AUDITD.CONF:(5) System Administration Utilities AUDITD.CONF:(5)NAMEauditd.conf - audit daemon configuration file
DESCRIPTION
The file /etc/audit/auditd.conf contains configuration information spe‐
cific 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 , dis‐
patcher, 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_lis‐
ten_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 informa‐
tion 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 rota‐
tion 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 cho‐
sen, 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 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.
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
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 noth‐
ing. 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 can‐
not 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 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.
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 parame‐
ters 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. Sys‐
log 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 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.
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 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 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 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.
FILES
/etc/audit/auditd.conf
Audit daemon configuration file
SEE ALSOauditd(8), audisp-remote.conf(5).
AUTHOR
Steve Grubb
Red Hat Dec 2008 AUDITD.CONF:(5)
