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=pod

=head1 NAME

apparmor.d - syntax of security profiles for AppArmor.

=head1 DESCRIPTION

AppArmor profiles describe mandatory access rights granted to given
programs and are fed to the AppArmor policy enforcement module using
apparmor_parser(8). This man page describes the format of the AppArmor
configuration files; see apparmor(7) for an overview of AppArmor.

=head1 FORMAT

AppArmor policy is written in a declarative language, in which the
order of rules within a given section or block does not
matter. Policy is by convention written so that it is contained in
multiple files, but this is not a requirement. It could just as easily
be written in a single file. The policy language is compiled to a
architecture independent binary format that is loaded into the kernel
for enforcement.

The base unit of AppArmor confinement is the profile. It contains a
set of rules which are enforced when the profile is associated with a
running program. The rules within the profile provide a whitelist of
different permission that are allowed, along with a few other special
rules.

The text in AppArmor policy is split into two sections, the preamble
and the profile definitions. The preamble must occur at the head of
the file and once profile definitions begin, no more preamble rules
are allowed (even in files that are included into the profile). When
AppArmor policy (set of profiles) is split across multiple files, each
file can have its own preamble section, which may be the same or
different from other files preamble. Files included within a profile
section can not have a preamble section.

The following is a BNF-style description of AppArmor policy
configuration files; see below for an example AppArmor policy file.
AppArmor configuration files are line-oriented; B<#> introduces a
comment, similar to shell scripting languages. The exception to this
rule is that B<#include> will I<include> the contents of a file inline
to the policy; this behaviour is modelled after cpp(1).

=over 4

B<PROFILE FILE> = ( [ I<PREAMBLE> ] [ I<PROFILE> ] )*

B<PREAMBLE> = ( I<COMMENT> | I<VARIABLE ASSIGNMENT> | I<ALIAS RULE> | I<INCLUDE> | I<ABI> )*
  Variable assignment and alias rules must come before the profile.

B<VARIABLE ASSIGNMENT> = I<VARIABLE> ('=' | '+=') (space separated values)

B<VARIABLE> = '@{' I<ALPHA> [ ( I<ALPHANUMERIC> | '_' ) ... ] '}'

B<ALIAS RULE> = 'alias' I<ABS PATH> '-E<gt>' I<REWRITTEN ABS PATH> ','

B<INCLUDE> = ( '#include' | 'include' ) [ 'if exists' ] ( I<ABS PATH> | I<MAGIC PATH> )

B<ABI> = ( 'abi' ) ( I<ABS PATH> | I<MAGIC PATH> ) ','

B<ABS PATH> = '"' path '"' (the path is passed to open(2))

B<MAGIC PATH> = 'E<lt>' relative path 'E<gt>'
  The path is relative to F</etc/apparmor.d/>.

B<COMMENT> = '#' I<TEXT> [ '\r' ] '\n'

B<TEXT> = any characters

B<PROFILE> = ( I<PROFILE HEAD> ) [ I<ATTACHMENT SPECIFICATION> ] [ I<PROFILE FLAG CONDS> ] '{' ( I<RULES> )* '}'

B<PROFILE HEAD> = [ 'profile' ] I<FILEGLOB> | 'profile' I<PROFILE NAME>

B<PROFILE NAME> ( I<UNQUOTED PROFILE NAME> | I<QUOTED PROFILE NAME> )

B<QUOTED PROFILE NAME> = '"' I<UNQUOTED PROFILE NAME> '"'

B<UNQUOTED PROFILE NAME> = (must start with alphanumeric character (after variable expansion), or '/' B<AARE> have special meanings; see below. May include I<VARIABLE>. Rules with embedded spaces or tabs must be quoted.)

B<ATTACHMENT SPECIFICATION> = [ I<PROFILE_EXEC_COND> ] [ I<PROFILE XATTR CONDS> ]

B<PROFILE_EXEC_COND> = I<FILEGLOB>

B<PROFILE XATTR CONDS> =  [ 'xattrs=' ] '(' comma or white space separated list of I<PROFILE XATTR> ')'

B<PROFILE XATTR> = extended attribute name '=' I<XATTR VALUE FILEGLOB>

B<XATTR VALUE FILEGLOB> = I<FILEGLOB>

B<PROFILE FLAG CONDS> =  [ 'flags=' ] '(' comma or white space separated list of I<PROFILE FLAGS> ')'

B<PROFILE FLAGS> = I<PROFILE MODE> | I<AUDIT_MODE> | 'mediate_deleted'
| 'attach_disconnected' | 'attach_disconneced.path='I<ABS PATH> | 'chroot_relative'
| 'debug' | 'interruptible' | 'kill.signal='I<SIGNAL> | 'error='I<ERROR CODE>

B<ERROR CODE> = (case insensitive error code name starting with 'E'; see errno(3))

B<PROFILE MODE> = 'enforce' | 'complain' | 'kill' | 'default_allow' | 'unconfined' | 'prompt'

B<AUDIT MODE> = 'audit'

B<RULES> = [ ( I<LINE RULES> | I<COMMA RULES> ',' | I<BLOCK RULES> )

B<LINE RULES> = ( I<COMMENT> | I<INCLUDE> ) [ '\r' ] '\n'

B<COMMA RULES> = ( I<CAPABILITY RULE> | I<NETWORK RULE> | I<MOUNT RULE> | I<PIVOT ROOT RULE> | I<UNIX RULE> | I<FILE RULE> | I<LINK RULE> | I<CHANGE_PROFILE RULE> | I<RLIMIT RULE> | I<DBUS RULE> | I<MQUEUE RULE> | I<IO_URING RULE> | I<USERNS RULE> | I<ALL RULE>)

B<BLOCK RULES> = ( I<SUBPROFILE> | I<HAT> | I<QUALIFIER BLOCK> )

B<SUBPROFILE> = 'profile' I<PROFILE NAME> [ I<ATTACHMENT SPECIFICATION> ] [ I<PROFILE FLAG CONDS> ] '{' ( I<RULES> )* '}'

B<HAT> = ('hat' | '^') I<HATNAME> [ I<PROFILE FLAG CONDS> ] '{' ( I<RULES> )* '}'

B<HATNAME> = (must start with alphanumeric character. See aa_change_hat(2) for a description of how this "hat" is used. If '^' is used to start a hat then there is no space between the '^' and I<HATNAME>)

B<QUALIFIER BLOCK> = I<QUALIFIERS> I<BLOCK>

B<INTEGER> = (+ | -)? [[:digit:]]+

B<ACCESS TYPE> = ( 'allow' | 'deny' )

B<QUALIFIERS> = [ 'priority' '=' <INTEGER> ] [ 'audit' ] [ I<ACCESS TYPE> ]

B<CAPABILITY RULE> = [ I<QUALIFIERS> ] 'capability' [ I<CAPABILITY LIST> ]

B<CAPABILITY LIST> = ( I<CAPABILITY> )+

B<CAPABILITY> = (lowercase capability name without 'CAP_' prefix; see
capabilities(7))

B<NETWORK RULE> = [ I<QUALIFIERS> ] 'network' [ I<NETWORK ACCESS EXPR> ] [ I<DOMAIN> ] [ I<TYPE> | I<PROTOCOL> ] [ I<NETWORK LOCAL EXPR> ] [ I<NETWORK PEER EXPR> ]

B<NETWORK ACCESS EXPR> = ( I<NETWORK ACCESS> | I<NETWORK ACCESS LIST> )

B<NETWORK ACCESS> = ( 'create' | 'bind' | 'listen' | 'accept' | 'connect' | 'shutdown' | 'getattr' | 'setattr' | 'getopt' | 'setopt' | 'send' | 'receive' | 'r' | 'w' | 'rw' )
  Some access modes are incompatible with some rules.

B<NETWORK ACCESS LIST> = '(' I<NETWORK ACCESS> ( [','] I<NETWORK ACCESS> )* ')'

B<DOMAIN> = ( 'unix' | 'inet' | 'ax25' | 'ipx' | 'appletalk' | 'netrom' | 'bridge' | 'atmpvc' | 'x25' | 'inet6' | 'rose' | 'netbeui' | 'security' | 'key' | 'netlink' | 'packet' | 'ash' | 'econet' | 'atmsvc' | 'rds' | 'sna' | 'irda' | 'pppox' | 'wanpipe' | 'llc' | 'ib' | 'mpls' | 'can' | 'tipc' | 'bluetooth' | 'iucv' | 'rxrpc' | 'isdn' | 'phonet' | 'ieee802154' | 'caif' | 'alg' | 'nfc' | 'vsock' | 'kcm' | 'qipcrtr' | 'smc' | 'xdp' | 'mctp' ) ','

B<TYPE> = ( 'stream' | 'dgram' | 'seqpacket' |  'rdm' | 'raw' | 'packet' )

B<PROTOCOL> = ( 'tcp' | 'udp' | 'icmp' )

B<NETWORK LOCAL EXPR> = ( I<NETWORK IP COND> | I<NETWORK PORT COND> )*
  Each cond can appear at most once.

B<NETWORK PEER EXPR> = 'peer' '=' '(' ( I<NETWORK IP COND> | I<NETWORK PORT COND> )+ ')'
  Each cond can appear at most once.

B<NETWORK IP COND> = 'ip' '=' ( 'none' | I<NETWORK IPV4> | I<NETWORK IPV6> )

B<NETWORK PORT COND> = 'port' '=' ( I<NETWORK PORT> | I<NETWORK PORT> '-' I<NETWORK PORT> )

B<NETWORK IPV4> = IPv4, represented by four 8-bit decimal numbers separated by '.'

