Removing Administrator Privilages from Process

Question

With the help of this great MSDN article, my first idea was to simply check if the process is using an elevated Administrator group, and using AdjustTokenGroups() I would set the Administrator group to SE_GROUP_USE_FOR_DENY_ONLY. Unfortunately though, we can't modify the administrator group on the currently running process as it also has the SE_GROUP_MANDATORY attribute, which makes it inelligable for changing.

The MSDN document has this to say about it:

The AdjustTokenGroups function cannot disable groups with the SE_GROUP_MANDATORY attribute in the TOKEN_GROUPS structure. Use CreateRestrictedToken instead.

So, I am done the following code to achieve this;

bool _IsNewProcessLaunched()
{
    HANDLE hToken = NULL;   
    bool hasRestarted = false;

    if (!OpenProcessToken( GetCurrentProcess(), 
        TOKEN_ASSIGN_PRIMARY | TOKEN_QUERY | TOKEN_DUPLICATE | TOKEN_ADJUST_GROUPS, 
        &hToken )) 
    {
        return hasRestarted;
    }

    PSECURITY_DESCRIPTOR pSID = NULL;
    SID_IDENTIFIER_AUTHORITY SIDAuth = SECURITY_NT_AUTHORITY;

    if(! AllocateAndInitializeSid( &SIDAuth, 2,
        SECURITY_BUILTIN_DOMAIN_RID,
        DOMAIN_ALIAS_RID_ADMINS,
        0, 0, 0, 0, 0, 0,
        &pSID) ) 
    {
        CloseHandle(hToken);
        hToken = NULL;
        return hasRestarted;
    }

    BOOL isAdmin = FALSE;
    BOOL ok = CheckTokenMembership(NULL, pSID, &isAdmin);

    // Create the SID structure for the administrator SID
    SID_AND_ATTRIBUTES adminSID = {0};
    adminSID.Sid = pSID;

    // Create a restricted token which denies the administrator group
    HANDLE restrictedToken;

    CreateRestrictedToken(hToken,RESTR,DISABLE_MAX_PRIVILEGE,&adminSID,NULL,NULL,NULL,NULL,&restrictedToken);

    //Create startup info
    STARTUPINFO si = {0};
    PROCESS_INFORMATION pi = {0};
    si.lpDesktop = L"winsta0\\default";
    si.cb = sizeof( si );

    // Get the current executables name
    TCHAR exePath[MAX_PATH];
    GetModuleFileName(NULL,exePath,MAX_PATH);

    // Start the new (non-administrator elevated) restricted process
    if( CreateProcessAsUser(restrictedToken,exePath,NULL,NULL,NULL,TRUE,NORMAL_PRIORITY_CLASS,NULL,NULL,&si,&pi) == 0)
        hasRestarted = false;
    else
        hasRestarted  = true;

    return hasRestarted;
}

But new process is still running as administrator rather than as the normal user.

How do I accomplish that?

Hexachord

You have a very sloppy programming style. RESTR is never defined, and the parameters for CreateRestrictedToken() are completely out of order. If you pass SidsToDisable, you must set DisableSidCount = 1. Any errors returned from the API are completely ignored. – Hereinafter

Answer 1

Since you are restricting the calling process's token, the launched process will be run with the same user account as the calling process, just with restricted permissions. Remember, under UAC, administrators do not have full admin rights without elevation. CreateRestrictedToken() creates a token with restricted permissions. So even though the user may be administrator does not mean the launched process will run with administrative rights.

BTW, there is a simplier API, known as the Safer API, that you can use instead of CreateRestrictedToken():

#include <WinSafer.h>

bool _IsNewProcessLaunched()
{
    // Create the restricted token.

    SAFER_LEVEL_HANDLE hLevel = NULL;
    if (!SaferCreateLevel(SAFER_SCOPEID_USER, SAFER_LEVELID_NORMALUSER, SAFER_LEVEL_OPEN, &hLevel, NULL))
    {
        return false;
    }

    HANDLE hRestrictedToken = NULL;
    if (!SaferComputeTokenFromLevel(hLevel, NULL, &hRestrictedToken, 0, NULL))
    {
        SaferCloseLevel(hLevel);
        return false;
    }

    SaferCloseLevel(hLevel);

    // Set the token to medium integrity.

    TOKEN_MANDATORY_LABEL tml = {0};
    tml.Label.Attributes = SE_GROUP_INTEGRITY; 
    // alternatively, use CreateWellKnownSid(WinMediumLabelSid) instead...
    if (!ConvertStringSidToSid(TEXT("S-1-16-8192"), &(tml.Label.Sid)))
    {
        CloseHandle(hRestrictedToken);
        return false;
    }

    if (!SetTokenInformation(hRestrictedToken, TokenIntegrityLevel, &tml, sizeof(tml) + GetLengthSid(tml.Label.Sid))))
    {
        LocalFree(tml.Label.Sid);
        CloseHandle(hRestrictedToken);
        return false;
    }

    LocalFree(tml.Label.Sid);

    // Create startup info

    STARTUPINFO si = {0};
    si.cb = sizeof( si );
    si.lpDesktop = L"winsta0\\default";

    PROCESS_INFORMATION pi = {0};

    // Get the current executable's name
    TCHAR exePath[MAX_PATH+1] = {0};
    GetModuleFileName(NULL, exePath, MAX_PATH);

    // Start the new (non-elevated) restricted process
    if (!CreateProcessAsUser(hRestrictedToken, exePath, NULL, NULL, NULL, TRUE, NORMAL_PRIORITY_CLASS, NULL, NULL, &si, &pi))
    {
        CloseHandle(hRestrictedToken);
        return false;
    }

    CloseHandle(hRestrictedToken);
    CloseHandle(pi.hThread);
    CloseHandle(pi.hProcess);

    return true;
}

Tude

Interesting API that I have never seen before! Please note that your code creates a token which has the Admin group removed, but the new process starts with Integrity Level = High if the calling process also runs High. So this is definitely a big bug in your code. After creating the Token you must call SetTokenInformation() with TokenIntegrityLevel and SDDL_ML_MEDIUM. – Hereinafter

Apart from that there is a BIG FAT BUG in Windows 10: When you create a process with the above code and set Integrity Level = Medium the new process will be elevated!! GetTokenInformation(TokenElevation) On Windows 7 this does not happen. – Hereinafter