AUDITCTL:

Section: System Administration Utilities (8)
Updated: Jan 2008
Index Return to Main Contents
 

NAME

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

SYNOPSIS

auditctl [options]  

DESCRIPTION

The auditctl program is used to control the behavior, get status, and add or delete rules into the 2.6 kernel's audit system.  

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.
-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 flag 0=silent 1=printk 2=panic. This option lets you determine how you want the kernel to handle critical errors. Example conditions where this flag is consulted 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
-l
List all rules 1 per line.
-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 the watch.
-m text
Send a user space message into the audit system. This can only be done by the root user.
-p [r|w|x|a]
Set permissions filter for a file system watch. r=read, w=write, x=execute, a=attribute change. These permissions are not the standard file permissions, but rather the kind of syscall that would do this kind of thing. The read & write syscalls are omitted from this set since they would overwhelm the logs. But rather for reads or writes, the open flags are looked at to see what permission was requested.
-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
Set limit in messages/sec (0=none). If this rate is non-zero and is exceeded, the failure flag is consulted by the kernel for action. The default value is 0.
-R file
Read rules from a file. The rules must be 1 per line and in the order that they are to be executed in. The rule file must be owned by root and not readable by other users or it will be rejected. The rule file may have comments embedded by starting the line with a '#' character. Rules that are read from a file are identical to what you would type on a command line except they are not preceeded by auditctl (since auditctl is the one executing the file).
-s
Report status
-t
Trim the subtrees after a mount command.
-a list,action
Append rule to the end of list with action. Please note the comma separating the two values. Omitting it will cause errors. 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.
entry
Add a rule to the syscall entry list. This list is used upon entry to a system call to determine if an audit event should be created.
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, and pid. All other fields will be treated as non-matching.
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 general, 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 record at syscall exit time.
-A list,action
Add rule to the beginning list with action.
-d list,action
Delete rule from list with action. The rule is deleted only if it exactly matches syscall name and field names.
-D
Delete all rules and watches.
-S [Syscall name or number|all]
Any syscall name or number may be used. The word 'all' may also be used. If this syscall is made by a program, then start an audit record. If a field rule is given and no syscall is specified, it will default to all syscalls. You may also specify multiple syscalls in the same rule as a comma separated list with no spaces in between. Doing so improves performance since fewer rules need to be evaluated. 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, for example, the open syscall has the same number on both 32 and 64 bit interfaces. You may 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.
-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 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 supported. 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 independent 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 preceed 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 text or number may be used.
devmajor
Device Major Number
devminor
Device Minor Number
dir
Full Path of Directory to watch. See "-w". Should only be used on exit list.
egid
Effective Group ID
euid
Effective User ID
exit
Exit value from a syscall. If the exit code is an errno, you may use the text representation, too.
fsgid
Filesystem Group ID
fsuid
Filesystem User ID
gid
Group ID
inode
Inode Number
key
This is another way of setting a filter key. See discussion above for -k option.
msgtype
This is used to match the message type number. It should only be used on the exclude filter list.
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. See "-w". Should only be used on exit list.
perm
Permission filter for file operations. See "-p". Should only be used on exit list.
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
Set Group ID
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
Set User ID
uid
User ID
-w path
Insert a watch for the file system object at path. You cannot insert a watch to the top level directory. 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. This means that if you put a watch on a directory, you will see what appears to be file events, but it is really just the updating of meta data. You might miss a few events by doing this. If you need to watch all files in a directory, its recommended to place an individual watch on each file. Unlike syscall auditing rules, watches do not impact performance based on the number of rules sent to the kernel.
-W path
Remove a watch for the file system object at path.
 

PERFORMANCE TIPS

Syscall rules get evaluated for each syscall for each program. If you have 10 syscall rules, every program on your system will delay during a syscall while the audit system evaulates each one. 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 exit,always -S open -F success=no
auditctl -a exit,always -S truncate -F success=no

could be re-written as one rule:

auditctl -a exit,always -S open -S truncate -F success=no

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 exit,always -S open -S truncate -F dir=/etc -F success=no

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

EXAMPLES

To see all syscalls made by a specific program:

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

To see files opened by a specific user:

auditctl -a exit,always -S open -F auid=510

To see unsuccessful open call's:

auditctl -a exit,always -S open -F success!=0

 

FILES

/etc/audit/audit.rules

 

SEE ALSO

auditd(8).

 

AUTHOR

Steve Grubb


 

Index

NAME
SYNOPSIS
DESCRIPTION
OPTIONS
PERFORMANCE TIPS
EXAMPLES
FILES
SEE ALSO
AUTHOR

linux.jgfs.net manual pages