#!/bin/bash

# Copyright (C) 2014 Timothe Litt litt at acm dot org

# This script may be freely copied, used and modified providing that
# this notice and the copyright statement are included in all copies
# and derivative works.  No warranty is offered, and use is entirely at
# your own risk.  Bugfixes and improvements would be appreciated by the
# author.

VERSION="1.003"

# leap-seconds file manager/updater

# Depends on:
#  wget sed, tr, shasum, logger

# ########## Default configuration ##########
#
# Where to get the file
LEAPSRC="ftp://time.nist.gov/pub/leap-seconds.list"

# How many times to try to download new file
MAXTRIES=6
INTERVAL=10

# Where to find ntp config file
NTPCONF=/etc/ntp.conf

# How long before expiration to get updated file
PREFETCH="60 days"

# How to restart NTP - older NTP: service ntpd? try-restart | condrestart
# Recent NTP checks for new file daily, so there's nothing to do
RESTART=

# Where to put temporary copy before it's validated
TMPFILE="/tmp/leap-seconds.$$.tmp"

# Syslog facility
LOGFAC=daemon
# ###########################################

# Places to look for commands.  Allows for CRON having path to
# old utilities on embedded systems

PATHLIST="/opt/sbin:/opt/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:"

REQUIREDCMDS=" wget logger tr sed shasum"

SELF="`basename $0`"

function displayHelp {
           cat <<EOF
Usage: $SELF [options] [leapfile]

Verifies and if necessary, updates leap-second definition file

All arguments are optional:  Default (or current value) shown:
   -s    Specify the URL of the master copy to download
         $LEAPSRC
   -4    Use only IPv4
   -6    Use only IPv6
   -p 4|6
         Prefer IPv4 or IPv6 (as specified) addresses, but use either
   -d    Specify the filename on the local system
         $LEAPFILE
   -e    Specify how long before expiration the file is to be refreshed
         Units are required, e.g. "-e 60 days"  Note that larger values
         imply more frequent refreshes.
         "$PREFETCH"
   -f    Specify location of ntp.conf (used to make sure leapfile directive is
         present and to default  leapfile)
         $NTPCONF
   -F    Force update even if current file is OK and not close to expiring.
   -c    Command to restart NTP after installing a new file
         <none> - ntpd checks file daily
   -r    Specify number of times to retry on get failure
         $MAXTRIES
   -i    Specify number of minutes between retries
         $INTERVAL
   -l    Use syslog for output (Implied if CRONJOB is set)
   -L    Don't use syslog for output
   -P    Specify the syslog facility for logging
         $LOGFAC
   -t    Name of temporary file used in validation
         $TMPFILE
   -q    Only report errors to stdout
   -v    Verbose output
   -z    Specify path for utilities
         $PATHLIST
   -Z    Only use system path

$SELF will validate the file currently on the local system

Ordinarily, the file is found using the "leapfile" directive in $NTPCONF.
However, an alternate location can be specified on the command line.

If the file does not exist, is not valid, has expired, or is expiring soon,
a new copy will be downloaded.  If the new copy validates, it is installed and
NTP is (optionally) restarted.

If the current file is acceptable, no download or restart occurs.

-c can also be used to invoke another script to perform administrative
functions, e.g. to copy the file to other local systems.

This can be run as a cron job.  As the file is rarely updated, and leap
seconds are announced at least one month in advance (usually longer), it
need not be run more frequently than about once every three weeks.

For cron-friendly behavior, define CRONJOB=1 in the crontab.

This script depends on$REQUIREDCMDS

Version $VERSION
EOF
  return 0
}

# Default: Use syslog for logging if running under cron

SYSLOG="$CRONJOB"

