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openssh-portable/nchan.c

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/* $OpenBSD: nchan.c,v 1.71 2020/10/18 11:32:01 djm Exp $ */
/*
* Copyright (c) 1999, 2000, 2001, 2002 Markus Friedl. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. 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.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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 "includes.h"
#include <sys/types.h>
#include <sys/socket.h>
#include <errno.h>
#include <string.h>
#include <stdarg.h>
#include "openbsd-compat/sys-queue.h"
#include "ssh2.h"
#include "sshbuf.h"
#include "ssherr.h"
#include "packet.h"
#include "channels.h"
#include "compat.h"
#include "log.h"
/*
* SSH Protocol 1.5 aka New Channel Protocol
* Thanks to Martina, Axel and everyone who left Erlangen, leaving me bored.
* Written by Markus Friedl in October 1999
*
* Protocol versions 1.3 and 1.5 differ in the handshake protocol used for the
* tear down of channels:
*
* 1.3: strict request-ack-protocol:
* CLOSE ->
* <- CLOSE_CONFIRM
*
* 1.5: uses variations of:
* IEOF ->
* <- OCLOSE
* <- IEOF
* OCLOSE ->
* i.e. both sides have to close the channel
*
* 2.0: the EOF messages are optional
*
* See the debugging output from 'ssh -v' and 'sshd -d' of
* ssh-1.2.27 as an example.
*
*/
/* functions manipulating channel states */
/*
* EVENTS update channel input/output states execute ACTIONS
*/
/*
* ACTIONS: should never update the channel states
*/
static void chan_send_eof2(struct ssh *, Channel *);
static void chan_send_eow2(struct ssh *, Channel *);
/* helper */
static void chan_shutdown_write(struct ssh *, Channel *);
static void chan_shutdown_read(struct ssh *, Channel *);
static void chan_shutdown_extended_read(struct ssh *, Channel *);
static const char *ostates[] = { "open", "drain", "wait_ieof", "closed" };
static const char *istates[] = { "open", "drain", "wait_oclose", "closed" };
static void
chan_set_istate(Channel *c, u_int next)
{
if (c->istate > CHAN_INPUT_CLOSED || next > CHAN_INPUT_CLOSED)
fatal("chan_set_istate: bad state %d -> %d", c->istate, next);
debug2("channel %d: input %s -> %s", c->self, istates[c->istate],
istates[next]);
c->istate = next;
}
static void
chan_set_ostate(Channel *c, u_int next)
{
if (c->ostate > CHAN_OUTPUT_CLOSED || next > CHAN_OUTPUT_CLOSED)
fatal("chan_set_ostate: bad state %d -> %d", c->ostate, next);
debug2("channel %d: output %s -> %s", c->self, ostates[c->ostate],
ostates[next]);
c->ostate = next;
}
void
chan_read_failed(struct ssh *ssh, Channel *c)
{
debug2("channel %d: read failed", c->self);
switch (c->istate) {
case CHAN_INPUT_OPEN:
chan_shutdown_read(ssh, c);
chan_set_istate(c, CHAN_INPUT_WAIT_DRAIN);
break;
default:
error("channel %d: chan_read_failed for istate %d",
c->self, c->istate);
break;
}
}
void
chan_ibuf_empty(struct ssh *ssh, Channel *c)
{
debug2("channel %d: ibuf empty", c->self);
if (sshbuf_len(c->input)) {
error("channel %d: chan_ibuf_empty for non empty buffer",
c->self);
return;
}
switch (c->istate) {
case CHAN_INPUT_WAIT_DRAIN:
if (!(c->flags & (CHAN_CLOSE_SENT|CHAN_LOCAL)))
chan_send_eof2(ssh, c);
chan_set_istate(c, CHAN_INPUT_CLOSED);
break;
default:
error("channel %d: chan_ibuf_empty for istate %d",
c->self, c->istate);
break;
}
}
void
chan_obuf_empty(struct ssh *ssh, Channel *c)
{
debug2("channel %d: obuf empty", c->self);
if (sshbuf_len(c->output)) {
error("channel %d: chan_obuf_empty for non empty buffer",
c->self);
return;
}
switch (c->ostate) {
