NAME¶
auditd.conf - audit daemon configuration file
DESCRIPTION¶
The file
/etc/audit/auditd.conf contains configuration information
specific 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 keywords
recognized are listed and described below. Each line should be limited to 160
characters or the line will be skipped. You may add comments to the file by
starting the line with a '#' character.
- 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. 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.
- 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. 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.
- 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. 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.
- 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. The script is also responsible for telling the auditd daemon to
resume loggin 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
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