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common-channel.c
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common-channel.c
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/*
* Dropbear SSH
*
* Copyright (c) 2002-2004 Matt Johnston
* All rights reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE. */
/* Handle the multiplexed channels, such as sessions, x11, agent connections */
#include "includes.h"
#include "session.h"
#include "packet.h"
#include "ssh.h"
#include "buffer.h"
#include "circbuffer.h"
#include "dbutil.h"
#include "channel.h"
#include "listener.h"
#include "runopts.h"
#include "netio.h"
static void send_msg_channel_open_failure(unsigned int remotechan, int reason,
const char *text, const char *lang);
static void send_msg_channel_open_confirmation(const struct Channel* channel,
unsigned int recvwindow,
unsigned int recvmaxpacket);
static int writechannel(struct Channel* channel, int fd, circbuffer *cbuf,
const unsigned char *moredata, unsigned int *morelen);
static void send_msg_channel_window_adjust(const struct Channel *channel,
unsigned int incr);
static void send_msg_channel_data(struct Channel *channel, int isextended);
static void send_msg_channel_eof(struct Channel *channel);
static void send_msg_channel_close(struct Channel *channel);
static void remove_channel(struct Channel *channel);
static unsigned int write_pending(const struct Channel * channel);
static void check_close(struct Channel *channel);
static void close_chan_fd(struct Channel *channel, int fd, int how);
#define FD_UNINIT (-2)
#define FD_CLOSED (-1)
#define ERRFD_IS_READ(channel) ((channel)->extrabuf == NULL)
#define ERRFD_IS_WRITE(channel) (!ERRFD_IS_READ(channel))
/* allow space for:
* 1 byte byte SSH_MSG_CHANNEL_DATA
* 4 bytes uint32 recipient channel
* 4 bytes string data
*/
#define RECV_MAX_CHANNEL_DATA_LEN (RECV_MAX_PAYLOAD_LEN-(1+4+4))
/* Initialise all the channels */
void chaninitialise(const struct ChanType *chantypes[]) {
/* may as well create space for a single channel */
ses.channels = (struct Channel**)m_malloc(sizeof(struct Channel*));
ses.chansize = 1;
ses.channels[0] = NULL;
ses.chancount = 0;
ses.chantypes = chantypes;
#if DROPBEAR_LISTENERS
listeners_initialise();
#endif
}
/* Clean up channels, freeing allocated memory */
void chancleanup() {
unsigned int i;
TRACE(("enter chancleanup"))
for (i = 0; i < ses.chansize; i++) {
if (ses.channels[i] != NULL) {
TRACE(("channel %d closing", i))
remove_channel(ses.channels[i]);
}
}
m_free(ses.channels);
TRACE(("leave chancleanup"))
}
/* Create a new channel entry, send a reply confirm or failure */
/* If remotechan, transwindow and transmaxpacket are not know (for a new
* outgoing connection, with them to be filled on confirmation), they should
* all be set to 0 */
static struct Channel* newchannel(unsigned int remotechan,
const struct ChanType *type,
unsigned int transwindow, unsigned int transmaxpacket) {
struct Channel * newchan;
unsigned int i, j;
TRACE(("enter newchannel"))
/* first see if we can use existing channels */
for (i = 0; i < ses.chansize; i++) {
if (ses.channels[i] == NULL) {
break;
}
}
/* otherwise extend the list */
if (i == ses.chansize) {
if (ses.chansize >= MAX_CHANNELS) {
TRACE(("leave newchannel: max chans reached"))
return NULL;
}
/* extend the channels */
ses.channels = (struct Channel**)m_realloc(ses.channels,
(ses.chansize+CHAN_EXTEND_SIZE)*sizeof(struct Channel*));
ses.chansize += CHAN_EXTEND_SIZE;
/* set the new channels to null */
for (j = i; j < ses.chansize; j++) {
ses.channels[j] = NULL;
}
}
newchan = (struct Channel*)m_malloc(sizeof(struct Channel));
newchan->type = type;
newchan->index = i;
newchan->sent_close = newchan->recv_close = 0;
newchan->sent_eof = newchan->recv_eof = 0;
newchan->close_handler_done = 0;
newchan->remotechan = remotechan;
newchan->transwindow = transwindow;
newchan->transmaxpacket = transmaxpacket;
newchan->typedata = NULL;
newchan->writefd = FD_UNINIT;
newchan->readfd = FD_UNINIT;
newchan->errfd = FD_CLOSED; /* this isn't always set to start with */
newchan->await_open = 0;
newchan->flushing = 0;
newchan->writebuf = cbuf_new(opts.recv_window);
newchan->recvwindow = opts.recv_window;
newchan->extrabuf = NULL; /* The user code can set it up */
newchan->recvdonelen = 0;
newchan->recvmaxpacket = RECV_MAX_CHANNEL_DATA_LEN;
newchan->prio = DROPBEAR_CHANNEL_PRIO_EARLY; /* inithandler sets it */
ses.channels[i] = newchan;
ses.chancount++;
TRACE(("leave newchannel"))
return newchan;
}
/* Returns the channel structure corresponding to the channel in the current
* data packet (ses.payload must be positioned appropriately).
