net/tlsdial: bake in LetsEncrypt's ISRG Root X1 root

We still try the host's x509 roots first, but if that fails (like if
the host is old), we fall back to using LetsEncrypt's root and
retrying with that.

tlsdial was used in the three main places: logs, control, DERP. But it
was missing in dnsfallback. So added it there too, so we can run fine
now on a machine with no DNS config and no root CAs configured.

Also, move SSLKEYLOGFILE support out of DERP. tlsdial is the logical place
for that support.

Fixes #1609

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
pull/2978/head
Brad Fitzpatrick 3 years ago committed by Brad Fitzpatrick
parent b10a55e4ed
commit 7cf8ec8108

@ -19,11 +19,9 @@ import (
"fmt"
"io"
"io/ioutil"
"log"
"net"
"net/http"
"net/url"
"os"
"strings"
"sync"
"time"
@ -430,19 +428,14 @@ func (c *Client) dialRegion(ctx context.Context, reg *tailcfg.DERPRegion) (net.C
func (c *Client) tlsClient(nc net.Conn, node *tailcfg.DERPNode) *tls.Conn {
tlsConf := tlsdial.Config(c.tlsServerName(node), c.TLSConfig)
if node != nil {
tlsConf.InsecureSkipVerify = node.InsecureForTests
if node.InsecureForTests {
tlsConf.InsecureSkipVerify = true
tlsConf.VerifyConnection = nil
}
if node.CertName != "" {
tlsdial.SetConfigExpectedCert(tlsConf, node.CertName)
}
}
if n := os.Getenv("SSLKEYLOGFILE"); n != "" {
f, err := os.OpenFile(n, os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0600)
if err != nil {
log.Fatal(err)
}
log.Printf("WARNING: writing to SSLKEYLOGFILE %v", n)
tlsConf.KeyLogWriter = f
}
return tls.Client(nc, tlsConf)
}

@ -3,6 +3,7 @@ module tailscale.com
go 1.17
require (
filippo.io/mkcert v1.4.3
github.com/alexbrainman/sspi v0.0.0-20210105120005-909beea2cc74
github.com/anmitsu/go-shlex v0.0.0-20200514113438-38f4b401e2be // indirect
github.com/aws/aws-sdk-go v1.38.52
@ -188,8 +189,10 @@ require (
gopkg.in/warnings.v0 v0.1.2 // indirect
gopkg.in/yaml.v2 v2.4.0 // indirect
gopkg.in/yaml.v3 v3.0.0-20200615113413-eeeca48fe776 // indirect
howett.net/plist v0.0.0-20181124034731-591f970eefbb // indirect
mvdan.cc/gofumpt v0.0.0-20201129102820-5c11c50e9475 // indirect
mvdan.cc/interfacer v0.0.0-20180901003855-c20040233aed // indirect
mvdan.cc/lint v0.0.0-20170908181259-adc824a0674b // indirect
mvdan.cc/unparam v0.0.0-20200501210554-b37ab49443f7 // indirect
software.sslmate.com/src/go-pkcs12 v0.0.0-20180114231543-2291e8f0f237 // indirect
)

