feat: handle cloudflare captcha in under attack mode

app/build.gradle

@@ -83,6 +83,7 @@ android {
         jvmTarget = '1.8'
     }
     buildFeatures {
+        viewBinding true
         compose true
     }
     composeOptions {
@@ -163,6 +164,9 @@ dependencies {
     implementation "androidx.datastore:datastore-preferences:1.1.0-alpha01"
     implementation "androidx.datastore:datastore:1.1.0-alpha01"
 
+    // Libraries used for legacy View-based UI
+    implementation "androidx.constraintlayout:constraintlayout:2.2.0-alpha09"
+
     // JDK Desugaring - polyfill for new Java APIs
     coreLibraryDesugaring 'com.android.tools:desugar_jdk_libs:2.0.2'
 

app/src/main/AndroidManifest.xml

@@ -19,10 +19,10 @@
         <meta-data
             android:name="io.sentry.auto-init"
             android:value="false" />
+
         <activity
             android:name=".MainActivity"
             android:exported="true"
-            android:label="@string/app_name"
             android:theme="@style/Theme.Revolt">
             <intent-filter>
                 <action android:name="android.intent.action.MAIN" />
@@ -30,6 +30,9 @@
                 <category android:name="android.intent.category.LAUNCHER" />
             </intent-filter>
         </activity>
+        <activity
+            android:name=".activities.WebChallengeActivity"
+            android:theme="@style/Theme.Revolt" />
     </application>
 
 </manifest>

app/src/main/java/chat/revolt/activities/WebChallengeActivity.kt

@@ -0,0 +1,47 @@
+package chat.revolt.activities
+
+import android.annotation.SuppressLint
+import android.os.Bundle
+import android.webkit.WebView
+import android.webkit.WebViewClient
+import androidx.appcompat.app.AppCompatActivity
+import chat.revolt.api.REVOLT_BASE
+import chat.revolt.api.buildUserAgent
+import chat.revolt.databinding.ActivityWebchallengeBinding
+
+private class WebChallengeClient(val pageLoaded: () -> Unit) : WebViewClient() {
+    @Override
+    override fun onPageFinished(view: WebView, url: String) {
+        super.onPageFinished(view, url)
+        pageLoaded()
+    }
+}
+
+class WebChallengeActivity : AppCompatActivity() {
+    private lateinit var binding: ActivityWebchallengeBinding
+
+    @SuppressLint("SetJavaScriptEnabled")
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        binding = ActivityWebchallengeBinding.inflate(layoutInflater)
+        setContentView(binding.root)
+
+        binding.webView.settings.apply {
+            javaScriptEnabled = true
+            domStorageEnabled = true
+            userAgentString = buildUserAgent("WebChallenge")
+        }
+
+        binding.webView.webViewClient = WebChallengeClient {
+            binding.webView.evaluateJavascript(
+                "(function() { return document.getElementById('cf-wrapper') != null; })();"
+            ) { result ->
+                if (result == "false") { // No challenge
+                    finish()
+                }
+            }
+        }
+
+        binding.webView.loadUrl(REVOLT_BASE)
+    }
+}

app/src/main/java/chat/revolt/api/RevoltAPI.kt

@@ -41,6 +41,10 @@ fun asJanuaryProxyUrl(url: String): String {
     return "$REVOLT_JANUARY/proxy?url=${url}"
 }
 
