Provided by: apparmor_4.0.0~alpha2-0ubuntu5_amd64 
NAME
apparmor.d - syntax of security profiles for AppArmor.
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.
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; #
introduces a comment, similar to shell scripting languages. The exception to this rule is
that #include will include the contents of a file inline to the policy; this behaviour is
modelled after cpp(1).
PROFILE FILE = ( [ PREAMBLE ] [ PROFILE ] )*
PREAMBLE = ( COMMENT | VARIABLE ASSIGNMENT | ALIAS RULE | INCLUDE | ABI )*
Variable assignment and alias rules must come before the profile.
VARIABLE ASSIGNMENT = VARIABLE ('=' | '+=') (space separated values)
VARIABLE = '@{' ALPHA [ ( ALPHANUMERIC | '_' ) ... ] '}'
ALIAS RULE = 'alias' ABS PATH '->' REWRITTEN ABS PATH ','
INCLUDE = ( '#include' | 'include' ) [ 'if exists' ] ( ABS PATH | MAGIC PATH )
ABI = ( 'abi' ) ( ABS PATH | MAGIC PATH ) ','
ABS PATH = '"' path '"' (the path is passed to open(2))
MAGIC PATH = '<' relative path '>'
The path is relative to /etc/apparmor.d/.
COMMENT = '#' TEXT [ '\r' ] '\n'
TEXT = any characters
PROFILE = ( PROFILE HEAD ) [ ATTACHMENT SPECIFICATION ] [ PROFILE FLAG CONDS ] '{' (
RULES )* '}'
PROFILE HEAD = [ 'profile' ] FILEGLOB | 'profile' PROFILE NAME
PROFILE NAME ( UNQUOTED PROFILE NAME | QUOTED PROFILE NAME )
QUOTED PROFILE NAME = '"' UNQUOTED PROFILE NAME '"'
UNQUOTED PROFILE NAME = (must start with alphanumeric character (after variable
expansion), or '/' AARE have special meanings; see below. May include VARIABLE. Rules
with embedded spaces or tabs must be quoted.)
ATTACHMENT SPECIFICATION = [ PROFILE_EXEC_COND ] [ PROFILE XATTR CONDS ]
PROFILE_EXEC_COND = FILEGLOB
PROFILE XATTR CONDS = [ 'xattrs=' ] '(' comma or white space separated list of
PROFILE XATTR ')'
PROFILE XATTR = extended attribute name '=' XATTR VALUE FILEGLOB
XATTR VALUE FILEGLOB = FILEGLOB
PROFILE FLAG CONDS = [ 'flags=' ] '(' comma or white space separated list of PROFILE
FLAGS ')'
PROFILE FLAGS = PROFILE MODE | AUDIT_MODE | 'mediate_deleted' | 'attach_disconnected'
| 'attach_disconneced.path='ABS PATH | 'chroot_relative' | 'debug'
PROFILE MODE = 'enforce' | 'complain' | 'kill' | 'unconfined' | 'prompt'
AUDIT MODE = 'audit'
RULES = [ ( LINE RULES | COMMA RULES ',' | BLOCK RULES )
LINE RULES = ( COMMENT | INCLUDE ) [ '\r' ] '\n'
COMMA RULES = ( CAPABILITY RULE | NETWORK RULE | MOUNT RULE | PIVOT ROOT RULE | UNIX
RULE | FILE RULE | LINK RULE | CHANGE_PROFILE RULE | RLIMIT RULE | DBUS RULE | MQUEUE
RULE )
BLOCK RULES = ( SUBPROFILE | HAT | QUALIFIER BLOCK )
SUBPROFILE = 'profile' PROFILE NAME [ ATTACHMENT SPECIFICATION ] [ PROFILE FLAG CONDS
] '{' ( RULES )* '}'
HAT = ('hat' | '^') HATNAME [ PROFILE FLAG CONDS ] '{' ( RULES )* '}'
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 HATNAME)
