1 /*- 2 * Copyright (c) 1999-2008 Apple Inc. 3 * Copyright (c) 2006-2008 Robert N. M. Watson 4 * All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 3. Neither the name of Apple Inc. ("Apple") nor the names of 15 * its contributors may be used to endorse or promote products derived 16 * from this software without specific prior written permission. 17 * 18 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND 19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21 * ARE DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR 22 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 26 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING 27 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 28 * POSSIBILITY OF SUCH DAMAGE. 29 */ 30 31 #include <sys/cdefs.h> 32 __FBSDID("$FreeBSD$"); 33 34 #include <sys/param.h> 35 #include <sys/condvar.h> 36 #include <sys/conf.h> 37 #include <sys/file.h> 38 #include <sys/filedesc.h> 39 #include <sys/fcntl.h> 40 #include <sys/ipc.h> 41 #include <sys/kernel.h> 42 #include <sys/kthread.h> 43 #include <sys/malloc.h> 44 #include <sys/mount.h> 45 #include <sys/namei.h> 46 #include <sys/proc.h> 47 #include <sys/queue.h> 48 #include <sys/socket.h> 49 #include <sys/socketvar.h> 50 #include <sys/protosw.h> 51 #include <sys/domain.h> 52 #include <sys/sx.h> 53 #include <sys/sysproto.h> 54 #include <sys/sysent.h> 55 #include <sys/systm.h> 56 #include <sys/ucred.h> 57 #include <sys/uio.h> 58 #include <sys/un.h> 59 #include <sys/unistd.h> 60 #include <sys/vnode.h> 61 62 #include <bsm/audit.h> 63 #include <bsm/audit_internal.h> 64 #include <bsm/audit_kevents.h> 65 66 #include <netinet/in.h> 67 #include <netinet/in_pcb.h> 68 69 #include <security/audit/audit.h> 70 #include <security/audit/audit_private.h> 71 72 #include <vm/uma.h> 73 74 #include <machine/stdarg.h> 75 76 /* 77 * Worker thread that will schedule disk I/O, etc. 78 */ 79 static struct proc *audit_thread; 80 81 /* 82 * audit_cred and audit_vp are the stored credential and vnode to use for 83 * active audit trail. They are protected by the audit worker lock, which 84 * will be held across all I/O and all rotation to prevent them from being 85 * replaced (rotated) while in use. The audit_file_rotate_wait flag is set 86 * when the kernel has delivered a trigger to auditd to rotate the trail, and 87 * is cleared when the next rotation takes place. It is also protected by 88 * the audit worker lock. 89 */ 90 static int audit_file_rotate_wait; 91 static struct ucred *audit_cred; 92 static struct vnode *audit_vp; 93 static off_t audit_size; 94 static struct sx audit_worker_lock; 95 96 #define AUDIT_WORKER_LOCK_INIT() sx_init(&audit_worker_lock, \ 97 "audit_worker_lock"); 98 #define AUDIT_WORKER_LOCK_ASSERT() sx_assert(&audit_worker_lock, \ 99 SA_XLOCKED) 100 #define AUDIT_WORKER_LOCK() sx_xlock(&audit_worker_lock) 101 #define AUDIT_WORKER_UNLOCK() sx_xunlock(&audit_worker_lock) 102 103 static void 104 audit_worker_sync_vp(struct vnode *vp, struct mount *mp, const char *fmt, ...) 105 { 106 struct mount *mp1; 107 int error; 108 va_list va; 109 110 va_start(va, fmt); 111 error = vn_start_write(vp, &mp1, 0); 112 if (error == 0) { 113 VOP_LOCK(vp, LK_EXCLUSIVE | LK_RETRY); 114 (void)VOP_FSYNC(vp, MNT_WAIT, curthread); 115 VOP_UNLOCK(vp, 0); 116 vn_finished_write(mp1); 117 } 118 vfs_unbusy(mp); 119 vpanic(fmt, va); 120 va_end(va); 121 } 122 123 /* 124 * Write an audit record to a file, performed as the last stage after both 125 * preselection and BSM conversion. Both space management and write failures 126 * are handled in this function. 127 * 128 * No attempt is made to deal with possible failure to deliver a trigger to 129 * the audit daemon, since the message is asynchronous anyway. 