/* * Copyright (c) 1999-2005 Apple Computer, Inc. * Copyright (c) 2006 Robert N. M. Watson * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. Neither the name of Apple Computer, Inc. ("Apple") nor the names of * its contributors may be used to endorse or promote products derived * from this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. * * $FreeBSD: head/sys/security/audit/audit_worker.c 172836 2007-10-20 23:23:23Z julian $ */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* * Worker thread that will schedule disk I/O, etc. */ static struct proc *audit_thread; /* * When an audit log is rotated, the actual rotation must be performed by the * audit worker thread, as it may have outstanding writes on the current * audit log. audit_replacement_vp holds the vnode replacing the current * vnode. We can't let more than one replacement occur at a time, so if more * than one thread requests a replacement, only one can have the replacement * "in progress" at any given moment. If a thread tries to replace the audit * vnode and discovers a replacement is already in progress (i.e., * audit_replacement_flag != 0), then it will sleep on audit_replacement_cv * waiting its turn to perform a replacement. When a replacement is * completed, this cv is signalled by the worker thread so a waiting thread * can start another replacement. We also store a credential to perform * audit log write operations with. * * The current credential and vnode are thread-local to audit_worker. */ static struct cv audit_replacement_cv; static int audit_replacement_flag; static struct vnode *audit_replacement_vp; static struct ucred *audit_replacement_cred; /* * Flags related to Kernel->user-space communication. */ static int audit_file_rotate_wait; /* * Write an audit record to a file, performed as the last stage after both * preselection and BSM conversion. Both space management and write failures * are handled in this function. * * No attempt is made to deal with possible failure to deliver a trigger to * the audit daemon, since the message is asynchronous anyway. */ static void audit_record_write(struct vnode *vp, struct ucred *cred, struct thread *td, void *data, size_t len) { static struct timeval last_lowspace_trigger; static struct timeval last_fail; static int cur_lowspace_trigger; struct statfs *mnt_stat; int error, vfslocked; static int cur_fail; struct vattr vattr; long temp; if (vp == NULL) return; mnt_stat = &vp->v_mount->mnt_stat; vfslocked = VFS_LOCK_GIANT(vp->v_mount); /* * First, gather statistics on the audit log file and file system so * that we know how we're doing on space. Consider failure of these * operations to indicate a future inability to write to the file. */ error = VFS_STATFS(vp->v_mount, mnt_stat, td); if (error) goto fail; vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, td); error = VOP_GETATTR(vp, &vattr, cred, td); VOP_UNLOCK(vp, 0, td); if (error) goto fail; audit_fstat.af_currsz = vattr.va_size; /* * We handle four different space-related limits: * * - A fixed (hard) limit on the minimum free blocks we require on * the file system, and results in record loss, a trigger, and * possible fail stop due to violating invariants. * * - An administrative (soft) limit, which when fallen below, results * in the kernel notifying the audit daemon of low space. * * - An audit trail size limit, which when gone above, results in the * kernel notifying the audit daemon that rotation is desired. * * - The total depth of the kernel audit record exceeding free space, * which can lead to possible fail stop (with drain), in order to * prevent violating invariants. Failure here doesn't halt * immediately, but prevents new records from being generated. * * Possibly, the