auditctl

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 configuration, and to load discretionary
       audit rules.

CONFIGURATION OPTIONS
       -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.

       --signalsignal
              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
       -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
       -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 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 -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
       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

       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


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


SEE ALSO
       audit.rules(7), auditd(8).


AUTHOR
       Steve Grubb



Red Hat                             Aug 2018                        AUDITCTL:(8)