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 static struct rmslock mac_policy_rms; 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 rms_rlock(&mac_policy_rms); 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 rms_runlock(&mac_policy_rms); 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 rms_wlock(&mac_policy_rms); 254 rm_wlock(&mac_policy_rm); 255 #endif 256 } 257 258 static void 259 mac_policy_xunlock(void) 260 { 261 262 #ifndef MAC_STATIC 263 if (!mac_late) 264 return; 265 266 rm_wunlock(&mac_policy_rm); 267 rms_wunlock(&mac_policy_rms); 268 sx_xunlock(&mac_policy_sx); 269 #endif 270 } 271 272 static void 273 mac_policy_xlock_assert(void) 274 { 275 276 #ifndef MAC_STATIC 277 if (!mac_late) 278 return; 279 280 /* XXXRW: rm_assert(&mac_policy_rm, RA_WLOCKED); */ 281 sx_assert(&mac_policy_sx, SA_XLOCKED); 282 #endif 283 } 284 285 /* 286 * Initialize the MAC subsystem, including appropriate SMP locks. 287 */ 288 static void 289 mac_init(void) 290 { 291 292 LIST_INIT(&mac_static_policy_list); 293 LIST_INIT(&mac_policy_list); 294 mac_labelzone_init(); 295 296 #ifndef MAC_STATIC 297 rm_init_flags(&mac_policy_rm, "mac_policy_rm", RM_NOWITNESS | 298 RM_RECURSE); 299 sx_init_flags(&mac_policy_sx, "mac_policy_sx", SX_NOWITNESS); 300 rms_init(&mac_policy_rms, "mac_policy_rms"); 301 #endif 302 } 303 304 /* 305 * For the purposes of modules that want to know if they were loaded "early", 306 * set the mac_late flag once we've processed modules either linked into the 307 * kernel, or loaded before the kernel startup. 308 */ 309 static void 310 mac_late_init(void) 311 { 312 313 mac_late = 1; 314 } 315 316 /* 317 * Given a policy, derive from its set of non-NULL label init methods what 318 * object types the policy is interested in. 319 */ 320 static uint64_t 321 mac_policy_getlabeled(struct mac_policy_conf *mpc) 322 { 323 uint64_t labeled; 324 325 #define MPC_FLAG(method, flag) \ 326 if (mpc->mpc_ops->mpo_ ## method != NULL) \ 327 labeled |= (flag); \ 328 329 labeled = 0; 330 MPC_FLAG(cred_init_label, MPC_OBJECT_CRED); 331 MPC_FLAG(proc_init_label, MPC_OBJECT_PROC); 332 MPC_FLAG(vnode_init_label, MPC_OBJECT_VNODE); 333 MPC_FLAG(inpcb_init_label, MPC_OBJECT_INPCB); 334 MPC_FLAG(socket_init_label, MPC_OBJECT_SOCKET); 335 MPC_FLAG(devfs_init_label, MPC_OBJECT_DEVFS); 336 MPC_FLAG(mbuf_init_label, MPC_OBJECT_MBUF); 337 MPC_FLAG(ipq_init_label, MPC_OBJECT_IPQ); 338 MPC_FLAG(ifnet_init_label, MPC_OBJECT_IFNET); 339 MPC_FLAG(bpfdesc_init_label, MPC_OBJECT_BPFDESC); 340 MPC_FLAG(pipe_init_label, MPC_OBJECT_PIPE); 341 MPC_FLAG(mount_init_label, MPC_OBJECT_MOUNT); 342 MPC_FLAG(posixsem_init_label, MPC_OBJECT_POSIXSEM); 343 MPC_FLAG(posixshm_init_label, MPC_OBJECT_POSIXSHM); 344 MPC_FLAG(sysvmsg_init_label, MPC_OBJECT_SYSVMSG); 345 MPC_FLAG(sysvmsq_init_label, MPC_OBJECT_SYSVMSQ); 346 MPC_FLAG(sysvsem_init_label, MPC_OBJECT_SYSVSEM); 347 MPC_FLAG(sysvshm_init_label, MPC_OBJECT_SYSVSHM); 348 MPC_FLAG(syncache_init_label, MPC_OBJECT_SYNCACHE); 349 MPC_FLAG(ip6q_init_label, MPC_OBJECT_IP6Q); 350 351 #undef MPC_FLAG 352 return (labeled); 353 } 354 355 /* 356 * When policies are loaded or unloaded, walk the list of registered policies 357 * and built mac_labeled, a bitmask representing the union of all objects 358 * requiring labels across all policies. 