/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/*
 * Copyright 2000, 2004, 2007, 2008  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.
 */
/*
 * Copyright 1993 by OpenVision Technologies, Inc.
 *
 * Permission to use, copy, modify, distribute, and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appears in all copies and
 * that both that copyright notice and this permission notice appear in
 * supporting documentation, and that the name of OpenVision not be used
 * in advertising or publicity pertaining to distribution of the software
 * without specific, written prior permission. OpenVision makes no
 * representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied warranty.
 *
 * OPENVISION DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
 * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
 * EVENT SHALL OPENVISION BE LIABLE FOR ANY SPECIAL, INDIRECT OR
 * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF
 * USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
 * OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 * PERFORMANCE OF THIS SOFTWARE.
 */

/*
 * Copyright (C) 1998 by the FundsXpress, INC.
 *
 * 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 FundsXpress. not be used in advertising or publicity pertaining
 * to distribution of the software without specific, written prior
 * permission.  FundsXpress makes no representations about the suitability of
 * this software for any purpose.  It is provided "as is" without express
 * or implied warranty.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */
/*
 * Copyright (c) 2006-2008, Novell, Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   * Redistributions of source code must retain the above copyright notice,
 *       this list of conditions and the following disclaimer.
 *   * 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.
 *   * The copyright holder's name is not used to endorse or promote products
 *       derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 COPYRIGHT OWNER 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 "k5-int.h"
#include "gssapiP_krb5.h"
#ifdef HAVE_MEMORY_H
#include <memory.h>
#endif
#include <assert.h>

#ifdef CFX_EXERCISE
#define CFX_ACCEPTOR_SUBKEY (time(0) & 1)
#else
#define CFX_ACCEPTOR_SUBKEY 1
#endif

#ifndef LEAN_CLIENT

static OM_uint32
create_constrained_deleg_creds(OM_uint32 *minor_status,
                               krb5_gss_cred_id_t verifier_cred_handle,
                               krb5_ticket *ticket,
                               krb5_gss_cred_id_t *out_cred,
                               krb5_context context)
{
    OM_uint32 major_status;
    krb5_creds krb_creds;
    krb5_data *data;
    krb5_error_code code;

    assert(out_cred != NULL);
    assert(verifier_cred_handle->usage == GSS_C_BOTH);

    memset(&krb_creds, 0, sizeof(krb_creds));
    krb_creds.client = ticket->enc_part2->client;
    krb_creds.server = ticket->server;
    krb_creds.keyblock = *(ticket->enc_part2->session);
    krb_creds.ticket_flags = ticket->enc_part2->flags;
    krb_creds.times = ticket->enc_part2->times;
    krb_creds.magic = KV5M_CREDS;
    krb_creds.authdata = NULL;

    code = encode_krb5_ticket(ticket, &data);
    if (code) {
        *minor_status = code;
        return GSS_S_FAILURE;
    }

    krb_creds.ticket = *data;

    major_status = kg_compose_deleg_cred(minor_status,
                                         verifier_cred_handle,
                                         &krb_creds,
                                         GSS_C_INDEFINITE,
                                         out_cred,
                                         NULL,
                                         context);

    krb5_free_data(context, data);

    return major_status;
}

/* Decode, decrypt and store the forwarded creds in the local ccache. */
static krb5_error_code
rd_and_store_for_creds(context, auth_context, inbuf, out_cred)
    krb5_context context;
    krb5_auth_context auth_context;
    krb5_data *inbuf;
    krb5_gss_cred_id_t *out_cred;
{
    krb5_creds ** creds = NULL;
    krb5_error_code retval;
    krb5_ccache ccache = NULL;
    krb5_gss_cred_id_t cred = NULL;
    krb5_auth_context new_auth_ctx = NULL;
    krb5_int32 flags_org;

    if ((retval = krb5_auth_con_getflags(context, auth_context, &flags_org)))
        return retval;
    krb5_auth_con_setflags(context, auth_context,
                           0);

    /*
     * By the time krb5_rd_cred is called here (after krb5_rd_req has been
     * called in krb5_gss_accept_sec_context), the "keyblock" field of
     * auth_context contains a pointer to the session key, and the
     * "recv_subkey" field might contain a session subkey.  Either of
     * these (the "recv_subkey" if it isn't NULL, otherwise the
     * "keyblock") might have been used to encrypt the encrypted part of
     * the KRB_CRED message that contains the forwarded credentials.  (The
     * Java Crypto and Security Implementation from the DSTC in Australia
     * always uses the session key.  But apparently it never negotiates a
     * subkey, so this code works fine against a JCSI client.)  Up to the
     * present, though, GSSAPI clients linked against the MIT code (which
     * is almost all GSSAPI clients) don't encrypt the KRB_CRED message at
     * all -- at this level.  So if the first call to krb5_rd_cred fails,
     * we should call it a second time with another auth context freshly
     * created by krb5_auth_con_init.  All of its keyblock fields will be
     * NULL, so krb5_rd_cred will assume that the KRB_CRED message is
     * unencrypted.  (The MIT code doesn't actually send the KRB_CRED
     * message in the clear -- the "authenticator" whose "checksum" ends up
     * containing the KRB_CRED message does get encrypted.)
     */
    if (krb5_rd_cred(context, auth_context, inbuf, &creds, NULL)) {
        if ((retval = krb5_auth_con_init(context, &new_auth_ctx)))
            goto cleanup;
        krb5_auth_con_setflags(context, new_auth_ctx, 0);
        if ((retval = krb5_rd_cred(context, new_auth_ctx, inbuf,
                                   &creds, NULL)))
            goto cleanup;
    }

    if ((retval = krb5_cc_new_unique(context, "MEMORY", NULL, &ccache))) {
        ccache = NULL;
        goto cleanup;
    }

    if ((retval = krb5_cc_initialize(context, ccache, creds[0]->client)))
        goto cleanup;

    if ((retval = krb5_cc_store_cred(context, ccache, creds[0])))
        goto cleanup;

