diff options
Diffstat (limited to 'synapse/handlers/oidc.py')
| -rw-r--r-- | synapse/handlers/oidc.py | 54 |
1 files changed, 47 insertions, 7 deletions
diff --git a/synapse/handlers/oidc.py b/synapse/handlers/oidc.py index 24e1cec5b6..0fc829acf7 100644 --- a/synapse/handlers/oidc.py +++ b/synapse/handlers/oidc.py @@ -36,6 +36,7 @@ from authlib.jose import JsonWebToken, JWTClaims from authlib.jose.errors import InvalidClaimError, JoseError, MissingClaimError from authlib.oauth2.auth import ClientAuth from authlib.oauth2.rfc6749.parameters import prepare_grant_uri +from authlib.oauth2.rfc7636.challenge import create_s256_code_challenge from authlib.oidc.core import CodeIDToken, UserInfo from authlib.oidc.discovery import OpenIDProviderMetadata, get_well_known_url from jinja2 import Environment, Template @@ -475,6 +476,16 @@ class OidcProvider: ) ) + # If PKCE support is advertised ensure the wanted method is available. + if m.get("code_challenge_methods_supported") is not None: + m.validate_code_challenge_methods_supported() + if "S256" not in m["code_challenge_methods_supported"]: + raise ValueError( + '"S256" not in "code_challenge_methods_supported" ({supported!r})'.format( + supported=m["code_challenge_methods_supported"], + ) + ) + if m.get("response_types_supported") is not None: m.validate_response_types_supported() @@ -602,6 +613,11 @@ class OidcProvider: if self._config.jwks_uri: metadata["jwks_uri"] = self._config.jwks_uri + if self._config.pkce_method == "always": + metadata["code_challenge_methods_supported"] = ["S256"] + elif self._config.pkce_method == "never": + metadata.pop("code_challenge_methods_supported", None) + self._validate_metadata(metadata) return metadata @@ -653,7 +669,7 @@ class OidcProvider: return jwk_set - async def _exchange_code(self, code: str) -> Token: + async def _exchange_code(self, code: str, code_verifier: str) -> Token: """Exchange an authorization code for a token. This calls the ``token_endpoint`` with the authorization code we @@ -666,6 +682,7 @@ class OidcProvider: Args: code: The authorization code we got from the callback. + code_verifier: The PKCE code verifier to send, blank if unused. Returns: A dict containing various tokens. @@ -696,6 +713,8 @@ class OidcProvider: "code": code, "redirect_uri": self._callback_url, } + if code_verifier: + args["code_verifier"] = code_verifier body = urlencode(args, True) # Fill the body/headers with credentials @@ -914,11 +933,14 @@ class OidcProvider: - ``scope``: the list of scopes set in ``oidc_config.scopes`` - ``state``: a random string - ``nonce``: a random string + - ``code_challenge``: a RFC7636 code challenge (if PKCE is supported) - In addition generating a redirect URL, we are setting a cookie with - a signed macaroon token containing the state, the nonce and the - client_redirect_url params. Those are then checked when the client - comes back from the provider. + In addition to generating a redirect URL, we are setting a cookie with + a signed macaroon token containing the state, the nonce, the + client_redirect_url, and (optionally) the code_verifier params. The state, + nonce, and client_redirect_url are then checked when the client comes back + from the provider. The code_verifier is passed back to the server during + the token exchange and compared to the code_challenge sent in this request. Args: request: the incoming request from the browser. @@ -935,10 +957,25 @@ class OidcProvider: state = generate_token() nonce = generate_token() + code_verifier = "" if not client_redirect_url: client_redirect_url = b"" + metadata = await self.load_metadata() + + # Automatically enable PKCE if it is supported. + extra_grant_values = {} + if metadata.get("code_challenge_methods_supported"): + code_verifier = generate_token(48) + + # Note that we verified the server supports S256 earlier (in + # OidcProvider._validate_metadata). + extra_grant_values = { + "code_challenge_method": "S256", + "code_challenge": create_s256_code_challenge(code_verifier), + } + cookie = self._macaroon_generaton.generate_oidc_session_token( state=state, session_data=OidcSessionData( @@ -946,6 +983,7 @@ class OidcProvider: nonce=nonce, client_redirect_url=client_redirect_url.decode(), ui_auth_session_id=ui_auth_session_id or "", + code_verifier=code_verifier, ), ) @@ -966,7 +1004,6 @@ class OidcProvider: ) ) - metadata = await self.load_metadata() authorization_endpoint = metadata.get("authorization_endpoint") return prepare_grant_uri( authorization_endpoint, @@ -976,6 +1013,7 @@ class OidcProvider: scope=self._scopes, state=state, nonce=nonce, + **extra_grant_values, ) async def handle_oidc_callback( @@ -1003,7 +1041,9 @@ class OidcProvider: # Exchange the code with the provider try: logger.debug("Exchanging OAuth2 code for a token") - token = await self._exchange_code(code) + token = await self._exchange_code( + code, code_verifier=session_data.code_verifier + ) except OidcError as e: logger.warning("Could not exchange OAuth2 code: %s", e) self._sso_handler.render_error(request, e.error, e.error_description) |