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SYMSA-2006-003: Cisco Secure ACS for Windows - Administrator Password Disclosure



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                    Symantec Vulnerability Research                             
      
                    https://www.symantec.com/research
                          Security Advisory

Advisory ID   : SYMSA-2006-003
Advisory Title: Cisco Secure ACS for Windows - Administrator 
                Password Disclosure
Author        : Andreas Junestam
Release Date  : 05-08-2006
Application   : Cisco Secure ACS 3.x for Windows
Platform      : Microsoft Windows
Severity      : System access / exploit available 
Vendor status : Vendor verified, workaround available
CVE Number    : CVE-2006-0561
Reference     : http://www.securityfocus.com/bid/16743


Overview: 

        Cisco Secure ACS is a central administration platform for 
        Cisco network devices. It controls authentication and 
        authorization for enrolled devices. Administrative 
        passwords for locally-defined users are stored in such a 
        way they can be obtained from the Windows registry. If 
        remote registry access is enabled, this can be done over 
        the network.

        If Cisco Secure ACS is configured to use an external 
        authentication service such as Windows Active Directory or
        LDAP, the passwords for users stored by those services are
        not vulnerable to this issue.


Details: 

        Cisco Secure ACS 3.x for Windows stores passwords for 
        administrative users in the registry. The passwords are 
        encrypted using the Crypto API Microsoft Base Cryptographic 
        Provider v1.0. Along with the passwords, ACS also stores 
        the key used to encrypt the information. This information 
        can easily be obtained locally by a Windows administrator, 
        and if remote registry access is enabled, it can be 
        obtained over the network. With this, the clear-text 
        passwords can be recovered by decrypting the information 
        in the registry with the supplied key. Access to these 
        passwords provides access to all Cisco devices controlled 
        by the ACS server.


Vendor Response:


        Cisco Secure ACS 3.x for Windows stores the passwords of 
        ACS administrators in the Windows registry in an encrypted 
        format. A locally generated master key is used to 
        encrypt/decrypt the ACS administrator passwords. The master
        key is also stored in the Windows registry in an encrypted 
        format. Using Microsoft cryptographic routines, it is 
        possible for a user with administrative privileges to a 
        system running Cisco Secure ACS to obtain the clear-text 
        version of the master key. With the master key, the user 
        can decrypt and obtain the clear-text passwords for all 
        ACS administrators. With administrative credentials to 
        Cisco Secure ACS, it is possible to change the password 
        for any locally defined users. This may be used to gain 
        access to network devices configured to use Cisco Secure 
        ACS for authentication.

        If remote registry access is enabled on a system running 
        Cisco Secure ACS, it is possible for a user with
        administrative privileges (typically domain administrators) 
        to exploit this vulnerability.

        If Cisco Secure ACS is configured to use an external 
        authentication service such as Windows Active Directory / 
        Domains or LDAP, the passwords for users stored by those 
        services are not at risk to compromise via this 
        vulnerability.

        This vulnerability only affects version 3.x of Cisco Secure 
        ACS for Windows. Cisco Secure ACS for Windows 4.0.1 and Cisco 
        Secure ACS for UNIX are not vulnerable. Cisco Secure ACS 3.x 
        appliances do not permit local or remote Windows registry 
        access and are not vulnerable.
     
Workaround:

        It is possible to mitigate this vulnerability by 
        restricting access to the registry key containing the 
        ACS administrators' passwords. One feature of Windows 
        operating systems is the ability to modify the permissions 
        of a registry key to remove access even for local or 
        domain administrators. Using this feature, the registry 
        key containing the ACS administrators' passwords can be 
        restricted to only the Windows users with a need to 
        maintain the ACS installation or operate the ACS services.

        The following registry key and all of its sub-keys need to 
        be protected.

HKEY_LOCAL_MACHINE\SOFTWARE\Cisco\CiscoAAAv3.3\CSAdmin\Administrators

        Note: The "CiscoAAAv3.3" portion of the registry key path
        may differ slightly depending on the version of Cisco Secure
        ACS for Windows that is installed.

        There are two general deployment scenarios for Cisco Secure
        ACS. The Windows users that need permissions to the registry
        key will depend on the deployment type.

        * If Cisco Secure ACS is not installed on a Windows domain 
        controller, access to the registry key should be limited to
        only the local Windows SYSTEM account and specific local / 
        domain administrators who will be performing software 
        maintenance on the ACS installation. 
        
        * If Cisco Secure ACS is installed on a Windows domain 
        controller, access to the registry key should be limited to 
        the domain account which ACS is configured to use for its 
        services, the local Windows SYSTEM account and specific 
        local / domain administrators who will be performing 
        software maintenance on the ACS installation.

        For information about editing the Windows registry, please 
        consult the following Microsoft documentation.

        "Description of the Microsoft Windows registry"

        http://support.microsoft.com/default.aspx?scid=kb;EN-US;256986

        Further mitigation against remote exploitation can be 
        achieved by restricting access to authorized users or 
        disabling remote access to the Windows registry on systems
        running Cisco Secure ACS for Windows. For information on
        restricting remote registry access, please consult the
        following Microsoft documentation.

        "How to restrict access to the registry from a remote computer"

        http://support.microsoft.com/kb/q153183

        "How to Manage Remote Access to the Registry"

        http://support.microsoft.com/kb/q314837
        
Recommendation:
        
        Follow your organization's testing procedures before 
        applying patches or workarounds.  See Cisco's instructions
        on how to place an ACL on the Registry Key, and also how 
        to restrict remote access to the Windows registry.

        These recommendations do not eliminate the vulnerability, 
        but provide some mitigation.


Common Vulnerabilities and Exposures (CVE) Information:

The Common Vulnerabilities and Exposures (CVE) project has assigned 
the following names to these issues.  These are candidates for 
inclusion in the CVE list (http://cve.mitre.org), which standardizes 
names for security problems.


        CVE-2006-0561

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