    /* generate a delegated credential handle */
    if (out_cred) {
        /* allocate memory for a cred_t... */
        if (!(cred =
              (krb5_gss_cred_id_t) xmalloc(sizeof(krb5_gss_cred_id_rec)))) {
            retval = ENOMEM; /* out of memory? */
            goto cleanup;
        }

        /* zero it out... */
        memset(cred, 0, sizeof(krb5_gss_cred_id_rec));

        retval = k5_mutex_init(&cred->lock);
        if (retval) {
            xfree(cred);
            cred = NULL;
            goto cleanup;
        }

        /* copy the client principle into it... */
        if ((retval =
             kg_init_name(context, creds[0]->client, NULL, NULL, NULL, 0,
                          &cred->name))) {
            k5_mutex_destroy(&cred->lock);
            retval = ENOMEM; /* out of memory? */
            xfree(cred); /* clean up memory on failure */
            cred = NULL;
            goto cleanup;
        }

        cred->usage = GSS_C_INITIATE; /* we can't accept with this */
        /* cred->name already set */
        cred->keytab = NULL; /* no keytab associated with this... */
        cred->expire = creds[0]->times.endtime; /* store the end time */
        cred->ccache = ccache; /* the ccache containing the credential */
        cred->destroy_ccache = 1;
        ccache = NULL; /* cred takes ownership so don't destroy */
    }

    /* If there were errors, there might have been a memory leak
       if (!cred)
       if ((retval = krb5_cc_close(context, ccache)))
       goto cleanup;
    */
cleanup:
    if (creds)
        krb5_free_tgt_creds(context, creds);

    if (ccache)
        (void)krb5_cc_destroy(context, ccache);

    if (out_cred)
        *out_cred = cred; /* return credential */

    if (new_auth_ctx)
        krb5_auth_con_free(context, new_auth_ctx);

    krb5_auth_con_setflags(context, auth_context, flags_org);

    return retval;
}


/*
 * Performs third leg of DCE authentication
 */
static OM_uint32
kg_accept_dce(minor_status, context_handle, verifier_cred_handle,
              input_token, input_chan_bindings, src_name, mech_type,
              output_token, ret_flags, time_rec, delegated_cred_handle)
    OM_uint32 *minor_status;
    gss_ctx_id_t *context_handle;
    gss_cred_id_t verifier_cred_handle;
    gss_buffer_t input_token;
    gss_channel_bindings_t input_chan_bindings;
    gss_name_t *src_name;
    gss_OID *mech_type;
    gss_buffer_t output_token;
    OM_uint32 *ret_flags;
    OM_uint32 *time_rec;
    gss_cred_id_t *delegated_cred_handle;
{
    krb5_error_code code;
    krb5_gss_ctx_id_rec *ctx = 0;
    krb5_timestamp now;
    krb5_gss_name_t name = NULL;
    krb5_ui_4 nonce = 0;
    krb5_data ap_rep;
    OM_uint32 major_status = GSS_S_FAILURE;

    output_token->length = 0;
    output_token->value = NULL;

    if (mech_type)
        *mech_type = GSS_C_NULL_OID;
    /* return a bogus cred handle */
    if (delegated_cred_handle)
        *delegated_cred_handle = GSS_C_NO_CREDENTIAL;

    ctx = (krb5_gss_ctx_id_rec *)*context_handle;

    code = krb5_timeofday(ctx->k5_context, &now);
    if (code != 0) {
        major_status = GSS_S_FAILURE;
        goto fail;
    }

    ap_rep.data = input_token->value;
    ap_rep.length = input_token->length;

    code = krb5_rd_rep_dce(ctx->k5_context,
                           ctx->auth_context,
                           &ap_rep,
                           &nonce);
    if (code != 0) {
        major_status = GSS_S_FAILURE;
        goto fail;
    }

    ctx->established = 1;

    if (src_name) {
        code = kg_duplicate_name(ctx->k5_context, ctx->there, &name);
        if (code) {
            major_status = GSS_S_FAILURE;
            goto fail;
        }
        *src_name = (gss_name_t) name;
    }

    if (mech_type)
        *mech_type = ctx->mech_used;

    if (time_rec) {
        *time_rec = ts_delta(ctx->krb_times.endtime, now) +
            ctx->k5_context->clockskew;
    }

    /* Never return GSS_C_DELEG_FLAG since we don't support DCE credential
     * delegation yet. */
    if (ret_flags)
        *ret_flags = (ctx->gss_flags & ~GSS_C_DELEG_FLAG);

