/* packet-gssapi.c
 * Dissector for GSS-API tokens as described in rfc2078, section 3.1
 * Copyright 2002, Tim Potter <tpot@samba.org>
 * Copyright 2002, Richard Sharpe <rsharpe@samba.org> Added a few 
 *		   bits and pieces ...
 *
 * $Id: packet-gssapi.c,v 1.28 2003/11/16 23:17:19 guy Exp $
 *
 * 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.
 */

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

#ifdef HAVE_SYS_TYPES_H
# include <sys/types.h>
#endif

#include <string.h>

#include <glib.h>
#include <epan/packet.h>

#include "asn1.h"
#include "format-oid.h"
#include "packet-dcerpc.h"
#include "packet-gssapi.h"
#include "packet-frame.h"
#include "epan/conversation.h"

static int proto_gssapi = -1;

static int hf_gssapi = -1;

static gint ett_gssapi = -1;

/*
 * Subdissectors
 */

static GHashTable *gssapi_oids;

static gint gssapi_oid_equal(gconstpointer k1, gconstpointer k2)
{
	const char *key1 = (const char *)k1;
	const char *key2 = (const char *)k2;

	return strcmp(key1, key2) == 0;
}

static guint
gssapi_oid_hash(gconstpointer k)
{
	const char *key = (const char *)k;
	guint hash = 0, i;

	for (i = 0; i < strlen(key); i++)
		hash += key[i];

	return hash;
}

void
gssapi_init_oid(char *oid, int proto, int ett, dissector_handle_t handle,
		dissector_handle_t wrap_handle, gchar *comment)
{
	char *key = g_strdup(oid);
	gssapi_oid_value *value = g_malloc(sizeof(*value));

	value->proto = find_protocol_by_id(proto);
	value->ett = ett;
	value->handle = handle;
	value->wrap_handle = wrap_handle;
	value->comment = comment;

	g_hash_table_insert(gssapi_oids, key, value);
}

/*
 * This takes an OID in binary form, not an OID as a text string, as
 * an argument.
 */
gssapi_oid_value *
gssapi_lookup_oid(subid_t *oid, guint oid_len)
{
	gchar *oid_key;
	gchar *p;
	unsigned int i;
	int len;
	gssapi_oid_value *value;

	/*
	 * Convert the OID to a string, as text strings are used as
	 * keys in the OID hash table.
	 */
	oid_key = g_malloc(oid_len * 22 + 1);
	p = oid_key;
	len = sprintf(p, "%lu", (unsigned long)oid[0]);
	p += len;
	for (i = 1; i < oid_len;i++) {
		len = sprintf(p, ".%lu", (unsigned long)oid[i]);
		p += len;
	}

	value = g_hash_table_lookup(gssapi_oids, oid_key);
	g_free(oid_key);
	return value;
}

/* Display an ASN1 parse error.  Taken from packet-snmp.c */

static dissector_handle_t data_handle;

static void
dissect_parse_error(tvbuff_t *tvb, int offset, packet_info *pinfo,
		    proto_tree *tree, const char *field_name, int ret)
{
	char *errstr;

	errstr = asn1_err_to_str(ret);

	if (tree != NULL) {
		proto_tree_add_text(tree, tvb, offset, 0,
		    "ERROR: Couldn't parse %s: %s", field_name, errstr);
		call_dissector(data_handle,
		    tvb_new_subset(tvb, offset, -1, -1), pinfo, tree);
	}
}

static int
dissect_gssapi_work(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
    gboolean is_verifier)
{
	proto_item *item;
	proto_tree *subtree;
	ASN1_SCK hnd;
	int ret, offset = 0;
	volatile int return_offset = 0;
	gboolean def;
	guint len1, oid_len, cls, con, tag, nbytes;
	subid_t *oid;
	gchar *oid_string;
	gssapi_oid_value *value;
	volatile dissector_handle_t handle;
	conversation_t *volatile conversation;
	tvbuff_t *oid_tvb;
	int len;

	/*
	 * We need this later, so lets get it now ...
	 */

	conversation = find_conversation(&pinfo->src, &pinfo->dst,
					 pinfo->ptype, pinfo->srcport,
					 pinfo->destport, 0);

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

	subtree = proto_item_add_subtree(item, ett_gssapi);