@ -14,6 +14,8 @@ cloud.google.com/go/firestore v1.1.0/go.mod h1:ulACoGHTpvq5r8rxGJ4ddJZBZqakUQqCl
cloud.google.com/go/pubsub v1.0.1/go.mod h1:R0Gpsv3s54REJCy4fxDixWD93lHJMoZTyQ2kNxGRt3I=
cloud.google.com/go/storage v1.0.0/go.mod h1:IhtSnM/ZTZV8YYJWCY8RULGVqBDmpoyjwiyrjsg+URw=
dmitri.shuralyov.com/gpu/mtl v0.0.0-20190408044501-666a987793e9/go.mod h1:H6x//7gZCb22OMCxBHrMx7a5I7Hp++hsVxbQ4BYO7hU=
filippo.io/mkcert v1.4.3 h1:axpnmtrZMM8u5Hf4N3UXxboGemMOV+Tn+e+pkHM6E3o=
filippo.io/mkcert v1.4.3/go.mod h1:64ke566uBwAQcdK3vRDABgsgVHqrfORPTw6YytZCTxk=
github.com/BurntSushi/toml v0.3.1 h1:WXkYYl6Yr3qBf1K79EBnL4mak0OimBfB0XUf9Vl28OQ=
github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
github.com/BurntSushi/xgb v0.0.0-20160522181843-27f122750802/go.mod h1:IVnqGOEym/WlBOVXweHU+Q+/VP0lqqI8lqeDx9IjBqo=
@ -876,6 +878,7 @@ golang.org/x/tools v0.0.0-20201011145850-ed2f50202694/go.mod h1:z6u4i615ZeAfBE4X
golang.org/x/tools v0.0.0-20201013201025-64a9e34f3752/go.mod h1:z6u4i615ZeAfBE4XtMziQW1fSVJXACjjbWkB/mvPzlU=
golang.org/x/tools v0.0.0-20201118003311-bd56c0adb394/go.mod h1:emZCQorbCU4vsT4fOWvOPXz4eW1wZW4PmDk9uLelYpA=
golang.org/x/tools v0.0.0-20201121010211-780cb80bd7fb/go.mod h1:emZCQorbCU4vsT4fOWvOPXz4eW1wZW4PmDk9uLelYpA=
golang.org/x/tools v0.0.0-20201124202034-299f270db459/go.mod h1:emZCQorbCU4vsT4fOWvOPXz4eW1wZW4PmDk9uLelYpA=
golang.org/x/tools v0.0.0-20201208233053-a543418bbed2/go.mod h1:emZCQorbCU4vsT4fOWvOPXz4eW1wZW4PmDk9uLelYpA=
golang.org/x/tools v0.0.0-20201211185031-d93e913c1a58/go.mod h1:emZCQorbCU4vsT4fOWvOPXz4eW1wZW4PmDk9uLelYpA=
golang.org/x/tools v0.1.0/go.mod h1:xkSsbof2nBLbhDlRMhhhyNLN/zl3eTqcnHD5viDpcZ0=
@ -957,6 +960,8 @@ honnef.co/go/tools v0.0.1-2019.2.3/go.mod h1:a3bituU0lyd329TUQxRnasdCoJDkEUEAqEt
honnef.co/go/tools v0.0.1-2020.1.6/go.mod h1:pyyisuGw24ruLjrr1ddx39WE0y9OooInRzEYLhQB2YY=
honnef.co/go/tools v0.2.1 h1:/EPr//+UMMXwMTkXvCCoaJDq8cpjMO80Ou+L4PDo2mY=
honnef.co/go/tools v0.2.1/go.mod h1:lPVVZ2BS5TfnjLyizF7o7hv7j9/L+8cZY2hLyjP9cGY=
howett.net/plist v0.0.0-20181124034731-591f970eefbb h1:jhnBjNi9UFpfpl8YZhA9CrOqpnJdvzuiHsl/dnxl11M=
howett.net/plist v0.0.0-20181124034731-591f970eefbb/go.mod h1:vMygbs4qMhSZSc4lCUl2OEE+rDiIIJAIdR4m7MiMcm0=
inet.af/netaddr v0.0.0-20210515010201-ad03edc7c841/go.mod h1:z0nx+Dh+7N7CC8V5ayHtHGpZpxLQZZxkIaaz6HN65Ls=
inet.af/netaddr v0.0.0-20210721214506-ce7a8ad02cc1 h1:mxmfTV6kjXTlFqqFETnG9FQZzNFc6AKunZVAgQ3b7WA=
inet.af/netaddr v0.0.0-20210721214506-ce7a8ad02cc1/go.mod h1:z0nx+Dh+7N7CC8V5ayHtHGpZpxLQZZxkIaaz6HN65Ls=
@ -976,3 +981,5 @@ mvdan.cc/lint v0.0.0-20170908181259-adc824a0674b/go.mod h1:2odslEg/xrtNQqCYg2/jC
mvdan.cc/unparam v0.0.0-20200501210554-b37ab49443f7 h1:kAREL6MPwpsk1/PQPFD3Eg7WAQR5mPTWZJaBiG5LDbY=
mvdan.cc/unparam v0.0.0-20200501210554-b37ab49443f7/go.mod h1:HGC5lll35J70Y5v7vCGb9oLhHoScFwkHDJm/05RdSTc=
rsc.io/binaryregexp v0.2.0/go.mod h1:qTv7/COck+e2FymRvadv62gMdZztPaShugOCi3I+8D8=
software.sslmate.com/src/go-pkcs12 v0.0.0-20180114231543-2291e8f0f237 h1:iAEkCBPbRaflBgZ7o9gjVUuWuvWeV4sytFWg9o+Pj2k=
software.sslmate.com/src/go-pkcs12 v0.0.0-20180114231543-2291e8f0f237/go.mod h1:/xvNRWUqm0+/ZMiF4EX00vrSCMsE4/NHb+Pt3freEeQ=

