Add option to return various status codes rather than killing during …

…server replay (#6465)

#### Description

Designed to satisfy the requirements of
#3489

Add `server_replay_404_extra` which behaves similarly to the kill flag,
but returns 404 responses rather than killing

#### Checklist

 - [x] I have updated tests where applicable.
 - [x] I have added an entry to the CHANGELOG.

---------

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

CHANGELOG.md

@@ -8,6 +8,9 @@
 * Update savehar addon to handle scenarios where "path" key in cookie
   attrs dict is missing.
   ([#6458](https://github.com/mitmproxy/mitmproxy/pull/6458), @pogzyb)
+* Add `server_replay_extra` option to serverplayback to define behaviour
+  when replayable response is missing.
+  ([#6465](https://github.com/mitmproxy/mitmproxy/pull/6465), @dkarandikar)
 
 
 ## 04 November 2023: mitmproxy 10.1.3

mitmproxy/addons/serverplayback.py

@@ -30,7 +30,16 @@ def load(self, loader):
             "server_replay_kill_extra",
             bool,
             False,
-            "Kill extra requests during replay (for which no replayable response was found).",
+            "Kill extra requests during replay (for which no replayable response was found)."
+            "[Deprecated, prefer to use server_replay_extra='kill']",
+        )
+        loader.add_option(
+            "server_replay_extra",
+            str,
+            "forward",
+            "Behaviour for extra requests during replay for which no replayable response was found. "
+            "Setting a numeric string value will return an empty HTTP response with the respective status code.",
+            choices=["forward", "kill", "204", "400", "404", "500"],
         )
         loader.add_option(
             "server_replay_reuse",
@@ -230,6 +239,11 @@ def next_flow(self, flow: http.HTTPFlow) -> http.HTTPFlow | None:
             return None
 
     def configure(self, updated):
+        if ctx.options.server_replay_kill_extra:
+            logger.warning(
+                "server_replay_kill_extra has been deprecated, "
+                "please update your config to use server_replay_extra='kill'."
+            )
         if ctx.options.server_replay_nopop:  # pragma: no cover
             logger.error(
                 "server_replay_nopop has been renamed to server_replay_reuse, please update your config."
@@ -252,10 +266,21 @@ def request(self, f: http.HTTPFlow) -> None:
                     response.refresh()
                 f.response = response
                 f.is_replay = "response"
-            elif ctx.options.server_replay_kill_extra:
+            elif (
+                ctx.options.server_replay_kill_extra
+                or ctx.options.server_replay_extra == "kill"
+            ):
                 logging.warning(
                     "server_playback: killed non-replay request {}".format(
                         f.request.url
                     )
                 )
                 f.kill()
+            elif ctx.options.server_replay_extra != "forward":
+                logging.warning(
+                    "server_playback: returned {} non-replay request {}".format(
+                        ctx.options.server_replay_extra, f.request.url
+                    )
+                )
+                f.response = http.Response.make(int(ctx.options.server_replay_extra))
+                f.is_replay = "response"

mitmproxy/tools/cmdline.py

@@ -83,6 +83,7 @@ def common_options(parser, opts):
     group = parser.add_argument_group("Server Replay")
     opts.make_parser(group, "server_replay", metavar="PATH", short="S")
     opts.make_parser(group, "server_replay_kill_extra")
+    opts.make_parser(group, "server_replay_extra")
     opts.make_parser(group, "server_replay_reuse")
     opts.make_parser(group, "server_replay_refresh")
 

mitmproxy/tools/console/statusbar.py

@@ -280,6 +280,8 @@ def get_status(self) -> list[tuple[str, str] | str]:
             opts.append("norefresh")
         if self.master.options.server_replay_kill_extra:
             opts.append("killextra")
+        if self.master.options.server_replay_extra:
+            opts.append("replay-extra")
         if not self.master.options.upstream_cert:
             opts.append("no-upstream-cert")
         if self.master.options.console_focus_follow:

test/mitmproxy/addons/test_serverplayback.py

@@ -364,6 +364,45 @@ async def test_server_playback_kill():
         assert f.error
 
 
+async def test_server_playback_kill_new_option():
+    s = serverplayback.ServerPlayback()
+    with taddons.context(s) as tctx:
+        tctx.configure(s, server_replay_refresh=True, server_replay_extra="kill")
+
+        f = tflow.tflow()
+        f.response = mitmproxy.test.tutils.tresp(content=f.request.content)
+        s.load_flows([f])
+
+        f = tflow.tflow()
+        f.request.host = "nonexistent"
+        await tctx.cycle(s, f)
+        assert f.error
+
+
+@pytest.mark.parametrize(
+    "option,status",
+    [
+        ("204", 204),
+        ("400", 400),
+        ("404", 404),
+        ("500", 500),
+    ],
+)
+async def test_server_playback_404(option, status):
+    s = serverplayback.ServerPlayback()
+    with taddons.context(s) as tctx:
+        tctx.configure(s, server_replay_refresh=True, server_replay_extra=option)
+
+        f = tflow.tflow()
+        f.response = mitmproxy.test.tutils.tresp(content=f.request.content)
+        s.load_flows([f])
+
+        f = tflow.tflow()
+        f.request.host = "nonexistent"
+        s.request(f)
+        assert f.response.status_code == status
+
+
 def test_server_playback_response_deleted():
     """
     The server playback addon holds references to flows that can be modified by the user in the meantime.

test/mitmproxy/tools/console/test_statusbar.py

@@ -18,7 +18,7 @@ async def test_statusbar(console, monkeypatch):
         anticomp=True,
         showhost=True,
         server_replay_refresh=False,
-        server_replay_kill_extra=True,
+        server_replay_extra="kill",
         upstream_cert=False,
         stream_large_bodies="3m",
         mode=["transparent"],

web/src/js/ducks/_options_gen.ts

@@ -51,6 +51,7 @@ export interface OptionsState {
     scripts: string[];
     server: boolean;
     server_replay: string[];
+    server_replay_extra: string;
     server_replay_ignore_content: boolean;
     server_replay_ignore_host: boolean;
     server_replay_ignore_params: string[];
@@ -146,6 +147,7 @@ export const defaultState: OptionsState = {
     scripts: [],
     server: true,
     server_replay: [],
+    server_replay_extra: "forward",
     server_replay_ignore_content: false,
     server_replay_ignore_host: false,
     server_replay_ignore_params: [],