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fix(mcp): return client's own redirect_uris from DCR relay register response

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The MCP OAuth DCR relay's client-facing /register response echoed the upstream
registration verbatim, which for the short-circuit (non-bridge) arm carries
LiteLLM's own /callback as redirect_uris. A spec-compliant DCR client adopts that
value for its /authorize calls, so /callback redirects back to itself and the
second hit fails to decrypt the client's opaque state, producing a self-redirect
loop. The response now echoes the client's own redirect_uris while still
registering the gateway callback upstream
This commit is contained in:
Devin AI 2026-07-17 15:11:52 +00:00
parent 4d33964898
commit a6ffc0ffce
2 changed files with 149 additions and 2 deletions
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12
litellm/proxy/_experimental/mcp_server/discoverable_endpoints.py
View file

@ -1161,10 +1161,15 @@ async def register_client_with_server(
_raise_if_not_oauth2(mcp_server)
request_base_url = get_request_base_url(request)
current_redirect_uri = f"{request_base_url}/callback"
# In the short-circuit arm the gateway is the client's authorization server and loops the
# authorization code back through /callback, so the client-facing registration must echo the
# client's own redirect_uris. Echoing current_redirect_uri (the gateway callback) instead makes
# a spec-compliant DCR client adopt /callback as its own redirect_uri and self-redirect loop.
client_facing_redirect_uris = client_redirect_uris or [current_redirect_uri]
dummy_return = {
"client_id": fallback_client_id or mcp_server.server_name,
"client_secret": "dummy",
"redirect_uris": [current_redirect_uri],
"redirect_uris": client_facing_redirect_uris,
}
if mcp_server.client_id and not (
@ -1232,6 +1237,9 @@ async def register_client_with_server(
if persistence_result == "reused":
return dummy_return
if client_redirect_uris and not bridge_relay and isinstance(token_response, dict):
token_response = {**token_response, "redirect_uris": client_facing_redirect_uris}
return JSONResponse(token_response)
@ -1986,7 +1994,7 @@ async def register_client(request: Request, mcp_server_name: Optional[str] = Non
dummy_return = {
"client_id": mcp_server_name or "dummy_client",
"client_secret": "dummy",
"redirect_uris": [f"{request_base_url}/callback"],
"redirect_uris": data.get("redirect_uris") or [f"{request_base_url}/callback"],
}
client_ip = IPAddressUtils.get_mcp_client_ip(request)
if not mcp_server_name:

139
tests/test_litellm/proxy/_experimental/mcp_server/test_discoverable_endpoints.py
View file

