feature: Added an internally only exposed status web service.

ADR.md

@@ -26,3 +26,52 @@ because `vpn-router-docker` is already active. A published
 port is reachable from the external interface only when it is in `exposed_ports`. Other rules
 in `DOCKER-USER` are not touched, because the package owns only its own chain. Restarting Docker
 restores the rules. The rules cover IPv4 only.
+
+## ADR-2: A status web service of the standard library, bound to the internal address
+
+Status: Accepted
+
+Context: The router has no way to see its state without a shell. A check from the protected
+network, by a person or by a monitor, needs a page or an endpoint. The router is an
+internet-facing host, so what the service shows and where it listens matter.
+
+Decision: The `vpn-router-web` unit runs one Python script that uses only the standard library, in
+the way of a small test server. It binds to the address of the internal interface and to
+`web.port`, on by default at 8080. `/` is for people, in plain text for `curl` and `wget` and as
+a Tailwind CSS page for a browser, and `/status` is the same status as JSON. It shows the
+state of the services, the package version and the state of the site-to-site, road-warrior and
+WireGuard features, and nothing from the configuration. `vpn-router-setup` resolves the
+interface address, writes it with the port and the features to `/run/vpn-router/web.json`,
+opens the port on the internal interface in UFW and restarts the service, so the service does
+not need the package's configuration code, which needs Jinja2.
+
+Consequences: Nothing outside the internal network can reach it, since it listens on the internal
+address only and the firewall opens the port on the internal interface only. It has no
+authentication, which is acceptable because it is read only and shows no configuration. It runs
+as root, because `swanctl` and `wg` need it, with `NoNewPrivileges`, `ProtectSystem=strict`,
+`ProtectHome` and `PrivateTmp`. The Tailwind style comes from a CDN, so a browser on a network
+without internet shows the unstyled page, and `curl` is unaffected. A change of the internal
+address is picked up at the next run of `vpn-router-setup`.
+
+## ADR-3: /config is authenticated with a short-lived JWT signed with a shared secret
+
+Status: Accepted
+
+Context: A client such as manage-ui needs the configuration and the resolved state of the
+router, which `/` and `/status` must not show. The service has only the standard library, listens
+on plain HTTP on the internal network, and its configuration file is readable by root only.
+
+Decision: `/config` needs a JWT in an `Authorization: Bearer` header. The service verifies HS256
+tokens with `hmac` and `hashlib`, with the secret `web.jwt_secret`, and accepts no other
+algorithm, because verifying RS256 or ES256 needs a library outside the standard library. The
+token must carry `exp`, not more than ten minutes ahead, so that the client makes a fresh token for
+each use and a leaked one expires. Without a secret the page is not served. The secrets in the
+configuration shown are masked by name (`psk`, and options with `secret`, `password`, `token` or a
+`_key` ending in the name).
+
+Consequences: The client and the router share one secret, and whoever holds it can make tokens,
+so it is long and random; it is checked to have at least 32 characters. The secret is in the
+configuration file and in `/run/vpn-router/web.json`, both readable by root only. The token and
+the answer cross the network unencrypted, so the page is for a trusted internal network; HTTPS
+would need a certificate that the package does not have. The masking is by option name, so a new
+secret option needs a name that matches.

README.md

@@ -115,6 +115,9 @@ must have the type shown below; an unknown section or setting is an error.
 | `wireguard` | `listen_port` | integer | `51820` | UDP port |
 | `docker` | `mode` | string | `auto` | `auto` secures Docker when its service is installed, `on` requires it, `off` removes the rules |
 | `docker` | `exposed_ports` | list | | TCP ports and port ranges (`8000:8100`) reachable from the external interface; at most 15, a range counting as two |
+| `web` | `enabled` | boolean | `true` | The status web service on the internal address |
+| `web` | `port` | integer | `8080` | TCP port of the status web service |
+| `web` | `jwt_secret` | string | | Secret, at least 32 characters, that signs the tokens for `/config`; without it `/config` is not served |
 
 A minimal site-to-site configuration in `auto` mode:
 
@@ -321,6 +324,74 @@ EXTRA_LOCAL_TS = '192.0.2.53/32'
 Set `general.platform` to `example` and restart the service. The debconf question offers only the
 modules shipped with the package; the configuration file accepts any module installed.
 
