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openssh/channels.c

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/*
*
* channels.c
*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
*
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
* All rights reserved
*
* Created: Fri Mar 24 16:35:24 1995 ylo
*
* 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.
*
*/
#include "includes.h"
RCSID("$Id: channels.c,v 1.11 1999/12/07 05:47:28 damien Exp $");
#include "ssh.h"
#include "packet.h"
#include "xmalloc.h"
#include "buffer.h"
#include "authfd.h"
#include "uidswap.h"
#include "readconf.h"
#include "servconf.h"
#include "channels.h"
#include "nchan.h"
#include "compat.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; /* Host name. */
u_short port; /* 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;
}
/*
* Allocate a new channel object and set its type and socket. This will cause
* remote_name to be freed.
*/
int
channel_allocate(int type, int sock, char *remote_name)
{
int i, found;
Channel *c;
/* Update the maximum file descriptor value. */
if (sock > channel_max_fd_value)
channel_max_fd_value = sock;
/* XXX set close-on-exec -markus */
/* Do initial allocation if this is the first call. */
if (channels_alloc == 0) {
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;
debug("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);
chan_init_iostates(c);
c->self = found;
c->type = type;
c->sock = sock;
c->remote_id = -1;
c->remote_name = remote_name;
debug("channel %d: new [%s]", found, remote_name);
return found;
}
/* Free the channel and close its socket. */
void
channel_free(int channel)
{
if (channel < 0 || channel >= channels_alloc ||
channels[channel].type == SSH_CHANNEL_FREE)
packet_disconnect("channel free: bad local channel %d", channel);
if (compat13)
shutdown(channels[channel].sock, SHUT_RDWR);
close(channels[channel].sock);
buffer_free(&channels[channel].input);
buffer_free(&channels[channel].output);
channels[channel].type = SSH_CHANNEL_FREE;
if (channels[channel].remote_name) {
xfree(channels[channel].remote_name);
channels[channel].remote_name = NULL;
}
}
/*
* This is called just before select() to add any bits relevant to channels
* in the select bitmasks.
*/
void
channel_prepare_select(fd_set * readset, fd_set * writeset)
{
int i;
Channel *ch;
unsigned char *ucp;
unsigned int proto_len, data_len;
for (i = 0; i < channels_alloc; i++) {
ch = &channels[i];
redo:
switch (ch->type) {
case SSH_CHANNEL_X11_LISTENER:
case SSH_CHANNEL_PORT_LISTENER:
case SSH_CHANNEL_AUTH_SOCKET:
FD_SET(ch->sock, readset);
break;
case SSH_CHANNEL_OPEN:
if (compat13) {
if (buffer_len(&ch->input) < packet_get_maxsize())
FD_SET(ch->sock, readset);
if (buffer_len(&ch->output) > 0)
FD_SET(ch->sock, writeset);
break;
}
/* test whether sockets are 'alive' for read/write */
if (ch->istate == CHAN_INPUT_OPEN)
if (buffer_len(&ch->input) < packet_get_maxsize())
FD_SET(ch->sock, readset);
if (ch->ostate == CHAN_OUTPUT_OPEN ||
ch->ostate == CHAN_OUTPUT_WAIT_DRAIN) {
if (buffer_len(&ch->output) > 0) {
FD_SET(ch->sock, writeset);
} else if (ch->ostate == CHAN_OUTPUT_WAIT_DRAIN) {
chan_obuf_empty(ch);
}
}
break;
case SSH_CHANNEL_INPUT_DRAINING:
if (!compat13)
fatal("cannot happen: IN_DRAIN");
if (buffer_len(&ch->input) == 0) {
packet_start(SSH_MSG_CHANNEL_CLOSE);
packet_put_int(ch->remote_id);
packet_send();
ch->type = SSH_CHANNEL_CLOSED;
debug("Closing channel %d after input drain.", i);
break;
}
break;
case SSH_CHANNEL_OUTPUT_DRAINING:
if (!compat13)
fatal("cannot happen: OUT_DRAIN");
if (buffer_len(&ch->output) == 0) {
channel_free(i);
break;
}
FD_SET(ch->sock, writeset);
break;
case SSH_CHANNEL_X11_OPEN:
/*
* 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.
