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Citrix XenDesktop 7.x Windows VDA Security Technical Implementation Guide - V1R3

  • Version/Release: V1R3
  • Published: 2025-06-23
  • Released: 2025-07-02
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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.
c
Citrix Windows Virtual Delivery Agent must implement DoD-approved encryption.
SC-23 - High - CCI-001184 - V-213213 - SV-213213r960759_rule
RMF Control
SC-23
Severity
High
CCI
CCI-001184
Version
CXEN-VD-000030
Vuln IDs
  • V-213213
  • V-81433
Rule IDs
  • SV-213213r960759_rule
  • SV-96147
Without confidentiality protection mechanisms, unauthorized individuals may gain access to sensitive information via a remote access session. Remote access is access to DoD nonpublic information systems by an authorized user (or an information system) communicating through an external, non-organization-controlled network. Remote access methods include, for example, dial-up, broadband, and wireless. Encryption provides a means to secure the remote connection to prevent unauthorized access to the data traversing the remote access connection thereby providing a degree of confidentiality. The encryption strength of mechanism is selected based on the security categorization of the information. Satisfies: SRG-APP-000014, SRG-APP-000015, SRG-APP-000039, SRG-APP-000219, SRG-APP-000439, SRG-APP-000440, SRG-APP-000441, SRG-APP-000442
Checks: C-14443r288960_chk

NOTE: If an approved DoD VPN or proxy device is used for external connections, this requirement is Not Applicable. Verify TLS Certificate is installed in the Local Computer >> Personal >> Certificates area of the certificate store. 1. Launch the Microsoft Management Console (MMC): Start >> Run >> mmc.exe. 2. Add the Certificates snap-in to the MMC: - Select File >> Add/Remove Snap-in. - Select "Certificates" and then click "Add". 3. When prompted with "This snap-in will always manage certificates for:" choose "Computer account" and then click "Next". 4. When prompted with "Select the computer you want this snap-in to manage", choose "Local computer" and then click "Finish". 5. Under Certificates (Local Computer) >> Personal >> Certificates, right-click the certificate and then select All Tasks >> Manage Private Keys. 6. The Access Control List Editor displays "Permissions for (FriendlyName) private keys" where (FriendlyName) is the name of the SSL certificate. Verify one of the following services is listed with Read access: - For a VDA for Windows Desktop OS, "PORTICASERVICE" - For a VDA for Windows Server OS, "TERMSERVICE" If one of the associated services is not listed with "Read" access, this is a finding.

Fix: F-14441r288961_fix

Configure TLS on a VDA using the PowerShell script: Install the TLS Certificate in the Local Computer >> Personal >> Certificates area of the certificate store. If more than one certificate resides in that location, supply the thumbprint of the certificate to the PowerShell script. The "Enable-VdaSSL.ps1" script enables or disables the TLS listener on a VDA. This script is available in the Support >> Tools >> SslSupport folder on the installation media. When you enable TLS, the script disables all existing Windows Firewall rules for the specified TCP port. It then adds a new rule that allows the ICA Service to accept incoming connections only on the TLS, TCP, and UDP ports. It also disables the Windows Firewall rules for: - Citrix ICA (default: 1494) - Citrix CGP (default: 2598) - Citrix WebSocket (default: 8008) The effect is that users can only connect using TLS or DTLS. They cannot use ICA/HDX, ICA/HDX with Session Reliability, or HDX over WebSocket without TLS or DTLS. The PowerShell script configures TLS on static VDAs; it does not configure TLS on pooled VDAs that are provisioned by Machine Creation Services or Provisioning Services, where the machine image resets on each restart. Manually configure TLS on a VDA: When configuring TLS on a VDA manually, you grant generic read access to the TLS certificate's private key for the appropriate service on each VDA: NT SERVICE\PorticaService for a VDA for Windows Desktop OS, or NT SERVICE\TermService for a VDA for Windows Server OS. On the machine where the VDA is installed: 1. Launch the Microsoft Management Console (MMC): Start >> Run >> mmc.exe. 2. Add the Certificates snap-in to the MMC: a) Select File >> Add/Remove Snap-in. b) Select "Certificates" and then click "Add". c) When prompted with "This snap-in will always manage certificates for:" choose "Computer account" and then click "Next". d) When prompted with "Select the computer you want this snap-in to manage", choose "Local computer" and then click "Finish". 3. Under Certificates (Local Computer) >> Personal >> Certificates, right-click the certificate and then select All Tasks >> Manage Private Keys. 4. The Access Control List Editor displays "Permissions for (FriendlyName) private keys" where (FriendlyName) is the name of the TLS certificate. Add one of the following services and give it Read access: - For a VDA for Windows Desktop OS, "PORTICASERVICE" - For a VDA for Windows Server OS, "TERMSERVICE" 5. Double-click the installed TLS certificate. In the certificate dialog, select the "Details" tab and then scroll to the bottom. Click "Thumbprint". 6. Run "regedit" and go to "HKLM\SYSTEM\CurrentControlSet\Control\Terminal Server\Wds\icawd". a) Edit the SSL Thumbprint key and copy the value of the TLS certificate's thumbprint into this binary value. You can safely ignore unknown items in the Edit Binary Value dialog box (such as "0000" and special characters). b) Edit the SSLEnabled key and change the DWORD value to "1". (To disable SSL later, change the DWORD value to "0".) c) To change the default settings (optional), use the following in the same registry path: SSLPort DWORD – SSL port number. Default: 443. SSLMinVersion DWORD – 1 = SSL 3.0, 2 = TLS 1.0, 3 = TLS 1.1, 4 = TLS 1.2. Default: 2 (TLS 1.0). SSLCipherSuite DWORD – 1 = GOV, 2 = COM, 3 = ALL. Default: 3 (ALL). 7. Ensure the TLS TCP port is open in the Windows Firewall if it is not the default "443". (When creating the inbound rule in Windows Firewall, make sure its properties have the "Allow the connection" and "Enabled" entries selected.) 8. Ensure that no other applications or services (such as IIS) are using the TLS TCP port. 9. For VDAs for Windows Server OS, restart the machine for the changes to take effect. (You do not need to restart machines containing VDAs for Windows Desktop OS.) Configure TLS on Delivery Groups: Complete this procedure for each Delivery Group that contains VDAs that have been configured for TLS connections. 1. From "Studio", open the PowerShell console. 2. Run "asnp Citrix.*" to load the Citrix product cmdlets. 3. Run the following command Get-BrokerAccessPolicyRule -DesktopGroupName '<delivery-group-name>' | Set-BrokerAccessPolicyRule -HdxSslEnabled $true. 4. Run the following command Set-BrokerSite -DnsResolutionEnabled $true.