+## Status web service
+
+The `vpn-router-web` service shows the state of the router on its internal address and
+`web.port` (8080 by default). It uses only the Python standard library, serves HTTP without
+authentication, and shows no configuration: no key, identity, address or subnet.
+
+| Page | Content |
+| --- | --- |
+| `/` | The status for people: plain text for `curl` and `wget`, a page styled with Tailwind CSS for a browser (the style sheet is loaded from a CDN, so the browser needs internet access; the text is readable without it) |
+| `/status` | The same status as JSON |
+| `/config` | The configuration with its secrets masked, and what the router resolved and runs, as JSON; needs a token |
+
+The status holds the state of `vpn-router-setup`, of `strongswan` when site-to-site or road-warrior
+access is configured, and of `wg-quick@wg0` when WireGuard is; the package version; whether
+Docker is installed, and when it is, the state of `docker.service` and of `vpn-router-docker`
+(the Docker rules), which do not change `status`; whether the
+site-to-site tunnel is established; the number of connected road-warrior (IPsec P2S) clients; and
+the WireGuard peers with the age of their last handshake and their traffic. `status` is `ok` when
+all these services are active, and `degraded` otherwise.
+
+```bash
+curl http://10.0.0.4:8080/
+curl http://10.0.0.4:8080/status
+```
+
+### The /config page
+
+`/config` shows what `/` and `/status` leave out, for a client such as manage-ui:
+
+| Key | Content |
+| --- | --- |
+| `configuration` | `vpn-router.json` with the defaults applied and the secrets masked (`psk`, `jwt_secret`, and any option named like a password, token or key) |
+| `network` | The external and internal interface, their addresses, the internal gateway, the local and remote IKE identities and subnets, and the IPv4 routes |
+| `ipsec` | The output of `swanctl --list-conns` and `swanctl --list-sas`, as lists of lines |
+| `wireguard` | The public key and port of `wg0`, and each peer's public key, endpoint, allowed IPs, handshake age and traffic; no private or preshared key |
+| `docker` | `docker.exposed_ports` and the rules of the `VPN-ROUTER-DOCKER` chain |
+
+The page needs a JWT in an `Authorization: Bearer` header, signed with HS256 by `web.jwt_secret`.
+The token must have an `exp` claim, not more than ten minutes from now (a minute of clock
+difference is allowed); `nbf` is checked when present. Other algorithms are refused, with 401 and
+`WWW-Authenticate: Bearer`. While `web.jwt_secret` is not set the page is not served (404). The
+token and the page travel over plain HTTP on the internal network, and the token can be used
+until it expires, so keep the lifetime short. A client makes a token from the secret with only
+HMAC-SHA256; with Python:
+
+```python
+import base64, hashlib, hmac, json, time
+
+def b64(data):
+    return base64.urlsafe_b64encode(data).rstrip(b'=').decode()
+
+secret = 'the web.jwt_secret value'
+head = b64(json.dumps({'alg': 'HS256', 'typ': 'JWT'}).encode())
+body = b64(json.dumps({'exp': int(time.time()) + 300}).encode())
+sign = b64(hmac.new(secret.encode(), f'{head}.{body}'.encode(), hashlib.sha256).digest())
+print(f'{head}.{body}.{sign}')
+```
+
+```bash
+curl -H "Authorization: Bearer $TOKEN" http://10.0.0.4:8080/config
+```
+
+`vpn-router-setup` opens `web.port` on the internal interface in the firewall, writes the address,
+the port, the secret and the facts for `/config` to `/run/vpn-router/web.json` (readable by root
+only) and restarts the service, so a changed `web` section
+applies with `systemctl restart vpn-router-setup`. The service ends without an error when
+`web.enabled` is `false`, and keeps trying to start until the router has an internal address.
+
 ## Removal
 
