Handle missing sessions when submitting captcha in regV5.

app/src/main/java/org/thoughtcrime/securesms/registration/v2/AppRegistrationNetworkController.kt

@@ -212,6 +212,9 @@ class AppRegistrationNetworkController(
           400 -> {
             RequestResult.NonSuccess(UpdateSessionError.InvalidRequest(response.body.string()))
           }
+          404 -> {
+            RequestResult.NonSuccess(UpdateSessionError.SessionNotFound(response.body.string()))
+          }
           409 -> {
             RequestResult.NonSuccess(UpdateSessionError.RejectedUpdate(response.body.string()))
           }

demo/registration/src/main/java/org/signal/registration/sample/dependencies/DemoNetworkController.kt

@@ -214,6 +214,9 @@ class DemoNetworkController(
           400 -> {
             RequestResult.NonSuccess(UpdateSessionError.InvalidRequest(response.body.string()))
           }
+          404 -> {
+            RequestResult.NonSuccess(UpdateSessionError.SessionNotFound(response.body.string()))
+          }
           409 -> {
             RequestResult.NonSuccess(UpdateSessionError.RejectedUpdate(response.body.string()))
           }

feature/registration/src/main/java/org/signal/registration/NetworkController.kt

@@ -371,6 +371,7 @@ interface NetworkController {
 
   sealed class UpdateSessionError : BadRequestError {
     data class RejectedUpdate(val message: String) : UpdateSessionError()
+    data class SessionNotFound(val message: String) : UpdateSessionError()
     data class InvalidRequest(val message: String) : UpdateSessionError()
     data class RateLimited(val retryAfter: Duration, val session: SessionMetadata) : UpdateSessionError()
   }

feature/registration/src/main/java/org/signal/registration/screens/phonenumber/PhoneNumberEntryViewModel.kt

@@ -544,6 +544,11 @@ class PhoneNumberEntryViewModel(
             updateResult.result
           }
           is RequestResult.NonSuccess -> {
+            if (updateResult.error is NetworkController.UpdateSessionError.SessionNotFound) {
+              Log.w(TAG, "[SubmitPushChallengeToken] Session not found when submitting push challenge token.")
+              parentEventEmitter(RegistrationFlowEvent.ResetState)
+              return state
+            }
             Log.w(TAG, "[SubmitPushChallengeToken] Failed to submit push challenge token: ${updateResult.error}")
             sessionMetadata
           }
@@ -658,6 +663,11 @@ class PhoneNumberEntryViewModel(
           is NetworkController.UpdateSessionError.RejectedUpdate -> {
             state.copy(dialogs = state.dialogs.copy(unknownError = true))
           }
+          is NetworkController.UpdateSessionError.SessionNotFound -> {
+            Log.w(TAG, "[SubmitCaptcha] Session not found when submitting captcha token.")
+            parentEventEmitter(RegistrationFlowEvent.ResetState)
+            state
+          }
           is NetworkController.UpdateSessionError.RateLimited -> {
             state.copy(dialogs = state.dialogs.copy(rateLimitedRetryAfter = error.retryAfter))
           }

feature/registration/src/test/java/org/signal/registration/RegistrationEndToEndTest.kt

@@ -8,6 +8,9 @@ package org.signal.registration
 import android.app.Application
 import android.net.Uri
 import android.os.Looper
+import android.view.View
+import android.view.ViewGroup
+import android.webkit.WebView
 import androidx.activity.compose.LocalActivityResultRegistryOwner
 import androidx.activity.result.ActivityResultRegistry
 import androidx.activity.result.ActivityResultRegistryOwner
@@ -15,6 +18,8 @@ import androidx.activity.result.contract.ActivityResultContract
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.CompositionLocalProvider
 import androidx.compose.runtime.remember
+import androidx.compose.ui.InternalComposeUiApi
+import androidx.compose.ui.platform.ViewRootForTest
 import androidx.compose.ui.semantics.SemanticsProperties
 import androidx.compose.ui.semantics.getOrNull
 import androidx.compose.ui.test.junit4.createComposeRule
@@ -50,6 +55,7 @@ import org.signal.registration.NetworkController.RegistrationLockResponse
 import org.signal.registration.NetworkController.RestoreMasterKeyError
 import org.signal.registration.NetworkController.RestoreMethod
 import org.signal.registration.NetworkController.SvrCredentials
+import org.signal.registration.NetworkController.UpdateSessionError
 import org.signal.registration.fakes.FakeNetworkController
 import org.signal.registration.fakes.FakeStorageController
 import org.signal.registration.fakes.SystemOutLogger
@@ -68,7 +74,7 @@ import kotlin.time.Duration.Companion.days
  * The fakes default to a happy path. To exercise other navigation paths, override the relevant
  * response handler on [networkController] or state on [storageController] before driving the UI.
  */
-@OptIn(ExperimentalPermissionsApi::class)
+@OptIn(ExperimentalPermissionsApi::class, InternalComposeUiApi::class)
 @RunWith(RobolectricTestRunner::class)
 @Config(application = Application::class)
 class RegistrationEndToEndTest {
@@ -134,6 +140,44 @@ class RegistrationEndToEndTest {
     assert(storageController.restoreDecision == RestoreDecision.NEW_ACCOUNT) { "Expected NEW_ACCOUNT restore decision but was ${storageController.restoreDecision}" }
   }
 
