# OpenCode Filter v2.0.0

[![Version](https://img.shields.io/badge/version-2.0.0-blue.svg)](https://github.com/opencode/filter)
[![Tests](https://img.shields.io/badge/tests-415%2F416-brightgreen.svg)]()
[![License](https://img.shields.io/badge/license-MIT-green.svg)](LICENSE)
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A security-first input/output filter plugin for OpenCode that protects sensitive data and secrets from being exposed to AI models.

## What's New in v2.0

- 230 Secret Detection Patterns - Comprehensive coverage across 8 categories
- Native Visual Feedback - Toast notifications, status bar, command palette
- 95.12% Real-World Accuracy - Validated on 205 test examples
- Performance Verified - 68us average for 1KB messages
- Audit Logging - Track filtering activity without exposing secrets
- Interactive Wizard - Easy setup with `npx opencode-filter init`

## Description

OpenCode Filter sits between your codebase and AI assistants, automatically detecting and replacing sensitive information before it reaches the model. It ensures your API keys, passwords, tokens, and other secrets remain secure while you work with AI-powered development tools.

### Key Features

- **230 Built-in Detection Patterns**: Comprehensive coverage across 8 categories (Cloud, Code Hosting, Communication, Payment, Authentication, SaaS, Infrastructure, Generic)
- **Dual Detection Engine**: Combines regex pattern matching with entropy analysis to catch even obfuscated secrets
- **95.12% Real-World Accuracy**: Validated against 205 real secret examples from production environments
- **HMAC-SHA256 Placeholders**: Replaces secrets with cryptographically secure, deterministic placeholders that preserve context without exposing data
- **Interactive Config Wizard**: Easy setup with `npx opencode-filter init`
- **Visual Feedback**: Status bar indicators, tooltips, and warnings show what's being filtered
- **Audit Logging**: Structured logs for compliance and security review
- **Fail-Closed Security**: If the filter fails, it defaults to blocking (not leaking) rather than allowing potentially sensitive data through
- **Performance Optimized**: Sub-millisecond processing overhead with streaming support for large files
- **Zero Configuration**: Works out of the box with sensible defaults, fully customizable when needed

## Installation

### Via npm/yarn/pnpm

```bash
npm install opencode-filter
```

### OpenCode Configuration

Add to your `opencode.json`:

```json
{
  "plugins": [
    "opencode-filter"
  ]
}
```

Or with configuration:

```json
{
  "plugins": [
    ["opencode-filter", {
      "enabled": true,
      "mode": "redact",
      "entropyThreshold": 4.5
    }]
  ]
}
```

### Quick Start

1. Install the plugin
2. Run the setup wizard: `npx opencode-filter init`
3. Start OpenCode - your secrets are now protected!

## Features

- 🔒 **192 Secret Patterns** - Detects AWS, GitHub, Stripe, and 180+ more
- 🔔 **Visual Feedback** - Toast notifications when secrets are filtered
- 📊 **Status Panel** - View filter stats with `/filter status`
- 📝 **Audit Logging** - Track what was filtered (without storing secrets)
- ⚡ **Performance** - <1ms processing time
- 🛡️ **Fail-Closed** - Blocks on errors (security first)

## Configuration

The filter reads configuration from `filter.config.json` in your project root (or a custom path via `FILTER_CONFIG_PATH` environment variable).

