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path: root/asn1/spnego/packet-spnego-template.c
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/* packet-spnego.c
 * Routines for the simple and protected GSS-API negotiation mechanism
 * as described in RFC 2478.
 * Copyright 2002, Tim Potter <tpot@samba.org>
 * Copyright 2002, Richard Sharpe <rsharpe@ns.aus.com>
 * Copyright 2003, Richard Sharpe <rsharpe@richardsharpe.com>
 * Copyright 2005, Ronnie Sahlberg (krb decryption)
 * Copyright 2005, Anders Broman (converted to asn2eth generated dissector)
 *
 * $Id$
 *
 * Ethereal - Network traffic analyzer
 * By Gerald Combs <gerald@ethereal.com>
 * Copyright 1998 Gerald Combs
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */
/* The heimdal code for decryption of GSSAPI wrappers using heimdal comes from
   Heimdal 1.6 and has been modified for ethereal's requirements.
*/

#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

#include <glib.h>
#include <epan/packet.h>
#include "packet-dcerpc.h"
#include "packet-gssapi.h"
#include "packet-kerberos.h"
#include <epan/crypt-rc4.h>
#include <epan/conversation.h>
#include <epan/emem.h>

#include <stdio.h>
#include <string.h>

#include "packet-ber.h"


#define PNAME  "Simple Protected Negotiation"
#define PSNAME "SPNEGO"
#define PFNAME "spnego"

/* Initialize the protocol and registered fields */
static int proto_spnego = -1;
static int proto_spnego_krb5 = -1;


static int hf_spnego = -1;
static int hf_spnego_wraptoken = -1;
static int hf_spnego_krb5_oid;
static int hf_spnego_krb5 = -1;
static int hf_spnego_krb5_tok_id = -1;
static int hf_spnego_krb5_sgn_alg = -1;
static int hf_spnego_krb5_seal_alg = -1;
static int hf_spnego_krb5_snd_seq = -1;
static int hf_spnego_krb5_sgn_cksum = -1;
static int hf_spnego_krb5_confounder = -1;

#include "packet-spnego-hf.c"

/* Global variables */
gchar MechType_oid[MAX_OID_STR_LEN];
gssapi_oid_value *next_level_value;
gboolean saw_mechanism = FALSE;


/* Initialize the subtree pointers */
static gint ett_spnego;
static gint ett_spnego_wraptoken;
static gint ett_spnego_krb5 = -1;

#include "packet-spnego-ett.c"

static dissector_handle_t data_handle;

static dissector_handle_t

gssapi_dissector_handle(gssapi_oid_value *next_level_value) {
	if (next_level_value == NULL) {
		return NULL;
	}
	return next_level_value->handle;
}


#include "packet-spnego-fn.c"
/*
 * This is the SPNEGO KRB5 dissector. It is not true KRB5, but some ASN.1
 * wrapped blob with an OID, USHORT token ID, and a Ticket, that is also 
 * ASN.1 wrapped by the looks of it. It conforms to RFC1964.
 */ 

#define KRB_TOKEN_AP_REQ		0x0001
#define KRB_TOKEN_AP_REP		0x0002
#define KRB_TOKEN_AP_ERR		0x0003
#define KRB_TOKEN_GETMIC		0x0101
#define KRB_TOKEN_WRAP			0x0102
#define KRB_TOKEN_DELETE_SEC_CONTEXT	0x0201

static const value_string spnego_krb5_tok_id_vals[] = {
  { KRB_TOKEN_AP_REQ,             "KRB5_AP_REQ"},
  { KRB_TOKEN_AP_REP,             "KRB5_AP_REP"},
  { KRB_TOKEN_AP_ERR,             "KRB5_ERROR"},
  { KRB_TOKEN_GETMIC,             "KRB5_GSS_GetMIC" },
  { KRB_TOKEN_WRAP,               "KRB5_GSS_Wrap" },
  { KRB_TOKEN_DELETE_SEC_CONTEXT, "KRB5_GSS_Delete_sec_context" },
  { 0, NULL}
};

#define KRB_SGN_ALG_DES_MAC_MD5	0x0000
#define KRB_SGN_ALG_MD2_5	0x0001
#define KRB_SGN_ALG_DES_MAC	0x0002
#define KRB_SGN_ALG_HMAC	0x0011

static const value_string spnego_krb5_sgn_alg_vals[] = {
  { KRB_SGN_ALG_DES_MAC_MD5, "DES MAC MD5"},
  { KRB_SGN_ALG_MD2_5,       "MD2.5"},
  { KRB_SGN_ALG_DES_MAC,     "DES MAC"},
  { KRB_SGN_ALG_HMAC,        "HMAC"},
  { 0, NULL}
};

