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Example C Program: Certificate Store Operations

The following example demonstrates a number of common certificate store operations as well as the following tasks and CryptoAPI functions:

This example uses the function MyHandleError. The code for this function is included with the sample. Code for this and other auxiliary functions is also listed under General Purpose Functions.

This example uses the CreateMyDACL function, defined in the Creating a DACL topic, to ensure the open file is created with a proper DACL.

This example creates a certificate store in memory. A system store is opened and duplicated. A certificate is retrieved from the system store. A new certificate is created from the encoded portion of the certificate retrieved. The certificate retrieved is added to the memory store. A second certificate is retrieved from the My store and a link to that certificate is added to the memory store. The certificate and the link are then retrieved from the memory store and the memory is saved to disk. All of the stores and files are closed. Next, the file store is reopened and a search is done for the certificate link. The success of this program depends upon a My store being available. That store must include a certificate with the subject "Insert_cert_subject_name1," and a second certificate with the subject "Insert_cert_subject_name2." The names of the subjects must be changed to the names of certificate subjects known to be in the My store.



#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.

HCERTSTORE  hSystemStore;              // System store handle
HCERTSTORE  hMemoryStore;              // Memory store handle
HCERTSTORE  hDuplicateStore;           // Handle for a store to be 
                                       // created
                                       // as a duplicate of an open 
                                       // store
PCCERT_CONTEXT  pDesiredCert = NULL;   // Set to NULL for the first 
                                       // call to
                                       // CertFindCertificateInStore
PCCERT_CONTEXT  pCertContext;
HANDLE  hStoreFileHandle ;             // Output file handle
LPWSTR  pszFileName = L"TestStor.sto";  // Output file name
SECURITY_ATTRIBUTES sa;                // For DACL

//-------------------------------------------------------------------
// Open a new certificate store in memory.

if(hMemoryStore = CertOpenStore(
      CERT_STORE_PROV_MEMORY,    // Memory store
      0,                         // Encoding type
                                 // not used with a memory store
      NULL,                      // Use the default provider
      0,                         // No flags
      NULL))                     // Not needed
{
   printf("Opened a memory store. \n");
}
else
{
   MyHandleError( "Error opening a memory store.");
}
//-------------------------------------------------------------------
// Open the My system store using CertOpenStore.

if(hSystemStore = CertOpenStore(
     CERT_STORE_PROV_SYSTEM, // System store will be a 
                             // virtual store
     0,                      // Encoding type not needed 
                             // with this PROV
     NULL,                   // Accept the default HCRYPTPROV
     CERT_SYSTEM_STORE_CURRENT_USER,
                             // Set the system store location in the
                             // registry
     L"MY"))                 // Could have used other predefined 
                             // system stores
                             // including Trust, CA, or Root
{
   printf("Opened the MY system store. \n");
}
else
{
   MyHandleError( "Could not open the MY system store.");
}
//-------------------------------------------------------------------
// Create a duplicate of the My store.

if(hDuplicateStore = CertDuplicateStore(hSystemStore))
{
  printf("The MY store is duplicated.\n");
}
else
{
  printf("Duplication of the MY store failed.\n.");
}

//-------------------------------------------------------------------
// Close the duplicate store. 

if(hDuplicateStore)
    CertCloseStore(
        hDuplicateStore, 
        CERT_CLOSE_STORE_CHECK_FLAG);


//-------------------------------------------------------------------
// Get a certificate that has the string "Insert_cert_subject_name1" 
// in its subject. 

if(pDesiredCert=CertFindCertificateInStore(
      hSystemStore,
      MY_ENCODING_TYPE,             // Use X509_ASN_ENCODING
      0,                            // No dwFlags needed 
      CERT_FIND_SUBJECT_STR,        // Find a certificate with a
                                    // subject that matches the 
                                    // string in the next parameter
      L"Insert_cert_subject_name1", // The Unicode string to be found
                                    // in a certificate's subject
      NULL))                        // NULL for the first call to the
                                    // function 
                                    // In all subsequent
                                    // calls, it is the last pointer
                                    // returned by the function
{
  printf("The desired certificate was found. \n");
}
else
{
   MyHandleError("Could not find the desired certificate.");
}
//-------------------------------------------------------------------
// pDesiredCert is a pointer to a certificate with a subject that 
// includes the string "Insert_cert_subject_name1", the string is 
// passed as parameter #5 to the function.

