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[gnutls.git] / lib / gnutls_record.c

/*
 *      Copyright (C) 2000,2001,2002 Nikos Mavroyanopoulos
 *
 * 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
 *
 */

#include "gnutls_int.h"
#include "gnutls_errors.h"
#include "debug.h"
#include "gnutls_compress.h"
#include "gnutls_cipher.h"
#include "gnutls_buffers.h"
#include "gnutls_handshake.h"
#include "gnutls_hash_int.h"
#include "gnutls_cipher_int.h"
#include "gnutls_priority.h"
#include "gnutls_algorithms.h"
#include "gnutls_db.h"
#include "gnutls_auth_int.h"
#include "gnutls_num.h"
#include "gnutls_record.h"
#include "gnutls_datum.h"
#include "ext_max_record.h"
#include <gnutls_state.h>
#include <gnutls_alert.h>
#include <gnutls_dh.h>

/**
  * gnutls_protocol_get_version - Returns the version of the currently used protocol
  * @state: is a &GNUTLS_STATE structure.
  *
  * Returns the version of the currently used protocol. 
  *
  **/
GNUTLS_Version gnutls_protocol_get_version(GNUTLS_STATE state) {
        return state->security_parameters.version;
}

void _gnutls_set_current_version(GNUTLS_STATE state, GNUTLS_Version version) {
        state->security_parameters.version = version;
}

/**
  * gnutls_transport_set_lowat - Used to set the lowat value in order for select to check for pending data.
  * @state: is a &GNUTLS_STATE structure.
  * @num: is the low water value.
  *
  * Used to set the lowat value in order for select to check
  * if there are pending data to socket buffer. Used only   
  * if you have changed the default low water value (default is 1).
  * Normally you will not need that function. 
  * This function is only usefull if using berkeley style sockets.
  * Otherwise it must be called and set lowat to zero.
  *
  **/
void gnutls_transport_set_lowat(GNUTLS_STATE state, int num) {
        state->gnutls_internals.lowat = num;
}

/**
  * gnutls_transport_set_ptr - Used to set first argument of the transport functions
  * @state: is a &GNUTLS_STATE structure.
  * @ptr: is the value.
  *
  * Used to set the first argument of the transport function (like PUSH and
  * PULL). In berkeley style sockets this function will set the connection
  * handle.
  *
  **/
void gnutls_transport_set_ptr(GNUTLS_STATE state, GNUTLS_TRANSPORT_PTR ptr) {
        state->gnutls_internals.transport_ptr = ptr;
}

/**
  * gnutls_transport_get_ptr - Used to return the first argument of the transport functions
  * @state: is a &GNUTLS_STATE structure.
  *
  * Used to get the first argument of the transport function (like PUSH and
  * PULL). This must have been set using gnutls_transport_set_ptr().
  *
  **/
GNUTLS_TRANSPORT_PTR gnutls_transport_get_ptr(GNUTLS_STATE state) {
        return state->gnutls_internals.transport_ptr;
}

/**
  * gnutls_bye - This function terminates the current TLS/SSL connection.
  * @state: is a &GNUTLS_STATE structure.
  * @how: is an integer
  *
  * Terminates the current TLS/SSL connection. The connection should
  * have been initiated using gnutls_handshake().
  * 'how' should be one of GNUTLS_SHUT_RDWR, GNUTLS_SHUT_WR.
  *
  * In case of GNUTLS_SHUT_RDWR then the TLS connection gets terminated and
  * further receives and sends will be disallowed. If the return
  * value is zero you may continue using the connection.
  * GNUTLS_SHUT_RDWR actually sends an alert containing a close request
  * and waits for the peer to reply with the same message.
  *
  * In case of GNUTLS_SHUT_WR then the TLS connection gets terminated and
  * further sends will be disallowed. In order to reuse the connection
  * you should wait for an EOF from the peer.
  * GNUTLS_SHUT_WR sends an alert containing a close request.
  *
  * This function may also return GNUTLS_E_AGAIN, or GNUTLS_E_INTERRUPTED.
  *
  **/
int gnutls_bye( GNUTLS_STATE state, GNUTLS_CloseRequest how)
{
        int ret = 0, ret2 = 0;

        switch (STATE) {
                case STATE0:
                case STATE60:
                        if (STATE==STATE60) {
                                ret = _gnutls_io_write_flush( state);
                        } else {
                                ret = gnutls_alert_send( state, GNUTLS_AL_WARNING, GNUTLS_A_CLOSE_NOTIFY);
                                STATE = STATE60;
                        }

