source: protocols/jabber/s5bytestream.c @ 4c17d19

/***************************************************************************\
*                                                                           *
*  BitlBee - An IRC to IM gateway                                           *
*  Jabber module - SOCKS5 Bytestreams ( XEP-0065 )                          *
*                                                                           *
*  Copyright 2007 Uli Meis <a.sporto+bee@gmail.com>                         *
*                                                                           *
*  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.,  *
*  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.              *
*                                                                           *
\***************************************************************************/

#include "jabber.h"
#include "sha1.h"
#include "lib/ftutil.h"
#include <poll.h>

struct bs_transfer {

        struct jabber_transfer *tf;

        jabber_streamhost_t *sh;
        GSList *streamhosts;

        enum 
        { 
                BS_PHASE_CONNECT, 
                BS_PHASE_CONNECTED, 
                BS_PHASE_REQUEST, 
                BS_PHASE_REPLY
        } phase;

        /* SHA1( SID + Initiator JID + Target JID) */
        char *pseudoadr;

        gint connect_timeout;
        
        char peek_buf[64];
        int peek_buf_len;
};

struct socks5_message
{
        unsigned char ver;
        union
        {
                unsigned char cmd;
                unsigned char rep;
        } cmdrep;
        unsigned char rsv;
        unsigned char atyp;
        unsigned char addrlen;
        unsigned char address[40];
        in_port_t port;
} __attribute__ ((packed)); 

char *socks5_reply_code[] = {
        "succeeded",
        "general SOCKS server failure",
        "connection not allowed by ruleset",
        "Network unreachable",
        "Host unreachable",
        "Connection refused",
        "TTL expired",
        "Command not supported",
        "Address type not supported",
        "unassigned"};

/* connect() timeout in seconds. */
#define JABBER_BS_CONTIMEOUT 15
/* listen timeout */
#define JABBER_BS_LISTEN_TIMEOUT  90

/* very useful */
#define ASSERTSOCKOP(op, msg) \
        if( (op) == -1 ) \
                return jabber_bs_abort( bt , msg ": %s", strerror( errno ) );

gboolean jabber_bs_abort( struct bs_transfer *bt, char *format, ... );
void jabber_bs_canceled( file_transfer_t *ft , char *reason );
void jabber_bs_free_transfer( file_transfer_t *ft );
gboolean jabber_bs_connect_timeout( gpointer data, gint fd, b_input_condition cond );
gboolean jabber_bs_poll( struct bs_transfer *bt, int fd, short *revents );
gboolean jabber_bs_peek( struct bs_transfer *bt, void *buffer, int buflen );

void jabber_bs_recv_answer_request( struct bs_transfer *bt );
gboolean jabber_bs_recv_read( gpointer data, gint fd, b_input_condition cond );
gboolean jabber_bs_recv_write_request( file_transfer_t *ft );
gboolean jabber_bs_recv_handshake( gpointer data, gint fd, b_input_condition cond );
gboolean jabber_bs_recv_handshake_abort( struct bs_transfer *bt, char *error );
int jabber_bs_recv_request( struct im_connection *ic, struct xt_node *node, struct xt_node *qnode );

gboolean jabber_bs_send_handshake_abort( struct bs_transfer *bt, char *error );
gboolean jabber_bs_send_request( struct jabber_transfer *tf, GSList *streamhosts );
gboolean jabber_bs_send_handshake( gpointer data, gint fd, b_input_condition cond );
static xt_status jabber_bs_send_handle_activate( struct im_connection *ic, struct xt_node *node, struct xt_node *orig );
void jabber_bs_send_activate( struct bs_transfer *bt );

/*
 * Frees a bs_transfer struct and calls the SI free function
 */
void jabber_bs_free_transfer( file_transfer_t *ft) {
        struct jabber_transfer *tf = ft->data;
        struct bs_transfer *bt = tf->streamhandle;
        jabber_streamhost_t *sh;

        if ( bt->connect_timeout )
        {
                b_event_remove( bt->connect_timeout );
                bt->connect_timeout = 0;
        }

        if ( tf->watch_in )
                b_event_remove( tf->watch_in );
        
        if( tf->watch_out )
                b_event_remove( tf->watch_out );
        
        g_free( bt->pseudoadr );

        while( bt->streamhosts )
        {
                sh = bt->streamhosts->data;
                bt->streamhosts = g_slist_remove( bt->streamhosts, sh );
                g_free( sh->jid );
                g_free( sh->host );
                g_free( sh );
        }
        
        g_free( bt );

        jabber_si_free_transfer( ft );
}

/*
 * Checks if buflen data is available on the socket and
 * writes it to buffer if that's the case.
 */
gboolean jabber_bs_peek( struct bs_transfer *bt, void *buffer, int buflen )
{
        int ret;
        int fd = bt->tf->fd;

        if( buflen > sizeof( bt->peek_buf ) )
                return jabber_bs_abort( bt, "BUG: %d > sizeof(peek_buf)", buflen );