b
Citrix Windows Virtual Delivery Agent must be configured to prohibit or restrict the use of ports, as defined in the PPSM CAL and vulnerability assessments.
CM-7 - Medium - CCI-000382 - V-213214 - SV-213214r1043177_rule
RMF Control
CM-7
Severity
Medium
CCI
CCI-000382
Version
CXEN-VD-000275
Vuln IDs
  • V-213214
  • V-81435
Rule IDs
  • SV-213214r1043177_rule
  • SV-96149
In order to prevent unauthorized connection of devices, unauthorized transfer of information, or unauthorized tunneling (i.e., embedding of data types within data types), organizations must disable or restrict unused or unnecessary physical and logical ports/protocols on information systems. 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. Additionally, it is sometimes convenient to provide multiple services from a single component (e.g., email and web services; however, doing so increases risk over limiting the services provided by any one component. To support the requirements and principles of least functionality, the application must support the organizational requirements providing only essential capabilities and limiting the use of ports, protocols, and/or services to only those required, authorized, and approved to conduct official business or to address authorized quality of life issues.
Checks: C-14444r288963_chk

On Delivery Controllers, verify that only approved ports are used. 1. Open a command prompt. 2. Navigate to the XenDesktop install directory Program Files\Citrix\Broker\Service 3. Enter BrokerService.exe /Show to display the currently used ports. If an unapproved port is used, this is a finding.

Fix: F-14442r288964_fix

To change the VDA registration port from the default "80", create the Citrix Machine Policy and update the DDCs, as explained below: 1. Create a new Citrix Machine policy or edit an existing one. 2. Navigate to the Settings tab and select "Control Registration Port". 3. Update the Value to reflect the new port. 4. Select "OK". 5. Restart all desktops and wait until all the desktops report as Unregistered. 6. Update the DDCs' VDA registration Port. 7. Restart all desktops and verify that all VDAs register successfully.

c
The version of XenDesktop Windows VDA running on the system must be a supported version.
SI-2 - High - CCI-002605 - V-275977 - SV-275977r1115921_rule
RMF Control
SI-2
Severity
High
CCI
CCI-002605
Version
CXEN-VD-999999
Vuln IDs
  • V-275977
Rule IDs
  • SV-275977r1115921_rule
Security flaws with software applications are discovered daily. Vendors are constantly updating and patching their products to address newly discovered security vulnerabilities. Organizations (including any contractor to the organization) are required to promptly install security-relevant software updates (e.g., patches, service packs, and hot fixes). Flaws discovered during security assessments, continuous monitoring, incident response activities, or information system error handling must also be addressed expeditiously. Organization-defined time periods for updating security-relevant software may vary based on a variety of factors including, for example, the security category of the information system or the criticality of the update (i.e., severity of the vulnerability related to the discovered flaw). This requirement will apply to software patch management solutions that are used to install patches across the enclave and also to applications that are not part of that patch management solution. For example, many browsers provide the capability to install their own patch software. Patch criticality, as well as system criticality, will vary. Therefore, the tactical situations regarding the patch management process will also vary. This means that the time period used must be a configurable parameter. Time frames for application of security-relevant software updates may depend on the Information Assurance Vulnerability Management (IAVM) process. The application will be configured to check for and install security-relevant software updates within an identified time period from the availability of the update. The specific time period will be defined by an authoritative source (e.g., IAVM, CTOs, DTMs, and STIGs).
Checks: C-80095r1111788_chk

XenDesktop Windows VDA 7.x is no longer supported by the vendor. If the system is running XenDesktop Windows VDA 7.x, this is a finding.

Fix: F-80000r1111789_fix

Upgrade to a supported version.