apparmor

APPARMOR(7)                        AppArmor                        APPARMOR(7)

NAME
       AppArmor - kernel enhancement to confine programs to a limited set of
       resources.

DESCRIPTION
       AppArmor is a kernel enhancement to confine programs to a limited set
       of resources. AppArmor's unique security model is to bind access
       control attributes to programs rather than to users.

       AppArmor confinement is provided via profiles loaded into the kernel
       via apparmor_parser(8), typically through the /etc/init.d/apparmor SysV
       initscript, which is used like this:

               # /etc/init.d/apparmor start
               # /etc/init.d/apparmor stop
               # /etc/init.d/apparmor restart

       AppArmor can operate in two modes: enforcement, and complain or
       learning:

       o   enforcement -  Profiles loaded in enforcement mode will result in
           enforcement of the policy defined in the profile as well as
           reporting policy violation attempts to syslogd.

       o   complain - Profiles loaded in  "complain" mode will not enforce
           policy.  Instead, it will report policy violation attempts. This
           mode is convenient for developing profiles. To manage complain mode
           for individual profiles the utilities aa-complain(8) and
           aa-enforce(8) can be used.  These utilities take a program name as
           an argument.

       Profiles are traditionally stored in files in /etc/apparmor.d/ under
       filenames with the convention of replacing the / in pathnames with .
       (except for the root /) so profiles are easier to manage (e.g. the
       /usr/sbin/nscd profile would be named usr.sbin.nscd).

       Profiles are applied to a process at exec(3) time (as seen through the
       execve(2) system call): once a profile is loaded for a program, that
       program will be confined on the next exec(3). If a process is already
       running under a profile, when one replaces that profile in the kernel,
       the updated profile is applied immediately to that process.  On the
       other hand, a process that is already running unconfined cannot be
       confined.

       AppArmor supports the Linux kernel's securityfs filesystem, and makes
       available the list of the profiles currently loaded; to mount the
       filesystem:

               # mount -tsecurityfs securityfs /sys/kernel/security
               $ cat /sys/kernel/security/apparmor/profiles
               /usr/bin/mutt
               /usr/bin/gpg
                  ...

       Normally, the initscript will mount securityfs if it has not already
       been done.

       AppArmor also restricts what privileged operations a confined process
       may execute, even if the process is running as root. A confined process
       cannot call the following system calls:

               create_module(2) delete_module(2) init_module(2) ioperm(2)
               iopl(2) ptrace(2) reboot(2) setdomainname(2)
               sethostname(2) swapoff(2) swapon(2) sysctl(2)

ERRORS
       When a confined process tries to access a file it does not have
       permission to access, the kernel will report a message through audit,
       similar to:

               audit(1386511672.612:238): apparmor="DENIED" operation="exec"
                 parent=7589 profile="/tmp/sh" name="/bin/uname" pid=7605
                 comm="sh" requested_mask="x" denied_mask="x" fsuid=0 ouid=0

               audit(1386511672.613:239): apparmor="DENIED" operation="open"
                 parent=7589 profile="/tmp/sh" name="/bin/uname" pid=7605
                 comm="sh" requested_mask="r" denied_mask="r" fsuid=0 ouid=0

               audit(1386511772.804:246): apparmor="DENIED" operation="capable"
                 parent=7246 profile="/tmp/sh" pid=7589 comm="sh" pid=7589
                 comm="sh" capability=2  capname="dac_override"

       The permissions requested by the process are described in the
       operation= and denied_mask= (for files - capabilities etc. use a
       slightly different log format).  The "name" and process id of the
       running program are reported, as well as the profile name including any
       "hat" that may be active, separated by "//". ("Name" is in quotes,
       because the process name is limited to 15 bytes; it is the same as
       reported through the Berkeley process accounting.)

       For confined processes running under a profile that has been loaded in
       complain mode, enforcement will not take place and the log messages
       reported to audit will be of the form:

               audit(1386512577.017:275): apparmor="ALLOWED" operation="open"
                 parent=8012 profile="/usr/bin/du" name="/etc/apparmor.d/tunables/"
                 pid=8049 comm="du" requested_mask="r" denied_mask="r" fsuid=1000 ouid=0

               audit(1386512577.017:276): apparmor="ALLOWED" operation="open"
                 parent=8012 profile="/usr/bin/du" name="/etc/apparmor.d/tunables/"
                 pid=8049 comm="du" requested_mask="r" denied_mask="r" fsuid=1000 ouid=0

       If the userland auditd is not running, the kernel will send audit
       events to klogd; klogd will send the messages to syslog, which will log
       the messages with the KERN facility. Thus, REJECTING and PERMITTING
       messages may go to either /var/log/audit/audit.log or
       /var/log/messages, depending upon local configuration.

DEBUGGING
       AppArmor provides a few facilities to log more information, which can
       help debugging profiles.

   Enable debug mode
       When debug mode is enabled, AppArmor will log a few extra messages to
       dmesg (not via the audit subsystem). For example, the logs will tell
       whether environment scrubbing has been applied.

       To enable debug mode, run:

               echo 1 > /sys/module/apparmor/parameters/debug

   Turn off deny audit quieting
       By default, operations that trigger "deny" rules are not logged.  This
       is called deny audit quieting.

       To turn off deny audit quieting, run:

               echo -n noquiet >/sys/module/apparmor/parameters/audit

   Force audit mode
       AppArmor can log a message for every operation that triggers a rule
       configured in the policy. This is called force audit mode.

       Warning! Force audit mode can be extremely noisy even for a single
       profile, let alone when enabled globally.

       To set a specific profile in force audit mode, add the "audit" flag:

               profile foo flags=(audit) { ... }

       To enable force audit mode globally, run:

               echo -n all > /sys/module/apparmor/parameters/audit

       If auditd is not running, to avoid losing too many of the extra log
       messages, you will likely have to turn off rate limiting by doing:

               echo 0 > /proc/sys/kernel/printk_ratelimit

       But even then the kernel ring buffer may overflow and you might lose
       messages.

       Else, if auditd is running, see auditd(8) and auditd.conf(5).

FILES
       /etc/init.d/apparmor
       /etc/apparmor.d/
       /var/lib/apparmor/
       /var/log/audit/audit.log
       /var/log/messages

SEE ALSO
       apparmor_parser(8), aa_change_hat(2), apparmor.d(5), aa-autodep(1),
       clean(1), auditd(8), aa-unconfined(8), aa-enforce(1), aa-complain(1),
       and <https://wiki.apparmor.net>.

AppArmor 2.13.3                   2023-10-10                       APPARMOR(7)