Skip to main content

Validates X.509 certificates and paths; forked from wbond/certvalidator

Project description


This library started as a fork of wbond/certvalidator with patches for pyHanko, but has since diverged considerably from its parent repository.

Bugs and questions regarding this library should be asked in the pyHanko repository rather than here.

pyhanko-certvalidator is a Python library for validating X.509 certificates paths. It supports various options, including: validation at a specific moment in time, whitelisting and revocation checks.


  • X.509 path building
  • X.509 basic path validation
    • Signatures
      • RSA (including PSS padding), DSA, ECDSA and EdDSA algorithms.
    • Name chaining
    • Validity dates
    • Basic constraints extension
      • CA flag
      • Path length constraint
    • Key usage extension
    • Extended key usage extension
    • Certificate policies
      • Policy constraints
      • Policy mapping
      • Inhibit anyPolicy
    • Failure on unknown/unsupported critical extensions
  • TLS/SSL server validation
  • Whitelisting certificates
  • Blacklisting hash algorithms
  • Revocation checks
    • CRLs
      • Indirect CRLs
      • Delta CRLs
    • OCSP checks
      • Delegated OCSP responders
    • Disable, require or allow soft failures
    • Caching of CRLs/OCSP responses
  • CRL and OCSP HTTP clients
  • Point-in-time validation
  • Name constraints
  • Attribute certificate support

Current Release

pypi - changelog


  • asn1crypto
  • cryptography
  • uritools
  • oscrypto
  • requests or aiohttp (use the latter for more efficient asyncio, requires resource management)
  • Python 3.7 or higher

Note on compatibility

Starting with pyhanko-certvalidator version 0.17.0, the library has been refactored to use asynchronous I/O as much as possible. Most high-level API entrypoints can still be used synchronously, but have been deprecated in favour of their asyncio equivalents. As part of this move, the OCSP and CRL clients now have two separate implementations: a requests-based one, and an aiohttp-based one. The latter is probably more performant, but requires more resource management efforts on the caller's part, which was impossible to implement without making major breaking changes to the public API that would make the migration path more complicated. Therefore, the requests-based fetcher will remain the default for the time being.


pip install pyhanko-certvalidator


certvalidator is licensed under the terms of the MIT license. See the LICENSE file for the exact license text.


Test framework

Tests are written using pytest and require an asynchronous test case backend such as pytest-asyncio.

Test cases

The test cases for the library are comprised of:

Existing releases can be found at

Project details

Download files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

Source Distribution

pyhanko-certvalidator-0.26.3.tar.gz (102.7 kB view hashes)

Uploaded Source

Built Distribution

pyhanko_certvalidator-0.26.3-py3-none-any.whl (109.4 kB view hashes)

Uploaded Python 3

Supported by

AWS AWS Cloud computing and Security Sponsor Datadog Datadog Monitoring Fastly Fastly CDN Google Google Download Analytics Microsoft Microsoft PSF Sponsor Pingdom Pingdom Monitoring Sentry Sentry Error logging StatusPage StatusPage Status page