@ -23,6 +23,7 @@ import (
"inet.af/netaddr"
"tailscale.com/net/netns"
"tailscale.com/net/tlsdial"
"tailscale.com/net/tshttpproxy"
"tailscale.com/tailcfg"
)
@ -95,6 +96,7 @@ func bootstrapDNSMap(ctx context.Context, serverName string, serverIP netaddr.IP
tr.DialContext = func(ctx context.Context, netw, addr string) (net.Conn, error) {
return dialer.DialContext(ctx, "tcp", net.JoinHostPort(serverIP.String(), "443"))
}
tr.TLSClientConfig = tlsdial.Config(serverName, tr.TLSClientConfig)
c := &http.Client{Transport: tr}
req, err := http.NewRequestWithContext(ctx, "GET", "https://"+serverName+"/bootstrap-dns?q="+url.QueryEscape(queryName), nil)
if err != nil {

@ -15,9 +15,24 @@ import (
"crypto/tls"
"crypto/x509"
"errors"
"log"
"os"
"strconv"
"sync"
"sync/atomic"
"time"
)
var counterFallbackOK int32 // atomic
// If SSLKEYLOGFILE is set, it's a file to which we write our TLS private keys
// in a way that WireShark can read.
//
// See https://developer.mozilla.org/en-US/docs/Mozilla/Projects/NSS/Key_Log_Format
var sslKeyLogFile = os.Getenv("SSLKEYLOGFILE")
var debug, _ = strconv.ParseBool(os.Getenv("TS_DEBUG_TLS_DIAL"))
// Config returns a tls.Config for connecting to a server.
// If base is non-nil, it's cloned as the base config before
// being configured and returned.
@ -30,11 +45,65 @@ func Config(host string, base *tls.Config) *tls.Config {
}
conf.ServerName = host
if n := sslKeyLogFile; n != "" {
f, err := os.OpenFile(n, os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0600)
if err != nil {
log.Fatal(err)
}
log.Printf("WARNING: writing to SSLKEYLOGFILE %v", n)
conf.KeyLogWriter = f
}
if conf.InsecureSkipVerify {
panic("unexpected base.InsecureSkipVerify")
}
if conf.VerifyConnection != nil {
panic("unexpected base.VerifyConnection")
}
// Set InsecureSkipVerify to prevent crypto/tls from doing its
// own cert verification, as do the same work that it'd do
// (with the baked-in fallback root) in the VerifyConnection hook.
conf.InsecureSkipVerify = true
conf.VerifyConnection = func(cs tls.ConnectionState) error {
// First try doing x509 verification with the system's
// root CA pool.
opts := x509.VerifyOptions{
DNSName: cs.ServerName,
Intermediates: x509.NewCertPool(),
}
for _, cert := range cs.PeerCertificates[1:] {
opts.Intermediates.AddCert(cert)
}
_, errSys := cs.PeerCertificates[0].Verify(opts)
if debug {
log.Printf("tlsdial(sys %q): %v", host, errSys)
}
