RFC: AWS STS Authentication for MCP Servers (THV-0027) #33
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Propose centralized AWS credential management for ToolHive to enable OIDC-to-AWS authentication for the AWS MCP Server. Key features: - Exchange OIDC tokens for temporary AWS credentials via AssumeRoleWithWebIdentity - Priority-based role mapping from JWT claims to IAM roles - SigV4 request signing for AWS MCP Server requests - MCPExternalAuthConfig CRD extension for Kubernetes configuration This allows organizations to use their existing IdP (Okta, Azure AD, etc.) to authenticate users accessing AWS MCP Server without distributing AWS credentials to developer machines.
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@JAORMX thanks for the review here and on Slack! I changed the proposal is use CEL for expresiveness, but also as the single and only engine, meaning that the simple claim-matching case would be just syntactical sugar unrolled to CEL in the background. |
ChrisJBurns
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ChrisJBurns
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Apologies for late feedback on this, ever since the CODEOWNERS stuff, my Github Notifications are going crazy.
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| - **Role Mapper**: Selects an IAM role based on JWT claims. When multiple claims match configured roles, the one with the lowest priority number wins. A default role is used if no claims match. | ||
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| - **STS Exchanger**: Calls `AssumeRoleWithWebIdentity` to exchange the user's OIDC token for temporary AWS credentials. |
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Is this performed on every request? This adds latency if so and may hit AWS STS rate limits under load (depending on the scale). Not sure what our positions is on caching the creds for the time they are valid?
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I should have spelled that out in the RFC explicitly, but I /do/ have caching implemented in my local branch - stacklok/toolhive@a567e02#diff-19c2048f3153cafc974acb282dcfc414dc9f40395592b7b6d31aa2db8b44198eR28
(yes this is vibe-coded. No, I won't submit vibe-code, I am now redoing the branch with proper SWE included. Vibe coding was good enough for a demo)
Propose centralized AWS credential management for ToolHive to enable OIDC-to-AWS authentication for the AWS MCP Server. Key features:
This allows organizations to use their existing IdP (Okta, Azure AD, etc.) to authenticate users accessing AWS MCP Server without distributing AWS credentials to developer machines.