lib/dns/spnego.c

	spnego.c revision 6a1a8186afb298c87b3e5ae3fbbda95ea94f6bbd
cb73e2bfacb60eed27a3e4940f6dbe0c0580fc18David Lawrence/*
0c27b3fe77ac1d5094ba3521e8142d9e7973133fMark Andrews * Copyright (C) 2006-2009  Internet Systems Consortium, Inc. ("ISC")
40f53fa8d9c6a4fc38c0014495e7a42b08f52481David Lawrence *
0c27b3fe77ac1d5094ba3521e8142d9e7973133fMark Andrews * Permission to use, copy, modify, and/or distribute this software for any
0c27b3fe77ac1d5094ba3521e8142d9e7973133fMark Andrews * purpose with or without fee is hereby granted, provided that the above
0c27b3fe77ac1d5094ba3521e8142d9e7973133fMark Andrews * copyright notice and this permission notice appear in all copies.
cb73e2bfacb60eed27a3e4940f6dbe0c0580fc18David Lawrence *
cb73e2bfacb60eed27a3e4940f6dbe0c0580fc18David Lawrence * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
ec5347e2c775f027573ce5648b910361aa926c01Automatic Updater * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
cb73e2bfacb60eed27a3e4940f6dbe0c0580fc18David Lawrence * AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
cb73e2bfacb60eed27a3e4940f6dbe0c0580fc18David Lawrence * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
cb73e2bfacb60eed27a3e4940f6dbe0c0580fc18David Lawrence * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
e35c1bb3ecd9a6597360b9160b397c8053af69bfDanny Mayer * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
e35c1bb3ecd9a6597360b9160b397c8053af69bfDanny Mayer * PERFORMANCE OF THIS SOFTWARE.
cb73e2bfacb60eed27a3e4940f6dbe0c0580fc18David Lawrence */
cb73e2bfacb60eed27a3e4940f6dbe0c0580fc18David Lawrence
cb73e2bfacb60eed27a3e4940f6dbe0c0580fc18David Lawrence/* $Id: spnego.c,v 1.12 2009/07/21 06:53:09 marka Exp $ */
cb73e2bfacb60eed27a3e4940f6dbe0c0580fc18David Lawrence
e35c1bb3ecd9a6597360b9160b397c8053af69bfDanny Mayer/*! \file
cb73e2bfacb60eed27a3e4940f6dbe0c0580fc18David Lawrence * \brief
cb73e2bfacb60eed27a3e4940f6dbe0c0580fc18David Lawrence * Portable SPNEGO implementation.
e76d4c91bfadf823f04dcca1c1c5bcc14c67671dAndreas Gustafsson *
cb73e2bfacb60eed27a3e4940f6dbe0c0580fc18David Lawrence * This is part of a portable implementation of the SPNEGO protocol
cb73e2bfacb60eed27a3e4940f6dbe0c0580fc18David Lawrence * (RFCs 2478 and 4178).  This implementation uses the RFC 4178 ASN.1
40f53fa8d9c6a4fc38c0014495e7a42b08f52481David Lawrence * module but is not a full implementation of the RFC 4178 protocol;
40f53fa8d9c6a4fc38c0014495e7a42b08f52481David Lawrence * at the moment, we only support GSS-TSIG with Kerberos
cb73e2bfacb60eed27a3e4940f6dbe0c0580fc18David Lawrence * authentication, so we only need enough of the SPNEGO protocol to
cb73e2bfacb60eed27a3e4940f6dbe0c0580fc18David Lawrence * support that.
cb73e2bfacb60eed27a3e4940f6dbe0c0580fc18David Lawrence *
cb73e2bfacb60eed27a3e4940f6dbe0c0580fc18David Lawrence * The files that make up this portable SPNEGO implementation are:
cb73e2bfacb60eed27a3e4940f6dbe0c0580fc18David Lawrence * \li  spnego.c    (this file)
cb73e2bfacb60eed27a3e4940f6dbe0c0580fc18David Lawrence * \li  spnego.h    (API SPNEGO exports to the rest of lib/dns)
cb73e2bfacb60eed27a3e4940f6dbe0c0580fc18David Lawrence * \li  spnego.asn1 (SPNEGO ASN.1 module)
cb73e2bfacb60eed27a3e4940f6dbe0c0580fc18David Lawrence * \li  spnego_asn1.c   (routines generated from spngo.asn1)
0c27b3fe77ac1d5094ba3521e8142d9e7973133fMark Andrews * \li  spnego_asn1.pl  (perl script to generate spnego_asn1.c)
0c27b3fe77ac1d5094ba3521e8142d9e7973133fMark Andrews *
f05a4bf2bfac3aaff0462560b2793cd99a85a297Mark Andrews * Everything but the functions exported in spnego.h is static, to
cb73e2bfacb60eed27a3e4940f6dbe0c0580fc18David Lawrence * avoid possible conflicts with other libraries (particularly Heimdal,
f05a4bf2bfac3aaff0462560b2793cd99a85a297Mark Andrews * since much of this code comes from Heimdal by way of mod_auth_kerb).
cb73e2bfacb60eed27a3e4940f6dbe0c0580fc18David Lawrence *
cb73e2bfacb60eed27a3e4940f6dbe0c0580fc18David Lawrence * spnego_asn1.c is shipped as part of lib/dns because generating it
cb73e2bfacb60eed27a3e4940f6dbe0c0580fc18David Lawrence * requires both Perl and the Heimdal ASN.1 compiler.  See
cb73e2bfacb60eed27a3e4940f6dbe0c0580fc18David Lawrence * spnego_asn1.pl for further details.  We've tried to eliminate all
cb73e2bfacb60eed27a3e4940f6dbe0c0580fc18David Lawrence * compiler warnings from the generated code, but you may see a few
cb73e2bfacb60eed27a3e4940f6dbe0c0580fc18David Lawrence * when using a compiler version we haven't tested yet.
 */