    *minor_status = 0;

    return GSS_S_COMPLETE;

fail:
    /* real failure code follows */

    (void) krb5_gss_delete_sec_context(minor_status, (gss_ctx_id_t *) &ctx,
                                       NULL);
    *context_handle = GSS_C_NO_CONTEXT;
    *minor_status = code;

    return major_status;
}

static krb5_error_code
kg_process_extension(krb5_context context,
                     krb5_auth_context auth_context,
                     int ext_type,
                     krb5_data *ext_data,
                     krb5_gss_ctx_ext_t exts)
{
    krb5_error_code code = 0;

    assert(exts != NULL);

    switch (ext_type) {
    case KRB5_GSS_EXTS_IAKERB_FINISHED:
        if (exts->iakerb.conv == NULL) {
            code = KRB5KRB_AP_ERR_MSG_TYPE; /* XXX */
        } else {
            krb5_key key;

            code = krb5_auth_con_getrecvsubkey_k(context, auth_context, &key);
            if (code != 0)
                break;

            code = iakerb_verify_finished(context, key, exts->iakerb.conv,
                                          ext_data);
            if (code == 0)
                exts->iakerb.verified = 1;

            krb5_k_free_key(context, key);
        }
        break;
    default:
        break;
    }

    return code;
}

static OM_uint32
kg_accept_krb5(minor_status, context_handle,
               verifier_cred_handle, input_token,
               input_chan_bindings, src_name, mech_type,
               output_token, ret_flags, time_rec,
               delegated_cred_handle, exts)
    OM_uint32 *minor_status;
    gss_ctx_id_t *context_handle;
    gss_cred_id_t verifier_cred_handle;
    gss_buffer_t input_token;
    gss_channel_bindings_t input_chan_bindings;
    gss_name_t *src_name;
    gss_OID *mech_type;
    gss_buffer_t output_token;
    OM_uint32 *ret_flags;
    OM_uint32 *time_rec;
    gss_cred_id_t *delegated_cred_handle;
    krb5_gss_ctx_ext_t exts;
{
    krb5_context context;
    unsigned char *ptr, *ptr2;
    char *sptr;
    OM_uint32 tmp;
    size_t md5len;
    krb5_gss_cred_id_t cred = 0;
    krb5_data ap_rep, ap_req;
    unsigned int i;
    krb5_error_code code;
    krb5_address addr, *paddr;
    krb5_authenticator *authdat = 0;
    krb5_checksum reqcksum;
    krb5_gss_name_t name = NULL;
    krb5_ui_4 gss_flags = 0;
    krb5_gss_ctx_id_rec *ctx = NULL;
    krb5_timestamp now;
    gss_buffer_desc token;
    krb5_auth_context auth_context = NULL;
    krb5_ticket * ticket = NULL;
    int option_id;
    krb5_data option;
    const gss_OID_desc *mech_used = NULL;
    OM_uint32 major_status = GSS_S_FAILURE;
    OM_uint32 tmp_minor_status;
    krb5_error krb_error_data;
    krb5_data scratch;
    gss_cred_id_t defcred = GSS_C_NO_CREDENTIAL;
    krb5_gss_cred_id_t deleg_cred = NULL;
    krb5int_access kaccess;
    int cred_rcache = 0;
    int no_encap = 0;
    int token_deleg_flag = 0;
    krb5_flags ap_req_options = 0;
    krb5_enctype negotiated_etype;
    krb5_authdata_context ad_context = NULL;
    krb5_principal accprinc = NULL;
    krb5_ap_req *request = NULL;

    code = krb5int_accessor (&kaccess, KRB5INT_ACCESS_VERSION);
    if (code) {
        *minor_status = code;
        return(GSS_S_FAILURE);
    }

    code = krb5_gss_init_context(&context);
    if (code) {
        *minor_status = code;
        return GSS_S_FAILURE;
    }

    /* set up returns to be freeable */

    if (src_name)
        *src_name = (gss_name_t) NULL;
    output_token->length = 0;
    output_token->value = NULL;
    token.value = 0;
    reqcksum.contents = 0;
    ap_req.data = 0;
    ap_rep.data = 0;

    if (mech_type)
        *mech_type = GSS_C_NULL_OID;
    /* return a bogus cred handle */
    if (delegated_cred_handle)
        *delegated_cred_handle = GSS_C_NO_CREDENTIAL;

    /* handle default cred handle */
    if (verifier_cred_handle == GSS_C_NO_CREDENTIAL) {
        major_status = krb5_gss_acquire_cred(minor_status, GSS_C_NO_NAME,
                                             GSS_C_INDEFINITE, GSS_C_NO_OID_SET,
                                             GSS_C_ACCEPT, &defcred,
                                             NULL, NULL);
        if (major_status != GSS_S_COMPLETE) {
            code = *minor_status;
            goto fail;
        }
        verifier_cred_handle = defcred;
    }

    /* Resolve any initiator state in the verifier cred and lock it. */
    major_status = kg_cred_resolve(minor_status, context, verifier_cred_handle,
                                   GSS_C_NO_NAME);
    if (GSS_ERROR(major_status)) {
        code = *minor_status;
        goto fail;
    }
    cred = (krb5_gss_cred_id_t)verifier_cred_handle;

    /* make sure the supplied credentials are valid for accept */

    if ((cred->usage != GSS_C_ACCEPT) &&
        (cred->usage != GSS_C_BOTH)) {
        code = 0;
        major_status = GSS_S_NO_CRED;
        goto fail;
    }