*/
/* Check if the fixed size part of the packet is in buffer. */
if (buffer_len(&ch->output) < 12)
break;
/* Parse the lengths of variable-length fields. */
ucp = (unsigned char *) buffer_ptr(&ch->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]);
ch->type = SSH_CHANNEL_OPEN;
goto reject;
}
/* Check if the whole packet is in buffer. */
if (buffer_len(&ch->output) <
12 + ((proto_len + 3) & ~3) + ((data_len + 3) & ~3))
break;
/* 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.");
ch->type = SSH_CHANNEL_OPEN;
goto reject;
}
/* 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.");
ch->type = SSH_CHANNEL_OPEN;
goto reject;
}
/* 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);
ch->type = SSH_CHANNEL_OPEN;
goto reject;
}
/*
* 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);
/* Start normal processing for the channel. */
ch->type = SSH_CHANNEL_OPEN;
goto redo;
reject:
/*
* We have received an X11 connection that has bad
* authentication information.
*/
log("X11 connection rejected because of wrong authentication.\r\n");
buffer_clear(&ch->input);
buffer_clear(&ch->output);
if (compat13) {
close(ch->sock);
ch->sock = -1;
ch->type = SSH_CHANNEL_CLOSED;
packet_start(SSH_MSG_CHANNEL_CLOSE);
packet_put_int(ch->remote_id);
packet_send();
} else {
debug("X11 rejected %d i%d/o%d", ch->self, ch->istate, ch->ostate);
chan_read_failed(ch);
chan_write_failed(ch);
debug("X11 rejected %d i%d/o%d", ch->self, ch->istate, ch->ostate);
}
break;
case SSH_CHANNEL_FREE:
default:
continue;
}
}
}
/*
* After select, perform any appropriate operations for channels which have
* events pending.
*/
void
channel_after_select(fd_set * readset, fd_set * writeset)
{
struct sockaddr addr;
int addrlen, newsock, i, newch, len;
Channel *ch;
char buf[16384], *remote_hostname;
/* Loop over all channels... */
for (i = 0; i < channels_alloc; i++) {
ch = &channels[i];
switch (ch->type) {
case SSH_CHANNEL_X11_LISTENER:
/* This is our fake X11 server socket. */
if (FD_ISSET(ch->sock, readset)) {
debug("X11 connection requested.");
addrlen = sizeof(addr);
newsock = accept(ch->sock, &addr, &addrlen);
if (newsock < 0) {
error("accept: %.100s", strerror(errno));
break;
}
remote_hostname = get_remote_hostname(newsock);
snprintf(buf, sizeof buf, "X11 connection from %.200s port %d",
remote_hostname, get_peer_port(newsock));
xfree(remote_hostname);
newch = channel_allocate(SSH_CHANNEL_OPENING, newsock,
xstrdup(buf));
packet_start(SSH_SMSG_X11_OPEN);
packet_put_int(newch);
if (have_hostname_in_open)
packet_put_string(buf, strlen(buf));
packet_send();
}
break;
case SSH_CHANNEL_PORT_LISTENER:
/*
* This socket is listening for connections to a
* forwarded TCP/IP port.
*/
if (FD_ISSET(ch->sock, readset)) {
debug("Connection to port %d forwarding to %.100s:%d requested.",
ch->listening_port, ch->path, ch->host_port);
addrlen = sizeof(addr);
newsock = accept(ch->sock, &addr, &addrlen);
if (newsock < 0) {
error("accept: %.100s", strerror(errno));
break;
}
remote_hostname = get_remote_hostname(newsock);
snprintf(buf, sizeof buf, "listen port %d:%.100s:%d, connect from %.200s:%d",
ch->listening_port, ch->path, ch->host_port,
remote_hostname, get_peer_port(newsock));
xfree(remote_hostname);
newch = channel_allocate(SSH_CHANNEL_OPENING, newsock,
xstrdup(buf));
packet_start(SSH_MSG_PORT_OPEN);
packet_put_int(newch);
packet_put_string(ch->path, strlen(ch->path));
packet_put_int(ch->host_port);
if (have_hostname_in_open)
packet_put_string(buf, strlen(buf));
packet_send();
}
break;
case SSH_CHANNEL_AUTH_SOCKET:
/*
* This is the authentication agent socket listening
* for connections from clients.
