audit.c revision 181053
1228753Smm/*- 2228753Smm * Copyright (c) 1999-2005 Apple Inc. 3228753Smm * Copyright (c) 2006-2007 Robert N. M. Watson 4228753Smm * All rights reserved. 5228753Smm * 6228753Smm * Redistribution and use in source and binary forms, with or without 7228753Smm * modification, are permitted provided that the following conditions 8228753Smm * are met: 9228753Smm * 1. Redistributions of source code must retain the above copyright 10228753Smm * notice, this list of conditions and the following disclaimer. 11228753Smm * 2. Redistributions in binary form must reproduce the above copyright 12228753Smm * notice, this list of conditions and the following disclaimer in the 13228753Smm * documentation and/or other materials provided with the distribution. 14228753Smm * 3. Neither the name of Apple Inc. ("Apple") nor the names of 15228753Smm * its contributors may be used to endorse or promote products derived 16228753Smm * from this software without specific prior written permission. 17228753Smm * 18228753Smm * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND 19228753Smm * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20228753Smm * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21228753Smm * ARE DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR 22228753Smm * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23228753Smm * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24228753Smm * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25228753Smm * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 26228753Smm * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING 27228753Smm * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 28228753Smm * POSSIBILITY OF SUCH DAMAGE. 29228753Smm */ 30228753Smm 31228753Smm#include <sys/cdefs.h> 32228753Smm__FBSDID("$FreeBSD: head/sys/security/audit/audit.c 181053 2008-07-31 09:54:35Z rwatson $"); 33228753Smm 34228753Smm#include <sys/param.h> 35228753Smm#include <sys/condvar.h> 36228753Smm#include <sys/conf.h> 37228753Smm#include <sys/file.h> 38228753Smm#include <sys/filedesc.h> 39228753Smm#include <sys/fcntl.h> 40228753Smm#include <sys/ipc.h> 41228753Smm#include <sys/kernel.h> 42228753Smm#include <sys/kthread.h> 43228753Smm#include <sys/malloc.h> 44228753Smm#include <sys/mount.h> 45228753Smm#include <sys/namei.h> 46228753Smm#include <sys/priv.h> 47228753Smm#include <sys/proc.h> 48228753Smm#include <sys/queue.h> 49228753Smm#include <sys/socket.h> 50228753Smm#include <sys/socketvar.h> 51228753Smm#include <sys/protosw.h> 52228753Smm#include <sys/domain.h> 53228753Smm#include <sys/sysctl.h> 54228753Smm#include <sys/sysproto.h> 55228753Smm#include <sys/sysent.h> 56228753Smm#include <sys/systm.h> 57228753Smm#include <sys/ucred.h> 58228753Smm#include <sys/uio.h> 59228753Smm#include <sys/un.h> 60228753Smm#include <sys/unistd.h> 61228753Smm#include <sys/vnode.h> 62228753Smm 63228753Smm#include <bsm/audit.h> 64228753Smm#include <bsm/audit_internal.h> 65228753Smm#include <bsm/audit_kevents.h> 66228753Smm 67228753Smm#include <netinet/in.h> 68228753Smm#include <netinet/in_pcb.h> 69228753Smm 70228753Smm#include <security/audit/audit.h> 71228753Smm#include <security/audit/audit_private.h> 72228753Smm 73228753Smm#include <vm/uma.h> 74228753Smm 75228753Smmstatic uma_zone_t