krb5/krb5kdc/do_tgs_req.c

	do_tgs_req.c revision 56a424cca6b3f91f31bdab72a4626c48c779fe8b
/*
 * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

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

/*
 * kdc/do_tgs_req.c
 *
 * Copyright 1990,1991,2001 by the Massachusetts Institute of Technology.
 * All Rights Reserved.
 *
 * 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.
 *
 *
 * KDC Routines to deal with TGS_REQ's
 */

#define NEED_SOCKETS
#include "k5-int.h"
#include "com_err.h"

#include <syslog.h>
#ifdef HAVE_NETINET_IN_H
#include <sys/types.h>
#include <netinet/in.h>
#ifndef hpux
#include <arpa/inet.h>
#endif
#endif

#include "kdc_util.h"
#include "policy.h"
#include "extern.h"
#include "adm_proto.h"

extern krb5_error_code setup_server_realm(krb5_principal);

static void find_alternate_tgs (krb5_kdc_req *, krb5_db_entry *,
                krb5_boolean *, int *,
                const krb5_fulladdr *from, char *cname);

static krb5_error_code prepare_error_tgs (krb5_kdc_req *, krb5_ticket *,
                      int, const char *, krb5_data **,
                      const char *);

/*ARGSUSED*/
krb5_error_code
process_tgs_req(krb5_data *pkt, const krb5_fulladdr *from,
        krb5_data **response)
{
    krb5_keyblock * subkey;
    krb5_kdc_req *request = 0;
    krb5_db_entry server;
    krb5_kdc_rep reply;
    krb5_enc_kdc_rep_part reply_encpart;
    krb5_ticket ticket_reply, *header_ticket = 0;
    int st_idx = 0;
    krb5_enc_tkt_part enc_tkt_reply;
    krb5_transited enc_tkt_transited;
    int newtransited = 0;
    krb5_error_code retval = 0;
    int nprincs = 0;
    krb5_boolean more;
    krb5_timestamp kdc_time, authtime=0;
    krb5_keyblock session_key;
    krb5_timestamp until, rtime;
    krb5_keyblock encrypting_key;
    krb5_key_data  *server_key;
    char *cname = 0, *sname = 0, *tmp = 0;
    const char *fromstring = 0;
    krb5_last_req_entry *nolrarray[2], nolrentry;
/*    krb5_address *noaddrarray[1]; */
    krb5_enctype useenctype;
    int errcode, errcode2;
    register int i;
    int firstpass = 1;
    const char  *status = 0;
    char ktypestr[128];
    char rep_etypestr[128];
    char fromstringbuf[70];
    long long tmp_server_times, tmp_realm_times;

    (void) memset(&encrypting_key, 0, sizeof(krb5_keyblock));
    (void) memset(&session_key, 0, sizeof(krb5_keyblock));

    retval = decode_krb5_tgs_req(pkt, &request);
    if (retval)
    return retval;

    ktypes2str(ktypestr, sizeof(ktypestr),
           request->nktypes, request->ktype);
    /*
     * setup_server_realm() sets up the global realm-specific data pointer.
     */
    if ((retval = setup_server_realm(request->server)))
    return retval;

    fromstring = inet_ntop(ADDRTYPE2FAMILY(from->address->addrtype),
               from->address->contents,
               fromstringbuf, sizeof(fromstringbuf));
    if (!fromstring)
    fromstring = "<unknown>";

    if ((errcode = krb5_unparse_name(kdc_context, request->server, &sname))) {
    status = "UNPARSING SERVER";
    goto cleanup;
    }
    limit_string(sname);

   /* errcode = kdc_process_tgs_req(request, from, pkt, &req_authdat); */
    errcode = kdc_process_tgs_req(request, from, pkt, &header_ticket, &subkey);

    if (header_ticket && header_ticket->enc_part2 &&
    (errcode2 = krb5_unparse_name(kdc_context,
                      header_ticket->enc_part2->client,
                      &cname))) {
    status = "UNPARSING CLIENT";
    errcode = errcode2;
    goto cleanup;
    }
    limit_string(cname);

    if (errcode) {
    status = "PROCESS_TGS";
    goto cleanup;
    }

    if (!header_ticket) {
    errcode = KRB5_NO_TKT_SUPPLIED; /* XXX? */
    status="UNEXPECTED NULL in header_ticket";
    goto cleanup;
    }

