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freebsd-dev/crypto/openssh/channels.c
Brian Feldman e0fbb1d2de Make password attacks based on traffic analysis harder by requiring that 
"non-echoed" characters are still echoed back in a null packet, as well
as pad passwords sent to not give hints to the length otherwise.

Obtained from:	OpenBSD
2001-03-20 02:06:40 +00:00

2362 lines
63 KiB
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/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
* All rights reserved
* This file contains functions for generic socket connection forwarding.
* There is also code for initiating connection forwarding for X11 connections,
* arbitrary tcp/ip connections, and the authentication agent connection.
*
* As far as I am concerned, the code I have written for this software
* can be used freely for any purpose. Any derived versions of this
* software must be clearly marked as such, and if the derived work is
* incompatible with the protocol description in the RFC file, it must be
* called by a name other than "ssh" or "Secure Shell".
*
*
* SSH2 support added by Markus Friedl.
* Copyright (c) 1999,2000 Markus Friedl. All rights reserved.
* Copyright (c) 1999 Dug Song. All rights reserved.
* Copyright (c) 1999 Theo de Raadt. 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"
RCSID("$FreeBSD$");
RCSID("$OpenBSD: channels.c,v 1.72 2000/10/27 07:48:22 markus Exp $");
#include "ssh.h"
#include "packet.h"
#include "xmalloc.h"
#include "buffer.h"
#include "uidswap.h"
#include "readconf.h"
#include "servconf.h"
#include "channels.h"
#include "nchan.h"
#include "compat.h"
#include "ssh2.h"
#include <openssl/rsa.h>
#include <openssl/dsa.h>
#include "key.h"
#include "authfd.h"
/* Maximum number of fake X11 displays to try. */
#define MAX_DISPLAYS 1000
/* Max len of agent socket */
#define MAX_SOCKET_NAME 100
/*
* Pointer to an array containing all allocated channels. The array is
* dynamically extended as needed.
*/
static Channel *channels = NULL;
/*
* Size of the channel array. All slots of the array must always be
* initialized (at least the type field); unused slots are marked with type
* SSH_CHANNEL_FREE.
*/
static int channels_alloc = 0;
/*
* Maximum file descriptor value used in any of the channels. This is
* updated in channel_allocate.
*/
static int channel_max_fd_value = 0;
/* Name and directory of socket for authentication agent forwarding. */
static char *channel_forwarded_auth_socket_name = NULL;
static char *channel_forwarded_auth_socket_dir = NULL;
/* Saved X11 authentication protocol name. */
char *x11_saved_proto = NULL;
/* Saved X11 authentication data. This is the real data. */
char *x11_saved_data = NULL;
unsigned int x11_saved_data_len = 0;
/*
* Fake X11 authentication data. This is what the server will be sending us;
* we should replace any occurrences of this by the real data.
*/
char *x11_fake_data = NULL;
unsigned int x11_fake_data_len;
/*
* Data structure for storing which hosts are permitted for forward requests.
* The local sides of any remote forwards are stored in this array to prevent
* a corrupt remote server from accessing arbitrary TCP/IP ports on our local
* network (which might be behind a firewall).
*/
typedef struct {
char *host_to_connect; /* Connect to 'host'. */
u_short port_to_connect; /* Connect to 'port'. */
u_short listen_port; /* Remote side should listen port number. */
} ForwardPermission;
/* List of all permitted host/port pairs to connect. */
static ForwardPermission permitted_opens[SSH_MAX_FORWARDS_PER_DIRECTION];
/* Number of permitted host/port pairs in the array. */
static int num_permitted_opens = 0;
/*
* If this is true, all opens are permitted. This is the case on the server
* on which we have to trust the client anyway, and the user could do
* anything after logging in anyway.
*/
static int all_opens_permitted = 0;
/* This is set to true if both sides support SSH_PROTOFLAG_HOST_IN_FWD_OPEN. */
static int have_hostname_in_open = 0;
/* Sets specific protocol options. */
void
channel_set_options(int hostname_in_open)
{
have_hostname_in_open = hostname_in_open;
}
/*
* Permits opening to any host/port in SSH_MSG_PORT_OPEN. This is usually
* called by the server, because the user could connect to any port anyway,
* and the server has no way to know but to trust the client anyway.
*/
void
channel_permit_all_opens()
{
all_opens_permitted = 1;
}
/* lookup channel by id */
Channel *
channel_lookup(int id)
{
Channel *c;
if (id < 0 || id > channels_alloc) {
log("channel_lookup: %d: bad id", id);
return NULL;
}
c = &channels[id];
if (c->type == SSH_CHANNEL_FREE) {
log("channel_lookup: %d: bad id: channel free", id);
return NULL;
}
return c;
}
/*
* Register filedescriptors for a channel, used when allocating a channel or
* when the channel consumer/producer is ready, e.g. shell exec'd
*/
void
channel_register_fds(Channel *c, int rfd, int wfd, int efd,
int extusage, int nonblock)
{
/* Update the maximum file descriptor value. */
if (rfd > channel_max_fd_value)
channel_max_fd_value = rfd;
if (wfd > channel_max_fd_value)
channel_max_fd_value = wfd;
if (efd > channel_max_fd_value)
channel_max_fd_value = efd;
/* XXX set close-on-exec -markus */
c->rfd = rfd;
c->wfd = wfd;
c->sock = (rfd == wfd) ? rfd : -1;
c->efd = efd;
c->extended_usage = extusage;
/* XXX ugly hack: nonblock is only set by the server */
if (nonblock && isatty(c->rfd)) {
debug("channel: %d: rfd %d isatty", c->self, c->rfd);
c->isatty = 1;
if (!isatty(c->wfd)) {
error("channel: %d: wfd %d is not a tty?",
c->self, c->wfd);
}
} else {
c->isatty = 0;
}
/* enable nonblocking mode */
if (nonblock) {
if (rfd != -1)
set_nonblock(rfd);
if (wfd != -1)
set_nonblock(wfd);
if (efd != -1)
set_nonblock(efd);
}
}
/*
* Allocate a new channel object and set its type and socket. This will cause
* remote_name to be freed.
*/
int
channel_new(char *ctype, int type, int rfd, int wfd, int efd,
int window, int maxpack, int extusage, char *remote_name, int nonblock)
{
int i, found;
Channel *c;
/* Do initial allocation if this is the first call. */
if (channels_alloc == 0) {
chan_init();
channels_alloc = 10;
channels = xmalloc(channels_alloc * sizeof(Channel));
for (i = 0; i < channels_alloc; i++)
channels[i].type = SSH_CHANNEL_FREE;
/*
* Kludge: arrange a call to channel_stop_listening if we
* terminate with fatal().
*/
fatal_add_cleanup((void (*) (void *)) channel_stop_listening, NULL);
}
/* Try to find a free slot where to put the new channel. */
for (found = -1, i = 0; i < channels_alloc; i++)
if (channels[i].type == SSH_CHANNEL_FREE) {
/* Found a free slot. */
found = i;
break;
}
if (found == -1) {
/* There are no free slots. Take last+1 slot and expand the array. */
found = channels_alloc;
channels_alloc += 10;
debug2("channel: expanding %d", channels_alloc);
channels = xrealloc(channels, channels_alloc * sizeof(Channel));
for (i = found; i < channels_alloc; i++)
channels[i].type = SSH_CHANNEL_FREE;
}
/* Initialize and return new channel number. */
c = &channels[found];
buffer_init(&c->input);
buffer_init(&c->output);
buffer_init(&c->extended);
chan_init_iostates(c);
channel_register_fds(c, rfd, wfd, efd, extusage, nonblock);
c->self = found;
c->type = type;
c->ctype = ctype;
c->local_window = window;
c->local_window_max = window;
c->local_consumed = 0;
c->local_maxpacket = maxpack;
c->remote_id = -1;
c->remote_name = remote_name;
c->remote_window = 0;
c->remote_maxpacket = 0;
c->cb_fn = NULL;
c->cb_arg = NULL;
c->cb_event = 0;
c->dettach_user = NULL;
c->input_filter = NULL;
debug("channel %d: new [%s]", found, remote_name);
return found;
}
/* old interface XXX */
int
channel_allocate(int type, int sock, char *remote_name)
{
return channel_new("", type, sock, sock, -1, 0, 0, 0, remote_name, 1);
}
/* Close all channel fd/socket. */
void
channel_close_fds(Channel *c)
{
if (c->sock != -1) {
close(c->sock);
c->sock = -1;
}
if (c->rfd != -1) {
close(c->rfd);
c->rfd = -1;
}
if (c->wfd != -1) {
close(c->wfd);
c->wfd = -1;
}
if (c->efd != -1) {
close(c->efd);
c->efd = -1;
}
}
/* Free the channel and close its fd/socket. */
void
channel_free(int id)
{
Channel *c = channel_lookup(id);
if (c == NULL)
packet_disconnect("channel free: bad local channel %d", id);
debug("channel_free: channel %d: status: %s", id, channel_open_message());
if (c->dettach_user != NULL) {
debug("channel_free: channel %d: dettaching channel user", id);
c->dettach_user(c->self, NULL);
}
if (c->sock != -1)
shutdown(c->sock, SHUT_RDWR);
channel_close_fds(c);
buffer_free(&c->input);
buffer_free(&c->output);
buffer_free(&c->extended);
c->type = SSH_CHANNEL_FREE;
if (c->remote_name) {
xfree(c->remote_name);
c->remote_name = NULL;
}
}
/*
* 'channel_pre*' are called just before select() to add any bits relevant to
* channels in the select bitmasks.
