Ensure that backupSecretRestoreRequired is properly set.

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

@@ -578,6 +578,9 @@ class AppRegistrationStorageController(private val context: Context) : StorageCo
       try {
         when (val result = BackupRepository.restoreRemoteBackup()) {
           is RemoteRestoreResult.Success -> {
+            // The restore adopted the account's existing SVRB chain, so there's nothing left for BackupMessagesJob to re-init.
+            SignalStore.backup.backupSecretRestoreRequired = false
+
             send(
               RemoteBackupRestoreProgress.Complete(
                 restoredSvrPin = SignalStore.svr.pin,
@@ -761,6 +764,13 @@ class AppRegistrationStorageController(private val context: Context) : StorageCo
       SignalStore.backup.mediaRootBackupKey = MediaRootBackupKey(it.toByteArray())
     }
 
+    if (accountData.reRegistration) {
+      // The account may already have SVRB data for this backup key. Until we've adopted that chain (either by restoring a backup, or by reading
+      // the remote metadata during the first BackupMessagesJob) we must not start a new chain, or the existing remote backup becomes unrestorable.
+      Log.i(TAG, "[applyAccountData] Re-registration. Marking that we need to restore SVRB secrets before backing up.")
+      SignalStore.backup.backupSecretRestoreRequired = true
+    }
+
     SignalStore.account.setServicePassword(accountData.servicePassword)
     SignalStore.account.setRegistered(registered = true, isAciChanged = isAciChanged)
     TextSecurePreferences.setPromptedPushRegistration(context, true)

app/src/test/java/org/thoughtcrime/securesms/registration/v2/AppRegistrationStorageControllerTest.kt

@@ -230,6 +230,34 @@ class AppRegistrationStorageControllerTest {
     assertThat(SignalStore.svr.hasOptedOut()).isTrue()
   }
 
+  @Test
+  fun `commit - re-registration - requires svrb secret restore before backing up`() = runBlocking<Unit> {
+    seedInProgressData(
+      RegistrationData(
+        accountData = accountData(reRegistration = true),
+        accountEntropyPool = aep.value
+      )
+    )
+
+    controller.commitRegistrationData()
+
+    assertThat(SignalStore.backup.backupSecretRestoreRequired).isTrue()
+  }
+
+  @Test
+  fun `commit - new account - does not require svrb secret restore`() = runBlocking<Unit> {
+    seedInProgressData(
+      RegistrationData(
+        accountData = accountData(reRegistration = false),
+        accountEntropyPool = aep.value
+      )
+    )
+
+    controller.commitRegistrationData()
+
+    assertThat(SignalStore.backup.backupSecretRestoreRequired).isFalse()
+  }
+
   @Test
   fun `commit - called twice - only applies account data once`() = runBlocking<Unit> {
     seedInProgressData(
@@ -396,7 +424,7 @@ class AppRegistrationStorageControllerTest {
 
   private fun readInProgressData(): RegistrationData = runBlocking { controller.readInProgressRegistrationData() }
 
-  private fun accountData(servicePassword: String = SERVICE_PASSWORD, linkedDeviceData: LinkedDeviceData? = null): AccountData {
+  private fun accountData(servicePassword: String = SERVICE_PASSWORD, linkedDeviceData: LinkedDeviceData? = null, reRegistration: Boolean = false): AccountData {
     return AccountData(
       aciIdentityKeyPair = aciIdentity.serialize().toByteString(),
       pniIdentityKeyPair = pniIdentity.serialize().toByteString(),
@@ -410,7 +438,8 @@ class AppRegistrationStorageControllerTest {
       pni = pni.toString(),
       e164 = E164,
       servicePassword = servicePassword,
-      linkedDeviceData = linkedDeviceData
+      linkedDeviceData = linkedDeviceData,
+      reRegistration = reRegistration
     )
   }
 }

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

@@ -683,6 +683,7 @@ class RegistrationRepository(val context: Context, val networkController: Networ
         this.aci = result.result.aci
         this.pni = result.result.pni
         this.servicePassword = keyMaterial.servicePassword
+        this.reRegistration = result.result.reregistration
       }
       storageController.commitRegistrationData()
     }

feature/registration/src/main/protowire/Registration.proto

@@ -45,6 +45,9 @@ message AccountData {
   bool fetchesMessages = 14;
 
   LinkedDeviceData linkedDeviceData = 15;
+
+  // Whether the service reported this registration as a re-registration of an existing account.
+  bool reRegistration = 16;
 }
 
 message SvrCredential {

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

@@ -141,6 +141,7 @@ class RegistrationEndToEndTest {
     assert(committed.accountData?.pni?.isNotEmpty() == true) { "Expected committed PNI to be populated" }
     assert(committed.pin == PIN) { "Expected committed pin $PIN but was ${committed.pin}" }
     assert(committed.accountEntropyPool.isNotEmpty()) { "Expected committed AEP to be populated" }
+    assert(committed.accountData?.reRegistration == false) { "Expected a new registration to not be flagged as a re-registration" }
 
     assert(networkController.lastCreateSessionE164 == E164) { "Expected a session for $E164 but was ${networkController.lastCreateSessionE164}" }
     assert(networkController.lastRegisterAccountRequest?.e164 == E164) { "Expected registration for $E164 but was ${networkController.lastRegisterAccountRequest}" }
@@ -643,6 +644,7 @@ class RegistrationEndToEndTest {
     assert(committed != null) { "Expected registration data to be committed" }
     assert(committed!!.accountData?.e164 == E164) { "Expected committed e164 $E164 but was ${committed.accountData?.e164}" }
     assert(committed.pin == PIN) { "Expected committed pin $PIN but was ${committed.pin}" }
+    assert(committed.accountData?.reRegistration == true) { "Expected the committed account data to be flagged as a re-registration" }
   }
 
   @Test