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Broker Service causing Audit Failures in Windows Security Event Log


Jamie Rojas

Question

Getting a bit of a weird Authentication issue on some of my Citrix DDC's.

Citrix Version: Citrix XenApp 7.15LTSR

- Setup between 2 Datacenters (primary and secondary)

- 2 x Storefront Servers in each DC (Total of 4)

- 2 x Delivery controllers in each DC (Total of 4)

- Mulitple XenApp workers across both DC's.

 

3 days ago the following security event starting popping up on both of the DDCs in my secondary site, every 30 seconds..

svc-pac-p-xenapp is the dedicated service account for Citrix XenApp, so is used within Citrix and and our F5 Load Balancers (APM)

Quote

 

Log Name:      Security
Source:        Microsoft-Windows-Security-Auditing
Date:          20/01/2020 3:57:35 PM
Event ID:      4625
Task Category: Logon
Level:         Information
Keywords:      Audit Failure
User:          N/A
Computer:      AUNRE01-CIP004.DOMAIN.ads.ParentDomain.com
Description:
An account failed to log on.

Subject:
    Security ID:        NETWORK SERVICE
    Account Name:        AUNRE01-CIP004$
    Account Domain:        DOMAIN
    Logon ID:        0x3E4

Logon Type:            8

Account For Which Logon Failed:
    Security ID:        NULL SID
    Account Name:        DOMAIN\svc-pac-p-xenapp
    Account Domain:        DOMAIN

Failure Information:
    Failure Reason:        Unknown user name or bad password.
    Status:            0xC000006D
    Sub Status:        0xC0000064

Process Information:
    Caller Process ID:    0x1e64
    Caller Process Name:    C:\Program Files\Citrix\Broker\Service\BrokerService.exe

Network Information:
    Workstation Name:    AUNRE01-CIP004
    Source Network Address:    -
    Source Port:        -

Detailed Authentication Information:
    Logon Process:        Advapi  
    Authentication Package:    Negotiate
    Transited Services:    -
    Package Name (NTLM only):    -
    Key Length:        0

This event is generated when a logon request fails. It is generated on the computer where access was attempted.

The Subject fields indicate the account on the local system which requested the logon. This is most commonly a service such as the Server service, or a local process such as Winlogon.exe or Services.exe.

The Logon Type field indicates the kind of logon that was requested. The most common types are 2 (interactive) and 3 (network).

The Process Information fields indicate which account and process on the system requested the logon.

The Network Information fields indicate where a remote logon request originated. Workstation name is not always available and may be left blank in some cases.

The authentication information fields provide detailed information about this specific logon request.
    - Transited services indicate which intermediate services have participated in this logon request.
    - Package name indicates which sub-protocol was used among the NTLM protocols.
    - Key length indicates the length of the generated session key. This will be 0 if no session key was requested.
Event Xml:
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
  <System>
    <Provider Name="Microsoft-Windows-Security-Auditing" Guid="{54849625-5478-4994-A5BA-3E3B0328C30D}" />
    <EventID>4625</EventID>
    <Version>0</Version>
    <Level>0</Level>
    <Task>12544</Task>
    <Opcode>0</Opcode>
    <Keywords>0x8010000000000000</Keywords>
    <TimeCreated SystemTime="2020-01-20T04:57:35.455586000Z" />
    <EventRecordID>24844471</EventRecordID>
    <Correlation />
    <Execution ProcessID="572" ThreadID="1080" />
    <Channel>Security</Channel>
    <Computer>AUNRE01-CIP004.DOMAIN.ads.ParentDomain.com</Computer>
    <Security />
  </System>
  <EventData>
    <Data Name="SubjectUserSid">S-1-5-20</Data>
    <Data Name="SubjectUserName">AUNRE01-CIP004$</Data>
    <Data Name="SubjectDomainName">DOMAIN</Data>
    <Data Name="SubjectLogonId">0x3e4</Data>
    <Data Name="TargetUserSid">S-1-0-0</Data>
    <Data Name="TargetUserName">DOMAIN\svc-pac-p-xenapp</Data>
    <Data Name="TargetDomainName">DOMAIN</Data>
    <Data Name="Status">0xc000006d</Data>
    <Data Name="FailureReason">%%2313</Data>
    <Data Name="SubStatus">0xc0000064</Data>
    <Data Name="LogonType">8</Data>
    <Data Name="LogonProcessName">Advapi  </Data>
    <Data Name="AuthenticationPackageName">Negotiate</Data>
    <Data Name="WorkstationName">AUNRE01-CIP004</Data>
    <Data Name="TransmittedServices">-</Data>
    <Data Name="LmPackageName">-</Data>
    <Data Name="KeyLength">0</Data>
    <Data Name="ProcessId">0x1e64</Data>
    <Data Name="ProcessName">C:\Program Files\Citrix\Broker\Service\BrokerService.exe</Data>
    <Data Name="IpAddress">-</Data>
    <Data Name="IpPort">-</Data>
  </EventData>
</Event>

