tailscale/ipn/ipnlocal/peerapi.go

// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package ipnlocal

import (
	"context"
	"errors"
	"fmt"
	"hash/crc32"
	"html"
	"io"
	"net"
	"net/http"
	"runtime"
	"strconv"

	"inet.af/netaddr"
	"tailscale.com/net/interfaces"
	"tailscale.com/tailcfg"
)

var initListenConfig func(*net.ListenConfig, netaddr.IP, *interfaces.State, string) error

func peerAPIListen(ip netaddr.IP, ifState *interfaces.State, tunIfName string) (ln net.Listener, err error) {
	ipStr := ip.String()

	var lc net.ListenConfig
	if initListenConfig != nil {
		// On iOS/macOS, this sets the lc.Control hook to
		// setsockopt the interface index to bind to, to get
		// out of the network sandbox.
		if err := initListenConfig(&lc, ip, ifState, tunIfName); err != nil {
			return nil, err
		}
		if runtime.GOOS == "darwin" || runtime.GOOS == "ios" {
			ipStr = ""
		}
	}

	tcp4or6 := "tcp4"
	if ip.Is6() {
		tcp4or6 = "tcp6"
	}

	// Make a best effort to pick a deterministic port number for
	// the ip The lower three bytes are the same for IPv4 and IPv6
	// Tailscale addresses (at least currently), so we'll usually
	// get the same port number on both address families for
	// dev/debugging purposes, which is nice. But it's not so
	// deterministic that people will bake this into clients.
	// We try a few times just in case something's already
	// listening on that port (on all interfaces, probably).
	for try := uint8(0); try < 5; try++ {
		a16 := ip.As16()
		hashData := a16[len(a16)-3:]
		hashData[0] += try
		tryPort := (32 << 10) | uint16(crc32.ChecksumIEEE(hashData))
		ln, err = lc.Listen(context.Background(), tcp4or6, net.JoinHostPort(ipStr, strconv.Itoa(int(tryPort))))
		if err == nil {
			return ln, nil
		}
	}
	// Fall back to random ephemeral port.
	return lc.Listen(context.Background(), tcp4or6, net.JoinHostPort(ipStr, "0"))
}

type peerAPIListener struct {
	ln       net.Listener
	lb       *LocalBackend
	urlStr   string
	selfNode *tailcfg.Node
}

func (pln *peerAPIListener) Port() int {
	ta, ok := pln.ln.Addr().(*net.TCPAddr)
	if !ok {
		return 0
	}
	return ta.Port
}

func (pln *peerAPIListener) serve() {
	defer pln.ln.Close()
	logf := pln.lb.logf
	for {
		c, err := pln.ln.Accept()
		if errors.Is(err, net.ErrClosed) {
			return
		}
		if err != nil {
			logf("peerapi.Accept: %v", err)
			return
		}
		ta, ok := c.RemoteAddr().(*net.TCPAddr)
		if !ok {
			c.Close()
			logf("peerapi: unexpected RemoteAddr %#v", c.RemoteAddr())
			continue
		}
		ipp, ok := netaddr.FromStdAddr(ta.IP, ta.Port, "")
		if !ok {
			logf("peerapi: bogus TCPAddr %#v", ta)
			c.Close()
			continue
		}
		peerNode, peerUser, ok := pln.lb.WhoIs(ipp)
		if !ok {
			logf("peerapi: unknown peer %v", ipp)
			c.Close()
			continue
		}
		h := &peerAPIHandler{
			isSelf:     pln.selfNode.User == peerNode.User,
			remoteAddr: ipp,
			peerNode:   peerNode,
			peerUser:   peerUser,
			lb:         pln.lb,
		}
		httpServer := &http.Server{
			Handler: h,
		}
		go httpServer.Serve(&oneConnListener{Listener: pln.ln, conn: c})
	}
}

type oneConnListener struct {
	net.Listener
	conn net.Conn
}

func (l *oneConnListener) Accept() (c net.Conn, err error) {
	c = l.conn
	if c == nil {
		err = io.EOF
		return
	}
	err = nil
	l.conn = nil
	return
}

