examples: Add 'ssh X11 client' sample

Signed-off-by: Marco Fortina <marco.fortina@atlantica.it>
Reviewed-by: Jakub Jelen <jjelen@redhat.com>

examples/ssh_X11_client.c

@@ -0,0 +1,859 @@
+/*
+ * ssh.c - Simple example of SSH X11 client using libssh
+ *
+ * Copyright (C) 2022 Marco Fortina
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor,
+ * Boston, MA  02110-1301, USA.
+ *
+ *  In addition, as a special exception, the copyright holders give
+ *  permission to link the code of portions of this program with the
+ *  OpenSSL library under certain conditions as described in each
+ *  individual source file, and distribute linked combinations
+ *  including the two.
+ *  You must obey the GNU General Public License in all respects
+ *  for all of the code used other than OpenSSL. *  If you modify
+ *  file(s) with this exception, you may extend this exception to your
+ *  version of the file(s), but you are not obligated to do so. *  If you
+ *  do not wish to do so, delete this exception statement from your
+ *  version. *  If you delete this exception statement from all source
+ *  files in the program, then also delete it here.
+ *
+ *
+ *
+ * ssh_X11_client
+ * ==============
+ *
+ * AUTHOR URL
+ * https://gitlab.com/marco.fortina/libssh-x11-client/
+ *
+ * This is a simple example of SSH X11 client using libssh.
+ *
+ * Features:
+ *
+ * - support local display (e.g. :0)
+ * - support remote display (e.g. localhost:10.0)
+ * - using callbacks and event polling to significantly reduce CPU utilization
+ * - use X11 forwarding with authentication spoofing (like openssh)
+ *
+ * Note:
+ *
+ * - part of this code was inspired by openssh's one.
+ *
+ * Dependencies:
+ *
+ * - gcc >= 7.5.0
+ * - libssh >= 0.8.0
+ * - libssh-dev >= 0.8.0
+ *
+ * To Build:
+ * gcc -o ssh_X11_client ssh_X11_client.c -lssh -g
+ *
+ * Donations:
+ *
+ * If you liked this work and wish to support the developer please donate to:
+ * Bitcoin: 1N2rQimKbeUQA8N2LU5vGopYQJmZsBM2d6
+ *
+*/
+
+#include <errno.h>
+#include <fcntl.h>
+#include <poll.h>
+#include <pthread.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <termios.h>
+#include <time.h>
+
+#include <libssh/libssh.h>
+#include <libssh/callbacks.h>
+
+#include <netinet/in.h>
+#include <netinet/tcp.h>
+
+#include <sys/un.h>
+#include <sys/time.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+
+/*
+ * Data Structures and Macros
+*/
+
+#define _PATH_UNIX_X 	"/tmp/.X11-unix/X%d"
+#define _XAUTH_CMD	"/usr/bin/xauth list %s 2>/dev/null"
+
+typedef struct item {
+	ssh_channel channel;
+	int fd_in;
+	int fd_out;
+	int protected;
+	struct item *next;
+} node_t;
+
+node_t *node = NULL;
+
+
+/*
+ * Mutex
+*/
+
+pthread_mutex_t mutex;
+
+
+/*
+ * Function declarations
+*/
+
+/* Linked nodes to manage channel/fd tuples */
+static void insert_item(ssh_channel channel, int fd_in, int fd_out, int protected);