*/
/*
* 'channel_post*': perform any appropriate operations for channels which
* have events pending.
*/
typedef void chan_fn(Channel *c, fd_set * readset, fd_set * writeset);
chan_fn *channel_pre[SSH_CHANNEL_MAX_TYPE];
chan_fn *channel_post[SSH_CHANNEL_MAX_TYPE];
void
channel_pre_listener(Channel *c, fd_set * readset, fd_set * writeset)
{
FD_SET(c->sock, readset);
}
void
channel_pre_open_13(Channel *c, fd_set * readset, fd_set * writeset)
{
if (buffer_len(&c->input) < packet_get_maxsize())
FD_SET(c->sock, readset);
if (buffer_len(&c->output) > 0)
FD_SET(c->sock, writeset);
}
void
channel_pre_open_15(Channel *c, fd_set * readset, fd_set * writeset)
{
/* test whether sockets are 'alive' for read/write */
if (c->istate == CHAN_INPUT_OPEN)
if (buffer_len(&c->input) < packet_get_maxsize())
FD_SET(c->sock, readset);
if (c->ostate == CHAN_OUTPUT_OPEN ||
c->ostate == CHAN_OUTPUT_WAIT_DRAIN) {
if (buffer_len(&c->output) > 0) {
FD_SET(c->sock, writeset);
} else if (c->ostate == CHAN_OUTPUT_WAIT_DRAIN) {
chan_obuf_empty(c);
}
}
}
void
channel_pre_open_20(Channel *c, fd_set * readset, fd_set * writeset)
{
if (c->istate == CHAN_INPUT_OPEN &&
c->remote_window > 0 &&
buffer_len(&c->input) < c->remote_window)
FD_SET(c->rfd, readset);
if (c->ostate == CHAN_OUTPUT_OPEN ||
c->ostate == CHAN_OUTPUT_WAIT_DRAIN) {
if (buffer_len(&c->output) > 0) {
FD_SET(c->wfd, writeset);
} else if (c->ostate == CHAN_OUTPUT_WAIT_DRAIN) {
chan_obuf_empty(c);
}
}
/** XXX check close conditions, too */
if (c->efd != -1) {
if (c->extended_usage == CHAN_EXTENDED_WRITE &&
buffer_len(&c->extended) > 0)
FD_SET(c->efd, writeset);
else if (c->extended_usage == CHAN_EXTENDED_READ &&
buffer_len(&c->extended) < c->remote_window)
FD_SET(c->efd, readset);
}
}
void
channel_pre_input_draining(Channel *c, fd_set * readset, fd_set * writeset)
{
if (buffer_len(&c->input) == 0) {
packet_start(SSH_MSG_CHANNEL_CLOSE);
packet_put_int(c->remote_id);
packet_send();
c->type = SSH_CHANNEL_CLOSED;
debug("Closing channel %d after input drain.", c->self);
}
}
void
channel_pre_output_draining(Channel *c, fd_set * readset, fd_set * writeset)
{
if (buffer_len(&c->output) == 0)
channel_free(c->self);
else
FD_SET(c->sock, writeset);
}
/*
* This is a special state for X11 authentication spoofing. An opened X11
* connection (when authentication spoofing is being done) remains in this
* state until the first packet has been completely read. The authentication
* data in that packet is then substituted by the real data if it matches the
* fake data, and the channel is put into normal mode.
* XXX All this happens at the client side.
*/
int
x11_open_helper(Channel *c)
{
unsigned char *ucp;
unsigned int proto_len, data_len;
/* Check if the fixed size part of the packet is in buffer. */
if (buffer_len(&c->output) < 12)
return 0;
/* Parse the lengths of variable-length fields. */
ucp = (unsigned char *) buffer_ptr(&c->output);
if (ucp[0] == 0x42) { /* Byte order MSB first. */
proto_len = 256 * ucp[6] + ucp[7];
data_len = 256 * ucp[8] + ucp[9];
} else if (ucp[0] == 0x6c) { /* Byte order LSB first. */
proto_len = ucp[6] + 256 * ucp[7];
data_len = ucp[8] + 256 * ucp[9];
} else {
debug("Initial X11 packet contains bad byte order byte: 0x%x",
ucp[0]);
return -1;
}
/* Check if the whole packet is in buffer. */
if (buffer_len(&c->output) <
12 + ((proto_len + 3) & ~3) + ((data_len + 3) & ~3))
return 0;
/* Check if authentication protocol matches. */
if (proto_len != strlen(x11_saved_proto) ||
memcmp(ucp + 12, x11_saved_proto, proto_len) != 0) {
debug("X11 connection uses different authentication protocol.");
return -1;
}
/* Check if authentication data matches our fake data. */
if (data_len != x11_fake_data_len ||
memcmp(ucp + 12 + ((proto_len + 3) & ~3),
x11_fake_data, x11_fake_data_len) != 0) {
debug("X11 auth data does not match fake data.");
return -1;
}
/* Check fake data length */
if (x11_fake_data_len != x11_saved_data_len) {
error("X11 fake_data_len %d != saved_data_len %d",
x11_fake_data_len, x11_saved_data_len);
return -1;
}
/*
* Received authentication protocol and data match
* our fake data. Substitute the fake data with real
* data.
*/
memcpy(ucp + 12 + ((proto_len + 3) & ~3),
x11_saved_data, x11_saved_data_len);
return 1;
}
void
channel_pre_x11_open_13(Channel *c, fd_set * readset, fd_set * writeset)
{
int ret = x11_open_helper(c);
if (ret == 1) {
/* Start normal processing for the channel. */
c->type = SSH_CHANNEL_OPEN;
channel_pre_open_13(c, readset, writeset);
} else if (ret == -1) {
/*
* We have received an X11 connection that has bad
* authentication information.
*/
log("X11 connection rejected because of wrong authentication.\r\n");
buffer_clear(&c->input);
buffer_clear(&c->output);
close(c->sock);
c->sock = -1;
c->type = SSH_CHANNEL_CLOSED;
packet_start(SSH_MSG_CHANNEL_CLOSE);
packet_put_int(c->remote_id);
packet_send();
}
}
void
channel_pre_x11_open(Channel *c, fd_set * readset, fd_set * writeset)
{
int ret = x11_open_helper(c);
if (ret == 1) {
c->type = SSH_CHANNEL_OPEN;
if (compat20)
channel_pre_open_20(c, readset, writeset);
else
channel_pre_open_15(c, readset, writeset);
} else if (ret == -1) {
debug("X11 rejected %d i%d/o%d", c->self, c->istate, c->ostate);
chan_read_failed(c); /** force close? */
chan_write_failed(c);
debug("X11 closed %d i%d/o%d", c->self, c->istate, c->ostate);
}
}
/* This is our fake X11 server socket. */
void
channel_post_x11_listener(Channel *c, fd_set * readset, fd_set * writeset)
{
struct sockaddr addr;
int newsock, newch;
socklen_t addrlen;
char buf[16384], *remote_hostname;
int remote_port;
if (FD_ISSET(c->sock, readset)) {
debug("X11 connection requested.");
addrlen = sizeof(addr);
newsock = accept(c->sock, &addr, &addrlen);
if (newsock < 0) {
error("accept: %.100s", strerror(errno));
return;
}
remote_hostname = get_remote_hostname(newsock);
remote_port = get_peer_port(newsock);
snprintf(buf, sizeof buf, "X11 connection from %.200s port %d",
remote_hostname, remote_port);
newch = channel_new("x11",
SSH_CHANNEL_OPENING, newsock, newsock, -1,
c->local_window_max, c->local_maxpacket,
0, xstrdup(buf), 1);
if (compat20) {
packet_start(SSH2_MSG_CHANNEL_OPEN);
packet_put_cstring("x11");
packet_put_int(newch);
packet_put_int(c->local_window_max);
packet_put_int(c->local_maxpacket);
/* originator host and port */
packet_put_cstring(remote_hostname);
if (datafellows & SSH_BUG_X11FWD) {
debug("ssh2 x11 bug compat mode");
} else {
packet_put_int(remote_port);
}
packet_send();
} else {
packet_start(SSH_SMSG_X11_OPEN);
packet_put_int(newch);
if (have_hostname_in_open)
packet_put_string(buf, strlen(buf));
packet_send();
}
xfree(remote_hostname);
}
}
/*
* This socket is listening for connections to a forwarded TCP/IP port.
