forked from andybalholm/redwood
/
tls.go
609 lines (546 loc) · 15.5 KB
/
tls.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
package redwood
import (
"bytes"
"crypto/md5"
"crypto/rand"
"crypto/tls"
"crypto/x509"
"crypto/x509/pkix"
"encoding/pem"
"errors"
"fmt"
"io"
"io/ioutil"
"log"
"math/big"
"net"
"net/http"
"net/url"
"runtime"
"strings"
"sync"
"time"
)
// Intercept TLS (HTTPS) connections.
// unverifiedClientConfig is a TLS configuration that doesn't verify server
// certificates.
var unverifiedClientConfig = &tls.Config{
InsecureSkipVerify: true,
}
// loadCertificate loads the TLS certificate specified by certFile and keyFile
// into tlsCert.
func (c *config) loadCertificate() {
if c.CertFile != "" && c.KeyFile != "" {
cert, err := tls.LoadX509KeyPair(c.CertFile, c.KeyFile)
if err != nil {
log.Println("Error loading TLS certificate:", err)
return
}
c.TLSCert = cert
parsed, err := x509.ParseCertificate(cert.Certificate[0])
if err != nil {
log.Println("Error parsing X509 certificate:", err)
return
}
c.ParsedTLSCert = parsed
c.TLSReady = true
c.ServeMux.HandleFunc("/cert.der", func(w http.ResponseWriter, r *http.Request) {
tlsCert := c.TLSCert
w.Header().Set("Content-Type", "application/x-x509-ca-cert")
w.Write(tlsCert.Certificate[len(tlsCert.Certificate)-1])
})
}
}
// connectDirect connects to serverAddr and copies data between it and conn.
// extraData is sent to the server first.
func connectDirect(conn net.Conn, serverAddr string, extraData []byte) {
activeConnections.Add(1)
defer activeConnections.Done()
serverConn, err := net.Dial("tcp", serverAddr)
if err != nil {
log.Printf("error with pass-through of SSL connection to %s: %s", serverAddr, err)
conn.Close()
return
}
if extraData != nil {
// There may also be data waiting in the socket's input buffer;
// read it before we send the data on, so that the first packet of
// the connection doesn't get split in two.
conn.SetReadDeadline(time.Now().Add(time.Millisecond))
buf := make([]byte, 2000)
n, _ := conn.Read(buf)
conn.SetReadDeadline(time.Time{})
if n > 0 {
extraData = append(extraData, buf[:n]...)
}
serverConn.Write(extraData)
}
go func() {
io.Copy(conn, serverConn)
time.Sleep(time.Second)
conn.Close()
}()
io.Copy(serverConn, conn)
serverConn.Close()
return
}
// SSLBump performs a man-in-the-middle attack on conn, to filter the HTTPS
// traffic. serverAddr is the address (host:port) of the server the client was
// trying to connect to. user is the username to use for logging; authUser is
// the authenticated user, if any.
func SSLBump(conn net.Conn, serverAddr, user, authUser string) {
defer func() {
if err := recover(); err != nil {
buf := make([]byte, 4096)
buf = buf[:runtime.Stack(buf, false)]
log.Printf("SSLBump: panic serving connection to %s: %v\n%s", serverAddr, err, buf)
conn.Close()
}
}()
conf := GetConfig()
if serverAddr == localServer+":443" {
// The internal server gets special treatment, since there is no remote
// server to connect to.
cert, err := imitateCertificate(&x509.Certificate{
Subject: pkix.Name{CommonName: localServer},
NotBefore: conf.ParsedTLSCert.NotBefore,
NotAfter: conf.ParsedTLSCert.NotAfter,
KeyUsage: x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
ExtKeyUsage: []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
}, false, conf)
if err != nil {
log.Printf("Error generataing HTTPS certificate for local server (%s): %v", serverAddr, err)
conn.Close()
return
}
config := &tls.Config{
NextProtos: []string{"http/1.1"},
Certificates: []tls.Certificate{cert, conf.TLSCert},
}
tlsConn := tls.Server(conn, config)
err = tlsConn.Handshake()
if err != nil {
logTLS(user, serverAddr, localServer, fmt.Errorf("error in handshake with client: %v", err))
conn.Close()
return
}
listener := &singleListener{conn: tlsConn}
server := http.Server{Handler: conf.ServeMux}
logTLS(user, serverAddr, localServer, nil)
server.Serve(listener)
return
}
obsoleteVersion := false
// Read the client hello so that we can find out the name of the server (not
// just the address).
