1 /*- 2 * Copyright (c) 1999-2002, 2006, 2009 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 * This software was developed at the University of Cambridge Computer 21 * Laboratory with support from a grant from Google, Inc. 22 * 23 * Redistribution and use in source and binary forms, with or without 24 * modification, are permitted provided that the following conditions 25 * are met: 26 * 1. Redistributions of source code must retain the above copyright 27 * notice, this list of conditions and the following disclaimer. 28 * 2. Redistributions in binary form must reproduce the above copyright 29 * notice, this list of conditions and the following disclaimer in the 30 * documentation and/or other materials provided with the distribution. 31 * 32 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 33 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 34 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 35 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 36 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 37 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 38 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 39 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 40 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 41 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 42 * SUCH DAMAGE. 43 */ 44 45 /*- 46 * Framework for extensible kernel access control. This file contains core 47 * kernel infrastructure for the TrustedBSD MAC Framework, including policy 48 * registration, versioning, locking, error composition operator, and system 49 * calls. 50 * 51 * The MAC Framework implements three programming interfaces: 52 * 53 * - The kernel MAC interface, defined in mac_framework.h, and invoked 54 * throughout the kernel to request security decisions, notify of security 55 * related events, etc. 56 * 57 * - The MAC policy module interface, defined in mac_policy.h, which is 58 * implemented by MAC policy modules and invoked by the MAC Framework to 59 * forward kernel security requests and notifications to policy modules. 60 * 61 * - The user MAC API, defined in mac.h, which allows user programs to query 62 * and set label state on objects. 63 * 64 * The majority of the MAC Framework implementation may be found in 65 * src/sys/security/mac. Sample policy modules may be found in 66 * src/sys/security/mac_*. 67 */ 68 69 #include "opt_kdtrace.h" 70 #include "opt_mac.h" 71 72 #include <sys/cdefs.h> 73 __FBSDID("$FreeBSD$"); 74 75 #include <sys/param.h> 76 #include <sys/systm.h> 77 #include <sys/condvar.h> 78 #include <sys/kernel.h> 79 #include <sys/lock.h> 80 #include <sys/mac.h> 81 #include <sys/module.h> 82 #include <sys/rmlock.h> 83 #include <sys/sdt.h> 84 #include <sys/sx.h> 85 #include <sys/sysctl.h> 86 87 #include <security/mac/mac_framework.h> 88 #include <security/mac/mac_internal.h> 89 #include <security/mac/mac_policy.h> 90 91 /* 92 * DTrace SDT providers for MAC. 93 */ 94 SDT_PROVIDER_DEFINE(mac); 95 SDT_PROVIDER_DEFINE(mac_framework); 96 97 SDT_PROBE_DEFINE2(mac, kernel, policy, modevent, modevent, "int", 98 "struct mac_policy_conf *"); 99 SDT_PROBE_DEFINE1(mac, kernel, policy, register, register, 100 "struct mac_policy_conf *"); 101 SDT_PROBE_DEFINE1(mac, kernel, policy, unregister, unregister, 102 "struct mac_policy_conf *"); 103 104 /* 105 * Root sysctl node for all MAC and MAC policy controls. 106 */ 107 SYSCTL_NODE(_security, OID_AUTO, mac, CTLFLAG_RW, 0, 108 "TrustedBSD MAC policy controls"); 109 110 /* 111 * Declare that the kernel provides MAC support, version 3 (FreeBSD 7.x). 