use special header replacement to skip emptied headers

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

@@ -25,6 +25,7 @@ from bubble_config import bubble_port, debug_capture_fqdn, \
 from mitmproxy import http
 from mitmproxy.net.http import headers as nheaders
 from mitmproxy.proxy.protocol.async_stream_body import AsyncStreamBody
+from mitmproxy.utils import strutils
 
 bubble_log = logging.getLogger(__name__)
 
@@ -449,6 +450,44 @@ def original_flex_ip(client_addr, fqdns):
     return None
 
 
+def _replace_in_headers(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).
+
+    Replaces a regular expression pattern with repl in each "name: value"
+    header line.
+
+    Returns:
+        The number of replacements made.
+    """
+    pattern = re.compile(strutils.escaped_str_to_bytes(pattern))
+    replacement = strutils.escaped_str_to_bytes(replacement)
+    repl_count = 0
+    fields = []
+
+    for name, value in headers.fields:
+        line, n = pattern.subn(replacement, name + b": " + value)
+
+        if len(line) == 0:
+            # Skip/remove this header line and go with the next one:
+            continue
+
+        try:
+            name, value = line.split(b": ", 1)
+        except ValueError:
+            # We get a ValueError if the replacement removed the ": "
+            # There's not much we can do about this, so we just keep the header as-is.
+            pass
+        else:
+            repl_count += n
+
+        fields.append((name, value))
+
+    headers.fields = tuple(fields)
+    return repl_count
+
+
 def response_header_modify(flow):
     return None if flow.response is None else _header_modify(flow.client_conn.address[0], flow.response.headers)
 
@@ -461,7 +500,7 @@ def _header_modify(client_addr, headers):
     if modifiers:
         for modifier in modifiers:
             modifier_config = json.loads(modifier)
-            repl_count += headers.replace(modifier_config['regex'], modifier_config['replacement'])
+            repl_count += _replace_in_headers(headers, modifier_config['regex'], modifier_config['replacement'])
 
     if bubble_log.isEnabledFor(DEBUG):
         bubble_log.debug('_header_modify: replacing headers - replacements count: ' + repl_count)