FreeBSD/Linux Kernel Cross Reference
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: releng/6.2/sys/security/audit/audit.c 164286 2006-11-14 20:42:41Z cvs2svn $
     */
    
    #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_internal.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>
    
    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;
    int                     audit_argv;
    int                     audit_arge;
    
    /*
     * Are we currently "failing stop" due to out of disk space?
     */
   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.
    */
   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.
    */
   struct kaudit_queue     audit_q;
   int                     audit_q_len;
   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.
    */
   struct cv               audit_worker_cv;
   
   /*
    * Condition variable to flag when crossing the low watermark, meaning that
    * threads blocked due to hitting the high watermark can wake up and continue
    * to commit records.
    */
   struct cv               audit_watermark_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;
   
   /*
    * 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.
            */
           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];
           PROC_LOCK(td->td_proc);
           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);
           PROC_UNLOCK(td->td_proc);
   
           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);
           if (ar->k_ar.ar_arg_argv != NULL)
                   free(ar->k_ar.ar_arg_argv, M_AUDITTEXT);
           if (ar->k_ar.ar_arg_envv != NULL)
                   free(ar->k_ar.ar_arg_envv, M_AUDITTEXT);
   }
   
   /*
    * 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)
   {
   
           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_argv = 0;
           audit_arge = 0;
   
           audit_fstat.af_filesz = 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_worker_cv, "audit_worker_cv");
           cv_init(&audit_watermark_cv, "audit_watermark_cv");
           cv_init(&audit_fail_cv, "audit_fail_cv");
   
           audit_record_zone = uma_zcreate("audit_record",
               sizeof(struct kaudit_record), audit_record_ctor,
               audit_record_dtor, NULL, NULL, UMA_ALIGN_PTR, 0);
   
           /* Initialize the BSM audit subsystem. */
           kau_init();
   
           audit_trigger_init();
   
           /* Register shutdown handler. */
           EVENTHANDLER_REGISTER(shutdown_pre_sync, audit_shutdown, NULL,
               SHUTDOWN_PRI_FIRST);
   
           /* Start audit worker thread. */
           audit_worker_init();
   }
   
   SYSINIT(audit_init, SI_SUB_AUDIT, SI_ORDER_FIRST, audit_init, NULL)
   
   /*
    * 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);
   }
   
   void
   audit_free(struct kaudit_record *ar)
   {
   
           uma_zfree(audit_record_zone, ar);
   }
   
   /*
    * MPSAFE
    */
   void
   audit_commit(struct kaudit_record *ar, int error, int retval)
   {
           au_event_t event;
           au_class_t class;
           au_id_t auid;
           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;
           }
   
           auid = ar->k_ar.ar_subj_auid;
           event = ar->k_ar.ar_event;
           class = au_event_class(event);
   
           ar->k_ar_commit |= AR_COMMIT_KERNEL;
           if (au_preselect(event, class, aumask, sorf) != 0)
                   ar->k_ar_commit |= AR_PRESELECT_TRAIL;
           if (audit_pipe_preselect(auid, event, class, sorf,
               ar->k_ar_commit & AR_PRESELECT_TRAIL) != 0)
                   ar->k_ar_commit |= AR_PRESELECT_PIPE;
           if ((ar->k_ar_commit & (AR_PRESELECT_TRAIL | AR_PRESELECT_PIPE |
               AR_PRESELECT_USER_TRAIL | AR_PRESELECT_USER_PIPE)) == 0) {
                   mtx_lock(&audit_mtx);
                   audit_pre_q_len--;
                   mtx_unlock(&audit_mtx);
                   audit_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_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_watermark_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_worker_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)
   {
           struct au_mask *aumask;
           au_class_t class;
           au_event_t event;
           au_id_t auid;
   
           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;
   
           event = td->td_proc->p_sysent->sv_table[code].sy_auevent;
           if (event == AUE_NULL)
                   return;
   
           /*
            * Check which audit mask to use; either the kernel non-attributable
            * event mask or the process audit mask.
            */
           auid = td->td_proc->p_au->ai_auid;
           if (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.
            */
           class = au_event_class(event);
           if (au_preselect(event, class, aumask, AU_PRS_BOTH)) {
                   /*
                    * 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(event, td);
           } else if (audit_pipe_preselect(auid, event, class, AU_PRS_BOTH, 0))
                   td->td_ar = audit_new(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;
   }

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