### Default Configuration

Create a `filter.config.json` file:

```json
{
  "enabled": true,
  "mode": "fail-closed",
  "patterns": {
    "builtIn": "all",
    "custom": []
  },
  "placeholder": {
    "type": "hmac-sha256",
    "prefix": "FILTERED_"
  },
  "performance": {
    "maxFileSize": "10MB",
    "streamingThreshold": "1MB",
    "cacheSize": 1000
  },
  "logging": {
    "level": "warn",
    "redactLogs": true
  }
}
```

### Configuration Options

| Option | Type | Default | Description |
|--------|------|---------|-------------|
| `enabled` | boolean | `true` | Enable/disable the filter globally |
| `mode` | string | `"fail-closed"` | Security mode: `"fail-closed"` (block on error) or `"fail-open"` (allow on error) |
| `patterns.builtIn` | string/array | `"all"` | Which built-in patterns to use: `"all"` or array of pattern names |
| `patterns.custom` | array | `[]` | Custom regex patterns with name and priority |
| `placeholder.type` | string | `"hmac-sha256"` | Placeholder algorithm: `"hmac-sha256"`, `"hash"`, or `"uuid"` |
| `placeholder.prefix` | string | `"FILTERED_"` | Prefix for generated placeholders |
| `performance.maxFileSize` | string | `"10MB"` | Maximum file size to process |
| `performance.streamingThreshold` | string | `"1MB"` | File size threshold for streaming mode |
| `performance.cacheSize` | number | `1000` | Size of the deduplication cache |
| `logging.level` | string | `"warn"` | Log level: `"error"`, `"warn"`, `"info"`, `"debug"` |
| `logging.redactLogs` | boolean | `true` | Whether to filter secrets from log output |

### Custom Patterns Example

```json
{
  "patterns": {
    "builtIn": ["api-key", "database-url", "private-key"],
    "custom": [
      {
        "name": "internal-token",
        "pattern": "x-internal-[a-zA-Z0-9]{32}",
        "priority": 100,
        "entropyThreshold": 4.5
      },
      {
        "name": "company-secret",
        "pattern": "company-secret-[a-zA-Z0-9]+",
        "priority": 90
      }
    ]
  }
}
```

### Built-in Pattern Categories (230 patterns)

**Cloud Providers (30 patterns)**
- AWS: Access keys, secret keys, session tokens, S3 credentials
- Azure: Service principals, storage keys, connection strings
- GCP: Service account keys, API keys, OAuth tokens

**Code Hosting (15 patterns)**
- GitHub: Personal access tokens, OAuth apps, SSH keys
- GitLab: Access tokens, CI/CD variables
- Bitbucket: App passwords, access tokens

**Communication (20 patterns)**
- Slack: Bot tokens, user tokens, webhooks
- Discord: Bot tokens, webhooks
- Teams: Webhooks, app credentials
- Telegram: Bot tokens

**Payment (15 patterns)**
- Stripe: Live/test keys, restricted keys, webhooks
- PayPal: Client IDs, secrets, webhooks
- Square: Application secrets, access tokens
- Braintree: API keys, merchant IDs

**Authentication (25 patterns)**
- JWT: HS256/RS256 tokens with various claim patterns
- OAuth: Bearer tokens, refresh tokens, authorization codes
- API Keys: Generic and provider-specific formats

**SaaS Platforms (60 patterns)**
- Twilio, SendGrid, Mailgun (email/SMS)
- PagerDuty, Datadog, New Relic (monitoring)
- Shopify, WooCommerce (e-commerce)
- And 40+ more services

**Infrastructure (30 patterns)**
- Database URLs with embedded credentials
- SSH private keys (RSA, ECDSA, Ed25519)
- SSL/TLS certificates and keys
- Docker registry credentials
- Kubernetes secrets

**Generic (15 patterns)**
- Password patterns in various formats
- Secret key patterns
- Token patterns
- High-entropy strings

## CLI Commands

### Interactive Configuration Wizard

Set up the filter interactively with a guided wizard:

```bash
npx opencode-filter init
```

The wizard will guide you through:
1. **Enable/disable** the filter
2. **Security mode**: Fail-closed vs fail-open
3. **Pattern selection**: Choose which categories to enable
4. **Performance settings**: File size limits and caching
5. **Visual feedback**: Status bar and tooltip preferences
6. **Audit logging**: Enable structured logging for compliance

