fix: add client_credentials fallback for outbound token acquisition#152
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mrsabath wants to merge 1 commit into
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fix: add client_credentials fallback for outbound token acquisition#152mrsabath wants to merge 1 commit into
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The go-processor outbound handler only supported token exchange (RFC 8693) which requires a valid subject_token from the outbound request Authorization header. When the agent does not forward a token (or forwards an invalid one), the exchange fails and the request reaches the tool without authentication. Add a clientCredentialsGrant() function that obtains a token using the OAuth 2.0 client_credentials grant as a fallback. The outbound handler now tries token exchange first, and if that fails (or no auth header is present), falls back to client_credentials using the agent registered SPIFFE ID client and secret. This enables end-to-end AuthBridge flows where agents do not forward inbound tokens on their outbound MCP requests. Part of: rossoctl/rossoctl#767 Signed-off-by: Mariusz Sabath <mrsabath@gmail.com> Made-with: Cursor
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/run-e2e |
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@mrsabath is this going to be a temporary solution? When token exchange fails, and we fall back to the agent's own credentials to perform token exchange, this doesn't sound secure. |
mrsabath
marked this pull request as draft
February 27, 2026 22:25
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Closing: superseded by #171 (merged Mar 6), which implemented the same client_credentials fallback for outbound token acquisition. |
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Summary
clientCredentialsGrant()fallback: the outbound handler tries token exchange first, then falls back to OAuth 2.0 client_credentials grant using the agent's registered SPIFFE ID client credentialskagentirealmContext
Discovered during end-to-end testing of the realm migration (rossoctl/rossoctl#767). The git-issue-agent does not forward the inbound JWT on its outbound MCP requests to the GitHub tool. The go-processor saw no Authorization header and skipped token acquisition entirely, causing the tool to call GitHub's API without authentication.
The fallback flow is:
Test plan
envoy-with-processorimage to Kind cluster[Client Credentials] Successfully obtained token)Part of: rossoctl/rossoctl#767
Made with Cursor