audit_record_zone; 76228753Smmstatic MALLOC_DEFINE(M_AUDITCRED, "audit_cred", "Audit cred storage"); 77228753SmmMALLOC_DEFINE(M_AUDITDATA, "audit_data", "Audit data storage"); 78228753SmmMALLOC_DEFINE(M_AUDITPATH, "audit_path", "Audit path storage"); 79228753SmmMALLOC_DEFINE(M_AUDITTEXT, "audit_text", "Audit text storage"); 80228753Smm 81228753SmmSYSCTL_NODE(_security, OID_AUTO, audit, CTLFLAG_RW, 0, 82228753Smm "TrustedBSD audit controls"); 83228753Smm 84228753Smm/* 85228753Smm * Audit control settings that are set/read by system calls and are hence 86228753Smm * non-static. 87228753Smm * 88228753Smm * Define the audit control flags. 89228753Smm */ 90228753Smmint audit_enabled; 91228753Smmint audit_suspended; 92228753Smm 93228753Smm/* 94228753Smm * Flags controlling behavior in low storage situations. Should we panic if 95228753Smm * a write fails? Should we fail stop if we're out of disk space? 96228753Smm */ 97228753Smmint audit_panic_on_write_fail; 98228753Smmint audit_fail_stop; 99228753Smmint audit_argv; 100228753Smmint audit_arge; 101228753Smm 102228753Smm/* 103228753Smm * Are we currently "failing stop" due to out of disk space? 104228753Smm */ 105228753Smmint audit_in_failure; 106228753Smm 107228753Smm/* 108228753Smm * Global audit statistics. 109228753Smm */ 110228753Smmstruct audit_fstat audit_fstat; 111228753Smm 112228753Smm/* 113228753Smm * Preselection mask for non-attributable events. 114228753Smm */ 115228753Smmstruct au_mask audit_nae_mask; 116228753Smm 117228753Smm/* 118228753Smm * Mutex to protect global variables shared between various threads and 119228753Smm * processes. 120228753Smm */ 121228753Smmstruct mtx audit_mtx; 122228753Smm 123228753Smm/* 124228753Smm * Queue of audit records ready for delivery to disk. We insert new records 125228753Smm * at the tail, and remove records from the head. Also, a count of the 126228753Smm * number of records used for checking queue depth. In addition, a counter 127228753Smm * of records that we have allocated but are not yet in the queue, which is 128228753Smm * needed to estimate the total size of the combined set of records 129228753Smm * outstanding in the system. 130228753Smm */ 131228753Smmstruct kaudit_queue audit_q; 132228753Smmint audit_q_len; 133228753Smmint audit_pre_q_len; 134228753Smm 135228753Smm/* 136228753Smm * Audit queue control settings (minimum free, low/high water marks, etc.) 137228753Smm */ 138struct au_qctrl audit_qctrl; 139 140/* 141 * Condition variable to signal to the worker that it has work to do: either 142 * new records are in the queue, or a log replacement is taking place. 143 */ 144struct cv audit_worker_cv; 145 146/* 147 * Condition variable to flag when crossing the low watermark, meaning that 148 * threads blocked due to hitting the high watermark can wake up and continue 149 * to commit records. 150 */ 151struct cv audit_watermark_cv; 152 153/* 154 * Condition variable for auditing threads wait on when in fail-stop mode. 155 * Threads wait on this CV forever (and ever), never seeing the light of day 156 * again. 157 */ 158static struct cv audit_fail_cv; 159 160/* 161 * Construct an audit record for the passed thread. 