audit_worker.c revision 162599
1/* 2 * Copyright (c) 1999-2005 Apple Computer, Inc. 3 * Copyright (c) 2006 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 Computer, 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 * $FreeBSD: head/sys/security/audit/audit_worker.c 162599 2006-09-24 13:35:58Z rwatson $ 31 */ 32 33#include <sys/param.h> 34#include <sys/condvar.h> 35#include <sys/conf.h> 36#include <sys/file.h> 37#include <sys/filedesc.h> 38#include <sys/fcntl.h> 39#include <sys/ipc.h> 40#include <sys/kernel.h> 41#include <sys/kthread.h> 42#include <sys/malloc.h> 43#include <sys/mount.h> 44#include <sys/namei.h> 45#include <sys/proc.h> 46#include <sys/queue.h> 47#include <sys/socket.h> 48#include <sys/socketvar.h> 49#include <sys/protosw.h> 50#include <sys/domain.h> 51#include <sys/sysproto.h> 52#include <sys/sysent.h> 53#include <sys/systm.h> 54#include <sys/ucred.h> 55#include <sys/uio.h> 56#include <sys/un.h> 57#include <sys/unistd.h> 58#include <sys/vnode.h> 59 60#include <bsm/audit.h> 61#include <bsm/audit_internal.h> 62#include <bsm/audit_kevents.h> 63 64#include <netinet/in.h> 65#include <netinet/in_pcb.h> 66 67#include <security/audit/audit.h> 68#include <security/audit/audit_private.h> 69 70#include <vm/uma.h> 71 72/* 73 * Worker thread that will schedule disk I/O, etc. 74 */ 75static struct proc *audit_thread; 76 77/* 78 * When an audit log is rotated, the actual rotation must be performed by the 79 * audit worker thread, as it may have outstanding writes on the current 80 * audit log. audit_replacement_vp holds the vnode replacing the current 81 * vnode. We can't let more than one replacement occur at a time, so if more 82 * than one thread requests a replacement, only one can have the replacement 83 * "in progress" at any given moment. If a thread tries to replace the audit 84 * vnode and discovers a replacement is already in progress (i.e., 85 * audit_replacement_flag != 0), then it will sleep on audit_replacement_cv 86 * waiting its turn to perform a replacement. When a replacement is 87 * completed, this cv is signalled by the worker thread so a waiting thread 88 * can start another replacement. We also store a credential to perform 89 * audit log write operations with. 90 * 91 * The current credential and vnode are thread-local to audit_worker. 92 */ 93static struct cv audit_replacement_cv; 94 95static int audit_replacement_flag; 96static struct vnode *audit_replacement_vp; 97static struct ucred *audit_replacement_cred; 98 99/* 100 * Flags related to Kernel->user-space communication. 101 */ 102static int audit_file_rotate_wait; 103 104/* 105 * Write an audit record to a file, performed as the last stage after both 106 * preselection and BSM conversion. Both space management and write failures 107 * are handled in this function. 108 * 109 * No attempt is made to deal with possible failure to deliver a trigger to 110 * the audit daemon, since the message is asynchronous anyway. 111 */ 112static void 113audit_record_write(struct vnode *vp, struct ucred *cred, struct thread *td, 114 void *data, size_t len) 115{ 116 static struct timeval last_lowspace_trigger; 117 static struct timeval last_fail; 118 static int cur_lowspace_trigger; 119 struct statfs *mnt_stat; 120 int error, vfslocked; 121 static int cur_fail; 122 struct vattr vattr; 123 long temp; 124 125 if (vp == NULL) 126 return; 127 128 mnt_stat = &vp->v_mount->mnt_stat; 129 vfslocked = VFS_LOCK_GIANT(vp->v_mount); 130 131 /* 132 * First, gather statistics on the audit log file and file system so 133 * that we know how we're doing on space. Consider failure of these 134 * operations to indicate a future inability to write to the file. 135 */ 136 error = VFS_STATFS(vp->v_mount, mnt_stat, td); 137 if (error) 138 goto fail; 139 vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, td); 140 error = VOP_GETATTR(vp, &vattr, cred, td); 141 VOP_UNLOCK(vp, 0, td); 142 if (error) 143 goto fail; 144 audit_fstat.af_currsz = vattr.va_size; 145 146 /* 147 * We handle four different space-related limits: 148 * 149 * - A fixed (hard) limit on the minimum free blocks we require on 150 * the file system, and results in record loss, a trigger, and 151 * possible fail stop due to violating invariants. 