QUALIFIER BLOCK = QUALIFIERS BLOCK
ACCESS TYPE = ( 'allow' | 'deny' )
QUALIFIERS = [ 'audit' ] [ ACCESS TYPE ]
CAPABILITY RULE = [ QUALIFIERS ] 'capability' [ CAPABILITY LIST ]
CAPABILITY LIST = ( CAPABILITY )+
CAPABILITY = (lowercase capability name without 'CAP_' prefix; see capabilities(7))
NETWORK RULE = [ QUALIFIERS ] 'network' [ DOMAIN ] [ TYPE | PROTOCOL ]
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' ) ','
TYPE = ( 'stream' | 'dgram' | 'seqpacket' | 'rdm' | 'raw' | 'packet' )
PROTOCOL = ( 'tcp' | 'udp' | 'icmp' )
MOUNT RULE = ( MOUNT | REMOUNT | UMOUNT )
MOUNT = [ QUALIFIERS ] 'mount' [ MOUNT CONDITIONS ] [ SOURCE FILEGLOB ] [ '->' [
MOUNTPOINT FILEGLOB ]
REMOUNT = [ QUALIFIERS ] 'remount' [ MOUNT CONDITIONS ] MOUNTPOINT FILEGLOB
UMOUNT = [ QUALIFIERS ] 'umount' [ MOUNT CONDITIONS ] MOUNTPOINT FILEGLOB
MOUNT CONDITIONS = [ ( 'fstype' | 'vfstype' ) ( '=' | 'in' ) MOUNT FSTYPE EXPRESSION ]
[ 'options' ( '=' | 'in' ) MOUNT FLAGS EXPRESSION ]
MOUNT FSTYPE EXPRESSION = ( MOUNT FSTYPE LIST | MOUNT EXPRESSION )
MOUNT FSTYPE LIST = Comma separated list of valid filesystem and virtual filesystem
types (eg ext4, debugfs, devfs, etc)
MOUNT FLAGS EXPRESSION = ( MOUNT FLAGS LIST | MOUNT EXPRESSION )
MOUNT FLAGS LIST = Comma separated list of MOUNT FLAGS.
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' )
MOUNT EXPRESSION = ( ALPHANUMERIC | AARE ) ...
MQUEUE_RULE = [ QUALIFIERS ] 'mqueue' [ MQUEUE ACCESS PERMISSIONS ] [ MQUEUE TYPE ] [
MQUEUE LABEL ] [ MQUEUE NAME ]
MQUEUE ACCESS PERMISSIONS = MQUEUE ACCESS | MQUEUE ACCESS LIST
MQUEUE ACCESS LIST = '(' Comma or space separated list of MQUEUE ACCESS ')'
MQUEUE ACCESS = ( 'r' | 'w' | 'rw' | 'read' | 'write' | 'create' | 'open' | 'delete' |
'getattr' | 'setattr' )
MQUEUE TYPE = 'type' '=' ( 'posix' | 'sysv' )
MQUEUE LABEL = 'label' '=' '(' '"' AARE '"' | AARE ')'
MQUEUE NAME = AARE
PIVOT ROOT RULE = [ QUALIFIERS ] pivot_root [ oldroot=OLD PUT FILEGLOB ] [ NEW ROOT
FILEGLOB ] [ '->' PROFILE NAME ]
SOURCE FILEGLOB = FILEGLOB
MOUNTPOINT FILEGLOB = FILEGLOB
OLD PUT FILEGLOB = FILEGLOB
PTRACE_RULE = [ QUALIFIERS ] 'ptrace' [ PTRACE ACCESS PERMISSIONS ] [ PTRACE PEER ]
PTRACE ACCESS PERMISSIONS = PTRACE ACCESS | PTRACE ACCESS LIST
PTRACE ACCESS LIST = '(' Comma or space separated list of PTRACE ACCESS ')'
PTRACE ACCESS = ( 'r' | 'w' | 'rw' | 'read' | 'readby' | 'trace' | 'tracedby' )
PTRACE PEER = 'peer' '=' AARE
SIGNAL_RULE = [ QUALIFIERS ] 'signal' [ SIGNAL ACCESS PERMISSIONS ] [ SIGNAL SET ] [
SIGNAL PEER ]
SIGNAL ACCESS PERMISSIONS = SIGNAL ACCESS | SIGNAL ACCESS LIST
SIGNAL ACCESS LIST = '(' Comma or space separated list of SIGNAL ACCESS ')'
SIGNAL ACCESS = ( 'r' | 'w' | 'rw' | 'read' | 'write' | 'send' | 'receive' )
SIGNAL SET = 'set' '=' '(' SIGNAL LIST ')'
