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Filename : rc.apparmor.functions
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#!/bin/sh
# ----------------------------------------------------------------------
#    Copyright (c) 1999-2008 NOVELL (All rights reserved)
#    Copyright (c) 2009-2018 Canonical Ltd. (All rights reserved)
#
#    This program is free software; you can redistribute it and/or
#    modify it under the terms of version 2 of the GNU General Public
#    License published by the Free Software Foundation.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU General Public License for more details.
#
#    You should have received a copy of the GNU General Public License
#    along with this program; if not, contact Novell, Inc.
# ----------------------------------------------------------------------
# rc.apparmor.functions by Steve Beattie
#
# NOTE: rc.apparmor initscripts that source this file need to implement
# the following set of functions:
#	aa_action
#	aa_log_action_start
#	aa_log_action_end
#	aa_log_success_msg
#	aa_log_warning_msg
#	aa_log_failure_msg
#	aa_log_skipped_msg
#	aa_log_daemon_msg
#	aa_log_end_msg

# Some nice defines that we use

PARSER=/sbin/apparmor_parser
PARSER_OPTS=--write-cache
# Suppress warnings when booting in quiet mode
if [ "${QUIET:-no}" = yes ] || [ "${quiet:-n}" = y ]; then
	PARSER_OPTS="$PARSER_OPTS --quiet"
fi

if [ -d /etc/apparmor.d ] ; then
	PROFILE_DIRS=/etc/apparmor.d
else
	aa_log_warning_msg "Unable to find profiles directory, installation problem?"
fi

# Eg. snapd policy might need this on some systems if loading policy
#     during early boot if not using the snapd unit file
ADDITIONAL_PROFILE_DIR=
if [ -n "$ADDITIONAL_PROFILE_DIR" ] && [ -d "$ADDITIONAL_PROFILE_DIR" ]; then
	PROFILE_DIRS="$PROFILE_DIRS $ADDITIONAL_PROFILE_DIR"
fi
AA_STATUS=/usr/sbin/aa-status
SECURITYFS=/sys/kernel/security
SFS_MOUNTPOINT="${SECURITYFS}/apparmor"

# keep exit status from parser during profile load.  0 is good, 1 is bad
STATUS=0

# Test if the apparmor "module" is present.
is_apparmor_present() {
	[ -d /sys/module/apparmor ]
}

# Checks to see if the current container is capable of having internal AppArmor
# profiles that should be loaded. Callers of this function should have already
# verified that they're running inside of a container environment with
# something like `systemd-detect-virt --container`.
#
# The only known container environments capable of supporting internal policy
# are LXD and LXC environments, and Windows Subsystem for Linux.
#
# Returns 0 if the container environment is capable of having its own internal
# policy and non-zero otherwise.
#
# IMPORTANT: This function will return 0 in the case of a non-LXD/non-LXC
# system container technology being nested inside of a LXD/LXC container that
# utilized an AppArmor namespace and profile stacking. The reason 0 will be
# returned is because .ns_stacked will be "yes" and .ns_name will still match
# "lx[dc]-*" since the nested system container technology will not have set up
# a new AppArmor profile namespace. This will result in the nested system
# container's boot process to experience failed policy loads but the boot
# process should continue without any loss of functionality. This is an
# unsupported configuration that cannot be properly handled by this function.
is_container_with_internal_policy() {
	# this function is sometimes called independently of
	# is_apparmor_loaded(), so also define this here.
	local ns_stacked_path="${SFS_MOUNTPOINT}/.ns_stacked"
	local ns_name_path="${SFS_MOUNTPOINT}/.ns_name"
	local ns_stacked
	local ns_name

	# WSL needs to be detected explicitly
	if [ -x /usr/bin/systemd-detect-virt ] && \
	   [ "$(systemd-detect-virt --container)" = "wsl" ]; then
		return 0
	fi

	if ! [ -f "$ns_stacked_path" ] || ! [ -f "$ns_name_path" ]; then
		return 1
	fi

	read -r ns_stacked < "$ns_stacked_path"
	if [ "$ns_stacked" != "yes" ]; then
		return 1
	fi