func (l *oneConnListener) Close() error { return nil }

// peerAPIHandler serves the Peer API for a source specific client.
type peerAPIHandler struct {
	remoteAddr netaddr.IPPort
	isSelf     bool                // whether peerNode is owned by same user as this node
	peerNode   *tailcfg.Node       // peerNode is who's making the request
	peerUser   tailcfg.UserProfile // profile of peerNode
	lb         *LocalBackend
}

func (h *peerAPIHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	who := h.peerUser.DisplayName
	fmt.Fprintf(w, `<html>
<meta name="viewport" content="width=device-width, initial-scale=1">
<body>
<h1>Hello, %s (%v)</h1>
This is my Tailscale device. Your device is %v.
`, html.EscapeString(who), h.remoteAddr.IP, html.EscapeString(h.peerNode.ComputedName))

	if h.isSelf {
		fmt.Fprintf(w, "<p>You are the owner of this node.\n")
	}
}
ipn/ipnlocal: start of peerapi between nodes Also some necessary refactoring of the ipn/ipnstate too. Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com> 3 years ago			`// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.`
			`// Use of this source code is governed by a BSD-style`
			`// license that can be found in the LICENSE file.`

			`package ipnlocal`

			`import (`
			`"context"`
			`"errors"`
			`"fmt"`
			`"hash/crc32"`
			`"html"`
			`"io"`
			`"net"`
			`"net/http"`
ipn/ipnlocal: get peerapi ~working in macOS/iOS NetworkExtension sandbox IPv4 and IPv6 both work remotely, but IPv6 doesn't yet work from the machine itself due to routing mysteries. Untested yet on iOS, but previous prototype worked on iOS, so should work the same. Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com> 3 years ago			`"runtime"`
ipn/ipnlocal: start of peerapi between nodes Also some necessary refactoring of the ipn/ipnstate too. Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com> 3 years ago			`"strconv"`

			`"inet.af/netaddr"`
ipn/ipnlocal: pass down interface state to peerapi ListenConfig hook Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com> 3 years ago			`"tailscale.com/net/interfaces"`
ipn/ipnlocal: start of peerapi between nodes Also some necessary refactoring of the ipn/ipnstate too. Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com> 3 years ago			`"tailscale.com/tailcfg"`
			`)`

ipn/ipnlocal: get peerapi ~working in macOS/iOS NetworkExtension sandbox IPv4 and IPv6 both work remotely, but IPv6 doesn't yet work from the machine itself due to routing mysteries. Untested yet on iOS, but previous prototype worked on iOS, so should work the same. Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com> 3 years ago			`var initListenConfig func(net.ListenConfig, netaddr.IP, interfaces.State, string) error`

			`func peerAPIListen(ip netaddr.IP, ifState *interfaces.State, tunIfName string) (ln net.Listener, err error) {`
			`ipStr := ip.String()`
ipn/ipnlocal: start of peerapi between nodes Also some necessary refactoring of the ipn/ipnstate too. Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com> 3 years ago
			`var lc net.ListenConfig`
			`if initListenConfig != nil {`
			`// On iOS/macOS, this sets the lc.Control hook to`
			`// setsockopt the interface index to bind to, to get`
			`// out of the network sandbox.`
ipn/ipnlocal: get peerapi ~working in macOS/iOS NetworkExtension sandbox IPv4 and IPv6 both work remotely, but IPv6 doesn't yet work from the machine itself due to routing mysteries. Untested yet on iOS, but previous prototype worked on iOS, so should work the same. Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com> 3 years ago			`if err := initListenConfig(&lc, ip, ifState, tunIfName); err != nil {`
ipn/ipnlocal: start of peerapi between nodes Also some necessary refactoring of the ipn/ipnstate too. Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com> 3 years ago			`return nil, err`
			`}`
ipn/ipnlocal: get peerapi ~working in macOS/iOS NetworkExtension sandbox IPv4 and IPv6 both work remotely, but IPv6 doesn't yet work from the machine itself due to routing mysteries. Untested yet on iOS, but previous prototype worked on iOS, so should work the same. Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com> 3 years ago			`if runtime.GOOS == "darwin" \|\| runtime.GOOS == "ios" {`
			`ipStr = ""`
			`}`
			`}`