        ASSERTSOCKOP( ret = recv( fd, bt->peek_buf + bt->peek_buf_len,
                buflen - bt->peek_buf_len, 0 ), "recv() on SOCKS5 connection" );

        if( ret == 0 )
                return jabber_bs_abort( bt, "Remote end closed connection" );
        
        bt->peek_buf_len += ret;
        memcpy( buffer, bt->peek_buf, bt->peek_buf_len );
        
        if( bt->peek_buf_len == buflen )
        {
                /* If we have everything the caller wanted, reset the peek buffer. */
                bt->peek_buf_len = 0;
                return buflen;
        }
        else
                return bt->peek_buf_len;
}


/* 
 * This function is scheduled in bs_handshake via b_timeout_add after a (non-blocking) connect().
 */
gboolean jabber_bs_connect_timeout( gpointer data, gint fd, b_input_condition cond )
{
        struct bs_transfer *bt = data;

        bt->connect_timeout = 0;

        jabber_bs_abort( bt, "no connection after %d seconds", bt->tf->ft->sending ? JABBER_BS_LISTEN_TIMEOUT : JABBER_BS_CONTIMEOUT );

        return FALSE;
}

/* 
 * Polls the socket, checks for errors and removes a connect timer
 * if there is one.
 */
gboolean jabber_bs_poll( struct bs_transfer *bt, int fd, short *revents )
{
        struct pollfd pfd = { .fd = fd, .events = POLLHUP|POLLERR };
        
        if ( bt->connect_timeout )
        {
                b_event_remove( bt->connect_timeout );
                bt->connect_timeout = 0;
        }

        ASSERTSOCKOP( poll( &pfd, 1, 0 ), "poll()" )

        if( pfd.revents & POLLERR )
        {
                int sockerror;
                socklen_t errlen = sizeof( sockerror );

                if ( getsockopt( fd, SOL_SOCKET, SO_ERROR, &sockerror, &errlen ) )
                        return jabber_bs_abort( bt, "getsockopt() failed, unknown socket error during SOCKS5 handshake (weird!)" );

                if ( bt->phase == BS_PHASE_CONNECTED )
                        return jabber_bs_abort( bt, "connect failed: %s", strerror( sockerror ) );

                return jabber_bs_abort( bt, "Socket error during SOCKS5 handshake(weird!): %s", strerror( sockerror ) );
        }

        if( pfd.revents & POLLHUP )
                return jabber_bs_abort( bt, "Remote end closed connection" );
        
        *revents = pfd.revents;
        
        return TRUE;
}

/*
 * Used for receive and send path.
 */
gboolean jabber_bs_abort( struct bs_transfer *bt, char *format, ... )
{
        va_list params;
        va_start( params, format );
        char error[128];

        if( vsnprintf( error, 128, format, params ) < 0 )
                sprintf( error, "internal error parsing error string (BUG)" );
        va_end( params );
        if( bt->tf->ft->sending )
                return jabber_bs_send_handshake_abort( bt, error );
        else
                return jabber_bs_recv_handshake_abort( bt, error );
}

/* Bad luck */
void jabber_bs_canceled( file_transfer_t *ft , char *reason )
{
        struct jabber_transfer *tf = ft->data;

        imcb_log( tf->ic, "File transfer aborted: %s", reason );
}

/*
 * Parses an incoming bytestream request and calls jabber_bs_handshake on success.
 */
int jabber_bs_recv_request( struct im_connection *ic, struct xt_node *node, struct xt_node *qnode)
{
        char *sid, *ini_jid, *tgt_jid, *mode, *iq_id;
        struct jabber_data *jd = ic->proto_data;
        struct jabber_transfer *tf = NULL;
        GSList *tflist;
        struct bs_transfer *bt;
        GSList *shlist=NULL;
        struct xt_node *shnode;

        sha1_state_t sha;
        char hash_hex[41];
        unsigned char hash[20];
        int i;
        
        if( !(iq_id   = xt_find_attr( node, "id" ) ) ||
            !(ini_jid = xt_find_attr( node, "from" ) ) ||
            !(tgt_jid = xt_find_attr( node, "to" ) ) ||
            !(sid     = xt_find_attr( qnode, "sid" ) ) )
        {
                imcb_log( ic, "WARNING: Received incomplete SI bytestream request");
                return XT_HANDLED;
        }

        if( ( mode = xt_find_attr( qnode, "mode" ) ) &&
              ( strcmp( mode, "tcp" ) != 0 ) ) 
        {
                imcb_log( ic, "WARNING: Received SI Request for unsupported bytestream mode %s", xt_find_attr( qnode, "mode" ) );
                return XT_HANDLED;
        }

        shnode = qnode->children;
        while( ( shnode = xt_find_node( shnode, "streamhost" ) ) )
        {
                char *jid, *host, *port_s;
                int port;
                if( ( jid = xt_find_attr( shnode, "jid" ) ) &&
                    ( host = xt_find_attr( shnode, "host" ) ) &&
                    ( port_s = xt_find_attr( shnode, "port" ) ) &&
                    ( sscanf( port_s, "%d", &port ) == 1 ) )
                {
                        jabber_streamhost_t *sh = g_new0( jabber_streamhost_t, 1 );
                        sh->jid = g_strdup(jid);
                        sh->host = g_strdup(host);
                        sprintf( sh->port, "%u", port );
                        shlist = g_slist_append( shlist, sh );
                }
                shnode = shnode->next;
        }
        
        if( !shlist )
        {
                imcb_log( ic, "WARNING: Received incomplete SI bytestream request, no parseable streamhost entries");
                return XT_HANDLED;
        }

