libssh2/src/packet.c

/* Copyright (c) 2004-2007, Sara Golemon <sarag@libssh2.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms,
 * with or without modification, are permitted provided
 * that the following conditions are met:
 *
 *   Redistributions of source code must retain the above
 *   copyright notice, this list of conditions and the
 *   following disclaimer.
 *
 *   Redistributions in binary form must reproduce the above
 *   copyright notice, this list of conditions and the following
 *   disclaimer in the documentation and/or other materials
 *   provided with the distribution.
 *
 *   Neither the name of the copyright holder nor the names
 *   of any other contributors may be used to endorse or
 *   promote products derived from this software without
 *   specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
 * USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
 * OF SUCH DAMAGE.
 */

#include "libssh2_priv.h"
#include <errno.h>
#include <fcntl.h>

#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

#ifdef HAVE_SYS_TIME_H
#include <sys/time.h>
#endif

#ifdef HAVE_INTTYPES_H
#include <inttypes.h>
#endif

/* Needed for struct iovec on some platforms */
#ifdef HAVE_SYS_UIO_H
#include <sys/uio.h>
#endif

#include <sys/types.h>

/* {{{ libssh2_packet_queue_listener
 * Queue a connection request for a listener
 */
static inline int libssh2_packet_queue_listener(LIBSSH2_SESSION *session,
                                                unsigned char *data,
                                                unsigned long datalen)
{
    /* Look for a matching listener */
    unsigned char *s = data + (sizeof("forwarded-tcpip") - 1) + 5;
    /* 17 = packet_type(1) + channel(4) + reason(4) + descr(4) + lang(4) */
    unsigned long packet_len = 17 + (sizeof("Forward not requested") - 1);
    unsigned char *p, packet[17 + (sizeof("Forward not requested") - 1)];
    LIBSSH2_LISTENER *l = session->listeners;
    char failure_code = 1; /* SSH_OPEN_ADMINISTRATIVELY_PROHIBITED */
    uint32_t sender_channel, initial_window_size, packet_size;
    unsigned char *host, *shost;
    uint32_t port, sport, host_len, shost_len;
    (void)datalen;
    
    sender_channel = libssh2_ntohu32(s);            s += 4;
    
    initial_window_size = libssh2_ntohu32(s);       s += 4;
    packet_size = libssh2_ntohu32(s);               s += 4;
    
    host_len = libssh2_ntohu32(s);                  s += 4;
    host = s;                                       s += host_len;
    port = libssh2_ntohu32(s);                      s += 4;
    
    shost_len = libssh2_ntohu32(s);                 s += 4;
    shost = s;                                      s += shost_len;
    sport = libssh2_ntohu32(s);                     s += 4;
    
    _libssh2_debug(session, LIBSSH2_DBG_CONN, "Remote received connection from %s:%ld to %s:%ld", shost, sport, host, port);
    
    while (l) {
        if ((l->port == (int)port) &&
            (strlen(l->host) == host_len) &&
            (memcmp(l->host, host, host_len) == 0)) {
            /* This is our listener */
            LIBSSH2_CHANNEL *channel, *last_queued = l->queue;
            
            if (l->queue_maxsize &&
                (l->queue_maxsize <= l->queue_size)) {
                /* Queue is full */
                failure_code = 4; /* SSH_OPEN_RESOURCE_SHORTAGE */
                _libssh2_debug(session, LIBSSH2_DBG_CONN, "Listener queue full, ignoring");
                break;
            }
            
            channel = LIBSSH2_ALLOC(session, sizeof(LIBSSH2_CHANNEL));
            if (!channel) {
                libssh2_error(session, LIBSSH2_ERROR_ALLOC, "Unable to allocate a channel for new connection", 0);
                failure_code = 4; /* SSH_OPEN_RESOURCE_SHORTAGE */
                break;
            }
            memset(channel, 0, sizeof(LIBSSH2_CHANNEL));
            
            channel->session = session;
            channel->channel_type_len = sizeof("forwarded-tcpip") - 1;
            channel->channel_type = LIBSSH2_ALLOC(session, channel->channel_type_len + 1);
            if (!channel->channel_type) {
                libssh2_error(session, LIBSSH2_ERROR_ALLOC, "Unable to allocate a channel for new connection", 0);
                LIBSSH2_FREE(session, channel);
                failure_code = 4; /* SSH_OPEN_RESOURCE_SHORTAGE */
                break;
            }
            memcpy(channel->channel_type, "forwarded-tcpip", channel->channel_type_len + 1);
            