SIGNAL LIST = Comma or space separated list of SIGNALS
SIGNALS = ( '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' )
SIGNAL PEER = 'peer' '=' AARE
DBUS RULE = ( DBUS MESSAGE RULE | DBUS SERVICE RULE | DBUS EAVESDROP RULE | DBUS
COMBINED RULE )
DBUS MESSAGE RULE = [ QUALIFIERS ] 'dbus' [ DBUS ACCESS EXPRESSION ] [ DBUS BUS ] [
DBUS PATH ] [ DBUS INTERFACE ] [ DBUS MEMBER ] [ DBUS PEER ]
DBUS SERVICE RULE = [ QUALIFIERS ] 'dbus' [ DBUS ACCESS EXPRESSION ] [ DBUS BUS ] [
DBUS NAME ]
DBUS EAVESDROP RULE = [ QUALIFIERS ] 'dbus' [ DBUS ACCESS EXPRESSION ] [ DBUS BUS ]
DBUS COMBINED RULE = [ QUALIFIERS ] 'dbus' [ DBUS ACCESS EXPRESSION ] [ DBUS BUS ]
DBUS ACCESS EXPRESSION = ( DBUS ACCESS | '(' DBUS ACCESS LIST ')' )
DBUS BUS = 'bus' '=' '(' 'system' | 'session' | '"' AARE '"' | AARE ')'
DBUS PATH = 'path' '=' '(' '"' AARE '"' | AARE ')'
DBUS INTERFACE = 'interface' '=' '(' '"' AARE '"' | AARE ')'
DBUS MEMBER = 'member' '=' '(' '"' AARE '"' | AARE ')'
DBUS PEER = 'peer' '=' '(' [ DBUS NAME ] [ DBUS LABEL ] ')'
DBUS NAME = 'name' '=' '(' '"' AARE '"' | AARE ')'
DBUS LABEL = 'label' '=' '(' '"' AARE '"' | AARE ')'
DBUS ACCESS LIST = Comma separated list of DBUS ACCESS
DBUS ACCESS = ( 'send' | 'receive' | 'bind' | 'eavesdrop' | 'r' | 'read' | 'w' |
'write' | 'rw' )
Some accesses are incompatible with some rules; see below.
UNIX RULE = [ QUALIFIERS ] 'unix' [ UNIX ACCESS EXPR ] [ UNIX RULE CONDS ] [ UNIX
LOCAL EXPR ] [ UNIX PEER EXPR ]
UNIX ACCESS EXPR = ( UNIX ACCESS | UNIX ACCESS LIST )
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.
UNIX ACCESS LIST = '(' UNIX ACCESS ( [','] UNIX ACCESS )* ')'
UNIX RULE CONDS = ( TYPE COND | PROTO COND )
Each cond can appear at most once.
TYPE COND = 'type' '=' ( AARE | '(' ( '"' AARE '"' | AARE )+ ')' )
PROTO COND = 'protocol' '=' ( AARE | '(' ( '"' AARE '"' | AARE )+ ')' )
UNIX LOCAL EXPR = ( UNIX ADDRESS COND | UNIX LABEL COND | UNIX ATTR COND | UNIX OPT
COND )*
Each cond can appear at most once.
UNIX PEER EXPR = 'peer' '=' ( UNIX ADDRESS COND | UNIX LABEL COND )+
Each cond can appear at most once.
UNIX ADDRESS COND 'addr' '=' ( AARE | '(' '"' AARE '"' | AARE ')' )
UNIX LABEL COND 'label' '=' ( AARE | '(' '"' AARE '"' | AARE ')' )
UNIX ATTR COND 'attr' '=' ( AARE | '(' '"' AARE '"' | AARE ')' )
UNIX OPT COND 'opt' '=' ( AARE | '(' '"' AARE '"' | AARE ')' )
RLIMIT RULE = 'set' 'rlimit' [RLIMIT '<=' RLIMIT VALUE ]
RLIMIT = ( 'cpu' | 'fsize' | 'data' | 'stack' | 'core' | 'rss' | 'nofile' | 'ofile' |
'as' | 'nproc' | 'memlock' | 'locks' | 'sigpending' | 'msgqueue' | 'nice' | 'rtprio' |
'rttime' )
RLIMIT VALUE = ( RLIMIT SIZE | RLIMIT NUMBER | RLIMIT TIME | RLIMIT NICE )
RLIMIT SIZE = NUMBER ( 'K' | 'M' | 'G' )
Only applies to RLIMIT of 'fsize', 'data', 'stack', 'core', 'rss', 'as', 'memlock',
'msgqueue'.
