Support setting response header size limits (#6559)

<!-- Thank you for your contribution! -->

## What do these changes do?

Allow the user to set the response header limits. The properties
max_line_size, max_headers and max_field_size can be set on
ClientSession creation. Default values are: `max_line_size=8190`
`max_headers=32768` and `max_field_size=8190`.
Thus the user can set and - when needed - receive bigger response
headers.

## Are there changes in behavior for the user?

No

## Related issue number

#2304

## Checklist

- [x] I think the code is well written
- [x] Unit tests for the changes exist
- [ ] Documentation reflects the changes
- [ ] If you provide code modification, please add yourself to
`CONTRIBUTORS.txt`
  * The format is &lt;Name&gt; &lt;Surname&gt;.
  * Please keep alphabetical order, the file is sorted by names.
- [x] Add a new news fragment into the `CHANGES` folder
  * name it `<issue_id>.<type>` for example (588.bugfix)
* if you don't have an `issue_id` change it to the pr id after creating
the pr
  * ensure type is one of the following:
    * `.feature`: Signifying a new feature.
    * `.bugfix`: Signifying a bug fix.
    * `.doc`: Signifying a documentation improvement.
    * `.removal`: Signifying a deprecation or removal of public API.
* `.misc`: A ticket has been closed, but it is not of interest to users.
* Make sure to use full sentences with correct case and punctuation, for
example: "Fix issue with non-ascii contents in doctest text files."

---------

Co-authored-by: Josef Prenner <josef@cloudomation.com>
Co-authored-by: Sam Bull <aa6bs0@sambull.org>

CHANGES/2304.feature

@@ -0,0 +1 @@
+Support setting response header parameters max_line_size and max_field_size.

aiohttp/client.py

@@ -186,6 +186,8 @@ class ClientSession:
         "_ws_response_class",
         "_trace_configs",
         "_read_bufsize",
+        "_max_line_size",
+        "_max_field_size",
     )
 
     def __init__(
@@ -213,6 +215,8 @@ def __init__(
         requote_redirect_url: bool = True,
         trace_configs: Optional[List[TraceConfig]] = None,
         read_bufsize: int = 2**16,
+        max_line_size: int = 8190,
+        max_field_size: int = 8190,
     ) -> None:
         if base_url is None or isinstance(base_url, URL):
             self._base_url: Optional[URL] = base_url
@@ -261,6 +265,8 @@ def __init__(
         self._trust_env = trust_env
         self._requote_redirect_url = requote_redirect_url
         self._read_bufsize = read_bufsize
+        self._max_line_size = max_line_size
+        self._max_field_size = max_field_size
 
         # Convert to list of tuples
         if headers:
@@ -342,6 +348,8 @@ async def _request(
         trace_request_ctx: Optional[SimpleNamespace] = None,
         read_bufsize: Optional[int] = None,
         auto_decompress: Optional[bool] = None,
+        max_line_size: Optional[int] = None,
+        max_field_size: Optional[int] = None,
     ) -> ClientResponse:
         # NOTE: timeout clamps existing connect and read timeouts.  We cannot
         # set the default to None because we need to detect if the user wants
@@ -404,6 +412,12 @@ async def _request(
         if auto_decompress is None:
             auto_decompress = self._auto_decompress
 
+        if max_line_size is None:
+            max_line_size = self._max_line_size
+
+        if max_field_size is None:
+            max_field_size = self._max_field_size
+
         traces = [
             Trace(
                 self,
@@ -510,6 +524,8 @@ async def _request(
                         read_timeout=real_timeout.sock_read,
                         read_bufsize=read_bufsize,
                         timeout_ceil_threshold=self._connector._timeout_ceil_threshold,
+                        max_line_size=max_line_size,
+                        max_field_size=max_field_size,
                     )
 
                     try:
@@ -1186,6 +1202,8 @@ def request(
     version: HttpVersion = http.HttpVersion11,
     connector: Optional[BaseConnector] = None,
     read_bufsize: Optional[int] = None,
+    max_line_size: int = 8190,
+    max_field_size: int = 8190,
 ) -> _SessionRequestContextManager:
     """Constructs and sends a request.
 
