usr.bin/telnet/kerberos5.c

/*
 * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

/*
 * usr/src/cmd/cmd-inet/usr.bin/telnet/kerberos5.c
 *
 * 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. All advertising materials mentioning features or use of this software
 *  must display the following acknowledgement:
 *  This product includes software developed by the University of
 *  California, Berkeley and its contributors.
 * 4. 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.
 */

/* based on @(#)kerberos5.c 8.1 (Berkeley) 6/4/93 */

/*
 * 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.  Furthermore if you modify this software you must label
 * your software as modified software and not distribute it in such a
 * fashion that it might be confused with the original M.I.T. software.
 * 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.
 */


#include <arpa/telnet.h>
#include <stdio.h>
#include <ctype.h>
#include <syslog.h>
#include <stdlib.h>

/* the following are from the kerberos tree */
#include <k5-int.h>
#include <com_err.h>
#include <netdb.h>
#include <profile/prof_int.h>
#include <sys/param.h>
#include "externs.h"

extern  char *RemoteHostName;
extern  boolean_t auth_debug_mode;
extern  int net;

#define ACCEPTED_ENCTYPE(a) \
    (a == ENCTYPE_DES_CBC_CRC || a == ENCTYPE_DES_CBC_MD5)
/* for comapatibility with non-Solaris KDC's, this has to be big enough */
#define KERBEROS_BUFSIZ 8192

int forward_flags = 0;  /* Flags get set in telnet/main.c on -f and -F */
static  void kerberos5_forward(Authenticator *);

static  unsigned char str_data[KERBEROS_BUFSIZ] = { IAC, SB,
        TELOPT_AUTHENTICATION, 0, AUTHTYPE_KERBEROS_V5, };
static  char *appdef[] = { "appdefaults", "telnet", NULL };
static  char *realmdef[] = { "realms", NULL, "telnet", NULL };

static  krb5_auth_context auth_context = 0;

static  krb5_data auth; /* telnetd gets session key from here */
static  krb5_ticket *ticket = NULL;
    /* telnet matches the AP_REQ and AP_REP with this */

static  krb5_keyblock   *session_key = 0;
char    *telnet_krb5_realm = NULL;

/*
 * Change the kerberos realm
 */
void
set_krb5_realm(char *name)
{
    if (name == NULL) {
        (void) fprintf(stderr, gettext("Could not set Kerberos realm, "
            "no realm provided.\n"));
        return;
    }

    if (telnet_krb5_realm)
        free(telnet_krb5_realm);

    telnet_krb5_realm = (char *)strdup(name);

    if (telnet_krb5_realm == NULL)
        (void) fprintf(stderr, gettext(
            "Could not set Kerberos realm, malloc failed\n"));
}

#define RETURN_NOMEM    { errno = ENOMEM; return (-1); }

static int
krb5_send_data(Authenticator *ap, int type, krb5_pointer d, int c)
{
    /* the first 3 bytes are control chars */
    unsigned char *p = str_data + 4;
    unsigned char *cd = (unsigned char *)d;
    /* spaceleft is incremented whenever p is decremented */
    size_t spaceleft = sizeof (str_data) - 4;

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

    if (auth_debug_mode) {
        (void) printf("%s:%d: [%d] (%d)",
            str_data[3] == TELQUAL_IS ? ">>>IS" : ">>>REPLY",
            str_data[3], type, c);
        printd(d, c);
        (void) printf("\r\n");
    }

    if (spaceleft < 3)
        RETURN_NOMEM;
    *p++ = ap->type;
    *p++ = ap->way;
    *p++ = type;
    spaceleft -= 3;

    while (c-- > 0) {
        if (spaceleft < 2)
            RETURN_NOMEM;
        if ((*p++ = *cd++) == IAC) {
            *p++ = IAC;
            spaceleft -= 2;
        }
    }

    if (spaceleft < 2)
        RETURN_NOMEM;
    *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));
}

krb5_context telnet_context = 0;

