descambles cisco IOS type-7 passwords

                                                /*   
* * descambles cisco IOS type-7 passwords   
* * found somewhere on the internet, slightly modified, [email protected]   
* *   
* * gcc -Wall -o ciscocrack ciscocrack.c   
* * ./ciscocrack 080949420516  
* *   
* */   
   
#include <stdio.h>    
#include <ctype.h>    
   
char xlat[] = {    
        0x64, 0x73, 0x66, 0x64, 0x3b, 0x6b, 0x66, 0x6f,    
        0x41, 0x2c, 0x2e, 0x69, 0x79, 0x65, 0x77, 0x72,    
        0x6b, 0x6c, 0x64, 0x4a, 0x4b, 0x44, 0x48, 0x53,     
        0x55, 0x42     
};    
   
   
int   
cdecrypt(char *enc_pw, char *dec_pw)    
{    
        unsigned int seed, i, val = 0;    
   
        if(strlen(enc_pw) & 1)    
                return(-1);    
   
        seed = (enc_pw[0] - '0') * 10 + enc_pw[1] - '0';    
   
        if (seed > 15 || !isdigit(enc_pw[0]) || !isdigit(enc_pw[1]))    
                return(-1);    
   
        for (i = 2 ; i <= strlen(enc_pw); i++) {    
                if(i !=2 && !(i & 1)) {    
                        dec_pw[i / 2 - 2] = val ^ xlat[seed++];    
                        val = 0;    
                }    
   
                val *= 16;    
   
                if(isdigit(enc_pw[i] = toupper(enc_pw[i]))) {    
                        val += enc_pw[i] - '0';    
                        continue;    
                }    
   
                if(enc_pw[i] >= 'A' && enc_pw[i] <= 'F') {    
                        val += enc_pw[i] - 'A' + 10;    
                        continue;    
                }    
   
                if(strlen(enc_pw) != i)    
                        return(-1);    
        }    
   
        dec_pw[++i / 2] = 0;    
   
        return(0);    
}    
   
void   
usage()    
{    
        fprintf(stdout, "Usage: ciscocrack <encrypted password>\n");    
}    
   
int   
main(int argc, char *argv[])    
{    
    char passwd[65];    
   
    memset(passwd, 0, sizeof(passwd));    
   
    if(argc != 2)    
    {    
          usage();    
          exit(1);    
    }    
   
    if(cdecrypt(argv[1], passwd)) {    
          fprintf(stderr, "Error\n");    
          exit(1);    
    }    
    printf("Passwd: %s\n", passwd);    
   
    return 0;    
}