+fun buildUserAgent(accessMethod: String = "Ktor"): String {
+    return "$accessMethod RevoltAndroid/${BuildConfig.VERSION_NAME} (Android ${android.os.Build.VERSION.SDK_INT}; ${android.os.Build.MANUFACTURER} ${android.os.Build.DEVICE})"
+}
+
 private const val BACKEND_IS_STABLE = false
 
 val RevoltJson = Json { ignoreUnknownKeys = true }
@@ -70,10 +74,7 @@ val RevoltHttp = HttpClient(OkHttp) {
 
     defaultRequest {
         url(REVOLT_BASE)
-        header(
-            "User-Agent",
-            "Ktor RevoltAndroid/${BuildConfig.VERSION_NAME} (Android ${android.os.Build.VERSION.SDK_INT}; ${android.os.Build.MANUFACTURER} ${android.os.Build.DEVICE})"
-        )
+        header("User-Agent", buildUserAgent())
     }
 }
 

app/src/main/java/chat/revolt/api/internals/WebChallenge.kt

@@ -0,0 +1,15 @@
+package chat.revolt.api.internals
+
+import chat.revolt.api.REVOLT_BASE
+import chat.revolt.api.RevoltHttp
+import io.ktor.client.request.get
+import io.ktor.client.statement.bodyAsText
+
+object WebChallenge {
+    suspend fun needsCloudflare(): Boolean {
+        RevoltHttp.get(REVOLT_BASE).let {
+            val text = it.bodyAsText()
+            return text.contains("window._cf_chl_opt") // FIXME Naive, prone to captcha page changing
+        }
+    }
+}

app/src/main/java/chat/revolt/screens/SplashScreen.kt

@@ -2,8 +2,10 @@ package chat.revolt.screens
 
 import android.annotation.SuppressLint
 import android.content.Context
+import android.content.Intent
 import android.net.ConnectivityManager
 import android.net.NetworkCapabilities
+import android.util.Log
 import androidx.compose.foundation.Image
 import androidx.compose.foundation.background
 import androidx.compose.foundation.layout.*
@@ -11,6 +13,7 @@ import androidx.compose.runtime.*
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.layout.ContentScale
+import androidx.compose.ui.platform.LocalContext
 import androidx.compose.ui.res.painterResource
 import androidx.compose.ui.unit.dp
 import androidx.hilt.navigation.compose.hiltViewModel
@@ -18,7 +21,9 @@ import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
 import androidx.navigation.NavController
 import chat.revolt.R
+import chat.revolt.activities.WebChallengeActivity
 import chat.revolt.api.RevoltAPI
+import chat.revolt.api.internals.WebChallenge
 import chat.revolt.api.settings.GlobalState
 import chat.revolt.api.settings.SyncedSettings
 import chat.revolt.components.screens.splash.DisconnectedScreen
@@ -70,11 +75,19 @@ class SplashScreenViewModel @Inject constructor(
     }
 
     fun checkLoggedInState() {
+        Log.d("SplashScreenViewModel", "Checking logged in state")
         viewModelScope.launch {
             setIsConnected(hasInternetConnection())
 
             if (!isConnected) return@launch
 
+            val needsCloudflare = WebChallenge.needsCloudflare()
+
+            if (needsCloudflare) {
+                setNavigateTo("webchallenge")
+                return@launch
+            }
+
             val token = kvStorage.get("sessionToken") ?: return@launch setNavigateTo("login")
 
             val valid = RevoltAPI.checkSessionToken(token)
@@ -107,6 +120,8 @@ fun SplashScreen(
     navController: NavController,
     viewModel: SplashScreenViewModel = hiltViewModel()
 ) {
+    val context = LocalContext.current
+
     if (!viewModel.isConnected) {
         DisconnectedScreen(
             onRetry = {
@@ -143,6 +158,17 @@ fun SplashScreen(
                     }
                 }
             }
+
+            "webchallenge" -> {
+                context.startActivity(
+                    Intent(
+                        context,
+                        WebChallengeActivity::class.java
+                    )
+                )
+                viewModel.checkLoggedInState()
+            }
+
             "home" -> {
                 navController.navigate("chat") {
                     popUpTo("splash") {

app/src/main/res/layout/activity_webchallenge.xml

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <WebView
+        android:layout_width="match_parent"
+        android:layout_height="match_parent"
+        android:id="@+id/webView" />
+</androidx.constraintlayout.widget.ConstraintLayout>