            channel->remote.id = sender_channel;
            channel->remote.window_size_initial = LIBSSH2_CHANNEL_WINDOW_DEFAULT;
            channel->remote.window_size = LIBSSH2_CHANNEL_WINDOW_DEFAULT;
            channel->remote.packet_size = LIBSSH2_CHANNEL_PACKET_DEFAULT;
            
            channel->local.id = libssh2_channel_nextid(session);
            channel->local.window_size_initial = initial_window_size;
            channel->local.window_size = initial_window_size;
            channel->local.packet_size = packet_size;
            
            _libssh2_debug(session, LIBSSH2_DBG_CONN, "Connection queued: channel %lu/%lu win %lu/%lu packet %lu/%lu",
                           channel->local.id, channel->remote.id,
                           channel->local.window_size, channel->remote.window_size,
                           channel->local.packet_size, channel->remote.packet_size);
            
            p = packet;
            *(p++) = SSH_MSG_CHANNEL_OPEN_CONFIRMATION;
            libssh2_htonu32(p, channel->remote.id);                         p += 4;
            libssh2_htonu32(p, channel->local.id);                          p += 4;
            libssh2_htonu32(p, channel->remote.window_size_initial);        p += 4;
            libssh2_htonu32(p, channel->remote.packet_size);                p += 4;
            
            if (libssh2_packet_write(session, packet, 17)) {
                libssh2_error(session, LIBSSH2_ERROR_SOCKET_SEND, "Unable to send channel open confirmation", 0);
                return -1;
            }
            
            /* Link the channel into the end of the queue list */
            
            if (!last_queued) {
                l->queue = channel;
                return 0;
            }
            
            while (last_queued->next) last_queued = last_queued->next;
            
            last_queued->next = channel;
            channel->prev = last_queued;
            
            l->queue_size++;
            
            return 0;
        }
        
        l = l->next;
    }
    
    /* We're not listening to you */
    {
        
        p = packet;
        *(p++) = SSH_MSG_CHANNEL_OPEN_FAILURE;
        libssh2_htonu32(p, sender_channel);                                             p += 4;
        libssh2_htonu32(p, failure_code);                                               p += 4;
        libssh2_htonu32(p, sizeof("Forward not requested") - 1);                        p += 4;
        memcpy(s, "Forward not requested", sizeof("Forward not requested") - 1);        p += sizeof("Forward not requested") - 1;
        libssh2_htonu32(p, 0);
        
        if (libssh2_packet_write(session, packet, packet_len)) {
            libssh2_error(session, LIBSSH2_ERROR_SOCKET_SEND, "Unable to send open failure", 0);
            return -1;
        }
        return 0;
    }
}
/* }}} */

/* {{{ libssh2_packet_x11_open
 * Accept a forwarded X11 connection
 */
static inline int libssh2_packet_x11_open(LIBSSH2_SESSION *session,
                                          unsigned char *data, unsigned long datalen)
{
    int failure_code = 2; /* SSH_OPEN_CONNECT_FAILED */
    unsigned char *s = data + (sizeof("x11") - 1) + 5;
    unsigned long packet_len = 17 + (sizeof("X11 Forward Unavailable") - 1);
    unsigned char *p, packet[17 + (sizeof("X11 Forward Unavailable") - 1)];
    /* packet_type(1) + channel(4) + reason(4) + descr(4) + lang(4) */
    LIBSSH2_CHANNEL *channel;
    unsigned long sender_channel, initial_window_size, packet_size;
    unsigned char *shost;
    unsigned long sport, shost_len;
    (void)datalen;
    
    sender_channel = libssh2_ntohu32(s);                    s += 4;
    initial_window_size = libssh2_ntohu32(s);               s += 4;
    packet_size = libssh2_ntohu32(s);                               s += 4;
    shost_len = libssh2_ntohu32(s);                                 s += 4;
    shost = s;                                                                              s += shost_len;
    sport = libssh2_ntohu32(s);                                             s += 4;
    
