remote: spawn a separate thread to avoid deadlocks

Author: tesuji

pwnlib/tubes/remote.py

@@ -2,6 +2,7 @@
 from __future__ import division
 
 import asyncio
+import concurrent
 import socket
 import socks
 
@@ -118,21 +119,21 @@ async def async_getaddrinfo(host, port, fam=0, typ=0, proto=0, flags=0):
                 result = []
             return result
 
+        def run_async_in_thread(coro):
+            loop = asyncio.new_event_loop()
+            asyncio.set_event_loop(loop)
+            future = loop.run_until_complete(coro)
+            loop.close()
+            return future
+
         # Using asyncio to avoid blocking when DNS resolution fail. It's probably better
         # to use async all the ways to `sock.connect`. However, let's keep the changes
         # small until we have the needs.
         def sync_getaddrinfo(*args):
-            coro = async_getaddrinfo(*args)
-            try:
-                loop = asyncio.get_event_loop()
-                if loop.is_running():
-                    # If an event loop is already running, use it to run the async function
-                    future = asyncio.run_coroutine_threadsafe(coro, loop)
-                    return future.result()
-            except RuntimeError:
-                pass
-            # If no event loop is running, create a new one
-            return asyncio.run(coro)
+            # Run in a a seperate thread to avoid deadlocks when users nest eventloops.
+            with concurrent.futures.ThreadPoolExecutor() as executor:
+                future = executor.submit(run_async_in_thread, async_getaddrinfo(*args))
+                return future.result()
 
         with self.waitfor('Opening connection to %s on port %s' % (self.rhost, self.rport)) as h:
             hostnames = sync_getaddrinfo(self.rhost, self.rport, fam, typ, 0, socket.AI_PASSIVE)