    /* verify the token's integrity, and leave the token in ap_req.
       figure out which mech oid was used, and save it */

    ptr = (unsigned char *) input_token->value;

    if (!(code = g_verify_token_header(gss_mech_krb5,
                                       &(ap_req.length),
                                       &ptr, KG_TOK_CTX_AP_REQ,
                                       input_token->length, 1))) {
        mech_used = gss_mech_krb5;
    } else if ((code == G_WRONG_MECH)
               &&!(code = g_verify_token_header((gss_OID) gss_mech_iakerb,
                                                &(ap_req.length),
                                                &ptr, KG_TOK_CTX_AP_REQ,
                                                input_token->length, 1))) {
        mech_used = gss_mech_iakerb;
    } else if ((code == G_WRONG_MECH)
               &&!(code = g_verify_token_header((gss_OID) gss_mech_krb5_wrong,
                                                &(ap_req.length),
                                                &ptr, KG_TOK_CTX_AP_REQ,
                                                input_token->length, 1))) {
        mech_used = gss_mech_krb5_wrong;
    } else if ((code == G_WRONG_MECH) &&
               !(code = g_verify_token_header(gss_mech_krb5_old,
                                              &(ap_req.length),
                                              &ptr, KG_TOK_CTX_AP_REQ,
                                              input_token->length, 1))) {
        /*
         * Previous versions of this library used the old mech_id
         * and some broken behavior (wrong IV on checksum
         * encryption).  We support the old mech_id for
         * compatibility, and use it to decide when to use the
         * old behavior.
         */
        mech_used = gss_mech_krb5_old;
    } else if (code == G_WRONG_TOKID) {
        major_status = GSS_S_CONTINUE_NEEDED;
        code = KRB5KRB_AP_ERR_MSG_TYPE;
        mech_used = gss_mech_krb5;
        goto fail;
    } else if (code == G_BAD_TOK_HEADER) {
        /* DCE style not encapsulated */
        ap_req.length = input_token->length;
        ap_req.data = input_token->value;
        mech_used = gss_mech_krb5;
        no_encap = 1;
    } else {
        major_status = GSS_S_DEFECTIVE_TOKEN;
        goto fail;
    }

    sptr = (char *) ptr;
    TREAD_STR(sptr, ap_req.data, ap_req.length);

    /* construct the sender_addr */

    if ((input_chan_bindings != GSS_C_NO_CHANNEL_BINDINGS) &&
        (input_chan_bindings->initiator_addrtype == GSS_C_AF_INET)) {
        /* XXX is this right? */
        addr.addrtype = ADDRTYPE_INET;
        addr.length = input_chan_bindings->initiator_address.length;
        addr.contents = input_chan_bindings->initiator_address.value;

        paddr = &addr;
    } else {
        paddr = NULL;
    }

    /* decode the AP_REQ message */
    code = decode_krb5_ap_req(&ap_req, &request);
    if (code) {
        major_status = GSS_S_FAILURE;
        goto done;
    }
    ticket = request->ticket;

    /* decode the message */

    if ((code = krb5_auth_con_init(context, &auth_context))) {
        major_status = GSS_S_FAILURE;
        save_error_info((OM_uint32)code, context);
        goto fail;
    }
    if (cred->rcache) {
        cred_rcache = 1;
        if ((code = krb5_auth_con_setrcache(context, auth_context, cred->rcache))) {
            major_status = GSS_S_FAILURE;
            goto fail;
        }
    }
    if ((code = krb5_auth_con_setaddrs(context, auth_context, NULL, paddr))) {
        major_status = GSS_S_FAILURE;
        goto fail;
    }

    /* Limit the encryption types negotiated (if requested). */
    if (cred->req_enctypes) {
        if ((code = krb5_auth_con_setpermetypes(context, auth_context,
                                                cred->req_enctypes))) {
            major_status = GSS_S_FAILURE;
            goto fail;
        }
    }

    if (!cred->default_identity) {
        if ((code = kg_acceptor_princ(context, cred->name, &accprinc))) {
            major_status = GSS_S_FAILURE;
            goto fail;
        }
    }

    code = krb5_rd_req_decoded(context, &auth_context, request, accprinc,
                               cred->keytab, &ap_req_options, NULL);

    krb5_free_principal(context, accprinc);
    if (code) {
        major_status = GSS_S_FAILURE;
        goto fail;
    }
    krb5_auth_con_setflags(context, auth_context,
                           KRB5_AUTH_CONTEXT_DO_SEQUENCE);

    krb5_auth_con_getauthenticator(context, auth_context, &authdat);

#if 0
    /* make sure the necessary parts of the authdat are present */

    if ((authdat->authenticator->subkey == NULL) ||
        (authdat->ticket->enc_part2 == NULL)) {
        code = KG_NO_SUBKEY;
        major_status = GSS_S_FAILURE;
        goto fail;
    }
#endif

    if (authdat->checksum == NULL) {
        /*
         * Some SMB client implementations use handcrafted GSSAPI code that
         * does not provide a checksum.  MS-KILE documents that the Microsoft
         * implementation considers a missing checksum acceptable; the server
         * assumes all flags are unset in this case, and does not check channel
         * bindings.
         */
        gss_flags = 0;
    } else if (authdat->checksum->checksum_type != CKSUMTYPE_KG_CB) {
        /* Samba does not send 0x8003 GSS-API checksums */
        krb5_boolean valid;
        krb5_key subkey;
        krb5_data zero;

        code = krb5_auth_con_getkey_k(context, auth_context, &subkey);
        if (code) {
            major_status = GSS_S_FAILURE;
            goto fail;
        }

        zero.length = 0;
        zero.data = "";

        code = krb5_k_verify_checksum(context,
                                      subkey,
                                      KRB5_KEYUSAGE_AP_REQ_AUTH_CKSUM,
                                      &zero,
                                      authdat->checksum,
                                      &valid);
        krb5_k_free_key(context, subkey);
        if (code || !valid) {
            major_status = GSS_S_BAD_SIG;
            goto fail;
        }