    _libssh2_debug(session, LIBSSH2_DBG_CONN, "X11 Connection Received from %s:%ld on channel %lu", shost, sport, sender_channel);
    if (session->x11) {
        channel = LIBSSH2_ALLOC(session, sizeof(LIBSSH2_CHANNEL));
        if (!channel) {
            libssh2_error(session, LIBSSH2_ERROR_ALLOC, "Unable to allocate a channel for new connection", 0);
            failure_code = 4; /* SSH_OPEN_RESOURCE_SHORTAGE */
            goto x11_exit;
        }
        memset(channel, 0, sizeof(LIBSSH2_CHANNEL));
        
        channel->session = session;
        channel->channel_type_len = sizeof("x11") - 1;
        channel->channel_type = LIBSSH2_ALLOC(session, channel->channel_type_len + 1);
        if (!channel->channel_type) {
            libssh2_error(session, LIBSSH2_ERROR_ALLOC, "Unable to allocate a channel for new connection", 0);
            LIBSSH2_FREE(session, channel);
            failure_code = 4; /* SSH_OPEN_RESOURCE_SHORTAGE */
            goto x11_exit;
        }
        memcpy(channel->channel_type, "x11", channel->channel_type_len + 1);
        
        channel->remote.id = sender_channel;
        channel->remote.window_size_initial = LIBSSH2_CHANNEL_WINDOW_DEFAULT;
        channel->remote.window_size = LIBSSH2_CHANNEL_WINDOW_DEFAULT;
        channel->remote.packet_size = LIBSSH2_CHANNEL_PACKET_DEFAULT;
        
        channel->local.id = libssh2_channel_nextid(session);
        channel->local.window_size_initial = initial_window_size;
        channel->local.window_size = initial_window_size;
        channel->local.packet_size = packet_size;
        
        _libssh2_debug(session, LIBSSH2_DBG_CONN, "X11 Connection established: channel %lu/%lu win %lu/%lu packet %lu/%lu",
                       channel->local.id, channel->remote.id,
                       channel->local.window_size, channel->remote.window_size,
                       channel->local.packet_size, channel->remote.packet_size);
        p = packet;
        *(p++) = SSH_MSG_CHANNEL_OPEN_CONFIRMATION;
        libssh2_htonu32(p, channel->remote.id);                                         p += 4;
        libssh2_htonu32(p, channel->local.id);                                          p += 4;
        libssh2_htonu32(p, channel->remote.window_size_initial);        p += 4;
        libssh2_htonu32(p, channel->remote.packet_size);                        p += 4;
        
        if (libssh2_packet_write(session, packet, 17)) {
            libssh2_error(session, LIBSSH2_ERROR_SOCKET_SEND, "Unable to send channel open confirmation", 0);
            return -1;
        }
        
        /* Link the channel into the session */
        if (session->channels.tail) {
            session->channels.tail->next = channel;
            channel->prev = session->channels.tail;
        } else {
            session->channels.head = channel;
            channel->prev = NULL;
        }
        channel->next = NULL;
        session->channels.tail = channel;
        
        /*
         * Pass control to the callback, they may turn right around and
         * free the channel, or actually use it
         */
        LIBSSH2_X11_OPEN(channel, (char *)shost, sport);
        
        return 0;
    } else {
        failure_code = 4; /* SSH_OPEN_RESOURCE_SHORTAGE */
    }
    
x11_exit:
    p = packet;
    *(p++) = SSH_MSG_CHANNEL_OPEN_FAILURE;
    libssh2_htonu32(p, sender_channel);                                             p += 4;
    libssh2_htonu32(p, failure_code);                                               p += 4;
    libssh2_htonu32(p, sizeof("X11 Forward Unavailable") - 1);                      p += 4;
    memcpy(s, "X11 Forward Unavailable", sizeof("X11 Forward Unavailable") - 1);    p += sizeof("X11 Forward Unavailable") - 1;
    libssh2_htonu32(p, 0);
    
    if (libssh2_packet_write(session, packet, packet_len)) {
        libssh2_error(session, LIBSSH2_ERROR_SOCKET_SEND, "Unable to send open failure", 0);
        return -1;
    }
    return 0;
}
/* }}} */

