source: protocols/jabber/s5bytestream.c @ fa8f57b

/***************************************************************************\
*                                                                           *
*  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 "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 *pseudoaddr;

        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, ...) G_GNUC_PRINTF(2, 3);
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);
                tf->watch_in = 0;
        }

        if (tf->watch_out) {
                b_event_remove(tf->watch_out);
                tf->watch_out = 0;
        }

        g_free(bt->pseudoaddr);

        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);
        }
}

void jabber_bs_remove_events(struct bs_transfer *bt)
{
        struct jabber_transfer *tf = bt->tf;

        if (tf->watch_out) {
                b_event_remove(tf->watch_out);
                tf->watch_out = 0;
        }

        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;
        }
}

/* 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);
}

static struct jabber_transfer *get_ft_by_sid(GSList *tflist, char *sid) {
        GSList *l;
        for (l = tflist; l; l = g_slist_next(l)) {
                struct jabber_transfer *tft = l->data;
                if ((strcmp(tft->sid, sid) == 0)) { 
                        return tft;
                }
        }
        return NULL;
}

/* SHA1( SID + Initiator JID + Target JID ) is given to the streamhost which it will match against the initiator's value
 * Returns a newly allocated string */
static char *generate_pseudoaddr(char *sid, char *ini_jid, char *tgt_jid) {
        char *contents = g_strconcat(sid, ini_jid, tgt_jid, NULL);
        char *hash_hex = g_compute_checksum_for_string(G_CHECKSUM_SHA1, contents, -1);
        g_free(contents);
        return hash_hex;
}

static jabber_streamhost_t *jabber_streamhost_new(char *jid, char *host, int port)
{
        jabber_streamhost_t *sh = g_new0(jabber_streamhost_t, 1);
        sh->jid = g_strdup(jid);
        sh->host = g_strdup(host);
        if (port) {
                g_snprintf(sh->port, sizeof(sh->port), "%u", port);
        }
        return sh;
}

/*
 * 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;
        struct bs_transfer *bt;
        GSList *shlist = NULL;
        struct xt_node *shnode;

        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)) {
                        shlist = g_slist_append(shlist, jabber_streamhost_new(jid, host, port));
                }
                shnode = shnode->next;
        }

        if (!shlist) {
                imcb_log(ic, "WARNING: Received incomplete SI bytestream request, no parseable streamhost entries");
                return XT_HANDLED;
        }

        if (!(tf = get_ft_by_sid(jd->filetransfers, sid))) {
                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;

        bt = g_new0(struct bs_transfer, 1);
        bt->tf = tf;
        bt->streamhosts = shlist;
        bt->sh = shlist->data;
        bt->phase = BS_PHASE_CONNECT;
        bt->pseudoaddr = generate_pseudoaddr(sid, ini_jid, tgt_jid);
        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, B_EV_IO_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, B_EV_IO_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->pseudoaddr),
                        .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->pseudoaddr, 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 should not 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 necessary. 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;
                jabber_bs_remove_events(bt);
                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");

        /* 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, B_EV_IO_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, B_EV_IO_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, B_EV_IO_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;
        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... */

        if (!(tf = get_ft_by_sid(jd->filetransfers, sid))) {
                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 */

                jabber_bs_remove_events(bt);

                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;
        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");

        if (!(tf = get_ft_by_sid(jd->filetransfers, sid))) {
                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 = jabber_streamhost_new(jid, host, 0);
        strncpy(sh->port, port, sizeof(sh->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, jd->fd, FALSE, &errmsg)) != -1) {
                                sh = jabber_streamhost_new(tf->ini_jid, host, 0);
                                strncpy(sh->port, port, sizeof(sh->port));
                                bt->streamhosts = g_slist_append(bt->streamhosts, sh);

                                bt->tf->watch_in = b_input_add(tf->fd, B_EV_IO_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;

        bt = g_new0(struct bs_transfer, 1);
        bt->tf = tf;
        bt->phase = BS_PHASE_CONNECT;
        bt->pseudoaddr = generate_pseudoaddr(tf->sid, tf->ini_jid, tf->tgt_jid);
        tf->streamhandle = bt;
        tf->ft->free = jabber_bs_free_transfer;
        tf->ft->canceled = jabber_bs_canceled;

        jabber_si_set_proxies(bt);

        return jabber_bs_send_request(tf, bt->streamhosts);
}

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, B_EV_IO_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->pseudoaddr, 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