02db089038
## Motivation and Context `MCP::Client::HTTP` caps a single message from the server at 4 MiB, but the OAuth flow talks to authorization endpoints over its own Faraday connection, and that one had no cap. Discovery, dynamic client registration, and token responses were buffered in full and handed to `JSON.parse`, so a server that answered an OAuth request with an endless body grew the client's memory for as long as it kept sending. `Flow` and `IDJAGTokenExchange` each build their own connection, so both needed the bound. The new `BoundedBody` counts bytes in a Faraday `on_data` callback and refuses the response once it passes `MAX_RESPONSE_BYTES`, which matches the 4 MiB of `MCP::Client::HTTP::MAX_MESSAGE_BYTES` and `MCP::Client::Stdio::MAX_LINE_BYTES`. It hands back the status paired with the bounded body rather than the Faraday response, so no later caller can reach the unbounded `response.body`. Those bytes are counted after decompression. The default Net::HTTP adapter negotiates `Accept-Encoding` itself and reads the body through `Net::HTTPResponse#inflater`, so a small compressed body that expands past the cap is refused partway through the expansion. That holds only while the connection leaves `Accept-Encoding` alone, which is now recorded in a comment on both `default_http_client` definitions. An over-cap response is refused rather than truncated: a partial discovery or token document cannot be validated. Protected resource metadata is the one place where refusing is not fatal, since any PRM discovery failure already selects the legacy authorization path by design. ## How Has This Been Tested? New unit tests in `test/mcp/client/oauth/bounded_body_test.rb` cover the streaming path, the at-limit boundary, and the fallback for adapters that ignore `on_data`. One of them serves a gzip body over a real socket rather than through WebMock, which returns a stubbed body verbatim and never runs the inflater; it fails if the cap ever starts measuring compressed bytes. New tests in `test/mcp/client/oauth/flow_test.rb` and `test/mcp/client/oauth/id_jag_token_exchange_test.rb` drive each of the four request wrappers end to end with an over-cap body; all five fail without the cap in place. ## Breaking Changes An OAuth endpoint response larger than 4 MiB is now rejected instead of parsed.
25 lines
929 B
Ruby
25 lines
929 B
Ruby
# frozen_string_literal: true
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require_relative "oauth/bounded_body"
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require_relative "oauth/discovery"
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require_relative "oauth/flow"
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require_relative "oauth/in_memory_storage"
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require_relative "oauth/pkce"
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require_relative "oauth/storage_backed_provider"
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require_relative "oauth/jwt_client_assertion"
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require_relative "oauth/provider"
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require_relative "oauth/client_credentials_provider"
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require_relative "oauth/id_jag_token_exchange"
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require_relative "oauth/cross_app_access_provider"
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module MCP
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class Client
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# OAuth client support for the MCP Authorization spec (PRM discovery,
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# Authorization Server metadata discovery, Dynamic Client Registration,
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# OAuth 2.1 Authorization Code + PKCE, the client_credentials grant,
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# and the SEP-990 Enterprise Managed Authorization jwt-bearer grant).
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# https://modelcontextprotocol.io/specification/2025-11-25/basic/authorization
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module OAuth
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end
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end
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end
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