        /* Let's see if we can find out what this bytestream should be for... */

        for( tflist = jd->filetransfers ; tflist; tflist = g_slist_next(tflist) )
        {
                struct jabber_transfer *tft = tflist->data;
                if( ( strcmp( tft->sid, sid ) == 0 ) &&
                    ( strcmp( tft->ini_jid, ini_jid ) == 0 ) &&
                    ( strcmp( tft->tgt_jid, tgt_jid ) == 0 ) )
                {
                        tf = tft;
                        break;
                }
        }

        if (!tf) 
        {
                imcb_log( ic, "WARNING: Received bytestream request from %s that doesn't match an SI request", ini_jid );
                return XT_HANDLED;
        }

        /* iq_id and canceled can be reused since SI is done */
        g_free( tf->iq_id );
        tf->iq_id = g_strdup( iq_id );

        tf->ft->canceled = jabber_bs_canceled;

        /* SHA1( SID + Initiator JID + Target JID ) is given to the streamhost which it will match against the initiator's value */
        sha1_init( &sha );
        sha1_append( &sha, (unsigned char*) sid, strlen( sid ) );
        sha1_append( &sha, (unsigned char*) ini_jid, strlen( ini_jid ) );
        sha1_append( &sha, (unsigned char*) tgt_jid, strlen( tgt_jid ) );
        sha1_finish( &sha, hash );
        
        for( i = 0; i < 20; i ++ )
                sprintf( hash_hex + i * 2, "%02x", hash[i] );
                
        bt = g_new0( struct bs_transfer, 1 );
        bt->tf = tf;
        bt->streamhosts = shlist;
        bt->sh = shlist->data;
        bt->phase = BS_PHASE_CONNECT;
        bt->pseudoadr = g_strdup( hash_hex );
        tf->streamhandle = bt;
        tf->ft->free = jabber_bs_free_transfer;

        jabber_bs_recv_handshake( bt, -1, 0 ); 

        return XT_HANDLED;
}

/*
 * This is what a protocol handshake can look like in cooperative multitasking :)
 * Might be confusing at first because it's called from different places and is recursing.
 * (places being the event thread, bs_request, bs_handshake_abort, and itself)
 *
 * All in all, it turned out quite nice :)
 */
gboolean jabber_bs_recv_handshake( gpointer data, gint fd, b_input_condition cond )
{

        struct bs_transfer *bt = data;
        short revents;
        int gret;

        if ( ( fd != -1 ) && !jabber_bs_poll( bt, fd, &revents ) )
                return FALSE;
        
        switch( bt->phase ) 
        {
        case BS_PHASE_CONNECT:
                {
                        struct addrinfo hints, *rp;

                        memset( &hints, 0, sizeof( struct addrinfo ) );
                        hints.ai_socktype = SOCK_STREAM;

                        if ( ( gret = getaddrinfo( bt->sh->host, bt->sh->port, &hints, &rp ) ) != 0 )
                                return jabber_bs_abort( bt, "getaddrinfo() failed: %s", gai_strerror( gret ) );

                        ASSERTSOCKOP( bt->tf->fd = fd = socket( rp->ai_family, rp->ai_socktype, 0 ), "Opening socket" );

                        sock_make_nonblocking( fd );

                        imcb_log( bt->tf->ic, "File %s: Connecting to streamhost %s:%s", bt->tf->ft->file_name, bt->sh->host, bt->sh->port );

                        if( ( connect( fd, rp->ai_addr, rp->ai_addrlen ) == -1 ) &&
                            ( errno != EINPROGRESS ) )
                                return jabber_bs_abort( bt , "connect() failed: %s", strerror( errno ) );

                        freeaddrinfo( rp );

                        bt->phase = BS_PHASE_CONNECTED;
                        
                        bt->tf->watch_out = b_input_add( fd, GAIM_INPUT_WRITE, jabber_bs_recv_handshake, bt );

                        /* since it takes forever(3mins?) till connect() fails on itself we schedule a timeout */
                        bt->connect_timeout = b_timeout_add( JABBER_BS_CONTIMEOUT * 1000, jabber_bs_connect_timeout, bt );

                        bt->tf->watch_in = 0;
                        return FALSE;
                }
        case BS_PHASE_CONNECTED:
                {
                        struct {
                                unsigned char ver;
                                unsigned char nmethods;
                                unsigned char method;
                        } socks5_hello = {
                                .ver = 5,
                                .nmethods = 1,
                                .method = 0x00 /* no auth */
                                /* one could also implement username/password. If you know
                                 * a jabber client or proxy that actually does it, tell me.
                                 */
                        };
                        
                        ASSERTSOCKOP( send( fd, &socks5_hello, sizeof( socks5_hello ) , 0 ), "Sending auth request" );

                        bt->phase = BS_PHASE_REQUEST;

                        bt->tf->watch_in = b_input_add( fd, GAIM_INPUT_READ, jabber_bs_recv_handshake, bt );

                        bt->tf->watch_out = 0;
                        return FALSE;
                }
        case BS_PHASE_REQUEST:
                {
                        struct socks5_message socks5_connect = 
                        {
                                .ver = 5,
                                .cmdrep.cmd = 0x01,
                                .rsv = 0,
                                .atyp = 0x03,
                                .addrlen = strlen( bt->pseudoadr ),
                                .port = 0
                        };
                        int ret;
                        char buf[2];