//------------------------------------------------------------------ 
//  Create a new certificate from the encoded part of
//  an available certificate.

if(pCertContext = CertCreateCertificateContext(
    MY_ENCODING_TYPE  ,            // Encoding type
    pDesiredCert->pbCertEncoded,   // Encoded data from
                                   // the certificate retrieved
    pDesiredCert->cbCertEncoded))  // Length of the encoded data
{
  printf("A new certificate has been created.\n");
}
else
{
  MyHandleError("A new certificate could not be created.");
}

//-------------------------------------------------------------------
// Add the certificate from the My store to the new memory store.

if(CertAddCertificateContextToStore(
      hMemoryStore,                // Store handle
      pDesiredCert,                // Pointer to a certificate
      CERT_STORE_ADD_USE_EXISTING,
      NULL))
{
   printf("Certificate added to the memory store. \n");
}
else
{
   MyHandleError("Could not add the certificate "
       "to the memory store.");
}
//-------------------------------------------------------------------
// Find a different certificate in the My store, and add to it a link
// to the memory store.

//-------------------------------------------------------------------
// Find the certificate context just added to the memory store.

if(pDesiredCert)
    CertFreeCertificateContext(pDesiredCert);

if(pDesiredCert=CertFindCertificateInStore(
      hSystemStore,
      MY_ENCODING_TYPE,            // Use X509_ASN_ENCODING
      0,                           // no dwFlags needed 
      CERT_FIND_SUBJECT_STR,       // Find a certificate with a
                                   // subject that matches the 
                                   // string in the next parameter
      L"Insert_cert_subject_name2",// The Unicode string to be found
                                   // in a certificate's subject
      NULL))                       // NULL for the first call to the
                                   // function 
                                   // In all subsequent
                                   // calls, it is the last pointer
                                   // returned by the function
{
  printf("The second certificate was found. \n");
}
else
{
   MyHandleError("Could not find the second certificate.");
}
//-------------------------------------------------------------------
// Add a link to the second certificate from the My store to 
// the new memory store.

if(CertAddCertificateLinkToStore(
      hMemoryStore,           // Store handle
      pDesiredCert,           // Pointer to a certificate
      CERT_STORE_ADD_USE_EXISTING,
      NULL))
{
   printf("Certificate link added to the memory store. \n");
}
else
{
   MyHandleError("Could not add the certificate link to the "
       "memory store.");
}
//--------------------------------------------------------------------
// Find the first certificate in the memory store.

if(pDesiredCert)
    CertFreeCertificateContext(pDesiredCert);

if(pDesiredCert=CertFindCertificateInStore(
      hMemoryStore,
      MY_ENCODING_TYPE,            // Use X509_ASN_ENCODING
      0,                           // No dwFlags needed 
      CERT_FIND_SUBJECT_STR,       // Find a certificate with a
                                   // subject that matches the string
                                   // in the next parameter
      L"Insert_cert_subject_name1",// The Unicode string to be found
                                   // in a certificate's subject
      NULL))                       // NULL for the first call to the
                                   // function
                                   // In all subsequent
                                   // calls, it is the last pointer
                                   // returned by the function
{
  printf("The desired certificate was found in the "
      "memory store. \n");
}
else
{
   printf("Certificate not in the memory store.\n");
}
//-------------------------------------------------------------------
// Find the certificate link in the memory store.

if(pDesiredCert)
    CertFreeCertificateContext(pDesiredCert);

if(pDesiredCert=CertFindCertificateInStore(
      hMemoryStore,
      MY_ENCODING_TYPE,            // Use X509_ASN_ENCODING
      0,                           // No dwFlags needed 
      CERT_FIND_SUBJECT_STR,       // Find a certificate with a
                                   // subject that matches the 
                                   // string in the next parameter
      L"Insert_cert_subject_name1",// The Unicode string to be found
                                   // in a certificate's subject
      NULL))                       // NULL for the first call to the
                                   // function
                                   // In all subsequent
                                   // calls, it is the last pointer
                                   // returned by the function
{
  printf("The certificate link was found in the memory store. \n");
}
else
{
   printf("The certificate link was not in the memory store.\n");
}
//-------------------------------------------------------------------
// Create a file in which to save the new store and certificate.

