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// Copyright (c) 2020 RethinkDNS and its authors.
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.
//
// This file incorporates work covered by the following copyright and
// permission notice:
//
// Copyright 2019 The Outline Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Derived from go-tun2socks's "direct" handler under the Apache 2.0 license.
package intra
import (
"context"
"errors"
"net"
"net/netip"
"sync"
"time"
"github.com/celzero/firestack/intra/core"
"github.com/celzero/firestack/intra/dnsx"
"github.com/celzero/firestack/intra/ipn"
"github.com/celzero/firestack/intra/log"
"github.com/celzero/firestack/intra/netstack"
"github.com/celzero/firestack/intra/protect"
"github.com/celzero/firestack/intra/settings"
"gvisor.dev/gvisor/pkg/tcpip/adapters/gonet"
)
type tcpHandler struct {
*baseHandler
nat *tcpNat
}
type tcpNat struct {
sync.Mutex
m map[string]map[netip.AddrPort]netip.AddrPort // proxyID => src => ext
}
func newTCPNat() *tcpNat {
return &tcpNat{m: make(map[string]map[netip.AddrPort]netip.AddrPort)}
}
func (t *tcpNat) assoc(pid string, src, ext netip.AddrPort) {
if t == nil || len(pid) == 0 || !sameFamily(src.Addr(), ext.Addr()) {
return
}
t.Lock()
defer t.Unlock()
m := t.m[pid]
if m == nil {
m = make(map[netip.AddrPort]netip.AddrPort)
t.m[pid] = m
}
m[src] = ext
}
func (t *tcpNat) lookup(pid string, src netip.AddrPort) (zz netip.AddrPort, ok bool) {
if t == nil || len(pid) == 0 || !src.IsValid() {
return
}
t.Lock()
defer t.Unlock()
if m := t.m[pid]; m != nil {
if ext, ok := m[src]; ok {
return ext, true
}
}
return
}
type ioinfo struct {
bytes int64
err error
}
const (
retryTimeout = 15 * time.Second
onFlowTimeout = 5 * time.Second
)
var (
errTcpFirewalled = errors.New("tcp: firewalled")
errTcpSetupConn = errors.New("tcp: could not create conn")
)
var _ netstack.GTCPConnHandler = (*tcpHandler)(nil)
// NewTCPHandler returns a TCP forwarder with Intra-style behavior.
// Connections to `fakedns` are redirected to DOH.
// All other traffic is forwarded using `dialer`.
// `listener` is provided with a summary of each socket when it is closed.
func NewTCPHandler(pctx context.Context, resolver dnsx.Resolver, prox ipn.ProxyProvider, listener SocketListener) netstack.GTCPConnHandler {
if listener == nil || core.IsNil(listener) {
log.W("tcp: using noop listener")
listener = nooplistener
}
h := &tcpHandler{
baseHandler: newBaseHandler(pctx, dnsx.NetTypeTCP, resolver, prox, listener),
nat: newTCPNat(),
}
core.Gx("tcp.ps", h.processSummaries)
log.I("tcp: new handler created")
return h
}
// Error implements netstack.GTCPConnHandler.
// It must be called from a goroutine.
func (h *tcpHandler) Error(gconn *netstack.GTCPConn, src, dst netip.AddrPort, err error) {
err = log.EE("tcp: error: %s => %s; err %v", src, dst, err)
if !src.IsValid() || !dst.IsValid() {
return
}
res, undidAlg, realips, domains := h.onFlow(src, dst)
h.maybeReplaceDest(res, &dst)
cid, uid, fid, pids := h.judge(res)
smm := tcpSummary(cid, uid, src.Addr(), dst.Addr())
if isAnyBlockPid(pids) {
smm.PID = ipn.Block
if undidAlg && len(realips) <= 0 && len(domains) > 0 {
err = core.JoinErr(err, errNoIPsForDomain)
} else {
err = core.JoinErr(errTcpFirewalled, err)
}
core.Go("tcp.stall."+fid, func() {
defer clos(gconn)
defer h.queueSummary(smm.done(err))
secs := h.stall(fid)
log.I("tcp: error: %s firewalled from %s => %s (dom: %s / real: %s) for %s; stall? %ds; err %v",
cid, src, dst, domains, realips, uid, secs, err)
})
return
}
h.queueSummary(smm.done(err))
}
func (h *tcpHandler) ReverseProxy(gconn *netstack.GTCPConn, in net.Conn, to, from netip.AddrPort) (open bool) {
fm := h.onInflow(to, from)
cid, uid, _, pids := h.judge(fm)
smm := tcpSummary(cid, uid, to.Addr(), from.Addr())
if settings.Debug {
log.VV("tcp: %s [%s]: reverse: %s => %s; pids: %v", cid, uid, from, to, pids)
}
if isAnyBlockPid(pids) {
log.I("tcp: %s [%s]: reverse: block %s => %s", cid, uid, from, to)
clos(gconn, in)
h.queueSummary(smm.done(errUdpInFirewalled))
return true
} // else: pid is ipn.Ingress
// handshake; since we assume a duplex-stream from here on
if open, err := gconn.Establish(); !open {
err = log.EE("tcp: %s [%s]: reverse: gconn.Est, err %v; %s => %s for %s",
cid, uid, err, to, from, uid)
h.queueSummary(smm.done(err))
return false
}
core.Go("tcp.reverse:"+cid, func() {
h.forward(gconn, rwext{in, tcptimeout}, smm)
})
return true
}
func (h *tcpHandler) handshakeIfNeededOrClose(gconn *netstack.GTCPConn, smm *SocketSummary) (bool, error) {
const allow bool = true // allowed
const deny bool = !allow // blocked
if _, err := gconn.Establish(); err != nil {
err = log.EE("tcp: %s handshake err %v; %s => %s for %s",