@@ -1256,6 +1274,8 @@ def request(
             proxy=proxy,
             proxy_auth=proxy_auth,
             read_bufsize=read_bufsize,
+            max_line_size=max_line_size,
+            max_field_size=max_field_size,
         ),
         session,
     )

aiohttp/client_proto.py

@@ -153,6 +153,8 @@ def set_response_params(
         read_timeout: Optional[float] = None,
         read_bufsize: int = 2**16,
         timeout_ceil_threshold: float = 5,
+        max_line_size: int = 8190,
+        max_field_size: int = 8190,
     ) -> None:
         self._skip_payload = skip_payload
 
@@ -169,6 +171,8 @@ def set_response_params(
             response_with_body=not skip_payload,
             read_until_eof=read_until_eof,
             auto_decompress=auto_decompress,
+            max_line_size=max_line_size,
+            max_field_size=max_field_size,
         )
 
         if self._tail:

tests/test_client_functional.py

@@ -3065,3 +3065,105 @@ async def handler(request):
         assert resp.status == 200
         assert await resp.text() == "ok"
         assert resp.headers["Content-Type"] == "text/plain; charset=utf-8"
+
+
+async def test_max_field_size_session_default(aiohttp_client: Any) -> None:
+    async def handler(request):
+        return web.Response(headers={"Custom": "x" * 8190})
+
+    app = web.Application()
+    app.add_routes([web.get("/", handler)])
+
+    client = await aiohttp_client(app)
+
+    async with await client.get("/") as resp:
+        assert resp.headers["Custom"] == "x" * 8190
+
+
+async def test_max_field_size_session_default_fail(aiohttp_client: Any) -> None:
+    async def handler(request):
+        return web.Response(headers={"Custom": "x" * 8191})
+
+    app = web.Application()
+    app.add_routes([web.get("/", handler)])
+
+    client = await aiohttp_client(app)
+    with pytest.raises(aiohttp.ClientResponseError):
+        await client.get("/")
+
+
+async def test_max_field_size_session_explicit(aiohttp_client: Any) -> None:
+    async def handler(request):
+        return web.Response(headers={"Custom": "x" * 8191})
+
+    app = web.Application()
+    app.add_routes([web.get("/", handler)])
+
+    client = await aiohttp_client(app, max_field_size=8191)
+
+    async with await client.get("/") as resp:
+        assert resp.headers["Custom"] == "x" * 8191
+
+
+async def test_max_field_size_request_explicit(aiohttp_client: Any) -> None:
+    async def handler(request):
+        return web.Response(headers={"Custom": "x" * 8191})
+
+    app = web.Application()
+    app.add_routes([web.get("/", handler)])
+
+    client = await aiohttp_client(app)
+
+    async with await client.get("/", max_field_size=8191) as resp:
+        assert resp.headers["Custom"] == "x" * 8191
+
+
+async def test_max_line_size_session_default(aiohttp_client: Any) -> None:
+    async def handler(request):
+        return web.Response(status=200, reason="x" * 8190)
+
+    app = web.Application()
+    app.add_routes([web.get("/", handler)])
+
+    client = await aiohttp_client(app)
+
+    async with await client.get("/") as resp:
+        assert resp.reason == "x" * 8190
+
+
+async def test_max_line_size_session_default_fail(aiohttp_client: Any) -> None:
+    async def handler(request):
+        return web.Response(status=200, reason="x" * 8192)
+
+    app = web.Application()
+    app.add_routes([web.get("/", handler)])
+
+    client = await aiohttp_client(app)
+    with pytest.raises(aiohttp.ClientResponseError):
+        await client.get("/")
+
+
+async def test_max_line_size_session_explicit(aiohttp_client: Any) -> None:
+    async def handler(request):
+        return web.Response(status=200, reason="x" * 8191)
+
+    app = web.Application()
+    app.add_routes([web.get("/", handler)])
+
+    client = await aiohttp_client(app, max_line_size=8191)
+
+    async with await client.get("/") as resp:
+        assert resp.reason == "x" * 8191
+
+
+async def test_max_line_size_request_explicit(aiohttp_client: Any) -> None:
+    async def handler(request):
+        return web.Response(status=200, reason="x" * 8191)
+
+    app = web.Application()
+    app.add_routes([web.get("/", handler)])
+
+    client = await aiohttp_client(app)
+
+    async with await client.get("/", max_line_size=8191) as resp:
+        assert resp.reason == "x" * 8191