#define KRB_SEAL_ALG_DES_CBC	0x0000
#define KRB_SEAL_ALG_RC4	0x0010
#define KRB_SEAL_ALG_NONE	0xffff

static const value_string spnego_krb5_seal_alg_vals[] = {
  { KRB_SEAL_ALG_DES_CBC, "DES CBC"},
  { KRB_SEAL_ALG_RC4,     "RC4"},
  { KRB_SEAL_ALG_NONE,    "None"},
  { 0, NULL}
};

/*
 * XXX - is this for SPNEGO or just GSS-API?
 * RFC 1964 is "The Kerberos Version 5 GSS-API Mechanism"; presumably one
 * can directly designate Kerberos V5 as a mechanism in GSS-API, rather
 * than designating SPNEGO as the mechanism, offering Kerberos V5, and
 * getting it accepted.
 */
static int
dissect_spnego_krb5_getmic_base(tvbuff_t *tvb, int offset, packet_info *pinfo, proto_tree *tree);
static int
dissect_spnego_krb5_wrap_base(tvbuff_t *tvb, int offset, packet_info *pinfo, proto_tree *tree, guint16 token_id);

static void
dissect_spnego_krb5(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
	proto_item *item;
	proto_tree *subtree;
	int offset = 0;
	guint16 token_id;
	gchar oid[MAX_OID_STR_LEN];
	gssapi_oid_value *value;
	tvbuff_t *krb5_tvb;
	gint8 class;
	gboolean pc, ind = 0;
	gint32 tag;
	guint32 len;


	item = proto_tree_add_item(tree, hf_spnego_krb5, tvb, offset, 
				   -1, FALSE);

	subtree = proto_item_add_subtree(item, ett_spnego_krb5);

	/*
	 * The KRB5 blob conforms to RFC1964:
	 * [APPLICATION 0] {
	 *   OID,
	 *   USHORT (0x0001 == AP-REQ, 0x0002 == AP-REP, 0x0003 == ERROR),
	 *   OCTET STRING } 
         *
         * However, for some protocols, the KRB5 blob starts at the SHORT
	 * and has no DER encoded header etc.
	 *
	 * It appears that for some other protocols the KRB5 blob is just
	 * a Kerberos message, with no [APPLICATION 0] header, no OID,
	 * and no USHORT.
	 *
	 * So:
	 *
	 *	If we see an [APPLICATION 0] HEADER, we show the OID and
	 *	the USHORT, and then dissect the rest as a Kerberos message.
	 *
	 *	If we see an [APPLICATION 14] or [APPLICATION 15] header,
	 *	we assume it's an AP-REQ or AP-REP message, and dissect
	 *	it all as a Kerberos message.
	 *
	 *	Otherwise, we show the USHORT, and then dissect the rest
	 *	as a Kerberos message.
	 */

	/*
	 * Get the first header ...
	 */
	offset = dissect_ber_identifier(pinfo, subtree, tvb, offset, &class, &pc, &tag);
	offset = dissect_ber_length(pinfo, subtree, tvb, offset, &len, &ind);

	if (class == BER_CLASS_APP && pc == 1) {
	    /*
	     * [APPLICATION <tag>]
	     */
	    switch (tag) {

	    case 0:
		/*
		 * [APPLICATION 0]
		 */

		/* Next, the OID */
		offset=dissect_ber_object_identifier(FALSE, pinfo, subtree, tvb, offset, hf_spnego_krb5_oid, oid);

		value = gssapi_lookup_oid_str(oid);

		token_id = tvb_get_letohs(tvb, offset);
		proto_tree_add_uint(subtree, hf_spnego_krb5_tok_id, tvb, offset, 2,
				    token_id);

		offset += 2;

		break;

	    case 14:	/* [APPLICATION 14] */
	    case 15:	/* [APPLICATION 15] */
		/*
		 * No token ID - just dissect as a Kerberos message and
		 * return.
		 */
		offset = dissect_kerberos_main(tvb, pinfo, subtree, FALSE, NULL);
		return;

	    default:
		proto_tree_add_text(subtree, tvb, offset, 0,
			"Unknown header (class=%d, pc=%d, tag=%d)",
			class, pc, tag);
		goto done;
	    }
	} else {
	    /* Next, the token ID ... */

	    token_id = tvb_get_letohs(tvb, offset);
	    proto_tree_add_uint(subtree, hf_spnego_krb5_tok_id, tvb, offset, 2,
				token_id);

	    offset += 2;
	}

	switch (token_id) {

	case KRB_TOKEN_AP_REQ:
	case KRB_TOKEN_AP_REP:
	case KRB_TOKEN_AP_ERR:
	  krb5_tvb = tvb_new_subset(tvb, offset, -1, -1); 
	  offset = dissect_kerberos_main(krb5_tvb, pinfo, subtree, FALSE, NULL);
	  break;

