AUDITD.CONF(5) System Administration Utilities AUDITD.CONF(5)
NAME
auditd.conf - audit daemon configuration file
DESCRIPTION
The file /etc/audit/auditd.conf contains configuration information spe-
cific to the audit daemon. Each line should contain one configuration
keyword, an equal sign, and then followed by appropriate configuration
information. All option names and values are case insensitive. The key-
words recognized are listed and described below. Each line should be
limited to 160 characters or the line will be skipped. You may add com-
ments to the file by starting the line with a '#' character.
local_events
This yes/no keyword specifies whether or not to include local
events. Normally you want local events so the default value is
yes. Cases where you would set this to no is when you want to
aggregate events only from the network. At the moment, this is
useful if the audit daemon is running in a container. This
option can only be set once at daemon start up. Reloading the
config file has no effect.
log_file
This keyword specifies the full path name to the log file where
audit records will be stored. It must be a regular file.
write_logs
This yes/no keyword determines whether or not to write logs to
the disk. Normally you want this so the default is yes.
log_format
The log format describes how the information should be stored on
disk. There are 2 options: raw and enriched. If set to RAW, the
audit records will be stored in a format exactly as the kernel
sends it. The ENRICHED option will resolve all uid, gid,
syscall, architecture, and socket address information before
writing the event to disk. This aids in making sense of events
created on one system but reported/analyzed on another system.
The NOLOG option is now deprecated. If you were setting this
format, now you should set the write_logs option to no.
log_group
This keyword specifies the group that is applied to the log
file's permissions. The default is root. The group name can be
either numeric or spelled out.
priority_boost
This is a non-negative number that tells the audit daemon how
much of a priority boost it should take. The default is 4. No
change is 0.
flush Valid values are none, incremental, incremental_async, data,
and sync. If set to none, no special effort is made to flush
the audit records to disk. If set to incremental, Then the freq
parameter is used to determine how often an explicit flush to
disk is issued. The incremental_async parameter is very much
like incremental except the flushing is done asynchronously for
higher performance. The data parameter tells the audit daemon to
keep the data portion of the disk file sync'd at all times. The
sync option tells the audit daemon to keep both the data and
meta-data fully sync'd with every write to disk. The default
value is incremental_async.
freq This is a non-negative number that tells the audit daemon how
many records to write before issuing an explicit flush to disk
command. This value is only valid when the flush keyword is set
to incremental or incremental_async.
num_logs
This keyword specifies the number of log files to keep if rotate
is given as the max_log_file_action. If the number is < 2, logs
are not rotated. This number must be 999 or less. The default
is 0 - which means no rotation. As you increase the number of
log files being rotated, you may need to adjust the kernel back-
log setting upwards since it takes more time to rotate the
files. This is typically done in /etc/audit/audit.rules. If log
rotation is configured to occur, the daemon will check for
excess logs and remove them in effort to keep disk space avail-
able. The excess log check is only done on startup and when a
reconfigure results in a space check.
name_format
This option controls how computer node names are inserted into
the audit event stream. It has the following choices: none,
hostname, fqd, numeric, and user. None means that no computer
name is inserted into the audit event. hostname is the name
returned by the gethostname syscall. The fqd means that it takes
the hostname and resolves it with dns for a fully qualified
domain name of that machine. Numeric is similar to fqd except
it resolves the IP address of the machine. In order to use this
option, you might want to test that 'hostname -i' or 'domainname
-i' returns a numeric address. Also, this option is not recom-
mended if dhcp is used because you could have different
addresses over time for the same machine. User is an admin
defined string from the name option. The default value is none.
name This is the admin defined string that identifies the machine if
user is given as the name_format option.
max_log_file
This keyword specifies the maximum file size in megabytes. When
this limit is reached, it will trigger a configurable action.
The value given must be numeric.
max_log_file_action
This parameter tells the system what action to take when the
system has detected that the max file size limit has been
reached. Valid values are ignore, syslog, suspend, rotate and
keep_logs. If set to ignore, the audit daemon does nothing.
syslog means that it will issue a warning to syslog. suspend
will cause the audit daemon to stop writing records to the disk.