152 * 153 * - An administrative (soft) limit, which when fallen below, results 154 * in the kernel notifying the audit daemon of low space. 155 * 156 * - An audit trail size limit, which when gone above, results in the 157 * kernel notifying the audit daemon that rotation is desired. 158 * 159 * - The total depth of the kernel audit record exceeding free space, 160 * which can lead to possible fail stop (with drain), in order to 161 * prevent violating invariants. Failure here doesn't halt 162 * immediately, but prevents new records from being generated. 163 * 164 * Possibly, the last of these should be handled differently, always 165 * allowing a full queue to be lost, rather than trying to prevent 166 * loss. 167 * 168 * First, handle the hard limit, which generates a trigger and may 169 * fail stop. This is handled in the same manner as ENOSPC from 170 * VOP_WRITE, and results in record loss. 171 */ 172 if (mnt_stat->f_bfree < AUDIT_HARD_LIMIT_FREE_BLOCKS) { 173 error = ENOSPC; 174 goto fail_enospc; 175 } 176 177 /* 178 * Second, handle falling below the soft limit, if defined; we send 179 * the daemon a trigger and continue processing the record. Triggers 180 * are limited to 1/sec. 181 */ 182 if (audit_qctrl.aq_minfree != 0) { 183 /* 184 * XXXAUDIT: Check math and block size calculations here. 185 */ 186 temp = mnt_stat->f_blocks / (100 / audit_qctrl.aq_minfree); 187 if (mnt_stat->f_bfree < temp) { 188 if (ppsratecheck(&last_lowspace_trigger, 189 &cur_lowspace_trigger, 1)) { 190 (void)send_trigger(AUDIT_TRIGGER_LOW_SPACE); 191 printf("Warning: audit space low\n"); 192 } 193 } 194 } 195 196 /* 197 * If the current file is getting full, generate a rotation trigger 198 * to the daemon. This is only approximate, which is fine as more 199 * records may be generated before the daemon rotates the file. 200 */ 201 if ((audit_fstat.af_filesz != 0) && (audit_file_rotate_wait == 0) && 202 (vattr.va_size >= audit_fstat.af_filesz)) { 203 audit_file_rotate_wait = 1; 204 (void)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 * XXXRW: 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, td); 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 * XXXRW: If we handle recovery from audit_in_failure, then we need 250 * to 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_DRAIN | LK_INTERLOCK, td); 255 (void)VOP_FSYNC(vp, MNT_WAIT, td); 256 VOP_UNLOCK(vp, 0, td); 257 panic("Audit store overflow; record queue drained."); 258 } 259 } 260 261 VFS_UNLOCK_GIANT(vfslocked); 262 return; 263 264fail_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_DRAIN | LK_INTERLOCK, td); 272 (void)VOP_FSYNC(vp, MNT_WAIT, td); 273 VOP_UNLOCK(vp, 0, td); 274 panic("Audit log space exhausted and fail-stop set."); 275 } 276 (void)send_trigger(AUDIT_TRIGGER_NO_SPACE); 277 audit_suspended = 1; 278 279 /* FALLTHROUGH */ 280fail: 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_DRAIN | LK_INTERLOCK, td); 287 (void)VOP_FSYNC(vp, MNT_WAIT, td); 288 VOP_UNLOCK(vp, 0, td); 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 * If an appropriate signal has been received rotate the audit log based on 297 * the global replacement variables. Signal consumers as needed that the 298 * rotation has taken place. 299 * 300 * XXXRW: The global variables and CVs used to signal the audit_worker to 301 * perform a rotation are essentially a message queue of depth 1. It would 302 * be much nicer to actually use a message queue. 