+static void delete_item(ssh_channel channel);
+static node_t * search_item(ssh_channel channel);
+
+/* X11 Display */
+const char * ssh_gai_strerror(int gaierr);
+static int x11_get_proto(const char *display, char **_proto, char **_data);
+static void set_nodelay(int fd);
+static int connect_local_xsocket_path(const char *pathname);
+static int connect_local_xsocket(int display_number);
+static int x11_connect_display(void);
+
+/* Send data to channel */
+static int copy_fd_to_channel_callback(int fd, int revents, void *userdata);
+
+/* Read data from channel */
+static int copy_channel_to_fd_callback(ssh_session session, ssh_channel channel, void *data, uint32_t len, int is_stderr, void *userdata);
+
+/* EOF&Close channel */
+static void channel_close_callback(ssh_session session, ssh_channel channel, void *userdata);
+
+/* X11 Request */
+static ssh_channel x11_open_request_callback(ssh_session session, const char *shost, int sport, void *userdata);
+
+/* Main loop */
+static int main_loop(ssh_channel channel);
+
+/* Internals */
+int64_t _current_timestamp(void);
+
+/* Global variables */
+const char *hostname = NULL;
+int enableX11 = 1;
+
+/*
+ * Callbacks Data Structures
+*/
+
+/* SSH Channel Callbacks */
+struct ssh_channel_callbacks_struct channel_cb =
+{
+	.channel_data_function = copy_channel_to_fd_callback,
+	.channel_eof_function = channel_close_callback,
+	.channel_close_function = channel_close_callback,
+	.userdata = NULL
+};
+
+/* SSH Callbacks */
+struct ssh_callbacks_struct cb =
+{
+	.channel_open_request_x11_function = x11_open_request_callback,
+	.userdata = NULL
+};
+
+
+/*
+ * SSH Event Context
+*/
+
+short events = POLLIN | POLLPRI | POLLERR | POLLHUP | POLLNVAL;
+ssh_event event;
+
+
+/*
+ * Internal data structures
+*/
+
+struct termios _saved_tio;
+
+
+/*
+ * Internal functions
+*/
+
+int64_t
+_current_timestamp(void) {
+	struct timeval tv;
+	int64_t milliseconds;
+
+	gettimeofday(&tv, NULL);
+	milliseconds = (int64_t)(tv.tv_sec) * 1000 + (tv.tv_usec / 1000);
+
+	return milliseconds;
+}
+
+static void
+_logging_callback(int priority, const char *function, const char *buffer, void *userdata)
+{
+	FILE *fp = NULL;
+	char buf[100];
+	int64_t milliseconds;
+
+	time_t now = time (0);
+
+	(void)userdata;
+
+	strftime(buf, 100, "%Y-%m-%d %H:%M:%S", localtime (&now));
+
+	fp = fopen("debug.log","a");
+	if(fp == NULL)
+	{
+		printf("Error!");
+		exit(-11);
+	}
+
+	milliseconds = _current_timestamp();
+
+	fprintf(fp, "[%s.%jd, %d] %s: %s\n", buf, milliseconds, priority, function, buffer);
+	fclose(fp);
+}
+
+static int
+_enter_term_raw_mode(void)
+{
+	struct termios tio;
+	int ret = tcgetattr(fileno(stdin), &tio);
+	if (ret != -1) {
+		_saved_tio = tio;
+		tio.c_iflag |= IGNPAR;
+		tio.c_iflag &= ~(ISTRIP | INLCR | IGNCR | ICRNL | IXON | IXANY | IXOFF);
+#ifdef IUCLC
+		tio.c_iflag &= ~IUCLC;
+#endif