 `apt-get remove` stops `vpn-router-docker`, which removes the Docker rules. It terminates the

debian-package/debian/changelog

@@ -1,3 +1,24 @@
+vpn-router (0.4.0-1) unstable; urgency=medium
+
+  * Add the vpn-router-web service, a small status web service that uses only
+    the Python standard library. It listens on the internal address and on
+    web.port, 8080 by default. / shows the state of the router for people,
+    as plain text for curl and wget and as a Tailwind CSS page for a
+    browser, and /status shows the same as JSON: the state of the services,
+    the package version, whether Docker is installed, and the state of
+    site-to-site, road-warrior and WireGuard, with no configuration data.
+  * Add the web configuration section. web.enabled (true by default) and
+    web.port. vpn-router-setup opens the port on the internal interface in
+    UFW and restarts the service.
+  * Add /config to the status web service, for a client such as manage-ui. It
+    shows the configuration with its secrets masked, the interfaces,
+    addresses, identities and routes the router resolved, the IPsec
+    connections and SAs, the WireGuard peers (no keys) and the Docker rules.
+    It needs a JWT signed with HS256 by web.jwt_secret, with an exp claim
+    within ten minutes, and is not served while web.jwt_secret is not set.
+
+ -- Slawomir Koszewski <slawek@koszewscy.waw.pl>  Fri, 23 Oct 2026 19:00:00 +0200
+
 vpn-router (0.3.2-1) unstable; urgency=medium
 
   * Accept an IPv4 or IPv6 address as remote.id and as wan.local_fqdn. The

debian-package/debian/install

@@ -4,6 +4,7 @@ src/usr/lib/vpn-router/simple-ca                      usr/lib/vpn-router/
 src/usr/lib/vpn-router/configure                      usr/lib/vpn-router/
 src/usr/lib/vpn-router/docker-rules                   usr/lib/vpn-router/
 src/usr/lib/vpn-router/setup                          usr/lib/vpn-router/
+src/usr/lib/vpn-router/web                            usr/lib/vpn-router/
 src/usr/lib/vpn-router/generate-config                usr/lib/vpn-router/
 src/usr/lib/vpn-router/vpnrouter_platforms/*.py       usr/lib/vpn-router/vpnrouter_platforms/
 src/usr/share/vpn-router/templates/*                  usr/share/vpn-router/templates/

debian-package/debian/rules

@@ -5,3 +5,4 @@
 override_dh_installsystemd:
 	dh_installsystemd --name=vpn-router-setup
 	dh_installsystemd --name=vpn-router-docker
+	dh_installsystemd --name=vpn-router-web

debian-package/debian/vpn-router.vpn-router-web.service

@@ -0,0 +1,18 @@
+[Unit]
+Description=VPN Router status web service
+Documentation=file:/usr/share/doc/vpn-router/README.md
+After=network-online.target vpn-router-setup.service
+Wants=network-online.target
+
+[Service]
+Type=simple
+ExecStart=/usr/bin/python3 /usr/lib/vpn-router/web
+Restart=on-failure
+RestartSec=15
+NoNewPrivileges=yes
+ProtectSystem=strict
+ProtectHome=yes
+PrivateTmp=yes
+
+[Install]
+WantedBy=multi-user.target

debian-package/src/usr/lib/vpn-router/setup

@@ -10,8 +10,10 @@ firewall and NAT rules are written against them, so choosing the wrong one
 would be a silent and security-relevant mistake.
 """
 
+import json
 import os
 import pathlib
+import re
 import socket
 import subprocess
 import sys
@@ -24,13 +26,18 @@ from vpnrouter import fail
 BEFORE_RULES = pathlib.Path('/etc/ufw/before.rules')
 UFW_DEFAULTS = pathlib.Path('/etc/default/ufw')
 WG_DIR       = pathlib.Path('/etc/wireguard')
+WEB_STATE    = pathlib.Path('/run/vpn-router/web.json')
 
 FILTER_ANCHOR = '# End required lines'
 
