#!/bin/sh
# Copyright 2011 CyberLeo, All Rights Reserved
# http://wiki.cyberleo.net/wiki/CyberLeo/COPYRIGHT

: ${ORIG_USER=$(id -un)}

# Need root beyond here
[ "$(id -u)" -eq 0 ] || exec sudo env "J_ARCH=${J_ARCH}" "J_BASE=${J_BASE}" "J_NAME=${J_NAME}" "J_USER=${J_USER:-${USER}}" "ORIG_USER=${ORIG_USER}" "DISPLAY=${DISPLAY}" "${0}" "${@}"

meh() { printf " \033[1;32m*\033[0m %s%s\n" "${jname:+${jname}: }" "${*}"; }
omg() { printf " \033[1;33m*\033[0m %s%s\n" "${jname:+${jname}: }" "${*}"; }
wtf() { printf " \033[1;31m*\033[0m %s%s\n" "${jname:+${jname}: }" "${*}"; exit 1; }
pebkac() {
  [ "${*}" ] && printf "%s\n\n" "${*}"
  cat <<EOF
Usage:
  <command> <name> [arguments]
  list
  ls      list available chroots

  status  show jail status

  start   prepare an existing chroot for use

  stop    undo what 'start' did

  kill    Forcefully kill all processes; only applicable with cgroups

  enter
  shell   spawn a shell or command within the chroot

  eval    evaluate a shell command line within the chroot

EOF
  exit 1
}

cmd="$(basename "${0}")"
jarch="${J_ARCH:-$(uname -m)}"
jbase="${J_BASE:-$(realpath "$(dirname "${0}")/../")}"
jname="${J_NAME:-$(basename "${1}")}" #"
juser="${J_USER}"

# cgroup to use; if not found, cgroup support will not be used
jcgroup="freezer"
# cgroup parent to use (${cgroup}/${parent}/${jname})
jcgparent="j"

# Remove chroot name from argument stack, if passed in
[ "${J_NAME}" ] || shift

# Propagate certain environment variables; sterilize the rest of the environment
jenv="
  LANG=${LANG}
  TERM=${TERM}
  USER=${USER}
"

# Debian-specific init: prepare Debian chroot with debootstrap
j_init_debian() {
  jdir="${1}"
  suite="$(echo "${2:-squeeze}" | tr 'A-Z' 'a-z')"

  # Validation
  [ "$(which debootstrap 2>&-)" ] || pebkac "j_init_debian: debootstrap not found"
  [ "${jdir}" ] || pebkac "j_init_debian: jdir must be specified"
  [ ! -d "${jdir}" ] || pebkac "j_init_debian: jdir must not exist ('${jdir}')"
  [ -d "$(dirname "${jdir}")" ] || pebkac "j_init_debian: parent of jdir must exist ('${jdir}')"

  # Figure out arch
  case "${jarch}" in
  x86|i386) arch=i386 ;;
  amd64|x86_64|x64) arch=amd64 ;;
  *) pebkac "Unsupported arch '${jarch}'" ;;
  esac

  cmd="debootstrap --arch=${arch} --include=curl,file,less,locales,sudo,build-essential,libreadline-dev,zlib1g-dev '${suite}' '${jdir}'"
  echo "Executing ${cmd}"
  eval "${cmd}"

  # Make sure locales are generated on first start
  mkdir -p "${jdir}/etc/rcJ.d"
  cat > "${jdir}/etc/rcJ.d/S00localegen" <<"EOF"
#!/bin/sh
/bin/sed -i '/en_US/s/^# //' /etc/locale.gen
/usr/sbin/locale-gen
/bin/rm -f "${0}"
EOF
  chmod 755 "${jdir}/etc/rcJ.d/S00localegen"
}

# Gentoo-specific init: prepare Gentoo chroot with stage3+portage tarballs
j_init_gentoo() {
  arch="$(uname -m)"
  base="http://distfiles.gentoo.org/releases/${arch}/autobuilds"
  pointer="${base}/latest-stage3.txt"
  # Fetch stage3
  # Fetch portage
  # Validate signatures
  # Unpack stage3
  # Unpack portage
}

# Create a new chroot, somehow
j_init() {
  # Make sure this does NOT exist
  jname="${1:-jname}"
  dist="$(echo "${2:-debian}" | tr 'A-Z' 'a-z')"
  jdir="${jbase}/${jname}"
  [ -d "${jdir}" ] && pebkac "j_init: ${jname} already exists"
  shift 2
  case "${dist}" in
  debian) j_init_debian "${jdir}" "${@}" ;;
  gentoo) j_init_gentoo "${jdir}" "${@}" ;;
  *) pebkac "Unsupported distro '${dist}'" ;;
  esac
}

