path: root/lib/gnutls_extensions.c

/*
 * Copyright (C) 2001,2002,2003 Nikos Mavroyanopoulos
 * Copyright (C) 2004 Free Software Foundation
 *
 * This file is part of GNUTLS.
 *
 *  The GNUTLS library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public   
 *  License as published by the Free Software Foundation; either 
 *  version 2.1 of the License, or (at your option) any later version.
 *
 *  This library 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
 *  Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public
 *  License along with this library; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307  USA
 *
 */

/* Functions that relate to the TLS hello extension parsing.
 * Hello extensions are packets appended in the TLS hello packet, and
 * allow for extra functionality.
 */

#include "gnutls_int.h"
#include "gnutls_extensions.h"
#include "gnutls_errors.h"
#include "ext_max_record.h"
#include <ext_cert_type.h>
#include <ext_server_name.h>
#include "gnutls_num.h"

/* Key Exchange Section */
#define GNUTLS_EXTENSION_ENTRY(type, ext_func_recv, ext_func_send) \
	{ #type, type, ext_func_recv, ext_func_send }


#define MAX_EXT_SIZE 10
const int _gnutls_extensions_size = MAX_EXT_SIZE;

gnutls_extension_entry _gnutls_extensions[MAX_EXT_SIZE] = {
    GNUTLS_EXTENSION_ENTRY(GNUTLS_EXTENSION_MAX_RECORD_SIZE,
			   _gnutls_max_record_recv_params,
			   _gnutls_max_record_send_params),
    GNUTLS_EXTENSION_ENTRY(GNUTLS_EXTENSION_CERT_TYPE,
			   _gnutls_cert_type_recv_params,
			   _gnutls_cert_type_send_params),
    GNUTLS_EXTENSION_ENTRY(GNUTLS_EXTENSION_SERVER_NAME,
			   _gnutls_server_name_recv_params,
			   _gnutls_server_name_send_params),
    {0, 0, 0, 0}
};

#define GNUTLS_EXTENSION_LOOP2(b) \
        gnutls_extension_entry *p; \
                for(p = _gnutls_extensions; p->name != NULL; p++) { b ; }

#define GNUTLS_EXTENSION_LOOP(a) \
                        GNUTLS_EXTENSION_LOOP2( if(p->type == type) { a; break; } )


/* EXTENSION functions */

ext_recv_func _gnutls_ext_func_recv(uint16 type)
{
    ext_recv_func ret = NULL;
    GNUTLS_EXTENSION_LOOP(ret = p->gnutls_ext_func_recv);
    return ret;

}

ext_send_func _gnutls_ext_func_send(uint16 type)
{
    ext_send_func ret = NULL;
    GNUTLS_EXTENSION_LOOP(ret = p->gnutls_ext_func_send);
    return ret;

}

const char *_gnutls_extension_get_name(uint16 type)
{
    const char *ret = NULL;

    /* avoid prefix */
    GNUTLS_EXTENSION_LOOP(ret = p->name + sizeof("GNUTLS_EXTENSION_") - 1);

    return ret;
}

/* Checks if the extension we just received is one of the 
 * requested ones. Otherwise it's a fatal error.
 */
static int _gnutls_extension_list_check(gnutls_session_t session,
					uint16 type)
{
    if (session->security_parameters.entity == GNUTLS_CLIENT) {
	int i;
	for (i = 0; i < session->internals.extensions_sent_size; i++) {
	    if (type == session->internals.extensions_sent[i])
		return 0;	/* ok found */
	}
	return GNUTLS_E_RECEIVED_ILLEGAL_EXTENSION;
    }

    return 0;
}

int _gnutls_parse_extensions(gnutls_session_t session, const opaque * data,
			     int data_size)
{
    int next, ret;
    int pos = 0;
    uint16 type;
    const opaque *sdata;
    ext_recv_func ext_recv;
    uint16 size;

