Import kernel audit framework:

- Management of audit state on processes.
- Audit system calls to configure process and system audit state.
- Reliable audit record queue implementation, audit_worker kernel
  thread to asynchronously store records on disk.
- Audit event argument.
- Internal audit data structure -> BSM audit trail conversion library.
- Audit event pre-selection.
- Audit pseudo-device permitting kernel->user upcalls to notify auditd
  of kernel audit events.

Much work by:	wsalamon
Obtained from:	TrustedBSD Project, Apple Computer, Inc.

1 files changed, 1083 insertions, 0 deletions

diff --git a/sys/security/audit/audit.c b/sys/security/audit/audit.c
new file mode 100644
index 0000000..b2f1143
--- /dev/null
+++ b/sys/security/audit/audit.c
@@ -0,0 +1,1083 @@
+/*
+ * Copyright (c) 1999-2005 Apple Computer, Inc.
+ * 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.
+ *
+ * $FreeBSD$
+ */
+
+#include <sys/param.h>
+#include <sys/condvar.h>
+#include <sys/conf.h>
+#include <sys/file.h>
+#include <sys/filedesc.h>
+#include <sys/fcntl.h>
+#include <sys/ipc.h>
+#include <sys/kernel.h>
+#include <sys/kthread.h>
+#include <sys/malloc.h>
+#include <sys/mount.h>
+#include <sys/namei.h>
+#include <sys/proc.h>
+#include <sys/queue.h>
+#include <sys/socket.h>
+#include <sys/socketvar.h>
+#include <sys/protosw.h>
+#include <sys/domain.h>
+#include <sys/sysproto.h>
+#include <sys/sysent.h>
+#include <sys/systm.h>
+#include <sys/ucred.h>
+#include <sys/uio.h>
+#include <sys/un.h>
+#include <sys/unistd.h>
+#include <sys/vnode.h>
+
+#include <netinet/in.h>
+#include <netinet/in_pcb.h>
+
+#include <bsm/audit.h>
+#include <bsm/audit_kevents.h>
+#include <security/audit/audit.h>
+#include <security/audit/audit_private.h>
+
+/*
+ * The AUDIT_EXCESSIVELY_VERBOSE define enables a number of
+ * gratuitously noisy printf's to the console.  Due to the
+ * volume, it should be left off unless you want your system
+ * to churn a lot whenever the audit record flow gets high.
+ */
+//#define	AUDIT_EXCESSIVELY_VERBOSE
+#ifdef AUDIT_EXCESSIVELY_VERBOSE
+#define	AUDIT_PRINTF(x)	printf x
+#else
+#define	AUDIT_PRINTF(X)
+#endif
+
+static MALLOC_DEFINE(M_AUDITPROC, "audit_proc", "Audit process storage");
+static MALLOC_DEFINE(M_AUDITREC, "audit_rec", "Audit event records");
+MALLOC_DEFINE(M_AUDITDATA, "audit_data", "Audit data storage");
+MALLOC_DEFINE(M_AUDITPATH, "audit_path", "Audit path storage");
+MALLOC_DEFINE(M_AUDITTEXT, "audit_text", "Audit text storage");
+
+/*
+ * Audit control settings that are set/read by system calls and are 
+ * hence non-static.
+ */
+/* 
+ * Define the audit control flags.
+ */
+int					audit_enabled;
+int					audit_suspended;
+
+/*
+ * Flags controlling behavior in low storage situations.
+ * Should we panic if a write fails?  Should we fail stop
+ * if we're out of disk space?
+ */
+int					audit_panic_on_write_fail;
+int					audit_fail_stop;
+
+/*
+ * Are we currently "failing stop" due to out of disk space?
+ */
+static int				 audit_in_failure;
+
+/*
+ * Global audit statistiscs. 
+ */
+struct audit_fstat 			audit_fstat;
+
+/*
+ * Preselection mask for non-attributable events.
+ */
+struct au_mask			 	audit_nae_mask;
+
+/*
+ * Mutex to protect global variables shared between various threads and
+ * processes.
+ */
+static struct mtx			audit_mtx;
+
+/*
+ * Queue of audit records ready for delivery to disk.  We insert new
+ * records at the tail, and remove records from the head.  Also,
+ * a count of the number of records used for checking queue depth.
+ * In addition, a counter of records that we have allocated but are
+ * not yet in the queue, which is needed to estimate the total
+ * size of the combined set of records outstanding in the system.
