Support for netscape / html5 SPKAC client certificate request
This library supports the format of browser-generated SPKAC certificate requests.
The HTML keygen tag which previously was supported by most Mozilla-based browsers is now in the HTML-5 standard. The keygen tag is used in a HTML form element and displays a key generation widget to the user. When submitted, the browser locally generates a public key pair, locally stores the private key, and submits the public key to the web server in the SPKAC format.
When generating a form with a keygen element, the web server can include a challenge string in the form. This challenge string is returned in the SPKAC generated by the browser. It is signed together with the public key by the private key retained by the browser.
This package is intended for server-side support of SPKAC. It uses a submitted SPKAC and checks for correct challenge string and that the public key and challenge are properly signed by the browser. It supports a method for generating a certificate from the data in the SPKAC and additional data supplied by the web application.
The generated certificate can then typically be used for client authentication to a web application and is therefore called a client certificate. The web browser (or other client-side application) supplies the certificate in the SSL handshake and proves it is in the posession of the necessary private key.
When building certificates it is also a good idea to have a certificate revocation list (CRL). The package provides routines to generate a revocation list from scratch using a list of certificate serial numbers and revocation dates.
Install using the standard python setup.py mechanism, e.g.:
python setup.py install --prefix=/usr/local
For a usage example see the doctests in spkac.py and crl.py
Notes for Building
When doing a release the following commands should be issued:
python setup.py clean --all python setup.py sdist --manifest-only git status python setup.py sdist --quiet git status python setup.py register python setup.py sdist upload --sign
The interleaved git status commands work around a bug in older git versions that, when git describe with --dirty option is used, will erroneously detect dirty status when the directory is stat-dirty. Since setup.py sdist will create symlinks this will make the directory stat-dirty.
The –manifest-only will re-create the MANIFEST file even if neither setup.py nor MANIFEST.in have changed.
Version 0.6: Bug fix
Release now contains missing files from 0.5.
- Add Notes for Building section and document release procedure to avoid missing files in the future
- Remove relative import statements
- Add version import to __init__.py
Version 0.5: Major feature enhancements
Implement Certificate Revocation Lists (CRL)
- Implementation of CRL (with MD5 hash, this probably needs to be fixed later on, don’t know yet if there is a format with a stronger hash)
- factor pem_object
- Fix timezone of default valid_from for generated certificate: We used a timezone correction on a timestamp which is already UTC.
Version 0.4: Bug fix
Fix incompatibility with newer versions of pyasn1.
- BitString serialisation in pyasn1 changed method names, the old inofficial serialisation method with ‘_’ is now official without the ‘_’.
Version 0.3: Bug fix
Import of version.py failed if dependecies were missing. This prevented a pip install from succeeding in case of missing dependencies.
- Guard import in __init__.py to not fail for missing dependencies
Version 0.2: Minor feature additions
Move example from end of spkac.py into a doctest. Change of API: set_email no longer supported. Now extensions can be given as unnamed arguments in the constructor. Named arguments are interpreted as subject parameters for the resulting certificate. All this is shown in the doctest.
- Remove set_email
- Change constructor: Allow extensions as args and subject parameters as keyword args
- Add doctest
- Fix setup.py to include install_requires to auto-install required packages
- Easier import: from pyspkac import SPKAC works now.
Version 0.1: Initial Release