kerberos5.c

经典的unix下telnetd代码

/*     $OpenBSD: kerberos5.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 may
 * 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: kerberos5.c,v 1.47 2001/01/09 18:45:33 assar Exp $ */

#ifdef	KRB5

#include <arpa/telnet.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <netdb.h>
#include <ctype.h>
#include <pwd.h>
#include <errno.h>
#define Authenticator k5_Authenticator
#include <kerberosV/krb5.h>
#undef Authenticator
#include <err.h>

#include "encrypt.h"
#include "auth.h"
#include "misc.h"

#if defined(DCE)
int dfsk5ok = 0;
int dfspag = 0;
int dfsfwd = 0;
#endif

int forward_flags = 0;  /* Flags get set in telnet/main.c on -f and -F */

int forward(int);
int forwardable(int);

/* These values need to be the same as those defined in telnet/main.c. */
/* Either define them in both places, or put in some common header file. */
#define OPTS_FORWARD_CREDS	0x00000002
#define OPTS_FORWARDABLE_CREDS	0x00000001


void kerberos5_forward (Authenticator *);

static unsigned char str_data[1024] = { IAC, SB, TELOPT_AUTHENTICATION, 0,
			  		AUTHTYPE_KERBEROS_V5, };

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

#define KRB_FORWARD     	4       /* Forwarded credentials follow */
#define KRB_FORWARD_ACCEPT     	5       /* Forwarded credentials accepted */
#define KRB_FORWARD_REJECT     	6       /* Forwarded credentials rejected */

static	krb5_data auth;
static  krb5_ticket *ticket;

static krb5_context context;
static krb5_auth_context auth_context;

int
check_krb5_tickets()
{
    krb5_error_code ret;
    krb5_context context;
    krb5_ccache ccache;
    krb5_principal principal;
    int retval = 1;

    ret = krb5_init_context(&context);
    if(ret)
	errx(1, "krb5_init_context failt: %d", ret);

    ret = krb5_cc_default(context, &ccache);
    if(ret)
	errx(1, "krb5_cc_default: %d", ret);

    ret = krb5_cc_get_principal (context, ccache, &principal);
    switch(ret) {
    case ENOENT:
	retval = 0;
	goto done;
    case 0:
	retval = 1;
	goto done;
    default:
	errx(1, "krb5_cc_get_principal: %d", ret);
	break;
    }

 done:
    krb5_free_context(context);
    return retval;
}

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

    if (c == -1)
	c = strlen(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
kerberos5_init(Authenticator *ap, int server)
{
    krb5_error_code ret;

    ret = krb5_init_context(&context);
    if (ret)
	return 0;
    if (server) {
	krb5_keytab kt;
	krb5_kt_cursor cursor;

	ret = krb5_kt_default(context, &kt);
	if (ret)
	    return 0;

	ret = krb5_kt_start_seq_get (context, kt, &cursor);
	if (ret) {
	    krb5_kt_close (context, kt);
	    return 0;
	}
	krb5_kt_end_seq_get (context, kt, &cursor);
	krb5_kt_close (context, kt);

	str_data[3] = TELQUAL_REPLY;
    } else
	str_data[3] = TELQUAL_IS;
    return(1);
}

extern int net;
static int
kerberos5_send(char *name, Authenticator *ap)
{
    krb5_error_code ret;
    krb5_ccache ccache;
    int ap_opts;
    krb5_data cksum_data;
    char foo[2];

    if(check_krb5_tickets() != 1)
	return 0;
    
    if (!UserNameRequested) {
	if (auth_debug_mode) {
	    printf("Kerberos V5: no user name supplied\r\n");
	}
	return(0);
    }
    
    ret = krb5_cc_default(context, &ccache);
    if (ret) {
	if (auth_debug_mode) {
	    printf("Kerberos V5: could not get default ccache: %s\r\n",
		   krb5_get_err_text (context, ret));
	}
	return 0;
    }
	
    if ((ap->way & AUTH_HOW_MASK) == AUTH_HOW_MUTUAL)
	ap_opts = AP_OPTS_MUTUAL_REQUIRED;
    else
	ap_opts = 0;
    
    ap_opts |= AP_OPTS_USE_SUBKEY;
    
    ret = krb5_auth_con_init (context, &auth_context);
    if (ret) {
	if (auth_debug_mode) {
	    printf("Kerberos V5: krb5_auth_con_init failed (%s)\r\n",
		   krb5_get_err_text(context, ret));
	}
	return(0);
    }

    ret = krb5_auth_con_setaddrs_from_fd (context,
					  auth_context,
					  &net);
    if (ret) {
	if (auth_debug_mode) {
	    printf ("Kerberos V5:"
		    " krb5_auth_con_setaddrs_from_fd failed (%s)\r\n",
		    krb5_get_err_text(context, ret));
	}
	return(0);
    }

    krb5_auth_con_setkeytype (context, auth_context, KEYTYPE_DES);

    foo[0] = ap->type;
    foo[1] = ap->way;

    cksum_data.length = sizeof(foo);
    cksum_data.data   = foo;


