Description

assignee = 'https://github.com/tiran'
closed_at = None
created_at = <Date 2021-08-02.12:25:20.022>
labels = ['expert-SSL', 'type-feature', '3.11']
title = 'Change default signature algorithms for context in the ssl library'
updated_at = <Date 2021-10-01.14:03:30.841>
user = 'https://github.com/anisgandoura'

activity = <Date 2021-10-01.14:03:30.841>
actor = 'ramikg'
assignee = 'christian.heimes'
closed = False
closed_date = None
closer = None
components = ['SSL']
creation = <Date 2021-08-02.12:25:20.022>
creator = 'anis.gandoura'
dependencies = []
files = []
hgrepos = []
issue_num = 44811
keywords = ['patch']
message_count = 4.0
messages = ['398762', '398769', '398772', '403016']
nosy_count = 4.0
nosy_names = ['christian.heimes', 'python-dev', 'anis.gandoura', 'ramikg']
pr_nums = ['27550']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue44811'
versions = ['Python 3.11']

Activity

1. anisgandoura commented on Aug 2, 2021

   

   anisgandouramannequin

   on Aug 2, 2021

   MannequinAuthor

   More actions

   Expose the OpenSSL function SSL_CTX_set1_sigalgs_list to allow the user to modify the supported signature algorithms for a given SSL Context.
   OpenSSL documentation: https://www.openssl.org/docs/man1.1.0/man3/SSL_CTX_set1_sigalgs_list.html
2. anisgandoura

   added

   topic-SSL

   3.11only security fixesonly security fixes

   on Aug 2, 2021
3. anisgandoura

   assigned

   tiran

   on Aug 2, 2021
4. tiran commented on Aug 2, 2021

   

   tiran

   on Aug 2, 2021

   Member

   More actions

   Thanks for your PR. Before we move forward, let's discuss reasoning and API design first.

   Why should a Python application be able to modify the signature algorithms? The default settings are safe and sane. Security properties should rather be set system-wide with a crypto policy in OpenSSL's global config file. Application specific settings can cause security or compatibility issues.

   **If** there is a solid reason to expose the feature, then

   • the API should be modeled after SSLContext.set_alpn_protocols() and accept a sequence of strings.
   • the API should also be able to return currently enabled and perhaps currently available algorithms.
   • the ssl module should get an enum of common algorithms with names based on IANA's TLS parameter list.
   • the PR needs tests and documentation
5. tiran

   added

   type-featureA feature request or enhancementA feature request or enhancement

   on Aug 2, 2021
6. anisgandoura commented on Aug 2, 2021

   

   anisgandouramannequin

   on Aug 2, 2021

   MannequinAuthor

   More actions

   Hello, thank you for your message.

   The default signatures list is very different from what a usual Internet Browser (like Chrome or Firefox) displays.

   Here is an example:

   With Chrome I have:
   SHA256/ECDSA, RSA_PSS_SHA256, SHA256/RSA, SHA384/ECDSA, RSA_PSS_SHA384, SHA384/RSA, RSA_PSS_SHA512, SHA512/RSA

   With default SSL settings:
   SHA256/ECDSA, SHA384/ECDSA, SHA512/ECDSA, Ed25519, Ed448, Unknown (0x8)/Unknown (0x9), Unknown (0x8)/Unknown (0xa), Unknown (0x8)/Unknown (0xb), RSA_PSS_SHA256, RSA_PSS_SHA384, RSA_PSS_SHA512, SHA256/RSA, SHA384/RSA, SHA512/RSA, SHA224/ECDSA, SHA1/ECDSA, SHA224/RSA, SHA1/RSA, SHA224/DSA, SHA1/DSA, SHA256/DSA, SHA384/DSA, SHA512/DSA

   You can use this website for testing: https://clienttest.ssllabs.com:8443/ssltest/viewMyClient.html

   We are building a security suite in Python to protect websites from DDOS attacks and we are not able to run "Chrome like" tests due to this limitation.
7. ramikg commented on Oct 1, 2021

   

   ramikgmannequin

   on Oct 1, 2021

   Mannequin

   More actions

   As a side note, while the ideal solution would be for Python to expose the appropriate API, there exists a hacky solution using ctypes:
   https://github.com/ramikg/ssl-context-configurator
8. ezio-melotti

   transferred this issue fromon Apr 10, 2022
9. bantu commented on May 2, 2023

   

   bantu

   on May 2, 2023

   More actions

   @tiran

   Why should a Python application be able to modify the signature algorithms? The default settings are safe and sane.

   One of our applications needs to support two types of TLS connections:
   i) Connections made to web resources. In this case, using the Python defaults is fine.
   ii) Connections made using a TLS-based protocol with its own specification. In order to be spec-compliant, we need to explicitly enforce: TLS version, ciphersuites, ECDHE curves (e.g. BrainpoolP256r1 is mandatory), handshake signature algorithms, compression, renegotiation, etc.

   Security properties should rather be set system-wide with a crypto policy in OpenSSL's global config file.

   I don't see how that approach could be used to support i) and ii) within the same application.
10. pinterior commented on Mar 14, 2025

    

    pinterior

    on Mar 14, 2025

    More actions

    Why should a Python application be able to modify the signature algorithms?

    At least one embedded SSL library rejects signature_algorithms extension with more than 16 elements, which can occur with the current default settings.
    This compatibility issue can be avoided by setting maximum_version to TLSv1_1, but it would be better to have an alternative solution.
11. picnixz

    added

    extension-modulesC modules in the Modules dirC modules in the Modules dir

    and removed

    3.11only security fixesonly security fixes

    on Mar 14, 2025
12. ronf commented on Sep 8, 2025

    

    ronf

    on Sep 8, 2025

    Contributor

    More actions

    The changes mentioned in #138252 to get/set signature algorithms are now merged into python:main.

    Reacted by pinterior

Issue actions