Integration Security - MLS Implementation

Overview

Security analysis of MLS integration points, including MLSCipherLayer, cascading cipher integration, module federation, and state persistence.

MLSCipherLayer Analysis

Location: src/crypto/CascadingCipher/layers/MLSCipherLayer.ts Purpose: Wrap MLS protocol for cascading cipher system

Security Review

export class MLSCipherLayer implements CipherLayer {
  private mlsManager: MLSManager | null = null;
  private groupId: string | null = null;

Assessment:

✅ Clean interface design
✅ Proper encapsulation
⚠️ Stores manager/groupId in memory (state management)
⚠️ No input validation at layer boundary

Encryption Flow Security

async encrypt(data: Uint8Array, keys: MLSKeys): Promise<EncryptedPayload> {
  const base64Data = this.arrayBufferToBase64(data);
  const envelope = await manager.encryptMessage(groupId, base64Data);

  return {
    ciphertext: envelope.ciphertext,
    layerMetadata: {
      processingTime: endTime - startTime,  // ⚠️ Timing info
      inputSize: data.length,               // ⚠️ Size info
      // ...
    }
  };
}

Issues Identified

Base64 Encoding Overhead
- MLS expects strings, binary data encoded as base64
- 33% size increase
- Performance impact
- Assessment: Acceptable (MLS design constraint)
Timing Information Exposure
- processingTime included in metadata
- Enables timing analysis
- Severity: MEDIUM
- Fix: Remove timing measurements
Size Information Exposure
- inputSize and outputSize in metadata
- Correlation attacks possible
- Severity: MEDIUM
- Fix: Remove size information

Decryption Flow Security

async decrypt(payload: EncryptedPayload, keys: MLSKeys): Promise<Uint8Array> {
  const envelope: MLSMessageEnvelope = {
    groupId: payload.parameters.groupId,
    ciphertext: payload.ciphertext,
    timestamp: payload.parameters.timestamp,
  };

  const base64Data = await manager.decryptMessage(envelope);
  return this.base64ToArrayBuffer(base64Data);
}

Analysis:

✅ Proper envelope reconstruction
✅ Correct parameter passing
⚠️ No validation of payload structure
⚠️ Trusts all parameters

Risk: If cascading cipher framework passes malicious payload, no validation

Cascading Cipher Integration

Layer Ordering Security

Typical Order:

Noise Protocol (optional)
MLS Layer ← Position critical
PQ Kyber (optional)
Traditional DH
AES layers

Security Implications:

✅ MLS after Noise = authenticated channel first
✅ MLS provides group security
⚠️ If MLS first = potential metadata leakage
⚠️ Multiple encryption layers = performance cost

Recommendation: MLS should be second layer (after Noise/authentication)

Module Federation Security

Export Configuration

Location: Webpack config (module federation)

exposes: {
  './MLS/MLSManager': './src/crypto/MLS/MLSManager.tsx',
  './MLS/mlsCodec': './src/crypto/MLS/mlsCodec.ts'
}

Security Analysis:

Strengths:

✅ Explicit exports (not wildcard)
✅ Only public API exposed
✅ Internal helpers not exported

Concerns:

⚠️ mlsCodec exposed (serialization functions)
⚠️ No version pinning in federation
⚠️ Runtime module loading = potential injection

Cross-Origin Risks

Scenario: Remote module loaded from different origin

Risks:

Supply Chain Attack
- Compromised remote server
- Malicious module injection
- Backdoored crypto code
Version Confusion
- Incompatible versions loaded
- Breaking changes undetected
- State corruption

Mitigations:

✅ Use HTTPS for remote modules
⚠️ Implement Subresource Integrity (SRI)
⚠️ Version pinning/semver enforcement
⚠️ Content Security Policy (CSP)

State Persistence Security

Current Implementation

async exportGroupState(groupId: string): Promise<any> {
  const exportData = {
    groupId,
    epoch: groupState.groupContext.epoch.toString(),
    exported: Date.now(),
  };
  return exportData;
}

Analysis:

⚠️ Minimal export (only metadata)
⚠️ No actual state serialization
⚠️ Cannot restore from export
⚠️ Production note: "ts-mls ClientState contains non-serializable crypto keys"

Security Issues

No Encryption of Persisted State
- If state were serialized, would be plaintext
- Contains secret keys
- Risk: HIGH if persistence added
No Integrity Protection
- No HMAC or signature on export
- State could be tampered with
- Risk: MEDIUM
No Version Control
- Format could change between versions
- No migration strategy
- Risk: LOW (operational)

Recommendation: If adding persistence:

async exportGroupState(groupId: string, encryptionKey: Uint8Array): Promise<string> {
  const state = serializeState(groupState);
  const encrypted = await encryptWithAES(state, encryptionKey);
  const hmac = await calculateHMAC(encrypted, encryptionKey);
  return JSON.stringify({ version: 1, encrypted, hmac });
}

API Security

Constructor Injection

constructor(mlsManager?: MLSManager, groupId?: string) {
  if (mlsManager) this.mlsManager = mlsManager;
  if (groupId) this.groupId = groupId;
}

Analysis:

