Why my program isn't working: Crack password using crypt function DES based.

**roy_000** · 07-13-2017

Code:

/* DES Based crypt. Assuming the password is upto 4 letters, alphabets both upper and lower case. I'm new to coding, please help.
example: Hash : 50fkUxYHbnXGw has a key: "rofl" ... where salt: 50*/

#define _XOPEN_SOURCE
#include <unistd.h>
#include <stdio.h>
#include <cs50.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>


int main(int argc, string argv[])
{
    
    
    char salt[2];
    
    string k = argv[1];
    
    if( argc != 2 )
    {
        printf("Hash cannot be determined. Terminate Program. \n");
        return 1;
    }
    
    if(strlen(k) != 13)
        {
           printf("Invalid Hash Length. Terminate Program. \n");
           return 1; 
        }    
    
    
    salt[0] = k[0];
    salt[1] = k[1];
    
    
    int m, i, j, h, g;
    // for 1 space
    char c[5]; c[1] = '\0';
    
    for (i=65; i<=90; i++)
    {
           c[0] = i;
         
           if(strcmp(crypt(c,salt),k) == 0)
           {
               printf("Password: %s\n", c);
               return 0;
           }
           
           c[0] = tolower(c[0]);
         
           if(strcmp(crypt(c,salt),k) == 0)
           {
               
               printf("Password: %s\n", c);
               return 0;
           }
           
    }
       
    // for 2 spaces
    c[0] = '\0'; c[2] = '\0';
    
    m=0;
        for(i=65; i<=90; i++)
        {
            
        
            c[m] = i;
            for (j=65; j<=90; j++)
            {
                c[m+1] = j;
             
                if(strcmp(crypt(c,salt),k) == 0)
                {
                    printf("Password: %s\n", c);
                    return 0;
                }
           
                c[m] = tolower(c[m]);
                
                if(strcmp(crypt(c,salt),k) == 0)
                {
               
                    printf("Password: %s\n", c);
                    return 0;
                }
           
                c[m+1] = tolower(c[m+1]);
                if(strcmp(crypt(c,salt),k) == 0)
                {
               
                    printf("Password: %s\n", c);
                    return 0;
                }
           
                c[m] = toupper(c[m]);
                if(strcmp(crypt(c,salt),k) == 0)
                {
               
                    printf("Password: %s\n", c);
                    return 0;
                }
           
           
            }
        
        }
        
    
    
    // for 3 spaces
    
    c[0] = '\0'; c[3] = '\0';
    
    m=0;
        for(i=65; i<=90; i++)
        {
            c[m] = i;
            for(h = 65; h<=90; h++)
            {
                c[m+1] = h;
                for (j=65; j<=90; j++)
                {
                    c[m+2] = j;
                    if(strcmp(crypt(c,salt),k) == 0)
                    {
                        printf("Password: %s\n", c);
                        return 0;
                    }
           
                    c[m+2] = tolower(c[m]);
                    if(strcmp(crypt(c,salt),k) == 0)
                    {
               
                        printf("Password: %s\n", c);
                        return 0;
                    }
           
                    c[m+1] = tolower(c[m+1]);
                    c[m+2] = toupper(c[m+2]);
                    if(strcmp(crypt(c,salt),k) == 0)
                    {
               
                        printf("Password: %s\n", c);
                        return 0;
                    }
           
                    c[m+2] = tolower(c[m+2]);
                    if(strcmp(crypt(c,salt),k) == 0)
                    {
               
                        printf("Password: %s\n", c);
                        return 0;
                    }
                    
                    c[m] = tolower(c[m]);
                    c[m+1] = toupper(c[m+1]);
                    c[m+2] = toupper(c[m+2]);
                    if(strcmp(crypt(c,salt),k) == 0)
                    {
               
                        printf("Password: %s\n", c);
                        return 0;
                    }
           
                    c[m+1] = toupper(c[m+1]);
                    c[m+2] = tolower(c[m+2]);
                    if(strcmp(crypt(c,salt),k) == 0)
                    {
               
                        printf("Password: %s\n", c);
                        return 0;
                    }
                    
                    c[m+1] = tolower(c[m+1]);
                    c[m+2] = toupper(c[m+2]);
                    if(strcmp(crypt(c,salt),k) == 0)
                    {
               
                        printf("Password: %s\n", c);
                        return 0;
                    }
                    
                    c[m+1] = tolower(c[m+1]);
                    c[m+2] = tolower(c[m+2]);
                    if(strcmp(crypt(c,salt),k) == 0)
                    {
               
                        printf("Password: %s\n", c);
                        return 0;
                    }
           
