1 /*- 2 * Copyright (c) 1999-2002 Robert N. M. Watson 3 * Copyright (c) 2001 Ilmar S. Habibulin 4 * Copyright (c) 2001-2003 Networks Associates Technology, Inc. 5 * All rights reserved. 6 * 7 * This software was developed by Robert Watson and Ilmar Habibulin for the 8 * TrustedBSD Project. 9 * 10 * This software was developed for the FreeBSD Project in part by Network 11 * Associates Laboratories, the Security Research Division of Network 12 * Associates, Inc. under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), 13 * as part of the DARPA CHATS research program. 14 * 15 * Redistribution and use in source and binary forms, with or without 16 * modification, are permitted provided that the following conditions 17 * are met: 18 * 1. Redistributions of source code must retain the above copyright 19 * notice, this list of conditions and the following disclaimer. 20 * 2. Redistributions in binary form must reproduce the above copyright 21 * notice, this list of conditions and the following disclaimer in the 22 * documentation and/or other materials provided with the distribution. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 */ 36 37 #include <sys/cdefs.h> 38 __FBSDID("$FreeBSD$"); 39 40 #include "opt_mac.h" 41 42 #include <sys/param.h> 43 #include <sys/condvar.h> 44 #include <sys/imgact.h> 45 #include <sys/kernel.h> 46 #include <sys/lock.h> 47 #include <sys/malloc.h> 48 #include <sys/mutex.h> 49 #include <sys/mac.h> 50 #include <sys/proc.h> 51 #include <sys/sbuf.h> 52 #include <sys/systm.h> 53 #include <sys/vnode.h> 54 #include <sys/mount.h> 55 #include <sys/file.h> 56 #include <sys/namei.h> 57 #include <sys/sysctl.h> 58 59 #include <vm/vm.h> 60 #include <vm/pmap.h> 61 #include <vm/vm_map.h> 62 #include <vm/vm_object.h> 63 64 #include <sys/mac_policy.h> 65 66 #include <security/mac/mac_internal.h> 67 68 int mac_enforce_process = 1; 69 SYSCTL_INT(_security_mac, OID_AUTO, enforce_process, CTLFLAG_RW, 70 &mac_enforce_process, 0, "Enforce MAC policy on inter-process operations"); 71 TUNABLE_INT("security.mac.enforce_process", &mac_enforce_process); 72 73 int mac_enforce_vm = 1; 74 SYSCTL_INT(_security_mac, OID_AUTO, enforce_vm, CTLFLAG_RW, 75 &mac_enforce_vm, 0, "Enforce MAC policy on vm operations"); 76 TUNABLE_INT("security.mac.enforce_vm", &mac_enforce_vm); 77 78 static int mac_mmap_revocation = 1; 79 SYSCTL_INT(_security_mac, OID_AUTO, mmap_revocation, CTLFLAG_RW, 80 &mac_mmap_revocation, 0, "Revoke mmap access to files on subject " 81 "relabel"); 82 83 static int mac_mmap_revocation_via_cow = 0; 84 SYSCTL_INT(_security_mac, OID_AUTO, mmap_revocation_via_cow, CTLFLAG_RW, 85 &mac_mmap_revocation_via_cow, 0, "Revoke mmap access to files via " 86 "copy-on-write semantics, or by removing all write access"); 87 88 #ifdef MAC_DEBUG 89 static unsigned int nmaccreds, nmacprocs; 90 SYSCTL_UINT(_security_mac_debug_counters, OID_AUTO, creds, CTLFLAG_RD, 91 &nmaccreds, 0, "number of ucreds in use"); 92 SYSCTL_UINT(_security_mac_debug_counters, OID_AUTO, procs, CTLFLAG_RD, 93 &nmacprocs, 0, "number of procs in use"); 94 #endif 95 96 static void mac_cred_mmapped_drop_perms_recurse(struct thread *td, 97 struct ucred *cred, struct vm_map *map); 98 99 struct label * 100 mac_cred_label_alloc(void) 101 { 102 struct label *label; 103 104 label = mac_labelzone_alloc(M_WAITOK); 105 