shell-wrapper-guard — Claude Code hook: what it does, how to install
Checks Bash commands for destructive actions concealed in shell wrappers. It helps catch bypasses that direct command checks can miss.
npx claude-code-templates@latest --hook security/shell-wrapper-guardWhat shell-wrapper-guard does
This hook checks Bash commands before they run, looking for destructive actions nested inside wrappers. It covers interpreter one-liners, nested wrappers, commands piped into a shell, here-strings, and env-based wrappers; the description lists eight bypass patterns.
The executable shell-wrapper-guard.sh runs as a PreToolUse hook matched to Bash. It complements dangerous-command-blocker rather than replacing direct command checks. Install it with npx claude-code-templates@latest --hook security/shell-wrapper-guard; .claude/settings.json is the associated settings file. It only runs for Bash tool calls.
What it helps with
- catch file deletion hidden in
sh -c - inspect destructive code passed to
python3 -c - check nested shell wrappers before execution
- detect commands piped into a shell
Example prompts for the agent
- Check whether
sh -c "rm -rf /"hides a destructive command before running it. - Inspect this
python3 -ccall for destructive actions. - Check this nested shell command before executing it.
How to install shell-wrapper-guard
1claude-code-templates
npx claude-code-templates@latest --hook security/shell-wrapper-guard2Manually: put the files in place
.claude/settings.jsonThe hooks block: event (PreToolUse, PostToolUse, Stop…) → command. Personal ones go to ~/.claude/settings.json
Step by step, with commands for each platform: Claude Code hooks: what they are, where to configure them, how to block a risky command
Questions about shell-wrapper-guard
How do I install shell-wrapper-guard in Claude Code?
Run npx claude-code-templates@latest --hook security/shell-wrapper-guard, then use .claude/settings.json to configure the hook.
What does shell-wrapper-guard do?
It checks Bash commands before execution and detects destructive commands concealed inside wrappers or interpreter calls.
Which wrappers and bypass patterns does it cover?
The listed calls include sh -c, bash -c, python3 -c, node -e, perl -e, and ruby -e. It also covers nested wrappers, pipe-to-shell commands, here-strings, and env-based wrappers.
Source text
shell-wrapper-guard.json · MIT
{
"description": "Detects destructive commands hidden inside shell wrappers (sh -c, bash -c, python3 -c, node -e, perl -e, ruby -e). Complements dangerous-command-blocker by catching bypass vectors like 'sh -c \"rm -rf /\"' that evade direct command checks. Covers 8 bypass patterns: interpreter one-liners, nested wrappers, pipe-to-shell, here-strings, and env-based wrappers.",
"supportingFiles": [
{
"source": "shell-wrapper-guard.sh",
"destination": ".claude/hooks/shell-wrapper-guard.sh",
"executable": true
}
],
"hooks": {
"PreToolUse": [
{
"matcher": "Bash",
"hooks": [
{
"type": "command",
"command": "bash .claude/hooks/shell-wrapper-guard.sh"
}
]
}
]
}
}
© davila7 · MIT · davila7/claude-code-templates
