channels.c

C＋＋编写

		originator_string = packet_get_string(NULL);
	} else {
		originator_string = xstrdup("unknown (remote did not supply name)");
	}
	packet_check_eom();
	sock = channel_connect_to(host, host_port);
	if (sock != -1) {
		c = channel_new("connected socket",
		    SSH_CHANNEL_CONNECTING, sock, sock, -1, 0, 0, 0,
		    originator_string, 1);
		c->remote_id = remote_id;
	}
	if (c == NULL) {
		xfree(originator_string);
		packet_start(SSH_MSG_CHANNEL_OPEN_FAILURE);
		packet_put_int(remote_id);
		packet_send();
	}
	xfree(host);
}


/* -- tcp forwarding */

void
channel_set_af(int af)
{
	IPv4or6 = af;
}

static int
channel_setup_fwd_listener(int type, const char *listen_addr, u_short listen_port,
    const char *host_to_connect, u_short port_to_connect, int gateway_ports)
{
	Channel *c;
	int success, sock, on = 1;
	struct addrinfo hints, *ai, *aitop;
	const char *host;
	char ntop[NI_MAXHOST], strport[NI_MAXSERV];

	success = 0;
	host = (type == SSH_CHANNEL_RPORT_LISTENER) ?
	    listen_addr : host_to_connect;

	if (host == NULL) {
		error("No forward host name.");
		return success;
	}
	if (strlen(host) > SSH_CHANNEL_PATH_LEN - 1) {
		error("Forward host name too long.");
		return success;
	}

	/*
	 * 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", listen_port);
	if (getaddrinfo(NULL, strport, &hints, &aitop) != 0)
		packet_disconnect("getaddrinfo: fatal error");

	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_setup_fwd_listener: 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.
		 * Allow local port reuse in TIME_WAIT.
		 */
		if (setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &on,
		    sizeof(on)) == -1)
			error("setsockopt SO_REUSEADDR: %s", strerror(errno));

		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. */
		c = channel_new("port listener", type, sock, sock, -1,
		    CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT,
		    0, xstrdup("port listener"), 1);
		strlcpy(c->path, host, sizeof(c->path));
		c->host_port = port_to_connect;
		c->listening_port = listen_port;
		success = 1;
	}
	if (success == 0)
		error("channel_setup_fwd_listener: cannot listen to port: %d",
		    listen_port);
	freeaddrinfo(aitop);
	return success;
}

/* protocol local port fwd, used by ssh (and sshd in v1) */
int
channel_setup_local_fwd_listener(u_short listen_port,
    const char *host_to_connect, u_short port_to_connect, int gateway_ports)
{
	return channel_setup_fwd_listener(SSH_CHANNEL_PORT_LISTENER,
	    NULL, listen_port, host_to_connect, port_to_connect, gateway_ports);
}

/* protocol v2 remote port fwd, used by sshd */
int
channel_setup_remote_fwd_listener(const char *listen_address,
    u_short listen_port, int gateway_ports)
{
	return channel_setup_fwd_listener(SSH_CHANNEL_RPORT_LISTENER,
	    listen_address, listen_port, NULL, 0, gateway_ports);
}

/*
 * 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 type, success = 0;

	/* 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");

	/* 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(1);			/* boolean: want reply */
		packet_put_cstring(address_to_bind);
		packet_put_int(listen_port);
		packet_send();
		packet_write_wait();
		/* Assume that server accepts the request */
		success = 1;
	} 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. */
		type = packet_read();
		switch (type) {
		case SSH_SMSG_SUCCESS:
			success = 1;
			break;
		case SSH_SMSG_FAILURE:
			log("Warning: Server denied remote port forwarding.");
			break;
		default:
			/* Unknown packet */
			packet_disconnect("Protocol error for port forward request:"
			    "received packet type %d.", type);
		}
	}
	if (success) {
		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++;
	}
}

/*
 * 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_setup_local_fwd_listener(port, hostname, host_port, gateway_ports);

