Initial commit

files/captive-portal.py

@@ -0,0 +1,87 @@
+import re
+
+from flask import Flask, abort, request, redirect
+import nftables
+from pyroute2 import IPDB
+
+app = Flask(__name__)
+app.config.from_pyfile('/etc/captive-portal.conf')
+
+ipdb = IPDB()
+nft = nftables.Nftables()
+
+NFT_TIMEOUT_RE = re.compile(r'((?P<days>[0-9]+)d)?((?P<hours>[0-9]+)h)?((?P<minutes>[0-9]+)m)?((?P<seconds>[0-9]+)s)?((?P<milliseconds>[0-9]+)ms)?')
+def parse_timeout(val):
+    m = NFT_TIMEOUT_RE.fullmatch(val)
+    if not m:
+        return 0
+    groups = m.groupdict()
+    result = int(groups['days'] or '0') * 24*60*60*1000
+    result += int(groups['hours'] or '0') * 60*60*1000
+    result += int(groups['minutes'] or '0') * 60*1000
+    result += int(groups['seconds'] or '0') * 1000
+    result += int(groups['milliseconds'] or '0')
+    return result
+
+NFT_SET_ELEM_EXPIRES_RE = re.compile(r'elements = \{ (?P<val>[^ ]+) expires (?P<expires>[^ ]+) \}')
+def get_allowed_mac_timeout(mac_addr):
+    # As of libnftables 1.0.6 JSON output mode does not support get element
+    rc, output, error = nft.cmd(f'get element inet captive_portal allowed_macs {{ {mac_addr} }}')
+    if rc != 0:
+        return None
+    m = NFT_SET_ELEM_EXPIRES_RE.search(output)
+    if not m:
+        return None
+    _mac_addr, expires = m.groups()
+    if _mac_addr != mac_addr:
+        return None
+    return parse_timeout(expires)
+
+def add_allowed_mac(mac_addr):
+    # "add" does not reset the timeout if mac_addr is already in set
+    # "delete" fails if mac_addr is not in set
+    # We first make sure mac_addr is in set, then delete, then add so timeout is reset
+    rc, output, error = nft.cmd(f'''
+        add element inet captive_portal allowed_macs {{ {mac_addr} }}
+        delete element inet captive_portal allowed_macs {{ {mac_addr} }}
+        add element inet captive_portal allowed_macs {{ {mac_addr} }}
+    ''')
+    return rc == 0
+
+def del_allowed_mac(mac_addr):
+    rc, output, error = nft.cmd(f'''
+        add element inet captive_portal allowed_macs {{ {mac_addr} }}
+        delete element inet captive_portal allowed_macs {{ {mac_addr} }}
+    ''')
+    return rc == 0
+
+@app.before_request
+def set_remote_mac_addr():
+    inet_addr = request.environ.get('HTTP_X_FORWARDED_FOR') or request.remote_addr
+    request.remote_mac_addr = ipdb.interfaces[app.config['INTERFACE']].neighbours[inet_addr]['lladdr']
+
+@app.route('/api/status')
+def status():
+    result = {
+        "captive": True,
+        "user-portal-url": app.config['USER_PORTAL_URL'],
+    }
+    mac_timeout = get_allowed_mac_timeout(request.remote_mac_addr)
+    if mac_timeout:
+        result['captive'] = False
+        result['venue-info-url'] = app.config['VENUE_INFO_URL']
+        result['seconds-remaining'] = mac_timeout // 1000
+        result['can-extend-session'] = True
+    return result
+
+@app.route('/api/login', methods=['POST'])
+def login():
+    if add_allowed_mac(request.remote_mac_addr):
+        return redirect(app.config['VENUE_INFO_URL'])
+    return redirect(app.config['USER_PORTAL_URL'])
+
+@app.route('/api/logout', methods=['POST'])
+def logout():
+    del_allowed_mac(request.remote_mac_addr)
+    return redirect(app.config['USER_PORTAL_URL'])
+

