Skill Vettr

Static analysis security scanner for third-party OpenClaw skills. Detects eval/spawn risks, malicious dependencies, typosquatting, and prompt injection patte...

skill-vettr v2.0.3

Security scanner for third-party OpenClaw skills. Analyses source code, dependencies, and metadata before installation using tree-sitter AST parsing and regex pattern matching.

Installation

npm install

This installs all Node.js dependencies, including tree-sitter .wasm grammar files required at runtime for AST-based analysis. The .wasm files are located in node_modules and must be present for the skill to function.

⚠️ Install safety: npm install runs dependency lifecycle scripts, which can execute arbitrary code. For stronger isolation, run npm ci --ignore-scripts — but note that tree-sitter native/WASM artifacts may not build, breaking AST analysis. Prefer installing inside a container or VM when possible.

External Binaries

The vet-url and vet-clawhub commands invoke external binaries via execSafe (which uses execFile — no shell is spawned). Only the following commands are permitted:

Binary	Used By	Purpose
git	vet-url	Clone .git URLs (with hooks disabled)
curl	vet-url	Download archive URLs
tar	vet-url	Extract downloaded archives
clawhub	vet-clawhub	Fetch skills from ClawHub registry

The /skill:vet command (local path vetting) requires only node and no external binaries.

Commands

• /skill:vet --path <directory> — Vet a local skill directory
• /skill:vet-url --url <https://...> — Download and vet from URL
• /skill:vet-clawhub --skill <slug> — Fetch and vet from ClawHub

Detection Categories

Category	Method	Examples
Code execution	AST	eval(), new Function(), vm.runInThisContext()
Shell injection	AST	exec(), execSync(), spawn("bash"), child_process imports
Dynamic require	AST	require(variable), require(templateString)
Prototype pollution	AST	proto assignment
Prompt injection	Regex	Instruction override patterns, control tokens (in string literals)
Homoglyph attacks	Regex	Cyrillic/Greek lookalike characters in identifiers
Encoded names	Regex	Unicode/hex-escaped "eval", "exec"
Credential paths	Regex	Cloud and SSH credential directory references, system credential store access
Network calls	AST	fetch() with literal URLs (checked against allowlist)
Malicious deps	Config	Known bad packages, lifecycle scripts, git/http deps
Typosquatting	Levenshtein	Skill names within edit distance 2 of targets
Dangerous permissions	Config	shell:exec, credentials:read in SKILL.md

Limitations

⚠️ This is a heuristic scanner with inherent limitations. It cannot guarantee safety.

• Static analysis only — Cannot detect runtime behaviour (e.g., code that fetches malware after install)
• Evasion possible — Sophisticated obfuscation or multi-stage string construction can evade detection
• JS/TS only — Binary payloads, images, and non-text files are skipped
• Limited network detection — Only detects fetch() with literal URL strings; misses axios, http module, dynamic URLs
• No sandboxing — Does not execute or isolate target code
• Comment scanning — Prompt injection detection scans string literals, not comments
• Filesystem scope — vet-url downloads and extracts remote archives into a temp directory; vet accepts paths under os.tmpdir(), ~/.openclaw, and ~/Downloads by default. Set allowCwd: true in config to also permit process.cwd() (see Configuration below)
• External binary trust — vet-url and vet-clawhub invoke git, curl, tar, and clawhub via execFile. These binaries must be trusted and present on PATH

For high-security environments, combine with sandboxing, network isolation, and manual source review. Run inside a disposable container when vetting untrusted URLs.

Configuration

allowCwd

By default, process.cwd() is not included in the set of allowed vetting roots. The default allowed roots are:

• os.tmpdir()
• ~/.openclaw
• ~/Downloads

To allow vetting paths under the current working directory, set allowCwd: true in your vetting config:

{
  "allowCwd": true
}

⚠️ Security implication: Enabling allowCwd means the scanner will accept any path under the directory you launched it from. If you run from / or $HOME, this effectively grants access to your entire filesystem. Only enable this when running from a scoped project directory or inside a container.

.vettrignore

Place a .vettrignore file in the root of the skill directory being scanned to exclude files or directories from analysis. This is useful for excluding test fixtures that contain deliberate malicious patterns.

Format

• One glob pattern per line
• Lines starting with # are comments
• Empty lines are ignored
• Patterns ending with / match entire directories
• * matches any sequence of non-separator characters
• ** matches any sequence including path separators (recursive)
• ? matches a single non-separator character

Example

# Exclude test fixtures containing deliberate prompt injection vectors
test/fixtures/

# Exclude generated files
dist/
*.min.js

If the .vettrignore file is unreadable or contains invalid UTF-8, the engine logs an INFO-level warning and proceeds with a full scan.