                        /* If someone's trying to be funny and sends only one byte at a time we'll fail :) */
                        ASSERTSOCKOP( ret = recv( fd, buf, 2, 0 ) , "Receiving auth reply" );

                        if( !( ret == 2 ) ||
                            !( buf[0] == 5 ) ||
                            !( buf[1] == 0 ) )
                                return jabber_bs_abort( bt, "Auth not accepted by streamhost (reply: len=%d, ver=%d, status=%d)",
                                                                        ret, buf[0], buf[1] );

                        /* copy hash into connect message */
                        memcpy( socks5_connect.address, bt->pseudoadr, socks5_connect.addrlen );

                        ASSERTSOCKOP( send( fd, &socks5_connect, sizeof( struct socks5_message ), 0 ) , "Sending SOCKS5 Connect" );

                        bt->phase = BS_PHASE_REPLY;

                        return TRUE;
                }
        case BS_PHASE_REPLY:
                {
                        struct socks5_message socks5_reply;
                        int ret;

                        if ( !( ret = jabber_bs_peek( bt, &socks5_reply, sizeof( struct socks5_message ) ) ) )
                                return FALSE;

                        if ( ret < 5 ) /* header up to address length */
                                return TRUE;
                        else if( ret < sizeof( struct socks5_message ) )
                        {
                                /* Either a buggy proxy or just one that doesnt regard
                                 * the SHOULD in XEP-0065 saying the reply SHOULD
                                 * contain the address. We'll take it, so make sure the
                                 * next jabber_bs_peek starts with an empty buffer. */
                                bt->peek_buf_len = 0;
                        }

                        if( !( socks5_reply.ver == 5 ) ||
                            !( socks5_reply.cmdrep.rep == 0 ) ) {
                                char errstr[128] = "";
                                if( ( socks5_reply.ver == 5 ) && ( socks5_reply.cmdrep.rep < 
                                    ( sizeof( socks5_reply_code ) / sizeof( socks5_reply_code[0] ) ) ) ) {
                                        sprintf( errstr, "with \"%s\" ", socks5_reply_code[ socks5_reply.cmdrep.rep ] );
                                }
                                return jabber_bs_abort( bt, "SOCKS5 CONNECT failed %s(reply: ver=%d, rep=%d, atyp=%d, addrlen=%d)", 
                                        errstr,
                                        socks5_reply.ver,
                                        socks5_reply.cmdrep.rep,
                                        socks5_reply.atyp,
                                        socks5_reply.addrlen);
                        }
                        
                        /* usually a proxy sends back the 40 bytes address but I encountered at least one (of jabber.cz) 
                         * that sends atyp=0 addrlen=0 and only 6 bytes (one less than one would expect).
                         * Therefore I removed the wait for more bytes. Since we don't care about what else the proxy
                         * is sending, it shouldnt matter */

                        if( bt->tf->ft->sending )
                                jabber_bs_send_activate( bt );
                        else
                                jabber_bs_recv_answer_request( bt );

                        return FALSE;
                }
        default:
                /* BUG */
                imcb_log( bt->tf->ic, "BUG in file transfer code: undefined handshake phase" );

                bt->tf->watch_in = 0;
                return FALSE;
        }
}

/*
 * If the handshake failed we can try the next streamhost, if there is one.
 * An intelligent sender would probably specify himself as the first streamhost and
 * a proxy as the second (Kopete and PSI are examples here). That way, a (potentially) 
 * slow proxy is only used if neccessary. This of course also means, that the timeout
 * per streamhost should be kept short. If one or two firewalled adresses are specified,
 * they have to timeout first before a proxy is tried.
 */
gboolean jabber_bs_recv_handshake_abort( struct bs_transfer *bt, char *error )
{
        struct jabber_transfer *tf = bt->tf;
        struct xt_node *reply, *iqnode;
        GSList *shlist;

        imcb_log( tf->ic, "Transferring file %s: connection to streamhost %s:%s failed (%s)", 
                  tf->ft->file_name, 
                  bt->sh->host,
                  bt->sh->port,
                  error );

        /* Alright, this streamhost failed, let's try the next... */
        bt->phase = BS_PHASE_CONNECT;
        shlist = g_slist_find( bt->streamhosts, bt->sh );
        if( shlist && shlist->next )
        {
                bt->sh = shlist->next->data;
                return jabber_bs_recv_handshake( bt, -1, 0 );
        }


        /* out of stream hosts */

        iqnode = jabber_make_packet( "iq", "result", tf->ini_jid, NULL );
        reply = jabber_make_error_packet( iqnode, "item-not-found", "cancel" , "404" );
        xt_free_node( iqnode );

        xt_add_attr( reply, "id", tf->iq_id );
                
        if( !jabber_write_packet( tf->ic, reply ) )
                imcb_log( tf->ic, "WARNING: Error transmitting bytestream response" );
        xt_free_node( reply );

        imcb_file_canceled( tf->ic, tf->ft, "couldn't connect to any streamhosts" );

        bt->tf->watch_in = 0;
        /* MUST always return FALSE! */
        return FALSE;
}

