docs/SECURITY.md

# Security Guidelines - Crossword App

## 🔒 Environment Variables & API Keys

### ✅ **Secure Practices Implemented**

#### **1. Environment Files**
- ✅ `.env` files are gitignored
- ✅ `.env.example` template provided
- ✅ No real secrets in source code
- ✅ Automatic setup script provided

#### **2. API Key Management**

**Local Development:**
```bash
# 1. Set up environment
./setup-env.sh

# 2. Edit .env with your real key
HUGGINGFACE_API_KEY=hf_your_real_key_here

# 3. .env is automatically gitignored
```

**Production Deployment:**
- **HuggingFace Spaces**: Use Settings → Environment Variables
- **Railway/Heroku**: Use config vars
- **Docker**: Pass as runtime environment variables

#### **3. Default Security**
- 🛡️ **Graceful fallback** when API keys missing
- 🛡️ **No crashes** on missing configuration
- 🛡️ **Warning messages** instead of errors
- 🛡️ **Safe defaults** for all settings

### 🚨 **What NOT to Do**

❌ Never commit real API keys:
```javascript
// ❌ NEVER DO THIS
const apiKey = 'hf_real_key_here';
```

❌ Never hardcode secrets:
```javascript
// ❌ NEVER DO THIS
const config = {
  huggingfaceKey: 'hf_abcd1234...'
};
```

❌ Never share .env files:
```bash
# ❌ NEVER DO THIS
git add .env
git commit -m "added config"
```

### ✅ **Safe Patterns**

✅ Always use environment variables:
```javascript
// ✅ SAFE
const apiKey = process.env.HUGGINGFACE_API_KEY;
```

✅ Always check for existence:
```javascript
// ✅ SAFE WITH FALLBACK
if (!apiKey || apiKey === 'hf_xxxxxxxxxx') {
  console.warn('API key not configured, using fallback');
  return this.fallbackMethod();
}
```

✅ Always use templates:
```bash
# ✅ SAFE
cp .env.example .env
# Edit .env with real values
```

## 📁 **File Security**

### **Gitignore Coverage**
```gitignore
# Environment files
.env
.env.local
.env.*.local

# Security files
*.key
*.pem
.secret
secrets/
```

### **File Structure**
```
backend/
├── .env.example          # ✅ Safe template (committed)
├── .env                  # 🔒 Real values (gitignored)
├── .env.backup           # 🔒 Backup (gitignored)
└── setup-env.sh          # ✅ Setup script (committed)
```

## 🚀 **Deployment Security**

### **HuggingFace Spaces**
1. Go to Space Settings
2. Add Environment Variable: `HUGGINGFACE_API_KEY`
3. Set value to your real API key
4. Restart space

### **Docker Deployment**
```bash
# Runtime environment variable
docker run -e HUGGINGFACE_API_KEY=hf_your_key app
```

### **CI/CD Pipelines**
```yaml
# GitHub Actions example
env:
  HUGGINGFACE_API_KEY: ${{ secrets.HUGGINGFACE_API_KEY }}
```

## 🔍 **Security Verification**

### **Pre-commit Checklist**
- [ ] No real API keys in code
- [ ] .env in .gitignore
- [ ] Only .env.example committed
- [ ] All secrets use environment variables
- [ ] Fallback mechanisms working

### **Testing Security**
```bash
# Test without API key
unset HUGGINGFACE_API_KEY
npm run dev
# Should work with fallback

# Test with invalid key
export HUGGINGFACE_API_KEY="invalid"
npm run dev
# Should gracefully fallback
```

## 📚 **Resources**

- [HuggingFace API Keys](https://huggingface.co/settings/tokens)
- [Environment Variable Best Practices](https://12factor.net/config)
- [Git Security Guidelines](https://docs.github.com/en/authentication/keeping-your-account-and-data-secure)

## 🆘 **If API Key Gets Exposed**

1. **Immediately revoke** the key at https://huggingface.co/settings/tokens
2. **Generate new key** with appropriate permissions
3. **Update** all deployment environments
4. **Check git history** for any committed secrets
5. **Consider repository security scan**

---

**Remember**: Security is a process, not a destination. Always be vigilant! 🛡️