* A valid channel is always returns, it will fail fatally with an unknown
* channel */
static struct Channel* getchannel_msg(const char* kind) {
unsigned int chan;
chan = buf_getint(ses.payload);
if (chan >= ses.chansize || ses.channels[chan] == NULL) {
if (kind) {
dropbear_exit("%s for unknown channel %d", kind, chan);
} else {
dropbear_exit("Unknown channel %d", chan);
}
}
return ses.channels[chan];
}
struct Channel* getchannel() {
return getchannel_msg(NULL);
}
/* Iterate through the channels, performing IO if available */
void channelio(const fd_set *readfds, const fd_set *writefds) {
/* Listeners such as TCP, X11, agent-auth */
struct Channel *channel;
unsigned int i;
/* foreach channel */
for (i = 0; i < ses.chansize; i++) {
/* Close checking only needs to occur for channels that had IO events */
int do_check_close = 0;
channel = ses.channels[i];
if (channel == NULL) {
/* only process in-use channels */
continue;
}
/* read data and send it over the wire */
if (channel->readfd >= 0 && FD_ISSET(channel->readfd, readfds)) {
TRACE(("send normal readfd"))
send_msg_channel_data(channel, 0);
do_check_close = 1;
}
/* read stderr data and send it over the wire */
if (ERRFD_IS_READ(channel) && channel->errfd >= 0
&& FD_ISSET(channel->errfd, readfds)) {
TRACE(("send normal errfd"))
send_msg_channel_data(channel, 1);
do_check_close = 1;
}
/* write to program/pipe stdin */
if (channel->writefd >= 0 && FD_ISSET(channel->writefd, writefds)) {
writechannel(channel, channel->writefd, channel->writebuf, NULL, NULL);
do_check_close = 1;
}
/* stderr for client mode */
if (ERRFD_IS_WRITE(channel)
&& channel->errfd >= 0 && FD_ISSET(channel->errfd, writefds)) {
writechannel(channel, channel->errfd, channel->extrabuf, NULL, NULL);
do_check_close = 1;
}
if (ses.channel_signal_pending) {
/* SIGCHLD can change channel state for server sessions */
do_check_close = 1;
}
/* handle any channel closing etc */
if (do_check_close) {
check_close(channel);
}
}
#if DROPBEAR_LISTENERS
handle_listeners(readfds);
#endif
}
/* Returns true if there is data remaining to be written to stdin or
* stderr of a channel's endpoint. */
static unsigned int write_pending(const struct Channel * channel) {
if (channel->writefd >= 0 && cbuf_getused(channel->writebuf) > 0) {
return 1;
} else if (channel->errfd >= 0 && channel->extrabuf &&
cbuf_getused(channel->extrabuf) > 0) {
return 1;
}
return 0;
}
/* EOF/close handling */
static void check_close(struct Channel *channel) {
int close_allowed = 0;
TRACE2(("check_close: writefd %d, readfd %d, errfd %d, sent_close %d, recv_close %d",
channel->writefd, channel->readfd,
channel->errfd, channel->sent_close, channel->recv_close))
TRACE2(("writebuf size %d extrabuf size %d",
channel->writebuf ? cbuf_getused(channel->writebuf) : 0,
channel->extrabuf ? cbuf_getused(channel->extrabuf) : 0))
if (!channel->flushing
&& !channel->close_handler_done
&& channel->type->check_close
&& channel->type->check_close(channel))
{
channel->flushing = 1;
}
/* if a type-specific check_close is defined we will only exit
once that has been triggered. this is only used for a server "session"
channel, to ensure that the shell has exited (and the exit status
retrieved) before we close things up. */
if (!channel->type->check_close
|| channel->close_handler_done
|| channel->type->check_close(channel)) {
close_allowed = 1;
}
if (channel->recv_close && !write_pending(channel) && close_allowed) {
if (!channel->sent_close) {
TRACE(("Sending MSG_CHANNEL_CLOSE in response to same."))
