kernel-modsign.bbclass: add support for kernel modules signing

Add bbclass responsible for handling signing of kernel modules.

Signed-off-by: Dmitry Eremin-Solenikov <dmitry_eremin-solenikov@mentor.com>

fixup class to avoid including in every configure task

Signed-off-by: Armin Kuster <akuster808@gmail.com>

meta-integrity/classes/kernel-modsign.bbclass

@@ -0,0 +1,29 @@
+# No default! Either this or MODSIGN_PRIVKEY/MODSIGN_X509 have to be
+# set explicitly in a local.conf before activating kernel-modsign.
+# To use the insecure (because public) example keys, use
+# MODSIGN_KEY_DIR = "${INTEGRITY_BASE}/data/debug-keys"
+MODSIGN_KEY_DIR ?= "MODSIGN_KEY_DIR_NOT_SET"
+
+# Private key for modules signing. The default is okay when
+# using the example key directory.
+MODSIGN_PRIVKEY ?= "${MODSIGN_KEY_DIR}/privkey_modsign.pem"
+
+# Public part of certificates used for modules signing.
+# The default is okay when using the example key directory.
+MODSIGN_X509 ?= "${MODSIGN_KEY_DIR}/x509_modsign.crt"
+
+# If this class is enabled, disable stripping signatures from modules
+INHIBIT_PACKAGE_STRIP = "1"
+
+kernel_do_configure_prepend() {
+    if [ -f "${MODSIGN_PRIVKEY}" -a -f "${MODSIGN_X509}" ]; then
+        cat "${MODSIGN_PRIVKEY}" "${MODSIGN_X509}" \
+            > "${B}/modsign_key.pem"
+    else
+        bberror "Either modsign key or certificate are invalid"
+    fi
+}
+
+do_shared_workdir_append() {
+    cp modsign_key.pem $kerneldir/
+}