// Create a DACL for the file.
sa.nLength = sizeof(SECURITY_ATTRIBUTES);
sa.bInheritHandle = FALSE;  

// Call the function to set the DACL. The DACL
// is set in the SECURITY_ATTRIBUTES 
// lpSecurityDescriptor member.
// if !CreateMyDACL(&sa), call MyHandleError("CreateMyDACL failed.");

if(hStoreFileHandle = CreateFile(
      pszFileName,        // File path
      GENERIC_WRITE,      // Access mode
      0,                  // Share mode
      &sa,                // Security 
      CREATE_ALWAYS,      // How to create the file
      FILE_ATTRIBUTE_NORMAL,
                          // File attributes
      NULL))              // Template
{
   printf("Created a new file on disk. \n");
}
else
{
   MyHandleError("Could not create a file on disk.");
}
//-------------------------------------------------------------------
// hStoreFileHandle is the output file handle.
// Save the memory store and its certificate to the output file.

if( CertSaveStore(
      hMemoryStore,        // Store handle
      0,                   // Encoding type not needed here
      CERT_STORE_SAVE_AS_STORE,
      CERT_STORE_SAVE_TO_FILE,
      hStoreFileHandle,    // This is the handle of an open disk file
      0))                  // dwFlags
                           // No flags needed here
{
   printf("Saved the memory store to disk. \n");
}
else
{
   MyHandleError("Could not save the memory store to disk.");
}
//-------------------------------------------------------------------
// Close the stores and the file. Reopen the file store, 
// and check its contents.

if(hMemoryStore)
    CertCloseStore(
        hMemoryStore, 
        CERT_CLOSE_STORE_CHECK_FLAG);

if(hSystemStore)
    CertCloseStore(
        hSystemStore, 
        CERT_CLOSE_STORE_CHECK_FLAG);

if(hStoreFileHandle)
     CloseHandle(hStoreFileHandle);

printf("All of the stores and files are closed. \n");

//-------------------------------------------------------------------
//  Reopen the file store.

if(hMemoryStore = CertOpenStore(
       CERT_STORE_PROV_FILENAME,    // Store provider type
       MY_ENCODING_TYPE,            // If needed, use the usual
                                    // encoding types
       NULL,                        // Use the default HCRYPTPROV
       0,                           // Accept the default for all
                                    // dwFlags
       L"TestStor.sto" ))           // The name of an existing file
                                    // as a Unicode string
{
     printf("The file store has been reopened. \n");
}
else
{
    printf("The file store could not be reopened. \n");
}
//-------------------------------------------------------------------
// Find the certificate link in the reopened file store.

if(pDesiredCert)
    CertFreeCertificateContext(pDesiredCert);

if(pDesiredCert=CertFindCertificateInStore(
      hMemoryStore,
      MY_ENCODING_TYPE,            // Use X509_ASN_ENCODING
      0,                           // No dwFlags needed 
      CERT_FIND_SUBJECT_STR,       // Find a certificate with a
                                   // subject that matches the string
                                   // in the next parameter
      L"Insert_cert_subject_name1",// The Unicode string to be found
                                   // in a certificate's subject
      NULL))                       // NULL for the first call to the
                                   // function
                                   // In all subsequent
                                   // calls, it is the last pointer
                                   // returned by the function
{
  printf("The certificate link was found in the file store. \n");
}
else
{
   printf("The certificate link was not in the file store.\n");
}
//-------------------------------------------------------------------
// Clean up memory and end.

if(pDesiredCert)
    CertFreeCertificateContext(pDesiredCert);
if(hMemoryStore)
    CertCloseStore(
        hMemoryStore, 
        CERT_CLOSE_STORE_CHECK_FLAG);
if(hSystemStore)
    CertCloseStore(
        hSystemStore, 
        CERT_CLOSE_STORE_CHECK_FLAG);
if(hStoreFileHandle)
     CloseHandle(hStoreFileHandle);
printf("All of the stores and files are closed. \n");
return;
} // 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


 

 

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