/* 
 * After the SOCKS5 handshake succeeds we need to inform the initiator which streamhost we chose.
 * If he is the streamhost himself, he might already know that. However, if it's a proxy,
 * the initiator will have to make a connection himself.
 */
void jabber_bs_recv_answer_request( struct bs_transfer *bt )
{
        struct jabber_transfer *tf = bt->tf;
        struct xt_node *reply;

        imcb_log( tf->ic, "File %s: established SOCKS5 connection to %s:%s", 
                  tf->ft->file_name, 
                  bt->sh->host,
                  bt->sh->port );

        tf->ft->data = tf;
        tf->watch_in = b_input_add( tf->fd, GAIM_INPUT_READ, jabber_bs_recv_read, bt );
        tf->ft->write_request = jabber_bs_recv_write_request;

        reply = xt_new_node( "streamhost-used", NULL, NULL );
        xt_add_attr( reply, "jid", bt->sh->jid );

        reply = xt_new_node( "query", NULL, reply );
        xt_add_attr( reply, "xmlns", XMLNS_BYTESTREAMS );

        reply = jabber_make_packet( "iq", "result", tf->ini_jid, reply );

        xt_add_attr( reply, "id", tf->iq_id );
                
        if( !jabber_write_packet( tf->ic, reply ) )
                imcb_file_canceled( tf->ic, tf->ft, "Error transmitting bytestream response" );
        xt_free_node( reply );
}

/* 
 * This function is called from write_request directly. If no data is available, it will install itself
 * as a watcher for input on fd and once that happens, deliver the data and unschedule itself again.
 */
gboolean jabber_bs_recv_read( gpointer data, gint fd, b_input_condition cond )
{
        int ret;
        struct bs_transfer *bt = data;
        struct jabber_transfer *tf = bt->tf;

        if( fd != -1 ) /* called via event thread */
        {
                tf->watch_in = 0;
                ASSERTSOCKOP( ret = recv( fd, tf->ft->buffer, sizeof( tf->ft->buffer ), 0 ) , "Receiving" );
        }
        else
        {
                /* called directly. There might not be any data available. */
                if( ( ( ret = recv( tf->fd, tf->ft->buffer, sizeof( tf->ft->buffer ), 0 ) ) == -1 ) &&
                    ( errno != EAGAIN ) )
                    return jabber_bs_abort( bt, "Receiving: %s", strerror( errno ) );

                if( ( ret == -1 ) && ( errno == EAGAIN ) )
                {
                        tf->watch_in = b_input_add( tf->fd, GAIM_INPUT_READ, jabber_bs_recv_read, bt );
                        return FALSE;
                }
        }

        /* shouldn't happen since we know the file size */
        if( ret == 0 )
                return jabber_bs_abort( bt, "Remote end closed connection" );
        
        tf->bytesread += ret;

        if( tf->bytesread >= tf->ft->file_size )
                imcb_file_finished( tf->ic, tf->ft );

        tf->ft->write( tf->ft, tf->ft->buffer, ret );   

        return FALSE;
}

/* 
 * imc callback that is invoked when it is ready to receive some data.
 */
gboolean jabber_bs_recv_write_request( file_transfer_t *ft )
{
        struct jabber_transfer *tf = ft->data;

        if( tf->watch_in )
        {
                imcb_file_canceled( tf->ic, ft, "BUG in jabber file transfer: write_request called when already watching for input" );
                return FALSE;
        }
        
        jabber_bs_recv_read( tf->streamhandle, -1 , 0 );

        return TRUE;
}

/* 
 * Issues a write_request to imc.
 * */
gboolean jabber_bs_send_can_write( gpointer data, gint fd, b_input_condition cond )
{
        struct bs_transfer *bt = data;

        bt->tf->watch_out = 0;

        bt->tf->ft->write_request( bt->tf->ft );

        return FALSE;
}

/*
 * This should only be called if we can write, so just do it.
 * Add a write watch so we can write more during the next cycle (if possible).
 */
gboolean jabber_bs_send_write( file_transfer_t *ft, char *buffer, unsigned int len )
{
        struct jabber_transfer *tf = ft->data;
        struct bs_transfer *bt = tf->streamhandle;
        int ret;

        if( tf->watch_out )
                return jabber_bs_abort( bt, "BUG: write() called while watching " );
        
        /* TODO: catch broken pipe */
        ASSERTSOCKOP( ret = send( tf->fd, buffer, len, 0 ), "Sending" );

        tf->byteswritten += ret;
        
        /* TODO: this should really not be fatal */
        if( ret < len )
                return jabber_bs_abort( bt, "send() sent %d instead of %d (send buffer too big!)", ret, len );

        if( tf->byteswritten >= ft->file_size )
                imcb_file_finished( tf->ic, ft );
        else
                bt->tf->watch_out = b_input_add( tf->fd, GAIM_INPUT_WRITE, jabber_bs_send_can_write, bt );
                
        return TRUE;
}

/*
 * Handles the reply by the receiver containing the used streamhost.
 */
static xt_status jabber_bs_send_handle_reply(struct im_connection *ic, struct xt_node *node, struct xt_node *orig ) {
        struct jabber_transfer *tf = NULL;
        struct jabber_data *jd = ic->proto_data;
        struct bs_transfer *bt;
        GSList *tflist;
        struct xt_node *c;
        char *sid, *jid;

        if( !( c = xt_find_node( node->children, "query" ) ) ||
            !( c = xt_find_node( c->children, "streamhost-used" ) ) ||
            !( jid = xt_find_attr( c, "jid" ) ) )