if errSys == nil {
return nil
}
// If that failed, because the system's CA roots are old
// or broken, fall back to trying LetsEncrypt at least.
opts.Roots = bakedInRoots()
_, err := cs.PeerCertificates[0].Verify(opts)
if debug {
log.Printf("tlsdial(bake %q): %v", host, err)
}
if err == nil {
atomic.AddInt32(&counterFallbackOK, 1)
return nil
}
return errSys
}
return conf
}
// SetConfigExpectedCert modifies c to expect and verify that the server returns
// a certificate for the provided certDNSName.
//
// This is for user-configurable client-side domain fronting support,
// where we send one SNI value but validate a different cert.
func SetConfigExpectedCert(c *tls.Config, certDNSName string) {
if c.ServerName == certDNSName {
return
@ -50,6 +119,7 @@ func SetConfigExpectedCert(c *tls.Config, certDNSName string) {
// own cert verification, but do the same work that it'd do
// (but using certDNSName) in the VerifyPeerCertificate hook.
c.InsecureSkipVerify = true
c.VerifyConnection = nil
c.VerifyPeerCertificate = func(rawCerts [][]byte, _ [][]*x509.Certificate) error {
if len(rawCerts) == 0 {
return errors.New("no certs presented")
@ -70,7 +140,102 @@ func SetConfigExpectedCert(c *tls.Config, certDNSName string) {
for _, cert := range certs[1:] {
opts.Intermediates.AddCert(cert)
}
_, errSys := certs[0].Verify(opts)
if debug {
log.Printf("tlsdial(sys %q/%q): %v", c.ServerName, certDNSName, errSys)
}
if errSys == nil {
return nil
}
opts.Roots = bakedInRoots()
_, err := certs[0].Verify(opts)
return err
if debug {
log.Printf("tlsdial(bake %q/%q): %v", c.ServerName, certDNSName, err)
}
if err == nil {
return nil
}
return errSys
}
}
/*
letsEncryptX1 is the LetsEncrypt X1 root:
Certificate:
Data:
Version: 3 (0x2)
Serial Number:
82:10:cf:b0:d2:40:e3:59:44:63:e0:bb:63:82:8b:00
Signature Algorithm: sha256WithRSAEncryption
Issuer: C = US, O = Internet Security Research Group, CN = ISRG Root X1
Validity
Not Before: Jun 4 11:04:38 2015 GMT
Not After : Jun 4 11:04:38 2035 GMT
Subject: C = US, O = Internet Security Research Group, CN = ISRG Root X1
Subject Public Key Info:
Public Key Algorithm: rsaEncryption
RSA Public-Key: (4096 bit)
We bake it into the binary as a fallback verification root,
in case the system we're running on doesn't have it.
(Tailscale runs on some ancient devices.)
To test that this code is working on Debian/Ubuntu:
$ sudo mv /usr/share/ca-certificates/mozilla/ISRG_Root_X1.crt{,.old}