303 */ 304static void 305audit_worker_rotate(struct ucred **audit_credp, struct vnode **audit_vpp, 306 struct thread *audit_td) 307{ 308 int do_replacement_signal, vfslocked; 309 struct ucred *old_cred; 310 struct vnode *old_vp; 311 312 mtx_assert(&audit_mtx, MA_OWNED); 313 314 do_replacement_signal = 0; 315 while (audit_replacement_flag != 0) { 316 old_cred = *audit_credp; 317 old_vp = *audit_vpp; 318 *audit_credp = audit_replacement_cred; 319 *audit_vpp = audit_replacement_vp; 320 audit_replacement_cred = NULL; 321 audit_replacement_vp = NULL; 322 audit_replacement_flag = 0; 323 324 audit_enabled = (*audit_vpp != NULL); 325 326 /* 327 * XXX: What to do about write failures here? 328 */ 329 if (old_vp != NULL) { 330 AUDIT_PRINTF(("Closing old audit file\n")); 331 mtx_unlock(&audit_mtx); 332 vfslocked = VFS_LOCK_GIANT(old_vp->v_mount); 333 vn_close(old_vp, AUDIT_CLOSE_FLAGS, old_cred, 334 audit_td); 335 VFS_UNLOCK_GIANT(vfslocked); 336 crfree(old_cred); 337 mtx_lock(&audit_mtx); 338 old_cred = NULL; 339 old_vp = NULL; 340 AUDIT_PRINTF(("Audit file closed\n")); 341 } 342 if (*audit_vpp != NULL) { 343 AUDIT_PRINTF(("Opening new audit file\n")); 344 } 345 do_replacement_signal = 1; 346 } 347 348 /* 349 * Signal that replacement have occurred to wake up and 350 * start any other replacements started in parallel. We can 351 * continue about our business in the mean time. We 352 * broadcast so that both new replacements can be inserted, 353 * but also so that the source(s) of replacement can return 354 * successfully. 355 */ 356 if (do_replacement_signal) 357 cv_broadcast(&audit_replacement_cv); 358} 359 360/* 361 * Given a kernel audit record, process as required. Kernel audit records 362 * are converted to one, or possibly two, BSM records, depending on whether 363 * there is a user audit record present also. Kernel records need be 364 * converted to BSM before they can be written out. Both types will be 365 * written to disk, and audit pipes. 366 */ 367static void 368audit_worker_process_record(struct vnode *audit_vp, struct ucred *audit_cred, 369 struct thread *audit_td, struct kaudit_record *ar) 370{ 371 struct au_record *bsm; 372 au_class_t class; 373 au_event_t event; 374 au_id_t auid; 375 int error, sorf; 376 377 /* 378 * First, handle the user record, if any: commit to the system trail 379 * and audit pipes as selected. 380 */ 381 if ((ar->k_ar_commit & AR_COMMIT_USER) && 382 (ar->k_ar_commit & AR_PRESELECT_USER_TRAIL)) 383 audit_record_write(audit_vp, audit_cred, audit_td, 384 ar->k_udata, ar->k_ulen); 385 386 if ((ar->k_ar_commit & AR_COMMIT_USER) && 387 (ar->k_ar_commit & AR_PRESELECT_USER_PIPE)) 388 audit_pipe_submit_user(ar->k_udata, ar->k_ulen); 389 390 if (!(ar->k_ar_commit & AR_COMMIT_KERNEL) || 391 ((ar->k_ar_commit & AR_PRESELECT_PIPE) == 0 && 392 (ar->k_ar_commit & AR_PRESELECT_TRAIL) == 0)) 393 return; 394 395 auid = ar->k_ar.ar_subj_auid; 396 event = ar->k_ar.ar_event; 397 class = au_event_class(event); 398 if (ar->k_ar.ar_errno == 0) 399 sorf = AU_PRS_SUCCESS; 400 else 401 sorf = AU_PRS_FAILURE; 402 403 error = kaudit_to_bsm(ar, &bsm); 404 switch (error) { 405 case BSM_NOAUDIT: 406 return; 407 408 case BSM_FAILURE: 409 printf("audit_worker_process_record: BSM_FAILURE\n"); 410 return; 411 412 case BSM_SUCCESS: 413 break; 414 415 default: 416 panic("kaudit_to_bsm returned %d", error); 417 } 418 419 if (ar->k_ar_commit & AR_PRESELECT_TRAIL) 420 audit_record_write(audit_vp, audit_cred, audit_td, bsm->data, 421 bsm->len); 422 423 if (ar->k_ar_commit & AR_PRESELECT_PIPE) 424 audit_pipe_submit(auid, event, class, sorf, 425 ar->k_ar_commit & AR_PRESELECT_TRAIL, bsm->data, 426 bsm->len); 427 428 kau_free(bsm); 429} 430 431/* 432 * The audit_worker thread is responsible for watching the event queue, 433 * dequeueing records, converting them to BSM format, and committing them to 434 * disk. In order to minimize lock thrashing, records are dequeued in sets 435 * to a thread-local work queue. In addition, the audit_work performs the 436 * actual exchange of audit log vnode pointer, as audit_vp is a thread-local 437 * variable. 438 */ 439static void 440audit_worker(void *arg) 441{ 442 struct kaudit_queue ar_worklist; 443 struct kaudit_record *ar; 444 struct ucred *audit_cred; 445 struct thread *audit_td; 446 struct vnode *audit_vp; 447 int lowater_signal; 448 449 AUDIT_PRINTF(("audit_worker starting\n")); 450 451 /* 452 * These are thread-local variables requiring no synchronization. 453 */ 454 TAILQ_INIT(&ar_worklist); 455 audit_cred = NULL; 456 audit_td = curthread; 457 audit_vp = NULL; 458 459 mtx_lock(&audit_mtx); 460 while (1) { 461 mtx_assert(&audit_mtx, MA_OWNED); 462 463 /* 464 * Wait for record or rotation events. 