path: root/tmate-ssh-client.c

#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/tcp.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <event.h>
#include <assert.h>

#include "tmate.h"
#include "window-copy.h"

static void on_ssh_client_event(struct tmate_ssh_client *client);
static void __on_ssh_client_event(evutil_socket_t fd, short what, void *arg);

static void printflike(2, 3) kill_ssh_client(struct tmate_ssh_client *client,
					     const char *fmt, ...);
static void printflike(2, 3) kill_ssh_client(struct tmate_ssh_client *client,
						  const char *fmt, ...);

static void read_channel(struct tmate_ssh_client *client)
{
	struct tmate_decoder *decoder = &client->tmate_session->decoder;
	char *buf;
	ssize_t len;

	for (;;) {
		tmate_decoder_get_buffer(decoder, &buf, &len);
		len = ssh_channel_read_nonblocking(client->channel, buf, len, 0);
		if (len < 0) {
			kill_ssh_client(client, "Error reading from channel: %s",
					ssh_get_error(client->session));
			break;
		}

		if (len == 0)
			break;

		tmate_decoder_commit(decoder, len);
	}
}

static void on_decoder_read(void *userdata, struct tmate_unpacker *uk)
{
	struct tmate_ssh_client *client = userdata;
	tmate_dispatch_slave_message(client->tmate_session, uk);
}

static void on_encoder_write(void *userdata, struct evbuffer *buffer)
{
	struct tmate_ssh_client *client = userdata;
	ssize_t len, written;
	unsigned char *buf;

	if (!client->channel)
		return;

	for(;;) {
		len = evbuffer_get_length(buffer);
		if (!len)
			break;

		buf = evbuffer_pullup(buffer, -1);

		written = ssh_channel_write(client->channel, buf, len);
		if (written < 0) {
			kill_ssh_client(client, "Error writing to channel: %s",
					ssh_get_error(client->session));
			break;
		}

		evbuffer_drain(buffer, written);
	}
}

static void on_ssh_auth_server_complete(struct tmate_ssh_client *connected_client)
{
	/*
	 * The first ssh connection succeeded. Hopefully this one offers the
	 * best latency. We can now kill the other ssh clients that are trying
	 * to connect.
	 */
	struct tmate_session *session = connected_client->tmate_session;
	struct tmate_ssh_client *client, *tmp_client;

	TAILQ_FOREACH_SAFE(client, &session->clients, node, tmp_client) {
		if (client == connected_client)
			continue;

		kill_ssh_client(client, NULL);
	}
}

static char *get_identity(void)
{
	char *identity;

	identity = options_get_string(global_options, "tmate-identity");
	if (!strlen(identity))
		return NULL;

	if (strchr(identity, '/'))
		identity = xstrdup(identity);
	else
		xasprintf(&identity, "%%d/%s", identity);

	return identity;
}

static int passphrase_callback(__unused const char *prompt, char *buf, size_t len,
			       __unused int echo, __unused int verify, void *userdata)
{
	struct tmate_ssh_client *client = userdata;

	client->tmate_session->need_passphrase = 1;

	if (client->tmate_session->passphrase)
		strlcpy(buf, client->tmate_session->passphrase, len);
	else
		strcpy(buf, "");

	return 0;
}

static void on_passphrase_read(const char *passphrase, void *private)
{
	struct tmate_ssh_client *client = private;

	client->tmate_session->passphrase = xstrdup(passphrase);
	on_ssh_client_event(client);
}

static void request_passphrase(struct tmate_ssh_client *client)
{
	struct window_pane *wp;
	struct window_copy_mode_data *data;

