auth: Add HTTP Caching in Validator

The Validator needs to fetch the OpenID Connect configuration and the
signing keys of the issuer every time it wants to authenticate a user.
Since this can happen quite frequently in the Hub, cache the responses.

not_my_board/_auth/_openid.py

@@ -8,6 +8,8 @@
 
 import jwt
 
+import not_my_board._http as http
+
 
 @dataclasses.dataclass
 class IdentityProvider:
@@ -17,11 +19,11 @@ class IdentityProvider:
     jwks_uri: str
 
     @classmethod
-    async def from_url(cls, issuer_url, http_client):
+    async def from_url(cls, issuer_url, http_client, cache=None):
         config_url = urllib.parse.urljoin(
             f"{issuer_url}/", ".well-known/openid-configuration"
         )
-        config = await http_client.get_json(config_url)
+        config = await http_client.get_json(config_url, cache=cache)
 
         init_args = {
             field.name: config[field.name] for field in dataclasses.fields(cls)
@@ -149,6 +151,11 @@ def __init__(self, client_id, http_client, trusted_issuers=None):
         self._client_id = client_id
         self._http = http_client
         self._trusted_issuers = trusted_issuers
+        if trusted_issuers is not None:
+            self._caches = {
+                issuer: (http.CacheEntry(), http.CacheEntry())
+                for issuer in trusted_issuers
+            }
 
     async def extract_claims(self, id_token, leeway=0):
         unverified_token = jwt.api_jwt.decode_complete(
@@ -157,11 +164,18 @@ async def extract_claims(self, id_token, leeway=0):
         key_id = unverified_token["header"]["kid"]
         issuer = unverified_token["payload"]["iss"]
 
-        if self._trusted_issuers is not None and issuer not in self._trusted_issuers:
-            raise RuntimeError(f"Unknown issuer: {issuer}")
+        if self._trusted_issuers is not None:
+            if issuer not in self._trusted_issuers:
+                raise RuntimeError(f"Unknown issuer: {issuer}")
+
+            idp_cache, jwk_cache = self._caches[issuer]
+        else:
+            idp_cache = jwk_cache = None
 
-        identity_provider = await IdentityProvider.from_url(issuer, self._http)
-        jwk_set_raw = await self._http.get_json(identity_provider.jwks_uri)
+        identity_provider = await IdentityProvider.from_url(
+            issuer, self._http, idp_cache
+        )
+        jwk_set_raw = await self._http.get_json(identity_provider.jwks_uri, jwk_cache)
         jwk_set = jwt.PyJWKSet.from_dict(jwk_set_raw)
 
         for key in jwk_set.keys:

tests/test_auth.py

@@ -43,7 +43,7 @@ def set_hub(self, hub_):
     def set_sub(self, sub):
         self._sub = sub
 
-    async def get_json(self, url):
+    async def get_json(self, url, cache=None):  # noqa: ARG002
         if url == f"{HUB_URL}/api/v1/auth-info":
             response = self._hub.auth_info()
         elif url == f"{ISSUER_URL}/.well-known/openid-configuration":