    /*
     * We've already dealt with the AP_REQ authentication, so we can
     * use header_ticket freely.  The encrypted part (if any) has been
     * decrypted with the session key.
     */

    authtime = header_ticket->enc_part2->times.authtime;

    /* XXX make sure server here has the proper realm...taken from AP_REQ
       header? */

    nprincs = 1;
    if ((errcode = krb5_db_get_principal(kdc_context, request->server, &server,
                    &nprincs, &more))) {
    status = "LOOKING_UP_SERVER";
    nprincs = 0;
    goto cleanup;
    }
tgt_again:
    if (more) {
    status = "NON_UNIQUE_PRINCIPAL";
    errcode = KRB5KDC_ERR_PRINCIPAL_NOT_UNIQUE;
    goto cleanup;
    } else if (nprincs != 1) {
    /*
     * might be a request for a TGT for some other realm; we
     * should do our best to find such a TGS in this db
     */
    if (firstpass && krb5_is_tgs_principal(request->server) == TRUE) {
        if (krb5_princ_size(kdc_context, request->server) == 2) {
        krb5_data *server_1 =
            krb5_princ_component(kdc_context, request->server, 1);
        krb5_data *tgs_1 =
            krb5_princ_component(kdc_context, tgs_server, 1);

        if (!tgs_1 || server_1->length != tgs_1->length ||
            memcmp(server_1->data, tgs_1->data, tgs_1->length)) {
            krb5_db_free_principal(kdc_context, &server, nprincs);
            find_alternate_tgs(request, &server, &more, &nprincs,
                      from, cname);
            firstpass = 0;
            goto tgt_again;
        }
        }
    }
    krb5_db_free_principal(kdc_context, &server, nprincs);
    status = "UNKNOWN_SERVER";
    errcode = KRB5KDC_ERR_S_PRINCIPAL_UNKNOWN;
    goto cleanup;
    }

    if ((errcode = krb5_timeofday(kdc_context, &kdc_time))) {
    status = "TIME_OF_DAY";
    goto cleanup;
    }

    if ((retval = validate_tgs_request(request, server, header_ticket,
                      kdc_time, &status))) {
    if (!status)
        status = "UNKNOWN_REASON";
    errcode = retval + ERROR_TABLE_BASE_krb5;
    goto cleanup;
    }

    /*
     * We pick the session keytype here....
     *
     * Some special care needs to be taken in the user-to-user
     * case, since we don't know what keytypes the application server
     * which is doing user-to-user authentication can support.  We
     * know that it at least must be able to support the encryption
     * type of the session key in the TGT, since otherwise it won't be
     * able to decrypt the U2U ticket!  So we use that in preference
     * to anything else.
     */
    useenctype = 0;
    if (isflagset(request->kdc_options, KDC_OPT_ENC_TKT_IN_SKEY)) {
    krb5_keyblock * st_sealing_key;
    krb5_kvno   st_srv_kvno;
    krb5_enctype    etype;

    /*
     * Get the key for the second ticket, and decrypt it.
     */
    if ((errcode = kdc_get_server_key(request->second_ticket[st_idx],
                     &st_sealing_key,
                     &st_srv_kvno))) {
        status = "2ND_TKT_SERVER";
        goto cleanup;
    }
    errcode = krb5_decrypt_tkt_part(kdc_context, st_sealing_key,
                       request->second_ticket[st_idx]);
    krb5_free_keyblock(kdc_context, st_sealing_key);
    if (errcode) {
        status = "2ND_TKT_DECRYPT";
        goto cleanup;
    }

    etype = request->second_ticket[st_idx]->enc_part2->session->enctype;
    if (!krb5_c_valid_enctype(etype)) {
        status = "BAD_ETYPE_IN_2ND_TKT";
        errcode = KRB5KDC_ERR_ETYPE_NOSUPP;
        goto cleanup;
    }

    for (i = 0; i < request->nktypes; i++) {
        if (request->ktype[i] == etype) {
        useenctype = etype;
        break;
        }
    }
    }

