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_mac.h" 70 71 #include <sys/cdefs.h> 72 __FBSDID("$FreeBSD$"); 73 74 #include <sys/param.h> 75 #include <sys/systm.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/sysctl.h> 85 86 #include <security/mac/mac_framework.h> 87 #include <security/mac/mac_internal.h> 88 #include <security/mac/mac_policy.h> 89 90 /* 91 * DTrace SDT providers for MAC. 92 */ 93 SDT_PROVIDER_DEFINE(mac); 94 SDT_PROVIDER_DEFINE(mac_framework); 95 96 SDT_PROBE_DEFINE2(mac, , policy, modevent, "int", 97 "struct mac_policy_conf *"); 98 SDT_PROBE_DEFINE1(mac, , policy, register, 99 "struct mac_policy_conf *"); 100 SDT_PROBE_DEFINE1(mac, , policy, unregister, 101 "struct mac_policy_conf *"); 102 103 /* 104 * Root sysctl node for all MAC and MAC policy controls. 105 */ 106 SYSCTL_NODE(_security, OID_AUTO, mac, CTLFLAG_RW, 0, 107 "TrustedBSD MAC policy controls"); 108 109 /* 110 * Declare that the kernel provides MAC support, version 3 (FreeBSD 7.x). 111 * This permits modules to refuse to be loaded if the necessary support isn't 112 * present, even if it's pre-boot. 113 */ 114 MODULE_VERSION(kernel_mac_support, MAC_VERSION); 115 116 static unsigned int mac_version = MAC_VERSION; 117 SYSCTL_UINT(_security_mac, OID_AUTO, version, CTLFLAG_RD, &mac_version, 0, 118 ""); 119 120 /* 121 * Labels consist of a indexed set of "slots", which are allocated policies 122 * as required. The MAC Framework maintains a bitmask of slots allocated so 123 * far to prevent reuse. Slots cannot be reused, as the MAC Framework 124 * guarantees that newly allocated slots in labels will be NULL unless 125 * otherwise initialized, and because we do not have a mechanism to garbage 126 * collect slots on policy unload. As labeled policies tend to be statically 127 * loaded during boot, and not frequently unloaded and reloaded, this is not 128 * generally an issue. 129 */ 130 #if MAC_MAX_SLOTS > 32 131 #error "MAC_MAX_SLOTS too large" 132 #endif 133 134 static unsigned int mac_max_slots = MAC_MAX_SLOTS; 135 static unsigned int mac_slot_offsets_free = (1 << MAC_MAX_SLOTS) - 1; 136 SYSCTL_UINT(_security_mac, OID_AUTO, max_slots, CTLFLAG_RD, &mac_max_slots, 137 0, ""); 138 139 /* 140 * Has the kernel started generating labeled objects yet? All read/write 141 * access to this variable is serialized during the boot process. Following 142 * the end of serialization, we don't update this flag; no locking. 143 */ 144 static int mac_late = 0; 145 146 /* 147 * Each policy declares a mask of object types requiring labels to be 148 * allocated for them. For convenience, we combine and cache the bitwise or 149 * of the per-policy object flags to track whether we will allocate a label 150 * for an object type at run-time. 151 */ 152 uint64_t mac_labeled; 153 SYSCTL_UQUAD(_security_mac, OID_AUTO, labeled, CTLFLAG_RD, &mac_labeled, 0, 154 "Mask of object types being labeled"); 155 156 MALLOC_DEFINE(M_MACTEMP, "mactemp", "MAC temporary label storage"); 157 158 /* 159 * MAC policy modules are placed in one of two lists: mac_static_policy_list, 160 * for policies that are loaded early and cannot be unloaded, and 161 * mac_policy_list, which holds policies either loaded later in the boot 162 * cycle or that may be unloaded. The static policy list does not require 163 * locks to iterate over, but the dynamic list requires synchronization. 164 * Support for dynamic policy loading can be compiled out using the 165 * MAC_STATIC kernel option. 