如何确定在用户的本地管理员帐户的上下文中运行的线程

https://support.microsoft.com/zh-cn/kb/118626

概要

若要确定是否在本地管理员帐户下运行一个线程，您必须检查与线程相关联的访问令牌。本文介绍如何执行此操作。

Windows 2000 及更高版本，您可以使用CheckTokenMembership() API 而不是在这篇文章中介绍的步骤。有关其他信息，请参阅 Microsoft 平台 SDK 文档。

详细信息

默认情况下，与线程相关联的标记是进程的其包含。"用户上下文"被取代任何直接连接到该线程的标识。因此，要确定线程的用户上下文，您应首先尝试获取具有OpenThreadToken函数的线程令牌。如果此方法失败并且时出错函数报告 ERROR_NO_TOKEN，然后您可以使用OpenProcessToken函数的进程令牌。

获取当前用户的令牌之后，可以使用访问权限检查功能来检测用户是否为管理员。若要执行此操作，请按照下列步骤操作：

1. 通过使用AllocateAndInitializeSid函数创建本地管理员组的安全标识符 (SID)。
2. 构建新的安全描述符 (SD) 的自由访问控制列表 (DACL)，其中包含访问控制项 (ACE) 的管理员组的 SID。
3. 调用与当前用户和新构造的 SD，来检测用户是否为管理员令牌访问权限检查。

下面的代码示例使用来测试是否当前线程运行本地计算机上的管理员的用户作为本文中前面提到的函数。

示例代码

#include <windows.h>
#include <stdio.h>
#include <lmcons.h>


BOOL IsCurrentUserLocalAdministrator(void);


void main(int argc, char **argv)
{
   if (IsCurrentUserLocalAdministrator())
      printf("You are an administrator\n");
   else
      printf("You are not an administrator\n");
}



/*-------------------------------------------------------------------------

-
IsCurrentUserLocalAdministrator ()

This function checks the token of the calling thread to see if the caller
belongs to the Administrators group.

Return Value:
   TRUE if the caller is an administrator on the local machine.
   Otherwise, FALSE.
--------------------------------------------------------------------------*

/
BOOL IsCurrentUserLocalAdministrator(void)
{
   BOOL   fReturn         = FALSE;
   DWORD  dwStatus;
   DWORD  dwAccessMask;
   DWORD  dwAccessDesired;
   DWORD  dwACLSize;
   DWORD  dwStructureSize = sizeof(PRIVILEGE_SET);
   PACL   pACL            = NULL;
   PSID   psidAdmin       = NULL;

   HANDLE hToken              = NULL;
   HANDLE hImpersonationToken = NULL;

   PRIVILEGE_SET   ps;
   GENERIC_MAPPING GenericMapping;

   PSECURITY_DESCRIPTOR     psdAdmin           = NULL;
   SID_IDENTIFIER_AUTHORITY SystemSidAuthority = SECURITY_NT_AUTHORITY;


   /*
      Determine if the current thread is running as a user that is a member 

of
      the local admins group.  To do this, create a security descriptor 

that
      has a DACL which has an ACE that allows only local aministrators 

access.
      Then, call AccessCheck with the current thread's token and the 

security
      descriptor.  It will say whether the user could access an object if 

it
      had that security descriptor.  Note: you do not need to actually 

create
      the object.  Just checking access against the security descriptor 

alone
      will be sufficient.
   */
   const DWORD ACCESS_READ  = 1;
   const DWORD ACCESS_WRITE = 2;


   __try
   {

      /*
         AccessCheck() requires an impersonation token.  We first get a 

primary
         token and then create a duplicate impersonation token.  The
         impersonation token is not actually assigned to the thread, but is
         used in the call to AccessCheck.  Thus, this function itself never
         impersonates, but does use the identity of the thread.  If the 

thread
         was impersonating already, this function uses that impersonation 

context.
      */
      if (!OpenThreadToken(GetCurrentThread(), TOKEN_DUPLICATE|TOKEN_QUERY, 

TRUE, &hToken))
      {
         if (GetLastError() != ERROR_NO_TOKEN)
            __leave;

         if (!OpenProcessToken(GetCurrentProcess(), 

TOKEN_DUPLICATE|TOKEN_QUERY, &hToken))
            __leave;
      }

      if (!DuplicateToken (hToken, SecurityImpersonation, 

&hImpersonationToken))
          __leave;


      /*
        Create the binary representation of the well-known SID that
        represents the local administrators group.  Then create the 

security
        descriptor and DACL with an ACE that allows only local admins 

access.
        After that, perform the access check.  This will determine whether
        the current user is a local admin.
      */
      if (!AllocateAndInitializeSid(&SystemSidAuthority, 2,
                                    SECURITY_BUILTIN_DOMAIN_RID,
                                    DOMAIN_ALIAS_RID_ADMINS,
                                    0, 0, 0, 0, 0, 0, &psidAdmin))
         __leave;

      psdAdmin = LocalAlloc(LPTR, SECURITY_DESCRIPTOR_MIN_LENGTH);
      if (psdAdmin == NULL)
         __leave;

      if (!InitializeSecurityDescriptor(psdAdmin, 

SECURITY_DESCRIPTOR_REVISION))
         __leave;

      // Compute size needed for the ACL.
      dwACLSize = sizeof(ACL) + sizeof(ACCESS_ALLOWED_ACE) +
                  GetLengthSid(psidAdmin) - sizeof(DWORD);

      pACL = (PACL)LocalAlloc(LPTR, dwACLSize);
      if (pACL == NULL)
         __leave;

      if (!InitializeAcl(pACL, dwACLSize, ACL_REVISION2))
         __leave;

      dwAccessMask= ACCESS_READ | ACCESS_WRITE;

      if (!AddAccessAllowedAce(pACL, ACL_REVISION2, dwAccessMask, 

psidAdmin))
         __leave;

      if (!SetSecurityDescriptorDacl(psdAdmin, TRUE, pACL, FALSE))
         __leave;

      /*
         AccessCheck validates a security descriptor somewhat; set the 

group
         and owner so that enough of the security descriptor is filled out 

to
         make AccessCheck happy.
      */
      SetSecurityDescriptorGroup(psdAdmin, psidAdmin, FALSE);
      SetSecurityDescriptorOwner(psdAdmin, psidAdmin, FALSE);

      if (!IsValidSecurityDescriptor(psdAdmin))
         __leave;

      dwAccessDesired = ACCESS_READ;

      /*
         Initialize GenericMapping structure even though you
         do not use generic rights.
      */
      GenericMapping.GenericRead    = ACCESS_READ;
      GenericMapping.GenericWrite   = ACCESS_WRITE;
      GenericMapping.GenericExecute = 0;
      GenericMapping.GenericAll     = ACCESS_READ | ACCESS_WRITE;

      if (!AccessCheck(psdAdmin, hImpersonationToken, dwAccessDesired,
                       &GenericMapping, &ps, &dwStructureSize, &dwStatus,
                       &fReturn))
      {
         fReturn = FALSE;
         __leave;
      }
   }
   __finally
   {
      // Clean up.
      if (pACL) LocalFree(pACL);
      if (psdAdmin) LocalFree(psdAdmin);
      if (psidAdmin) FreeSid(psidAdmin);
      if (hImpersonationToken) CloseHandle (hImpersonationToken);
      if (hToken) CloseHandle (hToken);
   }

   return fReturn;
}