I have to find the encryption key from a list of words, I have the plain and cipher text and have written a code which decrypts the cipher text using the words from the file and then compares the plain text, if its same it should print the key used.I used the EVP_BytesToKey to convert the word into key. The IV used for encryption was 0 and the Key is not more than 16 characters long. Problem is i get error Segmentation fault(core dumped). Can anyone help me with this?
#include <stdio.h>
#include <assert.h>
#include <ctype.h>
#include <string.h>
#include <stdlib.h>
#include <openssl/aes.h>
#include <openssl/evp.h>
int main(int argc, char *argv[])
{
int ret = 0;
unsigned char pltmp[1024];
unsigned char citmp[1024];
unsigned char iv2[16] = {0};
unsigned char plaintext[1024] ;
FILE *fp;
/* opening file for reading plaintext*/
fp = fopen("some.txt" , "rb");
if(fp == NULL)
{
perror("Error opening file");
return(-1);
}
fgets (plaintext, 1024, fp);
fclose(fp);
/*opening file to read key*/
FILE *keyf;
keyf = fopen("words.txt", "r");
/*opening file to read cipher text*/
FILE *ct;
ct = fopen("some.aes-128-cbc" , "rb");
if(ct == NULL)
{
perror("Error opening file");
return(-1);
}
fgets (citmp, 1024, ct);
fclose(ct);
const char *password;
/* Creating while loop to read keys until correct key found*/
while(fgets((unsigned char *)password,16,keyf))
{
const EVP_CIPHER *cipher;
const EVP_MD *dgst = NULL;
unsigned char key[EVP_MAX_KEY_LENGTH], iv[EVP_MAX_IV_LENGTH];
const unsigned char *salt = NULL;
int i;
OpenSSL_add_all_algorithms();
cipher = EVP_get_cipherbyname("aes-128-cbc");
if(!cipher) { fprintf(stderr, "no such cipher\n"); return 1; }
dgst=EVP_get_digestbyname("md5");
if(!dgst) { fprintf(stderr, "no such digest\n"); return 1; }
if(!EVP_BytesToKey(cipher, dgst, salt,
(unsigned char *) password,
strlen(password), 1, key, iv))
{
fprintf(stderr, "EVP_BytesToKey failed\n");
return 1;
}
//printf("Key: "); for(i=0; i<cipher->key_len; ++i) { printf("%02x", key[i]); } printf("\n");
//printf("IV: "); for(i=0; i<cipher->iv_len; ++i) { printf("%02x", iv[i]); } printf("\n");
/*Decrypting using the key generated by EVP_BytesToKey and IV is 0*/
EVP_CIPHER_CTX ctx;
EVP_CIPHER_CTX_init(&ctx);
EVP_CipherInit_ex(&ctx, EVP_aes_128_cbc(),NULL, key, iv2, 0);
printf("dec\n");
EVP_Cipher(&ctx, pltmp, citmp, 1024);
printf("compare\n");
if (strcmp(pltmp, plaintext)==0)
{printf("success");
printf("%s Key: ",(unsigned char *)password);
break;}
else {printf("prob");}
EVP_CIPHER_CTX_cleanup(&ctx);
}
}
