/*-
 * 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.
 */

#include <sys/cdefs.h>

__FBSDID("$FreeBSD$");

#ifndef lint
static const char sccsid[] = "@(#)kerberos.c    8.3 (Berkeley) 5/30/95";
#endif /* not lint */

/*
 * 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.
 */

#ifdef  KRB4
#include <sys/types.h>
#include <arpa/telnet.h>
#include <openssl/des.h>        /* BSD wont include this in krb.h, so we do it here */
#include <krb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

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

int kerberos4_cksum(unsigned char *, int);
int kuserok(AUTH_DAT *, char *);

extern int auth_debug_mode;

static unsigned char str_data[1024] = { 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. */

static  KTEXT_ST auth;
static  char name[ANAME_SZ];
static  AUTH_DAT adat = { 0, "", "", "", 0, {}, 0, 0, 0, { 0, "", 0 } };
#ifdef  ENCRYPTION
static Block    session_key     = { 0 };
static DES_key_schedule sched;
static Block    challenge       = { 0 };
#endif  /* ENCRYPTION */

static char krb_service_name[] = "rcmd";
static char empty[] = "";

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

int
kerberos4_init(Authenticator *ap __unused, 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;

int
kerberos4_send(Authenticator *ap)
{
        KTEXT_ST lauth;
        char instance[INST_SZ];
        char *realm;
        CREDENTIALS cred;
        int r;

        printf("[ Trying KERBEROS4 ... ]\n");
        if (!UserNameRequested) {
                if (auth_debug_mode) {
                        printf("Kerberos V4: no user name supplied\r\n");
                }
                return(0);
        }

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

        if ((realm = krb_get_phost(RemoteHostName)))
                strncpy(instance, realm, sizeof(instance));

        instance[sizeof(instance)-1] = '\0';

        realm = dest_realm ? dest_realm : krb_realmofhost(RemoteHostName);

        if (!realm) {
                printf("Kerberos V4: no realm for %s\r\n", RemoteHostName);
                return(0);
        }
        if ((r = krb_mk_req(&lauth, krb_service_name, instance, realm, 0L))) {
                printf("mk_req failed: %s\r\n", krb_err_txt[r]);
                return(0);
        }
        if ((r = krb_get_cred(krb_service_name, instance, realm, &cred))) {
                printf("get_cred failed: %s\r\n", krb_err_txt[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", lauth.length);
        if (!Data(ap, KRB_AUTH, (void *)lauth.dat, lauth.length)) {
                if (auth_debug_mode)
                        printf("Not enough room for authentication data\r\n");
                return(0);
        }
#ifdef  ENCRYPTION
        /*
         * If we are doing mutual authentication, get set up to send
         * the challenge, and verify it when the response comes back.
         */
        if ((ap->way & AUTH_HOW_MASK) == AUTH_HOW_MUTUAL) {
                register int i;

                DES_key_sched(&cred.session, sched);
                DES_random_key(&session_key);
                DES_ecb_encrypt(&session_key, &session_key, sched, 0);
                DES_ecb_encrypt(&session_key, &challenge, sched, 0);
                /*
                 * Increment the challenge by 1, and encrypt it for
                 * later comparison.
                 */
                for (i = 7; i >= 0; --i) {
                        register int x;
                        x = (unsigned int)challenge[i] + 1;
                        challenge[i] = x;       /* ignore overflow */
                        if (x < 256)            /* if no overflow, all done */
                                break;
                }
                DES_ecb_encrypt(&challenge, &challenge, sched, 1);
        }
#endif  /* ENCRYPTION */

        if (auth_debug_mode) {
                printf("CK: %d:", kerberos4_cksum(lauth.dat, lauth.length));
                printd(lauth.dat, lauth.length);
                printf("\r\n");
                printf("Sent Kerberos V4 credentials to server\r\n");
        }
        return(1);
}

void
kerberos4_is(Authenticator *ap, unsigned char *data, int cnt)
{
#ifdef  ENCRYPTION
        Session_Key skey;
        Block datablock;
#endif  /* ENCRYPTION */
        char realm[REALM_SZ];
        char instance[INST_SZ];
        int r;

        if (cnt-- < 1)
                return;
        switch (*data++) {
        case KRB_AUTH:
                if (krb_get_lrealm(realm, 1) != KSUCCESS) {
                        Data(ap, KRB_REJECT, "No local V4 Realm.", -1);
                        auth_finished(ap, AUTH_REJECT);
                        if (auth_debug_mode)
                                printf("No local realm\r\n");
                        return;
                }
                memmove((void *)auth.dat, (void *)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");
                }
                instance[0] = '*'; instance[1] = 0;
                if ((r = krb_rd_req(&auth, krb_service_name,
                                   instance, 0, &adat, empty))) {
                        if (auth_debug_mode)
                                printf("Kerberos failed him as %s\r\n", name);
                        Data(ap, KRB_REJECT, krb_err_txt[r], -1);
                        auth_finished(ap, AUTH_REJECT);
                        return;
                }
#ifdef  ENCRYPTION
                memmove((void *)session_key, (void *)adat.session, sizeof(Block));
#endif  /* ENCRYPTION */
                krb_kntoln(&adat, name);

                if (UserNameRequested && !kuserok(&adat, UserNameRequested))
                        Data(ap, KRB_ACCEPT, NULL, 0);
                else
                        Data(ap, KRB_REJECT, "user is not authorized", -1);
                auth_finished(ap, AUTH_USER);
                break;

        case KRB_CHALLENGE:
#ifndef ENCRYPTION
                Data(ap, KRB_RESPONSE, NULL, 0);
#else   /* ENCRYPTION */
                if (!VALIDKEY(session_key)) {
                        /*
                         * We don't have a valid session key, so just
                         * send back a response with an empty session
                         * key.
                         */
                        Data(ap, KRB_RESPONSE, NULL, 0);
                        break;
                }

