xref: /src/lib/libtelnet/kerberos5.c

/*	$NetBSD: kerberos5.c,v 1.14 2005/04/19 03:19:46 christos 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.
 */

/*
 * 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.
 */

#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>
#define Authenticator k5_Authenticator
#include <krb5.h>
#undef Authenticator
/* #include <roken.h> */

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

extern int net;

int forward_flags;	/* Flags get set in telnet/main.c on -f and -F */
int got_forwarded_creds;/* Tell telnetd to pass -F or -f to login. */

int require_hwpreauth;

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;

krb5_context telnet_context;
static krb5_auth_context auth_context;

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;

	if (telnet_context == 0) {
		ret = krb5_init_context(&telnet_context);
		if (ret)
			return 0;
	}

	if (server) {
		krb5_keytab kt;
		krb5_kt_cursor cursor;

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

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

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

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

	printf("[ Trying KERBEROS5 ... ]\r\n");

	if (!UserNameRequested) {
		if (auth_debug_mode) {
			printf("Kerberos V5: no user name supplied\r\n");
		}
		return (0);
	}
	ret = krb5_cc_default(telnet_context, &ccache);
	if (ret) {
		if (auth_debug_mode) {
			printf(
			"Kerberos V5: could not get default ccache: %s\r\n",
			    krb5_get_err_text(telnet_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(telnet_context, &auth_context);
	if (ret) {
		if (auth_debug_mode) {
			printf(
			"Kerberos V5: krb5_auth_con_init failed: %s\r\n",
			    krb5_get_err_text(telnet_context, ret));
		}
		return (0);
	}
	ret = krb5_auth_con_setaddrs_from_fd(telnet_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(telnet_context, ret));
		}
		return (0);
	}
	krb5_auth_con_setkeytype(telnet_context, auth_context, KEYTYPE_DES);

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

	cksum_data.length = sizeof(foo);
	cksum_data.data = foo;
	ret = krb5_mk_req(telnet_context, &auth_context, ap_opts, "host",
	    RemoteHostName, &cksum_data, ccache, &auth);
	if (ret) {
		if (1 || auth_debug_mode) {
			printf("Kerberos V5: mk_req failed (%s)\r\n",
			    krb5_get_err_text(telnet_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);
}

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(telnet_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(telnet_context, ret));
			return;
		}
		ret = krb5_auth_con_setaddrs_from_fd(telnet_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(telnet_context, ret));
			return;
		}
		ret = krb5_sock_to_principal(telnet_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(telnet_context, ret));
			return;
		}
		ret = krb5_rd_req(telnet_context, &auth_context, &auth,
		    server, NULL, NULL, &ticket);
		krb5_free_principal(telnet_context, server);

		if (ret) {
			char *errbuf;

			asprintf(&errbuf,
			    "Read req failed: %s",
			    krb5_get_err_text(telnet_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(telnet_context,
			    auth_context, foo, sizeof(foo));

			if (ret) {
				char *errbuf;
				asprintf(&errbuf, "Bad checksum: %s",
				    krb5_get_err_text(telnet_context, ret));
				Data(ap, KRB_REJECT, errbuf, -1);
				if (auth_debug_mode)
					printf("%s\r\n", errbuf);
				free(errbuf);
				return;
			}
		}
		ret = krb5_auth_con_getremotesubkey(telnet_context,
		    auth_context, &key_block);