The daemon will still be alive. The rotate option will cause the
audit daemon to rotate the logs. It should be noted that logs
with higher numbers are older than logs with lower numbers. This
is the same convention used by the logrotate utility. The
keep_logs option is similar to rotate except it does not use the
num_logs setting. This prevents audit logs from being overwrit-
ten. The effect is that logs accumulate and are not deleted -
which will trigger the space_left_action if the volume fills up.
This is best used in combination with an external script used to
archive logs on a periodic basis.
verify_email
This option determines if the email address given in
action_mail_acct is checked to see if the domain name can be
resolved. This option must be given before action_mail_acct or
the default value of yes will be used.
action_mail_acct
This option should contain a valid email address or alias. The
default address is root. If the email address is not local to
the machine, you must make sure you have email properly config-
ured on your machine and network. Also, this option requires
that /usr/lib/sendmail exists on the machine.
space_left
If the free space in the filesystem containing log_file drops
below this value, the audit daemon takes the action specified by
space_left_action. If the value of space_left is specified as a
whole number, it is interpreted as an absolute size in megabytes
(MiB). If the value is specified as a number between 1 and 99
followed by a percentage sign (e.g., 5%), the audit daemon cal-
culates the absolute size in megabytes based on the size of the
filesystem containing log_file. (E.g., if the filesystem con-
taining log_file is 2 gigabytes in size, and space_left is set
to 25%, then the audit daemon sets space_left to approximately
500 megabytes. Note that this calculation is performed when the
audit daemon starts, so if you resize the filesystem containing
log_file while the audit daemon is running, you should send the
audit daemon SIGHUP to re-read the configuration file and recal-
culate the correct percentage.
space_left_action
This parameter tells the system what action to take when the
system has detected that it is starting to get low on disk
space. Valid values are ignore, syslog, rotate, email, exec,
suspend, single, and halt. If set to ignore, the audit daemon
does nothing. syslog means that it will issue a warning to sys-
log. rotate will rotate logs, losing the oldest to free up
space. Email means that it will send a warning to the email
account specified in action_mail_acct as well as sending the
message to syslog. exec /path-to-script will execute the
script. You cannot pass parameters to the script. The script is
also responsible for telling the auditd daemon to resume logging
once its completed its action. This can be done by adding ser-
vice auditd resume to the script. suspend will cause the audit
daemon to stop writing records to the disk. The daemon will
still be alive. The single option will cause the audit daemon to
put the computer system in single user mode. The halt option
will cause the audit daemon to shutdown the computer system.
Except for rotate, it will perform this action just one time.
admin_space_left
This is a numeric value in megabytes that tells the audit daemon
when to perform a configurable action because the system is run-
ning low on disk space. This should be considered the last
chance to do something before running out of disk space. The
numeric value for this parameter should be lower than the number
for space_left. You may also append a percent sign (e.g. 1%) to
the number to have the audit daemon calculate the number based
on the disk partition size.
admin_space_left_action
This parameter tells the system what action to take when the
system has detected that it is low on disk space. Valid values
are ignore, syslog, rotate, email, exec, suspend, single, and
halt. If set to ignore, the audit daemon does nothing. Syslog
means that it will issue a warning to syslog. rotate will
rotate logs, losing the oldest to free up space. Email means
that it will send a warning to the email account specified in
action_mail_acct as well as sending the message to syslog. exec
/path-to-script will execute the script. You cannot pass parame-
ters to the script. The script is also responsible for telling
the auditd daemon to resume logging once its completed its
action. This can be done by adding service auditd resume to the
script. Suspend will cause the audit daemon to stop writing
records to the disk. The daemon will still be alive. The single
option will cause the audit daemon to put the computer system in
single user mode. The halt option will cause the audit daemon to
shutdown the computer system. Except for rotate, it will perform
this action just one time.
disk_full_action
This parameter tells the system what action to take when the
system has detected that the partition to which log files are
written has become full. Valid values are ignore, syslog,
rotate, exec, suspend, single, and halt. If set to ignore, the
audit daemon will issue a syslog message but no other action is
taken. Syslog means that it will issue a warning to syslog.
rotate will rotate logs, losing the oldest to free up space.
