Entering a Special Device Name in the Favorites of WinRAR Crashes the Application

 

Summary

We are going to perform Risk Based testing by inputting reserved device names for filenames in WinRAR v3.30. It turns out that the application allows the user to enter a reserved device name like AUX or COM1 in the Favorites - > Add to Favorites input box. When the newly added favorite is selected, the application tries to access the Windows device and crashes.

Application Description

WinRAR is an archive manager. It can backup data and reduce size of email attachments, decompress RAR, ZIP and other files downloaded from Internet and create new archives in RAR and ZIP file format. (Source: www.rarsoft.com).

For our tests we will focus on these two functions:

Favorites -> Add to favorites

 

File -> Open archive

The first function allows the user to add a directory or an archive to a list of favorites, so that it can be accessed faster later. The second function allows the user to browse for an existing archive, which can be later decompressed, deleted, and so on.

Test Design

This example demonstrates the use of attacks in Risk Based Testing. One possible risk is that the application will fail to recognize a reserved device name in the input, and will try to access it as if it were a file. (Exploring allowable character sets and data types - James Whittaker, How to break Software). Some of the reserved device names are CON, AUX, NUL, PRN, LPT1, and COM1.

To apply this test we have to identify input fields that will be used by the application as file names to access files. Two examples of such fields are offered by the functions Favorites -> Add to favorites and File -> Open archive. We will enter the reserved name in these fields and examine the results.

The expected (correct) behavior is that the application will refuse to accept such device name as an input and will show a correct error message instead.

Performing the Test

  1. Select Favorites - > Add to favorites.


  2. The Add favorite input box appears. Let's try entering aux in the first field. Click "OK".

  3. The application accepted the input. Now the question is: if we click on the first entry, will WinRAR try to open aux as if it were an archive? Let's see what will happen.

Results/Relevance

It looks like the application tried to access the device and failed, which caused it to crash.


Probably many of the of the WinRAR users wouldn’t know that there are reserved device names, so there has to be code to prevent them from entering such names and crashing the application.

Since there is very small probability that the user will enter such name by accident, this bug most likely wouldn't be very interesting to developers.

This kind of bug is unlikely to be found by any other type of testing.

Similar Tests

We can apply this test to other fields. For example, we can test the Open Archives function. To open archives the application uses the common dialog box. Usually common dialog boxes do not allow entering reserved device names but let’s try it anyway. Enter aux and click "Open".

 

The input was not accepted and the correct error message was displayed. This is a good example of how the application should respond to such invalid input.

The test didn't cause the application to fail in this case, but if we try it with Commands -> Add files to archive, it would expose the bug previously described.

Configuration Notes

Testing RarSoft's WinRAR v3.30 (evaluation version):

Created 19 May 2004 for the CSTER

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