                        if (ret < 0)
                                return ret;
                case STATE61:
                        if ( how == GNUTLS_SHUT_RDWR && ret >= 0) {
                                ret2 = gnutls_recv_int( state, GNUTLS_ALERT, -1, NULL, 0); 
                                if (ret2 >= 0) state->gnutls_internals.may_read = 1;
                        }
                        STATE = STATE61;

                        if (ret2 < 0)
                                return ret2;

        }

        STATE = STATE0;
        
        state->gnutls_internals.may_write = 1;
        return 0;
}

inline
static void _gnutls_session_invalidate( GNUTLS_STATE state) {
        state->gnutls_internals.valid_connection = VALID_FALSE;
}


inline
static void _gnutls_session_unresumable( GNUTLS_STATE state) {
        state->gnutls_internals.resumable = RESUME_FALSE;
}

/* returns 0 if session is valid
 */
inline
static int _gnutls_session_is_valid( GNUTLS_STATE state) {
        if (state->gnutls_internals.valid_connection==VALID_FALSE)
                return GNUTLS_E_INVALID_SESSION;
        
        return 0;
}

static
ssize_t _gnutls_create_empty_record( GNUTLS_STATE state, ContentType type,
        opaque* erecord, int erecord_size)
{
        int cipher_size;
        int retval;
        int data2send;
        uint8 headers[5];
        GNUTLS_Version lver;

        if (type!=GNUTLS_APPLICATION_DATA ||
                _gnutls_cipher_is_block( gnutls_cipher_get(state))!=CIPHER_BLOCK) 
                /* alert messages and stream ciphers
                 * do not need this protection 
                 */
                return 0;

        headers[0]=type;
        
        lver = gnutls_protocol_get_version(state);
        if (lver==GNUTLS_VERSION_UNKNOWN) {
                gnutls_assert();
                return GNUTLS_E_INTERNAL_ERROR;
        }

        headers[1]=_gnutls_version_get_major( lver);
        headers[2]=_gnutls_version_get_minor( lver);

        data2send = 0;

        cipher_size = _gnutls_encrypt( state, headers, RECORD_HEADER_SIZE, NULL, 0, erecord, erecord_size, type, 0);
        if (cipher_size <= 0) {
                gnutls_assert();
                if (cipher_size==0) cipher_size = GNUTLS_E_ENCRYPTION_FAILED;
                return cipher_size; /* error */
        }

        retval = cipher_size;

        /* increase sequence number
         */
        if (_gnutls_uint64pp( &state->connection_state.write_sequence_number) != 0) {
                _gnutls_session_invalidate( state);
                gnutls_assert();
                return GNUTLS_E_RECORD_LIMIT_REACHED;
        }

        return retval;
}

/* This function behave exactly like write(). The only difference is 
 * that it accepts, the gnutls_state and the ContentType of data to
 * send (if called by the user the Content is specific)
 * It is intended to transfer data, under the current state.    
 *
 * Oct 30 2001: Removed capability to send data more than MAX_RECORD_SIZE.
 * This makes the function much easier to read, and more error resistant
 * (there were cases were the old function could mess everything up).
 * --nmav
 *
 */
ssize_t gnutls_send_int( GNUTLS_STATE state, ContentType type, HandshakeType htype, const void *_data, size_t sizeofdata)
{
        uint8 *cipher;
        int cipher_size;
        int retval, ret;
        int data2send_size;
        uint8 headers[5];
        const uint8 *data=_data;
        GNUTLS_Version lver;
        int erecord_size = 0;
        opaque* erecord = NULL;

        if (sizeofdata == 0 || _data==NULL) {
                gnutls_assert();
                return GNUTLS_E_INVALID_PARAMETERS;
        }