#ifdef DEBUG
    int i;

    if (session->security_parameters.entity == GNUTLS_CLIENT)
	for (i = 0; i < session->internals.extensions_sent_size; i++) {
	    _gnutls_debug_log("EXT[%d]: expecting extension '%s'\n",
			      session,
			      _gnutls_extension_get_name(session->
							 internals.
							 extensions_sent
							 [i]));
	}
#endif

    DECR_LENGTH_RET(data_size, 2, 0);
    next = _gnutls_read_uint16(data);
    pos += 2;

    DECR_LENGTH_RET(data_size, next, 0);

    do {
	DECR_LENGTH_RET(next, 2, 0);
	type = _gnutls_read_uint16(&data[pos]);
	pos += 2;

	_gnutls_debug_log("EXT[%x]: Received extension '%s'\n", session,
			  _gnutls_extension_get_name(type));

	if ((ret = _gnutls_extension_list_check(session, type)) < 0) {
	    gnutls_assert();
	    return ret;
	}

	DECR_LENGTH_RET(next, 2, 0);
	size = _gnutls_read_uint16(&data[pos]);
	pos += 2;

	DECR_LENGTH_RET(next, size, 0);
	sdata = &data[pos];
	pos += size;

	ext_recv = _gnutls_ext_func_recv(type);
	if (ext_recv == NULL)
	    continue;
	if ((ret = ext_recv(session, sdata, size)) < 0) {
	    gnutls_assert();
	    return ret;
	}

    } while (next > 2);

    return 0;

}

/* Adds the extension we want to send in the extensions list.
 * This list is used to check whether the (later) received
 * extensions are the ones we requested.
 */
static void _gnutls_extension_list_add(gnutls_session_t session, uint16 type)
{

    if (session->security_parameters.entity == GNUTLS_CLIENT) {
	if (session->internals.extensions_sent_size < MAX_EXT_TYPES) {
	    session->internals.extensions_sent[session->internals.
					       extensions_sent_size] =
		type;
	    session->internals.extensions_sent_size++;
	} else {
	    _gnutls_debug_log("extensions: Increase MAX_EXT_TYPES\n");
	}
    }
}

int _gnutls_gen_extensions(gnutls_session_t session, opaque * data,
			   size_t data_size)
{
    int next, size;
    uint16 pos = 0;
    opaque *sdata;
    int sdata_size;
    ext_send_func ext_send;


    if (data_size < 2) {
	gnutls_assert();
	return GNUTLS_E_INTERNAL_ERROR;
    }

    /* allocate enough data for each extension.
     */
    sdata_size = data_size;
    sdata = gnutls_malloc(sdata_size);
    if (sdata == NULL) {
	gnutls_assert();
	return GNUTLS_E_MEMORY_ERROR;
    }

    pos += 2;
    next = MAX_EXT_TYPES;	/* maximum supported extensions */
    do {
	next--;
	ext_send = _gnutls_ext_func_send(next);
	if (ext_send == NULL)
	    continue;
	size = ext_send(session, sdata, sdata_size);
	if (size > 0) {
	    if (data_size < pos + (size_t) size + 4) {
		gnutls_assert();
		gnutls_free(sdata);
		return GNUTLS_E_INTERNAL_ERROR;
	    }

	    /* write extension type */
	    _gnutls_write_uint16(next, &data[pos]);
	    pos += 2;

	    /* write size */
	    _gnutls_write_uint16(size, &data[pos]);
	    pos += 2;

	    memcpy(&data[pos], sdata, size);
	    pos += size;

	    /* add this extension to the extension list
	     */
	    _gnutls_extension_list_add(session, next);

	    _gnutls_debug_log("EXT[%x]: Sending extension %s\n", session,
			      _gnutls_extension_get_name(next));
	} else if (size < 0) {
	    gnutls_assert();
	    gnutls_free(sdata);
	    return size;
	}

    } while (next >= 0);

    size = pos;
    pos -= 2;			/* remove the size of the size header! */

    _gnutls_write_uint16(pos, data);

    if (size == 2) {		/* empty */
	size = 0;
    }

    gnutls_free(sdata);
    return size;

}