+ */
+static TAILQ_HEAD(, kaudit_record)	audit_q;
+static int				audit_q_len;
+static int				audit_pre_q_len;
+
+/*
+ * Audit queue control settings (minimum free, low/high water marks, etc.)
+ */
+struct au_qctrl				audit_qctrl;
+
+/*
+ * Condition variable to signal to the worker that it has work to do:
+ * either new records are in the queue, or a log replacement is taking
+ * place.
+ */
+static struct cv			audit_cv;
+
+/*
+ * 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;
+
+/*
+ * Condition variable to signal to the worker that it has work to do:
+ * either new records are in the queue, or a log replacement is taking
+ * place.
+ */
+static struct cv			audit_commit_cv;
+
+/* 
+ * Condition variable for  auditing threads wait on when in fail-stop mode. 
+ * Threads wait on this CV forever (and ever), never seeing the light of 
+ * day again.
+ */
+static struct cv			audit_fail_cv;
+
+/*
+ * Flags related to Kernel->user-space communication.
+ */
+static int			audit_file_rotate_wait;
+
+/*
+ * Perform a deep free of an audit record (core record and referenced objects)
+ */
+static void
+audit_record_free(struct kaudit_record *ar)
+{
+
+	if (ar->k_ar.ar_arg_upath1 != NULL) {
+		free(ar->k_ar.ar_arg_upath1, M_AUDITPATH);
+	}
+	if (ar->k_ar.ar_arg_upath2 != NULL) {
+		free(ar->k_ar.ar_arg_upath2, M_AUDITPATH);
+	}
+	if (ar->k_ar.ar_arg_text != NULL) {
+		free(ar->k_ar.ar_arg_text, M_AUDITTEXT);
+	}
+	if (ar->k_udata != NULL) {
+		free(ar->k_udata, M_AUDITDATA);
+	}
+	free(ar, M_AUDITREC);
+}
+
+/*
+ * XXXAUDIT: Should adjust comments below to make it clear that we get to
+ * this point only if we believe we have storage, so not having space here
+ * is a violation of invariants derived from administrative procedures.
+ * I.e., someone else has written to the audit partition, leaving less space
+ * than we accounted for.
+ */
+static int
+audit_record_write(struct vnode *vp, struct kaudit_record *ar, 
+    struct ucred *cred, struct thread *td)
+{
+	int ret;
+	long temp;
+	struct au_record *bsm;
+	struct vattr vattr;
+	struct statfs *mnt_stat = &vp->v_mount->mnt_stat;
+	int vfslocked;
+
+	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.  In both cases,
+	 * if we're unable to perform the operation, we drop the record
+	 * and return.  However, this is arguably an assertion failure.
+	 * XXX Need a FreeBSD equivalent.
+	 */
+	ret = VFS_STATFS(vp->v_mount, mnt_stat, td);
+	if (ret)
+		goto out;
+
+	ret = VOP_GETATTR(vp, &vattr, cred, td);
+	if (ret)
+		goto out;
+
+	/* update the global stats struct */
+	audit_fstat.af_currsz = vattr.va_size; 
+
+	/*
+	 * XXX Need to decide what to do if the trigger to the audit daemon
+	 * fails.
+	 */
+
+	/* 
+	 * If we fall below minimum free blocks (hard limit), tell the audit
+	 * daemon to force a rotation off of the file system. We also stop
+	 * writing, which means this audit record is probably lost.
+	 * If we fall below the minimum percent free blocks (soft limit), 
+	 * then kindly suggest to the audit daemon to do something.
+	 */
+	if (mnt_stat->f_bfree < AUDIT_HARD_LIMIT_FREE_BLOCKS) {
+		send_trigger(AUDIT_TRIGGER_NO_SPACE);
+		/* Hopefully userspace did something about all the previous
+		 * triggers that were sent prior to this critical condition.
+		 * If fail-stop is set, then we're done; goodnight Gracie.
+		 */
+		if (audit_fail_stop)
+			panic("Audit log space exhausted and fail-stop set.");
+		else {
+			audit_suspended = 1;
+			ret = ENOSPC;
+			goto out;
+		}
+	} else
+		/* 
+		 * Send a message to the audit daemon that disk space 
+		 * is getting low.
+		 *
+		 * XXXAUDIT: Check math and block size calculation here.