RLIMIT NUMBER = number from 0 to max rlimit value.
Only applies to RLIMIT of 'ofile', 'nofile', 'locks', 'sigpending', 'nproc',
'rtprio'.
RLIMIT TIME = 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 >=
'seconds'.
RLIMIT NICE = a number between -20 and 19.
Only applies to RLIMIT of 'nice'.
FILE RULE = [ QUALIFIERS ] [ 'owner' ] ( 'file' | [ 'file' ] ( FILEGLOB ACCESS |
ACCESS FILEGLOB ) [ '->' EXEC TARGET ] )
FILEGLOB = ( QUOTED FILEGLOB | UNQUOTED FILEGLOB )
QUOTED FILEGLOB = '"' UNQUOTED FILEGLOB '"'
UNQUOTED FILEGLOB = (must start with '/' (after variable expansion), AARE have special
meanings; see below. May include VARIABLE. Rules with embedded spaces or tabs must be
quoted. Rules must end with '/' to apply to directories.)
AARE = ?*[]{}^
See section "Globbing (AARE)" below for meanings.
ACCESS = ( 'r' | 'w' | 'a' | 'l' | 'k' | 'm' | EXEC TRANSITION )+ (not all
combinations are allowed; see below.)
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.
EXEC TARGET = name
Requires EXEC TRANSITION specified.
LINK RULE = QUALIFIERS [ 'owner' ] 'link' [ 'subset' ] FILEGLOB '->' FILEGLOB
ALPHA = ('a', 'b', 'c', ... 'z', 'A', 'B', ... 'Z')
ALPHANUMERIC = ('0', '1', '2', ... '9', 'a', 'b', 'c', ... 'z', 'A', 'B', ... 'Z')
CHANGE_PROFILE RULE = 'change_profile' [ [ EXEC MODE ] EXEC COND ] [ '->' PROFILE NAME
]
EXEC_MODE = ( 'safe' | 'unsafe' )
EXEC COND = FILEGLOB
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 change_profile(2) transition permanently to the specified profile. libvirt
is one such application.
Profile Head
The profile head consists of a required name that is unique and optional attachment
conditionals and control flags.
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. firefox for the firefox web
browser or its functional role eg. log_admin.
If the name is an applications full absolute path name eg. /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.
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.
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 px or cx (or their derivatives) transition type. The exec
attachment conditional will also be used by tasks that are unconfined as they use a 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 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.
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.
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.
Profile Mode
The profile mode allow controlling the enforcement behavior of the profile rules.
If no mode is specified the profile defaults to enforce mode.
enforce For a given action, if the profile rules do not grant permission the action will
be denied, with an EACCES or EPERM error code returned to userspace, and the violation
will be logged with a tag of the access being DENIED.
kill This is a variant of enforce mode where in addition to returning EACCES or EPERM for
a violation, the task is also sent a signal to kill it.
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 ALLOWED.
unconfined This mode allows a task confined by the profile to behave as though they are
unconfined. This mode allow for an unconfined behavior that can be later changed to
confinement by using profile replacement. This mode is should not be used under regular
deployment but can be useful during debugging and some system initialization scenarios.
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.
Audit Mode
The audit mode allows control of how AppArmor messages are are logged to the audit system.
audit This flag causes all actions whether allowed or denied to be logged.
Misc modes
mediate_deleted This forces AppArmor to mediate deleted files as if they still exist in
the file system.
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.
attach_disconnected.path=ABS PATH Like attach_disconnected, but attach disconnected
objects to the supplied path instead of the root of the namespace.
chroot_relative This forces file names to be relative to a chroot and behave as if the
chroot is a mount namespace.
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.
