winapi - 在 Visual Basic 6 中使用 GetTokenInformation 确定用户是否为管理员

Question

我正在使用 GetTokenInformation 作为确定当前线程是否以管理员身份运行的代码的一部分。

无论如何，我的 token 信息结构如下所示:

Private Type TOKEN_GROUPS
   GroupCount As Long
   Groups(500) As SID_AND_ATTRIBUTES
End Type

然后，我像这样调用 GetTokenInformation:

res = GetTokenInformation(<Process Handle>, 2, <TOKEN_GROUPS>, _
                            <Token Info Length>, <Buffer Length)

第一次调用是获取缓冲区长度，然后我再次调用它来获取 token 信息。

无论如何，当运行应用程序的帐户连接到域时，应用程序会突然崩溃。显然，大小，

Groups(500) As SID.AND.ATTRIBUTES

不够，导致缓冲区溢出。我不知道这是为什么(MSDN 说我应该提供一个 ANYSIZE_ARRAY 或 1)。将组的大小增加到 1000 可以解决此问题。

作为快速修复并且由于我不知道如何获得适当大小的组，我计划只 ReDim 组直到调用成功。

这是我的问题:

1. 我有一个 On Error 子句，但是当缓冲区溢出发生时，On Error 无法捕获它，我的应用程序突然崩溃了。这是为什么？

2. 给出下面的代码

Private Type TOKEN_GROUPS
   GroupCount As Long
   Groups() As SID_AND_ATTRIBUTES 'FAILING
   'Groups(1000) As SID_AND_ATTRIBUTES DOES NOT FAIL
End Type

Dim X as TOKEN_GROUPS
ReDim Preserve X.Groups(1000) As SID_AND_ATTRIBUTES 'FAILING

res = GetTokenInformation(<Process Handle>, 2, <TOKEN_GROUPS>, <Token Info Length>, <Buffer Length)

res = GetTokenInformation(<Process Handle>, 2, <TOKEN_GROUPS>, <Token Info Length>, <Buffer Length)

为什么当我将 Groups 声明为 1000 时，GetTokenInformation 调用没有失败，但是当我声明一个“空”Groups() 并将其重新调整为1000，失败了？

Answer 1

如果您想为Groups 使用动态大小的数组，您将需要“自定义API 调用编码”代码。基本上几个 CopyMemory 和一个数组大小调整

Option Explicit

'--- for OpenProcessToken
Private Const TOKEN_READ                    As Long = &H20008

Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (pTo As Any, uFrom As Any, ByVal lSize As Long)
Private Declare Function GetCurrentProcess Lib "kernel32" () As Long
Private Declare Function CloseHandle Lib "kernel32" (ByVal hObject As Long) As Long
Private Declare Function OpenProcessToken Lib "advapi32.dll" (ByVal ProcessHandle As Long, ByVal DesiredAccess As Long, TokenHandle As Long) As Long
Private Declare Function GetTokenInformation Lib "advapi32.dll" (ByVal TokenHandle As Long, ByVal TokenInformationClass As Long, TokenInformation As Any, ByVal TokenInformationLength As Long, ReturnLength As Long) As Long

Private Type SID_AND_ATTRIBUTES
    Sid             As Long
    Attributes      As Long
End Type

Private Type VB_TOKEN_GROUPS
    GroupCount      As Long
    Groups()        As SID_AND_ATTRIBUTES
End Type


Private Sub Command1_Click()
    Dim hProcessID      As Long
    Dim hToken          As Long
    Dim lNeeded         As Long
    Dim baBuffer()      As Byte
    Dim uGroups         As VB_TOKEN_GROUPS

    hProcessID = GetCurrentProcess()
    If hProcessID <> 0 Then
        If OpenProcessToken(hProcessID, TOKEN_READ, hToken) = 1 Then
            Call GetTokenInformation(hToken, 2, ByVal 0, 0, lNeeded)
            ReDim baBuffer(0 To lNeeded)
            '--- enum TokenInformationClass { TokenUser = 1, TokenGroups = 2, ... }
            If GetTokenInformation(hToken, 2, baBuffer(0), UBound(baBuffer), lNeeded) = 1 Then
                Call CopyMemory(uGroups.GroupCount, baBuffer(0), 4)
                ReDim uGroups.Groups(0 To uGroups.GroupCount - 1)
                Call CopyMemory(uGroups.Groups(0), baBuffer(4), uGroups.GroupCount * Len(uGroups.Groups(0)))
            End If
            Call CloseHandle(hToken)
        End If
        Call CloseHandle(hProcessID)
    End If
End Sub