case CHAN_OUTPUT_WAIT_DRAIN:
chan_shutdown_write(ssh, c);
chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
break;
default:
error("channel %d: internal error: obuf_empty for ostate %d",
c->self, c->ostate);
break;
}
}
void
chan_rcvd_eow(struct ssh *ssh, Channel *c)
{
debug2("channel %d: rcvd eow", c->self);
switch (c->istate) {
case CHAN_INPUT_OPEN:
chan_shutdown_read(ssh, c);
chan_set_istate(c, CHAN_INPUT_CLOSED);
break;
}
}
static void
chan_send_eof2(struct ssh *ssh, Channel *c)
{
int r;
debug2("channel %d: send eof", c->self);
switch (c->istate) {
case CHAN_INPUT_WAIT_DRAIN:
if (!c->have_remote_id)
fatal_f("channel %d: no remote_id", c->self);
if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_EOF)) != 0 ||
(r = sshpkt_put_u32(ssh, c->remote_id)) != 0 ||
(r = sshpkt_send(ssh)) != 0)
fatal_fr(r, "send CHANNEL_EOF");
c->flags |= CHAN_EOF_SENT;
break;
default:
error("channel %d: cannot send eof for istate %d",
c->self, c->istate);
break;
}
}
static void
chan_send_close2(struct ssh *ssh, Channel *c)
{
int r;
debug2("channel %d: send close", c->self);
if (c->ostate != CHAN_OUTPUT_CLOSED ||
c->istate != CHAN_INPUT_CLOSED) {
error("channel %d: cannot send close for istate/ostate %d/%d",
c->self, c->istate, c->ostate);
} else if (c->flags & CHAN_CLOSE_SENT) {
error("channel %d: already sent close", c->self);
} else {
if (!c->have_remote_id)
fatal_f("channel %d: no remote_id", c->self);
if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_CLOSE)) != 0 ||
(r = sshpkt_put_u32(ssh, c->remote_id)) != 0 ||
(r = sshpkt_send(ssh)) != 0)
fatal_fr(r, "send CHANNEL_EOF");
c->flags |= CHAN_CLOSE_SENT;
}
}
static void
chan_send_eow2(struct ssh *ssh, Channel *c)
{
int r;
debug2("channel %d: send eow", c->self);
if (c->ostate == CHAN_OUTPUT_CLOSED) {
error("channel %d: must not sent eow on closed output",
c->self);
return;
}
if (!(datafellows & SSH_NEW_OPENSSH))
return;
if (!c->have_remote_id)
fatal_f("channel %d: no remote_id", c->self);
if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_REQUEST)) != 0 ||
(r = sshpkt_put_u32(ssh, c->remote_id)) != 0 ||
(r = sshpkt_put_cstring(ssh, "eow@openssh.com")) != 0 ||
(r = sshpkt_put_u8(ssh, 0)) != 0 ||
(r = sshpkt_send(ssh)) != 0)
fatal_fr(r, "send CHANNEL_EOF");
}
/* shared */
void
chan_rcvd_ieof(struct ssh *ssh, Channel *c)
{
debug2("channel %d: rcvd eof", c->self);
c->flags |= CHAN_EOF_RCVD;
if (c->ostate == CHAN_OUTPUT_OPEN)
chan_set_ostate(c, CHAN_OUTPUT_WAIT_DRAIN);
if (c->ostate == CHAN_OUTPUT_WAIT_DRAIN &&
sshbuf_len(c->output) == 0 &&
!CHANNEL_EFD_OUTPUT_ACTIVE(c))
chan_obuf_empty(ssh, c);
}
void
chan_rcvd_oclose(struct ssh *ssh, Channel *c)
{
debug2("channel %d: rcvd close", c->self);
if (!(c->flags & CHAN_LOCAL)) {
if (c->flags & CHAN_CLOSE_RCVD)
error("channel %d: protocol error: close rcvd twice",
c->self);
c->flags |= CHAN_CLOSE_RCVD;
}
if (c->type == SSH_CHANNEL_LARVAL) {
/* tear down larval channels immediately */
chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
chan_set_istate(c, CHAN_INPUT_CLOSED);
return;
}
switch (c->ostate) {
case CHAN_OUTPUT_OPEN:
/*
* wait until a data from the channel is consumed if a CLOSE
* is received
*/
chan_set_ostate(c, CHAN_OUTPUT_WAIT_DRAIN);
break;
}
switch (c->istate) {
case CHAN_INPUT_OPEN:
chan_shutdown_read(ssh, c);
chan_shutdown_extended_read(ssh, c);
chan_set_istate(c, CHAN_INPUT_CLOSED);
break;
case CHAN_INPUT_WAIT_DRAIN:
if (!(c->flags & CHAN_LOCAL))
chan_send_eof2(ssh, c);
chan_shutdown_extended_read(ssh, c);
chan_set_istate(c, CHAN_INPUT_CLOSED);
break;
}
}
void
