#!/usr/bin/env python
#
# A simple utility to receive volume_key escrow packets via e-mail
#
# Copyright (C) 2010 Marko Myllynen <myllynen@redhat.com>
#
# 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 2
# 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, see <http://www.gnu.org/licenses/>.

import datetime
import smtplib
import hashlib
import base64
import email
import sys
import os

from email.MIMEText import MIMEText

MAX_EMAIL_SIZE = 4096
SMTP_SERVER = "localhost"
ADMIN_EMAIL = "root@localhost.localdomain"
ESCROW_DIR = "/var/local/escrows"
LOG = "/var/log/escrow.log"

checksum = escrow = sender = None
log = open(LOG, 'a')
now = datetime.datetime.now().strftime("%Y-%m-%d %H:%M:%S")

# Read in and process the received email escrow packet
log.write("INFO: Starting to process an email escrow packet on " + now + "\n")
msg = email.message_from_string(sys.stdin.read(MAX_EMAIL_SIZE))
if msg.is_multipart():
    for part in msg.walk():
        # Parse packet source information from the message body
        if not part.get('Content-Disposition'):
            for line in str(part.get_payload()).split('\n'):
                if "MD5 checksum: " in line:
                    checksum = line.split("MD5 checksum: ")[-1]
                if "packet from: " in line:
                    sender = line.split("packet from: ")[-1]
        # Save the escrow packet
        else:
            if not sender:
                continue
            escrow = ESCROW_DIR + "/" + sender.replace("/", "_") + "-" + now.replace(" ", "-")
            os.umask(0266)
            f = open(escrow, 'wb')
            f.write(base64.b64decode(part.get_payload()))
            f.close()

if checksum is None or escrow is None or sender is None:
    log.write("ERROR: Malformed email escrow packet received.\n")
    now = datetime.datetime.now().strftime("%Y-%m-%d %H:%M:%S")
    log.write("INFO: Processing completed on " + now + "\n")
    log.close()
    sys.exit(1)

# Verify packet checksum
checksum_ok = checksum == hashlib.md5(file(escrow).read()).hexdigest()
if checksum_ok:
    reply = "Your backup passphrase has been successfully received.\n"
    reply = reply + "\nYou should now remove the escrow packet file from your computer.\n"
    status = "-VALID-PACKET"
    log.write("INFO: Received valid escrow packet from " + sender + "\n")
else:
    reply = "Error receiving your backup passphrase packet!\n"
    status = "-CHECKSUM-ERROR"
    log.write("WARNING: Received invalid email escrow packet from " + sender + "\n")
    log.write("WARNING: Marking escrow packet invalid: " + escrow + "\n")

# Inform the sender
msg = MIMEText(reply)
msg['Subject'] = reply.split('\n')[0]
msg['From'] = ADMIN_EMAIL
msg['To'] = sender
s = smtplib.SMTP(SMTP_SERVER)
try:
    s.sendmail(ADMIN_EMAIL, sender, msg.as_string())
    if checksum_ok:
        log.write("INFO: Marking escrow packet valid: " + escrow + "\n")
except smtplib.SMTPRecipientsRefused:
    log.write("WARNING: Invalid escrow packet sender: " + sender + "\n")
    log.write("WARNING: Marking escrow packet invalid: " + escrow + "\n")
    status = status + "-UNKNOWN-SENDER"
s.quit()

os.rename(escrow, escrow + status)
now = datetime.datetime.now().strftime("%Y-%m-%d %H:%M:%S")
log.write("INFO: Processing completed on " + now + "\n")
log.close()