		if (ret) {
			Data(ap, KRB_REJECT, "krb5_auth_con_getremotesubkey failed", -1);
			auth_finished(ap, AUTH_REJECT);
			if (auth_debug_mode)
				printf("Kerberos V5: "
				    "krb5_auth_con_getremotesubkey failed (%s)\r\n",
				    krb5_get_err_text(telnet_context, ret));
			return;
		}
		if (key_block == NULL) {
			ret = krb5_auth_con_getkey(telnet_context,
						   auth_context,
						   &key_block);
		}
		if (ret) {
			Data(ap, KRB_REJECT, "krb5_auth_con_getkey failed", -1);
			auth_finished(ap, AUTH_REJECT);
			if (auth_debug_mode)
				printf("Kerberos V5: "
				       "krb5_auth_con_getkey failed (%s)\r\n",
				       krb5_get_err_text(telnet_context, ret));
			return;
		}
		if (key_block == NULL) {
			Data(ap, KRB_REJECT, "no subkey received", -1);
			auth_finished(ap, AUTH_REJECT);
			if (auth_debug_mode)
				printf("Kerberos V5: "
				       "krb5_auth_con_getremotesubkey returned NULL key\r\n");
			return;
		}
		if ((ap->way & AUTH_HOW_MASK) == AUTH_HOW_MUTUAL) {
			ret = krb5_mk_rep(telnet_context,
			    auth_context, &outbuf);
			if (ret) {
				Data(ap, KRB_REJECT,
				    "krb5_mk_rep failed", -1);
				auth_finished(ap, AUTH_REJECT);
				if (auth_debug_mode)
					printf("Kerberos V5: "
					    "krb5_mk_rep failed (%s)\r\n",
					    krb5_get_err_text(telnet_context,
					    ret));
				return;
			}
			Data(ap, KRB_RESPONSE, outbuf.data, outbuf.length);
		}
		if (krb5_unparse_name(telnet_context, ticket->client, &name))
			name = 0;

		if (UserNameRequested && krb5_kuserok(telnet_context,
		    ticket->client, UserNameRequested)) {
			Data(ap, KRB_ACCEPT, name, name ? -1 : 0);
			if (auth_debug_mode) {
				printf("Kerberos5 identifies him as ``%s''\r\n",
				    name ? name : "");
			}
			if (key_block->keytype == ETYPE_DES_CBC_MD5 ||
			    key_block->keytype == ETYPE_DES_CBC_MD4 ||
			    key_block->keytype == ETYPE_DES_CBC_CRC) {
				Session_Key skey;

				skey.type = SK_DES;
				skey.length = 8;
				skey.data = key_block->keyvalue.data;
				encrypt_session_key(&skey, 0);
			}
		} else {
			char *msg;

			asprintf(&msg, "user `%s' is not authorized to "
			    "login as `%s'",
			    name ? name : "<unknown>",
			    UserNameRequested ? UserNameRequested : "<nobody>");
			if (msg == NULL)
				Data(ap, KRB_REJECT, NULL, 0);
			else {
				Data(ap, KRB_REJECT, (void *) msg, -1);
				free(msg);
			}
			auth_finished(ap, AUTH_REJECT);
			krb5_free_keyblock_contents(telnet_context, key_block);
			break;
		}
		auth_finished(ap, AUTH_USER);
		krb5_free_keyblock_contents(telnet_context, key_block);

		break;
	case KRB_FORWARD:{
			struct passwd pws, *pwd;
			char pwbuf[1024];
			char ccname[1024];	/* XXX */
			krb5_data inbuf;
			krb5_ccache ccache;
			inbuf.data = (char *) data;
			inbuf.length = cnt;

			if (getpwnam_r(UserNameRequested, &pws, pwbuf,
			    sizeof(pwbuf), &pwd) != 0 || pwd == NULL)
				break;

			snprintf(ccname, sizeof(ccname),
			    "FILE:/tmp/krb5cc_%u", pwd->pw_uid);

			ret = krb5_cc_resolve(telnet_context, ccname, &ccache);
			if (ret) {
				if (auth_debug_mode)
					printf("Kerberos V5: could not get ccache: %s\r\n",
					    krb5_get_err_text(telnet_context,
					    ret));
				break;
			}
			ret = krb5_cc_initialize(telnet_context, ccache,
			    ticket->client);
			if (ret) {
				if (auth_debug_mode)
					printf("Kerberos V5: could not init ccache: %s\r\n",
					    krb5_get_err_text(telnet_context,
					        ret));
				break;
			}
			ret = krb5_rd_cred2(telnet_context, auth_context,
			    ccache, &inbuf);
			if (ret) {
				char *errbuf;