        /* Use ap_options from the request to guess the mutual flag. */
        gss_flags = GSS_C_REPLAY_FLAG | GSS_C_SEQUENCE_FLAG;
        if (ap_req_options & AP_OPTS_MUTUAL_REQUIRED)
            gss_flags |= GSS_C_MUTUAL_FLAG;
    } else {
        /* gss krb5 v1 */

        /* stash this now, for later. */
        code = krb5_c_checksum_length(context, CKSUMTYPE_RSA_MD5, &md5len);
        if (code) {
            major_status = GSS_S_FAILURE;
            goto fail;
        }

        /* verify that the checksum is correct */

        /*
          The checksum may be either exactly 24 bytes, in which case
          no options are specified, or greater than 24 bytes, in which case
          one or more options are specified. Currently, the only valid
          option is KRB5_GSS_FOR_CREDS_OPTION ( = 1 ).
        */

        if ((authdat->checksum->checksum_type != CKSUMTYPE_KG_CB) ||
            (authdat->checksum->length < 24)) {
            code = 0;
            major_status = GSS_S_BAD_BINDINGS;
            goto fail;
        }

        ptr = (unsigned char *) authdat->checksum->contents;

        TREAD_INT(ptr, tmp, 0);

        if (tmp != md5len) {
            code = KG_BAD_LENGTH;
            major_status = GSS_S_FAILURE;
            goto fail;
        }

        /*
          The following section of code attempts to implement the
          optional channel binding facility as described in RFC2743.

          Since this facility is optional channel binding may or may
          not have been provided by either the client or the server.

          If the server has specified input_chan_bindings equal to
          GSS_C_NO_CHANNEL_BINDINGS then we skip the check.  If
          the server does provide channel bindings then we compute
          a checksum and compare against those provided by the
          client.         */

        if ((code = kg_checksum_channel_bindings(context,
                                                 input_chan_bindings,
                                                 &reqcksum))) {
            major_status = GSS_S_BAD_BINDINGS;
            goto fail;
        }

        /* Always read the clients bindings - eventhough we might ignore them */
        TREAD_STR(ptr, ptr2, reqcksum.length);

        if (input_chan_bindings != GSS_C_NO_CHANNEL_BINDINGS ) {
            if (memcmp(ptr2, reqcksum.contents, reqcksum.length) != 0) {
                xfree(reqcksum.contents);
                reqcksum.contents = 0;
                code = 0;
                major_status = GSS_S_BAD_BINDINGS;
                goto fail;
            }

        }

        xfree(reqcksum.contents);
        reqcksum.contents = 0;

        /* Read the token flags.  Remember if GSS_C_DELEG_FLAG was set, but
         * mask it out until we actually read a delegated credential. */
        TREAD_INT(ptr, gss_flags, 0);
        token_deleg_flag = (gss_flags & GSS_C_DELEG_FLAG);
        gss_flags &= ~GSS_C_DELEG_FLAG;

        /* if the checksum length > 24, there are options to process */

        i = authdat->checksum->length - 24;
        if (i && token_deleg_flag) {
            if (i >= 4) {
                TREAD_INT16(ptr, option_id, 0);
                TREAD_INT16(ptr, option.length, 0);
                i -= 4;

                if (i < option.length) {
                    code = KG_BAD_LENGTH;
                    major_status = GSS_S_FAILURE;
                    goto fail;
                }

                /* have to use ptr2, since option.data is wrong type and
                   macro uses ptr as both lvalue and rvalue */

                TREAD_STR(ptr, ptr2, option.length);
                option.data = (char *) ptr2;

                i -= option.length;

                if (option_id != KRB5_GSS_FOR_CREDS_OPTION) {
                    major_status = GSS_S_FAILURE;
                    goto fail;
                }

                /* store the delegated credential */

                code = rd_and_store_for_creds(context, auth_context, &option,
                                              (delegated_cred_handle) ?
                                              &deleg_cred : NULL);
                if (code) {
                    major_status = GSS_S_FAILURE;
                    goto fail;
                }

                gss_flags |= GSS_C_DELEG_FLAG;
            } /* if i >= 4 */
            /* ignore any additional trailing data, for now */
        }
        while (i > 0) {
            /* Process Type-Length-Data options */
            if (i < 8) {
                code = KG_BAD_LENGTH;
                major_status = GSS_S_FAILURE;
                goto fail;
            }
            TREAD_INT(ptr, option_id, 1);
            TREAD_INT(ptr, option.length, 1);
            i -= 8;
            if (i < option.length) {
                code = KG_BAD_LENGTH;
                major_status = GSS_S_FAILURE;
                goto fail;
            }
            TREAD_STR(ptr, ptr2, option.length);
            option.data = (char *)ptr2;

            i -= option.length;

            code = kg_process_extension(context, auth_context,
                                        option_id, &option, exts);
            if (code != 0) {
                major_status = GSS_S_FAILURE;
                goto fail;
            }
        }
    }

    if (exts->iakerb.conv && !exts->iakerb.verified) {
        major_status = GSS_S_BAD_SIG;
        goto fail;
    }

    /* only DCE_STYLE clients are allowed to send raw AP-REQs */
    if (no_encap != ((gss_flags & GSS_C_DCE_STYLE) != 0)) {
        major_status = GSS_S_DEFECTIVE_TOKEN;
        goto fail;
    }