130 */ 131 static void 132 audit_record_write(struct vnode *vp, struct ucred *cred, void *data, 133 size_t len) 134 { 135 static struct timeval last_lowspace_trigger; 136 static struct timeval last_fail; 137 static int cur_lowspace_trigger; 138 struct statfs *mnt_stat; 139 struct mount *mp; 140 int error; 141 static int cur_fail; 142 long temp; 143 144 AUDIT_WORKER_LOCK_ASSERT(); 145 146 if (vp == NULL) 147 return; 148 149 mp = vp->v_mount; 150 if (mp == NULL) { 151 error = EINVAL; 152 goto fail; 153 } 154 error = vfs_busy(mp, 0); 155 if (error != 0) { 156 mp = NULL; 157 goto fail; 158 } 159 mnt_stat = &mp->mnt_stat; 160 161 /* 162 * First, gather statistics on the audit log file and file system so 163 * that we know how we're doing on space. Consider failure of these 164 * operations to indicate a future inability to write to the file. 165 */ 166 error = VFS_STATFS(mp, mnt_stat); 167 if (error != 0) 168 goto fail; 169 170 /* 171 * We handle four different space-related limits: 172 * 173 * - A fixed (hard) limit on the minimum free blocks we require on 174 * the file system, and results in record loss, a trigger, and 175 * possible fail stop due to violating invariants. 176 * 177 * - An administrative (soft) limit, which when fallen below, results 178 * in the kernel notifying the audit daemon of low space. 179 * 180 * - An audit trail size limit, which when gone above, results in the 181 * kernel notifying the audit daemon that rotation is desired. 182 * 183 * - The total depth of the kernel audit record exceeding free space, 184 * which can lead to possible fail stop (with drain), in order to 185 * prevent violating invariants. Failure here doesn't halt 186 * immediately, but prevents new records from being generated. 187 * 188 * Possibly, the last of these should be handled differently, always 189 * allowing a full queue to be lost, rather than trying to prevent 190 * loss. 191 * 192 * First, handle the hard limit, which generates a trigger and may 193 * fail stop. This is handled in the same manner as ENOSPC from 194 * VOP_WRITE, and results in record loss. 195 */ 196 if (mnt_stat->f_bfree < AUDIT_HARD_LIMIT_FREE_BLOCKS) { 197 error = ENOSPC; 198 goto fail_enospc; 199 } 200 201 /* 202 * Second, handle falling below the soft limit, if defined; we send 203 * the daemon a trigger and continue processing the record. Triggers 204 * are limited to 1/sec. 205 */ 206 if (audit_qctrl.aq_minfree != 0) { 207 temp = mnt_stat->f_blocks / (100 / audit_qctrl.aq_minfree); 208 if (mnt_stat->f_bfree < temp) { 209 if (ppsratecheck(&last_lowspace_trigger, 210 &cur_lowspace_trigger, 1)) { 211 (void)audit_send_trigger( 212 AUDIT_TRIGGER_LOW_SPACE); 213 printf("Warning: disk space low (< %d%% free) " 214 "on audit log file-system\n", 215 audit_qctrl.aq_minfree); 216 } 217 } 218 } 219 220 /* 221 * If the current file is getting full, generate a rotation trigger 222 * to the daemon. This is only approximate, which is fine as more 223 * records may be generated before the daemon rotates the file. 224 */ 225 if (audit_fstat.af_filesz != 0 && 226 audit_size >= audit_fstat.af_filesz * (audit_file_rotate_wait + 1)) { 227 AUDIT_WORKER_LOCK_ASSERT(); 228 229 audit_file_rotate_wait++; 230 (void)audit_send_trigger(AUDIT_TRIGGER_ROTATE_KERNEL); 231 } 232 233 /* 234 * If the estimated amount of audit data in the audit event queue 235 * (plus records allocated but not yet queued) has reached the amount 236 * of free space on the disk, then we need to go into an audit fail 237 * stop state, in which we do not permit the allocation/committing of 238 * any new audit records. We continue to process records but don't 239 * allow any activities that might generate new records. In the 240 * future, we might want to detect when space is available again and 241 * allow operation to continue, but this behavior is sufficient to 242 * meet fail stop requirements in CAPP. 243 */ 244 if (audit_fail_stop) { 245 if ((unsigned long)((audit_q_len + audit_pre_q_len + 1) * 246 MAX_AUDIT_RECORD_SIZE) / mnt_stat->f_bsize >= 247 (unsigned long)(mnt_stat->f_bfree)) { 248 if (ppsratecheck(&last_fail, &cur_fail, 1)) 249 printf("audit_record_write: free space " 250 "below size of audit queue, failing " 251 "stop\n"); 252 audit_in_failure = 