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Merged
merged 10 commits into from
May 26, 2025
+85 −21
Merged

Fix building auth metadata paths #779

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5577323
fix auth metadata paths
Rodriguespn May 21, 2025
521d3bc
fix lint
Rodriguespn May 22, 2025
18f88ff
more robust solution
Rodriguespn May 22, 2025
628b492
Merge branch 'modelcontextprotocol:main' into main
Rodriguespn May 23, 2025
c7068b3
refactor append_path
Rodriguespn May 23, 2025
99ef0d4
delete modify_url_path function
Rodriguespn May 25, 2025
edd2e09
Update src/mcp/server/auth/routes.py
Kludex May 26, 2025
f85bf8d
Merge branch 'main' into main
Kludex May 26, 2025
045da79
Add tests
Kludex May 26, 2025
762d4e8
Merge branch 'main' into main
Kludex May 26, 2025
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30 changes: 9 additions & 21 deletions src/mcp/server/auth/routes.py
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Original file line number Diff line number Diff line change
Expand Up @@ -147,31 +147,19 @@ def create_auth_routes(
return routes


def modify_url_path(url: AnyHttpUrl, path_mapper: Callable[[str], str]) -> AnyHttpUrl:
return AnyHttpUrl.build(
scheme=url.scheme,
username=url.username,
password=url.password,
host=url.host,
port=url.port,
path=path_mapper(url.path or ""),
query=url.query,
fragment=url.fragment,
)


def build_metadata(
issuer_url: AnyHttpUrl,
service_documentation_url: AnyHttpUrl | None,
client_registration_options: ClientRegistrationOptions,
revocation_options: RevocationOptions,
) -> OAuthMetadata:
authorization_url = modify_url_path(
issuer_url, lambda path: path.rstrip("/") + AUTHORIZATION_PATH.lstrip("/")
authorization_url = AnyHttpUrl(
str(issuer_url).rstrip("/") + AUTHORIZATION_PATH
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There's no need to strip in any of those.

Suggested change
str(issuer_url).rstrip("/") + AUTHORIZATION_PATH
urljoin(str(issuer_url), AUTHORIZATION_PATH)

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Thanks for the suggestion, @Kludex!

I initially thought the same — that urljoin(str(issuer_url), "/authorize") would be enough. But it actually breaks in some cases where the base_url includes a path.

For example, when the base_url is https://example.com/auth/oidc/op/Customer/, urljoin returns https://example.com/authorize, which drops the intended path entirely. That’s because urljoin treats the /authorize as an absolute path and replaces everything after the domain.

To illustrate this, I added a test suite comparing both approaches:

import unittest
from urllib.parse import urljoin
from pydantic import AnyHttpUrl

class TestModifyUrlPath(unittest.TestCase):
    def test_append_authorize_to_urls_with_urljoin(self):
        """Test appending /authorize to various URL formats using urljoin"""
        test_cases = [
            ("https://example.com", "https://example.com/authorize"),
            ("https://example.com/", "https://example.com/authorize"),
            ("https://example.com/auth/oidc/op/Customer", "https://example.com/auth/oidc/op/Customer/authorize"),
            ("https://example.com/auth/oidc/op/Customer/", "https://example.com/auth/oidc/op/Customer/authorize"),
            ("http://localhost:8000", "http://localhost:8000/authorize"),
            ("http://localhost:8000/", "http://localhost:8000/authorize"),
        ]

        for base_url, expected in test_cases:
            any_http_url = AnyHttpUrl(base_url)
            with self.subTest(base_url=any_http_url):
                result = AnyHttpUrl(urljoin(str(any_http_url), "/authorize"))
                self.assertEqual(result, AnyHttpUrl(expected))

    def test_append_authorize_to_urls_with_rstrip(self):
        """Test appending /authorize to various URL formats using rstrip"""
        test_cases = [
            ("https://example.com", "https://example.com/authorize"),
            ("https://example.com/", "https://example.com/authorize"),
            ("https://example.com/auth/oidc/op/Customer", "https://example.com/auth/oidc/op/Customer/authorize"),
            ("https://example.com/auth/oidc/op/Customer/", "https://example.com/auth/oidc/op/Customer/authorize"),
            ("http://localhost:8000", "http://localhost:8000/authorize"),
            ("http://localhost:8000/", "http://localhost:8000/authorize"),
        ]

        for base_url, expected in test_cases:
            any_http_url = AnyHttpUrl(base_url)
            with self.subTest(base_url=any_http_url):
                result = AnyHttpUrl(str(any_http_url).rstrip("/") + "/authorize")
                self.assertEqual(result, AnyHttpUrl(expected))

if __name__ == "__main__":
    unittest.main()

So for consistency across all cases, I believe we need to keep the rstrip("/") approach.