/*
 * Portions of this code were derived from mod_auth_kerb and Heimdal.
 * These packages are available from:
 *
 *   http://modauthkerb.sourceforge.net/
 *   http://www.pdc.kth.se/heimdal/
 *
 * and were released under the following licenses:
 *
 * ----------------------------------------------------------------
 *
 * Copyright (c) 2004 Masarykova universita
 * (Masaryk University, Brno, Czech Republic)
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * 3. Neither the name of the University nor the names of its contributors may
 *    be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE 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.
 *
 * ----------------------------------------------------------------
 *
 * Copyright (c) 1997 - 2003 Kungliga Tekniska H�gskolan
 * (Royal Institute of Technology, Stockholm, Sweden).
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * 3. Neither the name of the Institute 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 INSTITUTE 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 INSTITUTE 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.
 */

/*
 * XXXSRA We should omit this file entirely in Makefile.in via autoconf,
 * but this will keep it from generating errors until that's written.
 */

#ifdef GSSAPI

/*
 * XXXSRA Some of the following files are almost certainly unnecessary,
 * but using this list (borrowed from gssapictx.c) gets rid of some
 * whacky compilation errors when building with MSVC and should be
 * harmless in any case.
 */

#include <config.h>

#include <stdlib.h>
#include <errno.h>

#include <isc/buffer.h>
#include <isc/dir.h>
#include <isc/entropy.h>
#include <isc/lex.h>
#include <isc/mem.h>
#include <isc/once.h>
#include <isc/random.h>
#include <isc/string.h>
#include <isc/time.h>
#include <isc/util.h>

#include <dns/fixedname.h>
#include <dns/name.h>
#include <dns/rdata.h>
#include <dns/rdataclass.h>
#include <dns/result.h>
#include <dns/types.h>
#include <dns/keyvalues.h>
#include <dns/log.h>

#include <dst/gssapi.h>
#include <dst/result.h>

#include "dst_internal.h"

/*
 * The API we export
 */
#include "spnego.h"

/* asn1_err.h */
/* Generated from ../../../lib/asn1/asn1_err.et */

typedef enum asn1_error_number {
    ASN1_BAD_TIMEFORMAT = 1859794432,
    ASN1_MISSING_FIELD = 1859794433,
    ASN1_MISPLACED_FIELD = 1859794434,
    ASN1_TYPE_MISMATCH = 1859794435,
    ASN1_OVERFLOW = 1859794436,
    ASN1_OVERRUN = 1859794437,
    ASN1_BAD_ID = 1859794438,
    ASN1_BAD_LENGTH = 1859794439,
    ASN1_BAD_FORMAT = 1859794440,
    ASN1_PARSE_ERROR = 1859794441
} asn1_error_number;

#define ERROR_TABLE_BASE_asn1 1859794432

#define __asn1_common_definitions__

typedef struct octet_string {
    size_t length;
    void *data;
} octet_string;

typedef char *general_string;

typedef char *utf8_string;

typedef struct oid {
    size_t length;
    unsigned *components;
} oid;

/* der.h */

typedef enum {
    ASN1_C_UNIV = 0, ASN1_C_APPL = 1,
    ASN1_C_CONTEXT = 2, ASN1_C_PRIVATE = 3
} Der_class;

typedef enum {
    PRIM = 0, CONS = 1
} Der_type;

/* Universal tags */

enum {
    UT_Boolean = 1,
    UT_Integer = 2,
    UT_BitString = 3,
    UT_OctetString = 4,
    UT_Null = 5,
    UT_OID = 6,
    UT_Enumerated = 10,
    UT_Sequence = 16,
    UT_Set = 17,
    UT_PrintableString = 19,
    UT_IA5String = 22,
    UT_UTCTime = 23,
    UT_GeneralizedTime = 24,
    UT_VisibleString = 26,
    UT_GeneralString = 27
};

#define ASN1_INDEFINITE 0xdce0deed

static int
der_get_length(const unsigned char *p, size_t len,
           size_t * val, size_t * size);

static int
der_get_octet_string(const unsigned char *p, size_t len,
             octet_string * data, size_t * size);
static int
der_get_oid(const unsigned char *p, size_t len,
        oid * data, size_t * size);
static int
der_get_tag(const unsigned char *p, size_t len,
        Der_class * class, Der_type * type,
        int *tag, size_t * size);

static int
der_match_tag(const unsigned char *p, size_t len,
          Der_class class, Der_type type,
          int tag, size_t * size);
static int
der_match_tag_and_length(const unsigned char *p, size_t len,
             Der_class class, Der_type type, int tag,
             size_t * length_ret, size_t * size);

static int
decode_oid(const unsigned char *p, size_t len,
       oid * k, size_t * size);

static int
decode_enumerated(const unsigned char *p, size_t len, void *num, size_t *size);

static int
decode_octet_string(const unsigned char *, size_t, octet_string *, size_t *);

static int
der_put_int(unsigned char *p, size_t len, int val, size_t *);

static int
der_put_length(unsigned char *p, size_t len, size_t val, size_t *);

static int
der_put_octet_string(unsigned char *p, size_t len,
             const octet_string * data, size_t *);
static int
der_put_oid(unsigned char *p, size_t len,
        const oid * data, size_t * size);
static int
der_put_tag(unsigned char *p, size_t len, Der_class class, Der_type type,
        int tag, size_t *);
static int
der_put_length_and_tag(unsigned char *, size_t, size_t,
               Der_class, Der_type, int, size_t *);

static int
encode_enumerated(unsigned char *p, size_t len, const void *data, size_t *);

static int
encode_octet_string(unsigned char *p, size_t len,
            const octet_string * k, size_t *);
static int
encode_oid(unsigned char *p, size_t len,
       const oid * k, size_t *);

static void
free_octet_string(octet_string * k);

static void
free_oid  (oid * k);

static size_t
length_len(size_t len);

static int
fix_dce(size_t reallen, size_t * len);

/*
 * Include stuff generated by the ASN.1 compiler.
 */

#include "spnego_asn1.c"

static unsigned char gss_krb5_mech_oid_bytes[] = {
    0x2a, 0x86, 0x48, 0x86, 0xf7, 0x12, 0x01, 0x02, 0x02
};

static gss_OID_desc gss_krb5_mech_oid_desc = {
    sizeof(gss_krb5_mech_oid_bytes),
    gss_krb5_mech_oid_bytes
};

static gss_OID GSS_KRB5_MECH = &gss_krb5_mech_oid_desc;

static unsigned char gss_mskrb5_mech_oid_bytes[] = {
    0x2a, 0x86, 0x48, 0x82, 0xf7, 0x12, 0x01, 0x02, 0x02
};

static gss_OID_desc gss_mskrb5_mech_oid_desc = {
    sizeof(gss_mskrb5_mech_oid_bytes),
    gss_mskrb5_mech_oid_bytes
};

static gss_OID GSS_MSKRB5_MECH = &gss_mskrb5_mech_oid_desc;

static unsigned char gss_spnego_mech_oid_bytes[] = {
    0x2b, 0x06, 0x01, 0x05, 0x05, 0x02
};

static gss_OID_desc gss_spnego_mech_oid_desc = {
    sizeof(gss_spnego_mech_oid_bytes),
    gss_spnego_mech_oid_bytes
};

static gss_OID GSS_SPNEGO_MECH = &gss_spnego_mech_oid_desc;

