bpf_patcher.sh

#!/usr/bin/env bash

# Original sequences to search for.
ORIGINAL_SEQUENCES=('0a2450292801080a087d0a1b28010035' '48010035822240b980420491e10313aa')

# Patch sequences to replace the original sequences with.
PATCH_SEQUENCES=('0a2450292801080a087d0a1b1f2003d5' '1f2003d5822240b980420491e10313aa')

function log() {
  local colors=( "\e[34m" "\033[1;33m" "\033[1;31m" "\033[1;32m" )
  local levels=( "[INFO]" "[WARNING]" "[ERROR]" "[SUCCESS]" )
  echo -e "${colors[$1]}${levels[$1]}: $2\033[0m"
  [[ $1 -eq 2 ]] && exit 1 # Bail out if we fail.
}

function run() {
  local output
  output=$(eval "$@" 2>&1)
  if [[ $? -ne 0 ]]; then
    log 2 "Failed to run '$@'!"
  fi
}

function dump_image_info() {
  local image="$1"
  log 0 "Image name: $1"
  log 0 "Image size: $(du -h "$image" | cut -f1)"
  log 0 "Image type: $(file "$1" | cut -d ':' -f 2- | sed 's/^ *//')"
  log 0 "Image hash: $(sha256sum "$1" | cut -d ' ' -f 1)"
  log 0 "Image version: $(strings "$1" | grep -m 1 'Linux version' | grep -oP 'Linux version \K[^\s]+' | head -1)"
}

function patch_kernel() {
  output_kernel="$1"
  local patched=false

  for i in "${!ORIGINAL_SEQUENCES[@]}"; do
    if [[ $(xxd -p -c 1000 "$output_kernel" | grep -c "${ORIGINAL_SEQUENCES[$i]}") -gt 0 ]]; then
      log 1 "Using patch sequence ${PATCH_SEQUENCES[$i]} to patch the kernel..."
      xxd -p -c 1000 "$output_kernel" | sed "s/${ORIGINAL_SEQUENCES[$i]}/${PATCH_SEQUENCES[$i]}/g" | xxd -r -p > "$output_kernel".tmp
      run "mv $output_kernel.tmp $output_kernel"
      if [[ $(xxd -p -c 1000 "$output_kernel" | grep -c "${PATCH_SEQUENCES[$i]}") -gt 0 ]]; then
        log 3 "Successfully patched the kernel!"
        patched=true
      fi
      break
    fi
  done

  if [[ $patched == false ]]; then
    log 2 "Failed to patch the kernel!"
  fi
}

function main() {
  local original_kernel="$1"
  local output_kernel="$2"
  local compressed=false

  if [[ $(head -c 2 "$original_kernel") == $'\x1f\x8b' ]]; then
    compressed=true
    log 1 "The original kernel is compressed. Uncompressing..."
    run "gzip -d -c $original_kernel > $output_kernel"
  else
    log 1 "The original kernel is not compressed. Copying..."
    run "cp $original_kernel $output_kernel"
  fi

  dump_image_info "$output_kernel"
  log 0 "Patching the kernel..."
  patch_kernel "$output_kernel"

  if [[ $compressed == true ]]; then
    log 1 "Compressing the patched kernel..."
    run "gzip -f -9 -n $output_kernel"
    output_kernel="$output_kernel.gz"
  fi

  log 3 "Done! The patched kernel is located at '$output_kernel'."
}

if [[ ! $(which gzip) ]]; then
  log 2 "gzip is not installed. Please install it and try again."
fi

if [[ $# -lt 2 ]]; then
  log 2 "Usage: $0 <path to original kernel> <path to output kernel>"
fi

if [[ $2 == *.* ]]; then
  log 2 "The output kernel '$2' should not have an extension!"
fi

if [[ ! -f "$1" ]]; then
  log 2 "The original kernel '$1' does not exist!"
fi

main "$@"