Fix Cloudflare Interceptor when User-Agent is Empty (#2677)

app/src/main/java/eu/kanade/tachiyomi/network/CloudflareInterceptor.kt

@@ -55,7 +55,19 @@ class CloudflareInterceptor(private val context: Context) : Interceptor {
             val oldCookie = networkHelper.cookieManager.get(originalRequest.url)
                     .firstOrNull { it.name == "cf_clearance" }
             resolveWithWebView(originalRequest, oldCookie)
-            return chain.proceed(originalRequest)
+
+            // Avoid use empty User-Agent
+            return if (originalRequest.header("User-Agent").isNullOrEmpty()) {
+                val newRequest = originalRequest
+                        .newBuilder()
+                        .removeHeader("User-Agent")
+                        .addHeader("User-Agent",
+                                DEFAULT_USERAGENT)
+                        .build()
+                chain.proceed(newRequest)
+            } else {
+                chain.proceed(originalRequest)
+            }
         } catch (e: Exception) {
             // Because OkHttp's enqueue only handles IOExceptions, wrap the exception so that
             // we don't crash the entire app
@@ -77,20 +89,23 @@ class CloudflareInterceptor(private val context: Context) : Interceptor {
 
         val origRequestUrl = request.url.toString()
         val headers = request.headers.toMultimap().mapValues { it.value.getOrNull(0) ?: "" }
+        val withUserAgent = request.header("User-Agent").isNullOrEmpty()
 
         handler.post {
             val webview = WebView(context)
             webView = webview
-
             webview.settings.javaScriptEnabled = true
+
+            // Avoid set empty User-Agent, Chromium WebView will reset to default if empty
             webview.settings.userAgentString = request.header("User-Agent")
+                    ?: DEFAULT_USERAGENT
 
             webview.webViewClient = object : WebViewClientCompat() {
                 override fun onPageFinished(view: WebView, url: String) {
                     fun isCloudFlareBypassed(): Boolean {
                         return networkHelper.cookieManager.get(origRequestUrl.toHttpUrl())
                                 .firstOrNull { it.name == "cf_clearance" }
-                                .let { it != null && it != oldCookie }
+                                .let { it != null && (it != oldCookie || withUserAgent) }
                     }
 
                     if (isCloudFlareBypassed()) {
@@ -156,5 +171,6 @@ class CloudflareInterceptor(private val context: Context) : Interceptor {
     companion object {
         private val SERVER_CHECK = arrayOf("cloudflare-nginx", "cloudflare")
         private val COOKIE_NAMES = listOf("__cfduid", "cf_clearance")
+        private const val DEFAULT_USERAGENT = "Mozilla/5.0 (Windows NT 6.3; WOW64)"
     }
 }