#!/bin/bash
# install.sh
<I>[<I>...<I>]<I>
# Enter the internal address to which system email usually goes here
INT_ADDRESS=
# EXT_ADDRESS define the external address of the server to which to send the encrypted system messages. Important: You need a public GPG key on the keyserver for this address ($KEYSERVER_ADDRESS, see Line 9)
EXT_ADDRESS=
# The URL of the keyserver
KEYSERVER_ADDRESS=

# Install dependencies
apt-get install sudo gpg python-gpgme

# Create the system user without home directory and without login permission
adduser --system --no-create-home --disabled-login zeyple

# Download the Python script zeyple.py
wget https://github.com/infertux/zeyple/blob/master/zeyple/zeyple.py
# Download configuration file
wget https://github.com/infertux/zeyple/blob/master/zeyple/zeyple.conf.example

# Set up a directory under /etc for configuration file and key management
mkdir -p /etc/zeyple/keys && chmod 700 /etc/zeyple/keys && chown zeyple: /etc/zeyple/keys

# Fetch the public key from the keyserver for $EXT_ADDRESS and import with gpg
sudo -u zeyple gpg --homedir /etc/zeyple/keys --keyserver $KEYSERVER_ADDRESS --search $EXT_ADDRESS

# Move the example configuration file to /etc/zeyple
mv zeyple.conf.example /etc/zeyple/zeyple.conf
# Move zeyple.py to /usr/local/bin and apply user rights
mv zeyple.py /usr/local/bin/zeyple.py
chmod 744 /usr/local/bin/zeyple.py && chown zeyple: /usr/local/bin/zeyple.py

# Create logfile and set user rights
touch /var/log/zeyple.log && chown zeyple: /var/log/zeyple.log

# Prepare Postfix for Zeyple: expand main.cf and master.cf to include filter entries
cd /etc/postfix

cat >> master.cf <<END
zeyple  unix  -  n  n  -  -  pipe
  user=zeyple argv=/usr/local/bin/zeyple.py

localhost:10026  inet  n  -  n  -  10  smtpd
  -o content_filter=
  -o receive_override_options=no_unknown_recipient_checks,no_header_body_checks,no_milters
  -o smtpd_helo_restrictions=
  -o smtpd_client_restrictions=
  -o smtpd_sender_restrictions=
  -o smtpd_recipient_restrictions=permit_mynetworks,reject
  -o mynetworks=127.0.0.0/8
  -o smtpd_authorized_xforward_hosts=127.0.0.0/8
END

# Install the content filter in main.cf
cat >> main.cf <<END
content_filter = zeyple
END

# For Zeyple to assign keys correctly, it is recommended to redirect the internal email address for outgoing mail to the external address
cat >> recipient_canonical<<END
$INT_ADDRESS  $EXT_ADDRESS
END

# Create the new Postfix database recipient
postmap recipient_canonical
# Publish database in Postfix address rewriting
cat >> main.cf <<END
recipient_canonical_maps = hash:/etc/postfix/recipient_canonical
END
# Reload Postfix configuration
/etc/init.d/postfix reload

exit 0