smm.ID, err, smm.Source, smm.Target, smm.UID)
// clos(gconn)
// h.queueSummary(smm.done(err))
return deny, err // == !open
}
return allow, nil
}
func (h *tcpHandler) natAssoc(pid string, src netip.AddrPort, addr net.Addr) {
if ext := netAddrPort(addr); ext.IsValid() {
h.nat.assoc(pid, src, ext)
}
}
func (h *tcpHandler) natLookup(pid string, src, target netip.AddrPort) (zz netip.AddrPort) {
if ext, ok := h.nat.lookup(pid, src); ok && sameFamily(ext.Addr(), target.Addr()) {
return ext
}
return
}
func netAddrPort(addr net.Addr) (zz netip.AddrPort) {
if addr == nil {
return
}
if v, ok := addr.(*net.TCPAddr); ok {
return v.AddrPort()
} else if ap, err := netip.ParseAddrPort(addr.String()); err == nil {
return ap
}
return
}
func sameFamily(a, b netip.Addr) bool {
if !a.IsValid() || !b.IsValid() {
return false
}
return a.Is4() == b.Is4()
}
// Proxy implements netstack.GTCPConnHandler
// It must be called from a goroutine.
func (h *tcpHandler) Proxy(gconn *netstack.GTCPConn, src, target netip.AddrPort) (open bool) {
const allow bool = true // allowed
const deny bool = !allow // blocked
var smm *SocketSummary
var err error
defer core.Recover(core.Exit11, "tcp.Proxy")
if !src.IsValid() || !target.IsValid() {
log.E("tcp: nil addr %s => %s; close err? %v", src, target, err)
clos(gconn) // gconn may be nil
return deny
}
// flow/dns-override are nat-aware, as in, they can deal with
// nat-ed ips just fine, and so, use target as-is instead of ipx4
res, undidAlg, realips, domains := h.onFlow(src, target)
h.maybeReplaceDest(res, &target)
// TODO: use res.IP only if set
filtered, excluded, fallingback := filterFamilyForDialingWithFailSafe(realips)
actualTargets := makeIPPorts(filtered, target, !undidAlg, 0)
cid, uid, fid, pids := h.judge(res, domains, target.String())
if len(actualTargets) <= 0 { // unlikely
actualTargets = []netip.AddrPort{target}
}
// actualTargets[0] may be same as target
smm = tcpSummary(cid, uid, src.Addr(), actualTargets[0].Addr())
if h.status.Load() == HDLEND {
err = log.EE("tcp: proxy: %s end %s => %s [%v]", cid, src, target, actualTargets)
clos(gconn)
h.queueSummary(smm.done(err))
return deny
}
if isAnyBlockPid(pids) {
smm.PID = ipn.Block
if undidAlg && len(realips) <= 0 && len(domains) > 0 {
err = errNoIPsForDomain
} else {
err = errTcpFirewalled
}
core.Go("tcp.stall."+fid, func() {
defer clos(gconn)
defer h.queueSummary(smm.done(err))
secs := h.stall(fid)
log.I("tcp: %s firewalled from %s => %s (dom: %s / real: %s) for %s; stall? %ds",
cid, src, target, domains, realips, uid, secs)
})
return deny
}
is6 := target.Addr().Is6() || src.Addr().Is6()
happyeyeballs := settings.HappyEyeballs.Load()
delayForHappyEyeballs := happyeyeballs && is6
if isAnyBasePid(pids) && h.isDNS(target) { // see udp.go:Connect
synack, synackerr := h.handshakeIfNeededOrClose(gconn, smm)
if !synack {
// if IPv6, stall a bit more so apps doing HappyEyeballs will try IPv4
if delayForHappyEyeballs {
time.Sleep(400 * time.Millisecond)
}
clos(gconn)
h.queueSummary(smm.done(synackerr))
return deny
}
if h.dnsOverride(gconn, uid) {
// SocketSummary not sent; x.DNSSummary supercedes it
// conn closed by resolver
return allow
} // else not a dns request
} // if ipn.Exit then let it connect as-is (aka exit)
if settings.Debug {
log.VV("tcp: %s proxying %s => %s [%v] (excluded: %v) for %s; pids: %s",
cid, src, target, actualTargets, excluded, uid, pids)
}
cont := true
// pick all realips to connect to
for i, dstipp := range actualTargets {
// dstipp may be v4 or v6 regardless of target addr
targetstr := dstipp.Addr().String()
var px ipn.Proxy = nil
px, err = h.prox.ProxyTo(dstipp, uid, pids)
// last chosen (but not dialed in) proxy (which error)
smm.Target = targetstr // addr may be invalid
smm.PID = pidstr(px) // px may be nil
smm.RPID = ipn.ViaID(px)
if err != nil || px == nil {
err = log.WE("tcp: dial: #%d: %s proxy(%s) to dst(%s) for %s; err %v",
i, cid, pidstr(px), dstipp, uid, err)
continue
}
if cont, err = h.handle(px, gconn, src, dstipp, delayForHappyEyeballs, smm); err == nil {
return allow // smm instead queued by handle() => forward()
} else {
end := time.Since(smm.start)
err = log.WE("tcp: dial: #%d: %s failed; addr(%s) / fallback? %t / cont? %t / he? %t; for uid %s (%s); w err(%v)",
i, cid, dstipp, fallingback, cont, happyeyeballs, uid, core.FmtPeriod(end), err)
if !cont || end > retryTimeout {
break // return err
} // else: continue; try the next realip
}
}
// if IPv6, stall a bit more so apps doing HappyEyeballs will try IPv4
if delayForHappyEyeballs {
time.Sleep(400 * time.Millisecond)
}
h.queueSummary(smm.done(err))
clos(gconn) // denied
return deny
}
// handle connects to the target via the proxy, and pipes data between the src, target; thread-safe.
