Correct OAuth discovery metadata for public clients (#184254)

homeassistant/components/auth/login_flow.py

@@ -121,6 +121,7 @@ class WellKnownOAuthInfoView(HomeAssistantView):
     """View to host the OAuth2 information."""
 
     requires_auth = False
+    cors_allowed = True
     url = "/.well-known/oauth-authorization-server"
     name = "well-known/oauth-authorization-server"
 
@@ -138,6 +139,9 @@ class WellKnownOAuthInfoView(HomeAssistantView):
             "authorization_endpoint": f"{url_prefix}/auth/authorize",
             "token_endpoint": f"{url_prefix}/auth/token",
             "revocation_endpoint": f"{url_prefix}/auth/revoke",
+            "grant_types_supported": ["authorization_code", "refresh_token"],
+            "token_endpoint_auth_methods_supported": ["none"],
+            "revocation_endpoint_auth_methods_supported": ["none"],
             # Home Assistant accepts URL-based client_ids via IndieAuth without
             # prior registration, and discovers allowed redirect URIs from link
             # tags or a Client ID Metadata Document served at the client_id URL.
@@ -162,6 +166,7 @@ class WellKnownProtectedResourceView(HomeAssistantView):
     """View to host the OAuth2 Protected Resource Metadata per RFC9728."""
 
     requires_auth = False
+    cors_allowed = True
     url = "/.well-known/oauth-protected-resource"
     name = "well-known/oauth-protected-resource"
 

tests/components/auth/test_login_flow.py

@@ -425,6 +425,9 @@ async def test_well_known_auth_info(
         "authorization_endpoint": f"{expected_url_prefix}/auth/authorize",
         "token_endpoint": f"{expected_url_prefix}/auth/token",
         "revocation_endpoint": f"{expected_url_prefix}/auth/revoke",
+        "grant_types_supported": ["authorization_code", "refresh_token"],
+        "token_endpoint_auth_methods_supported": ["none"],
+        "revocation_endpoint_auth_methods_supported": ["none"],
         "client_id_metadata_document_supported": True,
         "code_challenge_methods_supported": ["S256"],
         "response_types_supported": ["code"],
@@ -564,3 +567,27 @@ async def test_login_flow_pkce_validation(
     assert resp.status == HTTPStatus.BAD_REQUEST
     result = await resp.json()
     assert expected_message in result["message"]
+
+
+@pytest.mark.parametrize(
+    "path",
+    [
+        pytest.param(
+            "/.well-known/oauth-authorization-server", id="authorization-server"
+        ),
+        pytest.param("/.well-known/oauth-protected-resource", id="protected-resource"),
+    ],
+)
+async def test_well_known_auth_info_allows_cors(
+    hass: HomeAssistant, aiohttp_client: ClientSessionGenerator, path: str
+) -> None:
+    """Test browser clients can discover authorization server capabilities."""
+    client = await async_setup_auth(hass, aiohttp_client, setup_api=True)
+
+    resp = await client.get(
+        path,
+        headers={"origin": "https://client.example"},
+    )
+
+    assert resp.status == HTTPStatus.OK
+    assert resp.headers["Access-Control-Allow-Origin"] == "https://client.example"