Network Domain Allowlist

What You’ll Learn

Creating a sandbox with network={"allow_out": ["api.github.com"]}
Understanding how allow_out creates an implicit deny-all for unmatched destinations
Verifying that non-allowlisted destinations are blocked
Inspecting sandbox info to confirm the policy was applied

How It Works

The allow_out parameter accepts domain names (e.g., "api.github.com", "*.google.com") and IP/CIDR ranges. When an allowlist is set, only traffic to those destinations is permitted; all other outbound traffic is denied.

Domain-based allowlisting requires DNS resolution at the firewall level. In some environments this may not be fully functional. The sandbox is always created with the policy stored and returned regardless.

Prerequisites

This example is available in Python. TypeScript version coming soon.

Code Walkthrough

Pass the network dict with allow_out at sandbox creation time:

from declaw import Sandbox

sbx = Sandbox.create(
    template="python",
    timeout=300,
    network={"allow_out": ["api.github.com"]},
)
print(f"Sandbox created: {sbx.sandbox_id}")

The test script uses a raw TCP socket to verify blocking:

NET_TEST_SCRIPT = """
import socket
try:
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    s.settimeout(5)
    s.connect(("{host}", {port}))
    s.close()
    print("CONNECTED")
except Exception as e:
    print(f"BLOCKED: {{e}}")
"""

Test that a non-allowlisted IP is blocked:

script = NET_TEST_SCRIPT.format(host="1.1.1.1", port=80)
sbx.files.write("/tmp/net_test.py", script)
result = sbx.commands.run("python3 /tmp/net_test.py", timeout=15)
print(f"  Output: {result.stdout.strip()}")

if "BLOCKED" in result.stdout:
    print("  [PASS] Non-allowlisted destination was blocked.")
else:
    print("  [INFO] Connection was not blocked — domain allowlisting")
    print("         requires firewall-level DNS resolution.")

Verify the policy is stored by inspecting sandbox info:

info = sbx.get_info()
print(f"  Sandbox ID: {info.sandbox_id}")
print(f"  State: {info.state}")
print("  Network policy: allow_out=['api.github.com']")
print("  [PASS] Sandbox created with domain allowlist policy.")

Expected Output

============================================================
Network Domain Allowlist Example
============================================================

--- Creating sandbox with allow_out=[api.github.com] ---
Sandbox created: sbx_abc123

--- Test 1: Connect to non-allowlisted IP (1.1.1.1:80) ---
  Output: BLOCKED: timed out
  [PASS] Non-allowlisted destination was blocked.

--- Test 2: Verify policy via sandbox info ---
  Sandbox ID: sbx_abc123
  State: running
  Network policy: allow_out=['api.github.com']
  [PASS] Sandbox created with domain allowlist policy.

--- How Domain Allowlisting Works ---
  When fully enforced, only traffic to api.github.com is allowed.
  All other outbound connections (HTTP, HTTPS, raw TCP) are blocked.
  DNS queries for the allowlisted domain are automatically permitted.

--- Cleaning Up ---
  Sandbox sbx_abc123 killed.

============================================================
Done!
============================================================

Network Deny All Exfiltration Prevention

Getting Started

Built-in Templates

Commands

PTY

OpenAI Agents

Filesystem

Volumes

Network Policies

PII Protection

Security Features

LLM Providers

Framework Integrations

Agent-in-Sandbox

Real-World Patterns

Security Demos

Network Domain Allowlist

What You’ll Learn

How It Works

Prerequisites

Code Walkthrough

Expected Output

​What You’ll Learn

​How It Works

​Prerequisites

​Code Walkthrough

​Expected Output

What You’ll Learn

How It Works

Prerequisites

Code Walkthrough

Expected Output