Let me know what you think!

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Unfortunate, but it makes sense.

)
token_url = modify_url_path(
issuer_url, lambda path: path.rstrip("/") + TOKEN_PATH.lstrip("/")
token_url = AnyHttpUrl(
str(issuer_url).rstrip("/") + TOKEN_PATH
)

# Create metadata
metadata = OAuthMetadata(
issuer=issuer_url,
Expand All @@ -193,14 +181,14 @@ def build_metadata(

# Add registration endpoint if supported
if client_registration_options.enabled:
metadata.registration_endpoint = modify_url_path(
issuer_url, lambda path: path.rstrip("/") + REGISTRATION_PATH.lstrip("/")
metadata.registration_endpoint = AnyHttpUrl(
str(issuer_url).rstrip("/") + REGISTRATION_PATH
)

# Add revocation endpoint if supported
if revocation_options.enabled:
metadata.revocation_endpoint = modify_url_path(
issuer_url, lambda path: path.rstrip("/") + REVOCATION_PATH.lstrip("/")
metadata.revocation_endpoint = AnyHttpUrl(
str(issuer_url).rstrip("/") + REVOCATION_PATH
)
metadata.revocation_endpoint_auth_methods_supported = ["client_secret_post"]

Expand Down
76 changes: 76 additions & 0 deletions tests/client/test_auth.py
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Original file line number Diff line number Diff line change
Expand Up @@ -10,9 +10,12 @@

import httpx
import pytest
from inline_snapshot import snapshot
from pydantic import AnyHttpUrl

from mcp.client.auth import OAuthClientProvider
from mcp.server.auth.routes import build_metadata
from mcp.server.auth.settings import ClientRegistrationOptions, RevocationOptions
from mcp.shared.auth import (
OAuthClientInformationFull,
OAuthClientMetadata,
Expand Down Expand Up @@ -905,3 +908,76 @@ async def test_token_exchange_error_basic(self, oauth_provider, oauth_client_inf
await oauth_provider._exchange_code_for_token(
"invalid_auth_code", oauth_client_info
)


@pytest.mark.parametrize(
(
"issuer_url",
"service_documentation_url",
"authorization_endpoint",
"token_endpoint",
"registration_endpoint",
"revocation_endpoint",
),
(
pytest.param(
"https://auth.example.com",
"https://auth.example.com/docs",
"https://auth.example.com/authorize",
"https://auth.example.com/token",
"https://auth.example.com/register",
"https://auth.example.com/revoke",
id="simple-url",
),
pytest.param(
"https://auth.example.com/",
"https://auth.example.com/docs",
"https://auth.example.com/authorize",
"https://auth.example.com/token",
"https://auth.example.com/register",
"https://auth.example.com/revoke",
id="with-trailing-slash",
),
pytest.param(
"https://auth.example.com/v1/mcp",
"https://auth.example.com/v1/mcp/docs",
"https://auth.example.com/v1/mcp/authorize",
"https://auth.example.com/v1/mcp/token",
"https://auth.example.com/v1/mcp/register",
"https://auth.example.com/v1/mcp/revoke",
id="with-path-param",
),
),
)
def test_build_metadata(
issuer_url: str,
service_documentation_url: str,
authorization_endpoint: str,
token_endpoint: str,
registration_endpoint: str,
revocation_endpoint: str,
):
metadata = build_metadata(
issuer_url=AnyHttpUrl(issuer_url),
service_documentation_url=AnyHttpUrl(service_documentation_url),
client_registration_options=ClientRegistrationOptions(
enabled=True, valid_scopes=["read", "write", "admin"]
),
revocation_options=RevocationOptions(enabled=True),
)

assert metadata == snapshot(
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@Kludex Kludex May 26, 2025 •
edited
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I've added inline-snapshot as a test dependency. It's super useful.

OAuthMetadata(
issuer=AnyHttpUrl(issuer_url),
authorization_endpoint=AnyHttpUrl(authorization_endpoint),
token_endpoint=AnyHttpUrl(token_endpoint),
registration_endpoint=AnyHttpUrl(registration_endpoint),
scopes_supported=["read", "write", "admin"],
grant_types_supported=["authorization_code", "refresh_token"],
token_endpoint_auth_methods_supported=["client_secret_post"],
service_documentation=AnyHttpUrl(service_documentation_url),
revocation_endpoint=AnyHttpUrl(revocation_endpoint),
revocation_endpoint_auth_methods_supported=["client_secret_post"],
code_challenge_methods_supported=["S256"],
)
)
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