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Troubleshoot Windows logon issues 编辑

This article describes the logs and error messages Windows provides when a user logs on using certificates and/or smart cards. These logs provide information you can use to troubleshoot authentication failures.

Certificates and public key infrastructure

Windows Active Directory maintains several certificate stores that manage certificates for users logging on.

NTAuth certificate store: To authenticate to Windows, the certificate authority immediately issuing user certificates (that is, no chaining is supported) must be placed in the NTAuth store. To see these certificates, from the certutil program, enter: certutil –viewstore –enterprise NTAuth.
Root and intermediate certificate stores: Usually, certificate logon systems can provide only a single certificate, so if a chain is in use, the intermediate certificate store on all machines must include these certificates. The root certificate must be in the Trusted Root Store, and the penultimate certificate must be in the NTAuth store.
Logon certificate extensions and Group Policy: Windows can be configured to enforce verification of EKUs and other certificate policies. See the Microsoft documentation: https://docs.microsoft.com/en-us/previous-versions/windows/it-pro/windows-server-2008-R2-and-2008/ff404287(v=ws.10).

Registry policy	Description
AllowCertificatesWithNoEKU	When disabled, certificates must include the smart card logon Extended Key Usage (EKU).
AllowSignatureOnlyKeys	By default, Windows filters out certificates private keys that do not allow RSA decryption. This option overrides that filter.
AllowTimeInvalidCertificates	By default, Windows filters out expired certificates. This option overrides that filter.
EnumerateECCCerts	Enables elliptic curve authentication.
X509HintsNeeded	If a certificate does not contain a unique User Principal Name (UPN), or it could be ambiguous, this option allows users to manually specify their Windows logon account.
UseCachedCRLOnlyAnd, IgnoreRevocationUnknownErrors	Disables revocation checking (usually set on the domain controller).

Domain controller certificates: To authenticate Kerberos connections, all servers must have appropriate “Domain Controller” certificates. These can be requested using the “Local Computer Certificate Personal Store” MMC snap-in menu.

UPN name and certificate mapping

It is recommended that user certificates include a unique User Principal Name (UPN) in the Subject Alternate Name extension.

UPN names in Active Directory

By default, every user in Active Directory has an implicit UPN based on the pattern <samUsername>@<domainNetBios> and <samUsername>@<domainFQDN>. The available domains and FQDNs are included in the RootDSE entry for the forest. Note that a single domain can have multiple FQDN addresses registered in the RootDSE.

Additionally, every user in Active Directory has an explicit UPN and altUserPrincipalNames. These are LDAP entries that specify the UPN for the user.

When searching for users by UPN, Windows looks first in the current domain (based on the identity of the process looking up the UPN) for explicit UPNs, then alterative UPNs. If there are no matches, it looks up the implicit UPN, which may resolve to different domains in the forest.

Certificate Mapping Service

If a certificate does not include an explicit UPN, Active Directory has the option to store an exact public certificate for each use in an “x509certificate” attribute. To resolve such a certificate to a user, a computer can query for this attribute directly (by default, in a single domain).

An option is provided for the user to specify a user account that speeds up this search, and also allows this feature to be used in a cross-domain environment.

If there are multiple domains in the forest, and the user does not explicitly specify a domain, the Active Directory rootDSE specifies the location of the Certificate Mapping Service. This is usually located on a global catalog machine, and has a cached view of all x509certificate attributes in the forest. This computer can be used to efficiently find a user account in any domain, based on only the certificate.

Control logon domain controller selection

When an environment contains multiple domain controllers, it is useful to see and restrict which domain controller is used for authentication, so that logs can be enabled and retrieved.

Control domain controller selection

To force Windows to use a particular Windows domain controller for logon, you can explicitly set the list of domain controllers that a Windows machine uses by configuring the lmhosts file: \Windows\System32\drivers\etc\lmhosts.

There is usually a sample file named “lmhosts.sam” in that location. Simply include a line:

1.2.3.4 dcnetbiosname #PRE #DOM:mydomai

Where “1.2.3.4” is the IP address of the domain controller named “dcnetbiosname” in the “mydomain” domain.

After a restart, the Windows machine uses that information to log on to mydomain. Note that this configuration must be reverted when debugging is complete.

Identify the domain controller in use

At logon, Windows sets an MSDOS environment variable with the domain controller that logged the user on. To see this, start the command prompt with the command: echo %LOGONSERVER%.

