.\" Copyright (c) 2006 Robert N. M. Watson
.\" All rights reserved.
.\"
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.\" modification, are permitted provided that the following conditions
.\" are met:
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
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.\" $FreeBSD$
.\"
.Dd February 6, 2006
.Os
.Dt AUDIT 4
.Sh NAME
.Nm audit
.Nd Security Event Audit
.Sh SYNOPSIS
.Cd "options AUDIT"
.Sh DESCRIPTION
Security Event Audit is a facility to provide fine-grained, configurable
logging of security-relevant events, and is intended to meet the requirements
of the Common Criteria (CC) Common Access Protection Profile (CAPP)
evaluation.
The
.Fx
audit facility implements the de facto industry standard BSM API, file
formats, and command line interface, first found in the Solaris operating
system.
Information on the user space implementation can be found in
.Xr libbsm 3 .
.Pp
Audit support is enabled at boot, if present in the kernel, using an
.Xr rc.conf 5
flag.
The audit daemon,
.Xr auditd 8 ,
is responsible for configuring the kernel to perform audit, pushing
configuration data from the various audit configuration files into the
kernel.
.Ss Audit Special Device
The kernel audit facility provides a special device,
.Pa /dev/audit ,
which is used by
.Xr auditd 8
to monitor for audit events, such as requests to cycle the log, low disk
space conditions, and requests to terminate auditing.
This device is not intended for use by applications.
.Ss Audit Pipe Special Devices
While audit trail files maintained by
.Xr 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 montoring 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.
.Pp
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,
.Pa /dev/auditpipe ,
subject to the permissions on the device node, and provide a 
.Qq 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 access to all records.
.Pp
The audit pipe device provides discreet 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 support for polled operation via
.Xr select 2
and
.Xr poll 2 .
.Sh SEE ALSO
.Xr auditreduce 1 ,
.Xr praudit 1 ,
.Xr audit 2 ,
.Xr auditctl 2 ,
.Xr auditon 2 ,
.Xr getaudit 2 ,
.Xr getauid 2 ,
.Xr poll 2 ,
.Xr select 2 ,
.Xr setaudit 2 ,
.Xr setauid 2 ,
.Xr libbsm 3 ,
.Xr audit.log 5 ,
.Xr audit_class 5 ,
.Xr audit_control 5 ,
.Xr audit_event 5 ,
.Xr audit_user 5 ,
.Xr audit_warn 5 ,
.Xr rc.conf 5 ,
.Xr audit 8 ,
.Xr auditd 8
.Sh AUTHORS
This software was created by McAfee Research, the security research division
of McAfee, Inc., under contract to Apple Computer Inc.
Additional authors include Wayne Salamon, Robert Watson, and SPARTA Inc.
.Pp
The Basic Security Module (BSM) interface to audit records and audit event
stream format were defined by Sun Microsystems.
.Pp
This manual page was written by
.An Robert Watson Aq rwatson@FreeBSD.org .
.Sh 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.
.Pp
Support for kernel audit first appeared in
.Fx 6.1 .
.Sh BUGS
The audit facility in
.Fx
is considered experimental, and production deployment should occur only after
careful consideration of the risks of deploying experimental software.
.Pp
The
.Fx
kernel does not fully validate that audit records submitted by user
applications are syntactically valid BSM; as submission of records is limited
to privileged processes, this is not a critical bug.
.Pp
Instrumentation of auditable events in the kernel is not complete, as some
system calls do not generate audit records, or generate audit records with
incomplete argument information.
.Pp
Mandatory Access Control (MAC) labels, as provided by the
.Xr mac 4
facility, are not audited as part of records involving MAC decisions.