    /*
     * Select the keytype for the ticket session key.
     */
    if ((useenctype == 0) &&
    (useenctype = select_session_keytype(kdc_context, &server,
                         request->nktypes,
                         request->ktype)) == 0) {
    /* unsupported ktype */
    status = "BAD_ENCRYPTION_TYPE";
    errcode = KRB5KDC_ERR_ETYPE_NOSUPP;
    goto cleanup;
    }

    errcode = krb5_c_make_random_key(kdc_context, useenctype, &session_key);

    if (errcode) {
    /* random key failed */
    status = "RANDOM_KEY_FAILED";
    goto cleanup;
    }

    ticket_reply.server = request->server; /* XXX careful for realm... */

    enc_tkt_reply.flags = 0;
    enc_tkt_reply.times.starttime = 0;

    /*
     * Fix header_ticket's starttime; if it's zero, fill in the
     * authtime's value.
     */
    if (!(header_ticket->enc_part2->times.starttime))
    header_ticket->enc_part2->times.starttime =
        header_ticket->enc_part2->times.authtime;

    /* don't use new addresses unless forwarded, see below */

    enc_tkt_reply.caddrs = header_ticket->enc_part2->caddrs;
    /* noaddrarray[0] = 0; */
    reply_encpart.caddrs = 0;       /* optional...don't put it in */

    /* It should be noted that local policy may affect the  */
    /* processing of any of these flags.  For example, some */
    /* realms may refuse to issue renewable tickets         */

    if (isflagset(request->kdc_options, KDC_OPT_FORWARDABLE))
    setflag(enc_tkt_reply.flags, TKT_FLG_FORWARDABLE);

    if (isflagset(request->kdc_options, KDC_OPT_FORWARDED)) {
    setflag(enc_tkt_reply.flags, TKT_FLG_FORWARDED);

    /* include new addresses in ticket & reply */

    enc_tkt_reply.caddrs = request->addresses;
    reply_encpart.caddrs = request->addresses;
    }
    if (isflagset(header_ticket->enc_part2->flags, TKT_FLG_FORWARDED))
    setflag(enc_tkt_reply.flags, TKT_FLG_FORWARDED);

    if (isflagset(request->kdc_options, KDC_OPT_PROXIABLE))
    setflag(enc_tkt_reply.flags, TKT_FLG_PROXIABLE);

    if (isflagset(request->kdc_options, KDC_OPT_PROXY)) {
    setflag(enc_tkt_reply.flags, TKT_FLG_PROXY);

    /* include new addresses in ticket & reply */

    enc_tkt_reply.caddrs = request->addresses;
    reply_encpart.caddrs = request->addresses;
    }

    if (isflagset(request->kdc_options, KDC_OPT_ALLOW_POSTDATE))
    setflag(enc_tkt_reply.flags, TKT_FLG_MAY_POSTDATE);

    if (isflagset(request->kdc_options, KDC_OPT_POSTDATED)) {
    setflag(enc_tkt_reply.flags, TKT_FLG_POSTDATED);
    setflag(enc_tkt_reply.flags, TKT_FLG_INVALID);
    enc_tkt_reply.times.starttime = request->from;
    } else
    enc_tkt_reply.times.starttime = kdc_time;

    if (isflagset(request->kdc_options, KDC_OPT_VALIDATE)) {
    /* BEWARE of allocation hanging off of ticket & enc_part2, it belongs
       to the caller */
    ticket_reply = *(header_ticket);
    enc_tkt_reply = *(header_ticket->enc_part2);
    clear(enc_tkt_reply.flags, TKT_FLG_INVALID);
    }

    if (isflagset(request->kdc_options, KDC_OPT_RENEW)) {
    krb5_deltat old_life;

