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tailscale/control/controlclient/noise.go

511 lines
15 KiB
Go

// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause
package controlclient
import (
"bytes"
"context"
"encoding/binary"
"encoding/json"
"errors"
"io"
"math"
"net/http"
"net/url"
"sync"
"time"
"golang.org/x/net/http2"
"tailscale.com/control/controlbase"
"tailscale.com/control/controlhttp"
"tailscale.com/net/dnscache"
"tailscale.com/net/netmon"
"tailscale.com/net/tsdial"
"tailscale.com/tailcfg"
"tailscale.com/tstime"
"tailscale.com/types/key"
"tailscale.com/types/logger"
"tailscale.com/util/mak"
"tailscale.com/util/multierr"
"tailscale.com/util/singleflight"
)
// noiseConn is a wrapper around controlbase.Conn.
// It allows attaching an ID to a connection to allow
// cleaning up references in the pool when the connection
// is closed.
type noiseConn struct {
*controlbase.Conn
id int
pool *NoiseClient
h2cc *http2.ClientConn
readHeaderOnce sync.Once // guards init of reader field
reader io.Reader // (effectively Conn.Reader after header)
earlyPayloadReady chan struct{} // closed after earlyPayload is set (including set to nil)
earlyPayload *tailcfg.EarlyNoise
earlyPayloadErr error
}
func (c *noiseConn) RoundTrip(r *http.Request) (*http.Response, error) {
return c.h2cc.RoundTrip(r)
}
// getEarlyPayload waits for the early noise payload to arrive.
// It may return (nil, nil) if the server begins HTTP/2 without one.
func (c *noiseConn) getEarlyPayload(ctx context.Context) (*tailcfg.EarlyNoise, error) {
select {
case <-c.earlyPayloadReady:
return c.earlyPayload, c.earlyPayloadErr
case <-ctx.Done():
return nil, ctx.Err()
}
}
// The first 9 bytes from the server to client over Noise are either an HTTP/2
// settings frame (a normal HTTP/2 setup) or, as we added later, an "early payload"
// header that's also 9 bytes long: 5 bytes (earlyPayloadMagic) followed by 4 bytes
// of length. Then that many bytes of JSON-encoded tailcfg.EarlyNoise.
// The early payload is optional. Some servers may not send it.
const (
hdrLen = 9 // http2 frame header size; also size of our early payload size header
earlyPayloadMagic = "\xff\xff\xffTS"
)
// returnErrReader is an io.Reader that always returns an error.
type returnErrReader struct {
err error // the error to return
}
func (r returnErrReader) Read([]byte) (int, error) { return 0, r.err }
// Read is basically the same as controlbase.Conn.Read, but it first reads the
// "early payload" header from the server which may or may not be present,
// depending on the server.
func (c *noiseConn) Read(p []byte) (n int, err error) {
c.readHeaderOnce.Do(c.readHeader)
return c.reader.Read(p)
}
// readHeader reads the optional "early payload" from the server that arrives
// after the Noise handshake but before the HTTP/2 session begins.
//
// readHeader is responsible for reading the header (if present), initializing
// c.earlyPayload, closing c.earlyPayloadReady, and initializing c.reader for
// future reads.
func (c *noiseConn) readHeader() {
defer close(c.earlyPayloadReady)
setErr := func(err error) {
c.reader = returnErrReader{err}
c.earlyPayloadErr = err
}
var hdr [hdrLen]byte
if _, err := io.ReadFull(c.Conn, hdr[:]); err != nil {
setErr(err)
return
}
if string(hdr[:len(earlyPayloadMagic)]) != earlyPayloadMagic {
// No early payload. We have to return the 9 bytes read we already
// consumed.
c.reader = io.MultiReader(bytes.NewReader(hdr[:]), c.Conn)
return
}
epLen := binary.BigEndian.Uint32(hdr[len(earlyPayloadMagic):])
if epLen > 10<<20 {
setErr(errors.New("invalid early payload length"))
return
}
payBuf := make([]byte, epLen)
if _, err := io.ReadFull(c.Conn, payBuf); err != nil {
setErr(err)
return
}
if err := json.Unmarshal(payBuf, &c.earlyPayload); err != nil {
setErr(err)
return
}
c.reader = c.Conn
}
func (c *noiseConn) Close() error {
if err := c.Conn.Close(); err != nil {
return err
}
c.pool.connClosed(c.id)
return nil
}
// NoiseClient provides a http.Client to connect to tailcontrol over
// the ts2021 protocol.
type NoiseClient struct {
// Client is an HTTP client to talk to the coordination server.
