Contoh Program C: Menggunakan CryptAcquireContext

Contoh berikut menunjukkan beberapa cara berbeda untuk menggunakanCryptAcquireContext dan fungsi CryptoAPI terkait untuk bekerja dengan penyedia layanan kriptografi (CSP) dan kontainer kunci .

Contoh ini menunjukkan tugas dan fungsi CryptoAPI berikut:

• Gunakan fungsiCryptAcquireContext untuk memperoleh handel untuk CSP default dan kontainer kunci default. Jika tidak ada kontainer kunci default, gunakan fungsi CryptAcquireContext untuk membuat kontainer kunci default.
• Gunakan fungsiCryptGetProvParam untuk mengambil informasi tentang CSP dan kontainer kunci.
• Tingkatkanjumlah referensipada penyedia dengan menggunakan fungsiCryptContextAddRef.
• Rilis CSP dengan menggunakan fungsiCryptReleaseContext.
• Buat kontainer kunci bernama dengan menggunakan fungsiCryptAcquireContext.
• Dapatkan handel untuk CSP dengan menggunakan kontainer kunci yang baru dibuat.
• Hapus kontainer kunci dengan menggunakan fungsiCryptAcquireContext.

Contoh ini menggunakan fungsi MyHandleError. Kode untuk fungsi ini disertakan dengan sampel. Kode untuk fungsi ini dan tambahan lainnya juga tercantum di bawah General Purpose Functions.

//-------------------------------------------------------------------
//  Copyright (C) Microsoft.  All rights reserved.
//  Example code using CryptAcquireContext.
#pragma comment(lib, "crypt32.lib")

#include <stdio.h>
#include <tchar.h>
#include <windows.h>
#include <Wincrypt.h>

//-------------------------------------------------------------------
// This example uses the function MyHandleError, a simple error
// handling function to print an error message and exit 
// the program. 
// For most applications, replace this function with one 
// that does more extensive error reporting.

void MyHandleError(LPTSTR psz)
{
    _ftprintf(stderr, TEXT("An error occurred in the program. \n"));
    _ftprintf(stderr, TEXT("%s\n"), psz);
    _ftprintf(stderr, TEXT("Error number %x.\n"), GetLastError());
    _ftprintf(stderr, TEXT("Program terminating. \n"));
    exit(1);
} // End of MyHandleError.

void main(void)
{
    //---------------------------------------------------------------
    // Declare and initialize variables.
    HCRYPTPROV hCryptProv;

    //---------------------------------------------------------------
    // Get a handle to the default PROV_RSA_FULL provider.
    if(CryptAcquireContext(
        &hCryptProv, 
        NULL, 
        NULL, 
        PROV_RSA_FULL, 
        0)) 
    {
        _tprintf(TEXT("CryptAcquireContext succeeded.\n"));
    }
    else
    {
        if (GetLastError() == NTE_BAD_KEYSET)
        {
            // No default container was found. Attempt to create it.
            if(CryptAcquireContext(
                &hCryptProv, 
                NULL, 
                NULL, 
                PROV_RSA_FULL, 
                CRYPT_NEWKEYSET)) 
            {
                _tprintf(TEXT("CryptAcquireContext succeeded.\n"));
            }
            else
            {
                MyHandleError(TEXT("Could not create the default ")
                    TEXT("key container.\n"));
            }
        }
        else
        {
            MyHandleError(TEXT("A general error running ")
                TEXT("CryptAcquireContext."));
        }
    }

    CHAR pszName[1000];
    DWORD cbName;

    //---------------------------------------------------------------
    // Read the name of the CSP.
    cbName = 1000;
    if(CryptGetProvParam(
        hCryptProv, 
        PP_NAME, 
        (BYTE*)pszName, 
        &cbName, 
        0))
    {
        _tprintf(TEXT("CryptGetProvParam succeeded.\n"));
        printf("Provider name: %s\n", pszName);
    }
    else
    {
        MyHandleError(TEXT("Error reading CSP name.\n"));
    }

    //---------------------------------------------------------------
    // Read the name of the key container.
    cbName = 1000;
    if(CryptGetProvParam(
        hCryptProv, 
        PP_CONTAINER, 
        (BYTE*)pszName, 
        &cbName, 
        0))
    {
        _tprintf(TEXT("CryptGetProvParam succeeded.\n"));
        printf("Key Container name: %s\n", pszName);
    }
    else
    {
        MyHandleError(TEXT("Error reading key container name.\n"));
    }
    //---------------------------------------------------------------
    // Perform cryptographic operations.
    //...

