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 /* 75 * Worker thread that will schedule disk I/O, etc. 76 */ 77 static struct proc *audit_thread; 78 79 /* 80 * audit_cred and audit_vp are the stored credential and vnode to use for 81 * active audit trail. They are protected by the audit worker lock, which 82 * will be held across all I/O and all rotation to prevent them from being 83 * replaced (rotated) while in use. The audit_file_rotate_wait flag is set 84 * when the kernel has delivered a trigger to auditd to rotate the trail, and 85 * is cleared when the next rotation takes place. It is also protected by 86 * the audit worker lock. 87 */ 88 static int audit_file_rotate_wait; 89 static struct ucred *audit_cred; 90 static struct vnode *audit_vp; 91 static struct sx audit_worker_lock; 92 93 #define AUDIT_WORKER_LOCK_INIT() sx_init(&audit_worker_lock, \ 94 "audit_worker_lock"); 95 #define AUDIT_WORKER_LOCK_ASSERT() sx_assert(&audit_worker_lock, \ 96 SA_XLOCKED) 97 #define AUDIT_WORKER_LOCK() sx_xlock(&audit_worker_lock) 98 #define AUDIT_WORKER_UNLOCK() sx_xunlock(&audit_worker_lock) 99 100 /* 101 * Write an audit record to a file, performed as the last stage after both 102 * preselection and BSM conversion. Both space management and write failures 103 * are handled in this function. 104 * 105 * No attempt is made to deal with possible failure to deliver a trigger to 106 * the audit daemon, since the message is asynchronous anyway. 107 */ 108 static void 109 audit_record_write(struct vnode *vp, struct ucred *cred, void *data, 110 size_t len) 111 { 112 static struct timeval last_lowspace_trigger; 113 static struct timeval last_fail; 114 static int cur_lowspace_trigger; 115 struct statfs *mnt_stat; 116 int error, vfslocked; 117 static int cur_fail; 118 struct vattr vattr; 119 long temp; 120 121 AUDIT_WORKER_LOCK_ASSERT(); 122 123 if (vp == NULL) 124 return; 125 126 mnt_stat = &vp->v_mount->mnt_stat; 127 vfslocked = VFS_LOCK_GIANT(vp->v_mount); 128 129 /* 130 * First, gather statistics on the audit log file and file system so 131 * that we know how we're doing on space. Consider failure of these 132 * operations to indicate a future inability to write to the file. 133 */ 134 error = VFS_STATFS(vp->v_mount, mnt_stat, curthread); 135 if (error) 136 goto fail; 137 vn_lock(vp, LK_EXCLUSIVE | LK_RETRY); 138 error = VOP_GETATTR(vp, &vattr, cred); 139 VOP_UNLOCK(vp, 0); 140 if (error) 141 goto fail; 142 audit_fstat.af_currsz = vattr.va_size; 143 144 /* 145 * We handle four different space-related limits: 146 * 147 * - A fixed (hard) limit on the minimum free blocks we require on 148 * the file system, and results in record loss, a trigger, and 149 * possible fail stop due to violating invariants. 150 * 151 * - An administrative (soft) limit, which when fallen below, results 152 * in the kernel notifying the audit daemon of low space. 153 * 154 * - An audit trail size limit, which when gone above, results in the 155 * kernel notifying the audit daemon that rotation is desired. 156 * 157 * - The total depth of the kernel audit record exceeding free space, 158 * which can lead to possible fail stop (with drain), in order to 159 * prevent violating invariants. Failure here doesn't halt 160 * immediately, but prevents new records from being generated. 