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NAME

     auditpipe - pseudo-device for live audit event tracking

SYNOPSIS

     options AUDIT

DESCRIPTION

     While audit trail files generated with audit(4) and maintained by
     auditd(8) provide a reliable long-term store for audit log information,
     current log files are owned by the audit daemon until terminated making
     them somewhat unwieldy for live monitoring applications such as host-
     based intrusion detection.  For example, the log may be cycled and new
     records written to a new file without notice to applications that may be
     accessing the file.

     The audit facility provides an audit pipe facility for applications
     requiring direct access to live BSM audit data for the purposes of real-
     time monitoring.  Audit pipes are available via a clonable special
     device, /dev/auditpipe, subject to the permissions on the device node,
     and provide a "tee" of the audit event stream.  As the device is
     clonable, more than one instance of the device may be opened at a time;
     each device instance will provide independent access to all records.

     The audit pipe device provides discrete BSM audit records; if the read
     buffer passed by the application is too small to hold the next record in
     the sequence, it will be dropped.  Unlike audit data written to the audit
     trail, the reliability of record delivery is not guaranteed.  In
     particular, when an audit pipe queue fills, records will be dropped.
     Audit pipe devices are blocking by default, but support non-blocking I/O,
     asynchronous I/O using SIGIO, and polled operation via select(2) and
     poll(2).

     Applications may choose to track the global audit trail, or configure
     local preselection parameters independent of the global audit trail
     parameters.

   Audit Pipe Queue Ioctls
     The following ioctls retrieve and set various audit pipe record queue
     properties:

     AUDITPIPE_GET_QLEN          Query the current number of records available
                                 for reading on the pipe.

     AUDITPIPE_GET_QLIMIT        Retrieve the current maximum number of
                                 records that may be queued for reading on the
                                 pipe.

     AUDITPIPE_SET_QLIMIT        Set the current maximum number of records
                                 that may be queued for reading on the pipe.
                                 The new limit must fall between the queue
                                 limit minimum and queue limit maximum
                                 queryable using the following two ioctls.

     AUDITPIPE_GET_QLIMIT_MIN    Query the lowest possible maximum number of
                                 records that may be queued for reading on the
                                 pipe.

     AUDITPIPE_GET_QLIMIT_MAX    Query the highest possible maximum number of
                                 records that may be queued for reading on the
                                 pipe.

     AUDITPIPE_FLUSH             Flush all outstanding records on the audit
                                 pipe; useful after setting initial
                                 preselection properties to delete records
                                 queued during the configuration process which
                                 may not match the interests of the user
                                 process.

     AUDITPIPE_GET_MAXAUDITDATA  Query the maximum size of an audit record,
                                 which is a useful minimum size for a user
                                 space buffer intended to hold audit records
                                 read from the audit pipe.

   Audit Pipe Preselection Mode Ioctls
     By default, the audit pipe facility configures pipes to present records
     matched by the system-wide audit trail, configured by auditd(8).
     However, the preselection mechanism for audit pipes can be configured
     using alternative criteria, including pipe-local flags and naflags
     settings, as well as auid-specific selection masks.  This allows
     applications to track events not captured in the global audit trail, as
     well as limit records presented to those of specific interest to the
     application.

     The following ioctls configure the preselection mode on an audit pipe:

     AUDITPIPE_GET_PRESELECT_MODE  Return the current preselect mode on the
                                   audit pipe.  The ioctl argument should be
                                   of type int.

     AUDITPIPE_SET_PRESELECT_MODE  Set the current preselection mode on the
                                   audit pipe.  The ioctl argument should be
                                   of type int.

     Possible preselection mode values are:

     AUDITPIPE_PRESELECT_MODE_TRAIL  Use the global audit trail preselection
                                     parameters to select records for the
                                     audit pipe.

     AUDITPIPE_PRESELECT_MODE_LOCAL  Use local audit pipe preselection; this
                                     model is similar to the global audit
                                     trail configuration model, consisting of
                                     global flags and naflags parameters, as
                                     well as a set of per-auid masks.  These
                                     parameters are configured using further
                                     ioctls.