162 */ 163static int 164audit_record_ctor(void *mem, int size, void *arg, int flags) 165{ 166 struct kaudit_record *ar; 167 struct thread *td; 168 169 KASSERT(sizeof(*ar) == size, ("audit_record_ctor: wrong size")); 170 171 td = arg; 172 ar = mem; 173 bzero(ar, sizeof(*ar)); 174 ar->k_ar.ar_magic = AUDIT_RECORD_MAGIC; 175 nanotime(&ar->k_ar.ar_starttime); 176 177 /* 178 * Export the subject credential. 179 */ 180 cru2x(td->td_ucred, &ar->k_ar.ar_subj_cred); 181 ar->k_ar.ar_subj_ruid = td->td_ucred->cr_ruid; 182 ar->k_ar.ar_subj_rgid = td->td_ucred->cr_rgid; 183 ar->k_ar.ar_subj_egid = td->td_ucred->cr_groups[0]; 184 ar->k_ar.ar_subj_auid = td->td_ucred->cr_audit.ai_auid; 185 ar->k_ar.ar_subj_asid = td->td_ucred->cr_audit.ai_asid; 186 ar->k_ar.ar_subj_pid = td->td_proc->p_pid; 187 ar->k_ar.ar_subj_amask = td->td_ucred->cr_audit.ai_mask; 188 ar->k_ar.ar_subj_term_addr = td->td_ucred->cr_audit.ai_termid; 189 return (0); 190} 191 192static void 193audit_record_dtor(void *mem, int size, void *arg) 194{ 195 struct kaudit_record *ar; 196 197 KASSERT(sizeof(*ar) == size, ("audit_record_dtor: wrong size")); 198 199 ar = mem; 200 if (ar->k_ar.ar_arg_upath1 != NULL) 201 free(ar->k_ar.ar_arg_upath1, M_AUDITPATH); 202 if (ar->k_ar.ar_arg_upath2 != NULL) 203 free(ar->k_ar.ar_arg_upath2, M_AUDITPATH); 204 if (ar->k_ar.ar_arg_text != NULL) 205 free(ar->k_ar.ar_arg_text, M_AUDITTEXT); 206 if (ar->k_udata != NULL) 207 free(ar->k_udata, M_AUDITDATA); 208 if (ar->k_ar.ar_arg_argv != NULL) 209 free(ar->k_ar.ar_arg_argv, M_AUDITTEXT); 210 if (ar->k_ar.ar_arg_envv != NULL) 211 free(ar->k_ar.ar_arg_envv, M_AUDITTEXT); 212} 213 214/* 215 * Initialize the Audit subsystem: configuration state, work queue, 216 * synchronization primitives, worker thread, and trigger device node. Also 217 * call into the BSM assembly code to initialize it. 218 */ 219static void 220audit_init(void) 221{ 222 223 audit_enabled = 0; 224 audit_suspended = 0; 225 audit_panic_on_write_fail = 0; 226 audit_fail_stop = 0; 227 audit_in_failure = 0; 228 audit_argv = 0; 229 audit_arge = 0; 230 231 audit_fstat.af_filesz = 0; /* '0' means unset, unbounded. */ 232 audit_fstat.af_currsz = 0; 233 audit_nae_mask.am_success = 0; 234 audit_nae_mask.am_failure = 0; 235 236 TAILQ_INIT(&audit_q); 237 audit_q_len = 0; 238 audit_pre_q_len = 0; 239 audit_qctrl.aq_hiwater = AQ_HIWATER; 240 audit_qctrl.aq_lowater = AQ_LOWATER; 241 audit_qctrl.aq_bufsz = AQ_BUFSZ; 242 audit_qctrl.aq_minfree = AU_FS_MINFREE; 243 244 mtx_init(&audit_mtx, "audit_mtx", NULL, MTX_DEF); 245 cv_init(&audit_worker_cv, "audit_worker_cv"); 246 cv_init(&audit_watermark_cv, "audit_watermark_cv"); 247 cv_init(&audit_fail_cv, "audit_fail_cv"); 248 249 audit_record_zone = uma_zcreate("audit_record", 250 sizeof(struct kaudit_record), audit_record_ctor, 251 audit_record_dtor, NULL, NULL, UMA_ALIGN_PTR, 0); 252 253 /* Initialize the BSM audit subsystem. */ 254 kau_init(); 255 256 audit_trigger_init(); 257 258 /* Register shutdown handler. */ 259 EVENTHANDLER_REGISTER(shutdown_pre_sync, audit_shutdown, NULL, 260 SHUTDOWN_PRI_FIRST); 261 262 /* Start audit worker thread. */ 263 audit_worker_init(); 264} 265 266SYSINIT(audit_init, SI_SUB_AUDIT, SI_ORDER_FIRST, audit_init, NULL); 267 268/* 269 * Drain the audit queue and close the log at shutdown. Note that this can 270 * be called both from the system shutdown path and also from audit 271 * configuration syscalls, so 'arg' and 'howto' are ignored. 