1 /*- 2 * Copyright (c) 1999-2002, 2006 Robert N. M. Watson 3 * Copyright (c) 2001 Ilmar S. Habibulin 4 * Copyright (c) 2001-2005 Networks Associates Technology, Inc. 5 * Copyright (c) 2005-2006 SPARTA, Inc. 6 * Copyright (c) 2008-2009 Apple Inc. 7 * All rights reserved. 8 * 9 * This software was developed by Robert Watson and Ilmar Habibulin for the 10 * TrustedBSD Project. 11 * 12 * This software was developed for the FreeBSD Project in part by Network 13 * Associates Laboratories, the Security Research Division of Network 14 * Associates, Inc. under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), 15 * as part of the DARPA CHATS research program. 16 * 17 * This software was enhanced by SPARTA ISSO under SPAWAR contract 18 * N66001-04-C-6019 ("SEFOS"). 19 * 20 * Redistribution and use in source and binary forms, with or without 21 * modification, are permitted provided that the following conditions 22 * are met: 23 * 1. Redistributions of source code must retain the above copyright 24 * notice, this list of conditions and the following disclaimer. 25 * 2. Redistributions in binary form must reproduce the above copyright 26 * notice, this list of conditions and the following disclaimer in the 27 * documentation and/or other materials provided with the distribution. 28 * 29 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 30 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 31 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 32 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 33 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 34 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 35 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 36 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 37 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 38 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 39 * SUCH DAMAGE. 40 */ 41 42 /*- 43 * Framework for extensible kernel access control. This file contains core 44 * kernel infrastructure for the TrustedBSD MAC Framework, including policy 45 * registration, versioning, locking, error composition operator, and system 46 * calls. 47 * 48 * The MAC Framework implements three programming interfaces: 49 * 50 * - The kernel MAC interface, defined in mac_framework.h, and invoked 51 * throughout the kernel to request security decisions, notify of security 52 * related events, etc. 53 * 54 * - The MAC policy module interface, defined in mac_policy.h, which is 55 * implemented by MAC policy modules and invoked by the MAC Framework to 56 * forward kernel security requests and notifications to policy modules. 57 * 58 * - The user MAC API, defined in mac.h, which allows user programs to query 59 * and set label state on objects. 60 * 61 * The majority of the MAC Framework implementation may be found in 62 * src/sys/security/mac. Sample policy modules may be found in 63 * src/sys/security/mac_*. 64 */ 65 66 #include "opt_mac.h" 67 68 #include <sys/cdefs.h> 69 __FBSDID("$FreeBSD$"); 70 71 #include <sys/param.h> 72 #include <sys/condvar.h> 73 #include <sys/kernel.h> 74 #include <sys/lock.h> 75 #include <sys/mutex.h> 76 #include <sys/mac.h> 77 #include <sys/module.h> 78 #include <sys/systm.h> 79 #include <sys/sysctl.h> 80 81 #include <security/mac/mac_framework.h> 82 #include <security/mac/mac_internal.h> 83 #include <security/mac/mac_policy.h> 84 85 /* 86 * Root sysctl node for all MAC and MAC policy controls. 87 */ 88 SYSCTL_NODE(_security, OID_AUTO, mac, CTLFLAG_RW, 0, 89 "TrustedBSD MAC policy controls"); 90 91 /* 92 * Declare that the kernel provides MAC support, version 3 (FreeBSD 7.x). 