last of these should be handled differently, always * allowing a full queue to be lost, rather than trying to prevent * loss. * * First, handle the hard limit, which generates a trigger and may * fail stop. This is handled in the same manner as ENOSPC from * VOP_WRITE, and results in record loss. */ if (mnt_stat->f_bfree < AUDIT_HARD_LIMIT_FREE_BLOCKS) { error = ENOSPC; goto fail_enospc; } /* * Second, handle falling below the soft limit, if defined; we send * the daemon a trigger and continue processing the record. Triggers * are limited to 1/sec. */ if (audit_qctrl.aq_minfree != 0) { /* * XXXAUDIT: Check math and block size calculations here. */ temp = mnt_stat->f_blocks / (100 / audit_qctrl.aq_minfree); if (mnt_stat->f_bfree < temp) { if (ppsratecheck(&last_lowspace_trigger, &cur_lowspace_trigger, 1)) { (void)send_trigger(AUDIT_TRIGGER_LOW_SPACE); printf("Warning: audit space low\n"); } } } /* * If the current file is getting full, generate a rotation trigger * to the daemon. This is only approximate, which is fine as more * records may be generated before the daemon rotates the file. */ if ((audit_fstat.af_filesz != 0) && (audit_file_rotate_wait == 0) && (vattr.va_size >= audit_fstat.af_filesz)) { audit_file_rotate_wait = 1; (void)send_trigger(AUDIT_TRIGGER_ROTATE_KERNEL); } /* * If the estimated amount of audit data in the audit event queue * (plus records allocated but not yet queued) has reached the amount * of free space on the disk, then we need to go into an audit fail * stop state, in which we do not permit the allocation/committing of * any new audit records. We continue to process records but don't * allow any activities that might generate new records. In the * future, we might want to detect when space is available again and * allow operation to continue, but this behavior is sufficient to * meet fail stop requirements in CAPP. */ if (audit_fail_stop) { if ((unsigned long)((audit_q_len + audit_pre_q_len + 1) * MAX_AUDIT_RECORD_SIZE) / mnt_stat->f_bsize >= (unsigned long)(mnt_stat->f_bfree)) { if (ppsratecheck(&last_fail, &cur_fail, 1)) printf("audit_record_write: free space " "below size of audit queue, failing " "stop\n"); audit_in_failure = 1; } else if (audit_in_failure) { /* * Note: if we want to handle recovery, this is the * spot to do it: unset audit_in_failure, and issue a * wakeup on the cv. */ } } error = vn_rdwr(UIO_WRITE, vp, data, len, (off_t)0, UIO_SYSSPACE, IO_APPEND|IO_UNIT, cred, NULL, NULL, td); if (error == ENOSPC) goto fail_enospc; else if (error) goto fail; /* * Catch completion of a queue drain here; if we're draining and the * queue is now empty, fail stop. That audit_fail_stop is implicitly * true, since audit_in_failure can only be set of audit_fail_stop is * set. * * Note: if we handle recovery from audit_in_failure, then we need to * make panic here conditional. */ if (audit_in_failure) { if (audit_q_len == 0 && audit_pre_q_len == 0) { VOP_LOCK(vp, LK_DRAIN | LK_INTERLOCK, td); (void)VOP_FSYNC(vp, MNT_WAIT, td); VOP_UNLOCK(vp, 0, td); panic("Audit store overflow; record queue drained."); } } VFS_UNLOCK_GIANT(vfslocked); return; fail_enospc: /* * ENOSPC is considered a special case with respect to failures, as * this can reflect either our preemptive detection of insufficient * space, or ENOSPC returned by the vnode write call. */ if (audit_fail_stop) { VOP_LOCK(vp, LK_DRAIN | LK_INTERLOCK, td); (void)VOP_FSYNC(vp, MNT_WAIT, td); VOP_UNLOCK(vp, 0, td); panic("Audit log space exhausted and fail-stop set."); } (void)send_trigger(AUDIT_TRIGGER_NO_SPACE); audit_suspended = 1; /* FALLTHROUGH */ fail: /* * We have failed to write to the file, so the current record is * lost, which may require an immediate system