c# - 设置 GetTokenInformation 返回的 TOKEN_PRIVILEGES.LUID_AND_ATTRIBUTES 数组的大小

Question

我正在尝试检索与 C# 中的 token 关联的权限及其当前状态，但我不知道如何调整返回的 LUID_AND_ATTRIBUTES 数组的大小以适应元素的实际数量。

来自 MSDN

When MarshalAsAttribute.Value is set to ByValArray, the SizeConst must be set to indicate the number of elements in the array.

在调用 GetTokenInformation 后，我能够查看 TOKEN_PRIVILEGES.PrivilegeCount 属性，并看到我正在使用的 token 具有 35 个权限中列出的 24 个权限Privilege Constants引用页。更改 SizeConst = 24 将使我能够看到所有这些，而不仅仅是第一个(我最初根据 PInvoke 中的用法示例设置了 SizeConst = 1)

有没有办法在创建传入数组时指定传入数组的深度，或者我是否需要在编写代码之前知道将有多少权限？

代码片段

[DllImport("advapi32.dll", SetLastError = true)]
protected static extern bool GetTokenInformation(IntPtr TokenHandle, TOKEN_INFORMATION_CLASS TokenInformationClass, IntPtr TokenInformation, int TokenInformationLength, ref int ReturnLength);

[DllImport("advapi32.dll", SetLastError = true, CharSet = CharSet.Auto)][return: MarshalAs(UnmanagedType.Bool)]
protected static extern bool LookupPrivilegeName(string lpSystemName, IntPtr lpLuid,System.Text.StringBuilder lpName, ref int cchName);

protected struct TOKEN_PRIVILEGES {
  public UInt32 PrivilegeCount;
  [MarshalAs(UnmanagedType.ByValArray, SizeConst = 1)]
  public LUID_AND_ATTRIBUTES[] Privileges;
}//TOKEN_PRIVILEGES

[StructLayout(LayoutKind.Sequential)]
protected struct LUID_AND_ATTRIBUTES {
  public LUID Luid;
  public UInt32 Attributes;
}//LUID_AND_ATTRIBUTES

[StructLayout(LayoutKind.Sequential)]
protected struct LUID {
  public uint LowPart;
  public int HighPart;
}//LUID

int TokenInfLength = 0;
IntPtr ThisHandle = WindowsIdentity.GetCurrent().Token;
GetTokenInformation(ThisHandle, TOKEN_INFORMATION_CLASS.TokenPrivileges, IntPtr.Zero, TokenInfLength, ref TokenInfLength); //Get the TokenInformation length (returns false)
IntPtr TokenInformation = Marshal.AllocHGlobal(TokenInfLength);
if(GetTokenInformation(WindowsIdentity.GetCurrent().Token, TOKEN_INFORMATION_CLASS.TokenPrivileges, TokenInformation, TokenInfLength, ref TokenInfLength)){
  TOKEN_PRIVILEGES ThisPrivilegeSet = (TOKEN_PRIVILEGES)Marshal.PtrToStructure(TokenInformation, typeof(TOKEN_PRIVILEGES));
  //ThisPrivilegeSet now holds all of the LUID's i need to check out
  foreach(LUID_AND_ATTRIBUTES laa in ThisPrivilegeSet.Privileges){ //ThisPrivilegeSet.Privileges is only as deep as SizeConst will allow
    System.Text.StringBuilder StrBuilder = new System.Text.StringBuilder();
    int LuidNameLen = 0;
    IntPtr LuidPointer = Marshal.AllocHGlobal(Marshal.SizeOf(laa.Luid));
    Marshal.StructureToPtr(laa.Luid, LuidPointer, true);
    LookupPrivilegeName(null, LuidPointer, null, ref LuidNameLen); //Get the PrivilageName length (returns false)
    StrBuilder.EnsureCapacity(LuidNameLen + 1);
    if(LookupPrivilegeName(null, LuidPointer, StrBuilder, ref LuidNameLen)){ //StrBuilder gets the name this time
      Console.WriteLine("[{0}] : {1}", laa.Attributes.ToString(), StrBuilder.ToString());
    }//end if
    Marshal.FreeHGlobal(LuidPointer);
  }//next
}//end if