send_msg_channel_close(channel);
}
remove_channel(channel);
return;
}
if ((channel->recv_eof && !write_pending(channel))
/* have a server "session" and child has exited */
|| (channel->type->check_close && close_allowed)) {
close_chan_fd(channel, channel->writefd, SHUT_WR);
}
/* Special handling for flushing read data after an exit. We
read regardless of whether the select FD was set,
and if there isn't data available, the channel will get closed. */
if (channel->flushing) {
TRACE(("might send data, flushing"))
if (channel->readfd >= 0 && channel->transwindow > 0) {
TRACE(("send data readfd"))
send_msg_channel_data(channel, 0);
}
if (ERRFD_IS_READ(channel) && channel->errfd >= 0
&& channel->transwindow > 0) {
TRACE(("send data errfd"))
send_msg_channel_data(channel, 1);
}
}
/* If we're not going to send any more data, send EOF */
if (!channel->sent_eof
&& channel->readfd == FD_CLOSED
&& (ERRFD_IS_WRITE(channel) || channel->errfd == FD_CLOSED)) {
send_msg_channel_eof(channel);
}
/* And if we can't receive any more data from them either, close up */
if (channel->readfd == FD_CLOSED
&& channel->writefd == FD_CLOSED
&& (ERRFD_IS_WRITE(channel) || channel->errfd == FD_CLOSED)
&& !channel->sent_close
&& close_allowed
&& !write_pending(channel)) {
TRACE(("sending close, readfd is closed"))
send_msg_channel_close(channel);
}
}
/* Check whether a deferred (EINPROGRESS) connect() was successful, and
* if so, set up the channel properly. Otherwise, the channel is cleaned up, so
* it is important that the channel reference isn't used after a call to this
* function */
void channel_connect_done(int result, int sock, void* user_data, const char* UNUSED(errstring)) {
struct Channel *channel = user_data;
TRACE(("enter channel_connect_done"))
if (result == DROPBEAR_SUCCESS)
{
channel->readfd = channel->writefd = sock;
channel->conn_pending = NULL;
send_msg_channel_open_confirmation(channel, channel->recvwindow,
channel->recvmaxpacket);
TRACE(("leave channel_connect_done: success"))
}
else
{
send_msg_channel_open_failure(channel->remotechan,
SSH_OPEN_CONNECT_FAILED, "", "");
remove_channel(channel);
TRACE(("leave check_in_progress: fail"))
}
}
/* Send the close message and set the channel as closed */
static void send_msg_channel_close(struct Channel *channel) {
TRACE(("enter send_msg_channel_close %p", (void*)channel))
if (channel->type->closehandler
&& !channel->close_handler_done) {
channel->type->closehandler(channel);
channel->close_handler_done = 1;
}
CHECKCLEARTOWRITE();
buf_putbyte(ses.writepayload, SSH_MSG_CHANNEL_CLOSE);
buf_putint(ses.writepayload, channel->remotechan);
encrypt_packet();
channel->sent_eof = 1;
channel->sent_close = 1;
close_chan_fd(channel, channel->readfd, SHUT_RD);
close_chan_fd(channel, channel->errfd, SHUT_RDWR);
close_chan_fd(channel, channel->writefd, SHUT_WR);
TRACE(("leave send_msg_channel_close"))
}
/* call this when trans/eof channels are closed */
static void send_msg_channel_eof(struct Channel *channel) {
TRACE(("enter send_msg_channel_eof"))
CHECKCLEARTOWRITE();
buf_putbyte(ses.writepayload, SSH_MSG_CHANNEL_EOF);
buf_putint(ses.writepayload, channel->remotechan);
encrypt_packet();
channel->sent_eof = 1;
TRACE(("leave send_msg_channel_eof"))
}
#ifndef HAVE_WRITEV
static int writechannel_fallback(struct Channel* channel, int fd, circbuffer *cbuf,
const unsigned char *UNUSED(moredata), unsigned int *morelen) {
unsigned char *circ_p1, *circ_p2;
unsigned int circ_len1, circ_len2;
ssize_t written;
if (morelen) {
/* fallback doesn't consume moredata */
*morelen = 0;
}