    /* BEWARE of allocation hanging off of ticket & enc_part2, it belongs
       to the caller */
    ticket_reply = *(header_ticket);
    enc_tkt_reply = *(header_ticket->enc_part2);

    old_life = enc_tkt_reply.times.endtime - enc_tkt_reply.times.starttime;

    enc_tkt_reply.times.starttime = kdc_time;
    enc_tkt_reply.times.endtime =
        min(header_ticket->enc_part2->times.renew_till,
        kdc_time + old_life);
    } else {
    /* not a renew request */
    enc_tkt_reply.times.starttime = kdc_time;
    until = (request->till == 0) ? kdc_infinity : request->till;

    /* SUNW */
        tmp_server_times = (long long) enc_tkt_reply.times.starttime
      + server.max_life;

        tmp_realm_times = (long long) enc_tkt_reply.times.starttime
      + max_life_for_realm;

        enc_tkt_reply.times.endtime =
      min(until,
        min(tmp_server_times,
        min(tmp_realm_times,
            min(header_ticket->enc_part2->times.endtime,
                KRB5_KDB_EXPIRATION)))); /* SUNW */
/*
    enc_tkt_reply.times.endtime =
        min(until, min(enc_tkt_reply.times.starttime + server.max_life,
               min(enc_tkt_reply.times.starttime + max_life_for_realm,
                   min(header_ticket->enc_part2->times.endtime)));
*/
    if (isflagset(request->kdc_options, KDC_OPT_RENEWABLE_OK) &&
        (enc_tkt_reply.times.endtime < request->till) &&
        isflagset(header_ticket->enc_part2->flags,
          TKT_FLG_RENEWABLE)) {
        setflag(request->kdc_options, KDC_OPT_RENEWABLE);
        request->rtime =
        min(request->till,
            min(KRB5_KDB_EXPIRATION,
            header_ticket->enc_part2->times.renew_till));
    }
    }
    rtime = (request->rtime == 0) ? kdc_infinity : request->rtime;

    if (isflagset(request->kdc_options, KDC_OPT_RENEWABLE)) {
    /* already checked above in policy check to reject request for a
       renewable ticket using a non-renewable ticket */
    setflag(enc_tkt_reply.flags, TKT_FLG_RENEWABLE);
    tmp_realm_times =  (long long) enc_tkt_reply.times.starttime +
        min(server.max_renewable_life,max_renewable_life_for_realm);
    enc_tkt_reply.times.renew_till =
        min(rtime,
        min(header_ticket->enc_part2->times.renew_till,
                min (tmp_realm_times, KRB5_KDB_EXPIRATION)));
    } else {
    enc_tkt_reply.times.renew_till = 0;
    }

    /*
     * Set authtime to be the same as header_ticket's
     */
    enc_tkt_reply.times.authtime = header_ticket->enc_part2->times.authtime;

    /*
     * Propagate the preauthentication flags through to the returned ticket.
     */
    if (isflagset(header_ticket->enc_part2->flags, TKT_FLG_PRE_AUTH))
    setflag(enc_tkt_reply.flags, TKT_FLG_PRE_AUTH);

    if (isflagset(header_ticket->enc_part2->flags, TKT_FLG_HW_AUTH))
    setflag(enc_tkt_reply.flags, TKT_FLG_HW_AUTH);

    /* starttime is optional, and treated as authtime if not present.
       so we can nuke it if it matches */
    if (enc_tkt_reply.times.starttime == enc_tkt_reply.times.authtime)
    enc_tkt_reply.times.starttime = 0;

    /* assemble any authorization data */
    if (request->authorization_data.ciphertext.data) {
    krb5_data scratch;

    scratch.length = request->authorization_data.ciphertext.length;
    if (!(scratch.data =
          malloc(request->authorization_data.ciphertext.length))) {
        status = "AUTH_NOMEM";
        errcode = ENOMEM;
        goto cleanup;
    }

    if ((errcode = krb5_c_decrypt(kdc_context,
                      header_ticket->enc_part2->session,
                      KRB5_KEYUSAGE_TGS_REQ_AD_SESSKEY,
                      0, &request->authorization_data,
                      &scratch))) {
        status = "AUTH_ENCRYPT_FAIL";
        free(scratch.data);
        goto cleanup;
    }