        {
                imcb_log( ic, "WARNING: Received incomplete bytestream reply" );
                return XT_HANDLED;
        }
        
        if( !( c = xt_find_node( orig->children, "query" ) ) ||
            !( sid = xt_find_attr( c, "sid" ) ) )
        {
                imcb_log( ic, "WARNING: Error parsing request corresponding to the incoming bytestream reply" );
                return XT_HANDLED;
        }

        /* Let's see if we can find out what this bytestream should be for... */

        for( tflist = jd->filetransfers ; tflist; tflist = g_slist_next(tflist) )
        {
                struct jabber_transfer *tft = tflist->data;
                if( ( strcmp( tft->sid, sid ) == 0 ) )
                {
                        tf = tft;
                        break;
                }
        }

        if( !tf )
        {
                imcb_log( ic, "WARNING: Received SOCKS5 bytestream reply to unknown request" );
                return XT_HANDLED;
        }

        bt = tf->streamhandle;

        tf->accepted = TRUE;

        if( strcmp( jid, tf->ini_jid ) == 0 )
        {
                /* we're streamhost and target */
                if( bt->phase == BS_PHASE_REPLY )
                {
                        /* handshake went through, let's start transferring */
                        tf->ft->write_request( tf->ft );
                }
        } else
        {
                /* using a proxy, abort listen */

                if( tf->watch_in )
                {
                        b_event_remove( tf->watch_in );
                        tf->watch_in = 0;
                }
                
                if( tf->fd != -1 ) {
                        closesocket( tf->fd );
                        tf->fd = -1;
                }

                if ( bt->connect_timeout )
                {
                        b_event_remove( bt->connect_timeout );
                        bt->connect_timeout = 0;
                }

                GSList *shlist;
                for( shlist = jd->streamhosts ; shlist ; shlist = g_slist_next( shlist ) )
                {
                        jabber_streamhost_t *sh = shlist->data;
                        if( strcmp( sh->jid, jid ) == 0 )
                        {
                                bt->sh = sh;
                                jabber_bs_recv_handshake( bt, -1, 0 );
                                return XT_HANDLED;
                        }
                }

                imcb_log( ic, "WARNING: Received SOCKS5 bytestream reply with unknown streamhost %s", jid );
        }

        return XT_HANDLED;
}

/* 
 * Tell the proxy to activate the stream. Looks like this:
 *
 * <iq type=set>
 *      <query xmlns=bs sid=sid>
 *              <activate>tgt_jid</activate>
 *      </query>
 * </iq>
 */
void jabber_bs_send_activate( struct bs_transfer *bt )
{
        struct xt_node *node;

        node = xt_new_node( "activate", bt->tf->tgt_jid, NULL );
        node = xt_new_node( "query", NULL, node );
        xt_add_attr( node, "xmlns", XMLNS_BYTESTREAMS );
        xt_add_attr( node, "sid", bt->tf->sid );
        node = jabber_make_packet( "iq", "set", bt->sh->jid, node );

        jabber_cache_add( bt->tf->ic, node, jabber_bs_send_handle_activate );

        jabber_write_packet( bt->tf->ic, node );
}

/*
 * The proxy has activated the bytestream.
 * We can finally start pushing some data out.
 */
static xt_status jabber_bs_send_handle_activate( struct im_connection *ic, struct xt_node *node, struct xt_node *orig )
{
        char *sid;
        GSList *tflist;
        struct jabber_transfer *tf = NULL;
        struct xt_node *query;
        struct jabber_data *jd = ic->proto_data;

        query = xt_find_node( orig->children, "query" );
        sid = xt_find_attr( query, "sid" );

        for( tflist = jd->filetransfers ; tflist; tflist = g_slist_next(tflist) )
        {
                struct jabber_transfer *tft = tflist->data;
                if( ( strcmp( tft->sid, sid ) == 0 ) )
                {
                        tf = tft;
                        break;
                }
        }

        if( !tf )
        {
                imcb_log( ic, "WARNING: Received SOCKS5 bytestream activation for unknown stream" );
                return XT_HANDLED;
        }

        imcb_log( tf->ic, "File %s: SOCKS5 handshake and activation successful! Transfer about to start...", tf->ft->file_name );

        /* handshake went through, let's start transferring */
        tf->ft->write_request( tf->ft );

        return XT_HANDLED;
}

jabber_streamhost_t *jabber_si_parse_proxy( struct im_connection *ic, char *proxy )
{
        char *host, *port, *jid;
        jabber_streamhost_t *sh;

        if( ( ( host = strchr( proxy, ',' ) ) == 0 ) ||
             ( ( port = strchr( host+1, ',' ) ) == 0 ) ) {
                imcb_log( ic, "Error parsing proxy setting: \"%s\" (ignored)", proxy );
                return NULL;
        }
        
        jid = proxy;
        *host++ = '\0';
        *port++ = '\0';

        sh = g_new0( jabber_streamhost_t, 1 );
        sh->jid = g_strdup( jid );
        sh->host = g_strdup( host );
        strcpy( sh->port, port );