        if (type!=GNUTLS_ALERT) /* alert messages are sent anyway */
                if ( _gnutls_session_is_valid( state) || state->gnutls_internals.may_write != 0) {
                        return GNUTLS_E_INVALID_SESSION;
                }



        headers[0]=type;
        
        lver = gnutls_protocol_get_version(state);
        if (lver==GNUTLS_VERSION_UNKNOWN) {
                gnutls_assert();
                return GNUTLS_E_INTERNAL_ERROR;
        }

        headers[1]=_gnutls_version_get_major( lver);
        headers[2]=_gnutls_version_get_minor( lver);

        _gnutls_record_log( "REC: Sending Packet[%d] %s(%d) with length: %d\n",
                (int) _gnutls_uint64touint32(&state->connection_state.write_sequence_number), _gnutls_packet2str(type), type, sizeofdata);

        if ( sizeofdata > MAX_RECORD_SIZE)
                data2send_size = MAX_RECORD_SIZE;
        else 
                data2send_size = sizeofdata;

        /* Only encrypt if we don't have data to send 
         * from the previous run. - probably interrupted.
         */
        if (state->gnutls_internals.record_send_buffer.size > 0) {
                ret = _gnutls_io_write_flush( state);
                if (ret > 0) cipher_size = ret;
                else cipher_size = 0;
                
                cipher = NULL;

                retval = state->gnutls_internals.record_send_buffer_user_size;
        } else {

                /* Prepend our packet with an empty record. This is to
                 * avoid the recent CBC attacks.
                 */
                /* if this protection has been disabled
                 */
                if (state->gnutls_internals.cbc_protection_hack!=0) {
                        erecord_size = MAX_RECORD_OVERHEAD;
                        erecord = gnutls_alloca( erecord_size);
                        if (erecord==NULL) {
                                gnutls_assert();
                                return GNUTLS_E_MEMORY_ERROR;
                        }

                        erecord_size = 
                                _gnutls_create_empty_record( state, type, erecord, erecord_size);
                        if (erecord_size < 0) {
                                gnutls_assert();
                                return erecord_size;
                        }
                }

                /* now proceed to packet encryption
                 */
                cipher_size = data2send_size + MAX_RECORD_OVERHEAD;
                cipher = gnutls_alloca( cipher_size);
                if (cipher==NULL) {
                        gnutls_assert();
                        return GNUTLS_E_MEMORY_ERROR;
                }

                cipher_size = _gnutls_encrypt( state, headers, RECORD_HEADER_SIZE, data, data2send_size, cipher, 
                        cipher_size, type, 1);
                if (cipher_size <= 0) {
                        gnutls_assert();
                        if (cipher_size==0) cipher_size = GNUTLS_E_ENCRYPTION_FAILED;
                        gnutls_afree( erecord);
                        gnutls_afree( cipher);
                        return cipher_size; /* error */
                }

                retval = data2send_size;
                state->gnutls_internals.record_send_buffer_user_size =  data2send_size;

                /* increase sequence number
                 */
                if (_gnutls_uint64pp( &state->connection_state.write_sequence_number) != 0) {
                        _gnutls_session_invalidate( state);
                        gnutls_assert();
                        gnutls_afree( erecord);
                        gnutls_afree( cipher);
                        return GNUTLS_E_RECORD_LIMIT_REACHED;
                }

                ret = _gnutls_io_write_buffered2( state, erecord, erecord_size, cipher, cipher_size);
                gnutls_afree( erecord);
                gnutls_afree( cipher);
        }

        if ( ret != cipher_size + erecord_size) {
                if ( ret < 0 && gnutls_error_is_fatal(ret)==0) {
                        /* If we have sent any data then return
                         * that value.
                         */
                        gnutls_assert();
                        return ret;
                }
                
                if (ret > 0) {
                        gnutls_assert();
                        ret = GNUTLS_E_UNKNOWN_ERROR;
                }

                _gnutls_session_unresumable( state);
                _gnutls_session_invalidate( state);
                gnutls_assert();
                return ret;
        }

        state->gnutls_internals.record_send_buffer_user_size = 0;

