xtremflow/bin/api/proxy_handler.dart

import 'dart:async';
import 'dart:convert';
import 'dart:io';
import 'dart:typed_data';
import 'package:shelf/shelf.dart';
import 'package:http/http.dart' as http;
import '../database/database.dart';
import '../middleware/auth_middleware.dart';
import '../models/playlist_config.dart';
import '../utils/log_redactor.dart';
import 'asset_failure_cache.dart';

/// PNG transparent 1×1, servi à la place d'un logo introuvable.
final Uint8List _placeholderPixel = base64Decode(
  'iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAQAAAC1HAwCAAAAC0lEQVR42mNkYAAAAAYAAjCB0C8AAAAASUVORK5CYII=',
);

/// L'URL désigne-t-elle une image ou un logo ?
///
/// Ces URL échappent à l'allowlist de domaine (les revendeurs hébergent leurs
/// picons ailleurs que le panneau) et méritent un repli visuel plutôt qu'une
/// erreur propagée au navigateur.
bool _isStaticAssetUrl(Uri url) =>
    url.path.endsWith('.png') ||
    url.path.endsWith('.jpg') ||
    url.path.endsWith('.jpeg') ||
    url.path.endsWith('.gif') ||
    url.path.endsWith('.webp') ||
    url.path.endsWith('.ico') ||
    url.path.contains('/picons/') ||
    url.path.contains('/logos/');

/// Réponse de repli pour une image indisponible.
///
/// Le `max-age` est essentiel : sans lui le navigateur redemande le logo à
/// chaque affichage de la grille et le flot de requêtes mortes reprend
/// immédiatement, coupure serveur ou pas.
Response _placeholderImageResponse() => Response.ok(
      _placeholderPixel,
      headers: {
        'content-type': 'image/png',
        'cache-control': 'public, max-age=600',
        'access-control-allow-origin': '*',
      },
    );

/// Returns true when [host] must never be proxied (loopback, private LAN,
/// link-local/cloud-metadata ranges) — SSRF protection for asset URLs that
/// bypass the playlist-domain allowlist.
bool isForbiddenProxyHost(String host) {
  final lower = host.toLowerCase();
  if (lower == 'localhost' || lower == '::1') return true;

  final ip = InternetAddress.tryParse(lower);
  if (ip == null) return false; // Hostname: validated by domain allowlist path

  if (ip.isLoopback || ip.isLinkLocal) return true;
  if (ip.type == InternetAddressType.IPv4) {
    final parts = ip.address.split('.').map(int.parse).toList();
    if (parts[0] == 10) return true; // 10.0.0.0/8
    if (parts[0] == 172 && parts[1] >= 16 && parts[1] <= 31) return true;
    if (parts[0] == 192 && parts[1] == 168) return true; // 192.168.0.0/16
    if (parts[0] == 169 && parts[1] == 254) return true; // metadata/link-local
    if (parts[0] == 0) return true;
  }
  return false;
}

/// Handler for the Xtream Proxy
class ProxyHandler {
  final Future<PlaylistConfig?> Function(Request) _getPlaylist;
  final AppDatabase _db;
  final http.Client _client = http.Client();

  final Map<String, (PlaylistConfig, DateTime)> _playlistCache = {};
  static const _cacheDuration = Duration(minutes: 5);

  /// Hôtes d'images réputés hors service (voir [AssetFailureCache]).
  final AssetFailureCache _assetFailures = AssetFailureCache();

  static const _allowedHeaders = [
    'content-type',
    'content-range',
    'accept-ranges',
    'cache-control',
    'server',
    'date',
  ];

  static const _allowedRequestHeaders = [
    'user-agent',
    'accept',
    'range',
    'referer',
  ];

  Future<PlaylistConfig?> _getCachedPlaylist(Request request) async {
    // Basic caching to avoid DB overhead on every video segment
    final now = DateTime.now();
    const cacheKey =
        'global_playlist'; // Currently app has one primary playlist per user/global

    if (_playlistCache.containsKey(cacheKey)) {
      final (cached, expiry) = _playlistCache[cacheKey]!;
      if (now.isBefore(expiry)) return cached;
    }

    final playlist = await _getPlaylist(request);
    if (playlist != null) {
      _playlistCache[cacheKey] = (playlist, now.add(_cacheDuration));
    }
    return playlist;
  }

