extract shim initramfs

.gitignore

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+/data

README.md

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+todo

build.sh

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+#!/bin/bash
+
+#build the bootloader image
+
+set -e
+if [ "$DEBUG" ]; then
+  set -x
+fi
+
+print_help() {
+  echo "Usage: ./build.sh path_to_shim"
+}
+
+create_loop() {
+  local loop_device=$(losetup -f)
+  losetup -P $loop_device $1
+  echo $loop_device
+}
+
+if [ "$EUID" -ne 0 ]; then
+  echo "this needs to be run as root."
+  exit 1
+fi
+
+if [ -z "$1" ]; then
+  print_help
+  exit 1
+fi
+
+shim_path=$(realpath $1)
+
+echo "created loop device for shim"
+shim_loop=$(create_loop $shim_path)
+kernel_loop="${shim_loop}p2" #KERN-A should always be p2
+
+echo "copying shim kernel to new file in /tmp"
+kernel_dir=/tmp/shim_kernel
+rm -rf $kernel_dir
+mkdir $kernel_dir -p
+dd if=$kernel_loop of=$kernel_dir/kernel.bin bs=1M status=none
+
+echo "extracting data from kernel"
+previous_dir=$(pwd)
+cd $kernel_dir
+binwalk_out=$(binwalk --extract kernel.bin --run-as=root)
+#i can't be bothered to learn how to use sed
+extracted_file=$(echo $binwalk_out | pcregrep -o1 "\d+\s+0x([0-9A-F]+)\s+gzip compressed data")
+
+echo "extracting initramfs archive from kernel"
+cd _kernel.bin.extracted/
+binwalk --extract $extracted_file --run-as=root > /dev/null
+cd "_${extracted_file}.extracted/"
+cpio_file=$(file ./* | pcregrep -o1 "([0-9A-F]+):\s+ASCII cpio archive")
+
+echo "extracting initramfs cpio archive"
+initramfs_dir=/tmp/shim_initramfs
+rm -rf $initramfs_dir
+cat $cpio_file | cpio -D $initramfs_dir -imd --quiet
+
+echo "shim initramfs extracted to ${initramfs_dir}"
+
+cd $previous_dir
+
+echo "cleaning up loop devices"
+losetup -d $shim_loop