/* {{{ libssh2_packet_new
 * Create a new packet and attach it to the brigade
 */
int libssh2_packet_add(LIBSSH2_SESSION *session, unsigned char *data, size_t datalen, int macstate)
{
    LIBSSH2_PACKET *packet;
    unsigned long data_head = 0;
    
    _libssh2_debug(session, LIBSSH2_DBG_TRANS, "Packet type %d received, length=%d", (int)data[0], (int)datalen);
    if (macstate == LIBSSH2_MAC_INVALID) {
        if (session->macerror) {
            if (LIBSSH2_MACERROR(session, (char *)data, datalen) == 0) {
                /* Calling app has given the OK, Process it anyway */
                macstate = LIBSSH2_MAC_CONFIRMED;
            } else {
                libssh2_error(session, LIBSSH2_ERROR_INVALID_MAC, "Invalid Message Authentication Code received", 0);
                if (session->ssh_msg_disconnect) {
                    LIBSSH2_DISCONNECT(session, SSH_DISCONNECT_MAC_ERROR, "Invalid MAC received", sizeof("Invalid MAC received") - 1, "", 0);
                }
                LIBSSH2_FREE(session, data);
                return -1;
            }
        } else {
            libssh2_error(session, LIBSSH2_ERROR_INVALID_MAC, "Invalid Message Authentication Code received", 0);
            if (session->ssh_msg_disconnect) {
                LIBSSH2_DISCONNECT(session, SSH_DISCONNECT_MAC_ERROR, "Invalid MAC received", sizeof("Invalid MAC received") - 1, "", 0);
            }
            LIBSSH2_FREE(session, data);
            return -1;
        }
    }
    
    /* A couple exceptions to the packet adding rule: */
    switch (data[0]) {
        case SSH_MSG_DISCONNECT:
            {
                char *message, *language;
                int reason, message_len, language_len;
                
                reason = libssh2_ntohu32(data + 1);
                message_len = libssh2_ntohu32(data + 5);
                message = (char *)data + 9; /* packet_type(1) + reason(4) + message_len(4) */
                language_len = libssh2_ntohu32(data + 9 + message_len);
                /* This is where we hack on the data a little,
                 * Use the MSB of language_len to to a terminating NULL (In all liklihood it is already)
                 * Shift the language tag back a byte (In all likelihood it's zero length anyway
                 * Store a NULL in the last byte of the packet to terminate the language string
                 * With the lengths passed this isn't *REALLY* necessary, but it's "kind"
                 */
                message[message_len] = '\0';
                language = (char *)data + 9 + message_len + 3;
                if (language_len) {
                    memcpy(language, language + 1, language_len);
                }
                language[language_len] = '\0';
                
                if (session->ssh_msg_disconnect) {
                    LIBSSH2_DISCONNECT(session, reason, message, message_len, language, language_len);
                }
                _libssh2_debug(session, LIBSSH2_DBG_TRANS, "Disconnect(%d): %s(%s)", reason, message, language);
                LIBSSH2_FREE(session, data);
                session->socket_state = LIBSSH2_SOCKET_DISCONNECTED;
                return -1;
            }
            break;
        case SSH_MSG_IGNORE:
            /* As with disconnect, back it up one and add a trailing NULL */
            memcpy(data + 4, data + 5, datalen - 5);
            data[datalen] = '\0';
            if (session->ssh_msg_ignore) {
                LIBSSH2_IGNORE(session, (char *)data + 4, datalen - 5);
            }
                LIBSSH2_FREE(session, data);
            return 0;
            break;
        case SSH_MSG_DEBUG:
            {
                int always_display = data[0];
                char *message, *language;
                int message_len, language_len;
                
                message_len = libssh2_ntohu32(data + 2);
                message = (char *)data + 6; /* packet_type(1) + display(1) + message_len(4) */
                language_len = libssh2_ntohu32(data + 6 + message_len);
                /* This is where we hack on the data a little,
                 * Use the MSB of language_len to to a terminating NULL (In all liklihood it is already)
                 * Shift the language tag back a byte (In all likelihood it's zero length anyway
                 * Store a NULL in the last byte of the packet to terminate the language string
                 * With the lengths passed this isn't *REALLY* necessary, but it's "kind"
                 */
                message[message_len] = '\0';
                language = (char *)data + 6 + message_len + 3;
                if (language_len) {
                    memcpy(language, language + 1, language_len);
                }
                language[language_len] = '\0';
                