        _gnutls_record_log( "REC: Sent Packet[%d] %s(%d) with length: %d\n",
        (int) _gnutls_uint64touint32(&state->connection_state.write_sequence_number), _gnutls_packet2str(type), type, cipher_size);

        return retval;
}

/* This function is to be called if the handshake was successfully 
 * completed. This sends a Change Cipher Spec packet to the peer.
 */
ssize_t _gnutls_send_change_cipher_spec( GNUTLS_STATE state, int again)
{
        opaque data[1] = { GNUTLS_TYPE_CHANGE_CIPHER_SPEC };

        _gnutls_handshake_log( "REC: Sent ChangeCipherSpec\n");

        if (again==0)
                return gnutls_send_int( state, GNUTLS_CHANGE_CIPHER_SPEC, -1, data, 1);
        else {
                return _gnutls_io_write_flush( state);
        }
}

static int _gnutls_check_recv_type( ContentType recv_type) {
        switch( recv_type) {
        case GNUTLS_CHANGE_CIPHER_SPEC:
        case GNUTLS_ALERT:
        case GNUTLS_HANDSHAKE:
        case GNUTLS_APPLICATION_DATA:
                return 0;
        default:
                gnutls_assert();
                return GNUTLS_E_UNSUPPORTED_VERSION_PACKET;
        }

}


/* Checks if there are pending data into the record buffers. If there are
 * then it copies the data.
 */
static int _gnutls_check_buffers( GNUTLS_STATE state, ContentType type, opaque* data, int sizeofdata) {
        int ret = 0, ret2=0;
        if ( (type == GNUTLS_APPLICATION_DATA || type == GNUTLS_HANDSHAKE) && _gnutls_record_buffer_get_size(type, state) > 0) {
                ret = _gnutls_record_buffer_get(type, state, data, sizeofdata);
                if (ret < 0) {
                        gnutls_assert();
                        return ret;
                }
                
                /* if the buffer just got empty */
                if (_gnutls_record_buffer_get_size(type, state)==0) {
                        if ( (ret2=_gnutls_io_clear_peeked_data( state)) < 0) {
                                gnutls_assert();
                                return ret2;
                        }
                }

                return ret;
        }
        
        return 0;
}


#define CHECK_RECORD_VERSION

/* Checks the record headers and returns the length, version and
 * content type.
 */
static int _gnutls_check_record_headers( GNUTLS_STATE state, uint8 headers[RECORD_HEADER_SIZE], ContentType type, 
        HandshakeType htype, /*output*/ ContentType *recv_type, GNUTLS_Version *version, uint16 *length, uint16* header_size) {

        /* Read the first two bytes to determine if this is a 
         * version 2 message 
         */

        if ( htype == GNUTLS_CLIENT_HELLO && type==GNUTLS_HANDSHAKE && headers[0] > 127) { 

                /* if msb set and expecting handshake message
                 * it should be SSL 2 hello 
                 */
                *version = GNUTLS_VERSION_UNKNOWN; /* assume unknown version */
                *length = (((headers[0] & 0x7f) << 8)) | headers[1];

                /* SSL 2.0 headers */
                *header_size = 2;
                *recv_type = GNUTLS_HANDSHAKE; /* we accept only v2 client hello
                                               */
                
                /* in order to assist the handshake protocol.
                 * V2 compatibility is a mess.
                 */
                state->gnutls_internals.v2_hello = *length;

                _gnutls_record_log( "REC: V2 packet received. Length: %d\n", *length);

        } else {
                /* version 3.x 
                 */
                *recv_type = headers[0];
#ifdef CHECK_RECORD_VERSION
                *version = _gnutls_version_get( headers[1], headers[2]);
#endif

                /* No DECR_LEN, since headers has enough size. 
                 */
                *length = _gnutls_read_uint16( &headers[3]);
        }

        return 0;
}

/* Here we check if the advertized version is the one we
 * negotiated in the handshake.
 */
inline
static int _gnutls_check_record_version( GNUTLS_STATE state, HandshakeType htype, GNUTLS_Version version) 
{
#ifdef CHECK_RECORD_VERSION
        if ( (htype!=GNUTLS_CLIENT_HELLO && htype!=GNUTLS_SERVER_HELLO) && gnutls_protocol_get_version(state) != version) {
                gnutls_assert();