+		tio.c_lflag &= ~(ISIG | ICANON | ECHO | ECHOE | ECHOK | ECHONL);
+#ifdef IEXTEN
+		tio.c_lflag &= ~IEXTEN;
+#endif
+		tio.c_oflag &= ~OPOST;
+		tio.c_cc[VMIN] = 1;
+		tio.c_cc[VTIME] = 0;
+		ret = tcsetattr(fileno(stdin), TCSADRAIN, &tio);
+	}
+	return ret;
+}
+
+static int
+_leave_term_raw_mode(void)
+{
+	int ret = tcsetattr(fileno(stdin), TCSADRAIN, &_saved_tio);
+	return ret;
+}
+
+
+/*
+ * Functions
+*/
+
+static void
+insert_item(ssh_channel channel, int fd_in, int fd_out, int protected)
+{
+	node_t *node_iterator = NULL, *new = NULL;
+
+	pthread_mutex_lock(&mutex);
+
+	if (node == NULL) {
+		/* Calloc ensure that node is full of 0 */
+		node = (node_t *) calloc(1, sizeof(node_t));
+		node->channel = channel;
+		node->fd_in = fd_in;
+		node->fd_out = fd_out;
+		node->protected = protected;
+		node->next = NULL;
+	} else {
+		node_iterator = node;
+		while (node_iterator->next != NULL)
+			node_iterator = node_iterator->next;
+		/* Create the new node */
+		new = (node_t *) malloc(sizeof(node_t));
+		new->channel = channel;
+		new->fd_in = fd_in;
+		new->fd_out = fd_out;
+		new->protected = protected;
+		new->next = NULL;
+		node_iterator->next = new;
+
+	}
+
+	pthread_mutex_unlock(&mutex);
+}
+
+
+static void
+delete_item(ssh_channel channel)
+{
+	node_t *current = NULL, *previous = NULL;
+
+	pthread_mutex_lock(&mutex);
+
+	for (current = node; current; previous = current, current = current->next) {
+		if (current->channel != channel)
+			continue;
+
+		if (previous == NULL)
+			node = current->next;
+		else
+			previous->next = current->next;
+
+		free(current);
+		pthread_mutex_unlock(&mutex);
+		return;
+	}
+
+	pthread_mutex_unlock(&mutex);
+}
+
+
+static node_t *
+search_item(ssh_channel channel)
+{
+	node_t *current = node;
+
+	pthread_mutex_lock(&mutex);
+
+	while (current != NULL) {
+		if (current->channel == channel) {
+			pthread_mutex_unlock(&mutex);
+			return current;
+		} else {
+			current = current->next;
+		}
+	}
+
+	pthread_mutex_unlock(&mutex);
+
+	return NULL;
+}
+
+
+
+static void
+set_nodelay(int fd)
+{
+	int opt;
+	socklen_t optlen;
+
+	optlen = sizeof(opt);
+	if (getsockopt(fd, IPPROTO_TCP, TCP_NODELAY, &opt, &optlen) == -1) {
+		_ssh_log(SSH_LOG_FUNCTIONS, __func__, "getsockopt TCP_NODELAY: %.100s", strerror(errno));
+		return;
+	}
+	if (opt == 1) {
+		_ssh_log(SSH_LOG_FUNCTIONS, __func__, "fd %d is TCP_NODELAY", fd);
+		return;
+	}
+	opt = 1;
+	_ssh_log(SSH_LOG_FUNCTIONS, __func__, "fd %d setting TCP_NODELAY", fd);
+	if (setsockopt(fd, IPPROTO_TCP, TCP_NODELAY, &opt, sizeof(opt)) == -1)
+		_ssh_log(SSH_LOG_FUNCTIONS, __func__, "setsockopt TCP_NODELAY: %.100s", strerror(errno));
+}
+
+
+const char *
+ssh_gai_strerror(int gaierr)
+{
+	if (gaierr == EAI_SYSTEM && errno != 0)
+		return strerror(errno);
+	return gai_strerror(gaierr);
+}
+
+
+
+static int
+x11_get_proto(const char *display, char **_proto, char **_cookie)
+{
