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 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     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.

       -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,
                          and msgtype. 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 or
                          subject context.  The action is ignored and uses its
                          default of "never".

       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. This can only be used on
                          the exit list.

              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

              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
              audispd 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 -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 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


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


AUTHOR
       Steve Grubb



Red Hat                            Jan 2017                       AUDITCTL:(8)