    /* create the ctx struct and start filling it in */

    if ((ctx = (krb5_gss_ctx_id_rec *) xmalloc(sizeof(krb5_gss_ctx_id_rec)))
        == NULL) {
        code = ENOMEM;
        major_status = GSS_S_FAILURE;
        goto fail;
    }

    memset(ctx, 0, sizeof(krb5_gss_ctx_id_rec));
    ctx->magic = KG_CONTEXT;
    ctx->mech_used = (gss_OID) mech_used;
    ctx->auth_context = auth_context;
    ctx->initiate = 0;
    ctx->gss_flags = (GSS_C_TRANS_FLAG |
                      ((gss_flags) & (GSS_C_INTEG_FLAG | GSS_C_CONF_FLAG |
                                      GSS_C_MUTUAL_FLAG | GSS_C_REPLAY_FLAG |
                                      GSS_C_SEQUENCE_FLAG | GSS_C_DELEG_FLAG |
                                      GSS_C_DCE_STYLE | GSS_C_IDENTIFY_FLAG |
                                      GSS_C_EXTENDED_ERROR_FLAG)));
    ctx->seed_init = 0;
    ctx->cred_rcache = cred_rcache;

    /* XXX move this into gss_name_t */
    if (        (code = krb5_merge_authdata(context,
                                            ticket->enc_part2->authorization_data,
                                            authdat->authorization_data,
                                            &ctx->authdata))) {
        major_status = GSS_S_FAILURE;
        goto fail;
    }
    if ((code = kg_init_name(context, ticket->server, NULL, NULL, NULL, 0,
                             &ctx->here))) {
        major_status = GSS_S_FAILURE;
        goto fail;
    }
    if ((code = krb5_auth_con_get_authdata_context(context, auth_context,
                                                   &ad_context))) {
        major_status = GSS_S_FAILURE;
        goto fail;
    }
    if ((code = kg_init_name(context, authdat->client, NULL, NULL,
                             ad_context, KG_INIT_NAME_NO_COPY, &ctx->there))) {
        major_status = GSS_S_FAILURE;
        goto fail;
    }
    /* Now owned by ctx->there */
    authdat->client = NULL;
    krb5_auth_con_set_authdata_context(context, auth_context, NULL);

    if ((code = krb5_auth_con_getrecvsubkey_k(context, auth_context,
                                              &ctx->subkey))) {
        major_status = GSS_S_FAILURE;
        goto fail;
    }

    /* use the session key if the subkey isn't present */

    if (ctx->subkey == NULL) {
        if ((code = krb5_auth_con_getkey_k(context, auth_context,
                                           &ctx->subkey))) {
            major_status = GSS_S_FAILURE;
            goto fail;
        }
    }

    if (ctx->subkey == NULL) {
        /* this isn't a very good error, but it's not clear to me this
           can actually happen */
        major_status = GSS_S_FAILURE;
        code = KRB5KDC_ERR_NULL_KEY;
        goto fail;
    }

    ctx->enc = NULL;
    ctx->seq = NULL;
    ctx->have_acceptor_subkey = 0;
    /* DCE_STYLE implies acceptor_subkey */
    if ((ctx->gss_flags & GSS_C_DCE_STYLE) == 0) {
        code = kg_setup_keys(context, ctx, ctx->subkey, &ctx->cksumtype);
        if (code) {
            major_status = GSS_S_FAILURE;
            goto fail;
        }
    }
    ctx->krb_times = ticket->enc_part2->times; /* struct copy */
    ctx->krb_flags = ticket->enc_part2->flags;

    if (delegated_cred_handle != NULL &&
        deleg_cred == NULL && /* no unconstrained delegation */
        cred->usage == GSS_C_BOTH &&
        (ticket->enc_part2->flags & TKT_FLG_FORWARDABLE)) {
        /*
         * Now, we always fabricate a delegated credentials handle
         * containing the service ticket to ourselves, which can be
         * used for S4U2Proxy.
         */
        major_status = create_constrained_deleg_creds(minor_status, cred,
                                                      ticket, &deleg_cred,
                                                      context);
        if (GSS_ERROR(major_status))
            goto fail;
        ctx->gss_flags |= GSS_C_DELEG_FLAG;
    }

    {
        krb5_int32 seq_temp;
        krb5_auth_con_getremoteseqnumber(context, auth_context, &seq_temp);
        ctx->seq_recv = seq_temp;
    }

    if ((code = krb5_timeofday(context, &now))) {
        major_status = GSS_S_FAILURE;
        goto fail;
    }

    code = g_seqstate_init(&ctx->seqstate, ctx->seq_recv,
                           (ctx->gss_flags & GSS_C_REPLAY_FLAG) != 0,
                           (ctx->gss_flags & GSS_C_SEQUENCE_FLAG) != 0,
                           ctx->proto);
    if (code) {
        major_status = GSS_S_FAILURE;
        goto fail;
    }

    /* DCE_STYLE implies mutual authentication */
    if (ctx->gss_flags & GSS_C_DCE_STYLE)
        ctx->gss_flags |= GSS_C_MUTUAL_FLAG;

    /* at this point, the entire context structure is filled in,
       so it can be released.  */

    /* generate an AP_REP if necessary */

    if (ctx->gss_flags & GSS_C_MUTUAL_FLAG) {
        unsigned char * ptr3;
        krb5_int32 seq_temp;
        int cfx_generate_subkey;