+		 */
+		if (audit_qctrl.aq_minfree != 0) {
+			temp = mnt_stat->f_blocks / (100 / 
+			    audit_qctrl.aq_minfree);
+			if (mnt_stat->f_bfree < temp)
+				send_trigger(AUDIT_TRIGGER_LOW_SPACE);
+		}
+
+	/* Check if the current log file is full; if so, call for
+	 * a log rotate. This is not an exact comparison; we may
+	 * write some records over the limit. If that's not
+	 * acceptable, then add a fudge factor here.
+	 */
+	if ((audit_fstat.af_filesz != 0) &&
+	    (audit_file_rotate_wait == 0) && 
+	    (vattr.va_size >= audit_fstat.af_filesz)) {
+		audit_file_rotate_wait = 1;
+		send_trigger(AUDIT_TRIGGER_OPEN_NEW);
+	}
+
+	/*
+	 * 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 packets 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 &&
+	    (unsigned long)
+	    ((audit_q_len + audit_pre_q_len + 1) * MAX_AUDIT_RECORD_SIZE) /
+	    mnt_stat->f_bsize >= (unsigned long)(mnt_stat->f_bfree)) {
+		printf(
+    "audit_worker: free space below size of audit queue, failing stop\n");
+		audit_in_failure = 1;
+	}
+
+	/* 
+	 * If there is a user audit record attached to the kernel record,
+	 * then write the user record.
+	 */
+	/* XXX Need to decide a few things here: IF the user audit 
+	 * record is written, but the write of the kernel record fails,
+	 * what to do? Should the kernel record come before or after the
+	 * user record? For now, we write the user record first, and
+	 * we ignore errors.
+	 */
+	if (ar->k_ar_commit & AR_COMMIT_USER) {
+		ret = vn_rdwr(UIO_WRITE, vp, (void *)ar->k_udata, ar->k_ulen,
+		          (off_t)0, UIO_SYSSPACE, IO_APPEND|IO_UNIT, cred, NULL,
+			  NULL, td); 
+		if (ret)
+			goto out;
+	}
+
+	/* 
+	 * Convert the internal kernel record to BSM format and write it
+	 * out if everything's OK.
+	 */
+	if (!(ar->k_ar_commit & AR_COMMIT_KERNEL)) {
+		ret = 0;
+		goto out;
+	}
+
+	/*
+	 * XXXAUDIT: Should we actually allow this conversion to fail?  With
+	 * sleeping memory allocation and invariants checks, perhaps not.
+	 */
+	ret = kaudit_to_bsm(ar, &bsm);
+	if (ret == BSM_NOAUDIT) {
+		ret = 0;
+		goto out;
+	}
+
+	/*
+	 * XXX: We drop the record on BSM conversion failure, but really
+	 * this is an assertion failure.
+	 */
+	if (ret == BSM_FAILURE) {
+		AUDIT_PRINTF(("BSM conversion failure\n"));
+		ret = EINVAL;
+		goto out;
+	}
+	
+	/*
+	 * XXX
+	 * We should break the write functionality away from the BSM record
+	 * generation and have the BSM generation done before this function
+	 * is called. This function will then take the BSM record as a
+	 * parameter.
+	 */
+	ret = (vn_rdwr(UIO_WRITE, vp, (void *)bsm->data, bsm->len,
+	    (off_t)0, UIO_SYSSPACE, IO_APPEND|IO_UNIT, cred, NULL, NULL, td));
+
+	kau_free(bsm);
+
+out:
+	/*
+	 * When we're done processing the current record, we have to
+	 * check to see if we're in a failure mode, and if so, whether
+	 * this was the last record left to be drained.  If we're done
+	 * draining, then we fsync the vnode and panic.
+	 */
+	if (audit_in_failure &&
+	    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 (ret);
+}
+
+/*
+ * 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)
+{
+	int do_replacement_signal, error;
+	TAILQ_HEAD(, kaudit_record) ar_worklist;
+	struct kaudit_record *ar;
+	struct vnode *audit_vp, *old_vp;
+	int vfslocked;
+
+	struct ucred *audit_cred, *old_cred;
+	struct thread *audit_td;
+
+	AUDIT_PRINTF(("audit_worker starting\n"));
+
+	/*
+	 * 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) {
+		/*
+		 * First priority: replace the audit log target if requested.
+		 * Accessing the vnode here requires dropping the audit_mtx;
+		 * in case another replacement was scheduled while the mutex
+		 * was released, we loop.
