context.c File Reference

#include "precomp.h"

Include dependency graph for context.c:

Go to the source code of this file.

Functions
BOOL WINAPI	ImpersonatePrinterClient (HANDLE hToken)
HANDLE WINAPI	RevertToPrinterSelf (VOID)

Function Documentation

ImpersonatePrinterClient()

BOOL WINAPI ImpersonatePrinterClient

(

HANDLE

hToken

)

See also

RevertToPrinterSelf

Definition at line 14 of file context.c.

{
    DWORD cbReturned;
    DWORD dwErrorCode;
    TOKEN_TYPE Type;

    // Sanity check
    if (!hToken)
    {
        dwErrorCode = ERROR_INVALID_HANDLE;
        goto Cleanup;
    }

    // Get the type of the supplied token.
    if (!GetTokenInformation(hToken, TokenType, &Type, sizeof(TOKEN_TYPE), &cbReturned))
    {
        dwErrorCode = GetLastError();
        ERR("GetTokenInformation failed with error %lu!\n", dwErrorCode);
        goto Cleanup;
    }

    // Check if this is an impersonation token and only set it as the thread token in this case.
    // This is not always an impersonation token, see RevertToPrinterSelf.
    if (Type == TokenImpersonation)
    {
        if (!SetThreadToken(NULL, hToken))
        {
            dwErrorCode = GetLastError();
            ERR("SetThreadToken failed with error %lu!\n", dwErrorCode);
            goto Cleanup;
        }
    }

Cleanup:
    if (hToken)
        CloseHandle(hToken);

    SetLastError(dwErrorCode);
    return (dwErrorCode == ERROR_SUCCESS);
}

RevertToPrinterSelf()

HANDLE WINAPI RevertToPrinterSelf

(

VOID

)

RevertToPrinterSelf reverts the security context from the current user's context back to the process context. As spoolss.dll is used by spoolsv.exe, this is usually the SYSTEM security context.

Unlike the traditional ImpersonateClient and then RevertToSelf approach, we do it the other way round here, because spoolss.dll is delay-loaded by spoolsv.exe in the current user's context. Use RevertToPrinterSelf then to return to the SYSTEM context for specific tasks.

Definition at line 64 of file context.c.

{
    DWORD dwErrorCode;
    HANDLE hReturnValue = NULL;
    HANDLE hToken = NULL;

    // All spoolss code is usually called after impersonating the client. In this case, we can retrieve our current thread impersonation token using OpenThreadToken.
    // But in rare occasions, spoolss code is also called from a higher-privileged thread that doesn't impersonate the client. Then we don't get an impersonation token.
    // Anyway, we can't just return nothing in this case, because this is being treated as failure by the caller. So we return the token of the current process.
    // This behaviour is verified with Windows!
    if (OpenThreadToken(GetCurrentThread(), TOKEN_IMPERSONATE, TRUE, &hToken))
    {
        // Tell the thread to stop impersonating.
        if (!SetThreadToken(NULL, NULL))
        {
            dwErrorCode = GetLastError();
            ERR("SetThreadToken failed with error %lu!\n", dwErrorCode);
            goto Cleanup;
        }
    }
    else if (!OpenProcessToken(GetCurrentProcess(), TOKEN_QUERY, &hToken))
    {
        dwErrorCode = GetLastError();
        ERR("OpenProcessToken failed with error %lu!\n", dwErrorCode);
        goto Cleanup;
    }

    // We were successful, return a token!
    dwErrorCode = ERROR_SUCCESS;
    hReturnValue = hToken;

    // Don't let the cleanup routine close this.
    hToken = NULL;

Cleanup:
    if (hToken)
        CloseHandle(hToken);

    SetLastError(dwErrorCode);
    return hReturnValue;
}

Referenced by _CreateNonspooledPort(), _HandleAddPort(), _HandleConfigureLPTPortCommandOK(), _HandleDeletePort(), and _HandleSetDefaultCommConfig().