@ -572,6 +572,145 @@ async def test_register_client_remote_registration_success():
assert call_args.kwargs["json"]["token_endpoint_auth_method"] == request_payload["token_endpoint_auth_method"]
@pytest.mark.asyncio
async def test_register_client_non_bridge_returns_client_redirect_uris_not_gateway_callback():
"""Regression for the DCR self-redirect loop (#33699): a non-bridge oauth2 server relays the
gateway's own callback upstream, but the client-facing registration response must echo the
client's own redirect_uris. Returning the upstream-echoed gateway /callback makes a
spec-compliant DCR client adopt /callback as its redirect_uri and loop back into /callback."""
try:
from fastapi import Request
from litellm.proxy._experimental.mcp_server.discoverable_endpoints import (
register_client,
)
from litellm.proxy._experimental.mcp_server.mcp_server_manager import (
global_mcp_server_manager,
)
from litellm.proxy._types import MCPTransport
from litellm.types.mcp import MCPAuth
from litellm.types.mcp_server.mcp_server_manager import MCPServer
except ImportError:
pytest.skip("MCP discoverable endpoints not available")
global_mcp_server_manager.registry.clear()
oauth2_server = MCPServer(
server_id="remote_server",
name="remote_server",
server_name="remote_server",
alias="remote_server",
transport=MCPTransport.http,
auth_type=MCPAuth.oauth2,
client_id=None,
client_secret=None,
authorization_url="https://provider.example/oauth/authorize",
token_url="https://provider.example/oauth/token",
registration_url="https://provider.example/oauth/register",
)
global_mcp_server_manager.registry[oauth2_server.server_id] = oauth2_server
mock_request = MagicMock(spec=Request)
mock_request.base_url = "https://proxy.litellm.example/"
mock_request.headers = {}
client_redirect = "https://open-webui.example/oauth/oidc/callback"
request_payload = {
"client_name": "Open WebUI",
"grant_types": ["authorization_code", "refresh_token"],
"response_types": ["code"],
"redirect_uris": [client_redirect],
}
mock_response = MagicMock()
mock_response.json.return_value = {
"client_id": "generated-client",
"client_secret": "generated-secret",
"redirect_uris": ["https://proxy.litellm.example/callback"],
}
mock_response.raise_for_status = MagicMock()
mock_async_client = MagicMock()
mock_async_client.post = AsyncMock(return_value=mock_response)
try:
with (
patch(
"litellm.proxy._experimental.mcp_server.discoverable_endpoints._read_request_body",
new=AsyncMock(return_value=request_payload),
),
patch(
"litellm.proxy._experimental.mcp_server.discoverable_endpoints.get_async_httpx_client",
return_value=mock_async_client,
),
):
response = await register_client(request=mock_request, mcp_server_name=oauth2_server.server_name)
finally:
global_mcp_server_manager.registry.clear()
payload = json.loads(response.body.decode("utf-8"))
assert payload["redirect_uris"] == [client_redirect]
assert payload["client_id"] == "generated-client"
posted = mock_async_client.post.call_args.kwargs["json"]
assert posted["redirect_uris"] == ["https://proxy.litellm.example/callback"]
@pytest.mark.asyncio
async def test_register_client_admin_configured_client_echoes_client_redirect_uris():
"""A server with an admin-configured client_id short-circuits registration to a placeholder, but
that placeholder must still echo the client's own redirect_uris so a DCR client does not adopt
the gateway /callback and self-redirect loop (#33699)."""
try:
from fastapi import Request
from litellm.proxy._experimental.mcp_server.discoverable_endpoints import (
register_client,
)
from litellm.proxy._experimental.mcp_server.mcp_server_manager import (
global_mcp_server_manager,
)
from litellm.proxy._types import MCPTransport
from litellm.types.mcp import MCPAuth
from litellm.types.mcp_server.mcp_server_manager import MCPServer
except ImportError:
pytest.skip("MCP discoverable endpoints not available")
global_mcp_server_manager.registry.clear()
oauth2_server = MCPServer(
server_id="stored_server",
name="stored_server",
server_name="stored_server",
alias="stored_server",
transport=MCPTransport.http,
auth_type=MCPAuth.oauth2,
client_id="existing-client",
client_secret="existing-secret",
authorization_url="https://provider.example/oauth/authorize",
token_url="https://provider.example/oauth/token",
)
global_mcp_server_manager.registry[oauth2_server.server_id] = oauth2_server
mock_request = MagicMock(spec=Request)
mock_request.base_url = "https://proxy.litellm.example/"
mock_request.headers = {}
client_redirect = "https://open-webui.example/oauth/oidc/callback"
try:
with patch(
"litellm.proxy._experimental.mcp_server.discoverable_endpoints._read_request_body",
new=AsyncMock(return_value={"redirect_uris": [client_redirect]}),
):
result = await register_client(request=mock_request, mcp_server_name=oauth2_server.server_name)
finally:
global_mcp_server_manager.registry.clear()
assert result == {
"client_id": "stored_server",
"client_secret": "dummy",
"redirect_uris": [client_redirect],
}
@pytest.mark.asyncio
async def test_register_client_persists_dcr_client_identity():
"""A dynamic client registration (RFC 7591) must persist the issued client_id /