channels.c

OpenSSH 是 SSH （Secure SHell） 协议的免费开源实现。它用安全、加密的网络连接工具代替了 telnet、ftp、 rlogin、rsh 和 rcp 工具。OpenSSH 支持

	}

}

void
channel_input_close(int type, u_int32_t seq, void *ctxt)
{
	int id;
	Channel *c;

	id = packet_get_int();
	packet_check_eom();
	c = channel_lookup(id);
	if (c == NULL)
		packet_disconnect("Received close for nonexistent channel %d.", id);

	/*
	 * 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(c->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 (c->type != SSH_CHANNEL_CLOSED) {
		/*
		 * Not a closed channel - mark it as draining, which will
		 * cause it to be freed later.
		 */
		buffer_clear(&c->input);
		c->type = SSH_CHANNEL_OUTPUT_DRAINING;
	}
}

/* proto version 1.5 overloads CLOSE_CONFIRMATION with OCLOSE */
void
channel_input_oclose(int type, u_int32_t seq, void *ctxt)
{
	int id = packet_get_int();
	Channel *c = channel_lookup(id);

	packet_check_eom();
	if (c == NULL)
		packet_disconnect("Received oclose for nonexistent channel %d.", id);
	chan_rcvd_oclose(c);
}

void
channel_input_close_confirmation(int type, u_int32_t seq, void *ctxt)
{
	int id = packet_get_int();
	Channel *c = channel_lookup(id);

	packet_check_eom();
	if (c == NULL)
		packet_disconnect("Received close confirmation for "
		    "out-of-range channel %d.", id);
	if (c->type != SSH_CHANNEL_CLOSED)
		packet_disconnect("Received close confirmation for "
		    "non-closed channel %d (type %d).", id, c->type);
	channel_free(c);
}

void
channel_input_open_confirmation(int type, u_int32_t seq, void *ctxt)
{
	int id, remote_id;
	Channel *c;

	id = packet_get_int();
	c = channel_lookup(id);

	if (c==NULL || c->type != SSH_CHANNEL_OPENING)
		packet_disconnect("Received open confirmation for "
		    "non-opening channel %d.", id);
	remote_id = packet_get_int();
	/* Record the remote channel number and mark that the channel is now open. */
	c->remote_id = remote_id;
	c->type = SSH_CHANNEL_OPEN;

	if (compat20) {
		c->remote_window = packet_get_int();
		c->remote_maxpacket = packet_get_int();
		if (c->confirm) {
			debug2("callback start");
			c->confirm(c->self, c->confirm_ctx);
			debug2("callback done");
		}
		debug2("channel %d: open confirm rwindow %u rmax %u", c->self,
		    c->remote_window, c->remote_maxpacket);
	}
	packet_check_eom();
}

static char *
reason2txt(int reason)
{
	switch (reason) {
	case SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED:
		return "administratively prohibited";
	case SSH2_OPEN_CONNECT_FAILED:
		return "connect failed";
	case SSH2_OPEN_UNKNOWN_CHANNEL_TYPE:
		return "unknown channel type";
	case SSH2_OPEN_RESOURCE_SHORTAGE:
		return "resource shortage";
	}
	return "unknown reason";
}

void
channel_input_open_failure(int type, u_int32_t seq, void *ctxt)
{
	int id, reason;
	char *msg = NULL, *lang = NULL;
	Channel *c;

	id = packet_get_int();
	c = channel_lookup(id);

	if (c==NULL || c->type != SSH_CHANNEL_OPENING)
		packet_disconnect("Received open failure for "
		    "non-opening channel %d.", id);
	if (compat20) {
		reason = packet_get_int();
		if (!(datafellows & SSH_BUG_OPENFAILURE)) {
			msg  = packet_get_string(NULL);
			lang = packet_get_string(NULL);
		}
		logit("channel %d: open failed: %s%s%s", id,
		    reason2txt(reason), msg ? ": ": "", msg ? msg : "");
		if (msg != NULL)
			xfree(msg);
		if (lang != NULL)
			xfree(lang);
	}
	packet_check_eom();
	/* Free the channel.  This will also close the socket. */
	channel_free(c);
}

void
channel_input_window_adjust(int type, u_int32_t seq, void *ctxt)
{
	Channel *c;
	int id;
	u_int adjust;

	if (!compat20)
		return;

	/* Get the channel number and verify it. */
	id = packet_get_int();
	c = channel_lookup(id);

	if (c == NULL || c->type != SSH_CHANNEL_OPEN) {
		logit("Received window adjust for "
		    "non-open channel %d.", id);
		return;
	}
	adjust = packet_get_int();
	packet_check_eom();
	debug2("channel %d: rcvd adjust %u", id, adjust);
	c->remote_window += adjust;
}

void
channel_input_port_open(int type, u_int32_t seq, void *ctxt)
{
	Channel *c = NULL;
	u_short host_port;
	char *host, *originator_string;
	int remote_id, sock = -1;

	remote_id = packet_get_int();
	host = packet_get_string(NULL);
	host_port = packet_get_int();

	if (packet_get_protocol_flags() & SSH_PROTOFLAG_HOST_IN_FWD_OPEN) {
		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;
	}
	xfree(originator_string);
	if (c == NULL) {
		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 sock, r, success = 0, on = 1, wildcard = 0, is_client;
	struct addrinfo hints, *ai, *aitop;
	const char *host, *addr;
	char ntop[NI_MAXHOST], strport[NI_MAXSERV];

	host = (type == SSH_CHANNEL_RPORT_LISTENER) ?
	    listen_addr : host_to_connect;
	is_client = (type == SSH_CHANNEL_PORT_LISTENER);