+#: Configuration options whose values are masked wherever the configuration is shown.
+SECRET_OPTION = re.compile(r'(^psk$)|secret|password|token|_key$')
+
 BLOCKS = (
     ('# IPSEC RULES START',         '# IPSEC RULES END'),
     ('# WIREGUARD RULES START',     '# WIREGUARD RULES END'),
     ('# P2S DNS RULES START',       '# P2S DNS RULES END'),
+    ('# WEB RULES START',           '# WEB RULES END'),
     ('# ROUTER FORWARD RULES START', '# ROUTER FORWARD RULES END'),
     ('# ROUTER NAT RULES START',    '# ROUTER NAT RULES END'),
     ('# ROUTER MSS RULES START',    '# ROUTER MSS RULES END'),
@@ -149,6 +156,14 @@ def filter_block(ctx):
             ]
         lines += ['# P2S DNS RULES END']
 
+    if ctx['web_enabled'] and ctx['int_iface']:
+        lines += [
+            '',
+            '# WEB RULES START',
+            f'-A ufw-before-input -i {ctx["int_iface"]} -p tcp --dport {ctx["web_port"]} -j ACCEPT',
+            '# WEB RULES END',
+        ]
+
     if vpnrouter.routing_ready(ctx):
         lines += ['', '# ROUTER FORWARD RULES START']
         for subnet in ctx['local_cidr_list']:
@@ -309,6 +324,48 @@ def refresh_docker_rules():
         run(['systemctl', 'restart', 'vpn-router-docker.service'], check=False)
 
 
+def refresh_web(cfg, ctx):
+    """Hand the web service what it needs and restart it.
+
+    The service takes the address to bind to, the port, the features of the
+    router, the secret that signs its tokens, the configuration with its
+    secrets masked and the facts resolved from the system from a file here, so
+    that it needs nothing but the standard library and the configuration code.
+    The file is readable by root only. The service ends quietly when
+    web.enabled is false.
+    """
+    masked = {
+        section: {option: '********' if SECRET_OPTION.search(option) and value else value
+                  for option, value in options.items()}
+        for section, options in cfg.items()
+    }
+    WEB_STATE.parent.mkdir(parents=True, exist_ok=True)
+    WEB_STATE.touch(mode=0o600)
+    WEB_STATE.chmod(0o600)
+    WEB_STATE.write_text(json.dumps({
+        'enabled': bool(ctx['web_enabled']),
+        'bind': ctx['int_addr'],
+        'port': ctx['web_port'],
+        'jwt_secret': cfg['web']['jwt_secret'],
+        'site_to_site': bool(vpnrouter.s2s_ready(ctx)),
+        'p2s': bool(vpnrouter.p2s_ready(ctx)),
+        'wireguard': bool(vpnrouter.wg_ready(ctx)),
+        'configuration': masked,
+        'network': {
+            'external_interface': ctx['wan_iface'],
+            'internal_interface': ctx['int_iface'],
+            'external_addresses': ctx['local_addr_list'],
+            'internal_address': ctx['int_addr'],
+            'internal_gateway': ctx['int_gateway_ip'],
+            'local_identity': ctx['local_id'],
+            'remote_identity': ctx['remote_id'],
+            'local_cidrs': ctx['local_cidr_list'],
+            'remote_cidrs': ctx['remote_cidr_list'],
+        },
+    }) + '\n', encoding='utf-8')
+    run(['systemctl', 'restart', 'vpn-router-web.service'], check=False)
+
+
 def main():
     cfg = vpnrouter.load_config()
     ctx, changed = vpnrouter.configure(cfg)
@@ -348,6 +405,7 @@ def main():
 
     run_platform_setup(cfg, ctx)
     refresh_docker_rules()
+    refresh_web(cfg, ctx)
     return 0
 
 

debian-package/src/usr/lib/vpn-router/vpnrouter.py

@@ -48,8 +48,12 @@ SCHEMA = {
     'p2s':        {'enabled': False, 'address_pool': '', 'ca_name': 'VPN Router CA'},
     'wireguard':  {'enabled': False, 'address': '', 'listen_port': 51820},
     'docker':     {'mode': 'auto', 'exposed_ports': []},
+    'web':        {'enabled': True, 'port': 8080, 'jwt_secret': ''},
 }
 
+#: The shortest secret that signs the tokens of the status web service.
+WEB_SECRET_MIN = 32
+
 DOCKER_MODES = ('auto', 'on', 'off')
 
