enc_des.c

经典的unix下telnetd代码

}


int fb64_reply(unsigned char *data, int cnt, struct fb *fbp)
{
	int state = fbp->state[DIR_ENCRYPT-1];

	if (cnt-- < 1)
		goto failure;

	switch (*data++) {
	case FB64_IV_OK:
		fb64_stream_iv(fbp->temp_feed, &fbp->streams[DIR_ENCRYPT-1]);
		if (state == FAILED)
			state = IN_PROGRESS;
		state &= ~NO_RECV_IV;
		encrypt_send_keyid(DIR_ENCRYPT, (unsigned char *)"\0", 1, 1);
		break;

	case FB64_IV_BAD:
		memset(fbp->temp_feed, 0, sizeof(des_cblock));
		fb64_stream_iv(fbp->temp_feed, &fbp->streams[DIR_ENCRYPT-1]);
		state = FAILED;
		break;

	default:
		if (encrypt_debug_mode) {
			printf("Unknown option type: %d\r\n", data[-1]);
			printd(data, cnt);
			printf("\r\n");
		}
		/* FALL THROUGH */
	failure:
		state = FAILED;
		break;
	}
	return(fbp->state[DIR_ENCRYPT-1] = state);
}

void cfb64_session(Session_Key *key, int server)
{
	fb64_session(key, server, &fb[CFB]);
}

void ofb64_session(Session_Key *key, int server)
{
	fb64_session(key, server, &fb[OFB]);
}

static void fb64_session(Session_Key *key, int server, struct fb *fbp)
{

	if (!key || key->type != SK_DES) {
		if (encrypt_debug_mode)
			printf("Can't set krbdes's session key (%d != %d)\r\n",
				key ? key->type : -1, SK_DES);
		return;
	}
	memcpy(fbp->krbdes_key, key->data, sizeof(des_cblock));

	fb64_stream_key(fbp->krbdes_key, &fbp->streams[DIR_ENCRYPT-1]);
	fb64_stream_key(fbp->krbdes_key, &fbp->streams[DIR_DECRYPT-1]);

	if (fbp->once == 0) {
#ifndef OLD_DES_RANDOM_KEY
		des_init_random_number_generator(&fbp->krbdes_key);
#endif
		fbp->once = 1;
	}
	des_key_sched(&fbp->krbdes_key, fbp->krbdes_sched);
	/*
	 * Now look to see if krbdes_start() was was waiting for
	 * the key to show up.  If so, go ahead an call it now
	 * that we have the key.
	 */
	if (fbp->need_start) {
		fbp->need_start = 0;
		fb64_start(fbp, DIR_ENCRYPT, server);
	}
}

/*
 * We only accept a keyid of 0.  If we get a keyid of
 * 0, then mark the state as SUCCESS.
 */

int cfb64_keyid(int dir, unsigned char *kp, int *lenp)
{
	return(fb64_keyid(dir, kp, lenp, &fb[CFB]));
}

int ofb64_keyid(int dir, unsigned char *kp, int *lenp)
{
	return(fb64_keyid(dir, kp, lenp, &fb[OFB]));
}

int fb64_keyid(int dir, unsigned char *kp, int *lenp, struct fb *fbp)
{
	int state = fbp->state[dir-1];

	if (*lenp != 1 || (*kp != '\0')) {
		*lenp = 0;
		return(state);
	}

	if (state == FAILED)
		state = IN_PROGRESS;

	state &= ~NO_KEYID;

	return(fbp->state[dir-1] = state);
}

void fb64_printsub(unsigned char *data, int cnt, 
		   unsigned char *buf, int buflen, char *type)
{
	char lbuf[32];
	int i;
	char *cp;

	buf[buflen-1] = '\0';		/* make sure it's NULL terminated */
	buflen -= 1;

	switch(data[2]) {
	case FB64_IV:
		snprintf(lbuf, sizeof(lbuf), "%s_IV", type);
		cp = lbuf;
		goto common;

	case FB64_IV_OK:
		snprintf(lbuf, sizeof(lbuf), "%s_IV_OK", type);
		cp = lbuf;
		goto common;

	case FB64_IV_BAD:
		snprintf(lbuf, sizeof(lbuf), "%s_IV_BAD", type);
		cp = lbuf;
		goto common;

	default:
		snprintf(lbuf, sizeof(lbuf), " %d (unknown)", data[2]);
		cp = lbuf;
	common:
		for (; (buflen > 0) && (*buf = *cp++); buf++)
			buflen--;
		for (i = 3; i < cnt; i++) {
			snprintf(lbuf, sizeof(lbuf), " %d", data[i]);
			for (cp = lbuf; (buflen > 0) && (*buf = *cp++); buf++)
				buflen--;
		}
		break;
	}
}

void cfb64_printsub(unsigned char *data, int cnt, 
		    unsigned char *buf, int buflen)
{
	fb64_printsub(data, cnt, buf, buflen, "CFB64");
}

void ofb64_printsub(unsigned char *data, int cnt,
		    unsigned char *buf, int buflen)
{
	fb64_printsub(data, cnt, buf, buflen, "OFB64");
}

