feat(mcp): rfc 0047 slice 3 — tool gate (RFC0047.9) - #707
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Every MCP tool call passes the per-tool gate after the tenant binding and the two-step: a tenant-wide content reader calls everything without a round-trip (the model's can_call: caller or can_read_content from parent); every other graph-bound principal needs Check(principal, can_call, tool:<tenant>/<tool>) — per call, contextual group tuples, never cached — and a denial names the tool. Asserted end-to-end on the served binary against the real container (bot may call query_logs, scoped exactly as the JSON API; template_drift denied naming the tool; alice calls everything); the served-binary helper now enables MCP. Signed-off-by: Jens Holdgaard Pedersen <Jens@holdgaard.org>
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📝 WalkthroughWalkthroughThe MCP server adds a shared OpenFGA tool gate. Integration tests cover scoped tool access, denied calls, and tenant-wide readers. CI and RFC0047 documentation now include slice 9. ChangesMCP tool authorization
Estimated code review effort: 4 (Complex) | ~45 minutes Merge Risk: ⚪ Minimal · up to The PR adds per-tool authorization while preserving tenant and scoped access behavior. Remaining follow-ups are localized test and documentation fixes, with no concrete merge-blocking correctness or security defect identified. Sequence Diagram(s)sequenceDiagram
participant Client
participant MCPServer
participant OpenFGA
participant MCPTool
Client->>MCPServer: Send MCP tool request
MCPServer->>OpenFGA: Resolve tenant visibility
OpenFGA-->>MCPServer: Return visibility
MCPServer->>OpenFGA: Check contextual can_call grant
OpenFGA-->>MCPServer: Return authorization result
MCPServer->>MCPTool: Execute authorized tool
MCPTool-->>Client: Return MCP response
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Pull request overview
Implements RFC 0047 slice 3 by adding a per-tool authorization gate to the MCP /mcp tool surface, composing with existing RFC 0026 tenant binding and RFC 0047 visibility (two-step) so tool invocation is fail-closed and tool-specific.
Changes:
- Add
OuriosMcp::gate()and apply it to MCP tools (query_logs,list_templates,template_drift) with per-toolcan_callchecks for non-tenant-wide principals. - Extend the RFC0047 visibility served-binary integration test to cover the MCP tool gate, and enable MCP in the served-binary helper config.
- Update RFC 0047 status/decisions and CI job to reference RFC0047.4–.9 coverage.
Reviewed changes
Copilot reviewed 5 out of 5 changed files in this pull request and generated 4 comments.
Show a summary per file
| File | Description |
|---|---|
| docs/rfcs/0047-rebac-resolver-and-graph-visibility.md | Updates RFC status banner and records slice-3 (tool gate) implementation decisions. |
| crates/ourios-server/tests/it/rfc0047_visibility.rs | Adds an HTTP /mcp tools/call helper and extends the OpenFGA container E2E test through RFC0047.9. |
| crates/ourios-server/tests/it/rfc0029_oidc.rs | Enables MCP in the served-binary test config helper so /mcp is available in container tests. |
| crates/ourios-server/src/mcp.rs | Introduces and wires the per-tool gate into MCP tool handlers after tenant binding and visibility resolution. |
| .github/workflows/ci.yml | Updates the required OpenFGA container test invocation to the renamed RFC0047.4–.9 test. |
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Actionable comments posted: 3
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Inline comments:
In `@crates/ourios-server/src/mcp.rs`:
- Around line 297-354: Add local unit tests alongside gate covering tenant-wide
bypass, scoped-principal denial, and OpenFGA resolver failure. Assert that
bypass returns successfully, denial rejects the tool call, and resolver errors
return internal_error without permitting access; use existing test helpers and
authorization fixtures where available.
In `@crates/ourios-server/tests/it/rfc0047_visibility.rs`:
- Around line 199-204: Update the notifications/initialized call in the test to
retain its response instead of discarding it, then assert that the response
indicates success before continuing. Keep the existing session and request
payload unchanged.
In `@docs/rfcs/0047-rebac-resolver-and-graph-visibility.md`:
- Around line 404-406: Fix the malformed inline-code markup in the denial
example near the text containing template_drift and acme by using an HTML code
element or a valid multi-backtick delimiter, while preserving the rendered
message. Validate the documentation with mdbook build.
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…atus asserts, docs Copilot/CodeRabbit on #707: rfc0047_9_tool_gate (fake OpenFGA, no container) pins the tenant-wide bypass (zero can_call checks), per-tool grants with denials naming the tool, no-grant denial, and fail-closed on an unanswerable graph; the served-binary arm asserts every MCP status and adds the list_templates denial; RFC banner grammar + code-span fix. Signed-off-by: Jens Holdgaard Pedersen <Jens@holdgaard.org>
…atus asserts, docs Copilot/CodeRabbit on #707: rfc0047_9_tool_gate (fake OpenFGA, no container) pins the tenant-wide bypass (zero can_call checks), per-tool grants with denials naming the tool, no-grant denial, and fail-closed on an unanswerable graph; the served-binary arm asserts every MCP status and adds the list_templates denial; RFC banner grammar + code-span fix. Signed-off-by: Jens Holdgaard Pedersen <Jens@holdgaard.org>
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Pull request overview
Copilot reviewed 8 out of 8 changed files in this pull request and generated no new comments.
Suppressed comments (1)
crates/ourios-server/tests/it/rfc0047_9_tool_gate.rs:5
- The file header says the tenant-wide bypass issues no
Check, but the visibility two-step still performs at least aCheck(can_read_content, tenant); only the per-toolcan_callcheck is bypassed. Tightening this wording will avoid confusion when debugging OpenFGA call counts.
//! Scenario RFC0047.9 — the MCP tool gate, in-process against a fake
//! `OpenFGA` (no container): the tenant-wide bypass issues no `Check`, a
//! scoped principal needs an explicit `caller` grant per tool, and an
//! unanswerable graph fails the call closed. Complements the served-binary
//! arm in `rfc0047_visibility` (real container).
Summary
RFC 0047 implementation slice 3 of 4 — the MCP tool gate (RFC0047.9, §3.5). Follows #705 (resolver) and #706 (visibility).
query_logs,list_templates,template_drift) passes a per-tool gate after the RFC 0026 tenant binding and the §3.4 two-step: a tenant-wide content reader may call every tool without a round-trip (that is what the model'scan_call: caller or can_read_content from parentsays, and it does not depend on an operator having written thetool#parenttuple); every other graph-bound principal needs an explicitcallergrant —Check(principal, can_call, tool:<tenant>/<tool>), per call, with the session's contextual group tuples, never cached (a revoked grant is honoured on the next call). The denial names the tool.query_logsreads exactly its own conversations); template-level tools additionally keep the slice-2 tenant-wide rule.rfc0047_visibility::rfc0047_4_to_9_visibility_end_to_end, driven over HTTP/mcp):agent:botwithcallerontool:acme/query_logsonly →query_logsproceeds and returns exactly its scoped rows;template_drift→ permission denial naming the tool;alice(tenant-wide) calls everything. The served-binary test helper now enables MCP. Green locally against the real container.Slice 4 (emitter + erasure, RFC0047.10–.11, RFC → green) follows immediately.
Invariants / hazards touched
internal_error, retry), denial names the tool.Related
RFC: docs/rfcs/0047-rebac-resolver-and-graph-visibility.md (spec #704; slices #705, #706).
Checklist
cargo fmtcleancargo clippyclean (no new warnings)🤖 Generated with Claude Code
https://claude.ai/code/session_01JZXtbyWoQY19ZGtNecDfgv
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