System Administration Guide: Security Services

Files Used in the Audit Service

The audit service uses the following files:

system File

The /etc/system file contains commands that the kernel reads during initialization to customize the system operations. The bsmconv and bsmunconv shell scripts, which are used to activate and deactivate auditing, modify the /etc/system file. The bsmconv shell script adds the following line to the /etc/system file:

set c2audit:audit_load=1

The set c2audit:audit_load=1 entry causes the kernel module for auditing to be loaded when the system is booted. The bsmunconv shell script disables auditing when the system is rebooted. The command removes the c2audit line from the /etc/system file.

syslog.conf File

The /etc/syslog.conf file works with the audit_control file to store audit records in text format. The syslog.conf file can be configured to enable the syslog utility to store audit records. For an example, see How to Configure syslog Audit Logs.

audit_class File

The /etc/security/audit_class file defines the audit classes. Audit classes are groups of audit events. You use the class name in the audit_control file to preselect the classes whose events you want to audit. The classes accept prefixes to select only failed events or only successful events. For more information, see Audit Class Syntax.

The superuser, or an administrator in an equivalent role, can modify the definitions of audit classes. This administrator can define new audit classes, rename existing classes, or otherwise change existing classes by editing the audit_class file in a text editor. For more information, see the audit_class(4) man page.

audit_control File

The /etc/security/audit_control file on each system contains configuration information for the auditd daemon. The file enables every system to mount a remote audit file system to store their audit records.

You can specify five kinds of information in the audit_control file. Each line of information begins with a keyword.

For more information about the audit_control file, see the audit_control(4) man page. For information about the plugins, see Audit Plugins and the audit_binfile(5) and audit_syslog(5) man pages.

Example 31–2 Sample audit_control File

The following is a sample audit_control file for the system noddy. noddy uses two audit file systems on the audit server blinken, and a third audit file system that is mounted from the second audit server winken. The third file system is used only when the audit file systems on blinken become full or unavailable. The p_minfree value of 20 percent specifies that the warning script is run when the file systems are 80 percent full. The settings specify that logins and administrative operations are to be audited. The operations are audited for success and for failure. Failures of all types, except failures to create a file system object, are to be audited. Nonattributable events are also audited. The syslog audit log records fewer audit events. This log contains text summaries of failed logins and failed administrative operations.

In the following example, the plugin lines do not contain a line break.

naflags:lo,nt; p_minfree=20; p_dir=/var/audit/blinken/files,
/var/audit/blinken.1/files,/var/audit/winken; p_flags=-lo,-am

audit_event File

The /etc/security/audit_event file contains the default audit event-class mappings. You can edit this file to change the class mappings. When you change class mappings, you must reboot the system or run the auditconfig -conf command to read the changed mappings into the kernel. For more information, see the audit_event(4) man page.

audit_user Database

The /etc/security/audit_user database modifies the system-wide preselected classes for an individual user. The classes that you add to a user's entry in the audit_user database modify the settings in the audit_control file in two ways:

Each user entry in the audit_user database contains three fields:


The audit fields are processed in sequence.

Suppose that you want to apply the system-wide audit settings to the user tamiko, except for successful reads of file system objects. Note the placement of the second colon (:) in the following audit_user entry:

tamiko:^+fr:no  modify system defaults for fr

The preceding entry means, “always audit everything, except for successful file reads.”

If you want to audit everything for user tamiko with the exception of successful file reads, you use the following entry:

tamiko:all,^+fr:no  audit everything except fr

Suppose that you want to override system defaults for successful file-reads for user tamiko. The following entry means “always audit everything, but never audit successful file reads.”

tamiko:all:+fr    override system defaults for fr

Note –

Successful events and failed events are treated separately. A process could generate more audit records for failed events than for successful events.

audit_warn Script

The /etc/security/audit_warn script notifies an email alias when the auditd daemon encounters an unusual condition while writing audit records. You can customize this script for your site to warn of conditions that might require manual intervention. Or, you could specify how to handle those conditions automatically. For all error conditions, the audit_warn script writes a message to syslog with the severity of daemon.alert. You can use syslog.conf to configure console display of syslog messages. The audit_warn script also sends a message to the audit_warn email alias. You set up this alias as part of audit configuration.

When the auditd daemon detects the following conditions, the daemon invokes the audit_warn script. The script sends email to the audit_warn alias.

If the perzone audit policy is set, the non-global zone's instance of auditd calls the zone's audit_warn script. For further information, see the audit_warn(1M) man page.

bsmconv Script

The /etc/security/bsmconv script enables the audit service. The bsmunconv command disables the audit service. After the bsmconv script is run, you configure the audit directories and audit configuration files. Upon reboot, auditing is enabled.

For further information, see the bsmconv(1M) man page.