enc_des.c

经典的unix下telnetd代码

/*     $OpenBSD: enc_des.c,v 1.2 2003/06/02 19:38:25 millert Exp $ */

/*-
 * Copyright (c) 1991, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/* $KTH: enc_des.c,v 1.16 1998/07/09 23:16:23 assar Exp $ */

#if	defined(AUTHENTICATION) && defined(ENCRYPTION) && defined(DES_ENCRYPTION)
#include <arpa/telnet.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "encrypt.h"
#include "misc-proto.h"
#include <des.h>

extern int encrypt_debug_mode;

#define	CFB	0
#define	OFB	1

#define	NO_SEND_IV	1
#define	NO_RECV_IV	2
#define	NO_KEYID	4
#define	IN_PROGRESS	(NO_SEND_IV|NO_RECV_IV|NO_KEYID)
#define	SUCCESS		0
#define	FAILED		-1


struct stinfo {
  des_cblock	str_output;
  des_cblock	str_feed;
  des_cblock	str_iv;
  des_cblock	str_ikey;
  des_key_schedule str_sched;
  int		str_index;
  int		str_flagshift;
};

struct fb {
	des_cblock krbdes_key;
	des_key_schedule krbdes_sched;
	des_cblock temp_feed;
	unsigned char fb_feed[64];
	int need_start;
	int state[2];
	int keyid[2];
	int once;
	struct stinfo streams[2];
};

static struct fb fb[2];

struct keyidlist {
	char	*keyid;
	int	keyidlen;
	char	*key;
	int	keylen;
	int	flags;
} keyidlist [] = {
	{ "\0", 1, 0, 0, 0 },		/* default key of zero */
	{ 0, 0, 0, 0, 0 }
};

#define	KEYFLAG_MASK	03

#define	KEYFLAG_NOINIT	00
#define	KEYFLAG_INIT	01
#define	KEYFLAG_OK	02
#define	KEYFLAG_BAD	03

#define	KEYFLAG_SHIFT	2

#define	SHIFT_VAL(a,b)	(KEYFLAG_SHIFT*((a)+((b)*2)))

#define	FB64_IV		1
#define	FB64_IV_OK	2
#define	FB64_IV_BAD	3


void fb64_stream_iv (des_cblock, struct stinfo *);
void fb64_init (struct fb *);
static int fb64_start (struct fb *, int, int);
int fb64_is (unsigned char *, int, struct fb *);
int fb64_reply (unsigned char *, int, struct fb *);
static void fb64_session (Session_Key *, int, struct fb *);
void fb64_stream_key (des_cblock, struct stinfo *);
int fb64_keyid (int, unsigned char *, int *, struct fb *);

void cfb64_init(int server)
{
	fb64_init(&fb[CFB]);
	fb[CFB].fb_feed[4] = ENCTYPE_DES_CFB64;
	fb[CFB].streams[0].str_flagshift = SHIFT_VAL(0, CFB);
	fb[CFB].streams[1].str_flagshift = SHIFT_VAL(1, CFB);
}


void ofb64_init(int server)
{
	fb64_init(&fb[OFB]);
	fb[OFB].fb_feed[4] = ENCTYPE_DES_OFB64;
	fb[CFB].streams[0].str_flagshift = SHIFT_VAL(0, OFB);
	fb[CFB].streams[1].str_flagshift = SHIFT_VAL(1, OFB);
}

void fb64_init(struct fb *fbp)
{
	memset(fbp,0, sizeof(*fbp));
	fbp->state[0] = fbp->state[1] = FAILED;
	fbp->fb_feed[0] = IAC;
	fbp->fb_feed[1] = SB;
	fbp->fb_feed[2] = TELOPT_ENCRYPT;
	fbp->fb_feed[3] = ENCRYPT_IS;
}

/*
 * Returns:
 *	-1: some error.  Negotiation is done, encryption not ready.
 *	 0: Successful, initial negotiation all done.
 *	 1: successful, negotiation not done yet.
 *	 2: Not yet.  Other things (like getting the key from
 *	    Kerberos) have to happen before we can continue.
 */
int cfb64_start(int dir, int server)
{
	return(fb64_start(&fb[CFB], dir, server));
}

int ofb64_start(int dir, int server)
{
	return(fb64_start(&fb[OFB], dir, server));
}

static int fb64_start(struct fb *fbp, int dir, int server)
{
	int x;
	unsigned char *p;
	int state;

	switch (dir) {
	case DIR_DECRYPT:
		/*
		 * This is simply a request to have the other side
		 * start output (our input).  He will negotiate an
		 * IV so we need not look for it.
		 */
		state = fbp->state[dir-1];
		if (state == FAILED)
			state = IN_PROGRESS;
		break;