 #: A port or a port range as iptables multiport takes it: 443 or 8000:8100.
@@ -228,6 +232,14 @@ def validate(cfg):
     if not 1 <= port <= 65535:
         raise ConfigError(f'wireguard.listen_port: {port} is not a valid port')
 
+    web_port = _get(cfg, 'web', 'port')
+    if isinstance(web_port, bool) or not isinstance(web_port, int) or not 1 <= web_port <= 65535:
+        raise ConfigError(f'web.port: {web_port!r} is not a valid port')
+
+    web_secret = _get(cfg, 'web', 'jwt_secret')
+    if web_secret and len(web_secret) < WEB_SECRET_MIN:
+        raise ConfigError(f'web.jwt_secret: use at least {WEB_SECRET_MIN} characters')
+
     docker_mode = _get(cfg, 'docker', 'mode')
     if docker_mode not in DOCKER_MODES:
         raise ConfigError(
@@ -465,6 +477,8 @@ def build_context(cfg, local_id_override=None):
         'wg_enabled':      _get(cfg, 'wireguard', 'enabled'),
         'wg_address':      _get(cfg, 'wireguard', 'address'),
         'wg_listen_port':  _get(cfg, 'wireguard', 'listen_port'),
+        'web_enabled':     _get(cfg, 'web', 'enabled'),
+        'web_port':        _get(cfg, 'web', 'port'),
     }
 
 

