petrified/petrified

#!/bin/bash
#
## petrified - bash client to update dynamic DNS at freedns.afraid.org
## Copyright (c) 2015 Troy Engel
## Version: 1.0.5
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
#

## One of these must exist - '-c <config>' ignores global/local entirely
CONF_GLOBAL=/etc/petrified.conf
CONF_LOCAL=~/.petrifiedrc
CONF_NAMED=""

# Check our arguments for a config file
while getopts ":c:" opt; do
  case $opt in
    c)
      CONF_NAMED="$OPTARG"
      ;;
    :)
      echo "Option -$OPTARG requires the name of a config file." >&2
      exit 1
      ;;
  esac
done

## How to update DNS - DDNS_KEY is unique per domain
DDNS_URL=https://freedns.afraid.org/dynamic/update.php
DDNS_KEY=""

## Which URL to use to get an IP
# IPv4 icanhazip (http://major.io/icanhazip-com-faq/)
DDNS_CHECK="http://4.icanhazip.com"
# IPv6 icanhazip (http://major.io/icanhazip-com-faq/)
#DDNS_CHECK="http://6.icanhazip.com"

## How many seconds should curl wait when either checking your IP or
## trying to update the remote DNS
CURL_WAIT=10

## Report an internal IP instead of the public IP - useful if you're
## using dynamic DNS for machines on the internal network
LOCAL_MODE=0
# Specify which interface
LOCAL_IF=eth0
# Should we use IPv4 or IPv6
LOCAL_IV=4

## How to log - multiple supported
USE_JOURNAL=1
USE_SYSLOG=0
USE_STDOUT=0
USE_LOGFILE=0

## If USE_LOGFILE is 1, where to log
PET_LOG=/var/log/petrified.log

## Prevent race conditions, i.e. stuck crons piling up
USE_PID=1
PET_PID=/run/petrified.pid

## Save the IP from our last check
USE_LIP=1
PET_LIP=/var/cache/petrified/lastip.dat

## Dependencies:
# logger (util-linux)
# kill   (util-linux)
# printf (coreutils)
# touch  (coreutils)
# date   (coreutils)
# stat   (coreutils)
# cat    (coreutils)
# rm     (coreutils)
# bash   (bash)
# ip     (iproute2)
# curl   (curl)

####

# Read in our configs
if [[ -z "${CONF_NAMED}" ]]; then
  [[ -r "${CONF_GLOBAL}" ]] && source "${CONF_GLOBAL}"
  [[ -r "${CONF_LOCAL}" ]] && source "${CONF_LOCAL}"
else
  [[ -r "${CONF_NAMED}" ]] && source "${CONF_NAMED}"
fi

# Check that we have all the needed variables
if [[ -z "${DDNS_KEY}" ]]; then
  echo "DDNS_KEY must be configured, exiting."
  exit 1
fi

# Make sure that PET_LOG will work if required
if (( ${USE_LOGFILE} == 1 )); then
  if [[ -z "${PET_LOG}" ]]; then
    echo "USE_LOGFILE=1 but PET_LOG is an empty string, exiting."
    exit 1
  elif (( $(touch "${PET_LOG}" 2>/dev/null; echo $?;) != 0 )); then
    echo "USE_LOGFILE=1 but cannot write to ${PET_LOG}, exiting."
    exit 1
  fi
fi

# Logging
logmsg () {
  LMSG=$1
  if (( ${USE_JOURNAL} == 1 )); then
    printf "%s\n%s\n" "SYSLOG_IDENTIFIER=petrified" "MESSAGE=${LMSG}" | \
      logger --journald
  fi
  if (( ${USE_SYSLOG} == 1 )); then
    echo "${LMSG}" | logger -t petrified
  fi
  if (( ${USE_STDOUT} == 1 )); then
    DTS=$(date +"%Y-%m-%d %H:%M:%S")
    echo "[${DTS}] [petrified] ${LMSG}"
  fi
  if (( ${USE_LOGFILE} == 1 )); then
    DTS=$(date +"%Y-%m-%d %H:%M:%S")
    echo "[${DTS}] [petrified] ${LMSG}" >> "${PET_LOG}"
  fi
  return
}

