How to start a process as another user from Visual Basic

Summary

This article shows you how to programmatically start a process as another user from Microsoft Visual Basic. To do this, you can use the LogonUser and CreateProcessAsUser Win32 APIs on a computer that is running Microsoft Windows NT 4.0, or you can use the CreateProcessWithLogonW Win32 API on a computer that is running Microsoft Windows 2000 or later. CreateProcessWithLogonW cannot be called from a process under the LocalSystem account.

More Information

This article contains sample Visual Basic code that detects the version of the operating system. It then uses the corresponding APIs to start a process as another user.

Windows NT 4.0

To use LogonUser and CreateProcessAsUser, the calling user account must have certain permissions.


To use LogonUser(), the calling user account must have the following permission:


Permission Display Name
------------------------------------------------------------------
SE_TCB_NAME Act as part of the operating system

To use CreateProcessAsUser(), the calling user account must have the following two permissions:

Permission Display Name
------------------------------------------------------------
SE_ASSIGNPRIMARYTOKEN_NAME Replace a process level token
SE_INCREASE_QUOTA_NAME Increase quotas

If the calling user account does not have the permission to "act as part of the operating system," the LogonUser() API fails and generates a return value of zero. If you call Err.LastDllError, you receive error message 1314. This message means that a required permission is not held by the client. Similarly, if the calling user account does not have the two permissions to "replace a process level token" and to "increase quotas," the CreateProcessAsUser() API fails and generates the error message 1314.

If you start an interactive application as another user, you must have access to the interactive window station and desktop that is named winsta0\default. If the application is interactive, the caller needs to programmatically add the required permission to winsta0\default. After this, the caller can call the RunAsUser helper function in the sample Visual Basic code below.


You must give enough permissions to the user account that is specified in LogonUser() so that the interactive application can start successfully. The following Knowledge Base article has sample Visual Basic code that you can use to update permissions on a window station and desktop.

316440 How To Use Low-Level Access Control APIs from Visual Basic

Windows 2000 and Later

The CreateProcessWithLogonW() API was introduced in Windows 2000. A call to CreateProcessWithLogonW() does not require permissions to be granted for the calling user account, as it does with the LogonUser and CreateProcessAsUser APIs.


In the future, use the CreateProcessWithLogonW() API. It handles the permissions that are associated with the inherited window station and desktop. In this scenario, the application just calls the RunAsUser helper function in the following sample Visual Basic code.

Option Explicit

Private Const CREATE_DEFAULT_ERROR_MODE = &H4000000

Private Const LOGON_WITH_PROFILE = &H1
Private Const LOGON_NETCREDENTIALS_ONLY = &H2

Private Const LOGON32_LOGON_INTERACTIVE = 2
Private Const LOGON32_PROVIDER_DEFAULT = 0

Private Type STARTUPINFO
cb As Long
lpReserved As Long ' !!! must be Long for Unicode string
lpDesktop As Long ' !!! must be Long for Unicode string
lpTitle As Long ' !!! must be Long for Unicode string
dwX As Long
dwY As Long
dwXSize As Long
dwYSize As Long
dwXCountChars As Long
dwYCountChars As Long
dwFillAttribute As Long
dwFlags As Long
wShowWindow As Integer
cbReserved2 As Integer
lpReserved2 As Long
hStdInput As Long
hStdOutput As Long
hStdError As Long
End Type

Private Type PROCESS_INFORMATION
hProcess As Long
hThread As Long
dwProcessId As Long
dwThreadId As Long
End Type

' LogonUser() requires that the caller has the following permission
' Permission Display Name
' --------------------------------------------------------------------
' SE_TCB_NAME Act as part of the operating system

' CreateProcessAsUser() requires that the caller has the following permissions
' Permission Display Name
' ---------------------------------------------------------------
' SE_ASSIGNPRIMARYTOKEN_NAME Replace a process level token
' SE_INCREASE_QUOTA_NAME Increase quotas

Private Declare Function LogonUser Lib "advapi32.dll" Alias _
"LogonUserA" _
(ByVal lpszUsername As String, _
ByVal lpszDomain As String, _
ByVal lpszPassword As String, _
ByVal dwLogonType As Long, _
ByVal dwLogonProvider As Long, _
phToken As Long) As Long

Private Declare Function CreateProcessAsUser Lib "advapi32.dll" _
Alias "CreateProcessAsUserA" _
(ByVal hToken As Long, _
ByVal lpApplicationName As Long, _
ByVal lpCommandLine As String, _
ByVal lpProcessAttributes As Long, _
ByVal lpThreadAttributes As Long, _
ByVal bInheritHandles As Long, _
ByVal dwCreationFlags As Long, _
ByVal lpEnvironment As Long, _
ByVal lpCurrentDirectory As String, _
lpStartupInfo As STARTUPINFO, _
lpProcessInformation As PROCESS_INFORMATION) As Long

' CreateProcessWithLogonW API is available only on Windows 2000 and later.
Private Declare Function CreateProcessWithLogonW Lib "advapi32.dll" _
(ByVal lpUsername As String, _
ByVal lpDomain As String, _
ByVal lpPassword As String, _
ByVal dwLogonFlags As Long, _
ByVal lpApplicationName As Long, _
ByVal lpCommandLine As String, _
ByVal dwCreationFlags As Long, _
ByVal lpEnvironment As Long, _
ByVal lpCurrentDirectory As String, _
ByRef lpStartupInfo As STARTUPINFO, _
ByRef lpProcessInformation As PROCESS_INFORMATION) As Long