93 * This permits modules to refuse to be loaded if the necessary support isn't 94 * present, even if it's pre-boot. 95 */ 96 MODULE_VERSION(kernel_mac_support, MAC_VERSION); 97 98 static unsigned int mac_version = MAC_VERSION; 99 SYSCTL_UINT(_security_mac, OID_AUTO, version, CTLFLAG_RD, &mac_version, 0, 100 ""); 101 102 /* 103 * Labels consist of a indexed set of "slots", which are allocated policies 104 * as required. The MAC Framework maintains a bitmask of slots allocated so 105 * far to prevent reuse. Slots cannot be reused, as the MAC Framework 106 * guarantees that newly allocated slots in labels will be NULL unless 107 * otherwise initialized, and because we do not have a mechanism to garbage 108 * collect slots on policy unload. As labeled policies tend to be statically 109 * loaded during boot, and not frequently unloaded and reloaded, this is not 110 * generally an issue. 111 */ 112 #if MAC_MAX_SLOTS > 32 113 #error "MAC_MAX_SLOTS too large" 114 #endif 115 116 static unsigned int mac_max_slots = MAC_MAX_SLOTS; 117 static unsigned int mac_slot_offsets_free = (1 << MAC_MAX_SLOTS) - 1; 118 SYSCTL_UINT(_security_mac, OID_AUTO, max_slots, CTLFLAG_RD, &mac_max_slots, 119 0, ""); 120 121 /* 122 * Has the kernel started generating labeled objects yet? All read/write 123 * access to this variable is serialized during the boot process. Following 124 * the end of serialization, we don't update this flag; no locking. 125 */ 126 static int mac_late = 0; 127 128 /* 129 * Each policy declares a mask of object types requiring labels to be 130 * allocated for them. For convenience, we combine and cache the bitwise or 131 * of the per-policy object flags to track whether we will allocate a label 132 * for an object type at run-time. 133 */ 134 uint64_t mac_labeled; 135 SYSCTL_QUAD(_security_mac, OID_AUTO, labeled, CTLFLAG_RD, &mac_labeled, 0, 136 "Mask of object types being labeled"); 137 138 MALLOC_DEFINE(M_MACTEMP, "mactemp", "MAC temporary label storage"); 139 140 /* 141 * mac_static_policy_list holds a list of policy modules that are not loaded 142 * while the system is "live", and cannot be unloaded. These policies can be 143 * invoked without holding the busy count. 144 * 145 * mac_policy_list stores the list of dynamic policies. A busy count is 146 * maintained for the list, stored in mac_policy_busy. The busy count is 147 * protected by mac_policy_mtx; the list may be modified only while the busy 148 * count is 0, requiring that the lock be held to prevent new references to 149 * the list from being acquired. For almost all operations, incrementing the 150 * busy count is sufficient to guarantee consistency, as the list cannot be 151 * modified while the busy count is elevated. For a few special operations 152 * involving a change to the list of active policies, the mtx itself must be 153 * held. A condition variable, mac_policy_cv, is used to signal potential 154 * exclusive consumers that they should try to acquire the lock if a first 155 * attempt at exclusive access fails. 156 * 157 * This design intentionally avoids fairness, and may starve attempts to 158 * acquire an exclusive lock on a busy system. This is required because we 159 * do not ever want acquiring a read reference to perform an unbounded length 160 * sleep. Read references are acquired in ithreads, network isrs, etc, and 161 * any unbounded blocking could lead quickly to deadlock. 162 * 163 * Another reason for never blocking on read references is that the MAC 164 * Framework may recurse: if a policy calls a VOP, for example, this might 165 * lead to vnode life cycle operations (such as init/destroy). 166 * 167 * If the kernel option MAC_STATIC has been compiled in, all locking becomes 168 * a no-op, and the global list of policies is not allowed to change after 169 * early boot. 170 * 171 * XXXRW: Currently, we signal mac_policy_cv every time the framework becomes 172 * unbusy and there is a thread waiting to enter it exclusively. Since it 173 * may take some time before the thread runs, we may issue a lot of signals. 