*/
void
channel_post_port_listener(Channel *c, fd_set * readset, fd_set * writeset)
{
struct sockaddr addr;
int newsock, newch;
socklen_t addrlen;
char buf[1024], *remote_hostname;
int remote_port;
if (FD_ISSET(c->sock, readset)) {
debug("Connection to port %d forwarding "
"to %.100s port %d requested.",
c->listening_port, c->path, c->host_port);
addrlen = sizeof(addr);
newsock = accept(c->sock, &addr, &addrlen);
if (newsock < 0) {
error("accept: %.100s", strerror(errno));
return;
}
remote_hostname = get_remote_hostname(newsock);
remote_port = get_peer_port(newsock);
snprintf(buf, sizeof buf,
"listen port %d for %.100s port %d, "
"connect from %.200s port %d",
c->listening_port, c->path, c->host_port,
remote_hostname, remote_port);
newch = channel_new("direct-tcpip",
SSH_CHANNEL_OPENING, newsock, newsock, -1,
c->local_window_max, c->local_maxpacket,
0, xstrdup(buf), 1);
if (compat20) {
packet_start(SSH2_MSG_CHANNEL_OPEN);
packet_put_cstring("direct-tcpip");
packet_put_int(newch);
packet_put_int(c->local_window_max);
packet_put_int(c->local_maxpacket);
/* target host and port */
packet_put_string(c->path, strlen(c->path));
packet_put_int(c->host_port);
/* originator host and port */
packet_put_cstring(remote_hostname);
packet_put_int(remote_port);
packet_send();
} else {
packet_start(SSH_MSG_PORT_OPEN);
packet_put_int(newch);
packet_put_string(c->path, strlen(c->path));
packet_put_int(c->host_port);
if (have_hostname_in_open) {
packet_put_string(buf, strlen(buf));
}
packet_send();
}
xfree(remote_hostname);
}
}
/*
* This is the authentication agent socket listening for connections from
* clients.
*/
void
channel_post_auth_listener(Channel *c, fd_set * readset, fd_set * writeset)
{
struct sockaddr addr;
int newsock, newch;
socklen_t addrlen;
if (FD_ISSET(c->sock, readset)) {
addrlen = sizeof(addr);
newsock = accept(c->sock, &addr, &addrlen);
if (newsock < 0) {
error("accept from auth socket: %.100s", strerror(errno));
return;
}
newch = channel_allocate(SSH_CHANNEL_OPENING, newsock,
xstrdup("accepted auth socket"));
packet_start(SSH_SMSG_AGENT_OPEN);
packet_put_int(newch);
packet_send();
}
}
int
channel_handle_rfd(Channel *c, fd_set * readset, fd_set * writeset)
{
char buf[16*1024];
int len;
if (c->rfd != -1 &&
FD_ISSET(c->rfd, readset)) {
len = read(c->rfd, buf, sizeof(buf));
if (len < 0 && (errno == EINTR || errno == EAGAIN))
return 1;
if (len <= 0) {
debug("channel %d: read<=0 rfd %d len %d",
c->self, c->rfd, len);
if (compat13) {
buffer_consume(&c->output, buffer_len(&c->output));
c->type = SSH_CHANNEL_INPUT_DRAINING;
debug("Channel %d status set to input draining.", c->self);
} else {
chan_read_failed(c);
}
return -1;
}
if(c->input_filter != NULL) {
if (c->input_filter(c, buf, len) == -1) {
debug("filter stops channel %d", c->self);
chan_read_failed(c);
}
} else {
buffer_append(&c->input, buf, len);
}
}
return 1;
}
int
channel_handle_wfd(Channel *c, fd_set * readset, fd_set * writeset)
{
int len;
/* Send buffered output data to the socket. */
if (c->wfd != -1 &&
FD_ISSET(c->wfd, writeset) &&
buffer_len(&c->output) > 0) {
len = write(c->wfd, buffer_ptr(&c->output),
buffer_len(&c->output));
if (len < 0 && (errno == EINTR || errno == EAGAIN))
return 1;
if (len <= 0) {
if (compat13) {
buffer_consume(&c->output, buffer_len(&c->output));
debug("Channel %d status set to input draining.", c->self);
c->type = SSH_CHANNEL_INPUT_DRAINING;
} else {
chan_write_failed(c);
}
return -1;
}
if (compat20 && c->isatty) {
struct termios tio;
if (tcgetattr(c->wfd, &tio) == 0 &&
!(tio.c_lflag & ECHO) && (tio.c_lflag & ICANON)) {
/*
* Simulate echo to reduce the impact of
* traffic analysis.
*/
packet_start(SSH2_MSG_IGNORE);
memset(buffer_ptr(&c->output), 0, len);
packet_put_string(buffer_ptr(&c->output), len);
packet_send();
}
}
buffer_consume(&c->output, len);
if (compat20 && len > 0) {
c->local_consumed += len;
}
}
return 1;
}
int
channel_handle_efd(Channel *c, fd_set * readset, fd_set * writeset)
{
char buf[16*1024];
int len;
/** XXX handle drain efd, too */
if (c->efd != -1) {
if (c->extended_usage == CHAN_EXTENDED_WRITE &&
FD_ISSET(c->efd, writeset) &&
buffer_len(&c->extended) > 0) {
len = write(c->efd, buffer_ptr(&c->extended),
buffer_len(&c->extended));
debug2("channel %d: written %d to efd %d",
c->self, len, c->efd);
if (len > 0) {
buffer_consume(&c->extended, len);
c->local_consumed += len;
}
} else if (c->extended_usage == CHAN_EXTENDED_READ &&
FD_ISSET(c->efd, readset)) {
len = read(c->efd, buf, sizeof(buf));
debug2("channel %d: read %d from efd %d",
c->self, len, c->efd);
if (len == 0) {
debug("channel %d: closing efd %d",
c->self, c->efd);
close(c->efd);
c->efd = -1;
} else if (len > 0)
buffer_append(&c->extended, buf, len);
}
}
return 1;
}
int
channel_check_window(Channel *c, fd_set * readset, fd_set * writeset)
{
if (!(c->flags & (CHAN_CLOSE_SENT|CHAN_CLOSE_RCVD)) &&
c->local_window < c->local_window_max/2 &&
c->local_consumed > 0) {
packet_start(SSH2_MSG_CHANNEL_WINDOW_ADJUST);
packet_put_int(c->remote_id);
packet_put_int(c->local_consumed);
packet_send();
debug2("channel %d: window %d sent adjust %d",
c->self, c->local_window,
c->local_consumed);
c->local_window += c->local_consumed;
c->local_consumed = 0;
}
return 1;
}
void
channel_post_open_1(Channel *c, fd_set * readset, fd_set * writeset)
{
channel_handle_rfd(c, readset, writeset);
channel_handle_wfd(c, readset, writeset);
}
void
channel_post_open_2(Channel *c, fd_set * readset, fd_set * writeset)
{
channel_handle_rfd(c, readset, writeset);
channel_handle_wfd(c, readset, writeset);
channel_handle_efd(c, readset, writeset);
channel_check_window(c, readset, writeset);
}
void
channel_post_output_drain_13(Channel *c, fd_set * readset, fd_set * writeset)
{
int len;
/* Send buffered output data to the socket. */
if (FD_ISSET(c->sock, writeset) && buffer_len(&c->output) > 0) {
len = write(c->sock, buffer_ptr(&c->output),
buffer_len(&c->output));
if (len <= 0)
buffer_consume(&c->output, buffer_len(&c->output));
else
buffer_consume(&c->output, len);
}
}
void
channel_handler_init_20(void)
{
channel_pre[SSH_CHANNEL_OPEN] = &channel_pre_open_20;
channel_pre[SSH_CHANNEL_X11_OPEN] = &channel_pre_x11_open;
channel_pre[SSH_CHANNEL_PORT_LISTENER] = &channel_pre_listener;
channel_pre[SSH_CHANNEL_X11_LISTENER] = &channel_pre_listener;
channel_post[SSH_CHANNEL_OPEN] = &channel_post_open_2;
channel_post[SSH_CHANNEL_PORT_LISTENER] = &channel_post_port_listener;
channel_post[SSH_CHANNEL_X11_LISTENER] = &channel_post_x11_listener;
}
void
channel_handler_init_13(void)
{
channel_pre[SSH_CHANNEL_OPEN] = &channel_pre_open_13;
channel_pre[SSH_CHANNEL_X11_OPEN] = &channel_pre_x11_open_13;
channel_pre[SSH_CHANNEL_X11_LISTENER] = &channel_pre_listener;
channel_pre[SSH_CHANNEL_PORT_LISTENER] = &channel_pre_listener;
channel_pre[SSH_CHANNEL_AUTH_SOCKET] = &channel_pre_listener;
channel_pre[SSH_CHANNEL_INPUT_DRAINING] = &channel_pre_input_draining;
channel_pre[SSH_CHANNEL_OUTPUT_DRAINING] = &channel_pre_output_draining;
channel_post[SSH_CHANNEL_OPEN] = &channel_post_open_1;
channel_post[SSH_CHANNEL_X11_LISTENER] = &channel_post_x11_listener;
channel_post[SSH_CHANNEL_PORT_LISTENER] = &channel_post_port_listener;
