Treat Accept-Encoding header as case-insensitive for gzip file check (#8127)

Author: steverep

CHANGES/8104.bugfix.rst

@@ -0,0 +1 @@
+Treated values of ``Accept-Encoding`` header as case-insensitive when checking for gzip files -- by :user:`steverep`.

CONTRIBUTORS.txt

@@ -307,6 +307,7 @@ Stepan Pletnev
 Stephan Jaensch
 Stephen Cirelli
 Stephen Granade
+Steve Repsher
 Steven Seguin
 Sunghyun Hwang
 Sunit Deshpande

aiohttp/web_fileresponse.py

@@ -142,7 +142,11 @@ def _get_file_path_stat_and_gzip(
 
     async def prepare(self, request: "BaseRequest") -> Optional[AbstractStreamWriter]:
         loop = asyncio.get_event_loop()
-        check_for_gzipped_file = "gzip" in request.headers.get(hdrs.ACCEPT_ENCODING, "")
+        # Encoding comparisons should be case-insensitive
+        # https://www.rfc-editor.org/rfc/rfc9110#section-8.4.1
+        check_for_gzipped_file = (
+            "gzip" in request.headers.get(hdrs.ACCEPT_ENCODING, "").lower()
+        )
         filepath, st, gzip = await loop.run_in_executor(
             None, self._get_file_path_stat_and_gzip, check_for_gzipped_file
         )

aiohttp/web_response.py

@@ -326,6 +326,8 @@ async def _start_compression(self, request: "BaseRequest") -> None:
         if self._compression_force:
             await self._do_start_compression(self._compression_force)
         else:
+            # Encoding comparisons should be case-insensitive
+            # https://www.rfc-editor.org/rfc/rfc9110#section-8.4.1
             accept_encoding = request.headers.get(hdrs.ACCEPT_ENCODING, "").lower()
             for coding in ContentCoding:
                 if coding.value in accept_encoding:

tests/test_web_sendfile.py

@@ -9,7 +9,10 @@
 
 def test_using_gzip_if_header_present_and_file_available(loop: Any) -> None:
     request = make_mocked_request(
-        "GET", "http://python.org/logo.png", headers={hdrs.ACCEPT_ENCODING: "gzip"}
+        "GET",
+        "http://python.org/logo.png",
+        # Header uses some uppercase to ensure case-insensitive treatment
+        headers={hdrs.ACCEPT_ENCODING: "GZip"},
     )
 
     gz_filepath = mock.create_autospec(Path, spec_set=True)