+		 *
+		 * XXX It could well be we should drain existing records
+		 * first to ensure that the timestamps and ordering
+		 * are right.
+		 */
+		do_replacement_signal = 0;
+		while (audit_replacement_flag != 0) {
+			old_cred = audit_cred;
+			old_vp = audit_vp;
+			audit_cred = audit_replacement_cred;
+			audit_vp = audit_replacement_vp;
+			audit_replacement_cred = NULL;
+			audit_replacement_vp = NULL;
+			audit_replacement_flag = 0;
+
+			audit_enabled = (audit_vp != NULL);
+
+			/*
+			 * XXX: What to do about write failures here?
+			 */
+			if (old_vp != NULL) {
+				AUDIT_PRINTF(("Closing old audit file\n"));
+				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;
+				AUDIT_PRINTF(("Audit file closed\n"));
+			}
+			if (audit_vp != NULL) {
+				AUDIT_PRINTF(("Opening new audit file\n"));
+			}
+			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);
+
+		/*
+		 * Next, check to see if we have any records to drain into
+		 * the vnode.  If not, go back to waiting for an event.
+		 */
+		if (TAILQ_EMPTY(&audit_q)) {
+			AUDIT_PRINTF(("audit_worker waiting\n"));
+			cv_wait(&audit_cv, &audit_mtx);
+			AUDIT_PRINTF(("audit_worker woken up\n"));
+	AUDIT_PRINTF(("audit_worker: new vp = %p; value of flag %d\n",
+	    audit_replacement_vp, audit_replacement_flag));
+			continue;
+		}
+
+		/*
+		 * If we have records, but there's no active vnode to
+		 * write to, drain the record queue.  Generally, we
+		 * prevent the unnecessary allocation of records
+		 * elsewhere, but we need to allow for races between
+		 * conditional allocation and queueing.  Go back to
+		 * waiting when we're done.
+		 *
+		 * XXX: We go out of our way to avoid calling 
+		 * audit_record_free().
+		 * with the audit_mtx held, to avoid a lock order reversal
+		 * as free() may grab Giant.  This should be fixed at
+		 * some point.
+		 */
+		if (audit_vp == NULL) {
+			while ((ar = TAILQ_FIRST(&audit_q))) {
+				TAILQ_REMOVE(&audit_q, ar, k_q);
+				audit_q_len--;
+				if (audit_q_len <= audit_qctrl.aq_lowater)
+					cv_broadcast(&audit_commit_cv);
+
+				TAILQ_INSERT_TAIL(&ar_worklist, ar, k_q);
+			}
+			mtx_unlock(&audit_mtx);
+			while ((ar = TAILQ_FIRST(&ar_worklist))) {
+				TAILQ_REMOVE(&ar_worklist, ar, k_q);
+				audit_record_free(ar);
+			}
+			mtx_lock(&audit_mtx);
+			continue;
+		}
+
+		/*
+		 * We have both records to write and an active vnode
+		 * to write to.  Dequeue a record, and start the write.
+		 * Eventually, it might make sense to dequeue several
+		 * records and perform our own clustering, if the lower
+		 * layers aren't doing it automatically enough.
+		 *
+		 * XXX: We go out of our way to avoid calling
+		 * audit_record_free()
+		 * with the audit_mtx held, to avoid a lock order reversal
+		 * as free() may grab Giant.  This should be fixed at
+		 * some point.
+		 *
+		 * XXXAUDIT: free() no longer grabs Giant.
+		 */
+		while ((ar = TAILQ_FIRST(&audit_q))) {
+			TAILQ_REMOVE(&audit_q, ar, k_q);
+			audit_q_len--;
+			if (audit_q_len <= audit_qctrl.aq_lowater)
+				cv_broadcast(&audit_commit_cv);
+
+			TAILQ_INSERT_TAIL(&ar_worklist, ar, k_q);
+		}
+
+		mtx_unlock(&audit_mtx);
+		while ((ar = TAILQ_FIRST(&ar_worklist))) {
+			TAILQ_REMOVE(&ar_worklist, ar, k_q);
+			if (audit_vp != NULL) {
+				error = audit_record_write(audit_vp, ar, 
+				    audit_cred, audit_td);
+				if (error && audit_panic_on_write_fail)
+					panic("audit_worker: write error %d\n",
+					    error);
+				else if (error)
+					printf("audit_worker: write error %d\n",
+					    error);
+			}
+			audit_record_free(ar);
+		}
+		mtx_lock(&audit_mtx);
+	}
+}
+
+/*
+ * Initialize the Audit subsystem: configuration state, work queue,
+ * synchronization primitives, worker thread, and trigger device node.  Also
+ * call into the BSM assembly code to initialize it.
