2 * SPDX-License-Identifier: BSD-3-Clause
4 * Copyright (c) 1999-2008 Apple Inc.
5 * Copyright (c) 2006-2008, 2016, 2018 Robert N. M. Watson
8 * Portions of this software were developed by BAE Systems, the University of
9 * Cambridge Computer Laboratory, and Memorial University under DARPA/AFRL
10 * contract FA8650-15-C-7558 ("CADETS"), as part of the DARPA Transparent
11 * Computing (TC) research program.
13 * Redistribution and use in source and binary forms, with or without
14 * modification, are permitted provided that the following conditions
16 * 1. Redistributions of source code must retain the above copyright
17 * notice, this list of conditions and the following disclaimer.
18 * 2. Redistributions in binary form must reproduce the above copyright
19 * notice, this list of conditions and the following disclaimer in the
20 * documentation and/or other materials provided with the distribution.
21 * 3. Neither the name of Apple Inc. ("Apple") nor the names of
22 * its contributors may be used to endorse or promote products derived
23 * from this software without specific prior written permission.
25 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND
26 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
27 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
28 * ARE DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR
29 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
30 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
31 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
32 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
33 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
34 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
35 * POSSIBILITY OF SUCH DAMAGE.
38 #include <sys/cdefs.h>
39 __FBSDID("$FreeBSD$");
41 #include <sys/param.h>
42 #include <sys/condvar.h>
45 #include <sys/filedesc.h>
46 #include <sys/fcntl.h>
48 #include <sys/kernel.h>
49 #include <sys/kthread.h>
50 #include <sys/malloc.h>
51 #include <sys/mount.h>
52 #include <sys/namei.h>
54 #include <sys/queue.h>
55 #include <sys/socket.h>
56 #include <sys/socketvar.h>
57 #include <sys/protosw.h>
58 #include <sys/domain.h>
60 #include <sys/sysproto.h>
61 #include <sys/sysent.h>
62 #include <sys/systm.h>
63 #include <sys/ucred.h>
66 #include <sys/unistd.h>
67 #include <sys/vnode.h>
69 #include <bsm/audit.h>
70 #include <bsm/audit_internal.h>
71 #include <bsm/audit_kevents.h>
73 #include <netinet/in.h>
74 #include <netinet/in_pcb.h>
76 #include <security/audit/audit.h>
77 #include <security/audit/audit_private.h>
81 #include <machine/stdarg.h>
84 * Worker thread that will schedule disk I/O, etc.
86 static struct proc *audit_thread;
89 * audit_cred and audit_vp are the stored credential and vnode to use for
90 * active audit trail. They are protected by the audit worker lock, which
91 * will be held across all I/O and all rotation to prevent them from being
92 * replaced (rotated) while in use. The audit_file_rotate_wait flag is set
93 * when the kernel has delivered a trigger to auditd to rotate the trail, and
94 * is cleared when the next rotation takes place. It is also protected by
95 * the audit worker lock.
97 static int audit_file_rotate_wait;
98 static struct ucred *audit_cred;
99 static struct vnode *audit_vp;
100 static off_t audit_size;
101 static struct sx audit_worker_lock;
103 #define AUDIT_WORKER_LOCK_INIT() sx_init(&audit_worker_lock, \
104 "audit_worker_lock");
105 #define AUDIT_WORKER_LOCK_ASSERT() sx_assert(&audit_worker_lock, \
107 #define AUDIT_WORKER_LOCK() sx_xlock(&audit_worker_lock)
108 #define AUDIT_WORKER_UNLOCK() sx_xunlock(&audit_worker_lock)
111 audit_worker_sync_vp(struct vnode *vp, struct mount *mp, const char *fmt, ...)
118 error = vn_start_write(vp, &mp1, 0);
120 VOP_LOCK(vp, LK_EXCLUSIVE | LK_RETRY);
121 (void)VOP_FSYNC(vp, MNT_WAIT, curthread);
123 vn_finished_write(mp1);
131 * Write an audit record to a file, performed as the last stage after both
132 * preselection and BSM conversion. Both space management and write failures
133 * are handled in this function.
