Cannot connect to TLS enabled servers with pyOpenSSL 26.2.0

[gavtroy]

Connecting to a TLS syncplay server fails with the looping message:

Unhandled Error
Traceback (most recent call last):
  File "/usr/lib/syncplay/syncplay/vendor/qt5reactor.py", line 153, in _read
    why = w.doRead()
  File "/usr/lib/python3.14/site-packages/twisted/internet/tcp.py", line 250, in doRead
    return self._dataReceived(data)
  File "/usr/lib/python3.14/site-packages/twisted/internet/tcp.py", line 255, in _dataReceived
    rval = self.protocol.dataReceived(data)
  File "/usr/lib/python3.14/site-packages/twisted/protocols/tls.py", line 324, in dataReceived
    self._checkHandshakeStatus()
  File "/usr/lib/python3.14/site-packages/twisted/protocols/tls.py", line 255, in _checkHandshakeStatus
    self.wrappedProtocol.handshakeCompleted()
  File "/usr/lib/python3.14/site-packages/twisted/internet/endpoints.py", line 189, in handshakeCompleted
    self._wrappedProtocol.handshakeCompleted()
  File "/usr/lib/syncplay/syncplay/protocols.py", line 405, in handshakeCompleted
    if (self._serverCertificateTLS.get_extension(x).get_short_name() == b'subjectAltName'):
builtins.AttributeError: 'X509' object has no attribute 'get_extension'

To Reproduce

• With a fully updated Arch install, attempt to connect to syncplay.pl:8999

Version and platform:

• OS: Arch Linux
• Syncplay version and build type: syncplay-git 1.7.5.r0.gd1c5f85a-1
• Media player and version: mpv v0.41.0

Additional context

pyOpenSSL 26.2.0 released a few days ago. The changelog notes:

• Removed deprecated OpenSSL.crypto.X509Extension, OpenSSL.crypto.X509Req.add_extension, OpenSSL.crypto.X509Req.get_extensions, OpenSSL.crypto.X509.add_extension, OpenSSL.crypto.X509.get_extensions. cryptography.x509 should be used instead.

[Et0h]

I can confirm the issue and have tried to fix it, but I've only tested it on Windows. I think your additional context was spot on with the problem.

Please test #775 fix directly or using the artefacts.

[gavtroy]

Thanks, it works again with that change.

As a side note, I suspect many Arch users won't have even bothered installing the libraries needed for TLS support since they're only optional dependencies. (It's a bit of a strange package imo, even the GUI is optional.) The positive side is that they were probably immune to this bug.

[pythongirl325]

For anyone else encountering this issue: As a short term workaround, downgrading to PyOpenSSL v26.1.0 seems to work.

[Et0h]

@gavtroy Thanks for testing it.
@pythongirl325 Thanks for the workaround

I've now merged the pull request. I'll keep this issue open for a short while as others might come across this issue.

[Qwerty-Space]

Brilliant thanks for that.
For better searchability, I was getting the following error in the syncplay chat:

<class 'twisted.python.failure.Failure'>

[17:45:20] [Failure instance: Traceback (failure with no frames): <class 'twisted.internet.error.ConnectionLost'>: Connection to the other side was lost in a non-clean fashion: Connection lost.

[tippl]

Hello, what are the plans for releasing a new version with this fix?

Thanks.