+ */
+static void
+audit_init(void)
+{
+	int error;
+
+	printf("Security auditing service present\n");
+	audit_enabled = 0;
+	audit_suspended = 0;
+	audit_panic_on_write_fail = 0;
+	audit_fail_stop = 0;
+	audit_in_failure = 0;
+
+	audit_replacement_vp = NULL;
+	audit_replacement_cred = NULL;
+	audit_replacement_flag = 0;
+
+	audit_fstat.af_filesz = 0;	/* '0' means unset, unbounded */
+	audit_fstat.af_currsz = 0; 
+	audit_nae_mask.am_success = AU_NULL;
+	audit_nae_mask.am_failure = AU_NULL;
+
+	TAILQ_INIT(&audit_q);
+	audit_q_len = 0;
+	audit_pre_q_len = 0;
+	audit_qctrl.aq_hiwater = AQ_HIWATER;
+	audit_qctrl.aq_lowater = AQ_LOWATER;
+	audit_qctrl.aq_bufsz = AQ_BUFSZ;
+	audit_qctrl.aq_minfree = AU_FS_MINFREE;
+
+	mtx_init(&audit_mtx, "audit_mtx", NULL, MTX_DEF);
+	cv_init(&audit_cv, "audit_cv");
+	cv_init(&audit_replacement_cv, "audit_replacement_cv");
+	cv_init(&audit_commit_cv, "audit_commit_cv");
+	cv_init(&audit_fail_cv, "audit_fail_cv");
+
+	/* Initialize the BSM audit subsystem. */
+	kau_init();
+
+	audit_file_rotate_wait = 0;
+	audit_trigger_init();
+
+	/* Register shutdown handler. */
+	EVENTHANDLER_REGISTER(shutdown_pre_sync, audit_shutdown, NULL,
+	    SHUTDOWN_PRI_FIRST);
+
+	error = kthread_create(audit_worker, NULL, &audit_thread, RFHIGHPID,
+	    0, "audit_worker");
+	if (error != 0)
+		panic("audit_init: kthread_create returned %d", error);
+}
+
+SYSINIT(audit_init, SI_SUB_AUDIT, SI_ORDER_FIRST, audit_init, NULL)
+
+/*
+ * 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.
+ *
+ * XXXAUDIT: Enhance the comments below to indicate that we are basically
+ * 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) {
+		AUDIT_PRINTF(("audit_rotate_vnode: sleeping to wait for "
+		    "flag\n"));
+		cv_wait(&audit_replacement_cv, &audit_mtx);
+		AUDIT_PRINTF(("audit_rotate_vnode: woken up (flag %d)\n",
+		    audit_replacement_flag));
+	}
+	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_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.
+	 */
+	AUDIT_PRINTF(("audit_rotate_vnode: waiting for news of "
+	    "replacement\n"));
+	cv_wait(&audit_replacement_cv, &audit_mtx);
+	AUDIT_PRINTF(("audit_rotate_vnode: change acknowledged by "
+	    "audit_worker (flag " "now %d)\n", audit_replacement_flag));
+	mtx_unlock(&audit_mtx);
+
+	audit_file_rotate_wait = 0; /* We can now request another rotation */
+}
+
+/*
+ * Drain the audit queue and close the log at shutdown.  Note that this can
+ * be called both from the system shutdown path and also from audit
+ * configuration syscalls, so 'arg' and 'howto' are ignored.
+ */
+void
+audit_shutdown(void *arg, int howto)
+{
+
+	audit_rotate_vnode(NULL, NULL);
+}
+
+/*
+ * Return the current thread's audit record, if any.
+ */
+__inline__ struct kaudit_record *
+currecord(void)
+{
+
+	return (curthread->td_ar);
+}
+
+/*
+ * MPSAFE
+ *
+ * XXXAUDIT: There are a number of races present in the code below due to
+ * release and re-grab of the mutex.  The code should be revised to become
+ * slightly less racy.
+ *
+ * XXXAUDIT: Shouldn't there be logic here to sleep waiting on available
+ * pre_q space, suspending the system call until there is room?