channel_post[SSH_CHANNEL_AUTH_SOCKET] = &channel_post_auth_listener;
channel_post[SSH_CHANNEL_OUTPUT_DRAINING] = &channel_post_output_drain_13;
}
void
channel_handler_init_15(void)
{
channel_pre[SSH_CHANNEL_OPEN] = &channel_pre_open_15;
channel_pre[SSH_CHANNEL_X11_OPEN] = &channel_pre_x11_open;
channel_pre[SSH_CHANNEL_X11_LISTENER] = &channel_pre_listener;
channel_pre[SSH_CHANNEL_PORT_LISTENER] = &channel_pre_listener;
channel_pre[SSH_CHANNEL_AUTH_SOCKET] = &channel_pre_listener;
channel_post[SSH_CHANNEL_X11_LISTENER] = &channel_post_x11_listener;
channel_post[SSH_CHANNEL_PORT_LISTENER] = &channel_post_port_listener;
channel_post[SSH_CHANNEL_AUTH_SOCKET] = &channel_post_auth_listener;
channel_post[SSH_CHANNEL_OPEN] = &channel_post_open_1;
}
void
channel_handler_init(void)
{
int i;
for(i = 0; i < SSH_CHANNEL_MAX_TYPE; i++) {
channel_pre[i] = NULL;
channel_post[i] = NULL;
}
if (compat20)
channel_handler_init_20();
else if (compat13)
channel_handler_init_13();
else
channel_handler_init_15();
}
void
channel_handler(chan_fn *ftab[], fd_set * readset, fd_set * writeset)
{
static int did_init = 0;
int i;
Channel *c;
if (!did_init) {
channel_handler_init();
did_init = 1;
}
for (i = 0; i < channels_alloc; i++) {
c = &channels[i];
if (c->type == SSH_CHANNEL_FREE)
continue;
if (ftab[c->type] == NULL)
continue;
(*ftab[c->type])(c, readset, writeset);
chan_delete_if_full_closed(c);
}
}
void
channel_prepare_select(fd_set * readset, fd_set * writeset)
{
channel_handler(channel_pre, readset, writeset);
}
void
channel_after_select(fd_set * readset, fd_set * writeset)
{
channel_handler(channel_post, readset, writeset);
}
/* If there is data to send to the connection, send some of it now. */
void
channel_output_poll()
{
int len, i;
Channel *c;
for (i = 0; i < channels_alloc; i++) {
c = &channels[i];
/* We are only interested in channels that can have buffered incoming data. */
if (compat13) {
if (c->type != SSH_CHANNEL_OPEN &&
c->type != SSH_CHANNEL_INPUT_DRAINING)
continue;
} else {
if (c->type != SSH_CHANNEL_OPEN)
continue;
if (c->istate != CHAN_INPUT_OPEN &&
c->istate != CHAN_INPUT_WAIT_DRAIN)
continue;
}
if (compat20 &&
(c->flags & (CHAN_CLOSE_SENT|CHAN_CLOSE_RCVD))) {
debug("channel: %d: no data after CLOSE", c->self);
continue;
}
/* Get the amount of buffered data for this channel. */
len = buffer_len(&c->input);
if (len > 0) {
/* Send some data for the other side over the secure connection. */
if (compat20) {
if (len > c->remote_window)
len = c->remote_window;
if (len > c->remote_maxpacket)
len = c->remote_maxpacket;
} else {
if (packet_is_interactive()) {
if (len > 1024)
len = 512;
} else {
/* Keep the packets at reasonable size. */
if (len > packet_get_maxsize()/2)
len = packet_get_maxsize()/2;
}
}
if (len > 0) {
packet_start(compat20 ?
SSH2_MSG_CHANNEL_DATA : SSH_MSG_CHANNEL_DATA);
packet_put_int(c->remote_id);
packet_put_string(buffer_ptr(&c->input), len);
packet_send();
buffer_consume(&c->input, len);
c->remote_window -= len;
}
} else if (c->istate == CHAN_INPUT_WAIT_DRAIN) {
if (compat13)
fatal("cannot happen: istate == INPUT_WAIT_DRAIN for proto 1.3");
/*
* input-buffer is empty and read-socket shutdown:
* tell peer, that we will not send more data: send IEOF
*/
chan_ibuf_empty(c);
}
/* Send extended data, i.e. stderr */
if (compat20 &&
c->remote_window > 0 &&
(len = buffer_len(&c->extended)) > 0 &&
c->extended_usage == CHAN_EXTENDED_READ) {
if (len > c->remote_window)
len = c->remote_window;
if (len > c->remote_maxpacket)
len = c->remote_maxpacket;
packet_start(SSH2_MSG_CHANNEL_EXTENDED_DATA);
packet_put_int(c->remote_id);
packet_put_int(SSH2_EXTENDED_DATA_STDERR);
packet_put_string(buffer_ptr(&c->extended), len);
packet_send();
buffer_consume(&c->extended, len);
c->remote_window -= len;
}
}
}
/*
* This is called when a packet of type CHANNEL_DATA has just been received.
* The message type has already been consumed, but channel number and data is
* still there.
*/
void
channel_input_data(int type, int plen, void *ctxt)
{
int id;
char *data;
unsigned int data_len;
Channel *c;
/* Get the channel number and verify it. */
id = packet_get_int();
c = channel_lookup(id);
if (c == NULL)
packet_disconnect("Received data for nonexistent channel %d.", id);
/* Ignore any data for non-open channels (might happen on close) */
if (c->type != SSH_CHANNEL_OPEN &&
c->type != SSH_CHANNEL_X11_OPEN)
return;
/* same for protocol 1.5 if output end is no longer open */
if (!compat13 && c->ostate != CHAN_OUTPUT_OPEN)
return;
/* Get the data. */
data = packet_get_string(&data_len);
packet_done();
if (compat20){
if (data_len > c->local_maxpacket) {
log("channel %d: rcvd big packet %d, maxpack %d",
c->self, data_len, c->local_maxpacket);
}
if (data_len > c->local_window) {
log("channel %d: rcvd too much data %d, win %d",
c->self, data_len, c->local_window);
xfree(data);
return;
}
c->local_window -= data_len;
}else{
packet_integrity_check(plen, 4 + 4 + data_len, type);
}
buffer_append(&c->output, data, data_len);
xfree(data);
}
void
channel_input_extended_data(int type, int plen, void *ctxt)
{
int id;
int tcode;
char *data;
unsigned int data_len;
Channel *c;
/* Get the channel number and verify it. */
id = packet_get_int();
c = channel_lookup(id);
if (c == NULL)
packet_disconnect("Received extended_data for bad channel %d.", id);
if (c->type != SSH_CHANNEL_OPEN) {
log("channel %d: ext data for non open", id);
return;
}
tcode = packet_get_int();
if (c->efd == -1 ||
c->extended_usage != CHAN_EXTENDED_WRITE ||
tcode != SSH2_EXTENDED_DATA_STDERR) {
log("channel %d: bad ext data", c->self);
return;
}
data = packet_get_string(&data_len);
packet_done();
if (data_len > c->local_window) {
log("channel %d: rcvd too much extended_data %d, win %d",
c->self, data_len, c->local_window);
xfree(data);
return;
}
debug2("channel %d: rcvd ext data %d", c->self, data_len);
c->local_window -= data_len;
buffer_append(&c->extended, data, data_len);
xfree(data);
}
/*
* Returns true if no channel has too much buffered data, and false if one or
* more channel is overfull.
*/
int
channel_not_very_much_buffered_data()
{
unsigned int i;
Channel *c;
for (i = 0; i < channels_alloc; i++) {
c = &channels[i];
if (c->type == SSH_CHANNEL_OPEN) {
if (!compat20 && buffer_len(&c->input) > packet_get_maxsize()) {
debug("channel %d: big input buffer %d",
c->self, buffer_len(&c->input));
return 0;
}
if (buffer_len(&c->output) > packet_get_maxsize()) {
debug("channel %d: big output buffer %d",
c->self, buffer_len(&c->output));
return 0;
}
}
}
return 1;
}
void
channel_input_ieof(int type, int plen, void *ctxt)
{
int id;
Channel *c;
packet_integrity_check(plen, 4, type);
id = packet_get_int();
c = channel_lookup(id);
if (c == NULL)
packet_disconnect("Received ieof for nonexistent channel %d.", id);
chan_rcvd_ieof(c);
}
void
channel_input_close(int type, int plen, void *ctxt)
{
int id;
Channel *c;
packet_integrity_check(plen, 4, type);
id = packet_get_int();
c = channel_lookup(id);
if (c == NULL)
packet_disconnect("Received close for nonexistent channel %d.", id);
/*
* Send a confirmation that we have closed the channel and no more
* data is coming for it.
