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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

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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.

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Prerequisites

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

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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.")

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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.

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Done!
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