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tailscale/net/portmapper/upnp.go

372 lines
12 KiB
Go

// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause
//go:build !js
// (no raw sockets in JS/WASM)
package portmapper
import (
"bufio"
"bytes"
"context"
"fmt"
"math/rand"
"net"
"net/http"
"net/netip"
"net/url"
"strings"
"time"
"github.com/tailscale/goupnp"
"github.com/tailscale/goupnp/dcps/internetgateway2"
"tailscale.com/control/controlknobs"
"tailscale.com/net/netns"
"tailscale.com/types/logger"
)
// References:
//
// WANIP Connection v2: http://upnp.org/specs/gw/UPnP-gw-WANIPConnection-v2-Service.pdf
// upnpMapping is a port mapping over the upnp protocol. After being created it is immutable,
// but the client field may be shared across mapping instances.
type upnpMapping struct {
gw netip.Addr
external netip.AddrPort
internal netip.AddrPort
goodUntil time.Time
renewAfter time.Time
// client is a connection to a upnp device, and may be reused across different UPnP mappings.
client upnpClient
}
// upnpProtocolUDP represents the protocol name for UDP, to be used in the UPnP
// <AddPortMapping> message in the <NewProtocol> field.
//
// NOTE: this must be an upper-case string, or certain routers will reject the
// mapping request. Other implementations like miniupnp send an upper-case
// protocol as well. See:
//
// https://github.com/tailscale/tailscale/issues/7377
const upnpProtocolUDP = "UDP"
func (u *upnpMapping) GoodUntil() time.Time { return u.goodUntil }
func (u *upnpMapping) RenewAfter() time.Time { return u.renewAfter }
func (u *upnpMapping) External() netip.AddrPort { return u.external }
func (u *upnpMapping) Release(ctx context.Context) {
u.client.DeletePortMapping(ctx, "", u.external.Port(), upnpProtocolUDP)
}
// upnpClient is an interface over the multiple different clients exported by goupnp,
// exposing the functions we need for portmapping. Those clients are auto-generated from XML-specs,
// which is why they're not very idiomatic.
type upnpClient interface {
AddPortMapping(
ctx context.Context,
// remoteHost is the remote device sending packets to this device, in the format of x.x.x.x.
// The empty string, "", means any host out on the internet can send packets in.
remoteHost string,
// externalPort is the exposed port of this port mapping. Visible during NAT operations.
// 0 will let the router select the port, but there is an additional call,
// `AddAnyPortMapping`, which is available on 1 of the 3 possible protocols,
// which should be used if available. See `addAnyPortMapping` below, which calls this if
// `AddAnyPortMapping` is not supported.
externalPort uint16,
// protocol is whether this is over TCP or UDP. Either "TCP" or "UDP".
protocol string,
// internalPort is the port that the gateway device forwards the traffic to.
internalPort uint16,
// internalClient is the IP address that packets will be forwarded to for this mapping.
// Internal client is of the form "x.x.x.x".
internalClient string,
// enabled is whether this portmapping should be enabled or disabled.
enabled bool,
// portMappingDescription is a user-readable description of this portmapping.
portMappingDescription string,
// leaseDurationSec is the duration of this portmapping. The value of this argument must be
// greater than 0. From the spec, it appears if it is set to 0, it will switch to using
// 604800 seconds, but not sure why this is desired. The recommended time is 3600 seconds.
leaseDurationSec uint32,
) error
DeletePortMapping(ctx context.Context, remoteHost string, externalPort uint16, protocol string) error
GetExternalIPAddress(ctx context.Context) (externalIPAddress string, err error)
}
// tsPortMappingDesc gets sent to UPnP clients as a human-readable label for the portmapping.
// It is not used for anything other than labelling.
const tsPortMappingDesc = "tailscale-portmap"
// addAnyPortMapping abstracts over different UPnP client connections, calling
// the available AddAnyPortMapping call if available for WAN IP connection v2,
// otherwise picking either the previous port (if one is present) or a random
// port and trying to obtain a mapping using AddPortMapping.
//
// It returns the new external port (which may not be identical to the external
// port specified), or an error.