        return sh;
}

void jabber_si_set_proxies( struct bs_transfer *bt )
{
        struct jabber_transfer *tf = bt->tf;
        struct jabber_data *jd = tf->ic->proto_data;
        char *proxysetting = g_strdup ( set_getstr( &tf->ic->acc->set, "proxy" ) );
        char *proxy, *next, *errmsg = NULL;
        char port[6];
        char host[HOST_NAME_MAX+1];
        jabber_streamhost_t *sh, *sh2;
        GSList *streamhosts = jd->streamhosts;

        proxy = proxysetting;
        while ( proxy && ( *proxy!='\0' ) ) {
                if( ( next = strchr( proxy, ';' ) ) )
                        *next++ = '\0'; 
                
                if( strcmp( proxy, "<local>" ) == 0 ) {
                        if( ( tf->fd = ft_listen( &tf->saddr, host, port, FALSE, &errmsg ) ) != -1 ) {
                                sh = g_new0( jabber_streamhost_t, 1 );
                                sh->jid = g_strdup( tf->ini_jid );
                                sh->host = g_strdup( host );
                                strcpy( sh->port, port );
                                bt->streamhosts = g_slist_append( bt->streamhosts, sh );

                                bt->tf->watch_in = b_input_add( tf->fd, GAIM_INPUT_READ, jabber_bs_send_handshake, bt );
                                bt->connect_timeout = b_timeout_add( JABBER_BS_LISTEN_TIMEOUT * 1000, jabber_bs_connect_timeout, bt );
                        } else {
                                imcb_log( tf->ic, "Transferring file %s: couldn't listen locally(non fatal, check your ft_listen setting in bitlbee.conf): %s",
                                          tf->ft->file_name,
                                          errmsg );
                        }
                } else if( strcmp( proxy, "<auto>" ) == 0 ) {
                        while ( streamhosts ) {
                                sh = g_new0( jabber_streamhost_t, 1 );
                                sh2 = streamhosts->data;
                                sh->jid = g_strdup( sh2->jid );
                                sh->host = g_strdup( sh2->host );
                                strcpy( sh->port, sh2->port );
                                bt->streamhosts = g_slist_append( bt->streamhosts, sh );
                                streamhosts = g_slist_next( streamhosts );
                        }
                } else if( ( sh = jabber_si_parse_proxy( tf->ic, proxy ) ) )
                        bt->streamhosts = g_slist_append( bt->streamhosts, sh );
                proxy = next;
        }
}

/*
 * Starts a bytestream.
 */
gboolean jabber_bs_send_start( struct jabber_transfer *tf )
{
        struct bs_transfer *bt;
        sha1_state_t sha;
        char hash_hex[41];
        unsigned char hash[20];
        int i,ret;

        /* SHA1( SID + Initiator JID + Target JID ) is given to the streamhost which it will match against the initiator's value */
        sha1_init( &sha );
        sha1_append( &sha, (unsigned char*) tf->sid, strlen( tf->sid ) );
        sha1_append( &sha, (unsigned char*) tf->ini_jid, strlen( tf->ini_jid ) );
        sha1_append( &sha, (unsigned char*) tf->tgt_jid, strlen( tf->tgt_jid ) );
        sha1_finish( &sha, hash );
        
        for( i = 0; i < 20; i ++ )
                sprintf( hash_hex + i * 2, "%02x", hash[i] );
                
        bt = g_new0( struct bs_transfer, 1 );
        bt->tf = tf;
        bt->phase = BS_PHASE_CONNECT;
        bt->pseudoadr = g_strdup( hash_hex );
        tf->streamhandle = bt;
        tf->ft->free = jabber_bs_free_transfer;
        tf->ft->canceled = jabber_bs_canceled;

        jabber_si_set_proxies( bt );

        ret = jabber_bs_send_request( tf, bt->streamhosts);

        return ret;
}

gboolean jabber_bs_send_request( struct jabber_transfer *tf, GSList *streamhosts )
{
        struct xt_node *shnode, *query, *iq;

        query = xt_new_node( "query", NULL, NULL );
        xt_add_attr( query, "xmlns", XMLNS_BYTESTREAMS );
        xt_add_attr( query, "sid", tf->sid );
        xt_add_attr( query, "mode", "tcp" );

        while( streamhosts ) {
                jabber_streamhost_t *sh = streamhosts->data;
                shnode = xt_new_node( "streamhost", NULL, NULL );
                xt_add_attr( shnode, "jid", sh->jid );
                xt_add_attr( shnode, "host", sh->host );
                xt_add_attr( shnode, "port", sh->port );

                xt_add_child( query, shnode );

                streamhosts = g_slist_next( streamhosts );
        }


        iq = jabber_make_packet( "iq", "set", tf->tgt_jid, query );
        xt_add_attr( iq, "from", tf->ini_jid );

        jabber_cache_add( tf->ic, iq, jabber_bs_send_handle_reply );

        if( !jabber_write_packet( tf->ic, iq ) )
                imcb_file_canceled( tf->ic, tf->ft, "Error transmitting bytestream request" );
        return TRUE;
}

gboolean jabber_bs_send_handshake_abort(struct bs_transfer *bt, char *error )
{
        struct jabber_transfer *tf = bt->tf;
        struct jabber_data *jd = tf->ic->proto_data;