clientHello, err := readClientHello(conn)
if err != nil {
logTLS(user, serverAddr, "", fmt.Errorf("error reading client hello: %v", err))
if err == ErrObsoleteSSLVersion {
obsoleteVersion = true
if conf.BlockObsoleteSSL {
conn.Close()
return
}
} else {
connectDirect(conn, serverAddr, clientHello)
}
}
serverName := ""
if !obsoleteVersion {
if sn, ok := clientHelloServerName(clientHello); ok {
serverName = sn
}
}
if serverName == "" {
serverName, _, err = net.SplitHostPort(serverAddr)
if err != nil {
serverName = serverAddr
}
if ip := net.ParseIP(serverName); ip != nil {
// All we have is an IP address, not a name from a CONNECT request.
// See if we can do better by reverse DNS.
names, err := net.LookupAddr(serverName)
if err == nil && len(names) > 0 {
serverName = strings.TrimSuffix(names[0], ".")
}
}
}
// Filter a virtual CONNECT request.
cr := &http.Request{
Method: "CONNECT",
Header: make(http.Header),
Host: serverName,
URL: &url.URL{Host: serverName},
RemoteAddr: conn.RemoteAddr().String(),
}
tally := conf.URLRules.MatchingRules(cr.URL)
scores := conf.categoryScores(tally)
categories := conf.significantCategories(scores)
reqACLs := conf.ACLs.requestACLs(cr, authUser)
possibleActions := []string{
"allow",
"block",
}
if conf.TLSReady && !obsoleteVersion {
possibleActions = append(possibleActions, "ssl-bump")
}
rule, ignored := conf.ChooseACLCategoryAction(reqACLs, categories, possibleActions...)
logAccess(cr, nil, 0, false, user, tally, scores, rule, "", ignored, "")
switch rule.Action {
case "allow", "":
connectDirect(conn, serverAddr, clientHello)
return
case "block":
conn.Close()
return
}
serverConn, err := tls.Dial("tcp", serverAddr, &tls.Config{
ServerName: serverName,
InsecureSkipVerify: true,
})
if err != nil {
logTLS(user, serverAddr, serverName, err)
connectDirect(conn, serverAddr, clientHello)
return
}
state := serverConn.ConnectionState()
serverCert := state.PeerCertificates[0]
intermediates := x509.NewCertPool()
for _, ic := range state.PeerCertificates[1:] {
intermediates.AddCert(ic)
}
valid := conf.validCert(serverCert, intermediates)
cert, err := imitateCertificate(serverCert, !valid, conf)
if err != nil {
serverConn.Close()
logTLS(user, serverAddr, serverName, fmt.Errorf("error generating certificate: %v", err))
connectDirect(conn, serverAddr, clientHello)
return
}
config := &tls.Config{
NextProtos: []string{"http/1.1"},
Certificates: []tls.Certificate{cert, conf.TLSCert},
}
tlsConn := tls.Server(&insertingConn{conn, clientHello}, config)
err = tlsConn.Handshake()
if err != nil {
logTLS(user, serverAddr, serverName, fmt.Errorf("error in handshake with client: %v", err))
conn.Close()
return
}
_, port, err := net.SplitHostPort(serverAddr)
if err != nil {
port = ""
}
listener := &singleListener{conn: tlsConn}
server := http.Server{
Handler: ProxyHandler{
TLS: true,
connectPort: port,
user: authUser,
rt: NewTLSRedialTransport(serverConn, serverName),
},
}
logTLS(user, serverAddr, serverName, nil)
server.Serve(listener)
}
// A insertingConn is a net.Conn that inserts extra data at the start of the
// incoming data stream.
type insertingConn struct {
net.Conn
extraData []byte
}
func (c *insertingConn) Read(p []byte) (n int, err error) {
if len(c.extraData) == 0 {
return c.Conn.Read(p)
}
n = copy(p, c.extraData)
c.extraData = c.extraData[n:]
return
}
// A singleListener is a net.Listener that returns a single connection, then
// gives the error io.EOF.
