Mixtasy - an openPGP based remailer

This is a prototype which implements a subset of the Mixtasy remailer specification written in python. An existing Postfix SMTP server can easily be turned into a Mixtasy mix. The python script can be injected to the Postfix flow as a simple after-queue content filter (see http://www.postfix.org/FILTER_README.html). When setup as explained below the script will process Mixtasy messages and inject the output to Postfix and re-inject all other messages untouched.

• python 2.7
• fitted python module python-gnupg (fork of https://bitbucket.org/vinay.sajip/python-gnupg/)
• GnuPG

For help on how to invoke the python program execute mixtasy.py -h

To create a Mixtasy message just execute mixtasy.py create. The message (including header and body) will be read from stdin as long you specify an input file with the -i option. The input must contain a To: header field which holds the final recipient of the message. The created Mixtasy message ready to send to the first mix (specified in the To: header field of the outputted mix message) is printed to stdout unless you specify an output file with -o.

To unpack one layer of a Mixtasy message execute mixtasy.py unpack Like for the message creation command the -i/-o options can be used to specify files for input/output instead of using stdin and stdout.

1. Setup a Postfix SMTP server

2. Create an user named 'mixtasy'

3. Create an openPGP key with the 'mixtasy' user for your mix node and publish it on a public openPGP keyserver.

   Note: The openPGP key must follow the Mixtasy protol specification.

4. Copy the mixtasy.py to a location the 'mixtasy' user has permissions to execute them.

   Note: Permissions granted via groups seems not to be considered.

5. To define the Postfix Mixtasy filter service add the following block to your Postfix's master.cf

   /etc/postfix/master.cf:

   mixtasy    unix  -       n       n       -       10      pipe
     flags=Rq user=mixtasy null_sender=
     argv=/path/to/mixtasy.py -o /dev/null -v3 -l /var/log/mixtasy.log unpack -s ${sender} ${recipient}
   

6. To enable the Mixtasy filter add the -o content_filter=mixtasy:dummy option to the Postfix SMTP service.

   /etc/postfix/master.cf:

   smtp      inet  n       -       -       -       -       smtpd
     -o content_filter=mixtasy:dummy