/* Write the first portion of the circular buffer */
cbuf_readptrs(cbuf, &circ_p1, &circ_len1, &circ_p2, &circ_len2);
written = write(fd, circ_p1, circ_len1);
if (written < 0) {
if (errno != EINTR && errno != EAGAIN) {
TRACE(("channel IO write error fd %d %s", fd, strerror(errno)))
close_chan_fd(channel, fd, SHUT_WR);
return DROPBEAR_FAILURE;
}
} else {
cbuf_incrread(cbuf, written);
channel->recvdonelen += written;
}
return DROPBEAR_SUCCESS;
}
#endif /* !HAVE_WRITEV */
#ifdef HAVE_WRITEV
static int writechannel_writev(struct Channel* channel, int fd, circbuffer *cbuf,
const unsigned char *moredata, unsigned int *morelen) {
struct iovec iov[3];
unsigned char *circ_p1, *circ_p2;
unsigned int circ_len1, circ_len2;
int io_count = 0;
ssize_t written;
cbuf_readptrs(cbuf, &circ_p1, &circ_len1, &circ_p2, &circ_len2);
if (circ_len1 > 0) {
TRACE(("circ1 %d", circ_len1))
iov[io_count].iov_base = circ_p1;
iov[io_count].iov_len = circ_len1;
io_count++;
}
if (circ_len2 > 0) {
TRACE(("circ2 %d", circ_len2))
iov[io_count].iov_base = circ_p2;
iov[io_count].iov_len = circ_len2;
io_count++;
}
if (morelen) {
assert(moredata);
TRACE(("more %d", *morelen))
iov[io_count].iov_base = (void*)moredata;
iov[io_count].iov_len = *morelen;
io_count++;
}
if (io_count == 0) {
/* writechannel may sometimes be called twice in a main loop iteration.
From common_recv_msg_channel_data() then channelio().
The second call may not have any data to write, so we just return. */
TRACE(("leave writechannel, no data"))
return DROPBEAR_SUCCESS;
}
if (morelen) {
/* Default return value, none consumed */
*morelen = 0;
}
written = writev(fd, iov, io_count);
if (written < 0) {
if (errno != EINTR && errno != EAGAIN) {
TRACE(("channel IO write error fd %d %s", fd, strerror(errno)))
close_chan_fd(channel, fd, SHUT_WR);
return DROPBEAR_FAILURE;
}
} else {
int cbuf_written = MIN(circ_len1+circ_len2, (unsigned int)written);
cbuf_incrread(cbuf, cbuf_written);
if (morelen) {
*morelen = written - cbuf_written;
}
channel->recvdonelen += written;
}
return DROPBEAR_SUCCESS;
}
#endif /* HAVE_WRITEV */
/* Called to write data out to the local side of the channel.
Writes the circular buffer contents and also the "moredata" buffer
if not null. Will ignore EAGAIN.
Returns DROPBEAR_FAILURE if writing to fd had an error and the channel is being closed, DROPBEAR_SUCCESS otherwise */
static int writechannel(struct Channel* channel, int fd, circbuffer *cbuf,
const unsigned char *moredata, unsigned int *morelen) {
int ret = DROPBEAR_SUCCESS;
TRACE(("enter writechannel fd %d", fd))
#ifdef HAVE_WRITEV
ret = writechannel_writev(channel, fd, cbuf, moredata, morelen);
#else
ret = writechannel_fallback(channel, fd, cbuf, moredata, morelen);
#endif
/* Window adjust handling */
if (channel->recvdonelen >= RECV_WINDOWEXTEND) {
send_msg_channel_window_adjust(channel, channel->recvdonelen);
channel->recvwindow += channel->recvdonelen;
channel->recvdonelen = 0;
}
dropbear_assert(channel->recvwindow <= opts.recv_window);
dropbear_assert(channel->recvwindow <= cbuf_getavail(channel->writebuf));
dropbear_assert(channel->extrabuf == NULL ||
channel->recvwindow <= cbuf_getavail(channel->extrabuf));
TRACE(("leave writechannel"))
return ret;
}
/* Set the file descriptors for the main select in session.c
* This avoid channels which don't have any window available, are closed, etc*/
void setchannelfds(fd_set *readfds, fd_set *writefds, int allow_reads) {
unsigned int i;
struct Channel * channel;
for (i = 0; i < ses.chansize; i++) {
channel = ses.channels[i];
if (channel == NULL) {
continue;
}
/* Stuff to put over the wire.