                _gnutls_record_log( "REC: INVALID VERSION PACKET: (%d) %d.%d\n", htype, _gnutls_version_get_major(version), _gnutls_version_get_minor(version));

                return GNUTLS_E_UNSUPPORTED_VERSION_PACKET;
        }
#endif

        return 0;
}

/* This function will check if the received record type is
 * the one we actually expecting for.
 */
static int _gnutls_record_check_type( GNUTLS_STATE state, ContentType recv_type,
        ContentType type, HandshakeType htype, opaque* data, int data_size) {
        
        int ret;

        if ( (recv_type == type) && (type == GNUTLS_APPLICATION_DATA || type == GNUTLS_HANDSHAKE)) {
                _gnutls_record_buffer_put(type, state, (void *) data, data_size);
        } else {
                switch (recv_type) {
                case GNUTLS_ALERT:

                        _gnutls_record_log( "REC: Alert[%d|%d] - %s - was received\n", data[0], data[1], gnutls_alert_get_name((int)data[1]));

                        state->gnutls_internals.last_alert = data[1];

                        /* if close notify is received and
                         * the alert is not fatal
                         */
                        if (data[1] == GNUTLS_A_CLOSE_NOTIFY && data[0] != GNUTLS_AL_FATAL) {
                                /* If we have been expecting for an alert do 
                                 */

                                return GNUTLS_E_INT_RET_0; /* EOF */
                        } else {
                        
                                /* if the alert is FATAL or WARNING
                                 * return the apropriate message
                                 */
                                
                                gnutls_assert();                
                                ret = GNUTLS_E_WARNING_ALERT_RECEIVED;
                                if (data[0] == GNUTLS_AL_FATAL) {
                                        _gnutls_session_unresumable( state);
                                        _gnutls_session_invalidate( state);

                                        ret = GNUTLS_E_FATAL_ALERT_RECEIVED;
                                }

                                return ret;
                        }
                        break;

                case GNUTLS_CHANGE_CIPHER_SPEC:
                        /* this packet is now handled above */
                        gnutls_assert();
        
                        return GNUTLS_E_UNEXPECTED_PACKET;

                case GNUTLS_APPLICATION_DATA:
                        /* even if data is unexpected put it into the buffer */
                        if ( (ret=_gnutls_record_buffer_put(recv_type, state, (void *) data, data_size)) < 0) {
                                gnutls_assert();
                                return ret;
                        }

                        gnutls_assert();
                        
                        /* the got_application data is only returned
                         * if expecting client hello (for rehandshake
                         * reasons). Otherwise it is an unexpected packet
                         */
                        if (htype == GNUTLS_CLIENT_HELLO && type==GNUTLS_HANDSHAKE)
                                return GNUTLS_E_GOT_APPLICATION_DATA;
                        else return GNUTLS_E_UNEXPECTED_PACKET;
                        
                        break;
                case GNUTLS_HANDSHAKE:
                        /* This is only legal if HELLO_REQUEST is received - and we are a client 
                         */
                        if ( state->security_parameters.entity==GNUTLS_SERVER) {
                                gnutls_assert();
                                return GNUTLS_E_UNEXPECTED_PACKET;
                        }
                        gnutls_assert();
                        
                        return _gnutls_recv_hello_request( state, data, data_size);

                        break;
                default:

                        _gnutls_record_log( "REC: Received Unknown packet %d expecting %d\n", recv_type, type);

                        gnutls_assert();
                        return GNUTLS_E_UNKNOWN_ERROR;
                }
        }
        
        return 0;