	case DIR_ENCRYPT:
		state = fbp->state[dir-1];
		if (state == FAILED)
			state = IN_PROGRESS;
		else if ((state & NO_SEND_IV) == 0) {
			break;
		}

		if (!VALIDKEY(fbp->krbdes_key)) {
		        fbp->need_start = 1;
			break;
		}

		state &= ~NO_SEND_IV;
		state |= NO_RECV_IV;
		if (encrypt_debug_mode)
			printf("Creating new feed\r\n");
		/*
		 * Create a random feed and send it over.
		 */
#ifndef OLD_DES_RANDOM_KEY
		des_new_random_key(&fbp->temp_feed);
#else
		/*
		 * From des_cryp.man "If the des_check_key flag is non-zero,
		 *  des_set_key will check that the key passed is
		 *  of odd parity and is not a week or semi-weak key."
		 */
		do {
			des_random_key(fbp->temp_feed);
			des_set_odd_parity(fbp->temp_feed);
		} while (des_is_weak_key(fbp->temp_feed));
#endif
		des_ecb_encrypt(&fbp->temp_feed,
				&fbp->temp_feed,
				fbp->krbdes_sched, 1);
		p = fbp->fb_feed + 3;
		*p++ = ENCRYPT_IS;
		p++;
		*p++ = FB64_IV;
		for (x = 0; x < sizeof(des_cblock); ++x) {
			if ((*p++ = fbp->temp_feed[x]) == IAC)
				*p++ = IAC;
		}
		*p++ = IAC;
		*p++ = SE;
		printsub('>', &fbp->fb_feed[2], p - &fbp->fb_feed[2]);
		telnet_net_write(fbp->fb_feed, p - fbp->fb_feed);
		break;
	default:
		return(FAILED);
	}
	return(fbp->state[dir-1] = state);
}

/*
 * Returns:
 *	-1: some error.  Negotiation is done, encryption not ready.
 *	 0: Successful, initial negotiation all done.
 *	 1: successful, negotiation not done yet.
 */

int cfb64_is(unsigned char *data, int cnt)
{
	return(fb64_is(data, cnt, &fb[CFB]));
}

int ofb64_is(unsigned char *data, int cnt)
{
	return(fb64_is(data, cnt, &fb[OFB]));
}


int fb64_is(unsigned char *data, int cnt, struct fb *fbp)
{
	unsigned char *p;
	int state = fbp->state[DIR_DECRYPT-1];

	if (cnt-- < 1)
		goto failure;

	switch (*data++) {
	case FB64_IV:
		if (cnt != sizeof(des_cblock)) {
			if (encrypt_debug_mode)
				printf("CFB64: initial vector failed on size\r\n");
			state = FAILED;
			goto failure;
		}

		if (encrypt_debug_mode)
			printf("CFB64: initial vector received\r\n");

		if (encrypt_debug_mode)
			printf("Initializing Decrypt stream\r\n");

		fb64_stream_iv(data, &fbp->streams[DIR_DECRYPT-1]);

		p = fbp->fb_feed + 3;
		*p++ = ENCRYPT_REPLY;
		p++;
		*p++ = FB64_IV_OK;
		*p++ = IAC;
		*p++ = SE;
		printsub('>', &fbp->fb_feed[2], p - &fbp->fb_feed[2]);
		telnet_net_write(fbp->fb_feed, p - fbp->fb_feed);

		state = fbp->state[DIR_DECRYPT-1] = IN_PROGRESS;
		break;

	default:
		if (encrypt_debug_mode) {
			printf("Unknown option type: %d\r\n", *(data-1));
			printd(data, cnt);
			printf("\r\n");
		}
		/* FALL THROUGH */
	failure:
		/*
		 * We failed.  Send an FB64_IV_BAD option
		 * to the other side so it will know that
		 * things failed.
		 */
		p = fbp->fb_feed + 3;
		*p++ = ENCRYPT_REPLY;
		p++;
		*p++ = FB64_IV_BAD;
		*p++ = IAC;
		*p++ = SE;
		printsub('>', &fbp->fb_feed[2], p - &fbp->fb_feed[2]);
		telnet_net_write(fbp->fb_feed, p - fbp->fb_feed);

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

/*
 * Returns:
 *	-1: some error.  Negotiation is done, encryption not ready.
 *	 0: Successful, initial negotiation all done.
 *	 1: successful, negotiation not done yet.
 */

int cfb64_reply(unsigned char *data, int cnt)
{
	return(fb64_reply(data, cnt, &fb[CFB]));
}

int ofb64_reply(unsigned char *data, int cnt)
{
	return(fb64_reply(data, cnt, &fb[OFB]));