/* ARGSUSED */
int
kerberos5_init(Authenticator *ap)
{
    krb5_error_code retval;

    str_data[3] = TELQUAL_IS;
    if (krb5auth_flag && (telnet_context == 0)) {
        retval = krb5_init_context(&telnet_context);
        if (retval)
            return (0);
    }
    return (1);
}

int
kerberos5_send(Authenticator *ap)
{
    krb5_error_code retval;
    krb5_ccache ccache;
    krb5_creds creds;       /* telnet gets session key from here */
    krb5_creds *new_creds = 0;
    int ap_opts;
    char type_check[2];
    krb5_data check_data;

    krb5_keyblock *newkey = 0;

    int i;
    krb5_enctype *ktypes;

    if (!UserNameRequested) {
        if (auth_debug_mode)
            (void) printf(gettext("telnet: Kerberos V5: "
                "no user name supplied\r\n"));
        return (0);
    }

    if ((retval = krb5_cc_default(telnet_context, &ccache))) {
        if (auth_debug_mode)
            (void) printf(gettext("telnet: Kerberos V5: "
            "could not get default ccache\r\n"));
        return (0);
    }

    (void) memset((char *)&creds, 0, sizeof (creds));
    if (auth_debug_mode)
        printf("telnet: calling krb5_sname_to_principal\n");
    if ((retval = krb5_sname_to_principal(telnet_context, RemoteHostName,
        "host", KRB5_NT_SRV_HST, &creds.server))) {
        if (auth_debug_mode)
            (void) printf(gettext("telnet: Kerberos V5: error "
            "while constructing service name: %s\r\n"),
            error_message(retval));
        return (0);
    }
    if (auth_debug_mode)
        printf("telnet: done calling krb5_sname_to_principal\n");

    if (telnet_krb5_realm != NULL) {
        krb5_data rdata;

        rdata.magic = 0;
        rdata.length = strlen(telnet_krb5_realm);
        rdata.data = (char *)malloc(rdata.length + 1);
        if (rdata.data == NULL) {
            (void) fprintf(stderr, gettext("malloc failed\n"));
            return (0);
        }
        (void) strcpy(rdata.data, telnet_krb5_realm);
        krb5_princ_set_realm(telnet_context, creds.server, &rdata);
        if (auth_debug_mode)
            (void) printf(gettext(
            "telnet: Kerberos V5: set kerberos realm to %s\r\n"),
            telnet_krb5_realm);
    }

    if ((retval = krb5_cc_get_principal(telnet_context, ccache,
        &creds.client)) != NULL) {
        if (auth_debug_mode) {
            (void) printf(gettext(
                "telnet: Kerberos V5: failure on principal "
                "(%s)\r\n"), error_message(retval));
        }
        krb5_free_cred_contents(telnet_context, &creds);
        return (0);
    }
/*
 * Check to to confirm that at least one of the supported
 * encryption types (des-cbc-md5, des-cbc-crc is available. If
 * one is available then use it to obtain credentials.
 */

    if ((retval = krb5_get_tgs_ktypes(telnet_context, creds.server,
        &ktypes))) {
        if (auth_debug_mode) {
            (void) printf(gettext(
                "telnet: Kerberos V5: could not determine "
                "TGS encryption types "
                "(see default_tgs_enctypes in krb5.conf) "
                "(%s)\r\n"), error_message(retval));
        }
        krb5_free_cred_contents(telnet_context, &creds);
        return (0);
    }

    for (i = 0; ktypes[i]; i++) {
        if (ACCEPTED_ENCTYPE(ktypes[i]))
            break;
    }

    if (ktypes[i] == 0) {
        if (auth_debug_mode) {
            (void) printf(gettext(
                "telnet: Kerberos V5: "
                "failure on encryption types. "
                "Cannot find des-cbc-md5 or des-cbc-crc "
                "in list of TGS encryption types "
                "(see default_tgs_enctypes in krb5.conf)\n"));
        }
        krb5_free_cred_contents(telnet_context, &creds);
        return (0);
    }

    creds.keyblock.enctype = ktypes[i];
    if ((retval = krb5_get_credentials(telnet_context, 0,
        ccache, &creds, &new_creds))) {
        if (auth_debug_mode) {
            (void) printf(gettext(
                "telnet: Kerberos V5: failure on credentials "
                "(%s)\r\n"), error_message(retval));
        }
        krb5_free_cred_contents(telnet_context, &creds);
        return (0);
    }

    ap_opts = ((ap->way & AUTH_HOW_MASK) == AUTH_HOW_MUTUAL) ?
            AP_OPTS_MUTUAL_REQUIRED : 0;

    ap_opts |= AP_OPTS_USE_SUBKEY;

    if (auth_context) {
        krb5_auth_con_free(telnet_context, auth_context);
        auth_context = 0;
    }
    if ((retval = krb5_auth_con_init(telnet_context, &auth_context))) {
        if (auth_debug_mode) {
            (void) printf(gettext(
                "Kerberos V5: failed to init auth_context "
                "(%s)\r\n"), error_message(retval));
        }
        return (0);
    }