166 * 167 * The dynamic policy list is protected by two locks: modifying the list 168 * requires both locks to be held exclusively. One of the locks, 169 * mac_policy_rm, is acquired over policy entry points that will never sleep; 170 * the other, mac_policy_sx, is acquire over policy entry points that may 171 * sleep. The former category will be used when kernel locks may be held 172 * over calls to the MAC Framework, during network processing in ithreads, 173 * etc. The latter will tend to involve potentially blocking memory 174 * allocations, extended attribute I/O, etc. 175 */ 176 #ifndef MAC_STATIC 177 static struct rmlock mac_policy_rm; /* Non-sleeping entry points. */ 178 static struct sx mac_policy_sx; /* Sleeping entry points. */ 179 #endif 180 181 struct mac_policy_list_head mac_policy_list; 182 struct mac_policy_list_head mac_static_policy_list; 183 u_int mac_policy_count; /* Registered policy count. */ 184 185 static void mac_policy_xlock(void); 186 static void mac_policy_xlock_assert(void); 187 static void mac_policy_xunlock(void); 188 189 void 190 mac_policy_slock_nosleep(struct rm_priotracker *tracker) 191 { 192 193 #ifndef MAC_STATIC 194 if (!mac_late) 195 return; 196 197 rm_rlock(&mac_policy_rm, tracker); 198 #endif 199 } 200 201 void 202 mac_policy_slock_sleep(void) 203 { 204 205 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, 206 "mac_policy_slock_sleep"); 207 208 #ifndef MAC_STATIC 209 if (!mac_late) 210 return; 211 212 sx_slock(&mac_policy_sx); 213 #endif 214 } 215 216 void 217 mac_policy_sunlock_nosleep(struct rm_priotracker *tracker) 218 { 219 220 #ifndef MAC_STATIC 221 if (!mac_late) 222 return; 223 224 rm_runlock(&mac_policy_rm, tracker); 225 #endif 226 } 227 228 void 229 mac_policy_sunlock_sleep(void) 230 { 231 232 #ifndef MAC_STATIC 233 if (!mac_late) 234 return; 235 236 sx_sunlock(&mac_policy_sx); 237 #endif 238 } 239 240 static void 241 mac_policy_xlock(void) 242 { 243 244 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, 245 "mac_policy_xlock()"); 246 247 #ifndef MAC_STATIC 248 if (!mac_late) 249 return; 250 251 sx_xlock(&mac_policy_sx); 252 rm_wlock(&mac_policy_rm); 253 #endif 254 } 255 256 static void 257 mac_policy_xunlock(void) 258 { 259 260 #ifndef MAC_STATIC 261 if (!mac_late) 262 return; 263 264 rm_wunlock(&mac_policy_rm); 265 sx_xunlock(&mac_policy_sx); 266 #endif 267 } 268 269 static void 270 mac_policy_xlock_assert(void) 271 { 272 273 #ifndef MAC_STATIC 274 if (!mac_late) 275 return; 276 277 /* XXXRW: rm_assert(&mac_policy_rm, RA_WLOCKED); */ 278 sx_assert(&mac_policy_sx, SA_XLOCKED); 279 #endif 280 } 281 282 /* 283 * Initialize the MAC subsystem, including appropriate SMP locks. 284 */ 285 static void 286 mac_init(void) 287 { 288 289 LIST_INIT(&mac_static_policy_list); 290 LIST_INIT(&mac_policy_list); 291 mac_labelzone_init(); 292 293 #ifndef MAC_STATIC 294 rm_init_flags(&mac_policy_rm, "mac_policy_rm", RM_NOWITNESS | 295 RM_RECURSE); 296 sx_init_flags(&mac_policy_sx, "mac_policy_sx", SX_NOWITNESS); 297 #endif 298 } 299 300 /* 301 * For the purposes of modules that want to know if they were loaded "early", 302 * set the mac_late flag once we've processed modules either linked into the 303 * kernel, or loaded before the kernel startup. 304 */ 305 static void 306 mac_late_init(void) 307 { 308 309 mac_late = 1; 310 } 311 312 /* 313 * Given a policy, derive from its set of non-NULL label init methods what 314 * object types the policy is interested in. 315 */ 316 static uint64_t 317 mac_policy_getlabeled(struct mac_policy_conf *mpc) 318 { 319 uint64_t labeled; 320 321 #define MPC_FLAG(method, flag) \ 322 if (mpc->mpc_ops->mpo_ ## method != NULL) \ 323 labeled |= (flag); \ 324 325 labeled = 0; 326 MPC_FLAG(cred_init_label, MPC_OBJECT_CRED); 327 MPC_FLAG(proc_init_label, MPC_OBJECT_PROC); 328 MPC_FLAG(vnode_init_label, MPC_OBJECT_VNODE); 329 MPC_FLAG(inpcb_init_label, MPC_OBJECT_INPCB); 330 MPC_FLAG(socket_init_label, MPC_OBJECT_SOCKET); 331 