174 * We should instead keep track of the fact that we've signalled, taking into 175 * account that the framework may be busy again by the time the thread runs, 176 * requiring us to re-signal. 177 */ 178 #ifndef MAC_STATIC 179 static struct mtx mac_policy_mtx; 180 static struct cv mac_policy_cv; 181 static int mac_policy_count; 182 static int mac_policy_wait; 183 #endif 184 struct mac_policy_list_head mac_policy_list; 185 struct mac_policy_list_head mac_static_policy_list; 186 187 /* 188 * We manually invoke WITNESS_WARN() to allow Witness to generate warnings 189 * even if we don't end up ever triggering the wait at run-time. The 190 * consumer of the exclusive interface must not hold any locks (other than 191 * potentially Giant) since we may sleep for long (potentially indefinite) 192 * periods of time waiting for the framework to become quiescent so that a 193 * policy list change may be made. 194 */ 195 void 196 mac_policy_grab_exclusive(void) 197 { 198 199 #ifndef MAC_STATIC 200 if (!mac_late) 201 return; 202 203 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, 204 "mac_policy_grab_exclusive() at %s:%d", __FILE__, __LINE__); 205 mtx_lock(&mac_policy_mtx); 206 while (mac_policy_count != 0) { 207 mac_policy_wait++; 208 cv_wait(&mac_policy_cv, &mac_policy_mtx); 209 mac_policy_wait--; 210 } 211 #endif 212 } 213 214 void 215 mac_policy_assert_exclusive(void) 216 { 217 218 #ifndef MAC_STATIC 219 if (!mac_late) 220 return; 221 222 mtx_assert(&mac_policy_mtx, MA_OWNED); 223 KASSERT(mac_policy_count == 0, 224 ("mac_policy_assert_exclusive(): not exclusive")); 225 #endif 226 } 227 228 void 229 mac_policy_release_exclusive(void) 230 { 231 #ifndef MAC_STATIC 232 int dowakeup; 233 234 if (!mac_late) 235 return; 236 237 KASSERT(mac_policy_count == 0, 238 ("mac_policy_release_exclusive(): not exclusive")); 239 dowakeup = (mac_policy_wait != 0); 240 mtx_unlock(&mac_policy_mtx); 241 if (dowakeup) 242 cv_signal(&mac_policy_cv); 243 #endif 244 } 245 246 void 247 mac_policy_list_busy(void) 248 { 249 250 #ifndef MAC_STATIC 251 if (!mac_late) 252 return; 253 254 mtx_lock(&mac_policy_mtx); 255 mac_policy_count++; 256 mtx_unlock(&mac_policy_mtx); 257 #endif 258 } 259 260 int 261 mac_policy_list_conditional_busy(void) 262 { 263 #ifndef MAC_STATIC 264 int ret; 265 266 if (!mac_late) 267 return (1); 268 269 mtx_lock(&mac_policy_mtx); 270 if (!LIST_EMPTY(&mac_policy_list)) { 271 mac_policy_count++; 272 ret = 1; 273 } else 274 ret = 0; 275 mtx_unlock(&mac_policy_mtx); 276 return (ret); 277 #else 278 return (1); 279 #endif 280 } 281 282 void 283 mac_policy_list_unbusy(void) 284 { 285 #ifndef MAC_STATIC 286 int dowakeup; 287 288 if (!mac_late) 289 return; 290 291 mtx_lock(&mac_policy_mtx); 292 mac_policy_count--; 293 KASSERT(mac_policy_count >= 0, ("MAC_POLICY_LIST_LOCK")); 294 dowakeup = (mac_policy_count == 0 && mac_policy_wait != 0); 295 mtx_unlock(&mac_policy_mtx); 296 297 if (dowakeup) 298 cv_signal(&mac_policy_cv); 299 #endif 300 } 301 302 /* 303 * Initialize the MAC subsystem, including appropriate SMP locks. 304 */ 305 static void 306 mac_init(void) 307 { 308 309 LIST_INIT(&mac_static_policy_list); 310 LIST_INIT(&mac_policy_list); 311 mac_labelzone_init(); 312 313 #ifndef MAC_STATIC 314 mtx_init(&mac_policy_mtx, "mac_policy_mtx", NULL, MTX_DEF); 315 cv_init(&mac_policy_cv, "mac_policy_cv"); 316 #endif 317 } 318 319 /* 320 * For the purposes of modules that want to know if they were loaded "early", 321 * set the mac_late flag once we've processed modules either linked into the 322 * kernel, or loaded before the kernel startup. 