        /*
         * Do not generate a subkey per RFC 4537 unless we are upgrading to CFX,
         * because pre-CFX tokens do not indicate which key to use. (Note that
         * DCE_STYLE implies that we will use a subkey.)
         */
        if (ctx->proto == 0 &&
            (ctx->gss_flags & GSS_C_DCE_STYLE) == 0 &&
            (ap_req_options & AP_OPTS_USE_SUBKEY)) {
            code = (*kaccess.auth_con_get_subkey_enctype)(context,
                                                          auth_context,
                                                          &negotiated_etype);
            if (code != 0) {
                major_status = GSS_S_FAILURE;
                goto fail;
            }

            switch (negotiated_etype) {
            case ENCTYPE_DES_CBC_MD5:
            case ENCTYPE_DES_CBC_MD4:
            case ENCTYPE_DES_CBC_CRC:
            case ENCTYPE_DES3_CBC_SHA1:
            case ENCTYPE_ARCFOUR_HMAC:
            case ENCTYPE_ARCFOUR_HMAC_EXP:
                /* RFC 4121 accidentally omits RC4-HMAC-EXP as a "not-newer"
                 * enctype, even though RFC 4757 treats it as one. */
                ap_req_options &= ~(AP_OPTS_USE_SUBKEY);
                break;
            }
        }

        if (ctx->proto == 1 || (ctx->gss_flags & GSS_C_DCE_STYLE) ||
            (ap_req_options & AP_OPTS_USE_SUBKEY))
            cfx_generate_subkey = CFX_ACCEPTOR_SUBKEY;
        else
            cfx_generate_subkey = 0;

        if (cfx_generate_subkey) {
            krb5_int32 acflags;
            code = krb5_auth_con_getflags(context, auth_context, &acflags);
            if (code == 0) {
                acflags |= KRB5_AUTH_CONTEXT_USE_SUBKEY;
                code = krb5_auth_con_setflags(context, auth_context, acflags);
            }
            if (code) {
                major_status = GSS_S_FAILURE;
                goto fail;
            }
        }

        if ((code = krb5_mk_rep(context, auth_context, &ap_rep))) {
            major_status = GSS_S_FAILURE;
            goto fail;
        }

        krb5_auth_con_getlocalseqnumber(context, auth_context, &seq_temp);
        ctx->seq_send = seq_temp & 0xffffffffL;

        if (cfx_generate_subkey) {
            /* Get the new acceptor subkey.  With the code above, there
               should always be one if we make it to this point.  */
            code = krb5_auth_con_getsendsubkey_k(context, auth_context,
                                                 &ctx->acceptor_subkey);
            if (code != 0) {
                major_status = GSS_S_FAILURE;
                goto fail;
            }
            ctx->have_acceptor_subkey = 1;

            code = kg_setup_keys(context, ctx, ctx->acceptor_subkey,
                                 &ctx->acceptor_subkey_cksumtype);
            if (code) {
                major_status = GSS_S_FAILURE;
                goto fail;
            }
        }

        /* the reply token hasn't been sent yet, but that's ok. */
        if (ctx->gss_flags & GSS_C_DCE_STYLE) {
            assert(ctx->have_acceptor_subkey);

            /* in order to force acceptor subkey to be used, don't set PROT_READY */

            /* Raw AP-REP is returned */
            code = data_to_gss(&ap_rep, output_token);
            if (code)
            {
                major_status = GSS_S_FAILURE;
                goto fail;
            }

            ctx->established = 0;

            *context_handle = (gss_ctx_id_t)ctx;
            *minor_status = 0;
            major_status = GSS_S_CONTINUE_NEEDED;

            /* Only last leg should set return arguments */
            goto fail;
        } else
            ctx->gss_flags |= GSS_C_PROT_READY_FLAG;

        ctx->established = 1;

        token.length = g_token_size(mech_used, ap_rep.length);

        if ((token.value = (unsigned char *) gssalloc_malloc(token.length))
            == NULL) {
            major_status = GSS_S_FAILURE;
            code = ENOMEM;
            goto fail;
        }
        ptr3 = token.value;
        g_make_token_header(mech_used, ap_rep.length,
                            &ptr3, KG_TOK_CTX_AP_REP);

        TWRITE_STR(ptr3, ap_rep.data, ap_rep.length);

        ctx->established = 1;

    } else {
        token.length = 0;
        token.value = NULL;
        ctx->seq_send = ctx->seq_recv;

        ctx->established = 1;
    }

    /* set the return arguments */

    if (src_name) {
        code = kg_duplicate_name(context, ctx->there, &name);
        if (code) {
            major_status = GSS_S_FAILURE;
            goto fail;
        }
    }

    if (mech_type)
        *mech_type = (gss_OID) mech_used;

    /* Add the maximum allowable clock skew as a grace period for context
     * expiration, just as we do for the ticket. */
    if (time_rec)
        *time_rec = ts_delta(ctx->krb_times.endtime, now) + context->clockskew;

    if (ret_flags)
        *ret_flags = ctx->gss_flags;

    *context_handle = (gss_ctx_id_t)ctx;
    *output_token = token;

    if (src_name)
        *src_name = (gss_name_t) name;

    if (delegated_cred_handle)
        *delegated_cred_handle = (gss_cred_id_t) deleg_cred;

    /* finally! */

    *minor_status = 0;
    major_status = GSS_S_COMPLETE;

fail:
    if (authdat)
        krb5_free_authenticator(context, authdat);
    /* The ctx structure has the handle of the auth_context */
    if (auth_context && !ctx) {
        if (cred_rcache)
            (void)krb5_auth_con_setrcache(context, auth_context, NULL);

        krb5_auth_con_free(context, auth_context);
    }
    if (reqcksum.contents)
        xfree(reqcksum.contents);
    if (ap_rep.data)
        krb5_free_data_contents(context, &ap_rep);
    if (major_status == GSS_S_COMPLETE ||
        (major_status == GSS_S_CONTINUE_NEEDED && code != KRB5KRB_AP_ERR_MSG_TYPE)) {
        ctx->k5_context = context;
        context = NULL;
        goto done;
    }