112 * This permits modules to refuse to be loaded if the necessary support isn't 113 * present, even if it's pre-boot. 114 */ 115 MODULE_VERSION(kernel_mac_support, MAC_VERSION); 116 117 static unsigned int mac_version = MAC_VERSION; 118 SYSCTL_UINT(_security_mac, OID_AUTO, version, CTLFLAG_RD, &mac_version, 0, 119 ""); 120 121 /* 122 * Labels consist of a indexed set of "slots", which are allocated policies 123 * as required. The MAC Framework maintains a bitmask of slots allocated so 124 * far to prevent reuse. Slots cannot be reused, as the MAC Framework 125 * guarantees that newly allocated slots in labels will be NULL unless 126 * otherwise initialized, and because we do not have a mechanism to garbage 127 * collect slots on policy unload. As labeled policies tend to be statically 128 * loaded during boot, and not frequently unloaded and reloaded, this is not 129 * generally an issue. 130 */ 131 #if MAC_MAX_SLOTS > 32 132 #error "MAC_MAX_SLOTS too large" 133 #endif 134 135 static unsigned int mac_max_slots = MAC_MAX_SLOTS; 136 static unsigned int mac_slot_offsets_free = (1 << MAC_MAX_SLOTS) - 1; 137 SYSCTL_UINT(_security_mac, OID_AUTO, max_slots, CTLFLAG_RD, &mac_max_slots, 138 0, ""); 139 140 /* 141 * Has the kernel started generating labeled objects yet? All read/write 142 * access to this variable is serialized during the boot process. Following 143 * the end of serialization, we don't update this flag; no locking. 144 */ 145 static int mac_late = 0; 146 147 /* 148 * Each policy declares a mask of object types requiring labels to be 149 * allocated for them. For convenience, we combine and cache the bitwise or 150 * of the per-policy object flags to track whether we will allocate a label 151 * for an object type at run-time. 152 */ 153 uint64_t mac_labeled; 154 SYSCTL_UQUAD(_security_mac, OID_AUTO, labeled, CTLFLAG_RD, &mac_labeled, 0, 155 "Mask of object types being labeled"); 156 157 MALLOC_DEFINE(M_MACTEMP, "mactemp", "MAC temporary label storage"); 158 159 /* 160 * MAC policy modules are placed in one of two lists: mac_static_policy_list, 161 * for policies that are loaded early and cannot be unloaded, and 162 * mac_policy_list, which holds policies either loaded later in the boot 163 * cycle or that may be unloaded. The static policy list does not require 164 * locks to iterate over, but the dynamic list requires synchronization. 165 * Support for dynamic policy loading can be compiled out using the 166 * MAC_STATIC kernel option. 167 * 168 * The dynamic policy list is protected by two locks: modifying the list 169 * requires both locks to be held exclusively. One of the locks, 170 * mac_policy_rm, is acquired over policy entry points that will never sleep; 171 * the other, mac_policy_sx, is acquire over policy entry points that may 172 * sleep. The former category will be used when kernel locks may be held 173 * over calls to the MAC Framework, during network processing in ithreads, 174 * etc. The latter will tend to involve potentially blocking memory 175 * allocations, extended attribute I/O, etc. 176 */ 177 #ifndef MAC_STATIC 178 static struct rmlock mac_policy_rm; /* Non-sleeping entry points. */ 179 static struct sx mac_policy_sx; /* Sleeping entry points. */ 180 #endif 181 182 struct mac_policy_list_head mac_policy_list; 183 struct mac_policy_list_head mac_static_policy_list; 184 u_int mac_policy_count; /* Registered policy count. */ 185 186 static void mac_policy_xlock(void); 