323 */ 324 static void 325 mac_late_init(void) 326 { 327 328 mac_late = 1; 329 } 330 331 /* 332 * Given a policy, derive from its set of non-NULL label init methods what 333 * object types the policy is interested in. 334 */ 335 static uint64_t 336 mac_policy_getlabeled(struct mac_policy_conf *mpc) 337 { 338 uint64_t labeled; 339 340 #define MPC_FLAG(method, flag) \ 341 if (mpc->mpc_ops->mpo_ ## method != NULL) \ 342 labeled |= (flag); \ 343 344 labeled = 0; 345 MPC_FLAG(cred_init_label, MPC_OBJECT_CRED); 346 MPC_FLAG(proc_init_label, MPC_OBJECT_PROC); 347 MPC_FLAG(vnode_init_label, MPC_OBJECT_VNODE); 348 MPC_FLAG(inpcb_init_label, MPC_OBJECT_INPCB); 349 MPC_FLAG(socket_init_label, MPC_OBJECT_SOCKET); 350 MPC_FLAG(devfs_init_label, MPC_OBJECT_DEVFS); 351 MPC_FLAG(mbuf_init_label, MPC_OBJECT_MBUF); 352 MPC_FLAG(ipq_init_label, MPC_OBJECT_IPQ); 353 MPC_FLAG(ifnet_init_label, MPC_OBJECT_IFNET); 354 MPC_FLAG(bpfdesc_init_label, MPC_OBJECT_BPFDESC); 355 MPC_FLAG(pipe_init_label, MPC_OBJECT_PIPE); 356 MPC_FLAG(mount_init_label, MPC_OBJECT_MOUNT); 357 MPC_FLAG(posixsem_init_label, MPC_OBJECT_POSIXSEM); 358 MPC_FLAG(posixshm_init_label, MPC_OBJECT_POSIXSHM); 359 MPC_FLAG(sysvmsg_init_label, MPC_OBJECT_SYSVMSG); 360 MPC_FLAG(sysvmsq_init_label, MPC_OBJECT_SYSVMSQ); 361 MPC_FLAG(sysvsem_init_label, MPC_OBJECT_SYSVSEM); 362 MPC_FLAG(sysvshm_init_label, MPC_OBJECT_SYSVSHM); 363 MPC_FLAG(syncache_init_label, MPC_OBJECT_SYNCACHE); 364 MPC_FLAG(ip6q_init_label, MPC_OBJECT_IP6Q); 365 366 #undef MPC_FLAG 367 return (labeled); 368 } 369 370 /* 371 * When policies are loaded or unloaded, walk the list of registered policies 372 * and built mac_labeled, a bitmask representing the union of all objects 373 * requiring labels across all policies. 374 */ 375 static void 376 mac_policy_updateflags(void) 377 { 378 struct mac_policy_conf *mpc; 379 380 mac_policy_assert_exclusive(); 381 382 mac_labeled = 0; 383 LIST_FOREACH(mpc, &mac_static_policy_list, mpc_list) 384 mac_labeled |= mac_policy_getlabeled(mpc); 385 LIST_FOREACH(mpc, &mac_policy_list, mpc_list) 386 mac_labeled |= mac_policy_getlabeled(mpc); 387 } 388 389 static int 390 mac_policy_register(struct mac_policy_conf *mpc) 391 { 392 struct mac_policy_conf *tmpc; 393 int error, slot, static_entry; 394 395 error = 0; 396 397 /* 398 * We don't technically need exclusive access while !mac_late, but 399 * hold it for assertion consistency. 400 */ 401 mac_policy_grab_exclusive(); 402 403 /* 404 * If the module can potentially be unloaded, or we're loading late, 405 * we have to stick it in the non-static list and pay an extra 406 * performance overhead. Otherwise, we can pay a light locking cost 407 * and stick it in the static list. 408 */ 409 static_entry = (!mac_late && 410 !(mpc->mpc_loadtime_flags & MPC_LOADTIME_FLAG_UNLOADOK)); 411 412 if (static_entry) { 413 LIST_FOREACH(tmpc, &mac_static_policy_list, mpc_list) { 414 if (strcmp(tmpc->mpc_name, mpc->mpc_name) == 0) { 415 error = EEXIST; 416 goto out; 417 } 418 } 419 } else { 420 LIST_FOREACH(tmpc, &mac_policy_list, mpc_list) { 421 if (strcmp(tmpc->mpc_name, mpc->mpc_name) == 0) { 422 error = EEXIST; 423 goto out; 424 } 425 } 426 } 427 if (mpc->mpc_field_off != NULL) { 428 slot = ffs(mac_slot_offsets_free); 429 if (slot == 0) { 430 error = ENOMEM; 431 goto out; 432 } 433 slot--; 434 mac_slot_offsets_free &= ~(1 << slot); 435 *mpc->mpc_field_off = slot; 436 } 437 mpc->mpc_runtime_flags |= MPC_RUNTIME_FLAG_REGISTERED; 438 439 /* 440 * If we're loading a MAC module after the framework has initialized, 441 * it has to go into the dynamic list. If we're loading it before 442 * we've finished initializing, it can go into the static list with 443 * weaker locker requirements. 444 */ 445 if (static_entry) 446 LIST_INSERT_HEAD(&mac_static_policy_list, mpc, mpc_list); 447 else 448 LIST_INSERT_HEAD(&mac_policy_list, mpc, mpc_list); 449 450 /* 451 * Per-policy initialization. Currently, this takes place under the 452 * exclusive lock, so policies must not sleep in their init method. 453 * In the future, we may want to separate "init" from "start", with 454 * "init" occuring without the lock held. Likewise, on tear-down, 455 * breaking out "stop" from "destroy". 