From 6c1a1fb9ad815062d4175873c2037d0fa608b555 Mon Sep 17 00:00:00 2001
From: Moxie Marlinspike <moxie@thoughtcrime.org>
Date: Mon, 23 Apr 2018 18:39:43 -0700
Subject: [PATCH] Use cache directory on removable storage for backups if
 present

Fixes #7692
---
 .../securesms/jobs/LocalBackupJob.java        |  2 +-
 .../securesms/util/StorageUtil.java           | 29 +++++++++++++++----
 2 files changed, 24 insertions(+), 7 deletions(-)

diff --git a/src/org/thoughtcrime/securesms/jobs/LocalBackupJob.java b/src/org/thoughtcrime/securesms/jobs/LocalBackupJob.java
index 9d556a2a2..f436cdde8 100644
--- a/src/org/thoughtcrime/securesms/jobs/LocalBackupJob.java
+++ b/src/org/thoughtcrime/securesms/jobs/LocalBackupJob.java
@@ -52,7 +52,7 @@ public class LocalBackupJob extends ContextJob {
 
     try {
       String backupPassword  = TextSecurePreferences.getBackupPassphrase(context);
-      File   backupDirectory = StorageUtil.getBackupDirectory(context);
+      File   backupDirectory = StorageUtil.getBackupCacheDirectory(context);
       String timestamp       = new SimpleDateFormat("yyyy-MM-dd-HH-mm-ss", Locale.US).format(new Date());
       String fileName        = String.format("signal-%s.backup", timestamp);
       File   backupFile      = new File(backupDirectory, fileName);
diff --git a/src/org/thoughtcrime/securesms/util/StorageUtil.java b/src/org/thoughtcrime/securesms/util/StorageUtil.java
index 6a7b160f9..2bcd34f0f 100644
--- a/src/org/thoughtcrime/securesms/util/StorageUtil.java
+++ b/src/org/thoughtcrime/securesms/util/StorageUtil.java
@@ -22,12 +22,7 @@ public class StorageUtil
       File[] directories = context.getExternalFilesDirs(null);
 
       if (directories != null) {
-        storage = Stream.of(directories)
-                        .withoutNulls()
-                        .filterNot(f -> f.getAbsolutePath().contains("emulated"))
-                        .limit(1)
-                        .findSingle()
-                        .orElse(null);
+        storage = getNonEmulated(directories);
       }
     }
 
@@ -52,6 +47,28 @@ public class StorageUtil
     return backups;
   }
 
+  public static File getBackupCacheDirectory(Context context) {
+    if (Build.VERSION.SDK_INT >= 19) {
+      File[] directories = context.getExternalCacheDirs();
+
+      if (directories != null) {
+        File result = getNonEmulated(directories);
+        if (result != null) return result;
+      }
+    }
+
+    return context.getExternalCacheDir();
+  }
+
+  private static @Nullable File getNonEmulated(File[] directories) {
+    return Stream.of(directories)
+                 .withoutNulls()
+                 .filterNot(f -> f.getAbsolutePath().contains("emulated"))
+                 .limit(1)
+                 .findSingle()
+                 .orElse(null);
+  }
+
   private static File getSignalStorageDir() throws NoExternalStorageException {
     final File storage = Environment.getExternalStorageDirectory();