187 static void mac_policy_xlock_assert(void); 188 static void mac_policy_xunlock(void); 189 190 void 191 mac_policy_slock_nosleep(struct rm_priotracker *tracker) 192 { 193 194 #ifndef MAC_STATIC 195 if (!mac_late) 196 return; 197 198 rm_rlock(&mac_policy_rm, tracker); 199 #endif 200 } 201 202 void 203 mac_policy_slock_sleep(void) 204 { 205 206 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, 207 "mac_policy_slock_sleep"); 208 209 #ifndef MAC_STATIC 210 if (!mac_late) 211 return; 212 213 sx_slock(&mac_policy_sx); 214 #endif 215 } 216 217 void 218 mac_policy_sunlock_nosleep(struct rm_priotracker *tracker) 219 { 220 221 #ifndef MAC_STATIC 222 if (!mac_late) 223 return; 224 225 rm_runlock(&mac_policy_rm, tracker); 226 #endif 227 } 228 229 void 230 mac_policy_sunlock_sleep(void) 231 { 232 233 #ifndef MAC_STATIC 234 if (!mac_late) 235 return; 236 237 sx_sunlock(&mac_policy_sx); 238 #endif 239 } 240 241 static void 242 mac_policy_xlock(void) 243 { 244 245 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, 246 "mac_policy_xlock()"); 247 248 #ifndef MAC_STATIC 249 if (!mac_late) 250 return; 251 252 sx_xlock(&mac_policy_sx); 253 rm_wlock(&mac_policy_rm); 254 #endif 255 } 256 257 static void 258 mac_policy_xunlock(void) 259 { 260 261 #ifndef MAC_STATIC 262 if (!mac_late) 263 return; 264 265 rm_wunlock(&mac_policy_rm); 266 sx_xunlock(&mac_policy_sx); 267 #endif 268 } 269 270 static void 271 mac_policy_xlock_assert(void) 272 { 273 274 #ifndef MAC_STATIC 275 if (!mac_late) 276 return; 277 278 /* XXXRW: rm_assert(&mac_policy_rm, RA_WLOCKED); */ 279 sx_assert(&mac_policy_sx, SA_XLOCKED); 280 #endif 281 } 282 283 /* 284 * Initialize the MAC subsystem, including appropriate SMP locks. 285 */ 286 static void 287 mac_init(void) 288 { 289 290 LIST_INIT(&mac_static_policy_list); 291 LIST_INIT(&mac_policy_list); 292 mac_labelzone_init(); 293 294 #ifndef MAC_STATIC 295 rm_init_flags(&mac_policy_rm, "mac_policy_rm", RM_NOWITNESS | 296 RM_RECURSE); 297 sx_init_flags(&mac_policy_sx, "mac_policy_sx", SX_NOWITNESS); 298 #endif 299 } 300 301 /* 302 * For the purposes of modules that want to know if they were loaded "early", 303 * set the mac_late flag once we've processed modules either linked into the 304 * kernel, or loaded before the kernel startup. 305 */ 306 static void 307 mac_late_init(void) 308 { 309 310 mac_late = 1; 311 } 312 313 /* 314 * Given a policy, derive from its set of non-NULL label init methods what 315 * object types the policy is interested in. 316 */ 317 static uint64_t 318 mac_policy_getlabeled(struct mac_policy_conf *mpc) 319 { 320 uint64_t labeled; 321 322 #define MPC_FLAG(method, flag) \ 323 if (mpc->mpc_ops->mpo_ ## method != NULL) \ 324 labeled |= (flag); \ 325 326 labeled = 0; 327 MPC_FLAG(cred_init_label, MPC_OBJECT_CRED); 328 MPC_FLAG(proc_init_label, MPC_OBJECT_PROC); 329 MPC_FLAG(vnode_init_label, MPC_OBJECT_VNODE); 330 MPC_FLAG(inpcb_init_label, MPC_OBJECT_INPCB); 331 MPC_FLAG(socket_init_label, MPC_OBJECT_SOCKET); 332 MPC_FLAG(devfs_init_label, MPC_OBJECT_DEVFS); 333 MPC_FLAG(mbuf_init_label, MPC_OBJECT_MBUF); 334 MPC_FLAG(ipq_init_label, MPC_OBJECT_IPQ); 335 MPC_FLAG(ifnet_init_label, MPC_OBJECT_IFNET); 336 MPC_FLAG(bpfdesc_init_label, MPC_OBJECT_BPFDESC); 337 MPC_FLAG(pipe_init_label, MPC_OBJECT_PIPE); 338 MPC_FLAG(mount_init_label, MPC_OBJECT_MOUNT); 339 MPC_FLAG(posixsem_init_label, MPC_OBJECT_POSIXSEM); 340 MPC_FLAG(posixshm_init_label, MPC_OBJECT_POSIXSHM); 341 MPC_FLAG(sysvmsg_init_label, MPC_OBJECT_SYSVMSG); 342 MPC_FLAG(sysvmsq_init_label, MPC_OBJECT_SYSVMSQ); 343 MPC_FLAG(sysvsem_init_label, MPC_OBJECT_SYSVSEM); 344 MPC_FLAG(sysvshm_init_label, MPC_OBJECT_SYSVSHM); 345 MPC_FLAG(syncache_init_label, MPC_OBJECT_SYNCACHE); 346 MPC_FLAG(ip6q_init_label, MPC_OBJECT_IP6Q); 347 348 #undef MPC_FLAG 349 return (labeled); 350 } 351 352 /* 353 * When policies are loaded or unloaded, walk the list of registered policies 354 * and built mac_labeled, a bitmask representing the union of all objects 355 * requiring labels across all policies. 