465 */ 466 while (!audit_replacement_flag && TAILQ_EMPTY(&audit_q)) { 467 AUDIT_PRINTF(("audit_worker waiting\n")); 468 cv_wait(&audit_worker_cv, &audit_mtx); 469 AUDIT_PRINTF(("audit_worker woken up\n")); 470 AUDIT_PRINTF(("audit_worker: new vp = %p; value of " 471 "flag %d\n", audit_replacement_vp, 472 audit_replacement_flag)); 473 } 474 475 /* 476 * First priority: replace the audit log target if requested. 477 */ 478 audit_worker_rotate(&audit_cred, &audit_vp, audit_td); 479 480 /* 481 * If there are records in the global audit record queue, 482 * transfer them to a thread-local queue and process them 483 * one by one. If we cross the low watermark threshold, 484 * signal any waiting processes that they may wake up and 485 * continue generating records. 486 */ 487 lowater_signal = 0; 488 while ((ar = TAILQ_FIRST(&audit_q))) { 489 TAILQ_REMOVE(&audit_q, ar, k_q); 490 audit_q_len--; 491 if (audit_q_len == audit_qctrl.aq_lowater) 492 lowater_signal++; 493 TAILQ_INSERT_TAIL(&ar_worklist, ar, k_q); 494 } 495 if (lowater_signal) 496 cv_broadcast(&audit_watermark_cv); 497 498 mtx_unlock(&audit_mtx); 499 while ((ar = TAILQ_FIRST(&ar_worklist))) { 500 TAILQ_REMOVE(&ar_worklist, ar, k_q); 501 audit_worker_process_record(audit_vp, audit_cred, 502 audit_td, ar); 503 audit_free(ar); 504 } 505 mtx_lock(&audit_mtx); 506 } 507} 508 509/* 510 * audit_rotate_vnode() is called by a user or kernel thread to configure or 511 * de-configure auditing on a vnode. The arguments are the replacement 512 * credential and vnode to substitute for the current credential and vnode, 513 * if any. If either is set to NULL, both should be NULL, and this is used 514 * to indicate that audit is being disabled. The real work is done in the 515 * audit_worker thread, but audit_rotate_vnode() waits synchronously for that 516 * to complete. 517 * 518 * The vnode should be referenced and opened by the caller. The credential 519 * should be referenced. audit_rotate_vnode() will own both references as of 520 * this call, so the caller should not release either. 521 * 522 * XXXAUDIT: Review synchronize communication logic. Really, this is a 523 * message queue of depth 1. 524 * 525 * XXXAUDIT: Enhance the comments below to indicate that we are basically 526 * acquiring ownership of the communications queue, inserting our message, 527 * and waiting for an acknowledgement. 528 */ 529void 530audit_rotate_vnode(struct ucred *cred, struct vnode *vp) 531{ 532 533 /* 534 * If other parallel log replacements have been requested, we wait 535 * until they've finished before continuing. 536 */ 537 mtx_lock(&audit_mtx); 538 while (audit_replacement_flag != 0) { 539 AUDIT_PRINTF(("audit_rotate_vnode: sleeping to wait for " 540 "flag\n")); 541 cv_wait(&audit_replacement_cv, &audit_mtx); 542 AUDIT_PRINTF(("audit_rotate_vnode: woken up (flag %d)\n", 543 audit_replacement_flag)); 544 } 545 audit_replacement_cred = cred; 546 audit_replacement_flag = 1; 547 audit_replacement_vp = vp; 548 549 /* 550 * Wake up the audit worker to perform the exchange once we 551 * release the mutex. 552 */ 553 cv_signal(&audit_worker_cv); 554 555 /* 556 * Wait for the audit_worker to broadcast that a replacement has 557 * taken place; we know that once this has happened, our vnode 558 * has been replaced in, so we can return successfully. 559 */ 560 AUDIT_PRINTF(("audit_rotate_vnode: waiting for news of " 561 "replacement\n")); 562 cv_wait(&audit_replacement_cv, &audit_mtx); 563 AUDIT_PRINTF(("audit_rotate_vnode: change acknowledged by " 564 "audit_worker (flag " "now %d)\n", audit_replacement_flag)); 565 mtx_unlock(&audit_mtx); 566 567 audit_file_rotate_wait = 0; /* We can now request another rotation */ 568} 569 570void 571audit_worker_init(void) 572{ 573 int error; 574 575 cv_init(&audit_replacement_cv, "audit_replacement_cv"); 576 error = kthread_create(audit_worker, NULL, &audit_thread, RFHIGHPID, 577 0, "audit_worker"); 578 if (error) 579 panic("audit_worker_init: kthread_create returned %d", error); 580} 581