL; |
| 359 | bus_sid = SECSID_WILD; |
| 360 | |
| 361 | if (getcon (&bus_context) < 0) |
| 362 | { |
| 363 | _dbus_verbose ("Error getting context of bus: %s\n", |
| 364 | _dbus_strerror (errno)); |
| 365 | return FALSE; |
| 366 | } |
| 367 | |
| 368 | if (avc_context_to_sid (bus_context, &bus_sid) < 0) |
| 369 | { |
| 370 | _dbus_verbose ("Error getting SID from bus context: %s\n", |
| 371 | _dbus_strerror (errno)); |
| 372 | freecon (bus_context); |
| 373 | return FALSE; |
| 374 | } |
| 375 | |
| 376 | freecon (bus_context); |
| 377 | |
| 378 | #endif /* HAVE_SELINUX */ |
| 379 | return TRUE; |
| 380 | } |
| 381 | |
| 382 | /** |
| 383 | * Decrement SID reference count. |
| 384 | * |
| 385 | * @param sid the SID to decrement |
| 386 | */ |
| 387 | void |
| 388 | bus_selinux_id_unref (BusSELinuxID *sid) |
| 389 | { |
| 390 | #ifdef HAVE_SELINUX |
| 391 | if (!selinux_enabled) |
| 392 | return; |
| 393 | |
| 394 | _dbus_assert (sid != NULL); |
| 395 | |
| 396 | sidput (SELINUX_SID_FROM_BUS (sid)); |
| 397 | #endif /* HAVE_SELINUX */ |
| 398 | } |
| 399 | |
| 400 | void |
| 401 | bus_selinux_id_ref (BusSELinuxID *sid) |
| 402 | { |
| 403 | #ifdef HAVE_SELINUX |
| 404 | if (!selinux_enabled) |
| 405 | return; |
| 406 | |
| 407 | _dbus_assert (sid != NULL); |
| 408 | |
| 409 | sidget (SELINUX_SID_FROM_BUS (sid)); |
| 410 | #endif /* HAVE_SELINUX */ |
| 411 | } |
| 412 | |
| 413 | /** |
| 414 | * Determine if the SELinux security policy allows the given sender |
| 415 | * security context to go to the given recipient security context. |
| 416 | * This function determines if the requested permissions are to be |
| 417 | * granted from the connection to the message bus or to another |
| 418 | * optionally supplied security identifier (e.g. for a service |
| 419 | * context). Currently these permissions are either send_msg or |
| 420 | * acquire_svc in the dbus class. |
| 421 | * |
| 422 | * @param sender_sid source security context |
| 423 | * @param override_sid is the target security context. If SECSID_WILD this will |
| 424 | * use the context of the bus itself (e.g. the default). |
| 425 | * @param target_class is the target security class. |
| 426 | * @param requested is the requested permissions. |
| 427 | * @returns #TRUE if security policy allows the send. |
| 428 | */ |
| 429 | #ifdef HAVE_SELINUX |
| 430 | static dbus_bool_t |
| 431 | bus_selinux_check (BusSELinuxID *sender_sid, |
| 432 | BusSELinuxID *override_sid, |
| 433 | security_class_t target_class, |
| 434 | access_vector_t requested, |
| 435 | DBusString *auxdata) |
| 436 | { |
| 437 | if (!selinux_enabled) |
| 438 | return TRUE; |
| 439 | |
| 440 | /* Make the security check. AVC checks enforcing mode here as well. */ |
| 441 | if (avc_has_perm (SELINUX_SID_FROM_BUS (sender_sid), |
| 442 | override_sid ? |
| 443 | SELINUX_SID_FROM_BUS (override_sid) : |
| 444 | SELINUX_SID_FROM_BUS (bus_sid), |