//
// TODO(bradfitz): also returned the actual lease duration obtained. and check it regularly.
func addAnyPortMapping(
ctx context.Context,
upnp upnpClient,
externalPort uint16,
internalPort uint16,
internalClient string,
leaseDuration time.Duration,
) (newPort uint16, err error) {
// Some devices don't let clients add a port mapping for privileged
// ports (ports below 1024). Additionally, per section 2.3.18 of the
// UPnP spec, regarding the ExternalPort field:
//
// If this value is specified as a wildcard (i.e. 0), connection
// request on all external ports (that are not otherwise mapped)
// will be forwarded to InternalClient. In the wildcard case, the
// value(s) of InternalPort on InternalClient are ignored by the IGD
// for those connections that are forwarded to InternalClient.
// Obviously only one such entry can exist in the NAT at any time
// and conflicts are handled with a “first write wins” behavior.
//
// We obviously do not want to open all ports on the user's device to
// the internet, so we want to do this prior to calling either
// AddAnyPortMapping or AddPortMapping.
//
// Pick an external port that's greater than 1024 by getting a random
// number in [0, 65535 - 1024] and then adding 1024 to it, shifting the
// range to [1024, 65535].
if externalPort < 1024 {
externalPort = uint16(rand.Intn(65535-1024) + 1024)
}
// First off, try using AddAnyPortMapping; if there's a conflict, the
// router will pick another port and return it.
if upnp, ok := upnp.(*internetgateway2.WANIPConnection2); ok {
return upnp.AddAnyPortMapping(
ctx,
"",
externalPort,
upnpProtocolUDP,
internalPort,
internalClient,
true,
tsPortMappingDesc,
uint32(leaseDuration.Seconds()),
)
}
// Fall back to using AddPortMapping, which requests a mapping to/from
// a specific external port.
err = upnp.AddPortMapping(
ctx,
"",
externalPort,
upnpProtocolUDP,
internalPort,
internalClient,
true,
tsPortMappingDesc,
uint32(leaseDuration.Seconds()),
)
return externalPort, err
}
// getUPnPClient gets a client for interfacing with UPnP, ignoring the underlying protocol for
// now.
// Adapted from https://github.com/huin/goupnp/blob/master/GUIDE.md.
//
// The gw is the detected gateway.
//
// The meta is the most recently parsed UDP discovery packet response
// from the Internet Gateway Device.
//
// The provided ctx is not retained in the returned upnpClient, but
// its associated HTTP client is (if set via goupnp.WithHTTPClient).
func getUPnPClient(ctx context.Context, logf logger.Logf, debug DebugKnobs, gw netip.Addr, meta uPnPDiscoResponse) (client upnpClient, err error) {
if controlknobs.DisableUPnP() || debug.DisableUPnP {
return nil, nil
}
if meta.Location == "" {
return nil, nil
}
if debug.VerboseLogs {
logf("fetching %v", meta.Location)
}
u, err := url.Parse(meta.Location)
if err != nil {
return nil, err
}
ipp, err := netip.ParseAddrPort(u.Host)
if err != nil {
return nil, fmt.Errorf("unexpected host %q in %q", u.Host, meta.Location)
}
if ipp.Addr() != gw {
// https://github.com/tailscale/tailscale/issues/5502
logf("UPnP discovered root %q does not match gateway IP %v; repointing at gateway which is assumed to be floating",
meta.Location, gw)
u.Host = net.JoinHostPort(gw.String(), u.Port())
}
// We're fetching a smallish XML document over plain HTTP
// across the local LAN, without using DNS. There should be
// very few round trips and low latency, so one second is a
// long time.
ctx, cancel := context.WithTimeout(ctx, time.Second)
defer cancel()
// This part does a network fetch.
root, err := goupnp.DeviceByURL(ctx, u)
if err != nil {
return nil, err
}
defer func() {
if client == nil {
return
}
logf("saw UPnP type %v at %v; %v (%v)",
strings.TrimPrefix(fmt.Sprintf("%T", client), "*internetgateway2."),
meta.Location, root.Device.FriendlyName, root.Device.Manufacturer)
}()
// These parts don't do a network fetch.