	case KRB_TOKEN_GETMIC:
	  offset = dissect_spnego_krb5_getmic_base(tvb, offset, pinfo, subtree); 
	  break;

	case KRB_TOKEN_WRAP:
          offset = dissect_spnego_krb5_wrap_base(tvb, offset, pinfo, subtree, token_id);
	  break;

	case KRB_TOKEN_DELETE_SEC_CONTEXT:

	  break;

	default:

	  break;
	}

 done:
	return;
}

#ifdef HAVE_KERBEROS
#include <epan/crypt-md5.h>

#ifndef KEYTYPE_ARCFOUR_56
# define KEYTYPE_ARCFOUR_56 24
#endif
/* XXX - We should probably do a configure-time check for this instead */
#ifndef KRB5_KU_USAGE_SEAL
# define KRB5_KU_USAGE_SEAL 22
#endif

static int
arcfour_mic_key(void *key_data, size_t key_size, int key_type,
		void *cksum_data, size_t cksum_size,
		void *key6_data)
{
    guint8 k5_data[16];
    guint8 T[4];

    memset(T, 0, 4);

    if (key_type == KEYTYPE_ARCFOUR_56) {
	guint8 L40[14] = "fortybits";

	memcpy(L40 + 10, T, sizeof(T));
	md5_hmac(
                L40, 14,  
                key_data,
                key_size, 
	    	k5_data);
	memset(&k5_data[7], 0xAB, 9);
    } else {
	md5_hmac(
                T, 4,  
                key_data,
                key_size,
	    	k5_data);
    }

    md5_hmac(
	cksum_data, cksum_size,  
	k5_data,
	16, 
	key6_data);

    return 0;
}

static int
usage2arcfour(int usage)
{
    switch (usage) {
    case 3: /*KRB5_KU_AS_REP_ENC_PART 3 */
    case 9: /*KRB5_KU_TGS_REP_ENC_PART_SUB_KEY 9 */
	return 8;
    case 22: /*KRB5_KU_USAGE_SEAL 22 */
	return 13;
    case 23: /*KRB5_KU_USAGE_SIGN 23 */
        return 15;
    case 24: /*KRB5_KU_USAGE_SEQ 24 */
	return 0;
    default :
	return 0;
    }
}

static int
arcfour_mic_cksum(guint8 *key_data, int key_length,
		  unsigned usage,
		  u_char sgn_cksum[8],
		  const void *v1, size_t l1,
		  const void *v2, size_t l2,
		  const void *v3, size_t l3)
{
    const guint8 signature[] = "signaturekey";
    guint8 ksign_c[16];
    unsigned char t[4];
    md5_state_t ms;
    unsigned char digest[16];
    int rc4_usage;
    guint8 cksum[16];
    
    rc4_usage=usage2arcfour(usage);
    md5_hmac(signature, sizeof(signature), 
		key_data, key_length, 
		ksign_c);
    md5_init(&ms);
    t[0] = (rc4_usage >>  0) & 0xFF;
    t[1] = (rc4_usage >>  8) & 0xFF;
    t[2] = (rc4_usage >> 16) & 0xFF;
    t[3] = (rc4_usage >> 24) & 0xFF;
    md5_append(&ms, t, 4);
    md5_append(&ms, v1, l1);
    md5_append(&ms, v2, l2);
    md5_append(&ms, v3, l3);
    md5_finish(&ms, digest);
    md5_hmac(digest, 16, ksign_c, 16, cksum);

    memcpy(sgn_cksum, cksum, 8);

    return 0;
}

/*
 * Verify padding of a gss wrapped message and return its length.
 */
static int
gssapi_verify_pad(unsigned char *wrapped_data, int wrapped_length, 
		   size_t datalen,
		   size_t *padlen)
{
    unsigned char *pad;
    size_t padlength;
    int i;

    pad = wrapped_data + wrapped_length - 1;
    padlength = *pad;

    if (padlength > datalen)
	return 1;

    for (i = padlength; i > 0 && *pad == padlength; i--, pad--)
	;
    if (i != 0)
	return 2;

    *padlen = padlength;

    return 0;
}

static int
decrypt_arcfour(packet_info *pinfo,
	 guint8 *input_message_buffer,
	 guint8 *output_message_buffer,
	 guint8 *key_value, int key_size, int key_type)
{
    guint8 Klocaldata[16];
    int ret;
    gint32 seq_number;
    size_t datalen;
    guint8 k6_data[16], SND_SEQ[8], Confounder[8];
    guint8 cksum_data[8];
    int cmp;
    int conf_flag;
    size_t padlen = 0;

    datalen = tvb_length(pinfo->gssapi_encrypted_tvb);

    if(tvb_get_ntohs(pinfo->gssapi_wrap_tvb, 4)==0x1000){
	conf_flag=1;
    } else if (tvb_get_ntohs(pinfo->gssapi_wrap_tvb, 4)==0xffff){
	conf_flag=0;
    } else {
	return -3;
    }

    if(tvb_get_ntohs(pinfo->gssapi_wrap_tvb, 6)!=0xffff){
	return -4;
    }

    ret = arcfour_mic_key(key_value, key_size, key_type,
			  (void *)tvb_get_ptr(pinfo->gssapi_wrap_tvb, 16, 8),
			  8, /* SGN_CKSUM */
			  k6_data);
    if (ret) {
	return -5;
    }

