diff --git a/changelog.d/18197.feature b/changelog.d/18197.feature
new file mode 100644
index 0000000000000000000000000000000000000000..4572ac3bdbbef947a0b9e2cab47d1fb4a4a29263
--- /dev/null
+++ b/changelog.d/18197.feature
@@ -0,0 +1 @@
+Add support for specifying/overriding `redirect_uri` in the authorization and token requests against an OpenID identity provider.
\ No newline at end of file
diff --git a/docs/usage/configuration/config_documentation.md b/docs/usage/configuration/config_documentation.md
index ffee089304a26dc4e3ebce8364df7df63620226b..d2d282f2037f5f8cfea7af2b4f7791a9f7408550 100644
--- a/docs/usage/configuration/config_documentation.md
+++ b/docs/usage/configuration/config_documentation.md
@@ -3662,6 +3662,13 @@ Options for each entry include:
not included in `scopes`. Set to `userinfo_endpoint` to always use the
userinfo endpoint.
+* `redirect_uri`: An optional string, that if set will override the `redirect_uri`
+ parameter sent in the requests to the authorization and token endpoints.
+ Useful if you want to redirect the client to another endpoint as part of the
+ OIDC login. Be aware that the client must then call Synapse's OIDC callback
+ URL (`<public_baseurl>/_synapse/client/oidc/callback`) manually afterwards.
+ Must be a valid URL including scheme and path.
+
* `additional_authorization_parameters`: String to string dictionary that will be passed as
additional parameters to the authorization grant URL.
diff --git a/synapse/config/oidc.py b/synapse/config/oidc.py
index fc4bc35b300070f2f4abcee11c4bf8f1a2c07afc..8ba0ba2c360ea6acba3f8947fdae9f8409f46c0c 100644
--- a/synapse/config/oidc.py
+++ b/synapse/config/oidc.py
@@ -141,6 +141,9 @@ OIDC_PROVIDER_CONFIG_SCHEMA = {
"type": "string",
"enum": ["auto", "userinfo_endpoint"],
},
+ "redirect_uri": {
+ "type": ["string", "null"],
+ },
"allow_existing_users": {"type": "boolean"},
"user_mapping_provider": {"type": ["object", "null"]},
"attribute_requirements": {
@@ -344,6 +347,7 @@ def _parse_oidc_config_dict(
),
skip_verification=oidc_config.get("skip_verification", False),
user_profile_method=oidc_config.get("user_profile_method", "auto"),
+ redirect_uri=oidc_config.get("redirect_uri"),
allow_existing_users=oidc_config.get("allow_existing_users", False),
user_mapping_provider_class=user_mapping_provider_class,
user_mapping_provider_config=user_mapping_provider_config,
@@ -467,6 +471,18 @@ class OidcProviderConfig:
# values are: "auto" or "userinfo_endpoint".
user_profile_method: str
+ redirect_uri: Optional[str]
+ """
+ An optional replacement for Synapse's hardcoded `redirect_uri` URL
+ (`<public_baseurl>/_synapse/client/oidc/callback`). This can be used to send
+ the client to a different URL after it receives a response from the
+ `authorization_endpoint`.
+
+ If this is set, the client is expected to call Synapse's OIDC callback URL
+ reproduced above itself with the necessary parameters and session cookie, in
+ order to complete OIDC login.
+ """
+
# whether to allow a user logging in via OIDC to match a pre-existing account
# instead of failing
allow_existing_users: bool
diff --git a/synapse/handlers/oidc.py b/synapse/handlers/oidc.py
index 76b692928db8b3a7ef8b83b49a26f3e5885d1d07..18efdd9f6eefc63bd3015cd4b3650ad063bff6a5 100644
--- a/synapse/handlers/oidc.py
+++ b/synapse/handlers/oidc.py
@@ -382,7 +382,12 @@ class OidcProvider:
self._macaroon_generaton = macaroon_generator
self._config = provider
- self._callback_url: str = hs.config.oidc.oidc_callback_url
+
+ self._callback_url: str
+ if provider.redirect_uri is not None:
+ self._callback_url = provider.redirect_uri
+ else:
+ self._callback_url = hs.config.oidc.oidc_callback_url
# Calculate the prefix for OIDC callback paths based on the public_baseurl.
# We'll insert this into the Path= parameter of any session cookies we set.
diff --git a/tests/handlers/test_oidc.py b/tests/handlers/test_oidc.py
index 5ffc5a90a8f32daad997e0ec40bf175f00ff9076..cfd9969563e4894046de345ac7c51967e38956fd 100644
--- a/tests/handlers/test_oidc.py
+++ b/tests/handlers/test_oidc.py
@@ -57,6 +57,7 @@ CLIENT_ID = "test-client-id"
CLIENT_SECRET = "test-client-secret"
BASE_URL = "https://synapse/"
CALLBACK_URL = BASE_URL + "_synapse/client/oidc/callback"
+TEST_REDIRECT_URI = "https://test/oidc/callback"
SCOPES = ["openid"]
# config for common cases
@@ -586,6 +587,24 @@ class OidcHandlerTestCase(HomeserverTestCase):
code_verifier = get_value_from_macaroon(macaroon, "code_verifier")
self.assertEqual(code_verifier, "")
+ @override_config(
+ {"oidc_config": {**DEFAULT_CONFIG, "redirect_uri": TEST_REDIRECT_URI}}
+ )
+ def test_redirect_request_with_overridden_redirect_uri(self) -> None:
+ """The authorization endpoint redirect has the overridden `redirect_uri` value."""
+ req = Mock(spec=["cookies"])
+ req.cookies = []
+
+ url = urlparse(
+ self.get_success(
+ self.provider.handle_redirect_request(req, b"http://client/redirect")
+ )
+ )
+
+ # Ensure that the redirect_uri in the returned url has been overridden.
+ params = parse_qs(url.query)
+ self.assertEqual(params["redirect_uri"], [TEST_REDIRECT_URI])
+
@override_config({"oidc_config": DEFAULT_CONFIG})
def test_callback_error(self) -> None:
"""Errors from the provider returned in the callback are displayed."""
@@ -953,6 +972,37 @@ class OidcHandlerTestCase(HomeserverTestCase):
self.assertEqual(args["client_id"], [CLIENT_ID])
self.assertEqual(args["redirect_uri"], [CALLBACK_URL])
+ @override_config(
+ {
+ "oidc_config": {
+ **DEFAULT_CONFIG,
+ "redirect_uri": TEST_REDIRECT_URI,
+ }
+ }
+ )
+ def test_code_exchange_with_overridden_redirect_uri(self) -> None:
+ """Code exchange behaves correctly and handles various error scenarios."""
+ # Set up a fake IdP with a token endpoint handler.
+ token = {
+ "type": "Bearer",
+ "access_token": "aabbcc",
+ }
+
+ self.fake_server.post_token_handler.side_effect = None
+ self.fake_server.post_token_handler.return_value = FakeResponse.json(
+ payload=token
+ )
+ code = "code"
+
+ # Exchange the code against the fake IdP.
+ self.get_success(self.provider._exchange_code(code, code_verifier=""))
+
+ # Check that the `redirect_uri` parameter provided matches our
+ # overridden config value.
+ kwargs = self.fake_server.request.call_args[1]
+ args = parse_qs(kwargs["data"].decode("utf-8"))
+ self.assertEqual(args["redirect_uri"], [TEST_REDIRECT_URI])
+
@override_config(
{
"oidc_config": {