| 445 | target_class, requested, &aeref, auxdata) < 0) |
| 446 | { |
| 447 | switch (errno) |
| 448 | { |
| 449 | case EACCES: |
| 450 | _dbus_verbose ("SELinux denying due to security policy.\n"); |
| 451 | return FALSE; |
| 452 | case EINVAL: |
| 453 | _dbus_verbose ("SELinux denying due to invalid security context.\n"); |
| 454 | return FALSE; |
| 455 | default: |
| 456 | _dbus_verbose ("SELinux denying due to: %s\n", _dbus_strerror (errno)); |
| 457 | return FALSE; |
| 458 | } |
| 459 | } |
| 460 | else |
| 461 | return TRUE; |
| 462 | } |
| 463 | #endif /* HAVE_SELINUX */ |
| 464 | |
| 465 | /** |
| 466 | * Returns true if the given connection can acquire a service, |
| 467 | * assuming the given security ID is needed for that service. |
| 468 | * |
| 469 | * @param connection connection that wants to own the service |
| 470 | * @param service_sid the SID of the service from the table |
| 471 | * @returns #TRUE if acquire is permitted. |
| 472 | */ |
| 473 | dbus_bool_t |
| 474 | bus_selinux_allows_acquire_service (DBusConnection *connection, |
| 475 | BusSELinuxID *service_sid, |
| 476 | const char *service_name, |
| 477 | DBusError *error) |
| 478 | { |
| 479 | #ifdef HAVE_SELINUX |
| 480 | BusSELinuxID *connection_sid; |
| 481 | unsigned long spid; |
| 482 | DBusString auxdata; |
| 483 | dbus_bool_t ret; |
| 484 | |
| 485 | if (!selinux_enabled) |
| 486 | return TRUE; |
| 487 | |
| 488 | connection_sid = bus_connection_get_selinux_id (connection); |
| 489 | if (!dbus_connection_get_unix_process_id (connection, &spid)) |
| 490 | spid = 0; |
| 491 | |
| 492 | if (!_dbus_string_init (&auxdata)) |
| 493 | goto oom; |
| 494 | |
| 495 | if (!_dbus_string_append (&auxdata, "service=")) |
| 496 | goto oom; |
| 497 | |
| 498 | if (!_dbus_string_append (&auxdata, service_name)) |
| 499 | goto oom; |
| 500 | |
| 501 | if (spid) |
| 502 | { |
| 503 | if (!_dbus_string_append (&auxdata, " spid=")) |
| 504 | goto oom; |
| 505 | |
| 506 | if (!_dbus_string_append_uint (&auxdata, spid)) |
| 507 | goto oom; |
| 508 | } |
| 509 | |
| 510 | ret = bus_selinux_check (connection_sid, |
| 511 | service_sid, |
| 512 | SECCLASS_DBUS, |
| 513 | DBUS__ACQUIRE_SVC, |
| 514 | &auxdata); |
| 515 | |
| 516 | _dbus_string_free (&auxdata); |
| 517 | return ret; |
| 518 | |
| 519 | oom: |
| 520 | _dbus_string_free (&auxdata); |
| 521 | BUS_SET_OOM (error); |
| 522 | return FALSE; |
| 523 | |
| 524 | #else |
| 525 | return TRUE; |
| 526 | #endif /* HAVE_SELINUX */ |
| 527 | } |
| 528 | |
| 529 | /** |
| 530 | * Check if SELinux security controls allow the message to be sent to a |
| 531 | * particular connection based on the security context of the sender and |
| 532 | * that of the receiver. The destination connection need not be the |
| 533 | * addressed recipient, it could be an "eavesdropper" |
| 534 | * |
| 535 | * @param sender the sender of the message. |