                if (session->ssh_msg_debug) {
                    LIBSSH2_DEBUG(session, always_display, message, message_len, language, language_len);
                }
                /* _libssh2_debug will actually truncate this for us so that it's not an inordinate about of data */
                _libssh2_debug(session, LIBSSH2_DBG_TRANS, "Debug Packet: %s", message);
                LIBSSH2_FREE(session, data);
                return 0;
            }
            break;
        case SSH_MSG_CHANNEL_EXTENDED_DATA:
            data_head += 4; /* streamid(4) */
        case SSH_MSG_CHANNEL_DATA:
            data_head += 9; /* packet_type(1) + channelno(4) + datalen(4) */
            {
                LIBSSH2_CHANNEL *channel = libssh2_channel_locate(session, libssh2_ntohu32(data + 1));
                
                if (!channel) {
                    libssh2_error(session, LIBSSH2_ERROR_CHANNEL_UNKNOWN, "Packet received for unknown channel, ignoring", 0);
                    LIBSSH2_FREE(session, data);
                    return 0;
                }
#ifdef LIBSSH2DEBUG
                {
                    unsigned long stream_id = 0;
                    
                    if (data[0] == SSH_MSG_CHANNEL_EXTENDED_DATA) {
                        stream_id = libssh2_ntohu32(data + 5);
                    }
                    
                    _libssh2_debug(session, LIBSSH2_DBG_CONN, "%d bytes received for channel %lu/%lu stream #%lu", (int)(datalen - data_head), channel->local.id, channel->remote.id, stream_id);
                }
#endif
                if ((channel->remote.extended_data_ignore_mode == LIBSSH2_CHANNEL_EXTENDED_DATA_IGNORE) && (data[0] == SSH_MSG_CHANNEL_EXTENDED_DATA)) {
                    /* Pretend we didn't receive this */
                    LIBSSH2_FREE(session, data);
                    
                    _libssh2_debug(session, LIBSSH2_DBG_CONN, "Ignoring extended data and refunding %d bytes", (int)(datalen - 13));
                    /* Adjust the window based on the block we just freed */
                    libssh2_channel_receive_window_adjust(channel, datalen - 13, 0);
                    
                    return 0;
                }
                
                /* REMEMBER! remote means remote as source of data, NOT remote window! */
                if (channel->remote.packet_size < (datalen - data_head)) {
                    /* Spec says we MAY ignore bytes sent beyond packet_size */
                    libssh2_error(session, LIBSSH2_ERROR_CHANNEL_PACKET_EXCEEDED, "Packet contains more data than we offered to receive, truncating", 0);
                    datalen = channel->remote.packet_size + data_head;
                }
                if (channel->remote.window_size <= 0) {
                    /* Spec says we MAY ignore bytes sent beyond window_size */
                    libssh2_error(session, LIBSSH2_ERROR_CHANNEL_WINDOW_EXCEEDED, "The current receive window is full, data ignored", 0);
                    LIBSSH2_FREE(session, data);
                    return 0;
                }
                /* Reset EOF status */
                channel->remote.eof = 0;
                
                if ((datalen - data_head) > channel->remote.window_size) {
                    libssh2_error(session, LIBSSH2_ERROR_CHANNEL_WINDOW_EXCEEDED, "Remote sent more data than current window allows, truncating", 0);
                    datalen = channel->remote.window_size + data_head;
                } else {
                    /* Now that we've received it, shrink our window */
                    channel->remote.window_size -= datalen - data_head;
                }
            }
            break;
        case SSH_MSG_CHANNEL_EOF:
            {
                LIBSSH2_CHANNEL *channel = libssh2_channel_locate(session, libssh2_ntohu32(data + 1));
                
                if (!channel) {
                    /* We may have freed already, just quietly ignore this... */
                    LIBSSH2_FREE(session, data);
                    return 0;
                }
                
                _libssh2_debug(session, LIBSSH2_DBG_CONN, "EOF received for channel %lu/%lu", channel->local.id, channel->remote.id);
                channel->remote.eof = 1;
                
