From 43a7e8759162fa25aea203ce732f177bc6f15cdb Mon Sep 17 00:00:00 2001
From: Dorian Stoll <dorian.stoll@tmsp.io>
Date: Sun, 22 Sep 2019 22:44:16 +0200
Subject: [PATCH] Add secureboot pre-signing to the kernel

If it detects a secure boot certificate at `keys/MOK.key` and `keys/MOK.cer`,
the kernel Makefile will automatically sign the vmlinux / bzImage file that
gets generated, and that is then used in packaging.

By integrating it into the kernel build system directly, it is fully integrated
with targets like `make deb-pkg` (opposed to `make all`, sign, `make bindeb-pkg`)
and it gets added to every tree by the same mechanism that is used to apply the
other surface patches anyways.

Signed-off-by: Dorian Stoll <dorian.stoll@tmsp.io>
---
 .gitignore             |  3 +++
 arch/x86/Makefile      |  1 +
 scripts/sign_kernel.sh | 30 ++++++++++++++++++++++++++++++
 3 files changed, 34 insertions(+)
 create mode 100755 scripts/sign_kernel.sh

diff --git a/.gitignore b/.gitignore
index 7f86e0837909..04aaae490610 100644
--- a/.gitignore
+++ b/.gitignore
@@ -152,6 +152,9 @@ signing_key.priv
 signing_key.x509
 x509.genkey
 
+# Secureboot certificate
+/keys/
+
 # Kconfig presets
 /all.config
 /alldef.config
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index fdc2e3abd615..c7a374c7ceaf 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -283,6 +283,7 @@ endif
 	$(Q)$(MAKE) $(build)=$(boot) $(KBUILD_IMAGE)
 	$(Q)mkdir -p $(objtree)/arch/$(UTS_MACHINE)/boot
 	$(Q)ln -fsn ../../x86/boot/bzImage $(objtree)/arch/$(UTS_MACHINE)/boot/$@
+	$(Q)$(srctree)/scripts/sign_kernel.sh $(objtree)/arch/$(UTS_MACHINE)/boot/$@
 
 $(BOOT_TARGETS): vmlinux
 	$(Q)$(MAKE) $(build)=$(boot) $@
diff --git a/scripts/sign_kernel.sh b/scripts/sign_kernel.sh
new file mode 100755
index 000000000000..d2526a279254
--- /dev/null
+++ b/scripts/sign_kernel.sh
@@ -0,0 +1,30 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+
+# The path to the compiled kernel image is passed as the first argument
+BUILDDIR=$(dirname $(dirname $0))
+VMLINUX=$1
+
+# Keys are stored in a toplevel directory called keys
+# The following files need to be there:
+#     * MOK.priv  (private key)
+#     * MOK.pem   (public key)
+#
+# If the files don't exist, this script will do nothing.
+if [ ! -f "$BUILDDIR/keys/MOK.key" ]; then
+    exit 0
+fi
+if [ ! -f "$BUILDDIR/keys/MOK.crt" ]; then
+    exit 0
+fi
+
+# Both required certificates were found. Check if sbsign is installed.
+echo "Keys for automatic secureboot signing found."
+if [ ! -x "$(command -v sbsign)" ]; then
+    echo "ERROR: sbsign not found!"
+    exit -2
+fi
+
+# Sign the kernel
+sbsign --key $BUILDDIR/keys/MOK.key --cert $BUILDDIR/keys/MOK.crt \
+    --output $VMLINUX $VMLINUX
-- 
2.41.0