chan_write_failed(struct ssh *ssh, Channel *c)
{
debug2("channel %d: write failed", c->self);
switch (c->ostate) {
case CHAN_OUTPUT_OPEN:
case CHAN_OUTPUT_WAIT_DRAIN:
chan_shutdown_write(ssh, c);
if (strcmp(c->ctype, "session") == 0)
chan_send_eow2(ssh, c);
chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
break;
default:
error("channel %d: chan_write_failed for ostate %d",
c->self, c->ostate);
break;
}
}
void
chan_mark_dead(struct ssh *ssh, Channel *c)
{
c->type = SSH_CHANNEL_ZOMBIE;
}
int
chan_is_dead(struct ssh *ssh, Channel *c, int do_send)
{
if (c->type == SSH_CHANNEL_ZOMBIE) {
debug2("channel %d: zombie", c->self);
return 1;
}
if (c->istate != CHAN_INPUT_CLOSED || c->ostate != CHAN_OUTPUT_CLOSED)
return 0;
if ((datafellows & SSH_BUG_EXTEOF) &&
c->extended_usage == CHAN_EXTENDED_WRITE &&
c->efd != -1 &&
sshbuf_len(c->extended) > 0) {
debug2("channel %d: active efd: %d len %zu",
c->self, c->efd, sshbuf_len(c->extended));
return 0;
}
if (c->flags & CHAN_LOCAL) {
debug2("channel %d: is dead (local)", c->self);
return 1;
}
if (!(c->flags & CHAN_CLOSE_SENT)) {
if (do_send) {
chan_send_close2(ssh, c);
} else {
/* channel would be dead if we sent a close */
if (c->flags & CHAN_CLOSE_RCVD) {
debug2("channel %d: almost dead",
c->self);
return 1;
}
}
}
if ((c->flags & CHAN_CLOSE_SENT) &&
(c->flags & CHAN_CLOSE_RCVD)) {
debug2("channel %d: is dead", c->self);
return 1;
}
return 0;
}
/* helper */
static void
chan_shutdown_write(struct ssh *ssh, Channel *c)
{
sshbuf_reset(c->output);
if (c->type == SSH_CHANNEL_LARVAL)
return;
/* shutdown failure is allowed if write failed already */
debug2_f("channel %d: (i%d o%d sock %d wfd %d efd %d [%s])",
c->self, c->istate, c->ostate, c->sock, c->wfd, c->efd,
channel_format_extended_usage(c));
if (c->sock != -1) {
if (shutdown(c->sock, SHUT_WR) == -1) {
debug2_f("channel %d: shutdown() failed for "
"fd %d [i%d o%d]: %.100s", c->self, c->sock,
c->istate, c->ostate, strerror(errno));
}
} else {
if (channel_close_fd(ssh, &c->wfd) < 0) {
logit_f("channel %d: close() failed for "
"fd %d [i%d o%d]: %.100s", c->self, c->wfd,
c->istate, c->ostate, strerror(errno));
}
}
}
static void
chan_shutdown_read(struct ssh *ssh, Channel *c)
{
if (c->type == SSH_CHANNEL_LARVAL)
return;
debug2_f("channel %d: (i%d o%d sock %d wfd %d efd %d [%s])",
c->self, c->istate, c->ostate, c->sock, c->rfd, c->efd,
channel_format_extended_usage(c));
if (c->sock != -1) {
/*
* shutdown(sock, SHUT_READ) may return ENOTCONN if the
* write side has been closed already. (bug on Linux)
* HP-UX may return ENOTCONN also.
*/
if (shutdown(c->sock, SHUT_RD) == -1 && errno != ENOTCONN) {
error_f("channel %d: shutdown() failed for "
"fd %d [i%d o%d]: %.100s", c->self, c->sock,
c->istate, c->ostate, strerror(errno));
}
} else {
if (channel_close_fd(ssh, &c->rfd) < 0) {
logit_f("channel %d: close() failed for "
"fd %d [i%d o%d]: %.100s", c->self, c->rfd,
c->istate, c->ostate, strerror(errno));
}
}
}
static void
chan_shutdown_extended_read(struct ssh *ssh, Channel *c)
{
if (c->type == SSH_CHANNEL_LARVAL || c->efd == -1)
return;
if (c->extended_usage != CHAN_EXTENDED_READ &&
c->extended_usage != CHAN_EXTENDED_IGNORE)
return;
debug_f("channel %d: (i%d o%d sock %d wfd %d efd %d [%s])",
c->self, c->istate, c->ostate, c->sock, c->rfd, c->efd,
channel_format_extended_usage(c));
if (channel_close_fd(ssh, &c->efd) < 0) {
logit_f("channel %d: close() failed for "
"extended fd %d [i%d o%d]: %.100s", c->self, c->efd,
c->istate, c->ostate, strerror(errno));
}
}
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