CSNC-2016-002 - Open Redirect in OpenAM

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# COMPASS SECURITY ADVISORY http://www.csnc.ch/en/downloads/advisories.html
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# CSNC ID:          CSNC-2016-002
# Product:          OpenAM [1]
# Vendor:           ForgeRock
# Subject:           Open Redirect
# Risk:                  Critical
# Effect:              Remotely exploitable
# Author:            Stephan Sekula (stephan.sekula@csnc.de)
# Date:                 February 23rd 2016
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Introduction:
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OpenAM provides core identity services to simplify the implementation of
transparent single sign-on (SSO) as a security component in a network
infrastructure. OpenAM provides the foundation for integrating diverse
web applications that might typically operate against a disparate set of
identity repositories and are hosted on a variety of platforms such as
web and application servers. [1]

Compass Security discovered a web application security flaw in the OpenAM
application which allows an attacker to launch phishing attacks against users
by redirecting them to a malicious website. An attacker is able to create a
link that, when visited, will redirect the user to a website of the attacker's
choosing once the victim attempts to login. This allows, for instance,
phishing of user credentials. Since it is the victim who needs to visit the
malicious link, this attack is possible for unauthenticated attackers who do
not have access to the affected websites.


Affected Versions:
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The following OpenAM versions are vulnerable:
- 9.5.5
- 10.0.2
- 10.1.0-Xpress
- 11.0.0-11.0.3
- 12.0.0-12.0.2

OpenAM version 13.0.0 is not vulnerable.


Patches:
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OpenAM released patches for each affected version as part of OpenAM
Security Advisory #201601 [2].


Technical Description:
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OpenAM provides a whitelist mechanism that allows specifying allowed
redirection URLs. If user input is not part of this whitelist, the user should
be redirected to an error page. However, this mechanism only works for
parameter values of the form "http://www.csnc.de" and "www.csnc.de". Parameter
values such as "//www.csnc.de" will not be caught, thus effectively bypassing
the whitelist mechanism.

Example:
/openam_sp/UI/Login?goto=//www.csnc.de&gotoOnFail=//www.csnc.de

Exploiting the vulnerability will lead to redirections to arbitrary websites
which allows phishing of user credentials.


Milestones:
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2015-12-16: Vulnerability discovered
2016-01-04: Vendor notified
2016-02-05: Vendor provided patched version
2016-02-23: Public disclosure


References:
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[1] http://openam.forgerock.org/
[2] https://forgerock.org/2016/02/openam-security-advisory-201601/