/* spnegokrb5_locl.h */

static OM_uint32
gssapi_spnego_encapsulate(OM_uint32 *,
              unsigned char *,
              size_t,
              gss_buffer_t,
              const gss_OID);

static OM_uint32
gssapi_spnego_decapsulate(OM_uint32 *,
              gss_buffer_t,
              unsigned char **,
              size_t *,
              const gss_OID);

/* mod_auth_kerb.c */

static int
cmp_gss_type(gss_buffer_t token, gss_OID oid)
{
    unsigned char *p;
    size_t len;

    if (token->length == 0)
        return (GSS_S_DEFECTIVE_TOKEN);

    p = token->value;
    if (*p++ != 0x60)
        return (GSS_S_DEFECTIVE_TOKEN);
    len = *p++;
    if (len & 0x80) {
        if ((len & 0x7f) > 4)
            return (GSS_S_DEFECTIVE_TOKEN);
        p += len & 0x7f;
    }
    if (*p++ != 0x06)
        return (GSS_S_DEFECTIVE_TOKEN);

    if (((OM_uint32) *p++) != oid->length)
        return (GSS_S_DEFECTIVE_TOKEN);

    return (memcmp(p, oid->elements, oid->length));
}

/* accept_sec_context.c */
/*
 * SPNEGO wrapper for Kerberos5 GSS-API kouril@ics.muni.cz, 2003 (mostly
 * based on Heimdal code)
 */

static OM_uint32
code_NegTokenArg(OM_uint32 * minor_status,
         const NegTokenResp * resp,
         unsigned char **outbuf,
         size_t * outbuf_size)
{
    OM_uint32 ret;
    u_char *buf;
    size_t buf_size, buf_len;

    buf_size = 1024;
    buf = malloc(buf_size);
    if (buf == NULL) {
        *minor_status = ENOMEM;
        return (GSS_S_FAILURE);
    }
    do {
        ret = encode_NegTokenResp(buf + buf_size - 1,
                      buf_size,
                      resp, &buf_len);
        if (ret == 0) {
            size_t tmp;

            ret = der_put_length_and_tag(buf + buf_size - buf_len - 1,
                             buf_size - buf_len,
                             buf_len,
                             ASN1_C_CONTEXT,
                             CONS,
                             1,
                             &tmp);
            if (ret == 0)
                buf_len += tmp;
        }
        if (ret) {
            if (ret == ASN1_OVERFLOW) {
                u_char *tmp;

                buf_size *= 2;
                tmp = realloc(buf, buf_size);
                if (tmp == NULL) {
                    *minor_status = ENOMEM;
                    free(buf);
                    return (GSS_S_FAILURE);
                }
                buf = tmp;
            } else {
                *minor_status = ret;
                free(buf);
                return (GSS_S_FAILURE);
            }
        }
    } while (ret == ASN1_OVERFLOW);

    *outbuf = malloc(buf_len);
    if (*outbuf == NULL) {
        *minor_status = ENOMEM;
        free(buf);
        return (GSS_S_FAILURE);
    }
    memcpy(*outbuf, buf + buf_size - buf_len, buf_len);
    *outbuf_size = buf_len;

    free(buf);

    return (GSS_S_COMPLETE);
}

static OM_uint32
send_reject(OM_uint32 * minor_status,
        gss_buffer_t output_token)
{
    NegTokenResp resp;
    OM_uint32 ret;

    resp.negState = malloc(sizeof(*resp.negState));
    if (resp.negState == NULL) {
        *minor_status = ENOMEM;
        return (GSS_S_FAILURE);
    }
    *(resp.negState) = reject;

    resp.supportedMech = NULL;
    resp.responseToken = NULL;
    resp.mechListMIC = NULL;

    ret = code_NegTokenArg(minor_status, &resp,
                   (unsigned char **)&output_token->value,
                   &output_token->length);
    free_NegTokenResp(&resp);
    if (ret)
        return (ret);

    return (GSS_S_BAD_MECH);
}

static OM_uint32
send_accept(OM_uint32 * minor_status,
        gss_buffer_t output_token,
        gss_buffer_t mech_token,
        const gss_OID pref)
{
    NegTokenResp resp;
    OM_uint32 ret;

    memset(&resp, 0, sizeof(resp));
    resp.negState = malloc(sizeof(*resp.negState));
    if (resp.negState == NULL) {
        *minor_status = ENOMEM;
        return (GSS_S_FAILURE);
    }
    *(resp.negState) = accept_completed;

    resp.supportedMech = malloc(sizeof(*resp.supportedMech));
    if (resp.supportedMech == NULL) {
        free_NegTokenResp(&resp);
        *minor_status = ENOMEM;
        return (GSS_S_FAILURE);
    }
    ret = der_get_oid(pref->elements,
              pref->length,
              resp.supportedMech,
              NULL);
    if (ret) {
        free_NegTokenResp(&resp);
        *minor_status = ENOMEM;
        return (GSS_S_FAILURE);
    }
    if (mech_token != NULL && mech_token->length != 0) {
        resp.responseToken = malloc(sizeof(*resp.responseToken));
        if (resp.responseToken == NULL) {
            free_NegTokenResp(&resp);
            *minor_status = ENOMEM;
            return (GSS_S_FAILURE);
        }
        resp.responseToken->length = mech_token->length;
        resp.responseToken->data = mech_token->value;
    }

    ret = code_NegTokenArg(minor_status, &resp,
                   (unsigned char **)&output_token->value,
                   &output_token->length);
    if (resp.responseToken != NULL) {
        free(resp.responseToken);
        resp.responseToken = NULL;
    }
    free_NegTokenResp(&resp);
    if (ret)
        return (ret);

    return (GSS_S_COMPLETE);
}

OM_uint32
gss_accept_sec_context_spnego(OM_uint32 *minor_status,
                  gss_ctx_id_t *context_handle,
                  const gss_cred_id_t acceptor_cred_handle,
                  const gss_buffer_t input_token_buffer,
                  const 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)
{
    NegTokenInit init_token;
    OM_uint32 major_status;
    OM_uint32 minor_status2;
    gss_buffer_desc ibuf, obuf;
    gss_buffer_t ot = NULL;
    gss_OID pref = GSS_KRB5_MECH;
    unsigned char *buf;
    size_t buf_size;
    size_t len, taglen, ni_len;
    int found = 0;
    int ret;
    unsigned i;

