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fix(tcpclient): close SSLIOStream on TLS handshake timeout to prevent socket leak #3615

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fix(tcpclient): close SSLIOStream on TLS handshake timeout to prevent socket leak #3615

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6 changes: 6 additions & 0 deletions tornado/iostream.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1256,6 +1256,12 @@ def start_tls(
ssl_stream._ssl_connect_future = future
ssl_stream.max_buffer_size = self.max_buffer_size
ssl_stream.read_chunk_size = self.read_chunk_size

def _on_cancel(fut: Future[SSLIOStream]) -> None:
if fut.cancelled():
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@bdarnell bdarnell Apr 22, 2026

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This needs a test to make sure we are in fact closing the stream here. I think that when tornado.gen.with_timeout reaches its timeout, the Future is terminated with a TimeoutError, but not cancelled, so this condition is never true (the call to tls_future.cancel() in tcpclient is a no-op because the future has already been terminated).

What we probably want to do here is close the stream in a done_callback if fut.exception() is None.

ssl_stream.close()

future.add_done_callback(_on_cancel) # type: ignore[arg-type]
return future

def _handle_connect(self) -> None:
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18 changes: 9 additions & 9 deletions tornado/tcpclient.py
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Original file line number Diff line number Diff line change
Expand Up @@ -272,17 +272,17 @@ async def connect(
# information here and re-use it on subsequent connections to
# the same host. (http://tools.ietf.org/html/rfc6555#section-4.2)
if ssl_options is not None:
tls_future = stream.start_tls(
False, ssl_options=ssl_options, server_hostname=host
)
if timeout is not None:
stream = await gen.with_timeout(
timeout,
stream.start_tls(
False, ssl_options=ssl_options, server_hostname=host
),
)
try:
stream = await gen.with_timeout(timeout, tls_future)
except TimeoutError:
tls_future.cancel()
raise
else:
stream = await stream.start_tls(
False, ssl_options=ssl_options, server_hostname=host
)
stream = await tls_future
return stream

def _create_stream(
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