From 6bf300ada8f152ad04ae70640fe5f977d625e69e Mon Sep 17 00:00:00 2001
From: Alex Hart <alex@signal.org>
Date: Mon, 9 Nov 2020 09:32:21 -0400
Subject: [PATCH] Do not require write to read from single backup uri.

---
 .../fragments/RestoreBackupFragment.java      |  6 +---
 .../securesms/util/BackupUtil.java            | 29 ++++++++++---------
 2 files changed, 17 insertions(+), 18 deletions(-)

diff --git a/app/src/main/java/org/thoughtcrime/securesms/registration/fragments/RestoreBackupFragment.java b/app/src/main/java/org/thoughtcrime/securesms/registration/fragments/RestoreBackupFragment.java
index 401695de88..766525d899 100644
--- a/app/src/main/java/org/thoughtcrime/securesms/registration/fragments/RestoreBackupFragment.java
+++ b/app/src/main/java/org/thoughtcrime/securesms/registration/fragments/RestoreBackupFragment.java
@@ -8,9 +8,7 @@ import android.graphics.Canvas;
 import android.graphics.Paint;
 import android.net.Uri;
 import android.os.AsyncTask;
-import android.os.Build;
 import android.os.Bundle;
-import android.provider.DocumentsContract;
 import android.text.Editable;
 import android.text.Spanned;
 import android.text.TextWatcher;
@@ -28,7 +26,6 @@ import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.annotation.RequiresApi;
 import androidx.appcompat.app.AlertDialog;
-import androidx.documentfile.provider.DocumentFile;
 import androidx.navigation.Navigation;
 
 import com.dd.CircularProgressButton;
@@ -52,7 +49,6 @@ import org.thoughtcrime.securesms.notifications.NotificationChannels;
 import org.thoughtcrime.securesms.service.LocalBackupListener;
 import org.thoughtcrime.securesms.util.BackupUtil;
 import org.thoughtcrime.securesms.util.DateUtils;
-import org.thoughtcrime.securesms.util.StorageUtil;
 import org.thoughtcrime.securesms.util.TextSecurePreferences;
 import org.thoughtcrime.securesms.util.Util;
 import org.thoughtcrime.securesms.util.concurrent.SimpleTask;
@@ -206,7 +202,7 @@ public final class RestoreBackupFragment extends BaseRegistrationFragment {
                          @NonNull Uri backupUri,
                          @NonNull OnBackupSearchResultListener listener)
   {
-    SimpleTask.run(() -> BackupUtil.getBackupInfoForUri(context, backupUri),
+    SimpleTask.run(() -> BackupUtil.getBackupInfoFromSingleUri(context, backupUri),
                    listener::run);
   }
 
diff --git a/app/src/main/java/org/thoughtcrime/securesms/util/BackupUtil.java b/app/src/main/java/org/thoughtcrime/securesms/util/BackupUtil.java
index 644c07bfa4..9704597ba6 100644
--- a/app/src/main/java/org/thoughtcrime/securesms/util/BackupUtil.java
+++ b/app/src/main/java/org/thoughtcrime/securesms/util/BackupUtil.java
@@ -6,6 +6,7 @@ import android.content.Context;
 import android.content.Intent;
 import android.net.Uri;
 import android.os.Build;
+import android.text.TextUtils;
 
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
@@ -166,15 +167,13 @@ public class BackupUtil {
   }
 
   @RequiresApi(29)
-  public static @Nullable BackupInfo getBackupInfoForUri(@NonNull Context context, @NonNull Uri uri) {
-    DocumentFile documentFile = DocumentFile.fromSingleUri(context, uri);
-
-    if (documentFile != null && documentFile.exists() && documentFile.canRead() && documentFile.canWrite() && documentFile.getName().endsWith(".backup")) {
-      long backupTimestamp = getBackupTimestamp(documentFile.getName());
+  public static @Nullable BackupInfo getBackupInfoFromSingleUri(@NonNull Context context, @NonNull Uri singleUri) {
+    DocumentFile documentFile = DocumentFile.fromSingleUri(context, singleUri);
 
+    if (isBackupFileReadable(documentFile)) {
+      long backupTimestamp = getBackupTimestamp(Objects.requireNonNull(documentFile.getName()));
       return new BackupInfo(backupTimestamp, documentFile.length(), documentFile.getUri());
     } else {
-      logIssueWithDocumentFile(documentFile);
       Log.w(TAG, "Could not load backup info.");
       return null;
     }
@@ -260,17 +259,21 @@ public class BackupUtil {
     return -1;
   }
 
-  private static void logIssueWithDocumentFile(@Nullable DocumentFile documentFile) {
+  private static boolean isBackupFileReadable(@Nullable DocumentFile documentFile) {
     if (documentFile == null) {
       throw new AssertionError("We do not support platforms prior to KitKat.");
     } else if (!documentFile.exists()) {
-      Log.w(TAG, "The document at the specified Uri cannot be found.");
+      Log.w(TAG, "isBackupFileReadable: The document at the specified Uri cannot be found.");
+      return false;
     } else if (!documentFile.canRead()) {
-      Log.w(TAG, "The document at the specified Uri cannot be read.");
-    } else if (!documentFile.canWrite()) {
-      Log.w(TAG, "The document at the specified Uri cannot be written to.");
-    } else if (!documentFile.getName().endsWith(".backup")) {
-      Log.w(TAG, "The document at the specified Uri has an unsupported file extension.");
+      Log.w(TAG, "isBackupFileReadable: The document at the specified Uri cannot be read.");
+      return false;
+    } else if (TextUtils.isEmpty(documentFile.getName()) || !documentFile.getName().endsWith(".backup")) {
+      Log.w(TAG, "isBackupFileReadable: The document at the specified Uri has an unsupported file extension.");
+      return false;
+    } else {
+      Log.i(TAG, "isBackupFileReadable: The document at the specified Uri looks like a readable backup");
+      return true;
     }
   }