debian-package/src/usr/lib/vpn-router/web

@@ -0,0 +1,355 @@
+#!/usr/bin/python3
+"""Serve the status of the router on its internal address.
+
+Run by vpn-router-web.service. It needs nothing but the Python standard library.
+
+Pages:
+  /        the status for people: plain text for curl and wget, a styled page
+           (Tailwind CSS from a CDN) for a browser
+  /status  the status as JSON
+  /config  the configuration without its secrets, and what the router resolved and
+           runs, as JSON; needs an HS256 JWT in an Authorization: Bearer header
+           that is signed with web.jwt_secret and expires within ten minutes; not
+           served (404) while web.jwt_secret is not set
+
+/ and /status show only the status: whether the services run, the package version, whether
+Docker is installed, and the state of site-to-site, road-warrior (IPsec P2S) and
+WireGuard. No configuration data, key or address is shown.
+
+The address to bind to, the port, the secret and the configuration shown by /config
+are not read from the configuration here: vpn-router-setup resolves them, with the
+interfaces, and writes them to /run/vpn-router/web.json, readable by root only, before
+it restarts this service. The service ends with
+success when the file says the service is disabled, and with failure, to be
+started again, when the file is missing or the router has no internal address yet.
+"""
+
+import base64
+import hashlib
+import hmac
+import json
+import os
+import re
+import signal
+import subprocess
+import sys
+import threading
+import time
+from html import escape
+from http.server import BaseHTTPRequestHandler, ThreadingHTTPServer
+
+STATE_FILE = '/run/vpn-router/web.json'
+COMMAND_TIMEOUT = 5
+CACHE_SECONDS = 2
+
+#: Seconds of clock difference accepted between a token and this router.
+LEEWAY = 60
+
+#: The longest a token may be valid, from now, in seconds.
+MAX_LIFETIME = 600
+
+TAILWIND = 'https://cdn.jsdelivr.net/npm/@tailwindcss/browser@4'
+SA_LINE = re.compile(r'^(\S+): #\d+, (\w+),')
+
+_cache = {'at': 0.0, 'data': None}
+_lock = threading.Lock()
+
+
+def run(*args):
+    """The finished process of a command, or None when it cannot be run."""
+    try:
+        return subprocess.run(args, capture_output=True, text=True, timeout=COMMAND_TIMEOUT)
+    except (OSError, subprocess.TimeoutExpired):
+        return None
+
+
+def unit_state(unit):
+    result = run('systemctl', 'is-active', unit)
+    return result.stdout.strip() if result and result.stdout.strip() else 'unknown'
+
+
+def package_version():
+    result = run('dpkg-query', '-W', '-f=${Version}', 'vpn-router')
+    return result.stdout.strip() if result and result.returncode == 0 else None
+
+
+def docker_status():
+    """Whether Docker is installed, and the state of its service and of the Docker rules when it is."""
+    result = run('systemctl', 'list-unit-files', '--no-legend', 'docker.service')
+    if result is None or result.returncode != 0 or not result.stdout.strip():
+        return {'installed': False}
+    return {
+        'installed': True,
+        'service': unit_state('docker.service'),
+        'rules': unit_state('vpn-router-docker.service'),
+    }
+
+
+def established(connection):
+    """The number of IKE SAs of the connection, or None when swanctl cannot be asked."""
+    result = run('swanctl', '--list-sas')
+    if result is None or result.returncode != 0:
+        return None
+    return sum(1 for line in result.stdout.splitlines()
+               if (match := SA_LINE.match(line)) and match.group(1) == connection and match.group(2) == 'ESTABLISHED')
+
+
+def wireguard_peers():
+    """One entry per WireGuard peer, with its handshake age and traffic, or None when wg0 is down."""
+    result = run('wg', 'show', 'wg0', 'dump')
+    if result is None or result.returncode != 0:
+        return None
+    now = int(time.time())
+    peers = []
+    for line in result.stdout.splitlines()[1:]:
+        fields = line.split('\t')
+        if len(fields) < 7:
+            continue
+        handshake = int(fields[4])
+        peers.append({
+            'handshake_seconds_ago': now - handshake if handshake else None,
+            'received_bytes': int(fields[5]),
+            'sent_bytes': int(fields[6]),
+        })
+    return peers
+
+
+def collect(state):
+    """The status document. state says which features the router has."""
+    units = {'vpn-router-setup': unit_state('vpn-router-setup.service')}
+    if state.get('site_to_site') or state.get('p2s'):
+        units['strongswan'] = unit_state('strongswan.service')
+    if state.get('wireguard'):
+        units['wg-quick@wg0'] = unit_state('wg-quick@wg0.service')
+
+    status = {
+        'status': 'ok' if all(value == 'active' for value in units.values()) else 'degraded',
+        'version': package_version(),
+        'time': time.strftime('%Y-%m-%dT%H:%M:%S%z'),
+        'units': units,
+        'docker': docker_status(),