	/*
	 * Catch the ReportedBoundsError exception; the stuff we've been
	 * handed doesn't necessarily run to the end of the packet, it's
	 * an item inside a packet, so if it happens to be malformed (or
	 * we, or a dissector we call, has a bug), so that an exception
	 * is thrown, we want to report the error, but return and let
	 * our caller dissect the rest of the packet.
	 *
	 * If it gets a BoundsError, we can stop, as there's nothing more
	 * in the packet after our blob to see, so we just re-throw the
	 * exception.
	 */
	TRY {
		/* Read header */

		asn1_open(&hnd, tvb, offset);

		ret = asn1_header_decode(&hnd, &cls, &con, &tag, &def, &len1);

		if (ret != ASN1_ERR_NOERROR) {
			dissect_parse_error(tvb, offset, pinfo, subtree,
				    "GSS-API header", ret);
			return_offset = tvb_length(tvb);
			goto done;
		}

		if (!(cls == ASN1_APL && con == ASN1_CON && tag == 0)) {
		  /* 
		   * If we do not recognise an Application class,
		   * then we are probably dealing with an inner context
		   * token or a wrap token, and we should retrieve the
		   * gssapi_oid_value pointer from the per-frame data or,
		   * if there is no per-frame data (as would be the case
		   * the first time we dissect this frame), from the
		   * conversation that exists or that we created from
		   * pinfo (and then make it per-frame data).
		   * We need to make it per-frame data as there can be
		   * more than one GSS-API negotiation in a conversation.
		   *
		   * Note! We "cheat". Since we only need the pointer,
		   * we store that as the data.  (That's not really
		   * "cheating" - the per-frame data and per-conversation
		   * data code doesn't care what you supply as a data
		   * pointer; it just treats it as an opaque pointer, it
		   * doesn't dereference it or free what it points to.)
		   */
		  value = p_get_proto_data(pinfo->fd, proto_gssapi);
		  if (!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. */
		    if (conversation)
		    {
		      value = conversation_get_proto_data(conversation, 
							   proto_gssapi);
		      if (value)
			p_add_proto_data(pinfo->fd, proto_gssapi, value);
		    }
		  }
		  if (!value)
		  {
		    proto_tree_add_text(subtree, tvb, offset, 0,
			"Unknown header (cls=%d, con=%d, tag=%d)",
			cls, con, tag);
		    return_offset = tvb_length(tvb);
		    goto done;
		  }
		  else 
		  {
		    tvbuff_t *oid_tvb;

		    /* Naughty ... no way to reset the offset */
		    /* Account for the fact we have consumed part of the */
		    /* ASN.1 and we want to get it back */

		    hnd.offset = offset;
		    oid_tvb = tvb_new_subset(tvb, offset, -1, -1);
		    if (is_verifier)
			handle = value->wrap_handle;
		    else
			handle = value->handle;
		    len = call_dissector(handle, oid_tvb, pinfo, subtree);
		    if (len == 0)
			return_offset = tvb_length(tvb);
		    else
			return_offset = offset + len;
		    goto done; /* We are finished here */
		  }
		}

		offset = hnd.offset;

		/* Read oid */

		ret = asn1_oid_decode(&hnd, &oid, &oid_len, &nbytes);

		if (ret != ASN1_ERR_NOERROR) {
			dissect_parse_error(tvb, offset, pinfo, subtree,
					    "GSS-API token", ret);
			return_offset = tvb_length(tvb);
			goto done;
		}

		oid_string = format_oid(oid, oid_len);

		/*
		 * Hand off to subdissector.
		 */

		if (((value = gssapi_lookup_oid(oid, oid_len)) == NULL) ||
		    !proto_is_protocol_enabled(value->proto)) {

		        proto_tree_add_text(subtree, tvb, offset, nbytes, 
					    "OID: %s",
					    oid_string);

			offset += nbytes;

			g_free(oid_string);

			/* No dissector for this oid */

			proto_tree_add_text(subtree, tvb, offset, -1,
					    "Token object");

			return_offset = tvb_length(tvb);
			goto done;
		}

		if (value)
		  proto_tree_add_text(subtree, tvb, offset, nbytes, 
				      "OID: %s (%s)",
				      oid_string, value->comment);
		else
		  proto_tree_add_text(subtree, tvb, offset, nbytes, "OID: %s",
				      oid_string);

		offset += nbytes;

		g_free(oid_string);

		/*
		 * This is not needed, as the sub-dissector adds a tree
		sub_item = proto_tree_add_item(subtree, value->proto, tvb,
					       offset, -1, FALSE);

		oid_subtree = proto_item_add_subtree(sub_item, value->ett);
		*/

		/* 
		 * Here we should create a conversation if needed and 
		 * save a pointer to the data for that OID for the
		 * GSSAPI protocol.
		 */

		if (!conversation) { /* Create one */
		  conversation = conversation_new(&pinfo->src,
						  &pinfo->dst, 
						  pinfo->ptype, 
						  pinfo->srcport, 
						  pinfo->destport, 0);
		}