B<NETWORK IPV6> = IPv6, represented by eight groups of four hexadecimal numbers separated by ':'. Shortened representation of contiguous zeros is allowed by using '::'

B<NETWORK PORT> = 16-bit number ranging from 0 to 65535

B<MOUNT RULE> = ( I<MOUNT> | I<REMOUNT> | I<UMOUNT> )

B<MOUNT> = [ I<QUALIFIERS> ] 'mount' [ I<MOUNT CONDITIONS> ] [ I<SOURCE FILEGLOB> ] [ '-E<gt>' [ I<MOUNTPOINT FILEGLOB> ]

B<REMOUNT> = [ I<QUALIFIERS> ] 'remount' [ I<MOUNT CONDITIONS> ] I<MOUNTPOINT FILEGLOB>

B<UMOUNT> = [ I<QUALIFIERS> ] 'umount' [ I<MOUNT CONDITIONS> ] I<MOUNTPOINT FILEGLOB>

B<MOUNT CONDITIONS> = [ ( 'fstype' | 'vfstype' ) ( '=' | 'in' ) I<MOUNT FSTYPE EXPRESSION> ] [ 'options' ( '=' | 'in' ) I<MOUNT FLAGS EXPRESSION> ]

B<MOUNT FSTYPE EXPRESSION> = ( I<MOUNT FSTYPE LIST> | I<MOUNT EXPRESSION> )

B<MOUNT FSTYPE LIST> = Comma separated list of valid filesystem and virtual filesystem types (eg ext4, debugfs, devfs, etc)

B<MOUNT FLAGS EXPRESSION> = ( I<MOUNT FLAGS LIST> | I<MOUNT EXPRESSION> )

B<MOUNT FLAGS LIST> = Comma separated list of I<MOUNT FLAGS>.

B<MOUNT FLAGS> = ( 'ro' | 'rw' | 'nosuid' | 'suid' | 'nodev' | 'dev' | 'noexec' | 'exec' | 'sync' | 'async' | 'remount' | 'mand' | 'nomand' | 'dirsync' | 'noatime' | 'atime' | 'nodiratime' | 'diratime' | 'bind' | 'rbind' | 'move' | 'verbose' | 'silent' | 'loud' | 'acl' | 'noacl' | 'unbindable' | 'runbindable' | 'private' | 'rprivate' | 'slave' | 'rslave' | 'shared' | 'rshared' | 'relatime' | 'norelatime' | 'iversion' | 'noiversion' | 'strictatime' | 'nostrictatime' | 'lazytime' | 'nolazytime' | 'nouser' | 'user' | 'symfollow' | 'nosymfollow' )

B<MOUNT EXPRESSION> = ( I<ALPHANUMERIC> | I<AARE> ) ...

B<MQUEUE_RULE> = [ I<QUALIFIERS> ] 'mqueue' [ I<MQUEUE ACCESS PERMISSIONS> ] [ I<MQUEUE TYPE> ] [ I<MQUEUE LABEL> ] [ I<MQUEUE NAME> ]

B<MQUEUE ACCESS PERMISSIONS> = I<MQUEUE ACCESS> | I<MQUEUE ACCESS LIST>

B<MQUEUE ACCESS LIST> = '(' Comma or space separated list of I<MQUEUE ACCESS> ')'

B<MQUEUE ACCESS> = ( 'r' | 'w' | 'rw' | 'read' | 'write' | 'create' | 'open' | 'delete' | 'getattr' | 'setattr' )

B<MQUEUE TYPE> = 'type' '=' ( 'posix' | 'sysv' )

B<MQUEUE LABEL> = 'label' '=' '(' '"' I<AARE> '"' | I<AARE> ')'

B<MQUEUE NAME> = I<AARE>

B<USERNS RULE> = [ I<QUALIFIERS> ] 'userns' [ I<USERNS ACCESS PERMISSIONS> ]

B<USERNS ACCESS PERMISSIONS> = ( 'create' )

B<IO_URING RULE> = [ I<QUALIFIERS> ] 'io_uring' [ I<IO_URING ACCESS PERMISSIONS> [ I<IO_URING LABEL> ]

B<IO_URING ACCESS PERMISSIONS> = ( 'sqpoll' | 'override_creds' )

B<IO_URING LABEL> = 'label' '=' '(' '"' I<AARE> '"' | I<AARE> ')'

B<PIVOT ROOT RULE> = [ I<QUALIFIERS> ] pivot_root [ oldroot=I<OLD PUT FILEGLOB> ] [ I<NEW ROOT FILEGLOB> ] [ '-E<gt>' I<PROFILE NAME> ]

B<SOURCE FILEGLOB> = I<FILEGLOB>

B<MOUNTPOINT FILEGLOB> = I<FILEGLOB>

B<OLD PUT FILEGLOB> = I<FILEGLOB>

B<PTRACE_RULE> = [ I<QUALIFIERS> ] 'ptrace' [ I<PTRACE ACCESS PERMISSIONS> ] [ I<PTRACE PEER> ]

B<PTRACE ACCESS PERMISSIONS> = I<PTRACE ACCESS> | I<PTRACE ACCESS LIST>

B<PTRACE ACCESS LIST> = '(' Comma or space separated list of I<PTRACE ACCESS> ')'

B<PTRACE ACCESS> = ( 'r' | 'w' | 'rw' | 'read' | 'readby' | 'trace' | 'tracedby' )

B<PTRACE PEER> = 'peer' '=' I<AARE>

B<SIGNAL_RULE> = [ I<QUALIFIERS> ] 'signal' [ I<SIGNAL ACCESS PERMISSIONS> ] [ I<SIGNAL SET> ] [ I<SIGNAL PEER> ]

B<SIGNAL ACCESS PERMISSIONS> = I<SIGNAL ACCESS> | I<SIGNAL ACCESS LIST>

B<SIGNAL ACCESS LIST> = '(' Comma or space separated list of I<SIGNAL ACCESS> ')'

B<SIGNAL ACCESS> = ( 'r' | 'w' | 'rw' | 'read' | 'write' | 'send' | 'receive' )

B<SIGNAL SET> = 'set' '=' '(' I<SIGNAL LIST> ')'

B<SIGNAL LIST> = Comma or space separated list of I<SIGNAL>s

B<SIGNAL> = ( 'hup' | 'int' | 'quit' | 'ill' | 'trap' | 'abrt' | 'bus' | 'fpe' | 'kill' | 'usr1' | 'segv' | 'usr2' | 'pipe' | 'alrm' | 'term' | 'stkflt' | 'chld' | 'cont' | 'stop' | 'stp' | 'ttin' | 'ttou' | 'urg' | 'xcpu' | 'xfsz' | 'vtalrm' | 'prof' | 'winch' | 'io' | 'pwr' | 'sys' | 'emt' | 'exists' | 'rtmin+0' ... 'rtmin+32' )

B<SIGNAL PEER> = 'peer' '=' I<AARE>

B<DBUS RULE> = ( I<DBUS MESSAGE RULE> | I<DBUS SERVICE RULE> | I<DBUS EAVESDROP RULE> | I<DBUS COMBINED RULE> )

B<DBUS MESSAGE RULE> = [ I<QUALIFIERS> ] 'dbus' [ I<DBUS ACCESS EXPRESSION> ] [ I<DBUS BUS> ] [ I<DBUS PATH> ] [ I<DBUS INTERFACE> ] [ I<DBUS MEMBER> ] [ I<DBUS PEER> ]

B<DBUS SERVICE RULE> = [ I<QUALIFIERS> ] 'dbus' [ I<DBUS ACCESS EXPRESSION> ] [ I<DBUS BUS> ] [ I<DBUS NAME> ]

B<DBUS EAVESDROP RULE> = [ I<QUALIFIERS> ] 'dbus' [ I<DBUS ACCESS EXPRESSION> ] [ I<DBUS BUS> ]

B<DBUS COMBINED RULE> = [ I<QUALIFIERS> ] 'dbus' [ I<DBUS ACCESS EXPRESSION> ] [ I<DBUS BUS> ]

B<DBUS ACCESS EXPRESSION> = ( I<DBUS ACCESS> | '(' I<DBUS ACCESS LIST> ')' )

B<DBUS BUS> = 'bus' '=' '(' 'system' | 'session' | '"' I<AARE> '"' | I<AARE> ')'

B<DBUS PATH> = 'path' '=' '(' '"' I<AARE> '"' | I<AARE> ')'

B<DBUS INTERFACE> = 'interface' '=' '(' '"' I<AARE> '"' | I<AARE> ')'

B<DBUS MEMBER> = 'member' '=' '(' '"' I<AARE> '"' | I<AARE> ')'

B<DBUS PEER> = 'peer' '=' '(' [ I<DBUS NAME> ] [ I<DBUS LABEL> ] ')'

B<DBUS NAME> = 'name' '=' '(' '"' I<AARE> '"' | I<AARE> ')'

B<DBUS LABEL> = 'label' '=' '(' '"' I<AARE> '"' | I<AARE> ')'

B<DBUS ACCESS LIST> = Comma separated list of I<DBUS ACCESS>

B<DBUS ACCESS> = ( 'send' | 'receive' | 'bind' | 'eavesdrop' | 'r' | 'read' | 'w' | 'write' | 'rw' )
  Some accesses are incompatible with some rules; see below.

B<UNIX RULE> = [ I<QUALIFIERS> ] 'unix' [ I<UNIX ACCESS EXPR> ] [ I<UNIX RULE CONDS> ] [ I<UNIX LOCAL EXPR> ] [ I<UNIX PEER EXPR> ]

B<UNIX ACCESS EXPR> = ( I<UNIX ACCESS> | I<UNIX ACCESS LIST> )

B<UNIX ACCESS> = ( 'create' | 'bind' | 'listen' | 'accept' | 'connect' | 'shutdown' | 'getattr' | 'setattr' | 'getopt' | 'setopt' | 'send' | 'receive' | 'r' | 'w' | 'rw' )
  Some access modes are incompatible with some rules or require additional parameters.

B<UNIX ACCESS LIST> = '(' I<UNIX ACCESS> ( [','] I<UNIX ACCESS> )* ')'

B<UNIX RULE CONDS> = ( I<TYPE COND> | I<PROTO COND> )
  Each cond can appear at most once.