    /*
     * Before doing anything else, see whether this is a SPNEGO
     * PDU.  If not, dispatch to the GSSAPI library and get out.
     */

    if (cmp_gss_type(input_token_buffer, GSS_SPNEGO_MECH))
        return (gss_accept_sec_context(minor_status,
                           context_handle,
                           acceptor_cred_handle,
                           input_token_buffer,
                           input_chan_bindings,
                           src_name,
                           mech_type,
                           output_token,
                           ret_flags,
                           time_rec,
                           delegated_cred_handle));

    /*
     * If we get here, it's SPNEGO.
     */

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

    ret = gssapi_spnego_decapsulate(minor_status, input_token_buffer,
                    &buf, &buf_size, GSS_SPNEGO_MECH);
    if (ret)
        return (ret);

    ret = der_match_tag_and_length(buf, buf_size, ASN1_C_CONTEXT, CONS,
                       0, &len, &taglen);
    if (ret)
        return (ret);

    ret = decode_NegTokenInit(buf + taglen, len, &init_token, &ni_len);
    if (ret) {
        *minor_status = EINVAL; /* XXX */
        return (GSS_S_DEFECTIVE_TOKEN);
    }

    for (i = 0; !found && i < init_token.mechTypes.len; ++i) {
        unsigned char mechbuf[17];
        size_t mech_len;

        ret = der_put_oid(mechbuf + sizeof(mechbuf) - 1,
                  sizeof(mechbuf),
                  &init_token.mechTypes.val[i],
                  &mech_len);
        if (ret)
            return (GSS_S_DEFECTIVE_TOKEN);
        if (mech_len == GSS_KRB5_MECH->length &&
            memcmp(GSS_KRB5_MECH->elements,
               mechbuf + sizeof(mechbuf) - mech_len,
               mech_len) == 0) {
            found = 1;
            break;
        }
        if (mech_len == GSS_MSKRB5_MECH->length &&
            memcmp(GSS_MSKRB5_MECH->elements,
               mechbuf + sizeof(mechbuf) - mech_len,
               mech_len) == 0) {
            found = 1;
            if (i == 0)
                pref = GSS_MSKRB5_MECH;
            break;
        }
    }

    if (!found)
        return (send_reject(minor_status, output_token));

    if (i == 0 && init_token.mechToken != NULL) {
        ibuf.length = init_token.mechToken->length;
        ibuf.value = init_token.mechToken->data;

        major_status = gss_accept_sec_context(minor_status,
                              context_handle,
                              acceptor_cred_handle,
                              &ibuf,
                              input_chan_bindings,
                              src_name,
                              mech_type,
                              &obuf,
                              ret_flags,
                              time_rec,
                              delegated_cred_handle);
        if (GSS_ERROR(major_status)) {
            send_reject(&minor_status2, output_token);
            return (major_status);
        }
        ot = &obuf;
    }
    ret = send_accept(&minor_status2, output_token, ot, pref);
    if (ot != NULL && ot->length != 0)
        gss_release_buffer(&minor_status2, ot);

    return (ret);
}

/* decapsulate.c */

static OM_uint32
gssapi_verify_mech_header(u_char ** str,
              size_t total_len,
              const gss_OID mech)
{
    size_t len, len_len, mech_len, foo;
    int e;
    u_char *p = *str;

    if (total_len < 1)
        return (GSS_S_DEFECTIVE_TOKEN);
    if (*p++ != 0x60)
        return (GSS_S_DEFECTIVE_TOKEN);
    e = der_get_length(p, total_len - 1, &len, &len_len);
    if (e || 1 + len_len + len != total_len)
        return (GSS_S_DEFECTIVE_TOKEN);
    p += len_len;
    if (*p++ != 0x06)
        return (GSS_S_DEFECTIVE_TOKEN);
    e = der_get_length(p, total_len - 1 - len_len - 1,
               &mech_len, &foo);
    if (e)
        return (GSS_S_DEFECTIVE_TOKEN);
    p += foo;
    if (mech_len != mech->length)
        return (GSS_S_BAD_MECH);
    if (memcmp(p, mech->elements, mech->length) != 0)
        return (GSS_S_BAD_MECH);
    p += mech_len;
    *str = p;
    return (GSS_S_COMPLETE);
}

/*
 * Remove the GSS-API wrapping from `in_token' giving `buf and buf_size' Does
 * not copy data, so just free `in_token'.
 */

static OM_uint32
gssapi_spnego_decapsulate(OM_uint32 *minor_status,
              gss_buffer_t input_token_buffer,
              unsigned char **buf,
              size_t *buf_len,
              const gss_OID mech)
{
    u_char *p;
    OM_uint32 ret;

    p = input_token_buffer->value;
    ret = gssapi_verify_mech_header(&p,
                    input_token_buffer->length,
                    mech);
    if (ret) {
        *minor_status = ret;
        return (GSS_S_FAILURE);
    }
    *buf_len = input_token_buffer->length -
        (p - (u_char *) input_token_buffer->value);
    *buf = p;
    return (GSS_S_COMPLETE);
}

/* der_free.c */

static void
free_octet_string(octet_string *k)
{
    free(k->data);
    k->data = NULL;
}

static void
free_oid(oid *k)
{
    free(k->components);
    k->components = NULL;
}