+	char cmd[1024], line[512], xdisplay[512];
+	static char proto[512], cookie[512];
+	FILE *f = NULL;
+	int ret = 0;
+
+	*_proto = proto;
+	*_cookie = cookie;
+
+	proto[0] = cookie[0] = '\0';
+
+	if (strncmp(display, "localhost:", 10) == 0) {
+		if ((ret = snprintf(xdisplay, sizeof(xdisplay), "unix:%s", display + 10)) < 0 || (size_t)ret >= sizeof(xdisplay)) {
+			_ssh_log(SSH_LOG_FUNCTIONS, __func__, "display name too long. display: %s", display);
+			return -1;
+		}
+		display = xdisplay;
+	}
+
+	snprintf(cmd, sizeof(cmd), _XAUTH_CMD, display);
+	_ssh_log(SSH_LOG_FUNCTIONS, __func__, "xauth cmd: %s", cmd);
+
+	f = popen(cmd, "r");
+	if (f && fgets(line, sizeof(line), f) && sscanf(line, "%*s %511s %511s", proto, cookie) == 2) {
+		ret = 0;
+	} else {
+		ret = 1;
+	}
+
+	if (f) pclose(f);
+
+	_ssh_log(SSH_LOG_FUNCTIONS, __func__, "proto: %s - cookie: %s - ret: %d", proto, cookie, ret);
+
+	return ret;
+}
+
+static int
+connect_local_xsocket_path(const char *pathname)
+{
+	int sock;
+	struct sockaddr_un addr;
+
+	sock = socket(AF_UNIX, SOCK_STREAM, 0);
+	if (sock == -1)
+		_ssh_log(SSH_LOG_FUNCTIONS, __func__, "socket: %.100s", strerror(errno));
+	memset(&addr, 0, sizeof(addr));
+	addr.sun_family = AF_UNIX;
+	addr.sun_path[0] = '\0';
+	memcpy(addr.sun_path + 1, pathname, strlen(pathname));
+	if (connect(sock, (struct sockaddr *)&addr, offsetof(struct sockaddr_un, sun_path) + 1 + strlen(pathname)) == 0)
+		return sock;
+	close(sock);
+	_ssh_log(SSH_LOG_FUNCTIONS, __func__, "connect %.100s: %.100s", addr.sun_path, strerror(errno));
+	return -1;
+}
+
+
+static int
+connect_local_xsocket(int display_number)
+{
+	char buf[1024];
+	snprintf(buf, sizeof(buf), _PATH_UNIX_X, display_number);
+	return connect_local_xsocket_path(buf);
+}
+
+
+static int
+x11_connect_display()
+{
+	int display_number;
+	const char *display = NULL;
+	char buf[1024], *cp = NULL;
+	struct addrinfo hints, *ai = NULL, *aitop = NULL;
+	char strport[NI_MAXSERV];
+	int gaierr = 0, sock = 0;
+
+	/* Try to open a socket for the local X server. */
+	display = getenv("DISPLAY");
+
+	_ssh_log(SSH_LOG_FUNCTIONS, __func__, "display: %s", display);
+
+	if (!display) {
+		return -1;
+	}
+
+	/* Check if it is a unix domain socket. */
+	if (strncmp(display, "unix:", 5) == 0 || display[0] == ':') {
+		/* Connect to the unix domain socket. */
+		if (sscanf(strrchr(display, ':') + 1, "%d", &display_number) != 1) {
+			_ssh_log(SSH_LOG_FUNCTIONS, __func__, "Could not parse display number from DISPLAY: %.100s", display);
+			return -1;
+		}
+
+		_ssh_log(SSH_LOG_FUNCTIONS, __func__, "display_number: %d", display_number);
+
+		/* Create a socket. */
+		sock = connect_local_xsocket(display_number);
+
+		_ssh_log(SSH_LOG_FUNCTIONS, __func__, "socket: %d", sock);
+
+		if (sock < 0)
+			return -1;
+
+		/* OK, we now have a connection to the display. */
+		return sock;
+	}
+
+	/* Connect to an inet socket. */