}

#define MAX_EMPTY_PACKETS_SEQUENCE 4

/* This function behave exactly like read(). The only difference is 
 * that it accepts, the gnutls_state and the ContentType of data to
 * send (if called by the user the Content is Userdata only)
 * It is intended to receive data, under the current state.
 */
ssize_t gnutls_recv_int( GNUTLS_STATE state, ContentType type, HandshakeType htype, char *data, size_t sizeofdata)
{
        uint8 *tmpdata;
        int tmplen;
        GNUTLS_Version version;
        uint8 *headers;
        ContentType recv_type;
        uint16 length;
        uint8 *ciphertext;
        uint8 *recv_data;
        int ret, ret2;
        uint16 header_size;
        int empty_packet = 0;

        begin:
        
        if (empty_packet > MAX_EMPTY_PACKETS_SEQUENCE) {
                gnutls_assert();
                return GNUTLS_E_TOO_MANY_EMPTY_PACKETS;
        }
        
        /* default headers for TLS 1.0
         */
        header_size = RECORD_HEADER_SIZE;
        ret = 0;

        if (sizeofdata == 0 || data == NULL) {
                return GNUTLS_E_INVALID_PARAMETERS;
        }

        if ( _gnutls_session_is_valid(state)!=0 || state->gnutls_internals.may_read!=0) {
                gnutls_assert();
                return GNUTLS_E_INVALID_SESSION;
        }
        
        /* If we have enough data in the cache do not bother receiving
         * a new packet. (in order to flush the cache)
         */
        ret = _gnutls_check_buffers( state, type, data, sizeofdata);
        if (ret != 0)
                return ret;


        if ( (ret = _gnutls_io_read_buffered( state, &headers, header_size, -1)) != header_size) {
                if (ret < 0 && gnutls_error_is_fatal(ret)==0) return ret;

                _gnutls_session_invalidate( state);
                if (type==GNUTLS_ALERT) {
                        gnutls_assert();
                        return 0; /* we were expecting close notify */
                }
                _gnutls_session_unresumable( state);
                gnutls_assert();
                return GNUTLS_E_UNEXPECTED_PACKET_LENGTH;
        }

        if ( (ret=_gnutls_check_record_headers( state, headers, type, htype, &recv_type, &version, &length, &header_size)) < 0) {
                gnutls_assert();
                return ret;
        }

        /* Here we check if the Type of the received packet is
         * ok. 
         */
        if ( (ret = _gnutls_check_recv_type( recv_type)) < 0) {
                
                gnutls_assert();
                return ret;
        }

        /* Here we check if the advertized version is the one we
         * negotiated in the handshake.
         */
        if ( (ret=_gnutls_check_record_version( state, htype, version)) < 0) {
                gnutls_assert();
                _gnutls_session_invalidate( state);
                return ret;
        }

        _gnutls_record_log( "REC: Expected Packet[%d] %s(%d) with length: %d\n",
                (int) _gnutls_uint64touint32(&state->connection_state.read_sequence_number), _gnutls_packet2str(type), type, sizeofdata);
        _gnutls_record_log( "REC: Received Packet[%d] %s(%d) with length: %d\n",
                (int) _gnutls_uint64touint32(&state->connection_state.read_sequence_number), _gnutls_packet2str(recv_type), recv_type, length);

        if (length > MAX_RECV_SIZE) {

                _gnutls_record_log( "REC: FATAL ERROR: Received packet with length: %d\n", length);

                _gnutls_session_unresumable( state);
                _gnutls_session_invalidate( state);
                gnutls_assert();
                return GNUTLS_E_UNEXPECTED_PACKET_LENGTH;
        }

        /* check if we have that data into buffer. 
         */
        if ( (ret = _gnutls_io_read_buffered( state, &recv_data, header_size+length, recv_type)) != length+header_size) {
                if (ret<0 && gnutls_error_is_fatal(ret)==0) return ret;

                _gnutls_session_unresumable( state);
                _gnutls_session_invalidate( state);
                gnutls_assert();
                return GNUTLS_E_UNEXPECTED_PACKET_LENGTH;               
        }
        
/* ok now we are sure that we can read all the data - so
 * move on !
 */
        _gnutls_io_clear_read_buffer( state);
        ciphertext = &recv_data[header_size];
        
