Thread: GetTokenInformation

Hi, hopefully somebody here can help me with this question. I am trying to build a client/server program where the client asks the server to serve a file. Its really a lab assignment where we are supposed to learn about secure programming in windows. Anyway, we are supposed to get the server processes' privilege information, log it, and then change it. I am running into the problem trying to get the information. Here is the relevant bit of code:

Code:

	HANDLE hProc = OpenProcess(PROCESS_ALL_ACCESS, TRUE, GetCurrentProcessId());
	HANDLE hToken;
	if(OpenProcessToken(
		hProc,
		TOKEN_QUERY,
		&hToken) == 0)
	{
		printf("I was unable to execute OpenProcessToken\r\nErrorCode: %d\r\n", GetLastError());
		return 1;
	}


    DWORD SizeReturned = 0;

	// Pass NULL pointer to return the size needed
	if(!GetTokenInformation(&hToken, TokenPrivileges, NULL, SizeReturned, &SizeReturned))
	{
		printf("1 GetTokenInformation failed. We needed a buffer this big: %d.\r\n", SizeReturned);
		printf("Error Code: %d\r\n", GetLastError());
		return 1;
	}

	TOKEN_PRIVILEGES TokenPrivilegesType = *(PTOKEN_PRIVILEGES)malloc(SizeReturned);

	if(!GetTokenInformation(&hToken, TokenPrivileges, &TokenPrivilegesType, SizeReturned, &SizeReturned))
	{
		printf("2 GetTokenInformation failed. We needed a buffer this big: %d. But ours was this big: %d\r\n", SizeReturned, sizeof(TokenPrivilegesType));
		printf("Error Code: %d\r\n", GetLastError());
		return 1;
	}

The first time that I call GetTokenInformation is where it fails. GetLastError() returns a value of 6, which if I am not mistaken means an invalid handle. I think I understand the process that I am supposed to do but I must be having a hard time understanding the API. Any suggestions? I can provide more information if you need. Thanks in advance for the help!

You've almost got it.
Remove the & from the &hToken in both GetTokenInformation (that's where error 6 comes from as you're inadvertantly passing the wrong thing, the API takes HANDLE not a HANDLE*)
Remove the * from the malloc line and make TokenPrivilegesType a pointer
Remove the & on TokenPrivilegesType from the second GetTokenInformation
And you're good to go

Unless you're creating child processes and want the handle to be inherited, you can simplify
HANDLE hProc = OpenProcess(PROCESS_ALL_ACCESS, TRUE, GetCurrentProcessId());
to
HANDLE hProc = GetCurrentProcess();

Just in case, don't forget to CloseHandle hToken when you're finished with it

Originally Posted by adeyblue

You've almost got it.
Remove the & from the &hToken in both GetTokenInformation (that's where error 6 comes from as you're inadvertantly passing the wrong thing, the API takes HANDLE not a HANDLE*)
Remove the * from the malloc line and make TokenPrivilegesType a pointer
Remove the & on TokenPrivilegesType from the second GetTokenInformation
And you're good to go

Unless you're creating child processes and want the handle to be inherited, you can simplify
HANDLE hProc = OpenProcess(PROCESS_ALL_ACCESS, TRUE, GetCurrentProcessId());
to
HANDLE hProc = GetCurrentProcess();

Just in case, don't forget to CloseHandle hToken when you're finished with it

Wow.... THANKS!! I love and hate how its the mistakes like these that keep me up at night.