type singleListener struct {
conn net.Conn
once sync.Once
}
func (s *singleListener) Accept() (net.Conn, error) {
var c net.Conn
s.once.Do(func() {
c = s.conn
})
if c != nil {
return c, nil
}
return nil, io.EOF
}
func (s *singleListener) Close() error {
s.once.Do(func() {
s.conn.Close()
})
return nil
}
func (s *singleListener) Addr() net.Addr {
return s.conn.LocalAddr()
}
// imitateCertificate returns a new TLS certificate that has most of the same
// data as serverCert but is signed by Redwood's root certificate, or
// self-signed.
func imitateCertificate(serverCert *x509.Certificate, selfSigned bool, conf *config) (cert tls.Certificate, err error) {
template := serverCert
if selfSigned {
template = &x509.Certificate{
SerialNumber: new(big.Int).SetInt64(0),
Subject: serverCert.Subject,
NotBefore: serverCert.NotBefore,
NotAfter: serverCert.NotAfter,
KeyUsage: x509.KeyUsageDigitalSignature | x509.KeyUsageKeyEncipherment,
ExtKeyUsage: serverCert.ExtKeyUsage,
DNSNames: serverCert.DNSNames,
}
} else {
// Use a hash of the real certificate as the serial number.
h := md5.New()
h.Write(serverCert.Raw)
h.Write([]byte{1}) // To give different serial numbers after the key usage change.
template.SerialNumber = big.NewInt(0).SetBytes(h.Sum(nil))
if err != nil {
return tls.Certificate{}, fmt.Errorf("failed to generate serial number: %s", err)
}
template.SubjectKeyId = nil
template.AuthorityKeyId = nil
template.OCSPServer = nil
template.IssuingCertificateURL = nil
template.CRLDistributionPoints = nil
template.KeyUsage = x509.KeyUsageDigitalSignature | x509.KeyUsageKeyEncipherment
template.BasicConstraintsValid = false
template.SignatureAlgorithm = x509.UnknownSignatureAlgorithm
}
var newCertBytes []byte
if selfSigned {
newCertBytes, err = x509.CreateCertificate(rand.Reader, template, template, conf.ParsedTLSCert.PublicKey, conf.TLSCert.PrivateKey)
} else {
newCertBytes, err = x509.CreateCertificate(rand.Reader, template, conf.ParsedTLSCert, conf.ParsedTLSCert.PublicKey, conf.TLSCert.PrivateKey)
}
if err != nil {
return tls.Certificate{}, err
}
newCert := tls.Certificate{
Certificate: [][]byte{newCertBytes},
PrivateKey: conf.TLSCert.PrivateKey,
}
if !selfSigned {
newCert.Certificate = append(newCert.Certificate, conf.TLSCert.Certificate...)
}
return newCert, nil
}
func (conf *config) validCert(cert *x509.Certificate, intermediates *x509.CertPool) bool {
_, err := cert.Verify(x509.VerifyOptions{Intermediates: intermediates})
if err == nil {
return true
}
if _, ok := err.(x509.UnknownAuthorityError); !ok {
// There was an error, but not because the certificate wasn't signed
// by a recognized CA. So we go ahead and use the cert and let
// the client experience the same error.
return true
}
if conf.ExtraRootCerts != nil {
_, err = cert.Verify(x509.VerifyOptions{Roots: conf.ExtraRootCerts, Intermediates: intermediates})
if err == nil {
return true
}
if _, ok := err.(x509.UnknownAuthorityError); !ok {
return true
}
}
// Before we give up, we'll try fetching some intermediate certificates.
if len(cert.IssuingCertificateURL) == 0 {
return false
}
toFetch := cert.IssuingCertificateURL
fetched := make(map[string]bool)
for i := 0; i < len(toFetch); i++ {
certURL := toFetch[i]
if fetched[certURL] {
continue
}
resp, err := http.Get(certURL)
if err == nil {
defer resp.Body.Close()
}
if err != nil || resp.StatusCode != 200 {
continue
}
fetchedCert, err := ioutil.ReadAll(resp.Body)
if err != nil {
continue
}
// The fetched certificate might be in either DER or PEM format.
if bytes.Contains(fetchedCert, []byte("-----BEGIN CERTIFICATE-----")) {
// It's PEM.
var certDER *pem.Block
for {
certDER, fetchedCert = pem.Decode(fetchedCert)
if certDER == nil {
break
}
if certDER.Type != "CERTIFICATE" {
continue
}
thisCert, err := x509.ParseCertificate(certDER.Bytes)
if err != nil {
continue
}
intermediates.AddCert(thisCert)
toFetch = append(toFetch, thisCert.IssuingCertificateURL...)
