b261a30c90
This is used to package up the grub bootloader into a firmware volume where it can be executed as a shell like the UEFI Shell. Grub itself is built as a minimal entity into a Fv and then added as a boot option. By default the UEFI shell isn't built but for debugging purposes it can be enabled and will then be presented as a boot option (This should never be allowed for secure boot in an external data centre but may be useful for local debugging). Finally all other boot options except grub and possibly the shell are stripped and the boot timeout forced to 0 so the system will not enter a setup menu and will only boot to grub. This is done by copying the Library/PlatformBootManagerLib into Library/PlatformBootManagerLibGrub and then customizing it. Boot failure is fatal to try to prevent secret theft. Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3077 Signed-off-by: James Bottomley <jejb@linux.ibm.com> Message-Id: <20201130202819.3910-4-jejb@linux.ibm.com> Acked-by: Ard Biesheuvel <ard.biesheuvel@arm.com> [lersek@redhat.com: replace local variable initialization with assignment] Reviewed-by: Laszlo Ersek <lersek@redhat.com> [lersek@redhat.com: squash 'OvmfPkg: add "gGrubFileGuid=Grub" to GuidCheck.IgnoreDuplicates', reviewed stand-alone by Phil (msgid <e6eae551-8563-ccfb-5547-7a97da6d46e5@redhat.com>) and Ard (msgid <10aeda37-def6-d9a4-6e02-4c66c1492f57@arm.com>)]
94 lines
2.1 KiB
Bash
94 lines
2.1 KiB
Bash
## @file
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# Build a version of grub capable of decrypting a luks volume with a SEV
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# Supplied secret
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#
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# Copyright (C) 2020 James Bottomley, IBM Corporation.
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#
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# SPDX-License-Identifier: BSD-2-Clause-Patent
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#
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##
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set -e
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remove_efi=1
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cleanup() {
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# remove the intermediates
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for f in disk.fat grub-bootstrap.cfg; do
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rm -f -- "${basedir}/$f"
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done
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if [ $remove_efi -eq 1 ]; then
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rm -f -- "${basedir}/grub.efi"
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fi
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}
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trap cleanup EXIT
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GRUB_MODULES="
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part_msdos
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part_gpt
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cryptodisk
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luks
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gcry_rijndael
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gcry_sha256
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ext2
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btrfs
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xfs
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fat
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configfile
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memdisk
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sleep
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normal
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echo
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test
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regexp
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linux
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linuxefi
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reboot
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sevsecret
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"
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basedir=$(dirname -- "$0")
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# don't run a build if grub.efi exists and is newer than the config files
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if [ -e "${basedir}/grub.efi" ] && \
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[ "${basedir}/grub.efi" -nt "${basedir}/grub.cfg" ] && \
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[ "${basedir}/grub.efi" -nt "${basedir}/grub.sh" ]; then
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remove_efi=0
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echo "preserving existing grub.efi" >&2
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exit 0
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fi
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##
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# different distributions have different names for grub-mkimage, so
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# search all the known ones
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##
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mkimage=
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for b in grub2-mkimage grub-mkimage; do
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if which "$b" > /dev/null 2>&1; then
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mkimage="$b"
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break
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fi
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done
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if [ -z "$mkimage" ]; then
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echo "Can't find grub mkimage" >&2
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exit 1
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fi
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# GRUB's rescue parser doesn't understand 'if'.
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echo 'normal (memdisk)/grub.cfg' > "${basedir}/grub-bootstrap.cfg"
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# Now build a memdisk with the correct grub.cfg
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rm -f -- "${basedir}/disk.fat"
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mkfs.msdos -C -- "${basedir}/disk.fat" 64
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mcopy -i "${basedir}/disk.fat" -- "${basedir}/grub.cfg" ::grub.cfg
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${mkimage} -O x86_64-efi \
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-p '(crypto0)' \
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-c "${basedir}/grub-bootstrap.cfg" \
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-m "${basedir}/disk.fat" \
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-o "${basedir}/grub.efi" \
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${GRUB_MODULES}
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remove_efi=0
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echo "grub.efi generated in ${basedir}"
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