这是我的第一篇文章，如果我做错了，我深表歉意，TIA 寻求帮助

Answer 1

我想跟进这个问题，因为我通过 VVS 提供的链接学到了一些东西。

如果您像我一样从未学习或使用过必须直接访问内存的编程语言，您可能也会发现这很有趣(顺便说一句，我已将 SwDevman81 的答案标记为正确答案，因为它运行良好)。

在 VVS 提供的博文中，作者谈到使用调用返回的指针的值(内存地址)+ 返回对象的大小来编码 block 中返回的数据，以动态检索可变数量的对象。在这种情况下以及博客文章中概述的情况下，我们受益于返回的第一个值包含以下数组中的元素数，我们还有一个从函数返回的整数告诉我们返回的结构有多大也可以用于检查我们是否已经到达结构的末尾，如果我们没有一个值告诉我们元素的数量的话。

我为任何对如何将上述博文应用于此场景感兴趣的人提供以下代码示例。

代码示例:

using System;
using System.Runtime.InteropServices;
using System.Security.Principal;

namespace MarshallingExample {
  class Program {

    protected struct TOKEN_PRIVILEGES {
      public UInt32 PrivilegeCount;
      [MarshalAs(UnmanagedType.ByValArray, SizeConst = 1)]
      public LUID_AND_ATTRIBUTES[] Privileges;
    }

    [StructLayout(LayoutKind.Sequential)]
    protected struct LUID_AND_ATTRIBUTES {
      public LUID Luid;
      public UInt32 Attributes;
    }

    [StructLayout(LayoutKind.Sequential)]
    protected struct LUID {
      public uint LowPart;
      public int HighPart;
    }

    //This enum was huge, I cut it down to save space
    protected enum TOKEN_INFORMATION_CLASS {
      /// <summary>
      /// The buffer receives a TOKEN_PRIVILEGES structure that contains the privileges of the token.
      /// </summary>
      TokenPrivileges = 3
    }

    [DllImport("advapi32.dll", SetLastError = true)]
    protected static extern bool GetTokenInformation(IntPtr TokenHandle, TOKEN_INFORMATION_CLASS TokenInformationClass, IntPtr TokenInformation, int TokenInformationLength, ref int ReturnLength);

    [DllImport("advapi32.dll", SetLastError = true, CharSet = CharSet.Auto)]
    [return: MarshalAs(UnmanagedType.Bool)]
    public static extern bool LookupPrivilegeName(string lpSystemName, IntPtr lpLuid, System.Text.StringBuilder lpName, ref int cchName);

    static void Main(string[] args) {
      //Check and print the privileges this token has
      CheckPrivileges(WindowsIdentity.GetCurrent().Token);
    }

    //test function to output privileges for an account
    private static bool CheckPrivileges(IntPtr thisHandle) {
      int iTokenInfLength = 0; //holds the length of the TOKEN_PRIVILEGES structure that will be returned by GetTokenInformation

      //First call to GetTokenInformation returns the length of the structure that will be returned on the next call
      GetTokenInformation(thisHandle, TOKEN_INFORMATION_CLASS.TokenPrivileges, IntPtr.Zero, iTokenInfLength, ref iTokenInfLength);

      //Allocate a block of memory large enough to hold the expected structure
      IntPtr ipTokenInformation = Marshal.AllocHGlobal(iTokenInfLength);
      //ipTokenInformation holds the starting location readable as an integer
      //you can view the memory location using Ctrl-Alt-M,1 or Debug->Windows->Memory->Memory1 in Visual Studio
      //and pasting the value of ipTokenInformation into the search box (it's still empty right now though)
      if(GetTokenInformation(thisHandle, TOKEN_INFORMATION_CLASS.TokenPrivileges, ipTokenInformation, iTokenInfLength, ref iTokenInfLength)) {
        //If GetTokenInformation doesn't return false then the structure should be sitting in the space reserved by ipTokenInformation
        //at this point