halt. */ if (audit_panic_on_write_fail) { VOP_LOCK(vp, LK_DRAIN | LK_INTERLOCK, td); (void)VOP_FSYNC(vp, MNT_WAIT, td); VOP_UNLOCK(vp, 0, td); panic("audit_worker: write error %d\n", error); } else if (ppsratecheck(&last_fail, &cur_fail, 1)) printf("audit_worker: write error %d\n", error); VFS_UNLOCK_GIANT(vfslocked); } /* * If an appropriate signal has been received rotate the audit log based on * the global replacement variables. Signal consumers as needed that the * rotation has taken place. * * The global variables and CVs used to signal the audit_worker to perform a * rotation are essentially a message queue of depth 1. It would be much * nicer to actually use a message queue. */ static void audit_worker_rotate(struct ucred **audit_credp, struct vnode **audit_vpp, struct thread *audit_td) { int do_replacement_signal, vfslocked; struct ucred *old_cred; struct vnode *old_vp; mtx_assert(&audit_mtx, MA_OWNED); do_replacement_signal = 0; while (audit_replacement_flag != 0) { old_cred = *audit_credp; old_vp = *audit_vpp; *audit_credp = audit_replacement_cred; *audit_vpp = audit_replacement_vp; audit_replacement_cred = NULL; audit_replacement_vp = NULL; audit_replacement_flag = 0; audit_enabled = (*audit_vpp != NULL); if (old_vp != NULL) { mtx_unlock(&audit_mtx); vfslocked = VFS_LOCK_GIANT(old_vp->v_mount); vn_close(old_vp, AUDIT_CLOSE_FLAGS, old_cred, audit_td); VFS_UNLOCK_GIANT(vfslocked); crfree(old_cred); mtx_lock(&audit_mtx); old_cred = NULL; old_vp = NULL; } do_replacement_signal = 1; } /* * Signal that replacement have occurred to wake up and start any * other replacements started in parallel. We can continue about our * business in the mean time. We broadcast so that both new * replacements can be inserted, but also so that the source(s) of * replacement can return successfully. */ if (do_replacement_signal) cv_broadcast(&audit_replacement_cv); } /* * Given a kernel audit record, process as required. Kernel audit records * are converted to one, or possibly two, BSM records, depending on whether * there is a user audit record present also. Kernel records need be * converted to BSM before they can be written out. Both types will be * written to disk, and audit pipes. */ static void audit_worker_process_record(struct vnode *audit_vp, struct ucred *audit_cred, struct thread *audit_td, struct kaudit_record *ar) { struct au_record *bsm; au_class_t class; au_event_t event; au_id_t auid; int error, sorf; /* * First, handle the user record, if any: commit to the system trail * and audit pipes as selected. */ if ((ar->k_ar_commit & AR_COMMIT_USER) && (ar->k_ar_commit & AR_PRESELECT_USER_TRAIL)) audit_record_write(audit_vp, audit_cred, audit_td, ar->k_udata, ar->k_ulen); if ((ar->k_ar_commit & AR_COMMIT_USER) && (ar->k_ar_commit & AR_PRESELECT_USER_PIPE)) audit_pipe_submit_user(ar->k_udata, ar->k_ulen); if (!(ar->k_ar_commit & AR_COMMIT_KERNEL) || ((ar->k_ar_commit & AR_PRESELECT_PIPE) == 0 && (ar->k_ar_commit & AR_PRESELECT_TRAIL) == 0)) return; auid = ar->k_ar.ar_subj_auid; event = ar->k_ar.ar_event; class = au_event_class(event); if (ar->k_ar.ar_errno == 0) sorf = AU_PRS_SUCCESS; else sorf = AU_PRS_FAILURE; error = kaudit_to_bsm(ar, &bsm); switch (error) { case BSM_NOAUDIT: return; case BSM_FAILURE: printf("audit_worker_process_record: BSM_FAILURE\n"); return; case BSM_SUCCESS: break; default: panic("kaudit_to_bsm returned %d", error); } if (ar->k_ar_commit & AR_PRESELECT_TRAIL) audit_record_write(audit_vp, audit_cred, audit_td, bsm->data, bsm->len); if (ar->k_ar_commit & AR_PRESELECT_PIPE) audit_pipe_submit(auid, event, class, sorf, ar->k_ar_commit & AR_PRESELECT_TRAIL, bsm->data, bsm->len); kau_free(bsm); } /* * The audit_worker thread is responsible for