示例 C 程序：将名称从证书转换为 ASN.1 和返回
以下示例枚举证书 存储中的证书，显示每个证书的主题和用户，并将每个证书的使用者名称转换为其 抽象语法表示法一 (ASN.1) 编码格式，然后返回到其解码形式。
此示例演示以下任务和 CryptoAPI 函数：
- 使用 CertOpenSystemStore 打开系统存储。
- 使用 CertEnumCertificatesInStore 从打开的存储中获取第一个证书。
- 使用 CertGetNameString 从证书中获取使用者名称和用户名。
- 使用 CertNameToStr 将证书中的使用者名称转换为其 ASN.1 编码形式。
- 使用 CertStrToName 将 ASN.1 编码的字符串转换为其解码形式。
- 使用 CertCloseStore 和 CERT_CLOSE_STORE_CHECK_FLAG 标志关闭证书存储。
#pragma comment(lib, "crypt32.lib")
//-------------------------------------------------------------------
// Example C Program:
// Converting a name from a certificate to an ASN.1 encoded string
// and back.
#include <stdio.h>
#include <tchar.h>
#include <windows.h>
#include <Wincrypt.h>
#define MY_ENCODING_TYPE (PKCS_7_ASN_ENCODING | X509_ASN_ENCODING)
#define MY_STRING_TYPE (CERT_OID_NAME_STR)
//-------------------------------------------------------------------
// Declare auxiliary functions
void MyHandleError(LPTSTR);
void Local_wait();
void main(void)
{
HCERTSTORE hCertStore;
PCCERT_CONTEXT pCertContext;
//---------------------------------------------------------------
// Begin Processing by opening a certificate store.
if(!(hCertStore = CertOpenStore(
CERT_STORE_PROV_SYSTEM,
MY_ENCODING_TYPE,
NULL,
CERT_SYSTEM_STORE_CURRENT_USER,
L"MY")))
{
MyHandleError(TEXT("The MY system store did not open."));
}
//---------------------------------------------------------------
// Loop through the certificates in the store.
// For each certificate,
// get and print the name of the
// certificate subject and issuer.
// convert the subject name from the certificate
// to an ASN.1 encoded string and print the
// octets from that string.
// convert the encoded string back into its form
// in the certificate.
pCertContext = NULL;
while(pCertContext = CertEnumCertificatesInStore(
hCertStore,
pCertContext))
{
LPTSTR pszString;
LPTSTR pszName;
DWORD cbSize;
CERT_BLOB blobEncodedName;
//-----------------------------------------------------------
// Get and display
// the name of subject of the certificate.
if(!(cbSize = CertGetNameString(
pCertContext,
CERT_NAME_SIMPLE_DISPLAY_TYPE,
0,
NULL,
NULL,
0)))
{
MyHandleError(TEXT("CertGetName 1 failed."));
}
if(!(pszName = (LPTSTR)malloc(cbSize * sizeof(TCHAR))))
{
MyHandleError(TEXT("Memory allocation failed."));
}
if(CertGetNameString(
pCertContext,
CERT_NAME_SIMPLE_DISPLAY_TYPE,
0,
NULL,
pszName,
cbSize))
{
_tprintf(TEXT("\nSubject -> %s.\n"), pszName);
//-------------------------------------------------------
// Free the memory allocated for the string.
free(pszName);
}
else
{
MyHandleError(TEXT("CertGetName failed."));
}
//-----------------------------------------------------------
// Get and display
// the name of Issuer of the certificate.
if(!(cbSize = CertGetNameString(
pCertContext,
CERT_NAME_SIMPLE_DISPLAY_TYPE,
CERT_NAME_ISSUER_FLAG,
NULL,
NULL,
0)))
{
MyHandleError(TEXT("CertGetName 1 failed."));
}
if(!(pszName = (LPTSTR)malloc(cbSize * sizeof(TCHAR))))
{
MyHandleError(TEXT("Memory allocation failed."));
}
if(CertGetNameString(
pCertContext,
CERT_NAME_SIMPLE_DISPLAY_TYPE,
CERT_NAME_ISSUER_FLAG,
NULL,
pszName,
cbSize))
{
_tprintf(TEXT("Issuer -> %s.\n"), pszName);
//-------------------------------------------------------
// Free the memory allocated for the string.
free(pszName);
}
else
{
MyHandleError(TEXT("CertGetName failed."));
}
//-----------------------------------------------------------
// Convert the subject name to an ASN.1 encoded
// string and print the octets in that string.
