#!/bin/bash

mkdir -p db

die() {
  echo >&2 $1
  exit 1
}

dump_symbols() {
  readelf -Ws $1 | perl -n -e '/: (\w*).*?(\w+)@@GLIBC_/ && print "$2 $1\n"'
}

extract_label() {
  perl -n -e '/(\w+)/ && print $1'
}

dump_libc_start_main_ret() {
  if [ `echo "$2" | egrep "i386|amd64" - ` ] \
    && [ -x "$(command -v objdump)" ]; then
    local call_main=`objdump -D $1 \
      | egrep -A 100 '<__libc_start_main.*>' \
      | grep call \
      | egrep -B 1 '<exit.*>' \
      | head -n 1 \
      | extract_label`
    local offset=`objdump -D $1 | egrep -A 1 "(^| )$call_main:" | tail -n 1 | extract_label`
  elif [ `echo "$2" | egrep "armel|armhf|arm64" - ` ] \
    && [ -x "$(command -v aarch64-linux-gnu-objdump)" ]; then
    local call_main=`aarch64-linux-gnu-objdump -D $1 \
      | egrep -A 100 '<__libc_start_main.*>' \
      | grep -Pe "(bl\t|blr\t|blx\t|bx\t)" \
      | egrep -B 1 '<exit.*>' \
      | head -n 1 \
      | extract_label`
    local offset=`aarch64-linux-gnu-objdump -D $1 \
      | egrep -A 1 "(^| )$call_main:" \
      | tail -n 1 \
      | extract_label`
  fi
  if [[ "$offset" != "" ]]; then
    echo "__libc_start_main_ret $offset"
  fi
}

dump_bin_sh() {
  local offset=`strings -a -t x $1 | grep '/bin/sh' | head -n 1 | extract_label`
  if [[ "$offset" != "" ]]; then
    echo "str_bin_sh $offset"
  fi
}

process_libc() {
  local libc=$1
  local id=$2
  local info=$3
  local sha256=$4
  [[ -d db/$info ]] || mkdir db/$info
  echo "  -> Writing libc to db/${info}/${id}.so"
  cp $libc db/${info}/${id}.so
  echo "  -> Writing symbols to db/${info}/${id}.symbols"
  (dump_symbols $libc; dump_libc_start_main_ret $libc $id; dump_bin_sh $libc) \
     > db/${info}/${id}.symbols
  echo "  -> Writing SHA-256 to db/${info}/${id}.sha256"
  echo "$sha256" > db/${info}/${id}.sha256
}

check_id() {
  local id=$1
  local info=$2
  if [[ -e db/${info}/${id}.sha256 ]]; then
    echo "  -> Already have this version, 'rm db/${info}/${id}.*' to force"
    return 1
  fi
  return 0
}

check_sha256() {
  local sha256=$1
  local libc=`grep -r $sha256 db/ 2>/dev/null | cut -d ':' -f 1 - 2>/dev/null | sed 's/\.sha256/\.so/gI'`
  if [[ "$libc" != "" ]]; then
    echo "  -> Found SHA-256 match: $libc"
    return 1
  fi
  return 0
}

# ===== Debian and Ubuntu ===== #

get_deb() {
  local url="$1"
  local info="$2"
  local tmp=`mktemp -d || mktemp -d -t "libc-database" || die "Cannot get temp dir"`
  echo "Getting $info"
  echo "  -> Location: $url"
  local id=`echo $url | perl -n -e '/(libc6[^\/]*)\./ && print $1' | sed 's/\%2b/+/gI'`
  echo "  -> ID: $id"
  check_id $id $info || return
  echo "  -> Downloading package"
  wget $url 2>/dev/null -O $tmp/pkg.deb || die "Failed to download package from $url"
  echo "  -> Extracting package"
  pushd $tmp 1>/dev/null
  ar x pkg.deb || die "ar failed"
  tar xf data.tar.* || die "tar failed"
  popd 1>/dev/null
  local libc=`find $tmp -name libc.so.6 || die "Cannot locate libc.so.6"`
  if [[ ! -e $libc ]]; then 
    echo "  -> The package does not seem to contain a valid libc (e.g. just contains a broken symbolic link)"
    return
  fi
  local sha256=`sha256sum $libc`
  check_sha256 $sha256 || return
  process_libc $libc $id $info $sha256
  rm -rf $tmp
}

get_current_ubuntu() {
  local version=$1
  local arch=$2
  local pkg=$3
  local info=ubuntu-$version-$arch-$pkg
  echo "Getting package location for ubuntu-$version-$arch"
  local url=`(wget http://packages.ubuntu.com/$version/$arch/$pkg/download -O - 2>/dev/null \
               | grep -oh 'http://[^"]*libc6[^"]*.deb') || die "Failed to get package version"`
  get_deb $url $info
}

get_all_debian() {
  local info=debian-$1
  local url=$2
  for f in `wget $url/ -O - 2>/dev/null | egrep -oh 'libc6(-i386|-i686|-amd64|-armel|-armhf|-arm64)?(-cross)?_[^"]*(i386|amd64|armel|armhf|arm64|all)\.deb' | grep -v "</a>"`; do
    get_deb $url/$f $info
  done
}

get_all_ubuntu() {
  local info=ubuntu-$1
  local url=$2
  for f in `wget $url/ -O - 2>/dev/null | egrep -oh 'libc6(-i386|-i686|-amd64|-armel|-armel-armhf|-armhf|-arm64)?(-cross)?_[^"]*(i386|amd64|armel|armhf|arm64|all)\.deb' | grep -v "</a>"`; do
    get_deb $url/$f $info
  done
}

# ===== Local ===== #

add_local() {
  local libc=$1
  [[ -e $libc ]] || return
  local info="local"
  local id="local-`sha256sum $libc`"
  echo "Adding local libc $libc (id $id)"
  check_id $id $info || return
  local sha256=`sha256sum $libc`
  check_sha256 $sha256 || return
  process_libc $libc $id $info $sha256
}