B<TYPE COND> = 'type' '='  ( I<AARE> | '(' ( '"' I<AARE> '"' | I<AARE> )+ ')' )

B<PROTO COND> = 'protocol' '='  ( I<AARE> | '(' ( '"' I<AARE> '"' | I<AARE> )+ ')' )

B<UNIX LOCAL EXPR> = ( I<UNIX ADDRESS COND> | I<UNIX LABEL COND> | I<UNIX ATTR COND> | I<UNIX OPT COND> )*
  Each cond can appear at most once.

B<UNIX PEER EXPR> = 'peer' '=' ( I<UNIX ADDRESS COND> | I<UNIX LABEL COND> )+
  Each cond can appear at most once.

B<UNIX ADDRESS COND> 'addr' '=' ( I<AARE> | '(' '"' I<AARE> '"' | I<AARE> ')' )

B<UNIX LABEL COND> 'label' '=' ( I<AARE> | '(' '"' I<AARE> '"' | I<AARE> ')' )

B<UNIX ATTR COND> 'attr' '=' ( I<AARE> | '(' '"' I<AARE> '"' | I<AARE> ')' )

B<UNIX OPT COND> 'opt' '=' ( I<AARE> | '(' '"' I<AARE> '"' | I<AARE> ')' )

B<RLIMIT RULE> = 'set' 'rlimit' [I<RLIMIT> 'E<lt>=' I<RLIMIT VALUE> ]

B<RLIMIT> = ( 'cpu' | 'fsize' | 'data' | 'stack' | 'core' | 'rss' | 'nofile' | 'ofile' | 'as' | 'nproc' | 'memlock' | 'locks' | 'sigpending' | 'msgqueue' | 'nice' | 'rtprio' | 'rttime' )

B<RLIMIT VALUE> = ( I<RLIMIT SIZE> | I<RLIMIT NUMBER> | I<RLIMIT TIME> | I<RLIMIT NICE> )

B<RLIMIT SIZE> = I<NUMBER> ( 'K' | 'M' | 'G' )
  Only applies to RLIMIT of 'fsize', 'data', 'stack', 'core', 'rss', 'as', 'memlock', 'msgqueue'.

B<RLIMIT NUMBER> = number from 0 to max rlimit value.
  Only applies to RLIMIT of 'ofile', 'nofile', 'locks', 'sigpending', 'nproc', 'rtprio'.

B<RLIMIT TIME> = I<NUMBER> ( 'us' | 'microsecond' | 'microseconds' | 'ms' | 'millisecond' | 'milliseconds' | 's' | 'sec' | 'second' | 'seconds' | 'min' | 'minute' | 'minutes' | 'h' | 'hour' | 'hours' | 'd' | 'day' | 'days' | 'week' | 'weeks' )
  Only applies to RLIMIT of 'cpu' and 'rttime'. RLIMIT 'cpu' only allows units E<gt>= 'seconds'.

B<RLIMIT NICE> = a number between -20 and 19.
  Only applies to RLIMIT of 'nice'.

B<FILE RULE> = [ I<QUALIFIERS> ] [ 'owner' ] ( 'file' | [ 'file' ] ( I<FILEGLOB> I<ACCESS>  | I<ACCESS> I<FILEGLOB> ) [ '-E<gt>' I<EXEC TARGET> ] )

B<FILEGLOB> = ( I<QUOTED FILEGLOB> | I<UNQUOTED FILEGLOB> )

B<QUOTED FILEGLOB> = '"' I<UNQUOTED FILEGLOB> '"'

B<UNQUOTED FILEGLOB> = (must start with '/' (after variable expansion), B<AARE> have special meanings; see below. May include I<VARIABLE>. Rules with embedded spaces or tabs must be quoted. Rules must end with '/' to apply to directories.)

B<AARE> = B<?*[]{}^>
  See section "Globbing (AARE)" below for meanings.

B<ACCESS> = ( 'r' | 'w' | 'a' | 'l' | 'k' | 'm' | I<EXEC TRANSITION> )+  (not all combinations are allowed; see below.)

B<EXEC TRANSITION> =  ( 'ix' | 'ux' | 'Ux' | 'px' | 'Px' | 'cx' | 'Cx' | 'pix' | 'Pix' | 'cix' | 'Cix' | 'pux' | 'PUx' | 'cux' | 'CUx' | 'x' )
  A bare 'x' is only allowed in rules with the deny qualifier, everything else only without the deny qualifier.

B<EXEC TARGET> = name
  Requires I<EXEC TRANSITION> specified.

B<LINK RULE> = I<QUALIFIERS> [ 'owner' ] 'link' [ 'subset' ] I<FILEGLOB> '-E<gt>' I<FILEGLOB>

B<ALPHA> = ('a', 'b', 'c', ... 'z', 'A', 'B', ... 'Z')

B<ALPHANUMERIC> = ('0', '1', '2', ... '9', 'a', 'b', 'c', ... 'z', 'A', 'B', ... 'Z')

B<CHANGE_PROFILE RULE> = 'change_profile' [ [ I<EXEC MODE> ] I<EXEC COND> ] [ '-E<gt>' I<PROFILE NAME> ]

B<EXEC_MODE> = ( 'safe' | 'unsafe' )

B<EXEC COND> = I<FILEGLOB>

B<ALL RULE> = 'all'

=back

All resources and programs need a full path. There may be any number of
subprofiles (aka child profiles) in a profile, limited only by kernel
memory. Subprofile names are limited to 974 characters.  Child profiles can
be used to confine an application in a special way, or when you want the
child to be unconfined on the system, but confined when called from the
parent.  Hats are a special child profile that can be used with the
aa_change_hat(2) API call.  Applications written or modified to use
aa_change_hat(2) can take advantage of subprofiles to run under different
confinements, dependent on program logic. Several aa_change_hat(2)-aware
applications exist, including an Apache module, mod_apparmor(5); a PAM
module, pam_apparmor; and a Tomcat valve, tomcat_apparmor. Applications
written or modified to use aa_change_profile(2) transition permanently to the
specified profile. libvirt is one such application.

=head2 Profile Head

The profile head consists of a required name that is unique and optional
attachment conditionals and control flags.

=head3 Name

The name of the profile is its identifier. It is what is displayed
during introspection (eg. ps -Z), and defines how the profile is
referenced by policy rules for any policy interaction via ipc or
domain changes. It is recommended that the name be kept short and have
meaning for the application it is being applied eg. I<firefox> for the
firefox web browser or its functional role eg. log_admin.

If the name is an applications full absolute path name
eg. I</usr/bin/firefox> and an exec attachment conditional is not
specified the name is also used as the profile's exec attachment
conditional. This use however has been deprecated and is discouraged
as it makes for long names that can make profile rules difficult to
understand, and may not be fully displayed by some introspection
tools.

=head3 Attachment Conditionals

The attachment conditionals are used during profile changes to
determine whether a profile is a match for the proposed profile
transition. The attachment conditionals are optional, how and when
they are applied is determined by the specific condition(s) used.

When attachment conditionals are used, the attachment conditionals for
all profiles in the namespace will be evaluated. The profile with the
set of attachments that result in the best match will become the new
profile after a transition operation. Attachments that don't match
will result in the profile not being available for transition.

If no conditionals are specified the profile will only be used if a
transition explicitly specifies the profile name.

=head4 Exec Attachment Conditional

The exec attachment conditional governs how closely the profile
matches an executable program. This conditional is only used during an
exec operation when the matching exec rule specifies either a B<px> or
B<cx> (or their derivatives) transition type. The exec attachment
conditional will also be used by tasks that are I<unconfined> as they
use a B<pix> transition rule.

If there are no attachment matches then it is up to the exec rule to
determine what happens (fail or a fallback option).

Note: see profile I<Name> for information around using the profile name
as an attachment conditional.

Exec attachment conditionals can contain variable names and pattern
matching.  They use a longest left match heuristic to deterime the
winner in the case of multiple matches at run time. The exact
implementation of this resolution is kernel specific and has improved
over time, while retaining backwards compatibility. If the heuristic
can not determine a winner between multiple matches the exec will be
denied.

=head4 Extended Attributes Attachment Conditional

AppArmor profiles have the ability to target files based on their xattr(7)
values in addition to their path. For example, the following profile matches
files in /usr/bin with the attribute "security.apparmor" and value "trusted":

  /usr/bin/* xattrs(security.apparmor="trusted") {
    # ...
  }

See apparmor_xattrs(7) for further details.


=head3 Flags

The profile flags allow modifying the behavior of the profile. If a
profile flag is specified it takes priority over any conflicting flags
that have been specified by rules in the profile body.

=head4 Profile Mode

The profile mode allow controlling the enforcement behavior of the
profile rules.

If no mode is specified the profile defaults to I<enforce> mode.

=over 8

=item B<enforce> For a given action, if the profile rules do not grant
permission the action will be denied, with an I<EACCES> or I<EPERM>
error code returned to userspace, and the violation will be logged
with a tag of the access being B<DENIED>.

=item B<kill> This is a variant of enforce mode where in addition to
returning I<EACCES> or I<EPERM> for a violation, the task is also sent
a signal to kill it.

=item B<complain> For a given action, if the profile rules do not grant
permission the action will be allowed, but the violation will be logged
with a tag of the access being B<ALLOWED>.

=item B<default_allow> This mode changes the default behavior of
apparmor from default deny to default allow. When default_allow is
specified the resulting profile will allow operations that the profile
does not have a rule for. This mode is similar to I<unconfined> but
allows for allow and deny rules, specifying audit, and domain
transitions.  Profiles in this mode may be be reported as being in
I<enforce> mode or I<allow> mode when introspected from the kernel.

Note: default_allow is similar and for many profiles will be equivalent
to specifying an I<allow all,> rule in the profile. The default_allow
flag does not provide all the same option that the I<allow all,> rule
provides.

=item B<unconfined> This mode allows a task confined by the profile to
behave as though it is I<unconfined>. The unconfined behavior can be
later changed to confinement by using profile replacement. This mode
should not be used under regular deployment but can be useful during
debugging and some system initialization scenarios.

This mode is similar to default_allow and may be emulated by
default_allow in kernels that no longer support a true unconfined
mode. It does not generally allow for specifying deny rules, or allow
rules that override the default behavior, except in a few custom
kernels where unconfined restricts a few operations. It relies on
special customized behavior of the unconfined profile in the kernel
and as such should only be used for debugging.