+ */
+struct kaudit_record *
+audit_new(int event, struct thread *td)
+{
+	struct kaudit_record *ar;
+	int no_record;
+
+	/*
+	 * Eventually, there may be certain classes of events that
+	 * we will audit regardless of the audit state at the time
+	 * the record is created.  These events will generally
+	 * correspond to changes in the audit state.  The dummy
+	 * code below is from our first prototype, but may also
+	 * be used in the final version (with modified event numbers).
+	 */
+#if 0
+	if (event != AUDIT_EVENT_FILESTOP && event != AUDIT_EVENT_FILESTART) {
+#endif
+		mtx_lock(&audit_mtx);
+		no_record = (audit_suspended || !audit_enabled);
+		mtx_unlock(&audit_mtx);
+		if (no_record)
+			return (NULL);
+#if 0
+	}
+#endif
+
+	/*
+	 * Initialize the audit record header.
+	 * XXX: We may want to fail-stop if allocation fails.
+	 * XXX: The number of outstanding uncommitted audit records is
+	 * limited by the number of concurrent threads servicing system
+	 * calls in the kernel.
+	 */
+
+	ar = malloc(sizeof(*ar), M_AUDITREC, M_WAITOK);
+	if (ar == NULL)
+		return NULL;
+
+	mtx_lock(&audit_mtx);
+	audit_pre_q_len++;
+	mtx_unlock(&audit_mtx);
+
+	bzero(ar, sizeof(*ar));
+	ar->k_ar.ar_magic = AUDIT_RECORD_MAGIC;
+	ar->k_ar.ar_event = event;
+	nanotime(&ar->k_ar.ar_starttime);
+
+	/*
+	 * Export the subject credential.
+	 *
+	 * XXXAUDIT: td_ucred access is OK without proc lock, but some other
+	 * fields here may require the proc lock.
+	 */
+	cru2x(td->td_ucred, &ar->k_ar.ar_subj_cred);
+	ar->k_ar.ar_subj_ruid = td->td_ucred->cr_ruid;
+	ar->k_ar.ar_subj_rgid = td->td_ucred->cr_rgid;
+	ar->k_ar.ar_subj_egid = td->td_ucred->cr_groups[0];
+	ar->k_ar.ar_subj_auid = td->td_proc->p_au->ai_auid;
+	ar->k_ar.ar_subj_asid = td->td_proc->p_au->ai_asid;
+	ar->k_ar.ar_subj_pid = td->td_proc->p_pid;
+	ar->k_ar.ar_subj_amask = td->td_proc->p_au->ai_mask;
+	ar->k_ar.ar_subj_term = td->td_proc->p_au->ai_termid;
+
+	bcopy(td->td_proc->p_comm, ar->k_ar.ar_subj_comm, MAXCOMLEN);
+
+	return (ar);
+}
+
+/*
+ * MPSAFE
+ */
+void
+audit_commit(struct kaudit_record *ar, int error, int retval)
+{
+	int sorf;
+	struct au_mask *aumask;
+
+	if (ar == NULL)
+		return;
+
+	/*
+	 * Decide whether to commit the audit record by checking the
+	 * error value from the system call and using the appropriate
+	 * audit mask.
+	 *
+	 * XXXAUDIT: Synchronize access to audit_nae_mask?
+	 */
+	if (ar->k_ar.ar_subj_auid == AU_DEFAUDITID)
+		aumask = &audit_nae_mask;
+	else
+		aumask = &ar->k_ar.ar_subj_amask;
+	
+	if (error)
+		sorf = AU_PRS_FAILURE;
+	else
+		sorf = AU_PRS_SUCCESS;
+
+	switch(ar->k_ar.ar_event) {
+
+	case AUE_OPEN_RWTC:
+		/* The open syscall always writes a AUE_OPEN_RWTC event; change
+		 * it to the proper type of event based on the flags and the 
+		 * error value.
