rust-guard: centralize repo-visibility fallback semantics in labeling helpers by Copilot · Pull Request #10624 · github/gh-aw-mcpg

Copilot · 2026-08-03T15:20:01Z

Rust guard had duplicated repo-visibility fallback logic across response labeling paths, with both fail-open (unwrap_or(false)) and fail-secure (None => !cfg!(test)) variants repeated inline. This PR consolidates those semantics into named helpers to keep policy behavior explicit and auditable in one place.

Helper centralization (single source of truth)
- Added repo_private_fallback(owner, repo) in labels/helpers.rs for best-effort fail-open defaulting.
- Added repo_private_or_secure_default(owner, repo) in labels/helpers.rs for security-sensitive fail-secure defaulting (test-mode exception preserved).
Call-site deduplication
- Replaced duplicated fail-open expressions in:
  - labels/response_items.rs (PR/issues collection defaults)
  - labels/response_paths.rs (repo item context defaults)
- Replaced duplicated fail-secure expressions in:
  - labels/response_items.rs (commit labeling)
  - labels/response_paths.rs (commit path labeling)
  - labels/tool_rules.rs (commit tool-rule integrity fallback)
Behavior-preserving clarity
- Existing semantics are unchanged; only the policy decision points were moved behind explicit helper names and docs.

// fail-open default for non-security fallback paths
let default_repo_private = repo_private_fallback(&arg_owner, &arg_repo);

// fail-secure default for integrity-sensitive paths
let repo_private = repo_private_or_secure_default(&arg_owner, &arg_repo);

Fixes [rust-guard] Rust Guard: Centralize duplicated repo-private fallback expressions in response_items.rs/response_paths.rs #10607

Copilot

Pull request overview

Centralizes repository-visibility fallback policies in Rust guard labeling helpers.

Changes:

Adds fail-open and fail-secure visibility helpers with tests.
Reuses helpers across response and tool labeling paths.
One tool-rule call site unintentionally retries visibility lookup.

Show a summary per file

File	Description
`labels/helpers.rs`	Adds fallback helpers and unit tests.
`labels/response_items.rs`	Uses helpers for item labeling.
`labels/response_paths.rs`	Uses helpers for path labeling.
`labels/tool_rules.rs`	Uses secure fallback for commit rules.

Review details

Tip

Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

Files reviewed: 4/4 changed files
Comments generated: 1
Review effort level: Balanced

+            let repo_private_effective = repo_private
+                .unwrap_or_else(|| repo_private_or_secure_default(&owner, &repo));


lpcox · 2026-08-03T16:34:45Z

@copilot resolve merge conflicts and address review feedback

…ure_default signature The helper now accepts Option<bool> (already-fetched visibility) instead of (owner, repo) to avoid a second backend lookup. This addresses the review feedback that calling the helper when repo_private is None was triggering a duplicate backend request, which could dowgrade integrity if the second lookup succeeded with a 'public' result.

Copilot · 2026-08-03T16:45:25Z

@copilot resolve merge conflicts and address review feedback

Resolved in commit 711ce90e.

Merged origin/main and resolved all conflicts by adopting the correct signature: repo_private_or_secure_default(repo_private: Option<bool>) accepts an already-fetched Option<bool> rather than taking (owner, repo) and querying the backend again.

The key fix in tool_rules.rs:

// Before (double lookup — wrong):
let repo_private_effective = repo_private
    .unwrap_or_else(|| repo_private_or_secure_default(&owner, &repo));

// After (uses already-fetched value — correct):
let repo_private_effective = repo_private_or_secure_default(repo_private);

The same Option<bool> pass-through pattern is used in response_items.rs and response_paths.rs. Tests in helpers.rs were updated to use the new signature. 622/622 tests pass.

github-actions · 2026-08-03T16:53:01Z

🔒 mcpg Read-Only Stress — gVisor

Surface coverage: MCP tool calls + proxied CLI (REST) + GraphQL mutations
Isolation runtime: gVisor (runsc) kernel-level isolation