    {
	rc4_state_struct rc4_state;
	
	crypt_rc4_init(&rc4_state, k6_data, sizeof(k6_data));
	memcpy(SND_SEQ, (unsigned char *)tvb_get_ptr(pinfo->gssapi_wrap_tvb, 8, 8), 8);
	crypt_rc4(&rc4_state, SND_SEQ, 8);

	memset(k6_data, 0, sizeof(k6_data));
    }

    seq_number=g_ntohl(*((guint32 *)SND_SEQ));

    cmp = memcmp(&SND_SEQ[4], "\xff\xff\xff\xff", 4);
    if(cmp){
	cmp = memcmp(&SND_SEQ[4], "\x00\x00\x00\x00", 4);
    }

    if (cmp != 0) {
	return -6;
    }

    {
	int i;

	for (i = 0; i < 16; i++)
	    Klocaldata[i] = ((u_char *)key_value)[i] ^ 0xF0;
    }
    ret = arcfour_mic_key(Klocaldata,sizeof(Klocaldata),key_type,
			  SND_SEQ, 4,
			  k6_data);
    memset(Klocaldata, 0, sizeof(Klocaldata));
    if (ret) {
	return -7;
    }

    if(conf_flag) {
	rc4_state_struct rc4_state;

	crypt_rc4_init(&rc4_state, k6_data, sizeof(k6_data));
	memcpy(Confounder, (unsigned char *)tvb_get_ptr(pinfo->gssapi_wrap_tvb, 24, 8), 8);
	crypt_rc4(&rc4_state, Confounder, 8);
	memcpy(output_message_buffer, input_message_buffer, datalen);
	crypt_rc4(&rc4_state, output_message_buffer, datalen);
    } else {
	memcpy(Confounder, 
		tvb_get_ptr(pinfo->gssapi_wrap_tvb, 24, 8), 
		8); /* Confounder */
	memcpy(output_message_buffer, 
		input_message_buffer, 
	        datalen);
    }
    memset(k6_data, 0, sizeof(k6_data));

    /* only normal (i.e. non DCE style  wrapping use padding ? */
    if(pinfo->decrypt_gssapi_tvb==DECRYPT_GSSAPI_NORMAL){
	ret = gssapi_verify_pad(output_message_buffer,datalen,datalen, &padlen);
    	if (ret) {
	    return -9;
	}
	datalen -= padlen;
    }

    /* dont know what the checksum looks like for dce style gssapi */
    if(pinfo->decrypt_gssapi_tvb==DECRYPT_GSSAPI_NORMAL){
	ret = arcfour_mic_cksum(key_value, key_size,
			    KRB5_KU_USAGE_SEAL,
			    cksum_data, 
			    tvb_get_ptr(pinfo->gssapi_wrap_tvb, 0, 8), 8,
			    Confounder, sizeof(Confounder),
			    output_message_buffer, 
			    datalen + padlen);
	if (ret) {
	    return -10;
	}

	cmp = memcmp(cksum_data, 
	    tvb_get_ptr(pinfo->gssapi_wrap_tvb, 16, 8),
	    8); /* SGN_CKSUM */
	if (cmp) {
	    return -11;
	}
    }

    return datalen;
}



#if defined(HAVE_HEIMDAL_KERBEROS) || defined(HAVE_MIT_KERBEROS)

static void
decrypt_gssapi_krb_arcfour_wrap(proto_tree *tree, packet_info *pinfo, tvbuff_t *tvb, int keytype)
{
	int ret;
	enc_key_t *ek;
	int length;
	const guint8 *original_data;

	static int omb_index=0;
	static guint8 *omb_arr[4]={NULL,NULL,NULL,NULL};
	static guint8 *cryptocopy=NULL; /* workaround for pre-0.6.1 heimdal bug */
	guint8 *output_message_buffer;

	omb_index++;
	if(omb_index>=4){
		omb_index=0;
	}
	output_message_buffer=omb_arr[omb_index];


	length=tvb_length(pinfo->gssapi_encrypted_tvb);
	original_data=tvb_get_ptr(pinfo->gssapi_encrypted_tvb, 0, length);

