auditctl - a utility to assist controlling the kernel's audit system at Linux.org

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AUDITCTL:(8) System Administration Utilities AUDITCTL:(8)

NAME
auditctl - a utility to assist controlling the kernel's audit system

SYNOPSIS
auditctl [options]

DESCRIPTION
The auditctl program is used to configure kernel options related to auditing, to see status of the configura‐
tion, and to load discretionary audit rules.

CONFIGURATION OPTIONS
-b backlog
Set max number of outstanding audit buffers allowed (Kernel Default=64) If all buffers are full, the
failure flag is consulted by the kernel for action.

--backlog_wait_time wait_time
Set the time for the kernel to wait (Kernel Default 60*HZ) when the backlog_limit is reached before
queuing more audit events to be transferred to auditd. The number must be greater than or equal to zero
and less that 10 times the default value.

-c Continue loading rules in spite of an error. This summarizes the results of loading the rules. The exit
code will not be success if any rule fails to load.

-D Delete all rules and watches. This can take a key option (-k), too.

-e [0..2]
Set enabled flag. When 0 is passed, this can be used to temporarily disable auditing. When 1 is passed
as an argument, it will enable auditing. To lock the audit configuration so that it can't be changed,
pass a 2 as the argument. Locking the configuration is intended to be the last command in audit.rules
for anyone wishing this feature to be active. Any attempt to change the configuration in this mode will
be audited and denied. The configuration can only be changed by rebooting the machine.

-f [0..2]
Set failure mode 0=silent 1=printk 2=panic. This option lets you determine how you want the kernel to
handle critical errors. Example conditions where this mode may have an effect includes: transmission
errors to userspace audit daemon, backlog limit exceeded, out of kernel memory, and rate limit
exceeded. The default value is 1. Secure environments will probably want to set this to 2.

-h Help

-i Ignore errors when reading rules from a file. This causes auditctl to always return a success exit
code.

--loginuid-immutable
This option tells the kernel to make loginuids unchangeable once they are set. Changing loginuids
requires CAP_AUDIT_CONTROL. So, its not something that can be done by unprivileged users. Setting this
makes loginuid tamper-proof, but can cause some problems in certain kinds of containers.

-q mount-point,subtree
If you have an existing directory watch and bind or move mount another subtree in the watched subtree,
you need to tell the kernel to make the subtree being mounted equivalent to the directory being
watched. If the subtree is already mounted at the time the directory watch is issued, the subtree is
automatically tagged for watching. Please note the comma separating the two values. Omitting it will
cause errors.

-r rate

STATUS OPTIONS
-l List all rules 1 per line. Two more options may be given to this command. You can give either a key
option (-k) to list rules that match a key or a (-i) to have a0 through a3 interpretted to help deter‐
mine the syscall argument values are correct .

-m text
Send a user space message into the audit system. This can only be done if you have CAP_AUDIT_WRITE
capability (normally the root user has this). The resulting event will be the USER type.

-s Report the kernel's audit subsystem status. It will tell you the in-kernel values that can be set by
-e, -f, -r, and -b options. The pid value is the process number of the audit daemon. Note that a pid of
0 indicates that the audit daemon is not running. The lost entry will tell you how many event records
that have been discarded due to the kernel audit queue overflowing. The backlog field tells how many
event records are currently queued waiting for auditd to read them. This option can be followed by the
-i to get a couple fields interpreted.

-v Print the version of auditctl.