Access Modes
File permission access modes consists of combinations of the following modes:
r - read
w - write -- conflicts with append
a - append -- conflicts with write
ux - unconfined execute
Ux - unconfined execute -- scrub the environment
px - discrete profile execute
Px - discrete profile execute -- scrub the environment
cx - transition to subprofile on execute
Cx - transition to subprofile on execute -- scrub the environment
ix - inherit execute
pix - discrete profile execute with inherit fallback
Pix - discrete profile execute with inherit fallback -- scrub the environment
cix - transition to subprofile on execute with inherit fallback
Cix - transition to subprofile on execute with inherit fallback -- scrub the
environment
pux - discrete profile execute with fallback to unconfined
PUx - discrete profile execute with fallback to unconfined -- scrub the environment
cux - transition to subprofile on execute with fallback to unconfined
CUx - transition to subprofile on execute with fallback to unconfined -- scrub the
environment
deny x - disallow execute (in rules with the deny qualifier)
m - allow PROT_EXEC with mmap(2) calls
l - link
k - lock
Access Modes Details
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.
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.
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.
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.
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 scrub the
environment of 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.
Ux - unconfined execute -- scrub the environment
'Ux' allows the named program to run in 'ux' mode, but AppArmor will invoke the Linux
Kernel's unsafe_exec routines to scrub the environment, similar to setuid programs.
(See ld.so(8) for some information on setuid/setgid environment scrubbing.)
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.
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.
WARNING 'px' does not scrub the environment of 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.
Px - Discrete Profile execute mode -- scrub the environment
'Px' allows the named program to run in 'px' mode, but AppArmor will invoke the Linux
Kernel's unsafe_exec routines to scrub the environment, similar to setuid programs.
(See ld.so(8) for some information on setuid/setgid environment scrubbing.)
Incompatible with other exec transition modes and the deny qualifier.
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.
WARNING 'cx' does not scrub the environment of 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.
Cx - Transition to Subprofile execute mode -- scrub the environment
'Cx' allows the named program to run in 'cx' mode, but AppArmor will invoke the Linux
Kernel's unsafe_exec routines to scrub the environment, similar to setuid programs.
(See ld.so(8) for some information on setuid/setgid environment scrubbing.)
Incompatible with other exec transition modes and the deny qualifier.
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 scrub the environment because 'ix'
executions don't change privileges.
Incompatible with other exec transition modes and the deny qualifier.
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.
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.
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.
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 '->' followed by the
name of the profile to transition to. Eg.
/bin/** px -> profile,
Incompatible with other exec transition modes.
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 -L flags given to ld(1) and LD_PRELOAD, LD_LIBRARY_PATH, given to
ld.so(8).
l - Link mode
Allows the program to be able to create a link with this name. When a link is
created, the new link 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.
k - lock mode
Allows the program to be able lock a file with this name. This permission covers both
advisory and mandatory locking.
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
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 -> /**,
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.
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.
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. There is no mediation
based of port number or protocol beyond tcp, udp, and raw. 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
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:
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 -E<gt> /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
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
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
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:
mount,
the 'mount' rule without any conditionals is the most generic and allows any mount.
Equivalent to 'mount fstype=** options=** ** -> /**'.
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
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
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
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
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
mount -> /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
mount options=ro -> /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
mount fstype=ext3 options=(rw,atime) /dev/sdb1 -> /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
mount options=(ro, atime) options in (nodev, user) /dev/foo -> /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
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,
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 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,
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,
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),
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,
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.
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 @ 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 \000 or \x00. The pattern
matching is the same as is used by file path matching so * will not match / 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 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 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 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 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.
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.
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),
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.
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,
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 unsafe_exec routines should be
used to scrub the environment, similar to setuid programs. (See ld.so(8) for some
information on setuid/setgid environment scrubbing.) The safe mode sets up environment
scrubbing to occur when the new application is executed and unsafe mode disables
AppArmor's requirement for environment scrubbing (the kernel and/or libc may still require
environment scrubbing). An exec mode can only be specified when an exec condition is
present.
change_profile safe /bin/bash -> new_profile,
Not all kernels support safe mode and the parser will downgrade rules to unsafe mode in
that situation. If no exec mode is specified, the default is safe mode in kernels that
support it.
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,
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 /etc/apparmor.d/tunables and are used in many of the
abstractions described later.