	/* dont do anything if we are not attempting to decrypt data */
/*
	if(!krb_decrypt){
		return;
	}
*/
	/* XXX we should only do this for first time, then store somewhere */
	/* XXX We also need to re-read the keytab when the preference changes */

	cryptocopy=ep_alloc(length);
	if(output_message_buffer){
		g_free(output_message_buffer);
		output_message_buffer=NULL;
	}
	output_message_buffer=g_malloc(length);

	for(ek=enc_key_list;ek;ek=ek->next){
		/* shortcircuit and bail out if enctypes are not matching */
		if(ek->keytype!=keytype){
			continue;
		}

		/* pre-0.6.1 versions of Heimdal would sometimes change
		  the cryptotext data even when the decryption failed.
		  This would obviously not work since we iterate over the
		  keys. So just give it a copy of the crypto data instead.
		  This has been seen for RC4-HMAC blobs.
		*/
		memcpy(cryptocopy, original_data, length);
		ret=decrypt_arcfour(pinfo,
				cryptocopy,
				output_message_buffer,
				ek->keyvalue,
				ek->keylength,
				ek->keytype
					    );
		if (ret >= 0) {
			proto_tree_add_text(tree, NULL, 0, 0, "[Decrypted using: %s]", ek->key_origin);
			pinfo->gssapi_decrypted_tvb=tvb_new_real_data(
				output_message_buffer,
				ret, ret);
			tvb_set_child_real_data_tvbuff(tvb, pinfo->gssapi_decrypted_tvb);
			add_new_data_source(pinfo, pinfo->gssapi_decrypted_tvb, "Decrypted GSS-Krb5");
			return;
		}
	}
	return;
}
#endif /* HAVE_HEIMDAL_KERBEROS || HAVE_MIT_KERBEROS */


#endif

/*
 * XXX - This is for GSSAPI Wrap tokens ...
 */
static int
dissect_spnego_krb5_wrap_base(tvbuff_t *tvb, int offset, packet_info *pinfo
#ifndef HAVE_KERBEROS
	_U_
#endif
    , proto_tree *tree, guint16 token_id
#ifndef HAVE_KERBEROS
	_U_
#endif
    )
{
	guint16 sgn_alg, seal_alg;
#ifdef HAVE_KERBEROS
	int start_offset=offset;
#endif

	/*
	 * The KRB5 blob conforms to RFC1964:
	 *   USHORT (0x0102 == GSS_Wrap)
	 *   and so on } 
	 */

	/* Now, the sign and seal algorithms ... */

	sgn_alg = tvb_get_letohs(tvb, offset);
	proto_tree_add_uint(tree, hf_spnego_krb5_sgn_alg, tvb, offset, 2,
			    sgn_alg);

	offset += 2;

	seal_alg = tvb_get_letohs(tvb, offset);
	proto_tree_add_uint(tree, hf_spnego_krb5_seal_alg, tvb, offset, 2,
			    seal_alg);

	offset += 2;

	/* Skip the filler */

	offset += 2;

	/* Encrypted sequence number */

	proto_tree_add_item(tree, hf_spnego_krb5_snd_seq, tvb, offset, 8,
			    TRUE);

	offset += 8;

	/* Checksum of plaintext padded data */

	proto_tree_add_item(tree, hf_spnego_krb5_sgn_cksum, tvb, offset, 8,
			    TRUE);

	offset += 8;

	/*
	 * At least according to draft-brezak-win2k-krb-rc4-hmac-04,
	 * if the signing algorithm is KRB_SGN_ALG_HMAC, there's an
	 * extra 8 bytes of "Random confounder" after the checksum.
	 * It certainly confounds code expecting all Kerberos 5
	 * GSS_Wrap() tokens to look the same....
	 */
	if (sgn_alg == KRB_SGN_ALG_HMAC) {
	  proto_tree_add_item(tree, hf_spnego_krb5_confounder, tvb, offset, 8,
			      TRUE);
	  offset += 8;
	}

	/* Is the data encrypted? */
	pinfo->gssapi_data_encrypted=(seal_alg!=KRB_SEAL_ALG_NONE);

#ifdef HAVE_KERBEROS
#define GSS_ARCFOUR_WRAP_TOKEN_SIZE 32
	if(pinfo->decrypt_gssapi_tvb){
		/* if the caller did not provide a tvb, then we just use
		   whatever is left of our current tvb.
		*/
		if(!pinfo->gssapi_encrypted_tvb){
			int len;
			len=tvb_reported_length_remaining(tvb,offset);
			if(len>tvb_length_remaining(tvb, offset)){
				/* no point in trying to decrypt, 
				   we dont have the full pdu.
				*/
				return offset;
			}
			pinfo->gssapi_encrypted_tvb = tvb_new_subset(
					tvb, offset, len, len);
		}
			