Note: true unconfined is being phased out, with unconfined becoming a
replaceable profile. As such unconfined mode will be emulated by a
special profile compiled with the default_allow flag in newer kernels.

=item B<prompt> This mode allows task mediation to send an up call to
userspace to ask for a decision when there isn't a rule covering the
permission request. If userspace does not respond then the access
will be denied.

=back

=head4 Audit Mode

The audit mode allows control of how AppArmor messages are are logged
to the audit system.

=over 8

=item B<audit> This flag causes all actions whether allowed or denied to be
logged.

=back

=head4 Misc modes

=over 8

=item B<mediate_deleted> This forces AppArmor to mediate deleted files
as if they still exist in the file system.

=item B<attach_disconnected> This forces AppArmor to attach
disconnected objects to the task's namespace and mediate them as
though they are part of the namespace. WARNING this mode is unsafe and
can result in aliasing and access to objects that should not be
allowed. Its intent is a debug and policy development tool.

=item B<attach_disconnected.path>=I<ABS PATH> Like attach_disconnected, but
attach disconnected objects to the supplied path instead of the root of
the namespace.

=item B<chroot_relative> This forces file names to be relative to a
chroot and behave as if the chroot is a mount namespace.

=item B<debug> This flag allows turning on kernel debug messages on
a per profile basis. It works in conjunction with other kernel debug
flags to control what messages will be output. Its effect is kernel
dependent, and it should never appear in policy except when trying
to debug kernel or policy problems.

=item B<interruptible> Enables interrupts for prompt upcall to userspace.

=item B<kill.signal>=I<SIGNAL> This changes the signal that will be
sent by AppArmor when in kill mode or a kill rule has been violated.

=item B<error>=I<ERROR CODE> This changes the error code returned by
AppArmor when a rule has been violated.

=back

=head2 Access Modes

File permission access modes consists of combinations of the following
modes:

=over 8

=item B<r>

- read

=item B<w>

- write -- conflicts with append

=item B<a>

- append -- conflicts with write

=item B<ux>

- unconfined execute

=item B<Ux>

- unconfined execute -- use ld.so(8) secure-execution mode

=item B<px>

- discrete profile execute

=item B<Px>

- discrete profile execute -- use ld.so(8) secure-execution mode

=item B<cx>

- transition to subprofile on execute

=item B<Cx>

- transition to subprofile on execute -- use ld.so(8) secure-execution mode

=item B<ix>

- inherit execute

=item B<pix>

- discrete profile execute with inherit fallback

=item B<Pix>

- discrete profile execute with inherit fallback -- use ld.so(8) secure-execution mode

=item B<cix>

- transition to subprofile on execute with inherit fallback

=item B<Cix>

- transition to subprofile on execute with inherit fallback -- use ld.so(8) secure-execution mode

=item B<pux>

- discrete profile execute with fallback to unconfined

=item B<PUx>

- discrete profile execute with fallback to unconfined -- use ld.so(8) secure-execution mode

=item B<cux>

- transition to subprofile on execute with fallback to unconfined

=item B<CUx>

- transition to subprofile on execute with fallback to unconfined -- use ld.so(8) secure-execution mode

=item B<deny x>

- disallow execute (in rules with the deny qualifier)

=item B<m>

- allow PROT_EXEC with mmap(2) calls

=item B<l>

- link

=item B<k>

- lock

=back

=head2 Access Modes Details

=over 4

=item B<r - Read mode>

Allows the program to have read access to the file or directory listing. Read access is
required for shell scripts and other interpreted content.

=item B<w - Write mode>

Allows the program to have write access to the file. Files and directories
must have this permission if they are to be unlinked (removed.)  Write mode
is not required on a directory to rename or create files within the directory.

This mode conflicts with append mode.

=item B<a - Append mode>

Allows the program to have a limited appending only write access to the file.
Append mode will prevent an application from opening the file for write unless
it passes the O_APPEND parameter flag on open.

The mode conflicts with Write mode.

=item B<ux - Unconfined execute mode>

Allows the program to execute the program without any AppArmor profile
being applied to the program.

This mode is useful when a confined program needs to be able to perform
a privileged operation, such as rebooting the machine. By placing the
privileged section in another executable and granting unconfined
execution rights, it is possible to bypass the mandatory constraints
imposed on all confined processes. For more information on what is
constrained, see the apparmor(7) man page.

B<WARNING> 'ux' should only be used in very special cases. It enables the
designated child processes to be run without any AppArmor protection.
'ux' does not use ld.so(8) secure-execution mode to clear variables such as 
LD_PRELOAD; as a result, the calling domain may have an undue amount of 
influence over the callee. Use this mode only if the child absolutely must be
run unconfined and LD_PRELOAD must be used. Any profile using this mode
provides negligible security. Use at your own risk.

Incompatible with other exec transition modes and the deny qualifier.

=item B<Ux - unconfined execute -- use ld.so(8) secure-execution mode>

'Ux' allows the named program to run in 'ux' mode, but AppArmor
will invoke the Linux Kernel's B<unsafe_exec> routines to set ld.so(8)
secure-execution mode and clear environment variables such as LD_PRELOAD, 
similar to setuid programs. (See ld.so(8) for more information.)

B<WARNING> 'Ux' should only be used in very special cases. It enables the
designated child processes to be run without any AppArmor protection.
Use this mode only if the child absolutely must be run unconfined. Use
at your own risk.

Incompatible with other exec transition modes and the deny qualifier.

=item B<px - Discrete Profile execute mode>

This mode requires that a discrete security profile is defined for a
program executed and forces an AppArmor domain transition. If there is
no profile defined then the access will be denied.

B<WARNING> 'px' does not use ld.so(8) secure-execution mode to clear variables 
such as LD_PRELOAD; as a result, the calling domain may have an undue amount of 
influence over the callee.

Incompatible with other exec transition modes and the deny qualifier.

=item B<Px - Discrete Profile execute mode -- use ld.so(8) secure-execution mode>

'Px' allows the named program to run in 'px' mode, but AppArmor
will invoke the Linux Kernel's B<unsafe_exec> routines to set ld.so(8)
secure-execution mode and clear environment variables such as LD_PRELOAD, 
similar to setuid programs. (See ld.so(8) for more information.)

Incompatible with other exec transition modes and the deny qualifier.

=item B<cx - Transition to Subprofile execute mode>

This mode requires that a local security profile is defined and forces an
AppArmor domain transition to the named profile. If there is no profile
defined then the access will be denied.

B<WARNING> 'cx' does not use ld.so(8) secure-execution mode to clear variables 
such as LD_PRELOAD; as a result, the calling domain may have an undue amount of 
influence over the callee.

Incompatible with other exec transition modes and the deny qualifier.

=item B<Cx - Transition to Subprofile execute mode -- use ld.so(8) secure-execution mode>

'Cx' allows the named program to run in 'cx' mode, but AppArmor
will invoke the Linux Kernel's B<unsafe_exec> routines to set ld.so(8)
secure-execution mode and clear environment variables such as LD_PRELOAD, 
similar to setuid programs. (See ld.so(8) for more information.)

Incompatible with other exec transition modes and the deny qualifier.

=item B<ix - Inherit execute mode>

Prevent the normal AppArmor domain transition on execve(2) when the
profiled program executes the named program. Instead, the executed resource
will inherit the current profile.

This mode is useful when a confined program needs to call another
confined program without gaining the permissions of the target's
profile, or losing the permissions of the current profile. There is no
version to set secure-execution mode because 'ix' executions don't change
privileges.

Incompatible with other exec transition modes and the deny qualifier.

=item B<Profile transition with inheritance fallback execute mode>

These modes attempt to perform a domain transition as specified by
the matching permission (shown below) and if that transition fails
to find the matching profile the domain transition proceeds using
the 'ix' transition mode.

  'Pix' == 'Px' with fallback to 'ix'
  'pix' == 'px' with fallback to 'ix'
  'Cix' == 'Cx' with fallback to 'ix'
  'cix' == 'cx' with fallback to 'ix'

Incompatible with other exec transition modes and the deny qualifier.

=item B<Profile transition with unconfined fallback execute mode>

These modes attempt to perform a domain transition as specified by
the matching permission (shown below) and if that transition fails
to find the matching profile the domain transition proceeds using
the 'ux' transition mode if 'pux', 'cux' or the 'Ux' transition mode
if 'PUx', 'CUx' is used.

  'PUx' == 'Px' with fallback to 'Ux'
  'pux' == 'px' with fallback to 'ux'
  'CUx' == 'Cx' with fallback to 'Ux'
  'cux' == 'cx' with fallback to 'ux'

Incompatible with other exec transition modes and the deny qualifier.

=item B<deny x - Deny execute>

For rules including the deny modifier, only 'x' is allowed to deny execute.

The 'ix', 'Px', 'px', 'Cx', 'cx' and the fallback modes conflict with the deny
modifier.

=item B<Directed profile transitions>

The directed ('px', 'Px', 'pix', 'Pix', 'pux', 'PUx') profile and
subprofile ('cx', 'Cx', 'cix', 'Cix', 'cux', 'CUx') transitions normally
determine the profile to transition to from the executable name. It
is however possible to specify the name of the profile that the transition
should use.

The name of the profile to transition to is specified using the '-E<gt>'
followed by the name of the profile to transition to. Eg.

  /bin/** px -> profile,

Incompatible with other exec transition modes.

=item B<m - Allow executable mapping>

This mode allows a file to be mapped into memory using mmap(2)'s
PROT_EXEC flag. This flag marks the pages executable; it is used on some
architectures to provide non-executable data pages, which can complicate
exploit attempts. AppArmor uses this mode to limit which files a
well-behaved program (or all programs on architectures that enforce
non-executable memory access controls) may use as libraries, to limit
the effect of invalid B<-L> flags given to ld(1) and B<LD_PRELOAD>,
B<LD_LIBRARY_PATH>, given to ld.so(8).