Logs relating to authentication are stored on the computer returned by this command.

Enable account audit events

By default, Windows domain controllers do not enable full account audit logs. This can be controlled through audit policies in the security settings in the Group Policy editor. After they are enabled, the domain controller produces extra event log information in the security log file.

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Certificate validation logs

Check certificate validity

If a smartcard certificate is exported as a DER certificate (no private key required), you can validate it with the command: certutil –verify user.cer

Enable CAPI logging

On the domain controller and users machine, open the event viewer and enable logging for Microsoft/Windows/CAPI2/Operational Logs.

You can control CAPI logging with the registry keys at: CurrentControlSet\Services\crypt32.

Value	Description
DiagLevel (DWORD)	Verbosity level (0 to 5)
DiagMatchAnyMask (QUADWORD)	Event filter (use 0xffffff for all)
DiagProcessName (MULTI_SZ)	Filter by process name (for example, LSASS.exe)

CAPI logs

Message	Description
Build Chain	LSA called CertGetCertificateChain (includes result)
Verify Revocation	LSA called CertVerifyRevocation (includes result)
X509 Objects	In verbose mode, certificates and Certificate Revocation Lists (CRLs) are dumped to AppData\LocalLow\Microsoft\X509Objects
Verify Chain Policy	LSA called CertVerifyChainPolicy (includes parameters)

Error messages

Error code	Description
Certificate not trusted	The smart card certificate could not be built using certificates in the computer’s intermediate and trusted root certificate stores.
Certificate revocation check error	The CRL for the smart card could not be downloaded from the address specified by the certificate CRL distribution point. If revocation checking is mandated, this prevents logon from succeeding. See the Certificates and public key infrastructure section.
Certificate Usage errors	The certificate is not suitable for logon. For example, it might be a server certificate or a signing certificate.

Kerberos logs

To enable Kerberos logging, on the domain controller and the end user machine, create the following registry values:

Hive	Value name	Value [DWORD]
CurrentControlSet\Control\Lsa\Kerberos\Parameters	LogLevel	0x1
CurrentControlSet\Control\Lsa\Kerberos\Parameters	KerbDebuglevel	0xffffffff
CurrentControlSet\Services\Kdc	KdcDebugLevel	0x1
CurrentControlSet\Services\Kdc	KdcExtraLogLevel	0x1f

Kerberos logging is output to the System event log.

Messages such as “untrusted certificate” should be easy to diagnose.
Two error codes are informational, and can be safely ignored:
- KDC_ERR_PREAUTH_REQUIRED (used for backward compatibility with older domain controllers)
- Unknown error 0x4b

Domain controller and workstation logs

This section describes the expected log entries on the domain controller and workstation when the user logs on with a certificate.

Domain controller CAPI2 log
Domain controller security logs
Virtual Delivery Agent (VDA) security log
VDA CAPI log
VDA system log

Domain controller CAPI2 log

During a logon, the domain controller validates the caller’s certificate, producing a sequence of log entries in the following form.

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The final event log message shows lsass.exe on the domain controller constructing a chain based on the certificate provided by the VDA, and verifying it for validity (including revocation). The result is returned as “ERROR_SUCCESS”.

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Domain controller security log

The domain controller shows a sequence of logon events, the key event being 4768, where the certificate is used to issue the Kerberos Ticket Granting Ticket (krbtgt).

The messages before this show the machine account of the server authenticating to the domain controller. The messages following this show the user account belonging to the new krbtgt being used to authenticate to the domain controller.

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VDA security log

The VDA security audit log corresponding to the logon event is the entry with event ID 4648, originating from winlogon.exe.

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VDA CAPI log

This example VDA CAPI log shows a single chain build and verification sequence from lsass.exe, validating the domain controller certificate (dc.citrixtest.net).

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VDA system log

When Kerberos logging is enabled, the system log shows the error KDC_ERR_PREAUTH_REQUIRED (which can be ignored), and an entry from Winlogon showing that the Kerberos logon was successful.

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Monitoring FAS using Windows event log

All FAS events are written to the Windows Application event log. You can use products such as System Centre Operations Manager (SCOM) to monitor the health of your FAS service using the processes and events described here.

Is the FAS service running?

To determine if the FAS service is running, monitor the process Citrix.Authentication.FederatedAuthenticationService.exe.

Only the most important events for monitoring the FAS service are described in this section. For the full list of FAS event codes, see FAS event logs.