+    }
+    if state.get('site_to_site'):
+        count = established('remote-site')
+        status['site_to_site'] = {'established': None if count is None else count > 0}
+    if state.get('p2s'):
+        status['p2s'] = {'clients': established('road-warrior')}
+    if state.get('wireguard'):
+        status['wireguard'] = {'peers': wireguard_peers()}
+    return status
+
+
+def b64decode(part):
+    return base64.urlsafe_b64decode(part + '=' * (-len(part) % 4))
+
+
+def verify(token, secret):
+    """The claims of a token signed with HS256 by the secret, or None when it is not acceptable.
+
+    Only HS256 is accepted, so a token cannot choose a weaker algorithm. The token
+    must expire (exp), and not later than MAX_LIFETIME seconds from now, so that a
+    stolen token is of little use; LEEWAY seconds of clock difference are allowed.
+    """
+    try:
+        header, payload, signature = token.split('.')
+        if json.loads(b64decode(header)).get('alg') != 'HS256':
+            return None
+        expected = hmac.new(secret.encode(), f'{header}.{payload}'.encode(), hashlib.sha256).digest()
+        if not hmac.compare_digest(expected, b64decode(signature)):
+            return None
+        claims = json.loads(b64decode(payload))
+        now = time.time()
+        expires = claims['exp']
+        if isinstance(expires, bool) or not isinstance(expires, (int, float)) or not now - LEEWAY <= expires <= now + MAX_LIFETIME + LEEWAY:
+            return None
+        not_before = claims.get('nbf')
+        if not_before is not None and (isinstance(not_before, bool) or not isinstance(not_before, (int, float)) or not_before > now + LEEWAY):
+            return None
+    except (ValueError, KeyError, TypeError, AttributeError):
+        return None
+    return claims
+
+
+def lines_of(*args):
+    """The output lines of a command, or None when it fails."""
+    result = run(*args)
+    return result.stdout.splitlines() if result and result.returncode == 0 else None
+
+
+def wireguard_details():
+    """The interface and the peers of wg0, with endpoints and allowed IPs; no private or preshared key."""
+    result = run('wg', 'show', 'wg0', 'dump')
+    if result is None or result.returncode != 0:
+        return None
+    rows = [line.split('\t') for line in result.stdout.splitlines()]
+    now = int(time.time())
+    return {
+        'public_key': rows[0][1] if rows and len(rows[0]) > 2 else None,
+        'listen_port': int(rows[0][2]) if rows and len(rows[0]) > 2 else None,
+        'peers': [{
+            'public_key': row[0],
+            'endpoint': None if row[2] == '(none)' else row[2],
+            'allowed_ips': row[3].split(','),
+            'handshake_seconds_ago': now - int(row[4]) if int(row[4]) else None,
+            'received_bytes': int(row[5]),
+            'sent_bytes': int(row[6]),
+        } for row in rows[1:] if len(row) >= 7],
+    }
+
+
+def details(state):
+    """What /config shows: the configuration without its secrets, and what the router resolved and runs."""
+    configuration = state.get('configuration', {})
+    return {
+        'configuration': configuration,
+        'network': dict(state.get('network', {}), routes=lines_of('ip', '-4', 'route', 'show')),
+        'ipsec': {
+            'connections': lines_of('swanctl', '--list-conns'),
+            'sas': lines_of('swanctl', '--list-sas'),
+        },
+        'wireguard': wireguard_details(),
+        'docker': {
+            'exposed_ports': configuration.get('docker', {}).get('exposed_ports', []),
+            'rules': lines_of('iptables', '-S', 'VPN-ROUTER-DOCKER'),
+        },
+    }
+
+
+def text_of(status):
+    """The status for people, as plain text."""
+    lines = ['VPN Router', f'Status: {status["status"]}', f'Version: {status["version"] or "unknown"}', '']
+    lines += [f'{name}: {value}' for name, value in status['units'].items()]
+    docker = status['docker']
+    lines.append('Docker: not installed' if not docker['installed']
+                 else f'Docker: installed, service {docker["service"]}, rules {docker["rules"]}')
+    if 'site_to_site' in status:
+        value = status['site_to_site']['established']
+        lines.append(f'Site to site: {"unknown" if value is None else "established" if value else "not established"}')
+    if 'p2s' in status:
+        clients = status['p2s']['clients']
+        lines.append(f'Road-warrior (IPsec P2S): {"unknown" if clients is None else f"{clients} connected"}')
+    if 'wireguard' in status:
+        peers = status['wireguard']['peers']
+        if peers is None:
+            lines.append('WireGuard: down')
+        else:
+            lines.append(f'WireGuard: {len(peers)} peers')
+            for number, peer in enumerate(peers, 1):
+                age = peer['handshake_seconds_ago']
+                lines.append(f'  peer {number}: {"no handshake yet" if age is None else f"handshake {age} s ago"}, '
