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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 specific to the audit daemon. It should contain one
configuration keyword per line, an equal sign, and then followed by appropriate configuration information. The keywords
recognized are: log_file, log_format, log_group, priority_boost, flush, freq, num_logs , disp_qos , dispatcher, name_for-
mat , name, max_log_file, max_log_file_action, space_left, action_mail_acct, space_left_action, admin_space_left,
admin_space_left_action, disk_full_action, disk_error_action, tcp_listen_port, tcp_listen_queue, tcp_max_per_addr,
use_libwrap, tcp_client_ports, tcp_client_max_idle, enable_krb5, krb5_principal, and krb5_key_file. These keywords are
described below.
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.
log_format
The log format describes how the information should be stored on disk. There are 2 options: raw and nolog. If set
to RAW, the audit records will be stored in a format exactly as the kernel sends it. If this option is set to
NOLOG then all audit information is discarded instead of writing to disk. This mode does not affect data sent to
the audit event dispatcher.
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, 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 data parameter tells the audit damon 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.
freq This is a non-negative number that tells the audit damon 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.
num_logs
This keyword specifies the number of log files to keep if rotate is given as the max_log_file_action. If the num-
ber is < 2, logs are not rotated. This number must be 99 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 backlog 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 available.
The excess log check is only done on startup and when a reconfigure results in a space check.
disp_qos
This option controls whether you want blocking/lossless or non-blocking/lossy communication between the audit dae-
mon and the dispatcher. There is a 128k buffer between the audit daemon and dispatcher. This is good enogh for
most uses. If lossy is chosen, incoming events going to the dispatcher are discarded when this queue is full.
(Events are still written to disk if log_format is not nolog.) Otherwise the auditd daemon will wait for the queue
to have an empty spot before logging to disk. The risk is that while the daemon is waiting for network IO, an
event is not being recorded to disk. Valid values are: lossy and lossless. Lossy is the default value.
dispatcher
The dispatcher is a program that is started by the audit daemon when it starts up. It will pass a copy of all
audit events to that application's stdin. Make sure you trust the application that you add to this line since it
runs with root privileges.
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 recommended 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 config-
urable 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 overwritten.
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 configured on your machine and network. Also,
this option requires that /usr/lib/sendmail exists on the machine.
space_left
This is a numeric value in megabytes that tells the audit daemon when to perform a configurable action because the
system is starting to run low on disk space.
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, 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. Email means that it will send a warn-
ing 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. 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.
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 running 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.
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, 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. 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. 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 com-
puter system in single user mode. halt
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, 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. exec /path-to-script will execute the script. You cannot pass parameters 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 issue a syslog message but no other action is taken. Syslog means that it will issue a warning
to syslog. exec /path-to-script will execute the script. You cannot pass parameters 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.
tcp_listen_port
This is a numeric value in the range 1..65535 which, if specified, 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.
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.
tcp_max_per_addr
This is a numeric value which indicates how many concurrent connections from one IP address is allowed. The
default is 1 and the maximum is 16. Setting this too large may allow for a Denial of Service attack on the logging
server. 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 separated 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 priviledged 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.
enable_krb5
If set to "yes", Kerberos 5 will be used for authentication and encryption. The default is "no".
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/hostnameATEXAMPLE.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
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 dependant 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 partition. 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 depending 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 recreate a connection with the same host addresses and ports until the connection closure TIME_WAIT state
times out.
FILES
/etc/audit/auditd.conf
Audit daemon configuration file
SEE ALSO
auditd(8), audisp-remote.conf(5).
AUTHOR
Steve Grubb
Red Hat Dec 2008 AUDITD.CONF:(5)