exec /path-to-script will execute the script. You cannot pass
parameters to the script. The script is also responsible for
telling the auditd daemon to resume logging g once its completed
its action. This can be done by adding service auditd resume to
the script. Suspend will cause the audit daemon to stop writing
records to the disk. The daemon will still be alive. The single
option will cause the audit daemon to put the computer system in
single user mode. halt option will cause the audit daemon to
shutdown the computer system.
disk_error_action
This parameter tells the system what action to take whenever
there is an error detected when writing audit events to disk or
rotating logs. Valid values are ignore, syslog, exec, suspend,
single, and halt. If set to ignore, the audit daemon will not
take any action. Syslog means that it will issue no more than 5
consecutive warnings to syslog. exec /path-to-script will exe-
cute the script. You cannot pass parameters to the script. Sus-
pend will cause the audit daemon to stop writing records to the
disk. The daemon will still be alive. The single option will
cause the audit daemon to put the computer system in single user
mode. halt option will cause the audit daemon to shutdown the
computer system.
tcp_listen_port
This is a numeric value in the range 1..65535 which, if speci-
fied, causes auditd to listen on the corresponding TCP port for
audit records from remote systems. The audit daemon may be
linked with tcp_wrappers. You may want to control access with an
entry in the hosts.allow and deny files. If this is deployed on
a systemd based OS, then you may need to adjust the 'After'
directive. See the note in the auditd.service file.
tcp_listen_queue
This is a numeric value which indicates how many pending
(requested but unaccepted) connections are allowed. The default
is 5. Setting this too small may cause connections to be
rejected if too many hosts start up at exactly the same time,
such as after a power failure. This setting is only used for
aggregating servers. Clients logging to a remote server should
keep this commented out.
tcp_max_per_addr
This is a numeric value which indicates how many concurrent con-
nections from one IP address is allowed. The default is 1 and
the maximum is 1024. Setting this too large may allow for a
Denial of Service attack on the logging server. Also note that
the kernel has an internal maximum that will eventually prevent
this even if auditd allows it by config. The default should be
adequate in most cases unless a custom written recovery script
runs to forward unsent events. In this case you would increase
the number only large enough to let it in too.
use_libwrap
This setting determines whether or not to use tcp_wrappers to
discern connection attempts that are from allowed machines.
Legal values are either yes, or no The default value is yes.
tcp_client_ports
This parameter may be a single numeric value or two values sepa-
rated by a dash (no spaces allowed). It indicates which client
ports are allowed for incoming connections. If not specified,
any port is allowed. Allowed values are 1..65535. For example,
to require the client use a privileged port, specify 1-1023 for
this parameter. You will also need to set the local_port option
in the audisp-remote.conf file. Making sure that clients send
from a privileged port is a security feature to prevent log
injection attacks by untrusted users.
tcp_client_max_idle
This parameter indicates the number of seconds that a client may
be idle (i.e. no data from them at all) before auditd complains.
This is used to close inactive connections if the client machine
has a problem where it cannot shutdown the connection cleanly.
Note that this is a global setting, and must be higher than any
individual client heartbeat_timeout setting, preferably by a
factor of two. The default is zero, which disables this check.
transport
If set to TCP, only clear text tcp connections will be used. If
set to KRB5, then Kerberos 5 will be used for authentication and
encryption. The default value is TCP.
enable_krb5
This option is deprecated. Use the transport option above
instead. If set to "yes", Kerberos 5 will be used for authenti-
cation and encryption. The default is "no". If this option is
set to "yes" and it follows the transport option, it will over-
ride the transport setting. This would be the normal expected
behavior for backwards compatibility.
krb5_principal
This is the principal for this server. The default is "auditd".
Given this default, the server will look for a key named like
auditd/hostname AT EXAMPLE.COM stored in /etc/audit/audit.key to
authenticate itself, where hostname is the canonical name for
the server's host, as returned by a DNS lookup of its IP
address.
krb5_key_file
Location of the key for this client's principal. Note that the
key file must be owned by root and mode 0400. The default is
/etc/audit/audit.key
distribute_network
If set to "yes", network originating events will be distributed
to the audit dispatcher for processing. The default is "no".
q_depth
This is a numeric value that tells how big to make the internal
queue of the audit event dispatcher. A bigger queue lets it han-
dle a flood of events better, but could hold events that are not
processed when the daemon is terminated. If you get messages in
syslog about events getting dropped, increase this value. The
default value is 2000.