                DES_key_sched(&session_key, sched);
                memmove((void *)datablock, (void *)data, sizeof(Block));
                /*
                 * Take the received encrypted challenge, and encrypt
                 * it again to get a unique session_key for the
                 * ENCRYPT option.
                 */
                DES_ecb_encrypt(&datablock, &session_key, sched, 1);
                skey.type = SK_DES;
                skey.length = 8;
                skey.data = session_key;
                encrypt_session_key(&skey, 1);
                /*
                 * Now decrypt the received encrypted challenge,
                 * increment by one, re-encrypt it and send it back.
                 */
                DES_ecb_encrypt(&datablock, &challenge, sched, 0);
                for (r = 7; r >= 0; r--) {
                        register int t;
                        t = (unsigned int)challenge[r] + 1;
                        challenge[r] = t;       /* ignore overflow */
                        if (t < 256)            /* if no overflow, all done */
                                break;
                }
                DES_ecb_encrypt(&challenge, &challenge, sched, 1);
                Data(ap, KRB_RESPONSE, challenge, sizeof(challenge));
#endif  /* ENCRYPTION */
                break;

        default:
                if (auth_debug_mode)
                        printf("Unknown Kerberos option %d\r\n", data[-1]);
                Data(ap, KRB_REJECT, NULL, 0);
                break;
        }
}

void
kerberos4_reply(Authenticator *ap, unsigned char *data, int cnt)
{
#ifdef  ENCRYPTION
        Session_Key skey;
#endif  /* ENCRYPTION */

        if (cnt-- < 1)
                return;
        switch (*data++) {
        case KRB_REJECT:
                if (cnt > 0) {
                        printf("[ Kerberos V4 refuses authentication because %.*s ]\r\n",
                                cnt, data);
                } else
                        printf("[ Kerberos V4 refuses authentication ]\r\n");
                auth_send_retry();
                return;
        case KRB_ACCEPT:
                printf("[ Kerberos V4 accepts you ]\n");
                if ((ap->way & AUTH_HOW_MASK) == AUTH_HOW_MUTUAL) {
                        /*
                         * Send over the encrypted challenge.
                         */
#ifndef ENCRYPTION
                        Data(ap, KRB_CHALLENGE, NULL, 0);
#else   /* ENCRYPTION */
                        Data(ap, KRB_CHALLENGE, session_key,
                                                sizeof(session_key));
                        DES_ecb_encrypt(&session_key, &session_key, sched, 1);
                        skey.type = SK_DES;
                        skey.length = 8;
                        skey.data = session_key;
                        encrypt_session_key(&skey, 0);
#endif  /* ENCRYPTION */
                        return;
                }
                auth_finished(ap, AUTH_USER);
                return;
        case KRB_RESPONSE:
#ifdef  ENCRYPTION
                /*
                 * Verify that the response to the challenge is correct.
                 */
                if ((cnt != sizeof(Block)) ||
                    (0 != memcmp((void *)data, (void *)challenge,
                                                sizeof(challenge))))
                {
#endif  /* ENCRYPTION */
                        printf("[ Kerberos V4 challenge failed!!! ]\r\n");
                        auth_send_retry();
                        return;
#ifdef  ENCRYPTION
                }
                printf("[ Kerberos V4 challenge successful ]\r\n");
                auth_finished(ap, AUTH_USER);
#endif  /* ENCRYPTION */
                break;
        default:
                if (auth_debug_mode)
                        printf("Unknown Kerberos option %d\r\n", data[-1]);
                return;
        }
}

int
kerberos4_status(Authenticator *ap __unused, char *nam, int level)
{
        if (level < AUTH_USER)
                return(level);

        if (UserNameRequested && !kuserok(&adat, UserNameRequested)) {
                strcpy(nam, UserNameRequested);
                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
kerberos4_printsub(unsigned char *data, int cnt, unsigned char *buf, int buflen)
{
        char lbuf[32];
        register int i;

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

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

        case KRB_ACCEPT:                /* Accepted (name might follow) */
                strncpy((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 */
                strncpy((char *)buf, " AUTH", buflen);
                goto common2;

        case KRB_CHALLENGE:
                strncpy((char *)buf, " CHALLENGE", buflen);
                goto common2;

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

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

int
kerberos4_cksum(unsigned char *d, int n)
{
        int ck = 0;

        /*
         * A comment is probably needed here for those not
         * well versed in the "C" language.  Yes, this is
         * supposed to be a "switch" with the body of the
         * "switch" being a "while" statement.  The whole
         * purpose of the switch is to allow us to jump into
         * the middle of the while() loop, and then not have
         * to do any more switch()s.
         *
         * Some compilers will spit out a warning message
         * about the loop not being entered at the top.
         */
        switch (n&03)
        while (n > 0) {
        case 0:
                ck ^= (int)*d++ << 24;
                --n;
        case 3:
                ck ^= (int)*d++ << 16;
                --n;
        case 2:
                ck ^= (int)*d++ << 8;
                --n;
        case 1:
                ck ^= (int)*d++;
                --n;
        }
        return(ck);
}
#endif