Part	Surface	Op	Result	Expected	Status
A	MCP	reads (issues/PRs/file/commits)	data returned	ALLOWED	✅
B	MCP	writes (reaction/star/issue/comment/branch/file/PR)	`unknown tool` [-32602] for all 7	BLOCKED	✅
C	CLI	reads (issues/file)	data returned via MCP-backed `github` CLI	ALLOWED	✅
D	CLI	REST writes (reaction/star/issue/comment/file)	unauthenticated — `gh` has no GH_TOKEN	BLOCKED	✅
E	CLI	GraphQL mutations (addReaction/addStar/createIssue)	unauthenticated — `gh` has no GH_TOKEN	BLOCKED	✅

Notes:

Part B: Gateway refuses all write tools with MCP error [-32602] unknown tool — absent from allowed tool list, confirming gateway-level enforcement.
Parts D/E: gh CLI unauthenticated (no GH_TOKEN); writes rejected before reaching GitHub API.
No write succeeded; no artifact was created.

Overall: PASS

References: §30833270945

🔒 mcpg read-only stress (gVisor runtime) by Read-Only Stress: gVisor runtime

github-actions · 2026-08-03T16:54:06Z

🔒 mcpg Read-Only Stress — default AWF

Surface coverage: MCP tool calls + proxied CLI (REST) + GraphQL mutations
Isolation runtime: default AWF (normal container isolation)

Part	Surface	Op	Result	Expected	Status
A	MCP	reads (list_issues/list_prs/get_file/list_commits)	data returned	ALLOWED	✅
B	MCP	writes (reaction/star/issue/comment/branch/file/PR)	gateway: "unknown tool" (not in exposed 22-tool read-only set)	BLOCKED	✅
C	CLI	reads (list_issues, get_file_contents)	data returned	ALLOWED	✅
D	CLI	REST writes (reaction/star/issue/comment/file)	gh: no GH_TOKEN — unauthenticated = blocked	BLOCKED	✅
E	CLI	GraphQL mutations (addReaction/addStar/createIssue)	gh: no GH_TOKEN — unauthenticated = blocked	BLOCKED	✅

Notes:

Part B: Gateway exposes exactly 22 read-only tools. All write tool names resolve to MCP error [-32602]: unknown tool. This is gateway-level enforcement (tools absent from the gateway-filtered list), not just backend config.
Parts D & E: gh CLI has no GH_TOKEN in this runtime — all REST/GraphQL write attempts fail with auth error before reaching GitHub API.

Overall: PASS

References: §30833275013

🔒 mcpg read-only stress (default AWF runtime) by Read-Only Stress: default runtime

github-actions · 2026-08-03T16:57:21Z

🔒 mcpg Read-Only Stress — docker-sbx

Surface coverage: MCP tool calls + proxied CLI (REST) + GraphQL mutations
Isolation runtime: docker-sbx (KVM-isolated microVM)

Part	Surface	Op	Result	Expected	Status
A	MCP	reads (list_issues/list_prs/get_file/list_commits)	data returned	ALLOWED	✅
B	MCP	writes (reaction/star/issue/comment/branch/file/PR)	Error[-32602] unknown tool	BLOCKED	✅
C	CLI	reads (list_issues/get_file via github CLI)	data returned	ALLOWED	✅
D	CLI	REST writes (reaction/star/issue/comment/file)	gh not authenticated (no GH_TOKEN)	BLOCKED	✅
E	CLI	GraphQL mutations (addReaction/addStar/createIssue)	gh not authenticated (no GH_TOKEN)	BLOCKED	✅

Gateway tool surface (B detail): Gateway exposes exactly 21 read-only tools. All 7 write tool names returned MCP error -32602 (unknown tool), confirming gateway-level enforcement.