RULE OPTIONS
-a [list,action|action,list]
Append rule to the end of list with action. Please note the comma separating the two values. Omitting
it will cause errors. The fields may be in either order. It could be list,action or action,list. The
following describes the valid list names:

task Add a rule to the per task list. This rule list is used only at the time a task is created
-- when fork() or clone() are called by the parent task. When using this list, you should
only use fields that are known at task creation time, such as the uid, gid, etc.

exit Add a rule to the syscall exit list. This list is used upon exit from a system call to
determine if an audit event should be created.

user Add a rule to the user message filter list. This list is used by the kernel to filter
events originating in user space before relaying them to the audit daemon. It should be
noted that the only fields that are valid are: uid, auid, gid, pid, subj_user, subj_role,
subj_type, subj_sen, subj_clr, and msgtype. All other fields will be treated as non-match‐
ing. It should be understood that any event originating from user space from a process that
has CAP_AUDIT_WRITE will be recorded into the audit trail. This means that the most likely
use for this filter is with rules that have an action of never since nothing has to be done
to allow events to be recorded.

exclude Add a rule to the event type exclusion filter list. This list is used to filter events that
you do not want to see. For example, if you do not want to see any avc messages, you would
using this list to record that. The message type that you do not wish to see is given with
the msgtype field.

The following describes the valid actions for the rule:

never No audit records will be generated. This can be used to suppress event generation. In gen‐
eral, you want suppressions at the top of the list instead of the bottom. This is because
the event triggers on the first matching rule.

always Allocate an audit context, always fill it in at syscall entry time, and always write out a

The two groups of uid and gid cannot be mixed. But any comparison within the group can be made. The
obj_uid/gid fields are collected from the object of the event such as a file or directory.

-d list,action
Delete rule from list with action. The rule is deleted only if it exactly matches syscall name(s) and
every field name and value.

-F [n=v | n!=v | n<v | n>v | n<=v | n>=v | n&v | n&=v]
Build a rule field: name, operation, value. You may have up to 64 fields passed on a single command
line. Each one must start with -F. Each field equation is anded with each other (as well as equations
starting with -C) to trigger an audit record. There are 8 operators supported - equal, not equal, less
than, greater than, less than or equal, and greater than or equal, bit mask, and bit test respectively.
Bit test will "and" the values and check that they are equal, bit mask just "ands" the values. Fields
that take a user ID may instead have the user's name; the program will convert the name to user ID. The
same is true of group names. Valid fields are:

a0, a1, a2, a3
Respectively, the first 4 arguments to a syscall. Note that string arguments are not sup‐
ported. This is because the kernel is passed a pointer to the string. Triggering on a
pointer address value is not likely to work. So, when using this, you should only use on
numeric values. This is most likely to be used on platforms that multiplex socket or IPC
operations.

arch The CPU architecture of the syscall. The arch can be found doing 'uname -m'. If you do not
know the arch of your machine but you want to use the 32 bit syscall table and your machine
supports 32 bit, you can also use b32 for the arch. The same applies to the 64 bit syscall
table, you can use b64. In this way, you can write rules that are somewhat arch indepen‐
dent because the family type will be auto detected. However, syscalls can be arch specific
and what is available on x86_64, may not be available on ppc. The arch directive should
precede the -S option so that auditctl knows which internal table to use to look up the
syscall numbers.

auid The original ID the user logged in with. Its an abbreviation of audit uid. Sometimes its
referred to as loginuid. Either the user account text or number may be used.

devmajor Device Major Number

devminor Device Minor Number

dir Full Path of Directory to watch. This will place a recursive watch on the directory and its
whole subtree. It can only be used on exit list. See "-w".

egid Effective Group ID. May be numeric or the groups name.

euid Effective User ID. May be numeric or the user account name.

exit Exit value from a syscall. If the exit code is an errno, you may use the text representa‐
tion, too.

fsgid Filesystem Group ID. May be numeric or the groups name.

fsuid Filesystem User ID. May be numeric or the user account name.
obj_uid Object's UID

obj_gid Object's GID

obj_user Resource's SE Linux User

obj_role Resource's SE Linux Role

obj_type Resource's SE Linux Type

obj_lev_low Resource's SE Linux Low Level

obj_lev_high
Resource's SE Linux High Level

path Full Path of File to watch. It can only be used on exit list.

perm Permission filter for file operations. See "-p". It can only be used on exit list. You can
use this without specifying a syscall and the kernel will select the syscalls that satisfy
the permissions being requested.

pers OS Personality Number

pid Process ID

ppid Parent's Process ID

subj_user Program's SE Linux User

subj_role Program's SE Linux Role

subj_type Program's SE Linux Type

subj_sen Program's SE Linux Sensitivity

subj_clr Program's SE Linux Clearance

sgid Saved Group ID. See getresgid(2) man page.

success If the exit value is >= 0 this is true/yes otherwise its false/no. When writing a rule, use
a 1 for true/yes and a 0 for false/no

suid Saved User ID. See getresuid(2) man page.

uid User ID. May be numeric or the user account name.

