takes a one-way hash as cmd-line input and attempts to match hash to letters

crack.c

#define _XOPEN_SOURCE
#include <unistd.h>

#include <stdio.h>
#include <cs50.h>
#include <string.h>
#include <ctype.h>



int main (int argc, string argv[])
{
    // checking if a command-line argument, hashed password was passed in
    if (argc != 2)
    {
        printf("Usage: %s hash\n", argv[0]);
        return 1;
    }

    // splitting the argument into salt and hash
    // salt
    char salt[2];
    salt[0] = argv[1][0];
    salt[1] = argv[1][1];
    string saltstr = salt;

    // determining argv[1]'s size
    int argv1size = strlen(argv[1]);
    int hashSize = argv1size - 2;

    // hash
    char hash[hashSize];
    for (int i = 0; i < hashSize; i++)
    {
        hash[i] = argv[1][i + 2]; // populating the hash
    }
    string hashstr = hash; // converting hash array into string
    string salthash = saltstr; // should look like this after concat e.g. 50fkUxYHbnXGw
    strcat(salthash, hashstr); // concatinating salt and hash

    // generating plaintext and comparing hashes
    // initializing plaintext with ascii character preceeding A
    char pas[4] = { '@', '@', '@', '@' };

    // will loop until I reach all character combinations posibilitties
    while ( pas[3] != '{')
    {
        pas[0]++;
        if (pas[0] == '[') // skipping over non alphabet characters for pas[0]
        {
            pas[0] = 'a';
        }
        if (pas[0] == '{') // if pas[0] is @ end of alphabet, reset to A 'n increase pas[1]
        {
            pas[0] = 'A';
            pas[1]++;
        }

        if (pas[1] == '[') // skipping over non alphabet characters for pas[1]
        {
            pas[1] = 'a';
        }
        if (pas[1] == '{') // if pas[1] is @ end of alphabet, reset to A 'n increase pas[2]
        {
            pas[1] = 'A';
            pas[2]++;
        }

        if (pas[2] == '[') // skipping over non alphabet characters for pas[2]
        {
            pas[2] = 'a';
        }

        if (pas[2] == '{') // if pas[2] is @ end of alphabet, reset to A 'n increase pas[3]
        {
            pas[2] = 'A';
            pas[3]++; // will increase until we hit character { and the whole loop stops
        }

        // converting 4 char array into appropriate sized string
        // determining size of string by the amount of valid chars
        int i = 0;
        int vallen = 0; // valid char length
        while (pas[i] != '@')
        {
            i++;
            vallen++;
        }
        char pasval[vallen]; // making a valid character array the size of valid char amount

        for (int j = 0; j < vallen; j++) // copying valid chars
        {
            pasval[i] = pas[j];
        }
        // converting to string
        string pastr = pasval;

        // converting local string pastr to hash
        string lhstr = crypt(pastr, hashstr);

        // converting to salt+hash
        string lsalthash = crypt(lhstr, saltstr);

        //               *****************************************************

        // comparing input hash to generated hash
        if (strcmp(salthash, lsalthash) == 0)
        {
            printf("%s\n", pasval); // printing the generated string if hashes match
            break; // if there's a match, breaking out of loop
        }
    }
    return 0;
}