| 536 | * @param proposed_recipient the connection the message is to be sent to. |
| 537 | * @returns whether to allow the send |
| 538 | */ |
| 539 | dbus_bool_t |
| 540 | bus_selinux_allows_send (DBusConnection *sender, |
| 541 | DBusConnection *proposed_recipient, |
| 542 | const char *msgtype, |
| 543 | const char *interface, |
| 544 | const char *member, |
| 545 | const char *error_name, |
| 546 | const char *destination, |
| 547 | DBusError *error) |
| 548 | { |
| 549 | #ifdef HAVE_SELINUX |
| 550 | BusSELinuxID *recipient_sid; |
| 551 | BusSELinuxID *sender_sid; |
| 552 | unsigned long spid, tpid; |
| 553 | DBusString auxdata; |
| 554 | dbus_bool_t ret; |
| 555 | dbus_bool_t string_alloced; |
| 556 | |
| 557 | if (!selinux_enabled) |
| 558 | return TRUE; |
| 559 | |
| 560 | if (!sender || !dbus_connection_get_unix_process_id (sender, &spid)) |
| 561 | spid = 0; |
| 562 | if (!proposed_recipient || !dbus_connection_get_unix_process_id (proposed_recipient, &tpid)) |
| 563 | tpid = 0; |
| 564 | |
| 565 | string_alloced = FALSE; |
| 566 | if (!_dbus_string_init (&auxdata)) |
| 567 | goto oom; |
| 568 | string_alloced = TRUE; |
| 569 | |
| 570 | if (!_dbus_string_append (&auxdata, "msgtype=")) |
| 571 | goto oom; |
| 572 | |
| 573 | if (!_dbus_string_append (&auxdata, msgtype)) |
| 574 | goto oom; |
| 575 | |
| 576 | if (interface) |
| 577 | { |
| 578 | if (!_dbus_string_append (&auxdata, " interface=")) |
| 579 | goto oom; |
| 580 | if (!_dbus_string_append (&auxdata, interface)) |
| 581 | goto oom; |
| 582 | } |
| 583 | |
| 584 | if (member) |
| 585 | { |
| 586 | if (!_dbus_string_append (&auxdata, " member=")) |
| 587 | goto oom; |
| 588 | if (!_dbus_string_append (&auxdata, member)) |
| 589 | goto oom; |
| 590 | } |
| 591 | |
| 592 | if (error_name) |
| 593 | { |
| 594 | if (!_dbus_string_append (&auxdata, " error_name=")) |
| 595 | goto oom; |
| 596 | if (!_dbus_string_append (&auxdata, error_name)) |
| 597 | goto oom; |
| 598 | } |
| 599 | |
| 600 | if (destination) |
| 601 | { |
| 602 | if (!_dbus_string_append (&auxdata, " dest=")) |
| 603 | goto oom; |
| 604 | if (!_dbus_string_append (&auxdata, destination)) |
| 605 | goto oom; |
| 606 | } |
| 607 | |
| 608 | if (spid) |
| 609 | { |
| 610 | if (!_dbus_string_append (&auxdata, " spid=")) |
| 611 | goto oom; |
| 612 | |
| 613 | if (!_dbus_string_append_uint (&auxdata, spid)) |
| 614 | goto oom; |
| 615 | } |
| 616 | |
| 617 | if (tpid) |
| 618 | { |
| 619 | if (!_dbus_string_append (&auxdata, " tpid=")) |
| 620 | goto oom; |
| 621 | |
| 622 | if (!_dbus_string_append_uint (&auxdata, tpid)) |
| 623 | goto oom; |
| 624 | } |
| 625 | |
| 626 | sender_sid = bus_connection_get_selinux_id (sender); |
| 627 | /* A NULL proposed_recipient means the bus itself. */ |
| 628 | if (proposed_recipient) |
| 629 | recipient_sid = bus_connection_get_selinux_id (proposed_recipient); |
