Add ClientResponse.certificate and populate it, if appropriate

Fixes aio-libs#2816.

CHANGES/2816.feature

@@ -0,0 +1 @@
+Add `ClientResponse.certificate` and populate it, if appropriate.

CONTRIBUTORS.txt

@@ -260,6 +260,7 @@ Pavol Vargovčík
 Pawel Kowalski
 Pawel Miech
 Pepe Osca
+Petros Blanis
 Philipp A.
 Pieter van Beek
 Qiao Han

aiohttp/client_reqrep.py

@@ -698,6 +698,7 @@ def __init__(
 
         self.method = method
         self.cookies: SimpleCookie[str] = SimpleCookie()
+        self.certificate: Optional[Dict[str, Union[Tuple[Any, ...], int, str]]] = None
 
         self._real_url = url
         self._url = url.with_fragment(None)
@@ -880,6 +881,10 @@ async def start(self, connection: "Connection") -> "ClientResponse":
                 self.cookies.load(hdr)
             except CookieError as exc:
                 client_logger.warning("Can not load response cookies: %s", exc)
+
+        # certificate
+        if self._connection is not None and self._connection.transport is not None:
+            self.certificate = self._connection.transport.get_extra_info("peercert")
         return self
 
     def _response_eof(self) -> None:

docs/client_reference.rst

@@ -1360,6 +1360,10 @@ Response object
       objects of preceding requests (earliest request first) if there were
       redirects, an empty sequence otherwise.
 
+   .. attribute:: certificate
+
+      The server certificate, if available.
+
    .. method:: close()
 
       Close response and underlying connection.

tests/test_client_request.py

@@ -1230,3 +1230,9 @@ def test_loose_cookies_types(loop: Any) -> None:
 def test_gen_default_accept_encoding(has_brotli: Any, expected: Any) -> None:
     with mock.patch("aiohttp.client_reqrep.HAS_BROTLI", has_brotli):
         assert _gen_default_accept_encoding() == expected
+
+
+async def test_certificate(loop: Any, conn: Any) -> None:
+    req = ClientRequest("get", URL("https://www.python.org"), loop=loop)
+    resp = await req.send(conn)
+    assert resp.certificate is not None