    krb5_auth_con_setflags(telnet_context, auth_context,
        KRB5_AUTH_CONTEXT_RET_TIME);

    type_check[0] = ap->type;
    type_check[1] = ap->way;
    check_data.magic = KV5M_DATA;
    check_data.length = 2;
    check_data.data = (char *)&type_check;

    retval = krb5_mk_req_extended(telnet_context, &auth_context, ap_opts,
        &check_data, new_creds, &auth);

    krb5_auth_con_getlocalsubkey(telnet_context, auth_context, &newkey);
    if (session_key) {
        krb5_free_keyblock(telnet_context, session_key);
        session_key = 0;
    }

    if (newkey) {
        /*
         * keep the key in our private storage, but don't use it
         * yet---see kerberos5_reply() below
         */
        if (!(ACCEPTED_ENCTYPE(newkey->enctype))) {
            if (!(ACCEPTED_ENCTYPE(new_creds->keyblock.enctype)))
            /* use the session key in credentials instead */
            krb5_copy_keyblock(telnet_context,
                &new_creds->keyblock, &session_key);
        } else
            krb5_copy_keyblock(telnet_context,
                newkey, &session_key);

        krb5_free_keyblock(telnet_context, newkey);
    }

    krb5_free_cred_contents(telnet_context, &creds);
    krb5_free_creds(telnet_context, new_creds);

    if (retval) {
        if (auth_debug_mode)
            (void) printf(gettext(
                "telnet: Kerberos V5: mk_req failed (%s)\r\n"),
                error_message(retval));
        return (0);
    }

    if ((auth_sendname((uchar_t *)UserNameRequested,
        strlen(UserNameRequested))) == NULL) {
        if (auth_debug_mode)
            (void) printf(gettext(
                "telnet: Not enough room for user name\r\n"));
        return (0);
    }
    retval = krb5_send_data(ap, KRB_AUTH, auth.data, auth.length);
    if (auth_debug_mode && retval) {
        (void) printf(gettext(
            "telnet: Sent Kerberos V5 credentials to server\r\n"));
    } else if (auth_debug_mode) {
        (void) printf(gettext(
            "telnet: Not enough room for authentication data\r\n"));
        return (0);
    }
    return (1);
}

void
kerberos5_reply(Authenticator *ap, unsigned char *data, int cnt)
{
    Session_Key skey;
    static boolean_t mutual_complete = B_FALSE;

    if (cnt-- < 1)
        return;
    switch (*data++) {
    case KRB_REJECT:
        if (cnt > 0)
            (void) printf(gettext(
            "[ Kerberos V5 refuses authentication because "
            "%.*s ]\r\n"), cnt, data);
        else
            (void) printf(gettext(
            "[ Kerberos V5 refuses authentication ]\r\n"));
        auth_send_retry();
        return;
    case KRB_ACCEPT:
        if (!mutual_complete) {
            if ((ap->way & AUTH_HOW_MASK) == AUTH_HOW_MUTUAL) {
                (void) printf(gettext(
                "[ Kerberos V5 accepted you, but didn't "
                "provide mutual authentication! ]\r\n"));
                auth_send_retry();
                return;
            }

            if (session_key) {
                skey.type = SK_DES;
                skey.length = 8;
                skey.data = session_key->contents;
                encrypt_session_key(&skey);
            }
        }
        if (cnt)
            (void) printf(gettext(
                "[ Kerberos V5 accepts you as ``%.*s'' ]\r\n"),
                cnt, data);
        else
            (void) printf(gettext(
                "[ Kerberos V5 accepts you ]\r\n"));
        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 retval;

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

            retval = krb5_rd_rep(telnet_context, auth_context,
                &inbuf, &reply);
            if (retval) {
                (void) printf(gettext(
                    "[ Mutual authentication failed: "
                    "%s ]\r\n"), error_message(retval));
                auth_send_retry();
                return;
            }
            krb5_free_ap_rep_enc_part(telnet_context, reply);

            if (session_key) {
                skey.type = SK_DES;
                skey.length = 8;
                skey.data = session_key->contents;
                encrypt_session_key(&skey);
            }
            mutual_complete = B_TRUE;
        }
        return;
    case KRB_FORWARD_ACCEPT:
        (void) printf(gettext(
            "[ Kerberos V5 accepted forwarded credentials ]\r\n"));
        return;
    case KRB_FORWARD_REJECT:
        (void) printf(gettext(
            "[ Kerberos V5 refuses forwarded credentials because "
            "%.*s ]\r\n"), cnt, data);
        return;
    default:
        if (auth_debug_mode)
            (void) printf(gettext(
                "Unknown Kerberos option %d\r\n"), data[-1]);
        return;
    }
}