	# LXD, Incus and LXC set up AppArmor namespaces starting with "lxd-",
	# "incus-" and "lxc-", respectively. Return non-zero for all other
	# namespace identifiers.
	read -r ns_name < "$ns_name_path"
	if [ "${ns_name#lxd-*}" = "$ns_name" ] && \
	   [ "${ns_name#incus-*}" = "$ns_name" ] && \
	   [ "${ns_name#lxc-*}" = "$ns_name" ]; then
		return 1
	fi

	return 0
}

__parse_profiles_dir() {
	local parser_cmd="$1"
	local profile_dir="$2"
	local status=0

	if [ ! -d "$profile_dir" ]; then
		aa_log_failure_msg "Profile directory not found: $profile_dir"
		return 1
	fi

	if [ -z "$(ls "$profile_dir"/)" ]; then
		aa_log_failure_msg "No profiles found in $profile_dir"
		return 1
	fi

	# shellcheck disable=SC2086
	if ! "$PARSER" $PARSER_OPTS "$parser_cmd" -- "$profile_dir"; then
		status=1
		aa_log_failure_msg "At least one profile failed to load"
	fi
	return "$status"
}

check_userns() {
	userns_restricted=$(sysctl -e -n kernel.apparmor_restrict_unprivileged_userns)
	unconfined_userns=$([ -f /sys/kernel/security/apparmor/features/policy/unconfined_restrictions/userns ] && cat /sys/kernel/security/apparmor/features/policy/unconfined_restrictions/userns || echo 0)
	if [ -n "$userns_restricted" ] && [ "$userns_restricted" -eq 1 ]; then
		if [ "$unconfined_userns" -eq 0 ]; then
			# userns restrictions rely on unconfined userns to be supported
			aa_action "disabling unprivileged userns restrictions since unconfined userns is not supported / enabled" \
				  sysctl -w kernel.apparmor_restrict_unprivileged_userns=0
		fi
	fi
}

parse_profiles() {
	check_userns

	# get parser arg
	case "$1" in
		load)
			PARSER_CMD="--add"
			PARSER_MSG="Loading AppArmor profiles "
			;;
		reload)
			PARSER_CMD="--replace"
			PARSER_MSG="Reloading AppArmor profiles "
			;;
		*)
			aa_log_failure_msg "required 'load' or 'reload'"
			exit 1
			;;
	esac
	aa_log_action_start "$PARSER_MSG"
	# run the parser on all of the apparmor profiles
	if [ ! -f "$PARSER" ]; then
		aa_log_failure_msg "AppArmor parser not found"
		exit 1
	fi

	for profile_dir in $PROFILE_DIRS; do
		__parse_profiles_dir "$PARSER_CMD" "$profile_dir" || STATUS=$?
	done

	aa_log_action_end "$STATUS"
	return "$STATUS"
}

is_apparmor_loaded() {
	if ! is_securityfs_mounted ; then
		mount_securityfs
	fi

	if [ -f "${SFS_MOUNTPOINT}/profiles" ]; then
		return 0
	fi

	is_apparmor_present

	return $?
}

is_securityfs_mounted() {
	test -d "$SECURITYFS" -a -d /sys/fs/cgroup/systemd || grep -q securityfs /proc/filesystems && grep -q securityfs /proc/mounts
	return $?
}

mount_securityfs() {
	if grep -q securityfs /proc/filesystems ; then
		aa_action "Mounting securityfs on $SECURITYFS" \
				mount -t securityfs securityfs "$SECURITYFS"
		return $?
	fi
	return 0
}