overflow_action
This option determines how the daemon should react to overflow-
ing its internal queue. When this happens, it means that more
events are being received than it can pass along to child pro-
cesses. This error means that it is going to lose the current
event that it's trying to dispatch. This option has the follow-
ing choices: ignore, syslog, suspend, single, and halt. If set
to ignore, the audit daemon does nothing. syslog means that it
will issue a warning to syslog. suspend will cause the audit
daemon to stop sending events to child processes. The daemon
will still be alive. The single option will cause the audit dae-
mon to put the computer system in single user mode. halt option
will cause the audit daemon to shutdown the computer system.
max_restarts
This is a non-negative number that tells the audit event dis-
patcher how many times it can try to restart a crashed plugin.
The default is 10.
plugin_dir
This is the location that auditd will use to search for its
plugin configuration files.
end_of_event_timeout
This is a non-negative number of seconds used by the userspace
auparse() library routines and the aureport(8) , ausearch(8)
utilities to consider an event is complete when parsing an event
log stream. For an event stream being processed, if the time of
the current event is over end_of_event_timeout seconds old, com-
pared to co-located events, then the event is considered com-
plete. See the NOTES section for more detail.
NOTES
In a CAPP environment, the audit trail is considered so important that
access to system resources must be denied if an audit trail cannot be
created. In this environment, it would be suggested that /var/log/audit
be on its own partition. This is to ensure that space detection is
accurate and that no other process comes along and consumes part of it.
The flush parameter should be set to sync or data.
Max_log_file and num_logs need to be adjusted so that you get complete
use of your partition. It should be noted that the more files that have
to be rotated, the longer it takes to get back to receiving audit
events. Max_log_file_action should be set to keep_logs.
Space_left should be set to a number that gives the admin enough time
to react to any alert message and perform some maintenance to free up
disk space. This would typically involve running the aureport -t report
and moving the oldest logs to an archive area. The value of space_left
is site dependent since the rate at which events are generated varies
with each deployment. The space_left_action is recommended to be set to
email. If you need something like an snmp trap, you can use the exec
option to send one.
Admin_space_left should be set to the amount of disk space on the audit
partition needed for admin actions to be recorded.
Admin_space_left_action would be set to single so that use of the
machine is restricted to just the console.
The disk_full_action is triggered when no more room exists on the par-
tition. All access should be terminated since no more audit capability
exists. This can be set to either single or halt.
The disk_error_action should be set to syslog, single, or halt depend-
ing on your local policies regarding handling of hardware malfunctions.
Specifying a single allowed client port may make it difficult for the
client to restart their audit subsystem, as it will be unable to recre-
ate a connection with the same host addresses and ports until the con-
nection closure TIME_WAIT state times out.
Auditd events are made up of one or more records. The auditd system
cannot guarantee that the set of records that make up an event will
occur atomically, that is the stream will have interleaved records of
different events, IE
event0_record0
event1_record0
event2_record0
event1_record3
event2_record1
event1_record4
event3_record0
The auditd system does not guarantee that the records that make up an
event will appear in order. Thus, when processing event streams, we
need to maintain a list of events with their own list of records hence
List of List (LOL) event processing.
When processing an event stream we define the end of an event via
record type = AUDIT_EOE (audit end of event type record), or
record type = AUDIT_PROCTITLE (we note the AUDIT_PROCTITLE is
always the last record), or
record type = AUDIT_KERNEL (kernel events are one record
events), or
record type < AUDIT_FIRST_EVENT (only single record events
appear before this type), or
record type >= AUDIT_FIRST_ANOM_MSG (only single record events
appear after this type), or
record type >= AUDIT_MAC_UNLBL_ALLOW && record type <=
AUDIT_MAC_CALIPSO_DEL (these are also one record events), or
for the stream being processed, the time of the event is over
end_of_event_timeout seconds old.
FILES
/etc/audit/auditd.conf
Audit daemon configuration file
SEE ALSO
auditd(8), audisp-remote.conf(5), auditd-plugins(5).
AUTHOR
Steve Grubb
Red Hat August 2018 AUDITD.CONF(5)
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Huschi als Linux-Admin