Sample Code
The following Visual Basic module contains a public function called SSPValidateUser(). This function attempts to validate the supplied user name, domain name, and password by using SSPI functions.

' Module Name: SSPLogon.bas
Option Explicit

Private Const HEAP_ZERO_MEMORY = &H8

Private Const SEC_WINNT_AUTH_IDENTITY_ANSI = &H1

Private Const SECBUFFER_TOKEN = &H2

Private Const SECURITY_NATIVE_DREP = &H10

Private Const SECPKG_CRED_INBOUND = &H1
Private Const SECPKG_CRED_OUTBOUND = &H2

Private Const SEC_I_CONTINUE_NEEDED = &H90312
Private Const SEC_I_COMPLETE_NEEDED = &H90313
Private Const SEC_I_COMPLETE_AND_CONTINUE = &H90314

Private Const VER_PLATFORM_WIN32_NT = &H2

Type SecPkgInfo
fCapabilities As Long
wVersion As Integer
wRPCID As Integer
cbMaxToken As Long
Name As Long
Comment As Long
End Type

Type SecHandle
dwLower As Long
dwUpper As Long
End Type

Type AUTH_SEQ
fInitialized As Boolean
fHaveCredHandle As Boolean
fHaveCtxtHandle As Boolean
hcred As SecHandle
hctxt As SecHandle
End Type

Type SEC_WINNT_AUTH_IDENTITY
User As String
UserLength As Long
Domain As String
DomainLength As Long
Password As String
PasswordLength As Long
Flags As Long
End Type

Type TimeStamp
LowPart As Long
HighPart As Long
End Type

Type SecBuffer
cbBuffer As Long
BufferType As Long
pvBuffer As Long
End Type

Type SecBufferDesc
ulVersion As Long
cBuffers As Long
pBuffers As Long
End Type

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

Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" _
(Destination As Any, Source As Any, ByVal Length As Long)

Private Declare Function NT4QuerySecurityPackageInfo Lib "security" _
Alias "QuerySecurityPackageInfoA" (ByVal PackageName As String, _
ByRef pPackageInfo As Long) As Long

Private Declare Function QuerySecurityPackageInfo Lib "secur32" _
Alias "QuerySecurityPackageInfoA" (ByVal PackageName As String, _
ByRef pPackageInfo As Long) As Long

Private Declare Function NT4FreeContextBuffer Lib "security" _
Alias "FreeContextBuffer" (ByVal pvContextBuffer As Long) As Long

Private Declare Function FreeContextBuffer Lib "secur32" _
(ByVal pvContextBuffer As Long) As Long

Private Declare Function NT4InitializeSecurityContext Lib "security" _
Alias "InitializeSecurityContextA" _
(ByRef phCredential As SecHandle, ByRef phContext As SecHandle, _
ByVal pszTargetName As Long, ByVal fContextReq As Long, _
ByVal Reserved1 As Long, ByVal TargetDataRep As Long, _
ByRef pInput As SecBufferDesc, ByVal Reserved2 As Long, _
ByRef phNewContext As SecHandle, ByRef pOutput As SecBufferDesc, _
ByRef pfContextAttr As Long, ByRef ptsExpiry As TimeStamp) As Long

Private Declare Function InitializeSecurityContext Lib "secur32" _
Alias "InitializeSecurityContextA" _
(ByRef phCredential As SecHandle, ByRef phContext As SecHandle, _
ByVal pszTargetName As Long, ByVal fContextReq As Long, _
ByVal Reserved1 As Long, ByVal TargetDataRep As Long, _
ByRef pInput As SecBufferDesc, ByVal Reserved2 As Long, _
ByRef phNewContext As SecHandle, ByRef pOutput As SecBufferDes