356 */ 357 static void 358 mac_policy_update(void) 359 { 360 struct mac_policy_conf *mpc; 361 362 mac_policy_xlock_assert(); 363 364 mac_labeled = 0; 365 mac_policy_count = 0; 366 LIST_FOREACH(mpc, &mac_static_policy_list, mpc_list) { 367 mac_labeled |= mac_policy_getlabeled(mpc); 368 mac_policy_count++; 369 } 370 LIST_FOREACH(mpc, &mac_policy_list, mpc_list) { 371 mac_labeled |= mac_policy_getlabeled(mpc); 372 mac_policy_count++; 373 } 374 } 375 376 static int 377 mac_policy_register(struct mac_policy_conf *mpc) 378 { 379 struct mac_policy_conf *tmpc; 380 int error, slot, static_entry; 381 382 error = 0; 383 384 /* 385 * We don't technically need exclusive access while !mac_late, but 386 * hold it for assertion consistency. 387 */ 388 mac_policy_xlock(); 389 390 /* 391 * If the module can potentially be unloaded, or we're loading late, 392 * we have to stick it in the non-static list and pay an extra 393 * performance overhead. Otherwise, we can pay a light locking cost 394 * and stick it in the static list. 395 */ 396 static_entry = (!mac_late && 397 !(mpc->mpc_loadtime_flags & MPC_LOADTIME_FLAG_UNLOADOK)); 398 399 if (static_entry) { 400 LIST_FOREACH(tmpc, &mac_static_policy_list, mpc_list) { 401 if (strcmp(tmpc->mpc_name, mpc->mpc_name) == 0) { 402 error = EEXIST; 403 goto out; 404 } 405 } 406 } else { 407 LIST_FOREACH(tmpc, &mac_policy_list, mpc_list) { 408 if (strcmp(tmpc->mpc_name, mpc->mpc_name) == 0) { 409 error = EEXIST; 410 goto out; 411 } 412 } 413 } 414 if (mpc->mpc_field_off != NULL) { 415 slot = ffs(mac_slot_offsets_free); 416 if (slot == 0) { 417 error = ENOMEM; 418 goto out; 419 } 420 slot--; 421 mac_slot_offsets_free &= ~(1 << slot); 422 *mpc->mpc_field_off = slot; 423 } 424 mpc->mpc_runtime_flags |= MPC_RUNTIME_FLAG_REGISTERED; 425 426 /* 427 * If we're loading a MAC module after the framework has initialized, 428 * it has to go into the dynamic list. If we're loading it before 429 * we've finished initializing, it can go into the static list with 430 * weaker locker requirements. 431 */ 432 if (static_entry) 433 LIST_INSERT_HEAD(&mac_static_policy_list, mpc, mpc_list); 434 else 435 LIST_INSERT_HEAD(&mac_policy_list, mpc, mpc_list); 436 437 /* 438 * Per-policy initialization. Currently, this takes place under the 439 * exclusive lock, so policies must not sleep in their init method. 440 * In the future, we may want to separate "init" from "start", with 441 * "init" occuring without the lock held. Likewise, on tear-down, 442 * breaking out "stop" from "destroy". 443 */ 444 if (mpc->mpc_ops->mpo_init != NULL) 445 (*(mpc->mpc_ops->mpo_init))(mpc); 446 mac_policy_update(); 447 448 SDT_PROBE(mac, kernel, policy, register, mpc, 0, 0, 0, 0); 449 printf("Security policy loaded: %s (%s)\n", mpc->mpc_fullname, 450 mpc->mpc_name); 451 452 out: 453 mac_policy_xunlock(); 454 return (error); 455 } 456 457 static int 458 mac_policy_unregister(struct mac_policy_conf *mpc) 459 { 460 461 /* 462 * If we fail the load, we may get a request to unload. Check to see 463 * if we did the run-time registration, and if not, silently succeed. 