fix(mcp): fail closed on Untrusted trust level with no tool_allowlist#6505
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July 19, 2026 18:41
apply_allowlist() exposed all tools for the default Untrusted trust level when tool_allowlist was unset, logging only a warning. Sandboxed already failed closed in the same situation, and the ACP bridge hardcodes Untrusted+None for every IDE-requested server, defeating its own sandboxing claim. Untrusted+None now returns zero tools by default, matching Sandboxed. A new per-server allow_untrusted_without_allowlist flag (default false) preserves the previous expose-all behavior for operators who opt in explicitly. The unmatched-trust-level catch-all also now fails closed instead of exposing all tools, closing a latent gap where a future non_exhaustive McpTrustLevel variant would silently expose everything. expected_tools attestation no longer substitutes as an implicit allowlist: an Untrusted server with expected_tools set but no tool_allowlist and the opt-in flag unset now exposes zero tools. Also removes a stale doc comment, TODO, and dead clippy allow left above IngestConfig after ingest_tools moved to its own module. Closes #6474 Closes #6477
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Summary
apply_allowlist()fail-opened the defaultUntrustedMCP trust level whentool_allowlistwas unset, exposing every tool with only awarn!log — including for every IDE-requested server via the ACP bridge, which hardcodes exactly this configuration.Untrusted+ no allowlist now fails closed (zero tools) by default, matchingSandboxed. A new per-server opt-in flagallow_untrusted_without_allowlist(defaultfalse) restores the previous expose-all behavior for operators who want it explicitly.#[non_exhaustive]McpTrustLevelvariants.expected_toolsattestation no longer acts as an implicit allowlist substitute — this is a documented behavior change (see CHANGELOG).TODO, and dead#[allow(...)]block orphaned aboveIngestConfigafteringest_toolsmoved to its own module.Closes #6474
Closes #6477
Test plan
cargo +nightly fmt --checkcargo clippy --profile ci --workspace --all-targets --features "desktop,ide,server,chat,pdf,scheduler,testing" -- -D warningscargo nextest run --config-file .github/nextest.toml --workspace --features "desktop,ide,server,chat,pdf,scheduler" --lib --bins— 14612 passed, 35 skipped, 0 failedRUSTFLAGS="-D warnings" RUSTDOCFLAGS="--deny rustdoc::broken_intra_doc_links" cargo doc --no-deps --workspace --features "desktop,ide,server,chat,pdf,scheduler"gitleaks protect --stagedclean