// It automatically makes a new Noise connection as needed.
// It does not support node key proofs. To do that, call
// noiseClient.getConn instead to make a connection.
*http.Client
// h2t is the HTTP/2 transport we use a bit to create new
// *http2.ClientConns. We don't use its connection pool and we don't use its
// dialing. We use it for exactly one reason: its idle timeout that can only
// be configured via the HTTP/1 config. And then we call NewClientConn (with
// an existing Noise connection) on the http2.Transport which sets up an
// http2.ClientConn using that idle timeout from an http1.Transport.
h2t *http2.Transport
// sfDial ensures that two concurrent requests for a noise connection only
// produce one shared one between the two callers.
sfDial singleflight.Group[struct{}, *noiseConn]
dialer *tsdial.Dialer
dnsCache *dnscache.Resolver
privKey key.MachinePrivate
serverPubKey key.MachinePublic
host string // the host part of serverURL
httpPort string // the default port to call
httpsPort string // the fallback Noise-over-https port
// dialPlan optionally returns a ControlDialPlan previously received
// from the control server; either the function or the return value can
// be nil.
dialPlan func() *tailcfg.ControlDialPlan
logf logger.Logf
netMon *netmon.Monitor
// mu only protects the following variables.
mu sync.Mutex
closed bool
last *noiseConn // or nil
nextID int
connPool map[int]*noiseConn // active connections not yet closed; see noiseConn.Close
}
// NoiseOpts contains options for the NewNoiseClient function. All fields are
// required unless otherwise specified.
type NoiseOpts struct {
// PrivKey is this node's private key.
PrivKey key.MachinePrivate
// ServerPubKey is the public key of the server.
ServerPubKey key.MachinePublic
// ServerURL is the URL of the server to connect to.
ServerURL string
// Dialer's SystemDial function is used to connect to the server.
Dialer *tsdial.Dialer
// DNSCache is the caching Resolver to use to connect to the server.
//
// This field can be nil.
DNSCache *dnscache.Resolver
// Logf is the log function to use. This field can be nil.
Logf logger.Logf
// NetMon is the network monitor that, if set, will be used to get the
// network interface state. This field can be nil; if so, the current
// state will be looked up dynamically.
NetMon *netmon.Monitor
// DialPlan, if set, is a function that should return an explicit plan
// on how to connect to the server.
DialPlan func() *tailcfg.ControlDialPlan
}
// NewNoiseClient returns a new noiseClient for the provided server and machine key.
// serverURL is of the form https://<host>:<port> (no trailing slash).
//
// netMon may be nil, if non-nil it's used to do faster interface lookups.
// dialPlan may be nil
func NewNoiseClient(opts NoiseOpts) (*NoiseClient, error) {
u, err := url.Parse(opts.ServerURL)
if err != nil {
return nil, err
}
var httpPort string
var httpsPort string
if u.Port() != "" {
// If there is an explicit port specified, trust the scheme and hope for the best
if u.Scheme == "http" {
httpPort = u.Port()
httpsPort = "443"
} else {
httpPort = "80"
httpsPort = u.Port()
}
} else {
// Otherwise, use the standard ports
httpPort = "80"
httpsPort = "443"
}
np := &NoiseClient{
serverPubKey: opts.ServerPubKey,
privKey: opts.PrivKey,
host: u.Hostname(),
httpPort: httpPort,
httpsPort: httpsPort,
dialer: opts.Dialer,
dnsCache: opts.DNSCache,
dialPlan: opts.DialPlan,
logf: opts.Logf,
netMon: opts.NetMon,
}
// Create the HTTP/2 Transport using a net/http.Transport
// (which only does HTTP/1) because it's the only way to
// configure certain properties on the http2.Transport. But we
// never actually use the net/http.Transport for any HTTP/1
// requests.