+	strncpy(buf, display, sizeof(buf) - 1);
+	cp = strchr(buf, ':');
+	if (!cp) {
+		_ssh_log(SSH_LOG_FUNCTIONS, __func__, "Could not find ':' in DISPLAY: %.100s", display);
+		return -1;
+	}
+	*cp = 0;
+	if (sscanf(cp + 1, "%d", &display_number) != 1) {
+		_ssh_log(SSH_LOG_FUNCTIONS, __func__, "Could not parse display number from DISPLAY: %.100s", display);
+		return -1;
+	}
+
+	/* Look up the host address */
+	memset(&hints, 0, sizeof(hints));
+	hints.ai_family = AF_INET;
+	hints.ai_socktype = SOCK_STREAM;
+	snprintf(strport, sizeof(strport), "%u", 6000 + display_number);
+	if ((gaierr = getaddrinfo(buf, strport, &hints, &aitop)) != 0) {
+		_ssh_log(SSH_LOG_FUNCTIONS, __func__, "%.100s: unknown host. (%s)", buf, ssh_gai_strerror(gaierr));
+		return -1;
+	}
+	for (ai = aitop; ai; ai = ai->ai_next) {
+		/* Create a socket. */
+		sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
+		if (sock == -1) {
+			_ssh_log(SSH_LOG_FUNCTIONS, __func__, "socket: %.100s", strerror(errno));
+			continue;
+		}
+		/* Connect it to the display. */
+		if (connect(sock, ai->ai_addr, ai->ai_addrlen) == -1) {
+			_ssh_log(SSH_LOG_FUNCTIONS, __func__, "connect %.100s port %u: %.100s", buf, 6000 + display_number, strerror(errno));
+			close(sock);
+			continue;
+		}
+		/* Success */
+		break;
+	}
+	freeaddrinfo(aitop);
+	if (!ai) {
+		_ssh_log(SSH_LOG_FUNCTIONS, __func__, "connect %.100s port %u: %.100s", buf, 6000 + display_number, strerror(errno));
+		return -1;
+	}
+	set_nodelay(sock);
+	return sock;
+}
+
+
+
+static int
+copy_fd_to_channel_callback(int fd, int revents, void *userdata)
+{
+	ssh_channel channel = (ssh_channel)userdata;
+	char buf[2097152];
+	int sz = 0, ret = 0;
+
+	node_t *temp_node = search_item(channel);
+
+	_ssh_log(SSH_LOG_FUNCTIONS, __func__, "event: %d - fd: %d", revents, fd);
+
+	if (!channel) {
+		_ssh_log(SSH_LOG_FUNCTIONS, __func__, "channel does not exist.");
+		if (temp_node->protected == 0) {
+			close(fd);
+		}
+		return -1;
+	}
+
+	if (fcntl(fd, F_GETFD) == -1) {
+		_ssh_log(SSH_LOG_FUNCTIONS, __func__, "fcntl error. fd: %d", fd);
+		ssh_channel_close(channel);
+		return -1;
+	}
+
+	if ((revents & POLLIN) || (revents & POLLPRI)) {
+		sz = read(fd, buf, sizeof(buf));
+		_ssh_log(SSH_LOG_FUNCTIONS, __func__, "sz: %d", sz);
+		if (sz > 0) {
+			ret = ssh_channel_write(channel, buf, sz);
+			_ssh_log(SSH_LOG_FUNCTIONS, __func__, "channel_write ret: %d", ret);
+		} else if (sz < 0) {
+			ssh_channel_close(channel);
+			return -1;
+		} else {
+			/* sz = 0. Why the hell I'm here? */
+			_ssh_log(SSH_LOG_FUNCTIONS, __func__, "Why the hell am I here?: sz: %d", sz);
+			if (temp_node->protected == 0) {
+				close(fd);
+			}
+			return -1;
+		}
+	}
+
+	if ((revents & POLLHUP) || (revents & POLLNVAL) || (revents & POLLERR)) {
+		ssh_channel_close(channel);
+		return -1;
+	}
+
+	return sz;
+}
+
+
+static int
