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