MAC_PERFORM(init_cred_label, label); 106 MAC_DEBUG_COUNTER_INC(&nmaccreds); 107 return (label); 108 } 109 110 void 111 mac_init_cred(struct ucred *cred) 112 { 113 114 cred->cr_label = mac_cred_label_alloc(); 115 } 116 117 static struct label * 118 mac_proc_label_alloc(void) 119 { 120 struct label *label; 121 122 label = mac_labelzone_alloc(M_WAITOK); 123 MAC_PERFORM(init_proc_label, label); 124 MAC_DEBUG_COUNTER_INC(&nmacprocs); 125 return (label); 126 } 127 128 void 129 mac_init_proc(struct proc *p) 130 { 131 132 p->p_label = mac_proc_label_alloc(); 133 } 134 135 void 136 mac_cred_label_free(struct label *label) 137 { 138 139 MAC_PERFORM(destroy_cred_label, label); 140 mac_labelzone_free(label); 141 MAC_DEBUG_COUNTER_DEC(&nmaccreds); 142 } 143 144 void 145 mac_destroy_cred(struct ucred *cred) 146 { 147 148 mac_cred_label_free(cred->cr_label); 149 cred->cr_label = NULL; 150 } 151 152 static void 153 mac_proc_label_free(struct label *label) 154 { 155 156 MAC_PERFORM(destroy_proc_label, label); 157 mac_labelzone_free(label); 158 MAC_DEBUG_COUNTER_DEC(&nmacprocs); 159 } 160 161 void 162 mac_destroy_proc(struct proc *p) 163 { 164 165 mac_proc_label_free(p->p_label); 166 p->p_label = NULL; 167 } 168 169 int 170 mac_externalize_cred_label(struct label *label, char *elements, 171 char *outbuf, size_t outbuflen) 172 { 173 int error; 174 175 MAC_EXTERNALIZE(cred, label, elements, outbuf, outbuflen); 176 177 return (error); 178 } 179 180 int 181 mac_internalize_cred_label(struct label *label, char *string) 182 { 183 int error; 184 185 MAC_INTERNALIZE(cred, label, string); 186 187 return (error); 188 } 189 190 /* 191 * Initialize MAC label for the first kernel process, from which other 192 * kernel processes and threads are spawned. 193 */ 194 void 195 mac_create_proc0(struct ucred *cred) 196 { 197 198 MAC_PERFORM(create_proc0, cred); 199 } 200 201 /* 202 * Initialize MAC label for the first userland process, from which other 203 * userland processes and threads are spawned. 204 */ 205 void 206 mac_create_proc1(struct ucred *cred) 207 { 208 209 MAC_PERFORM(create_proc1, cred); 210 } 211 212 void 213 mac_thread_userret(struct thread *td) 214 { 215 216 MAC_PERFORM(thread_userret, td); 217 } 218 219 /* 220 * When a new process is created, its label must be initialized. Generally, 221 * this involves inheritence from the parent process, modulo possible 222 * deltas. This function allows that processing to take place. 223 */ 224 void 225 mac_copy_cred(struct ucred *src, struct ucred *dest) 226 { 227 228 MAC_PERFORM(copy_cred_label, src->cr_label, dest->cr_label); 229 } 230 231 int 232 mac_execve_enter(struct image_params *imgp, struct mac *mac_p) 233 { 234 struct label *label; 235 struct mac mac; 236 char *buffer; 237 int error; 238 239 if (mac_p == NULL) 240 return (0); 241 242 error = copyin(mac_p, &mac, sizeof(mac)); 243 if (error) 244 return (error); 245 246 error = mac_check_structmac_consistent(&mac); 247 if (error) 248 return (error); 249 250 buffer = malloc(mac.m_buflen, M_MACTEMP, M_WAITOK); 251 error = copyinstr(mac.m_string, buffer, mac.m_buflen, NULL); 252 if (error) { 253 free(buffer, M_MACTEMP); 254 return (error); 255 } 256 257 label = mac_cred_label_alloc(); 258 error = mac_internalize_cred_label(label, buffer); 259 free(buffer, M_MACTEMP); 260 if (error) { 261 