Unix: preserve requested protection when mounting favorites

Keep caller protection unless a favorite requires read-only access.
Reuse cached outer credentials when recovering hidden-protection errors.

src/Main/FavoriteVolume.cpp

@@ -92,7 +92,9 @@ namespace VeraCrypt
 
 		options.Path.reset (new VolumePath (Path));
 		options.PartitionInSystemEncryptionScope = System;
-		options.Protection = (ReadOnly ? VolumeProtection::ReadOnly : VolumeProtection::None);
+		// A favorite may require read-only access, but must not weaken requested protection.
+		if (ReadOnly)
+			options.Protection = VolumeProtection::ReadOnly;
 		options.SlotNumber = SlotNumber;
 	}
 }

src/Main/UserInterface.cpp

@@ -847,13 +847,15 @@ namespace VeraCrypt
 					newMountedVolumes.push_back (Core->MountVolume (favoriteOptions));
 					mountPerformed = true;
 				}
-				catch (PasswordException&)
+				catch (PasswordException &e)
 				{
 					CloseSecurityTokenSessionsAfterMountScope closeTokenSessionsScope (Preferences.CloseSecurityTokenSessionsAfterMount);
 
-					// The initial silent mount attempt has already consulted cached passwords.
-					// Avoid repeating the same failed cache sweep before prompting the user.
-					shared_ptr <VolumeInfo> volume = MountVolume (favoriteOptions, false);
+					// A protection failure accepted the outer password. Let the UI recover
+					// using that cache; only skip a cache sweep that failed outer authentication.
+					bool protectionError = dynamic_cast <ProtectionPasswordIncorrect *> (&e)
+						|| dynamic_cast <ProtectionPasswordKeyfilesIncorrect *> (&e);
+					shared_ptr <VolumeInfo> volume = MountVolume (favoriteOptions, protectionError);
 
 					if (!volume)
 						break;