/* der_get.c */

/*
 * All decoding functions take a pointer `p' to first position in which to
 * read, from the left, `len' which means the maximum number of characters we
 * are able to read, `ret' were the value will be returned and `size' where
 * the number of used bytes is stored. Either 0 or an error code is returned.
 */

static int
der_get_unsigned(const unsigned char *p, size_t len,
         unsigned *ret, size_t *size)
{
    unsigned val = 0;
    size_t oldlen = len;

    while (len--)
        val = val * 256 + *p++;
    *ret = val;
    if (size)
        *size = oldlen;
    return (0);
}

static int
der_get_int(const unsigned char *p, size_t len,
        int *ret, size_t *size)
{
    int val = 0;
    size_t oldlen = len;

    if (len > 0) {
        val = (signed char)*p++;
        while (--len)
            val = val * 256 + *p++;
    }
    *ret = val;
    if (size)
        *size = oldlen;
    return (0);
}

static int
der_get_length(const unsigned char *p, size_t len,
           size_t *val, size_t *size)
{
    size_t v;

    if (len <= 0)
        return (ASN1_OVERRUN);
    --len;
    v = *p++;
    if (v < 128) {
        *val = v;
        if (size)
            *size = 1;
    } else {
        int e;
        size_t l;
        unsigned tmp;

        if (v == 0x80) {
            *val = ASN1_INDEFINITE;
            if (size)
                *size = 1;
            return (0);
        }
        v &= 0x7F;
        if (len < v)
            return (ASN1_OVERRUN);
        e = der_get_unsigned(p, v, &tmp, &l);
        if (e)
            return (e);
        *val = tmp;
        if (size)
            *size = l + 1;
    }
    return (0);
}

static int
der_get_octet_string(const unsigned char *p, size_t len,
             octet_string *data, size_t *size)
{
    data->length = len;
    data->data = malloc(len);
    if (data->data == NULL && data->length != 0)
        return (ENOMEM);
    memcpy(data->data, p, len);
    if (size)
        *size = len;
    return (0);
}

static int
der_get_oid(const unsigned char *p, size_t len,
        oid *data, size_t *size)
{
    int n;
    size_t oldlen = len;

    if (len < 1)
        return (ASN1_OVERRUN);

    data->components = malloc(len * sizeof(*data->components));
    if (data->components == NULL && len != 0)
        return (ENOMEM);
    data->components[0] = (*p) / 40;
    data->components[1] = (*p) % 40;
    --len;
    ++p;
    for (n = 2; len > 0; ++n) {
        unsigned u = 0;

        do {
            --len;
            u = u * 128 + (*p++ % 128);
        } while (len > 0 && p[-1] & 0x80);
        data->components[n] = u;
    }
    if (p[-1] & 0x80) {
        free_oid(data);
        return (ASN1_OVERRUN);
    }
    data->length = n;
    if (size)
        *size = oldlen;
    return (0);
}

static int
der_get_tag(const unsigned char *p, size_t len,
        Der_class *class, Der_type *type,
        int *tag, size_t *size)
{
    if (len < 1)
        return (ASN1_OVERRUN);
    *class = (Der_class) (((*p) >> 6) & 0x03);
    *type = (Der_type) (((*p) >> 5) & 0x01);
    *tag = (*p) & 0x1F;
    if (size)
        *size = 1;
    return (0);
}

static int
der_match_tag(const unsigned char *p, size_t len,
          Der_class class, Der_type type,
          int tag, size_t *size)
{
    size_t l;
    Der_class thisclass;
    Der_type thistype;
    int thistag;
    int e;

    e = der_get_tag(p, len, &thisclass, &thistype, &thistag, &l);
    if (e)
        return (e);
    if (class != thisclass || type != thistype)
        return (ASN1_BAD_ID);
    if (tag > thistag)
        return (ASN1_MISPLACED_FIELD);
    if (tag < thistag)
        return (ASN1_MISSING_FIELD);
    if (size)
        *size = l;
    return (0);
}

static int
der_match_tag_and_length(const unsigned char *p, size_t len,
             Der_class class, Der_type type, int tag,
             size_t *length_ret, size_t *size)
{
    size_t l, ret = 0;
    int e;

    e = der_match_tag(p, len, class, type, tag, &l);
    if (e)
        return (e);
    p += l;
    len -= l;
    ret += l;
    e = der_get_length(p, len, length_ret, &l);
    if (e)
        return (e);
    p += l;
    len -= l;
    ret += l;
    if (size)
        *size = ret;
    return (0);
}

static int
decode_enumerated(const unsigned char *p, size_t len, void *num, size_t *size)
{
    size_t ret = 0;
    size_t l, reallen;
    int e;

    e = der_match_tag(p, len, ASN1_C_UNIV, PRIM, UT_Enumerated, &l);
    if (e)
        return (e);
    p += l;
    len -= l;
    ret += l;
    e = der_get_length(p, len, &reallen, &l);
    if (e)
        return (e);
    p += l;
    len -= l;
    ret += l;
    e = der_get_int(p, reallen, num, &l);
    if (e)
        return (e);
    p += l;
    len -= l;
    ret += l;
    if (size)
        *size = ret;
    return (0);
}

static int
decode_octet_string(const unsigned char *p, size_t len,
            octet_string *k, size_t *size)
{
    size_t ret = 0;
    size_t l;
    int e;
    size_t slen;

    e = der_match_tag(p, len, ASN1_C_UNIV, PRIM, UT_OctetString, &l);
    if (e)
        return (e);
    p += l;
    len -= l;
    ret += l;

    e = der_get_length(p, len, &slen, &l);
    if (e)
        return (e);
    p += l;
    len -= l;
    ret += l;
    if (len < slen)
        return (ASN1_OVERRUN);

    e = der_get_octet_string(p, slen, k, &l);
    if (e)
        return (e);
    p += l;
    len -= l;
    ret += l;
    if (size)
        *size = ret;
    return (0);
}

static int
decode_oid(const unsigned char *p, size_t len,
       oid *k, size_t *size)
{
    size_t ret = 0;
    size_t l;
    int e;
    size_t slen;

    e = der_match_tag(p, len, ASN1_C_UNIV, PRIM, UT_OID, &l);
    if (e)
        return (e);
    p += l;
    len -= l;
    ret += l;

    e = der_get_length(p, len, &slen, &l);
    if (e)
        return (e);
    p += l;
    len -= l;
    ret += l;
    if (len < slen)
        return (ASN1_OVERRUN);

    e = der_get_oid(p, slen, k, &l);
    if (e)
        return (e);
    p += l;
    len -= l;
    ret += l;
    if (size)
        *size = ret;
    return (0);
}

static int
fix_dce(size_t reallen, size_t *len)
{
    if (reallen == ASN1_INDEFINITE)
        return (1);
    if (*len < reallen)
        return (-1);
    *len = reallen;
    return (0);
}

