Max Isbey
a1734460a1
When `AuthSettings.resource_server_url` is configured, `BearerAuthBackend`
previously ran the RFC 8707 audience comparison only for tokens whose
verifier populated `AccessToken.resource`: a token carrying no resource
indicator at all was accepted. The MCP authorization spec requires a
resource server to only accept tokens issued specifically for it, so the
gate now fails closed: a verified token with no `resource` is answered
`401 invalid_token` ("The access token carries no audience claim").
`resource_server_url=None` still means there is no audience to enforce.
For verifiers that validate the audience themselves and cannot surface
the claim (for example a JWT decoder configured with the expected
audience), the new `AuthSettings.verifier_validates_audience=True` opts
the gate out. The `AuthSettings.enforced_audience` property derives the
single value both server wirings pass to `BearerAuthBackend`, whose
signature is unchanged.
`RefreshToken` gains an optional `resource` field so an authorization
server provider can carry the original grant's audience binding through
`exchange_refresh_token`; without it every refreshed access token would
be audience-unbound and rejected by the hardened gate.
The docs tutorials and example servers now populate
`AccessToken.resource` (and the client-credentials demo token endpoint
honors the RFC 8707 `resource` parameter) so they pass the check they
teach. The migration guide entry for audience validation is rewritten
for the fail-closed behavior.
34 lines
904 B
Python
34 lines
904 B
Python
from pydantic import AnyHttpUrl
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from mcp.server import MCPServer
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from mcp.server.auth.provider import AccessToken, TokenVerifier
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from mcp.server.auth.settings import AuthSettings
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KNOWN_TOKENS = {
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"alice-token": AccessToken(
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token="alice-token", client_id="alice", scopes=["notes:read"], resource="http://127.0.0.1:8000/mcp"
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),
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}
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class StaticTokenVerifier(TokenVerifier):
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async def verify_token(self, token: str) -> AccessToken | None:
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return KNOWN_TOKENS.get(token)
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mcp = MCPServer(
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"Notes",
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token_verifier=StaticTokenVerifier(),
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auth=AuthSettings(
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issuer_url=AnyHttpUrl("https://auth.example.com"),
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resource_server_url=AnyHttpUrl("http://127.0.0.1:8000/mcp"),
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required_scopes=["notes:read"],
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),
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)
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@mcp.tool()
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def list_notes() -> list[str]:
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"""List every note in the notebook."""
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return ["Buy milk", "Ship the release"]
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