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gbalduzzi/rsaEncDecOpenSSL.c

Created May 26, 2016 09:51
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AES Encrypt a file using a random generated 256-bit key and encrypt the AES key using RSA public key, then decrypt AES key using private RSA key and decrypt file.
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rsaEncDecOpenSSL.c
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <openssl/evp.h>
#include <openssl/aes.h>
#include <openssl/bio.h>
#include <openssl/ssl.h>
#include <openssl/rsa.h>
void encrypt(EVP_PKEY **pub_key, FILE *ifp, FILE *ofp, unsigned char **key, int *ekl, unsigned char *ivec) {
const unsigned BUFSIZE=4096;
unsigned char *read_buf = malloc(BUFSIZE);
unsigned char *cipher_buf;
unsigned blocksize;
int out_len;
EVP_CIPHER_CTX ctx;
/* Encryption */
EVP_SealInit(&ctx, EVP_aes_256_cbc(), key,ekl, ivec, pub_key,1);
blocksize = EVP_CIPHER_CTX_block_size(&ctx);
cipher_buf = malloc(BUFSIZE + blocksize);
while (1) {
// Read in data in blocks until EOF. Update the ciphering with each read.
int numRead = fread(read_buf, sizeof(unsigned char), BUFSIZE, ifp);
EVP_SealUpdate(&ctx, cipher_buf, &out_len, read_buf, numRead);
fwrite(cipher_buf, sizeof(unsigned char), out_len, ofp);
if (numRead < BUFSIZE) { // EOF
break;
}
}
// Now cipher the final block and write it out.
EVP_SealFinal(&ctx, cipher_buf, &out_len);
fwrite(cipher_buf, sizeof(unsigned char), out_len, ofp);
// Free memory
free(cipher_buf);
free(read_buf);
}
void decrypt(EVP_PKEY *priv_key, FILE *ifp, FILE *ofp, unsigned char *key, int ekl, unsigned char *ivec) {
/* Decryption */
const unsigned BUFSIZE=4096;
unsigned char *read_buf = malloc(BUFSIZE);
unsigned char *cipher_buf;
unsigned blocksize;
int out_len;
EVP_CIPHER_CTX ctx;
EVP_OpenInit(&ctx, EVP_aes_256_cbc(), key,ekl, ivec, priv_key);
blocksize = EVP_CIPHER_CTX_block_size(&ctx);
cipher_buf = malloc(BUFSIZE + blocksize);
while (1) {
// Read in data in blocks until EOF
int numRead = fread(read_buf, sizeof(unsigned char), BUFSIZE, ifp);
EVP_OpenUpdate(&ctx, cipher_buf, &out_len, read_buf, numRead);
fwrite(cipher_buf, sizeof(unsigned char), out_len, ofp);
if (numRead < BUFSIZE) { // EOF
break;
}
}
// Now cipher the final block and write it out.
EVP_OpenFinal(&ctx, cipher_buf, &out_len);
fwrite(cipher_buf, sizeof(unsigned char), out_len, ofp);
// Free memory
free(cipher_buf);
free(read_buf);
}
int main(int argc, char *argv[]) {
if (argc < 5) {
printf("Not enough params");
return 1;
}
unsigned char **key = (unsigned char **)malloc(sizeof(unsigned char *) * 1);
unsigned char iv[16];
/* Get RSA public key */
FILE *rsa_public = fopen(argv[4],"rb");
RSA* pubkey = RSA_new();
pubkey = PEM_read_RSA_PUBKEY(rsa_public,&pubkey,NULL,NULL);
EVP_PKEY **pubk = (EVP_PKEY **)malloc(sizeof(EVP_PKEY *) * 1);
pubk[0] = EVP_PKEY_new();
EVP_PKEY_set1_RSA(pubk[0], pubkey);
FILE *rsa_private = fopen(argv[5],"rb");
RSA* privkey = RSA_new();
privkey = PEM_read_RSAPrivateKey(rsa_private,&privkey,NULL,NULL);
EVP_PKEY **privk = (EVP_PKEY **)malloc(sizeof(EVP_PKEY *) * 1);
privk[0] = EVP_PKEY_new();
EVP_PKEY_assign_RSA(privk[0], privkey);
key[0] = (unsigned char *)malloc(EVP_PKEY_size(pubk[0]));
int *ekl = (int *)malloc(sizeof(int));
FILE *fIN, *fOUT;
// First encrypt the file
fIN = fopen(argv[1], "rb"); //File to be encrypted; plain text
fOUT = fopen(argv[2], "wb"); //File to be written; cipher text
encrypt(pubk, fIN, fOUT, key,ekl, iv);
printf("%s\n",key[0]);
fclose(fIN);
fclose(fOUT);
//Decrypt file now
fIN = fopen(argv[2], "rb"); //File to be read; cipher text
fOUT = fopen(argv[3], "wb"); //File to be written; clear text
decrypt(privk[0], fIN, fOUT, key[0], ekl[0],iv);
return 0;
}
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