MPC_FLAG(devfs_init_label, MPC_OBJECT_DEVFS); 332 MPC_FLAG(mbuf_init_label, MPC_OBJECT_MBUF); 333 MPC_FLAG(ipq_init_label, MPC_OBJECT_IPQ); 334 MPC_FLAG(ifnet_init_label, MPC_OBJECT_IFNET); 335 MPC_FLAG(bpfdesc_init_label, MPC_OBJECT_BPFDESC); 336 MPC_FLAG(pipe_init_label, MPC_OBJECT_PIPE); 337 MPC_FLAG(mount_init_label, MPC_OBJECT_MOUNT); 338 MPC_FLAG(posixsem_init_label, MPC_OBJECT_POSIXSEM); 339 MPC_FLAG(posixshm_init_label, MPC_OBJECT_POSIXSHM); 340 MPC_FLAG(sysvmsg_init_label, MPC_OBJECT_SYSVMSG); 341 MPC_FLAG(sysvmsq_init_label, MPC_OBJECT_SYSVMSQ); 342 MPC_FLAG(sysvsem_init_label, MPC_OBJECT_SYSVSEM); 343 MPC_FLAG(sysvshm_init_label, MPC_OBJECT_SYSVSHM); 344 MPC_FLAG(syncache_init_label, MPC_OBJECT_SYNCACHE); 345 MPC_FLAG(ip6q_init_label, MPC_OBJECT_IP6Q); 346 347 #undef MPC_FLAG 348 return (labeled); 349 } 350 351 /* 352 * When policies are loaded or unloaded, walk the list of registered policies 353 * and built mac_labeled, a bitmask representing the union of all objects 354 * requiring labels across all policies. 355 */ 356 static void 357 mac_policy_update(void) 358 { 359 struct mac_policy_conf *mpc; 360 361 mac_policy_xlock_assert(); 362 363 mac_labeled = 0; 364 mac_policy_count = 0; 365 LIST_FOREACH(mpc, &mac_static_policy_list, mpc_list) { 366 mac_labeled |= mac_policy_getlabeled(mpc); 367 mac_policy_count++; 368 } 369 LIST_FOREACH(mpc, &mac_policy_list, mpc_list) { 370 mac_labeled |= mac_policy_getlabeled(mpc); 371 mac_policy_count++; 372 } 373 } 374 375 static int 376 mac_policy_register(struct mac_policy_conf *mpc) 377 { 378 struct mac_policy_conf *tmpc; 379 int error, slot, static_entry; 380 381 error = 0; 382 383 /* 384 * We don't technically need exclusive access while !mac_late, but 385 * hold it for assertion consistency. 386 */ 387 mac_policy_xlock(); 388 389 /* 390 * If the module can potentially be unloaded, or we're loading late, 391 * we have to stick it in the non-static list and pay an extra 392 * performance overhead. Otherwise, we can pay a light locking cost 393 * and stick it in the static list. 394 */ 395 static_entry = (!mac_late && 396 !(mpc->mpc_loadtime_flags & MPC_LOADTIME_FLAG_UNLOADOK)); 397 398 if (static_entry) { 399 LIST_FOREACH(tmpc, &mac_static_policy_list, mpc_list) { 400 if (strcmp(tmpc->mpc_name, mpc->mpc_name) == 0) { 401 error = EEXIST; 402 goto out; 403 } 404 } 405 } else { 406 LIST_FOREACH(tmpc, &mac_policy_list, mpc_list) { 407 if (strcmp(tmpc->mpc_name, mpc->mpc_name) == 0) { 408 error = EEXIST; 409 goto out; 410 } 411 } 412 } 413 if (mpc->mpc_field_off != NULL) { 414 slot = ffs(mac_slot_offsets_free); 415 if (slot == 0) { 416 error = ENOMEM; 417 goto out; 418 } 419 slot--; 420 mac_slot_offsets_free &= ~(1 << slot); 421 *mpc->mpc_field_off = slot; 422 } 423 mpc->mpc_runtime_flags |= MPC_RUNTIME_FLAG_REGISTERED; 424 425 /* 426 * If we're loading a MAC module after the framework has initialized, 427 * it has to go into the dynamic list. If we're loading it before 428 * we've finished initializing, it can go into the static list with 429 * weaker locker requirements. 430 */ 431 if (static_entry) 432 LIST_INSERT_HEAD(&mac_static_policy_list, mpc, mpc_list); 433 else 434 LIST_INSERT_HEAD(&mac_policy_list, mpc, mpc_list); 435 436 /* 437 * Per-policy initialization. Currently, this takes place under the 438 * exclusive lock, so policies must not sleep in their init method. 439 * In the future, we may want to separate "init" from "start", with 440 * "init" occurring without the lock held. Likewise, on tear-down, 441 * breaking out "stop" from "destroy". 