           
                }
            }
        
        }
        
    // for 4 spaces
    c[0] = '\0'; c[4] = '\0';
    m=0;
    
        for(i=65; i<=90; i++)
        {
            c[m] = i;
            for(h = 65; h<=90; h++)
            {
                c[m+1] = h;
                for (j=65; j<=90; j++)
                {
                    c[m+2] = j;
                    
                    for(g=65; g<=90; g++)
                    {
                        
                        c[m+3] = g;
                        if(strcmp(crypt(c,salt),k) == 0)
                        {
                            printf("Password: %s\n", c);
                            return 0;
                        }
           
                        c[m+3] = tolower(c[m]);
                        if(strcmp(crypt(c,salt),k) == 0)
                        {
               
                            printf("Password: %s\n", c);
                            return 0;
                        }
           
                        c[m+2] = tolower(c[m+2]);
                        c[m+3] = toupper(c[m+3]);
                        if(strcmp(crypt(c,salt),k) == 0)
                        {
               
                            printf("Password: %s\n", c);
                            return 0;
                        }
           
                        c[m+3] = tolower(c[m+3]);
                        if(strcmp(crypt(c,salt),k) == 0)
                        {
               
                            printf("Password: %s\n", c);
                            return 0;
                        }
                    
                        c[m+1] = tolower(c[m+1]);
                        c[m+2] = toupper(c[m+2]);
                        c[m+3] = toupper(c[m+3]);
                        if(strcmp(crypt(c,salt),k) == 0)
                        {
               
                            printf("Password: %s\n", c);
                            return 0;
                        }
           
                        c[m+2] = toupper(c[m+2]);
                        c[m+3] = tolower(c[m+3]);
                        if(strcmp(crypt(c,salt),k) == 0)
                        {
               
                            printf("Password: %s\n", c);
                            return 0;
                        }
                    
                        c[m+2] = tolower(c[m+2]);
                        c[m+3] = toupper(c[m+3]);
                        if(strcmp(crypt(c,salt),k) == 0)
                        {
               
                            printf("Password: %s\n", c);
                            return 0;
                        }
                    
                        c[m+2] = tolower(c[m+2]);
                        if(strcmp(crypt(c,salt),k) == 0)
                        {
               
                            printf("Password: %s\n", c);
                            return 0;
                        }
                        
                        c[m] = tolower(c[m]);  
                        c[m+1] = toupper(c[m+1]);
                        c[m+2] = toupper(c[m+2]);
                        c[m+3] = toupper(c[m+3]);
                        if(strcmp(crypt(c,salt),k) == 0)
                        {
               
                            printf("Password: %s\n", c);
                            return 0;
                        }
           
                        c[m] = tolower(c[m]);  
                        c[m+1] = toupper(c[m+1]);
                        c[m+2] = toupper(c[m+2]);
                        c[m+3] = tolower(c[m+3]);
                        if(strcmp(crypt(c,salt),k) == 0)
                        {
               
                            printf("Password: %s\n", c);
                            return 0;
                        }
                    
                        c[m] = tolower(c[m]);  
                        c[m+1] = toupper(c[m+1]);
                        c[m+2] = tolower(c[m+2]);
                        c[m+3] = toupper(c[m+3]);
                        if(strcmp(crypt(c,salt),k) == 0)
                        {
               
                            printf("Password: %s\n", c);
                            return 0;
                        }
                    
                        c[m] = tolower(c[m]);  
                        c[m+1] = toupper(c[m+1]);
                        c[m+2] = tolower(c[m+2]);
                        c[m+3] = tolower(c[m+3]);
                        if(strcmp(crypt(c,salt),k) == 0)
                        {
               
                            printf("Password: %s\n", c);
                            return 0;
                        }
                        
                        c[m] = tolower(c[m]);  
                        c[m+1] = tolower(c[m+1]);
                        c[m+2] = toupper(c[m+2]);
                        c[m+3] = toupper(c[m+3]);
                        if(strcmp(crypt(c,salt),k) == 0)
                        {
               
                            printf("Password: %s\n", c);
                            return 0;
                        }
                        
                        c[m] = tolower(c[m]);  
                        c[m+1] = tolower(c[m+1]);
                        c[m+2] = toupper(c[m+2]);
                        c[m+3] = tolower(c[m+3]);
                        if(strcmp(crypt(c,salt),k) == 0)
                        {
               
                            printf("Password: %s\n", c);
                            return 0;
                        }
                        
                        c[m] = tolower(c[m]);  
                        c[m+1] = tolower(c[m+1]);
                        c[m+2] = tolower(c[m+2]);
                        c[m+3] = toupper(c[m+3]);
                        if(strcmp(crypt(c,salt),k) == 0)
                        {
               