    /* scratch now has the authorization data, so we decode it */
    errcode = decode_krb5_authdata(&scratch, &(request->unenc_authdata));
    free(scratch.data);
    if (errcode) {
        status = "AUTH_DECODE";
        goto cleanup;
    }

    if ((errcode =
         concat_authorization_data(request->unenc_authdata,
                       header_ticket->enc_part2->authorization_data,
                       &enc_tkt_reply.authorization_data))) {
        status = "CONCAT_AUTH";
        goto cleanup;
    }
    } else
    enc_tkt_reply.authorization_data =
        header_ticket->enc_part2->authorization_data;

    enc_tkt_reply.session = &session_key;
    enc_tkt_reply.client = header_ticket->enc_part2->client;
    enc_tkt_reply.transited.tr_type = KRB5_DOMAIN_X500_COMPRESS;
    enc_tkt_reply.transited.tr_contents = empty_string; /* equivalent of "" */

    /*
     * Only add the realm of the presented tgt to the transited list if
     * it is different than the local realm (cross-realm) and it is different
     * than the realm of the client (since the realm of the client is already
     * implicitly part of the transited list and should not be explicitly
     * listed).
     */

    /* realm compare is like strcmp, but knows how to deal with these args */
    if (realm_compare(header_ticket->server, tgs_server) ||
    realm_compare(header_ticket->server, enc_tkt_reply.client)) {
    /* tgt issued by local realm or issued by realm of client */
    enc_tkt_reply.transited = header_ticket->enc_part2->transited;
    } else {
    /* tgt issued by some other realm and not the realm of the client */
    /* assemble new transited field into allocated storage */
    if (header_ticket->enc_part2->transited.tr_type !=
        KRB5_DOMAIN_X500_COMPRESS) {
        status = "BAD_TRTYPE";
        errcode = KRB5KDC_ERR_TRTYPE_NOSUPP;
        goto cleanup;
    }
    enc_tkt_transited.tr_type = KRB5_DOMAIN_X500_COMPRESS;
    enc_tkt_transited.tr_contents.data = 0;
    enc_tkt_transited.tr_contents.length = 0;
    enc_tkt_reply.transited = enc_tkt_transited;
    if ((errcode =
         add_to_transited(&header_ticket->enc_part2->transited.tr_contents,
                  &enc_tkt_reply.transited.tr_contents,
                  header_ticket->server,
                  enc_tkt_reply.client,
                  request->server))) {
        status = "ADD_TR_FAIL";
        goto cleanup;
    }
    newtransited = 1;
    }
    if (!isflagset (request->kdc_options, KDC_OPT_DISABLE_TRANSITED_CHECK)) {
    errcode = krb5_check_transited_list (kdc_context,
                         &enc_tkt_reply.transited.tr_contents,
                         krb5_princ_realm (kdc_context, header_ticket->enc_part2->client),
                         krb5_princ_realm (kdc_context, request->server));
    if (errcode == 0) {
        setflag (enc_tkt_reply.flags, TKT_FLG_TRANSIT_POLICY_CHECKED);
    } else if (errcode == KRB5KRB_AP_ERR_ILL_CR_TKT)
        krb5_klog_syslog (LOG_INFO,
                  "bad realm transit path from '%s' to '%s' via '%.*s'",
                  cname ? cname : "<unknown client>",
                  sname ? sname : "<unknown server>",
                  enc_tkt_reply.transited.tr_contents.length,
                  enc_tkt_reply.transited.tr_contents.data);
    else
        krb5_klog_syslog (LOG_ERR,
                  "unexpected error checking transit from '%s' to '%s' via '%.*s': %s",
                  cname ? cname : "<unknown client>",
                  sname ? sname : "<unknown server>",
                  enc_tkt_reply.transited.tr_contents.length,
                  enc_tkt_reply.transited.tr_contents.data,
                  error_message (errcode));
    } else
    krb5_klog_syslog (LOG_INFO, "not checking transit path");
    if (reject_bad_transit
    && !isflagset (enc_tkt_reply.flags, TKT_FLG_TRANSIT_POLICY_CHECKED)) {
    errcode = KRB5KDC_ERR_POLICY;
    status = "BAD_TRANSIT";
    goto cleanup;
    }

    ticket_reply.enc_part2 = &enc_tkt_reply;

