#include <openssl/conf.h>

#include <openssl/evp.h>

#include <string.h>

#include "crypto_err.h"

#include "crypto_sym.h"

unsigned char * gen_random_key(int keyleninbytes) {

unsigned char *buffer = (unsigned char *)malloc(keyleninbytes);

if(1 != RAND_bytes(buffer, keyleninbytes)) handleErrors();

return buffer;

}

int encrypt_sym(unsigned char *plaintext, int plaintext_len, unsigned char *key, unsigned char *iv, unsigned char *ciphertext) {

EVP_CIPHER_CTX *ctx;

int len;

int ciphertext_len;

if(!(ctx = EVP_CIPHER_CTX_new())) handleErrors();

if(1 != EVP_EncryptInit_ex(ctx, EVP_aes_256_cbc(), NULL, key, iv)) handleErrors();

if(1 != EVP_EncryptUpdate(ctx, ciphertext, &len, plaintext, plaintext_len)) handleErrors();

ciphertext_len = len;

if(1 != EVP_EncryptFinal_ex(ctx, ciphertext + len, &len)) handleErrors();

ciphertext_len += len;

EVP_CIPHER_CTX_free(ctx);

return ciphertext_len;

}

int decrypt_sym(unsigned char *ciphertext, int ciphertext_len, unsigned char *key, unsigned char *iv, unsigned char *plaintext) {

EVP_CIPHER_CTX *ctx;

int len;

int plaintext_len;

if(!(ctx = EVP_CIPHER_CTX_new())) handleErrors();

if(1 != EVP_DecryptInit_ex(ctx, EVP_aes_256_cbc(), NULL, key, iv)) handleErrors();

if(1 != EVP_DecryptUpdate(ctx, plaintext, &len, ciphertext, ciphertext_len)) handleErrors();

plaintext_len = len;

if(1 != EVP_DecryptFinal_ex(ctx, plaintext + len, &len)) handleErrors();

plaintext_len += len;

EVP_CIPHER_CTX_free(ctx);

return plaintext_len;

}