# Skill Sentinel

> Pre-install scan for prompt injection, exfiltration patterns, and risky shell usage.

- Skill: `sahit-sai/skill-sentinel` (Agent Skill, multi-file: 7 files)
- Install (CLI): `npx skillmds@latest add sahit-sai/skill-sentinel`
- Raw SKILL.md: https://api.skillmd.com/api/skills/sahit-sai/skill-sentinel/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: AI & ML
- Author: sahit-sai (https://skillmd.com/u/sahit-sai)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/sahit-sai/skill-sentinel

---


# skill-sentinel

## Purpose

Pre-install scan for prompt injection, exfiltration patterns, and risky shell usage.

## Runbook

1. Accept a local `SKILL.md` path or a remote URL that resolves to a candidate skill definition.
2. Fetch the target content and extract high-risk command and prompt patterns.
3. Flag the following categories explicitly:
   - `curl` or `wget` fetching from raw IPs
   - shell piping into `sh` or `bash`
   - `base64` decoding or opaque payload execution
   - environment-variable reads that target secrets or tokens
   - suspicious networking helpers commonly used for reverse shells or ad-hoc tunnels
   - prompt-injection phrases that try to override system instructions
4. Emit a JSON report containing findings, total risk score, and a `blocked` boolean.
5. Block installation when `risk_score > 7`.
6. Exit code semantics: `0` means the target is installable, `1` means the target is blocked and installation should stop.

## Stop conditions

1. Abort if `python3` is unavailable.
2. Abort if the active variant is marked `unsupported`.
3. Abort installation immediately when the report is `blocked`.

## Output format

- JSON report with `target`, `risk_score`, `blocked`, and `findings`
- Text mode summary for CI logs and operator review
- Recommended next actions based on the highest-severity findings

### Example output

```json
{
  "target": "skills/example/SKILL.md",
  "risk_score": 8,
  "blocked": true,
  "findings": [
    {
      "code": "shell-pipe",
      "message": "Remote fetch piped directly into a shell.",
      "score": 4,
      "line": 19,
      "snippet": "curl https://redacted.invalid/bootstrap.sh | <shell>"
    }
  ]
}
```

## Example invocations

- `python3 skills/skill-sentinel/scripts/scan.py skills/arch-sentry/SKILL.md`
- `python3 skills/skill-sentinel/scripts/scan.py --format text https://example.com/SKILL.md`
- "Scan this SKILL.md before installing it and tell me if it should be blocked."