| 630 | else |
| 631 | recipient_sid = BUS_SID_FROM_SELINUX (bus_sid); |
| 632 | |
| 633 | ret = bus_selinux_check (sender_sid, |
| 634 | recipient_sid, |
| 635 | SECCLASS_DBUS, |
| 636 | DBUS__SEND_MSG, |
| 637 | &auxdata); |
| 638 | |
| 639 | _dbus_string_free (&auxdata); |
| 640 | |
| 641 | return ret; |
| 642 | |
| 643 | oom: |
| 644 | if (string_alloced) |
| 645 | _dbus_string_free (&auxdata); |
| 646 | BUS_SET_OOM (error); |
| 647 | return FALSE; |
| 648 | |
| 649 | #else |
| 650 | return TRUE; |
| 651 | #endif /* HAVE_SELINUX */ |
| 652 | } |
| 653 | |
| 654 | dbus_bool_t |
| 655 | bus_selinux_append_context (DBusMessage *message, |
| 656 | BusSELinuxID *sid, |
| 657 | DBusError *error) |
| 658 | { |
| 659 | #ifdef HAVE_SELINUX |
| 660 | char *context; |
| 661 | |
| 662 | if (avc_sid_to_context (SELINUX_SID_FROM_BUS (sid), &context) < 0) |
| 663 | { |
| 664 | if (errno == ENOMEM) |
| 665 | BUS_SET_OOM (error); |
| 666 | else |
| 667 | dbus_set_error (error, DBUS_ERROR_FAILED, |
| 668 | "Error getting context from SID: %s\n", |
| 669 | _dbus_strerror (errno)); |
| 670 | return FALSE; |
| 671 | } |
| 672 | if (!dbus_message_append_args (message, |
| 673 | DBUS_TYPE_ARRAY, |
| 674 | DBUS_TYPE_BYTE, |
| 675 | &context, |
| 676 | strlen (context), |
| 677 | DBUS_TYPE_INVALID)) |
| 678 | { |
| 679 | _DBUS_SET_OOM (error); |
| 680 | return FALSE; |
| 681 | } |
| 682 | freecon (context); |
| 683 | return TRUE; |
| 684 | #else |
| 685 | return TRUE; |
| 686 | #endif |
| 687 | } |
| 688 | |
| 689 | /** |
| 690 | * Gets the security context of a connection to the bus. It is up to |
| 691 | * the caller to freecon() when they are done. |
| 692 | * |
| 693 | * @param connection the connection to get the context of. |
| 694 | * @param con the location to store the security context. |
| 695 | * @returns #TRUE if context is successfully obtained. |
| 696 | */ |
| 697 | #ifdef HAVE_SELINUX |
| 698 | static dbus_bool_t |
| 699 | bus_connection_read_selinux_context (DBusConnection *connection, |
| 700 | char **con) |
| 701 | { |
| 702 | int fd; |
| 703 | |
| 704 | if (!selinux_enabled) |
| 705 | return FALSE; |
| 706 | |
| 707 | _dbus_assert (connection != NULL); |
| 708 | |
| 709 | if (!dbus_connection_get_unix_fd (connection, &fd)) |
| 710 | { |
| 711 | _dbus_verbose ("Failed to get file descriptor of socket.\n"); |
| 712 | return FALSE; |
| 713 | } |
| 714 | |
| 715 | if (getpeercon (fd, con) < 0) |
| 716 | { |
| 717 | _dbus_verbose ("Error getting context of socket peer: %s\n", |
| 718 | _dbus_strerror (errno)); |
| 719 | return FALSE; |
| 720 | } |
| 721 | |
| 722 | _dbus_verbose ("Successfully read connection context.\n"); |
| 723 | return TRUE; |
| 724 | } |
| 725 | #endif /* HAVE_SELINUX */ |
| 726 | |
| 727 | /** |
| 728 | * Read the SELinux ID from the connection. |
| 729 | * |
| 730 | * @param connection the connection to read from |