		/*
		 * Now add the proto data ... 
		 * but only if it is not already there.
		 */

		if (!conversation_get_proto_data(conversation,
						 proto_gssapi)) {
		  conversation_add_proto_data(conversation,
					      proto_gssapi, value);
		}

		if (is_verifier) {
			handle = value->wrap_handle;
			if (handle != NULL) {
				oid_tvb = tvb_new_subset(tvb, offset, -1, -1);
				len = call_dissector(handle, oid_tvb, pinfo,
				    subtree);
				if (len == 0)
					return_offset = tvb_length(tvb);
				else
					return_offset = offset + len;
			} else {
				proto_tree_add_text(subtree, tvb, offset, -1,
				    "Authentication verifier");
				return_offset = tvb_length(tvb);
			}
		} else {
			handle = value->handle;
			if (handle != NULL) {
				oid_tvb = tvb_new_subset(tvb, offset, -1, -1);
				len = call_dissector(handle, oid_tvb, pinfo,
				    subtree);
				if (len == 0)
					return_offset = tvb_length(tvb);
				else
					return_offset = offset + len;
			} else {
				proto_tree_add_text(subtree, tvb, offset, -1,
				    "Authentication credentials");
				return_offset = tvb_length(tvb);
			}
		}

	 done:
		asn1_close(&hnd, &offset);
	} CATCH(BoundsError) {
		RETHROW;
	} CATCH(ReportedBoundsError) {
		show_reported_bounds_error(tvb, pinfo, tree);
	} ENDTRY;

	proto_item_set_len(item, return_offset);
	return return_offset;
}

static void
dissect_gssapi(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
	dissect_gssapi_work(tvb, pinfo, tree, FALSE);
}

static int
dissect_gssapi_verf(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
	return dissect_gssapi_work(tvb, pinfo, tree, TRUE);
}

void
proto_register_gssapi(void)
{
	static hf_register_info hf[] = {
		{ &hf_gssapi,
		  { "GSS-API", "gss-api", FT_NONE, BASE_NONE, NULL, 0x0,
		    "GSS-API", HFILL }},
	};

	static gint *ett[] = {
		&ett_gssapi,
	};

	proto_gssapi = proto_register_protocol(
		"Generic Security Service Application Program Interface",
		"GSS-API", "gss-api");

	proto_register_field_array(proto_gssapi, hf, array_length(hf));
	proto_register_subtree_array(ett, array_length(ett));

	register_dissector("gssapi", dissect_gssapi, proto_gssapi);
	new_register_dissector("gssapi_verf", dissect_gssapi_verf, proto_gssapi);

	gssapi_oids = g_hash_table_new(gssapi_oid_hash, gssapi_oid_equal);
}

static int wrap_dissect_gssapi(tvbuff_t *tvb, int offset, 
			       packet_info *pinfo, 
			       proto_tree *tree, char *drep _U_)
{
	tvbuff_t *auth_tvb;

	auth_tvb = tvb_new_subset(
		tvb, offset, tvb_length_remaining(tvb, offset),
		tvb_length_remaining(tvb, offset));

	dissect_gssapi(auth_tvb, pinfo, tree);

	return tvb_length_remaining(tvb, offset);
}

static int wrap_dissect_gssapi_verf(tvbuff_t *tvb, int offset, 
				    packet_info *pinfo, 
				    proto_tree *tree, char *drep _U_)
{
	tvbuff_t *auth_tvb;

	auth_tvb = tvb_new_subset(
		tvb, offset, tvb_length_remaining(tvb, offset),
		tvb_length_remaining(tvb, offset));

	return dissect_gssapi_verf(auth_tvb, pinfo, tree);
}

static dcerpc_auth_subdissector_fns gssapi_auth_fns = {
	wrap_dissect_gssapi,		        /* Bind */
	wrap_dissect_gssapi,	 	        /* Bind ACK */
	wrap_dissect_gssapi,			/* AUTH3 */
	wrap_dissect_gssapi_verf, 		/* Request verifier */
	wrap_dissect_gssapi_verf,		/* Response verifier */
	NULL,			                /* Request data */
	NULL			                /* Response data */
};

void
proto_reg_handoff_gssapi(void)
{
	data_handle = find_dissector("data");

	register_dcerpc_auth_subdissector(DCE_C_AUTHN_LEVEL_PKT_PRIVACY,
					  DCE_C_RPC_AUTHN_PROTOCOL_SPNEGO,
					  &gssapi_auth_fns);
}