#!/bin/sh
# cyrus-deliver --- wrapper for procmail to deliver to cyrus imap server
# Author: Noah Friedman <friedman@splode.com>
# Created: 2005-05-12
# Public domain

# $Id: cyrus-deliver,v 1.7 2011/05/04 20:30:20 friedman Exp $

# Commentary:

# The cyrus delivery agent requires access to a unix-domain socket which is
# only accessible to group `mail'.  If the restricted delivery wrapper is
# installed and is setgid, then use that.  Otherwise, try to use deliver
# directly.  If that STILL fails, it's up to procmail to deal with that.

# Code:

libdir=/usr/lib/cyrus-imapd
USER=${SUDO_USER-${USER-$LOGNAME}}

lockfile=/tmp/cyrus-deliver.$USER.lock

# The cyrus-imap `deliver' program does not gracefully handle temporary
# errors due to server-side locks while another message is in the process
# of being delivered.  Therefore, for all instances of this meta-wrapper,
# negotiate a client-side exclusive lock for the user before running the
# delivery agent.
get_lock()
{
  tmplock=$lockfile.$$
  echo $$ > $tmplock
  tmplstat=`stat -c "%i %Y" $tmplock`
  while : ; do
    if link $tmplock $lockfile 2> /dev/null ; then
      unlink $tmplock
      trap remove_lock 0 1 2 3 15
      return 0
    fi

    # Someone else has the lock; see if they're still alive.
    pid=`cat $lockfile 2> /dev/null`
    if [ -n "$pid" ] \
       && ! kill -0 $pid 2> /dev/null \
       && rm -f $lockfile \
       && link $tmplock $lockfile 2> /dev/null
    then
      lockstat=`stat -c "%i %Y" $lockfile`
      case $lockstat in
        $tmplstat )
          unlink $tmplock
          trap remove_lock 0 1 2 3 15
          return 0 ;;
      esac
    fi

    logger -i -p mail.notice -t cyrus-deliver \
      "waiting 5s for pid $pid to release lock"
    sleep 5
  done
}

remove_lock()
{
  e=$?
  rm -f "$lockfile"
  exit $e
}

do_delivery()
{
  # Remove envelope from incoming message.
  # Cyrus' lmtpd bombs if it sees a leading "From ".
  sed -e '1{/^From /d;}' \
   | {
       if [ -g $libdir/deliver-wrapper ]; then
         case $# in
           0 ) set INBOX    ;;
         esac

         $libdir/deliver-wrapper "$1"
       else
         case $# in
           0 ) $libdir/deliver -a "$USER" "$USER"         ;;
           * ) $libdir/deliver -a "$USER" -m "$1" "$USER" ;;
         esac
       fi
     }
}

main()
{
  if get_lock ; then
    do_delivery ${1+"$@"}
  fi
  remove_lock
}

main ${1+"$@"}

# eof