*/
packet_start(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION);
packet_put_int(c->remote_id);
packet_send();
/*
* If the channel is in closed state, we have sent a close request,
* and the other side will eventually respond with a confirmation.
* Thus, we cannot free the channel here, because then there would be
* no-one to receive the confirmation. The channel gets freed when
* the confirmation arrives.
*/
if (c->type != SSH_CHANNEL_CLOSED) {
/*
* Not a closed channel - mark it as draining, which will
* cause it to be freed later.
*/
buffer_consume(&c->input, buffer_len(&c->input));
c->type = SSH_CHANNEL_OUTPUT_DRAINING;
}
}
/* proto version 1.5 overloads CLOSE_CONFIRMATION with OCLOSE */
void
channel_input_oclose(int type, int plen, void *ctxt)
{
int id = packet_get_int();
Channel *c = channel_lookup(id);
packet_integrity_check(plen, 4, type);
if (c == NULL)
packet_disconnect("Received oclose for nonexistent channel %d.", id);
chan_rcvd_oclose(c);
}
void
channel_input_close_confirmation(int type, int plen, void *ctxt)
{
int id = packet_get_int();
Channel *c = channel_lookup(id);
packet_done();
if (c == NULL)
packet_disconnect("Received close confirmation for "
"out-of-range channel %d.", id);
if (c->type != SSH_CHANNEL_CLOSED)
packet_disconnect("Received close confirmation for "
"non-closed channel %d (type %d).", id, c->type);
channel_free(c->self);
}
void
channel_input_open_confirmation(int type, int plen, void *ctxt)
{
int id, remote_id;
Channel *c;
if (!compat20)
packet_integrity_check(plen, 4 + 4, type);
id = packet_get_int();
c = channel_lookup(id);
if (c==NULL || c->type != SSH_CHANNEL_OPENING)
packet_disconnect("Received open confirmation for "
"non-opening channel %d.", id);
remote_id = packet_get_int();
/* Record the remote channel number and mark that the channel is now open. */
c->remote_id = remote_id;
c->type = SSH_CHANNEL_OPEN;
if (compat20) {
c->remote_window = packet_get_int();
c->remote_maxpacket = packet_get_int();
packet_done();
if (c->cb_fn != NULL && c->cb_event == type) {
debug2("callback start");
c->cb_fn(c->self, c->cb_arg);
debug2("callback done");
}
debug("channel %d: open confirm rwindow %d rmax %d", c->self,
c->remote_window, c->remote_maxpacket);
}
}
void
channel_input_open_failure(int type, int plen, void *ctxt)
{
int id;
Channel *c;
if (!compat20)
packet_integrity_check(plen, 4, type);
id = packet_get_int();
c = channel_lookup(id);
if (c==NULL || c->type != SSH_CHANNEL_OPENING)
packet_disconnect("Received open failure for "
"non-opening channel %d.", id);
if (compat20) {
int reason = packet_get_int();
char *msg = packet_get_string(NULL);
char *lang = packet_get_string(NULL);
log("channel_open_failure: %d: reason %d: %s", id, reason, msg);
packet_done();
xfree(msg);
xfree(lang);
}
/* Free the channel. This will also close the socket. */
channel_free(id);
}
void
channel_input_channel_request(int type, int plen, void *ctxt)
{
int id;
Channel *c;
id = packet_get_int();
c = channel_lookup(id);
if (c == NULL ||
(c->type != SSH_CHANNEL_OPEN && c->type != SSH_CHANNEL_LARVAL))
packet_disconnect("Received request for "
"non-open channel %d.", id);
if (c->cb_fn != NULL && c->cb_event == type) {
debug2("callback start");
c->cb_fn(c->self, c->cb_arg);
debug2("callback done");
} else {
char *service = packet_get_string(NULL);
debug("channel: %d rcvd request for %s", c->self, service);
debug("cb_fn %p cb_event %d", c->cb_fn , c->cb_event);
xfree(service);
}
}
void
channel_input_window_adjust(int type, int plen, void *ctxt)
{
Channel *c;
int id, adjust;
if (!compat20)
return;
/* Get the channel number and verify it. */
id = packet_get_int();
c = channel_lookup(id);
if (c == NULL || c->type != SSH_CHANNEL_OPEN) {
log("Received window adjust for "
"non-open channel %d.", id);
return;
}
adjust = packet_get_int();
packet_done();
debug2("channel %d: rcvd adjust %d", id, adjust);
c->remote_window += adjust;
}
/*
* Stops listening for channels, and removes any unix domain sockets that we
* might have.
*/
void
channel_stop_listening()
{
int i;
for (i = 0; i < channels_alloc; i++) {
switch (channels[i].type) {
case SSH_CHANNEL_AUTH_SOCKET:
close(channels[i].sock);
remove(channels[i].path);
channel_free(i);
break;
case SSH_CHANNEL_PORT_LISTENER:
case SSH_CHANNEL_X11_LISTENER:
close(channels[i].sock);
channel_free(i);
break;
default:
break;
}
}
}
/*
* Closes the sockets/fds of all channels. This is used to close extra file
* descriptors after a fork.
*/
void
channel_close_all()
{
int i;
for (i = 0; i < channels_alloc; i++)
if (channels[i].type != SSH_CHANNEL_FREE)
channel_close_fds(&channels[i]);
}
/* Returns the maximum file descriptor number used by the channels. */
int
channel_max_fd()
{
return channel_max_fd_value;
}
/* Returns true if any channel is still open. */
int
channel_still_open()
{
unsigned int i;
for (i = 0; i < channels_alloc; i++)
switch (channels[i].type) {
case SSH_CHANNEL_FREE:
case SSH_CHANNEL_X11_LISTENER:
case SSH_CHANNEL_PORT_LISTENER:
case SSH_CHANNEL_CLOSED:
case SSH_CHANNEL_AUTH_SOCKET:
continue;
case SSH_CHANNEL_LARVAL:
if (!compat20)
fatal("cannot happen: SSH_CHANNEL_LARVAL");
continue;
case SSH_CHANNEL_OPENING:
case SSH_CHANNEL_OPEN:
case SSH_CHANNEL_X11_OPEN:
return 1;
case SSH_CHANNEL_INPUT_DRAINING:
case SSH_CHANNEL_OUTPUT_DRAINING:
if (!compat13)
fatal("cannot happen: OUT_DRAIN");
return 1;
default:
fatal("channel_still_open: bad channel type %d", channels[i].type);
/* NOTREACHED */
}
return 0;
}
/*
* Returns a message describing the currently open forwarded connections,
* suitable for sending to the client. The message contains crlf pairs for
* newlines.
*/
char *
channel_open_message()
{
Buffer buffer;
int i;
char buf[512], *cp;
buffer_init(&buffer);
snprintf(buf, sizeof buf, "The following connections are open:\r\n");
buffer_append(&buffer, buf, strlen(buf));
for (i = 0; i < channels_alloc; i++) {
Channel *c = &channels[i];
switch (c->type) {
case SSH_CHANNEL_FREE:
case SSH_CHANNEL_X11_LISTENER:
case SSH_CHANNEL_PORT_LISTENER:
case SSH_CHANNEL_CLOSED:
case SSH_CHANNEL_AUTH_SOCKET:
continue;
case SSH_CHANNEL_LARVAL:
case SSH_CHANNEL_OPENING:
case SSH_CHANNEL_OPEN:
case SSH_CHANNEL_X11_OPEN:
case SSH_CHANNEL_INPUT_DRAINING:
case SSH_CHANNEL_OUTPUT_DRAINING:
snprintf(buf, sizeof buf, " #%d %.300s (t%d r%d i%d/%d o%d/%d fd %d/%d)\r\n",
c->self, c->remote_name,
c->type, c->remote_id,
c->istate, buffer_len(&c->input),
c->ostate, buffer_len(&c->output),
c->rfd, c->wfd);
buffer_append(&buffer, buf, strlen(buf));
continue;
default:
fatal("channel_open_message: bad channel type %d", c->type);
/* NOTREACHED */
}
}
buffer_append(&buffer, "\0", 1);
cp = xstrdup(buffer_ptr(&buffer));
buffer_free(&buffer);
return cp;
}
/*
* Initiate forwarding of connections to local port "port" through the secure
* channel to host:port from remote side.
