Control network access

A sandbox has no network device of its own. Its traffic goes through a proxy in kumobad, which enforces the sandbox's policy and logs every connection.

Mode	The sandbox can reach
open (default)	The public internet
allowlist	Only the listed hosts, on ports 80 and 443. *.example.com matches subdomains
blocked	Nothing

Private, link-local and cloud metadata addresses are never reachable, whatever the mode.

Set the policy when you create a sandbox

kumoba create --image default --network.mode allowlist --network.hosts pypi.org,files.pythonhosted.org -q

kumoba run takes the same options.

Change the policy of a sandbox

Stop the sandbox first. A running sandbox keeps the policy it booted with.

kumoba stop "$id"
kumoba update "$id" --network.mode blocked
kumoba start "$id"

A sandbox with secrets can't switch to blocked, because secrets are injected by the HTTPS proxy. Remove its secrets first with kumoba set-secrets "$id" secrets='[]'.

See what a sandbox connected to

kumoba access-log

Each entry has the sandbox, host, port, whether the connection was allowed or denied, and the bytes in each direction. By default you get the last two hours; --since-ms and --until-ms choose another window.

Reach an intranet or go through a corporate proxy

These are daemon settings, set in kumobad's environment:

• KUMOBAD_ALLOW_PRIVATE_HOSTS=gitlab.corp.example,10.20.0.0/16 lets sandboxes reach those private hosts and ranges. Loopback, link-local and the host's own addresses stay blocked.
• KUMOBAD_UPSTREAM_PROXY=http://proxy.corp.example:3128 sends outbound traffic through your proxy, except hosts in KUMOBAD_NO_PROXY.

See Configuration for every setting.