watching the event queue, * dequeueing records, converting them to BSM format, and committing them to * disk. In order to minimize lock thrashing, records are dequeued in sets * to a thread-local work queue. In addition, the audit_work performs the * actual exchange of audit log vnode pointer, as audit_vp is a thread-local * variable. */ static void audit_worker(void *arg) { struct kaudit_queue ar_worklist; struct kaudit_record *ar; struct ucred *audit_cred; struct thread *audit_td; struct vnode *audit_vp; int lowater_signal; /* * These are thread-local variables requiring no synchronization. */ TAILQ_INIT(&ar_worklist); audit_cred = NULL; audit_td = curthread; audit_vp = NULL; mtx_lock(&audit_mtx); while (1) { mtx_assert(&audit_mtx, MA_OWNED); /* * Wait for record or rotation events. */ while (!audit_replacement_flag && TAILQ_EMPTY(&audit_q)) cv_wait(&audit_worker_cv, &audit_mtx); /* * First priority: replace the audit log target if requested. */ audit_worker_rotate(&audit_cred, &audit_vp, audit_td); /* * If there are records in the global audit record queue, * transfer them to a thread-local queue and process them * one by one. If we cross the low watermark threshold, * signal any waiting processes that they may wake up and * continue generating records. */ lowater_signal = 0; while ((ar = TAILQ_FIRST(&audit_q))) { TAILQ_REMOVE(&audit_q, ar, k_q); audit_q_len--; if (audit_q_len == audit_qctrl.aq_lowater) lowater_signal++; TAILQ_INSERT_TAIL(&ar_worklist, ar, k_q); } if (lowater_signal) cv_broadcast(&audit_watermark_cv); mtx_unlock(&audit_mtx); while ((ar = TAILQ_FIRST(&ar_worklist))) { TAILQ_REMOVE(&ar_worklist, ar, k_q); audit_worker_process_record(audit_vp, audit_cred, audit_td, ar); audit_free(ar); } mtx_lock(&audit_mtx); } } /* * audit_rotate_vnode() is called by a user or kernel thread to configure or * de-configure auditing on a vnode. The arguments are the replacement * credential and vnode to substitute for the current credential and vnode, * if any. If either is set to NULL, both should be NULL, and this is used * to indicate that audit is being disabled. The real work is done in the * audit_worker thread, but audit_rotate_vnode() waits synchronously for that * to complete. * * The vnode should be referenced and opened by the caller. The credential * should be referenced. audit_rotate_vnode() will own both references as of * this call, so the caller should not release either. * * XXXAUDIT: Review synchronize communication logic. Really, this is a * message queue of depth 1. We are essentially acquiring ownership of the * communications queue, inserting our message, and waiting for an * acknowledgement. */ void audit_rotate_vnode(struct ucred *cred, struct vnode *vp) { /* * If other parallel log replacements have been requested, we wait * until they've finished before continuing. */ mtx_lock(&audit_mtx); while (audit_replacement_flag != 0) cv_wait(&audit_replacement_cv, &audit_mtx); audit_replacement_cred = cred; audit_replacement_flag = 1; audit_replacement_vp = vp; /* * Wake up the audit worker to perform the exchange once we release * the mutex. */ cv_signal(&audit_worker_cv); /* * Wait for the audit_worker to broadcast that a replacement has * taken place; we know that once this has happened, our vnode has * been replaced in, so we can return successfully. */ cv_wait(&audit_replacement_cv, &audit_mtx); audit_file_rotate_wait = 0; /* We can now request another rotation */ mtx_unlock(&audit_mtx); } void audit_worker_init(void) { int error; cv_init(&audit_replacement_cv, "audit_replacement_cv"); error = kproc_create(audit_worker, NULL, &audit_thread, RFHIGHPID, 0, "audit"); if (error) panic("audit_worker_init: kproc_create returned %d", error); }