| 731 | * @returns the SID if successfully determined, #NULL otherwise. |
| 732 | */ |
| 733 | BusSELinuxID* |
| 734 | bus_selinux_init_connection_id (DBusConnection *connection, |
| 735 | DBusError *error) |
| 736 | { |
| 737 | #ifdef HAVE_SELINUX |
| 738 | char *con; |
| 739 | security_id_t sid; |
| 740 | |
| 741 | if (!selinux_enabled) |
| 742 | return NULL; |
| 743 | |
| 744 | if (!bus_connection_read_selinux_context (connection, &con)) |
| 745 | { |
| 746 | dbus_set_error (error, DBUS_ERROR_FAILED, |
| 747 | "Failed to read an SELinux context from connection"); |
| 748 | _dbus_verbose ("Error getting peer context.\n"); |
| 749 | return NULL; |
| 750 | } |
| 751 | |
| 752 | _dbus_verbose ("Converting context to SID to store on connection\n"); |
| 753 | |
| 754 | if (avc_context_to_sid (con, &sid) < 0) |
| 755 | { |
| 756 | if (errno == ENOMEM) |
| 757 | BUS_SET_OOM (error); |
| 758 | else |
| 759 | dbus_set_error (error, DBUS_ERROR_FAILED, |
| 760 | "Error getting SID from context \"%s\": %s\n", |
| 761 | con, _dbus_strerror (errno)); |
| 762 | |
| 763 | _dbus_warn ("Error getting SID from context \"%s\": %s\n", |
| 764 | con, _dbus_strerror (errno)); |
| 765 | |
| 766 | freecon (con); |
| 767 | return NULL; |
| 768 | } |
| 769 | |
| 770 | freecon (con); |
| 771 | return BUS_SID_FROM_SELINUX (sid); |
| 772 | #else |
| 773 | return NULL; |
| 774 | #endif /* HAVE_SELINUX */ |
| 775 | } |
| 776 | |
| 777 | |
| 778 | /** |
| 779 | * Function for freeing hash table data. These SIDs |
| 780 | * should no longer be referenced. |
| 781 | */ |
| 782 | static void |
| 783 | bus_selinux_id_table_free_value (BusSELinuxID *sid) |
| 784 | { |
| 785 | #ifdef HAVE_SELINUX |
| 786 | /* NULL sometimes due to how DBusHashTable works */ |
| 787 | if (sid) |
| 788 | bus_selinux_id_unref (sid); |
| 789 | #endif /* HAVE_SELINUX */ |
| 790 | } |
| 791 | |
| 792 | /** |
| 793 | * Creates a new table mapping service names to security ID. |
| 794 | * A security ID is a "compiled" security context, a security |
| 795 | * context is just a string. |
| 796 | * |
| 797 | * @returns the new table or #NULL if no memory |
| 798 | */ |
| 799 | DBusHashTable* |
| 800 | bus_selinux_id_table_new (void) |
| 801 | { |
| 802 | return _dbus_hash_table_new (DBUS_HASH_STRING, |
| 803 | (DBusFreeFunction) dbus_free, |
| 804 | (DBusFreeFunction) bus_selinux_id_table_free_value); |
| 805 | } |
| 806 | |
| 807 | /** |
| 808 | * Hashes a service name and service context into the service SID |
| 809 | * table as a string and a SID. |
| 810 | * |
| 811 | * @param service_name is the name of the service. |
| 812 | * @param service_context is the context of the service. |
| 813 | * @param service_table is the table to hash them into. |
| 814 | * @return #FALSE if not enough memory |
| 815 | */ |
| 816 | dbus_bool_t |
| 817 | bus_selinux_id_table_insert (DBusHashTable *service_table, |