+                             f'received {peer["received_bytes"]} B, sent {peer["sent_bytes"]} B')
+    return '\n'.join(lines) + '\n'
+
+
+def html_of(status):
+    """The status for a browser, as a page styled with Tailwind CSS."""
+    colour = 'bg-emerald-600' if status['status'] == 'ok' else 'bg-amber-600'
+    body = ''.join(f'<li>{escape(line)}</li>' for line in text_of(status).splitlines()[4:] if line)
+    return f"""<!doctype html>
+<html lang="en">
+  <head>
+    <meta charset="utf-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1">
+    <title>VPN Router</title>
+    <script src="{TAILWIND}"></script>
+  </head>
+  <body class="min-h-screen bg-slate-100 text-slate-900">
+    <div class="mx-auto max-w-2xl px-4 py-10">
+      <div class="overflow-hidden rounded-2xl border border-slate-200 bg-white shadow-lg">
+        <div class="{colour} px-6 py-4 text-white">
+          <h1 class="text-xl font-semibold">VPN Router</h1>
+          <p class="mt-1 text-sm">Status: {escape(status['status'])}, version {escape(status['version'] or 'unknown')}</p>
+        </div>
+        <ul class="space-y-2 px-6 py-6 font-mono text-sm">{body}</ul>
+        <p class="px-6 pb-6 text-xs text-slate-500">{escape(status['time'])} - <a class="underline" href="/status">JSON</a></p>
+      </div>
+    </div>
+  </body>
+</html>
+"""
+
+
+class Handler(BaseHTTPRequestHandler):
+    protocol_version = 'HTTP/1.1'
+
+    def status(self):
+        with _lock:
+            if _cache['data'] is None or time.monotonic() - _cache['at'] > CACHE_SECONDS:
+                _cache['data'] = collect(self.server.state)
+                _cache['at'] = time.monotonic()
+            return _cache['data']
+
+    def answer(self, send_body):
+        path = self.path.split('?', 1)[0]
+        extra = []
+        if path == '/config':
+            secret = self.server.state.get('jwt_secret')
+            header = self.headers.get('Authorization', '')
+            if not secret:
+                body, kind, code = b'Not found\n', 'text/plain; charset=utf-8', 404
+            elif not header.startswith('Bearer ') or verify(header[7:].strip(), secret) is None:
+                body, kind, code = b'Unauthorized\n', 'text/plain; charset=utf-8', 401
+                extra.append(('WWW-Authenticate', 'Bearer'))
+            else:
+                body, kind, code = json.dumps(details(self.server.state), indent=2).encode() + b'\n', 'application/json', 200
+        elif path == '/status':
+            body, kind, code = json.dumps(self.status(), indent=2).encode() + b'\n', 'application/json', 200
+        elif path == '/':
+            agent = self.headers.get('User-Agent', '').lower()
+            if 'curl' in agent or 'wget' in agent:
+                body, kind = text_of(self.status()).encode(), 'text/plain; charset=utf-8'
+            else:
+                body, kind = html_of(self.status()).encode(), 'text/html; charset=utf-8'
+            code = 200
+        else:
+            body, kind, code = b'Not found\n', 'text/plain; charset=utf-8', 404
+        self.send_response(code)
+        self.send_header('Content-Type', kind)
+        self.send_header('Content-Length', str(len(body)))
+        self.send_header('Cache-Control', 'no-store')
+        for name, value in extra:
+            self.send_header(name, value)
+        self.end_headers()
+        if send_body:
+            self.wfile.write(body)
+
+    def do_GET(self):
+        self.answer(True)
+
+    def do_HEAD(self):
+        self.answer(False)
+
+    def log_message(self, format, *args):
+        sys.stderr.write('%s - - [%s] %s\n' % (self.client_address[0], self.log_date_time_string(), format % args))
+
+
+def main():
+    try:
+        with open(STATE_FILE, encoding='utf-8') as handle:
+            state = json.load(handle)
+    except (OSError, ValueError) as exc:
+        print(f'vpn-router-web: cannot read {STATE_FILE}: {exc}', file=sys.stderr)
+        return 1
+
+    if not state.get('enabled'):
+        print('vpn-router-web: the web service is disabled in the configuration')
+        return 0
+    if not state.get('bind'):
+        print('vpn-router-web: the router has no internal address yet', file=sys.stderr)
+        return 1
+
+    server = ThreadingHTTPServer((state['bind'], state['port']), Handler)
+    server.state = state
+    signal.signal(signal.SIGTERM, lambda *_: sys.exit(0))
+    print(f'vpn-router-web: serving on http://{state["bind"]}:{state["port"]}')
+    try:
+        server.serve_forever()
+    except KeyboardInterrupt:
+        pass
+    finally:
+        server.server_close()
+    return 0
+
+
+if __name__ == '__main__':
+    sys.exit(main())

debian-package/src/usr/share/doc/vpn-router/vpn-router.json.example

@@ -36,5 +36,10 @@
   "docker": {
     "mode": "auto",
     "exposed_ports": ["443"]
+  },
+  "web": {
+    "enabled": true,
+    "port": 8080,
+    "jwt_secret": ""
   }
 }