Citrix XenDesktop 7.x Delivery Controller Security Technical Implementation Guide

Version/Release: V1R3
Published: 2020-03-27
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This Security Technical Implementation Guide is published as a tool to improve the security of Department of Defense (DoD) information systems. The requirements are derived from the National Institute of Standards and Technology (NIST) 800-53 and related documents. Comments or proposed revisions to this document should be sent via email to the following address: disa.stig_spt@mail.mil.

Delivery Controller must limit the number of concurrent sessions to an organization-defined number for all accounts and/or account types.

AC-10 - Medium - CCI-000054 - V-81403 - SV-96117r1_rule

RMF Control

AC-10

Severity

Medium

CCI

CCI-000054

Version

CXEN-DC-000005

Vuln IDs

V-81403

Rule IDs

SV-96117r1_rule

Application management includes the ability to control the number of users and user sessions that utilize an application. Limiting the number of allowed users and sessions per user is helpful in limiting risks related to Denial-of-Service (DoS) attacks. This requirement may be met via the application or by using information system session control provided by a web server with specialized session management capabilities. If it has been specified that this requirement will be handled by the application, the capability to limit the maximum number of concurrent single user sessions must be designed and built into the application. This requirement addresses concurrent sessions for information system accounts and does not address concurrent sessions by single users via multiple system accounts. The maximum number of concurrent sessions should be defined based on mission needs and the operational environment for each system.

Checks: C-81133r1_chk

Open Citrix Studio, right-click a Delivery Group, and choose "Edit Delivery Group". Verify the following check box is not checked: "Give access to unauthenticated (anonymous) users; no credentials are required to access StoreFront". If the check box is checked, this is a finding. A Citrix Studio administrator account is needed to perform this check. Performing this check does not impact system reliability or availability.

Fix: F-88209r1_fix

Open Citrix Studio, right-click a Delivery Group, and choose "Edit Delivery Group". Uncheck the following check box: "Give access to unauthenticated (anonymous) users; no credentials are required to access StoreFront". A Citrix Studio administrator account is needed to perform above fix.

Delivery Controller must be configured to disable non-essential capabilities.

CM-7 - Medium - CCI-000381 - V-81407 - SV-96121r1_rule

RMF Control

CM-7

Severity

Medium

CCI

CCI-000381

Version

CXEN-DC-000270

Vuln IDs

V-81407

Rule IDs

SV-96121r1_rule

It is detrimental for applications to provide or install by default functionality exceeding requirements or mission objectives. These unnecessary capabilities or services are often overlooked and therefore may remain unsecured. They increase the risk to the platform by providing additional attack vectors. Applications are capable of providing a wide variety of functions and services. Some of the functions and services provided by default may not be necessary to support essential organizational operations (e.g., key missions, functions). Examples of non-essential capabilities include but are not limited to advertising software or browser plug-ins not related to requirements or providing a wide array of functionality not required for every mission but that cannot be disabled.

Checks: C-81137r1_chk

Verify Citrix Customer Experience Improvement Program (CEIP) - PHONE HOME is disabled on XenDesktop Delivery Controller. 1. Launch Studio. 2. Select "Configuration" in the left navigation pane. 3. Select the Support tab. 4. Verify CEIP is disabled. If CEIP is not disabled, this is a finding.

Fix: F-88213r1_fix

To disable Citrix CEIP - Phone Home: 1. Launch Studio. 2. Select "Configuration" in the left navigation pane. 3. Select the Support tab. 4. Follow the prompts to end participation in CEIP. This prevents automatic upload of installation experience metrics that are collected locally during installation. XenDesktopServerStartup.exe /components "CONTROLLER,DESKTOPSTUDIO" /disableexperiencemetrics /exclude "Smart Tools Agent" /nosql /quiet /verboselog /noreboot

Delivery Controller must implement NIST FIPS-validated cryptography for the following: to provision digital signatures; to generate cryptographic hashes; and to protect unclassified information requiring confidentiality and cryptographic protection in accordance with applicable federal laws, Executive Orders, directives, policies, regulations, and standards.

SC-13 - High - CCI-002450 - V-81409 - SV-96123r2_rule

RMF Control

SC-13

Severity

High

CCI

CCI-002450

Version

CXEN-DC-001225

Vuln IDs

V-81409

Rule IDs

SV-96123r2_rule

Use of weak or untested encryption algorithms undermines the purposes of using encryption to protect data. The application must implement cryptographic modules adhering to the higher standards approved by the Federal Government since this provides assurance they have been tested and validated.

Checks: C-81139r15_chk

Enforcement is via FIPS encryption. To verify, open the Registry Editor on the XenDesktop Delivery Controller and find the following key name: HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\DesktopServer 1. Verify that the XmlServicesSslPort registry key exists with the correct value for SSL port. By default, it is set to "443". 2. Verify XmlServicesEnableNonSsl is set to "0". 3. Verify the corresponding registry value to ignore HTTPS traffic, XmlServicesEnableSsl, is not set to "0". If "XmlServicesSslPort" is not set to the desired port, this is a finding. If "XmlServicesEnableNonSsl" is not set to "0", this is a finding. If XmlServicesEnableSsl is not set to "1", this is a finding. To verify the FIPS Cipher Suites used: 1. From the Group Policy Management Console, go to Computer Configuration >> Administrative Templates >> Networks >> SSL Configuration Settings. 2. Double-click "SSL Cipher Suite Order" and verify the "Enabled" option is checked. 3. Verify the correct Cipher Suites are listed in the correct order per current DoD guidelines. If the "Enabled" option is not checked or the correct Cipher Suites are not listed in the correct order per current DoD guidelines, this is a finding.