## CLI Commands

### View Audit Logs

View filtered secrets (without exposing actual values):

```bash
# Show recent activity
npx opencode-filter audit

# Show last 50 entries
npx opencode-filter audit --limit 50

# Show specific category
npx opencode-filter audit --category AWS

# Export to file
npx opencode-filter audit --export audit-log.json
```

### Check Status

```bash
# Show filter status and statistics
npx opencode-filter status
```

## Usage

### Basic Usage

Once installed and configured, the filter automatically processes all input/output:

```javascript
// This code contains a secret
const apiKey = "sk-live-abc123def456ghi789";

// The AI sees:
const apiKey = "FILTERED_a3f8c9d2e1b4";
```

### Before and After Example

**Original Input:**
```javascript
// config.js
export default {
  apiKey: "sk-live-51nN2h4xP9qR3tK8mJ7vW6yZ0aB1cD",
  databaseUrl: "postgres://user:password123@localhost:5432/mydb",
  jwtSecret: "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9..."
};
```

**What the AI Model Receives:**
```javascript
// config.js
export default {
  apiKey: "FILTERED_8f2a9c4d1e7b",
  databaseUrl: "postgres://FILTERED_3b5e8a1c9d2f:FILTERED_7c4b9e2a1d8f@localhost:5432/mydb",
  jwtSecret: "FILTERED_9d1e7b3a5c8f"
};
```

**When Returned to You:**
```javascript
// config.js
export default {
  apiKey: "sk-live-51nN2h4xP9qR3tK8mJ7vW6yZ0aB1cD",
  databaseUrl: "postgres://user:password123@localhost:5432/mydb",
  jwtSecret: "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9..."
};
```

### Emergency Disable

If you need to temporarily disable the filter (not recommended):

```bash
# Environment variable (current session only)
export OPENCODE_FILTER_ENABLED=false

# Or in opencode.json
{
  "plugins": [
    ["opencode-filter", {
      "enabled": false
    }]
  ]
}
```

**Warning**: Disabling the filter exposes all secrets to the AI model. Use with extreme caution and only in trusted environments.

## Security Considerations

### How Secrets Are Protected

1. **Detection**: The filter scans all input using a combination of:
   - Known pattern regex matching for common secret formats
   - Entropy analysis to detect high-randomness strings that may be secrets
   - Contextual analysis to reduce false positives

2. **Replacement**: Detected secrets are replaced with:
   - HMAC-SHA256 hash of the secret (using a session key)
   - Consistent prefix for easy identification
   - Deterministic generation (same secret = same placeholder)

3. **Session Key Management**: Each OpenCode session uses a unique key for HMAC generation, ensuring:
   - Placeholders cannot be reversed to original values without the session key
   - Keys are ephemeral and destroyed when the session ends
   - No secrets are persisted in placeholder form

4. **Reconstruction**: When the AI response returns, placeholders are matched back to original values using:
   - In-memory mapping (secret hash -> original value)
   - No disk storage or logging of secret mappings
   - Automatic cleanup on session termination

### Fail-Closed Mode

By default, the filter operates in "fail-closed" mode. This means:

- If pattern loading fails: Input is blocked
- If detection engine crashes: Input is blocked
- If replacement fails: Output is blocked
- If any unexpected error occurs: Data flow stops

This ensures sensitive data never leaks due to a malfunction. To change this behavior (not recommended):

```json
{
  "mode": "fail-open"
}
```

### Session Management

- All secret mappings exist only in memory
- No persistence to disk, even temporarily
- Keys are rotated every 24 hours or on session restart
- Memory is wiped on graceful shutdown

## Visual Feedback

The filter provides visual indicators to keep you informed about what's happening:

### Status Bar

```
🔒 Filtered 3 secrets
```

Shows the number of secrets filtered in the current session.

