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  1. #define _XOPEN_SOURCE
  2. //#include <cs50.h>
  3. #include <stdio.h>
  4. #include <string.h>
  5. #include <unistd.h>
  6. #include <crypt.h>
  7.  
  8. // brute force crack a DES encrypted password
  9. // algorithm will attempt combinations up to 4 chars long, using only alphabetic chars
  10.  
  11. // set highest int to convert to string
  12. const unsigned long long ALPHA_52_MAX = 7311616;
  13. // set characters to be used for cracking attempts
  14. char ALPHA_52[52] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
  15.  
  16. char itoa52(long long int_52_modulo);
  17. int Thingie(char* pdKey, unsigned int udKeySize, unsigned int * pudResultLen);
  18.  
  19. int main(int argc, char *argv[])
  20. {
  21.     if (argc != 2)
  22.     {
  23.         // reject invalid parameters
  24.         printf("Usage: ./crack hash\n");
  25.         return 1;
  26.     }
  27.  
  28.     char salt[2] = {argv[1][0], argv[1][1]};
  29.  
  30.     // iterate over all combinations of 4 alphabetic characters
  31.     for (long long alpha_52_int = 0; alpha_52_int < ALPHA_52_MAX; alpha_52_int++)
  32.     {
  33.         char pdKey[4] = {0, 0, 0, 0};
  34.         unsigned int udResultLen = 0; 
  35.  
  36.         if (0 == Thingie(
  37.             pdKey, 
  38.             sizeof(pdKey) / sizeof(pdKey[0]), 
  39.             &udResultLen))
  40.         {
  41.             printf("error\n");
  42.             return 1;
  43.         }
  44.  
  45.         if (!strcmp(crypt(pdKey, salt), argv[1]))
  46.         {
  47.             printf("%s\n", pdKey);
  48.             return 0;
  49.         }    
  50.     }
  51.  
  52.     return 0;
  53. }
  54.  
  55. int Thingie(char* pdKey, unsigned int udKeySize, unsigned int * pudResultLen)
  56. { 
  57.     int digit_int_array[4] = {0, 0, 0, 0};
  58.     int digit_position = udKeySize - 1, digit_count = 1;
  59.     long long working_int = ALPHA_52_MAX;
  60.  
  61.     if (0 == pudResultLen || 0 == pdKey || udKeySize > 4)
  62.     {
  63.         // need valid input!
  64.         return 0;
  65.     }
  66.  
  67.     // always calculate the right most value
  68.     digit_int_array[digit_position] = working_int % 52;
  69.     while (working_int/52)
  70.     {
  71.         // working_int is divisible by 52, another digit is required to display characters
  72.         ++digit_count;
  73.         --digit_position;
  74.         working_int /= 52;
  75.         // value is assigned to correct position
  76.         digit_int_array[digit_position] = working_int % 52;
  77.     }
  78.     *pudResultLen = digit_count; // set the resulting relevent length of the key
  79.     // reset digit position
  80.     digit_position = 3;
  81.     while (digit_count > 0)
  82.     {
  83.         --digit_count;
  84.         char current_char = itoa52(digit_int_array[digit_position]);
  85.         // converted char is assigned to the correct position in the key
  86.         pdKey[digit_count] = current_char;
  87.         --digit_position;
  88.     } 
  89.  
  90.     return 1;
  91. }
  92.  
  93. char itoa52(long long int_52_modulo)
  94. {
  95.     return (ALPHA_52[int_52_modulo]);
  96. }
Compilation error #stdin compilation error #stdout 0s 0KB
comments (?)
stdin
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Standard input is empty
compilation info 
/home/ERKkD7/cc9ZKn6N.o: In function `main':
prog.c:(.text.startup+0x4b): undefined reference to `crypt'
collect2: error: ld returned 1 exit status
stdout
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Standard output is empty
https://ideone.com/kbzxfK
language:
C (gcc 8.3)
created:
6 years ago
visibility:
public

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