| 818 | const char *service_name, |
| 819 | const char *service_context) |
| 820 | { |
| 821 | #ifdef HAVE_SELINUX |
| 822 | dbus_bool_t retval; |
| 823 | security_id_t sid; |
| 824 | char *key; |
| 825 | |
| 826 | if (!selinux_enabled) |
| 827 | return TRUE; |
| 828 | |
| 829 | sid = SECSID_WILD; |
| 830 | retval = FALSE; |
| 831 | |
| 832 | key = _dbus_strdup (service_name); |
| 833 | if (key == NULL) |
| 834 | return retval; |
| 835 | |
| 836 | if (avc_context_to_sid ((char *) service_context, &sid) < 0) |
| 837 | { |
| 838 | if (errno == ENOMEM) |
| 839 | { |
| 840 | dbus_free (key); |
| 841 | return FALSE; |
| 842 | } |
| 843 | |
| 844 | _dbus_warn ("Error getting SID from context \"%s\": %s\n", |
| 845 | (char *) service_context, |
| 846 | _dbus_strerror (errno)); |
| 847 | goto out; |
| 848 | } |
| 849 | |
| 850 | if (!_dbus_hash_table_insert_string (service_table, |
| 851 | key, |
| 852 | BUS_SID_FROM_SELINUX (sid))) |
| 853 | goto out; |
| 854 | |
| 855 | _dbus_verbose ("Parsed \tservice: %s \n\t\tcontext: %s\n", |
| 856 | key, |
| 857 | sid->ctx); |
| 858 | |
| 859 | /* These are owned by the hash, so clear them to avoid unref */ |
| 860 | key = NULL; |
| 861 | sid = SECSID_WILD; |
| 862 | |
| 863 | retval = TRUE; |
| 864 | |
| 865 | out: |
| 866 | if (sid != SECSID_WILD) |
| 867 | sidput (sid); |
| 868 | |
| 869 | if (key) |
| 870 | dbus_free (key); |
| 871 | |
| 872 | return retval; |
| 873 | #else |
| 874 | return TRUE; |
| 875 | #endif /* HAVE_SELINUX */ |
| 876 | } |
| 877 | |
| 878 | |
| 879 | /** |
| 880 | * Find the security identifier associated with a particular service |
| 881 | * name. Return a pointer to this SID, or #NULL/SECSID_WILD if the |
| 882 | * service is not found in the hash table. This should be nearly a |
| 883 | * constant time operation. If SELinux support is not available, |
| 884 | * always return NULL. |
| 885 | * |
| 886 | * @param service_table the hash table to check for service name. |
| 887 | * @param service_name the name of the service to look for. |
| 888 | * @returns the SELinux ID associated with the service |
| 889 | */ |
| 890 | BusSELinuxID* |
| 891 | bus_selinux_id_table_lookup (DBusHashTable *service_table, |
| 892 | const DBusString *service_name) |
| 893 | { |
| 894 | #ifdef HAVE_SELINUX |
| 895 | security_id_t sid; |
| 896 | |
| 897 | sid = SECSID_WILD; /* default context */ |
| 898 | |
| 899 | if (!selinux_enabled) |
| 900 | return NULL; |
| 901 | |
| 902 | _dbus_verbose ("Looking up service SID for %s\n", |
| 903 | _dbus_string_get_const_data (service_name)); |
| 904 | |
| 905 | sid = _dbus_hash_table_lookup_string (service_table, |
| 906 | _dbus_string_get_const_data (service_name)); |
| 907 | |
| 908 | if (sid == SECSID_WILD) |
| 909 | _dbus_verbose ("Service %s not found\n", |
| 910 | _dbus_string_get_const_data (service_name)); |
| 911 | else |
| 912 | _dbus_verbose ("Service %s found\n", |