135 * No attempt is made to deal with possible failure to deliver a trigger to
136 * the audit daemon, since the message is asynchronous anyway.
139 audit_record_write(struct vnode *vp, struct ucred *cred, void *data,
142 static struct timeval last_lowspace_trigger;
143 static struct timeval last_fail;
144 static int cur_lowspace_trigger;
145 struct statfs *mnt_stat;
151 AUDIT_WORKER_LOCK_ASSERT();
161 error = vfs_busy(mp, 0);
166 mnt_stat = &mp->mnt_stat;
169 * First, gather statistics on the audit log file and file system so
170 * that we know how we're doing on space. Consider failure of these
171 * operations to indicate a future inability to write to the file.
173 error = VFS_STATFS(mp, mnt_stat);
178 * We handle four different space-related limits:
180 * - A fixed (hard) limit on the minimum free blocks we require on
181 * the file system, and results in record loss, a trigger, and
182 * possible fail stop due to violating invariants.
184 * - An administrative (soft) limit, which when fallen below, results
185 * in the kernel notifying the audit daemon of low space.
187 * - An audit trail size limit, which when gone above, results in the
188 * kernel notifying the audit daemon that rotation is desired.
190 * - The total depth of the kernel audit record exceeding free space,
191 * which can lead to possible fail stop (with drain), in order to
192 * prevent violating invariants. Failure here doesn't halt
193 * immediately, but prevents new records from being generated.
195 * Possibly, the last of these should be handled differently, always
196 * allowing a full queue to be lost, rather than trying to prevent
199 * First, handle the hard limit, which generates a trigger and may
200 * fail stop. This is handled in the same manner as ENOSPC from
201 * VOP_WRITE, and results in record loss.
203 if (mnt_stat->f_bfree < AUDIT_HARD_LIMIT_FREE_BLOCKS) {
209 * Second, handle falling below the soft limit, if defined; we send
210 * the daemon a trigger and continue processing the record. Triggers
211 * are limited to 1/sec.
213 if (audit_qctrl.aq_minfree != 0) {
214 temp = mnt_stat->f_blocks / (100 / audit_qctrl.aq_minfree);
215 if (mnt_stat->f_bfree < temp) {
216 if (ppsratecheck(&last_lowspace_trigger,
217 &cur_lowspace_trigger, 1)) {
218 (void)audit_send_trigger(
219 AUDIT_TRIGGER_LOW_SPACE);
220 printf("Warning: disk space low (< %d%% free) "
221 "on audit log file-system\n",
222 audit_qctrl.aq_minfree);
228 * If the current file is getting full, generate a rotation trigger
229 * to the daemon. This is only approximate, which is fine as more
230 * records may be generated before the daemon rotates the file.
232 if (audit_fstat.af_filesz != 0 &&
233 audit_size >= audit_fstat.af_filesz * (audit_file_rotate_wait + 1)) {
234 AUDIT_WORKER_LOCK_ASSERT();
236 audit_file_rotate_wait++;
237 (void)audit_send_trigger(AUDIT_TRIGGER_ROTATE_KERNEL);
241 * If the estimated amount of audit data in the audit event queue
242 * (plus records allocated but not yet queued) has reached the amount
243 * of free space on the disk, then we need to go into an audit fail
244 * stop state, in which we do not permit the allocation/committing of
245 * any new audit records. We continue to process records but don't
246 * allow any activities that might generate new records. In the
247 * future, we might want to detect when space is available again and
248 * allow operation to continue, but this behavior is sufficient to
249 * meet fail stop requirements in CAPP.