+		 */
+		ar->k_ar.ar_event = flags_and_error_to_openevent(
+		    ar->k_ar.ar_arg_fflags, error);
+		break;
+
+	case AUE_SYSCTL:
+		ar->k_ar.ar_event = ctlname_to_sysctlevent(
+		    ar->k_ar.ar_arg_ctlname, ar->k_ar.ar_valid_arg);
+		break;
+
+	case AUE_AUDITON:
+		/* Convert the auditon() command to an event */
+		ar->k_ar.ar_event = auditon_command_event(ar->k_ar.ar_arg_cmd);
+		break;
+	}
+
+	if (au_preselect(ar->k_ar.ar_event, aumask, sorf) != 0)
+		ar->k_ar_commit |= AR_COMMIT_KERNEL;
+
+	if ((ar->k_ar_commit & (AR_COMMIT_USER | AR_COMMIT_KERNEL)) == 0) {
+		mtx_lock(&audit_mtx);
+		audit_pre_q_len--;
+		mtx_unlock(&audit_mtx);
+		audit_record_free(ar);
+		return;
+	}
+
+	ar->k_ar.ar_errno = error;
+	ar->k_ar.ar_retval = retval;
+
+	/*
+	 * We might want to do some system-wide post-filtering
+	 * here at some point.
+	 */
+
+	/*
+	 * Timestamp system call end.
+	 */
+	nanotime(&ar->k_ar.ar_endtime);
+
+	mtx_lock(&audit_mtx);
+
+	/*
+	 * Note: it could be that some records initiated while audit was
+	 * enabled should still be committed?
+	 */
+	if (audit_suspended || !audit_enabled) {
+		audit_pre_q_len--;
+		mtx_unlock(&audit_mtx);
+		audit_record_free(ar);
+		return;
+	}
+	
+	/*
+	 * Constrain the number of committed audit records based on
+	 * the configurable parameter.
+	 */
+	while (audit_q_len >= audit_qctrl.aq_hiwater) {
+		AUDIT_PRINTF(("audit_commit: sleeping to wait for "
+		   "audit queue to drain below high water mark\n"));
+		cv_wait(&audit_commit_cv, &audit_mtx);
+		AUDIT_PRINTF(("audit_commit: woke up waiting for "
+		   "audit queue draining\n"));
+	}
+
+	TAILQ_INSERT_TAIL(&audit_q, ar, k_q);
+	audit_q_len++;
+	audit_pre_q_len--;
+	cv_signal(&audit_cv);
+	mtx_unlock(&audit_mtx);
+}
+
+/*
+ * audit_syscall_enter() is called on entry to each system call.  It is
+ * responsible for deciding whether or not to audit the call (preselection),
+ * and if so, allocating a per-thread audit record.  audit_new() will fill in
+ * basic thread/credential properties.
+ */
+void
+audit_syscall_enter(unsigned short code, struct thread *td)
+{
+	int audit_event;
+	struct au_mask *aumask;
+
+	KASSERT(td->td_ar == NULL, ("audit_syscall_enter: td->td_ar != NULL"));
+
+	/*
+	 * In FreeBSD, each ABI has its own system call table, and hence
+	 * mapping of system call codes to audit events.  Convert the code to
+	 * an audit event identifier using the process system call table
+	 * reference.  In Darwin, there's only one, so we use the global
+	 * symbol for the system call table.
+	 *
+	 * XXXAUDIT: Should we audit that a bad system call was made, and if
+	 * so, how?
+	 */
+	if (code >= td->td_proc->p_sysent->sv_size)
+		return;
+
+	audit_event = td->td_proc->p_sysent->sv_table[code].sy_auevent;
+	if (audit_event == AUE_NULL)
+		return;
+
+	/*
+	 * Check which audit mask to use; either the kernel non-attributable
+	 * event mask or the process audit mask.
+	 */
+	if (td->td_proc->p_au->ai_auid == AU_DEFAUDITID)
+		aumask = &audit_nae_mask;
+	else
+		aumask = &td->td_proc->p_au->ai_mask;
+	
+	/*
+	 * Allocate an audit record, if preselection allows it, and store 
+	 * in the thread for later use.
+	 */
+	if (au_preselect(audit_event, aumask,
+			AU_PRS_FAILURE | AU_PRS_SUCCESS)) {
+		/*
+		 * If we're out of space and need to suspend unprivileged
+		 * processes, do that here rather than trying to allocate
+		 * another audit record.
+		 *
+		 * XXXRW: We might wish to be able to continue here in the
+		 * future, if the system recovers.  That should be possible
+		 * by means of checking the condition in a loop around
+		 * cv_wait().  It might be desirable to reevaluate whether an
+		 * audit record is still required for this event by
+		 * re-calling au_preselect().
