Mini Shell

#!/usr/bin/bash
#
# This script helps set up IMA.
#
IMA_SYSTEMD_POLICY=/etc/ima/ima-policy
IMA_POLICY_SYSFS=/sys/kernel/security/ima/policy

usage() {
	echo "Set up IMA."
	cat <<EOF
usage: $0 --policy=IMA_POLICY_PATH [--reinstall_threshold=NUM]

       --policy
       The path of IMA policy to be loaded. Sample polices are inside
       /usr/share/ima/policies or you can use your own IMA policy
       The path of IMA policy to be loaded.  Sample polices are inside
       /usr/share/ima/policies or you can use your own IMA policy

       --reinstall_threshold
       When there are >reinstall_threshold packages in the RPM DB missing IMA signatures, reinstalling the packages to add IMA signatures to the packages.
       By default, IMA sigatures will be obtained from the RPM DB. However the RPM DB may not have the signatures. Dectect this case by checking if there are >reinstall_threshold package missing IMA signatures.

EOF
	exit 1
}

for _opt in "$@"; do
	case "$_opt" in
	--policy=*)
		ima_policy_path=${_opt#*=}
		if [[ ! -e $ima_policy_path ]]; then
			echo "$policy_file doesn't exist"
			exit 1
		fi
		;;
	--reinstall_threshold=*)
		reinstall_threshold=${_opt#*=}
		;;
	*)
		usage
		;;
	esac
done

if [[ $# -eq 0 ]]; then
	usage
fi

echo "Installing prerequisite package rpm-plugin-ima"
if ! dnf install rpm-plugin-ima -yq; then
	echo "Failed to install rpm-plugin-ima, abort"
	exit 1
fi

# Add IMA signatures
if test -f /run/ostree-booted; then
	echo "You are using OSTree, please enable IMA signatures as part of the OSTree creation process."
else
	echo "Adding IMA signatures to installed package files"
	if ! ima-add-sigs; then
		echo "Failed to add IMA signatures, abort"
		exit 1
	fi
fi

load_ima_keys() {
	local _key_loaded

	if line=$(keyctl describe %keyring:.ima); then
		_ima_id=${line%%:*}
	else
		echo "Failed to get ID of the .ima  keyring"
		exit 1
	fi

	for i in /etc/keys/ima/*; do
		if [ ! -f "${i}" ]; then
			echo "No IMA key exist"
			exit 1
		fi

		if ! evmctl import "${i}" "${_ima_id}" &>/dev/null; then
			echo "Failed to load IMA key ${i}"
		else
			_key_loaded=yes
		fi
	done

	if [[ $_key_loaded != yes ]]; then
		echo "No IMA key loaded"
		exit 1
	fi
}

load_ima_policy() {
	local ima_policy_path

	ima_policy_path=$1

	if ! test -f "$ima_policy_path"; then
		echo "$ima_policy_path doesn't exist"
		return 1
	fi
	if ! echo "$ima_policy_path" >"$IMA_POLICY_SYSFS"; then
		echo "$ima_policy_path can't be loaded"
		return 1
	fi
	# Let systemd load the IMA policy which will load LSM rules first so IMA
	# policy containing rules like "appraise obj_type=ifconfig_exec_t" can be
	# loaded
	[[ -e /etc/ima ]] || mkdir -p /etc/ima/
	if ! cp --preserve=xattr "$ima_policy_path" "$IMA_SYSTEMD_POLICY"; then
		echo "Failed to copy $ima_policy_path to $IMA_SYSTEMD_POLICY"
		return 1
	fi
}

echo "Loading IMA keys"
load_ima_keys

# Include the dracut integrity module to load the IMA keys and policy
# automatically when there is a system reboot
if ! lsinitrd --mod | grep -q integrity; then
	cp --preserve=xattr /usr/share/ima/dracut-98-integrity.conf /etc/dracut.conf.d/98-integrity.conf
	echo "Rebuilding the initramfs of kernel-$(uname -r) to include the dracut integrity module"
	dracut -f

	if command -v grubby >/dev/null; then
		_default_kernel=$(grubby --default-kernel | sed -En "s/.*vmlinuz-(.*)/\1/p")
		if [[ $_default_kernel != $(uname -r) ]]; then
			echo "Current kernel is not the default kernel ($_default_kernel), include dracut integrity for it as well"
			dracut -f --kver "$_default_kernel"
		fi
	fi

fi

if ! load_ima_policy "$ima_policy_path"; then
	echo "Failed to load IMA policy $ima_policy_path!"
	exit 1
fi