    //---------------------------------------------------------------
    //  Add to the reference count on the provider. When the 
    //  reference count on a provider is greater than one,  
    //  CryptReleaseContext reduces the reference count but does not 
    //  free the provider.

    if(CryptContextAddRef(
        hCryptProv, 
        NULL, 
        0)) 
    {
        _tprintf(TEXT("CryptcontextAddRef succeeded.\n"));
    }
    else
    {
        MyHandleError(TEXT("Error during CryptContextAddRef!\n"));
    }

    //---------------------------------------------------------------
    //  The reference count on hCryptProv is now greater than one. 
    //  The first call to CryptReleaseContext will not release the 
    //  provider handle. 

    //---------------------------------------------------------------
    //  Release the context once.
    if (CryptReleaseContext(hCryptProv, 0))
    {
        _tprintf(TEXT("The first call to CryptReleaseContext ")
            TEXT("succeeded.\n"));
    }
    else
    {
        MyHandleError(TEXT("Error during ")
            TEXT("CryptReleaseContext #1!\n"));
    }

    //---------------------------------------------------------------
    // Release the provider handle again.
    if (CryptReleaseContext(hCryptProv, 0)) 
    {
        _tprintf(TEXT("The second call to CryptReleaseContext ")
            TEXT("succeeded.\n"));
    }
    else
    {
        MyHandleError(TEXT("Error during ")
            TEXT("CryptReleaseContext #2!\n"));
    }

    //---------------------------------------------------------------
    // Get a handle to a PROV_RSA_FULL provider and
    // create a key container named "My Sample Key Container".
    LPCTSTR pszContainerName = TEXT("My Sample Key Container");

    hCryptProv = NULL;
    if(CryptAcquireContext(
        &hCryptProv, 
        pszContainerName,
        NULL, 
        PROV_RSA_FULL, 
        CRYPT_NEWKEYSET)) 
    {
        _tprintf(TEXT("CryptAcquireContext succeeded. \n"));
        _tprintf(TEXT("New key set created. \n")); 

        //-----------------------------------------------------------
        // Release the provider handle and the key container.
        if(hCryptProv)
        {
            if(CryptReleaseContext(hCryptProv, 0)) 
            {
                hCryptProv = NULL;
                _tprintf(TEXT("CryptReleaseContext succeeded. \n"));
            }
            else
            {
                MyHandleError(TEXT("Error during ")
                    TEXT("CryptReleaseContext!\n"));
            }
        }
    }
    else
    {
        if(GetLastError() == NTE_EXISTS)
        {
            _tprintf(TEXT("The named key container could not be ")
                TEXT("created because it already exists.\n"));
            
            // Just continue the program. The named container 
            // will be reopened below.
        }
        else
        {
            MyHandleError(TEXT("Error during CryptAcquireContext ")
                TEXT("for a new key container."));
        }
    }

    //---------------------------------------------------------------
    // Get a handle to the provider by using the new key container. 
    // Note: This key container will be empty until keys
    // are explicitly created by using the CryptGenKey function.
    if(CryptAcquireContext(
        &hCryptProv, 
        pszContainerName, 
        NULL, 
        PROV_RSA_FULL,
        0)) 
    {
        _tprintf(TEXT("Acquired the key set just created. \n"));
    }
    else
    {
        MyHandleError(TEXT("Error during CryptAcquireContext!\n"));
    }

    //---------------------------------------------------------------
    // Perform cryptographic operations.

    //---------------------------------------------------------------
    // Release the provider handle.
    if(CryptReleaseContext(
        hCryptProv, 
        0)) 
    {
        _tprintf(TEXT("CryptReleaseContext succeeded. \n"));
    }
    else
    {
        MyHandleError(TEXT("Error during CryptReleaseContext!\n"));
    }

    //---------------------------------------------------------------
    // Delete the new key container.
    if(CryptAcquireContext(
        &hCryptProv, 
        pszContainerName, 
        NULL, 
        PROV_RSA_FULL,
        CRYPT_DELETEKEYSET)) 
    {
        _tprintf(TEXT("Deleted the key container just created. \n"));
    }
    else
    {
        MyHandleError(TEXT("Error during CryptAcquireContext!\n"));
    }
} // End of main.