| 913 | _dbus_string_get_const_data (service_name)); |
| 914 | |
| 915 | return BUS_SID_FROM_SELINUX (sid); |
| 916 | #endif /* HAVE_SELINUX */ |
| 917 | return NULL; |
| 918 | } |
| 919 | |
| 920 | /** |
| 921 | * Get the SELinux policy root. This is used to find the D-Bus |
| 922 | * specific config file within the policy. |
| 923 | */ |
| 924 | const char * |
| 925 | bus_selinux_get_policy_root (void) |
| 926 | { |
| 927 | #ifdef HAVE_SELINUX |
| 928 | return selinux_policy_root (); |
| 929 | #else |
| 930 | return NULL; |
| 931 | #endif /* HAVE_SELINUX */ |
| 932 | } |
| 933 | |
| 934 | /** |
| 935 | * For debugging: Print out the current hash table of service SIDs. |
| 936 | */ |
| 937 | void |
| 938 | bus_selinux_id_table_print (DBusHashTable *service_table) |
| 939 | { |
| 940 | #ifdef DBUS_ENABLE_VERBOSE_MODE |
| 941 | #ifdef HAVE_SELINUX |
| 942 | DBusHashIter iter; |
| 943 | |
| 944 | if (!selinux_enabled) |
| 945 | return; |
| 946 | |
| 947 | _dbus_verbose ("Service SID Table:\n"); |
| 948 | _dbus_hash_iter_init (service_table, &iter); |
| 949 | while (_dbus_hash_iter_next (&iter)) |
| 950 | { |
| 951 | const char *key = _dbus_hash_iter_get_string_key (&iter); |
| 952 | security_id_t sid = _dbus_hash_iter_get_value (&iter); |
| 953 | _dbus_verbose ("The key is %s\n", key); |
| 954 | _dbus_verbose ("The context is %s\n", sid->ctx); |
| 955 | _dbus_verbose ("The refcount is %d\n", sid->refcnt); |
| 956 | } |
| 957 | #endif /* HAVE_SELINUX */ |
| 958 | #endif /* DBUS_ENABLE_VERBOSE_MODE */ |
| 959 | } |
| 960 | |
| 961 | |
| 962 | #ifdef DBUS_ENABLE_VERBOSE_MODE |
| 963 | #ifdef HAVE_SELINUX |
| 964 | /** |
| 965 | * Print out some AVC statistics. |
| 966 | */ |
| 967 | static void |
| 968 | bus_avc_print_stats (void) |
| 969 | { |
| 970 | struct avc_cache_stats cstats; |
| 971 | |
| 972 | if (!selinux_enabled) |
| 973 | return; |
| 974 | |
| 975 | _dbus_verbose ("AVC Statistics:\n"); |
| 976 | avc_cache_stats (&cstats); |
| 977 | avc_av_stats (); |
| 978 | _dbus_verbose ("AVC Cache Statistics:\n"); |
| 979 | _dbus_verbose ("Entry lookups: %d\n", cstats.entry_lookups); |
| 980 | _dbus_verbose ("Entry hits: %d\n", cstats.entry_hits); |
| 981 | _dbus_verbose ("Entry misses %d\n", cstats.entry_misses); |
| 982 | _dbus_verbose ("Entry discards: %d\n", cstats.entry_discards); |
| 983 | _dbus_verbose ("CAV lookups: %d\n", cstats.cav_lookups); |
| 984 | _dbus_verbose ("CAV hits: %d\n", cstats.cav_hits); |
| 985 | _dbus_verbose ("CAV probes: %d\n", cstats.cav_probes); |
| 986 | _dbus_verbose ("CAV misses: %d\n", cstats.cav_misses); |
| 987 | } |
| 988 | #endif /* HAVE_SELINUX */ |
| 989 | #endif /* DBUS_ENABLE_VERBOSE_MODE */ |
| 990 | |
| 991 | |
| 992 | /** |
| 993 | * Destroy the AVC before we terminate. |
| 994 | */ |
| 995 | void |
| 996 | bus_selinux_shutdown (void) |
| 997 | { |
| 998 | #ifdef HAVE_SELINUX |