Avoid queueing data to send if we're in the middle of a
key re-exchange (!dataallowed), but still read from the
FD if there's the possibility of "~."" to kill an
interactive session (the read_mangler) */
if (channel->transwindow > 0
&& ((ses.dataallowed && allow_reads) || channel->read_mangler)) {
if (channel->readfd >= 0) {
FD_SET(channel->readfd, readfds);
}
if (ERRFD_IS_READ(channel) && channel->errfd >= 0) {
FD_SET(channel->errfd, readfds);
}
}
/* Stuff from the wire */
if (channel->writefd >= 0 && cbuf_getused(channel->writebuf) > 0) {
FD_SET(channel->writefd, writefds);
}
if (ERRFD_IS_WRITE(channel) && channel->errfd >= 0
&& cbuf_getused(channel->extrabuf) > 0) {
FD_SET(channel->errfd, writefds);
}
} /* foreach channel */
#if DROPBEAR_LISTENERS
set_listener_fds(readfds);
#endif
}
/* handle the channel EOF event, by closing the channel filedescriptor. The
* channel isn't closed yet, it is left until the incoming (from the program
* etc) FD is also EOF */
void recv_msg_channel_eof() {
struct Channel * channel;
TRACE(("enter recv_msg_channel_eof"))
channel = getchannel_msg("EOF");
channel->recv_eof = 1;
check_close(channel);
TRACE(("leave recv_msg_channel_eof"))
}
/* Handle channel closure(), respond in kind and close the channels */
void recv_msg_channel_close() {
struct Channel * channel;
TRACE(("enter recv_msg_channel_close"))
channel = getchannel_msg("Close");
channel->recv_eof = 1;
channel->recv_close = 1;
check_close(channel);
TRACE(("leave recv_msg_channel_close"))
}
/* Remove a channel entry, this is only executed after both sides have sent
* channel close */
static void remove_channel(struct Channel * channel) {
TRACE(("enter remove_channel"))
TRACE(("channel index is %d", channel->index))
cbuf_free(channel->writebuf);
channel->writebuf = NULL;
if (channel->extrabuf) {
cbuf_free(channel->extrabuf);
channel->extrabuf = NULL;
}
if (IS_DROPBEAR_SERVER || (channel->writefd != STDOUT_FILENO)) {
/* close the FDs in case they haven't been done
* yet (they might have been shutdown etc) */
TRACE(("CLOSE writefd %d", channel->writefd))
m_close(channel->writefd);
TRACE(("CLOSE readfd %d", channel->readfd))
m_close(channel->readfd);
TRACE(("CLOSE errfd %d", channel->errfd))
m_close(channel->errfd);
}
if (!channel->close_handler_done
&& channel->type->closehandler) {
channel->type->closehandler(channel);
channel->close_handler_done = 1;
}
if (channel->conn_pending) {
cancel_connect(channel->conn_pending);
}
ses.channels[channel->index] = NULL;
m_free(channel);
ses.chancount--;
update_channel_prio();
TRACE(("leave remove_channel"))
}
/* Handle channel specific requests, passing off to corresponding handlers
* such as chansession or x11fwd */
void recv_msg_channel_request() {
struct Channel *channel;
channel = getchannel();
TRACE(("enter recv_msg_channel_request %p", (void*)channel))
if (channel->sent_close) {
TRACE(("leave recv_msg_channel_request: already closed channel"))
return;
}
if (channel->type->reqhandler
&& !channel->close_handler_done) {
channel->type->reqhandler(channel);
} else {
int wantreply;
buf_eatstring(ses.payload);
wantreply = buf_getbool(ses.payload);
if (wantreply) {
send_msg_channel_failure(channel);
}
}
TRACE(("leave recv_msg_channel_request"))
}
/* Reads data from the server's program/shell/etc, and puts it in a
* channel_data packet to send.
