Fix some test failures on openssl 1.1.1 / Ubuntu 18.10

See python-trio#817

We don't have CI for this yet, but at least on my laptop it helps.
However, it doesn't fix everything.

- Add OP_ENABLE_MIDDLEBOX_COMPAT to the list of static ssl constants
- Handle SSLZeroReturnError in more places
- Fix some -- but not all -- of the places where session tickets cause
  failures. See python-trio#819

trio/_ssl.py

@@ -605,7 +605,9 @@ async def receive_some(self, max_bytes):
                 # For some reason, EOF before handshake sometimes raises
                 # SSLSyscallError instead of SSLEOFError (e.g. on my linux
                 # laptop, but not on appveyor). Thanks openssl.
-                if (
+                if isinstance(exc.__cause__, _stdlib_ssl.SSLZeroReturnError):
+                    return b""
+                elif (
                     self._https_compatible and isinstance(
                         exc.__cause__,
                         (_stdlib_ssl.SSLEOFError, _stdlib_ssl.SSLSyscallError)
@@ -625,9 +627,18 @@ async def receive_some(self, max_bytes):
                 # BROKEN. But that's actually fine, because after getting an
                 # EOF on TLS then the only thing you can do is close the
                 # stream, and closing doesn't care about the state.
+                #
+                # SSLZeroReturnError means the TLS layer shut down cleanly, so
+                # that's always an application-level EOF.
+                # SSLEOFError means that the transport closed without the TLS
+                # layer shutting down cleanly, so that's an application-level
+                # EOF iff we're in https-compatible mode.
                 if (
-                    self._https_compatible
-                    and isinstance(exc.__cause__, _stdlib_ssl.SSLEOFError)
+                    isinstance(exc.__cause__, _stdlib_ssl.SSLZeroReturnError)
+                    or (
+                        self._https_compatible
+                        and isinstance(exc.__cause__, _stdlib_ssl.SSLEOFError)
+                    )
                 ):
                     return b""
                 else:

trio/ssl.py

@@ -82,7 +82,8 @@
         SSL_ERROR_SYSCALL, SSL_ERROR_WANT_CONNECT, SSL_ERROR_WANT_READ,
         SSL_ERROR_WANT_WRITE, SSL_ERROR_WANT_X509_LOOKUP,
         SSL_ERROR_ZERO_RETURN, VERIFY_CRL_CHECK_CHAIN, VERIFY_CRL_CHECK_LEAF,
-        VERIFY_DEFAULT, VERIFY_X509_STRICT, VERIFY_X509_TRUSTED_FIRST
+        VERIFY_DEFAULT, VERIFY_X509_STRICT, VERIFY_X509_TRUSTED_FIRST,
+        OP_ENABLE_MIDDLEBOX_COMPAT
     )
 except ImportError:
     pass

trio/tests/test_ssl.py

@@ -71,7 +71,7 @@ def ssl_echo_serve_sync(sock, *, expect_fail=False):
                 # other side has initiated a graceful shutdown; we try to
                 # respond in kind but it's legal for them to have already gone
                 # away.
-                exceptions = (BrokenPipeError,)
+                exceptions = (BrokenPipeError, stdlib_ssl.SSLZeroReturnError)
                 # Under unclear conditions, CPython sometimes raises
                 # SSLWantWriteError here. This is a bug (bpo-32219), but it's
                 # not our bug, so ignore it.
@@ -86,6 +86,7 @@ def ssl_echo_serve_sync(sock, *, expect_fail=False):
         if expect_fail:
             print("ssl_echo_serve_sync got error as expected:", exc)
         else:  # pragma: no cover
+            print("ssl_echo_serve_sync got unexpected error:", exc)
             raise
     else:
         if expect_fail:  # pragma: no cover
@@ -760,17 +761,34 @@ async def stream_maker():
 
     async def clogged_stream_maker():
         client, server = ssl_lockstep_stream_pair()
+
         # If we don't do handshakes up front, then we run into a problem in
         # the following situation:
         # - server does wait_send_all_might_not_block
         # - client does receive_some to unclog it
         # Then the client's receive_some will actually send some data to start
         # the handshake, and itself get stuck.
+        #
+        # And then we push a bit of application-level data from the
+        # server->client, in order to clear out any TLS 1.3 session tickets
+        # that could otherwise cause things to hang:
+        #   https://github.com/python-trio/trio/issues/819
+        async def client_handshake():
+            await client.do_handshake()
+            assert await client.receive_some(1) == b"x"
+
+        async def server_handshake():
+            await server.do_handshake()
+            await server.send_all(b"x")
+
         async with _core.open_nursery() as nursery:
-            nursery.start_soon(client.do_handshake)
-            nursery.start_soon(server.do_handshake)
+            nursery.start_soon(client_handshake)
+            nursery.start_soon(server_handshake)
         return client, server
 
+    with trio.fail_after(2):
+        await clogged_stream_maker()
+
     await check_two_way_stream(stream_maker, clogged_stream_maker)
 
 
@@ -880,18 +898,22 @@ async def server_closer():
             await client_ssl.do_handshake()
 
     # Check that a graceful close *before* handshaking gives a clean EOF on
-    # the other side
+    # the other side.
+    # Unfortunately with openssl 1.1.1 this can't work reliably if the client
+    # calls aclose() and the server calls receive_some():
+    #   https://github.com/python-trio/trio/issues/819
+    # so, we do it the other way around.
     client_ssl, server_ssl = ssl_memory_stream_pair()
 
-    async def expect_eof_server():
+    async def expect_eof_client():
         with assert_checkpoints():
-            assert await server_ssl.receive_some(10) == b""
+            assert await client_ssl.receive_some(10) == b""
         with assert_checkpoints():
-            await server_ssl.aclose()
+            await client_ssl.aclose()
 
     async with _core.open_nursery() as nursery:
-        nursery.start_soon(client_ssl.aclose)
-        nursery.start_soon(expect_eof_server)
+        nursery.start_soon(server_ssl.aclose)
+        nursery.start_soon(expect_eof_client)
 
 
 async def test_send_all_fails_in_the_middle():