# Figure out and set chroot parameters; needed for all functions that follow
j_params() {
  ( jname="${1:-jname}"

    # Make sure jname is not empty
    if [ -z "${jname}" ]
    then
      printf "jerror='%s'\n" "jname empty"
      return 1
    fi

    # Given a chroot name, find and set up the chroot dir
    jdir="${jbase}/${jname}"
    jroot="${jdir}/root"
    if [ ! -d "${jdir}" -o ! -d "${jroot}" ]
    then
      printf "jerror='%s'\n" "not a directory"
      return 1
    fi

    # Where is the shell?
    jshell=""
    for shell in /bin/bash /usr/bin/bash /usr/local/bin/bash /bin/sh
    do
      if [ -f "${jroot}/${shell}" ]
      then
        jshell=${shell}
        break
      fi
    done
    if [ -z "${jshell}" ]
    then
      printf "jerror='%s'\n" "unable to locate usable shell; is this a jail?"
      return 1
    fi

    printf "jerror='' jname='%s' jdir='%s' jroot='%s' jshell='%s'\n" "${jname}" "${jdir}" "${jroot}" "${jshell}"
  )
}

# Find the 'freezer' cgroup, to determine whether the chroot can be further isolated
j_locate_cgroup_mount() {
  cgroup="${1:-freezer}"
  cat /proc/mounts | while read src dir type opts fsck dump extra
  do
    [ "${type}" = "cgroup" ] || continue
    oldifs="${IFS}"
    IFS=','
    set -- ${opts}
    IFS=${oldifs}
    while [ "${1}" ]
    do
      [ "${1}" = "${cgroup}" ] && echo "${dir}" && break 2
      shift
    done
  done
}

# Cache and expose cgroup mountpoint for given chroot; make sure it exists
j_cgroup() {
  [ "${jcg}" ] && { echo "${jcg}"; return; }
  jcg="$(j_locate_cgroup_mount "${cgroup}")/${jcgparent}/${jname}"
  mkdir -p "${jcg}"
  echo "${jcg}"
}

j_cg_trap() {
  [ "$(j_cgroup)" ] || return
  while [ "${1}" ]
  do
    echo "${1}" > "$(j_cgroup)/tasks"
    shift
  done
}

# Run a command within a cgroup, if available
j_cg_eval() {
  j_cg="$(j_cgroup)"
  if [ "$(j_cgroup)" ]
  then
    sh -ex <<EOF
echo $$ > "$(j_cgroup)/tasks"
eval "${*}"
EOF
  else
    eval "${*}"
  fi
}

# Copy ipcc into the jail and add helpful symlinks, so it can communicate
# simple commands to the outside
j_ipc_setup() {
  ipcc="$(dirname "${0}")/ipcc"
  cp -f "${ipcc}" "${jroot}/bin"
  ( cd "${jroot}/bin"
    [ -e ee ] || ln -s ipcc ee
    [ -e ff ] || ln -s ipcc ff
    [ -e gitk ] || ln -s ipcc gitk
    [ -e gitka ] || ln -s ipcc gitka
  )
}

# Launch ipcd on jail
j_ipc_start() {
  ipcd_pid="${jdir}/ipcd.pid"
  # Kill any running IPCd; remove stale pid file and socket
  if [ -f "${ipcd_pid}" ]
  then
    pid="$(cat "${ipcd_pid}")"
    if [ "${pid}" ]
    then
      if ps ouser=,command= "${pid}" | grep "^${ORIG_USER}" | grep -q "ipcd"
      then
        omg "IPCd: already running! Killing"
        kill -TERM "${pid}"
      fi
      omg "IPCd: removing stale pid file"
      rm -f "${ipcd_pid}" "${jroot}/tmp/jipc"
    fi
  fi
  su "${ORIG_USER}" "${jbase}/j/ipcd" "${jdir}" &
  pid="${!}"
  echo "${pid}" > "${ipcd_pid}"
  j_cg_trap "${pid}"
}

# Stop ipcd on jail
j_ipc_stop() {
  ipcd_pid="${jdir}/ipcd.pid"
  [ -f "${ipcd_pid}" ] && pid="$(cat "${ipcd_pid}")"
  [ "${pid}" ] && kill -TERM ${pid}
  rm -f "${ipcd_pid}"
}