272 * 273 * XXXRW: In FreeBSD 7.x and 8.x, this fails to wait for the record queue to 274 * drain before returning, which could lead to lost records on shutdown. 275 */ 276void 277audit_shutdown(void *arg, int howto) 278{ 279 280 audit_rotate_vnode(NULL, NULL); 281} 282 283/* 284 * Return the current thread's audit record, if any. 285 */ 286struct kaudit_record * 287currecord(void) 288{ 289 290 return (curthread->td_ar); 291} 292 293/* 294 * XXXAUDIT: There are a number of races present in the code below due to 295 * release and re-grab of the mutex. The code should be revised to become 296 * slightly less racy. 297 * 298 * XXXAUDIT: Shouldn't there be logic here to sleep waiting on available 299 * pre_q space, suspending the system call until there is room? 300 */ 301struct kaudit_record * 302audit_new(int event, struct thread *td) 303{ 304 struct kaudit_record *ar; 305 int no_record; 306 307 mtx_lock(&audit_mtx); 308 no_record = (audit_suspended || !audit_enabled); 309 mtx_unlock(&audit_mtx); 310 if (no_record) 311 return (NULL); 312 313 /* 314 * Note: the number of outstanding uncommitted audit records is 315 * limited to the number of concurrent threads servicing system calls 316 * in the kernel. 317 */ 318 ar = uma_zalloc_arg(audit_record_zone, td, M_WAITOK); 319 ar->k_ar.ar_event = event; 320 321 mtx_lock(&audit_mtx); 322 audit_pre_q_len++; 323 mtx_unlock(&audit_mtx); 324 325 return (ar); 326} 327 328void 329audit_free(struct kaudit_record *ar) 330{ 331 332 uma_zfree(audit_record_zone, ar); 333} 334 335void 336audit_commit(struct kaudit_record *ar, int error, int retval) 337{ 338 au_event_t event; 339 au_class_t class; 340 au_id_t auid; 341 int sorf; 342 struct au_mask *aumask; 343 344 if (ar == NULL) 345 return; 346 347 /* 348 * Decide whether to commit the audit record by checking the error 349 * value from the system call and using the appropriate audit mask. 350 */ 351 if (ar->k_ar.ar_subj_auid == AU_DEFAUDITID) 352 aumask = &audit_nae_mask; 353 else 354 aumask = &ar->k_ar.ar_subj_amask; 355 356 if (error) 357 sorf = AU_PRS_FAILURE; 358 else 359 sorf = AU_PRS_SUCCESS; 360 361 switch(ar->k_ar.ar_event) { 362 case AUE_OPEN_RWTC: 363 /* 364 * The open syscall always writes a AUE_OPEN_RWTC event; 365 * change it to the proper type of event based on the flags 366 * and the error value. 367 */ 368 ar->k_ar.ar_event = audit_flags_and_error_to_openevent( 369 ar->k_ar.ar_arg_fflags, error); 370 break; 371 372 case AUE_SYSCTL: 373 ar->k_ar.ar_event = audit_ctlname_to_sysctlevent( 374 ar->k_ar.ar_arg_ctlname, ar->k_ar.ar_valid_arg); 375 break; 376 377 case AUE_AUDITON: 378 /* Convert the auditon() command to an event. */ 379 ar->k_ar.ar_event = auditon_command_event(ar->k_ar.ar_arg_cmd); 380 break; 381 } 382 383 auid = ar->k_ar.ar_subj_auid; 384 event = ar->k_ar.ar_event; 385 class = au_event_class(event); 386 387 ar->k_ar_commit |= AR_COMMIT_KERNEL; 388 if (au_preselect(event, class, aumask, sorf) != 0) 389 ar->k_ar_commit |= AR_PRESELECT_TRAIL; 390 if (audit_pipe_preselect(auid, event, class, sorf, 391 ar->k_ar_commit & AR_PRESELECT_TRAIL) != 0) 392 ar->k_ar_commit |= AR_PRESELECT_PIPE; 393 if ((ar->k_ar_commit & (AR_PRESELECT_TRAIL | AR_PRESELECT_PIPE | 394 AR_PRESELECT_USER_TRAIL | AR_PRESELECT_USER_PIPE)) == 0) { 395 mtx_lock(&audit_mtx); 396 audit_pre_q_len--; 397 mtx_unlock(&audit_mtx); 398 audit_free(ar); 399 return; 400 } 401 402 ar->k_ar.ar_errno = error; 403 ar->k_ar.ar_retval = retval; 404 nanotime(&ar->k_ar.ar_endtime); 405 406 /* 407 * Note: it could be that some records initiated while audit was 408 * enabled should still be committed? 