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Beispiel C-Programm: Löschen von Zertifikaten aus einem Zertifikat Store

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Im folgenden Beispiel werden die Zertifikate in einem Systemzertifikatspeicher aufgelistet, der den Namen des Betreffs jedes Zertifikats anzeigt und dem Benutzer ermöglicht, alle Zertifikate aus dem Speicher zu löschen. Das Beispiel ruft den Namen des Zertifikatspeichers vom Benutzer ab und kann somit verwendet werden, um den Inhalt eines systembasierten Zertifikatspeichers beizubehalten.

In diesem Beispiel werden die folgenden Aufgaben und CryptoAPI-Funktionen veranschaulicht:

In diesem Beispiel wird der Name eines Systemzertifikatspeichers vom Benutzer abgerufen, dieser Speicher geöffnet und die Zertifikate in diesem Speicher durchlaufen. Für jedes Zertifikat wird der Name des Betreffs des Zertifikats angezeigt, und der Benutzer erhält eine Option zum Löschen dieses Zertifikats.

#pragma comment(lib, "crypt32.lib")

#include <stdio.h>
#include <windows.h>
#include <Wincrypt.h>
#define MY_ENCODING_TYPE  (PKCS_7_ASN_ENCODING | X509_ASN_ENCODING)
void MyHandleError(char *s);

void main(void)
{
//-------------------------------------------------------------------
// Copyright (C) Microsoft.  All rights reserved.
// Declare and initialize variables.

HANDLE          hStoreHandle;
PCCERT_CONTEXT  pCertContext=NULL;   
PCCERT_CONTEXT  pDupCertContext; 
PCERT_PUBLIC_KEY_INFO pOldPubKey = NULL;
PCERT_PUBLIC_KEY_INFO pNewPubKey; 
char pszStoreName[256];
char pszNameString[256];
char fResponse ='n';  
char x;

//-------------------------------------------------------------------
// Get the name of the certificate store to open. 
printf("This program maintains the contents of a certificate\n");
printf("store by allowing you to delete any excess certificates\n");
printf("from a store. \n\n");
printf("Please enter the name of the system store to maintain:");
fgets(pszStoreName, 255, stdin);
if (pszStoreName[strlen(pszStoreName) - 1] =='\n')
   pszStoreName[strlen(pszStoreName) - 1] = '\0';
printf("Certificates will be deleted from "
       "the %s store.\n",pszStoreName);

//-------------------------------------------------------------------
// Open a system certificate store.

if ( hStoreHandle = CertOpenSystemStore(
     NULL,     
     pszStoreName))
{
     printf("The %s store has been opened. \n", pszStoreName);
}
else
{
     MyHandleError("The store was not opened.");
}
//-------------------------------------------------------------------
// Find the certificates in the system store. 

while(pCertContext= CertEnumCertificatesInStore(
    hStoreHandle,
    pCertContext)) // on the first call to the function,
                   //  this parameter is NULL
                   // on all subsequent
                   //  calls, it is the last pointer returned by 
                   //  the function
{
//-------------------------------------------------------------------
// Get and display the name of the subject of the certificate.

if(CertGetNameString(   
   pCertContext,   
   CERT_NAME_SIMPLE_DISPLAY_TYPE,   
   0,
   NULL,   
   pszNameString,   
   128))
{
   printf("\nCertificate for %s \n",pszNameString);
}
else
{
   MyHandleError("CertGetName failed.");
}
//-------------------------------------------------------------------
// Check to determine whether the issuer 
// and the subject are the same.

if(CertCompareCertificateName(
   MY_ENCODING_TYPE,
   &(pCertContext->pCertInfo->Issuer),
   &(pCertContext->pCertInfo->Subject)))
{
     printf("The certificate subject and issuer are the same.\n");
}
else
{
     printf("The certificate subject and issuer "
         "are not the same.\n");
}
//--------------------------------------------------------------------
// Determine whether this certificate's public key matches 
// the public key of the last certificate.

pNewPubKey = &(pCertContext->pCertInfo->SubjectPublicKeyInfo);
if(pOldPubKey)
   if(CertComparePublicKeyInfo(
       MY_ENCODING_TYPE,
       pOldPubKey,
       pNewPubKey))
   {
       printf("The public keys are the same.\n");
   }
   else
   {
       printf("This certificate has a different public key.\n");
   }
//-------------------------------------------------------------------
// Reset the old key.

pOldPubKey = pNewPubKey;

//-------------------------------------------------------------------
// Determine whether this certificate is to be deleted. 

printf("Would you like to delete this certificate? (y/n) ");
fResponse = getchar();
if(fResponse == 'y')
{
   //----------------------------------------------------------------
   // Create a duplicate pointer to the certificate to be 
   // deleted. In this way, the original pointer is not freed 
   // when the certificate is deleted from the store 
   // and the enumeration of the certificates in the store can
   // continue. If the original pointer is used, after the 
   // certificate is deleted, the enumeration loop stops.

   if(pDupCertContext = CertDuplicateCertificateContext(
      pCertContext))
   {
       printf("A duplicate pointer was created. Continue. \n");
   }
   else
   {
        MyHandleError("Duplication of the certificate "
            "pointer failed.");
   }

//-------------------------------------------------------------------
// Compare the pCertInfo members of the two certificates 
// to determine whether they are identical.

if(CertCompareCertificate(
      X509_ASN_ENCODING,
      pDupCertContext->pCertInfo, 
      pCertContext->pCertInfo))
{
     printf("The two certificates are identical. \n");
}
else
{
     printf("The two certificates are not identical. \n");
}
//-------------------------------------------------------------------
// Delete the certificate.
   if(CertDeleteCertificateFromStore(
     pDupCertContext))   
   {
       printf("The certificate has been deleted. Continue. \n");
   }
   else
   {
      printf("The deletion of the certificate failed.\n");
   }
} // end if

//-------------------------------------------------------------------
// Clear the input buffer.

x = getchar();

} // end while

//-------------------------------------------------------------------
// Clean up.

CertCloseStore(
   hStoreHandle,
   0);
printf("The program ran to completion successfully. \n");
} // end main

//-------------------------------------------------------------------
// 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(char *s)
{
    fprintf(stderr,"An error occurred in running the program. \n");
    fprintf(stderr,"%s\n",s);
    fprintf(stderr, "Error number %x.\n", GetLastError());
    fprintf(stderr, "Program terminating. \n");
    exit(1);
} // end MyHandleError