# Security warning
statchk () {
  _CFILE=$1
  if [[ -f "${_CFILE}" ]] && [[ -r "${_CFILE}" ]]; then
    if [[ $(stat -c "%a" "${_CFILE}") != 600 ]]; then
      logmsg "Security warning: ${_CFILE} is readable but not mode 0600"
    fi
  fi
}
[[ -n "${CONF_GLOBAL}" ]] && statchk "${CONF_GLOBAL}"
[[ -n "${CONF_LOCAL}" ]] && statchk "${CONF_LOCAL}"
[[ -n "${CONF_NAMED}" ]] && statchk "${CONF_NAMED}"

# Make sure that PET_PID will work if required
if (( ${USE_PID} == 1 )); then
  if [[ -z "${PET_PID}" ]]; then
    logmsg "USE_PID=1 but PET_PID is an empty string, exiting."
    exit 1
  elif (( $(touch "${PET_PID}" 2>/dev/null; echo $?;) != 0 )); then
    logmsg "USE_PID=1 but cannot write to ${PET_PID}, exiting."
    exit 1
  fi
fi

# PID actions
if (( ${USE_PID} == 1 )); then
  PIDNUM=$(cat "${PET_PID}" 2>/dev/null)
  # check if we have a number
  if [[ ${PIDMUM} =~ ^-?[0-9]+$ ]]; then
    kill -0 ${PIDNUM}
    if (( $? == 0 )); then
      logmsg "Detected a running process ${PIDNUM}, exiting."
      exit 1
    else
      logmsg "Stale PID ${PIDNUM} detected, overwriting."
    fi
  fi
  echo ${BASHPID} > "${PET_PID}"
fi

# Cleanup actions
cleanup () {
  (( ${USE_PID} == 1 )) && (rm -f "${PET_PID}" 1>/dev/null 2>&1)
  (( ${USE_LIP} == 0 )) && (rm -f "${PET_LIP}" 1>/dev/null 2>&1)
  return
}

# Trap the basic signals
sigexit () {
  logmsg "Trapped a kill signal, exiting."
  cleanup
  exit 3
}
trap sigexit SIGHUP SIGINT SIGTERM

# Get our IP address
NEWIP=""
if (( ${LOCAL_MODE} == 1 )); then
  NEWIP=$(ip -${LOCAL_IV} -o addr show dev ${LOCAL_IF} primary 2>/dev/null)
  NEWIP=${NEWIP%%/*}
  NEWIP=${NEWIP##* }
else
  NEWIP=$(curl -m ${CURL_WAIT} -s ${DDNS_CHECK} 2>/dev/null)
fi
if [[ -z "${NEWIP}" ]]; then
  logmsg "Error getting an IP address, exiting."
  cleanup
  exit 1
fi

# Check our saved IP against the new IP
OLDIP="0"
if (( ${USE_LIP} == 1 )); then
  OLDIP=$(cat "${PET_LIP}" 2>/dev/null)
fi

# If they don't match, tell upstream
if [[ "${OLDIP}" != "${NEWIP}" ]]; then
  UPDURL="${DDNS_URL}?${DDNS_KEY}&address=${NEWIP}"
  RESULT=$(curl -m ${CURL_WAIT} -sk "${UPDURL}" 2>/dev/null)
  logmsg "${RESULT}"
else
  logmsg "IP ${NEWIP} hasn't changed, not updating."
fi

# Save the new IP if configured
if (( ${USE_LIP} == 1 )); then
  if (( $(touch "${PET_LIP}" 2>/dev/null; echo $?;) != 0 )); then
    logmsg "USE_LIP=1 but cannot write to ${PET_LIP}."
  else
    echo "${NEWIP}" > "${PET_LIP}"
  fi
fi

# Take out the trash
cleanup

exit 0