			`tcp4or6 := "tcp4"`
			`if ip.Is6() {`
			`tcp4or6 = "tcp6"`
ipn/ipnlocal: start of peerapi between nodes Also some necessary refactoring of the ipn/ipnstate too. Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com> 3 years ago			`}`
ipn/ipnlocal: get peerapi ~working in macOS/iOS NetworkExtension sandbox IPv4 and IPv6 both work remotely, but IPv6 doesn't yet work from the machine itself due to routing mysteries. Untested yet on iOS, but previous prototype worked on iOS, so should work the same. Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com> 3 years ago
ipn/ipnlocal: start of peerapi between nodes Also some necessary refactoring of the ipn/ipnstate too. Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com> 3 years ago			`// Make a best effort to pick a deterministic port number for`
			`// the ip The lower three bytes are the same for IPv4 and IPv6`
			`// Tailscale addresses (at least currently), so we'll usually`
			`// get the same port number on both address families for`
			`// dev/debugging purposes, which is nice. But it's not so`
			`// deterministic that people will bake this into clients.`
			`// We try a few times just in case something's already`
			`// listening on that port (on all interfaces, probably).`
			`for try := uint8(0); try < 5; try++ {`
			`a16 := ip.As16()`
			`hashData := a16[len(a16)-3:]`
			`hashData[0] += try`
			`tryPort := (32 << 10) \| uint16(crc32.ChecksumIEEE(hashData))`
ipn/ipnlocal: get peerapi ~working in macOS/iOS NetworkExtension sandbox IPv4 and IPv6 both work remotely, but IPv6 doesn't yet work from the machine itself due to routing mysteries. Untested yet on iOS, but previous prototype worked on iOS, so should work the same. Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com> 3 years ago			`ln, err = lc.Listen(context.Background(), tcp4or6, net.JoinHostPort(ipStr, strconv.Itoa(int(tryPort))))`
ipn/ipnlocal: start of peerapi between nodes Also some necessary refactoring of the ipn/ipnstate too. Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com> 3 years ago			`if err == nil {`
			`return ln, nil`
			`}`
			`}`
			`// Fall back to random ephemeral port.`
ipn/ipnlocal: get peerapi ~working in macOS/iOS NetworkExtension sandbox IPv4 and IPv6 both work remotely, but IPv6 doesn't yet work from the machine itself due to routing mysteries. Untested yet on iOS, but previous prototype worked on iOS, so should work the same. Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com> 3 years ago			`return lc.Listen(context.Background(), tcp4or6, net.JoinHostPort(ipStr, "0"))`
ipn/ipnlocal: start of peerapi between nodes Also some necessary refactoring of the ipn/ipnstate too. Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com> 3 years ago			`}`

			`type peerAPIListener struct {`
ipn/ipnlocal: rename/document peerapi stuff a bit, pass self identity So handlers can vary based on whether owner of peer matches owner of local node. Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com> 3 years ago			`ln net.Listener`
			`lb *LocalBackend`
			`urlStr string`
			`selfNode *tailcfg.Node`
ipn/ipnlocal: get peerapi ~working in macOS/iOS NetworkExtension sandbox IPv4 and IPv6 both work remotely, but IPv6 doesn't yet work from the machine itself due to routing mysteries. Untested yet on iOS, but previous prototype worked on iOS, so should work the same. Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com> 3 years ago			`}`

			`func (pln *peerAPIListener) Port() int {`
			`ta, ok := pln.ln.Addr().(*net.TCPAddr)`
			`if !ok {`
			`return 0`
			`}`
			`return ta.Port`
ipn/ipnlocal: start of peerapi between nodes Also some necessary refactoring of the ipn/ipnstate too. Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com> 3 years ago			`}`

