Add fqdn variable support in header replacements

bubble-server/src/main/resources/packer/roles/mitmproxy/files/bubble_api.py

@@ -450,7 +450,7 @@ def original_flex_ip(client_addr, fqdns):
     return None
 
 
-def _replace_in_headers(headers, pattern: str, replacement: str):
+def _replace_in_headers(headers: nheaders.Headers, pattern: str, replacement: str):
     """
     Taken from original mitmproxy's Header class implementation with sligh change to allow replacement with empty string
     (resulting with actual removal/skip of the header line).
@@ -489,17 +489,19 @@ def _replace_in_headers(headers, pattern: str, replacement: str):
 
 
 def response_header_modify(flow):
-    return None if flow.response is None else _header_modify(flow.client_conn.address[0], flow.response.headers)
+    if flow.response is None:
+        return None
+    return _header_modify(flow.client_conn.address[0], flow.server_conn.address[0], flow.response.headers)
 
 
-def _header_modify(client_addr, headers):
+def _header_modify(client_addr: str, server_addr: str, headers: nheaders.Headers):
     modifiers_set = 'responseHeaderModifierLists~' + client_addr + '~UNION'
     modifiers = REDIS.smembers(modifiers_set)
 
     repl_count = 0
     if modifiers:
         for modifier in modifiers:
-            modifier_config = json.loads(modifier)
+            modifier_config = _extract_modifier_config(modifier, server_addr)
             repl_count += _replace_in_headers(headers, modifier_config['regex'], modifier_config['replacement'])
 
     if bubble_log.isEnabledFor(DEBUG):
@@ -508,6 +510,11 @@ def _header_modify(client_addr, headers):
     return repl_count
 
 
+def _extract_modifier_config(modifier: str, server_addr: str):
+    modifier.replace('{{fqdn}}', re.escape(server_addr))
+    return json.loads(modifier)
+
+
 def health_check_response(flow):
     # if bubble_log.isEnabledFor(DEBUG):
     #     bubble_log.debug('health_check_response: special bubble health check request, responding with OK')