    /*
     * If we are doing user-to-user authentication, then make sure
     * that the client for the second ticket matches the request
     * server, and then encrypt the ticket using the session key of
     * the second ticket.
     */
    if (isflagset(request->kdc_options, KDC_OPT_ENC_TKT_IN_SKEY)) {
    /*
     * Make sure the client for the second ticket matches
     * requested server.
     */
    krb5_enc_tkt_part *t2enc = request->second_ticket[st_idx]->enc_part2;
    krb5_principal client2 = t2enc->client;
    if (!krb5_principal_compare(kdc_context, request->server, client2)) {
        if ((errcode = krb5_unparse_name(kdc_context, client2, &tmp)))
            tmp = 0;
        audit_krb5kdc_tgs_req_2ndtktmm(
            (struct in_addr *)from->address->contents,
            (in_port_t)from->port,
            0, cname, sname);
        krb5_klog_syslog(LOG_INFO,
                 "TGS_REQ %s: 2ND_TKT_MISMATCH: "
                 "authtime %d, %s for %s, 2nd tkt client %s",
                 fromstring, authtime,
                 cname ? cname : "<unknown client>",
                 sname ? sname : "<unknown server>",
                 tmp ? tmp : "<unknown>");
        errcode = KRB5KDC_ERR_SERVER_NOMATCH;
        goto cleanup;
    }

    ticket_reply.enc_part.kvno = 0;
    ticket_reply.enc_part.enctype = t2enc->session->enctype;
    if ((errcode = krb5_encrypt_tkt_part(kdc_context, t2enc->session,
                         &ticket_reply))) {
        status = "2ND_TKT_ENCRYPT";
        goto cleanup;
    }
    st_idx++;
    } else {
    /*
     * Find the server key
     */
    if ((errcode = krb5_dbe_find_enctype(kdc_context, &server,
                         -1, /* ignore keytype */
                         -1, /* Ignore salttype */
                         0,     /* Get highest kvno */
                         &server_key))) {
        status = "FINDING_SERVER_KEY";
        goto cleanup;
    }
    /* convert server.key into a real key (it may be encrypted
     *        in the database) */
    if ((errcode = krb5_dbekd_decrypt_key_data(kdc_context,
                           &master_keyblock,
                           server_key, &encrypting_key,
                           NULL))) {
        status = "DECRYPT_SERVER_KEY";
        goto cleanup;
    }
    errcode = krb5_encrypt_tkt_part(kdc_context, &encrypting_key,
                    &ticket_reply);
    krb5_free_keyblock_contents(kdc_context, &encrypting_key);
    if (errcode) {
        status = "TKT_ENCRYPT";
        goto cleanup;
    }
    ticket_reply.enc_part.kvno = server_key->key_data_kvno;
    }

    /* Start assembling the response */
    reply.msg_type = KRB5_TGS_REP;
    reply.padata = 0;       /* always */
    reply.client = header_ticket->enc_part2->client;
    reply.enc_part.kvno = 0;        /* We are using the session key */
    reply.ticket = &ticket_reply;

    reply_encpart.session = &session_key;
    reply_encpart.nonce = request->nonce;

    /* copy the time fields EXCEPT for authtime; its location
       is used for ktime */
    reply_encpart.times = enc_tkt_reply.times;
    reply_encpart.times.authtime = header_ticket->enc_part2->times.authtime;

    /* starttime is optional, and treated as authtime if not present.
       so we can nuke it if it matches */
    if (enc_tkt_reply.times.starttime == enc_tkt_reply.times.authtime)
    enc_tkt_reply.times.starttime = 0;

    nolrentry.lr_type = KRB5_LRQ_NONE;
    nolrentry.value = 0;
    nolrarray[0] = &nolrentry;
    nolrarray[1] = 0;
    reply_encpart.last_req = nolrarray; /* not available for TGS reqs */
    reply_encpart.key_exp = 0;      /* ditto */
    reply_encpart.flags = enc_tkt_reply.flags;
    reply_encpart.server = ticket_reply.server;

