LogonUser info  Overview  Group

The LogonUser function attempts to perform a user logon operation. You specify the user with a user name and domain, and authenticate the user with a clear-text password. If the function succeeds, you receive a handle to a token that represents the logged-on user. You can then use this token handle to impersonate the specified user, or in most cases, to create a process running in the context of the specified user.

BOOL LogonUser(

Parameters

lpszUsername

Pointer to a null-terminated string that specifies the user name. This is the name of the user account to log on to.

lpszDomain

Pointer to a null-terminated string that specifies the domain or server to log on to. If this parameter is “.”, LogonUser searches only the local account database for the account specified in lpszUsername. If this parameter is NULL, LogonUser searches the local account database, and then searches trusted domain account databases, until it finds the lpszUsername account or the search is exhausted without finding the account name.

lpszPassword

Pointer to a null-terminated string that specifies the clear-text password for the user account specified by lpszUsername.

dwLogonType

Specifies the type of logon operation to perform. The following logon types are defined:

Value	Meaning
LOGON32_LOGON_BATCH	This logon type is intended for batch servers, where processes may be executing on behalf of a user without their direct intervention; or for higher performance servers that process many clear-text authentication attempts at a time, such as mail or web servers. LogonUser does not cache credentials for this logon type.
LOGON32_LOGON_INTERACTIVE	This logon type is intended for users who will be interactively using the machine, such as a user being logged on by a terminal server, remote shell, or similar process. This logon type has the additional expense of caching logon information for disconnected operation, and is therefore inappropriate for some client/server applications, such as a mail server.
LOGON32_LOGON_SERVICE	Indicates a service-type logon. The account provided must have the service privilege enabled.
LOGON32_LOGON_NETWORK	This logon type is intended for high performance servers to authenticate clear text passwords. LogonUser does not cache credentials for this logon type. This is the fastest logon path, but there are two limitations. First, the function returns an impersonation token, not a primary token. You cannot use this token directly in the CreateProcessAsUser function. However, you can call the DuplicateTokenEx function to convert the token to a primary token, and then use it in CreateProcessAsUser. Second, if you convert the token to a primary token and use it in CreateProcessAsUser to start a process, the new process will not be able to access other network resources, such as remote servers or printers, through the redirector.

dwLogonProvider

Specifies the logon provider. The following logon providers are defined:

Value	Meaning
LOGON32_PROVIDER_DEFAULT	Use the standard logon provider for the system. This is the recommended value for the dwLogonProvider parameter. It provides maximum compatibility with current and future releases of Windows NT.
LOGON32_PROVIDER_WINNT40	Use the Windows NT 4.0 logon provider
LOGON32_PROVIDER_WINNT35	Use the Windows NT 3.5 logon provider.

phToken

Pointer to a HANDLE variable that receives a handle to a token that represents the specified user.

You can use the returned handle in calls to the ImpersonateLoggedOnUser function.

In most cases, the returned handle is a primary token that you can use in calls to the CreateProcessAsUser function. However, if you specify the LOGON32_LOGON_NETWORK flag, LogonUser returns an impersonation token that you cannot use in CreateProcessAsUser unless you call DuplicateTokenEx to convert it to a primary token.

When you no longer need this handle, close it by calling the CloseHandle function.

Return Values

If the function succeeds, the return value is nonzero.

If the function fails, the return value is zero. To get extended error information, call GetLastError.

Remarks

The process that calls LogonUser must have the SE_TCB_NAME privilege. The privilege does not need to be enabled. The LogonUser function enables the privilege as necessary. If the calling process does not have this privilege, LogonUser fails and GetLastError returns ERROR_PRIVILEGE_NOT_HELD.

In some cases, the process that calls LogonUser must also have the SE_CHANGE_NOTIFY_NAME privilege enabled; otherwise, LogonUser fails and GetLastError returns ERROR_ACCESS_DENIED. This privilege is not required for the local system account or accounts that are members of the administrators group. By default, SE_CHANGE_NOTIFY_NAME is enabled for all users, but some administrators may disable it for everyone. For more information about privileges, see Privileges.

A user is considered logged on as long as at least one token exists. If you call CreateProcessAsUser and then close the token, the system considers the user as still logged on until the process (and all child processes) have ended.

If the LogonUser call is successful, the system notifies network providers that the logon occurred by calling the provider’s NPLogonNotify entry-point.

See Also

CreateProcessAsUser, ImpersonateLoggedOnUser

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