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

//Pad words not 16 characters long
void pad_word(char *word, int length);

int main() {
    FILE *key;
    unsigned char outBuffer[1024 + EVP_MAX_BLOCK_LENGTH];
    int outlen;
    int k;
    char word[16] = {0};
    char plaintext[] = "This is a top secret."; //As specified in task description
    int ptlen = strlen(plaintext);
    char ciphertext[] = "764aa26b55a4da654df6b19e4bce00f4ed05e09346fb0e762583cb7da2ac93a2";
    unsigned char iv[] = "aabbccddeeff00998877665544332211";
    key = fopen("words.txt", "r");
   //Set up OpenSSL cipher
    EVP_CIPHER_CTX ctx;
    EVP_CIPHER_CTX_init(&ctx);


    while ( fgets(word, 16, key) ) {

    int outbuf_len;
        k = strlen(word);
        word[k-1] = '\0';

        if (k < 16) {
            pad_word(word,16);
        }
        //Init the cipher with correct cipher type
        EVP_CipherInit_ex(&ctx, EVP_aes_128_cbc(), 0, 0, 0, 1);
    //printf("%s\n", word);
        //Pass in word to be tested as key with given iv.
        EVP_CipherInit_ex(&ctx, 0, 0, word, iv, 1);
        //Encrypt plaintext through CipherUpdate function, store in out buffer
        if (!EVP_CipherUpdate(&ctx, outBuffer, &outbuf_len, plaintext, ptlen)) {
            printf("Error\n");
            return 0;
        }

        outlen = outbuf_len;
        //printf("%02X\n", outBuffer);
        EVP_CipherFinal_ex(&ctx, outBuffer + outlen, &outbuf_len);
        outlen += outbuf_len;
        //Convert outbuffer to a string  (lines 50-58)
        int i;
        char* string = (char*) malloc(2*outlen + 1);
        char* str_ptr = string;

        for (i = 0; i < outlen; i++) {
            str_ptr += sprintf(str_ptr, "%02X", outBuffer[i]);
        }
        *(str_ptr + 1) = '\0';
        //Convert string to lower case
        for (int j = 0; j < strlen(string); j++) {
            string[j] = tolower(string[j]);
        }
        // printf("%d\n", outlen);
        //printf("%s\n", string);
        //Compare plaintext encrypted with padded word to ciphertext, if it
        //is the same output the word as correct answer.
        if (strcmp(string, ciphertext) == 0) {
            printf("%s is a match", word);
        return 1;
        }
    EVP_CIPHER_CTX_cleanup(&ctx); //cleanup
    }
    fclose(key);
    return 1;

}
 //Pad word as described in task instructions
void pad_word(char *word, int length) {
    int wordLen = strlen(word);
    while (wordLen < length) {
        word[wordLen] = '#';
        wordLen++;
    }
    word[wordLen] = '\0';
}