h2Transport, err := http2.ConfigureTransports(&http.Transport{
IdleConnTimeout: time.Minute,
})
if err != nil {
return nil, err
}
np.h2t = h2Transport
np.Client = &http.Client{Transport: np}
return np, nil
}
// GetSingleUseRoundTripper returns a RoundTripper that can be only be used once
// (and must be used once) to make a single HTTP request over the noise channel
// to the coordination server.
//
// In addition to the RoundTripper, it returns the HTTP/2 channel's early noise
// payload, if any.
func (nc *NoiseClient) GetSingleUseRoundTripper(ctx context.Context) (http.RoundTripper, *tailcfg.EarlyNoise, error) {
for tries := 0; tries < 3; tries++ {
conn, err := nc.getConn(ctx)
if err != nil {
return nil, nil, err
}
earlyPayloadMaybeNil, err := conn.getEarlyPayload(ctx)
if err != nil {
return nil, nil, err
}
if conn.h2cc.ReserveNewRequest() {
return conn, earlyPayloadMaybeNil, nil
}
}
return nil, nil, errors.New("[unexpected] failed to reserve a request on a connection")
}
// contextErr is an error that wraps another error and is used to indicate that
// the error was because a context expired.
type contextErr struct {
err error
}
func (e contextErr) Error() string {
return e.err.Error()
}
func (e contextErr) Unwrap() error {
return e.err
}
// getConn returns a noiseConn that can be used to make requests to the
// coordination server. It may return a cached connection or create a new one.
// Dials are singleflighted, so concurrent calls to getConn may only dial once.
// As such, context values may not be respected as there are no guarantees that
// the context passed to getConn is the same as the context passed to dial.
func (nc *NoiseClient) getConn(ctx context.Context) (*noiseConn, error) {
nc.mu.Lock()
if last := nc.last; last != nil && last.canTakeNewRequest() {
nc.mu.Unlock()
return last, nil
}
nc.mu.Unlock()
for {
// We singeflight the dial to avoid making multiple connections, however
// that means that we can't simply cancel the dial if the context is
// canceled. Instead, we have to additionally check that the context
// which was canceled is our context and retry if our context is still
// valid.
conn, err, _ := nc.sfDial.Do(struct{}{}, func() (*noiseConn, error) {
c, err := nc.dial(ctx)
if err != nil {
if ctx.Err() != nil {
return nil, contextErr{ctx.Err()}
}
return nil, err
}
return c, nil
})
var ce contextErr
if err == nil || !errors.As(err, &ce) {
return conn, err
}
if ctx.Err() == nil {
// The dial failed because of a context error, but our context
// is still valid. Retry.
continue
}
// The dial failed because our context was canceled. Return the
// underlying error.
return nil, ce.Unwrap()
}
}
func (nc *NoiseClient) RoundTrip(req *http.Request) (*http.Response, error) {
ctx := req.Context()
conn, err := nc.getConn(ctx)
if err != nil {
return nil, err
}
return conn.RoundTrip(req)
}
// connClosed removes the connection with the provided ID from the pool
// of active connections.
func (nc *NoiseClient) connClosed(id int) {
nc.mu.Lock()
defer nc.mu.Unlock()
conn := nc.connPool[id]
if conn != nil {
delete(nc.connPool, id)
if nc.last == conn {
nc.last = nil
}
}
}
// Close closes all the underlying noise connections.
// It is a no-op and returns nil if the connection is already closed.
func (nc *NoiseClient) Close() error {
nc.mu.Lock()
nc.closed = true
conns := nc.connPool
nc.connPool = nil
nc.mu.Unlock()
var errors []error
for _, c := range conns {
if err := c.Close(); err != nil {
errors = append(errors, err)
}
}
return multierr.New(errors...)