+copy_channel_to_fd_callback(ssh_session session, ssh_channel channel, void *data, uint32_t len, int is_stderr, void *userdata)
+{
+	node_t *temp_node = NULL;
+	int fd, sz;
+
+	(void)session;
+	(void)is_stderr;
+	(void)userdata;
+
+	temp_node = search_item(channel);
+
+	fd = temp_node->fd_out;
+
+	_ssh_log(SSH_LOG_FUNCTIONS, __func__, "len: %d - fd: %d - is_stderr: %d", len, fd, is_stderr);
+
+	sz = write(fd, data, len);
+
+	return sz;
+}
+
+
+static void
+channel_close_callback(ssh_session session, ssh_channel channel, void *userdata)
+{
+	node_t *temp_node = NULL;
+
+	(void)session;
+	(void)userdata;
+
+	temp_node = search_item(channel);
+
+	if (temp_node != NULL) {
+		int fd = temp_node->fd_in;
+
+		_ssh_log(SSH_LOG_FUNCTIONS, __func__, "fd: %d", fd);
+
+		delete_item(channel);
+		ssh_event_remove_fd(event, fd);
+
+		if (temp_node->protected == 0) {
+			close(fd);
+		}
+	}
+}
+
+
+static ssh_channel
+x11_open_request_callback(ssh_session session, const char *shost, int sport, void *userdata)
+{
+	ssh_channel channel = NULL;
+	int sock;
+
+	(void)shost;
+	(void)sport;
+	(void)userdata;
+
+	channel	= ssh_channel_new(session);
+
+	sock = x11_connect_display();
+
+	_ssh_log(SSH_LOG_FUNCTIONS, __func__, "sock: %d", sock);
+
+	insert_item(channel, sock, sock, 0);
+
+	ssh_event_add_fd(event, sock, events, copy_fd_to_channel_callback, channel);
+	ssh_event_add_session(event, session);
+
+	ssh_add_channel_callbacks(channel, &channel_cb);
+
+	return channel;
+}
+
+
+
+/*
+ * MAIN LOOP
+*/
+
+static int
+main_loop(ssh_channel channel)
+{
+	ssh_session session = ssh_channel_get_session(channel);
+
+	insert_item(channel, fileno(stdin), fileno(stdout), 1);
+
+	ssh_callbacks_init(&channel_cb);
+	ssh_set_channel_callbacks(channel, &channel_cb);
+
+	event = ssh_event_new();
+	if (event == NULL) {
+		printf("Couldn't get a event\n");
+		return -1;
+	}
+
+	if (ssh_event_add_fd(event, fileno(stdin), events, copy_fd_to_channel_callback, channel) != SSH_OK) {
+		printf("Couldn't add an fd to the event\n");
+		return -1;
+	}
+
+	if(ssh_event_add_session(event, session) != SSH_OK) {
+		printf("Couldn't add the session to the event\n");
+		return -1;
+	}
+
+	do {
+		ssh_event_dopoll(event, 1000);
+	} while (!ssh_channel_is_closed(channel));
+
+	delete_item(channel);
+	ssh_event_remove_fd(event, fileno(stdin));
+	ssh_event_remove_session(event, session);
+	ssh_event_free(event);
+
+	return 0;
+}
+
+
+/*
+ * USAGE
+ */
+
+static void
+usage(void)
+{
+	fprintf(stderr,
+		"Usage : ssh-X11-client [options] [login@]hostname\n"
+		"sample X11 client - libssh-%s\n"
+		"Options :\n"
+		"  -l user : Specifies the user to log in as on the remote machine.\n"
+		"  -p port : Port to connect to on the remote host.\n"
+		"  -v      : Verbose mode. Multiple -v options increase the verbosity. The maximum is 5.\n"
+		"  -C      : Requests compression of all data.\n"
+		"  -x      : Disables X11 forwarding.\n"
+		"\n",
