remote: workaround potential nested eventloops

Require python 3.7+ for `asyncio.get_running_loop()`

Author: tesuji

pwnlib/tubes/remote.py

@@ -110,19 +110,30 @@ def _connect(self, fam, typ):
         sock    = None
         timeout = self.timeout
 
-        async def resolve_hostname(host, port, fam=0, typ=0, proto=0, flags=0):
-            loop = asyncio.get_event_loop()
+        async def async_getaddrinfo(host, port, fam=0, typ=0, proto=0, flags=0):
+            loop = asyncio.get_running_loop()
             try:
                 result = await loop.getaddrinfo(host, port, family=fam, type=typ, proto=proto, flags=flags)
             except asyncio.exceptions.CancelledError:
                 result = []
             return result
 
+        # 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):
+            loop = asyncio.get_event_loop()
+            coro = async_getaddrinfo(*args)
+            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()
+            else:
+                # If no event loop is running, create a new one
+                return asyncio.run(coro)
+
         with self.waitfor('Opening connection to %s on port %s' % (self.rhost, self.rport)) as h:
-            # 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.
-            hostnames = asyncio.run(resolve_hostname(self.rhost, self.rport, fam, typ, 0, socket.AI_PASSIVE))
+            hostnames = sync_getaddrinfo(self.rhost, self.rport, fam, typ, 0, socket.AI_PASSIVE)
             for res in hostnames:
                 self.family, self.type, self.proto, _canonname, sockaddr = res