        /* decrypt the data we got
         */
        tmplen = length + MAX_RECORD_OVERHEAD;
        tmpdata = gnutls_alloca( tmplen);
        if (tmpdata==NULL) {
                gnutls_assert();
                return GNUTLS_E_MEMORY_ERROR;
        }

        tmplen = _gnutls_decrypt( state, ciphertext, length, tmpdata, tmplen, recv_type);
        if (tmplen < 0) {
                _gnutls_session_unresumable( state);
                _gnutls_session_invalidate( state);
                gnutls_afree(tmpdata);
                gnutls_assert();
                return tmplen;
        }

        /* Check if this is a CHANGE_CIPHER_SPEC
         */
        if (type == GNUTLS_CHANGE_CIPHER_SPEC && recv_type == GNUTLS_CHANGE_CIPHER_SPEC) {

                _gnutls_record_log( "REC: ChangeCipherSpec Packet was received\n");

                if (tmplen!=sizeofdata) { /* sizeofdata should be 1 */
                        gnutls_assert();
                        gnutls_afree(tmpdata);
                        return GNUTLS_E_UNEXPECTED_PACKET_LENGTH;
                }
                memcpy( data, tmpdata, sizeofdata);
                gnutls_afree(tmpdata);

                return tmplen;
        }

        _gnutls_record_log( "REC: Decrypted Packet[%d] %s(%d) with length: %d\n",
                (int) _gnutls_uint64touint32(&state->connection_state.read_sequence_number), _gnutls_packet2str(recv_type), recv_type, tmplen);

        /* increase sequence number */
        if (_gnutls_uint64pp( &state->connection_state.read_sequence_number)!=0) {
                _gnutls_session_invalidate( state);
                gnutls_afree(tmpdata);
                gnutls_assert();
                return GNUTLS_E_RECORD_LIMIT_REACHED;
        }

        if ( (ret=_gnutls_record_check_type( state, recv_type, type, htype, tmpdata, tmplen)) < 0) {
                gnutls_afree(tmpdata);

                if (ret==GNUTLS_E_INT_RET_0) return 0;

                gnutls_assert();
                return ret;
        }
        gnutls_afree(tmpdata);

        /* Get Application data from buffer */
        if ((type == GNUTLS_APPLICATION_DATA || type == GNUTLS_HANDSHAKE) && (recv_type == type)) {

                ret = _gnutls_record_buffer_get(type, state, data, sizeofdata);
                if (ret < 0) {
                        gnutls_assert();
                        return ret;
                }

                /* if the buffer just got empty */
                if (_gnutls_record_buffer_get_size(type, state)==0) {
                        if ( (ret2 = _gnutls_io_clear_peeked_data( state)) < 0) {
                                gnutls_assert();
                                return ret2;
                        }
                }

        } else {
                gnutls_assert();
                ret = GNUTLS_E_UNEXPECTED_PACKET; 
                /* we didn't get what we wanted to 
                 */
        }

        /* TLS 1.0 CBC protection. Read the next fragment.
         */
        if (ret==0) {
                empty_packet++;
                goto begin;
        }
        
        return ret;
}


/* Taken from libgcrypt */

static const char*
parse_version_number( const char *s, int *number )
{
    int val = 0;

    if( *s == '0' && isdigit(s[1]) )
        return NULL; /* leading zeros are not allowed */
    for ( ; isdigit(*s); s++ ) {
        val *= 10;
        val += *s - '0';
    }
    *number = val;
    return val < 0? NULL : s;
}


static const char *
parse_version_string( const char *s, int *major, int *minor, int *micro )
{
    s = parse_version_number( s, major );
    if( !s || *s != '.' )
        return NULL;
    s++;
    s = parse_version_number( s, minor );
    if( !s || *s != '.' )
        return NULL;
    s++;
    s = parse_version_number( s, micro );
    if( !s )
        return NULL;
    return s; /* patchlevel */
}