*/
if (FD_ISSET(ch->sock, readset)) {
int nchan;
len = sizeof(addr);
newsock = accept(ch->sock, &addr, &len);
if (newsock < 0) {
error("accept from auth socket: %.100s", strerror(errno));
break;
}
nchan = channel_allocate(SSH_CHANNEL_OPENING, newsock,
xstrdup("accepted auth socket"));
packet_start(SSH_SMSG_AGENT_OPEN);
packet_put_int(nchan);
packet_send();
}
break;
case SSH_CHANNEL_OPEN:
/*
* This is an open two-way communication channel. It
* is not of interest to us at this point what kind
* of data is being transmitted.
*/
/*
* Read available incoming data and append it to
* buffer; shutdown socket, if read or write failes
*/
if (FD_ISSET(ch->sock, readset)) {
len = read(ch->sock, buf, sizeof(buf));
if (len <= 0) {
if (compat13) {
buffer_consume(&ch->output, buffer_len(&ch->output));
ch->type = SSH_CHANNEL_INPUT_DRAINING;
debug("Channel %d status set to input draining.", i);
} else {
chan_read_failed(ch);
}
break;
}
buffer_append(&ch->input, buf, len);
}
/* Send buffered output data to the socket. */
if (FD_ISSET(ch->sock, writeset) && buffer_len(&ch->output) > 0) {
len = write(ch->sock, buffer_ptr(&ch->output),
buffer_len(&ch->output));
if (len <= 0) {
if (compat13) {
buffer_consume(&ch->output, buffer_len(&ch->output));
debug("Channel %d status set to input draining.", i);
ch->type = SSH_CHANNEL_INPUT_DRAINING;
} else {
chan_write_failed(ch);
}
break;
}
buffer_consume(&ch->output, len);
}
break;
case SSH_CHANNEL_OUTPUT_DRAINING:
if (!compat13)
fatal("cannot happen: OUT_DRAIN");
/* Send buffered output data to the socket. */
if (FD_ISSET(ch->sock, writeset) && buffer_len(&ch->output) > 0) {
len = write(ch->sock, buffer_ptr(&ch->output),
buffer_len(&ch->output));
if (len <= 0)
buffer_consume(&ch->output, buffer_len(&ch->output));
else
buffer_consume(&ch->output, len);
}
break;
case SSH_CHANNEL_X11_OPEN:
case SSH_CHANNEL_FREE:
default:
continue;
}
}
}
/* If there is data to send to the connection, send some of it now. */
void
channel_output_poll()
{
int len, i;
Channel *ch;
for (i = 0; i < channels_alloc; i++) {
ch = &channels[i];
/* We are only interested in channels that can have buffered incoming data. */
if (ch->type != SSH_CHANNEL_OPEN &&
ch->type != SSH_CHANNEL_INPUT_DRAINING)
continue;
/* Get the amount of buffered data for this channel. */
len = buffer_len(&ch->input);
if (len > 0) {
/* Send some data for the other side over the secure connection. */
if (packet_is_interactive()) {
if (len > 1024)
len = 512;
} else {
/* Keep the packets at reasonable size. */
if (len > 16384)
len = 16384;
}
packet_start(SSH_MSG_CHANNEL_DATA);
packet_put_int(ch->remote_id);
packet_put_string(buffer_ptr(&ch->input), len);
packet_send();
buffer_consume(&ch->input, len);
} else if (ch->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(ch);
}
}
}
/*
* 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 payload_len)
{
int channel;
char *data;
unsigned int data_len;
/* Get the channel number and verify it. */
channel = packet_get_int();
if (channel < 0 || channel >= channels_alloc ||
channels[channel].type == SSH_CHANNEL_FREE)
packet_disconnect("Received data for nonexistent channel %d.", channel);
/* Ignore any data for non-open channels (might happen on close) */
if (channels[channel].type != SSH_CHANNEL_OPEN &&
channels[channel].type != SSH_CHANNEL_X11_OPEN)
return;
/* Get the data. */
data = packet_get_string(&data_len);
packet_integrity_check(payload_len, 4 + 4 + data_len, SSH_MSG_CHANNEL_DATA);
buffer_append(&channels[channel].output, 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 *ch;
for (i = 0; i < channels_alloc; i++) {
ch = &channels[i];
switch (ch->type) {
case SSH_CHANNEL_X11_LISTENER:
case SSH_CHANNEL_PORT_LISTENER:
case SSH_CHANNEL_AUTH_SOCKET:
continue;
