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