Always combine IP set data with static network definitions from NetBox

Before we relied on the combined data being present in ipsets.json
when generating a new config, but ipsets.json is only updated through
the form at /ipsets. So submitting any other form after changing
NetBox definitions might crash when trying to find an entry from
networks.json in ipsets.json.

Now we introduce a helper functon to always read both files and
combine the prefixes fron networks.json with ipsets.json. This way it
is not necessary to save a new ipsets.json before other changes.

Also don’t crash when enumerating networks for each VPN group.

README.md

@@ -8,9 +8,17 @@ The firewall consists of two servers (or “bricks”) in active–backup config
 
 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` and added to static definitions in `networks.json` when generating firewall configuration.
+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
 

web/ipsets.py

@@ -8,6 +8,19 @@ from . import system
 
 blueprint = flask.Blueprint('ipsets', __name__)
 
+# return combined data for all IP sets, stored in two files:
+#   - networks.json: IP prefixes for networks defined in NetBox
+#   - ipsets.json: custom IP prefixes defined with this app, and NAT and other settings for all sets
+# database should be locked when calling this function
+def read():
+    # first read in static data
+    all_ipsets = db.read('networks')
+    # then add the custom definitions, not overriding any IP prefixes from NetBox
+    for name, data in db.read('ipsets').items():
+        # set “custom” flag for this set if it is not present in networks.json
+        all_ipsets[name] = data | all_ipsets.get(name, {'custom': True})
+    return all_ipsets
+
 @blueprint.route('/', methods=('GET', 'POST'))
 @flask_login.login_required
 def index():
@@ -17,25 +30,19 @@ def index():
     with db.locked():
         if flask.request.method == 'POST':
             # read network data from NetBox, merge in custom definitions and dump the lot
-            ipsets = db.read('networks')
+            sets = db.read('networks')
             formdata = zip(*(flask.request.form.getlist(e) for e in ('name', 'ip', 'ip6', 'nat', 'vpn')))
             for name, ip, ip6, nat, vpn in formdata:
                 # drop sets with empty names
                 if not name:
                     continue
                 # assign IPs for custom networks only
-                if name not in ipsets:
+                if name not in sets:
-                    ipsets[name] = { 'ip': ip.split(), 'ip6': ip6.split() }
+                    sets[name] = { 'ip': ip.split(), 'ip6': ip6.split() }
                 # assign NAT and VPN for all networks
-                ipsets[name] |= { 'nat': nat, 'vpn': vpn }
+                sets[name] |= { 'nat': nat, 'vpn': vpn }
-            db.write('ipsets', ipsets)
+            db.write('ipsets', sets)
             system.run(system.save_config)
             return flask.redirect(flask.url_for('ipsets.index'))
 
-        # read network data from NetBox and merge in custom definitions
+        return flask.render_template('ipsets/index.html', ipsets=read())
-        ipsets = db.read('networks')
-        for name, data in db.read('ipsets').items():
-            # keep static IPs if there are any, otherwise set custom flag for this set
-            ipsets[name] = data | ipsets.get(name, {'custom': True})
-
-        return flask.render_template('ipsets/index.html', ipsets=ipsets)

web/rules.py

@@ -2,6 +2,7 @@ import flask
 import flask_login
 
 from . import db
+from . import ipsets
 from . import system
 
 blueprint = flask.Blueprint('rules', __name__)
@@ -45,8 +46,7 @@ def edit(index):
             system.run(system.save_config)
 
         with db.locked():
-            ipsets = db.read('ipsets')
+            return flask.render_template('rules/edit.html', index=index, rule=db.load('rules')[index], ipsets=ipsets.read())
-        return flask.render_template('rules/edit.html', index=index, rule=db.load('rules')[index], ipsets=ipsets)
     except IndexError as e:
         return flask.Response(f'invalid rule: {index}', status=400, mimetype='text/plain')
 

web/system.py

@@ -18,6 +18,7 @@ import flask.cli
 import ldap3
 
 from . import db
+from . import ipsets
 
 def init_app(app):
     app.cli.add_command(generate)
@@ -49,7 +50,6 @@ def save_config():
         # Just load required settings here but keep the database unlocked
         # while we load group memberships from LDAP.
         with db.locked():
-            ipsets = db.read('ipsets')
             settings = db.read('settings')
 