}
} else {
// Hopefully it's DER.
thisCert, err := x509.ParseCertificate(fetchedCert)
if err != nil {
continue
}
intermediates.AddCert(thisCert)
toFetch = append(toFetch, thisCert.IssuingCertificateURL...)
}
}
_, err = cert.Verify(x509.VerifyOptions{Intermediates: intermediates})
if err == nil {
return true
}
if _, ok := err.(x509.UnknownAuthorityError); !ok {
// There was an error, but not because the certificate wasn't signed
// by a recognized CA. So we go ahead and use the cert and let
// the client experience the same error.
return true
}
return false
}
var ErrObsoleteSSLVersion = errors.New("obsolete SSL protocol version")
func readClientHello(conn net.Conn) (hello []byte, err error) {
var header [5]byte
n, err := io.ReadFull(conn, header[:])
hello = header[:n]
if err != nil {
return hello, err
}
if header[0] != 22 {
if header[0] == 128 {
return hello, ErrObsoleteSSLVersion
}
return hello, fmt.Errorf("expected content type of 22, got %d", header[0])
}
if header[1] != 3 {
return hello, fmt.Errorf("expected major version of 3, got %d", header[1])
}
recordLen := int(header[3])<<8 | int(header[4])
if recordLen > 0x3000 {
return hello, fmt.Errorf("expected length less than 12kB, got %d", recordLen)
}
if recordLen < 4 {
return hello, fmt.Errorf("expected length of at least 4 bytes, got %d", recordLen)
}
protocolData := make([]byte, recordLen)
n, err = io.ReadFull(conn, protocolData)
hello = append(hello, protocolData[:n]...)
if err != nil {
return hello, err
}
if protocolData[0] != 1 {
return hello, fmt.Errorf("Expected message type 1 (ClientHello), got %d", protocolData[0])
}
protocolLen := int(protocolData[1])<<16 | int(protocolData[2])<<8 | int(protocolData[3])
if protocolLen != recordLen-4 {
return hello, fmt.Errorf("recordLen=%d, protocolLen=%d", recordLen, protocolLen)
}
return hello, nil
}
func clientHelloServerName(data []byte) (name string, ok bool) {
if len(data) < 5 {
return "", false
}
// Strip off the record header.
data = data[5:]
if len(data) < 42 {
return "", false
}
sessionIdLen := int(data[38])
if sessionIdLen > 32 || len(data) < 39+sessionIdLen {
return "", false
}
data = data[39+sessionIdLen:]
if len(data) < 2 {
return "", false
}
cipherSuiteLen := int(data[0])<<8 | int(data[1])
if cipherSuiteLen%2 == 1 || len(data) < 2+cipherSuiteLen {
return "", false
}
data = data[2+cipherSuiteLen:]
if len(data) < 1 {
return "", false
}
compressionMethodsLen := int(data[0])
if len(data) < 1+compressionMethodsLen {
return "", false
}
data = data[1+compressionMethodsLen:]
if len(data) < 2 {
return "", false
}
extensionsLength := int(data[0])<<8 | int(data[1])
data = data[2:]
if extensionsLength != len(data) {
return "", false
}
for len(data) != 0 {
if len(data) < 4 {
return "", false
}
extension := uint16(data[0])<<8 | uint16(data[1])
length := int(data[2])<<8 | int(data[3])
data = data[4:]
if len(data) < length {
return "", false
}
if extension == 0 /* server name */ {
if length < 2 {
return "", false
}
numNames := int(data[0])<<8 | int(data[1])
d := data[2:]
for i := 0; i < numNames; i++ {
if len(d) < 3 {
return "", false
}
nameType := d[0]
nameLen := int(d[1])<<8 | int(d[2])
d = d[3:]
if len(d) < nameLen {
return "", false
}
if nameType == 0 {
return string(d[:nameLen]), true
}
d = d[nameLen:]
}
}
data = data[length:]
}
return "", true
}
func (c *config) addTrustedRoots(certPath string) error {
if c.ExtraRootCerts == nil {
c.ExtraRootCerts = x509.NewCertPool()
}
pem, err := ioutil.ReadFile(certPath)
if err != nil {
return err
}
if !c.ExtraRootCerts.AppendCertsFromPEM(pem) {
return fmt.Errorf("no certificates found in %s", certPath)
}
return nil
}