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[guard-coverage] Guard coverage gap: 3 operations from github-mcp-server / GitHub CLI not fully covered #8222
Description
Summary
The GitHub guard does not fully cover 3 operation(s) from the github-mcp-server and/or GitHub CLI. This may allow write operations to bypass DIFC classification or leave repo-scoped mutations without explicit secrecy/integrity labeling.
- MCP tools scanned: 114
- CLI write commands scanned: 79
- Guard-covered write tools (tools.rs): 117
- Tools with explicit DIFC rules (tool_rules.rs): 118
- New gaps found this run: 3
MCP Tool Classification Gaps (tools.rs)
These MCP tools perform write or mutating operations but are missing from WRITE_OPERATIONS or READ_WRITE_OPERATIONS in guards/github-guard/rust-guard/src/tools.rs:
| Tool Name | Operation Type | Suggested Classification | Notes |
|---|---|---|---|
add_issue_reaction |
write | WRITE_OPERATIONS |
Upstream tool: "Add a reaction to an issue or pull request." Mutates repo discussion state. |
add_issue_comment_reaction |
write | WRITE_OPERATIONS |
Upstream tool: "Add a reaction to an issue or pull request comment." Mutates repo discussion state. |
add_pull_request_review_comment_reaction |
write | WRITE_OPERATIONS |
Upstream tool: "Add a reaction to a pull request review comment." Mutates repo discussion state. |
Suggested fix for tools.rs
// Add to WRITE_OPERATIONS (keep sorted for binary_search correctness):
pub const WRITE_OPERATIONS: &[&str] = &[
// ... existing entries ...
"add_issue_comment_reaction", // POST reaction on issue/PR comment
"add_issue_reaction", // POST reaction on issue or PR
"add_pull_request_review_comment_reaction", // POST reaction on PR review comment
];MCP Tool DIFC Labeling Gaps (tool_rules.rs)
These MCP tools exist in the upstream server but have no explicit match arm in apply_tool_labels in guards/github-guard/rust-guard/src/labels/tool_rules.rs. They currently fall through to default handling even though they are repo-scoped writes:
| Tool Name | Data Scope | Suggested Labels | Risk |
|---|---|---|---|
add_issue_reaction |
repo-scoped | secrecy: S(repo), integrity: writer(repo) |
Medium |
add_issue_comment_reaction |
repo-scoped | secrecy: S(repo), integrity: writer(repo) |
Medium |
add_pull_request_review_comment_reaction |
repo-scoped | secrecy: S(repo), integrity: writer(repo) |
Medium |
Suggested fix for tool_rules.rs
Add an explicit repo-scoped write rule alongside the existing issue / PR write cases:
"add_issue_reaction"
| "add_issue_comment_reaction"
| "add_pull_request_review_comment_reaction" => {
secrecy = apply_repo_visibility_secrecy(&owner, &repo, repo_id, secrecy, ctx);
integrity = writer_integrity(repo_id, ctx);
}GitHub CLI-Only Gaps
No new CLI-only gaps were identified in this run beyond operations already modeled in the guard or already tracked in cache.
Stale Guard Entries (bonus)
No stale guard entries were identified in this run.
References
Generated by GitHub Guard Coverage Checker (MCP + CLI) · 238.1 AIC · ⊞ 30.8K · ◷
- expires on Jul 12, 2026, 3:26 AM UTC
Activity
fix(guard): add reaction operations to WRITE_OPERATIONS and DIFC rules
github-actions commentedon Jun 28, 2026
🤖 This is an automated response from Repo Assist.
I've implemented this fix in draft PR #8235.
The three reaction tools were inserted into
WRITE_OPERATIONS(sorted forbinary_search) intools.rsand added to the repo-scoped write match arm intool_rules.rs, following the same pattern as adjacent issue/PR write operations. Tests added for both classification and DIFC label assignment. All 539 Rust guard tests pass.Warning
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