                LIBSSH2_FREE(session, data);
                return 0;
            }
            break;
        case SSH_MSG_CHANNEL_REQUEST:
            {
                if (libssh2_ntohu32(data+5) == sizeof("exit-status") - 1
                    && !memcmp("exit-status", data + 9, sizeof("exit-status") - 1)) {
                    
                    /* we've got "exit-status" packet. Set the session value */
                    LIBSSH2_CHANNEL *channel = libssh2_channel_locate(session, libssh2_ntohu32(data+1));
                    
                    if (channel) {
                        channel->exit_status = libssh2_ntohu32(data + 9 + sizeof("exit-status"));
                        _libssh2_debug(session, LIBSSH2_DBG_CONN, "Exit status %lu received for channel %lu/%lu", channel->exit_status, channel->local.id, channel->remote.id);
                    }
                    
                    LIBSSH2_FREE(session, data);
                    return 0;
                }
            }
            break;
        case SSH_MSG_CHANNEL_CLOSE:
            {
                LIBSSH2_CHANNEL *channel = libssh2_channel_locate(session, libssh2_ntohu32(data + 1));
                
                if (!channel) {
                    /* We may have freed already, just quietly ignore this... */
                    LIBSSH2_FREE(session, data);
                    return 0;
                }
                _libssh2_debug(session, LIBSSH2_DBG_CONN, "Close received for channel %lu/%lu", channel->local.id, channel->remote.id);
                
                channel->remote.close = 1;
                channel->remote.eof = 1;
                /* TODO: Add a callback for this */
                
                LIBSSH2_FREE(session, data);
                return 0;
            }
            break;
        case SSH_MSG_CHANNEL_OPEN:
            if ((datalen >= (sizeof("forwarded-tcpip") + 4)) &&
                ((sizeof("forwarded-tcpip")-1) == libssh2_ntohu32(data + 1)) &&
                (memcmp(data + 5, "forwarded-tcpip", sizeof("forwarded-tcpip") - 1) == 0)) {
                int retval = libssh2_packet_queue_listener(session, data, datalen);
                
                LIBSSH2_FREE(session, data);
                return retval;
            }
            if ((datalen >= (sizeof("x11") + 4)) &&
                ((sizeof("x11")-1) == libssh2_ntohu32(data + 1)) &&
                (memcmp(data + 5, "x11", sizeof("x11") - 1) == 0)) {
                int retval = libssh2_packet_x11_open(session, data, datalen);
                
                LIBSSH2_FREE(session, data);
                return retval;
            }
            break;
        case SSH_MSG_CHANNEL_WINDOW_ADJUST:
            {
                LIBSSH2_CHANNEL *channel = libssh2_channel_locate(session, libssh2_ntohu32(data + 1));
                unsigned long bytestoadd = libssh2_ntohu32(data + 5);
                
                if (channel && bytestoadd) {
                    channel->local.window_size += bytestoadd;
                }
                _libssh2_debug(session, LIBSSH2_DBG_CONN, "Window adjust received for channel %lu/%lu, adding %lu bytes, new window_size=%lu", channel->local.id, channel->remote.id, bytestoadd, channel->local.window_size);
                
                LIBSSH2_FREE(session, data);
                return 0;
            }
            break;
        }
    
    packet = LIBSSH2_ALLOC(session, sizeof(LIBSSH2_PACKET));
    if (!packet) {
        _libssh2_debug(session, LIBSSH2_ERROR_ALLOC, "Unable to allocate memory for LIBSSH2_PACKET");
        LIBSSH2_FREE(session, data);
        return -1;
    }
    memset(packet, 0, sizeof(LIBSSH2_PACKET));
    
    packet->data = data;
    packet->data_len = datalen;
    packet->data_head = data_head;
    packet->mac = macstate;
    packet->brigade = &session->packets;
    packet->next = NULL;
    
    if (session->packets.tail) {
        packet->prev = session->packets.tail;
        packet->prev->next = packet;
        session->packets.tail = packet;
    } else {
        session->packets.head = packet;
        session->packets.tail = packet;
        packet->prev = NULL;
    }
    
    if (data[0] == SSH_MSG_KEXINIT && !(session->state & LIBSSH2_STATE_EXCHANGING_KEYS)) {
        /* Remote wants new keys
         * Well, it's already in the brigade,
         * let's just call back into ourselves
         */
        _libssh2_debug(session, LIBSSH2_DBG_TRANS,
                       "Renegotiating Keys");
        libssh2_kex_exchange(session, 1);
        /* If there was a key reexchange failure, let's just hope we didn't send NEWKEYS yet, otherwise remote will drop us like a rock */
    }
    
