dotclaude

Hook in security

sensitive-file-guard

A PreToolUse hook that blocks Read, Edit, Write, MultiEdit, and Bash operations that target sensitive files (.env, credentials, SSH private keys, certificates, secrets, AWS config, netrc, and similar). Use to prevent Claude from autonomously reading or exfiltrating credential files.

Install

As a plugin

Bundled in the security-hooks plugin. Add the marketplace once, then install the bundle; it updates with the marketplace.

/plugin marketplace add KhaledSaeed18/dotclaude
/plugin install security-hooks@dotclaude

As a single item

Run from the project root; the hook lands under .claude/. Copy it to ~/.claude/ to make it global.

npx shadcn@latest add KhaledSaeed18/dotclaude/sensitive-file-guard

Installed as a single item, a hook still needs the settings block documented below added to .claude/settings.json. The plugin route wires it automatically.

Files installed

  • .claude/hooks/sensitive-file-guard/HOOK.md
  • .claude/hooks/sensitive-file-guard/sensitive-file-guard.mjs

What it does

sensitive-file-guard

A Claude Code hook that intercepts file-access operations before they run and blocks any that target well-known sensitive-file patterns.

  • Closes the exfiltration gap. command-guard blocks destructive commands. But cat .env is not destructive; it reads a secret that could then be sent elsewhere. This hook prevents Claude from reading secrets in the first place.
  • Covers five tool surfaces. Intercepts Read, Edit, Write, and MultiEdit (by file path), and Bash (by command string and path extraction).
  • Fails open. Any error in the hook exits 0, so it can never break a legitimate file operation.
  • Zero dependencies. Node standard library only (node >= 18).

What it blocks

Pattern Examples blocked
.env files .env, .env.local, .env.production, .env.test
Credential files credentials.json, credentials.yaml
SSH private keys id_rsa, id_ed25519, id_ecdsa (public .pub files are not blocked)
Certificate and key files *.pem, *.p12, *.pfx, *.cer, *.key
AWS config ~/.aws/credentials, ~/.aws/config
Netrc .netrc, _netrc
macOS Keychain exports *.keychain, *.keychain-db
Token files .token, .tokens.json, .tokens.txt
Secret files secrets.json, secrets.yaml, secrets.env
API key files api_keys.json, api-keys.yaml
GPG exports *.gpg
OAuth token stores .oauth_token, .oauth_credentials.json
Service account files service_account.json, service-account.yaml
Shell env dumps env > file, printenv > file
Bash read patterns cat .env, less .env.local, cat credentials.json

Files

File Purpose
sensitive-file-guard.mjs The hook script. Checks every relevant tool call.
HOOK.md This file.

After npx shadcn@latest add KhaledSaeed18/dotclaude/sensitive-file-guard, both land in .claude/hooks/sensitive-file-guard/.

Activate it (required manual step)

Add this to .claude/settings.json (project), or ~/.claude/settings.json (global):

{
  "hooks": {
    "PreToolUse": [
      {
        "matcher": ".*",
        "hooks": [
          {
            "type": "command",
            "command": "node \"$CLAUDE_PROJECT_DIR/.claude/hooks/sensitive-file-guard/sensitive-file-guard.mjs\""
          }
        ]
      }
    ]
  }
}

The matcher: ".*" ensures the hook runs for Read, Edit, Write, and Bash. The script only acts on those four tools; anything else exits 0 immediately.

Tune it

Open sensitive-file-guard.mjs and edit SENSITIVE_PATH_PATTERNS and SENSITIVE_BASH_PATTERNS. Each is a list of regular expressions. Add patterns for secrets specific to your stack, or remove ones that clash with your project's file layout.

Verify it

# Attempt to Read .env: should be blocked (exit 2)
echo '{"tool_name":"Read","tool_input":{"file_path":".env"}}' \
  | node .claude/hooks/sensitive-file-guard/sensitive-file-guard.mjs; echo "exit: $?"

# Attempt to cat .env via Bash: should be blocked (exit 2)
echo '{"tool_name":"Bash","tool_input":{"command":"cat .env"}}' \
  | node .claude/hooks/sensitive-file-guard/sensitive-file-guard.mjs; echo "exit: $?"

# A safe read: should pass (exit 0)
echo '{"tool_name":"Read","tool_input":{"file_path":"README.md"}}' \
  | node .claude/hooks/sensitive-file-guard/sensitive-file-guard.mjs; echo "exit: $?"

This is the hook as installed, rendered from its source on GitHub. Read it as Markdown.

  • command-guardA PreToolUse hook that blocks catastrophic Bash commands before they run (recursive force deletes of root or home, fork bombs, writing to raw disk...
  • injection-guardA UserPromptSubmit hook that scans incoming prompts for prompt-injection and jailbreak patterns (instruction overrides, system-prompt extraction attempts...
  • smart-approveA PreToolUse hook that splits compound Bash commands (&&, ||, ;, |, $(), backticks, subshells) into their parts and checks each against the same deny list...
  • dependency-auditAudit a project's dependencies for outdated and vulnerable packages and surface breaking-change notes for upgrades. Works with any ecosystem, including...
  • owasp-securityReview code being written or modified against the OWASP Top 10:2025 and ASVS secure-coding requirements, in any language or stack, catching vulnerability...
  • secret-scanScan code or a diff for hardcoded secrets (API keys, tokens, passwords, private keys, and other exposed credentials) before they get committed or shipped....