                            printf("Password: %s\n", c);
                            return 0;
                        }
                        
                        c[m] = tolower(c[m]);  
                        c[m+1] = tolower(c[m+1]);
                        c[m+2] = tolower(c[m+2]);
                        c[m+3] = tolower(c[m+3]);
                        
                        
                        if(strcmp(crypt(c,salt),k) == 0)
                        {
               
                            printf("Password: %s\n", c);
                            return 0;
                        }
                        
                        
                        
                    }
           
           
                }
            }
        
        }
        
    
    
    
}

**Salem** · 07-13-2017

Well this seems odd - it isn't what you posted (missing last w)

Code:

  char *p = crypt("rofl","50");
  printf("Hash=%s\n",p);

...
$ gcc -g foo.c -lcrypt
$ ./a.out 
Hash=50fkUxYHbnXGw

Another more basic problem is so much copy/paste code which is going to be error prone (and simply not extendible to more characters).

**Salem** · 07-13-2017

Following on from that, error prone.

Use this to debug your key generation code to make sure it's working.

Code:

char *crypt ( char *c, char *salt ) {
  printf("%s\n",c);
  return ">";
}

It isn't by the way,

Code:

$ ./a.out | grep -i rofl
rofL

**roy_000** · 07-13-2017

Thank you for your reply. I tried checking the function and the logic of my posted program by running the code stated below. I'm sorry maybe I am too much of a beginner but it would be great if you could help me.

Code:

#define _XOPEN_SOURCE
#include <unistd.h>
#include <cs50.h>
#include <stdio.h>
#include <string.h>
#include <ctype.h>  


int main (void)
{ 
  printf("Hash: \n");
  string hash = get_string();
  char salt[2];
  salt[0] = hash[0];
  salt[1] = hash[1];
  
  string key = "rofl" ;
  
  
  if(strcmp(crypt(key,salt),hash) == 0)
 
     printf("Working\n");
     
  else
  
     printf("NO\n");
  
}

**Salem** · 07-13-2017

Works for me.

Code:

#define _XOPEN_SOURCE
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <ctype.h>


int main (void)
{
  printf("Hash: \n");
  char *hash = "50fkUxYHbnXGw";
  char salt[2];
  salt[0] = hash[0];
  salt[1] = hash[1];

  char * key = "rofl" ;


  if(strcmp(crypt(key,salt),hash) == 0)

     printf("Working\n");

  else

     printf("NO\n");

}

$ ./a.out 
Hash: 
Working

I don't have cs50.h, and don't know what get_string() does either.
Maybe it's got a \n on the end.

**roy_000** · 07-13-2017

Thank you again!

Yah get_string() function is in the cs50.h library that I'm using, It just accepts an input from the user.

That is the problem. the logic is correct, the code ( i've checked soo many times) is correct and is running. Only not showing any output, also I've checked the program is running smooth till the end, except the key(password) isn't being printed.

**Salem** · 07-13-2017

But I showed you in post #3 that your massive code only produces "rofL" and not "rofl" as a possible key.

You never test the real key with your brute-force loops.

**roy_000** · 07-13-2017

Oh Okay.
Thank you so much!

**rstanley** · 07-13-2017

Originally Posted by Salem

I don't have cs50.h, and don't know what get_string() does either.
Maybe it's got a \n on the end.

I located the library here. It does appear NOT to input a newline into the string.

**algorism** · 07-13-2017

When you find yourself repeating code like that, look for pattern and exploit it with a loop and/or function.

It's also important to note that even using only upper- and lower-case letters, the number of combinations grows like crazy:

Code:

up to
n chars    # of combos
1                   52
2                2,756
3              143,364
4            7,454,980
5          387,659,012
6       20,158,268,676
7    1,048,229,971,204
8   54,507,958,502,660

Code:

#include <stdio.h>

// Using only upper- and lower-case letters
int next(char *s, int size) {
    for (int i = 0; i < size; i++) {
        if (s[i] == '\0') {
            s[i] = 'A';
            break;
        }
        if (s[i] == 'Z') {
            s[i] = 'a';
            break;
        }
        if (s[i] == 'z') {
            if (i == size - 1)
                return 0;
            s[i] = 'A';
        }
        else {
            s[i]++;
            break;
        }
    }
    return 1;
}

int main() {
    char s[5] = {0};

    while (next(s, 2))
        printf("%s ", s);

    putchar('\n');
    return 0;
}

**roy_000** · 07-13-2017

Thank you so much everyone!

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