+		ssh_version(0));
+
+	exit(0);
+}
+
+static int opts(int argc, char **argv)
+{
+	int i;
+
+	while ((i = getopt(argc,argv,"x")) != -1) {
+		switch(i) {
+		case 'x':
+			enableX11 = 0;
+			break;
+		default:
+			fprintf(stderr, "Unknown option %c\n", optopt);
+			return -1;
+		}
+	}
+
+	if (optind < argc) {
+		hostname = argv[optind++];
+	}
+
+	if (hostname == NULL) {
+		return -1;
+	}
+
+	return 0;
+}
+
+/*
+ * MAIN
+*/
+
+int
+main(int argc, char **argv)
+{
+	char *password = NULL;
+
+	ssh_session session = NULL;
+	ssh_channel channel = NULL;
+
+	int ret;
+
+	const char *display = NULL;
+	char *proto = NULL, *cookie = NULL;
+
+	ssh_set_log_callback(_logging_callback);
+	ret = ssh_init();
+	if (ret != SSH_OK) return ret;
+
+	session = ssh_new();
+	if (session == NULL) exit(-1);
+
+	if (ssh_options_getopt(session, &argc, argv) || opts(argc, argv)) {
+		fprintf(stderr, "Error parsing command line: %s\n", ssh_get_error(session));
+		ssh_free(session);
+		ssh_finalize();
+		usage();
+	}
+
+	if (ssh_options_set(session, SSH_OPTIONS_HOST, hostname) < 0) {
+		return -1;
+	}
+
+	ret = ssh_connect(session);
+	if (ret != SSH_OK) {
+		fprintf(stderr, "Connection failed : %s\n", ssh_get_error(session));
+		exit(-1);
+	}
+
+	password = getpass("Password: ");
+	ret = ssh_userauth_password(session, NULL, password);
+	if (ret != SSH_AUTH_SUCCESS) {
+		fprintf(stderr, "Error authenticating with password: %s\n", ssh_get_error(session));
+		exit(-1);
+	}
+
+	channel = ssh_channel_new(session);
+	if (channel == NULL) return SSH_ERROR;
+
+	ret = ssh_channel_open_session(channel);
+	if (ret != SSH_OK) return ret;
+
+	ret = ssh_channel_request_pty(channel);
+	if (ret != SSH_OK) return ret;
+
+	ret = ssh_channel_change_pty_size(channel, 80, 24);
+	if (ret != SSH_OK) return ret;
+
+	if (enableX11 == 1) {
+		display = getenv("DISPLAY");
+
+		_ssh_log(SSH_LOG_FUNCTIONS, __func__, "display: %s", display);
+
+		if (display) {
+			ssh_callbacks_init(&cb);
+			ret = ssh_set_callbacks(session, &cb);
+			if (ret != SSH_OK) return ret;
+
+			if (x11_get_proto(display, &proto, &cookie) != 0) {
+				_ssh_log(SSH_LOG_FUNCTIONS, __func__, "Using fake authentication data for X11 forwarding");
+				proto = NULL;
+				cookie = NULL;
+			}
+
+			_ssh_log(SSH_LOG_FUNCTIONS, __func__, "proto: %s - cookie: %s", proto, cookie);
+			/* See https://gitlab.com/libssh/libssh-mirror/-/blob/master/src/channels.c#L2062 for details. */
+			ret = ssh_channel_request_x11(channel, 0, proto, cookie, 0);
+			if (ret != SSH_OK) return ret;
+		}
+	}
+
+	ret = _enter_term_raw_mode();
+	if (ret != 0) exit(-1);
+
+	ret = ssh_channel_request_shell(channel);
+	if (ret != SSH_OK) return ret;
+
+	ret = main_loop(channel);
+	if (ret != SSH_OK) return ret;
+
+	_leave_term_raw_mode();
+
+	ssh_channel_close(channel);
+	ssh_channel_free(channel);
+	ssh_disconnect(session);
+	ssh_free(session);
+	ssh_finalize();
+}