case SSH_CHANNEL_OPEN:
if (buffer_len(&ch->input) > packet_get_maxsize())
return 0;
if (buffer_len(&ch->output) > packet_get_maxsize())
return 0;
continue;
case SSH_CHANNEL_INPUT_DRAINING:
case SSH_CHANNEL_OUTPUT_DRAINING:
case SSH_CHANNEL_X11_OPEN:
case SSH_CHANNEL_FREE:
default:
continue;
}
}
return 1;
}
/* This is called after receiving CHANNEL_CLOSE/IEOF. */
void
channel_input_close()
{
int channel;
/* Get the channel number and verify it. */
channel = packet_get_int();
if (channel < 0 || channel >= channels_alloc ||
channels[channel].type == SSH_CHANNEL_FREE)
packet_disconnect("Received data for nonexistent channel %d.", channel);
if (!compat13) {
/* proto version 1.5 overloads CLOSE with IEOF */
chan_rcvd_ieof(&channels[channel]);
return;
}
/*
* 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(channels[channel].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 (channels[channel].type != SSH_CHANNEL_CLOSED) {
/*
* Not a closed channel - mark it as draining, which will
* cause it to be freed later.
*/
buffer_consume(&channels[channel].input,
buffer_len(&channels[channel].input));
channels[channel].type = SSH_CHANNEL_OUTPUT_DRAINING;
}
}
/* This is called after receiving CHANNEL_CLOSE_CONFIRMATION/OCLOSE. */
void
channel_input_close_confirmation()
{
int channel;
/* Get the channel number and verify it. */
channel = packet_get_int();
if (channel < 0 || channel >= channels_alloc)
packet_disconnect("Received close confirmation for out-of-range channel %d.",
channel);
if (!compat13) {
/* proto version 1.5 overloads CLOSE_CONFIRMATION with OCLOSE */
chan_rcvd_oclose(&channels[channel]);
return;
}
if (channels[channel].type != SSH_CHANNEL_CLOSED)
packet_disconnect("Received close confirmation for non-closed channel %d (type %d).",
channel, channels[channel].type);
/* Free the channel. */
channel_free(channel);
}
/* This is called after receiving CHANNEL_OPEN_CONFIRMATION. */
void
channel_input_open_confirmation()
{
int channel, remote_channel;
/* Get the channel number and verify it. */
channel = packet_get_int();
if (channel < 0 || channel >= channels_alloc ||
channels[channel].type != SSH_CHANNEL_OPENING)
packet_disconnect("Received open confirmation for non-opening channel %d.",
channel);
/* Get remote side's id for this channel. */
remote_channel = packet_get_int();
/* Record the remote channel number and mark that the channel is now open. */
channels[channel].remote_id = remote_channel;
channels[channel].type = SSH_CHANNEL_OPEN;
}
/* This is called after receiving CHANNEL_OPEN_FAILURE from the other side. */
void
channel_input_open_failure()
{
int channel;
/* Get the channel number and verify it. */
channel = packet_get_int();
if (channel < 0 || channel >= channels_alloc ||
channels[channel].type != SSH_CHANNEL_OPENING)
packet_disconnect("Received open failure for non-opening channel %d.",
channel);
/* Free the channel. This will also close the socket. */
channel_free(channel);
}
/*
* 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 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)
close(channels[i].sock);
}
}
/* 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_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_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 o%d)\r\n",
c->self, c->remote_name,
c->type, c->remote_id, c->istate, c->ostate);
buffer_append(&buffer, buf, strlen(buf));
continue;
default:
fatal("channel_still_open: 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 ch, sock, on = 1;
struct sockaddr_in sin;
extern Options options;
struct linger linger;
if (strlen(host) > sizeof(channels[0].path) - 1)
packet_disconnect("Forward host name too long.");
/* Create a port to listen for the host. */
sock = socket(AF_INET, SOCK_STREAM, 0);
