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.

Database

Application data is stored in a number of JSON files in the home directory of the user the application runs as. The db module defines utility functions to ensure consistency when manipulating data:

• lock(name) and unlock(name) acquire or release the lock for a given file or all files with no argument;
• read(name) and write(name, data) retrieve or store a dictionary in the given file, which should be locked;
• load(name) and save(name, data) do the same but lock the file first.

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. To read and combine data from both files, the ipsets.read utility function should be used. Combined data may then be modified and written back to ipsets.json, as with all other files.

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"]
}