161 * 162 * Possibly, the last of these should be handled differently, always 163 * allowing a full queue to be lost, rather than trying to prevent 164 * loss. 165 * 166 * First, handle the hard limit, which generates a trigger and may 167 * fail stop. This is handled in the same manner as ENOSPC from 168 * VOP_WRITE, and results in record loss. 169 */ 170 if (mnt_stat->f_bfree < AUDIT_HARD_LIMIT_FREE_BLOCKS) { 171 error = ENOSPC; 172 goto fail_enospc; 173 } 174 175 /* 176 * Second, handle falling below the soft limit, if defined; we send 177 * the daemon a trigger and continue processing the record. Triggers 178 * are limited to 1/sec. 179 */ 180 if (audit_qctrl.aq_minfree != 0) { 181 temp = mnt_stat->f_blocks / (100 / audit_qctrl.aq_minfree); 182 if (mnt_stat->f_bfree < temp) { 183 if (ppsratecheck(&last_lowspace_trigger, 184 &cur_lowspace_trigger, 1)) { 185 (void)audit_send_trigger( 186 AUDIT_TRIGGER_LOW_SPACE); 187 printf("Warning: disk space low (< %d%% free) " 188 "on audit log file-system\n", 189 audit_qctrl.aq_minfree); 190 } 191 } 192 } 193 194 /* 195 * If the current file is getting full, generate a rotation trigger 196 * to the daemon. This is only approximate, which is fine as more 197 * records may be generated before the daemon rotates the file. 198 */ 199 if ((audit_fstat.af_filesz != 0) && (audit_file_rotate_wait == 0) && 200 (vattr.va_size >= audit_fstat.af_filesz)) { 201 AUDIT_WORKER_LOCK_ASSERT(); 202 203 audit_file_rotate_wait = 1; 204 (void)audit_send_trigger(AUDIT_TRIGGER_ROTATE_KERNEL); 205 } 206 207 /* 208 * If the estimated amount of audit data in the audit event queue 209 * (plus records allocated but not yet queued) has reached the amount 210 * of free space on the disk, then we need to go into an audit fail 211 * stop state, in which we do not permit the allocation/committing of 212 * any new audit records. We continue to process records but don't 213 * allow any activities that might generate new records. In the 214 * future, we might want to detect when space is available again and 215 * allow operation to continue, but this behavior is sufficient to 216 * meet fail stop requirements in CAPP. 217 */ 218 if (audit_fail_stop) { 219 if ((unsigned long)((audit_q_len + audit_pre_q_len + 1) * 220 MAX_AUDIT_RECORD_SIZE) / mnt_stat->f_bsize >= 221 (unsigned long)(mnt_stat->f_bfree)) { 222 if (ppsratecheck(&last_fail, &cur_fail, 1)) 223 printf("audit_record_write: free space " 224 "below size of audit queue, failing " 225 "stop\n"); 226 audit_in_failure = 1; 227 } else if (audit_in_failure) { 228 /* 229 * Note: if we want to handle recovery, this is the 230 * spot to do it: unset audit_in_failure, and issue a 231 * wakeup on the cv. 232 */ 233 } 234 } 235 236 error = vn_rdwr(UIO_WRITE, vp, data, len, (off_t)0, UIO_SYSSPACE, 237 IO_APPEND|IO_UNIT, cred, NULL, NULL, curthread); 238 if (error == ENOSPC) 239 goto fail_enospc; 240 else if (error) 241 goto fail; 242 243 /* 244 * Catch completion of a queue drain here; if we're draining and the 245 * queue is now empty, fail stop. That audit_fail_stop is implicitly 246 * true, since audit_in_failure can only be set of audit_fail_stop is 247 * set. 248 * 249 * Note: if we handle recovery from audit_in_failure, then we need to 250 * make panic here conditional. 