Recupero di un certificato emesso da Active Directory

Un'autorità di certificazione (CA) aziendale pubblica i certificati rilasciati in Active Directory; Un'autorità di certificazione autonoma può anche pubblicare certificati rilasciati in Active Directory. L'esempio seguente illustra come acquisire un contesto di certificato per un certificato archiviato in Active Directory. Dopo aver acquisito il contesto del certificato, è possibile recuperare il contenuto del certificato o eseguire operazioni sui certificati usando le funzioni CryptoAPI.

L'esempio seguente mostra il recupero di un certificato da Active Directory.

//  Copyright (C) Microsoft.  All rights reserved.
//  Retrieve a user certificate from Active Directory.
//
//  This example uses CryptoAPI calls to retrieve 
//  a certificate previously published to Active Directory
//  by Microsoft Certificate Services.
//  Ensure Crypt32.lib and Secur32.lib are part of link libraries.
#pragma comment(lib, "crypt32.lib")

#define SECURITY_WIN32 1
#define UNICODE 1

#include <stdio.h>
#include <windows.h>
#include <Wincrypt.h>
#include <strsafe.h>
#include <security.h>

#define MAXBUFF 512

void __cdecl main()
{
    HCERTSTORE     hStore=NULL;

    PCCERT_CONTEXT pCertCtx = NULL;

    WCHAR          wszDN[MAXBUFF];
    ULONG          cchDN = MAXBUFF;
    
    WCHAR          wszQuery[MAXBUFF * 2];
    ULONG          cchQuery = MAXBUFF * 2;

    //  Determine the name of the user whose certificate is being
    //  retrieved. This value can be constructed by other means,
    //  but this example will use GetUserNameEx.
    if (!GetUserNameEx(NameFullyQualifiedDN,
                       wszDN,
                       &cchDN))
    {
        printf("Failed GetUserNameEx: %x\n",
               GetLastError());
        exit(1);
    }

    //  Build the LDAP query string.
    if (S_OK != StringCchPrintf(wszQuery,
                    cchQuery,
                    L"ldap:///%s?%s",
                    wszDN,
                    L"userCertificate"))
    {
        printf("Failed StringCchPrintf\n");
        exit(1);

    }

    //  Open the Active Directory certificate store.
    hStore = CertOpenStore(CERT_STORE_PROV_LDAP,
                           0,
                           0,
                           CERT_STORE_READONLY_FLAG,
                           wszQuery);
    if ( NULL == hStore)
    {
        printf("Failed CertOpenStore - %x\n", GetLastError());
        exit(1);
    }

    //  Retrieve a certificate context from this opened store.
    //  Here, retrieve any existing certificate stored for 
    //  the user in Active Directory.
    //  If more than one certificate exists, consult
    //  CertFindCertificateInStore documentation for search 
    //  types and calling instructions.
    pCertCtx = CertFindCertificateInStore(hStore,
                   X509_ASN_ENCODING | PKCS_7_ASN_ENCODING,
                   0,
                   CERT_FIND_ANY,
                   NULL,
                   NULL);
    if (NULL == pCertCtx)
    {
        DWORD dwErr;
        dwErr = GetLastError();
        if (CRYPT_E_NOT_FOUND == dwErr)
            printf("User does not have certificate"
                   "in Active Directory\n");
        else
            printf("Failed CertFindCertificateInStore - %x\n",
                   dwErr);
    }
    else
    {
        //  Use the certificate context as needed.
        //  Here, display the serial number.
        DWORD dwLen, i;
        dwLen = pCertCtx->pCertInfo->SerialNumber.cbData;
        //  The serial number bytes are stored
        //  least significant byte first.
        printf("Serial number: ");
        for (i = dwLen-1; i != MAXDWORD; i--)
            printf("%02x",
                   *(pCertCtx->pCertInfo->SerialNumber.pbData + i));
        printf("\n");
        //  Free the certificate context.
        CertFreeCertificateContext(pCertCtx);
    }

    //  Close the certificate store.
    CertCloseStore(hStore, 0);

}