kernel-build.eclass: add IUSE="modules-sign"

- Enable module signing configure options if requested by the user.

- Define the user variables MODULES_SIGN_HASH and MODULES_SIGN_KEY.
For controlling the used hashing algorithm and allowing the use of
external keys. These variables are the same as in linux-mod-r1.eclass

- Warn the user if we are letting the kernel build system generate the signing
key. This key will end up binary packages. Plus external modules will have to
be resigned if gentoo-kernel is re-emerged (i.e. a new key was generated).

Bug: https://bugs.gentoo.org/814344
Bug: https://bugs.gentoo.org/881651
Signed-off-by: Andrew Ammerlaan <andrewammerlaan@gentoo.org>

1 files changed, 89 insertions, 1 deletions

diff --git a/eclass/kernel-build.eclass b/eclass/kernel-build.eclass
index c6f3ebeca962..963e020b3746 100644
--- a/eclass/kernel-build.eclass
+++ b/eclass/kernel-build.eclass
@@ -43,6 +43,48 @@ BDEPEND="
 
 IUSE="+strip"
 
+# @ECLASS_VARIABLE: KERNEL_IUSE_MODULES_SIGN
+# @PRE_INHERIT
+# @DEFAULT_UNSET
+# @DESCRIPTION:
+# If set to a non-null value, adds IUSE=modules-sign and required
+# logic to manipulate the kernel config while respecting the
+# MODULES_SIGN_HASH and MODULES_SIGN_KEY user variables.
+
+# @ECLASS_VARIABLE: MODULES_SIGN_HASH
+# @USER_VARIABLE
+# @DEFAULT_UNSET
+# @DESCRIPTION:
+# Used with USE=modules-sign.  Can be set to hash algorithm to use
+# during signature generation (CONFIG_MODULE_SIG_SHA256).
+#
+# Valid values: sha512,sha384,sha256,sha224,sha1
+#
+# Default if unset: sha512
+
+# @ECLASS_VARIABLE: MODULES_SIGN_KEY
+# @USER_VARIABLE
+# @DEFAULT_UNSET
+# @DESCRIPTION:
+# Used with USE=modules-sign.  Can be set to the path of the private
+# key in PEM format to use, or a PKCS#11 URI (CONFIG_MODULE_SIG_KEY).
+#
+# If path is relative (e.g. "certs/name.pem"), it is assumed to be
+# relative to the kernel build directory being used.
+#
+# If the key requires a passphrase or PIN, the used kernel sign-file
+# utility recognizes the KBUILD_SIGN_PIN environment variable.  Be
+# warned that the package manager may store this value in binary
+# packages, database files, temporary files, and possibly logs.  This
+# eclass unsets the variable after use to mitigate the issue (notably
+# for shared binary packages), but use this with care.
+#
+# Default if unset: certs/signing_key.pem
+
+if [[ ${KERNEL_IUSE_MODULES_SIGN} ]]; then
+	IUSE+=" modules-sign"
+fi
+
 # @FUNCTION: kernel-build_src_configure
 # @DESCRIPTION:
 # Prepare the toolchain for building the kernel, get the default .config
@@ -259,6 +301,9 @@ kernel-build_src_install() {
 	dosym "../../../${kernel_dir}" "/lib/modules/${module_ver}/build"
 	dosym "../../../${kernel_dir}" "/lib/modules/${module_ver}/source"
 
+	# unset to at least be out of the environment file in, e.g. shared binpkgs
+	unset KBUILD_SIGN_PIN
+
 	save_config build/.config
 }
 
@@ -268,6 +313,26 @@ kernel-build_src_install() {
 kernel-build_pkg_postinst() {
 	kernel-install_pkg_postinst
 	savedconfig_pkg_postinst
+
+	if [[ ${KERNEL_IUSE_MODULES_SIGN} ]]; then
+		if use modules-sign && [[ -z ${MODULES_SIGN_KEY} ]]; then
+			ewarn
+			ewarn "MODULES_SIGN_KEY was not set, this means the kernel build system"
+			ewarn "automatically generated the signing key. This key was installed"
+			ewarn "in ${EROOT}/usr/src/linux-${PV}${KV_LOCALVERSION}/certs"
+			ewarn "and will also be included in any binary packages."
+			ewarn "Please take appropriate action to protect the key!"
+			ewarn
+			ewarn "Recompiling this package causes a new key to be generated. As"
+			ewarn "a result any external kernel modules will need to be resigned."
+			ewarn "Use emerge @module-rebuild, or manually sign the modules as"
+			ewarn "described on the wiki [1]"
+			ewarn
+			ewarn "Consider using the MODULES_SIGN_KEY variable to use an external key."
+			ewarn
+			ewarn "[1]: https://wiki.gentoo.org/wiki/Signed_kernel_module_support"
+		fi
+	fi
 }
 
 # @FUNCTION: kernel-build_merge_configs
@@ -290,16 +355,39 @@ kernel-build_merge_configs() {
 	local user_configs=( "${BROOT}"/etc/kernel/config.d/*.config )
 	shopt -u nullglob
 
+	local merge_configs=( "${@}" )
+
+	if [[ ${KERNEL_IUSE_MODULES_SIGN} ]]; then
+		if use modules-sign; then
+			: "${MODULES_SIGN_HASH:=sha512}"
+			cat <<-EOF > "${WORKDIR}/modules-sign.config" || die
+				## Enable module signing
+				CONFIG_MODULE_SIG=y
+				CONFIG_MODULE_SIG_ALL=y
+				CONFIG_MODULE_SIG_FORCE=y
+				CONFIG_MODULE_SIG_${MODULES_SIGN_HASH^^}=y
+			EOF
+			if [[ ${MODULES_SIGN_KEY} == pkcs11:* || -e ${MODULES_SIGN_KEY} ]]; then
+				echo "CONFIG_MODULE_SIG_KEY=\"${MODULES_SIGN_KEY}\"" \
+					>> "${WORKDIR}/modules-sign.config"
+			elif [[ -n ${MODULES_SIGN_KEY} ]]; then
+				die "MODULES_SIGN_KEY=${MODULES_SIGN_KEY} not found!"
+			fi
+			merge_configs+=( "${WORKDIR}/modules-sign.config" )
+		fi
+	fi
+
 	if [[ ${#user_configs[@]} -gt 0 ]]; then
 		elog "User config files are being applied:"
 		local x
 		for x in "${user_configs[@]}"; do
 			elog "- ${x}"
 		done
+		merge_configs+=( "${user_configs[@]}" )
 	fi
 
 	./scripts/kconfig/merge_config.sh -m -r \
-		.config "${@}" "${user_configs[@]}" || die
+		.config "${merge_configs[@]}"  || die
 }
 
 fi