* chan is the remote channel, isextended is 0 if it is normal data, 1
* if it is extended data. if it is extended, then the type is in
* exttype */
static void send_msg_channel_data(struct Channel *channel, int isextended) {
int len;
size_t maxlen, size_pos;
int fd;
CHECKCLEARTOWRITE();
TRACE(("enter send_msg_channel_data"))
dropbear_assert(!channel->sent_close);
if (isextended) {
fd = channel->errfd;
} else {
fd = channel->readfd;
}
TRACE(("enter send_msg_channel_data isextended %d fd %d", isextended, fd))
dropbear_assert(fd >= 0);
maxlen = MIN(channel->transwindow, channel->transmaxpacket);
/* -(1+4+4) is SSH_MSG_CHANNEL_DATA, channel number, string length, and
* exttype if is extended */
maxlen = MIN(maxlen,
ses.writepayload->size - 1 - 4 - 4 - (isextended ? 4 : 0));
TRACE(("maxlen %zd", maxlen))
if (maxlen == 0) {
TRACE(("leave send_msg_channel_data: no window"))
return;
}
buf_putbyte(ses.writepayload,
isextended ? SSH_MSG_CHANNEL_EXTENDED_DATA : SSH_MSG_CHANNEL_DATA);
buf_putint(ses.writepayload, channel->remotechan);
if (isextended) {
buf_putint(ses.writepayload, SSH_EXTENDED_DATA_STDERR);
}
/* a dummy size first ...*/
size_pos = ses.writepayload->pos;
buf_putint(ses.writepayload, 0);
/* read the data */
len = read(fd, buf_getwriteptr(ses.writepayload, maxlen), maxlen);
if (len <= 0) {
if (len == 0 || errno != EINTR) {
/* This will also get hit in the case of EAGAIN. The only
time we expect to receive EAGAIN is when we're flushing a FD,
in which case it can be treated the same as EOF */
close_chan_fd(channel, fd, SHUT_RD);
}
buf_setpos(ses.writepayload, 0);
buf_setlen(ses.writepayload, 0);
TRACE(("leave send_msg_channel_data: len %d read err %d or EOF for fd %d",
len, errno, fd))
return;
}
if (channel->read_mangler) {
channel->read_mangler(channel, buf_getwriteptr(ses.writepayload, len), &len);
if (len == 0) {
buf_setpos(ses.writepayload, 0);
buf_setlen(ses.writepayload, 0);
return;
}
}
TRACE(("send_msg_channel_data: len %d fd %d", len, fd))
buf_incrwritepos(ses.writepayload, len);
/* ... real size here */
buf_setpos(ses.writepayload, size_pos);
buf_putint(ses.writepayload, len);
channel->transwindow -= len;
encrypt_packet();
/* If we receive less data than we requested when flushing, we've
reached the equivalent of EOF */
if (channel->flushing && len < (ssize_t)maxlen)
{
TRACE(("closing from channel, flushing out."))
close_chan_fd(channel, fd, SHUT_RD);
}
TRACE(("leave send_msg_channel_data"))
}
/* We receive channel data */
void recv_msg_channel_data() {
struct Channel *channel;
channel = getchannel();
common_recv_msg_channel_data(channel, channel->writefd, channel->writebuf);
}
/* Shared for data and stderr data - when we receive data, put it in a buffer
* for writing to the local file descriptor */
void common_recv_msg_channel_data(struct Channel *channel, int fd,
circbuffer * cbuf) {
unsigned int datalen;
unsigned int maxdata;
unsigned int buflen;
unsigned int len;
unsigned int consumed;
int res;
TRACE(("enter recv_msg_channel_data"))
if (channel->recv_eof) {
dropbear_exit("Received data after eof");
}
if (fd < 0 || !cbuf) {
/* If we have encountered failed write, the far side might still
* be sending data without having yet received our close notification.
* We just drop the data. */
return;
}
datalen = buf_getint(ses.payload);
TRACE(("length %d", datalen))
maxdata = cbuf_getavail(cbuf);
/* Whilst the spec says we "MAY ignore data past the end" this could
* lead to corrupted file transfers etc (chunks missed etc). It's better to
* just die horribly */
if (datalen > maxdata) {
dropbear_exit("Oversized packet");
}
dropbear_assert(channel->recvwindow >= datalen);
channel->recvwindow -= datalen;
dropbear_assert(channel->recvwindow <= opts.recv_window);
/* Attempt to write the data immediately without having to put it in the circular buffer */
consumed = datalen;
res = writechannel(channel, fd, cbuf, buf_getptr(ses.payload, datalen), &consumed);
datalen -= consumed;
buf_incrpos(ses.payload, consumed);
/* We may have to run throught twice, if the buffer wraps around. Can't
* just "leave it for next time" like with writechannel, since this
* is payload data.