/* der_length.c */

static size_t
len_unsigned(unsigned val)
{
    size_t ret = 0;

    do {
        ++ret;
        val /= 256;
    } while (val);
    return (ret);
}

static size_t
length_len(size_t len)
{
    if (len < 128)
        return (1);
    else
        return (len_unsigned(len) + 1);
}


/* der_put.c */

/*
 * All encoding functions take a pointer `p' to first position in which to
 * write, from the right, `len' which means the maximum number of characters
 * we are able to write.  The function returns the number of characters
 * written in `size' (if non-NULL). The return value is 0 or an error.
 */

static int
der_put_unsigned(unsigned char *p, size_t len, unsigned val, size_t *size)
{
    unsigned char *base = p;

    if (val) {
        while (len > 0 && val) {
            *p-- = val % 256;
            val /= 256;
            --len;
        }
        if (val != 0)
            return (ASN1_OVERFLOW);
        else {
            *size = base - p;
            return (0);
        }
    } else if (len < 1)
        return (ASN1_OVERFLOW);
    else {
        *p = 0;
        *size = 1;
        return (0);
    }
}

static int
der_put_int(unsigned char *p, size_t len, int val, size_t *size)
{
    unsigned char *base = p;

    if (val >= 0) {
        do {
            if (len < 1)
                return (ASN1_OVERFLOW);
            *p-- = val % 256;
            len--;
            val /= 256;
        } while (val);
        if (p[1] >= 128) {
            if (len < 1)
                return (ASN1_OVERFLOW);
            *p-- = 0;
            len--;
        }
    } else {
        val = ~val;
        do {
            if (len < 1)
                return (ASN1_OVERFLOW);
            *p-- = ~(val % 256);
            len--;
            val /= 256;
        } while (val);
        if (p[1] < 128) {
            if (len < 1)
                return (ASN1_OVERFLOW);
            *p-- = 0xff;
            len--;
        }
    }
    *size = base - p;
    return (0);
}

static int
der_put_length(unsigned char *p, size_t len, size_t val, size_t *size)
{
    if (len < 1)
        return (ASN1_OVERFLOW);
    if (val < 128) {
        *p = val;
        *size = 1;
        return (0);
    } else {
        size_t l;
        int e;

        e = der_put_unsigned(p, len - 1, val, &l);
        if (e)
            return (e);
        p -= l;
        *p = 0x80 | l;
        *size = l + 1;
        return (0);
    }
}

static int
der_put_octet_string(unsigned char *p, size_t len,
             const octet_string *data, size_t *size)
{
    if (len < data->length)
        return (ASN1_OVERFLOW);
    p -= data->length;
    len -= data->length;
    memcpy(p + 1, data->data, data->length);
    *size = data->length;
    return (0);
}

static int
der_put_oid(unsigned char *p, size_t len,
        const oid *data, size_t *size)
{
    unsigned char *base = p;
    int n;

    for (n = data->length - 1; n >= 2; --n) {
        unsigned    u = data->components[n];

        if (len < 1)
            return (ASN1_OVERFLOW);
        *p-- = u % 128;
        u /= 128;
        --len;
        while (u > 0) {
            if (len < 1)
                return (ASN1_OVERFLOW);
            *p-- = 128 + u % 128;
            u /= 128;
            --len;
        }
    }
    if (len < 1)
        return (ASN1_OVERFLOW);
    *p-- = 40 * data->components[0] + data->components[1];
    *size = base - p;
    return (0);
}

static int
der_put_tag(unsigned char *p, size_t len, Der_class class, Der_type type,
        int tag, size_t *size)
{
    if (len < 1)
        return (ASN1_OVERFLOW);
    *p = (class << 6) | (type << 5) | tag;  /* XXX */
    *size = 1;
    return (0);
}

static int
der_put_length_and_tag(unsigned char *p, size_t len, size_t len_val,
               Der_class class, Der_type type, int tag, size_t *size)
{
    size_t ret = 0;
    size_t l;
    int e;

    e = der_put_length(p, len, len_val, &l);
    if (e)
        return (e);
    p -= l;
    len -= l;
    ret += l;
    e = der_put_tag(p, len, class, type, tag, &l);
    if (e)
        return (e);
    p -= l;
    len -= l;
    ret += l;
    *size = ret;
    return (0);
}

static int
encode_enumerated(unsigned char *p, size_t len, const void *data, size_t *size)
{
    unsigned num = *(const unsigned *)data;
    size_t ret = 0;
    size_t l;
    int e;

    e = der_put_int(p, len, num, &l);
    if (e)
        return (e);
    p -= l;
    len -= l;
    ret += l;
    e = der_put_length_and_tag(p, len, l, ASN1_C_UNIV, PRIM, UT_Enumerated, &l);
    if (e)
        return (e);
    p -= l;
    len -= l;
    ret += l;
    *size = ret;
    return (0);
}

static int
encode_octet_string(unsigned char *p, size_t len,
            const octet_string *k, size_t *size)
{
    size_t ret = 0;
    size_t l;
    int e;

    e = der_put_octet_string(p, len, k, &l);
    if (e)
        return (e);
    p -= l;
    len -= l;
    ret += l;
    e = der_put_length_and_tag(p, len, l, ASN1_C_UNIV, PRIM, UT_OctetString, &l);
    if (e)
        return (e);
    p -= l;
    len -= l;
    ret += l;
    *size = ret;
    return (0);
}

static int
encode_oid(unsigned char *p, size_t len,
       const oid *k, size_t *size)
{
    size_t ret = 0;
    size_t l;
    int e;

    e = der_put_oid(p, len, k, &l);
    if (e)
        return (e);
    p -= l;
    len -= l;
    ret += l;
    e = der_put_length_and_tag(p, len, l, ASN1_C_UNIV, PRIM, UT_OID, &l);
    if (e)
        return (e);
    p -= l;
    len -= l;
    ret += l;
    *size = ret;
    return (0);
}


