/*
*	netkey on unix (excluding linux)
*	
*	usage: netkey
*
*   compile:
*     	cc -o netkey netkey.c
*     	but if you feel ugly to use system("stty -echo"),
*     	cc -DBOYD -o netkey netkey.c
*
*	coded by
*	    Kenar ( Kenji Arisawa )
*		E-mail: arisawa@aichi-u.ac.jp
*/

#include <stdio.h>
#define DESKEYLEN 7
#define NAMELEN 22

#ifdef BOYD
#define echo(mode) ttyecho(0,mode)
/*
 * Here's some posix code for mangling tty echo
 * (for those who feel that way inclined):
 * Horrible system dependent tty routines,
 * - boyd@france3.FR (Boyd Roberts) -
 *
 * Thanks
 * -Kenar-
 */

#include        <termios.h>

/*
 * Is echo on?
 */
int
ttyechoing(int fd)
{
        struct termios  t;

        if (tcgetattr(fd, &t) == -1)
                return -1;

        return (t.c_lflag & ECHO) != 0;
}

/*
 * Turn echo off/on?
 */
int
ttyecho(int fd, int on)
{
        struct termios  t;

        if (tcgetattr(fd, &t) == -1)
                return -1;

        if (on)
                t.c_lflag |= ECHO;
        else
                t.c_lflag &= ~ECHO;
                
        return tcsetattr(fd, TCSADRAIN, &t);
}
#else
char *shcmd[2] = { "stty -echo", "stty echo;echo" };
#define echo(mode) system(shcmd[mode])
#endif


typedef unsigned char uchar;

uchar a[8] = { 128, 64, 32, 16, 8, 4, 2, 1 };

/* 	get bit status at the bit position n of string s
	uchar s[8]
	int n: 0 .. 63
*/
int strbit(uchar *s, int n)
{	int q,m;
	q = n / 8;
	m = n % 8;
	return (s[q] & a[m]?1:0);
}

/* 	uchar s[8]: 8 bits DES subblock for unix
	return: 8 bits DES subblock for plan9
	*/
uchar s2b(uchar *s)
{	int i;
	uchar x;
	x = 0;
	for(i = 0; i < 8; i++) if(s[i]) x |= a[i];
	return x;
}

/* 	uchar s[8]: 8 bits DES subblock for unix
	uchar x: 8 bits DES subblock for plan9
	*/
void b2s(uchar x, uchar *s)
{	int i;
	memset(s,0,8);
	for(i = 0; i < 8; i++) if(x & a[i]) s[i] = 1;
}

/* 	uchar s[64]  --- unix style DES block
	uchar x[8]   --- plan9 style DES block
	*/
void blk2str(uchar *x, uchar *s)
{	int i;
	for(i = 0; i < 8; i++) b2s(x[i],&s[8*i]);
}

/* 	uchar s[64]  --- unix style DES block
	uchar x[8]   --- plan9 style DES block
	*/
void str2blk(uchar *s, uchar *x)
{	int i;
	for(i = 0; i < 8; i++) x[i] = s2b(&s[8*i]);
}

/* Plan9 style encrypt for DES cypher block
   equivalent to encrypt(key,t,8) on plan9
   uchar key[7]   --- deskey
   uchar t[8]     --- target(des cypher block)
 */
void des(uchar *key, uchar *t)
{	int i,j;
	uchar s[64],u[64];
	for(j = 0; j < 8; j++){
		for(i = 0; i < 7; i++) s[8*j + i] = strbit(key, 7*j + i);
		s[8*j + 7] = 0;
	}
	setkey(s);
	blk2str(t,u);
	encrypt(u,0); /* encrypt */
	str2blk(u,t);
}

/* imported from plan9 - slitely modified -
   uchar p[NAMELEN]    --- password
   uchar key[DESKEYLEN] --- DES key
*/
int
pass2key(uchar *p, uchar *key)
{
        uchar buf[NAMELEN], *t;
        int i, n;

        n = strlen(p);
        if(n >= NAMELEN)
                n = NAMELEN-1;
        memset(buf, ' ', 8);
        t = buf;
        strncpy((char*)t, p, n);
        t[n] = 0;
        memset(key, 0, DESKEYLEN);
        for(;;){
                for(i = 0; i < DESKEYLEN; i++)
                        key[i] = (t[i] >> i) + (t[i+1] << (8 - (i+1)));
                if(n <= 8)
                        return 1;
                n -= 8;
                t += 8;
                if(n < 8){
                        t -= 8 - n;
                        n = 8;
                }
                des(key, t); /* encrypt(key,t,8) on plan9 */
        }
        return 1;       /* not reached */
}

void
getns(char *s, int size)
{	char *p;
	fgets(s, size, stdin);
	p = strchr(s,'\n');
	if(p)
		*p = 0;
}

main()
{	uchar buf[80];
	uchar key[DESKEYLEN];
	int i;

	echo(0);
	fprintf(stderr,"password: ");
	getns(buf,sizeof buf);
	pass2key(buf,key);
	echo(1);
	
	for(;;){
		memset(buf,0,8);
		fprintf(stderr,"challenge: ");
		getns(buf, sizeof buf);
		if(strlen(buf) == 0) break;
		buf[7] = 0;
		des(key,buf);
		printf("response: ");
		for(i = 0; i < 4; i++) printf("%02x",buf[i]);
		puts("");
	}
}