if (sock < 0)
packet_disconnect("socket: %.100s", strerror(errno));
/* Initialize socket address. */
memset(&sin, 0, sizeof(sin));
sin.sin_family = AF_INET;
if (options.gateway_ports == 1)
sin.sin_addr.s_addr = htonl(INADDR_ANY);
else
sin.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
sin.sin_port = htons(port);
/*
* 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));
/* Bind the socket to the address. */
if (bind(sock, (struct sockaddr *) & sin, sizeof(sin)) < 0)
packet_disconnect("bind: %.100s", strerror(errno));
/* Start listening for connections on the socket. */
if (listen(sock, 5) < 0)
packet_disconnect("listen: %.100s", strerror(errno));
/* Allocate a channel number for the socket. */
ch = channel_allocate(SSH_CHANNEL_PORT_LISTENER, sock,
xstrdup("port listener"));
strlcpy(channels[ch].path, host, sizeof(channels[ch].path));
channels[ch].host_port = host_port;
channels[ch].listening_port = port;
}
/*
* 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 port, const char *host,
u_short remote_port)
{
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 = xstrdup(host);
permitted_opens[num_permitted_opens].port = remote_port;
num_permitted_opens++;
/* Send the forward request to the remote side. */
packet_start(SSH_CMSG_PORT_FORWARD_REQUEST);
packet_put_int(port);
packet_put_string(host, strlen(host));
packet_put_int(remote_port);
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)
{
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);
/* Free the argument string. */
xfree(hostname);
}
/*
* 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 payload_len)
{
int remote_channel, sock, newch, i;
u_short host_port;
struct sockaddr_in sin;
char *host, *originator_string;
struct hostent *hp;
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(payload_len,
4 + 4 + host_len + 4 + originator_len,
SSH_MSG_PORT_OPEN);
/* Check if opening that port is permitted. */
if (!all_opens_permitted) {
/* Go trough all permitted ports. */
for (i = 0; i < num_permitted_opens; i++)
if (permitted_opens[i].port == host_port &&
strcmp(permitted_opens[i].host, 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);
packet_start(SSH_MSG_CHANNEL_OPEN_FAILURE);
packet_put_int(remote_channel);
packet_send();
}
}
memset(&sin, 0, sizeof(sin));
sin.sin_addr.s_addr = inet_addr(host);
if ((sin.sin_addr.s_addr & 0xffffffff) != 0xffffffff) {
/* It was a valid numeric host address. */
sin.sin_family = AF_INET;
} else {
/* Look up the host address from the name servers. */
hp = gethostbyname(host);
if (!hp) {
error("%.100s: unknown host.", host);
goto fail;
}
if (!hp->h_addr_list[0]) {
error("%.100s: host has no IP address.", host);
goto fail;
}
sin.sin_family = hp->h_addrtype;
memcpy(&sin.sin_addr, hp->h_addr_list[0],
sizeof(sin.sin_addr));
}
sin.sin_port = htons(host_port);
/* Create the socket. */
sock = socket(sin.sin_family, SOCK_STREAM, 0);
if (sock < 0) {
error("socket: %.100s", strerror(errno));
goto fail;
}
/* Connect to the host/port. */
if (connect(sock, (struct sockaddr *) & sin, sizeof(sin)) < 0) {
error("connect %.100s:%d: %.100s", host, host_port,
strerror(errno));
close(sock);
goto fail;
}
/* Successful connection. */
/* Allocate a channel for this connection. */
newch = channel_allocate(SSH_CHANNEL_OPEN, sock, originator_string);
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();
/* Free the argument string. */
xfree(host);
return;
fail:
/* Free the argument string. */
xfree(host);
/* Send refusal to the remote host. */
packet_start(SSH_MSG_CHANNEL_OPEN_FAILURE);
packet_put_int(remote_channel);
packet_send();
}
/*
* Creates an internet domain socket for listening for X11 connections.
* Returns a suitable value for the DISPLAY variable, or NULL if an error
* occurs.
