kerberos.c

经典的unix下telnetd代码

/*     $OpenBSD: kerberos.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.
 */

 /*
 * This source code is no longer held under any constraint of USA
 * `cryptographic laws' since it was exported legally.  The cryptographic
 * functions were removed from the code and a "Bones" distribution was
 * made.  A Commodity Jurisdiction Request #012-94 was filed with the
 * USA State Department, who handed it to the Commerce department.  The
 * code was determined to fall under General License GTDA under ECCN 5D96G,
 * and hence exportable.  The cryptographic interfaces were re-added by Eric
 * Young, and then KTH proceeded to maintain the code in the free world.
 *
 */

/*
 * Copyright (C) 1990 by the Massachusetts Institute of Technology
 *
 * Export of this software from the United States of America is assumed
 * to require a specific license from the United States Government.
 * It is the responsibility of any person or organization contemplating
 * export to obtain such a license before exporting.
 *
 * WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
 * distribute this software and its documentation for any purpose and
 * without fee is hereby granted, provided that the above copyright
 * notice appear in all copies and that both that copyright notice and
 * this permission notice appear in supporting documentation, and that
 * the name of M.I.T. not be used in advertising or publicity pertaining
 * to distribution of the software without specific, written prior
 * permission.  M.I.T. makes no representations about the suitability of
 * this software for any purpose.  It is provided "as is" without express
 * or implied warranty.
 */

/* $KTH: kerberos.c,v 1.50 2000/11/23 02:28:06 joda Exp $" */

#ifdef	KRB4
#include <sys/types.h>
#include <sys/socket.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <netinet/in.h>
#include <resolv.h>
#include <arpa/telnet.h>
#include <des.h>
#include <kerberosIV/krb.h>
#include <pwd.h>
#include <syslog.h>
#include <err.h>
#include "encrypt.h"
#include "auth.h"
#include "misc.h"

int kerberos4_cksum (unsigned char *, int);
extern int auth_debug_mode;

static unsigned char str_data[2048] = { IAC, SB, TELOPT_AUTHENTICATION, 0,
			  		AUTHTYPE_KERBEROS_V4, };

#define	KRB_AUTH	0		/* Authentication data follows */
#define	KRB_REJECT	1		/* Rejected (reason might follow) */
#define	KRB_ACCEPT	2		/* Accepted */
#define	KRB_CHALLENGE	3		/* Challenge for mutual auth. */
#define	KRB_RESPONSE	4		/* Response for mutual auth. */

#define KRB_FORWARD		5	/* */
#define KRB_FORWARD_ACCEPT	6	/* */
#define KRB_FORWARD_REJECT	7	/* */

#define KRB_SERVICE_NAME   "rcmd"

static	KTEXT_ST auth;
static	char name[ANAME_SZ];
static	AUTH_DAT adat;
static des_cblock session_key;
static des_cblock cred_session;
static des_key_schedule sched;
static des_cblock challenge;
static int auth_done; /* XXX */

static int pack_cred(CREDENTIALS *cred, unsigned char *buf);
static int unpack_cred(unsigned char *buf, int len, CREDENTIALS *cred);

int
check_krb4_tickets() {
    int ret;
    int retval = 0;
    char *file;
    krb_principal princ;
    
    file = getenv("KRBTKFILE");
    if(file == NULL)
	file = TKT_FILE;

    ret = krb_get_tf_realm(file, princ.realm);
    switch(ret) {
    case NO_TKT_FIL:
	retval = 0;
	goto done;
    case 0:
	retval = 1;
	goto done;
    default:
	errx(1, "krb_get_tf_realm: %d", ret);
    }

 done:
    return retval;
}

static int
Data(Authenticator *ap, int type, const void *d, int c)
{
    unsigned char *p = str_data + 4;
    const unsigned char *cd = (const unsigned char *)d;

    if (c == -1)
	c = strlen((const char *)cd);

    if (auth_debug_mode) {
	printf("%s:%d: [%d] (%d)",
	       str_data[3] == TELQUAL_IS ? ">>>IS" : ">>>REPLY",
	       str_data[3],
	       type, c);
	printd(d, c);
	printf("\r\n");
    }
    *p++ = ap->type;
    *p++ = ap->way;
    *p++ = type;
    while (c-- > 0) {
	if ((*p++ = *cd++) == IAC)
	    *p++ = IAC;
    }
    *p++ = IAC;
    *p++ = SE;
    if (str_data[3] == TELQUAL_IS)
	printsub('>', &str_data[2], p - (&str_data[2]));
    return(telnet_net_write(str_data, p - str_data));
}

int
kerberos4_init(Authenticator *ap, int server)
{
    FILE *fp;

    if (server) {
	str_data[3] = TELQUAL_REPLY;
	if ((fp = fopen(KEYFILE, "r")) == NULL)
	    return(0);
	fclose(fp);
    } else {
	str_data[3] = TELQUAL_IS;
    }
    return(1);
}

char dst_realm_buf[REALM_SZ], *dest_realm = NULL;
int dst_realm_sz = REALM_SZ;

static int
kerberos4_send(char *name, Authenticator *ap)
{
    KTEXT_ST auth;
    char instance[INST_SZ];
    char *realm;
    CREDENTIALS cred;
    int r;

    if(check_krb4_tickets() != 1)
	return 0;

    if (!UserNameRequested) {
	if (auth_debug_mode) {
	    printf("Kerberos V4: no user name supplied\r\n");
	}
	return(0);
    }

    memset(instance, 0, sizeof(instance));

    strlcpy (instance,
		     krb_get_phost(RemoteHostName),
		     INST_SZ);

    realm = dest_realm ? dest_realm : krb_realmofhost(RemoteHostName);