if [ "$1" = "--help" ]; then
   displayHelp
   exit 0
fi

# Parse options

while getopts 46p:P:s:e:f:Fc:r:i:lLt:hqvz:Z opt; do
   case $opt in
       4)
           PROTO="-4"
           ;;
       6)
           PROTO="-6"
           ;;
       p)
           if [ "$OPTARG" = '4' -o "$OPTARG" = '6' ]; then
               PREFER="--prefer-family=IPv$OPTARG"
           else
               echo "Invalid -p $OPTARG" >&2
               exit 1;
           fi
           ;;
       P)
           LOGFAC="$OPTARG"
           ;;
       s)
           LEAPSRC="$OPTARG"
           ;;
       e)
           PREFETCH="$OPTARG"
           ;;
       f)
           NTPCONF="$OPTARG"
           ;;
       F)
           FORCE="Y"
           ;;
       c)
           RESTART="$OPTARG"
           ;;
       r)
           MAXTRIES="$OPTARG"
           ;;
       i)
           INTERVAL="$OPTARG"
           ;;
       t)
           TMPFILE="$OPTARG"
           ;;
       l)
           SYSLOG="y"
           ;;
       L)
           SYSLOG=
           ;;
       h)
           displayHelp
           exit 0
           ;;
       q)
           QUIET="Y"
           ;;
       v)
           VERBOSE="Y"
           ;;
       z)
           PATHLIST="$OPTARG:"
           ;;
       Z)
           PATHLIST=
           ;;
       *)
           echo "$SELF -h for usage" >&2
           exit 1
           ;;
   esac
done
shift $((OPTIND-1))

export PATH="$PATHLIST$PATH"

# Add to path to deal with embedded systems
#
for P in $REQUIREDCMDS ; do
   if >/dev/null 2>&1 which "$P" ; then
       continue
   fi
   [ "$P" = "logger" ] && continue
   echo "FATAL: missing $P command, please install"
   exit 1
done

# Handle logging

if ! LOGGER="`2>/dev/null which logger`" ; then
   LOGGER=
fi

function log {
   # "priority" "message"
   #
   # Stdout unless syslog specified or logger isn't available
   #
   if [ -z "$SYSLOG" -o -z "$LOGGER" ]; then
       if [ -n "$QUIET" -a \( "$1" = "info" -o "$1" = "notice" -o "$1" = "debug" \) ]; then
           return 0
       fi
       echo "`echo \"$1\" | tr a-z A-Z`: $2"
       return 0
   fi

   # Also log to stdout if cron job && notice or higher
   local S
   if [ -n "$CRONJOB" -a \( "$1" != "info" \) -a \( "$1" != "debug" \) ] || [ -n "$VERBOSE" ]; then
       S="-s"
   fi
   $LOGGER $S -t "$SELF[$$]" -p "$LOGFAC.$1" "$2"
}

# Verify interval
INTERVAL=$(( $INTERVAL *1 ))

# Validate a leap-seconds file checksum
#
# File format: (full description in files)
# # marks comments, except:
# #$ number : the NTP date of the last update
# #@ number : the NTP date that the file expires
# Date (seconds since 1900) leaps : leaps is the # of seconds to add for times >= Date
# Date lines have comments.
# #h hex hex hex hex hex is the SHA-1 checksum of the data & dates, excluding whitespace w/o leading zeroes

function verifySHA {

   if [ ! -f "$1" ]; then
       return 1
   fi

   # Remove comments, except those that are markers for last update, expires and hash

   local RAW="`sed $1 -e'/^\\([0-9]\\|#[\$@h]\)/!d' -e'/^#[\$@h]/!s/#.*\$//g'`"

   # Extract just the data, removing all whitespace

   local DATA="`echo \"$RAW\" | sed -e'/^#h/d' -e's/^#[\$@]//g' | tr -d '[:space:]'`"

   # Compute the SHA hash of the data, removing the marker and filename
   # Computed in binary mode, which shouldn't matter since whitespace has been removed
   # shasum comes in several flavors; a portable one is available in Perl (with Digest::SHA)

   local DSHA="`echo -n \"$DATA\" | shasum | sed -e's/[? *].*$//'`"

   # Extract the file's hash. Restore any leading zeroes in hash segments.

   # The sed [] includes a tab (\t) and space; #h is followed by a tab and space
   local FSHA="`echo \"$RAW\" | sed -e'/^#h/!d' -e's/^#h//' -e's/[     ] */ 0x/g'`"
   FSHA=`printf '%08x%08x%08x%08x%08x' $FSHA`

   if [ -n "$FSHA" -a \( "$FSHA" = "$DSHA" \) ]; then
       if [ -n "$2" ]; then
           log "info" "Checksum of $1 validated"
       fi
   else
       log "error" "Checksum of $1 is invalid:"
       [ -z "$FSHA" ] && FSHA="(no checksum record found in file)"
       log "error" "EXPECTED: $FSHA"
       log "error" "COMPUTED: $DSHA"
       return 1
   fi

   # Check the expiration date, converting NTP epoch to Unix epoch used by date

   EXPIRES="`echo \"$RAW\" | sed -e'/^#@/!d' -e's/^#@//' | tr -d '[:space:]'`"
   EXPIRES="$(($EXPIRES - 2208988800 ))"

   if [ $EXPIRES -lt `date -u +%s` ]; then
       log "notice" "File expired on `date -u -d \"Jan 1, 1970 00:00:00 +0000 + $EXPIRES seconds\"`"
       return 2
   fi