mac_cred_label_free(label); 262 return (error); 263 } 264 imgp->execlabel = label; 265 return (0); 266 } 267 268 void 269 mac_execve_exit(struct image_params *imgp) 270 { 271 if (imgp->execlabel != NULL) { 272 mac_cred_label_free(imgp->execlabel); 273 imgp->execlabel = NULL; 274 } 275 } 276 277 /* 278 * When relabeling a process, call out to the policies for the maximum 279 * permission allowed for each object type we know about in its 280 * memory space, and revoke access (in the least surprising ways we 281 * know) when necessary. The process lock is not held here. 282 */ 283 void 284 mac_cred_mmapped_drop_perms(struct thread *td, struct ucred *cred) 285 { 286 287 /* XXX freeze all other threads */ 288 mac_cred_mmapped_drop_perms_recurse(td, cred, 289 &td->td_proc->p_vmspace->vm_map); 290 /* XXX allow other threads to continue */ 291 } 292 293 static __inline const char * 294 prot2str(vm_prot_t prot) 295 { 296 297 switch (prot & VM_PROT_ALL) { 298 case VM_PROT_READ: 299 return ("r--"); 300 case VM_PROT_READ | VM_PROT_WRITE: 301 return ("rw-"); 302 case VM_PROT_READ | VM_PROT_EXECUTE: 303 return ("r-x"); 304 case VM_PROT_READ | VM_PROT_WRITE | VM_PROT_EXECUTE: 305 return ("rwx"); 306 case VM_PROT_WRITE: 307 return ("-w-"); 308 case VM_PROT_EXECUTE: 309 return ("--x"); 310 case VM_PROT_WRITE | VM_PROT_EXECUTE: 311 return ("-wx"); 312 default: 313 return ("---"); 314 } 315 } 316 317 static void 318 mac_cred_mmapped_drop_perms_recurse(struct thread *td, struct ucred *cred, 319 struct vm_map *map) 320 { 321 struct vm_map_entry *vme; 322 int result; 323 vm_prot_t revokeperms; 324 vm_object_t object; 325 vm_ooffset_t offset; 326 struct vnode *vp; 327 328 if (!mac_mmap_revocation) 329 return; 330 331 vm_map_lock_read(map); 332 for (vme = map->header.next; vme != &map->header; vme = vme->next) { 333 if (vme->eflags & MAP_ENTRY_IS_SUB_MAP) { 334 mac_cred_mmapped_drop_perms_recurse(td, cred, 335 vme->object.sub_map); 336 continue; 337 } 338 /* 339 * Skip over entries that obviously are not shared. 340 */ 341 if (vme->eflags & (MAP_ENTRY_COW | MAP_ENTRY_NOSYNC) || 342 !vme->max_protection) 343 continue; 344 /* 345 * Drill down to the deepest backing object. 346 */ 347 offset = vme->offset; 348 object = vme->object.vm_object; 349 if (object == NULL) 350 continue; 351 while (object->backing_object != NULL) { 352 object = object->backing_object; 353 offset += object->backing_object_offset; 354 } 355 /* 356 * At the moment, vm_maps and objects aren't considered 357 * by the MAC system, so only things with backing by a 358 * normal object (read: vnodes) are checked. 359 */ 360 if (object->type != OBJT_VNODE) 361 continue; 362 vp = (struct vnode *)object->handle; 363 vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, td); 364 result = vme->max_protection; 365 mac_check_vnode_mmap_downgrade(cred, vp, &result); 366 VOP_UNLOCK(vp, 0, td); 367 /* 368 * Find out what maximum protection we may be allowing 369 * now but a policy needs to get removed. 