=item B<l - Link mode>

Allows the program to be able to create a link with this name.  When a
link is created, the new link B<MUST> have a subset of permissions as
the original file (with the exception that the destination does not have
to have link access.) If there is an 'x' rule on the new link, it must
match the original file exactly.

=item B<k - lock mode>

Allows the program to be able lock a file with this name.  This permission
covers both advisory and mandatory locking.

=item B<leading OR trailing access permissions>

File rules can be specified with the access permission either leading
or trailing the file glob. Eg.

  rw /**,		# leading permissions

  /** rw,		# trailing permissions

When leading permissions are used further rule options and context
may be allowed, Eg.

  l /foo -> /bar,	# lead 'l' link permission is equivalent to link rules

=back

=head2 Link rules

Link rules allow specifying permission to form a hard link as a link
target pair.  If the subset condition is specified then the permissions
to access the link file must be a subset of the profiles permissions
to access the target file. If there is an 'x' rule on the new link, it
must match the original file exactly.

Eg.

  /file1  r,
  /file2  rwk,
  /link*  rw,
  link subset /link* -> /**,

The link rule allows linking of /link to both /file1 or /file2 by
name however because the /link file has 'rw' permissions it is not
allowed to link to /file1 because that would grant an access path
to /file1 with more permissions than the 'r' permissions the profile
specifies.

A link of /link to /file2 would be allowed because the 'rw' permissions
of /link are a subset of the 'rwk' permissions for /file1.

The link rule is equivalent to specifying the 'l' link permission as
a leading permission with no other file access permissions. When this
is done the link rule options can be specified.

The following link rule is equivalent to the 'l' permission file rule

  link /foo -> bar,
  l /foo -> /bar,

File rules that specify the 'l' permission and don't specify the extend
link permissions map to link rules as follows.

  /foo l,
  l /foo,
  link subset /foo -> /**,

=head2 Comments

Comments start with # and may begin at any place within a line. The
comment ends when the line ends. This is the same comment style as
shell scripts.

=head2 Capabilities

The only capabilities a confined process may use may be enumerated; for
the complete list, please refer to capabilities(7). Note that granting
some capabilities renders AppArmor confinement for that domain advisory;
while open(2), read(2), write(2), etc., will still return error when
access is not granted, some capabilities allow loading kernel modules,
arbitrary access to IPC, ability to bypass discretionary access controls,
and other operations that are typically reserved for the root user.

=head2 Network Rules

AppArmor supports simple coarse grained network mediation.  The
network rule restrict all socket(2) based operations.  The mediation
done is a coarse-grained check on whether a socket of a given type and
family can be created, read, or written. Network netlink(7) rules may
only specify type 'dgram' and 'raw'.

AppArmor network rules are accumulated so that the granted network
permissions are the union of all the listed network rule permissions.

AppArmor network rules are broad and general and become more restrictive
as further information is specified.

eg.

 network,		#allow access to all networking
 network tcp,		#allow access to tcp
 network inet tcp,	#allow access to tcp only for inet4 addresses
 network inet6 tcp,	#allow access to tcp only for inet6 addresses
 network netlink raw,	#allow access to AF_NETLINK SOCK_RAW

=head3 Network permissions

Network rule permissions are implied when a rule does not explicitly
state an access list. By default if a rule does not have an access
list all permissions that are compatible with the specified set of
local and peer conditionals are implied.

The create, bind, listen, shutdown, getattr, setattr, getopt, and
setopt permissions are local socket permissions. They are only applied
to the local socket and can't be specified in rules that have a peer
conditional. The accept permission applies to the combination of a
local and peer socket. The connect, send, and receive permissions are
peer socket permissions.

=head3 Mediation of inet/inet6 family

AppArmor supports fine grained mediation of the inet and inet6
families by using the ip and port conditionals. The ip conditional
accepts both IPv4 and IPv6 using the regular representation of four
octets separated by '.' for IPv4 and eight groups of four hexadecimal
numbers separated by ':' for IPv6. Contiguous leading zeros can be
replaced by '::' once. On a connected socket, the sender and receiver
don't need to be specified in the recvfrom and sendto system calls. In
that case, and with unbounded sockets, the IP address is none, or
unknown. Unknown or Unbound IP addresses are represented in policy by the
'none' keyword. When the ip conditional is omitted, then all IP
addresses will be allowed: IPv4, IPv6 and none. If INADDR_ANY or
in6addr_any is used, then the ip conditional can be omitted or they
can be represented by:

 network ip=::,		#allow in6addr_any
 network ip=0.0.0.0;	#allow INADDR_ANY

The network rules support the specification of local and remote IP
addresses, ports, and port ranges.

 network ip=127.0.0.1 port=8080,
 network peer=(ip=10.139.15.23 port=8081),
 network ip=fd74:1820:b03a:b361::cf32 peer=(ip=fd74:1820:b03a:b361::a0f9),
 network port=8080 peer=(port=8081),
 network ip=127.0.0.1 port=8080 peer=(ip=10.139.15.23 port=8081),
 network ip=127.0.0.1 port=8080-8084,

=head2 Mount Rules

AppArmor supports mount mediation and allows specifying filesystem types and
mount flags. The syntax of mount rules in AppArmor is based on the mount(8)
command syntax. Mount rules must contain one of the mount, remount or umount
keywords, but all mount conditions are optional. Unspecified optional
conditionals are assumed to match all entries (eg, not specifying fstype means
all fstypes are matched). Due to the complexity of the mount command and how
options may be specified, AppArmor allows specifying conditionals three
different ways:

=over 4

=item 1.

If a conditional is specified using '=', then the rule only grants permission
for mounts matching the exactly specified options. For example, an AppArmor
policy with the following rule:

    mount options=ro /dev/foo -> /mnt/,

Would match:

    $ mount -o ro /dev/foo /mnt

but not either of these:

    $ mount -o ro,atime /dev/foo /mnt

    $ mount -o rw /dev/foo /mnt

=item 2.

If a conditional is specified using 'in', then the rule grants permission for
mounts matching any combination of the specified options. For example, if an
AppArmor policy has the following rule:

    mount options in (ro,atime) /dev/foo -> /mnt/,

all of these mount commands will match:

    $ mount -o ro /dev/foo /mnt

    $ mount -o ro,atime /dev/foo /mnt

    $ mount -o atime /dev/foo /mnt

but none of these will:

    $ mount -o ro,sync /dev/foo /mnt

    $ mount -o ro,atime,sync /dev/foo /mnt

    $ mount -o rw /dev/foo /mnt

    $ mount -o rw,noatime /dev/foo /mnt

    $ mount /dev/foo /mnt

=item 3.

If multiple conditionals are specified in a single mount rule, then the rule
grants permission for each set of options. This provides a shorthand when
writing mount rules which might help to logically break up a conditional. For
example, if an AppArmor policy has the following rule:

    mount options=ro options=atime,

both of these mount commands will match:

    $ mount -o ro /dev/foo /mnt

    $ mount -o atime /dev/foo /mnt

but this one will not:

    $ mount -o ro,atime /dev/foo /mnt

=back

Note that separate mount rules are distinct and the options do not accumulate.
For example, these AppArmor mount rules:

    mount options=ro,

    mount options=atime,

are not equivalent to either of these mount rules:

    mount options=(ro,atime),

    mount options in (ro,atime),

To help clarify the flexibility and complexity of mount rules, here are some
example rules with accompanying matching commands:

=over 4

=item B<mount,>

the 'mount' rule without any conditionals is the most generic and allows any
mount. Equivalent to 'mount fstype=** options=** ** -E<gt> /**'.

=item B<mount /dev/foo,>

allow mounting of /dev/foo anywhere with any options. Some matching mount
commands:

    $ mount /dev/foo /mnt

    $ mount -t ext3 /dev/foo /mnt

    $ mount -t vfat /dev/foo /mnt

    $ mount -o ro,atime,noexec,nodiratime /dev/foo /srv/some/mountpoint

=item B<mount options=ro /dev/foo,>

allow mounting of /dev/foo anywhere, as read only. Some matching mount
commands:

    $ mount -o ro /dev/foo /mnt

    $ mount -o ro /dev/foo /some/where/else

=item B<mount options=(ro,atime) /dev/foo,>

allow mount of /dev/foo anywhere, as read only and using inode access times.
Some matching mount commands:

    $ mount -o ro,atime /dev/foo /mnt

    $ mount -o ro,atime /dev/foo /some/where/else

=item B<mount options in (ro,atime) /dev/foo,>

allow mount of /dev/foo anywhere using some combination of 'ro' and 'atime'
(see above). Some matching mount commands:

    $ mount -o ro /dev/foo /mnt

    $ mount -o atime /dev/foo /some/where/else

    $ mount -o ro,atime /dev/foo /some/other/place

=item B<mount options=ro /dev/foo, mount options=atime /dev/foo,>

allow mount of /dev/foo anywhere as read only, and allow mount of /dev/foo
anywhere using inode access times. Note this is expressed as two different
rules. Matches:

    $ mount -o ro /dev/foo /mnt/1

    $ mount -o atime /dev/foo /mnt/2

=item B<< mount -E<gt> /mnt/**, >>

allow mounting anything under a directory in /mnt/**. Some matching mount
commands:

    $ mount /dev/foo1 /mnt/1

    $ mount -o ro,atime,noexec,nodiratime /dev/foo2 /mnt/deep/path/foo2

=item B<< mount options=ro -E<gt> /mnt/**, >>

allow mounting anything under /mnt/**, as read only. Some matching mount
commands:

    $ mount -o ro /dev/foo1 /mnt/1

    $ mount -o ro /dev/foo2 /mnt/deep/path/foo2

=item B<< mount fstype=ext3 options=(rw,atime) /dev/sdb1 -E<gt> /mnt/stick/, >>

allow mounting an ext3 filesystem in /dev/sdb1 on /mnt/stick as read/write and
using inode access times. Matches only:

    $ mount -o rw,atime /dev/sdb1 /mnt/stick

=item B<< mount options=(ro, atime) options in (nodev, user) /dev/foo -E<gt> /mnt/, >>

allow mounting /dev/foo on /mmt/ read only and using inode access times or
allow mounting /dev/foo on /mnt/ with some combination of 'nodev' and 'user'.
Matches only:

    $ mount -o ro,atime /dev/foo /mnt

    $ mount -o nodev /dev/foo /mnt

    $ mount -o user /dev/foo /mnt

    $ mount -o nodev,user /dev/foo /mnt

=back

=head2 Message Queue rules

AppArmor supports mediation of POSIX and SYSV message queues.

