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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