*/
void
channel_request_local_forwarding(u_short port, const char *host,
u_short host_port, int gateway_ports)
{
int success, ch, sock, on = 1;
struct addrinfo hints, *ai, *aitop;
char ntop[NI_MAXHOST], strport[NI_MAXSERV];
struct linger linger;
if (strlen(host) > sizeof(channels[0].path) - 1)
packet_disconnect("Forward host name too long.");
/*
* getaddrinfo returns a loopback address if the hostname is
* set to NULL and hints.ai_flags is not AI_PASSIVE
*/
memset(&hints, 0, sizeof(hints));
hints.ai_family = IPv4or6;
hints.ai_flags = gateway_ports ? AI_PASSIVE : 0;
hints.ai_socktype = SOCK_STREAM;
snprintf(strport, sizeof strport, "%d", port);
if (getaddrinfo(NULL, strport, &hints, &aitop) != 0)
packet_disconnect("getaddrinfo: fatal error");
success = 0;
for (ai = aitop; ai; ai = ai->ai_next) {
if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
continue;
if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop, sizeof(ntop),
strport, sizeof(strport), NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
error("channel_request_local_forwarding: getnameinfo failed");
continue;
}
/* Create a port to listen for the host. */
sock = socket(ai->ai_family, SOCK_STREAM, 0);
if (sock < 0) {
/* this is no error since kernel may not support ipv6 */
verbose("socket: %.100s", strerror(errno));
continue;
}
/*
* Set socket options. We would like the socket to disappear
* as soon as it has been closed for whatever reason.
*/
setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on));
linger.l_onoff = 1;
linger.l_linger = 5;
setsockopt(sock, SOL_SOCKET, SO_LINGER, (void *)&linger, sizeof(linger));
debug("Local forwarding listening on %s port %s.", ntop, strport);
/* Bind the socket to the address. */
if (bind(sock, ai->ai_addr, ai->ai_addrlen) < 0) {
/* address can be in use ipv6 address is already bound */
verbose("bind: %.100s", strerror(errno));
close(sock);
continue;
}
/* Start listening for connections on the socket. */
if (listen(sock, 5) < 0) {
error("listen: %.100s", strerror(errno));
close(sock);
continue;
}
/* Allocate a channel number for the socket. */
ch = channel_new(
"port listener", SSH_CHANNEL_PORT_LISTENER,
sock, sock, -1,
CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT,
0, xstrdup("port listener"), 1);
strlcpy(channels[ch].path, host, sizeof(channels[ch].path));
channels[ch].host_port = host_port;
channels[ch].listening_port = port;
success = 1;
}
if (success == 0)
packet_disconnect("cannot listen port: %d", port);
freeaddrinfo(aitop);
}
/*
* Initiate forwarding of connections to port "port" on remote host through
* the secure channel to host:port from local side.
*/
void
channel_request_remote_forwarding(u_short listen_port, const char *host_to_connect,
u_short port_to_connect)
{
int payload_len;
/* Record locally that connection to this host/port is permitted. */
if (num_permitted_opens >= SSH_MAX_FORWARDS_PER_DIRECTION)
fatal("channel_request_remote_forwarding: too many forwards");
permitted_opens[num_permitted_opens].host_to_connect = xstrdup(host_to_connect);
permitted_opens[num_permitted_opens].port_to_connect = port_to_connect;
permitted_opens[num_permitted_opens].listen_port = listen_port;
num_permitted_opens++;
/* Send the forward request to the remote side. */
if (compat20) {
const char *address_to_bind = "0.0.0.0";
packet_start(SSH2_MSG_GLOBAL_REQUEST);
packet_put_cstring("tcpip-forward");
packet_put_char(0); /* boolean: want reply */
packet_put_cstring(address_to_bind);
packet_put_int(listen_port);
} else {
packet_start(SSH_CMSG_PORT_FORWARD_REQUEST);
packet_put_int(listen_port);
packet_put_cstring(host_to_connect);
packet_put_int(port_to_connect);
packet_send();
packet_write_wait();
/*
* Wait for response from the remote side. It will send a disconnect
* message on failure, and we will never see it here.
*/
packet_read_expect(&payload_len, SSH_SMSG_SUCCESS);
}
}
/*
* This is called after receiving CHANNEL_FORWARDING_REQUEST. This initates
* listening for the port, and sends back a success reply (or disconnect
* message if there was an error). This never returns if there was an error.
*/
void
channel_input_port_forward_request(int is_root, int gateway_ports)
{
u_short port, host_port;
char *hostname;
/* Get arguments from the packet. */
port = packet_get_int();
hostname = packet_get_string(NULL);
host_port = packet_get_int();
/*
* Check that an unprivileged user is not trying to forward a
* privileged port.
*/
if (port < IPPORT_RESERVED && !is_root)
packet_disconnect("Requested forwarding of port %d but user is not root.",
port);
/*
* Initiate forwarding,
*/
channel_request_local_forwarding(port, hostname, host_port, gateway_ports);
/* Free the argument string. */
xfree(hostname);
}
/* XXX move to aux.c */
int
channel_connect_to(const char *host, u_short host_port)
{
struct addrinfo hints, *ai, *aitop;
char ntop[NI_MAXHOST], strport[NI_MAXSERV];
int gaierr;
int sock = -1;
memset(&hints, 0, sizeof(hints));
hints.ai_family = IPv4or6;
hints.ai_socktype = SOCK_STREAM;
snprintf(strport, sizeof strport, "%d", host_port);
if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0) {
error("%.100s: unknown host (%s)", host, gai_strerror(gaierr));
return -1;
}
for (ai = aitop; ai; ai = ai->ai_next) {
if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
continue;
if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop, sizeof(ntop),
strport, sizeof(strport), NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
error("channel_connect_to: getnameinfo failed");
continue;
}
/* Create the socket. */
sock = socket(ai->ai_family, SOCK_STREAM, 0);
if (sock < 0) {
error("socket: %.100s", strerror(errno));
continue;
}
/* Connect to the host/port. */
if (connect(sock, ai->ai_addr, ai->ai_addrlen) < 0) {
error("connect %.100s port %s: %.100s", ntop, strport,
strerror(errno));
close(sock);
continue; /* fail -- try next */
}
break; /* success */
}
freeaddrinfo(aitop);
if (!ai) {
error("connect %.100s port %d: failed.", host, host_port);
return -1;
}
/* success */
return sock;
}
/*
* This is called after receiving PORT_OPEN message. This attempts to
* connect to the given host:port, and sends back CHANNEL_OPEN_CONFIRMATION
* or CHANNEL_OPEN_FAILURE.
*/
void
channel_input_port_open(int type, int plen, void *ctxt)
{
u_short host_port;
char *host, *originator_string;
int remote_channel, sock = -1, newch, i, denied;
unsigned int host_len, originator_len;
/* Get remote channel number. */
remote_channel = packet_get_int();
/* Get host name to connect to. */
host = packet_get_string(&host_len);
/* Get port to connect to. */
host_port = packet_get_int();
/* Get remote originator name. */
if (have_hostname_in_open) {
originator_string = packet_get_string(&originator_len);
originator_len += 4; /* size of packet_int */
} else {
originator_string = xstrdup("unknown (remote did not supply name)");
originator_len = 0; /* no originator supplied */
}
packet_integrity_check(plen,
4 + 4 + host_len + 4 + originator_len, SSH_MSG_PORT_OPEN);
/* Check if opening that port is permitted. */
denied = 0;
if (!all_opens_permitted) {
/* Go trough all permitted ports. */
for (i = 0; i < num_permitted_opens; i++)
if (permitted_opens[i].port_to_connect == host_port &&
strcmp(permitted_opens[i].host_to_connect, host) == 0)
break;
/* Check if we found the requested port among those permitted. */
if (i >= num_permitted_opens) {
/* The port is not permitted. */
log("Received request to connect to %.100s:%d, but the request was denied.",
host, host_port);
denied = 1;
}
}
sock = denied ? -1 : channel_connect_to(host, host_port);
if (sock > 0) {
/* Allocate a channel for this connection. */
newch = channel_allocate(SSH_CHANNEL_OPEN, sock, originator_string);
channels[newch].remote_id = remote_channel;
packet_start(SSH_MSG_CHANNEL_OPEN_CONFIRMATION);
packet_put_int(remote_channel);
packet_put_int(newch);
packet_send();
} else {
packet_start(SSH_MSG_CHANNEL_OPEN_FAILURE);
packet_put_int(remote_channel);
packet_send();
}
xfree(host);
}
/*
* Creates an internet domain socket for listening for X11 connections.
* Returns a suitable value for the DISPLAY variable, or NULL if an error
* occurs.
