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. This can take a key option (-k),
too.
- -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.
- -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 preceded by auditctl (since
auditctl is the one executing the file).
- -s
- Report status. Note that a pid of 0 indicates that the
audit daemon is not running.
- -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. This can take a key option
(-k), too.
- -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 by using multiple -S options in the same rule.
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. This will place a
recursive watch on the directory and its whole subtree. Should only be
used on exit list. See " -w".
- 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
- filetype
- The target file's type. Can be either file, dir, socket,
symlink, char, block, or fifo.
- 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. Should only be used on exit
list.
- perm
- Permission filter for file operations. See
"-p". Should 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
- -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. 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 compatibility 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.
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=0
auditctl -a exit,always -S truncate -F success=0
could be re-written as one rule:
auditctl -a exit,always -S open -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 exit,always -S open -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 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
To watch a file for changes (2 ways to express):
auditctl -w /etc/shadow -p wa
auditctl -a exit,always -F path=/etc/shadow -F perm=wa
To recursively watch a directory for changes (2 ways to express):
auditctl -w /etc/ -p wa
auditctl -a exit,always -F dir=/etc/ -F perm=wa
FILES¶
- /etc/audit/audit.rules
-
SEE ALSO¶
audit.rules(7),
auditd(8).
AUTHOR¶
Steve Grubb