// First : Get the number of bytes that must
// be allocated for the string.
cbSize = CertNameToStr(
pCertContext->dwCertEncodingType,
&(pCertContext->pCertInfo->Subject),
MY_STRING_TYPE,
NULL,
0);
//-----------------------------------------------------------
// The function CertNameToStr returns the number
// of bytes needed for a string to hold the
// converted name, including the null terminator.
// If it returns one, the name is an empty string.
if (1 == cbSize)
{
MyHandleError(TEXT("Subject name is an empty string."));
}
//-----------------------------------------------------------
// Allocated the needed buffer. Note that this
// memory must be freed inside the loop or the
// application will leak memory.
if(!(pszString = (LPTSTR)malloc(cbSize * sizeof(TCHAR))))
{
MyHandleError(TEXT("Memory allocation failed."));
}
//-----------------------------------------------------------
// Call the function again to get the string.
cbSize = CertNameToStr(
pCertContext->dwCertEncodingType,
&(pCertContext->pCertInfo->Subject),
MY_STRING_TYPE,
pszString,
cbSize);
//-----------------------------------------------------------
// The function CertNameToStr returns the number
// of bytes in the string, including the null terminator.
// If it returns 1, the name is an empty string.
if (1 == cbSize)
{
MyHandleError(TEXT("Subject name is an empty string."));
}
//-----------------------------------------------------------
// Get the length needed to convert the string back
// back into the name as it was in the certificate.
if(!(CertStrToName(
MY_ENCODING_TYPE,
pszString,
MY_STRING_TYPE,
NULL,
NULL, // NULL to get the number of bytes
// needed for the buffer.
&cbSize, // Pointer to a DWORD to hold the
// number of bytes needed for the
// buffer
NULL ))) // Optional address of a pointer to
// old the location for an error in the
// input string.
{
MyHandleError(
TEXT("Could not get the length of the BLOB."));
}
if (!(blobEncodedName.pbData = (LPBYTE)malloc(cbSize)))
{
MyHandleError(
TEXT("Memory Allocation for the BLOB failed."));
}
blobEncodedName.cbData = cbSize;
if(CertStrToName(
MY_ENCODING_TYPE,
pszString,
MY_STRING_TYPE,
NULL,
blobEncodedName.pbData,
&blobEncodedName.cbData,
NULL))
{
_tprintf(TEXT("CertStrToName created the BLOB.\n"));
}
else
{
MyHandleError(TEXT("Could not create the BLOB."));
}
//-----------------------------------------------------------
// Free the memory.
free(blobEncodedName.pbData);
free(pszString);
//-----------------------------------------------------------
// Pause before information on the next certificate
// is displayed.
Local_wait();
} // End of while loop
_tprintf(
TEXT("\nThere are no more certificates in the store. \n"));
//---------------------------------------------------------------
// Close the MY store.
if(CertCloseStore(
hCertStore,
CERT_CLOSE_STORE_CHECK_FLAG))
{
_tprintf(TEXT("The store is closed. ")
TEXT("All certificates are released.\n"));
}
else
{
_tprintf(TEXT("The store was closed, ")
TEXT("but certificates still in use.\n"));
}
_tprintf(TEXT("This demonstration program ran to completion ")
TEXT("without error.\n"));
Local_wait();
} // End of main
//-------------------------------------------------------------------
// This example uses the function MyHandleError, a simple error
// handling function, to print an error message to the standard
// error (stderr) file 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 running 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 Local_wait()
{
//-------------------------------------------------------------------
// This function prints a prompt string
// and wait for the user to hit enter.
// It provides a pause with its length controlled by the user.
_tprintf(TEXT("Hit Enter to continue : "));
getchar();
}