456 */ 457 if (mpc->mpc_ops->mpo_init != NULL) 458 (*(mpc->mpc_ops->mpo_init))(mpc); 459 mac_policy_updateflags(); 460 461 printf("Security policy loaded: %s (%s)\n", mpc->mpc_fullname, 462 mpc->mpc_name); 463 464 out: 465 mac_policy_release_exclusive(); 466 return (error); 467 } 468 469 static int 470 mac_policy_unregister(struct mac_policy_conf *mpc) 471 { 472 473 /* 474 * If we fail the load, we may get a request to unload. Check to see 475 * if we did the run-time registration, and if not, silently succeed. 476 */ 477 mac_policy_grab_exclusive(); 478 if ((mpc->mpc_runtime_flags & MPC_RUNTIME_FLAG_REGISTERED) == 0) { 479 mac_policy_release_exclusive(); 480 return (0); 481 } 482 #if 0 483 /* 484 * Don't allow unloading modules with private data. 485 */ 486 if (mpc->mpc_field_off != NULL) { 487 MAC_POLICY_LIST_UNLOCK(); 488 return (EBUSY); 489 } 490 #endif 491 /* 492 * Only allow the unload to proceed if the module is unloadable by 493 * its own definition. 494 */ 495 if ((mpc->mpc_loadtime_flags & MPC_LOADTIME_FLAG_UNLOADOK) == 0) { 496 mac_policy_release_exclusive(); 497 return (EBUSY); 498 } 499 if (mpc->mpc_ops->mpo_destroy != NULL) 500 (*(mpc->mpc_ops->mpo_destroy))(mpc); 501 502 LIST_REMOVE(mpc, mpc_list); 503 mpc->mpc_runtime_flags &= ~MPC_RUNTIME_FLAG_REGISTERED; 504 mac_policy_updateflags(); 505 506 mac_policy_release_exclusive(); 507 508 printf("Security policy unload: %s (%s)\n", mpc->mpc_fullname, 509 mpc->mpc_name); 510 511 return (0); 512 } 513 514 /* 515 * Allow MAC policy modules to register during boot, etc. 516 */ 517 int 518 mac_policy_modevent(module_t mod, int type, void *data) 519 { 520 struct mac_policy_conf *mpc; 521 int error; 522 523 error = 0; 524 mpc = (struct mac_policy_conf *) data; 525 526 #ifdef MAC_STATIC 527 if (mac_late) { 528 printf("mac_policy_modevent: MAC_STATIC and late\n"); 529 return (EBUSY); 530 } 531 #endif 532 533 switch (type) { 534 case MOD_LOAD: 535 if (mpc->mpc_loadtime_flags & MPC_LOADTIME_FLAG_NOTLATE && 536 mac_late) { 537 printf("mac_policy_modevent: can't load %s policy " 538 "after booting\n", mpc->mpc_name); 539 error = EBUSY; 540 break; 541 } 542 error = mac_policy_register(mpc); 543 break; 544 case MOD_UNLOAD: 545 /* Don't unregister the module if it was never registered. */ 546 if ((mpc->mpc_runtime_flags & MPC_RUNTIME_FLAG_REGISTERED) 547 != 0) 548 error = mac_policy_unregister(mpc); 549 else 550 error = 0; 551 break; 552 default: 553 error = EOPNOTSUPP; 554 break; 555 } 556 557 return (error); 558 } 559 560 /* 561 * Define an error value precedence, and given two arguments, selects the 562 * value with the higher precedence. 563 */ 564 int 565 mac_error_select(int error1, int error2) 566 { 567 568 /* Certain decision-making errors take top priority. */ 569 if (error1 == EDEADLK || error2 == EDEADLK) 570 return (EDEADLK); 571 572 /* Invalid arguments should be reported where possible. */ 573 if (error1 == EINVAL || error2 == EINVAL) 574 return (EINVAL); 575 576 /* Precedence goes to "visibility", with both process and file. */ 577 if (error1 == ESRCH || error2 == ESRCH) 578 return (ESRCH); 579 580 if (error1 == ENOENT || error2 == ENOENT) 581 return (ENOENT); 582 583 /* Precedence goes to DAC/MAC protections. */ 584 if (error1 == EACCES || error2 == EACCES) 585 return (EACCES); 586 587 /* Precedence goes to privilege. */ 588 if (error1 == EPERM || error2 == EPERM) 589 return (EPERM); 590 591 /* Precedence goes to error over success; otherwise, arbitrary. */ 592 if (error1 != 0) 593 return (error1); 594 return (error2); 595 } 596 597 int 598 mac_check_structmac_consistent(struct mac *mac) 599 { 600 601 if (mac->m_buflen < 0 || 602 mac->m_buflen > MAC_MAX_LABEL_BUF_LEN) 603 return (EINVAL); 604 605 return (0); 606 } 607 608 SYSINIT(mac, SI_SUB_MAC, SI_ORDER_FIRST, mac_init, NULL); 609 SYSINIT(mac_late, SI_SUB_MAC_LATE, SI_ORDER_FIRST, mac_late_init, NULL); 610