*/
char *
x11_create_display_inet(int screen_number)
{
extern ServerOptions options;
int display_number, sock;
u_short port;
struct sockaddr_in sin;
char buf[512];
char hostname[MAXHOSTNAMELEN];
for (display_number = options.x11_display_offset;
display_number < MAX_DISPLAYS;
display_number++) {
port = 6000 + display_number;
memset(&sin, 0, sizeof(sin));
sin.sin_family = AF_INET;
sin.sin_addr.s_addr = htonl(INADDR_ANY);
sin.sin_port = htons(port);
sock = socket(AF_INET, SOCK_STREAM, 0);
if (sock < 0) {
error("socket: %.100s", strerror(errno));
return NULL;
}
if (bind(sock, (struct sockaddr *) & sin, sizeof(sin)) < 0) {
debug("bind port %d: %.100s", port, strerror(errno));
shutdown(sock, SHUT_RDWR);
close(sock);
continue;
}
break;
}
if (display_number >= MAX_DISPLAYS) {
error("Failed to allocate internet-domain X11 display socket.");
return NULL;
}
/* Start listening for connections on the socket. */
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(buf, sizeof buf, "%.400s:%d.%d", hostname,
display_number, screen_number);
/* Allocate a channel for the socket. */
(void) channel_allocate(SSH_CHANNEL_X11_LISTENER, sock,
xstrdup("X11 inet listener"));
/* Return a suitable value for the DISPLAY environment variable. */
return xstrdup(buf);
}
#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;
}
/*
* 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 payload_len)
{
int remote_channel, display_number, sock, newch;
const char *display;
struct sockaddr_in sin;
char buf[1024], *cp, *remote_host;
struct hostent *hp;
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(payload_len, 4 + remote_len, SSH_SMSG_X11_OPEN);
/* Try to open a socket for the local X server. */
display = getenv("DISPLAY");
if (!display) {
error("DISPLAY not set.");
goto fail;
}
/*
* 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);
goto fail;
}
/* Create a socket. */
sock = connect_local_xsocket(display_number);
if (sock < 0)
goto fail;
/* OK, we now have a connection to the display. */
goto success;
}
/*
* 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);
goto fail;
}
*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);
goto fail;
}
/* Try to parse the host name as a numeric IP address. */
memset(&sin, 0, sizeof(sin));
sin.sin_addr.s_addr = inet_addr(buf);
if ((sin.sin_addr.s_addr & 0xffffffff) != 0xffffffff) {
/* It was a valid numeric host address. */
sin.sin_family = AF_INET;
} else {
/* Not a numeric IP address. */
/* Look up the host address from the name servers. */
hp = gethostbyname(buf);
if (!hp) {
error("%.100s: unknown host.", buf);
goto fail;
}
if (!hp->h_addr_list[0]) {
error("%.100s: host has no IP address.", buf);
goto fail;
}
sin.sin_family = hp->h_addrtype;
memcpy(&sin.sin_addr, hp->h_addr_list[0],
sizeof(sin.sin_addr));
}
/* Set port number. */
sin.sin_port = htons(6000 + display_number);
/* Create a socket. */
sock = socket(sin.sin_family, SOCK_STREAM, 0);
if (sock < 0) {
error("socket: %.100s", strerror(errno));
goto fail;
}
/* Connect it to the display. */
if (connect(sock, (struct sockaddr *) & sin, sizeof(sin)) < 0) {
error("connect %.100s:%d: %.100s", buf, 6000 + display_number,
strerror(errno));
close(sock);
goto fail;
}
success:
/* We have successfully obtained a connection to the real X display. */
/* Allocate a channel for this connection. */
if (x11_saved_proto == NULL)
newch = channel_allocate(SSH_CHANNEL_OPEN, sock, remote_host);
else
newch = channel_allocate(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();
return;
fail:
/* Send refusal to the remote host. */
packet_start(SSH_MSG_CHANNEL_OPEN_FAILURE);
packet_put_int(remote_channel);
packet_send();
}
/*
* Requests forwarding of X11 connections, generates fake authentication
* data, and enables authentication spoofing.
*/
void
x11_request_forwarding_with_spoofing(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. */
packet_start(SSH_CMSG_X11_REQUEST_FORWARDING);
packet_put_string(proto, strlen(proto));
packet_put_string(new_data, strlen(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 if called to process SSH_CMSG_AGENT_REQUEST_FORWARDING on the server.
* This starts forwarding authentication requests.
*/
void
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_disconnect("mkdtemp: %.100s", strerror(errno));
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));
}
/* This is called to process an SSH_SMSG_AGENT_OPEN message. */
void
auth_input_open_request()
{
int remch, sock, newch;
char *dummyname;
/* 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();
}
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