Security Best Practices

Security is critical when running containerized sandboxes in production. This guide covers authentication, container hardening, network isolation, and operational security practices.

Authentication and Access Control

API Key Authentication

Always enable API key authentication in production:

[server]
api_key = "your-secret-api-key-change-this"

Best Practices:

Use a strong, randomly generated API key (minimum 32 characters)
Store keys in a secrets manager (Vault, AWS Secrets Manager, etc.)
Never commit keys to version control
Rotate keys regularly
Use different keys for different environments

Disable Authentication Only For:

Local development
Trusted internal networks
Testing environments

Authentication is enforced when api_key is set. If empty or missing, all API endpoints (except /health, /docs, /redoc) are accessible without authentication.

Client Request Authentication

All authenticated requests must include the OPEN-SANDBOX-API-KEY header:

curl -H "OPEN-SANDBOX-API-KEY: your-secret-api-key" \
  http://localhost:8080/v1/sandboxes

Protect API Keys:

Use HTTPS/TLS for all API communication
Avoid logging API keys in application logs
Monitor for unauthorized access attempts
Implement rate limiting at the reverse proxy level

Container Security Hardening

Drop Dangerous Capabilities

Linux capabilities control privileged operations. Drop unnecessary capabilities:

[docker]
drop_capabilities = [
  "AUDIT_WRITE",      # Prevent audit log manipulation
  "MKNOD",            # Block device node creation
  "NET_ADMIN",        # Disable network configuration
  "NET_RAW",          # Prevent raw socket creation
  "SYS_ADMIN",        # Block administrative operations
  "SYS_MODULE",       # Prevent kernel module loading
  "SYS_PTRACE",       # Disable process tracing
  "SYS_TIME",         # Block system clock changes
  "SYS_TTY_CONFIG"    # Prevent TTY configuration
]

Why Drop These Capabilities:

SYS_ADMIN: Prevents container escape vulnerabilities
NET_ADMIN: Blocks network spoofing and routing attacks
SYS_MODULE: Prevents kernel module injection
SYS_PTRACE: Prevents process memory inspection
NET_RAW: Prevents packet crafting and sniffing

Block Privilege Escalation

Prevent processes from gaining new privileges:

[docker]
no_new_privileges = true

This prevents:

Setuid/setgid binary exploitation
Privilege escalation via file capabilities
sudo/su within containers

Process Limits

Limit process creation to prevent fork bombs:

[docker]
pids_limit = 512  # Set to null to disable

Recommended values:

Light workloads: 256-512 processes
Heavy workloads: 1024-2048 processes
Unlimited: null (not recommended)

Seccomp Profiles

Seccomp filters system calls to reduce the attack surface:

[docker]
seccomp_profile = ""  # Empty uses Docker default

Options:

Empty string: Docker default seccomp profile (recommended)
Absolute path: Custom seccomp JSON profile
unconfined: Disable seccomp (not recommended)

Docker’s default profile blocks ~44 system calls including:

clone with dangerous flags
reboot
swapon/swapoff
mount/umount
Keyring manipulation

AppArmor Profiles

AppArmor provides mandatory access control:

[docker]
apparmor_profile = "docker-default"  # When AppArmor is available

Profile Options:

"": No AppArmor profile (default)
"docker-default": Docker’s default AppArmor profile
Custom profile name: Your organization’s profile

Check AppArmor Availability:

# Check if AppArmor is loaded
sudo aa-status

# View Docker's default profile
sudo cat /etc/apparmor.d/docker

Network Security

Network Isolation

Use bridge mode for network isolation:

[docker]
network_mode = "bridge"  # Isolated container networking

Bridge Mode Benefits:

Sandboxes cannot directly access each other
Host network is isolated from sandboxes
Port conflicts eliminated
Network policies enforceable

Host Mode Risks:

[docker]
network_mode = "host"  # Shared host network - use only when necessary

No network isolation
Port conflicts possible
Direct access to host network
Better performance but less secure

Network Policy Enforcement

Control outbound traffic with network policies:

[runtime]
type = "docker"
execd_image = "opensandbox/execd:v1.0.6"

[egress]
image = "opensandbox/egress:v1.0.1"

Requirements:

Bridge network mode only
Egress sidecar image configured
Main container drops NET_ADMIN capability
Sidecar retains NET_ADMIN for iptables management

Example Request:

{
  "image": {"uri": "python:3.11-slim"},
  "entrypoint": ["python", "-m", "http.server", "8000"],
  "timeout": 3600,
  "networkPolicy": {
    "defaultAction": "deny",
    "egress": [
      {"action": "allow", "target": "pypi.org"},
      {"action": "allow", "target": "*.python.org"},
      {"action": "deny", "target": "10.0.0.0/8"}  # Block private networks
    ]
  }
}

Network Policy Best Practices:

Default deny all egress traffic
Allowlist only required destinations
Block private IP ranges (RFC 1918)
Block cloud metadata endpoints (169.254.169.254)
Log denied connections for monitoring

TLS/HTTPS

Run OpenSandbox behind a reverse proxy with TLS:

[server]
host = "127.0.0.1"  # Bind to localhost only
port = 8080

Reverse Proxy Configuration (Nginx):

server {
  listen 443 ssl http2;
  server_name api.sandbox.example.com;

  ssl_certificate /etc/ssl/certs/sandbox.crt;
  ssl_certificate_key /etc/ssl/private/sandbox.key;
  ssl_protocols TLSv1.2 TLSv1.3;
  ssl_ciphers HIGH:!aNULL:!MD5;

  location / {
    proxy_pass http://127.0.0.1:8080;
    proxy_set_header Host $host;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header X-Forwarded-Proto $scheme;
  }
}

Resource Limits

Enforce resource quotas to prevent resource exhaustion:

{
  "resourceLimits": {
    "cpu": "500m",      // 0.5 CPU cores
    "memory": "512Mi"   // 512 MiB RAM
  }
}

Recommended Limits:

Workload Type	CPU	Memory
Light (web servers)	100m-500m	128Mi-512Mi
Medium (build tasks)	500m-2000m	512Mi-2Gi
Heavy (ML inference)	2000m-4000m	2Gi-8Gi

Why Resource Limits Matter:

Prevent single sandbox from consuming all host resources
Enable fair resource sharing
Predictable performance
Protection against resource exhaustion attacks

Storage Security

Host Path Restrictions

Limit bind mount access to trusted paths:

[storage]
allowed_host_paths = ["/data/opensandbox", "/tmp/sandbox"]

Security Implications:

Empty list: All paths allowed (dangerous in production)
Non-empty list: Only prefixes in list are allowed
Prevents access to sensitive host directories

Dangerous Paths to Block:

/etc: System configuration
/root: Root user home
/var/run/docker.sock: Docker daemon socket
/proc, /sys: Kernel interfaces
User home directories

Read-Only Filesystems

Mount root filesystem as read-only when possible:

{
  "rootfs": {
    "readonly": true
  },
  "tmpfs": ["/tmp", "/var/tmp"]  // Writable tmpfs
}

Benefits:

Prevents malware persistence
Protects against container modification
Forces use of volumes for state

Image Security

Use Trusted Images

Only allow vetted container images:

# Not yet implemented - planned feature
[image_policy]
allowed_registries = [
  "docker.io/opensandbox",
  "your-private-registry.example.com"
]
block_latest_tag = true
require_signature = true

Manual Image Vetting:

Use official images from trusted registries
Pin specific image tags (avoid latest)
Scan images for vulnerabilities
Review Dockerfiles before use
Use minimal base images (alpine, distroless)

Image Scanning

Scan images for vulnerabilities:

# Using Trivy
trivy image python:3.11-slim

# Using Grype
grype python:3.11-slim

# Using Docker Scout
docker scout cves python:3.11-slim

Private Registry Authentication

Configure Docker credential helpers:

# Configure Docker to use credential helper
docker login your-registry.example.com

# Or use environment variables
export DOCKER_CONFIG=/path/to/docker/config.json

Kubernetes Security

Pod Security Standards

Apply Pod Security Standards to the opensandbox namespace:

apiVersion: v1
kind: Namespace
metadata:
  name: opensandbox
  labels:
    pod-security.kubernetes.io/enforce: restricted
    pod-security.kubernetes.io/audit: restricted
    pod-security.kubernetes.io/warn: restricted

Network Policies

Restrict pod network access:

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: sandbox-isolation
  namespace: opensandbox
spec:
  podSelector:
    matchLabels:
      app: opensandbox-sandbox
  policyTypes:
  - Ingress
  - Egress
  egress:
  - to:
    - namespaceSelector:
        matchLabels:
          name: kube-system
    ports:
    - protocol: TCP
      port: 53  # DNS only

RBAC Configuration

Minimize service account permissions:

apiVersion: v1
kind: ServiceAccount
metadata:
  name: opensandbox-controller
  namespace: opensandbox
---
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  name: opensandbox-controller
  namespace: opensandbox
rules:
- apiGroups: ["sandbox.opensandbox.io"]
  resources: ["batchsandboxes", "pools"]
  verbs: ["get", "list", "watch", "create", "update", "patch", "delete"]
- apiGroups: [""]
  resources: ["pods"]
  verbs: ["get", "list", "watch", "create", "delete"]
---
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: opensandbox-controller
  namespace: opensandbox
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: Role
  name: opensandbox-controller
subjects:
- kind: ServiceAccount
  name: opensandbox-controller
  namespace: opensandbox

Monitoring and Auditing

Enable Logging

Collect logs for security monitoring:

[server]
log_level = "INFO"  # or "DEBUG" for detailed logs

Log Events to Monitor:

Authentication failures
Sandbox creation/deletion
Resource quota violations
Network policy denials
Container exits and crashes

Centralized Logging

Forward logs to a SIEM or log aggregator:

# Using Docker logging driver
docker run -d \
  --log-driver=syslog \
  --log-opt syslog-address=tcp://logs.example.com:514 \
  opensandbox-server

# Using Kubernetes Fluentd/Fluent Bit
# Deploy as DaemonSet to collect pod logs

Audit Trail

Track all API operations:

# Example middleware for audit logging
import logging
from datetime import datetime

logger = logging.getLogger("audit")

@app.middleware("http")
async def audit_log(request: Request, call_next):
    start = datetime.utcnow()
    response = await call_next(request)
    duration = (datetime.utcnow() - start).total_seconds()
    
    logger.info({
        "timestamp": start.isoformat(),
        "method": request.method,
        "path": request.url.path,
        "client": request.client.host,
        "status": response.status_code,
        "duration": duration
    })
    
    return response

Incident Response

Sandbox Compromise Detection

Monitor for indicators of compromise:

Unexpected network connections
High CPU/memory usage
Failed authentication attempts
Unusual process executions
Container escapes

Emergency Procedures

Immediate Actions:

Delete compromised sandboxes:

curl -X DELETE \
  -H "OPEN-SANDBOX-API-KEY: your-api-key" \
  http://localhost:8080/v1/sandboxes/{sandbox_id}

Rotate API keys:

[server]
api_key = "new-rotated-api-key"

Review logs for attack patterns
Update security policies
Patch vulnerabilities

​Authentication and Access Control

​API Key Authentication

​Client Request Authentication

​Container Security Hardening

​Drop Dangerous Capabilities

​Block Privilege Escalation

​Process Limits

​Seccomp Profiles

​AppArmor Profiles

​Network Security

​Network Isolation

​Network Policy Enforcement

​TLS/HTTPS

​Resource Limits

​Storage Security

​Host Path Restrictions

​Read-Only Filesystems

​Image Security

​Use Trusted Images

​Image Scanning

​Private Registry Authentication

​Kubernetes Security

​Pod Security Standards

​Network Policies

​RBAC Configuration

​Monitoring and Auditing

​Enable Logging

​Centralized Logging

​Audit Trail

​Incident Response

​Sandbox Compromise Detection

​Emergency Procedures

​Production Security Checklist

​Further Reading

​Next Steps