        //What was returned is a structure of type TOKEN_PRIVILEGES which has two values, a UInt32 followed by an array
        //of LUID_AND_ATTRIBUTES structures. Because we know what to expect and we know the order to expect it we can section
        //off the memory into marshalled structures and do some math to figure out where to start our next marshal

        uint uiPrivilegeCount = (uint)Marshal.PtrToStructure(ipTokenInformation, typeof(uint)); //Get the count

        //lets create the structure we should have had in the first place
        LUID_AND_ATTRIBUTES[] aLuidAa = new LUID_AND_ATTRIBUTES[uiPrivilegeCount]; //initialize an array to the right size
        LUID_AND_ATTRIBUTES cLuidAa = new LUID_AND_ATTRIBUTES();

        //ipPointer will hold our new location to read from by taking the last pointer plus the size of the last structure read
        IntPtr ipPointer = new IntPtr(ipTokenInformation.ToInt32() + sizeof(uint)); //first laa pointer
        cLuidAa = (LUID_AND_ATTRIBUTES)Marshal.PtrToStructure(ipPointer, typeof(LUID_AND_ATTRIBUTES)); //Read the memory location
        aLuidAa[0] = cLuidAa; //Add it to the array

        //After getting our first structure we can loop through the rest since they will all be the same
        for(int i = 1; i < uiPrivilegeCount; ++i) {
          ipPointer = new IntPtr(ipPointer.ToInt32() + Marshal.SizeOf(cLuidAa)); //Update the starting point in ipPointer
          cLuidAa = (LUID_AND_ATTRIBUTES)Marshal.PtrToStructure(ipPointer, typeof(LUID_AND_ATTRIBUTES)); //Read the memory location
          aLuidAa[i] = cLuidAa; //Add it to the array
        }//next

        TOKEN_PRIVILEGES cPrivilegeSet = new TOKEN_PRIVILEGES();
        cPrivilegeSet.PrivilegeCount = uiPrivilegeCount;
        cPrivilegeSet.Privileges = aLuidAa;
        //now we have what we should have had to begin with
        Console.WriteLine("Privilege Count: {0}", cPrivilegeSet.PrivilegeCount.ToString());


        //This loops through the LUID_AND_ATTRIBUTES array and resolves the LUID names with a
        //call to LookupPrivilegeName which requires us to first convert our managed structure into an unmanaged one
        //so we get to see what it looks like to do it backwards
        foreach(LUID_AND_ATTRIBUTES cLaa in cPrivilegeSet.Privileges) {
          System.Text.StringBuilder sb = new System.Text.StringBuilder();
          int iLuidNameLen = 0; //Holds the length of structure we will be receiving LookupPrivilagename
          IntPtr ipLuid = Marshal.AllocHGlobal(Marshal.SizeOf(cLaa.Luid)); //Allocate a block of memory large enough to hold the structure
          Marshal.StructureToPtr(cLaa.Luid, ipLuid, true); //Write the structure into the reserved space in unmanaged memory
          LookupPrivilegeName(null, ipLuid, null, ref iLuidNameLen); // call once to get the name length we will be receiving
          sb.EnsureCapacity(iLuidNameLen + 1); //Make sure there is enough room for it
          if(LookupPrivilegeName(null, ipLuid, sb, ref iLuidNameLen)) { // call again to get the name
            Console.WriteLine("[{0}] : {1}", cLaa.Attributes.ToString(), sb.ToString());
          }//end if
          Marshal.FreeHGlobal(ipLuid); //Free up the reserved space in unmanaged memory (Should be done any time AllocHGlobal is used)
        }//next
        Marshal.FreeHGlobal(ipTokenInformation);  //Free up the reserved space in unmanaged memory (Should be done any time AllocHGlobal is used)
      }//end if GetTokenInformation
      return true;
    }//CheckPrivileges
  }//Program
}//MarshallingExample