func (h *tcpHandler) handle(px ipn.Proxy, gconn *netstack.GTCPConn, src, target netip.AddrPort, errOnNoRoute bool, smm *SocketSummary) (cont bool, err error) {
cont = true
stop := !cont
targetstr := target.String()
if errOnNoRoute {
if canroute := px.Router().Contains(targetstr); !canroute {
// make sure to not delay in HappyEyeballs scenario?
return cont, log.WE("proxy(%s) has no route to %s (<= %s)", pidstr(px), targetstr, src)
}
}
var bindAddr netip.AddrPort
pid := pidstr(px)
eim := settings.EndpointIndependentMapping.Load()
portfwd := settings.PortForward.Load()
canportfwd := portfwd && ipn.Remote(pid)
if eim { // bindAddr may be invalid
bindAddr = h.natLookup(pid, src, target)
}
if !bindAddr.IsValid() && canportfwd { // port forwarding overriden by eim
bindAddr = makeAnyAddrPort(src)
}
var pc protect.Conn
var dst net.Conn
start := time.Now()
if settings.Debug {
log.VV("tcp: %s dial %s: attempt(eim? %t / fwd? %t / canfwd? %t): %s [%s [%s]] => %s for %s",
smm.ID, pid, eim, portfwd, canportfwd, src, gconn.LocalAddr(), bindAddr, targetstr, smm.UID)
}
dialbindOK := false
// github.com/google/gvisor/blob/5ba35f516b5c2/test/benchmarks/tcp/tcp_proxy.go#L359
// ref: stackoverflow.com/questions/63656117
// ref: stackoverflow.com/questions/40328025
if bindAddr.IsValid() {
pc, err = px.Dialer().DialBind("tcp", bindAddr.String(), targetstr)
dialbindOK = err == nil
logwif(!dialbindOK)("tcp: %s dialbind ok? %t (%s [%s] => %s via %s); err? %v",
smm.ID, dialbindOK, src, bindAddr, targetstr, pid, err)
}
if !dialbindOK {
pc, err = px.Dialer().Dial("tcp", targetstr)
}
if err == nil {
smm.Rtt = time.Since(start).Milliseconds()
switch uc := pc.(type) {
case *net.TCPConn: // usual
dst = uc
case *gonet.TCPConn: // from wgproxy
dst = uc
case core.DuplexConn: // using retrier (local proxies like: exit & base)
dst = uc
case core.TCPConn: // from confirming proxy dialers
dst = uc
case net.Conn: // from non-confirming proxy dialers
// TODO: log warn?
dst = uc
default:
err = errTcpSetupConn
}
}
// pc.RemoteAddr may be that of the proxy, not the actual dst
// ex: pc.RemoteAddr is 127.0.0.1 for Orbot
smm.Target = target.Addr().String()
smm.PID = pidstr(px)
smm.RPID = ipn.ViaID(px)
if err != nil {
clos(pc)
log.W("tcp: err dialing %s proxy(%s) %v [%v] => %v (bind? %t) for %s: %v",
smm.ID, smm.PID, src, bindAddr, smm.Target, dialbindOK, smm.UID, err)
return cont, err
}
if _, synackerr := h.handshakeIfNeededOrClose(gconn, smm); synackerr != nil {
clos(pc)
return stop, synackerr
}
core.Go("tcp.forward."+smm.ID, func() {
h.listener.PostFlow(smm.postMark())
h.forward(gconn, rwext{dst, tcptimeout}, smm) // src always *gonet.TCPConn
// TODO assoc if forward was successful
if eim {
h.natAssoc(smm.PID, src, dst.LocalAddr())
}
})
return cont, nil // handled; takes ownership of src
}