FRIwall

Web application for managing the main firewall at FRI.

Operation

The firewall consists of two servers (or “bricks”) in active–backup configuration, using weighted BGP routes for failover. Traffic filtering and VPN are done with nftables and WireGuard. Both are configured exactly the same on both servers. The settings are managed with this application.

On each configuration change, a tarball of relevant files in /etc is generated and pushed via SSH to both nodes. This happens for instance each time an IP set or a forwarding rule is modified, or a VPN key is added or removed. Firewall nodes and the current configuration version for each are stored in nodes.json.

IP sets

Names and IP prefixes for physical networks are configured in NetBox and stored in networks.json, which is never modified by the application. Custom IP sets used for forwarding rules may be defined at /ipsets, as well as NAT addresse and VPN access for all networks. These settings are stored in ipsets.json and added to static definitions in networks.json when generating firewall configuration.

Rules

Forwarding rules are configured at /rules and toggled at /rules/manage. Enabled rules are included directly in the nftables configuration. For each rule, one or more manager groups can be set; users in these AD groups may toggle the rule without admin access. This is used for instance to allow teachers to disable Internet access in classrooms.

VPN

WireGuard is used for remote access. Domain users can self‐register new keys at /vpn. The key database wireguard.json is a dictionary of entries like

"10.0.0.26": {
  "key": "ABC…XYZ=",
  "ip6": "aaaa:bbbb:cccc:dddd:1a::/80",
  "time": 1682166836.88937,
  "name": "machine1",
  "user": "user@domain"
}

IP addresses for new keys are assigned automatically from the subnets defined in wg_net and wg_net6 settings. When generating firewall configuration, each IP is placed in the nftables sets based on its user’s group and settings in ipsets.json.

Custom keys

Administrators can define custom keys with access to specified networks at /vpn/custom. These keys are used to connect machines into secure networks where users are not allowed to attach arbitrary devices themselves.

Custom keys are stored in the same database, but with a networks entry in place of user, for instance

"10.0.0.27": {
  "key": "FOO…BAR=",
  "ip6": "aaaa:bbbb:cccc:dddd:1b::/80",
  "time": 1682166836.88937,
  "name": "machine2",
  "networks": ["net1", "net2"]
}