* If the writechannel() failed then remaining data is discarded */
if (res == DROPBEAR_SUCCESS) {
len = datalen;
while (len > 0) {
buflen = cbuf_writelen(cbuf);
buflen = MIN(buflen, len);
memcpy(cbuf_writeptr(cbuf, buflen),
buf_getptr(ses.payload, buflen), buflen);
cbuf_incrwrite(cbuf, buflen);
buf_incrpos(ses.payload, buflen);
len -= buflen;
}
}
TRACE(("leave recv_msg_channel_data"))
}
/* Increment the outgoing data window for a channel - the remote end limits
* the amount of data which may be transmitted, this window is decremented
* as data is sent, and incremented upon receiving window-adjust messages */
void recv_msg_channel_window_adjust() {
struct Channel * channel;
unsigned int incr;
channel = getchannel();
incr = buf_getint(ses.payload);
TRACE(("received window increment %d", incr))
incr = MIN(incr, TRANS_MAX_WIN_INCR);
channel->transwindow += incr;
channel->transwindow = MIN(channel->transwindow, TRANS_MAX_WINDOW);
}
/* Increment the incoming data window for a channel, and let the remote
* end know */
static void send_msg_channel_window_adjust(const struct Channel* channel,
unsigned int incr) {
TRACE(("sending window adjust %d", incr))
CHECKCLEARTOWRITE();
buf_putbyte(ses.writepayload, SSH_MSG_CHANNEL_WINDOW_ADJUST);
buf_putint(ses.writepayload, channel->remotechan);
buf_putint(ses.writepayload, incr);
encrypt_packet();
}
/* Handle a new channel request, performing any channel-type-specific setup */
void recv_msg_channel_open() {
char *type;
unsigned int typelen;
unsigned int remotechan, transwindow, transmaxpacket;
struct Channel *channel;
const struct ChanType **cp;
const struct ChanType *chantype;
unsigned int errtype = SSH_OPEN_UNKNOWN_CHANNEL_TYPE;
int ret;
TRACE(("enter recv_msg_channel_open"))
/* get the packet contents */
type = buf_getstring(ses.payload, &typelen);
remotechan = buf_getint(ses.payload);
transwindow = buf_getint(ses.payload);
transwindow = MIN(transwindow, TRANS_MAX_WINDOW);
transmaxpacket = buf_getint(ses.payload);
transmaxpacket = MIN(transmaxpacket, TRANS_MAX_PAYLOAD_LEN);
/* figure what type of packet it is */
if (typelen > MAX_NAME_LEN) {
goto failure;
}
/* Get the channel type. Client and server style invokation will set up a
* different list for ses.chantypes at startup. We just iterate through
* this list and find the matching name */
for (cp = &ses.chantypes[0], chantype = (*cp);
chantype != NULL;
cp++, chantype = (*cp)) {
if (strcmp(type, chantype->name) == 0) {
break;
}
}
if (chantype == NULL) {
TRACE(("No matching type for '%s'", type))
goto failure;
}
TRACE(("matched type '%s'", type))
/* create the channel */
channel = newchannel(remotechan, chantype, transwindow, transmaxpacket);
if (channel == NULL) {
TRACE(("newchannel returned NULL"))
errtype = SSH_OPEN_RESOURCE_SHORTAGE;
goto failure;
}
if (channel->type->inithandler) {
ret = channel->type->inithandler(channel);
if (ret == SSH_OPEN_IN_PROGRESS) {
/* We'll send the confirmation later */
goto cleanup;
}
if (ret > 0) {
errtype = ret;
remove_channel(channel);
TRACE(("inithandler returned failure %d", ret))
goto failure;
}
}
if (channel->prio == DROPBEAR_CHANNEL_PRIO_EARLY) {
channel->prio = DROPBEAR_CHANNEL_PRIO_BULK;
}
/* success */
send_msg_channel_open_confirmation(channel, channel->recvwindow,
channel->recvmaxpacket);
goto cleanup;
failure:
TRACE(("recv_msg_channel_open failure"))
send_msg_channel_open_failure(remotechan, errtype, "", "");