auditctl(8) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | CONFIGURATION OPTIONS | STATUS OPTIONS | RULE OPTIONS | PERFORMANCE TIPS | EXAMPLES | DISABLED BY DEFAULT | FILES | SEE ALSO | AUTHOR | COLOPHON

AUDITCTL(8)          System Administration Utilities         AUDITCTL(8)

NAME         top

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

SYNOPSIS         top

       auditctl [options]

DESCRIPTION         top

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

CONFIGURATION OPTIONS         top

       -b backlog
              Set max number (limit) 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.

       --reset_backlog_wait_time_actual
              Reset the actual backlog wait time counter shown by the
              status command.

       -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     When given by itself, ignore errors when reading rules
              from a file. This causes auditctl to always return a
              success exit code. If passed as an argument to -s then it
              gives an interpretation of the numbers to human readable
              words if possible.

       --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
              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.

       --reset-lost
              Reset the lost record counter shown by the status command.

       -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)
              and you would not use shell escaping since auditctl is
              reading the file instead of bash.

       --signal signal
              Send a signal to the audit daemon. You must have
              privileges to do this. Supported signals are TERM, HUP,
              USR1, USR2, CONT.

       -t     Trim the subtrees after a mount command.

STATUS OPTIONS         top

       -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 interpreted to help determine 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         top

       -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, msgtype, and executable name. All other
                     fields will be treated as non-matching. 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. Events can be excluded by process ID,
                     user ID, group ID, login user ID, message type,
                     subject context, or executable name. The action is
                     ignored and uses its default of "never".

              filesystem
                     Add a rule that will be applied to a whole
                     filesystem. The filesystem must be identified with
                     a fstype field. Normally this filter is used to
                     exclude any events for a whole filesystem such as
                     tracefs or debugfs.

       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.

       -C [f=f | f!=f]
              Build an inter-field comparison rule: field, operation,
              field. You may pass multiple comparisons on a single
              command line. Each one must start with -C. Each inter-
              field equation is anded with each other as well as
              equations starting with -F to trigger an audit record.
              There are 2 operators supported - equal, and not equal.
              Valid fields are:

              auid, uid, euid, suid, fsuid, obj_uid; and gid, egid,
              sgid, fsgid, obj_gid

              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 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 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.

              exe    Absolute path to application that while executing
                     this rule will apply to. It supports = and !=
                     operators. Note that you can only use this once for
                     each rule.

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

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

              fsuid  Filesystem User ID. May be numeric or the user
                     account name.

              filetype
                     The target file's type. Can be either file, dir,
                     socket, link, character, block, or fifo.

              gid    Group ID. May be numeric or the groups name.

              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 event's record type. It
                     should only be used on the exclude or user filter
                     lists.

              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

              saddr_fam
                     Address family number as found in
                     /usr/include/bits/socket.h. For example, IPv4 would
                     be 2 and IPv6 would be 10.

              sessionid
                     User's login session 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 auditd plugin
              that uses a key to aid its analysis.

       -p [r|w|x|a]
              Describe the permission access type that a file system
              watch will trigger on. 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.

       -S [Syscall name or number|all]
              Any syscall name or number may be used. The word 'all' may
              also be used.  If the given 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. Alternatively, 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 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 do 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         top

       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 -F arch=b64 -S openat -F success=0
       auditctl -a always,exit -F arch=b64 -S truncate -F success=0

       could be re-written as one rule:

       auditctl -a always,exit -F arch=b64 -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 handled by the
       filesystem auditing code and only checked on filesystem related
       syscalls.

EXAMPLES         top

       To see all syscalls made by a specific program:

       # By pid:
       auditctl -a always,exit -S all -F pid=1005
       # By executable path
       auditctl -a always,exit -S all -F exe=/usr/bin/ls

       To see files opened by a specific user:

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

       To see unsuccessful openat calls:

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

       To watch a file for changes (2 ways to express):

       auditctl -w /etc/shadow -p wa
       auditctl -a always,exit -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 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

DISABLED BY DEFAULT         top

       On many systems auditd is configured to install an -a never,task
       rule by default. This rule causes every new process to skip all
       audit rule processing. This is usually done to avoid a small
       performance overhead imposed by syscall auditing. If you want to
       use auditd, you need to remove that rule by deleting 10-no-
       audit.rules and adding 10-base-config.rules to the audit rules
       directory.

       If you have defined audit rules that are not matching when they
       should, check auditctl -l to make sure there is no never,task
       rule there.

FILES         top

       /etc/audit/audit.rules /etc/audit/audit-stop.rules

SEE ALSO         top

       audit.rules(7), ausearch(8), aureport(8), auditd(8).

AUTHOR         top

       Steve Grubb

COLOPHON         top

       This page is part of the audit (Linux Audit) project.
       Information about the project can be found at 
       ⟨http://people.redhat.com/sgrubb/audit/⟩.  If you have a bug
       report for this manual page, send it to linux-audit@redhat.com.
       This page was obtained from the project's upstream Git repository
       ⟨https://github.com/linux-audit/audit-userspace.git⟩ on
       2021-08-27.  (At that time, the date of the most recent commit
       that was found in the repository was 2021-08-21.)  If you
       discover any rendering problems in this HTML version of the page,
       or you believe there is a better or more up-to-date source for
       the page, or you have corrections or improvements to the
       information in this COLOPHON (which is not part of the original
       manual page), send a mail to man-pages@man7.org

Red Hat                         July 2021                    AUDITCTL(8)

Pages that refer to this page: audit_add_rule_data(3)audit_delete_rule_data(3)audit_request_rules_list_data(3)audit_set_backlog_limit(3)audit_set_backlog_wait_time(3)audit_set_failure(3)audit.rules(7)auditd(8)augenrules(8)autrace(8)pam_loginuid(8)