*/
#define NUM_SOCKS 10
char *
x11_create_display_inet(int screen_number, int x11_display_offset)
{
int display_number, sock;
u_short port;
struct addrinfo hints, *ai, *aitop;
char strport[NI_MAXSERV];
int gaierr, n, num_socks = 0, socks[NUM_SOCKS];
char display[512];
char hostname[MAXHOSTNAMELEN];
for (display_number = x11_display_offset;
display_number < MAX_DISPLAYS;
display_number++) {
port = 6000 + display_number;
memset(&hints, 0, sizeof(hints));
hints.ai_family = IPv4or6;
hints.ai_flags = AI_PASSIVE; /* XXX loopback only ? */
hints.ai_socktype = SOCK_STREAM;
snprintf(strport, sizeof strport, "%d", port);
if ((gaierr = getaddrinfo(NULL, strport, &hints, &aitop)) != 0) {
error("getaddrinfo: %.100s", gai_strerror(gaierr));
return NULL;
}
for (ai = aitop; ai; ai = ai->ai_next) {
if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
continue;
sock = socket(ai->ai_family, SOCK_STREAM, 0);
if (sock < 0) {
error("socket: %.100s", strerror(errno));
return NULL;
}
if (bind(sock, ai->ai_addr, ai->ai_addrlen) < 0) {
debug("bind port %d: %.100s", port, strerror(errno));
shutdown(sock, SHUT_RDWR);
close(sock);
for (n = 0; n < num_socks; n++) {
shutdown(socks[n], SHUT_RDWR);
close(socks[n]);
}
num_socks = 0;
break;
}
socks[num_socks++] = sock;
if (num_socks == NUM_SOCKS)
break;
}
if (num_socks > 0)
break;
}
if (display_number >= MAX_DISPLAYS) {
error("Failed to allocate internet-domain X11 display socket.");
return NULL;
}
/* Start listening for connections on the socket. */
for (n = 0; n < num_socks; n++) {
sock = socks[n];
if (listen(sock, 5) < 0) {
error("listen: %.100s", strerror(errno));
shutdown(sock, SHUT_RDWR);
close(sock);
return NULL;
}
}
/* Set up a suitable value for the DISPLAY variable. */
if (gethostname(hostname, sizeof(hostname)) < 0)
fatal("gethostname: %.100s", strerror(errno));
snprintf(display, sizeof display, "%.400s:%d.%d", hostname,
display_number, screen_number);
/* Allocate a channel for each socket. */
for (n = 0; n < num_socks; n++) {
sock = socks[n];
(void) channel_new("x11 listener",
SSH_CHANNEL_X11_LISTENER, sock, sock, -1,
CHAN_X11_WINDOW_DEFAULT, CHAN_X11_PACKET_DEFAULT,
0, xstrdup("X11 inet listener"), 1);
}
/* Return a suitable value for the DISPLAY environment variable. */
return xstrdup(display);
}
#ifndef X_UNIX_PATH
#define X_UNIX_PATH "/tmp/.X11-unix/X"
#endif
static
int
connect_local_xsocket(unsigned int dnr)
{
static const char *const x_sockets[] = {
X_UNIX_PATH "%u",
"/var/X/.X11-unix/X" "%u",
"/usr/spool/sockets/X11/" "%u",
NULL
};
int sock;
struct sockaddr_un addr;
const char *const * path;
for (path = x_sockets; *path; ++path) {
sock = socket(AF_UNIX, SOCK_STREAM, 0);
if (sock < 0)
error("socket: %.100s", strerror(errno));
memset(&addr, 0, sizeof(addr));
addr.sun_family = AF_UNIX;
snprintf(addr.sun_path, sizeof addr.sun_path, *path, dnr);
if (connect(sock, (struct sockaddr *) & addr, sizeof(addr)) == 0)
return sock;
close(sock);
}
error("connect %.100s: %.100s", addr.sun_path, strerror(errno));
return -1;
}
int
x11_connect_display(void)
{
int display_number, sock = 0;
const char *display;
char buf[1024], *cp;
struct addrinfo hints, *ai, *aitop;
char strport[NI_MAXSERV];
int gaierr;
/* Try to open a socket for the local X server. */
display = getenv("DISPLAY");
if (!display) {
error("DISPLAY not set.");
return -1;
}
/*
* Now we decode the value of the DISPLAY variable and make a
* connection to the real X server.
*/
/*
* Check if it is a unix domain socket. Unix domain displays are in
* one of the following formats: unix:d[.s], :d[.s], ::d[.s]
*/
if (strncmp(display, "unix:", 5) == 0 ||
display[0] == ':') {
/* Connect to the unix domain socket. */
if (sscanf(strrchr(display, ':') + 1, "%d", &display_number) != 1) {
error("Could not parse display number from DISPLAY: %.100s",
display);
return -1;
}
/* Create a socket. */
sock = connect_local_xsocket(display_number);
if (sock < 0)
return -1;
/* OK, we now have a connection to the display. */
return sock;
}
/*
* Connect to an inet socket. The DISPLAY value is supposedly
* hostname:d[.s], where hostname may also be numeric IP address.
*/
strncpy(buf, display, sizeof(buf));
buf[sizeof(buf) - 1] = 0;
cp = strchr(buf, ':');
if (!cp) {
error("Could not find ':' in DISPLAY: %.100s", display);
return -1;
}
*cp = 0;
/* buf now contains the host name. But first we parse the display number. */
if (sscanf(cp + 1, "%d", &display_number) != 1) {
error("Could not parse display number from DISPLAY: %.100s",
display);
return -1;
}
/* Look up the host address */
memset(&hints, 0, sizeof(hints));
hints.ai_family = IPv4or6;
hints.ai_socktype = SOCK_STREAM;
snprintf(strport, sizeof strport, "%d", 6000 + display_number);
if ((gaierr = getaddrinfo(buf, strport, &hints, &aitop)) != 0) {
error("%.100s: unknown host. (%s)", buf, gai_strerror(gaierr));
return -1;
}
for (ai = aitop; ai; ai = ai->ai_next) {
/* Create a socket. */
sock = socket(ai->ai_family, SOCK_STREAM, 0);
if (sock < 0) {
debug("socket: %.100s", strerror(errno));
continue;
}
/* Connect it to the display. */
if (connect(sock, ai->ai_addr, ai->ai_addrlen) < 0) {
debug("connect %.100s port %d: %.100s", buf,
6000 + display_number, strerror(errno));
close(sock);
continue;
}
/* Success */
break;
}
freeaddrinfo(aitop);
if (!ai) {
error("connect %.100s port %d: %.100s", buf, 6000 + display_number,
strerror(errno));
return -1;
}
return sock;
}
/*
* This is called when SSH_SMSG_X11_OPEN is received. The packet contains
* the remote channel number. We should do whatever we want, and respond
* with either SSH_MSG_OPEN_CONFIRMATION or SSH_MSG_OPEN_FAILURE.
*/
void
x11_input_open(int type, int plen, void *ctxt)
{
int remote_channel, sock = 0, newch;
char *remote_host;
unsigned int remote_len;
/* Get remote channel number. */
remote_channel = packet_get_int();
/* Get remote originator name. */
if (have_hostname_in_open) {
remote_host = packet_get_string(&remote_len);
remote_len += 4;
} else {
remote_host = xstrdup("unknown (remote did not supply name)");
remote_len = 0;
}
debug("Received X11 open request.");
packet_integrity_check(plen, 4 + remote_len, SSH_SMSG_X11_OPEN);
/* Obtain a connection to the real X display. */
sock = x11_connect_display();
if (sock == -1) {
/* Send refusal to the remote host. */
packet_start(SSH_MSG_CHANNEL_OPEN_FAILURE);
packet_put_int(remote_channel);
packet_send();
} else {
/* Allocate a channel for this connection. */
newch = channel_allocate(
(x11_saved_proto == NULL) ?
SSH_CHANNEL_OPEN : SSH_CHANNEL_X11_OPEN,
sock, remote_host);
channels[newch].remote_id = remote_channel;
/* Send a confirmation to the remote host. */
packet_start(SSH_MSG_CHANNEL_OPEN_CONFIRMATION);
packet_put_int(remote_channel);
packet_put_int(newch);
packet_send();
}
}
/* dummy protocol handler that denies SSH-1 requests (agent/x11) */
void
deny_input_open(int type, int plen, void *ctxt)
{
int rchan = packet_get_int();
switch(type){
case SSH_SMSG_AGENT_OPEN:
error("Warning: ssh server tried agent forwarding.");
break;
case SSH_SMSG_X11_OPEN:
error("Warning: ssh server tried X11 forwarding.");
break;
default:
error("deny_input_open: type %d plen %d", type, plen);
break;
}
error("Warning: this is probably a break in attempt by a malicious server.");
packet_start(SSH_MSG_CHANNEL_OPEN_FAILURE);
packet_put_int(rchan);
packet_send();
}
/*
* Requests forwarding of X11 connections, generates fake authentication
* data, and enables authentication spoofing.
*/
void
x11_request_forwarding_with_spoofing(int client_session_id,
const char *proto, const char *data)
{
unsigned int data_len = (unsigned int) strlen(data) / 2;
unsigned int i, value;
char *new_data;
int screen_number;
const char *cp;
u_int32_t rand = 0;
cp = getenv("DISPLAY");
if (cp)
cp = strchr(cp, ':');
if (cp)
cp = strchr(cp, '.');
if (cp)
screen_number = atoi(cp + 1);
else
screen_number = 0;
/* Save protocol name. */
x11_saved_proto = xstrdup(proto);
/*
* Extract real authentication data and generate fake data of the
* same length.
