srslib - Sender Rewriting Scheme (SRS) library for Python

srslib is a modern Python implementation of the Sender Rewriting Scheme (SRS).

Highlights:

• Compatible with Python 2.7 and 3.x;
• Implements the standard "Guarded" SRS scheme as described in the original SRS paper;
• Simple to use and understand.

Installation

pip install srslib

Example Usage

import srslib

srs = srslib.SRS('my_secret_key')

# Rewrites an email from alice@A.com to B.com
rewritten_addr = srs.forward('alice@A.com', 'B.com')
# => 'SRS0=ZPM1=67=A.com=alice@B.com'

# Reverse it to get the address to bounce to.
try:
  bounce_addr = srs.reverse(rewritten_addr)
  # => 'alice@A.com'
except srslib.Error as e:
  ...  # Handle errors

# Check if addresses are valid SRS addresses.
assert not srslib.SRS.is_srs_address('alice@A.com')
assert srslib.SRS.is_srs_address(rewritten_addr)

Documentation

The full documentation for srslib lives at https://srslib.readthedocs.io/.

Implementation

This library is a clean re-implementation of SRS in modern Python based on the original SRS paper, and taking inspiration from the canonical libsrs2 C implementation and the older pysrs library (which itself is based on the Mail::SRS Perl package).

Compared to these two libraries, srslib

• ... is a clean, modern, pure-Python implementation and supports Python 3.x;
• ... discards baggage from Mail::SRS around legacy schemes and settings.

License

Licensed under the Apache License, Version 2.0.