AppArmor Message Queue permissions are implied when a rule does not explicitly
state an access list. By default, all Message Queue permissions are implied.

AppArmor Message Queue permissions become more restricted as further information
is specified. Policy can be specified by determining its access mode, type,
label, and message queue name.

Regarding access modes, 'r' and 'read' are used to read messages from the queue.
'w' and 'write' are used to write to the message queue. 'create' is used to create
the message queue, and 'open' is used to get the message queue identifier when the
queue is already created. 'delete' is used to remove the message queue. The access
modes to get and set attributes of the message queue are 'setattr' and 'getattr'.

The type of the policy can be either 'posix' or 'sysv'. This information is
relevant when the message queue name is not specified, and when specified can be
inferred by the queue name, since message queues' name for posix must start with '/',
and message queues' key for SYSV must be a positive integer.

The policy label is the label assigned to the message queue when it is created.

The message queue name can be either a string starting with '/' if the type
is POSIX, or a positive integer if the type is SYSV. If the type is not
specified, then it will be inferred by the queue name.

Example AppArmor Message Queue rules:

    # Allow all Message Queue access
    mqueue,

    # Explicitly allow all Message Queue access,
    mqueue (create, open, delete, read, write, getattr, setattr),

    # Explicitly deny use of Message Queue
    deny mqueue,

    # Allow all access for POSIX queue of name /bar
    mqueue type=posix /bar,

    # Allow create permission for a SYSV queue of label foo
    mqueue create label=foo 123,

=head2 User Namespace Rules

User namespaces are part of many sandboxing and containerization
solutions.  They provide a way for a non-system root process to be
root within the container. Unfortunately this opens up attack surface
in the kernel and has been part of several exploit chains. As such
AppArmor can be used to restrict the creation of user namespaces to
select processes.

User namespace permission are implied when a rule does not explicitly
state an access list. The rule becomes more restrictive as further
information is specified.

Note: user namespace creation may be restricted so that it is not
available to unprivieged unconfined processes. If this is the case any
process trying to create user namespaces will require a profile that
allows the necessary permissions.

=over 4

=item B<create>

Allow creation of user namespaces.

=back

Example userns rules:

=over 4

  # Allow all userns perms
  userns,

  # Allow creation of a userns
  userns create,

=back

=head2 IO_URing Rules

AppArmor supports mediation of the new Linux high speed IO interface.
There is limited mediation at this time to just a few permissions at
the moment.

IO Uring permission are implied when a rule does not explicitly state
an access list. The rule becomes more restrictive as further
information is specified.

Note: io_uring access may be restricted so that it is not available to
unprivileged unconfined processes. If this is the case any process
trying to use io_uring will require a profile that allows the
necessary io_uring permissions.

=over 4

=item B<sqpoll>

All the task confined by the profile to spawn a io_uring polling
thread.

=item B<override_creds>

Grants the task confined by the profile to override (change) its
credentials to the specified label, when executing an io_uring
operation.

=back

Example IO_URING rules:

=over 4

  # Allow io_uring operations
  io_uring,

  # Allow creation of a polling thread
  io_uring sqpoll,

  # Allow task to override credentials during io_uring operation
  io_uring override_creds label=new_creds,

=back

=head2 Pivot Root Rules

AppArmor mediates changing of the root filesystem through the pivot_root(2)
system call. The syntax of 'pivot_root' rules in AppArmor is based on the
pivot_root(2) system call parameters with the notable exception that the
ordering is reversed. The path corresponding to the put_old parameter of
pivot_root(2) is optionally specified in the 'pivot_root' rule using the
'oldroot=' prefix.

AppArmor 'pivot_root' rules can specify a profile transition to occur during
the pivot_root(2) system call. Note that currently, this feature is not
supported by any kernel. When this feature will be supported, AppArmor will
only transition the process calling pivot_root(2) to the new profile.

The paths specified in 'pivot_root' rules must end with '/' since they are
directories.

Here are some example 'pivot_root' rules:

    # Allow any pivot
    pivot_root,

    # Allow pivoting to any new root directory and putting the old root
    # directory at /mnt/root/old/
    pivot_root oldroot=/mnt/root/old/,

    # Allow pivoting the root directory to /mnt/root/
    pivot_root /mnt/root/,

    # Allow pivoting to /mnt/root/ and putting the old root directory at
    # /mnt/root/old/
    pivot_root oldroot=/mnt/root/old/ /mnt/root/,

    # Allow pivoting to /mnt/root/, putting the old root directory at
    # /mnt/root/old/ and transition to the /mnt/root/sbin/init profile
    pivot_root oldroot=/mnt/root/old/ /mnt/root/ -> /mnt/root/sbin/init,

=head2 PTrace rules

AppArmor supports mediation of ptrace(2). AppArmor PTrace rules are accumulated
so that the granted PTrace permissions are the union of all the listed PTrace
rule permissions.

AppArmor PTrace permissions are implied when a rule does not explicitly state
an access list. By default, all PTrace permissions are implied.

The trace and tracedby permissions govern ptrace(2) while read and readby
govern certain proc(5) filesystem accesses, kcmp(2), futexes
(get_robust_list(2)) and perf trace events.

For a ptrace operation to be allowed the profile of the tracing process and the
profile of the target task must both have the correct permissions. For example,
the profile of the process attaching to another task must have the trace
permission for the target task's profile, and the task being traced must have
the tracedby permission for the tracing process' profile.

Example AppArmor PTrace rules:

    # Allow all PTrace access
    ptrace,

    # Explicitly allow all PTrace access,
    ptrace (read, readby, trace, tracedby),

    # Explicitly deny use of ptrace(2)
    deny ptrace (trace),

    # Allow unconfined processes (eg, a debugger) to ptrace us
    ptrace (readby, tracedby) peer=unconfined,

    # Allow ptrace of a process running under the /usr/bin/foo profile
    ptrace (trace) peer=/usr/bin/foo,

=head2 Signal rules

AppArmor supports mediation of signal(7). AppArmor signal rules are accumulated
so that the granted signal permissions are the union of all the listed signal
rule permissions.

AppArmor signal permissions are implied when a rule does not explicitly state
an access list. By default, all signal permissions are implied.

For the sending of a signal to be allowed, the profile of the sending process
and the profile of the target task must both have the correct permissions. For
example, the profile of a process sending a signal to another task must have
the send permission for the target task's profile, and the task receiving the
signal must have a receive permission for the sending process' profile.

Example AppArmor signal rules:

    # Allow all signal access
    signal,

    # Explicitly deny sending the HUP and INT signals
    deny signal (send) set=(hup, int),

    # Allow unconfined processes to send us signals
    signal (receive) peer=unconfined,

    # Allow sending of signals to a process running under the /usr/bin/foo
    # profile
    signal (send) peer=/usr/bin/foo,

    # Allow checking for PID existence
    signal (receive, send) set=("exists"),

    # Allow us to signal ourselves using the built-in @{profile_name} variable
    signal peer=@{profile_name},

    # Allow two real-time signals
    signal set=(rtmin+0 rtmin+32),

=head2 DBus rules

AppArmor supports DBus mediation. The mediation is performed in conjunction
with the DBus daemon. The DBus daemon verifies that communications over the
bus are permitted by AppArmor policy.

AppArmor DBus rules are accumulated so that the granted DBus permissions are
the union of all the listed DBus rule permissions.

AppArmor DBus rules are broad and general and become more restrictive as
further information is specified. Policy may be specified down to the interface
member level (method or signal name), however the contents of messages are not
examined.

Some AppArmor DBus permissions are not compatible with all AppArmor DBus rules.
The 'bind' permission cannot be used in message rules. The 'send' and 'receive'
permissions cannot be used in service rules. The 'eavesdrop' permission cannot
be used in rules containing any conditionals outside of the 'bus' conditional.

'r' and 'read' are synonyms for 'receive'. 'w' and 'write' are synonyms for
'send'. 'rw' is a synonym for both 'send' and 'receive'.

AppArmor DBus permissions are implied when a rule does not explicitly state an
access list. By default, all DBus permissions are implied. Only message
permissions are implied for message rules and only service permissions are
implied for service rules.

Example AppArmor DBus rules:

    # Allow all DBus access
    dbus,

    # Explicitly allow all DBus access,
    dbus (send, receive, bind),

    # Deny send/receive/bind access to the session bus
    deny dbus bus=session,

    # Allow bind access for a particular name on any bus
    dbus bind name=com.example.ExampleName,

    # Allow receive access for a particular path and interface
    dbus receive path=/com/example/path interface=com.example.Interface,

    # Deny send/receive access to the system bus for a particular interface
    deny dbus bus=system interface=com.example.ExampleInterface,

    # Allow send access for a particular path, interface, member, and pair of
    # peer names:
    dbus send
         bus=session
         path=/com/example/path
         interface=com.example.Interface
         member=ExampleMethod
         peer=(name=(com.example.ExampleName1|com.example.ExampleName2)),

    # Allow receive access for all unconfined peers
    dbus receive peer=(label=unconfined),

    # Allow eavesdropping on the system bus
    dbus eavesdrop bus=system,

    # Allow and audit all eavesdropping
    audit dbus eavesdrop,

=head2 Unix socket rules

AppArmor supports fine grained mediation of unix domain abstract and
anonymous sockets. Unix domain sockets with file system paths are
mediated via file access rules.

Abstract unix domain sockets is a nonportable Linux extension of unix
domain sockets, see unix(7) for more information.