// Pick the best service type available.
if cc, _ := internetgateway2.NewWANIPConnection2ClientsFromRootDevice(ctx, root, u); len(cc) > 0 {
return cc[0], nil
}
if cc, _ := internetgateway2.NewWANIPConnection1ClientsFromRootDevice(ctx, root, u); len(cc) > 0 {
return cc[0], nil
}
if cc, _ := internetgateway2.NewWANPPPConnection1ClientsFromRootDevice(ctx, root, u); len(cc) > 0 {
return cc[0], nil
}
return nil, nil
}
func (c *Client) upnpHTTPClientLocked() *http.Client {
if c.uPnPHTTPClient == nil {
c.uPnPHTTPClient = &http.Client{
Transport: &http.Transport{
DialContext: netns.NewDialer(c.logf, c.netMon).DialContext,
IdleConnTimeout: 2 * time.Second, // LAN is cheap
},
}
}
return c.uPnPHTTPClient
}
// getUPnPPortMapping attempts to create a port-mapping over the UPnP protocol. On success,
// it will return the externally exposed IP and port. Otherwise, it will return a zeroed IP and
// port and an error.
func (c *Client) getUPnPPortMapping(
ctx context.Context,
gw netip.Addr,
internal netip.AddrPort,
prevPort uint16,
) (external netip.AddrPort, ok bool) {
if controlknobs.DisableUPnP() || c.debug.DisableUPnP {
return netip.AddrPort{}, false
}
now := time.Now()
upnp := &upnpMapping{
gw: gw,
internal: internal,
}
var client upnpClient
var err error
c.mu.Lock()
oldMapping, ok := c.mapping.(*upnpMapping)
meta := c.uPnPMeta
httpClient := c.upnpHTTPClientLocked()
c.mu.Unlock()
if ok && oldMapping != nil {
client = oldMapping.client
} else {
ctx := goupnp.WithHTTPClient(ctx, httpClient)
client, err = getUPnPClient(ctx, c.logf, c.debug, gw, meta)
if c.debug.VerboseLogs {
c.logf("getUPnPClient: %T, %v", client, err)
}
if err != nil {
return netip.AddrPort{}, false
}
}
if client == nil {
return netip.AddrPort{}, false
}
var newPort uint16
newPort, err = addAnyPortMapping(
ctx,
client,
prevPort,
internal.Port(),
internal.Addr().String(),
time.Second*pmpMapLifetimeSec,
)
if c.debug.VerboseLogs {
c.logf("addAnyPortMapping: %v, err=%q", newPort, err)
}
if err != nil {
return netip.AddrPort{}, false
}
// TODO cache this ip somewhere?
extIP, err := client.GetExternalIPAddress(ctx)
if c.debug.VerboseLogs {
c.logf("client.GetExternalIPAddress: %v, %v", extIP, err)
}
if err != nil {
// TODO this doesn't seem right
return netip.AddrPort{}, false
}
externalIP, err := netip.ParseAddr(extIP)
if err != nil {
return netip.AddrPort{}, false
}
upnp.external = netip.AddrPortFrom(externalIP, newPort)
d := time.Duration(pmpMapLifetimeSec) * time.Second
upnp.goodUntil = now.Add(d)
upnp.renewAfter = now.Add(d / 2)
upnp.client = client
c.mu.Lock()
defer c.mu.Unlock()
c.mapping = upnp
c.localPort = newPort
return upnp.external, true
}
type uPnPDiscoResponse struct {
Location string
// Server describes what version the UPnP is, such as MiniUPnPd/2.x.x
Server string
// USN is the serial number of the device, which also contains
// what kind of UPnP service is being offered, i.e. InternetGatewayDevice:2
USN string
}
// parseUPnPDiscoResponse parses a UPnP HTTP-over-UDP discovery response.
func parseUPnPDiscoResponse(body []byte) (uPnPDiscoResponse, error) {
var r uPnPDiscoResponse
res, err := http.ReadResponse(bufio.NewReaderSize(bytes.NewReader(body), 128), nil)
if err != nil {
return r, err
}
r.Location = res.Header.Get("Location")
r.Server = res.Header.Get("Server")
r.USN = res.Header.Get("Usn")
return r, nil
}