*/
x11_saved_data = xmalloc(data_len);
x11_fake_data = xmalloc(data_len);
for (i = 0; i < data_len; i++) {
if (sscanf(data + 2 * i, "%2x", &value) != 1)
fatal("x11_request_forwarding: bad authentication data: %.100s", data);
if (i % 4 == 0)
rand = arc4random();
x11_saved_data[i] = value;
x11_fake_data[i] = rand & 0xff;
rand >>= 8;
}
x11_saved_data_len = data_len;
x11_fake_data_len = data_len;
/* Convert the fake data into hex. */
new_data = xmalloc(2 * data_len + 1);
for (i = 0; i < data_len; i++)
sprintf(new_data + 2 * i, "%02x", (unsigned char) x11_fake_data[i]);
/* Send the request packet. */
if (compat20) {
channel_request_start(client_session_id, "x11-req", 0);
packet_put_char(0); /* XXX bool single connection */
} else {
packet_start(SSH_CMSG_X11_REQUEST_FORWARDING);
}
packet_put_cstring(proto);
packet_put_cstring(new_data);
packet_put_int(screen_number);
packet_send();
packet_write_wait();
xfree(new_data);
}
/* Sends a message to the server to request authentication fd forwarding. */
void
auth_request_forwarding()
{
packet_start(SSH_CMSG_AGENT_REQUEST_FORWARDING);
packet_send();
packet_write_wait();
}
/*
* Returns the name of the forwarded authentication socket. Returns NULL if
* there is no forwarded authentication socket. The returned value points to
* a static buffer.
*/
char *
auth_get_socket_name()
{
return channel_forwarded_auth_socket_name;
}
/* removes the agent forwarding socket */
void
cleanup_socket(void)
{
remove(channel_forwarded_auth_socket_name);
rmdir(channel_forwarded_auth_socket_dir);
}
/*
* This is called to process SSH_CMSG_AGENT_REQUEST_FORWARDING on the server.
* This starts forwarding authentication requests.
*/
int
auth_input_request_forwarding(struct passwd * pw)
{
int sock, newch;
struct sockaddr_un sunaddr;
if (auth_get_socket_name() != NULL)
fatal("Protocol error: authentication forwarding requested twice.");
/* Temporarily drop privileged uid for mkdir/bind. */
temporarily_use_uid(pw->pw_uid);
/* Allocate a buffer for the socket name, and format the name. */
channel_forwarded_auth_socket_name = xmalloc(MAX_SOCKET_NAME);
channel_forwarded_auth_socket_dir = xmalloc(MAX_SOCKET_NAME);
strlcpy(channel_forwarded_auth_socket_dir, "/tmp/ssh-XXXXXXXX", MAX_SOCKET_NAME);
/* Create private directory for socket */
if (mkdtemp(channel_forwarded_auth_socket_dir) == NULL) {
packet_send_debug("Agent forwarding disabled: mkdtemp() failed: %.100s",
strerror(errno));
restore_uid();
xfree(channel_forwarded_auth_socket_name);
xfree(channel_forwarded_auth_socket_dir);
channel_forwarded_auth_socket_name = NULL;
channel_forwarded_auth_socket_dir = NULL;
return 0;
}
snprintf(channel_forwarded_auth_socket_name, MAX_SOCKET_NAME, "%s/agent.%d",
channel_forwarded_auth_socket_dir, (int) getpid());
if (atexit(cleanup_socket) < 0) {
int saved = errno;
cleanup_socket();
packet_disconnect("socket: %.100s", strerror(saved));
}
/* Create the socket. */
sock = socket(AF_UNIX, SOCK_STREAM, 0);
if (sock < 0)
packet_disconnect("socket: %.100s", strerror(errno));
/* Bind it to the name. */
memset(&sunaddr, 0, sizeof(sunaddr));
sunaddr.sun_family = AF_UNIX;
strncpy(sunaddr.sun_path, channel_forwarded_auth_socket_name,
sizeof(sunaddr.sun_path));
if (bind(sock, (struct sockaddr *) & sunaddr, sizeof(sunaddr)) < 0)
packet_disconnect("bind: %.100s", strerror(errno));
/* Restore the privileged uid. */
restore_uid();
/* Start listening on the socket. */
if (listen(sock, 5) < 0)
packet_disconnect("listen: %.100s", strerror(errno));
/* Allocate a channel for the authentication agent socket. */
newch = channel_allocate(SSH_CHANNEL_AUTH_SOCKET, sock,
xstrdup("auth socket"));
strlcpy(channels[newch].path, channel_forwarded_auth_socket_name,
sizeof(channels[newch].path));
return 1;
}
/* This is called to process an SSH_SMSG_AGENT_OPEN message. */
void
auth_input_open_request(int type, int plen, void *ctxt)
{
int remch, sock, newch;
char *dummyname;
packet_integrity_check(plen, 4, type);
/* Read the remote channel number from the message. */
remch = packet_get_int();
/*
* Get a connection to the local authentication agent (this may again
* get forwarded).
*/
sock = ssh_get_authentication_socket();
/*
* If we could not connect the agent, send an error message back to
* the server. This should never happen unless the agent dies,
* because authentication forwarding is only enabled if we have an
* agent.
*/
if (sock < 0) {
packet_start(SSH_MSG_CHANNEL_OPEN_FAILURE);
packet_put_int(remch);
packet_send();
return;
}
debug("Forwarding authentication connection.");
/*
* Dummy host name. This will be freed when the channel is freed; it
* will still be valid in the packet_put_string below since the
* channel cannot yet be freed at that point.
*/
dummyname = xstrdup("authentication agent connection");
newch = channel_allocate(SSH_CHANNEL_OPEN, sock, dummyname);
channels[newch].remote_id = remch;
/* Send a confirmation to the remote host. */
packet_start(SSH_MSG_CHANNEL_OPEN_CONFIRMATION);
packet_put_int(remch);
packet_put_int(newch);
packet_send();
}
void
channel_start_open(int id)
{
Channel *c = channel_lookup(id);
if (c == NULL) {
log("channel_open: %d: bad id", id);
return;
}
debug("send channel open %d", id);
packet_start(SSH2_MSG_CHANNEL_OPEN);
packet_put_cstring(c->ctype);
packet_put_int(c->self);
packet_put_int(c->local_window);
packet_put_int(c->local_maxpacket);
}
void
channel_open(int id)
{
/* XXX REMOVE ME */
channel_start_open(id);
packet_send();
}
void
channel_request(int id, char *service, int wantconfirm)
{
channel_request_start(id, service, wantconfirm);
packet_send();
debug("channel request %d: %s", id, service) ;
}
void
channel_request_start(int id, char *service, int wantconfirm)
{
Channel *c = channel_lookup(id);
if (c == NULL) {
log("channel_request: %d: bad id", id);
return;
}
packet_start(SSH2_MSG_CHANNEL_REQUEST);
packet_put_int(c->remote_id);
packet_put_cstring(service);
packet_put_char(wantconfirm);
}
void
channel_register_callback(int id, int mtype, channel_callback_fn *fn, void *arg)
{
Channel *c = channel_lookup(id);
if (c == NULL) {
log("channel_register_callback: %d: bad id", id);
return;
}
c->cb_event = mtype;
c->cb_fn = fn;
c->cb_arg = arg;
}
void
channel_register_cleanup(int id, channel_callback_fn *fn)
{
Channel *c = channel_lookup(id);
if (c == NULL) {
log("channel_register_cleanup: %d: bad id", id);
return;
}
c->dettach_user = fn;
}
void
channel_cancel_cleanup(int id)
{
Channel *c = channel_lookup(id);
if (c == NULL) {
log("channel_cancel_cleanup: %d: bad id", id);
return;
}
c->dettach_user = NULL;
}
void
channel_register_filter(int id, channel_filter_fn *fn)
{
Channel *c = channel_lookup(id);
if (c == NULL) {
log("channel_register_filter: %d: bad id", id);
return;
}
c->input_filter = fn;
}
void
channel_set_fds(int id, int rfd, int wfd, int efd,
int extusage, int nonblock)
{
Channel *c = channel_lookup(id);
if (c == NULL || c->type != SSH_CHANNEL_LARVAL)
fatal("channel_activate for non-larval channel %d.", id);
channel_register_fds(c, rfd, wfd, efd, extusage, nonblock);
c->type = SSH_CHANNEL_OPEN;
/* XXX window size? */
c->local_window = c->local_window_max = c->local_maxpacket * 2;
packet_start(SSH2_MSG_CHANNEL_WINDOW_ADJUST);
packet_put_int(c->remote_id);
packet_put_int(c->local_window);
packet_send();
}
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