464 */ 465 mac_policy_xlock(); 466 if ((mpc->mpc_runtime_flags & MPC_RUNTIME_FLAG_REGISTERED) == 0) { 467 mac_policy_xunlock(); 468 return (0); 469 } 470 #if 0 471 /* 472 * Don't allow unloading modules with private data. 473 */ 474 if (mpc->mpc_field_off != NULL) { 475 mac_policy_xunlock(); 476 return (EBUSY); 477 } 478 #endif 479 /* 480 * Only allow the unload to proceed if the module is unloadable by 481 * its own definition. 482 */ 483 if ((mpc->mpc_loadtime_flags & MPC_LOADTIME_FLAG_UNLOADOK) == 0) { 484 mac_policy_xunlock(); 485 return (EBUSY); 486 } 487 if (mpc->mpc_ops->mpo_destroy != NULL) 488 (*(mpc->mpc_ops->mpo_destroy))(mpc); 489 490 LIST_REMOVE(mpc, mpc_list); 491 mpc->mpc_runtime_flags &= ~MPC_RUNTIME_FLAG_REGISTERED; 492 mac_policy_update(); 493 mac_policy_xunlock(); 494 495 SDT_PROBE(mac, kernel, policy, unregister, mpc, 0, 0, 0, 0); 496 printf("Security policy unload: %s (%s)\n", mpc->mpc_fullname, 497 mpc->mpc_name); 498 499 return (0); 500 } 501 502 /* 503 * Allow MAC policy modules to register during boot, etc. 504 */ 505 int 506 mac_policy_modevent(module_t mod, int type, void *data) 507 { 508 struct mac_policy_conf *mpc; 509 int error; 510 511 error = 0; 512 mpc = (struct mac_policy_conf *) data; 513 514 #ifdef MAC_STATIC 515 if (mac_late) { 516 printf("mac_policy_modevent: MAC_STATIC and late\n"); 517 return (EBUSY); 518 } 519 #endif 520 521 SDT_PROBE(mac, kernel, policy, modevent, type, mpc, 0, 0, 0); 522 switch (type) { 523 case MOD_LOAD: 524 if (mpc->mpc_loadtime_flags & MPC_LOADTIME_FLAG_NOTLATE && 525 mac_late) { 526 printf("mac_policy_modevent: can't load %s policy " 527 "after booting\n", mpc->mpc_name); 528 error = EBUSY; 529 break; 530 } 531 error = mac_policy_register(mpc); 532 break; 533 case MOD_UNLOAD: 534 /* Don't unregister the module if it was never registered. */ 535 if ((mpc->mpc_runtime_flags & MPC_RUNTIME_FLAG_REGISTERED) 536 != 0) 537 error = mac_policy_unregister(mpc); 538 else 539 error = 0; 540 break; 541 default: 542 error = EOPNOTSUPP; 543 break; 544 } 545 546 return (error); 547 } 548 549 /* 550 * Define an error value precedence, and given two arguments, selects the 551 * value with the higher precedence. 552 */ 553 int 554 mac_error_select(int error1, int error2) 555 { 556 557 /* Certain decision-making errors take top priority. */ 558 if (error1 == EDEADLK || error2 == EDEADLK) 559 return (EDEADLK); 560 561 /* Invalid arguments should be reported where possible. */ 562 if (error1 == EINVAL || error2 == EINVAL) 563 return (EINVAL); 564 565 /* Precedence goes to "visibility", with both process and file. */ 566 if (error1 == ESRCH || error2 == ESRCH) 567 return (ESRCH); 568 569 if (error1 == ENOENT || error2 == ENOENT) 570 return (ENOENT); 571 572 /* Precedence goes to DAC/MAC protections. */ 573 if (error1 == EACCES || error2 == EACCES) 574 return (EACCES); 575 576 /* Precedence goes to privilege. */ 577 if (error1 == EPERM || error2 == EPERM) 578 return (EPERM); 579 580 /* Precedence goes to error over success; otherwise, arbitrary. */ 581 if (error1 != 0) 582 return (error1); 583 return (error2); 584 } 585 586 int 587 mac_check_structmac_consistent(struct mac *mac) 588 { 589 590 if (mac->m_buflen < 0 || 591 mac->m_buflen > MAC_MAX_LABEL_BUF_LEN) 592 return (EINVAL); 593 594 return (0); 595 } 596 597 SYSINIT(mac, SI_SUB_MAC, SI_ORDER_FIRST, mac_init, NULL); 598 SYSINIT(mac_late, SI_SUB_MAC_LATE, SI_ORDER_FIRST, mac_late_init, NULL); 599