		/* if this is KRB5 wrapped rc4-hmac */
		if((token_id==KRB_TOKEN_WRAP)
		 &&(sgn_alg==KRB_SGN_ALG_HMAC)
		 &&(seal_alg==KRB_SEAL_ALG_RC4)){
			/* do we need to create a tvb for the wrapper
			   as well ?
			*/
			if(!pinfo->gssapi_wrap_tvb){
				pinfo->gssapi_wrap_tvb = tvb_new_subset(
					tvb, start_offset-2,
					GSS_ARCFOUR_WRAP_TOKEN_SIZE,
					GSS_ARCFOUR_WRAP_TOKEN_SIZE);
			}
#if defined(HAVE_HEIMDAL_KERBEROS) || defined(HAVE_MIT_KERBEROS)
			decrypt_gssapi_krb_arcfour_wrap(tree,
				pinfo,
				tvb,
				23 /* rc4-hmac */);
#endif /* HAVE_HEIMDAL_KERBEROS || HAVE_MIT_KERBEROS */
		}
	}	
#endif
	/*
	 * Return the offset past the checksum, so that we know where
	 * the data we're wrapped around starts.  Also, set the length
	 * of our top-level item to that offset, so it doesn't cover
	 * the data we're wrapped around.
	 * 
	 * Note that for DCERPC the GSSAPI blobs comes after the data it wraps,
	 * not before.
	 */
	return offset;
}

/*
 * XXX - This is for GSSAPI GetMIC tokens ...
 */
static int
dissect_spnego_krb5_getmic_base(tvbuff_t *tvb, int offset, packet_info *pinfo _U_, proto_tree *tree)
{
	guint16 sgn_alg;

	/*
	 * The KRB5 blob conforms to RFC1964:
	 *   USHORT (0x0101 == GSS_GetMIC)
	 *   and so on } 
	 */

	/* Now, the sign algorithm ... */

	sgn_alg = tvb_get_letohs(tvb, offset);
	proto_tree_add_uint(tree, hf_spnego_krb5_sgn_alg, tvb, offset, 2,
			    sgn_alg);

	offset += 2;

	/* Skip the filler */

	offset += 4;

	/* Encrypted sequence number */

	proto_tree_add_item(tree, hf_spnego_krb5_snd_seq, tvb, offset, 8,
			    TRUE);

	offset += 8;

	/* Checksum of plaintext padded data */

	proto_tree_add_item(tree, hf_spnego_krb5_sgn_cksum, tvb, offset, 8,
			    TRUE);

	offset += 8;

	/*
	 * At least according to draft-brezak-win2k-krb-rc4-hmac-04,
	 * if the signing algorithm is KRB_SGN_ALG_HMAC, there's an
	 * extra 8 bytes of "Random confounder" after the checksum.
	 * It certainly confounds code expecting all Kerberos 5
	 * GSS_Wrap() tokens to look the same....
	 */
	if (sgn_alg == KRB_SGN_ALG_HMAC) {
	  proto_tree_add_item(tree, hf_spnego_krb5_confounder, tvb, offset, 8,
			      TRUE);

	  offset += 8;
	}

	/*
	 * Return the offset past the checksum, so that we know where
	 * the data we're wrapped around starts.  Also, set the length
	 * of our top-level item to that offset, so it doesn't cover
	 * the data we're wrapped around.
	 */

	return offset;
}

/*
 * XXX - is this for SPNEGO or just GSS-API?
 * RFC 1964 is "The Kerberos Version 5 GSS-API Mechanism"; presumably one
 * can directly designate Kerberos V5 as a mechanism in GSS-API, rather
 * than designating SPNEGO as the mechanism, offering Kerberos V5, and
 * getting it accepted.
 */
static int
dissect_spnego_krb5_wrap(tvbuff_t *tvb, packet_info *pinfo _U_, proto_tree *tree)
{
	proto_item *item;
	proto_tree *subtree;
	int offset = 0;
	guint16 token_id;

	item = proto_tree_add_item(tree, hf_spnego_krb5, tvb, 0, -1, FALSE);

	subtree = proto_item_add_subtree(item, ett_spnego_krb5);

	/*
	 * The KRB5 blob conforms to RFC1964:
	 *   USHORT (0x0102 == GSS_Wrap)
	 *   and so on } 
	 */

	/* First, the token ID ... */

	token_id = tvb_get_letohs(tvb, offset);
	proto_tree_add_uint(subtree, hf_spnego_krb5_tok_id, tvb, offset, 2,
			    token_id);

	offset += 2;

        offset = dissect_spnego_krb5_wrap_base(tvb, offset, pinfo, subtree, token_id);