251 if (audit_fail_stop) {
252 if ((unsigned long)((audit_q_len + audit_pre_q_len + 1) *
253 MAX_AUDIT_RECORD_SIZE) / mnt_stat->f_bsize >=
254 (unsigned long)(mnt_stat->f_bfree)) {
255 if (ppsratecheck(&last_fail, &cur_fail, 1))
256 printf("audit_record_write: free space "
257 "below size of audit queue, failing "
259 audit_in_failure = 1;
260 } else if (audit_in_failure) {
262 * Note: if we want to handle recovery, this is the
263 * spot to do it: unset audit_in_failure, and issue a
269 error = vn_rdwr(UIO_WRITE, vp, data, len, (off_t)0, UIO_SYSSPACE,
270 IO_APPEND|IO_UNIT, cred, NULL, NULL, curthread);
275 AUDIT_WORKER_LOCK_ASSERT();
279 * Catch completion of a queue drain here; if we're draining and the
280 * queue is now empty, fail stop. That audit_fail_stop is implicitly
281 * true, since audit_in_failure can only be set of audit_fail_stop is
284 * Note: if we handle recovery from audit_in_failure, then we need to
285 * make panic here conditional.
287 if (audit_in_failure) {
288 if (audit_q_len == 0 && audit_pre_q_len == 0) {
289 audit_worker_sync_vp(vp, mp,
290 "Audit store overflow; record queue drained.");
299 * ENOSPC is considered a special case with respect to failures, as
300 * this can reflect either our preemptive detection of insufficient
301 * space, or ENOSPC returned by the vnode write call.
303 if (audit_fail_stop) {
304 audit_worker_sync_vp(vp, mp,
305 "Audit log space exhausted and fail-stop set.");
307 (void)audit_send_trigger(AUDIT_TRIGGER_NO_SPACE);
308 audit_trail_suspended = 1;
309 audit_syscalls_enabled_update();
314 * We have failed to write to the file, so the current record is
315 * lost, which may require an immediate system halt.
317 if (audit_panic_on_write_fail) {
318 audit_worker_sync_vp(vp, mp,
319 "audit_worker: write error %d\n", error);
320 } else if (ppsratecheck(&last_fail, &cur_fail, 1))
321 printf("audit_worker: write error %d\n", error);
327 * Given a kernel audit record, process as required. Kernel audit records
328 * are converted to one, or possibly two, BSM records, depending on whether
329 * there is a user audit record present also. Kernel records need be
330 * converted to BSM before they can be written out. Both types will be
331 * written to disk, and audit pipes.
334 audit_worker_process_record(struct kaudit_record *ar)
336 struct au_record *bsm;
344 * We hold the audit worker lock over both writes, if there are two,
345 * so that the two records won't be split across a rotation and end
346 * up in two different trail files.
348 if (((ar->k_ar_commit & AR_COMMIT_USER) &&
349 (ar->k_ar_commit & AR_PRESELECT_USER_TRAIL)) ||
350 (ar->k_ar_commit & AR_PRESELECT_TRAIL)) {
357 * First, handle the user record, if any: commit to the system trail
358 * and audit pipes as selected.
360 if ((ar->k_ar_commit & AR_COMMIT_USER) &&
361 (ar->k_ar_commit & AR_PRESELECT_USER_TRAIL)) {
362 AUDIT_WORKER_LOCK_ASSERT();
363 audit_record_write(audit_vp, audit_cred, ar->k_udata,
367 if ((ar->k_ar_commit & AR_COMMIT_USER) &&
368 (ar->k_ar_commit & AR_PRESELECT_USER_PIPE))
369 audit_pipe_submit_user(ar->k_udata, ar->k_ulen);
371 if (!(ar->k_ar_commit & AR_COMMIT_KERNEL) ||
372 ((ar->k_ar_commit & AR_PRESELECT_PIPE) == 0 &&
373 (ar->k_ar_commit & AR_PRESELECT_TRAIL) == 0 &&
374 (ar->k_ar_commit & AR_PRESELECT_DTRACE) == 0))
377 auid = ar->k_ar.ar_subj_auid;
378 event = ar->k_ar.ar_event;
379 class = au_event_class(event);
380 if (ar->k_ar.ar_errno == 0)
381 sorf = AU_PRS_SUCCESS;
383 sorf = AU_PRS_FAILURE;
385 error = kaudit_to_bsm(ar, &bsm);
391 printf("audit_worker_process_record: BSM_FAILURE\n");
398 panic("kaudit_to_bsm returned %d", error);
401 if (ar->k_ar_commit & AR_PRESELECT_TRAIL) {
402 AUDIT_WORKER_LOCK_ASSERT();
403 audit_record_write(audit_vp, audit_cred, bsm->data, bsm->len);
406 if (ar->k_ar_commit & AR_PRESELECT_PIPE)
407 audit_pipe_submit(auid, event, class, sorf,
408 ar->k_ar_commit & AR_PRESELECT_TRAIL, bsm->data,
413 * Version of the dtaudit commit hook that accepts BSM.
