Claude Shield

Security & protection hooks for Claude Code. Blocks destructive commands, protects sensitive files, prevents force-push to main/master, and maintains a full audit trail of all tool use.

What It Does

Claude Shield adds a security layer to Claude Code through hooks:

• Blocks destructive bash commands — rm -rf, DROP TABLE, git reset --hard, chmod 777, --force, --no-verify, and more
• Protects sensitive files — Prevents writes to .env, *.pem, *.key, id_rsa, credentials.*, .npmrc, and more
• Prevents force push — Blocks git push --force to main/master branches
• Audit trail — Logs every file modification, bash command, and search to SQLite
• Configurable — Add custom blocked patterns, protected files, and protected branches

Install

Option 1: Clone (recommended)

git clone https://github.com/bifrost-mcp/claude-shield.git ~/.claude/tools/claude-shield

Option 2: npm

npm install -g claude-shield

If using npm, find the install path for the next step:

echo "$(npm root -g)/claude-shield"

Configure Hooks

Add the following to your ~/.claude/settings.json. If using npm, replace ~/.claude/tools/claude-shield with the path from the command above.

{
  "hooks": {
    "PreToolUse": [
      {
        "matcher": ".*",
        "hooks": [
          {
            "type": "command",
            "command": "bash ~/.claude/tools/claude-shield/hooks/scripts/pre-tool-blocker.sh"
          }
        ]
      }
    ],
    "PostToolUse": [
      {
        "matcher": ".*",
        "hooks": [
          {
            "type": "command",
            "command": "bash ~/.claude/tools/claude-shield/hooks/scripts/post-tool-auditor.sh"
          }
        ]
      }
    ]
  }
}

Note: If you already have hooks in your settings.json, merge the arrays — don't replace them. Multiple hooks can coexist under the same event.

Verify It's Working

Start a Claude Code session and try a destructive command:

You: run rm -rf /tmp/test
Claude Shield: 🛡️ Blocked: rm -rf is a destructive command

How It Works

PreToolUse Hook — Security Blocker

Intercepts every tool call before execution. If a destructive command or protected file write is detected, the hook returns {"permissionDecision": "deny"} with a reason, preventing Claude Code from executing the action.

Blocked commands include:

| Pattern | Example | |---------|---------| | rm -rf | rm -rf /, rm -Rf ./src | | DROP TABLE | sqlite3 db 'DROP TABLE users' | | git reset --hard | git reset --hard HEAD~3 | | git clean -f | git clean -fd | | chmod 777 | chmod 777 /etc/passwd | | rm -r -f (separate flags) | rm -r -f /important | | git commit --no-verify | git commit --no-verify -m 'msg' | | git push --force to main/master | git push --force origin main |

Protected files include:

.env, .env.*, credentials.*, *.pem, *.key, id_rsa, id_ed25519, .npmrc, .pypirc, secrets.*, *.keystore

PostToolUse Hook — Audit Logger

Logs every tool use to SQLite (~/.claude-shield/audit.db):

• Bash commands executed
• Files written, edited, or read
• Search patterns used (Glob/Grep)

Commands

• /shield — View protection status, recent blocked attempts, and audit log
• /shield-config — View and update protection settings

Configuration

Config lives at ~/.claude-shield/config.json (auto-created on first use):

{
    "enabled": true,
    "block_destructive_commands": true,
    "block_protected_files": true,
    "block_force_push": true,
    "audit_logging": true,
    "audit_retention_days": 30,
    "blocked_commands": [],
    "protected_files": [],
    "protected_branches": ["main", "master"]
}

Custom Rules

Add your own blocked command patterns (regex):

{
    "blocked_commands": ["npm\\s+publish", "docker\\s+rm"]
}

Add your own protected file patterns (glob):

{
    "protected_files": ["*.secret", "config.production.*"]
}

Data Storage

All data is stored locally in ~/.claude-shield/:

| File | Purpose | |------|---------| | audit.db | SQLite database — blocked attempts + audit log | | config.json | Protection settings and custom rules |

No data is sent anywhere. Everything stays on your machine.

Requirements

• Claude Code (with hooks support)
• bash 3.2+ (ships with macOS)
• jq (brew install jq on macOS, apt install jq on Linux)
• sqlite3 (pre-installed on macOS and most Linux distributions)

If jq or sqlite3 are missing, Claude Shield will silently disable itself rather than break Claude Code.

Tests

npm test
# or
bash tests/run.sh

79 tests covering pattern matching, DB operations, hook I/O, config toggles, custom patterns, SQL injection prevention, and edge cases.

License

MIT