1; 253 } else if (audit_in_failure) { 254 /* 255 * Note: if we want to handle recovery, this is the 256 * spot to do it: unset audit_in_failure, and issue a 257 * wakeup on the cv. 258 */ 259 } 260 } 261 262 error = vn_rdwr(UIO_WRITE, vp, data, len, (off_t)0, UIO_SYSSPACE, 263 IO_APPEND|IO_UNIT, cred, NULL, NULL, curthread); 264 if (error == ENOSPC) 265 goto fail_enospc; 266 else if (error) 267 goto fail; 268 AUDIT_WORKER_LOCK_ASSERT(); 269 audit_size += len; 270 271 /* 272 * Catch completion of a queue drain here; if we're draining and the 273 * queue is now empty, fail stop. That audit_fail_stop is implicitly 274 * true, since audit_in_failure can only be set of audit_fail_stop is 275 * set. 276 * 277 * Note: if we handle recovery from audit_in_failure, then we need to 278 * make panic here conditional. 279 */ 280 if (audit_in_failure) { 281 if (audit_q_len == 0 && audit_pre_q_len == 0) { 282 audit_worker_sync_vp(vp, mp, 283 "Audit store overflow; record queue drained."); 284 } 285 } 286 287 vfs_unbusy(mp); 288 return; 289 290 fail_enospc: 291 /* 292 * ENOSPC is considered a special case with respect to failures, as 293 * this can reflect either our preemptive detection of insufficient 294 * space, or ENOSPC returned by the vnode write call. 295 */ 296 if (audit_fail_stop) { 297 audit_worker_sync_vp(vp, mp, 298 "Audit log space exhausted and fail-stop set."); 299 } 300 (void)audit_send_trigger(AUDIT_TRIGGER_NO_SPACE); 301 audit_suspended = 1; 302 303 /* FALLTHROUGH */ 304 fail: 305 /* 306 * We have failed to write to the file, so the current record is 307 * lost, which may require an immediate system halt. 308 */ 309 if (audit_panic_on_write_fail) { 310 audit_worker_sync_vp(vp, mp, 311 "audit_worker: write error %d\n", error); 312 } else if (ppsratecheck(&last_fail, &cur_fail, 1)) 313 printf("audit_worker: write error %d\n", error); 314 if (mp != NULL) 315 vfs_unbusy(mp); 316 } 317 318 /* 319 * Given a kernel audit record, process as required. Kernel audit records 320 * are converted to one, or possibly two, BSM records, depending on whether 321 * there is a user audit record present also. Kernel records need be 322 * converted to BSM before they can be written out. Both types will be 323 * written to disk, and audit pipes. 324 */ 325 static void 326 audit_worker_process_record(struct kaudit_record *ar) 327 { 328 struct au_record *bsm; 329 au_class_t class; 330 au_event_t event; 331 au_id_t auid; 332 int error, sorf; 333 int locked; 334 335 /* 336 * We hold the audit worker lock over both writes, if there are two, 337 * so that the two records won't be split across a rotation and end 338 * up in two different trail files. 339 */ 340 if (((ar->k_ar_commit & AR_COMMIT_USER) && 341 (ar->k_ar_commit & AR_PRESELECT_USER_TRAIL)) || 342 (ar->k_ar_commit & AR_PRESELECT_TRAIL)) { 343 AUDIT_WORKER_LOCK(); 344 locked = 1; 345 } else 346 locked = 0; 347 348 /* 349 * First, handle the user record, if any: commit to the system trail 350 * and audit pipes as selected. 351 */ 352 if ((ar->k_ar_commit & AR_COMMIT_USER) && 353 (ar->k_ar_commit & AR_PRESELECT_USER_TRAIL)) { 354 AUDIT_WORKER_LOCK_ASSERT(); 355 audit_record_write(audit_vp, audit_cred, ar->k_udata, 356 ar->k_ulen); 357 } 358 359 if ((ar->k_ar_commit & AR_COMMIT_USER) && 360 (ar->k_ar_commit & AR_PRESELECT_USER_PIPE)) 361 audit_pipe_submit_user(ar->k_udata, ar->k_ulen); 362 363 if (!(ar->k_ar_commit & AR_COMMIT_KERNEL) || 364 ((ar->k_ar_commit & AR_PRESELECT_PIPE) == 0 && 365 (ar->k_ar_commit & AR_PRESELECT_TRAIL) == 0)) 366 goto out; 367 368 auid = ar->k_ar.ar_subj_auid; 369 event = ar->k_ar.ar_event; 370 class = au_event_class(event); 371 if (ar->k_ar.ar_errno == 0) 372 sorf = AU_PRS_SUCCESS; 373 else 374 sorf = AU_PRS_FAILURE; 375 376 error = kaudit_to_bsm(ar, &bsm); 377 switch (error) { 378 case BSM_NOAUDIT: 379 goto out; 380 381 case BSM_FAILURE: 382 printf("audit_worker_process_record: BSM_FAILURE\n"); 383 goto out; 384 385 case BSM_SUCCESS: 386 break; 387 388 default: 389 