415 if (ar->k_ar_commit & AR_PRESELECT_DTRACE) {
416 if (dtaudit_hook_bsm != NULL)
417 dtaudit_hook_bsm(ar, auid, event, class, sorf,
418 bsm->data, bsm->len);
425 AUDIT_WORKER_UNLOCK();
429 * The audit_worker thread is responsible for watching the event queue,
430 * dequeueing records, converting them to BSM format, and committing them to
431 * disk. In order to minimize lock thrashing, records are dequeued in sets
432 * to a thread-local work queue.
434 * Note: this means that the effect bound on the size of the pending record
435 * queue is 2x the length of the global queue.
438 audit_worker(void *arg)
440 struct kaudit_queue ar_worklist;
441 struct kaudit_record *ar;
444 TAILQ_INIT(&ar_worklist);
445 mtx_lock(&audit_mtx);
447 mtx_assert(&audit_mtx, MA_OWNED);
452 while (TAILQ_EMPTY(&audit_q))
453 cv_wait(&audit_worker_cv, &audit_mtx);
456 * If there are records in the global audit record queue,
457 * transfer them to a thread-local queue and process them
458 * one by one. If we cross the low watermark threshold,
459 * signal any waiting processes that they may wake up and
460 * continue generating records.
463 while ((ar = TAILQ_FIRST(&audit_q))) {
464 TAILQ_REMOVE(&audit_q, ar, k_q);
466 if (audit_q_len == audit_qctrl.aq_lowater)
468 TAILQ_INSERT_TAIL(&ar_worklist, ar, k_q);
471 cv_broadcast(&audit_watermark_cv);
473 mtx_unlock(&audit_mtx);
474 while ((ar = TAILQ_FIRST(&ar_worklist))) {
475 TAILQ_REMOVE(&ar_worklist, ar, k_q);
476 audit_worker_process_record(ar);
479 mtx_lock(&audit_mtx);
484 * audit_rotate_vnode() is called by a user or kernel thread to configure or
485 * de-configure auditing on a vnode. The arguments are the replacement
486 * credential (referenced) and vnode (referenced and opened) to substitute
487 * for the current credential and vnode, if any. If either is set to NULL,
488 * both should be NULL, and this is used to indicate that audit is being
489 * disabled. Any previous cred/vnode will be closed and freed. We re-enable
490 * generating rotation requests to auditd.
493 audit_rotate_vnode(struct ucred *cred, struct vnode *vp)
495 struct ucred *old_audit_cred;
496 struct vnode *old_audit_vp;
499 KASSERT((cred != NULL && vp != NULL) || (cred == NULL && vp == NULL),
500 ("audit_rotate_vnode: cred %p vp %p", cred, vp));
503 vn_lock(vp, LK_SHARED | LK_RETRY);
504 if (VOP_GETATTR(vp, &vattr, cred) != 0)
512 * Rotate the vnode/cred, and clear the rotate flag so that we will
513 * send a rotate trigger if the new file fills.
516 old_audit_cred = audit_cred;
517 old_audit_vp = audit_vp;
520 audit_size = vattr.va_size;
521 audit_file_rotate_wait = 0;
522 audit_trail_enabled = (audit_vp != NULL);
523 audit_syscalls_enabled_update();
524 AUDIT_WORKER_UNLOCK();
527 * If there was an old vnode/credential, close and free.
529 if (old_audit_vp != NULL) {
530 vn_close(old_audit_vp, AUDIT_CLOSE_FLAGS, old_audit_cred,
532 crfree(old_audit_cred);
537 audit_worker_init(void)
541 AUDIT_WORKER_LOCK_INIT();
542 error = kproc_create(audit_worker, NULL, &audit_thread, RFHIGHPID,
545 panic("audit_worker_init: kproc_create returned %d", error);