This commit was generated by cvs2svn to compensate for changes in r155832,

[FreeBSD/FreeBSD.git] / sys / security / audit / audit.c

/*
 * 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.
 *
 * $FreeBSD$
 */

#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 <bsm/audit.h>
#include <bsm/audit_kevents.h>

#include <netinet/in.h>
#include <netinet/in_pcb.h>

#include <security/audit/audit.h>
#include <security/audit/audit_private.h>

#include <vm/uma.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 uma_zone_t audit_record_zone;
static MALLOC_DEFINE(M_AUDITPROC, "audit_proc", "Audit process storage");
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;

/*
 * Construct an audit record for the passed thread.
 */
static int
audit_record_ctor(void *mem, int size, void *arg, int flags)
{
        struct kaudit_record *ar;
        struct thread *td;

        KASSERT(sizeof(*ar) == size, ("audit_record_ctor: wrong size"));

        td = arg;
        ar = mem;
        bzero(ar, sizeof(*ar));
        ar->k_ar.ar_magic = AUDIT_RECORD_MAGIC;
        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 (0);
}

static void
audit_record_dtor(void *mem, int size, void *arg)
{
        struct kaudit_record *ar;

        KASSERT(sizeof(*ar) == size, ("audit_record_dtor: wrong size"));

        ar = mem;
        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);
}

/*
 * 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;

        vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, td);
        ret = VOP_GETATTR(vp, &vattr, cred, td);
        VOP_UNLOCK(vp, 0, 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) {
                /*
                 * Try submitting the record to any active audit pipes.
                 */
                audit_pipe_submit((void *)ar->k_udata, ar->k_ulen);

                /*
                 * And to disk.
                 */
                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;
        }

        /*
         * Try submitting the record to any active audit pipes.
         */
        audit_pipe_submit((void *)bsm->data, bsm->len);
        
        /*
         * 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.
                 */
                if (audit_vp == NULL) {
                        while ((ar = TAILQ_FIRST(&audit_q))) {
                                TAILQ_REMOVE(&audit_q, ar, k_q);
                                uma_zfree(audit_record_zone, ar);
                                audit_q_len--;
                                /*
                                 * XXXRW: Why broadcast if we hold the
                                 * mutex and know that audit_vp is NULL?
                                 */
                                if (audit_q_len <= audit_qctrl.aq_lowater)
                                        cv_broadcast(&audit_commit_cv);
                        }
                        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.
                 */
                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);
                        }
                        uma_zfree(audit_record_zone, 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");

        audit_record_zone = uma_zcreate("audit_record_zone",
            sizeof(struct kaudit_record), audit_record_ctor,
            audit_record_dtor, NULL, NULL, UMA_ALIGN_PTR, 0);

        /* 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;

        mtx_lock(&audit_mtx);
        no_record = (audit_suspended || !audit_enabled);
        mtx_unlock(&audit_mtx);
        if (no_record)
                return (NULL);

        /*
         * XXX: The number of outstanding uncommitted audit records is
         * limited to the number of concurrent threads servicing system
         * calls in the kernel.
         */
        ar = uma_zalloc_arg(audit_record_zone, td, M_WAITOK);
        ar->k_ar.ar_event = event;

        mtx_lock(&audit_mtx);
        audit_pre_q_len++;
        mtx_unlock(&audit_mtx);

        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;

        /*
         * XXXRW: Why is this necessary?  Should we ever accept a record that
         * we're not willing to commit?
         */
        if ((ar->k_ar_commit & (AR_COMMIT_USER | AR_COMMIT_KERNEL)) == 0) {
                mtx_lock(&audit_mtx);
                audit_pre_q_len--;
                mtx_unlock(&audit_mtx);
                uma_zfree(audit_record_zone, 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);
                uma_zfree(audit_record_zone, 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);
}

/*
 * Allocate storage for a new thread.
 */
void
audit_thread_alloc(struct thread *td)
{

        td->td_ar = NULL;
}

/*
 * Thread destruction.
 */
void
audit_thread_free(struct thread *td)
{

        KASSERT(td->td_ar == NULL, ("audit_thread_free: td_ar != NULL"));
}

/* 
 * 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));
        p->p_au->ai_auid = AU_DEFAUDITID;
}

/* 
 * 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;
}