panic("kaudit_to_bsm returned %d", error); 390 } 391 392 if (ar->k_ar_commit & AR_PRESELECT_TRAIL) { 393 AUDIT_WORKER_LOCK_ASSERT(); 394 audit_record_write(audit_vp, audit_cred, bsm->data, bsm->len); 395 } 396 397 if (ar->k_ar_commit & AR_PRESELECT_PIPE) 398 audit_pipe_submit(auid, event, class, sorf, 399 ar->k_ar_commit & AR_PRESELECT_TRAIL, bsm->data, 400 bsm->len); 401 402 kau_free(bsm); 403 out: 404 if (locked) 405 AUDIT_WORKER_UNLOCK(); 406 } 407 408 /* 409 * The audit_worker thread is responsible for watching the event queue, 410 * dequeueing records, converting them to BSM format, and committing them to 411 * disk. In order to minimize lock thrashing, records are dequeued in sets 412 * to a thread-local work queue. 413 * 414 * Note: this means that the effect bound on the size of the pending record 415 * queue is 2x the length of the global queue. 416 */ 417 static void 418 audit_worker(void *arg) 419 { 420 struct kaudit_queue ar_worklist; 421 struct kaudit_record *ar; 422 int lowater_signal; 423 424 TAILQ_INIT(&ar_worklist); 425 mtx_lock(&audit_mtx); 426 while (1) { 427 mtx_assert(&audit_mtx, MA_OWNED); 428 429 /* 430 * Wait for a record. 431 */ 432 while (TAILQ_EMPTY(&audit_q)) 433 cv_wait(&audit_worker_cv, &audit_mtx); 434 435 /* 436 * If there are records in the global audit record queue, 437 * transfer them to a thread-local queue and process them 438 * one by one. If we cross the low watermark threshold, 439 * signal any waiting processes that they may wake up and 440 * continue generating records. 441 */ 442 lowater_signal = 0; 443 while ((ar = TAILQ_FIRST(&audit_q))) { 444 TAILQ_REMOVE(&audit_q, ar, k_q); 445 audit_q_len--; 446 if (audit_q_len == audit_qctrl.aq_lowater) 447 lowater_signal++; 448 TAILQ_INSERT_TAIL(&ar_worklist, ar, k_q); 449 } 450 if (lowater_signal) 451 cv_broadcast(&audit_watermark_cv); 452 453 mtx_unlock(&audit_mtx); 454 while ((ar = TAILQ_FIRST(&ar_worklist))) { 455 TAILQ_REMOVE(&ar_worklist, ar, k_q); 456 audit_worker_process_record(ar); 457 audit_free(ar); 458 } 459 mtx_lock(&audit_mtx); 460 } 461 } 462 463 /* 464 * audit_rotate_vnode() is called by a user or kernel thread to configure or 465 * de-configure auditing on a vnode. The arguments are the replacement 466 * credential (referenced) and vnode (referenced and opened) to substitute 467 * for the current credential and vnode, if any. If either is set to NULL, 468 * both should be NULL, and this is used to indicate that audit is being 469 * disabled. Any previous cred/vnode will be closed and freed. We re-enable 470 * generating rotation requests to auditd. 471 */ 472 void 473 audit_rotate_vnode(struct ucred *cred, struct vnode *vp) 474 { 475 struct ucred *old_audit_cred; 476 struct vnode *old_audit_vp; 477 struct vattr vattr; 478 479 KASSERT((cred != NULL && vp != NULL) || (cred == NULL && vp == NULL), 480 ("audit_rotate_vnode: cred %p vp %p", cred, vp)); 481 482 if (vp != NULL) { 483 vn_lock(vp, LK_SHARED | LK_RETRY); 484 if (VOP_GETATTR(vp, &vattr, cred) != 0) 485 vattr.va_size = 0; 486 VOP_UNLOCK(vp, 0); 487 } else { 488 vattr.va_size = 0; 489 } 490 491 /* 492 * Rotate the vnode/cred, and clear the rotate flag so that we will 493 * send a rotate trigger if the new file fills. 494 */ 495 AUDIT_WORKER_LOCK(); 496 old_audit_cred = audit_cred; 497 old_audit_vp = audit_vp; 498 audit_cred = cred; 499 audit_vp = vp; 500 audit_size = vattr.va_size; 501 audit_file_rotate_wait = 0; 502 audit_enabled = (audit_vp != NULL); 503 AUDIT_WORKER_UNLOCK(); 504 505 /* 506 * If there was an old vnode/credential, close and free. 507 */ 508 if (old_audit_vp != NULL) { 509 vn_close(old_audit_vp, AUDIT_CLOSE_FLAGS, old_audit_cred, 510 curthread); 511 crfree(old_audit_cred); 512 } 513 } 514 515 void 516 audit_worker_init(void) 517 { 518 int error; 519 520 AUDIT_WORKER_LOCK_INIT(); 521 error = kproc_create(audit_worker, NULL, &audit_thread, RFHIGHPID, 522 0, "audit"); 523 if (error) 524 panic("audit_worker_init: kproc_create returned %d", error); 525 } 526