    {
	krb5_principal service;
	char sname[128];


	ret = krb5_sname_to_principal (context,
				       RemoteHostName,
				       NULL,
				       KRB5_NT_SRV_HST,
				       &service);
	if(ret) {
	    if (auth_debug_mode) {
		printf ("Kerberos V5:"
			" krb5_sname_to_principal(%s) failed (%s)\r\n",
			RemoteHostName, krb5_get_err_text(context, ret));
	    }
	    return 0;
	}
	ret = krb5_unparse_name_fixed(context, service, sname, sizeof(sname));
	if(ret) {
	    if (auth_debug_mode) {
		printf ("Kerberos V5:"
			" krb5_unparse_name_fixed failed (%s)\r\n",
			krb5_get_err_text(context, ret));
	    }
	    return 0;
	}
	printf("[ Trying %s (%s)... ]\r\n", name, sname);
	ret = krb5_mk_req_exact(context, &auth_context, ap_opts,
				service, 
				&cksum_data, ccache, &auth);
	krb5_free_principal (context, service);

    }
    if (ret) {
	if (1 || auth_debug_mode) {
	    printf("Kerberos V5: mk_req failed (%s)\r\n",
		   krb5_get_err_text(context, ret));
	}
	return(0);
    }

    if (!auth_sendname((unsigned char *)UserNameRequested,
		       strlen(UserNameRequested))) {
	if (auth_debug_mode)
	    printf("Not enough room for user name\r\n");
	return(0);
    }
    if (!Data(ap, KRB_AUTH, auth.data, auth.length)) {
	if (auth_debug_mode)
	    printf("Not enough room for authentication data\r\n");
	return(0);
    }
    if (auth_debug_mode) {
	printf("Sent Kerberos V5 credentials to server\r\n");
    }
    return(1);
}

int
kerberos5_send_mutual(Authenticator *ap)
{
    return kerberos5_send("mutual KERBEROS5", ap);
}

int
kerberos5_send_oneway(Authenticator *ap)
{
    return kerberos5_send("KERBEROS5", ap);
}

void
kerberos5_is(Authenticator *ap, unsigned char *data, int cnt)
{
    krb5_error_code ret;
    krb5_data outbuf;
    krb5_keyblock *key_block;
    char *name;
    krb5_principal server;
    int zero = 0;

    if (cnt-- < 1)
	return;
    switch (*data++) {
    case KRB_AUTH:
	auth.data = (char *)data;
	auth.length = cnt;

	auth_context = NULL;

	ret = krb5_auth_con_init (context, &auth_context);
	if (ret) {
	    Data(ap, KRB_REJECT, "krb5_auth_con_init failed", -1);
	    auth_finished(ap, AUTH_REJECT);
	    if (auth_debug_mode)
		printf("Kerberos V5: krb5_auth_con_init failed (%s)\r\n",
		       krb5_get_err_text(context, ret));
	    return;
	}

	ret = krb5_auth_con_setaddrs_from_fd (context,
					      auth_context,
					      &zero);
	if (ret) {
	    Data(ap, KRB_REJECT, "krb5_auth_con_setaddrs_from_fd failed", -1);
	    auth_finished(ap, AUTH_REJECT);
	    if (auth_debug_mode)
		printf("Kerberos V5: "
		       "krb5_auth_con_setaddrs_from_fd failed (%s)\r\n",
		       krb5_get_err_text(context, ret));
	    return;
	}

	ret = krb5_sock_to_principal (context,
				      0,
				      "host",
				      KRB5_NT_SRV_HST,
				      &server);
	if (ret) {
	    Data(ap, KRB_REJECT, "krb5_sock_to_principal failed", -1);
	    auth_finished(ap, AUTH_REJECT);
	    if (auth_debug_mode)
		printf("Kerberos V5: "
		       "krb5_sock_to_principal failed (%s)\r\n",
		       krb5_get_err_text(context, ret));
	    return;
	}

	ret = krb5_rd_req(context,
			  &auth_context,
			  &auth, 
			  server,
			  NULL,
			  NULL,
			  &ticket);

	krb5_free_principal (context, server);
	if (ret) {
	    char *errbuf;

	    asprintf(&errbuf,
		     "Read req failed: %s",
		     krb5_get_err_text(context, ret));
	    Data(ap, KRB_REJECT, errbuf, -1);
	    if (auth_debug_mode)
		printf("%s\r\n", errbuf);
	    free (errbuf);
	    return;
	}
	
	{
	    char foo[2];
	    
	    foo[0] = ap->type;
	    foo[1] = ap->way;
	    
	    ret = krb5_verify_authenticator_checksum(context,
						     auth_context,
						     foo, 
						     sizeof(foo));

	    if (ret) {
		char *errbuf;
		asprintf(&errbuf, "Bad checksum: %s", 
			 krb5_get_err_text(context, ret));
		Data(ap, KRB_REJECT, errbuf, -1);
		if (auth_debug_mode)
		    printf ("%s\r\n", errbuf);
		free(errbuf);
		return;
	    }
	}