FAS health events

The following events show whether your FAS service is healthy.

The event source is Citrix.Authentication.FederatedAuthenticationService.

Event	Event text	Explanation	Notes
[S003]	Administrator [{0}] setting Maintenance Mode to [{1}]	The FAS service was put into, or taken out of, maintenance mode.	While in maintenance mode, the FAS server is not usable for single sign-on.
[S022]	Administrator [{0}] setting Maintenance Mode to Off	The FAS service was taken out of maintenance mode.	Available from FAS 10.7 / CVAD 2109.
[S023]	Administrator [{0}] setting Maintenance Mode to On	The FAS service was put into maintenance mode.	Available from FAS 10.7 / CVAD 2109.
[S123]	Failed to issue a certificate for [upn: {0} role: {1}] [exception: {2}]	This event happens after [S124] if none of the CAs FAS is configured with successfully issued a user certificate. Single sign-on will fail for that user.	This event may indicate that all configured CAs are not working. If FAS is configured to use an HSM, it may also indicate that the HSM is not working.
[S124]	Failed to issue a certificate for [upn: {0} role: {1}] at [certifcate authority: {2}] [exception: {3}]	A failure occurred when FAS attempted to request a user certificate from the given CA. If FAS is configured with more than one CA, FAS will try the request at another CA.	This event may indicate that the CA is not working, or is not contactable. If FAS is configured to use an HSM, it may also indicate that the HSM is not working. The exception can be used to help identify the cause of the problem.
[S413]	Authorization certificate expiring soon ({0} days left). Certificate details: {1}	This event is generated periodically when the FAS authorization certificate is close to expiry. By default, the event is generated every day if the authorization certificate is within 30 days of expiry.	The default settings can be adjusted using the cmdlet Set-FasRaCertificateMonitor; see PowerShell cmdlets.
[S414]	Authorization certificate has expired. Certificate details: {0}	This event is generated periodically when the FAS authorization certificate has expired. By default, the event is generated every day.	Once expired, FAS is not able to generate new user certificates and single-sign on begins to fail.

Cloud-connected FAS events

If you are using FAS in conjunction with Citrix Cloud, the following events show whether your FAS service is healthy.

The event source is Citrix.Fas.Cloud.

Event	Event text	Explanation	Notes
[S012]	The FAS service is available for single sign-on from Citrix Cloud	This event indicates that single sign-on from Workspace (i.e. Citrix Cloud) should be working.	Before issuing this event, FAS checks (1) that it is configured, (2) is not in maintenance mode, and (3) is connected to Citrix Cloud.
[S013]	The FAS service is not available for single sign-on from Citrix Cloud. [{0}] Further details can be found in the admin console.	This event indicates that FAS is not able to provide single sign-on from Workspace (i.e. Citrix Cloud). The message includes the reason why single sign-on is not working.	FAS maintains a persistent connection to Citrix Cloud. From time-to-time, this connection may terminate for a variety of reasons (such as a network glitch, or a connection lifetime policy on a proxy server). When this happens, the event text contains “Service is not connected to the cloud”. This is normal behaviour, and FAS immediately attempts to re-establish a connection to Citrix Cloud.

Security events

The following events indicate that an unauthorized entity attempted to use FAS.

The event source is Citrix.Authentication.FederatedAuthenticationService.

Event	Event text	Explanation
[S001]	ACCESS DENIED: User [{0}] is not a member of Administrators group	An attempt was made to view or change te configuration of FAS, but the caller was not a FAS administrator.
[S002]	ACCESS DENIED: User [{0}] is not an Administrator of Role [{1}]	An attempt was made to view or change the configuration of a FAS rule, but the caller was not a FAS administrator.
[S101]	Server [{0}] is not authorized to assert identities in role [{1}]	An attempt was made to assert user identities, but the caller is not permitted to do so. Only StoreFront servers which have been permitted in the FAS rule configuration (and Workspace if applicable) are allowed to assert user identities.
[S104]	Server [{0}] failed to assert UPN [{1}] (UPN not allowed by role [{2}])	An attempt was made to assert a user identity, but the user’s account is not permitted according to the FAS rule configuration.
[S205]	Relying party access denied - the calling account [{0}] is not a permitted relying party of the rule [{1}]	A VDA attempted to perform single sign-on with FAS, but the VDA is not permitted according to the FAS rule configuration.