/python-smime

S/MIME encoder in pure python

Primary LanguagePythonApache License 2.0Apache-2.0

Python S/MIME Toolkit

This library implements a S/MIME handler. In this first version, it can only encrypt S/MIME messages using a public RSA key, in AES128-CBC, AES192-CBC or AES256-CBC modes.

The ASN.1 implementation does not depend on pyasn1, as it showed too broken for creating and reading CMS (Cryptographic Message Syntax). Instead, the asn1crypto was used in this project.

This implementation uses pycrypto instead of OpenSSL, so everything is 'pure python'.

Requirements

  • Python 2.7 or Python 3.3
  • pycrypto
  • asn1crypto

Example

The code below loads Alice's public key in PEM format and uses it to encrypt the e-mail in S/MIME format:

import sys
import smime

message = [
    'To: "Alice" <alice@foo.com>',
    'From: "Bob" <bob@bar.com>',
    'Subject: A message from python',
    '',
    'Now you see me.'
]

with open('alice-public-key.pem', 'rb') as pem:
    print(smime.encrypt('\n'.join(message), pem.read()))

Output:

To: "Alice" <alice@foo.com>
From: "Bob" <bob@bar.com>
Subject: A message from python
MIME-Version: 1.0
Content-Type: application/pkcs7-mime; smime-type=enveloped-data; name=smime.p7m
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename=smime.p7m

<base64-enveloped-data>

The same can be decrypted using OpenSSL from the command line:

$ openssl smime -decrypt -in smime.p7m -inkey alice-private-key.pem

License

This software is licensed under the Apache License 2.0. See the LICENSE file in the top distribution directory for the full license text.

Versioning

This software follows Semantic Versioning