Add auth server design proposals #19
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MCP servers need to authenticate users via OAuth/OIDC and obtain upstream identity tokens to call external APIs (GitHub, Google, Atlassian) on behalf of users. OAuth 2.0 requires pre-registered redirect URIs and client credentials at each Identity Provider, making it impractical for individual user clients to register directly. A centralized Authorization Server solves this by acting as the single registered OAuth client with upstream IDPs, enabling Dynamic Client Registration for MCP clients while managing the complexity of upstream token storage and retrieval. The solution implements an OAuth Authorization Server built on Fosite that authenticates users against upstream IDPs, stores their tokens, and issues its own JWTs with a tsid claim linking to the stored credentials. The server exposes standard OAuth 2.0/OIDC endpoints including authorization with PKCE, token exchange, dynamic client registration (RFC 7591), and JWKS for token validation. MCP servers and vMCP can then validate incoming JWTs and retrieve the upstream IDP tokens via the tsid to make authenticated API calls on behalf of users. The design documents in this commit outline the solution in detail.
tgrunnagle
approved these changes
Jan 12, 2026
tgrunnagle
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LGTM! added a few questions mostly for my own sake.
JAORMX
approved these changes
Jan 13, 2026
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MCP servers need to authenticate users via OAuth/OIDC and obtain upstream identity tokens to call external APIs (GitHub, Google, Atlassian) on behalf of users. OAuth 2.0 requires pre-registered redirect URIs and client credentials at each Identity Provider, making it impractical for individual user clients to register directly. A centralized Authorization Server solves this by acting as the single registered OAuth client with upstream IDPs, enabling Dynamic Client Registration for MCP clients while managing the complexity of upstream token storage and retrieval.
The solution implements an OAuth Authorization Server built on Fosite that authenticates users against upstream IDPs, stores their tokens, and issues its own JWTs with a tsid claim linking to the stored credentials. The server exposes standard OAuth 2.0/OIDC endpoints including authorization with PKCE, token exchange, dynamic client registration (RFC 7591), and JWKS for token validation. MCP servers and vMCP can then validate incoming JWTs and retrieve the upstream IDP tokens via the tsid to make authenticated API calls on behalf of users.
The design documents in this commit outline the solution in detail.