        /*
	 * Return the offset past the checksum, so that we know where
	 * the data we're wrapped around starts.  Also, set the length
	 * of our top-level item to that offset, so it doesn't cover
	 * the data we're wrapped around.
	 */
	proto_item_set_len(item, offset);
	return offset;
}

/* Spnego stuff from here */

static int
dissect_spnego_wrap(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
	proto_item *item;
	proto_tree *subtree;

	int offset = 0;


	/*
	 * We need this later, so lets get it now ...
	 * It has to be per-frame as there can be more than one GSS-API
	 * negotiation in a conversation.
	 */


	item = proto_tree_add_item(tree, hf_spnego, tvb, offset, 
				   -1, FALSE);

	subtree = proto_item_add_subtree(item, ett_spnego);
	/*
	 * The TVB contains a [0] header and a sequence that consists of an
	 * object ID and a blob containing the data ...
	 * XXX - is this RFC 2743's "Mechanism-Independent Token Format",
	 * with the "optional" "use in non-initial tokens" being chosen.
	 * ASN1 code addet to spnego.asn to handle this.
	 */

	offset = dissect_spnego_InitialContextToken(FALSE, tvb, offset, pinfo , subtree, -1);

	return offset;
}


static void
dissect_spnego(tvbuff_t *tvb, packet_info *pinfo, proto_tree *parent_tree)
{
	proto_item *item;
	proto_tree *subtree;
	int offset = 0;
	conversation_t *conversation;

	/*
	 * We need this later, so lets get it now ...
	 * It has to be per-frame as there can be more than one GSS-API
	 * negotiation in a conversation.
	 */

	next_level_value = p_get_proto_data(pinfo->fd, proto_spnego);
	if (!next_level_value && !pinfo->fd->flags.visited) {
	    /*
	     * No handle attached to this frame, but it's the first
	     * pass, so it'd be attached to the conversation.
	     * If we have a conversation, try to get the handle,
	     * and if we get one, attach it to the frame.
	     */
	    conversation = find_conversation(pinfo->fd->num, &pinfo->src, &pinfo->dst,
					     pinfo->ptype, pinfo->srcport,
					     pinfo->destport, 0);

	    if (conversation) {
		next_level_value = conversation_get_proto_data(conversation, 
							       proto_spnego);
		if (next_level_value)
		    p_add_proto_data(pinfo->fd, proto_spnego, next_level_value);
	    }
	}

	item = proto_tree_add_item(parent_tree, hf_spnego, tvb, offset, 
				   -1, FALSE);

	subtree = proto_item_add_subtree(item, ett_spnego);

	/*
	 * The TVB contains a [0] header and a sequence that consists of an
	 * object ID and a blob containing the data ...
	 * Actually, it contains, according to RFC2478:
     * NegotiationToken ::= CHOICE {
	 *          negTokenInit [0] NegTokenInit,
	 *          negTokenTarg [1] NegTokenTarg }
	 * NegTokenInit ::= SEQUENCE {
	 *          mechTypes [0] MechTypeList OPTIONAL,
	 *          reqFlags [1] ContextFlags OPTIONAL,
	 *          mechToken [2] OCTET STRING OPTIONAL,
	 *          mechListMIC [3] OCTET STRING OPTIONAL }
     * NegTokenTarg ::= SEQUENCE {
	 *          negResult [0] ENUMERATED {
	 *              accept_completed (0),
	 *              accept_incomplete (1),
	 *              reject (2) } OPTIONAL,
     *          supportedMech [1] MechType OPTIONAL,
     *          responseToken [2] OCTET STRING OPTIONAL,
     *          mechListMIC [3] OCTET STRING OPTIONAL }
     *
	 * Windows typically includes mechTypes and mechListMic ('NONE'
	 * in the case of NTLMSSP only).
     * It seems to duplicate the responseToken into the mechListMic field
     * as well. Naughty, naughty.
     *
	 */
	offset = dissect_spnego_NegotiationToken(FALSE, tvb, offset, pinfo, subtree, -1);

}

/*--- proto_register_spnego -------------------------------------------*/
void proto_register_spnego(void) {