	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;
	}

	/*
	 * Determine whether or not a port forward listens to loopback,
	 * specified address or wildcard. On the client, a specified bind 
	 * address will always override gateway_ports. On the server, a 
	 * gateway_ports of 1 (``yes'') will override the client's 
	 * specification and force a wildcard bind, whereas a value of 2 
	 * (``clientspecified'') will bind to whatever address the client 
	 * asked for.
	 *
	 * Special-case listen_addrs are:
	 *
	 * "0.0.0.0"               -> wildcard v4/v6 if SSH_OLD_FORWARD_ADDR
	 * "" (empty string), "*"  -> wildcard v4/v6
	 * "localhost"             -> loopback v4/v6
	 */
	addr = NULL;
	if (listen_addr == NULL) {
		/* No address specified: default to gateway_ports setting */
		if (gateway_ports)
			wildcard = 1;
	} else if (gateway_ports || is_client) {
		if (((datafellows & SSH_OLD_FORWARD_ADDR) &&
		    strcmp(listen_addr, "0.0.0.0") == 0) ||
		    *listen_addr == '\0' || strcmp(listen_addr, "*") == 0 ||
		    (!is_client && gateway_ports == 1))
			wildcard = 1;
		else if (strcmp(listen_addr, "localhost") != 0)
			addr = listen_addr;
	}

	debug3("channel_setup_fwd_listener: type %d wildcard %d addr %s",
	    type, wildcard, (addr == NULL) ? "NULL" : addr);

	/*
	 * 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 = wildcard ? AI_PASSIVE : 0;
	hints.ai_socktype = SOCK_STREAM;
	snprintf(strport, sizeof strport, "%d", listen_port);
	if ((r = getaddrinfo(addr, strport, &hints, &aitop)) != 0) {
		if (addr == NULL) {
			/* This really shouldn't happen */
			packet_disconnect("getaddrinfo: fatal error: %s",
			    gai_strerror(r));
		} else {
			verbose("channel_setup_fwd_listener: "
			    "getaddrinfo(%.64s): %s", addr, gai_strerror(r));
			packet_send_debug("channel_setup_fwd_listener: "
			    "getaddrinfo(%.64s): %s", addr, gai_strerror(r));
		}
		aitop = NULL;
	}

	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, ai->ai_socktype, ai->ai_protocol);
		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 */
			if (!ai->ai_next)
				error("bind: %.100s", strerror(errno));
			else
				verbose("bind: %.100s", strerror(errno));

			close(sock);
			continue;
		}
		/* Start listening for connections on the socket. */
		if (listen(sock, SSH_LISTEN_BACKLOG) < 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, "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;
}

int
channel_cancel_rport_listener(const char *host, u_short port)
{
	u_int i;
	int found = 0;

	for(i = 0; i < channels_alloc; i++) {
		Channel *c = channels[i];

		if (c != NULL && c->type == SSH_CHANNEL_RPORT_LISTENER &&
		    strncmp(c->path, host, sizeof(c->path)) == 0 &&
		    c->listening_port == port) {
			debug2("%s: close channel %d", __func__, i);
			channel_free(c);
			found = 1;
		}
	}

	return (found);
}

/* protocol local port fwd, used by ssh (and sshd in v1) */
int
channel_setup_local_fwd_listener(const char *listen_host, 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,
	    listen_host, 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(const char *listen_host, 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;
		if (listen_host == NULL)
			address_to_bind = "localhost";
		else if (*listen_host == '\0' || strcmp(listen_host, "*") == 0)
			address_to_bind = "";
		else
			address_to_bind = listen_host;

		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:
			logit("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++;
	}
}

/*
 * Request cancellation of remote forwarding of connection host:port from
 * local side.
 */
void
channel_request_rforward_cancel(const char *host, u_short port)
{
	int i;

	if (!compat20)
		return;

	for (i = 0; i < num_permitted_opens; i++) {
		if (permitted_opens[i].host_to_connect != NULL &&
		    permitted_opens[i].listen_port == port)
			break;
	}
	if (i >= num_permitted_opens) {
		debug("%s: requested forward not found", __func__);
		return;
	}
	packet_start(SSH2_MSG_GLOBAL_REQUEST);
	packet_put_cstring("cancel-tcpip-forward");
	packet_put_char(0);
	packet_put_cstring(host == NULL ? "" : host);
	packet_put_int(port);
	packet_send();

	permitted_opens[i].listen_port = 0;
	permitted_opens[i].por