MitM Attack against KeePass 2's Update Check

Metadata
===================================================
Release Date: 02-03-2016
Author: Florian Bogner @ Kapsch BusinessCom AG (https://www.kapsch.net/kbc)
Affected versions: all tested version up to the current 2.33
Tested on: Windows 7
CVE : CVE-2016-5119
URL: https://bogner.sh/2016/03/mitm-attack-against-keepass-2s-update-check/
Video: https://youtu.be/gOxcQSbpA-Q
Vulnerability Status: Won't fix

Abstract
===================================================
An attacker can abuse KeePass 2's recommended automatic update check – if enabled – to “release” a new version and redirect the user to a malicious download page.

Disclosure Timeline
===================================================
8.2.2016 @ 11:30: Issue privately reported to Dominik Reichl (http://keepass.info/contact.html)
8.2.2016 @ 12:00: CVE number requested
8.2.2016 @ 15:45: Received response from Dominik Reichl: The vulnerability will not be fixed. The indirect costs of switching to HTTPS (like lost advertisement revenue) make it a inviable solution.
30.5.2016 @ 18:00: MITRE assigned CVE-2016-5119; I reconfirmed that version 2.33 is still vulnerable

Technical Details
===================================================
During a recent traffic analysis I stumbled upon an interesting request to http://keepass.info/update/version2x.txt.gz. As I had a few hours spare I took a closer look.

It turned out that KeePass 2’s automatic update check uses HTTP to request the current version information. For that purpose it downloads the following text file from http://keepass.info/update/version2x.txt.gz

:
KeePass:2.31
ArcFour Cipher Plugin:2.0.9
CodeWallet3ImportPlugin:1
DataBaseBackup:2.0.8.6
DataBaseReorder:2.0.8
EnableGridLines:1.1
eWallet Liberated Data Importer:0.12
IOProtocolExt:1.11
ITanMaster:2.28.0.2
KdbxLite:1.1
KeeAutoExec:1.8
KeeOldFormatExport:1
KeeResize:1.7
KPScript - Scripting KeePass:2.31
OnScreenKeyboard2:1.2
OtpKeyProv:2.4
PwGen8U:1
PwGenBaliktad:1.2
QR Code Generator:2.0.12
QualityColumn:1.2
Sample Plugin for Developers:2.0.9
SpmImport:1.2
WinKee:2.28.0.1
:

If a new version is available a dialog is shown to the user. An attacker can modify – thought for example ARP spoofing or by providing a malicious Wifi Hotspot – the server response to introduce a new version and thereby force the new version dialog to be shown. (Already heard about the new KeePass 9 release?)

If the user now clicks within the update dialog to download the new version, the URL http://keepass.info/ is opened to manually download the new release. Guess what, we can also intercept that traffic as it again uses HTTP. Thereby an attacker can even indirectly control the downloaded “update”.

Suggested Solution
===================================================
For any security centric tool – like a password manager – it is essential to not expose its users to any additional risks.

Hence, I strongly recommend that all requests should be switch to encrypted HTTPS communication – especially version checks and updates! This should be fairly easy to implement and should not introduce any compatibility issues. Furthermore a valid certificate should be used for https://keepass.info and all unencrypted HTTP requests should be redirected to the encrypted version of the site. To provide even more security it is recommended to add the HTTP Strict Transport Security (HSTS) headers. As an alternative the update check feature could be removed.

Workaround
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Until the version check has been switched to HTTPS, update notifications should be taken with a grand of salt. To be on the safe side, new releases should be downloaded only directly from Keepass’s secured Sourceforge page: https://sourceforge.net/projects/keepass/
 

Florian Bogner | Security Solutions 
ICT Technology Solutions
Telefon Mobil +43 664 628 5491 | florian.bogner@kapsch.net <mailto:florian.bogner@kapsch.net>
 
Kapsch BusinessCom AG | Wienerbergstrasse 53 | 1120 Wien | Österreich 
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Firmenbuch HG Wien FN 178368g | Firmensitz Wien
 
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