Whitepaper on Downstream Authentication & Authorization Best Practices for MCP Servers #5
Description
Background: There's a common misconception among stakeholders that MCP provides protocol-level support for downstream authorization (AuthZ) propagation. In reality, authentication terminates at the MCP server boundary, and any downstream authorization or identity propagation is the responsibility of individual server implementations.
Proposal: Develop a whitepaper documenting best practices and proven architectural patterns for implementing secure downstream authorization and identity propagation in MCP servers.
Scope: The whitepaper should cover:
Best practices for preventing privilege escalation
Token exchange patterns (e.g., OAuth 2.0 Token Exchange RFC 8693)
On-behalf-of (OBO) flows
Identity propagation strategies
Trust boundary considerations
Security implications and common pitfalls
Goal: Provide server authors with clear guidance on implementing robust, enterprise-grade authorization mechanisms that maintain security guarantees across service boundaries.