442 */ 443 if (mpc->mpc_ops->mpo_init != NULL) 444 (*(mpc->mpc_ops->mpo_init))(mpc); 445 mac_policy_update(); 446 447 SDT_PROBE1(mac, , policy, register, mpc); 448 printf("Security policy loaded: %s (%s)\n", mpc->mpc_fullname, 449 mpc->mpc_name); 450 451 out: 452 mac_policy_xunlock(); 453 return (error); 454 } 455 456 static int 457 mac_policy_unregister(struct mac_policy_conf *mpc) 458 { 459 460 /* 461 * If we fail the load, we may get a request to unload. Check to see 462 * if we did the run-time registration, and if not, silently succeed. 463 */ 464 mac_policy_xlock(); 465 if ((mpc->mpc_runtime_flags & MPC_RUNTIME_FLAG_REGISTERED) == 0) { 466 mac_policy_xunlock(); 467 return (0); 468 } 469 #if 0 470 /* 471 * Don't allow unloading modules with private data. 472 */ 473 if (mpc->mpc_field_off != NULL) { 474 mac_policy_xunlock(); 475 return (EBUSY); 476 } 477 #endif 478 /* 479 * Only allow the unload to proceed if the module is unloadable by 480 * its own definition. 481 */ 482 if ((mpc->mpc_loadtime_flags & MPC_LOADTIME_FLAG_UNLOADOK) == 0) { 483 mac_policy_xunlock(); 484 return (EBUSY); 485 } 486 if (mpc->mpc_ops->mpo_destroy != NULL) 487 (*(mpc->mpc_ops->mpo_destroy))(mpc); 488 489 LIST_REMOVE(mpc, mpc_list); 490 mpc->mpc_runtime_flags &= ~MPC_RUNTIME_FLAG_REGISTERED; 491 mac_policy_update(); 492 mac_policy_xunlock(); 493 494 SDT_PROBE1(mac, , policy, unregister, mpc); 495 printf("Security policy unload: %s (%s)\n", mpc->mpc_fullname, 496 mpc->mpc_name); 497 498 return (0); 499 } 500 501 /* 502 * Allow MAC policy modules to register during boot, etc. 503 */ 504 int 505 mac_policy_modevent(module_t mod, int type, void *data) 506 { 507 struct mac_policy_conf *mpc; 508 int error; 509 510 error = 0; 511 mpc = (struct mac_policy_conf *) data; 512 513 #ifdef MAC_STATIC 514 if (mac_late) { 515 printf("mac_policy_modevent: MAC_STATIC and late\n"); 516 return (EBUSY); 517 } 518 #endif 519 520 SDT_PROBE2(mac, , policy, modevent, type, mpc); 521 switch (type) { 522 case MOD_LOAD: 523 if (mpc->mpc_loadtime_flags & MPC_LOADTIME_FLAG_NOTLATE && 524 mac_late) { 525 printf("mac_policy_modevent: can't load %s policy " 526 "after booting\n", mpc->mpc_name); 527 error = EBUSY; 528 break; 529 } 530 error = mac_policy_register(mpc); 531 break; 532 case MOD_UNLOAD: 533 /* Don't unregister the module if it was never registered. */ 534 if ((mpc->mpc_runtime_flags & MPC_RUNTIME_FLAG_REGISTERED) 535 != 0) 536 error = mac_policy_unregister(mpc); 537 else 538 error = 0; 539 break; 540 default: 541 error = EOPNOTSUPP; 542 break; 543 } 544 545 return (error); 546 } 547 548 /* 549 * Define an error value precedence, and given two arguments, selects the 550 * value with the higher precedence. 551 */ 552 int 553 mac_error_select(int error1, int error2) 554 { 555 556 /* Certain decision-making errors take top priority. */ 557 if (error1 == EDEADLK || error2 == EDEADLK) 558 return (EDEADLK); 559 560 /* Invalid arguments should be reported where possible. */ 561 if (error1 == EINVAL || error2 == EINVAL) 562 return (EINVAL); 563 564 /* Precedence goes to "visibility", with both process and file. */ 565 if (error1 == ESRCH || error2 == ESRCH) 566 return (ESRCH); 567 568 if (error1 == ENOENT || error2 == ENOENT) 569 return (ENOENT); 570 571 /* Precedence goes to DAC/MAC protections. */ 572 if (error1 == EACCES || error2 == EACCES) 573 return (EACCES); 574 575 /* Precedence goes to privilege. */ 576 if (error1 == EPERM || error2 == EPERM) 577 return (EPERM); 578 579 /* Precedence goes to error over success; otherwise, arbitrary. */ 580 if (error1 != 0) 581 return (error1); 582 return (error2); 583 } 584 585 int 586 mac_check_structmac_consistent(struct mac *mac) 587 { 588 589 /* Require that labels have a non-zero length. */ 590 if (mac->m_buflen > MAC_MAX_LABEL_BUF_LEN || 591 mac->m_buflen <= sizeof("")) 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