=head3 Unix socket address paths

The sun_path component (aka the socket address) of a unix domain socket is
specified by the

  addr=

conditional. If an address conditional is not specified as part of
a rule then the rule matches both abstract and anonymous sockets.

In apparmor the address of an abstract unix domain socket begins with
the I<@> character, similar to how they are reported (as paths) by
netstat -x. The address then follows and may contain pattern matching
and any characters including the null character. In apparmor null
characters must be specified by using an escape sequence I<\000> or
I<\x00>. The pattern matching is the same as is used by file path matching
so * will not match I</> even though it has no special meaning with
in an abstract socket name. Eg.

  unix addr=@*,

Autobound unix domain sockets have a unix sun_path assigned to them
by the kernel, as such specifying a policy based address is not possible.
The autobinding of sockets can be controlled by specifying the special
I<auto> keyword. Eg.

  unix addr=auto,

To indicate that the rule only applies to auto binding of unix domain
sockets. It is important to note this only applies to the I<bind>
permission as once the socket is bound to an address it is
indistinguishable from a socket that have an addr bound with a
specified name. When the I<auto> keyword is used with other permissions
or as part of a peer addr it will be replaced with a pattern that
can match an autobound socket. Eg. For some kernels

  unix rw addr=auto,

is transformed to

  unix rw addr=@[a-f0-9][a-f0-9][a-f0-9][a-f0-9][a-f0-9],

It is important to note, this pattern may match abstract sockets that
were not autobound but have an addr that fits what is generated by
the kernel when autobinding a socket.

Anonymous unix domain sockets have no sun_path associated with the socket
address, however it can be specified with the special I<none> keyword to
indicate the rule only applies to anonymous unix domain sockets. Eg.

  unix addr=none,

If the address component of a rule is not specified then the rule applies
to autobind, abstract and anonymous sockets.

=head3 Unix socket permissions

Unix domain socket rules are accumulated so that the granted unix
socket permissions are the union of all the listed unix rule permissions.

Unix domain socket rules are broad and general and become more restrictive
as further information is specified. Policy may be specified down to
the socket address (aka sun_path) and label level. The content of the
communication is not examined.

Unix socket rule permissions are implied when a rule does not explicitly
state an access list. By default if a rule does not have an access list
all permissions that are compatible with the specified set of local
and peer conditionals are implied.

The create, bind, listen, shutdown, getattr, setattr, getopt, and setopt
permissions are local socket permissions. They are only applied to the local
socket and can't be specified in rules that have a peer component. The accept
permission applies to the combination of a local and peer socket. The connect,
send, and receive permissions are peer socket permissions.

Only the peer socket permissions will be applied to rules that don't specify
permissions and contain a peer component.

=head3 Example Unix domain socket rules:

  # Allow all permissions to unix sockets
  unix,

  # Explicitly allow all unix permissions
  unix (create, listen, accept, connect, send, receive, getattr, setattr, setopt, getopt),

  # Explicitly deny unix socket access
  deny unix,

  # Allow create and use of abstract and anonymous sockets for profile_name
  unix peer=(label=@{profile_name}),

  # Allow receiving via unix sockets from unconfined
  unix (receive) peer=(label=unconfined),

  # Allow getattr and shutdown on anonymous sockets
  unix (getattr, shutdown) addr=none,

  # Allow SOCK_STREAM connect, receive and send on an abstract socket @bar
  # with peer running under profile '/foo'
  unix (connect, receive, send) type=stream peer=(label=/foo,addr="@bar"),

  # Allow accepting connections from and receiving from peer running under
  # profile '/bar' on abstract socket '@foo'
  unix (accept, receive) addr=@foo peer=(label=/bar),

=head3 Abstract unix domain sockets autobind

Abstract unix domain sockets can autobind to an address. The autobind
address is a unique 5 digit string of decimal numbers, eg. @00001. There
is nothing that prevents a task from manually binding to addresses with a
similar pattern so it is impossible to reliably identify autobind addresses
from a regular address.

=head3 Interaction of network rules and fine grained unix domain socket rules

The coarse grained networking rules can be used to control unix domain
sockets as well. When fine grained unix domain socket mediation is available
the coarse grained network rule is mapped into the equivalent unix socket
rule.

E.G.

    network unix,  =>  unix,

    network unix stream,   =>  unix stream,

Fine grained mediation rules however can not be losslessly converted back
to the coarse grained network rule; e.g.

   unix bind addr=@example,

Has no exact match under coarse grained network rules, the closest match is
the much wider permission rule of

   network unix,

=head2 change_profile rules

AppArmor supports self directed profile transitions via the change_profile
api. Change_profile rules control which permissions for which profiles
a confined task can transition to.  The profile name can contain apparmor
pattern matching to specify different profiles.

  change_profile -> **,

The change_profile api allows the transition to be delayed until when
a task executes another application. If an exec rule transition is
specified for the application and the change_profile api is used to
make a transition at exec time, the transition specified by the
change_profile api takes precedence.

The Change_profile permission can restrict which profiles can be transitioned
to based off of the executable name by specifying the exec condition.

  change_profile /bin/bash -> new_profile,

The restricting of the transition profile to a given executable at exec
time is only useful when then current task is allowed to make dynamic
decisions about what confinement should be, but the decision set needs
to be controlled. A list of profiles or multiple rules can be used to
specify the profiles in the set. Eg.

  change_profile /bin/bash -> {new_profile1,new_profile2,new_profile3},

An exec rule can be used to specify a transition for the executable, if
the transition should be allowed even if the change_profile api has not
been used to select a transition for those available in the change_profile
rule set.  Eg.

  /bin/bash Px -> new_profile1,
  change_profile /bin/bash -> {new_profile1,new_profile2,new_profile3},

The exec mode dictates whether or not the Linux Kernel's B<unsafe_exec>
routines should be used to set ld.so(8) secure-execution mode and clear 
environment variables such as LD_PRELOAD, similar to setuid programs. 
(See ld.so(8) for more information.) The B<safe> mode sets up secure-execution 
mode for the new application, and B<unsafe> mode disables AppArmor's 
requirement for it (the kernel and/or libc may still turn it on). An
exec mode can only be specified when an exec condition is present.

  change_profile safe /bin/bash -> new_profile,

Not all kernels support B<safe> mode and the parser will downgrade rules to
B<unsafe> mode in that situation. If no exec mode is specified, the default is
B<safe> mode in kernels that support it.

=head2 all rule

The all rule is used to add a generic rule for all supported rule types.
This is useful when policy wants to define a black list instead of
white list, but can also be useful to add an access qualifier to all
rules.

Eg. Black list

  allow all,
  # begin blacklist
  deny file,
  deny unix,


Eg. Adding audit qualifier

  audit access all,


=head2 rlimit rules

AppArmor can set and control the resource limits associated with a
profile as described in the setrlimit(2) man page.

The AppArmor rlimit controls allow setting of limits and restricting
changes of them and these actions can be audited. Enforcement of the
set limits is handled by the standard kernel enforcement mechanism
for rlimits and will not result in an audited apparmor message if
the limit is enforced.

If a profile does not have an rlimit rule associated with a given
rlimit then the rlimit is left alone and regular access, including
changing the limit, is allowed. However if the profile sets an rlimit
then the current limit is checked and if greater than the limit specified
in the rule it will be changed to the specified limit.

AppArmor rlimit rules control the hard limit of an application and
ensure that if the hard limit is lowered that the soft limit does not
exceed the hard limit value.

Eg.

  set rlimit data <= 100M,
  set rlimit nproc <= 10,
  set rlimit nice <= 5,

=head2 Variables

AppArmor's policy language allows embedding variables into file rules
to enable easier configuration for some common (and pervasive) setups.
Variables may have multiple values assigned, but any variable assignments
must be made before the start of the profile.

The parser will automatically expand variables to include all values
that they have been assigned; it is an error to reference a variable
without setting at least one value. You can use empty quotes ("") to
explicitly add an empty value.

At the time of this writing, the following variables are defined in the
provided AppArmor policy:

  @{HOME}
  @{HOMEDIRS}
  @{multiarch}
  @{pid}
  @{pids}
  @{PROC}
  @{securityfs}
  @{apparmorfs}
  @{sys}
  @{tid}
  @{run}
  @{XDG_DESKTOP_DIR}
  @{XDG_DOWNLOAD_DIR}
  @{XDG_TEMPLATES_DIR}
  @{XDG_PUBLICSHARE_DIR}
  @{XDG_DOCUMENTS_DIR}
  @{XDG_MUSIC_DIR}
  @{XDG_PICTURES_DIR}
  @{XDG_VIDEOS_DIR}

These are defined in files in F</etc/apparmor.d/tunables> and are used in many
of the abstractions described later.

You may also add files in F</etc/apparmor.d/tunables/home.d> for
site-specific customization of B<@{HOMEDIRS}>,
F</etc/apparmor.d/tunables/multiarch.d> for B<@{multiarch}> and
F</etc/apparmor.d/tunables/xdg-user-dirs.d> for B<@{XDG_*}>.

The special B<@{profile_name}> variable is set to the profile name and may be
used in all policy.

=head3 Notes on variable expansion and the / character

It is important to note that how AppArmor performs variable expansion
depends on the context where a variable is used. When a variable is
expanded it can result in a string with multiple path characters
next to each other, in a way that is not evident when looking at
policy.

Eg.

=over 4

Given the following variable definition and rule

@{HOME}=/home/*/
file rw @{HOME}/*,

The variable expansion results in a rule of

file rw /home/*//*.

=back

When this occurs in a context where a path is expected, AppArmor will
canonicalize the path by collapsing consecutive / characters into
a single character. For the above example, this would be

  file rw /home/*/*,

There is one exception to this rule, when the consecutive / characters
are at the beginning of a path, this indicates a posix namespace
and the characters will not be collapsed.

Eg.

=over 4

@{HOME}=/home/*/
file rw /@{HOME}/*,

will result in an expansion of

file rw //home/*//*,

which is collapsed to

file rw //home/*/*,

Note: that the leading // in the above example is not collapsed to a
single /. However the second // (that was also seen in the first
example) is collapsed.

