AUDIT_CONTROL(5) FreeBSD File Formats Manual AUDIT_CONTROL(5)
NAME
audit_control - audit system parameters
DESCRIPTION
The audit_control file contains several audit system parameters. Each
line of this file is of the form:
parameter:value
The parameters are:
dir The directory where audit log files are stored. There may be
more than one of these entries. Changes to this entry can only
be enacted by restarting the audit system. See audit(8) for a
description of how to restart the audit system.
dist When set to on or yes, auditd(8) will be creating hardlinks to
all trail files in /var/audit/dist directory. Those hardlinks
will be consumed by the auditdistd(8) daemon.
flags Specifies which audit event classes are audited for all users.
audit_user(5) describes how to audit events for individual users.
See the information below for the format of the audit flags.
host Specify the hostname or IP address to be used when setting the
local systems's audit host information. This hostname will be
converted into an IP or IPv6 address and will be included in the
header of each audit record. Due to the possibility of transient
errors coupled with the security issues in the DNS protocol
itself, the use of DNS should be avoided. Instead, it is
strongly recommended that the hostname be specified in the
/etc/hosts file. For more information see hosts(5).
naflags
Contains the audit flags that define what classes of events are
audited when an action cannot be attributed to a specific user.
minfree
The minimum free space required on the file system audit logs are
being written to. When the free space falls below this limit a
warning will be issued. If no value for the minimum free space
is set, the default of 20 percent is applied by the kernel.
policy A list of global audit policy flags specifying various behaviors,
such as fail stop, auditing of paths and arguments, etc.
filesz Maximum trail size in bytes; if set to a non-0 value, the audit
daemon will rotate the audit trail file at around this size.
Sizes less than the minimum trail size (default of 512K) will be
rejected as invalid. If 0, trail files will not be automatically
rotated based on file size. For convenience, the trail size may
be expressed with suffix letters: B (Bytes), K (Kilobytes), M
(Megabytes), or G (Gigabytes). For example, 2M is the same as
2097152.
expire-after
Specifies when audit log files will expire and be removed. This
may be after a time period has passed since the file was last
written to or when the aggregate of all the trail files have
reached a specified size or a combination of both. If no expire-
after parameter is given then audit log files will not expire and
be removed by the audit control system. See the information
below for the format of the expiration specification.
qsize Specifies the maximum number of outstanding committed audit
records that can be in the kernel's post-commit queue pending
write to disk. If this number has been reached, user threads
performing an auditable event will be suspended until the queue
has fallen below the limit. Depending on the underlying kernel
implementation, the number of in-flight records can exceed this
number, as it does not constrain uncommitted records (e.g., those
associated with incomplete auditable system calls), and may also
exclude the set of records extracted from the queue and currently
being prepared for or undergoing I/O. Other operational limits
may be affected by this parameter, such as the minimum free space
on disk required to continue system operation, estimated as the
maximum number of allowable in-flight records multiplied by the
maximum audit record size.
AUDIT FLAGS
Audit flags are a comma-delimited list of audit classes as defined in the
audit_class(5) file. Event classes may be preceded by a prefix which
changes their interpretation. The following prefixes may be used for
each class:
(none) Record both successful and failed events.
+ Record successful events.
- Record failed events.
^ Record neither successful nor failed events.
^+ Do not record successful events.
^- Do not record failed events.
AUDIT POLICY FLAGS
The policy flags field is a comma-delimited list of policy flags from the
following list:
cnt Allow processes to continue running even though
events are not being audited. If not set, processes
will be suspended when the audit store space is
exhausted. Currently, this is not a recoverable
state.
ahlt Fail stop the system if unable to audit an
event--this consists of first draining pending
records to disk, and then halting the operating
system.
argv Audit command line arguments to execve(2).
arge Audit environmental variable arguments to execve(2).
seq Include a unique audit sequence number token in
generated audit records (not implemented on FreeBSD
or Darwin).
group Include supplementary groups list in generated audit
records (not implemented on FreeBSD or Darwin;
supplementary groups are never included in records on
these systems).
trail Append a trailer token to each audit record (not
implemented on FreeBSD or Darwin; trailers are always
included in records on these systems).
path Include secondary file paths in audit records (not
implemented on FreeBSD or Darwin; secondary paths are
never included in records on these systems).
zonename Include a zone ID token with each audit record (not
implemented on FreeBSD or Darwin; FreeBSD audit
records do not currently include the jail ID or
name).
perzone Enable auditing for each local zone (not implemented
on FreeBSD or Darwin; on FreeBSD, audit records are
collected from all jails and placed in a single
global trail, and only limited audit controls are
permitted within a jail).
It is recommended that installations set the cnt flag but not ahlt flag
unless it is intended that audit logs exceeding available disk space halt
the system.
AUDIT LOG EXPIRATION SPECIFICATION
The expiration specification can be one value or two values with the
logical conjunction of AND/OR between them. Values for the audit log
file age are numbers with the following suffixes:
s Log file age in seconds.
h Log file age in hours.
d Log file age in days.
y Log file age in years.
Values for the disk space used are numbers with the following suffixes:
(space) or
B Disk space used in Bytes.
K Disk space used in Kilobytes.
M Disk space used in Megabytes.
G Disk space used in Gigabytes.
The suffixes on the values are case sensitive. If both an age and disk
space value are used they are separated by AND or OR and both values are
used to determine when audit log files expire. In the case of AND, both
the age and disk space conditions must be met before the log file is
removed. In the case of OR, either condition may expire the log file.
For example:
expire-after: 60d AND 1G
will expire files that are older than 60 days but only if 1 gigabyte of
disk space total is being used by the audit logs.
DEFAULT
The following settings appear in the default audit_control file:
dir:/var/audit
flags:lo,aa
minfree:5
naflags:lo,aa
policy:cnt,argv
filesz:2M
expire-after:10M
The flags parameter above specifies the system-wide mask corresponding to
login/logout as well as authentication and authorization events. The
policy parameter specifies that the system should neither fail stop nor
suspend processes when the audit store fills and that command line
arguments should be audited for AUE_EXECVE events. The trail file will
be automatically rotated by the audit daemon when the file size reaches
approximately 2MB. Trail files will expire when their aggregate size
exceeds 10MB.
FILES
/etc/security/audit_control
SEE ALSO
auditon(2), audit(4), audit_class(5), audit_event(5), audit_user(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.
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.
The Basic Security Module (BSM) interface to audit records and audit
event stream format were defined by Sun Microsystems.
FreeBSD 13.1-RELEASE-p6 August 19, 2016 FreeBSD 13.1-RELEASE-p6
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