files/captive-portal.service

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+After=network-online.target
+Wants=network-online.target
+
+[Service]
+Type=notify
+
+User=captive-portal
+Group=captive-portal
+AmbientCapabilities=CAP_NET_ADMIN
+
+ExecStartPre=!mkdir -p /run/captive-portal
+ExecStartPre=!chown captive-portal:www-data /run/captive-portal
+ExecStartPre=!chmod 0750 /run/captive-portal
+WorkingDirectory=/usr/local/lib/captive-portal/
+ExecStart=/bin/gunicorn --workers 2 --bind unix:/run/captive-portal/socket captive_portal:app

handlers/main.yml

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+- name: reload nftables
+  ansible.builtin.systemd_service:
+    name: nftables
+    enabled: True
+    state: reloaded
+
+- name: restart captive-portal
+  ansible.builtin.systemd_service:
+    name: captive-portal
+    state: restarted
+    enabled: true
+    daemon_reload: true

tasks/main.yml

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+- name: install dependencies
+  ansible.builtin.apt:
+    pkg:
+    - python3-pyroute2
+    - python3-nftables
+    - python3-flask
+    - gunicorn
+
+- name: copy nftables config
+  ansible.builtin.template:
+    src: captive-portal-rules.nft.j2
+    dest: /etc/nftables.d/captive-portal-rules.nft
+  notify: reload nftables
+
+- name: create captive-portal group
+  ansible.builtin.group:
+    name: captive-portal
+    system: true
+
+- name: create directory /usr/local/lib/captive-portal
+  ansible.builtin.file:
+    path: /usr/local/lib/captive-portal
+    state: directory
+
+- name: create captive-portal user
+  ansible.builtin.user:
+    name: captive-portal
+    group: captive-portal
+    home: /usr/local/lib/captive-portal
+    create_home: false
+    system: true
+
+- name: copy captive-portal config
+  ansible.builtin.template:
+    src: captive-portal.conf.j2
+    dest: /etc/captive-portal.conf
+    group: captive-portal
+    mode: '0640'
+  notify: restart captive-portal
+
+- name: copy captive-portal script
+  ansible.builtin.copy:
+    src: captive-portal.py
+    dest: /usr/local/lib/captive-portal/captive_portal.py
+  notify: restart captive-portal
+
+- name: copy captive-portal service
+  ansible.builtin.copy:
+    src: captive-portal.service
+    dest: /etc/systemd/system/captive-portal.service
+  notify: restart captive-portal
+
+- name: add cronjob to persist captive-portal allowed_macs set
+  ansible.builtin.cron:
+    name: persist captive-portal allowed_macs set
+    # captive-portal-sets.nft is loaded after captive-portal-rules.nft so it can overwrite the set
+    job: '/sbin/nft list set inet captive_portal allowed_macs > /etc/nftables.d/.captive-portal-sets.nft.tmp && mv /etc/nftables.d/.captive-portal-sets.nft.tmp /etc/nftables.d/captive-portal-sets.nft'

templates/captive-portal-rules.nft.j2

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+define captive_portal_interface = {{ captive_portal.interface }}
+define captive_portal_http_redirect_port = {{ captive_portal.http_redirect_port }}
+
+table inet captive_portal {
+        set allowed_macs {
+                type ether_addr;
+                timeout {{ captive_portal.timeout }};
+        }
+
+        chain forward {
+                type filter hook forward priority filter; policy accept;
+                iifname != $captive_portal_interface return
+                ether saddr @allowed_macs return
+
+                reject with icmpx type no-route
+        }
+
+        chain dstnat {
+                type nat hook prerouting priority dstnat; policy accept;
+                iifname != $captive_portal_interface return
+                ether saddr @allowed_macs return
+
+                tcp dport 80 redirect to :$captive_portal_http_redirect_port
+        }
+}

templates/captive-portal.conf.j2

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+
+INTERFACE = {{ captive_portal.interface|tojson }}
+USER_PORTAL_URL = {{ captive_portal.user_portal_url|tojson }}
+VENUE_INFO_URL = {{ captive_portal.venue_info_url|tojson }}