}
// dial opens a new connection to tailcontrol, fetching the server noise key
// if not cached.
func (nc *NoiseClient) dial(ctx context.Context) (*noiseConn, error) {
nc.mu.Lock()
connID := nc.nextID
nc.nextID++
nc.mu.Unlock()
if tailcfg.CurrentCapabilityVersion > math.MaxUint16 {
// Panic, because a test should have started failing several
// thousand version numbers before getting to this point.
panic("capability version is too high to fit in the wire protocol")
}
var dialPlan *tailcfg.ControlDialPlan
if nc.dialPlan != nil {
dialPlan = nc.dialPlan()
}
// If we have a dial plan, then set our timeout as slightly longer than
// the maximum amount of time contained therein; we assume that
// explicit instructions on timeouts are more useful than a single
// hard-coded timeout.
//
// The default value of 5 is chosen so that, when there's no dial plan,
// we retain the previous behaviour of 10 seconds end-to-end timeout.
timeoutSec := 5.0
if dialPlan != nil {
for _, c := range dialPlan.Candidates {
if v := c.DialStartDelaySec + c.DialTimeoutSec; v > timeoutSec {
timeoutSec = v
}
}
}
// After we establish a connection, we need some time to actually
// upgrade it into a Noise connection. With a ballpark worst-case RTT
// of 1000ms, give ourselves an extra 5 seconds to complete the
// handshake.
timeoutSec += 5
// Be extremely defensive and ensure that the timeout is in the range
// [5, 60] seconds (e.g. if we accidentally get a negative number).
if timeoutSec > 60 {
timeoutSec = 60
} else if timeoutSec < 5 {
timeoutSec = 5
}
timeout := time.Duration(timeoutSec * float64(time.Second))
ctx, cancel := context.WithTimeout(ctx, timeout)
defer cancel()
clientConn, err := (&controlhttp.Dialer{
Hostname: nc.host,
HTTPPort: nc.httpPort,
HTTPSPort: nc.httpsPort,
MachineKey: nc.privKey,
ControlKey: nc.serverPubKey,
ProtocolVersion: uint16(tailcfg.CurrentCapabilityVersion),
Dialer: nc.dialer.SystemDial,
DNSCache: nc.dnsCache,
DialPlan: dialPlan,
Logf: nc.logf,
NetMon: nc.netMon,
Clock: tstime.StdClock{},
}).Dial(ctx)
if err != nil {
return nil, err
}
ncc := &noiseConn{
Conn: clientConn.Conn,
id: connID,
pool: nc,
earlyPayloadReady: make(chan struct{}),
}
h2cc, err := nc.h2t.NewClientConn(ncc)
if err != nil {
return nil, err
}
ncc.h2cc = h2cc
nc.mu.Lock()
if nc.closed {
nc.mu.Unlock()
ncc.Close() // Needs to be called without holding the lock.
return nil, errors.New("noise client closed")
}
defer nc.mu.Unlock()
mak.Set(&nc.connPool, ncc.id, ncc)
nc.last = ncc
return ncc, nil
}
// post does a POST to the control server at the given path, JSON-encoding body.
// The provided nodeKey is an optional load balancing hint.
func (nc *NoiseClient) post(ctx context.Context, path string, nodeKey key.NodePublic, body any) (*http.Response, error) {
jbody, err := json.Marshal(body)
if err != nil {
return nil, err
}
req, err := http.NewRequestWithContext(ctx, "POST", "https://"+nc.host+path, bytes.NewReader(jbody))
if err != nil {
return nil, err
}
addLBHeader(req, nodeKey)
req.Header.Set("Content-Type", "application/json")
conn, err := nc.getConn(ctx)
if err != nil {
return nil, err
}
return conn.h2cc.RoundTrip(req)
}
func (c *noiseConn) canTakeNewRequest() bool {
return c.h2cc.CanTakeNewRequest()
}