Provided by: auditd_2.3.2-2ubuntu1_amd64 
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_format , 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
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.
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.
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 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 daemon 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 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 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 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 computer system in single user mode. The 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
computer system in single user mode. The halt option will cause the audit daemon to shutdown the
computer system.
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 not take any action. Syslog means that
it will issue no more than 5 consecutive warnings 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 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 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/hostname@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
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 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