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

    if (UserNameRequested && krb5_kuserok(telnet_context,
        ticket->enc_part2->client, UserNameRequested)) {

        /* the name buffer comes from telnetd/telnetd{-ktd}.c */
        (void) strncpy(name, UserNameRequested, MAXNAMELEN);
        name[MAXNAMELEN-1] = '\0';
        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); }

/*
 * Used with the set opt command to print suboptions
 */
void
kerberos5_printsub(unsigned char *data, int cnt, unsigned char *buf, int buflen)
{
    char lbuf[AUTH_LBUF_BUFSIZ];
    register int i;

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

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

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

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

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

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

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

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

void
krb5_profile_get_options(char *host, char *realm,
    profile_options_boolean *optionsp)
{
    char    **realms = NULL;
    krb5_error_code err = 0;

    if (!telnet_context) {
        err = krb5_init_context(&telnet_context);
        if (err) {
        (void) fprintf(stderr, gettext(
            "Error initializing Kerberos 5 library: %s\n"),
            error_message(err));
        return;
        }
    }

    if ((realmdef[1] = realm) == NULL) {
        err = krb5_get_host_realm(telnet_context, host, &realms);
        if (err) {
            (void) fprintf(stderr, gettext(
            "Error getting Kerberos 5 realms for: %s (%s)\n"),
            host, error_message(err));
            return;
        }
        realmdef[1] = realms[0];
    }

    profile_get_options_boolean(telnet_context->profile,
        realmdef, optionsp);
    profile_get_options_boolean(telnet_context->profile,
        appdef, optionsp);
}

static void
kerberos5_forward(Authenticator *ap)
{
    krb5_error_code retval;
    krb5_ccache ccache;
    krb5_principal client = 0;
    krb5_principal server = 0;
    krb5_data forw_creds;

    forw_creds.data = 0;

    if ((retval = krb5_cc_default(telnet_context, &ccache))) {
        if (auth_debug_mode)
        (void) printf(gettext(
            "Kerberos V5: could not get default ccache - %s\r\n"),
            error_message(retval));
        return;
    }

    retval = krb5_cc_get_principal(telnet_context, ccache, &client);
    if (retval) {
        if (auth_debug_mode)
            (void) printf(gettext(
                "Kerberos V5: could not get default "
                "principal - %s\r\n"), error_message(retval));
        goto cleanup;
    }

    retval = krb5_sname_to_principal(telnet_context, RemoteHostName,
        "host", KRB5_NT_SRV_HST, &server);
    if (retval) {
        if (auth_debug_mode)
            (void) printf(gettext(
                "Kerberos V5: could not make server "
                "principal - %s\r\n"), error_message(retval));
        goto cleanup;
    }

    retval = krb5_auth_con_genaddrs(telnet_context, auth_context, net,
                KRB5_AUTH_CONTEXT_GENERATE_LOCAL_FULL_ADDR);
    if (retval) {
        if (auth_debug_mode)
            (void) printf(gettext(
                "Kerberos V5: could not gen local full "
                "address - %s\r\n"), error_message(retval));
        goto cleanup;
    }

    retval = krb5_fwd_tgt_creds(telnet_context, auth_context, 0, client,
        server, ccache, forward_flags & OPTS_FORWARDABLE_CREDS,
        &forw_creds);
    if (retval) {
        if (auth_debug_mode)
            (void) printf(gettext(
                "Kerberos V5: error getting forwarded "
                "creds - %s\r\n"), error_message(retval));
        goto cleanup;
    }

    /* Send forwarded credentials */
    if (!krb5_send_data(ap, KRB_FORWARD, forw_creds.data,
        forw_creds.length)) {
            if (auth_debug_mode)
            (void) printf(gettext(
                "Not enough room for authentication data\r\n"));
    } else if (auth_debug_mode)
        (void) printf(gettext(
            "Forwarded local Kerberos V5 credentials to server\r\n"));
cleanup:
    if (client)
        krb5_free_principal(telnet_context, client);
    if (server)
        krb5_free_principal(telnet_context, server);
    if (forw_creds.data)
        free(forw_creds.data);
    /* LINTED */
    krb5_cc_close(telnet_context, ccache);
}