channels.c

Go to the documentation of this file.

/* -*- c-basic-offset: 8 -*-
   rdesktop: A Remote Desktop Protocol client.
   Protocol services - Virtual channels
   Copyright 2003 Erik Forsberg <forsberg@cendio.se> for Cendio AB
   Copyright (C) Matthew Chapman <matthewc.unsw.edu.au> 2003-2008

   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 3 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, see <http://www.gnu.org/licenses/>.
*/

#include "precomp.h"

#define MAX_CHANNELS            6
#define CHANNEL_CHUNK_LENGTH        1600
#define CHANNEL_FLAG_FIRST      0x01
#define CHANNEL_FLAG_LAST       0x02
#define CHANNEL_FLAG_SHOW_PROTOCOL  0x10

extern RDP_VERSION g_rdp_version;
extern RD_BOOL g_encryption;

VCHANNEL g_channels[MAX_CHANNELS];
unsigned int g_num_channels;

/* FIXME: We should use the information in TAG_SRV_CHANNELS to map RDP5
   channels to MCS channels.

   The format of TAG_SRV_CHANNELS seems to be

   global_channel_no (uint16le)
   number_of_other_channels (uint16le)
   ..followed by uint16les for the other channels.
*/

VCHANNEL *
channel_register(char *name, uint32 flags, void (*callback) (STREAM))
{
    VCHANNEL *channel;

    if (g_rdp_version < RDP_V5)
        return NULL;

    if (g_num_channels >= MAX_CHANNELS)
    {
        error("Channel table full, increase MAX_CHANNELS\n");
        return NULL;
    }

    channel = &g_channels[g_num_channels];
    channel->mcs_id = MCS_GLOBAL_CHANNEL + 1 + g_num_channels;
    strncpy(channel->name, name, 8);
    channel->flags = flags;
    channel->process = callback;
    g_num_channels++;
    return channel;
}

STREAM
channel_init(VCHANNEL * channel, uint32 length)
{
    STREAM s;

    s = sec_init(g_encryption ? SEC_ENCRYPT : 0, length + 8);
    s_push_layer(s, channel_hdr, 8);
    return s;
}

void
channel_send(STREAM s, VCHANNEL * channel)
{
    uint32 length, flags;
    uint32 thislength, remaining;
    uint8 *data;

#ifdef WITH_SCARD
    scard_lock(SCARD_LOCK_CHANNEL);
#endif

    /* first fragment sent in-place */
    s_pop_layer(s, channel_hdr);
    length = s->end - s->p - 8;

    DEBUG_CHANNEL(("channel_send, length = %d\n", length));

    thislength = MIN(length, CHANNEL_CHUNK_LENGTH);
/* Note: In the original clipboard implementation, this number was
   1592, not 1600. However, I don't remember the reason and 1600 seems
   to work so.. This applies only to *this* length, not the length of
   continuation or ending packets. */
    remaining = length - thislength;
    flags = (remaining == 0) ? CHANNEL_FLAG_FIRST | CHANNEL_FLAG_LAST : CHANNEL_FLAG_FIRST;
    if (channel->flags & CHANNEL_OPTION_SHOW_PROTOCOL)
        flags |= CHANNEL_FLAG_SHOW_PROTOCOL;

    out_uint32_le(s, length);
    out_uint32_le(s, flags);
    data = s->end = s->p + thislength;
    DEBUG_CHANNEL(("Sending %d bytes with FLAG_FIRST\n", thislength));
    sec_send_to_channel(s, g_encryption ? SEC_ENCRYPT : 0, channel->mcs_id);

    /* subsequent segments copied (otherwise would have to generate headers backwards) */
    while (remaining > 0)
    {
        thislength = MIN(remaining, CHANNEL_CHUNK_LENGTH);
        remaining -= thislength;
        flags = (remaining == 0) ? CHANNEL_FLAG_LAST : 0;
        if (channel->flags & CHANNEL_OPTION_SHOW_PROTOCOL)
            flags |= CHANNEL_FLAG_SHOW_PROTOCOL;

        DEBUG_CHANNEL(("Sending %d bytes with flags %d\n", thislength, flags));

        s = sec_init(g_encryption ? SEC_ENCRYPT : 0, thislength + 8);
        out_uint32_le(s, length);
        out_uint32_le(s, flags);
        out_uint8p(s, data, thislength);
        s_mark_end(s);
        sec_send_to_channel(s, g_encryption ? SEC_ENCRYPT : 0, channel->mcs_id);

        data += thislength;
    }

#ifdef WITH_SCARD
    scard_unlock(SCARD_LOCK_CHANNEL);
#endif
}

void
channel_process(STREAM s, uint16 mcs_channel)
{
    uint32 length, flags;
    uint32 thislength;
    VCHANNEL *channel = NULL;
    unsigned int i;
    STREAM in;

    for (i = 0; i < g_num_channels; i++)
    {
        channel = &g_channels[i];
        if (channel->mcs_id == mcs_channel)
            break;
    }

    if (i >= g_num_channels)
        return;

    in_uint32_le(s, length);
    in_uint32_le(s, flags);
    if ((flags & CHANNEL_FLAG_FIRST) && (flags & CHANNEL_FLAG_LAST))
    {
        /* single fragment - pass straight up */
        channel->process(s);
    }
    else
    {
        /* add fragment to defragmentation buffer */
        in = &channel->in;
        if (flags & CHANNEL_FLAG_FIRST)
        {
            if (length > in->size)
            {
                in->data = (uint8 *) xrealloc(in->data, length);
                in->size = length;
            }
            in->p = in->data;
        }

        thislength = MIN(s->end - s->p, in->data + in->size - in->p);
        memcpy(in->p, s->p, thislength);
        in->p += thislength;

        if (flags & CHANNEL_FLAG_LAST)
        {
            in->end = in->p;
            in->p = in->data;
            channel->process(in);
        }
    }
}