#include <stdio.h>
#include <algorithm>
#include <iostream.h>
#include <stdlib.h>
#include <string.h>
#include <fstream.h>
#include <sys/stat.h>
#include "openssl/crypto.h"
#include "openssl/x509.h"
#include "openssl/pem.h"
#include "openssl/ssl.h"
#include "openssl/err.h"
#include "openssl/rsa.h"

int passphrase_cb(char *buf, int len,int  flag, void *u)
{
char *passphrase="mypassword";
cout<<"Inside callback"<<endl;
int passphrase_len;
passphrase_len = strlen(passphrase);

/* Check sufficient space exists for the passphrase including
* the NULL terminator in the buffer, otherwise truncate.
*/
if (passphrase_len > (len-1))
passphrase_len = (len-1);
memcpy(buf, passphrase, passphrase_len);

/* return the actual passphrase length */
return (passphrase_len);
}

void generateRSAKeys(){
   cout<<"Generating RSA keys"<<endl;
   RSA *rsa=NULL;
   FILE *fp;
   OpenSSL_add_all_algorithms();
   if ((rsa=RSA_generate_key(2048,65537,NULL,NULL)) == NULL){
      cout<<"Creation of keys failed"<<endl;
    }else{
      cout << "success"<<endl;
   }
   fp = fopen("server_public.key","w");
   if (!PEM_write_RSAPublicKey(fp, rsa )){
       cout<<"Error writing public key"<<endl;
    }
    else{
       cout<<"Public key written succesfully"<<endl;
    }
   fclose(fp);
    fp = fopen("server_private.key","w");
     if (!PEM_write_RSAPrivateKey(fp, rsa, EVP_des_ede3_cbc(), (unsigned char *)"mypassword" , strlen("mypassword"),NULL, NULL)){
       cout<<"Error writing private key"<<endl;
    }
    else{
       cout<<"Private key written succesfully"<<endl;
    }
    fclose(fp);
    RSA_free(rsa);
}

/***************************************************************/


std::string newEncryptString(const char *input) {
   FILE *pubFile, *privFile;
   struct stat info;
   int pubRet=stat("/home/mtc/test/server_public.key",&info);
   int privRet=stat("/home/mtc/test/server_private.key",&info);
   cout<<"pubRet="<<pubRet<<endl;
   cout<<"privRet="<<privRet<<endl;
   if ((pubRet!=0) || (privRet!=0)) {
      cout<<"Public and Private key files not present"<<endl;
      generateRSAKeys();
   }
   pubFile=fopen("server_public.key","r");
   RSA *rsa=RSA_new();
   RSA_blinding_off(rsa);
   rsa = PEM_read_RSAPublicKey(pubFile, NULL, NULL, NULL);
   if (rsa==NULL){
      cout<<"Reading of Public key not successfull"<<endl;
   }
   char *encryptedString=(char *)malloc(RSA_size(rsa));
   if (RSA_public_encrypt(strlen(input)+1,(unsigned char*)input,(unsigned char*)encryptedString,rsa,RSA_PKCS1_PADDING)==-1){
      cout<<"encryption failed "<<endl;
   }
   RSA_free(rsa);
   fclose(pubFile);
   std::string cipherText=encryptedString;
   cout<<"Returning from encrypt"<<endl;
   return cipherText;
}


/*****************************************************************/
   std::string newDecryptString(std::string& input) {
   cout<<"Length here "<<sizeof(input)<<endl;
   OpenSSL_add_all_algorithms();
   cout<<"Reached after adding alogo"<<endl;
   FILE *privFile;
   privFile = fopen("/home/mtc/test/server_private.key","r");
   RSA *rsa=RSA_new();
   RSA_blinding_off(rsa);
   int (*cb)(char *buf, int buflen, int flag, void *u);
   cb=passphrase_cb;
   cout<<"Cb value inside decrypt:"<<cb<<endl;
   rsa = PEM_read_RSAPrivateKey(privFile, NULL, cb, NULL);
   if (rsa==NULL){
      cout<<"Reading of private key not successful"<<endl;
   }
   if (RSA_check_key(rsa) != 1){
      cout<<"RSA_check_key(): PrivateKey check failed\n";
   }
   char *plainText=(char *)malloc(RSA_size(rsa));
   if (RSA_private_decrypt(RSA_size(rsa),(unsigned char *)input.c_str(),(unsigned char*)plainText,rsa,RSA_PKCS1_PADDING)==-1){
      cout<<"Decryption failed "<<endl;
   }
   fclose(privFile);
   int len=RSA_size(rsa);
   RSA_free(rsa);
   std::string decryptedString(plainText);
   free(plainText);
   return decryptedString;
}


/*********************************************************************/


int main(int argc, char *argv[])
{
   std::string cipherOut(newEncryptString("trialstring"));
   cout<<"Plain string="<<newDecryptString(cipherOut)<<endl;
   return 0;
}