}

# Verify ntp.conf

if ! [ -f "$NTPCONF" ]; then
   log "critical" "Missing ntp configuration $NTPCONF"
   exit 1
fi

# Parse ntp.conf for leapfile directive

LEAPFILE="`sed $NTPCONF -e'/^ *leapfile  *.*$/!d' -e's/^ *leapfile  *//'`"
if [ -z "$LEAPFILE" ]; then
   log "error" "$NTPCONF does not specify a leapfile"
fi

# Allow placing the file someplace else - testing

if [ -n "$1" ]; then
   if [ "$1" != "$LEAPFILE" ]; then
       log "notice" "Requested install to $1, but $NTPCONF specifies $LEAPFILE"
   fi
   LEAPFILE="$1"
fi

# Verify the current file
# If it is missing, doesn't validate or expired
# Or is expiring soon
#  Download a new one

if [ -n "$FORCE" ] || ! verifySHA $LEAPFILE "$VERBOSE" || [ $EXPIRES -lt `date -d "NOW + $PREFETCH" +%s` ] ; then
   TRY=0
   while true; do
       TRY=$(( $TRY + 1 ))
       if [ -n "$VERBOSE" ]; then
           log "info" "Attempting download from $LEAPSRC, try $TRY.."
       fi
       if wget $PROTO $PREFER -o ${TMPFILE}.log $LEAPSRC -O $TMPFILE ; then
           log "info" "Download of $LEAPSRC succeeded"
           if [ -n "$VERBOSE" ]; then
               cat ${TMPFILE}.log
           fi

           if ! verifySHA $TMPFILE "$VERBOSE" ; then
               # There is no point in retrying, as the file on the server is almost
               # certainly corrupt.

               log "warning" "Downloaded file $TMPFILE rejected -- saved for diagnosis"
               cat ${TMPFILE}.log
               rm -f ${TMPFILE}.log
               exit 1
           fi
           rm -f ${TMPFILE}.log

           # Set correct permissions on temporary file

           REFFILE="$LEAPFILE"
           if [ ! -f $LEAPFILE ]; then
               log "notice" "$LEAPFILE was missing, creating new copy - check permissions"
               touch $LEAPFILE
               # Can't copy permissions from old file, copy from NTPCONF instead
               REFFILE="$NTPCONF"
           fi
           chmod --reference $REFFILE $TMPFILE
           chown --reference $REFFILE $TMPFILE
           ( which selinuxenabled && selinuxenabled && which chcon ) >/dev/null 2>&1
           if  [ $? == 0 ] ; then
               chcon --reference $REFFILE $TMPFILE
           fi

           # Replace current file with validated new one

           if mv -f $TMPFILE $LEAPFILE ; then
               log "notice" "Installed new $LEAPFILE from $LEAPSRC"
           else
               log "error" "Install $TMPFILE => $LEAPFILE failed -- saved for diagnosis"
               exit 1
           fi

           # Restart NTP (or whatever else is specified)

           if [ -n "$RESTART" ]; then
               if [ -n "$VERBOSE" ]; then
                   log "info" "Attempting restart action: $RESTART"
               fi
               R="$( 2>&1 $RESTART )"
               if [ $? -eq 0 ]; then
                   log "notice" "Restart action succeeded"
                   if [ -n "$VERBOSE" -a -n "$R" ]; then
                       log "info" "$R"
                   fi
               else
                   log "error" "Restart action failed"
                   if [ -n "$R" ]; then
                       log "error" "$R"
                   fi
                   exit 2
               fi
           fi
           exit 0
       fi

       # Failed to download.  See about trying again

       rm -f $TMPFILE
       if [ $TRY -ge $MAXTRIES ]; then
           break;
       fi
       if [ -n "$VERBOSE" ]; then
           cat ${TMPFILE}.log
           log "info" "Waiting $INTERVAL minutes before retrying..."
       fi
       sleep $(( $INTERVAL * 60))
   done

   # Failed and out of retries

   log "warning" "Download from $LEAPSRC failed after $TRY attempts"
   if [ -f ${TMPFILE}.log ]; then
       cat ${TMPFILE}.log
       rm -f ${TMPFILE}.log $TMPFILE
   fi
   exit 1
fi
log "info" "Not time to replace $LEAPFILE"

exit 0

# EOF