python-smime
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S/MIME encoder in pure python
===================== Python S/MIME Toolkit
This library implements a S/MIME handler. It supports only S/MIME messages encryption 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 does not use the deprecated pycrypto anymore; instead it
was switched to the more modern cryptography library. It is not 'pure python'
anymore (because of the latter dependency), but at least works.
Requirements
- Python 2.7 or Python 3.5+
- cryptography
- 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" <[email protected]>',
'From: "Bob" <[email protected]>',
'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" <[email protected]>
From: "Bob" <[email protected]>
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
OpenSSL expects that the smime.p7m file above should be in DER or PEM format.
The latter should be enclosed in -----BEGIN PKCS7----- and -----END PKCS7----- and the content should be in base64 encoding, just like the output
of the command above. Example::
-----BEGIN PKCS7-----
MIIBdgYJKoZIhvcNAQcDoIIBZzCCAWMCAQAxgb4wgbsCAQAwJjASMRAwDgYDVQQD
EwdDYXJsUlNBAhBGNGvHgABWvBHTbi7EELOwMAsGCSqGSIb3DQEBAQSBgCVAQwNg
LmJ5ESYxOM1YbOLz2gvzWY1Fk+LZZiylYe7+o1/e/MjtzNwhnu+8vziFwHbXEH1Y
jndIbUxiLyXb3omtNDunRICQin5bdo6BI7oE0MufUSqMjk0YUk8UQeNCiUfK89PR
RfDclb1/sM3XZ7mUJa2OzpnuQIWec3MuJ3k4MIGcBgkqhkiG9w0BBwEwHQYJYIZI
AWUDBAEqBBCVZVOt2lxSzmd+Ti1M372xgHDR0+ToLk1MJeTTtmJdnnNNH6631PN0
i3NJeJBKDDs4onI8xywqFtJP0of6GPoTGV/7D2vkgO2+jhCBTrzjYczbdOhh6Z5X
o0i/81NPSoaLhrfwKMQvT7sXX7c9YdbTjyglyGqhXUN8h+mIRlP9IStD
-----END PKCS7-----
Remember that the above formatting serves only for the purpose of testing the encryption with OpenSSL. Do not make such enclosing in e-mails.
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_
.. _asn1crypto: https://github.com/wbond/asn1crypto .. _Semantic Versioning: http://semver.org/
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