 

 

Turning on logging on the DDC's I can see the following in the Broker.log file which seems interesting, but no idea where this is used;

Quote

20/01/20 16:27:35.464 7780 0064 2108: BrokerXmlServices:Failed Windows logon, error code 1326
20/01/20 16:27:35.464 7780 0064 2108: BrokerXmlServices:ProcessCredentials: exception Citrix.Xms.XmlSupport.CredentialsException: Failed Windows logon, error code 1326
   at Citrix.Xms.XmlSupport.SidFinder.PopulateCredentials(ProcessedCredentials credentials, PasswordBasedCredentials pwdCreds, Boolean getPasswordExpiryInfo)
   at Citrix.Xms.XmlSupport.CredentialsProcessor.ProcessCredentials(Guid transactionId, CommonCredentials requestCredentials, CredentialType allowedFormats, CredentialOptions options)
20/01/20 16:27:35.464 7780 0064 2108: BrokerXmlServices:GetErrorIdFromCredentialsException: InvalidCredentials -> failed-credentials
20/01/20 16:27:35.464 7780 0064 2108: BrokerXmlServices:XmlPerf.TimeoutAction caught exception Citrix.Xms.XmlSupport.CredentialsException: Failed Windows logon, error code 1326
   at Citrix.Xms.XmlSupport.SidFinder.PopulateCredentials(ProcessedCredentials credentials, PasswordBasedCredentials pwdCreds, Boolean getPasswordExpiryInfo)
   at Citrix.Xms.XmlSupport.CredentialsProcessor.ProcessCredentials(Guid transactionId, CommonCredentials requestCredentials, CredentialType allowedFormats, CredentialOptions options)
   at Citrix.Cds.Xms.Wpnbr.BaseTransaction.ProcessCredentials(CredentialType SupportedCredentials, CredentialOptions ProcessingOptions)
   at Citrix.Cds.Xms.Wpnbr.AppDataTransaction.HandleRequest(IXmlMultiplexer multiplexer)
   at Citrix.Xms.XmlSupport.XmlPerf.WrapTransaction(Type t, Action transaction)
   at Citrix.Xms.XmlSupport.XmlPerf.<>c__DisplayClass11_1.<TimeoutAction>b__0(Object <state>)
20/01/20 16:27:35.464 7780 0018 7516: BrokerXmlServices:WPNBR.HandleRequest[NFuse#2645:RequestAppData]: Credential Exception, reason InvalidCredentials: Citrix.Xms.XmlSupport.CredentialsException: Failed Windows logon, error code 1326
   at Citrix.Xms.XmlSupport.SidFinder.PopulateCredentials(ProcessedCredentials credentials, PasswordBasedCredentials pwdCreds, Boolean getPasswordExpiryInfo)
   at Citrix.Xms.XmlSupport.CredentialsProcessor.ProcessCredentials(Guid transactionId, CommonCredentials requestCredentials, CredentialType allowedFormats, CredentialOptions options)
   at Citrix.Cds.Xms.Wpnbr.BaseTransaction.ProcessCredentials(CredentialType SupportedCredentials, CredentialOptions ProcessingOptions)
   at Citrix.Cds.Xms.Wpnbr.AppDataTransaction.HandleRequest(IXmlMultiplexer multiplexer)
   at Citrix.Xms.XmlSupport.XmlPerf.WrapTransaction(Type t, Action transaction)
   at Citrix.Xms.XmlSupport.XmlPerf.<>c__DisplayClass11_1.<TimeoutAction>b__0(Object <state>)
--- End of stack trace from previous location where exception was thrown ---

 

Otherwise the account is not locked, and is not locking due to these authentication attempts, its only happening on DDCs in the secondary site, the primary site is all OK, there are no scheduled tasks using this account on either server, these 2 DDCs have been recently rebooted twice and checking the various Citrix Services they all appear to be OK as well...
What would cause the BrokerService.exe service to use this particular domain account?

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Update: Managed to resolve the issue;

Issue: Ended up being a configuration on one of our F5 Load Balancers. 
Somehow the Monitor for Citrix-XenApp_xml_https (originally created from the Official F5 Citrix iApp) changed. It went back to an old password (sent in Plain Text) and updated the nHost record to a DNS name instead of an IP address.

I was able to compare this to the Load Balancer in the other site which was working all OK, and manually change the Send String configuration of the Monitor and boom, issue fixed! 

  • Like 1
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