$ sudo update-ca-certificates
Then restart tailscaled. To also test dnsfallback's use of it, nuke
your /etc/resolv.conf and it should still start & run fine.
*/
const letsEncryptX1 = `
-----BEGIN CERTIFICATE-----
MIIFazCCA1OgAwIBAgIRAIIQz7DSQONZRGPgu2OCiwAwDQYJKoZIhvcNAQELBQAw
TzELMAkGA1UEBhMCVVMxKTAnBgNVBAoTIEludGVybmV0IFNlY3VyaXR5IFJlc2Vh
cmNoIEdyb3VwMRUwEwYDVQQDEwxJU1JHIFJvb3QgWDEwHhcNMTUwNjA0MTEwNDM4
WhcNMzUwNjA0MTEwNDM4WjBPMQswCQYDVQQGEwJVUzEpMCcGA1UEChMgSW50ZXJu
ZXQgU2VjdXJpdHkgUmVzZWFyY2ggR3JvdXAxFTATBgNVBAMTDElTUkcgUm9vdCBY
MTCCAiIwDQYJKoZIhvcNAQEBBQADggIPADCCAgoCggIBAK3oJHP0FDfzm54rVygc
h77ct984kIxuPOZXoHj3dcKi/vVqbvYATyjb3miGbESTtrFj/RQSa78f0uoxmyF+
0TM8ukj13Xnfs7j/EvEhmkvBioZxaUpmZmyPfjxwv60pIgbz5MDmgK7iS4+3mX6U
A5/TR5d8mUgjU+g4rk8Kb4Mu0UlXjIB0ttov0DiNewNwIRt18jA8+o+u3dpjq+sW
T8KOEUt+zwvo/7V3LvSye0rgTBIlDHCNAymg4VMk7BPZ7hm/ELNKjD+Jo2FR3qyH
B5T0Y3HsLuJvW5iB4YlcNHlsdu87kGJ55tukmi8mxdAQ4Q7e2RCOFvu396j3x+UC
B5iPNgiV5+I3lg02dZ77DnKxHZu8A/lJBdiB3QW0KtZB6awBdpUKD9jf1b0SHzUv
KBds0pjBqAlkd25HN7rOrFleaJ1/ctaJxQZBKT5ZPt0m9STJEadao0xAH0ahmbWn
OlFuhjuefXKnEgV4We0+UXgVCwOPjdAvBbI+e0ocS3MFEvzG6uBQE3xDk3SzynTn
jh8BCNAw1FtxNrQHusEwMFxIt4I7mKZ9YIqioymCzLq9gwQbooMDQaHWBfEbwrbw
qHyGO0aoSCqI3Haadr8faqU9GY/rOPNk3sgrDQoo//fb4hVC1CLQJ13hef4Y53CI
rU7m2Ys6xt0nUW7/vGT1M0NPAgMBAAGjQjBAMA4GA1UdDwEB/wQEAwIBBjAPBgNV
HRMBAf8EBTADAQH/MB0GA1UdDgQWBBR5tFnme7bl5AFzgAiIyBpY9umbbjANBgkq
hkiG9w0BAQsFAAOCAgEAVR9YqbyyqFDQDLHYGmkgJykIrGF1XIpu+ILlaS/V9lZL
ubhzEFnTIZd+50xx+7LSYK05qAvqFyFWhfFQDlnrzuBZ6brJFe+GnY+EgPbk6ZGQ
3BebYhtF8GaV0nxvwuo77x/Py9auJ/GpsMiu/X1+mvoiBOv/2X/qkSsisRcOj/KK
NFtY2PwByVS5uCbMiogziUwthDyC3+6WVwW6LLv3xLfHTjuCvjHIInNzktHCgKQ5
ORAzI4JMPJ+GslWYHb4phowim57iaztXOoJwTdwJx4nLCgdNbOhdjsnvzqvHu7Ur
TkXWStAmzOVyyghqpZXjFaH3pO3JLF+l+/+sKAIuvtd7u+Nxe5AW0wdeRlN8NwdC
jNPElpzVmbUq4JUagEiuTDkHzsxHpFKVK7q4+63SM1N95R1NbdWhscdCb+ZAJzVc
oyi3B43njTOQ5yOf+1CceWxG1bQVs5ZufpsMljq4Ui0/1lvh+wjChP4kqKOJ2qxq
4RgqsahDYVvTH9w7jXbyLeiNdd8XM2w9U/t7y0Ff/9yi0GE44Za4rF2LN9d11TPA
mRGunUHBcnWEvgJBQl9nJEiU0Zsnvgc/ubhPgXRR4Xq37Z0j4r7g1SgEEzwxA57d
emyPxgcYxn/eR44/KJ4EBs+lVDR3veyJm+kXQ99b21/+jh5Xos1AnX5iItreGCc=
-----END CERTIFICATE-----
`
var bakedInRootsOnce struct {
sync.Once
p *x509.CertPool
}
func bakedInRoots() *x509.CertPool {
bakedInRootsOnce.Do(func() {
p := x509.NewCertPool()
if !p.AppendCertsFromPEM([]byte(letsEncryptX1)) {
panic("bogus PEM")
}
bakedInRootsOnce.p = p
})
return bakedInRootsOnce.p
}