    /* use the session key in the ticket, unless there's a subsession key
       in the AP_REQ */

    reply.enc_part.enctype = subkey ? subkey->enctype :
            header_ticket->enc_part2->session->enctype;
    errcode = krb5_encode_kdc_rep(kdc_context, KRB5_TGS_REP, &reply_encpart,
                  subkey ? 1 : 0,
                  subkey ? subkey :
                  header_ticket->enc_part2->session,
                  &reply, response);
    if (errcode) {
    status = "ENCODE_KDC_REP";
    } else {
    status = "ISSUE";
    }

    if (ticket_reply.enc_part.ciphertext.data) {
     memset(ticket_reply.enc_part.ciphertext.data, 0,
       ticket_reply.enc_part.ciphertext.length);
    free(ticket_reply.enc_part.ciphertext.data);
    ticket_reply.enc_part.ciphertext.data = NULL;
    }
    /* these parts are left on as a courtesy from krb5_encode_kdc_rep so we
       can use them in raw form if needed.  But, we don't... */
    if (reply.enc_part.ciphertext.data) {
     memset(reply.enc_part.ciphertext.data, 0,
       reply.enc_part.ciphertext.length);
    free(reply.enc_part.ciphertext.data);
    reply.enc_part.ciphertext.data = NULL;
    }

cleanup:
    if (status) {
        audit_krb5kdc_tgs_req((struct in_addr *)from->address->contents,
                (in_port_t)from->port, 0,
                cname ? cname : "<unknown client>",
                sname ? sname : "<unknown client>",
                errcode);
    if (!errcode)
        rep_etypes2str(rep_etypestr, sizeof(rep_etypestr), &reply);
        krb5_klog_syslog(LOG_INFO,
             "TGS_REQ (%s) %s: %s: authtime %d, "
             "%s%s %s for %s%s%s",
             ktypestr,
             fromstring, status, authtime,
             !errcode ? rep_etypestr : "",
             !errcode ? "," : "",
             cname ? cname : "<unknown client>",
             sname ? sname : "<unknown server>",
             errcode ? ", " : "",
             errcode ? error_message(errcode) : "");
    }

    if (errcode) {
    if (status == 0)
        status = error_message (errcode);
    errcode -= ERROR_TABLE_BASE_krb5;
    if (errcode < 0 || errcode > 128)
        errcode = KRB_ERR_GENERIC;

    retval = prepare_error_tgs(request, header_ticket, errcode,
                   fromstring, response, status);
    }

    if (header_ticket)
    krb5_free_ticket(kdc_context, header_ticket);
    if (request)
    krb5_free_kdc_req(kdc_context, request);
    if (cname)
    free(cname);
    if (sname)
    free(sname);
    if (nprincs)
    krb5_db_free_principal(kdc_context, &server, 1);
    if (session_key.contents)
    krb5_free_keyblock_contents(kdc_context, &session_key);
    if (newtransited)
    free(enc_tkt_reply.transited.tr_contents.data);

    return retval;
}

static krb5_error_code
prepare_error_tgs (krb5_kdc_req *request, krb5_ticket *ticket, int error,
           const char *ident, krb5_data **response, const char *status)
{
    krb5_error errpkt;
    krb5_error_code retval;
    krb5_data *scratch;

    errpkt.ctime = request->nonce;
    errpkt.cusec = 0;

    if ((retval = krb5_us_timeofday(kdc_context, &errpkt.stime,
                    &errpkt.susec)))
    return(retval);
    errpkt.error = error;
    errpkt.server = request->server;
    if (ticket && ticket->enc_part2)
    errpkt.client = ticket->enc_part2->client;
    else
    errpkt.client = 0;
    errpkt.text.length = strlen(status) + 1;
    if (!(errpkt.text.data = malloc(errpkt.text.length)))
    return ENOMEM;
    (void) strcpy(errpkt.text.data, status);