Private Declare Function CloseHandle Lib "kernel32.dll" _
(ByVal hObject As Long) As Long

Private Declare Function SetErrorMode Lib "kernel32.dll" _
(ByVal uMode As Long) As Long

Private Type OSVERSIONINFO
dwOSVersionInfoSize As Long
dwMajorVersion As Long
dwMinorVersion As Long
dwBuildNumber As Long
dwPlatformId As Long
szCSDVersion As String * 128
End Type

' Version Checking APIs
Private Declare Function GetVersionExA Lib "kernel32.dll" _
(lpVersionInformation As OSVERSIONINFO) As Integer

Private Const VER_PLATFORM_WIN32_NT = &H2

'********************************************************************

' RunAsUser for Windows 2000 and Later
'********************************************************************
Public Function W2KRunAsUser(ByVal UserName As String, _
ByVal Password As String, _
ByVal DomainName As String, _
ByVal CommandLine As String, _
ByVal CurrentDirectory As String) As Long

Dim si As STARTUPINFO
Dim pi As PROCESS_INFORMATION

Dim wUser As String
Dim wDomain As String
Dim wPassword As String
Dim wCommandLine As String
Dim wCurrentDir As String

Dim Result As Long

si.cb = Len(si)

wUser = StrConv(UserName + Chr$(0), vbUnicode)
wDomain = StrConv(DomainName + Chr$(0), vbUnicode)
wPassword = StrConv(Password + Chr$(0), vbUnicode)
wCommandLine = StrConv(CommandLine + Chr$(0), vbUnicode)
wCurrentDir = StrConv(CurrentDirectory + Chr$(0), vbUnicode)

Result = CreateProcessWithLogonW(wUser, wDomain, wPassword, _
LOGON_WITH_PROFILE, 0&, wCommandLine, _
CREATE_DEFAULT_ERROR_MODE, 0&, wCurrentDir, si, pi)
' CreateProcessWithLogonW() does not
If Result <> 0 Then
CloseHandle pi.hThread
CloseHandle pi.hProcess
W2KRunAsUser = 0
Else
W2KRunAsUser = Err.LastDllError
MsgBox "CreateProcessWithLogonW() failed with error " & Err.LastDllError, vbExclamation
End If

End Function

'********************************************************************
' RunAsUser for Windows NT 4.0
'********************************************************************
Public Function NT4RunAsUser(ByVal UserName As String, _
ByVal Password As String, _
ByVal DomainName As String, _
ByVal CommandLine As String, _
ByVal CurrentDirectory As String) As Long
Dim Result As Long
Dim hToken As Long
Dim si As STARTUPINFO
Dim pi As PROCESS_INFORMATION

Result = LogonUser(UserName, DomainName, Password, LOGON32_LOGON_INTERACTIVE, _
LOGON32_PROVIDER_DEFAULT, hToken)
If Result = 0 Then
NT4RunAsUser = Err.LastDllError
' LogonUser will fail with 1314 error code, if the user account associated
' with the calling security context does not have
' "Act as part of the operating system" permission
MsgBox "LogonUser() failed with error " & Err.LastDllError, vbExclamation
Exit Function
End If

si.cb = Len(si)
Result = CreateProcessAsUser(hToken, 0&, CommandLine, 0&, 0&, False, _
CREATE_DEFAULT_ERROR_MODE, _
0&, CurrentDirectory, si, pi)
If Result = 0 Then
NT4RunAsUser = Err.LastDllError
' CreateProcessAsUser will fail with 1314 error code, if the user
' account associated with the calling security context does not have
' the following two permissions
' "Replace a process level token"
' "Increase Quotoas"
MsgBox "CreateProcessAsUser() failed with error " & Err.LastDllError, vbExclamation
CloseHandle hToken
Exit Function
End If

CloseHandle hToken
CloseHandle pi.hThread
CloseHandle pi.hProcess
NT4RunAsUser = 0

End Function

Public Function RunAsUser(ByVal UserName As String, _
ByVal Password As String, _
ByVal DomainName As String, _
ByVal CommandLine As String, _
ByVal CurrentDirectory As String) As Long

Dim w2kOrAbove As Boolean
Dim osinfo As OSVERSIONINFO
Dim Result As Long
Dim uErrorMode As Long

' Determine if system is Windows 2000 or later
osinfo.dwOSVersionInfoSize = Len(osinfo)
osinfo.szCSDVersion = Space$(128)
GetVersionExA osinfo
w2kOrAbove = _
(osinfo.dwPlatformId = VER_PLATFORM_WIN32_NT And _
osinfo.dwMajorVersion >= 5)
If (w2kOrAbove) Then
Result = W2KRunAsUser(UserName, Password, DomainName, _
CommandLine, CurrentDirectory)
Else
Result = NT4RunAsUser(UserName, Password, DomainName, _
CommandLine, CurrentDirectory)
End If
RunAsUser = Result
End Function
Propriedades

ID do Artigo: 285879 - Última Revisão: 16 de jul de 2008 - Revisão: 1

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