  /* List of fields */
  static hf_register_info hf[] = {
		{ &hf_spnego,
		  { "SPNEGO", "spnego", FT_NONE, BASE_NONE, NULL, 0x0,
		    "SPNEGO", HFILL }},
	  { &hf_spnego_wraptoken,
		  { "wrapToken", "spnego.wraptoken",
		    FT_NONE, BASE_NONE, NULL, 0x0, "SPNEGO wrapToken",
		    HFILL}},
		{ &hf_spnego_krb5,
		  { "krb5_blob", "spnego.krb5.blob", FT_BYTES,
		    BASE_NONE, NULL, 0, "krb5_blob", HFILL }},
		{&hf_spnego_krb5_oid,
		{"KRB5 OID", "spnego.krb5_oid", FT_STRING, 
			BASE_NONE, NULL, 0, "KRB5 OID", HFILL }},
		{ &hf_spnego_krb5_tok_id,
		  { "krb5_tok_id", "spnego.krb5.tok_id", FT_UINT16, BASE_HEX,
		    VALS(spnego_krb5_tok_id_vals), 0, "KRB5 Token Id", HFILL}},
		{ &hf_spnego_krb5_sgn_alg,
		  { "krb5_sgn_alg", "spnego.krb5.sgn_alg", FT_UINT16, BASE_HEX,
		    VALS(spnego_krb5_sgn_alg_vals), 0, "KRB5 Signing Algorithm", HFILL}},
		{ &hf_spnego_krb5_seal_alg,
		  { "krb5_seal_alg", "spnego.krb5.seal_alg", FT_UINT16, BASE_HEX,
		    VALS(spnego_krb5_seal_alg_vals), 0, "KRB5 Sealing Algorithm", HFILL}},
		{ &hf_spnego_krb5_snd_seq,
		  { "krb5_snd_seq", "spnego.krb5.snd_seq", FT_BYTES, BASE_NONE,
		    NULL, 0, "KRB5 Encrypted Sequence Number", HFILL}},
		{ &hf_spnego_krb5_sgn_cksum,
		  { "krb5_sgn_cksum", "spnego.krb5.sgn_cksum", FT_BYTES, BASE_NONE,
		    NULL, 0, "KRB5 Data Checksum", HFILL}},
		{ &hf_spnego_krb5_confounder,
		  { "krb5_confounder", "spnego.krb5.confounder", FT_BYTES, BASE_NONE,
		    NULL, 0, "KRB5 Confounder", HFILL}},

#include "packet-spnego-hfarr.c"
  };

  /* List of subtrees */
  static gint *ett[] = {
		&ett_spnego,
		&ett_spnego_wraptoken,
		&ett_spnego_krb5,

#include "packet-spnego-ettarr.c"
  };

  /* Register protocol */
  proto_spnego = proto_register_protocol(PNAME, PSNAME, PFNAME);

	proto_spnego_krb5 = proto_register_protocol("SPNEGO-KRB5",
						    "SPNEGO-KRB5",
						    "spnego-krb5");
  /* Register fields and subtrees */
  proto_register_field_array(proto_spnego, hf, array_length(hf));
  proto_register_subtree_array(ett, array_length(ett));

}


/*--- proto_reg_handoff_spnego ---------------------------------------*/
void proto_reg_handoff_spnego(void) {

	dissector_handle_t spnego_handle, spnego_wrap_handle;
	dissector_handle_t spnego_krb5_handle, spnego_krb5_wrap_handle;

	/* Register protocol with GSS-API module */

	spnego_handle = create_dissector_handle(dissect_spnego, proto_spnego);
	spnego_wrap_handle = new_create_dissector_handle(dissect_spnego_wrap,
							 proto_spnego);
	gssapi_init_oid("1.3.6.1.5.5.2", proto_spnego, ett_spnego,
	    spnego_handle, spnego_wrap_handle,
	    "SPNEGO - Simple Protected Negotiation");

	/* Register both the one MS created and the real one */
	/*
	 * Thanks to Jean-Baptiste Marchand and Richard B Ward, the
	 * mystery of the MS KRB5 OID is cleared up. It was due to a library
	 * that did not handle OID components greater than 16 bits, and was
	 * fixed in Win2K SP2 as well as WinXP.
	 * See the archive of <ietf-krb-wg@anl.gov> for the thread topic
	 * SPNEGO implementation issues. 3-Dec-2002.
	 */
	spnego_krb5_handle = create_dissector_handle(dissect_spnego_krb5,
						     proto_spnego_krb5);
	spnego_krb5_wrap_handle = new_create_dissector_handle(dissect_spnego_krb5_wrap,
							      proto_spnego_krb5);
	gssapi_init_oid("1.2.840.48018.1.2.2", proto_spnego_krb5, ett_spnego_krb5,
			spnego_krb5_handle, spnego_krb5_wrap_handle,
			"MS KRB5 - Microsoft Kerberos 5");
	gssapi_init_oid("1.2.840.113554.1.2.2", proto_spnego_krb5, ett_spnego_krb5,
			spnego_krb5_handle, spnego_krb5_wrap_handle,
			"KRB5 - Kerberos 5");
	gssapi_init_oid("1.2.840.113554.1.2.2.3", proto_spnego_krb5, ett_spnego_krb5,
			spnego_krb5_handle, spnego_krb5_wrap_handle,
			"KRB5 - Kerberos 5 - User to User");

	/*
	 * Find the data handle for some calls
	 */
	data_handle = find_dissector("data");

}