Man Linux: Main Page and Category List


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


       auditctl [options]


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


       -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

       -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 preceeded 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),

       -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

              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

                          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

       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.


       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






       Steve Grubb