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31ec5a8b55cc90efb0bd1bb2be621e416f1444ef
libssh2/example/x11.c
Viktor Szakats 5cca650b1d tidy-up: prefer #ifdef / #ifndef (formatting) 
Closes #1532
2025-01-31 13:04:32 +01:00

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/* Copyright (C) The libssh2 project and its contributors.
*
* Sample showing how to makes SSH2 with X11 Forwarding works.
*
* $ ./x11 host user password [DEBUG]
*
* SPDX-License-Identifier: BSD-3-Clause
*/
#include "libssh2_setup.h"
#include <libssh2.h>
#include <stdio.h>
#ifdef HAVE_SYS_UN_H
#ifdef HAVE_SYS_IOCTL_H
#include <sys/ioctl.h>
#endif
#ifdef HAVE_NETINET_IN_H
#include <netinet/in.h>
#endif
#ifdef HAVE_SYS_SOCKET_H
#include <sys/socket.h>
#endif
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#ifdef HAVE_ARPA_INET_H
#include <arpa/inet.h>
#endif
#ifdef HAVE_SYS_UN_H
#include <sys/un.h>
#endif
#include <stdlib.h>
#include <string.h>
#include <termios.h>
#define _PATH_UNIX_X "/tmp/.X11-unix/X%d"
/*
* Chained list that contains channels and associated X11 socket for each X11
* connections
*/
struct chan_X11_list {
LIBSSH2_CHANNEL *chan;
libssh2_socket_t sock;
struct chan_X11_list *next;
};
static struct chan_X11_list * gp_x11_chan = NULL;
static struct termios _saved_tio;
/*
* Utility function to remove a Node of the chained list
*/
static void remove_node(struct chan_X11_list *elem)
{
struct chan_X11_list *current_node = NULL;
current_node = gp_x11_chan;
if(gp_x11_chan == elem) {
gp_x11_chan = gp_x11_chan->next;
free(current_node);
return;
}
while(current_node->next) {
if(current_node->next == elem) {
current_node->next = current_node->next->next;
current_node = current_node->next;
free(current_node);
break;
}
}
}
static void session_shutdown(LIBSSH2_SESSION *session)
{
libssh2_session_disconnect(session, "Normal Shutdown");
libssh2_session_free(session);
}
static int _raw_mode(void)
{
int rc;
struct termios tio;
rc = tcgetattr(fileno(stdin), &tio);
if(rc != -1) {
_saved_tio = tio;
/* do the equivalent of cfmakeraw() manually, to build on Solaris */
tio.c_iflag &= ~(tcflag_t)(IGNBRK|BRKINT|PARMRK|ISTRIP|
INLCR|IGNCR|ICRNL|IXON);
tio.c_oflag &= ~(tcflag_t)OPOST;
tio.c_lflag &= ~(tcflag_t)(ECHO|ECHONL|ICANON|ISIG|IEXTEN);
tio.c_cflag &= ~(tcflag_t)(CSIZE|PARENB);
tio.c_cflag |= CS8;
rc = tcsetattr(fileno(stdin), TCSADRAIN, &tio);
}
return rc;
}
static int _normal_mode(void)
{
int rc;
rc = tcsetattr(fileno(stdin), TCSADRAIN, &_saved_tio);
return rc;
}
/*
* CallBack to initialize the forwarding.
* Save the channel to loop on it, save the X11 forwarded socket to send
* and receive info from our X server.
*/
static void x11_callback(LIBSSH2_SESSION *session, LIBSSH2_CHANNEL *channel,
char *shost, int sport, void **abstract)
{
const char *display;
char *ptr;
char *temp_buff;
int display_port;
int rc;
libssh2_socket_t sock = LIBSSH2_INVALID_SOCKET;
struct sockaddr_un addr;
struct chan_X11_list *new;
struct chan_X11_list *chan_iter;
(void)session;
(void)shost;
(void)sport;
(void)abstract;
/*
* Connect to the display
* Inspired by x11_connect_display in openssh
*/
display = getenv("DISPLAY");
if(display) {
if(strncmp(display, "unix:", 5) == 0 ||
display[0] == ':') {
/* Connect to the local unix domain */
ptr = strrchr(display, ':');
temp_buff = (char *)calloc(strlen(ptr + 1) + 1, sizeof(char));
if(!temp_buff) {
fprintf(stderr, "failed to calloc().\n");
return;
}
memcpy(temp_buff, ptr + 1, strlen(ptr + 1));
display_port = atoi(temp_buff);
free(temp_buff);
sock = socket(AF_UNIX, SOCK_STREAM, 0);
if(sock == LIBSSH2_INVALID_SOCKET)
return;
memset(&addr, 0, sizeof(addr));
addr.sun_family = AF_UNIX;
snprintf(addr.sun_path, sizeof(addr.sun_path),
_PATH_UNIX_X, display_port);
rc = connect(sock, (struct sockaddr *) &addr, sizeof(addr));
if(rc != -1) {
/* Connection Successful */
if(!gp_x11_chan) {
/* Calloc ensure that gp_X11_chan is full of 0 */
gp_x11_chan = (struct chan_X11_list *)
calloc(1, sizeof(struct chan_X11_list));
gp_x11_chan->sock = sock;
gp_x11_chan->chan = channel;
gp_x11_chan->next = NULL;
}
else {
chan_iter = gp_x11_chan;
while(chan_iter->next)
chan_iter = chan_iter->next;
/* Create the new Node */
new = (struct chan_X11_list *)
malloc(sizeof(struct chan_X11_list));
new->sock = sock;
new->chan = channel;
new->next = NULL;
chan_iter->next = new;
}
}
else {
shutdown(sock, SHUT_RDWR);
LIBSSH2_SOCKET_CLOSE(sock);
}
}
}
return;
}
/*
* Send and receive Data for the X11 channel.