251 */ 252 if (audit_in_failure) { 253 if (audit_q_len == 0 && audit_pre_q_len == 0) { 254 VOP_LOCK(vp, LK_EXCLUSIVE | LK_RETRY); 255 (void)VOP_FSYNC(vp, MNT_WAIT, curthread); 256 VOP_UNLOCK(vp, 0); 257 panic("Audit store overflow; record queue drained."); 258 } 259 } 260 261 VFS_UNLOCK_GIANT(vfslocked); 262 return; 263 264 fail_enospc: 265 /* 266 * ENOSPC is considered a special case with respect to failures, as 267 * this can reflect either our preemptive detection of insufficient 268 * space, or ENOSPC returned by the vnode write call. 269 */ 270 if (audit_fail_stop) { 271 VOP_LOCK(vp, LK_EXCLUSIVE | LK_RETRY); 272 (void)VOP_FSYNC(vp, MNT_WAIT, curthread); 273 VOP_UNLOCK(vp, 0); 274 panic("Audit log space exhausted and fail-stop set."); 275 } 276 (void)audit_send_trigger(AUDIT_TRIGGER_NO_SPACE); 277 audit_suspended = 1; 278 279 /* FALLTHROUGH */ 280 fail: 281 /* 282 * We have failed to write to the file, so the current record is 283 * lost, which may require an immediate system halt. 284 */ 285 if (audit_panic_on_write_fail) { 286 VOP_LOCK(vp, LK_EXCLUSIVE | LK_RETRY); 287 (void)VOP_FSYNC(vp, MNT_WAIT, curthread); 288 VOP_UNLOCK(vp, 0); 289 panic("audit_worker: write error %d\n", error); 290 } else if (ppsratecheck(&last_fail, &cur_fail, 1)) 291 printf("audit_worker: write error %d\n", error); 292 VFS_UNLOCK_GIANT(vfslocked); 293 } 294 295 /* 296 * Given a kernel audit record, process as required. Kernel audit records 297 * are converted to one, or possibly two, BSM records, depending on whether 298 * there is a user audit record present also. Kernel records need be 299 * converted to BSM before they can be written out. Both types will be 300 * written to disk, and audit pipes. 301 */ 302 static void 303 audit_worker_process_record(struct kaudit_record *ar) 304 { 305 struct au_record *bsm; 306 au_class_t class; 307 au_event_t event; 308 au_id_t auid; 309 int error, sorf; 310 int locked; 311 312 /* 313 * We hold the audit worker lock over both writes, if there are two, 314 * so that the two records won't be split across a rotation and end 315 * up in two different trail files. 316 */ 317 if (((ar->k_ar_commit & AR_COMMIT_USER) && 318 (ar->k_ar_commit & AR_PRESELECT_USER_TRAIL)) || 319 (ar->k_ar_commit & AR_PRESELECT_TRAIL)) { 320 AUDIT_WORKER_LOCK(); 321 locked = 1; 322 } else 323 locked = 0; 324 325 /* 326 * First, handle the user record, if any: commit to the system trail 327 * and audit pipes as selected. 328 */ 329 if ((ar->k_ar_commit & AR_COMMIT_USER) && 330 (ar->k_ar_commit & AR_PRESELECT_USER_TRAIL)) { 331 AUDIT_WORKER_LOCK_ASSERT(); 332 audit_record_write(audit_vp, audit_cred, ar->k_udata, 333 ar->k_ulen); 334 } 335 336 if ((ar->k_ar_commit & AR_COMMIT_USER) && 337 (ar->k_ar_commit & AR_PRESELECT_USER_PIPE)) 338 audit_pipe_submit_user(ar->k_udata, ar->k_ulen); 339 340 if (!(ar->k_ar_commit & AR_COMMIT_KERNEL) || 341 ((ar->k_ar_commit & AR_PRESELECT_PIPE) == 0 && 342 (ar->k_ar_commit & AR_PRESELECT_TRAIL) == 0)) 343 goto out; 344 345 auid = ar->k_ar.ar_subj_auid; 346 event = ar->k_ar.ar_event; 347 class = au_event_class(event); 348 if (ar->k_ar.ar_errno == 0) 349 sorf = AU_PRS_SUCCESS; 350 else 351 sorf = AU_PRS_FAILURE; 352 353 error = kaudit_to_bsm(ar, &bsm); 354 switch (error) { 355 case BSM_NOAUDIT: 356 goto out; 357 358 case BSM_FAILURE: 359 printf("audit_worker_process_record: BSM_FAILURE\n"); 360 goto out; 361 362 case BSM_SUCCESS: 363 break; 364 365 default: 366 panic("kaudit_to_bsm returned %d", error); 367 } 368 369 if (ar->k_ar_commit & AR_PRESELECT_TRAIL) { 370 AUDIT_WORKER_LOCK_ASSERT(); 371 audit_record_write(audit_vp, audit_cred, bsm->data, bsm->len); 372 } 373 374 if (ar->k_ar_commit & AR_PRESELECT_PIPE) 375 audit_pipe_submit(auid, event, class, sorf, 376 ar->k_ar_commit & AR_PRESELECT_TRAIL, bsm->data, 377 bsm->len); 378 379 kau_free(bsm); 380 out: 381 if (locked) 382 AUDIT_WORKER_UNLOCK(); 383 } 384 385 /* 386 * The audit_worker thread is responsible for watching the event queue, 387 * dequeueing records, converting them to BSM format, and committing them to 388 * disk. In order to minimize lock thrashing, records are dequeued in sets 389 * to a thread-local work queue. 