Fix: F-88215r4_fix

Obtain and install root certificate(s) for server certificates installed on Desktop/Server VDAs, SQL Server(s), Storefront, and VM Host (VMware VCenter, Hyper-V, XenServer). To install a TLS server certificate on the Delivery Controller and to configure a port with TLS 1.x: 1. Log on to the Delivery Controller server with a domain account that has Administrator rights. 2. Obtain a TLS server certificate and install it on the Delivery Controller using Microsoft server instructions. 3. Configure the Delivery Controller with the certificate. When the Server Certificate is installed on IIS, set the Bindings to enable HTTPS on IIS by completing the following procedure: 1. Select the IIS site that you want to enable HTTPS and select "Bindings" under "Edit Site". 2. Click "Add", select "Type" as https and port number as "443". Select the SSL Certificate that was installed and click "OK". 3. Open the Registry Editor on the XenDesktop Controller and find the following key name: HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\DesktopServer 4. Verify that XmlServicesSslPort registry key exists with the correct value for SSL port. By default, it is set to "443". 5. Change the XML service port using PowerShell or by running the following command: BrokerService –WiSslPort <port number> Notes: a) If you decide to change the XML service port number on the XenDesktop controller, update the IIS port number as well under "Bindings" to match the new value. b) On XenDesktop 7.11, the parameter of brokerservice.exe has changed from "wisslport" to "storefronttlsport". The brokerservice.exe is found in c:\program files\citrix\broker\service. A reboot of the Delivery Controller is needed for this to take effect. To change the default VDA registration port: 1. Log on to the Delivery Controller server with a domain account that has Administrator rights. 2. Open the command prompt window and type these commands: %SystemDrive% Cd %ProgramFiles%\Citrix\Broker\Service BrokerService.exe –VDAport 8888 3. Launch Server Manager from the Start menu. 4. In the Server Manager, go to the "Local Server" properties window and edit the "Windows Firewall" setting. Click "Advanced Settings". 5. Click "Inbound Rules". 6. Create a new inbound rule with the following settings: a) In the Rule type screen, click "Port". Click "Next". b) In the Protocol and Ports screen, select "Specific local ports" and type "8888". Click "Next". c) In the Action screen, accept the default value "Allow the connection" and click "Next". d) In the Profile screen, accept the default values and click "Next". e) In the Name screen, type a name for the rule (example: Citrix VDA Registration Port) and click "Finish". For correct Cipher Suite order per DoD guidance: Apply the following to Computers OU containing XenDesktop infrastructure: - XD2017 CC - Computer - SSL Ciphersuite Order To configure the SSL Cipher Suite Order Group Policy setting manually, follow these steps: 1. At a command prompt, enter "gpedit.msc", and press "Enter". The Local Group Policy Editor is displayed. 2. Go to Computer Configuration >> Administrative Templates >> Network >> SSL Configuration Settings. 3. Under SSL Configuration Settings, select "SSL Cipher Suite Order". 4. In the SSL Cipher Suite Order pane, scroll to the bottom. Follow the instructions that are labeled "How to modify this setting".

Delivery Controller must be configured in accordance with the security configuration settings based on DoD security configuration or implementation guidance, including STIGs, NSA configuration guides, CTOs, and DTMs.

CM-6 - Medium - CCI-000366 - V-81411 - SV-96125r2_rule

RMF Control

CM-6

Severity

Medium

CCI

CCI-000366

Version

CXEN-DC-001235

Vuln IDs

V-81411

Rule IDs

SV-96125r2_rule

Configuring the application to implement organization-wide security implementation guides and security checklists ensures compliance with federal standards and establishes a common security baseline across DoD that reflects the most restrictive security posture consistent with operational requirements. Configuration settings are the set of parameters that can be changed that affects the security posture and/or functionality of the system. Security-related parameters are parameters impacting the security state of the application, including the parameters required to satisfy other security control requirements.

Checks: C-81141r2_chk

To verify that XenDesktop Controller and all other infrastructure server components are installable and manageable by authorized administrative accounts, the following policies must be modified: Go to Computer Configuration Policies >> Windows Settings >> Security Settings >> Local Policies/User Rights Assignment. Verify policy settings "Allow log on locally" and "Shut down the system" are both set to the global security group name containing the XenApp or XenDesktop administrators. "Local Administrators" may remain. If they are not set to the global security group name containing the XenApp or XenDesktop administrators, this is a finding.

Fix: F-88217r2_fix

To ensure that XenDesktop Controller and all other infrastructure server components are installable and manageable by authorized administrative accounts, the following policies must be modified: Go to Computer Configuration Policies >> Windows Settings >> Security Settings >> Local Policies/User Rights Assignment. 1. Edit "Allow log on locally". 2. Edit "Shut down the system". 3. Change both settings to the global security group name containing the XenApp or XenDesktop administrators. "Local Administrators" may remain.