	/*
	 * We'll display the prompt on the first pane.
	 * It doesn't make much sense, but it's simpler to reuse the copy mode
	 * and its key parsing logic compared to rolling something on our own.
	 */
	wp = RB_MIN(window_pane_tree, &all_window_panes);

	if (wp->mode) {
		data = wp->modedata;
		if (data->inputtype == WINDOW_COPY_PASSWORD) {
			/* We are already requesting the passphrase */
			return;
		}
		window_pane_reset_mode(wp);
	}

	window_pane_set_mode(wp, &window_copy_mode);
	window_copy_init_from_pane(wp, 0);
	data = wp->modedata;

	data->inputtype = WINDOW_COPY_PASSWORD;
	data->inputprompt = "SSH key passphrase";

	mode_key_init(&data->mdata, &mode_key_tree_vi_edit);

	window_copy_update_selection(wp, 1);
	window_copy_redraw_screen(wp);

	data->password_cb = on_passphrase_read;
	data->password_cb_private = client;
}

#define KEEPALIVE_IDLE		30
#define KEEPALIVE_CNT		4
#define KEEPALIVE_INTVL		11
#define WRITE_TIMEOUT		80

static void tune_socket_opts(int fd)
{
#define SSO(level, optname, val) ({							\
	int _flag = val;								\
	if (setsockopt(fd, level, optname, &(_flag), sizeof(int)) < 0) {		\
		/* If the connection has been closed, we'll get EINVAL */		\
		if (errno != EINVAL)							\
			tmate_info("setsockopt(" #level ", " #optname ", %d) failed %s", val, strerror(errno));	\
	}										\
})

	SSO(IPPROTO_TCP, TCP_NODELAY, 1);
	SSO(SOL_SOCKET, SO_KEEPALIVE, 1);
#ifdef TCP_KEEPALIVE
	/*
	 * The TCP_KEEPALIVE options enable to specify the amount of time, in
	 * seconds, that the connection must be idle before keepalive probes
	 * (if enabled) are sent.
	 */
	SSO(IPPROTO_TCP, TCP_KEEPALIVE, KEEPALIVE_IDLE);
#endif
#ifdef TCP_KEEPIDLE
	/*
	 * Same as TCP_KEEPALIVE, but on different systems
	 */
	SSO(IPPROTO_TCP, TCP_KEEPIDLE, KEEPALIVE_IDLE);
#endif
#ifdef TCP_KEEPCNT
	/*
	 * When keepalive probes are enabled, this option will set the number
	 * of times a keepalive probe should be repeated if the peer is not
	 * responding. After this many probes, the connection will be closed.
	 */
	SSO(IPPROTO_TCP, TCP_KEEPCNT, KEEPALIVE_CNT);
#endif
#ifdef TCP_KEEPINTVL
	/*
	 * When keepalive probes are enabled, this option will set the amount
	 * of time in seconds between successive keepalives sent to probe an
	 * unresponsive peer.
	 */
	SSO(IPPROTO_TCP, TCP_KEEPINTVL, KEEPALIVE_INTVL);
#endif
#ifdef TCP_USER_TIMEOUT
	/*
	 * This option takes an unsigned int as an argument.  When the
	 * value is greater than 0, it specifies the maximum amount of
	 * time in milliseconds that transmitted data may remain
	 * unacknowledged before TCP will forcibly close the
	 * corresponding connection and return ETIMEDOUT to the
	 * application.
	 */
	SSO(IPPROTO_TCP, TCP_USER_TIMEOUT, 1000*WRITE_TIMEOUT);
#endif
#undef SSO
}

static void init_conn_fd(struct tmate_ssh_client *client)
{
	int fd;

	if (client->ev_ssh)
		return;

	if ((fd = ssh_get_fd(client->session)) < 0)
		return;

	tune_socket_opts(fd);

	client->ev_ssh = event_new(client->tmate_session->ev_base, fd,
				   EV_READ | EV_PERSIST,
				   __on_ssh_client_event, client);
	if (!client->ev_ssh)
		tmate_fatal("out of memory");
	event_add(client->ev_ssh, NULL);
}

static void on_ssh_client_event(struct tmate_ssh_client *client)
{
	ssh_session session = client->session;
	ssh_channel channel = client->channel;

	switch (client->state) {
	case SSH_INIT: {
		client->session = session = ssh_new();
		if (