				asprintf(&errbuf,
				    "Read forwarded creds failed: %s",
				    krb5_get_err_text(telnet_context, ret));
				if (errbuf == NULL)
					Data(ap, KRB_FORWARD_REJECT, NULL, 0);
				else
					Data(ap, KRB_FORWARD_REJECT, errbuf, -1);
				if (auth_debug_mode)
					printf("Could not read forwarded credentials: %s\r\n",
					    errbuf);
				free(errbuf);
			} else
				Data(ap, KRB_FORWARD_ACCEPT, 0, 0);
			chown(ccname + 5, pwd->pw_uid, -1);
			if (auth_debug_mode)
				printf("Forwarded credentials obtained\r\n");
			break;
		}
	default:
		if (auth_debug_mode)
			printf("Unknown Kerberos option %d\r\n", data[-1]);
		Data(ap, KRB_REJECT, 0, 0);
		break;
	}
}

void
kerberos5_reply(Authenticator * ap, unsigned char *data, int cnt)
{
	static int mutual_complete = 0;

	if (cnt-- < 1)
		return;
	switch (*data++) {
	case KRB_REJECT:
		if (cnt > 0) {
			printf("[ Kerberos V5 refuses authentication because %.*s ]\r\n",
			    cnt, data);
		} else
			printf("[ Kerberos V5 refuses authentication ]\r\n");
		auth_send_retry();
		return;
	case KRB_ACCEPT:{
			krb5_error_code ret;
			Session_Key skey;
			krb5_keyblock *keyblock;

			if ((ap->way & AUTH_HOW_MASK) == AUTH_HOW_MUTUAL &&
			    !mutual_complete) {
				printf("[ Kerberos V5 accepted you, but didn't provide mutual authentication! ]\r\n");
				auth_send_retry();
				return;
			}
			if (cnt)
				printf("[ Kerberos V5 accepts you as ``%.*s'' ]\r\n", cnt, data);
			else
				printf("[ Kerberos V5 accepts you ]\r\n");

			ret = krb5_auth_con_getlocalsubkey(telnet_context,
			    auth_context, &keyblock);
			if (ret)
				ret = krb5_auth_con_getkey(telnet_context,
				    auth_context, &keyblock);
			if (ret) {
				printf("[ krb5_auth_con_getkey: %s ]\r\n",
				    krb5_get_err_text(telnet_context, ret));
				auth_send_retry();
				return;
			}
			skey.type = SK_DES;
			skey.length = 8;
			skey.data = keyblock->keyvalue.data;
			encrypt_session_key(&skey, 0);
			krb5_free_keyblock_contents(telnet_context, keyblock);
			auth_finished(ap, AUTH_USER);
			if (forward_flags & OPTS_FORWARD_CREDS)
				kerberos5_forward(ap);
			break;
		}
	case KRB_RESPONSE:
		if ((ap->way & AUTH_HOW_MASK) == AUTH_HOW_MUTUAL) {
			/* the rest of the reply should contain a krb_ap_rep */
			krb5_ap_rep_enc_part *reply;
			krb5_data inbuf;
			krb5_error_code ret;

			inbuf.length = cnt;
			inbuf.data = (char *) data;

			ret = krb5_rd_rep(telnet_context,
			    auth_context, &inbuf, &reply);
			if (ret) {
				printf("[ Mutual authentication failed: %s ]\r\n",
				    krb5_get_err_text(telnet_context, ret));
				auth_send_retry();
				return;
			}
			krb5_free_ap_rep_enc_part(telnet_context, reply);
			mutual_complete = 1;
		}
		return;
	case KRB_FORWARD_ACCEPT:
		printf("[ Kerberos V5 accepted forwarded credentials ]\r\n");
		return;
	case KRB_FORWARD_REJECT:
		printf("[ Kerberos V5 refuses forwarded credentials because %.*s ]\r\n",
		    cnt, data);
		return;
	default:
		if (auth_debug_mode)
			printf("Unknown Kerberos option %d\r\n", data[-1]);
		return;
	}
}

int
kerberos5_status(Authenticator *ap, char *name, size_t l, int level)
{
	if (level < AUTH_USER)
		return (level);

	if (UserNameRequested &&
	    krb5_kuserok(telnet_context, ticket->client, UserNameRequested)) {
		strlcpy(name, UserNameRequested, l);
		return (AUTH_VALID);
	} else
		return (AUTH_USER);
}
#define	BUMP(buf, len)		while (*(buf)) {++(buf), --(len);}
#define	ADDC(buf, len, c)	if ((len) > 0) {*(buf)++ = (c); --(len);}

void
kerberos5_printsub(unsigned char *data, int cnt, unsigned char *buf, int buflen)
{
	int i;

