test_ssl: test_client_sigalgs_mismatch() fails randomly on macOS with BrokenPipeError #139504
Description
Bug report
The test fails randomly on GitHub Action macOS CIs.
Example: https://github.com/python/cpython/actions/runs/18194966530/job/51798732964?pr=139498
0:03:17 load avg: 10.48 [1/1/1] test_ssl failed (1 error)
Re-running test_ssl in verbose mode (matching: test_client_sigalgs_mismatch)
test_ssl: testing with 'OpenSSL 3.0.17 1 Jul 2025' (3, 0, 0, 17, 0)
under Mac ('14.8', ('', '', ''), 'arm64')
HAS_SNI = True
OP_ALL = 0x80000050
OP_NO_TLSv1_1 = 0x10000000
test_client_sigalgs_mismatch (test.test_ssl.ThreadedTests.test_client_sigalgs_mismatch) ... server: new connection from ('127.0.0.1', 54259)
client: sending b'FOO\n'...
server: bad connection attempt from ('127.0.0.1', 54259):
Traceback (most recent call last):
File "/Users/admin/actions-runner/_work/cpython/cpython/Lib/test/test_ssl.py", line 2423, in wrap_conn
self.sslconn = self.server.context.wrap_socket(
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^
self.sock, server_side=True)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/admin/actions-runner/_work/cpython/cpython/Lib/ssl.py", line 459, in wrap_socket
return self.sslsocket_class._create(
~~~~~~~~~~~~~~~~~~~~~~~~~~~~^
sock=sock,
^^^^^^^^^^
...<5 lines>...
session=session
^^^^^^^^^^^^^^^
)
^
File "/Users/admin/actions-runner/_work/cpython/cpython/Lib/ssl.py", line 1096, in _create
self.do_handshake()
~~~~~~~~~~~~~~~~~^^
File "/Users/admin/actions-runner/_work/cpython/cpython/Lib/ssl.py", line 1427, in do_handshake
self._sslobj.do_handshake()
~~~~~~~~~~~~~~~~~~~~~~~~~^^
ssl.SSLError: [SSL: PEER_DID_NOT_RETURN_A_CERTIFICATE] peer did not return a certificate (_ssl.c:1108)
ERROR
======================================================================
ERROR: test_client_sigalgs_mismatch (test.test_ssl.ThreadedTests.test_client_sigalgs_mismatch)
----------------------------------------------------------------------
Traceback (most recent call last):
File "/Users/admin/actions-runner/_work/cpython/cpython/Lib/test/test_ssl.py", line 4351, in test_client_sigalgs_mismatch
server_params_test(client_context, server_context,
~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
chatty=True, connectionchatty=True,
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
sni_name=hostname)
^^^^^^^^^^^^^^^^^^
File "/Users/admin/actions-runner/_work/cpython/cpython/Lib/test/test_ssl.py", line 2832, in server_params_test
s.write(arg)
~~~~~~~^^^^^
File "/Users/admin/actions-runner/_work/cpython/cpython/Lib/ssl.py", line 1177, in write
return self._sslobj.write(data)
~~~~~~~~~~~~~~~~~~^^^^^^
BrokenPipeError: [Errno 32] Broken pipe