void fb64_stream_iv(des_cblock seed, struct stinfo *stp)
{

	memcpy(stp->str_iv, seed,sizeof(des_cblock));
	memcpy(stp->str_output, seed, sizeof(des_cblock));

	des_key_sched(&stp->str_ikey, stp->str_sched);

	stp->str_index = sizeof(des_cblock);
}

void fb64_stream_key(des_cblock key, struct stinfo *stp)
{
	memcpy(stp->str_ikey, key, sizeof(des_cblock));
	des_key_sched((des_cblock*)key, stp->str_sched);

	memcpy(stp->str_output, stp->str_iv, sizeof(des_cblock));

	stp->str_index = sizeof(des_cblock);
}

/*
 * DES 64 bit Cipher Feedback
 *
 *     key --->+-----+
 *          +->| DES |--+
 *          |  +-----+  |
 *	    |           v
 *  INPUT --(--------->(+)+---> DATA
 *          |             |
 *	    +-------------+
 *         
 *
 * Given:
 *	iV: Initial vector, 64 bits (8 bytes) long.
 *	Dn: the nth chunk of 64 bits (8 bytes) of data to encrypt (decrypt).
 *	On: the nth chunk of 64 bits (8 bytes) of encrypted (decrypted) output.
 *
 *	V0 = DES(iV, key)
 *	On = Dn ^ Vn
 *	V(n+1) = DES(On, key)
 */

void cfb64_encrypt(unsigned char *s, int c)
{
	struct stinfo *stp = &fb[CFB].streams[DIR_ENCRYPT-1];
	int index;

	index = stp->str_index;
	while (c-- > 0) {
		if (index == sizeof(des_cblock)) {
			des_cblock b;
			des_ecb_encrypt(&stp->str_output, &b,stp->str_sched, 1);
			memcpy(stp->str_feed, b, sizeof(des_cblock));
			index = 0;
		}

		/* On encryption, we store (feed ^ data) which is cypher */
		*s = stp->str_output[index] = (stp->str_feed[index] ^ *s);
		s++;
		index++;
	}
	stp->str_index = index;
}

int cfb64_decrypt(int data)
{
	struct stinfo *stp = &fb[CFB].streams[DIR_DECRYPT-1];
	int index;

	if (data == -1) {
		/*
		 * Back up one byte.  It is assumed that we will
		 * never back up more than one byte.  If we do, this
		 * may or may not work.
		 */
		if (stp->str_index)
			--stp->str_index;
		return(0);
	}

	index = stp->str_index++;
	if (index == sizeof(des_cblock)) {
		des_cblock b;
		des_ecb_encrypt(&stp->str_output,&b, stp->str_sched, 1);
		memcpy(stp->str_feed, b, sizeof(des_cblock));
		stp->str_index = 1;	/* Next time will be 1 */
		index = 0;		/* But now use 0 */ 
	}

	/* On decryption we store (data) which is cypher. */
	stp->str_output[index] = data;
	return(data ^ stp->str_feed[index]);
}

/*
 * DES 64 bit Output Feedback
 *
 * key --->+-----+
 *	+->| DES |--+
 *	|  +-----+  |
 *	+-----------+
 *	            v
 *  INPUT -------->(+) ----> DATA
 *
 * Given:
 *	iV: Initial vector, 64 bits (8 bytes) long.
 *	Dn: the nth chunk of 64 bits (8 bytes) of data to encrypt (decrypt).
 *	On: the nth chunk of 64 bits (8 bytes) of encrypted (decrypted) output.
 *
 *	V0 = DES(iV, key)
 *	V(n+1) = DES(Vn, key)
 *	On = Dn ^ Vn
 */

void ofb64_encrypt(unsigned char *s, int c)
{
	struct stinfo *stp = &fb[OFB].streams[DIR_ENCRYPT-1];
	int index;

	index = stp->str_index;
	while (c-- > 0) {
		if (index == sizeof(des_cblock)) {
			des_cblock b;
			des_ecb_encrypt(&stp->str_feed,&b, stp->str_sched, 1);
			memcpy(stp->str_feed, b, sizeof(des_cblock));
			index = 0;
		}
		*s++ ^= stp->str_feed[index];
		index++;
	}
	stp->str_index = index;
}

int ofb64_decrypt(int data)
{
	struct stinfo *stp = &fb[OFB].streams[DIR_DECRYPT-1];
	int index;

	if (data == -1) {
		/*
		 * Back up one byte.  It is assumed that we will
		 * never back up more than one byte.  If we do, this
		 * may or may not work.
		 */
		if (stp->str_index)
			--stp->str_index;
		return(0);
	}

	index = stp->str_index++;
	if (index == sizeof(des_cblock)) {
		des_cblock b;
		des_ecb_encrypt(&stp->str_feed,&b,stp->str_sched, 1);
		memcpy(stp->str_feed, b, sizeof(des_cblock));
		stp->str_index = 1;	/* Next time will be 1 */
		index = 0;		/* But now use 0 */ 
	}

	return(data ^ stp->str_feed[index]);
}
#endif