         # Build LDAP query for users and groups.
@@ -72,15 +72,15 @@ def save_config():
         # Now read the settings again while keeping the database locked until
         # config files are generated, and increment version before unlocking.
         with db.locked():
-            ipsets = db.read('ipsets')
+            sets = ipsets.read()
             wireguard = db.read('wireguard')
             settings = db.read('settings')
             version = settings['version'] = int(settings.get('version') or '0') + 1
 
             # Find networks accessible to VPN users for each AD group.
-            vpn_groups = {e['vpn'] for e in ipsets.values() if e.get('vpn')}
+            vpn_groups = {e['vpn'] for e in sets.values() if e.get('vpn')}
             group_networks = {
-                group: [name for name, data in ipsets.items() if data['vpn'] == group] for group in vpn_groups
+                group: [name for name, data in sets.items() if data.get('vpn') == group] for group in vpn_groups
             }
 
             # Add VPN addresses to IP sets.
@@ -92,9 +92,9 @@ def save_config():
                 for group in user_groups.get(key.get('user', ''), ()):
                     key_networks |= set(group_networks.get(group, ()))
                 for network in key_networks:
-                    ipsets[network]['ip'].append(f'{ip}/32')
+                    sets[network]['ip'].append(f'{ip}/32')
                     if ip6 := key.get('ip6'):
-                        ipsets[network]['ip6'].append(ip6)
+                        sets[network]['ip6'].append(ip6)
 
             # Create config files.
             output = pathlib.Path.home() / 'config' / f'{version}'
@@ -113,7 +113,7 @@ def save_config():
                 def make_set(ips):
                     # return "elements = { ip1, ip2, … }", prefixed with "# " if no ips
                     return f'{"" if ips else "# "}elements = {{ {", ".join(ips)} }}'
-                for name, data in ipsets.items():
+                for name, data in sets.items():
                     f.write(nft_set.format(name=name, ips=make_set(data.get('ip', ()))))
                     f.write(nft_set6.format(name=name, ips=make_set(data.get('ip6', ()))))
                     f.write('\n')
@@ -132,14 +132,14 @@ def save_config():
             # Print dynamic NAT rules.
             with open(output / 'etc/nftables.d/nat.nft', 'w', encoding='utf-8') as f:
                 nft_nat = 'iif @inside oif @outside ip saddr @{name} snat to {nat}\n'
-                for name, data in ipsets.items():
+                for name, data in sets.items():
                     if nat := data.get('nat'):
                         f.write(nft_nat.format(name=name, nat=nat))
 
             # Print forwarding rules.
             with open(output / 'etc/nftables.d/forward.nft', 'w', encoding='utf-8') as f:
                 # Forwarding rules for VPN users.
-                if vpn_networks := sorted(name for name, data in ipsets.items() if data.get('vpn')):
+                if vpn_networks := sorted(name for name, data in sets.items() if data.get('vpn')):
                     nft_forward = 'iif @inside oif @inside ip saddr @{name} ip daddr @{name} accept\n'
                     nft_forward6 = 'iif @inside oif @inside ip6 saddr @{name}/6 ip6 daddr @{name}/6 accept\n'
                     f.write('# forward from the VPN interface to physical networks and back\n')

web/vpn.py

@@ -8,6 +8,7 @@ import flask
 import flask_login
 
 from . import db
+from . import ipsets
 from . import system
 
 blueprint = flask.Blueprint('vpn', __name__)
@@ -25,8 +26,7 @@ def custom():
         return flask.Response('forbidden', status=403, mimetype='text/plain')
     with db.locked():
         keys = {ip: data for ip, data in db.read('wireguard').items() if data.get('networks') and not data.get('user')}
-        ipsets = db.read('networks') | db.read('ipsets')
+        return flask.render_template('vpn/custom.html', keys=keys, ipsets=ipsets.read().keys())
-        return flask.render_template('vpn/custom.html', keys=keys, ipsets=ipsets.keys())
 
 @blueprint.route('/list')
 @flask_login.login_required