/* encapsulate.c */

static void
gssapi_encap_length(size_t data_len,
            size_t *len,
            size_t *total_len,
            const gss_OID mech)
{
    size_t len_len;

    *len = 1 + 1 + mech->length + data_len;

    len_len = length_len(*len);

    *total_len = 1 + len_len + *len;
}

static u_char *
gssapi_mech_make_header(u_char *p,
            size_t len,
            const gss_OID mech)
{
    int e;
    size_t len_len, foo;

    *p++ = 0x60;
    len_len = length_len(len);
    e = der_put_length(p + len_len - 1, len_len, len, &foo);
    if (e || foo != len_len)
        return (NULL);
    p += len_len;
    *p++ = 0x06;
    *p++ = mech->length;
    memcpy(p, mech->elements, mech->length);
    p += mech->length;
    return (p);
}

/*
 * Give it a krb5_data and it will encapsulate with extra GSS-API wrappings.
 */

static OM_uint32
gssapi_spnego_encapsulate(OM_uint32 * minor_status,
              unsigned char *buf,
              size_t buf_size,
              gss_buffer_t output_token,
              const gss_OID mech)
{
    size_t len, outer_len;
    u_char *p;

    gssapi_encap_length(buf_size, &len, &outer_len, mech);

    output_token->length = outer_len;
    output_token->value = malloc(outer_len);
    if (output_token->value == NULL) {
        *minor_status = ENOMEM;
        return (GSS_S_FAILURE);
    }
    p = gssapi_mech_make_header(output_token->value, len, mech);
    if (p == NULL) {
        if (output_token->length != 0)
            gss_release_buffer(minor_status, output_token);
        return (GSS_S_FAILURE);
    }
    memcpy(p, buf, buf_size);
    return (GSS_S_COMPLETE);
}

/* init_sec_context.c */
/*
 * SPNEGO wrapper for Kerberos5 GSS-API kouril@ics.muni.cz, 2003 (mostly
 * based on Heimdal code)
 */

static int
add_mech(MechTypeList * mech_list, gss_OID mech)
{
    MechType *tmp;
    int ret;

    tmp = realloc(mech_list->val, (mech_list->len + 1) * sizeof(*tmp));
    if (tmp == NULL)
        return (ENOMEM);
    mech_list->val = tmp;

    ret = der_get_oid(mech->elements, mech->length,
              &mech_list->val[mech_list->len], NULL);
    if (ret)
        return (ret);

    mech_list->len++;
    return (0);
}

/*
 * return the length of the mechanism in token or -1
 * (which implies that the token was bad - GSS_S_DEFECTIVE_TOKEN
 */

static ssize_t
gssapi_krb5_get_mech(const u_char *ptr,
             size_t total_len,
             const u_char **mech_ret)
{
    size_t len, len_len, mech_len, foo;
    const u_char *p = ptr;
    int e;

    if (total_len < 1)
        return (-1);
    if (*p++ != 0x60)
        return (-1);
    e = der_get_length (p, total_len - 1, &len, &len_len);
    if (e || 1 + len_len + len != total_len)
        return (-1);
    p += len_len;
    if (*p++ != 0x06)
        return (-1);
    e = der_get_length (p, total_len - 1 - len_len - 1,
                &mech_len, &foo);
    if (e)
        return (-1);
    p += foo;
    *mech_ret = p;
    return (mech_len);
}

static OM_uint32
spnego_initial(OM_uint32 *minor_status,
           const gss_cred_id_t initiator_cred_handle,
           gss_ctx_id_t *context_handle,
           const gss_name_t target_name,
           const gss_OID mech_type,
           OM_uint32 req_flags,
           OM_uint32 time_req,
           const gss_channel_bindings_t input_chan_bindings,
           const gss_buffer_t input_token,
           gss_OID *actual_mech_type,
           gss_buffer_t output_token,
           OM_uint32 *ret_flags,
           OM_uint32 *time_rec)
{
    NegTokenInit token_init;
    OM_uint32 major_status, minor_status2;
    gss_buffer_desc krb5_output_token = GSS_C_EMPTY_BUFFER;
    unsigned char *buf = NULL;
    size_t buf_size;
    size_t len;
    int ret;

    (void)mech_type;

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

    ret = add_mech(&token_init.mechTypes, GSS_KRB5_MECH);
    if (ret) {
        *minor_status = ret;
        ret = GSS_S_FAILURE;
        goto end;
    }

    major_status = gss_init_sec_context(minor_status,
                        initiator_cred_handle,
                        context_handle,
                        target_name,
                        GSS_KRB5_MECH,
                        req_flags,
                        time_req,
                        input_chan_bindings,
                        input_token,
                        actual_mech_type,
                        &krb5_output_token,
                        ret_flags,
                        time_rec);
    if (GSS_ERROR(major_status)) {
        ret = major_status;
        goto end;
    }
    if (krb5_output_token.length > 0) {
        token_init.mechToken = malloc(sizeof(*token_init.mechToken));
        if (token_init.mechToken == NULL) {
            *minor_status = ENOMEM;
            ret = GSS_S_FAILURE;
            goto end;
        }
        token_init.mechToken->data = krb5_output_token.value;
        token_init.mechToken->length = krb5_output_token.length;
    }
    /*
     * The MS implementation of SPNEGO seems to not like the mechListMIC
     * field, so we omit it (it's optional anyway)
     */

    buf_size = 1024;
    buf = malloc(buf_size);

    do {
        ret = encode_NegTokenInit(buf + buf_size - 1,
                      buf_size,
                      &token_init, &len);
        if (ret == 0) {
            size_t tmp;

            ret = der_put_length_and_tag(buf + buf_size - len - 1,
                             buf_size - len,
                             len,
                             ASN1_C_CONTEXT,
                             CONS,
                             0,
                             &tmp);
            if (ret == 0)
                len += tmp;
        }
        if (ret) {
            if (ret == ASN1_OVERFLOW) {
                u_char *tmp;

                buf_size *= 2;
                tmp = realloc(buf, buf_size);
                if (tmp == NULL) {
                    *minor_status = ENOMEM;
                    ret = GSS_S_FAILURE;
                    goto end;
                }
                buf = tmp;
            } else {
                *minor_status = ret;
                ret = GSS_S_FAILURE;
                goto end;
            }
        }
    } while (ret == ASN1_OVERFLOW);