@ -0,0 +1,131 @@
// 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 tlsdial
import (
"crypto/x509"
"io"
"net"
"net/http"
"os"
"os/exec"
"path/filepath"
"reflect"
"runtime"
"sync/atomic"
"testing"
)
func resetOnce() {
rv := reflect.ValueOf(&bakedInRootsOnce).Elem()
rv.Set(reflect.Zero(rv.Type()))
}
func TestBakedInRoots(t *testing.T) {
resetOnce()
p := bakedInRoots()
got := p.Subjects()
if len(got) != 1 {
t.Errorf("subjects = %v; want 1", len(got))
}
}
func TestFallbackRootWorks(t *testing.T) {
defer resetOnce()
const debug = false
if runtime.GOOS != "linux" {
t.Skip("test assumes Linux")
}
d := t.TempDir()
crtFile := filepath.Join(d, "tlsdial.test.crt")
keyFile := filepath.Join(d, "tlsdial.test.key")
caFile := filepath.Join(d, "rootCA.pem")
cmd := exec.Command(filepath.Join(runtime.GOROOT(), "bin", "go"),
"run", "filippo.io/mkcert",
"--cert-file="+crtFile,
"--key-file="+keyFile,
"tlsdial.test")
cmd.Env = append(os.Environ(), "CAROOT="+d)
out, err := cmd.CombinedOutput()
if err != nil {
t.Fatalf("mkcert: %v, %s", err, out)
}
if debug {
t.Logf("Ran: %s", out)
dents, err := os.ReadDir(d)
if err != nil {
t.Fatal(err)
}
for _, de := range dents {
t.Logf(" - %v", de)
}
}
caPEM, err := os.ReadFile(caFile)
if err != nil {
t.Fatal(err)
}
resetOnce()
bakedInRootsOnce.Do(func() {
p := x509.NewCertPool()
if !p.AppendCertsFromPEM(caPEM) {
t.Fatal("failed to add")
}
bakedInRootsOnce.p = p
})
ln, err := net.Listen("tcp", "127.0.0.1:0")
if err != nil {
t.Fatal(err)
}
defer ln.Close()
if debug {
t.Logf("listener running at %v", ln.Addr())
}
done := make(chan struct{})
defer close(done)
errc := make(chan error, 1)
go func() {
err := http.ServeTLS(ln, http.HandlerFunc(sayHi), crtFile, keyFile)
select {
case <-done:
return
default:
t.Logf("ServeTLS: %v", err)
errc <- err
}
}()
tr := &http.Transport{
Dial: func(network, addr string) (net.Conn, error) {
return net.Dial("tcp", ln.Addr().String())
},
DisableKeepAlives: true, // for test cleanup ease
}
tr.TLSClientConfig = Config("tlsdial.test", tr.TLSClientConfig)
c := &http.Client{Transport: tr}
ctr0 := atomic.LoadInt32(&counterFallbackOK)
res, err := c.Get("https://tlsdial.test/")
if err != nil {
t.Fatal(err)
}
defer res.Body.Close()
if res.StatusCode != 200 {
t.Fatal(res.Status)
}
ctrDelta := atomic.LoadInt32(&counterFallbackOK) - ctr0
if ctrDelta != 1 {
t.Errorf("fallback root success count = %d; want 1", ctrDelta)
}
}
func sayHi(w http.ResponseWriter, r *http.Request) {
io.WriteString(w, "hi")
}
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