✅ Optional dependency injection (good for testing)
⚠️ No validation of injected manager
⚠️ No validation of groupId format
⚠️ Could inject malicious manager

Risk: LOW (application controls instantiation)

Key Management

Key Structure

export interface MLSKeys {
  mlsManager: MLSManager;
  groupId: string;
}

Analysis:

✅ Simple interface
✅ Manager reference (not keys directly)
⚠️ No key rotation API at layer level
⚠️ Trusts manager is initialized

Key Lifecycle

Creation: Via MLSManager.initialize()
Storage: In MLSManager (in-memory)
Usage: Passed to encrypt/decrypt
Rotation: Via MLSManager.updateKey()
Destruction: Via MLSManager.destroy()

Security Properties:

✅ Keys never exposed directly
✅ Encapsulated in manager
⚠️ No key derivation at layer level
⚠️ No key backup/recovery

Error Handling at Integration Points

Layer Error Propagation

} catch (error) {
  throw new CipherLayerError(
    `MLS encryption failed: ${error.message}`,  // ⚠️ Exposes internal error
    this.name,
    'encrypt',
    error as Error
  );
}

Issues:

⚠️ Internal error messages bubble up
⚠️ MLSManager errors exposed to layer above
⚠️ Could leak implementation details

Fix:

} catch (error) {
  throw new CipherLayerError(
    `MLS encryption failed`,  // Generic message
    this.name,
    'encrypt'
    // Don't pass original error
  );
}

Recommendations

Critical (P0)

Remove timing measurements from metadata

// Remove: processingTime, inputSize, outputSize

Add input validation at layer boundary

validateKeys(keys: MLSKeys): boolean {
  if (!keys.mlsManager) throw new Error('Invalid manager');
  if (!keys.groupId) throw new Error('Invalid groupId');
  // Add format validation
}

High (P1)

Implement secure state persistence
- Encrypt exported state
- Add integrity protection (HMAC)
- Version control for format changes
Add module federation security
- Implement SRI for remote modules
- Version pinning/enforcement
- CSP headers
Sanitize error messages
- Don't expose internal errors
- Generic messages at boundaries
- Secure logging only

Medium (P2)

Add layer-specific monitoring
- Track encryption failures
- Monitor for anomalies
- Alert on suspicious patterns
Implement key rotation at layer level
- Expose rotation API
- Handle rotation gracefully
- Update references

Integration Test Recommendations

Security-Focused Integration Tests

describe('MLSCipherLayer Integration Security', () => {
  test('should not leak timing information', async () => {
    const layer = new MLSCipherLayer(manager, groupId);
    const payload = await layer.encrypt(data, keys);

    // Verify no timing in metadata
    expect(payload.layerMetadata.processingTime).toBeUndefined();
  });

  test('should validate keys at boundary', async () => {
    const layer = new MLSCipherLayer();
    const invalidKeys = { mlsManager: null, groupId: null };

    await expect(
      layer.encrypt(data, invalidKeys)
    ).rejects.toThrow('Invalid keys');
  });

  test('should sanitize errors from MLSManager', async () => {
    // Mock MLSManager to throw detailed error
    const mockManager = {
      encryptMessage: jest.fn().mockRejectedValue(
        new Error('Internal: epoch 5 key not found at index 42')
      )
    };

    const layer = new MLSCipherLayer(mockManager, 'test');

    await expect(
      layer.encrypt(data, keys)
    ).rejects.toThrow('MLS encryption failed'); // Generic

    await expect(
      layer.encrypt(data, keys)
    ).rejects.not.toThrow(/epoch.*index/); // No details
  });
});

Conclusion

Integration Security: 🟡 MODERATE

Strengths:

✅ Clean API design
✅ Proper encapsulation
✅ Keys managed centrally
✅ Explicit module exports

Issues:

⚠️ Timing/size information exposure
⚠️ No input validation at boundaries
⚠️ Error messages not sanitized
⚠️ State persistence incomplete

Risk Level: 🟡 MEDIUM

Recommendation: Address P0 and P1 issues before production deployment.

Overview​

MLSCipherLayer Analysis​

Security Review​

Encryption Flow Security​

Issues Identified​

Decryption Flow Security​

Cascading Cipher Integration​

Layer Ordering Security​

Module Federation Security​

Export Configuration​

Cross-Origin Risks​

State Persistence Security​

Current Implementation​

Security Issues​

API Security​

Constructor Injection​

Key Management​

Key Structure​

Key Lifecycle​

Error Handling at Integration Points​

Layer Error Propagation​

Recommendations​

Critical (P0)​

High (P1)​

Medium (P2)​

Integration Test Recommendations​

Security-Focused Integration Tests​

Conclusion​

Overview

MLSCipherLayer Analysis

Security Review

Encryption Flow Security

Issues Identified

Decryption Flow Security

Cascading Cipher Integration

Layer Ordering Security

Module Federation Security

Export Configuration

Cross-Origin Risks

State Persistence Security

Current Implementation

Security Issues

API Security

Constructor Injection

Key Management

Key Structure

Key Lifecycle

Error Handling at Integration Points

Layer Error Propagation

Recommendations

Critical (P0)

High (P1)

Medium (P2)

Integration Test Recommendations

Security-Focused Integration Tests

Conclusion