範例 C 程式：ASN.1 編碼和解碼
下列範例示範如何使用 CryptEncodeObjectEx 和 CryptDecodeObjectEx。 這個範例可以輕鬆地修改為使用 CryptEncodeObject 和 CryptDecodeObject。
此範例也會使用修改過的 ByteToStr 函式版本來列印 抽象語法標記法 One (ASN.1) 編碼的八位數列。 它也會使用 MyHandleError。 這些函式的程式碼隨附于範例中。
#include <stdio.h>
#include <windows.h>
#include "Wincrypt.h"
//-------------------------------------------------------------------
// Copyright (C) Microsoft. All rights reserved.
// Only X509_ASN_ENCODING is needed with these
// functions.
#pragma comment(lib, "crypt32.lib")
#define MY_TYPE X509_ASN_ENCODING
//--------------------------------------------------------------------
// Declare function ByteToString.
void ByteToStr(
DWORD cb,
void* pv,
LPSTR sz);
//-------------------------------------------------------------------
// Declare function MyHandleError.
void MyHandleError(char *s);
//-------------------------------------------------------------------
// Begin main.
void main(void)
{
//-------------------------------------------------------------------
// Declare and initialize local variables.
char *Cert_Sub_Name ="Test User Name";
//-------------------------------------------------------------------
// Initialize a single RDN structure.
CERT_RDN_ATTR rgNameAttr =
{
szOID_COMMON_NAME, // the OID
CERT_RDN_PRINTABLE_STRING, // type of string
(DWORD)strlen(Cert_Sub_Name)+1, // string length including
// the terminating null
// character
(BYTE *)Cert_Sub_Name // pointer to the string
};
//-------------------------------------------------------------------
// Declare and initialize a structure to include
// the array of RDN structures.
CERT_RDN rgRDN[] =
{
1, // the number of elements in the array
&rgNameAttr // pointer to the array
};
//-------------------------------------------------------------------
// Declare and initialize a CERT_NAME_INFO
// structure that includes a CERT_RND.
CERT_NAME_INFO CertName =
{
1, // number of elements in the CERT_RND's array
rgRDN
};
//-------------------------------------------------------------------
// Declare additional variables.
CERT_NAME_INFO *pDecodeName; // point variable to hold
// the address of the decoded
// buffer
DWORD cbEncoded; // variable to hold the
// length of the encoded string
DWORD cbDecoded; // variable to hold the
// length of the decoded buffer
BYTE *pbEncoded; // variable to hold a pointer to the
// encoded buffer
BYTE *pbDecoded; // variable to hold a pointer to the
// decoded buffer
LPSTR sz;
//-------------------------------------------------------------------
// Allocate memory for a large buffer.
if(sz=(char *)malloc(512))
{
printf("Memory for sz allocated\n");
}
else
{
MyHandleError("Memory allocation failed.");
}
//-------------------------------------------------------------------
// Call CrypteEncodeObjectEx to get
// length to allocate for pbEncoded.
if( CryptEncodeObjectEx(
MY_TYPE, // the encoding/decoding type
X509_NAME,
&CertName,
0,
NULL,
NULL,
&cbEncoded)) // fill in the length needed for
// the encoded buffer
{
printf("The number of bytes needed is %d \n",cbEncoded);
}
else
{
MyHandleError("The first call to the function failed.\n");
}
if( pbEncoded = (BYTE*)malloc(cbEncoded))
{
printf("Memory for pvEncoded has been allocated.\n");
}
else
{
MyHandleError("Memory allocation failed.");
}
if(CryptEncodeObjectEx(
MY_TYPE,
X509_NAME,
&CertName,
0,
NULL,
pbEncoded,
&cbEncoded))
{
ByteToStr(cbEncoded, pbEncoded,sz);
printf("The Encoded octets are \n%s\n",sz);
}
else
{
MyHandleError("Encoding failed.");
}
//-------------------------------------------------------------------
// Decode the encoded buffer.
//-------------------------------------------------------------------
// Get the length needed for the decoded buffer.
if(CryptDecodeObjectEx(
MY_TYPE,
X509_NAME,
pbEncoded, // the buffer to be decoded
cbEncoded,
CRYPT_DECODE_NOCOPY_FLAG,
NULL,
NULL,
&cbDecoded))
{
printf("The needed buffer length is %d\n",cbDecoded);
}
else
{
MyHandleError("The first decode pass failed.");
}
//-------------------------------------------------------------------
// Allocate memory for the decoded information.
if(!(pbDecoded = (BYTE*)malloc(cbDecoded)))
{
MyHandleError("Decode buffer memory allocation failed.");
}
//-------------------------------------------------------------------
// Decode the encoded buffer.
if(CryptDecodeObjectEx(
MY_TYPE,
X509_NAME,
pbEncoded, // the buffer to be decoded
cbEncoded,
CRYPT_DECODE_NOCOPY_FLAG,
NULL,
pbDecoded,
&cbDecoded))
{
pDecodeName = ( CERT_NAME_INFO *)pbDecoded;
printf("The cRDN is -> %d \n",pDecodeName->cRDN);
printf("The OID is -> ");
printf("%s\n",pDecodeName->rgRDN->rgRDNAttr->pszObjId);
printf("The string is ->");
printf(" %s\n",pDecodeName->rgRDN->rgRDNAttr->Value.pbData);}
else
{
MyHandleError("Decode failed.");
}
// Clean up memory.
if(sz)
free(sz);
if(pbEncoded)
free(pbEncoded);
if(pbDecoded)
free(pbDecoded);
printf("Processing completed without error.\n");
} // end of main()
//-------------------------------------------------------------------
// Define ByteToStr.
void ByteToStr(
DWORD cb,
void* pv,
LPSTR sz)
//-------------------------------------------------------------------
// Parameters passed are:
// pv -- the Array of BYTES to be converted.
// cb -- the number of BYTEs in the array.
// sz -- a pointer to the string to be returned.
{
//-------------------------------------------------------------------
// Declare and initialize local variables.
BYTE* pb = (BYTE*) pv; // local pointer to a BYTE in the BYTE array
DWORD i; // local loop counter
int b; // local variable
// Ensure that sz is large enough to hold pv.
if(strlen(sz) < cb)
{
MyHandleError("The array of bytes is too long for the "
"allocated string.");
}
//-------------------------------------------------------------------
// Begin processing loop.
for (i=0; i<cb; i++)
{
b = (*pb & 0xF0) >> 4;
*sz++ = (b <= 9) ? b + '0' : (b - 10) + 'A';
b = *pb & 0x0F;
*sz++ = (b <= 9) ? b + '0' : (b - 10) + 'A';
pb++;
*sz++=' ';
}
*sz++ = 0;
} // end of ByteToStr
void MyHandleError(char *s)
{
printf("An error occurred in running the program.\n");
printf("%s\n",s);
printf("Program terminating.\n");
exit(1);
} // end of MyHandleError