    return 0;
}
/* }}} */

/* {{{ libssh2_packet_ask
 * Scan the brigade for a matching packet type, optionally poll the socket for
 * a packet first
 */
int libssh2_packet_ask_ex(LIBSSH2_SESSION *session, unsigned char packet_type,
                          unsigned char **data, unsigned long *data_len,
                          unsigned long match_ofs,
                          const unsigned char *match_buf,
                          unsigned long match_len, int poll_socket)
{
    LIBSSH2_PACKET *packet = session->packets.head;
    
    if (poll_socket) {
        libssh2pack_t rc = libssh2_packet_read(session);
        if ((rc < 0) && !packet) {
            return rc;
        }
    }
    _libssh2_debug(session, LIBSSH2_DBG_TRANS,
                   "Looking for packet of type: %d", (int)packet_type);
    
    while (packet) {
        if (packet->data[0] == packet_type &&
            (packet->data_len >= (match_ofs + match_len)) &&
            (!match_buf ||
             (memcmp(packet->data + match_ofs, match_buf, match_len) == 0))) {
            *data = packet->data;
            *data_len = packet->data_len;
            
            if (packet->prev) {
                packet->prev->next = packet->next;
            } else {
                session->packets.head = packet->next;
            }
            
            if (packet->next) {
                packet->next->prev = packet->prev;
            } else {
                session->packets.tail = packet->prev;
            }
            
            LIBSSH2_FREE(session, packet);
            
            return 0;
        }
        packet = packet->next;
    }
    return -1;
}
/* }}} */

/* {{{ libssh2_packet_askv
 * Scan for any of a list of packet types in the brigade, optionally poll the
 * socket for a packet first
 */
int libssh2_packet_askv_ex(LIBSSH2_SESSION *session,
                           const unsigned char *packet_types,
                           unsigned char **data,
                           unsigned long *data_len,
                           unsigned long match_ofs,
                           const unsigned char *match_buf,
                           unsigned long match_len, int poll_socket)
{
    int i, packet_types_len = strlen((char *)packet_types);
    
    for(i = 0; i < packet_types_len; i++) {
        if (0 == libssh2_packet_ask_ex(session, packet_types[i],
                                       data, data_len, match_ofs,
                                       match_buf, match_len,
                                       i ? 0 : poll_socket)) {
            return 0;
        }
    }
    
    return -1;
}
/* }}} */

/* {{{ waitsocket
 * Returns
 * negative on error
 * >0 on incoming data
 * 0 on timeout
 *
 * FIXME: convert to use poll on systems that have it.
 */
int libssh2_waitsocket(LIBSSH2_SESSION *session,
                       long seconds)
{
    struct timeval timeout;
    int rc;
    fd_set fd;
    
    timeout.tv_sec = seconds;
    timeout.tv_usec = 0;
    
    FD_ZERO(&fd);
    
    FD_SET(session->socket_fd, &fd);
    
    rc = select(session->socket_fd+1, &fd, NULL, NULL, &timeout);
    
    return rc;
}

/* {{{ libssh2_packet_require
 * [BLOCKING] for LIBSSH2_READ_TIMEOUT seconds
 * Loops libssh2_packet_read() until the packet requested is available
 * SSH_DISCONNECT or a SOCKET_DISCONNECTED will cause a bailout
 *
 * Returns negative on error
 * Returns 0 when it has taken care of the requested packet.
 */

int libssh2_packet_require_ex(LIBSSH2_SESSION *session,
                              unsigned char packet_type,
                              unsigned char **data, unsigned long *data_len,
                              unsigned long match_ofs,
                              const unsigned char *match_buf,
                              unsigned long match_len)
{
    time_t start = time(NULL);
    
    if (libssh2_packet_ask_ex(session, packet_type, data, data_len,
                              match_ofs, match_buf, match_len, 0) == 0) {
        /* A packet was available in the packet brigade */
        return 0;
    }
    
