Aug 21 - Fixed Forwarded host

tests/test_forwarded_host.py

@@ -0,0 +1,104 @@
+import pytest
+
+from werkzeug.test import EnvironBuilder
+
+
+def _drive(app, headers):
+    """Send one request through the app's REAL ProxyFix instance.
+
+    The middleware's wrapped application is swapped for a recorder for the
+    duration of the call, so what is measured is the exact ProxyFix object
+    create_app() installed — not a reconstruction of it — without needing a
+    second create_app() (blueprints cannot be registered twice per process)
+    or a route added after the app has served its first request.
+    """
+    seen = {}
+
+    def recorder(environ, start_response):
+        seen['host'] = environ.get('HTTP_HOST')
+        seen['scheme'] = environ.get('wsgi.url_scheme')
+        start_response('200 OK', [('Content-Type', 'text/plain')])
+        return [b'ok']
+
+    middleware = app.wsgi_app
+    original = middleware.app
+    middleware.app = recorder
+    try:
+        environ = EnvironBuilder(path='/', headers=headers).get_environ()
+        middleware(environ, lambda *a, **kw: None)
+    finally:
+        middleware.app = original
+    return seen
+
+
+def _observed_host(app, headers):
+    """Return the host the application resolves for a request."""
+    return _drive(app, headers).get('host')
+
+
+def test_forwarded_host_does_not_override_the_real_host(app):
+    """The core assertion: a forged header must be ignored."""
+    host = _observed_host(app, {
+        'Host': 'attacker.jqc.app',
+        'X-Forwarded-Host': 'victim.jqc.app',
+    })
+    assert host == 'attacker.jqc.app', (
+        'X-Forwarded-Host overrode the real Host header — tenant selection is '
+        'attacker-controlled. Check ProxyFix x_host in app/__init__.py.'
+    )
+    assert 'victim' not in (host or '')
+
+
+def test_real_host_is_still_used_normally(app):
+    """Without the forged header, nothing changes."""
+    assert _observed_host(app, {'Host': 'lts.jqc.app'}) == 'lts.jqc.app'
+
+
+def test_proxyfix_is_configured_without_x_host(app):
+    """Pin the setting itself, so a future edit has to be deliberate."""
+    from werkzeug.middleware.proxy_fix import ProxyFix
+
+    wsgi = app.wsgi_app
+    assert isinstance(wsgi, ProxyFix), 'ProxyFix is no longer installed'
+    assert wsgi.x_host == 0, (
+        'ProxyFix x_host must stay 0 — nginx sets Host from the real request, '
+        'and X-Forwarded-Host is client-controlled.'
+    )
+    # The two we DO want unwrapped, for rate limiting and HTTPS URL building.
+    assert wsgi.x_for == 1
+    assert wsgi.x_proto == 1
+
+
+def test_forwarded_proto_is_still_honoured(app):
+    """x_proto must keep working — email links depend on it."""
+    seen = _drive(app, {'Host': 'lts.jqc.app', 'X-Forwarded-Proto': 'https'})
+    assert seen.get('scheme') == 'https'
+
+
+# ── Config guard ─────────────────────────────────────────────────────────────
+
+def test_shipped_nginx_configs_pin_forwarded_host():
+    """Every proxying block in deploy/nginx must pin X-Forwarded-Host.
+
+    These files are the reference the server is deployed from. A block that
+    proxies without pinning the header reopens the hole on whichever host uses
+    it, so the omission should fail here rather than on the box.
+    """
+    import pathlib
+
+    conf_dir = pathlib.Path(__file__).resolve().parent.parent / 'deploy' / 'nginx'
+    configs = sorted(conf_dir.glob('*.conf'))
+    assert configs, 'no nginx reference configs found in deploy/nginx/'
+
+    offenders = []
+    for path in configs:
+        text = path.read_text(encoding='utf-8')
+        if 'proxy_pass' not in text:
+            continue
+        if 'proxy_set_header X-Forwarded-Host' not in text.replace('  ', ' '):
+            offenders.append(path.name)
+
+    assert not offenders, (
+        'nginx config proxies without pinning X-Forwarded-Host: '
+        + ', '.join(offenders)
+    )