/*
* OpenSSLDemo.cpp 
*/

#include "stdafx.h"
#include <stdio.h>

#include <openssl/rsa.h>
#include <openssl/x509.h>

#define HASHED_DATA_SIZE 20
#define SIGNATURE_SIZE 128
#define PUBLIC_KEY_SIZE 162

/*
* Proper error-checking and buffer guarding omitted for simplicity.
*/
int main(int argc, char * argv[])
{
/*
* Allocate arrays to store the raw input bytes.
*/
unsigned char hashed_data[HASHED_DATA_SIZE];
unsigned char signature[SIGNATURE_SIZE];
unsigned char public_key[PUBLIC_KEY_SIZE];

/*
* Read the binary files into their respective arrays.
*/
FILE * fp = fopen("c:\\hasheddata.bin", "rb");

if (HASHED_DATA_SIZE != fread(hashed_data, 1, HASHED_DATA_SIZE + 1, fp))
{
printf("Read of hashed data was NOT exactly 20 bytes.\n");
}

fclose(fp);

fp = fopen("c:\\signature.bin", "rb");

if (SIGNATURE_SIZE != fread(signature, 1, SIGNATURE_SIZE + 1, fp))
{
printf("Read of hashed data was NOT exactly 128 bytes.\n");
}

fclose(fp);

fp = fopen("c:\\pubkey.bin", "rb");

if (PUBLIC_KEY_SIZE != fread(public_key, 1, PUBLIC_KEY_SIZE + 1, fp))
{
printf("Read of hashed data was NOT exactly 162 bytes.\n");
}

fclose(fp);

/*
* Create OpenSSL RSA public key structure from my raw public key
* bytes.
*/
RSA * rsa_struct_ptr = NULL;
const unsigned char * public_key_pointer = public_key;

if (NULL == d2i_RSA_PUBKEY(&rsa_struct_ptr, &public_key_pointer, 
PUBLIC_KEY_SIZE))
{
printf("Creation of RSA public key structure FAILED!\n");
return -1;
}

/*
* Verify the signature against the hashed data that was previously
* signed with my private key.
*/
if (!RSA_verify(NID_sha1, hashed_data, HASHED_DATA_SIZE, 
signature, SIGNATURE_SIZE, rsa_struct_ptr)) 
{
printf("Signature verification FAILED!\n");
return -1;
}

printf("Signature successfully verified.\n");
return 0;
}