Add option to only accept signed backups

app/src/main/java/org/shadowice/flocke/andotp/BackupActivity.java

@@ -25,6 +25,7 @@ import android.widget.TextView;
 import android.widget.Toast;
 
 import org.openintents.openpgp.OpenPgpError;
+import org.openintents.openpgp.OpenPgpSignatureResult;
 import org.openintents.openpgp.util.OpenPgpApi;
 import org.openintents.openpgp.util.OpenPgpServiceConnection;
 
@@ -404,29 +405,35 @@ public class BackupActivity extends AppCompatActivity {
         }
     }
 
+    public String outputStreamToString(ByteArrayOutputStream os) {
+        String string = "";
+        try {
+            string = os.toString("UTF-8");
+        } catch (UnsupportedEncodingException e) {
+            e.printStackTrace();
+        }
+
+        return string;
+    }
+
     public void handleOpenPGPResult(Intent result, ByteArrayOutputStream os, Uri file, int requestCode) {
         if (result.getIntExtra(OpenPgpApi.RESULT_CODE, OpenPgpApi.RESULT_CODE_ERROR) == OpenPgpApi.RESULT_CODE_SUCCESS) {
             if (requestCode == INTENT_ENCRYPT) {
-                if (os != null) {
+                if (os != null)
-                    String encrypted = "";
+                    doExportEncrypted(file, outputStreamToString(os));
-                    try {
-                        encrypted = os.toString("UTF-8");
-                    } catch (UnsupportedEncodingException e) {
-                        e.printStackTrace();
-                    }
-
-                    doExportEncrypted(file, encrypted);
-                }
             } else if (requestCode == INTENT_DECRYPT) {
                 if (os != null) {
-                    String decrypted = "";
+                    if (settings.getBoolean(getString(R.string.settings_key_openpgp_verify), false)) {
-                    try {
+                        OpenPgpSignatureResult sigResult = result.getParcelableExtra(OpenPgpApi.RESULT_SIGNATURE);
-                        decrypted = os.toString("UTF-8");
-                    } catch (UnsupportedEncodingException e) {
-                        e.printStackTrace();
-                    }
 
-                    doImportEncrypted(decrypted);
+                        if (sigResult.getResult() == OpenPgpSignatureResult.RESULT_VALID_KEY_CONFIRMED) {
+                            doImportEncrypted(outputStreamToString(os));
+                        } else {
+                            Toast.makeText(this, R.string.backup_toast_openpgp_not_verified, Toast.LENGTH_LONG).show();
+                        }
+                    } else {
+                        doImportEncrypted(outputStreamToString(os));
+                    }
                 }
             }
         } else if (result.getIntExtra(OpenPgpApi.RESULT_CODE, OpenPgpApi.RESULT_CODE_ERROR) == OpenPgpApi.RESULT_CODE_USER_INTERACTION_REQUIRED) {
@@ -446,7 +453,7 @@ public class BackupActivity extends AppCompatActivity {
             }
         } else if (result.getIntExtra(OpenPgpApi.RESULT_CODE, OpenPgpApi.RESULT_CODE_ERROR) == OpenPgpApi.RESULT_CODE_ERROR) {
             OpenPgpError error = result.getParcelableExtra(OpenPgpApi.RESULT_ERROR);
-            Toast.makeText(this, "OpenPGP Error: " + error.getMessage(), Toast.LENGTH_LONG).show();
+            Toast.makeText(this, String.format(getString(R.string.backup_toast_openpgp_error), error.getMessage()), Toast.LENGTH_LONG).show();
         }
     }
 }

app/src/main/res/values/strings_backup.xml

@@ -36,4 +36,6 @@
     <string name="backup_toast_import_failed">Import from external storage failed</string>
     <string name="backup_toast_storage_not_accessible">External storage currently not accessible</string>
     <string name="backup_toast_storage_permissions">Storage permissions not granted</string>
+    <string name="backup_toast_openpgp_error">OpenPGP Error: %s</string>
+    <string name="backup_toast_openpgp_not_verified">No verified signature detected</string>
 </resources>

app/src/main/res/values/strings_settings.xml

@@ -12,7 +12,8 @@
 
     <string name="settings_title_openpgp_provider">Select OpenPGP provider</string>
     <string name="settings_title_openpgp_keyid">Select OpenPGP key</string>
-    <string name="settings_title_openpgp_sign">Sign encrypted backups?</string>
+    <string name="settings_title_openpgp_sign">Sign encrypted backups</string>
+    <string name="settings_title_openpgp_verify">Verify encrypted backups</string>
 
     <!-- Descriptions -->
     <string name="settings_desc_tap_to_reveal">If enabled the OTP token is hidden by default and has
@@ -25,9 +26,10 @@
     <string name="settings_desc_auth_device_not_secure">This feature requires a secure lock screen
         to be set up (Settings -> Security -> Screenlock).</string>
 
-    <string name="settings_desc_openpgp_sign">Should the encrypted backups also be signed with your
+    <string name="settings_desc_openpgp_sign">Every encrypted backup is additionally signed with
-        key (requires password during each encryption)?
+        your key (requires password).</string>
-    </string>
+    <string name="settings_desc_openpgp_verify">Encrypted backups are only imported if they are
+        signed with a valid key.</string>
 
     <!-- Keys -->
     <string name="settings_key_tap_to_reveal" translatable="false">pref_tap_to_reveal</string>
@@ -36,5 +38,6 @@
     <string name="settings_key_openpgp_provider">pref_openpgp_provider</string>
     <string name="settings_key_openpgp_keyid">pref_openpgp_keyid</string>
     <string name="settings_key_openpgp_sign">pref_openpgp_sign</string>
+    <string name="settings_key_openpgp_verify">pref_openpgp_verify</string>
 
 </resources>

app/src/main/res/xml/preferences.xml

@@ -35,6 +35,12 @@
             android:summary="@string/settings_desc_openpgp_sign"
             android:defaultValue="false" />
 
+        <CheckBoxPreference
+            android:key="@string/settings_key_openpgp_verify"
+            android:title="@string/settings_title_openpgp_verify"
+            android:summary="@string/settings_desc_openpgp_verify"
+            android:defaultValue="false" />
+
     </PreferenceCategory>
 
 </PreferenceScreen>