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

	switch (data[3]) {
	case KRB_REJECT:	/* Rejected (reason might follow) */
		strlcpy((char *) buf, " REJECT ", buflen);
		goto common;

	case KRB_ACCEPT:	/* Accepted (name might follow) */
		strlcpy((char *) buf, " ACCEPT ", buflen);
common:
		BUMP(buf, buflen);
		if (cnt <= 4)
			break;
		ADDC(buf, buflen, '"');
		for (i = 4; i < cnt; i++)
			ADDC(buf, buflen, data[i]);
		ADDC(buf, buflen, '"');
		ADDC(buf, buflen, '\0');
		break;


	case KRB_AUTH:		/* Authentication data follows */
		strlcpy((char *) buf, " AUTH", buflen);
		goto common2;

	case KRB_RESPONSE:
		strlcpy((char *) buf, " RESPONSE", buflen);
		goto common2;

	case KRB_FORWARD:	/* Forwarded credentials follow */
		strlcpy((char *) buf, " FORWARD", buflen);
		goto common2;

	case KRB_FORWARD_ACCEPT:	/* Forwarded credentials accepted */
		strlcpy((char *) buf, " FORWARD_ACCEPT", buflen);
		goto common2;

	case KRB_FORWARD_REJECT:	/* Forwarded credentials rejected */
		/* (reason might follow) */
		strlcpy((char *) buf, " FORWARD_REJECT", buflen);
		goto common2;

	default:
		snprintf(buf, buflen, " %d (unknown)", data[3]);
common2:
		BUMP(buf, buflen);
		for (i = 4; i < cnt; i++) {
			snprintf(buf, buflen, " %d", data[i]);
			BUMP(buf, buflen);
		}
		break;
	}
}

void
kerberos5_forward(Authenticator * ap)
{
	krb5_error_code ret;
	krb5_ccache ccache;
	krb5_creds creds;
	krb5_kdc_flags flags;
	krb5_data out_data;
	krb5_principal principal;

	ret = krb5_cc_default(telnet_context, &ccache);
	if (ret) {
		if (auth_debug_mode)
			printf("KerberosV5: could not get default ccache: %s\r\n",
			    krb5_get_err_text(telnet_context, ret));
		return;
	}
	ret = krb5_cc_get_principal(telnet_context, ccache, &principal);
	if (ret) {
		if (auth_debug_mode)
			printf("KerberosV5: could not get principal: %s\r\n",
			    krb5_get_err_text(telnet_context, ret));
		return;
	}
	memset(&creds, 0, sizeof(creds));

	creds.client = principal;

	ret = krb5_build_principal(telnet_context, &creds.server,
	    strlen(principal->realm), principal->realm, "krbtgt",
	    principal->realm, NULL);

	if (ret) {
		if (auth_debug_mode)
			printf("KerberosV5: could not get principal: %s\r\n",
			    krb5_get_err_text(telnet_context, ret));
		return;
	}
	creds.times.endtime = 0;

	flags.i = 0;
	flags.b.forwarded = 1;
	if (forward_flags & OPTS_FORWARDABLE_CREDS)
		flags.b.forwardable = 1;

	ret = krb5_get_forwarded_creds(telnet_context, auth_context,
	    ccache, flags.i, RemoteHostName, &creds, &out_data);
	if (ret) {
		if (auth_debug_mode)
			printf("Kerberos V5: error getting forwarded creds: %s\r\n",
			    krb5_get_err_text(telnet_context, ret));
		return;
	}
	if (!Data(ap, KRB_FORWARD, out_data.data, out_data.length)) {
		if (auth_debug_mode)
			printf("Not enough room for authentication data\r\n");
	} else {
		if (auth_debug_mode)
			printf("Forwarded local Kerberos V5 credentials to server\r\n");
	}
}
#endif /* KRB5 */