390 * 391 * Note: this means that the effect bound on the size of the pending record 392 * queue is 2x the length of the global queue. 393 */ 394 static void 395 audit_worker(void *arg) 396 { 397 struct kaudit_queue ar_worklist; 398 struct kaudit_record *ar; 399 int lowater_signal; 400 401 TAILQ_INIT(&ar_worklist); 402 mtx_lock(&audit_mtx); 403 while (1) { 404 mtx_assert(&audit_mtx, MA_OWNED); 405 406 /* 407 * Wait for a record. 408 */ 409 while (TAILQ_EMPTY(&audit_q)) 410 cv_wait(&audit_worker_cv, &audit_mtx); 411 412 /* 413 * If there are records in the global audit record queue, 414 * transfer them to a thread-local queue and process them 415 * one by one. If we cross the low watermark threshold, 416 * signal any waiting processes that they may wake up and 417 * continue generating records. 418 */ 419 lowater_signal = 0; 420 while ((ar = TAILQ_FIRST(&audit_q))) { 421 TAILQ_REMOVE(&audit_q, ar, k_q); 422 audit_q_len--; 423 if (audit_q_len == audit_qctrl.aq_lowater) 424 lowater_signal++; 425 TAILQ_INSERT_TAIL(&ar_worklist, ar, k_q); 426 } 427 if (lowater_signal) 428 cv_broadcast(&audit_watermark_cv); 429 430 mtx_unlock(&audit_mtx); 431 while ((ar = TAILQ_FIRST(&ar_worklist))) { 432 TAILQ_REMOVE(&ar_worklist, ar, k_q); 433 audit_worker_process_record(ar); 434 audit_free(ar); 435 } 436 mtx_lock(&audit_mtx); 437 } 438 } 439 440 /* 441 * audit_rotate_vnode() is called by a user or kernel thread to configure or 442 * de-configure auditing on a vnode. The arguments are the replacement 443 * credential (referenced) and vnode (referenced and opened) to substitute 444 * for the current credential and vnode, if any. If either is set to NULL, 445 * both should be NULL, and this is used to indicate that audit is being 446 * disabled. Any previous cred/vnode will be closed and freed. We re-enable 447 * generating rotation requests to auditd. 448 */ 449 void 450 audit_rotate_vnode(struct ucred *cred, struct vnode *vp) 451 { 452 struct ucred *old_audit_cred; 453 struct vnode *old_audit_vp; 454 int vfslocked; 455 456 KASSERT((cred != NULL && vp != NULL) || (cred == NULL && vp == NULL), 457 ("audit_rotate_vnode: cred %p vp %p", cred, vp)); 458 459 /* 460 * Rotate the vnode/cred, and clear the rotate flag so that we will 461 * send a rotate trigger if the new file fills. 462 */ 463 AUDIT_WORKER_LOCK(); 464 old_audit_cred = audit_cred; 465 old_audit_vp = audit_vp; 466 audit_cred = cred; 467 audit_vp = vp; 468 audit_file_rotate_wait = 0; 469 audit_enabled = (audit_vp != NULL); 470 AUDIT_WORKER_UNLOCK(); 471 472 /* 473 * If there was an old vnode/credential, close and free. 474 */ 475 if (old_audit_vp != NULL) { 476 vfslocked = VFS_LOCK_GIANT(old_audit_vp->v_mount); 477 vn_close(old_audit_vp, AUDIT_CLOSE_FLAGS, old_audit_cred, 478 curthread); 479 VFS_UNLOCK_GIANT(vfslocked); 480 crfree(old_audit_cred); 481 } 482 } 483 484 void 485 audit_worker_init(void) 486 { 487 int error; 488 489 AUDIT_WORKER_LOCK_INIT(); 490 error = kproc_create(audit_worker, NULL, &audit_thread, RFHIGHPID, 491 0, "audit"); 492 if (error) 493 panic("audit_worker_init: kproc_create returned %d", error); 494 } 495