/****************
 * Check that the the version of the library is at minimum the requested one
 * and return the version string; return NULL if the condition is not
 * satisfied.  If a NULL is passed to this function, no check is done,
 * but the version string is simply returned.
 */
const char *
gnutls_check_version( const char *req_version )
{
    const char *ver = GNUTLS_VERSION;
    int my_major, my_minor, my_micro;
    int rq_major, rq_minor, rq_micro;
    const char *my_plvl, *rq_plvl;

    if ( !req_version )
        return ver;

    my_plvl = parse_version_string( ver, &my_major, &my_minor, &my_micro );
    if ( !my_plvl )
        return NULL;  /* very strange our own version is bogus */
    rq_plvl = parse_version_string( req_version, &rq_major, &rq_minor,
                                                                &rq_micro );
    if ( !rq_plvl )
        return NULL;  /* req version string is invalid */

    if ( my_major > rq_major
        || (my_major == rq_major && my_minor > rq_minor)
        || (my_major == rq_major && my_minor == rq_minor
                                 && my_micro > rq_micro)
        || (my_major == rq_major && my_minor == rq_minor
                                 && my_micro == rq_micro
                                 && strcmp( my_plvl, rq_plvl ) >= 0) ) {
        return ver;
    }
    return NULL;
}


/**
  * gnutls_record_send - sends to the peer the specified data
  * @state: is a &GNUTLS_STATE structure.
  * @data: contains the data to send
  * @sizeofdata: is the length of the data
  *
  * This function has the similar semantics to write(). The only
  * difference is that is accepts a GNUTLS state, and uses different
  * error codes.
  *
  * If the EINTR is returned by the internal push function (write())
  * then GNUTLS_E_INTERRUPTED, will be returned. If GNUTLS_E_INTERRUPTED or
  * GNUTLS_E_AGAIN is returned you must call this function again, with the 
  * same parameters. Otherwise the write operation will be 
  * corrupted and the connection will be terminated.
  *
  * Returns the number of bytes sent, or a negative error code.
  *
  **/
ssize_t gnutls_record_send( GNUTLS_STATE state, const void *data, size_t sizeofdata) {
        return gnutls_send_int( state, GNUTLS_APPLICATION_DATA, -1, data, sizeofdata);
}

/**
  * gnutls_record_recv - reads data from the TLS record protocol
  * @state: is a &GNUTLS_STATE structure.
  * @data: contains the data to send
  * @sizeofdata: is the length of the data
  *
  * This function has the similar semantics to read(). The only
  * difference is that is accepts a GNUTLS state.
  * Also returns the number of bytes received, zero on EOF, but
  * a negative error code in case of an error.
  *
  * If this function returns GNUTLS_E_REHANDSHAKE, then you may
  * ignore this message, send an alert containing NO_RENEGOTIATION, 
  * or perform a handshake again. (only a client may receive this message)
  *
  **/
ssize_t gnutls_record_recv( GNUTLS_STATE state, void *data, size_t sizeofdata) {
        return gnutls_recv_int( state, GNUTLS_APPLICATION_DATA, -1, data, sizeofdata);
}

/**
  * gnutls_record_get_max_size - returns the maximum record size
  * @state: is a &GNUTLS_STATE structure.
  *
  * This function returns the maximum record size in this connection.
  * The maximum record size is negotiated by the client after the
  * first handshake message.
  *
  **/
size_t gnutls_record_get_max_size( GNUTLS_STATE state) {
        return state->security_parameters.max_record_size;
}


/**
  * gnutls_record_set_max_size - sets the maximum record size
  * @state: is a &GNUTLS_STATE structure.
  * @size: is the new size
  *
  * This function sets the maximum record size in this connection.
  * This property can only be set to clients. The server may
  * choose not to accept the requested size.
  *
  * Acceptable values are 2^9, 2^10, 2^11 and 2^12.
  * Returns 0 on success. The requested record size does not
  * get in effect immediately. It will be used after a successful
  * handshake.
  *
  * This function uses a TLS extension called 'max record size'.
  * Not all TLS implementations use or even understand this extension.
  *
  **/
ssize_t gnutls_record_set_max_size( GNUTLS_STATE state, size_t size) {
ssize_t new_size;

        if (state->security_parameters.entity==GNUTLS_SERVER)
                return GNUTLS_E_INVALID_REQUEST;

        new_size = _gnutls_mre_record2num( size);

        if (new_size < 0) {
                gnutls_assert();
                return new_size;
        }
        
        state->gnutls_internals.proposed_record_size = size;

        return 0;
}