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[v1.x] Add AuthSettings.validate_token_resource to check a bearer token's resource - #3451
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maxisbey merged 1 commit intoSep 5, 2026
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…en's resource v1.x backport. BearerAuthBackend takes an optional resource_server_url; when it is set, only a token the verifier reports as issued for that URL (AccessToken.resource, the RFC 8707 resource indicator, compared as a URL with a trailing slash tolerated) is accepted, and anything else is answered 401 like an unrecognized token. AuthSettings.validate_token_resource turns this on for FastMCP's SSE and Streamable HTTP apps; leaving it unset while resource_server_url is set emits a DeprecationWarning and behaves as False, and 3.0 makes True the default there. RefreshToken gains an optional resource so a provider can carry the binding through the refresh grant. TokenVerifier.verify_token's docstring and docs/authorization.md say where the token's audience goes and when to enable the option versus checking the audience in the verifier. The oauth_server snippet and the simple-auth example set it.
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docs/authorization.md
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examples/snippets/servers/oauth_server.py
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examples/servers/simple-auth/mcp_simple_auth/server.py
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src/mcp/server/auth/provider.py
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src/mcp/server/auth/middleware/bearer_auth.py
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examples/servers/simple-auth/mcp_simple_auth/server.py
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v1.x backport of #3447.
Adds AuthSettings.validate_token_resource. When set, the bearer gate only accepts a token that the TokenVerifier reports as issued for resource_server_url (via AccessToken.resource); a token reporting another resource, or none, gets the same 401 as an unrecognized token. Leaving it unset on a resource server emits a DeprecationWarning and behaves as off; 3.0 makes it the default there. RefreshToken gains an optional resource so providers can carry the binding through the refresh grant.
Differences from #3447
How Has This Been Tested?
Unit tests as above; driven end to end under uvicorn on FastMCP with an introspection-backed verifier over Streamable HTTP (option on: a token for another resource gets 401 and one for this server 200; unset: behaviour unchanged apart from the warning); full suite with coverage, ruff, pyright.
Breaking Changes
None. Unset behaves as off (with the deprecation warning); BearerAuthBackend(verifier) and existing verifiers behave as before. Setting it to True without a resource_server_url raises at construction.
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