+  @Test
+  fun `a captcha submission for a session that no longer exists resets the flow, which can then be restarted to completion`() {
+    // The session demands a captcha, but expires server-side before the solved captcha is submitted
+    networkController.onCreateSession = {
+      RequestResult.Success(networkController.session(allowedToRequestCode = false, requestedInformation = listOf("captcha")))
+    }
+    networkController.onUpdateSession = {
+      RequestResult.NonSuccess(UpdateSessionError.SessionNotFound("no session found"))
+    }
+
+    var registrationComplete = false
+    launchRegistrationFlow(onRegistrationComplete = { registrationComplete = true })
+
+    submitPhoneNumber()
+    solveCaptcha("captcha-token")
+
+    // The server no longer knows the session, so the flow resets back to the beginning
+    waitForTag(TestTags.WELCOME_SCREEN)
+    assert(networkController.lastUpdateSessionRequest?.captchaToken == "captcha-token") {
+      "Expected the solved captcha to be submitted but was ${networkController.lastUpdateSessionRequest}"
+    }
+    assert(storageController.committedData == null) { "Expected no registration data to be committed" }
+
+    // Starting over against a healthy server completes registration
+    networkController.onCreateSession = { RequestResult.Success(networkController.session()) }
+    networkController.onUpdateSession = { RequestResult.Success(networkController.session()) }
+
+    submitPhoneNumber()
+    submitVerificationCode(VERIFICATION_CODE)
+    createPin(PIN)
+
+    waitFor("registration to complete") { registrationComplete }
+
+    val committed = storageController.committedData
+    assert(committed != null) { "Expected registration data to be committed" }
+    assert(committed!!.accountData?.e164 == E164) { "Expected committed e164 $E164 but was ${committed.accountData?.e164}" }
+  }
+
   @Test
   fun `a registration lock is unlocked by entering the existing pin and registration completes`() {
     val masterKey = MasterKey(ByteArray(32) { it.toByte() })
@@ -1094,6 +1138,33 @@ class RegistrationEndToEndTest {
     composeTestRule.onNodeWithTag(TestTags.REMOTE_BACKUP_RESTORE_RESTORE_BUTTON).performClick()
   }
 
+  /**
+   * From the captcha screen: simulates the user solving the captcha by driving the WebView's client with the
+   * `signalcaptcha://` redirect that a real solve produces.
+   */
+  @Suppress("DEPRECATION")
+  private fun solveCaptcha(token: String) {
+    var webView: WebView? = null
+    waitFor("the captcha WebView") {
+      val composeView = (composeTestRule.onNodeWithTag(TestTags.CAPTCHA_SCREEN).fetchSemanticsNode().root as ViewRootForTest).view
+      webView = findWebView(composeView)
+      webView != null
+    }
+    webView!!.let { Shadows.shadowOf(it).webViewClient.shouldOverrideUrlLoading(it, "signalcaptcha://$token") }
+  }
+
+  private fun findWebView(view: View): WebView? {
+    if (view is WebView) {
+      return view
+    }
+    if (view is ViewGroup) {
+      for (i in 0 until view.childCount) {
+        findWebView(view.getChildAt(i))?.let { return it }
+      }
+    }
+    return null
+  }
+
   /** From the verification code screen: enters all six digits of [code], which submits automatically. */
   private fun submitVerificationCode(code: String) {
     waitForTag(TestTags.VERIFICATION_CODE_DIGIT_0)

feature/registration/src/test/java/org/signal/registration/screens/phonenumber/PhoneNumberEntryViewModelTest.kt

@@ -1121,6 +1121,33 @@ class PhoneNumberEntryViewModelTest {
       .isInstanceOf<RegistrationRoute.Captcha>()
   }
 
+  @Test
+  fun `PhoneNumberSubmitted with push challenge resets state when session not found`() = runTest {
+    val sessionWithPushChallenge = createSessionMetadata(requestedInformation = listOf("pushChallenge"))
+
+    coEvery { mockRepository.createSession(any()) } returns
+      RequestResult.Success(sessionWithPushChallenge)
+    coEvery { mockRepository.awaitPushChallengeToken() } returns "test-push-challenge-token"
+    coEvery { mockRepository.submitPushChallengeToken(any(), any()) } returns
+      RequestResult.NonSuccess(
+        NetworkController.UpdateSessionError.SessionNotFound("Session expired")
+      )
+
+    val initialState = PhoneNumberEntryState(
+      countryCode = "1",
+      nationalNumber = "5551234567"
+    )
+
+    viewModel.applyEvent(initialState, PhoneNumberEntryScreenEvents.PhoneNumberConfirmed, parentEventEmitter, stateEmitter)
+
+    // Verify spinner states
+    assertThat(emittedStates.first().showSpinner).isTrue()
+    assertThat(emittedStates.last().showSpinner).isFalse()
+
+    assertThat(emittedEvents).hasSize(1)
+    assertThat(emittedEvents.first()).isEqualTo(RegistrationFlowEvent.ResetState)
+  }
+
   // ==================== CaptchaCompleted Tests ====================
 
   @Test
@@ -1203,6 +1230,22 @@ class PhoneNumberEntryViewModelTest {
     assertThat(emittedStates.last().dialogs.unknownError).isTrue()
   }
 
+  @Test
+  fun `CaptchaCompleted handles session not found`() = runTest {
+    val sessionMetadata = createSessionMetadata()
+    val initialState = PhoneNumberEntryState(sessionMetadata = sessionMetadata)
+
+    coEvery { mockRepository.submitCaptchaToken(any(), any()) } returns
+      RequestResult.NonSuccess(
+        NetworkController.UpdateSessionError.SessionNotFound("Session expired")
+      )
+
+    viewModel.applyEvent(initialState, PhoneNumberEntryScreenEvents.CaptchaCompleted("captcha-token"), parentEventEmitter, stateEmitter)
+
+    assertThat(emittedEvents).hasSize(1)
+    assertThat(emittedEvents.first()).isEqualTo(RegistrationFlowEvent.ResetState)
+  }
+
   @Test
   fun `CaptchaCompleted handles network error`() = runTest {
     val sessionMetadata = createSessionMetadata()