standalone: Fix multiple challange handlers on same port

If you define challenge handlers on a per-domain basis multiple will be
created. This would cause the standalone handler to potientially try
to bind the same port (when configured) multiple times, which would only
work on the first try. Subsequent tries would fail with "Address already
in use". To fix this only bind the server between start and stop of the
challenge and cleanup afterwards.

acertmgr/modes/standalone.py

@@ -28,10 +28,20 @@ class HTTPServer6(HTTPServer):
 class ChallengeHandler(HTTPChallengeHandler):
     def __init__(self, config):
         HTTPChallengeHandler.__init__(self, config)
-        bind_address = config.get("bind_address", "")
-        port = int(config.get("port", 80))
+        self.bind_address = config.get("bind_address", "")
+        self.port = int(config.get("port", 80))
 
         self.challenges = {}  # Initialize the challenge data dict
+        self.server_thread = None
+        self.server = None
+
+    def create_challenge(self, domain, thumbprint, token):
+        self.challenges[token] = "{0}.{1}".format(token, thumbprint)
+
+    def destroy_challenge(self, domain, thumbprint, token):
+        del self.challenges[token]
+
+    def start_challenge(self, domain, thumbprint, token):
         _self = self
 
         # Custom HTTP request handler
@@ -54,19 +64,11 @@ class ChallengeHandler(HTTPChallengeHandler):
                 self.end_headers()
                 self.wfile.write(value)
 
-        self.server_thread = None
         try:
-            self.server = HTTPServer6((bind_address, port), _HTTPRequestHandler)
+            self.server = HTTPServer6((self.bind_address, self.port), _HTTPRequestHandler)
         except socket.gaierror:
-            self.server = HTTPServer((bind_address, port), _HTTPRequestHandler)
+            self.server = HTTPServer((self.bind_address, self.port), _HTTPRequestHandler)
 
-    def create_challenge(self, domain, thumbprint, token):
-        self.challenges[token] = "{0}.{1}".format(token, thumbprint)
-
-    def destroy_challenge(self, domain, thumbprint, token):
-        del self.challenges[token]
-
-    def start_challenge(self, domain, thumbprint, token):
         def _serve():
             self.server.serve_forever()
 
@@ -78,3 +80,6 @@ class ChallengeHandler(HTTPChallengeHandler):
         if self.server_thread.is_alive():
             self.server.shutdown()
             self.server_thread.join()
+            self.server.server_close()
+            self.server = None
+            self.server_thread = None