    if (!(scratch = (krb5_data *)malloc(sizeof(*scratch)))) {
    free(errpkt.text.data);
    return ENOMEM;
    }
    errpkt.e_data.length = 0;
    errpkt.e_data.data = 0;

    retval = krb5_mk_error(kdc_context, &errpkt, scratch);
    free(errpkt.text.data);
    if (retval)
    free(scratch);
    else
    *response = scratch;

    return retval;
}

/*
 * The request seems to be for a ticket-granting service somewhere else,
 * but we don't have a ticket for the final TGS.  Try to give the requestor
 * some intermediate realm.
 */
static void
find_alternate_tgs(krb5_kdc_req *request, krb5_db_entry *server,
           krb5_boolean *more, int *nprincs,
           const krb5_fulladdr *from, char *cname)
{
    krb5_error_code retval;
    krb5_principal *plist, *pl2;
    krb5_data tmp;

    *nprincs = 0;
    *more = FALSE;

    /*
     * Call to krb5_princ_component is normally not safe but is so
     * here only because find_alternate_tgs() is only called from
     * somewhere that has already checked the number of components in
     * the principal.
     */
    if ((retval = krb5_walk_realm_tree(kdc_context,
              krb5_princ_realm(kdc_context, request->server),
              krb5_princ_component(kdc_context, request->server, 1),
                      &plist, KRB5_REALM_BRANCH_CHAR)))
    return;

    /* move to the end */
    for (pl2 = plist; *pl2; pl2++);

    /* the first entry in this array is for krbtgt/local@local, so we
       ignore it */
    while (--pl2 > plist) {
    *nprincs = 1;
    tmp = *krb5_princ_realm(kdc_context, *pl2);
    krb5_princ_set_realm(kdc_context, *pl2,
                 krb5_princ_realm(kdc_context, tgs_server));
    retval = krb5_db_get_principal(kdc_context, *pl2, server, nprincs, more);
    krb5_princ_set_realm(kdc_context, *pl2, &tmp);
    if (retval) {
        *nprincs = 0;
        *more = FALSE;
        krb5_free_realm_tree(kdc_context, plist);
        return;
    }
    if (*more) {
        krb5_db_free_principal(kdc_context, server, *nprincs);
        continue;
    } else if (*nprincs == 1) {
        /* Found it! */
        krb5_principal tmpprinc;
        char *sname;

        tmp = *krb5_princ_realm(kdc_context, *pl2);
        krb5_princ_set_realm(kdc_context, *pl2,
                 krb5_princ_realm(kdc_context, tgs_server));
        if ((retval = krb5_copy_principal(kdc_context, *pl2, &tmpprinc))) {
        krb5_db_free_principal(kdc_context, server, *nprincs);
        krb5_princ_set_realm(kdc_context, *pl2, &tmp);
        continue;
        }
        krb5_princ_set_realm(kdc_context, *pl2, &tmp);

        krb5_free_principal(kdc_context, request->server);
        request->server = tmpprinc;
        if (krb5_unparse_name(kdc_context, request->server, &sname)) {

        audit_krb5kdc_tgs_req_alt_tgt(
            (struct in_addr *)from->address->contents,
            (in_port_t)from->port,
            0, cname, "<unparseable>", 0);
        krb5_klog_syslog(LOG_INFO,
               "TGS_REQ: issuing alternate <un-unparseable> TGT");
        } else {
        audit_krb5kdc_tgs_req_alt_tgt(
            (struct in_addr *)from->address->contents,
            (in_port_t)from->port,
            0, cname, sname, 0);
        krb5_klog_syslog(LOG_INFO,
               "TGS_REQ: issuing TGT %s", sname);
        free(sname);
        }
        return;
    }
    krb5_db_free_principal(kdc_context, server, *nprincs);
    continue;
    }

    *nprincs = 0;
    *more = FALSE;
    krb5_free_realm_tree(kdc_context, plist);
    return;
}