409 */ 410 mtx_lock(&audit_mtx); 411 if (audit_suspended || !audit_enabled) { 412 audit_pre_q_len--; 413 mtx_unlock(&audit_mtx); 414 audit_free(ar); 415 return; 416 } 417 418 /* 419 * Constrain the number of committed audit records based on the 420 * configurable parameter. 421 */ 422 while (audit_q_len >= audit_qctrl.aq_hiwater) 423 cv_wait(&audit_watermark_cv, &audit_mtx); 424 425 TAILQ_INSERT_TAIL(&audit_q, ar, k_q); 426 audit_q_len++; 427 audit_pre_q_len--; 428 cv_signal(&audit_worker_cv); 429 mtx_unlock(&audit_mtx); 430} 431 432/* 433 * audit_syscall_enter() is called on entry to each system call. It is 434 * responsible for deciding whether or not to audit the call (preselection), 435 * and if so, allocating a per-thread audit record. audit_new() will fill in 436 * basic thread/credential properties. 437 */ 438void 439audit_syscall_enter(unsigned short code, struct thread *td) 440{ 441 struct au_mask *aumask; 442 au_class_t class; 443 au_event_t event; 444 au_id_t auid; 445 446 KASSERT(td->td_ar == NULL, ("audit_syscall_enter: td->td_ar != NULL")); 447 448 /* 449 * In FreeBSD, each ABI has its own system call table, and hence 450 * mapping of system call codes to audit events. Convert the code to 451 * an audit event identifier using the process system call table 452 * reference. In Darwin, there's only one, so we use the global 453 * symbol for the system call table. No audit record is generated 454 * for bad system calls, as no operation has been performed. 455 */ 456 if (code >= td->td_proc->p_sysent->sv_size) 457 return; 458 459 event = td->td_proc->p_sysent->sv_table[code].sy_auevent; 460 if (event == AUE_NULL) 461 return; 462 463 /* 464 * Check which audit mask to use; either the kernel non-attributable 465 * event mask or the process audit mask. 466 */ 467 auid = td->td_ucred->cr_audit.ai_auid; 468 if (auid == AU_DEFAUDITID) 469 aumask = &audit_nae_mask; 470 else 471 aumask = &td->td_ucred->cr_audit.ai_mask; 472 473 /* 474 * Allocate an audit record, if preselection allows it, and store in 475 * the thread for later use. 476 */ 477 class = au_event_class(event); 478 if (au_preselect(event, class, aumask, AU_PRS_BOTH)) { 479 /* 480 * If we're out of space and need to suspend unprivileged 481 * processes, do that here rather than trying to allocate 482 * another audit record. 483 * 484 * Note: we might wish to be able to continue here in the 485 * future, if the system recovers. That should be possible 486 * by means of checking the condition in a loop around 487 * cv_wait(). It might be desirable to reevaluate whether an 488 * audit record is still required for this event by 489 * re-calling au_preselect(). 