			`func (pln *peerAPIListener) serve() {`
			`defer pln.ln.Close()`
			`logf := pln.lb.logf`
			`for {`
			`c, err := pln.ln.Accept()`
			`if errors.Is(err, net.ErrClosed) {`
			`return`
			`}`
			`if err != nil {`
			`logf("peerapi.Accept: %v", err)`
			`return`
			`}`
			`ta, ok := c.RemoteAddr().(*net.TCPAddr)`
			`if !ok {`
			`c.Close()`
			`logf("peerapi: unexpected RemoteAddr %#v", c.RemoteAddr())`
			`continue`
			`}`
			`ipp, ok := netaddr.FromStdAddr(ta.IP, ta.Port, "")`
			`if !ok {`
			`logf("peerapi: bogus TCPAddr %#v", ta)`
			`c.Close()`
			`continue`
			`}`
			`peerNode, peerUser, ok := pln.lb.WhoIs(ipp)`
			`if !ok {`
			`logf("peerapi: unknown peer %v", ipp)`
			`c.Close()`
			`continue`
			`}`
ipn/ipnlocal: rename/document peerapi stuff a bit, pass self identity So handlers can vary based on whether owner of peer matches owner of local node. Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com> 3 years ago			`h := &peerAPIHandler{`
			`isSelf: pln.selfNode.User == peerNode.User,`
ipn/ipnlocal: start of peerapi between nodes Also some necessary refactoring of the ipn/ipnstate too. Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com> 3 years ago			`remoteAddr: ipp,`
			`peerNode: peerNode,`
			`peerUser: peerUser,`
			`lb: pln.lb,`
			`}`
			`httpServer := &http.Server{`
ipn/ipnlocal: rename/document peerapi stuff a bit, pass self identity So handlers can vary based on whether owner of peer matches owner of local node. Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com> 3 years ago			`Handler: h,`
ipn/ipnlocal: start of peerapi between nodes Also some necessary refactoring of the ipn/ipnstate too. Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com> 3 years ago			`}`
			`go httpServer.Serve(&oneConnListener{Listener: pln.ln, conn: c})`
			`}`
			`}`

			`type oneConnListener struct {`
			`net.Listener`
			`conn net.Conn`
			`}`

			`func (l *oneConnListener) Accept() (c net.Conn, err error) {`
			`c = l.conn`
			`if c == nil {`
			`err = io.EOF`
			`return`
			`}`
			`err = nil`
			`l.conn = nil`
			`return`
			`}`

			`func (l *oneConnListener) Close() error { return nil }`

ipn/ipnlocal: rename/document peerapi stuff a bit, pass self identity So handlers can vary based on whether owner of peer matches owner of local node. Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com> 3 years ago			`// peerAPIHandler serves the Peer API for a source specific client.`
			`type peerAPIHandler struct {`
ipn/ipnlocal: start of peerapi between nodes Also some necessary refactoring of the ipn/ipnstate too. Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com> 3 years ago			`remoteAddr netaddr.IPPort`
ipn/ipnlocal: rename/document peerapi stuff a bit, pass self identity So handlers can vary based on whether owner of peer matches owner of local node. Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com> 3 years ago			`isSelf bool // whether peerNode is owned by same user as this node`
			`peerNode *tailcfg.Node // peerNode is who's making the request`
			`peerUser tailcfg.UserProfile // profile of peerNode`
ipn/ipnlocal: start of peerapi between nodes Also some necessary refactoring of the ipn/ipnstate too. Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com> 3 years ago			`lb *LocalBackend`
			`}`

ipn/ipnlocal: rename/document peerapi stuff a bit, pass self identity So handlers can vary based on whether owner of peer matches owner of local node. Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com> 3 years ago			`func (h peerAPIHandler) ServeHTTP(w http.ResponseWriter, r http.Request) {`
			`who := h.peerUser.DisplayName`
ipn/ipnlocal: start of peerapi between nodes Also some necessary refactoring of the ipn/ipnstate too. Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com> 3 years ago			fmt.Fprintf(w, `<html>
			`<meta name="viewport" content="width=device-width, initial-scale=1">`
			`<body>`
			`<h1>Hello, %s (%v)</h1>`
			`This is my Tailscale device. Your device is %v.`
ipn/ipnlocal: rename/document peerapi stuff a bit, pass self identity So handlers can vary based on whether owner of peer matches owner of local node. Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com> 3 years ago			`, html.EscapeString(who), h.remoteAddr.IP, html.EscapeString(h.peerNode.ComputedName))
ipn/ipnlocal: start of peerapi between nodes Also some necessary refactoring of the ipn/ipnstate too. Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com> 3 years ago
ipn/ipnlocal: rename/document peerapi stuff a bit, pass self identity So handlers can vary based on whether owner of peer matches owner of local node. Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com> 3 years ago			`if h.isSelf {`
			`fmt.Fprintf(w, "<p>You are the owner of this node.\n")`
			`}`
ipn/ipnlocal: start of peerapi between nodes Also some necessary refactoring of the ipn/ipnstate too. Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com> 3 years ago			`}`