	/* Free the argument string. */
	xfree(hostname);
}

/*
 * Permits opening to any host/port if permitted_opens[] is empty.  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(void)
{
	if (num_permitted_opens == 0)
		all_opens_permitted = 1;
}

void
channel_add_permitted_opens(char *host, int port)
{
	if (num_permitted_opens >= SSH_MAX_FORWARDS_PER_DIRECTION)
		fatal("channel_request_remote_forwarding: too many forwards");
	debug("allow port forwarding to host %s port %d", host, port);

	permitted_opens[num_permitted_opens].host_to_connect = xstrdup(host);
	permitted_opens[num_permitted_opens].port_to_connect = port;
	num_permitted_opens++;

	all_opens_permitted = 0;
}

void
channel_clear_permitted_opens(void)
{
	int i;

	for (i = 0; i < num_permitted_opens; i++)
		xfree(permitted_opens[i].host_to_connect);
	num_permitted_opens = 0;

}


/* return socket to remote host, port */
static int
connect_to(const char *host, u_short 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", port);
	if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0) {
		error("connect_to %.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("connect_to: getnameinfo failed");
			continue;
		}
		sock = socket(ai->ai_family, SOCK_STREAM, 0);
		if (sock < 0) {
			if (ai->ai_next == NULL)
				error("socket: %.100s", strerror(errno));
			else
				verbose("socket: %.100s", strerror(errno));
			continue;
		}
		if (fcntl(sock, F_SETFL, O_NONBLOCK) < 0)
			fatal("connect_to: F_SETFL: %s", strerror(errno));
		if (connect(sock, ai->ai_addr, ai->ai_addrlen) < 0 &&
		    errno != EINPROGRESS) {
			error("connect_to %.100s port %s: %.100s", ntop, strport,
			    strerror(errno));
			close(sock);
			continue;	/* fail -- try next */
		}
		break; /* success */

	}
	freeaddrinfo(aitop);
	if (!ai) {
		error("connect_to %.100s port %d: failed.", host, port);
		return -1;
	}
	/* success */
	set_nodelay(sock);
	return sock;
}

int
channel_connect_by_listen_address(u_short listen_port)
{
	int i;

	for (i = 0; i < num_permitted_opens; i++)
		if (permitted_opens[i].listen_port == listen_port)
			return connect_to(
			    permitted_opens[i].host_to_connect,
			    permitted_opens[i].port_to_connect);
	error("WARNING: Server requests forwarding for unknown listen_port %d",
	    listen_port);
	return -1;
}

/* Check if connecting to that port is permitted and connect. */
int
channel_connect_to(const char *host, u_short port)
{
	int i, permit;

	permit = all_opens_permitted;
	if (!permit) {
		for (i = 0; i < num_permitted_opens; i++)
			if (permitted_opens[i].port_to_connect == port &&
			    strcmp(permitted_opens[i].host_to_connect, host) == 0)
				permit = 1;

	}
	if (!permit) {
		log("Received request to connect to host %.100s port %d, "
		    "but the request was denied.", host, port);
		return -1;
	}
	return connect_to(host, port);
}

/* -- X11 forwarding */

/*
 * Creates an internet domain socket for listening for X11 connections.
 * Returns 0 and a suitable display number for the DISPLAY variable
 * stored in display_numberp , or -1 if an error occurs.
 */
int
x11_create_display_inet(int x11_display_offset, int x11_use_localhost,
    int single_connection, u_int *display_numberp)
{
	Channel *nc = NULL;
	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];

	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 = x11_use_localhost ? 0: AI_PASSIVE;
		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 -1;
		}
		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 -1;
			}
			if (bind(sock, ai->ai_addr, ai->ai_addrlen) < 0) {
				debug("bind port %d: %.100s", port, strerror(errno));
				close(sock);

				if (ai->ai_next)
					continue;

				for (n = 0; n < num_socks; n++) {
					close(socks[n]);
				}
				num_socks = 0;
				break;
			}
			socks[num_socks++] = sock;
			if (num_socks == NUM_SOCKS)
				break;
		}
		freeaddrinfo(aitop);
		if (num_socks > 0)
			break;
	}
	if (display_number >= MAX_DISPLAYS) {
		error("Failed to allocate internet-domain X11 display socket.");
		return -1;
	}
	/* 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));
			close(sock);
			return -1;
		}
	}

	/* Allocate a channel for each socket. */
	for (n = 0; n < num_socks; n++) {
		sock = socks[n];
		nc = 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);
		nc->single_connection = single_connection;
	}

	/* Return the display number for the DISPLAY environment variable. */
	*display_numberp = display_number;
	return (0);
}

static int
connect_local_xsocket(u_int dnr)
{
	int sock;
	struct sockaddr_un addr;

	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_UNIX_X, 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: %