* If the connection is closed, returns -1, 0 either.
*/
static int x11_send_receive(LIBSSH2_CHANNEL *channel, libssh2_socket_t sock)
{
char *buf;
unsigned int bufsize = 8192;
int rc;
unsigned int nfds = 1;
LIBSSH2_POLLFD *fds = NULL;
fd_set set;
struct timeval timeval_out;
timeval_out.tv_sec = 0;
timeval_out.tv_usec = 0;
FD_ZERO(&set);
#if defined(__GNUC__) || defined(__clang__)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wsign-conversion"
#endif
FD_SET(sock, &set);
#if defined(__GNUC__) || defined(__clang__)
#pragma GCC diagnostic pop
#endif
buf = calloc(bufsize, sizeof(char));
if(!buf)
return 0;
fds = malloc(sizeof(LIBSSH2_POLLFD));
if(!fds) {
free(buf);
return 0;
}
fds[0].type = LIBSSH2_POLLFD_CHANNEL;
fds[0].fd.channel = channel;
fds[0].events = LIBSSH2_POLLFD_POLLIN;
fds[0].revents = LIBSSH2_POLLFD_POLLIN;
rc = libssh2_poll(fds, nfds, 0);
if(rc > 0) {
ssize_t nread;
nread = libssh2_channel_read(channel, buf, bufsize);
if(nread > 0)
write(sock, buf, (size_t)nread);
}
rc = select((int)(sock + 1), &set, NULL, NULL, &timeval_out);
if(rc > 0) {
ssize_t nread;
memset(buf, 0, bufsize);
/* Data in sock */
nread = read(sock, buf, bufsize);
if(nread > 0) {
libssh2_channel_write(channel, buf, (size_t)nread);
}
else {
free(buf);
return -1;
}
}
free(fds);
free(buf);
if(libssh2_channel_eof(channel) == 1) {
return -1;
}
return 0;
}
/*
* Main, more than inspired by ssh2.c by Bagder
*/
int main(int argc, char *argv[])
{
uint32_t hostaddr = 0;
int rc;
libssh2_socket_t sock = LIBSSH2_INVALID_SOCKET;
struct sockaddr_in sin;
LIBSSH2_SESSION *session = NULL;
LIBSSH2_CHANNEL *channel;
char *username = NULL;
char *password = NULL;
size_t bufsiz = 8193;
char *buf = NULL;
int set_debug_on = 0;
unsigned int nfds = 1;
LIBSSH2_POLLFD *fds = NULL;
/* Chan List struct */
struct chan_X11_list *current_node = NULL;
/* Struct winsize for term size */
struct winsize w_size;
struct winsize w_size_bck;
/* For select on stdin */
fd_set set;
struct timeval timeval_out;
timeval_out.tv_sec = 0;
timeval_out.tv_usec = 10;
if(argc > 3) {
hostaddr = inet_addr(argv[1]);
username = argv[2];
password = argv[3];
}
else {
fprintf(stderr, "Usage: %s destination username password",
argv[0]);
return -1;
}
if(argc > 4) {
set_debug_on = 1;
fprintf(stderr, "DEBUG is ON: %d\n", set_debug_on);
}
rc = libssh2_init(0);
if(rc) {
fprintf(stderr, "libssh2 initialization failed (%d)\n", rc);
return 1;
}
sock = socket(AF_INET, SOCK_STREAM, 0);
if(sock == LIBSSH2_INVALID_SOCKET) {
fprintf(stderr, "failed to open socket.\n");
return -1;
}
sin.sin_family = AF_INET;
sin.sin_port = htons(22);
sin.sin_addr.s_addr = hostaddr;
if(connect(sock, (struct sockaddr*)(&sin), sizeof(struct sockaddr_in))) {
fprintf(stderr, "Failed to established connection.\n");
return -1;
}
/* Open a session */
session = libssh2_session_init();
rc = libssh2_session_handshake(session, sock);
if(rc) {
fprintf(stderr, "Failed Start the SSH session\n");
return -1;
}
if(set_debug_on == 1)
libssh2_trace(session, LIBSSH2_TRACE_CONN);
/* Set X11 Callback */
#ifdef __clang__
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wcast-function-type"
#endif
libssh2_session_callback_set2(session, LIBSSH2_CALLBACK_X11,
(libssh2_cb_generic *)x11_callback);
#ifdef __clang__
#pragma clang diagnostic pop
#endif