You may also add files in /etc/apparmor.d/tunables/home.d for site-specific customization
of @{HOMEDIRS}, /etc/apparmor.d/tunables/multiarch.d for @{multiarch} and
/etc/apparmor.d/tunables/xdg-user-dirs.d for @{XDG_*}.
The special @{profile_name} variable is set to the profile name and may be used in all
policy.
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 /etc/apparmor.d/tunables/alias, which is included by
/etc/apparmor.d/tunables/global. /etc/apparmor.d/tunables/global is typically included at
the beginning of an AppArmor profile.
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).
* can substitute for any number of characters, excepting '/'
** can substitute for any number of characters, including '/'
? can substitute for any single character excepting '/'
[abc]
will substitute for the single character a, b, or c
[a-c]
will substitute for the single character a, b, or c
[^a-c]
will substitute for any single character not matching a, b or c
{ab,cd}
will expand to one rule to match ab, one rule to match cd
Can also include variables.
@{variable}
will expand to all values assigned to the given variable.
When AppArmor looks up a directory the pathname being looked up will end with a slash
(e.g., /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 /tmp/ directory
itself, are:
/tmp/*
Files directly in /tmp.
/tmp/*/
Directories directly in /tmp.
/tmp/**
Files and directories anywhere underneath /tmp.
/tmp/**/
Directories anywhere underneath /tmp.
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.
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 deny
qualifier.
audit
Specifies that permissions requests that match the rule should be recorded to the
audit log.
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 allow
qualifier.
owner
Specifies that the task must have the same euid/fsuid as the object being referenced
by the permission check.
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,
}
#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.
#include "/absolute/path" specifies that /absolute/path should be used. #include
"relative/path" specifies that relative/path should be used, where the path is relative to
the current working directory. #include <magic/path> is the most common usage; it will
load magic/path relative to a directory specified to apparmor_parser(8). /etc/apparmor.d/
is the AppArmor default.
The supplied AppArmor profiles follow several conventions; the abstractions stored in
/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.
abstractions/audio
Includes accesses to device files used for audio applications.
abstractions/authentication
Includes access to files and services typically necessary for services that perform
user authentication.
abstractions/base
Includes files that should be readable and writable in all profiles.
abstractions/bash
Includes many files used by bash; useful for interactive shells and programs that call
system(3).
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.
abstractions/fonts
Includes access to fonts and the font libraries.
abstractions/gnome
Includes read and write access to GNOME configuration files, as well as read access to
GNOME libraries.
abstractions/kde
Includes read and write access to KDE configuration files, as well as read access to
KDE libraries.
abstractions/kerberosclient
Includes file access rules needed for common kerberos clients.
abstractions/nameservice
Includes file rules to allow DNS, LDAP, NIS, SMB, user and group password databases,
services, and protocols lookups.
abstractions/perl
Includes read access to perl modules.
abstractions/user-download
abstractions/user-mail
abstractions/user-manpages
abstractions/user-tmp
abstractions/user-write
Some profiles for typical "user" programs will use these include files to describe
rights that users have in the system.
abstractions/wutmp
Includes write access to files used to maintain wtmp(5) and utmp(5) databases, used
with the w(1) and associated commands.
abstractions/X
Includes read access to libraries, configuration files, X authentication files, and
the X socket.
Some of the abstractions rely on variables that are set in files in the
/etc/apparmor.d/tunables/ directory. These variables are currently @{HOME} and
@{HOMEDIRS}. Variables cannot be set in profile scope; they can only be set before the
profile. Therefore, any profiles that use abstractions should either #include
<tunables/global> or otherwise ensure that @{HOME} and @{HOMEDIRS} are set before starting
the profile definition. The aa-autodep(8) and aa-genprof(8) utilities will automatically
emit #include <tunables/global> in generated profiles.
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 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.
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.
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,
}
}
FILES
/etc/init.d/boot.apparmor
/etc/apparmor.d/
KNOWN BUGS
• 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)
• 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.
• 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)'.
• 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)'.
SEE ALSO
apparmor(7), apparmor_parser(8), apparmor_xattrs(7), aa-complain(1), aa-enforce(1),
aa_change_hat(2), mod_apparmor(5), and <https://wiki.apparmor.net>.