trailofbits/trailmark-variant-neighborhood

Trailmark Variant Neighborhood

Expand one seed issue into graph-derived variant candidates. This skill generates review targets, not confirmed findings.

When to Use

• A finding is confirmed or plausible and variants may exist
• The vulnerable pattern depends on call context
• The issue involves a shared sink, source, validator, interface, override, trait, hook, handler, adapter, or critical type
• The next step is to seed variant-analysis, semgrep-rule-creator, static-analysis, or manual review

When NOT to Use

• No seed issue exists. Use discovery or triage first.
• The pattern is purely syntactic and already obvious. Use semgrep-rule-creator directly.
• The question is exploit-chain composition across multiple findings. Use a composition workflow.
• The goal is remediation verification. Use a remediation-review workflow.
• The seed cannot be bound to a graph node.

Rationalizations to Reject

| Rationalization | Why It Is Wrong | Required Action | |---|---|---| | "Nearby code means variant" | Proximity is only a candidate reason | Rank it as a review target | | "Only exact same names matter" | Variants often share sinks or preconditions, not names | Expand across callers, callees, interfaces, and types | | "Every candidate is a finding" | This skill outputs candidates for review | Avoid vulnerability claims | | "Unreachable candidates can be ignored completely" | They may become reachable after refactors | Rank lower or list as deferred | | "Graph candidates replace semantic pattern work" | Graph structure finds locations, not root-cause semantics | Hand off to variant-analysis, Semgrep, CodeQL, or manual review |

Workflow

Variant Neighborhood Progress:
- [ ] Step 1: Normalize and bind the seed
- [ ] Step 2: Expand graph neighborhoods
- [ ] Step 3: Rank candidates
- [ ] Step 4: Extract variant pattern guidance
- [ ] Step 5: Emit handoff packet

Step 1: Normalize And Bind The Seed

Accept finding text, file/line, function name, or output from trailmark-finding-triage. Bind the seed to a Trailmark node and record the root cause in plain language.

If the seed has no concrete graph binding, stop before inventing variants.

Step 2: Expand Neighborhoods

Use the dimensions in references/neighborhood-patterns.md:

• shared callers
• shared callees and sinks
• entrypoint path neighbors
• interface, override, trait, and implementation siblings
• file or module cluster neighbors
• taint or privilege-boundary peers
• type and state-reference neighbors

Bound expansion to avoid candidate floods.

Step 3: Rank Candidates

Rank with references/ranking.md. Prioritize entrypoint-reachable, tainted, boundary-adjacent, high-blast-radius, shared sink, same-interface, and close-distance candidates. Penalize test, mock, generated, vendor, unreachable, and trusted-internal-only candidates.

Step 4: Extract Pattern Guidance

Summarize what should be searched for syntactically and what requires semantic review. Identify whether follow-up belongs in:

• variant-analysis
• semgrep-rule-creator
• static-analysis with CodeQL or SARIF-producing tools
• manual review

Step 5: Emit Handoff Packet

Use references/output-format.md. Include ranked candidates, inclusion reasons, exclusions, limitations, and the variant-analysis handoff.

Stop Conditions

• No graph binding exists
• Candidate count is too high and the root cause is underspecified
• Trailmark cannot analyze the target language
• The seed is only in test, generated, or vendor code and the user did not say that code is in scope