/* Authenticate via password */
rc = libssh2_userauth_password(session, username, password);
if(rc) {
fprintf(stderr, "Failed to authenticate\n");
session_shutdown(session);
shutdown(sock, SHUT_RDWR);
LIBSSH2_SOCKET_CLOSE(sock);
return -1;
}
/* Open a channel */
channel = libssh2_channel_open_session(session);
if(!channel) {
fprintf(stderr, "Failed to open a new channel\n");
session_shutdown(session);
shutdown(sock, SHUT_RDWR);
LIBSSH2_SOCKET_CLOSE(sock);
return -1;
}
/* Request a PTY */
rc = libssh2_channel_request_pty(channel, "xterm");
if(rc) {
fprintf(stderr, "Failed to request a pty\n");
session_shutdown(session);
shutdown(sock, SHUT_RDWR);
LIBSSH2_SOCKET_CLOSE(sock);
return -1;
}
/* Request X11 */
rc = libssh2_channel_x11_req(channel, 0);
if(rc) {
fprintf(stderr, "Failed to request X11 forwarding\n");
session_shutdown(session);
shutdown(sock, SHUT_RDWR);
LIBSSH2_SOCKET_CLOSE(sock);
return -1;
}
/* Request a shell */
rc = libssh2_channel_shell(channel);
if(rc) {
fprintf(stderr, "Failed to open a shell\n");
session_shutdown(session);
shutdown(sock, SHUT_RDWR);
LIBSSH2_SOCKET_CLOSE(sock);
return -1;
}
rc = _raw_mode();
if(rc) {
fprintf(stderr, "Failed to entered in raw mode\n");
session_shutdown(session);
shutdown(sock, SHUT_RDWR);
LIBSSH2_SOCKET_CLOSE(sock);
return -1;
}
memset(&w_size, 0, sizeof(struct winsize));
memset(&w_size_bck, 0, sizeof(struct winsize));
for(;;) {
FD_ZERO(&set);
#if defined(__GNUC__) || defined(__clang__)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wsign-conversion"
#endif
FD_SET(fileno(stdin), &set);
#if defined(__GNUC__) || defined(__clang__)
#pragma GCC diagnostic pop
#endif
/* Search if a resize pty has to be send */
ioctl(fileno(stdin), TIOCGWINSZ, &w_size);
if((w_size.ws_row != w_size_bck.ws_row) ||
(w_size.ws_col != w_size_bck.ws_col)) {
w_size_bck = w_size;
libssh2_channel_request_pty_size(channel,
w_size.ws_col,
w_size.ws_row);
}
buf = calloc(bufsiz, sizeof(char));
if(!buf)
break;
fds = malloc(sizeof(LIBSSH2_POLLFD));
if(!fds) {
free(buf);
break;
}
fds[0].type = LIBSSH2_POLLFD_CHANNEL;
fds[0].fd.channel = channel;
fds[0].events = LIBSSH2_POLLFD_POLLIN;
fds[0].revents = LIBSSH2_POLLFD_POLLIN;
rc = libssh2_poll(fds, nfds, 0);
if(rc > 0) {
libssh2_channel_read(channel, buf, sizeof(buf));
fprintf(stdout, "%s", buf);
fflush(stdout);
}
/* Looping on X clients */
if(gp_x11_chan) {
current_node = gp_x11_chan;
}
else
current_node = NULL;
while(current_node) {
struct chan_X11_list *next_node;
rc = x11_send_receive(current_node->chan, current_node->sock);
next_node = current_node->next;
if(rc == -1) {
shutdown(current_node->sock, SHUT_RDWR);
LIBSSH2_SOCKET_CLOSE(current_node->sock);
remove_node(current_node);
}
current_node = next_node;
}
rc = select((int)(fileno(stdin) + 1), &set, NULL, NULL, &timeval_out);
if(rc > 0) {
ssize_t nread;
/* Data in stdin */
nread = read(fileno(stdin), buf, 1);
if(nread > 0)
libssh2_channel_write(channel, buf, sizeof(buf));
}
free(fds);
free(buf);
if(libssh2_channel_eof(channel) == 1) {
break;
}
}
if(channel) {
libssh2_channel_free(channel);
channel = NULL;
}
_normal_mode();
libssh2_exit();
return 0;
}
#else
int main(void)
{
fprintf(stderr, "Sorry, this platform is not supported.");
return 1;
}
#endif /* HAVE_SYS_UN_H */
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