  ProxyHandler(this._getPlaylist, this._db);

  /// Create Xtream proxy handler with M3U8 URL rewriting support
  Handler get handler {
    return (Request request) async {
      final path = request.url.path;

      // Only handle /api/xtream/* requests
      // CRITICAL: Check path BEFORE anything else so non-proxy requests fall through to static handler
      if (!path.startsWith('api/xtream/')) {
        // Return 404 so Cascade tries next handler (streamingRouter)
        return Response.notFound(null);
      }

      // Authentification par session. Les requêtes initiées par le navigateur
      // (img src, hls.js) ne portent pas d'en-tête Authorization mais envoient
      // le cookie HttpOnly `session` (SameSite=Lax, même origine) posé au
      // login : extractAuthToken accepte les deux. Un proxy ouvert offrait un
      // rebond SSRF non authentifié vers n'importe quel hôte public via les
      // extensions d'image.
      final token = extractAuthToken(request);
      if (token == null || _db.findSessionByToken(token) == null) {
        return Response(401, body: 'Unauthorized');
      }

      Uri? targetUrl;

      // === PROXY LOGIC ===
      try {
        // Extract target URL from request
        // Format: /api/xtream/http://server:port/path
        String apiPath = path.substring('api/xtream/'.length);

        // Decode URL if it's encoded
        if (apiPath.startsWith('http%3A') || apiPath.startsWith('https%3A')) {
          apiPath = Uri.decodeComponent(apiPath);
        }

        if (!apiPath.startsWith('http://') && !apiPath.startsWith('https://')) {
          return Response.badRequest(
            body: 'Invalid API URL. Expected format: /api/xtream/http://...',
          );
        }

        String fullUrl = apiPath;
        if (request.url.query.isNotEmpty) {
          if (fullUrl.contains('?')) {
            fullUrl = '$fullUrl&${request.url.query}';
          } else {
            fullUrl = '$fullUrl?${request.url.query}';
          }
        }

        targetUrl = Uri.parse(fullUrl);

        // Only plain http(s) may be proxied
        if (targetUrl.scheme != 'http' && targetUrl.scheme != 'https') {
          return Response.forbidden('Unsupported URL scheme');
        }

        // Never proxy to loopback/private/link-local targets (SSRF)
        if (isForbiddenProxyHost(targetUrl.host)) {
          print('[Proxy] Blocked SSRF attempt to private host: ${targetUrl.host}');
          return Response.forbidden('Access to this host is forbidden');
        }

        // SSRF Protection - but allow images/static assets from any host
        // Xtream providers often use separate CDN servers for picons/images
        final isStaticAsset = _isStaticAssetUrl(targetUrl);

        // Hôte d'images déjà constaté mort : on sert le pixel tout de suite.
        // Aucun appel sortant, aucune entrée de log — c'est précisément le
        // flot qu'on cherche à éteindre.
        if (isStaticAsset && _assetFailures.isDown(targetUrl.host)) {
          return _placeholderImageResponse();
        }

        String? allowedHost;
        if (!isStaticAsset) {
          // For API calls, enforce domain allowlist
          final playlist = await _getCachedPlaylist(request);
          if (playlist == null) {
            return Response.forbidden(
              'No active playlist configuration found to validate request',
            );
          }

          final targetHost = targetUrl.host.toLowerCase();
          allowedHost = Uri.parse(playlist.dns).host.toLowerCase();

          if (targetHost != allowedHost) {
            print(
              '[Proxy] Blocked SSRF attempt to $targetHost (Allowed: $allowedHost)',
            );
            return Response.forbidden(
              'Access to this domain is forbidden by policy',
            );
          }
        }

        final proxyHeaders = <String, String>{
          'User-Agent': 'VLC/3.0.18 LibVLC/3.0.18',
          'Accept': '*/*',
          'Accept-Encoding': 'identity',
          'Keep-Alive': 'timeout=30, max=100', // Request persistent connection
        };

        // Forward Range header if present
        if (request.headers['range'] != null) {
          proxyHeaders['range'] = request.headers['range']!;
        }

        try {
          print('[Proxy] Forwarding to: ${LogRedactor.redactUrl(targetUrl.toString())}');

          // Forward safe request headers
          for (final header in _allowedRequestHeaders) {
            if (request.headers.containsKey(header)) {
              proxyHeaders[header] = request.headers[header]!;
            }
          }

