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Add test_sni_callback_race #150018

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89d0b19
Add test_sni_callback_race
kiri11 May 18, 2026
be11d8b
Improve test_sni_callback_race
kiri11 May 18, 2026
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63 changes: 63 additions & 0 deletions Lib/test/test_ssl.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1606,6 +1606,69 @@ def dummycallback(sock, servername, ctx, cycle=ctx):
gc.collect()
self.assertIs(wr(), None)

@unittest.skipUnless(support.Py_GIL_DISABLED,
"test is only useful if the GIL is disabled")
@threading_helper.requires_working_threading()
def test_sni_callback_race(self):
# Replacing sni_callback while handshakes are in-flight must not
# crash (use-after-free on the callback in free-threaded builds).
client_ctx, server_ctx, hostname = testing_context()

def make_callback(n):
def sni_cb(_ssl_obj, _servername, _ctx):
if n == -1 and _servername == "":
raise AssertionError("unreachable")
return None
return sni_cb

server_ctx.sni_callback = make_callback(0)
done = threading.Event()

def do_handshakes():
while not done.is_set():
c_in = ssl.MemoryBIO()
c_out = ssl.MemoryBIO()
s_in = ssl.MemoryBIO()
s_out = ssl.MemoryBIO()
client = client_ctx.wrap_bio(
c_in, c_out, server_hostname=hostname)
server = server_ctx.wrap_bio(s_in, s_out, server_side=True)
for _ in range(50):
try:
client.do_handshake()
except ssl.SSLWantReadError:
pass
except ssl.SSLError:
break
if c_out.pending:
s_in.write(c_out.read())
try:
server.do_handshake()
except ssl.SSLWantReadError:
pass
except ssl.SSLError:
break
if s_out.pending:
c_in.write(s_out.read())

def toggle_callback():
i = 0
while not done.is_set():
server_ctx.sni_callback = make_callback(i)
server_ctx.sni_callback = None
server_ctx.sni_callback = make_callback(-i)
i += 1

workers = max(4, (os.cpu_count() or 4) * 2)
threads = [threading.Thread(target=do_handshakes)
for _ in range(workers)]
threads.append(threading.Thread(target=toggle_callback))

with threading_helper.catch_threading_exception() as cm:
with threading_helper.start_threads(threads):
done.set()
self.assertIsNone(cm.exc_value)

def test_cert_store_stats(self):
ctx = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
self.assertEqual(ctx.cert_store_stats(),
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