verifier/crypto.cpp

#include <stdio.h> 
#include <string> 
#include <memory>
using std::unique_ptr;

#include <openssl/bn.h>
#include <openssl/rsa.h>
#include <openssl/sha.h>
using BN_ptr = std::unique_ptr<BIGNUM, decltype(&::BN_free)>;
using RSA_ptr = std::unique_ptr<RSA, decltype(&::RSA_free)>;

uint32_t generate_rsa_key(std::string& priv_key_str, std::string& pub_key_str)
{
    int rc;

    RSA_ptr rsa(RSA_new(), ::RSA_free);
    BN_ptr bn(BN_new(), ::BN_free);

    rc = BN_set_word(bn.get(), 3);
    if(rc != 1)
      return 0x1;

    rc = RSA_generate_key_ex(rsa.get(), 3072, bn.get(), NULL);
    if(rc != 1)
      return 0x2;
	printf("Generated key\n"); fflush(stdout); 
/*    int pub_key_der_encoded_len, priv_key_der_encoded_len;
    unsigned char *pub_key_der, priv_key_der;

    pub_key_der = NULL;
    pub_key_der_encoded_len = i2d_RSAPublicKey(rsa.get(), (unsigned char**) &pub_key_der);
    if (pub_key_der_encoded_len < 0)
      return 0x3;

    priv_key_der = NULL;
    priv_key_der_encoded_len = i2d_RSAPrivateKey(rsa.get(), (unsigned char**) &priv_key_der);
    if (priv_key_der_encoded_len < 0)
      return 0x4;
    printf("Done\n"); fflush(stdout); 
//   priv_key_str=std::string(priv_key_der, priv_key_der_encoded_len); //, priv_key_der); 
//   pub_key_str=std::string(pub_key_der, pub_key_der_encoded_len);  
*/

    const BIGNUM* n_internal_bigendian_struct;
    RSA_get0_key(rsa.get(), &n_internal_bigendian_struct, NULL, NULL);
    BIGNUM* n_bigendian_struct = BN_dup(n_internal_bigendian_struct); 

    uint32_t count; 
    int n_bignum_length=BN_num_bytes(n_bigendian_struct);
    unsigned char *n_bigendian = (unsigned char*) malloc(n_bignum_length);
    int length_bignum_le = BN_bn2bin(n_bigendian_struct, n_bigendian); 
    unsigned char* n_littleendian = (unsigned char*) malloc(length_bignum_le);
    for(count=0; count<length_bignum_le; count++)
		n_littleendian[count] = n_bigendian[length_bignum_le-count-1]; 
    unsigned char hash[SHA256_DIGEST_LENGTH];
    SHA256_CTX sha256;
    SHA256_Init(&sha256);
    SHA256_Update(&sha256, n_littleendian, length_bignum_le);
    SHA256_Final(hash, &sha256);
// TODO: Return hash of the public key for now
// TODO: Print public key 
// TODO: Use EVP funs - https://www.openssl.org/docs/man1.1.0/crypto/EVP_DigestInit.html
   free(n_bigendian); free(n_littleendian); 
   return 0; //length_bignum_le; 
}