    _libssh2_debug(session, LIBSSH2_DBG_TRANS,
                   "Blocking until packet of type %d becomes available",
                   (int)packet_type);
    
    while (session->socket_state == LIBSSH2_SOCKET_CONNECTED) {
        libssh2pack_t ret = libssh2_packet_read(session);
        if ((ret < 0)  && (ret != PACKET_EAGAIN)) {
            /* an error which is not just because of blocking */
            return ret;
        }
        if (packet_type == ret) {
            /* Be lazy, let packet_ask pull it out of the
            brigade */
            ret = libssh2_packet_ask_ex(session, packet_type,
                                        data, data_len, match_ofs,
                                        match_buf, match_len, 0);
            return ret;
        }
        else if (ret <= 0) {
            /* nothing available, wait until data arrives or
            we time out */
            long left = LIBSSH2_READ_TIMEOUT -
            (time(NULL) - start);
            
            if((left <= 0) ||
               (libssh2_waitsocket(session, left) <= 0)) {
                return PACKET_TIMEOUT;
            }
        }
    }
    
    /* Only reached if the socket died */
    return -1;
}
/* }}} */

/* {{{ libssh2_packet_burn
 * Loops libssh2_packet_read() until any packet is available and promptly discards it
 * Used during KEX exchange to discard badly guessed KEX_INIT packets
 */
int libssh2_packet_burn(LIBSSH2_SESSION *session)
{
    unsigned char *data;
    unsigned long data_len;
    unsigned char all_packets[255];
    int i;
    for(i = 1; i < 256; i++) all_packets[i - 1] = i;
    
    if (libssh2_packet_askv_ex(session, all_packets, &data, &data_len, 0,
                               NULL, 0, 0) == 0) {
        i = data[0];
        /* A packet was available in the packet brigade, burn it */
        LIBSSH2_FREE(session, data);
        return i;
    }
    
    _libssh2_debug(session, LIBSSH2_DBG_TRANS,
                   "Blocking until packet becomes available to burn");
    
    while (session->socket_state == LIBSSH2_SOCKET_CONNECTED) {
        int ret = libssh2_packet_read(session);
        if (ret < 0) {
            return ret;
        }
        if (ret == 0) {
            /* FIXME: this might busyloop */
            continue;
        }
        
        /* Be lazy, let packet_ask pull it out of the brigade */
        if (0 == libssh2_packet_ask_ex(session, ret, &data, &data_len,
                                       0, NULL, 0, 0)) {
            /* Smoke 'em if you got 'em */
            LIBSSH2_FREE(session, data);
            return ret;
        }
    }
    
    /* Only reached if the socket died */
    return -1;
}
/* }}} */

/* {{{ libssh2_packet_requirev
 * [BLOCKING]
 * Loops libssh2_packet_read() until one of a list of packet types requested is
 * available
 * SSH_DISCONNECT or a SOCKET_DISCONNECTED will cause a bailout
 * packet_types is a null terminated list of packet_type numbers
 */

int libssh2_packet_requirev_ex(LIBSSH2_SESSION *session,
                               const unsigned char *packet_types,
                               unsigned char **data, unsigned long *data_len,
                               unsigned long match_ofs,
                               const unsigned char *match_buf,
                               unsigned long match_len)
{
    time_t start = time(NULL);
    
    if (libssh2_packet_askv_ex(session, packet_types, data, data_len,
                               match_ofs, match_buf, match_len, 0) == 0) {
        /* One of the packets listed was available in the packet
        brigade */
        return 0;
    }
    
    while (session->socket_state != LIBSSH2_SOCKET_DISCONNECTED) {
        int ret = libssh2_packet_read(session);
        if ((ret < 0) && (ret != PACKET_EAGAIN)) {
            return ret;
        }
        if (ret <= 0) {
            long left = LIBSSH2_READ_TIMEOUT -
            (time(NULL) - start);
            
            if((left <= 0) ||
               (libssh2_waitsocket(session, left) <= 0 )) {
                return PACKET_TIMEOUT;
            }
        }
        
        if (strchr((char *)packet_types, ret)) {
            /* Be lazy, let packet_ask pull it out of the
            brigade */
            return libssh2_packet_askv_ex(session, packet_types,
                                          data, data_len,
                                          match_ofs, match_buf,
                                          match_len, 0);
        }
    }
    
    /* Only reached if the socket died */
    return -1;
}
/* }}} */