| 999 | if (!selinux_enabled) |
| 1000 | return; |
| 1001 | |
| 1002 | _dbus_verbose ("AVC shutdown\n"); |
| 1003 | |
| 1004 | if (bus_sid != SECSID_WILD) |
| 1005 | { |
| 1006 | sidput (bus_sid); |
| 1007 | bus_sid = SECSID_WILD; |
| 1008 | |
| 1009 | #ifdef DBUS_ENABLE_VERBOSE_MODE |
| 1010 | |
| 1011 | if (_dbus_is_verbose()) |
| 1012 | bus_avc_print_stats (); |
| 1013 | |
| 1014 | #endif /* DBUS_ENABLE_VERBOSE_MODE */ |
| 1015 | |
| 1016 | avc_destroy (); |
| 1017 | #ifdef HAVE_LIBAUDIT |
| 1018 | audit_close (audit_fd); |
| 1019 | #endif /* HAVE_LIBAUDIT */ |
| 1020 | } |
| 1021 | #endif /* HAVE_SELINUX */ |
| 1022 | } |
| 1023 | |
| 1024 | /* The !HAVE_LIBAUDIT case lives in dbus-sysdeps-util-unix.c */ |
| 1025 | #ifdef HAVE_LIBAUDIT |
| 1026 | /** |
| 1027 | * Changes the user and group the bus is running as. |
| 1028 | * |
| 1029 | * @param user the user to become |
| 1030 | * @param error return location for errors |
| 1031 | * @returns #FALSE on failure |
| 1032 | */ |
| 1033 | dbus_bool_t |
| 1034 | _dbus_change_to_daemon_user (const char *user, |
| 1035 | DBusError *error) |
| 1036 | { |
| 1037 | dbus_uid_t uid; |
| 1038 | dbus_gid_t gid; |
| 1039 | DBusString u; |
| 1040 | |
| 1041 | _dbus_string_init_const (&u, user); |
| 1042 | |
| 1043 | if (!_dbus_get_user_id_and_primary_group (&u, &uid, &gid)) |
| 1044 | { |
| 1045 | dbus_set_error (error, DBUS_ERROR_FAILED, |
| 1046 | "User '%s' does not appear to exist?", |
| 1047 | user); |
| 1048 | return FALSE; |
| 1049 | } |
| 1050 | |
| 1051 | /* If we were root */ |
| 1052 | if (_dbus_geteuid () == 0) |
| 1053 | { |
| 1054 | int rc; |
| 1055 | |
| 1056 | capng_clear (CAPNG_SELECT_BOTH); |
| 1057 | capng_update (CAPNG_ADD, CAPNG_EFFECTIVE | CAPNG_PERMITTED, |
| 1058 | CAP_AUDIT_WRITE); |
| 1059 | rc = capng_change_id (uid, gid, 0); |
| 1060 | if (rc) |
| 1061 | { |
| 1062 | switch (rc) { |
| 1063 | default: |
| 1064 | dbus_set_error (error, DBUS_ERROR_FAILED, |
| 1065 | "Failed to drop capabilities: %s\n", |
| 1066 | _dbus_strerror (errno)); |
| 1067 | break; |
| 1068 | case -4: |
| 1069 | dbus_set_error (error, _dbus_error_from_errno (errno), |
| 1070 | "Failed to set GID to %lu: %s", gid, |
| 1071 | _dbus_strerror (errno)); |
| 1072 | break; |
| 1073 | case -5: |
| 1074 | _dbus_warn ("Failed to drop supplementary groups: %s\n", |
| 1075 | _dbus_strerror (errno)); |
| 1076 | break; |
| 1077 | case -6: |
| 1078 | dbus_set_error (error, _dbus_error_from_errno (errno), |
| 1079 | "Failed to set UID to %lu: %s", uid, |
| 1080 | _dbus_strerror (errno)); |
| 1081 | break; |
| 1082 | case -7: |
| 1083 | dbus_set_error (error, _dbus_error_from_errno (errno), |
| 1084 | "Failed to unset keep-capabilities: %s\n", |
| 1085 | _dbus_strerror (errno)); |
| 1086 | break; |
| 1087 | } |
| 1088 | return FALSE; |
| 1089 | } |
| 1090 | } |
| 1091 | |
| 1092 | return TRUE; |
| 1093 | } |
| 1094 | #endif |