359 */ 360 static void 361 mac_policy_update(void) 362 { 363 struct mac_policy_conf *mpc; 364 365 mac_policy_xlock_assert(); 366 367 mac_labeled = 0; 368 mac_policy_count = 0; 369 LIST_FOREACH(mpc, &mac_static_policy_list, mpc_list) { 370 mac_labeled |= mac_policy_getlabeled(mpc); 371 mac_policy_count++; 372 } 373 LIST_FOREACH(mpc, &mac_policy_list, mpc_list) { 374 mac_labeled |= mac_policy_getlabeled(mpc); 375 mac_policy_count++; 376 } 377 } 378 379 static int 380 mac_policy_register(struct mac_policy_conf *mpc) 381 { 382 struct mac_policy_conf *tmpc; 383 int error, slot, static_entry; 384 385 error = 0; 386 387 /* 388 * We don't technically need exclusive access while !mac_late, but 389 * hold it for assertion consistency. 390 */ 391 mac_policy_xlock(); 392 393 /* 394 * If the module can potentially be unloaded, or we're loading late, 395 * we have to stick it in the non-static list and pay an extra 396 * performance overhead. Otherwise, we can pay a light locking cost 397 * and stick it in the static list. 398 */ 399 static_entry = (!mac_late && 400 !(mpc->mpc_loadtime_flags & MPC_LOADTIME_FLAG_UNLOADOK)); 401 402 if (static_entry) { 403 LIST_FOREACH(tmpc, &mac_static_policy_list, mpc_list) { 404 if (strcmp(tmpc->mpc_name, mpc->mpc_name) == 0) { 405 error = EEXIST; 406 goto out; 407 } 408 } 409 } else { 410 LIST_FOREACH(tmpc, &mac_policy_list, mpc_list) { 411 if (strcmp(tmpc->mpc_name, mpc->mpc_name) == 0) { 412 error = EEXIST; 413 goto out; 414 } 415 } 416 } 417 if (mpc->mpc_field_off != NULL) { 418 slot = ffs(mac_slot_offsets_free); 419 if (slot == 0) { 420 error = ENOMEM; 421 goto out; 422 } 423 slot--; 424 mac_slot_offsets_free &= ~(1 << slot); 425 *mpc->mpc_field_off = slot; 426 } 427 mpc->mpc_runtime_flags |= MPC_RUNTIME_FLAG_REGISTERED; 428 429 /* 430 * If we're loading a MAC module after the framework has initialized, 431 * it has to go into the dynamic list. If we're loading it before 432 * we've finished initializing, it can go into the static list with 433 * weaker locker requirements. 434 */ 435 if (static_entry) 436 LIST_INSERT_HEAD(&mac_static_policy_list, mpc, mpc_list); 437 else 438 LIST_INSERT_HEAD(&mac_policy_list, mpc, mpc_list); 439 440 /* 441 * Per-policy initialization. Currently, this takes place under the 442 * exclusive lock, so policies must not sleep in their init method. 443 * In the future, we may want to separate "init" from "start", with 444 * "init" occurring without the lock held. Likewise, on tear-down, 445 * breaking out "stop" from "destroy". 446 */ 447 if (mpc->mpc_ops->mpo_init != NULL) 448 (*(mpc->mpc_ops->mpo_init))(mpc); 449 mac_policy_update(); 450 451 SDT_PROBE1(mac, , policy, register, mpc); 452 printf("Security policy loaded: %s (%s)\n", mpc->mpc_fullname, 453 mpc->mpc_name); 454 455 out: 456 mac_policy_xunlock(); 457 return (error); 458 } 459 460 static int 461 mac_policy_unregister(struct mac_policy_conf *mpc) 462 { 463 464 /* 465 * If we fail the load, we may get a request to unload. Check to see 466 * if we did the run-time registration, and if not, silently succeed. 