    /* from here on is the real "fail" code */

    if (ctx)
        (void) krb5_gss_delete_sec_context(&tmp_minor_status,
                                           (gss_ctx_id_t *) &ctx, NULL);
    if (deleg_cred) { /* free memory associated with the deleg credential */
        if (deleg_cred->ccache)
            (void)krb5_cc_close(context, deleg_cred->ccache);
        if (deleg_cred->name)
            kg_release_name(context, &deleg_cred->name);
        xfree(deleg_cred);
    }
    if (token.value)
        xfree(token.value);
    if (name) {
        (void) kg_release_name(context, &name);
    }

    *minor_status = code;

    /* We may have failed before being able to read the GSS flags from the
     * authenticator, so also check the request AP options. */
    if (cred != NULL && request != NULL &&
        ((gss_flags & GSS_C_MUTUAL_FLAG) ||
         (request->ap_options & AP_OPTS_MUTUAL_REQUIRED) ||
         major_status == GSS_S_CONTINUE_NEEDED)) {
        unsigned int tmsglen;
        int toktype;

        /*
         * The client is expecting a response, so we can send an
         * error token back
         */
        memset(&krb_error_data, 0, sizeof(krb_error_data));

        code -= ERROR_TABLE_BASE_krb5;
        if (code < 0 || code > KRB_ERR_MAX)
            code = 60 /* KRB_ERR_GENERIC */;

        krb_error_data.error = code;
        (void) krb5_us_timeofday(context, &krb_error_data.stime,
                                 &krb_error_data.susec);

        krb_error_data.server = ticket->server;
        code = krb5_mk_error(context, &krb_error_data, &scratch);
        if (code)
            goto done;

        tmsglen = scratch.length;
        toktype = KG_TOK_CTX_ERROR;

        token.length = g_token_size(mech_used, tmsglen);
        token.value = gssalloc_malloc(token.length);
        if (!token.value)
            goto done;

        ptr = token.value;
        g_make_token_header(mech_used, tmsglen, &ptr, toktype);

        TWRITE_STR(ptr, scratch.data, scratch.length);
        krb5_free_data_contents(context, &scratch);

        *output_token = token;
    }

done:
    krb5_free_ap_req(context, request);
    if (cred)
        k5_mutex_unlock(&cred->lock);
    if (defcred)
        krb5_gss_release_cred(&tmp_minor_status, &defcred);
    if (context) {
        if (major_status && *minor_status)
            save_error_info(*minor_status, context);
        krb5_free_context(context);
    }
    return (major_status);
}
#endif /* LEAN_CLIENT */

OM_uint32 KRB5_CALLCONV
krb5_gss_accept_sec_context_ext(
    OM_uint32 *minor_status,
    gss_ctx_id_t *context_handle,
    gss_cred_id_t verifier_cred_handle,
    gss_buffer_t input_token,
    gss_channel_bindings_t input_chan_bindings,
    gss_name_t *src_name,
    gss_OID *mech_type,
    gss_buffer_t output_token,
    OM_uint32 *ret_flags,
    OM_uint32 *time_rec,
    gss_cred_id_t *delegated_cred_handle,
    krb5_gss_ctx_ext_t exts)
{
    krb5_gss_ctx_id_rec *ctx = (krb5_gss_ctx_id_rec *)*context_handle;

    /*
     * Context handle must be unspecified.  Actually, it must be
     * non-established, but currently, accept_sec_context never returns
     * a non-established context handle.
     */
    /*SUPPRESS 29*/
    if (ctx != NULL) {
        if (ctx->established == 0 && (ctx->gss_flags & GSS_C_DCE_STYLE)) {
            return kg_accept_dce(minor_status, context_handle,
                                 verifier_cred_handle, input_token,
                                 input_chan_bindings, src_name, mech_type,
                                 output_token, ret_flags, time_rec,
                                 delegated_cred_handle);
        } else {
            *minor_status = EINVAL;
            save_error_string(EINVAL, "accept_sec_context called with existing context handle");
            return GSS_S_FAILURE;
        }
    }

    return kg_accept_krb5(minor_status, context_handle,
                          verifier_cred_handle, input_token,
                          input_chan_bindings, src_name, mech_type,
                          output_token, ret_flags, time_rec,
                          delegated_cred_handle, exts);
}

OM_uint32 KRB5_CALLCONV
krb5_gss_accept_sec_context(minor_status, context_handle,
                            verifier_cred_handle, input_token,
                            input_chan_bindings, src_name, mech_type,
                            output_token, ret_flags, time_rec,
                            delegated_cred_handle)
    OM_uint32 *minor_status;
    gss_ctx_id_t *context_handle;
    gss_cred_id_t verifier_cred_handle;
    gss_buffer_t input_token;
    gss_channel_bindings_t input_chan_bindings;
    gss_name_t *src_name;
    gss_OID *mech_type;
    gss_buffer_t output_token;
    OM_uint32 *ret_flags;
    OM_uint32 *time_rec;
    gss_cred_id_t *delegated_cred_handle;
{
    krb5_gss_ctx_ext_rec exts;

    memset(&exts, 0, sizeof(exts));

    return krb5_gss_accept_sec_context_ext(minor_status,
                                           context_handle,
                                           verifier_cred_handle,
                                           input_token,
                                           input_chan_bindings,
                                           src_name,
                                           mech_type,
                                           output_token,
                                           ret_flags,
                                           time_rec,
                                           delegated_cred_handle,
                                           &exts);
}