          List<int>? postBody;
          if (request.method == 'POST') {
            final bodyBytes = await request.read().toList();
            postBody = bodyBytes.expand((i) => i).toList();
          }

          // Redirections suivies MANUELLEMENT : chaque destination est
          // revalidée (hôte privé, allowlist de domaine). Avec
          // followRedirects, la validation ne portait que sur l'URL
          // initiale — une 302 du serveur amont suffisait pour atteindre
          // un hôte interne malgré l'anti-SSRF.
          http.StreamedResponse response;
          var currentUrl = targetUrl;
          var redirects = 0;
          while (true) {
            final proxyRequest = http.Request(request.method, currentUrl);
            proxyRequest.headers.addAll(proxyHeaders);
            proxyRequest.followRedirects = false;
            if (postBody != null) proxyRequest.bodyBytes = postBody;

            // Added 90s timeout to allow frontend (60s) to time out gracefully first
            response = await _client
                .send(proxyRequest)
                .timeout(const Duration(seconds: 90));

            final location = response.headers['location'];
            final isRedirect = response.statusCode >= 300 &&
                response.statusCode < 400 &&
                location != null;
            if (!isRedirect) break;

            if (++redirects > 3) {
              return Response.forbidden('Too many redirects');
            }
            final next = Uri.parse(location);
            currentUrl = next.isAbsolute ? next : currentUrl.resolve(location);
            if (currentUrl.scheme != 'http' && currentUrl.scheme != 'https') {
              return Response.forbidden('Unsupported redirect scheme');
            }
            if (isForbiddenProxyHost(currentUrl.host)) {
              print(
                '[Proxy] Blocked SSRF redirect to private host: ${currentUrl.host}',
              );
              return Response.forbidden('Access to this host is forbidden');
            }
            if (allowedHost != null &&
                currentUrl.host.toLowerCase() != allowedHost) {
              print(
                '[Proxy] Blocked redirect to ${currentUrl.host} (Allowed: $allowedHost)',
              );
              return Response.forbidden(
                'Access to this domain is forbidden by policy',
              );
            }
          }

          // Une image en erreur n'a rien à transmettre au navigateur : le
          // relais du 503 déclenchait un nouveau cycle de requêtes à chaque
          // rendu. On sert le pixel, mis en cache, et on compte l'échec.
          if (isStaticAsset) {
            if (response.statusCode >= 400) {
              // Compté sur l'hôte demandé, pas sur la cible finale d'une
              // redirection : c'est cette clé-là que consulte le garde-fou
              // en tête de requête.
              _assetFailures.recordFailure(targetUrl.host);
              // Le corps d'erreur doit être consommé, sinon la connexion
              // reste ouverte jusqu'au timeout.
              unawaited(response.stream.drain<void>().catchError((_) {}));
              return _placeholderImageResponse();
            }
            _assetFailures.recordSuccess(targetUrl.host);
          }

          // Build response headers from source response
          final responseHeaders = <String, String>{
            'access-control-allow-origin': '*',
            'connection': 'keep-alive',
            'keep-alive': 'timeout=30',
          };

          // Forward specific safe headers
          for (final header in _allowedHeaders) {
            if (response.headers.containsKey(header)) {
              responseHeaders[header] = response.headers[header]!;
            }
          }

          // ALWAYS stream the response for maximum performance and to avoid memory issues with large JSONs
          return Response(
            response.statusCode,
            body: response.stream,
            headers: responseHeaders,
          );
        } catch (e) {
          rethrow;
        }
      } catch (e) {
        // Redaction : une ClientException porte l'URL amont, credentials
        // Xtream inclus. Jamais de détail d'exception vers le client.
        print(
          '[ProxyHandler] error on ${LogRedactor.redactUrl(path)}: '
          '${LogRedactor.redactUrl('$e')}',
        );

        // Return transparent 1x1 pixel image fallback for images
        if (targetUrl != null && _isStaticAssetUrl(targetUrl)) {
          _assetFailures.recordFailure(targetUrl.host);
          return _placeholderImageResponse();
        }

        return Response.internalServerError(
          body: jsonEncode({'error': 'Proxy error'}),
          headers: {'content-type': 'application/json'},
        );
      }
    };
  }
}