467 */ 468 mac_policy_xlock(); 469 if ((mpc->mpc_runtime_flags & MPC_RUNTIME_FLAG_REGISTERED) == 0) { 470 mac_policy_xunlock(); 471 return (0); 472 } 473 #if 0 474 /* 475 * Don't allow unloading modules with private data. 476 */ 477 if (mpc->mpc_field_off != NULL) { 478 mac_policy_xunlock(); 479 return (EBUSY); 480 } 481 #endif 482 /* 483 * Only allow the unload to proceed if the module is unloadable by 484 * its own definition. 485 */ 486 if ((mpc->mpc_loadtime_flags & MPC_LOADTIME_FLAG_UNLOADOK) == 0) { 487 mac_policy_xunlock(); 488 return (EBUSY); 489 } 490 if (mpc->mpc_ops->mpo_destroy != NULL) 491 (*(mpc->mpc_ops->mpo_destroy))(mpc); 492 493 LIST_REMOVE(mpc, mpc_list); 494 mpc->mpc_runtime_flags &= ~MPC_RUNTIME_FLAG_REGISTERED; 495 mac_policy_update(); 496 mac_policy_xunlock(); 497 498 SDT_PROBE1(mac, , policy, unregister, mpc); 499 printf("Security policy unload: %s (%s)\n", mpc->mpc_fullname, 500 mpc->mpc_name); 501 502 return (0); 503 } 504 505 /* 506 * Allow MAC policy modules to register during boot, etc. 507 */ 508 int 509 mac_policy_modevent(module_t mod, int type, void *data) 510 { 511 struct mac_policy_conf *mpc; 512 int error; 513 514 error = 0; 515 mpc = (struct mac_policy_conf *) data; 516 517 #ifdef MAC_STATIC 518 if (mac_late) { 519 printf("mac_policy_modevent: MAC_STATIC and late\n"); 520 return (EBUSY); 521 } 522 #endif 523 524 SDT_PROBE2(mac, , policy, modevent, type, mpc); 525 switch (type) { 526 case MOD_LOAD: 527 if (mpc->mpc_loadtime_flags & MPC_LOADTIME_FLAG_NOTLATE && 528 mac_late) { 529 printf("mac_policy_modevent: can't load %s policy " 530 "after booting\n", mpc->mpc_name); 531 error = EBUSY; 532 break; 533 } 534 error = mac_policy_register(mpc); 535 break; 536 case MOD_UNLOAD: 537 /* Don't unregister the module if it was never registered. */ 538 if ((mpc->mpc_runtime_flags & MPC_RUNTIME_FLAG_REGISTERED) 539 != 0) 540 error = mac_policy_unregister(mpc); 541 else 542 error = 0; 543 break; 544 default: 545 error = EOPNOTSUPP; 546 break; 547 } 548 549 return (error); 550 } 551 552 /* 553 * Define an error value precedence, and given two arguments, selects the 554 * value with the higher precedence. 555 */ 556 int 557 mac_error_select(int error1, int error2) 558 { 559 560 /* Certain decision-making errors take top priority. */ 561 if (error1 == EDEADLK || error2 == EDEADLK) 562 return (EDEADLK); 563 564 /* Invalid arguments should be reported where possible. */ 565 if (error1 == EINVAL || error2 == EINVAL) 566 return (EINVAL); 567 568 /* Precedence goes to "visibility", with both process and file. */ 569 if (error1 == ESRCH || error2 == ESRCH) 570 return (ESRCH); 571 572 if (error1 == ENOENT || error2 == ENOENT) 573 return (ENOENT); 574 575 /* Precedence goes to DAC/MAC protections. */ 576 if (error1 == EACCES || error2 == EACCES) 577 return (EACCES); 578 579 /* Precedence goes to privilege. */ 580 if (error1 == EPERM || error2 == EPERM) 581 return (EPERM); 582 583 /* Precedence goes to error over success; otherwise, arbitrary. */ 584 if (error1 != 0) 585 return (error1); 586 return (error2); 587 } 588 589 int 590 mac_check_structmac_consistent(struct mac *mac) 591 { 592 593 /* Require that labels have a non-zero length. */ 594 if (mac->m_buflen > MAC_MAX_LABEL_BUF_LEN || 595 mac->m_buflen <= sizeof("")) 596 return (EINVAL); 597 598 return (0); 599 } 600 601 SYSINIT(mac, SI_SUB_MAC, SI_ORDER_FIRST, mac_init, NULL); 602 SYSINIT(mac_late, SI_SUB_MAC_LATE, SI_ORDER_FIRST, mac_late_init, NULL); 603