Source Review Technique

source-review-technique

Goal: Discover zero-day vulnerabilities in source code by combining deterministic structural search with LLM-assisted data flow analysis.

When this technique applies

• A target's source code is available (open source, leaked, or decompiled/decompressed).
• You need to track tainted inputs to sensitive sinks (SAST).
• Pure regex/search is too noisy, but full manual review is too slow.

The Hybrid Workflow

Modern SAST effectively bridges static tools with LLMs. The LLM acts as the triage and data-flow validator, while tools like semgrep or grep map the initial graph.

1. Sink and Source Mapping (Deterministic)

Do not ask the LLM to "find bugs" across thousands of lines at once. It will hallucinate.

1. Identify Sources: HTTP requests, CLI args, file reads, database returns, IPC.
2. Identify Sinks: exec, system, query, eval, deserialize, UnsafeCell, memory allocators.
3. Map: Use ripgrep/semgrep/opengrep (or the IDE's code-usage search when available) to enumerate every invocation of the sinks.

2. Taint Evaluation (LLM-Assisted)

For each high-value sink found:

1. Traverse backward to find where the arguments originated.
2. Verify if the arguments are controllable by an attacker (the Source).
3. If the path crosses file boundaries (inter-procedural), explicitly read those files.
4. Context enrichment: Search locally for validators, sanitizers, or middleware.

3. Verification & Evidence

• Do not report a vulnerability unless you can trace a continuous line from Source to Sink.
• Document the exact file, line number, and variables involved at each step.
• Identify what conditions must be bypassed to reach the sink.

Quality Gates

• No generic bug reports: If the finding is "Xss vulnerability because print is used", reject it unless you can prove the input is strictly user-controlled and unescaped.
• Dependency boundaries: If the sink is in a third-party framework, check how the target application actually invokes that framework instance.
• Evidence format: Produce a markdown file detailing the exact Attack Path, required preconditions, and the affected code snippet blocks.

References

• references/bug-classes.md — Targeted sink patterns for common architectures (e.g. Deserialization, Path Traversal, Memory Corruption).