    ret = gssapi_spnego_encapsulate(minor_status,
                    buf + buf_size - len, len,
                    output_token, GSS_SPNEGO_MECH);
    if (ret == GSS_S_COMPLETE)
        ret = major_status;

end:
    if (token_init.mechToken != NULL) {
        free(token_init.mechToken);
        token_init.mechToken = NULL;
    }
    free_NegTokenInit(&token_init);
    if (krb5_output_token.length != 0)
        gss_release_buffer(&minor_status2, &krb5_output_token);
    if (buf)
        free(buf);

    return (ret);
}

static OM_uint32
spnego_reply(OM_uint32 *minor_status,
         const gss_cred_id_t initiator_cred_handle,
         gss_ctx_id_t *context_handle,
         const gss_name_t target_name,
         const gss_OID mech_type,
         OM_uint32 req_flags,
         OM_uint32 time_req,
         const gss_channel_bindings_t input_chan_bindings,
         const gss_buffer_t input_token,
         gss_OID *actual_mech_type,
         gss_buffer_t output_token,
         OM_uint32 *ret_flags,
         OM_uint32 *time_rec)
{
    OM_uint32 ret;
    NegTokenResp resp;
    unsigned char *buf;
    size_t buf_size;
    u_char oidbuf[17];
    size_t oidlen;
    gss_buffer_desc sub_token;
    ssize_t mech_len;
    const u_char *p;
    size_t len, taglen;

    (void)mech_type;

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

    /*
     * SPNEGO doesn't include gss wrapping on SubsequentContextToken
     * like the Kerberos 5 mech does. But lets check for it anyway.
     */

    mech_len = gssapi_krb5_get_mech(input_token->value,
                    input_token->length,
                    &p);

    if (mech_len < 0) {
        buf = input_token->value;
        buf_size = input_token->length;
    } else if ((size_t)mech_len == GSS_KRB5_MECH->length &&
           memcmp(GSS_KRB5_MECH->elements, p, mech_len) == 0)
        return (gss_init_sec_context(minor_status,
                         initiator_cred_handle,
                         context_handle,
                         target_name,
                         GSS_KRB5_MECH,
                         req_flags,
                         time_req,
                         input_chan_bindings,
                         input_token,
                         actual_mech_type,
                         output_token,
                         ret_flags,
                         time_rec));
    else if ((size_t)mech_len == GSS_SPNEGO_MECH->length &&
         memcmp(GSS_SPNEGO_MECH->elements, p, mech_len) == 0) {
        ret = gssapi_spnego_decapsulate(minor_status,
                        input_token,
                        &buf,
                        &buf_size,
                        GSS_SPNEGO_MECH);
        if (ret)
            return (ret);
    } else
        return (GSS_S_BAD_MECH);

    ret = der_match_tag_and_length(buf, buf_size,
                       ASN1_C_CONTEXT, CONS, 1, &len, &taglen);
    if (ret)
        return (ret);

    if(len > buf_size - taglen)
        return (ASN1_OVERRUN);

    ret = decode_NegTokenResp(buf + taglen, len, &resp, NULL);
    if (ret) {
        *minor_status = ENOMEM;
        return (GSS_S_FAILURE);
    }

    if (resp.negState == NULL ||
        *(resp.negState) == reject ||
        resp.supportedMech == NULL) {
        free_NegTokenResp(&resp);
        return (GSS_S_BAD_MECH);
    }

    ret = der_put_oid(oidbuf + sizeof(oidbuf) - 1,
              sizeof(oidbuf),
              resp.supportedMech,
              &oidlen);
    if (ret || oidlen != GSS_KRB5_MECH->length ||
        memcmp(oidbuf + sizeof(oidbuf) - oidlen,
           GSS_KRB5_MECH->elements,
           oidlen) != 0) {
        free_NegTokenResp(&resp);
        return GSS_S_BAD_MECH;
    }

    if (resp.responseToken != NULL) {
        sub_token.length = resp.responseToken->length;
        sub_token.value  = resp.responseToken->data;
    } else {
        sub_token.length = 0;
        sub_token.value  = NULL;
    }

    ret = gss_init_sec_context(minor_status,
                   initiator_cred_handle,
                   context_handle,
                   target_name,
                   GSS_KRB5_MECH,
                   req_flags,
                   time_req,
                   input_chan_bindings,
                   &sub_token,
                   actual_mech_type,
                   output_token,
                   ret_flags,
                   time_rec);
    if (ret) {
        free_NegTokenResp(&resp);
        return (ret);
    }

    /*
     * XXXSRA I don't think this limited implementation ever needs
     * to check the MIC -- our preferred mechanism (Kerberos)
     * authenticates its own messages and is the only mechanism
     * we'll accept, so if the mechanism negotiation completes
     * successfully, we don't need the MIC.  See RFC 4178.
     */

    free_NegTokenResp(&resp);
    return (ret);
}


OM_uint32
gss_init_sec_context_spnego(OM_uint32 *minor_status,
                const gss_cred_id_t initiator_cred_handle,
                gss_ctx_id_t *context_handle,
                const gss_name_t target_name,
                const gss_OID mech_type,
                OM_uint32 req_flags,
                OM_uint32 time_req,
                const gss_channel_bindings_t input_chan_bindings,
                const gss_buffer_t input_token,
                gss_OID *actual_mech_type,
                gss_buffer_t output_token,
                OM_uint32 *ret_flags,
                OM_uint32 *time_rec)
{
    /* Dirty trick to suppress compiler warnings */

    /* Figure out whether we're starting over or processing a reply */

    if (input_token == GSS_C_NO_BUFFER || input_token->length == 0)
        return (spnego_initial(minor_status,
                       initiator_cred_handle,
                       context_handle,
                       target_name,
                       mech_type,
                       req_flags,
                       time_req,
                       input_chan_bindings,
                       input_token,
                       actual_mech_type,
                       output_token,
                       ret_flags,
                       time_rec));
    else
        return (spnego_reply(minor_status,
                     initiator_cred_handle,
                     context_handle,
                     target_name,
                     mech_type,
                     req_flags,
                     time_req,
                     input_chan_bindings,
                     input_token,
                     actual_mech_type,
                     output_token,
                     ret_flags,
                     time_rec));
}

#endif /* GSSAPI */