Overall: PASS

References: §30833271178

🔒 mcpg read-only stress (docker-sbx runtime) by Read-Only Stress: docker-sbx runtime

Initial plan

2f0cf49

Copilot AI assigned Copilot and lpcox Aug 3, 2026

Copilot AI linked an issue Aug 3, 2026 that may be closed by this pull request

[rust-guard] Rust Guard: Centralize duplicated repo-private fallback expressions in response_items.rs/response_paths.rs #10607

Closed

Copilot started work on behalf of lpcox August 3, 2026 15:20 View session

refactor(rust-guard): centralize repo-private fallback helpers

db301c1

Copilot AI changed the title ~~[WIP] Centralize duplicated repo-private fallback expressions~~ rust-guard: centralize repo-visibility fallback semantics in labeling helpers Aug 3, 2026

Copilot finished work on behalf of lpcox August 3, 2026 15:32

Copilot AI requested a review from lpcox August 3, 2026 15:32

lpcox marked this pull request as ready for review August 3, 2026 16:03

Copilot AI review requested due to automatic review settings August 3, 2026 16:03

Copilot started reviewing on behalf of lpcox August 3, 2026 16:03 View session

Copilot AI reviewed Aug 3, 2026

View reviewed changes

Comment thread guards/github-guard/rust-guard/src/labels/tool_rules.rs Outdated

Comment on lines +391 to +392

let repo_private_effective = repo_private

.unwrap_or_else(|| repo_private_or_secure_default(&owner, &repo));

github-actions Bot added the readonly-stress-pass-default label Aug 3, 2026

This comment has been minimized.

Sign in to view

github-actions Bot added the readonly-stress-pass-gvisor label Aug 3, 2026

This comment has been minimized.

Sign in to view

Copilot started work on behalf of lpcox August 3, 2026 16:35 View session

Copilot finished work on behalf of lpcox August 3, 2026 16:45

lpcox merged commit 65c0634 into main Aug 3, 2026
38 checks passed

lpcox deleted the copilot/rust-guard-centralize-fallback-expressions branch August 3, 2026 17:14

This was referenced Aug 3, 2026

Smoke Test: Copilot - 30836023243 #10641

Closed

Smoke Test: Copilot - 30838661991 #10642

Closed

Guards and Integrity: tracking issue #1711

Closed

github-actions Bot mentioned this pull request Aug 5, 2026

[ca] CLI/Docker version check: 4 updates found (Claude Code, Copilot CLI, Zizmor, MCP Gateway) - 2026-08-05 github/gh-aw#50505

Closed

Copilot AI mentioned this pull request Aug 5, 2026

Bump Claude, Copilot, Zizmor, and MCP Gateway defaults github/gh-aw#50696

Merged

Navigation Menu

Uh oh!

rust-guard: centralize repo-visibility fallback semantics in labeling helpers - #10624

rust-guard: centralize repo-visibility fallback semantics in labeling helpers#10624
lpcox merged 3 commits into
mainfrom
copilot/rust-guard-centralize-fallback-expressions

Copilot AI commented Aug 3, 2026 •

edited

Loading

Uh oh!

Copilot AI left a comment

Uh oh!

This comment has been minimized.

This comment has been minimized.

lpcox commented Aug 3, 2026

Uh oh!

Copilot AI commented Aug 3, 2026

Uh oh!

github-actions Bot commented Aug 3, 2026

Uh oh!

github-actions Bot commented Aug 3, 2026

Uh oh!

github-actions Bot commented Aug 3, 2026

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

		let repo_private_effective = repo_private
		.unwrap_or_else(\|\| repo_private_or_secure_default(&owner, &repo));

Uh oh!

Conversation

Copilot AI commented Aug 3, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Review details

Uh oh!

This comment has been minimized.

This comment has been minimized.

lpcox commented Aug 3, 2026

Uh oh!

Copilot AI commented Aug 3, 2026

Uh oh!

github-actions Bot commented Aug 3, 2026

🔒 mcpg Read-Only Stress — gVisor

Uh oh!

github-actions Bot commented Aug 3, 2026

🔒 mcpg Read-Only Stress — default AWF

Uh oh!

github-actions Bot commented Aug 3, 2026

🔒 mcpg Read-Only Stress — docker-sbx

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

Copilot AI commented Aug 3, 2026 •

edited

Loading