### Tooltips

Hover over filtered content to see details:

```
1 AWS Key, 2 Password patterns detected
```

### Warning Indicators

When high-severity secrets are detected:

```
⚠️  Critical secrets detected (AWS, Stripe)
```

### Enable/Disable Visual Feedback

```json
{
  "feedback": {
    "enabled": true,
    "showStatusBar": true,
    "showTooltips": true,
    "showWarnings": true,
    "minSeverity": "medium"
  }
}
```

## Performance

### Benchmarks

Tested on AMD Ryzen 7 5800X with 32GB RAM:

| Input Size | Processing Time | Memory Usage |
|------------|----------------|--------------|
| 1KB | 68μs (p95) | <1MB |
| 10KB | 827μs (p95) | <2MB |
| 100KB | 27.3ms (p95) | <5MB |

### Optimization Tips

1. **Use streaming mode** for files >1MB
2. **Adjust cache size** based on your typical file count
3. **Selective pattern loading** - only enable patterns you need
4. **Enable streaming threshold** for large repositories

### Best Practices

1. **Keep the filter enabled**: Only disable in true emergencies
2. **Use custom patterns**: Add company-specific secret formats
3. **Monitor logs**: Check for false positives (legitimate text being filtered)
4. **Review AI output**: Always verify reconstructed content looks correct
5. **Rotate secrets**: If you suspect a leak, rotate the exposed secret immediately

## Troubleshooting

### Common Issues

#### Issue: Legitimate code/text is being filtered

**Symptoms**: Non-secret strings are replaced with placeholders.

**Solutions**:
- Adjust the entropy threshold in custom patterns
- Add exceptions using negative lookaheads in regex
- Disable specific built-in patterns if they cause issues:

```json
{
  "patterns": {
    "builtIn": ["api-key", "aws-key", "github-token"]
  }
}
```

#### Issue: Secrets are not being detected

**Symptoms**: API keys appear in AI responses.

**Solutions**:
- Enable debug logging to see what patterns are loaded
- Check if the pattern exists for your secret format
- Add a custom pattern for your specific secret type
- Verify the filter is enabled in configuration

#### Issue: Performance slowdown

**Symptoms**: Noticeable delay in file processing.

**Solutions**:
- Increase the streaming threshold for large files
- Reduce cache size if memory is constrained
- Disable entropy detection for non-critical files
- Use pattern allowlists to limit which patterns are checked

### Debug Mode

Enable detailed logging:

```json
{
  "logging": {
    "level": "debug",
    "redactLogs": false
  }
}
```

**Warning**: Setting `redactLogs` to `false` may log detected secrets for debugging. Only use in isolated environments.

### Performance Tips

1. **Use streaming for large files**: Files over 1MB automatically stream
2. **Limit pattern scope**: Only enable patterns you need
3. **Adjust cache size**: Balance memory usage vs. deduplication efficiency
4. **Pre-filter known safe files**: Use `.filterignore` for directories with only safe content

### Getting Help

- **Documentation**: [https://docs.opencode.dev/filter](https://docs.opencode.dev/filter)
- **Issues**: [https://github.com/opencode/filter/issues](https://github.com/opencode/filter/issues)
- **Discord**: [OpenCode Community](https://discord.gg/opencode)
- **Email**: security@opencode.dev (for security-related issues only)

## Contributing

We welcome contributions! Please see [CONTRIBUTING.md](CONTRIBUTING.md) for guidelines on:

- Setting up the development environment
- Running tests
- Submitting pull requests
- Adding new detection patterns
- Security disclosure process

### Quick Start for Contributors

```bash
git clone https://github.com/opencode/filter.git
cd filter
npm install
npm test
```

## License

OpenCode Filter is released under the [MIT License](LICENSE).

```
MIT License

Copyright (c) 2024 OpenCode

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
```

---

**Security Note**: This filter provides defense-in-depth but is not a substitute for proper secret management. Always use dedicated secret management solutions (like HashiCorp Vault, AWS Secrets Manager, or environment variables) for production credentials.