SSL transport drops buffered data when peer closes TCP without close_notify while reading is paused #792

"""Usage: python repro.py [uvloop|asyncio]"""
import asyncio, socket, ssl, subprocess, sys, tempfile, threading

SIZE = 2_000_000


def serve(listener, ctx):
    raw, _ = listener.accept()
    tls = ctx.wrap_socket(raw, server_side=True)
    tls.recv(2)
    tls.sendall(b"x" * SIZE)
    tls.close()  # TCP close, no unwrap(): no close_notify is sent


class SlowReader(asyncio.Protocol):
    def __init__(self, loop):
        self.loop, self.received = loop, 0
        self.closed = loop.create_future()

    def connection_made(self, transport):
        self.transport = transport
        transport.write(b"go")

    def data_received(self, data):
        self.received += len(data)
        self.transport.pause_reading()
        self.loop.call_later(0.02, self.transport.resume_reading)

    def connection_lost(self, exc):
        self.closed.set_result(exc)


async def main(port):
    loop = asyncio.get_running_loop()
    ctx = ssl.create_default_context()
    ctx.check_hostname, ctx.verify_mode = False, ssl.CERT_NONE
    _, proto = await loop.create_connection(lambda: SlowReader(loop), "127.0.0.1", port, ssl=ctx)
    exc = await asyncio.wait_for(proto.closed, 30)
    print(f"{type(loop).__module__}: received {proto.received} of {SIZE}, connection_lost({exc!r})")


with tempfile.TemporaryDirectory() as d:
    subprocess.run(
        ["openssl", "req", "-x509", "-newkey", "rsa:2048", "-nodes", "-days", "1",
         "-subj", "/CN=localhost", "-keyout", f"{d}/k.pem", "-out", f"{d}/c.pem"],
        check=True, capture_output=True,
    )
    server_ctx = ssl.SSLContext(ssl.PROTOCOL_TLS_SERVER)
    server_ctx.load_cert_chain(f"{d}/c.pem", f"{d}/k.pem")
listener = socket.create_server(("127.0.0.1", 0))
threading.Thread(target=serve, args=(listener, server_ctx), daemon=True).start()
port = listener.getsockname()[1]
if sys.argv[1:] == ["uvloop"]:
    import uvloop
    uvloop.run(main(port))
else:
    asyncio.run(main(port))