# Is this a chroot?
j_is() {
  eval $(j_params "${1}")
  [ "${jerror}" ] && return 1 || return 0
}

# List available chroots
j_ls() {
  ( cd "${jbase}"; ls -1 ) | while read jname
  do
    j_is "${jname}" && echo "${jname}"
  done
}

# Chroot is 'up' if /dev/pts and /proc are mounted
j_up() {
  jname="${1:-${jname}}"
  eval "$(j_params "${jname}")"
  [ "${jerror}" ] && wtf "${jerror}"
  grep -q "^devpts ${jroot}/dev/pts devpts" /proc/mounts || return 1
  grep -q "^proc ${jroot}/proc proc" /proc/mounts || return 1
  return 0
}

# Poll chroot status (j_up)
j_status() {
  [ -z "${1}" ] && set - $(j_ls)
  while [ "${1}" ]
  do
    j_up "${1}" && meh "$(printf '\033[1;32mup\033[0m')" || meh "$(printf '\033[1;31mdown\033[0m')"
    shift
  done
}

# Mount /dev/pts and /proc in the chroot
j_start() {
  jname="${1:-${jname}}"
  j_up "${jname}" && return 0
  eval "$(j_params "${jname}")"
  meh "starting ${jname} ..."
  mount -t devpts devpts "${jroot}/dev/pts"
  mount -t proc proc "${jroot}/proc"

  # Copy in ipcc and launch ipcd
  j_ipc_setup
  j_ipc_start

  # Start all services in /etc/rcJ.d
  j_root_eval "${jname}" '[ -d /etc/rcJ.d ] && ( ls -1 /etc/rcJ.d/* 2>&- | grep /S | sort | sed -e "s/$/ start/" | sh )'
}

# Execute command in chroot as root
j_root_eval() {
  jname="${1:-${jname}}"; shift
  j_up "${jname}" || wtf "chroot not running"
  eval "$(j_params "${jname}")"
  j_cg_trap $$
  env -i ${jenv} /usr/bin/chroot "${jroot}" /bin/sh -c "${*}"
}

# Execute command in chroot
j_eval() {
  jname="${1:-${jname}}"; shift
  j_up "${jname}" || wtf "chroot not running"
  eval "$(j_params "${jname}")"
  j_cg_trap $$
  env -i ${jenv} /usr/bin/chroot "${jroot}" /bin/su "${juser:-${USER}}" -c "${*}"
}

j_shell() {
  jname="${1:-${jname}}"
  eval "$(j_params "${jname}")"
  j_eval "${jname}" "cd; exec ${jshell} -l"
}

# Unmount /dev/pts and /proc in the chroot
j_stop() {
  jname="${1:-${jname}}"
  eval "$(j_params "${jname}")"
  j_up "${jname}" || return 0
  meh "stopping ${jname} ..."

  # Stop all services in /etc/rcJ.d
  j_root_eval "${jname}" '[ -d /etc/rcJ.d ] && ( ls -1 /etc/rcJ.d/* 2>&- | grep /S | sort -r | sed -e "s/$/ stop/" | sh )'

  # Terminate ipcd
  j_ipc_stop

  umount "${jroot}/proc"
  umount "${jroot}/dev/pts"
}

# Send a signal to all processes inside a chroot, if possible
j_signal() {
  sig="${1:-HUP}"
  jname="${2:-${jname}}"

  [ "$(j_cgroup)" ] || { echo "No cgroup support; cannot signal"; return 1; }
  pids="$(cat "$(j_cgroup)/tasks")"
  if [ "${pids}" ]
  then
    echo Sending ${sig} to ${pids} ...
    echo "FROZEN" > "$(j_cgroup)/freezer.state"
    kill -${sig} ${pids}
    echo "THAWED" > "$(j_cgroup)/freezer.state"
  fi
}

j_kill() {
  jname="${1:-${jname}}"
  eval "$(j_params "${jname}")"
  meh "killing ${jname} ..."

  j_signal "TERM" "${jname}"
  sleep 2
  j_signal "KILL" "${jname}"
}

case "${cmd}" in
init|create) j_init "${jname}" "${@}" ;;
ls|list) j_ls ;;
status) j_status "${jname}" "${@}" ;;
start) j_start "${jname}" ;;
shell|enter) j_shell "${jname}" ;;
eval) j_eval "${jname}" "${*}" ;;
stop) j_stop "${jname}" ;;
kill) j_kill "${jname}" ;;
*) pebkac ;;
esac