    if (!realm) {
	printf("Kerberos V4: no realm for %s\r\n", RemoteHostName);
	return(0);
    }
    printf("[ Trying %s (%s.%s@%s) ... ]\r\n", name, 
	   KRB_SERVICE_NAME, instance, realm);
    r = krb_mk_req(&auth, KRB_SERVICE_NAME, instance, realm, 0L);
    if (r) {
	printf("mk_req failed: %s\r\n", krb_get_err_text(r));
	return(0);
    }
    r = krb_get_cred(KRB_SERVICE_NAME, instance, realm, &cred);
    if (r) {
	printf("get_cred failed: %s\r\n", krb_get_err_text(r));
	return(0);
    }
    if (!auth_sendname(UserNameRequested, strlen(UserNameRequested))) {
	if (auth_debug_mode)
	    printf("Not enough room for user name\r\n");
	return(0);
    }
    if (auth_debug_mode)
	printf("Sent %d bytes of authentication data\r\n", auth.length);
    if (!Data(ap, KRB_AUTH, (void *)auth.dat, auth.length)) {
	if (auth_debug_mode)
	    printf("Not enough room for authentication data\r\n");
	return(0);
    }
#ifdef ENCRYPTION
    /* create challenge */
    if ((ap->way & AUTH_HOW_MASK)==AUTH_HOW_MUTUAL) {
	int i;

	des_key_sched(&cred.session, sched);
	memcpy (&cred_session, &cred.session, sizeof(cred_session));
	des_init_random_number_generator(&cred.session);
	des_new_random_key(&session_key);
	des_ecb_encrypt(&session_key, &session_key, sched, 0);
	des_ecb_encrypt(&session_key, &challenge, sched, 0);

	/*
	  old code
	  Some CERT Advisory thinks this is a bad thing...
	    
	  des_init_random_number_generator(&cred.session);
	  des_new_random_key(&challenge);
	  des_ecb_encrypt(&challenge, &session_key, sched, 1);
	  */
	  
	/*
	 * Increment the challenge by 1, and encrypt it for
	 * later comparison.
	 */
	for (i = 7; i >= 0; --i) 
	    if(++challenge[i] != 0) /* No carry! */
		break;
	des_ecb_encrypt(&challenge, &challenge, sched, 1);
    }

#endif

    if (auth_debug_mode) {
	printf("CK: %d:", kerberos4_cksum(auth.dat, auth.length));
	printd(auth.dat, auth.length);
	printf("\r\n");
	printf("Sent Kerberos V4 credentials to server\r\n");
    }
    return(1);
}
int
kerberos4_send_mutual(Authenticator *ap)
{
    return kerberos4_send("mutual KERBEROS4", ap);
}

int
kerberos4_send_oneway(Authenticator *ap)
{
    return kerberos4_send("KERBEROS4", ap);
}

void
kerberos4_is(Authenticator *ap, unsigned char *data, int cnt)
{
    struct sockaddr_in addr;
    char realm[REALM_SZ];
    char instance[INST_SZ];
    int r;
    socklen_t addr_len;

    if (cnt-- < 1)
	return;
    switch (*data++) {
    case KRB_AUTH:
	if (krb_get_lrealm(realm, 1) != KSUCCESS) {
	    Data(ap, KRB_REJECT, (void *)"No local V4 Realm.", -1);
	    auth_finished(ap, AUTH_REJECT);
	    if (auth_debug_mode)
		printf("No local realm\r\n");
	    return;
	}
	memmove(auth.dat, data, auth.length = cnt);
	if (auth_debug_mode) {
	    printf("Got %d bytes of authentication data\r\n", cnt);
	    printf("CK: %d:", kerberos4_cksum(auth.dat, auth.length));
	    printd(auth.dat, auth.length);
	    printf("\r\n");
	}
	k_getsockinst(0, instance, sizeof(instance));
	addr_len = sizeof(addr);
	if(getpeername(0, (struct sockaddr *)&addr, &addr_len) < 0) {
	    if(auth_debug_mode)
		printf("getpeername failed\r\n");
	    Data(ap, KRB_REJECT, "getpeername failed", -1);
	    auth_finished(ap, AUTH_REJECT);
	    return;
	}
	if (addr.sin_family != AF_INET) {
	    if (auth_debug_mode)
		printf("unknown address family: %d\r\n", addr.sin_family);
	    Data(ap, KRB_REJECT, "bad address family", -1);
	    auth_finished(ap, AUTH_REJECT);
	    return;
	}

	r = krb_rd_req(&auth, KRB_SERVICE_NAME,
		       instance, addr.sin_addr.s_addr, &adat, "");
	if (r) {
	    if (auth_debug_mode)
		printf("Kerberos failed him as %s\r\n", name);
	    Data(ap, KRB_REJECT, (void *)krb_get_err_text(r), -1);
	    auth_finished(ap, AUTH_REJECT);
	    return;
	}
	/* save the session key */
	memmove(session_key, adat.session, sizeof(adat.session));
	krb_kntoln(&adat, name);

	if (UserNameRequested && !kuserok(&adat, UserNameRequested)){
	    char ts[MAXPATHLEN];
	    struct passwd *pw = getpwnam(UserNameRequested);

	    if(pw){
		snprintf(ts, sizeof(ts),
			 "%s%u",
			 TKT_ROOT,
			 (unsigned)pw->pw_uid);
		esetenv("KRBTKFILE", ts, 1);

		if (pw->pw_uid == 0)
		    syslog(LOG_INFO|LOG_AUTH,
			   "ROOT Kerberos login from %s on %s",
			   krb_unparse_name_long(adat.pname,
						 adat.pinst,
						 adat.prealm),
			   RemoteHostName);
	    }
	    Data(ap, KRB_ACCEPT, NULL, 0);