-k key Set a filter key on an audit rule. The filter key is an arbitrary string of text that can be up to 31
bytes long. It can uniquely identify the audit records produced by a rule. Typical use is for when you
have several rules that together satisfy a security requirement. The key value can be searched on with
ausearch so that no matter which rule triggered the event, you can find its results. The key can also
be used on delete all (-D) and list rules (-l) to select rules with a specific key. You may have more
than one key on a rule if you want to be able to search logged events in multiple ways or if you have
an audispd plugin that uses a key to aid its analysis.

natively, you may pass a comma separated list of syscall names. If you are on a bi-arch system, like
x86_64, you should be aware that auditctl simply takes the text, looks it up for the native arch (in
this case b64) and sends that rule to the kernel. If there are no additional arch directives, IT WILL
APPLY TO BOTH 32 & 64 BIT SYSCALLS. This can have undesirable effects since there is no guarantee that
any syscall has the same number on both 32 and 64 bit interfaces. You will likely want to control this
and write 2 rules, one with arch equal to b32 and one with b64 to make sure the kernel finds the events
that you intend. See the arch field discussion for more info.

-w path
Insert a watch for the file system object at path. You cannot insert a watch to the top level direc‐
tory. This is prohibited by the kernel. Wildcards are not supported either and will generate a warning.
The way that watches work is by tracking the inode internally. If you place a watch on a file, its the
same as using the -F path option on a syscall rule. If you place a watch on a directory, its the same
as using the -F dir option on a syscall rule. The -w form of writing watches is for backwards compati‐
bility and the syscall based form is more expressive. Unlike most syscall auditing rules, watches do
not impact performance based on the number of rules sent to the kernel. The only valid options when
using a watch are the -p and -k. If you need to anything fancy like audit a specific user accessing a
file, then use the syscall auditing form with the path or dir fields. See the EXAMPLES section for an
example of converting one form to another.

-W path
Remove a watch for the file system object at path. The rule must match exactly. See -d discussion for
more info.

PERFORMANCE TIPS
Syscall rules get evaluated for each syscall for every program. If you have 10 syscall rules, every program on
your system will delay during a syscall while the audit system evaluates each rule. Too many syscall rules
will hurt performance. Try to combine as many as you can whenever the filter, action, key, and fields are
identical. For example:

auditctl -a always,exit -S openat -F success=0
auditctl -a always,exit -S truncate -F success=0

could be re-written as one rule:

auditctl -a always,exit -S openat -S truncate -F success=0

Also, try to use file system auditing wherever practical. This improves performance. For example, if you were
wanting to capture all failed opens & truncates like above, but were only concerned about files in /etc and
didn't care about /usr or /sbin, its possible to use this rule:

auditctl -a always,exit -S openat -S truncate -F dir=/etc -F success=0

This will be higher performance since the kernel will not evaluate it each and every syscall. It will be han‐
dled by the filesystem auditing code and only checked on filesystem related syscalls.

EXAMPLES
To see all syscalls made by a specific program:

auditctl -a always,exit -S all -F pid=1005

To see files opened by a specific user:

auditctl -a always,exit -S openat -F auid=510
auditctl -w /etc/ -p wa
auditctl -a always,exit -F dir=/etc/ -F perm=wa

To see if an admin is accessing other user's files:

auditctl -a always,exit -F dir=/home/ -F uid=0 -C auid!=obj_uid

FILES
/etc/audit/audit.rules