Encrypt decrypt file using openssl library

main.c

#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <openssl/evp.h>
#include <openssl/aes.h>

const unsigned char g_cKey[] = "thiskeyisverybad";
const unsigned char g_iVec[] = "dontusethisinput";

void encrypt(FILE *ifp, FILE *ofp)
{
    // Get file size.
    fseek(ifp, 0L, SEEK_END);
    int fsize = ftell(ifp);
    // Set back to normal.
    fseek(ifp, 0L, SEEK_SET);

    int outLen1 = 0;
    int outLen2 = 0;
    unsigned char *indata = malloc(fsize);
    unsigned char *outdata = malloc(fsize * 2);

    // Read file.
    fread(indata, sizeof(char), fsize, ifp); // Read entire file.

    // Set up encryption.
    EVP_CIPHER_CTX *ctx;
    ctx = EVP_CIPHER_CTX_new();

    EVP_EncryptInit(ctx, EVP_aes_128_cbc(), g_cKey, g_iVec);
    EVP_EncryptUpdate(ctx, outdata, &outLen1, indata, fsize);
    EVP_EncryptFinal(ctx, outdata + outLen1, &outLen2);
    fwrite(outdata, sizeof(char), outLen1 + outLen2, ofp);

    EVP_CIPHER_CTX_free(ctx);
}

void decrypt(FILE *ifp, FILE *ofp)
{
    // Get file size.
    fseek(ifp, 0L, SEEK_END);
    int fsize = ftell(ifp);
    // Set back to normal.
    fseek(ifp, 0L, SEEK_SET);

    int outLen1 = 0;
    int outLen2 = 0;
    unsigned char *indata = malloc(fsize);
    unsigned char *outdata = malloc(fsize);

    // Read file.
    fread(indata, sizeof(char), fsize, ifp); // Read entire file.

    // Setup decryption.
    EVP_CIPHER_CTX *ctx;
    ctx = EVP_CIPHER_CTX_new();

    EVP_DecryptInit(ctx, EVP_aes_128_cbc(), g_cKey, g_iVec);
    EVP_DecryptUpdate(ctx, outdata, &outLen1, indata, fsize);
    EVP_DecryptFinal(ctx, outdata + outLen1, &outLen2);
    fwrite(outdata, sizeof(char), outLen1 + outLen2, ofp);

    EVP_CIPHER_CTX_free(ctx);
}

int main(int argc, char *argv[])
{
    FILE *fIN, *fOUT;

    // Encrypt file now.
    fIN = fopen("plain", "rb");       // File to be encrypted. Plain text.
    fOUT = fopen("cyphertext", "wb"); // File to be written. Cipher text.
    encrypt(fIN, fOUT);
    fclose(fIN);
    fclose(fOUT);

    // Decrypt file now.
    fIN = fopen("cyphertext", "rb"); // File to be open. Cipher text.
    fOUT = fopen("decrypted", "wb"); // File to be written. Comeback to plain text.
    decrypt(fIN, fOUT);
    fclose(fIN);
    fclose(fOUT);

    return 0;
}

// Compile:
// gcc main.c -o main -lcrypto
// Need libssl-dev library.
// Check with hexdump:
// hexdump -n 100 -C plain
// hexdump -n 100 -C cyphertext
// hexdump -n 100 -C decrypted