370 */ 371 revokeperms = vme->max_protection & ~result; 372 if (!revokeperms) 373 continue; 374 printf("pid %ld: revoking %s perms from %#lx:%ld " 375 "(max %s/cur %s)\n", (long)td->td_proc->p_pid, 376 prot2str(revokeperms), (u_long)vme->start, 377 (long)(vme->end - vme->start), 378 prot2str(vme->max_protection), prot2str(vme->protection)); 379 vm_map_lock_upgrade(map); 380 /* 381 * This is the really simple case: if a map has more 382 * max_protection than is allowed, but it's not being 383 * actually used (that is, the current protection is 384 * still allowed), we can just wipe it out and do 385 * nothing more. 386 */ 387 if ((vme->protection & revokeperms) == 0) { 388 vme->max_protection -= revokeperms; 389 } else { 390 if (revokeperms & VM_PROT_WRITE) { 391 /* 392 * In the more complicated case, flush out all 393 * pending changes to the object then turn it 394 * copy-on-write. 395 */ 396 vm_object_reference(object); 397 vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, td); 398 VM_OBJECT_LOCK(object); 399 vm_object_page_clean(object, 400 OFF_TO_IDX(offset), 401 OFF_TO_IDX(offset + vme->end - vme->start + 402 PAGE_MASK), 403 OBJPC_SYNC); 404 VM_OBJECT_UNLOCK(object); 405 VOP_UNLOCK(vp, 0, td); 406 vm_object_deallocate(object); 407 /* 408 * Why bother if there's no read permissions 409 * anymore? For the rest, we need to leave 410 * the write permissions on for COW, or 411 * remove them entirely if configured to. 412 */ 413 if (!mac_mmap_revocation_via_cow) { 414 vme->max_protection &= ~VM_PROT_WRITE; 415 vme->protection &= ~VM_PROT_WRITE; 416 } if ((revokeperms & VM_PROT_READ) == 0) 417 vme->eflags |= MAP_ENTRY_COW | 418 MAP_ENTRY_NEEDS_COPY; 419 } 420 if (revokeperms & VM_PROT_EXECUTE) { 421 vme->max_protection &= ~VM_PROT_EXECUTE; 422 vme->protection &= ~VM_PROT_EXECUTE; 423 } 424 if (revokeperms & VM_PROT_READ) { 425 vme->max_protection = 0; 426 vme->protection = 0; 427 } 428 pmap_protect(map->pmap, vme->start, vme->end, 429 vme->protection & ~revokeperms); 430 vm_map_simplify_entry(map, vme); 431 } 432 vm_map_lock_downgrade(map); 433 } 434 vm_map_unlock_read(map); 435 } 436 437 /* 438 * When the subject's label changes, it may require revocation of privilege 439 * to mapped objects. This can't be done on-the-fly later with a unified 440 * buffer cache. 441 */ 442 void 443 mac_relabel_cred(struct ucred *cred, struct label *newlabel) 444 { 445 446 MAC_PERFORM(relabel_cred, cred, newlabel); 447 } 448 449 int 450 mac_check_cred_relabel(struct ucred *cred, struct label *newlabel) 451 { 452 int error; 453 454 MAC_CHECK(check_cred_relabel, cred, newlabel); 455 456 return (error); 457 } 458 459 int 460 mac_check_cred_visible(struct ucred *u1, struct ucred *u2) 461 { 462 int error; 463 464 if (!mac_enforce_process) 465 return (0); 466 467 MAC_CHECK(check_cred_visible, u1, u2); 468 469 return (error); 470 } 471 472 int 473 mac_check_proc_debug(struct ucred *cred, struct proc *proc) 474 { 475 int error; 476 477 PROC_LOCK_ASSERT(proc, MA_OWNED); 478 479 if (!mac_enforce_process) 480 return (0); 481 482 MAC_CHECK(check_proc_debug, cred, proc); 483 484 return (error); 485 } 486 487 int 488 mac_check_proc_sched(struct ucred *cred, struct proc *proc) 489 { 490 int error; 491 492 PROC_LOCK_ASSERT(proc, MA_OWNED); 493 494 if (!mac_enforce_process) 495 return (0); 496 497 MAC_CHECK(check_proc_sched, cred, proc); 498 499 return (error); 500 } 501 502 int 503 mac_check_proc_signal(struct ucred *cred, struct proc *proc, int signum) 504 { 505 int error; 506 507 PROC_LOCK_ASSERT(proc, MA_OWNED); 508 509 if (!mac_enforce_process) 510 return (0); 511 512 MAC_CHECK(check_proc_signal, cred, proc, signum); 513 514 return (error); 515 } 516