+		 */
+		if (audit_in_failure && suser(td) != 0) {
+			cv_wait(&audit_fail_cv, &audit_mtx);
+			panic("audit_failing_stop: thread continued");
+		}
+		td->td_ar = audit_new(audit_event, td);
+	} else
+		td->td_ar = NULL;
+}
+
+/*
+ * audit_syscall_exit() is called from the return of every system call, or in
+ * the event of exit1(), during the execution of exit1().  It is responsible
+ * for committing the audit record, if any, along with return condition.
+ */
+void
+audit_syscall_exit(int error, struct thread *td)
+{
+	int retval;
+
+	/*
+	 * Commit the audit record as desired; once we pass the record
+	 * into audit_commit(), the memory is owned by the audit
+	 * subsystem.
+	 * The return value from the system call is stored on the user
+	 * thread. If there was an error, the return value is set to -1,
+	 * imitating the behavior of the cerror routine.
+	 */
+	if (error)
+		retval = -1;
+	else
+		retval = td->td_retval[0];
+
+	audit_commit(td->td_ar, error, retval);
+	if (td->td_ar != NULL)
+		AUDIT_PRINTF(("audit record committed by pid %d\n", 
+			td->td_proc->p_pid));
+	td->td_ar = NULL;
+
+}
+
+/*
+ * Allocate storage for a new process (init, or otherwise).
+ */
+void
+audit_proc_alloc(struct proc *p)
+{
+
+	KASSERT(p->p_au == NULL, ("audit_proc_alloc: p->p_au != NULL (%d)",
+	    p->p_pid));
+	p->p_au = malloc(sizeof(*(p->p_au)), M_AUDITPROC, M_WAITOK);
+	/* XXXAUDIT: Zero?  Slab allocate? */
+	//printf("audit_proc_alloc: pid %d p_au %p\n", p->p_pid, p->p_au);
+}
+
+/* 
+ * Initialize the audit information for the a process, presumably the first 
+ * process in the system.
+ * XXX It is not clear what the initial values should be for audit ID, 
+ * session ID, etc. 
+ */
+void
+audit_proc_kproc0(struct proc *p)
+{
+
+	KASSERT(p->p_au != NULL, ("audit_proc_kproc0: p->p_au == NULL (%d)",
+	    p->p_pid));
+	//printf("audit_proc_kproc0: pid %d p_au %p\n", p->p_pid, p->p_au);
+	bzero(p->p_au, sizeof(*(p)->p_au));
+}
+
+void
+audit_proc_init(struct proc *p)
+{
+
+	KASSERT(p->p_au != NULL, ("audit_proc_init: p->p_au == NULL (%d)",
+	    p->p_pid));
+	//printf("audit_proc_init: pid %d p_au %p\n", p->p_pid, p->p_au);
+	bzero(p->p_au, sizeof(*(p)->p_au));
+}
+
+/* 
+ * Copy the audit info from the parent process to the child process when
+ * a fork takes place.
+ */
+void
+audit_proc_fork(struct proc *parent, struct proc *child)
+{
+
+	PROC_LOCK_ASSERT(parent, MA_OWNED);
+	PROC_LOCK_ASSERT(child, MA_OWNED);
+	KASSERT(parent->p_au != NULL,
+	    ("audit_proc_fork: parent->p_au == NULL (%d)", parent->p_pid));
+	KASSERT(child->p_au != NULL,
+	    ("audit_proc_fork: child->p_au == NULL (%d)", child->p_pid));
+	//printf("audit_proc_fork: parent pid %d p_au %p\n", parent->p_pid,
+	//    parent->p_au);
+	//printf("audit_proc_fork: child pid %d p_au %p\n", child->p_pid,
+	//    child->p_au);
+	bcopy(parent->p_au, child->p_au, sizeof(*child->p_au));
+	/*
+	 * XXXAUDIT: Zero pointers to external memory, or assert they are
+	 * zero?
+	 */
+}
+
+/*
+ * Free the auditing structure for the process. 
+ */
+void
+audit_proc_free(struct proc *p)
+{
+
+	KASSERT(p->p_au != NULL, ("p->p_au == NULL (%d)", p->p_pid));
+	//printf("audit_proc_free: pid %d p_au %p\n", p->p_pid, p->p_au);
+	/*
+	 * XXXAUDIT: Assert that external memory pointers are NULL?
+	 */
+	free(p->p_au, M_AUDITPROC);
+	p->p_au = NULL;
+}