apparmor_start() {
	aa_log_daemon_msg "Starting AppArmor"
	if ! is_apparmor_present ; then
		aa_log_failure_msg "Starting AppArmor - failed, To enable AppArmor, ensure your kernel is configured with CONFIG_SECURITY_APPARMOR=y then add 'security=apparmor apparmor=1' to the kernel command line"
		aa_log_end_msg 1
		return 1
	elif ! is_apparmor_loaded ; then
		aa_log_failure_msg "Starting AppArmor - AppArmor control files aren't available under /sys/kernel/security/, please make sure securityfs is mounted."
		aa_log_end_msg 1
		return 1
	fi

	if [ ! -w "$SFS_MOUNTPOINT/.load" ] ; then
		aa_log_failure_msg "Loading AppArmor profiles - failed, Do you have the correct privileges?"
		aa_log_end_msg 1
		return 1
	fi

	# if there is anything in the profiles file don't load
	if ! read -r _ < "$SFS_MOUNTPOINT/profiles"; then
		parse_profiles load
	else
		aa_log_skipped_msg ": already loaded with profiles."
		return 0
	fi
	aa_log_end_msg 0
	return 0
}

remove_profiles() {

	# removing profiles as we directly read from apparmorfs
	# doesn't work, since we are removing entries which screws up
	# our position.  Lets hope there are never enough profiles to
	# overflow the variable
	if ! is_apparmor_loaded ; then
		aa_log_failure_msg "AppArmor module is not loaded"
		return 1
	fi

	if [ ! -w "$SFS_MOUNTPOINT/.remove" ] ; then
		aa_log_failure_msg "Root privileges not available"
		return 1
	fi

	if [ ! -x "$PARSER" ] ; then
		aa_log_failure_msg "Unable to execute AppArmor parser"
		return 1
	fi

	retval=0
	# We filter child profiles as removing the parent will remove
	# the children
	sed -e "s/ (\(enforce\|complain\))$//" "$SFS_MOUNTPOINT/profiles" | \
	LC_COLLATE=C sort | grep -v // | {
		while read -r profile ; do
			printf "%s" "$profile" > "$SFS_MOUNTPOINT/.remove"
			rc=$?
			if [ "$rc" -ne 0 ] ; then
				retval=$rc
			fi
		done
		return "$retval"
	}
}

apparmor_stop() {
	aa_log_daemon_msg "Unloading AppArmor profiles"
	remove_profiles
	rc=$?
	aa_log_end_msg "$rc"
	return "$rc"
}

apparmor_kill() {
	if ! is_apparmor_loaded ; then
		aa_log_failure_msg "AppArmor module is not loaded"
		return 1
	fi

	aa_log_failure_msg "apparmor_kill() is no longer supported because AppArmor can't be built as a module"
	return 1
}

__apparmor_restart() {
	if [ ! -w "$SFS_MOUNTPOINT/.load" ] ; then
		aa_log_failure_msg "Loading AppArmor profiles - failed, Do you have the correct privileges?"
		return 4
	fi

	aa_log_daemon_msg "Restarting AppArmor"

	parse_profiles reload

	rc=$?
	aa_log_end_msg "$rc"
	return "$rc"
}

apparmor_restart() {
	if ! is_apparmor_loaded ; then
		apparmor_start
		rc=$?
		return "$rc"
	fi

	__apparmor_restart
	return $?
}

apparmor_try_restart() {
	if ! is_apparmor_loaded ; then
		return 0
	fi

	__apparmor_restart
	return $?
}

apparmor_status () {
	if test -x "$AA_STATUS" ; then
		"$AA_STATUS" --verbose
		return $?
	fi
	if ! is_apparmor_loaded ; then
		echo "AppArmor is not loaded."
		rc=1
	else
		echo "AppArmor is enabled."
		rc=0
	fi
	echo "Install the apparmor-utils package to receive more detailed"
	echo "status information here (or examine $SFS_MOUNTPOINT directly)."

	return "$rc"
}