490 */ 491 if (audit_in_failure && 492 priv_check(td, PRIV_AUDIT_FAILSTOP) != 0) { 493 cv_wait(&audit_fail_cv, &audit_mtx); 494 panic("audit_failing_stop: thread continued"); 495 } 496 td->td_ar = audit_new(event, td); 497 } else if (audit_pipe_preselect(auid, event, class, AU_PRS_BOTH, 0)) 498 td->td_ar = audit_new(event, td); 499 else 500 td->td_ar = NULL; 501} 502 503/* 504 * audit_syscall_exit() is called from the return of every system call, or in 505 * the event of exit1(), during the execution of exit1(). It is responsible 506 * for committing the audit record, if any, along with return condition. 507 */ 508void 509audit_syscall_exit(int error, struct thread *td) 510{ 511 int retval; 512 513 /* 514 * Commit the audit record as desired; once we pass the record into 515 * audit_commit(), the memory is owned by the audit subsystem. The 516 * return value from the system call is stored on the user thread. 517 * If there was an error, the return value is set to -1, imitating 518 * the behavior of the cerror routine. 519 */ 520 if (error) 521 retval = -1; 522 else 523 retval = td->td_retval[0]; 524 525 audit_commit(td->td_ar, error, retval); 526 td->td_ar = NULL; 527} 528 529void 530audit_cred_copy(struct ucred *src, struct ucred *dest) 531{ 532 533 bcopy(&src->cr_audit, &dest->cr_audit, sizeof(dest->cr_audit)); 534} 535 536void 537audit_cred_destroy(struct ucred *cred) 538{ 539 540} 541 542void 543audit_cred_init(struct ucred *cred) 544{ 545 546 bzero(&cred->cr_audit, sizeof(cred->cr_audit)); 547} 548 549/* 550 * Initialize audit information for the first kernel process (proc 0) and for 551 * the first user process (init). 552 */ 553void 554audit_cred_kproc0(struct ucred *cred) 555{ 556 557 cred->cr_audit.ai_auid = AU_DEFAUDITID; 558 cred->cr_audit.ai_termid.at_type = AU_IPv4; 559} 560 561void 562audit_cred_proc1(struct ucred *cred) 563{ 564 565 cred->cr_audit.ai_auid = AU_DEFAUDITID; 566 cred->cr_audit.ai_termid.at_type = AU_IPv4; 567} 568 569void 570audit_thread_alloc(struct thread *td) 571{ 572 573 td->td_ar = NULL; 574} 575 576void 577audit_thread_free(struct thread *td) 578{ 579 580 KASSERT(td->td_ar == NULL, ("audit_thread_free: td_ar != NULL")); 581} 582 583void 584audit_proc_coredump(struct thread *td, char *path, int errcode) 585{ 586 struct kaudit_record *ar; 587 struct au_mask *aumask; 588 au_class_t class; 589 int ret, sorf; 590 char **pathp; 591 au_id_t auid; 592 593 ret = 0; 594 595 /* 596 * Make sure we are using the correct preselection mask. 597 */ 598 auid = td->td_ucred->cr_audit.ai_auid; 599 if (auid == AU_DEFAUDITID) 600 aumask = &audit_nae_mask; 601 else 602 aumask = &td->td_ucred->cr_audit.ai_mask; 603 /* 604 * It's possible for coredump(9) generation to fail. Make sure that 605 * we handle this case correctly for preselection. 606 */ 607 if (errcode != 0) 608 sorf = AU_PRS_FAILURE; 609 else 610 sorf = AU_PRS_SUCCESS; 611 class = au_event_class(AUE_CORE); 612 if (au_preselect(AUE_CORE, class, aumask, sorf) == 0) 613 return; 614 /* 615 * If we are interested in seeing this audit record, allocate it. 616 * Where possible coredump records should contain a pathname and arg32 617 * (signal) tokens. 618 */ 619 ar = audit_new(AUE_CORE, td); 620 if (path != NULL) { 621 pathp = &ar->k_ar.ar_arg_upath1; 622 *pathp = malloc(MAXPATHLEN, M_AUDITPATH, M_WAITOK); 623 audit_canon_path(td, path, *pathp); 624 ARG_SET_VALID(ar, ARG_UPATH1); 625 } 626 ar->k_ar.ar_arg_signum = td->td_proc->p_sig; 627 ARG_SET_VALID(ar, ARG_SIGNUM); 628 if (errcode != 0) 629 ret = 1; 630 audit_commit(ar, errcode, ret); 631} 632