=back


=head2 Alias rules

AppArmor also provides alias rules for remapping paths for site-specific
layouts. They are an alternative form of path rewriting to using variables,
and are done after variable resolution. Alias rules must occur within the
preamble of the profile. System-wide aliases are found in
F</etc/apparmor.d/tunables/alias>, which is included by
F</etc/apparmor.d/tunables/global>. F</etc/apparmor.d/tunables/global> is
typically included at the beginning of an AppArmor profile.

=head2 Globbing (AARE)

File resources and other parameters accepting an AARE
may be specified with a globbing syntax similar to that
used by popular shells, such as csh(1), bash(1), zsh(1).

=over 4

=item B<*>

can substitute for any number of characters, excepting '/'

=item B<**>

can substitute for any number of characters, including '/'

=item B<?>

can substitute for any single character excepting '/'

=item B<[abc]>

will substitute for the single character a, b, or c

=item B<[a-c]>

will substitute for the single character a, b, or c

=item B<[^a-c]>

will substitute for any single character not matching a, b or c

=item B<{ab,cd}>

will expand to one rule to match ab, one rule to match cd

Can also include variables.

=item B<@{variable}>

will expand to all values assigned to the given variable.

=back

When AppArmor looks up a directory the pathname being looked up will
end with a slash (e.g., F</var/tmp/>); otherwise it will not end with a
slash. Only rules that match a trailing slash will match directories. Some
examples, none matching the F</tmp/> directory itself, are:

=over 4

=item B</tmp/*>

Files directly in F</tmp>.

=item B</tmp/*/>

Directories directly in F</tmp>.

=item B</tmp/**>

Files and directories anywhere underneath F</tmp>.

=item B</tmp/**/>

Directories anywhere underneath F</tmp>.

=back

=head2 Rule Qualifiers

There are several rule qualifiers that can be applied to permission rules.
Rule qualifiers can modify the rule and/or permissions within the rule.

=over 4

=item B<priority>

Specifies the priority of the rule. Currently the allowed range is
-1000 to 1000 with the default priority of rule is 0.  Rules with
higher priority are given preferences and will completely override
permissions of lower priority rules where they overlap. When rules
partially overlap the permissions of the higher priority rule will
completely override lower priority rules within in overlap. Within a
given priority level rules that overlap will accumulate permissions in
the standard apparmor fashion.

=item B<allow>

Specifies that permissions requests that match the rule are allowed. This
is the default value for rules and does not need to be specified. Conflicts
with the I<deny> qualifier.

=item B<audit>

Specifies that permissions requests that match the rule should be recorded
to the audit log.

=item B<deny>

Specifies that permissions requests that match the rule should be denied
without logging. Can be combined with 'audit' to enable logging. Conflicts
with the I<allow> qualifier.

=item B<owner>

Specifies that the task must have the same euid/fsuid as the object being
referenced by the permission check.

=back

=head3 Qualifier Blocks

Rule Qualifiers can be applied to multiple rules at a time by grouping the
rules into a rule block.

  audit {
     /foo r,
     network,
  }

=head2 #include mechanism

AppArmor provides an easy abstraction mechanism to group common
access requirements; this abstraction is an extremely flexible way to
grant site-specific rights and makes writing new AppArmor profiles very
simple by assembling the needed building blocks for any given program.

The use of '#include' is modelled directly after cpp(1); its use will
replace the '#include' statement with the specified file's contents.
The leading '#' is optional, and the '#include' keyword can be followed
by an option conditional 'if exists' that specifies profile compilation
should continue if the specified file or directory is not found.

B<#include "/absolute/path"> specifies that F</absolute/path> should be
used.  B<#include "relative/path"> specifies that F<relative/path> should
be used, where the path is relative to the current working directory.
B<#include E<lt>magic/pathE<gt>> is the most common usage; it will load
F<magic/path> relative to a directory specified to apparmor_parser(8).
F</etc/apparmor.d/> is the AppArmor default.

The supplied AppArmor profiles follow several conventions; the
abstractions stored in F</etc/apparmor.d/abstractions/> are some
large clusters that are used in most profiles. What follows are short
descriptions of how some of the abstractions are used.

=over 4


=item F<abstractions/audio>

Includes accesses to device files used for audio applications.

=item F<abstractions/authentication>

Includes access to files and services typically necessary for services
that perform user authentication.

=item F<abstractions/base>

Includes files that should be readable and writable in all profiles.

=item F<abstractions/bash>

Includes many files used by bash; useful for interactive shells and
programs that call system(3).

=item F<abstractions/consoles>

Includes read and write access to the device files controlling the
virtual console, sshd(8), xterm(1), etc. This abstraction is needed for
many programs that interact with users.

=item F<abstractions/fonts>

Includes access to fonts and the font libraries.

=item F<abstractions/gnome>

Includes read and write access to GNOME configuration files, as well as
read access to GNOME libraries.

=item F<abstractions/kde>

Includes read and write access to KDE configuration files, as well as
read access to KDE libraries.

=item F<abstractions/kerberosclient>

Includes file access rules needed for common kerberos clients.

=item F<abstractions/nameservice>

Includes file rules to allow DNS, LDAP, NIS, SMB, user and group password
databases, services, and protocols lookups.

=item F<abstractions/perl>

Includes read access to perl modules.

=item F<abstractions/user-download>

=item F<abstractions/user-mail>

=item F<abstractions/user-manpages>

=item F<abstractions/user-tmp>

=item F<abstractions/user-write>

Some profiles for typical "user" programs will use these include files
to describe rights that users have in the system.

=item F<abstractions/wutmp>

Includes write access to files used to maintain wtmp(5) and utmp(5)
databases, used with the w(1) and associated commands.

=item F<abstractions/X>

Includes read access to libraries, configuration files, X authentication
files, and the X socket.

=back

Some of the abstractions rely on variables that are set in files in the
F</etc/apparmor.d/tunables/> directory. These variables are currently
B<@{HOME}> and B<@{HOMEDIRS}>. Variables cannot be set in profile scope;
they can only be set before the profile. Therefore, any profiles that
use abstractions should either B<#include E<lt>tunables/globalE<gt>> or
otherwise ensure that B<@{HOME}> and B<@{HOMEDIRS}> are set before
starting the profile definition. The aa-autodep(8) and aa-genprof(8) utilities
will automatically emit B<#include E<lt>tunables/globalE<gt>> in
generated profiles.

=head2 Feature ABI

The feature abi tells AppArmor which feature set the policy was
developed under. This is important to ensure that kernels with a
different feature set don't enforce features that the policy doesn't
support, which can result in unexpected application failures.

When policy is compiled both the kernel feature abi and policy feature
abi are consulted to build a policy that will work for the system's
kernel.

If the kernel supports a feature not supported by the policy then
policy will be built so that the kernel does NOT enforce that feature.

If the policy supports a feature not supported by the kernel the
compile may downgrade the rule with the feature to something the
kernel supports, drop the rule completely, or fail the compile.

If the policy abi is specified as B<kernel> then the running kernel's
abi will be used. This should never be used in shipped policy as it
can cause system breakage when a new kernel is installed.

=head3 ABI compatibility with AppArmor 2.x

AppArmor 3 remains compatible with AppArmor 2.x by detecting when a
profile does not have a feature ABI specified. In this case the policy
compile will either apply the pinned feature ABI as specified by the
config file or the command line, or if neither of those are applied by
using a default feature ABI.

It is important to note that the default feature ABI does not support
new features added in AppArmor 3 or later.

=head1 EXAMPLE

An example AppArmor profile:

	# which feature abi the policy was developed with
        abi <abi/3.0>,

	# a variable definition in the preamble
	@{HOME} = /home/*/ /root/

	# a comment about foo.
	/usr/bin/foo {
	  /bin/mount          ux,
  	  /dev/{,u}random     r,
  	  /etc/ld.so.cache    r,
  	  /etc/foo.conf       r,
  	  /etc/foo/*          r,
  	  /lib/ld-*.so*       rmix,
  	  /lib/lib*.so*       r,
  	  /proc/[0-9]**       r,
  	  /usr/lib/**         r,
  	  /tmp/foo.pid        wr,
  	  /tmp/foo.*          lrw,
	  @{HOME}/.foo_file  rw,
	  /usr/bin/baz        Cx -> baz,

	  # a comment about foo's hat (subprofile), bar.
  	  ^bar {
  	    /lib/ld-*.so*       rmix,
  	    /usr/bin/bar        rmix,
  	    /var/spool/*        rwl,
  	  }

	  # a comment about foo's subprofile, baz.
	  profile baz {
	    #include <abstractions/bash>
	    owner /proc/[0-9]*/stat r,
	    /bin/bash ixr,
	    /var/lib/baz/ r,
	    owner /var/lib/baz/* rw,
	  }
  	}

=head1 FILES

=over 4

=item F</etc/apparmor.d/>

=back

=head1 KNOWN BUGS

=over 4

=item *

Mount options support the use of pattern matching but mount flags are not
correctly intersected against specified patterns. Eg, 'mount options=**,'
should be equivalent to 'mount,', but it is not. (LP: #965690)

=item *

The fstype may not be matched against when certain mount command flags are
used. Specifically fstype matching currently only works when creating a new
mount and not remount, bind, etc.

=item *

Mount rules with multiple 'options' conditionals are not applied as documented
but instead merged such that 'options in (ro,nodev) options in (atime)' is
equivalent to 'options in (ro,nodev,atime)'.

=item *

When specifying mount options with the 'in' conditional, both the positive and
negative values match when specifying one or the other. Eg, 'rw' matches when
'ro' is specified and 'dev' matches when 'nodev' is specified such that
'options in (ro,nodev)' is equivalent to 'options in (rw,dev)'.

=back

=head1 SEE ALSO

apparmor(7), apparmor_parser(8), apparmor_xattrs(7), aa-complain(1),
aa-enforce(1), aa_change_hat(2), aa_change_profile(2), mod_apparmor(5), and
L<https://wiki.apparmor.net>.

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