Disallow Claude from Reading Secrets

disallow.md

Disallowing Claude from Reading Secrets

There are files you don't want your agnet to read, especially ones with secrets in them. Here's how you can prevent it:

PreToolUse Hook

In ~/.claude/settings.json (or in the project directory .claude/settings.json)

{
  "hooks": {
    "PreToolUse": [
      {
        "matcher": "Read|Write|Edit",
        "hooks": [
          {
            "type": "command",
            "command": "python ~/.claude/hooks/block_env_files.py"
          }
        ]
      }
    ],
...

block_env_files.py

You can probably do it with shell and jq, but I find this nicer. Claude passes the data to the hook in JSON over stdin.

#!/usr/bin/env python

import json
import sys
from pathlib import Path

data = json.load(sys.stdin)
file_path = data.get('tool_input', {}).get('file_path', '')
if Path(file_path).name in {'.env', '.envrc'}:
    msg = {
        'continue': False,
        'stopReason': 'Blocked: reading .env/.envrc files is not allowed',
    }
    print(json.dumps(msg))