[C] - Simple text Crypt

[imation]

[C] - Simple text Crypt

so simple,

This is not my code, i cant remember where i got it but it worked for me for what i needed it for..

Code: [Select]

#include <windows.h>
#include <cstdio>

#define cryptkey  1

char sbuff[MAX_PATH];

char *crypt(char *str)
{
 unsigned char i;
 unsigned int size;

 size = lstrlen(str); //size of str

 lstrcpy(sbuff,str); //copy it to sbuff

 if (cryptkey && size < MAX_PATH) //if crypt key != 0 and size < MAX_PATH then
 {
  for (i = 0; i < size; i++)  //loop while i < size of str
    sbuff[i] = sbuff[i] ^ (cryptkey + (i * (cryptkey % 10) + 1));
    //xor curr char with (sum of cryptkey and i) multiplied by (cryptkey
    // and 10 remainder) +1
    //
 }
 return sbuff; //return sbuff
}

int main()
{
    printf(crypt("dwt+`fdeoe{dbk>r}=a~"));
    printf("\n");
    printf(crypt("alkiodmm"));
    printf("\n");
    printf(crypt("jljag6119"));
    printf("\n");
    printf(crypt("ujjmjw"));
    printf("\n");
    printf(crypt("alkiodmm {dbk>r}=a~"));
       
    return 1;
}

[xzid]

uhh:

Code: [Select]

char sbuff[MAX_PATH];
lstrcpy(sbuff,str);

also why MAX_PATH? don't pass strings directly to printf like that either.

this is a helpful comment:

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return sbuff; //return sbuff
in your function crypt, i is an "unsigned char". if you pass a string > 255 bytes in length it will cause an unlimited loop.

try this:

Code: [Select]

char *crypt(char *str, int cryptkey)
// ...

int main(void)
{
   char crypted[]=
      "dwt+`fdeoe{dbk>r}=a~";
   int i;

   for(i = 0; i < 0xffff; i++)
   if(strcmp("ftp.fallenwild.co.uk", crypt(crypted, i)) == 0)
         printf("key = %04x\n", i);

   return 0;
}

just to show you the pattern, here is the output:

Code: [Select]

key = 0001
key = 0501
key = 0a01
...
key = eb01
key = f001
key = f501
key = fa01
key = ff01

so it repeats every 500h(1280 decimal), so I know my range to brute... assuming it's not binary data, can slim the results:

Code: [Select]

int str_isascii(char *p, int len)
{
   for(; --len; p++)
   if(!isprint(*p) && !isspace(*p))
      return 0;
   return 1;
}

int main(void)
{
   /* 0x01 */
   char crypted[]=
      "dwt+`fdeoe{dbk>r}=a~";

   /* 0x90 */
   char crypted2[]=
      "\xf9\xf0\xf5\xf1\xce\x85\xde\xc2\xc3\xd9\xdd";

   /* 0x123 */
   char crypted3[] =
      "\x45\x4b\x06\x42\x5e\x4c\x44\x0b\x40\x42"
      "\x40\x48\x55\x43\x12\x40\x51\x5b\x42\x52"
      "\x56\x5a\x5f\x17\x1c\x5f\x52\x5e\x28\x6d"
      "\x62\x21\x28\x24\x2e\x69\x68\x2f\x25\x24"
      "\x2e\x2c\x3c\x63\x70\x3b\x37\x24\x3a\x34"
      "\x2c\x3e\x76";

   int i, count = 0;
   char *str;

   for(i = 1; i <= 0x500; i++)
   {
      str = crypt(crypted2, i);
      if(str_isascii(str, sizeof(crypted2)))
      {
         count++;
         printf("%03x: %s\n", i, str);
      }
   }

    printf("\ntotal: %d\n", count);
    return 0;
}


Code: [Select]

001: ftp.fallenwild.co.uk
014: qba>usqpzpnqw~+gh(tk
017: |lj
DANH_VM]^T|75v//
03d: ZH4j"%  )"3-( r?3r1/
046: #03l'!#"("<#%,y5:z&9
....
44c: ):9f-+)("(6)/&s?0p,3
456: 3 #|713282,35<i%*j6)

total: 45

crypted[] = 20 chars, 45 ascii results
crypted2[] = 11 chars, 64 ascii results
crypted3[] = 54 chars, 1 ascii result

edit: forgot a printf arg & return from main()

[imation]

Thanks for the comment mate, will help somebody in the future..
 
Again.. not my code, i have had it for along long time and thought i would share