     After changing the audit pipe preselection mode, records selected under
     earlier preselection configuration may still be in the audit pipe queue.
     The application may flush the current record queue after changing the
     configuration to remove possibly undesired records.

   Audit Pipe Local Preselection Mode Ioctls
     The following ioctls configure the preselection parameters used when an
     audit pipe is configured for the AUDITPIPE_PRESELECT_MODE_LOCAL
     preselection mode.

     AUDITPIPE_GET_PRESELECT_FLAGS    Retrieve the current default
                                      preselection flags for attributable
                                      events on the pipe.  These flags
                                      correspond to the flags field in
                                      audit_control(5).  The ioctl argument
                                      should be of type u_int.

     AUDITPIPE_SET_PRESELECT_FLAGS    Set the current default preselection
                                      flags for attributable events on the
                                      pipe.  These flags correspond to the
                                      flags field in audit_control(5).  The
                                      ioctl argument should be of type u_int.

     AUDITPIPE_GET_PRESELECT_NAFLAGS  Retrieve the current default
                                      preselection flags for non-attributable
                                      events on the pipe.  These flags
                                      correspond to the naflags field in
                                      audit_control(5).  The ioctl argument
                                      should be of type u_int.

     AUDITPIPE_SET_PRESELECT_NAFLAGS  Set the current default preselection
                                      flags for non-attributable events on the
                                      pipe.  These flags correspond to the
                                      naflags field in audit_control(5).  The
                                      ioctl argument should be of type u_int.

     AUDITPIPE_GET_PRESELECT_AUID     Query the current preselection masks for
                                      a specific auid on the pipe.  The ioctl
                                      argument should be of type struct
                                      auditpipe_ioctl_preselect.  The auid to
                                      query is specified via the ap_auid field
                                      of type au_id_t; the mask will be
                                      returned via ap_mask of type au_mask_t.

     AUDITPIPE_SET_PRESELECT_AUID     Set the current preselection masks for a
                                      specific auid on the pipe.  Arguments
                                      are identical to
                                      AUDITPIPE_GET_PRESELECT_AUID, except
                                      that the caller should properly
                                      initialize the ap_mask field to hold the
                                      desired preselection mask.

     AUDITPIPE_DELETE_PRESELECT_AUID  Delete the current preselection mask for
                                      a specific auid on the pipe.  Once
                                      called, events associated with the
                                      specified auid will use the default
                                      flags mask.  The ioctl argument should
                                      be of type au_id_t.

     AUDITPIPE_FLUSH_PRESELECT_AUID   Delete all auid specific preselection
                                      specifications.

EXAMPLES

     The praudit(1) utility may be directly executed on /dev/auditpipe to
     review the default audit trail.

SEE ALSO

     poll(2), select(2), audit(4), audit_control(5), audit(8), auditd(8)

HISTORY

     The OpenBSM implementation was created by McAfee Research, the security
     division of McAfee Inc., under contract to Apple Computer Inc. in 2004.
     It was subsequently adopted by the TrustedBSD Project as the foundation
     for the OpenBSM distribution.

     Support for kernel audit first appeared in FreeBSD 6.2.

AUTHORS

     The audit pipe facility was designed and implemented by Robert Watson
     〈rwatson@FreeBSD.org〉.

     The Basic Security Module (BSM) interface to audit records and audit
     event stream format were defined by Sun Microsystems.

BUGS

     See the audit(4) manual page for information on audit-related bugs and
     limitations.

     The configurable preselection mechanism mirrors the selection model
     present for the global audit trail.  It might be desirable to provided a
     more flexible selection model.

     The per-pipe audit event queue is fifo, with drops occurring if either
     the user thread provides in sufficient for the record on the queue head,
     or on enqueue if there is insufficient room.  It might be desirable to
     support partial reads of records, which would be more compatible with
     buffered I/O as implemented in system libraries, and to allow
     applications to select which records are dropped, possibly in the style
     of preselection.