        /* TODO: did the receiver get here somehow??? */
        imcb_log( tf->ic, "Transferring file %s: SOCKS5 handshake failed: %s", 
                  tf->ft->file_name, 
                  error );

        if( jd->streamhosts==NULL ) /* we're done here unless we have a proxy to try */
                imcb_file_canceled( tf->ic, tf->ft, error );

        /* MUST always return FALSE! */
        return FALSE;
}

/*
 * SOCKS5BYTESTREAM protocol for the sender
 */
gboolean jabber_bs_send_handshake( gpointer data, gint fd, b_input_condition cond )
{
        struct bs_transfer *bt = data;
        struct jabber_transfer *tf = bt->tf;
        short revents;

        if ( !jabber_bs_poll( bt, fd, &revents ) )
                return FALSE;
        
        switch( bt->phase ) 
        {
        case BS_PHASE_CONNECT:
                {
                        struct sockaddr_storage clt_addr;
                        socklen_t ssize = sizeof( clt_addr );
                        
                        /* Connect */

                        ASSERTSOCKOP( tf->fd = accept( fd, (struct sockaddr *) &clt_addr, &ssize ), "Accepting connection" );

                        closesocket( fd );
                        fd = tf->fd;
                        sock_make_nonblocking( fd );
                        
                        bt->phase = BS_PHASE_CONNECTED;

                        bt->tf->watch_in = b_input_add( fd, GAIM_INPUT_READ, jabber_bs_send_handshake, bt );
                        return FALSE;
                }
        case BS_PHASE_CONNECTED:
                {
                        int ret, have_noauth=FALSE;
                        struct {
                                unsigned char ver;
                                unsigned char method;
                        } socks5_auth_reply = { .ver = 5, .method = 0 };
                        struct {
                                unsigned char ver;
                                unsigned char nmethods;
                                unsigned char method;
                        } socks5_hello;

                        if( !( ret = jabber_bs_peek( bt, &socks5_hello, sizeof( socks5_hello ) ) ) )
                                return FALSE;

                        if( ret < sizeof( socks5_hello ) )
                                return TRUE;

                        if( !( socks5_hello.ver == 5 ) ||
                            !( socks5_hello.nmethods >= 1 ) ||
                            !( socks5_hello.nmethods < 32 ) )
                                return jabber_bs_abort( bt, "Invalid auth request ver=%d nmethods=%d method=%d", socks5_hello.ver, socks5_hello.nmethods, socks5_hello.method );

                        have_noauth = socks5_hello.method == 0;

                        if( socks5_hello.nmethods > 1 )
                        {
                                char mbuf[32];
                                int i;
                                ASSERTSOCKOP( ret = recv( fd, mbuf, socks5_hello.nmethods - 1, 0 ) , "Receiving auth methods" );
                                if( ret < ( socks5_hello.nmethods - 1 ) )
                                        return jabber_bs_abort( bt, "Partial auth request");
                                for( i = 0 ; !have_noauth && ( i < socks5_hello.nmethods - 1 ) ; i ++ )
                                        if( mbuf[i] == 0 )
                                                have_noauth = TRUE;
                        }
                        
                        if( !have_noauth )
                                return jabber_bs_abort( bt, "Auth request didn't include no authentication" );

                        ASSERTSOCKOP( send( fd, &socks5_auth_reply, sizeof( socks5_auth_reply ) , 0 ), "Sending auth reply" );

                        bt->phase = BS_PHASE_REQUEST;

                        return TRUE;
                }
        case BS_PHASE_REQUEST:
                {
                        struct socks5_message socks5_connect;
                        int msgsize = sizeof( struct socks5_message );
                        int ret;

                        if( !( ret = jabber_bs_peek( bt, &socks5_connect, msgsize ) ) )
                                return FALSE;

                        if( ret < msgsize )
                                return TRUE;

                        if( !( socks5_connect.ver == 5) ||
                            !( socks5_connect.cmdrep.cmd == 1 ) ||
                            !( socks5_connect.atyp == 3 ) ||
                            !(socks5_connect.addrlen == 40 ) )
                                return jabber_bs_abort( bt, "Invalid SOCKS5 Connect message (addrlen=%d, ver=%d, cmd=%d, atyp=%d)", socks5_connect.addrlen, socks5_connect.ver, socks5_connect.cmdrep.cmd, socks5_connect.atyp );
                        if( !( memcmp( socks5_connect.address, bt->pseudoadr, 40 ) == 0 ) )
                                return jabber_bs_abort( bt, "SOCKS5 Connect message contained wrong digest");

                        socks5_connect.cmdrep.rep = 0;

                        ASSERTSOCKOP( send( fd, &socks5_connect, msgsize, 0 ), "Sending connect reply" );

                        bt->phase = BS_PHASE_REPLY;

                        imcb_log( tf->ic, "File %s: SOCKS5 handshake successful! Transfer about to start...", tf->ft->file_name );

                        if( tf->accepted )
                        {
                                /* streamhost-used message came already in(possible?), let's start sending */
                                tf->ft->write_request( tf->ft );
                        }

                        tf->watch_in = 0;
                        return FALSE;

                }
        default:
                /* BUG */
                imcb_log( bt->tf->ic, "BUG in file transfer code: undefined handshake phase" );

                bt->tf->watch_in = 0;
                return FALSE;
        }
}
#undef ASSERTSOCKOP