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