-
Notifications
You must be signed in to change notification settings - Fork 1.3k
/
tsweb.go
670 lines (607 loc) · 20.5 KB
/
tsweb.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
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause
// Package tsweb contains code used in various Tailscale webservers.
package tsweb
import (
"bufio"
"bytes"
"cmp"
"context"
"errors"
"expvar"
"fmt"
"net"
"net/http"
_ "net/http/pprof"
"net/netip"
"net/url"
"os"
"path/filepath"
"regexp"
"strconv"
"strings"
"sync"
"time"
"go4.org/mem"
"tailscale.com/envknob"
"tailscale.com/metrics"
"tailscale.com/net/tsaddr"
"tailscale.com/tsweb/varz"
"tailscale.com/types/logger"
"tailscale.com/util/vizerror"
)
// DevMode controls whether extra output in shown, for when the binary is being run in dev mode.
var DevMode bool
func DefaultCertDir(leafDir string) string {
cacheDir, err := os.UserCacheDir()
if err == nil {
return filepath.Join(cacheDir, "tailscale", leafDir)
}
return ""
}
// IsProd443 reports whether addr is a Go listen address for port 443.
func IsProd443(addr string) bool {
_, port, _ := net.SplitHostPort(addr)
return port == "443" || port == "https"
}
// AllowDebugAccess reports whether r should be permitted to access
// various debug endpoints.
func AllowDebugAccess(r *http.Request) bool {
if allowDebugAccessWithKey(r) {
return true
}
if r.Header.Get("X-Forwarded-For") != "" {
// TODO if/when needed. For now, conservative:
return false
}
ipStr, _, err := net.SplitHostPort(r.RemoteAddr)
if err != nil {
return false
}
ip, err := netip.ParseAddr(ipStr)
if err != nil {
return false
}
if tsaddr.IsTailscaleIP(ip) || ip.IsLoopback() || ipStr == envknob.String("TS_ALLOW_DEBUG_IP") {
return true
}
return false
}
func allowDebugAccessWithKey(r *http.Request) bool {
if r.Method != "GET" {
return false
}
urlKey := r.FormValue("debugkey")
keyPath := envknob.String("TS_DEBUG_KEY_PATH")
if urlKey != "" && keyPath != "" {
slurp, err := os.ReadFile(keyPath)
if err == nil && string(bytes.TrimSpace(slurp)) == urlKey {
return true
}
}
return false
}
// AcceptsEncoding reports whether r accepts the named encoding
// ("gzip", "br", etc).
func AcceptsEncoding(r *http.Request, enc string) bool {
h := r.Header.Get("Accept-Encoding")
if h == "" {
return false
}
if !strings.Contains(h, enc) && !mem.ContainsFold(mem.S(h), mem.S(enc)) {
return false
}
remain := h
for len(remain) > 0 {
var part string
part, remain, _ = strings.Cut(remain, ",")
part = strings.TrimSpace(part)
part, _, _ = strings.Cut(part, ";")
if part == enc {
return true
}
}
return false
}
// Protected wraps a provided debug handler, h, returning a Handler
// that enforces AllowDebugAccess and returns forbidden replies for
// unauthorized requests.
func Protected(h http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
if !AllowDebugAccess(r) {
msg := "debug access denied"
if DevMode {
ipStr, _, _ := net.SplitHostPort(r.RemoteAddr)
msg += fmt.Sprintf("; to permit access, set TS_ALLOW_DEBUG_IP=%v", ipStr)
}
http.Error(w, msg, http.StatusForbidden)
return
}
h.ServeHTTP(w, r)
})
}
// Port80Handler is the handler to be given to
// autocert.Manager.HTTPHandler. The inner handler is the mux
// returned by NewMux containing registered /debug handlers.
type Port80Handler struct {
Main http.Handler
// FQDN is used to redirect incoming requests to https://<FQDN>.
// If it is not set, the hostname is calculated from the incoming
// request.
FQDN string
}
func (h Port80Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
path := r.RequestURI
if path == "/debug" || strings.HasPrefix(path, "/debug") {
h.Main.ServeHTTP(w, r)
return
}
if r.Method != "GET" && r.Method != "HEAD" {
http.Error(w, "Use HTTPS", http.StatusBadRequest)
return
}
if path == "/" && AllowDebugAccess(r) {
// Redirect authorized user to the debug handler.
path = "/debug/"
}
host := cmp.Or(h.FQDN, r.Host)
target := "https://" + host + path
http.Redirect(w, r, target, http.StatusFound)
}
// ReturnHandler is like net/http.Handler, but the handler can return an
// error instead of writing to its ResponseWriter.
type ReturnHandler interface {
// ServeHTTPReturn is like http.Handler.ServeHTTP, except that
// it can choose to return an error instead of writing to its
// http.ResponseWriter.
//
// If ServeHTTPReturn returns an error, it caller should handle
// an error by serving an HTTP 500 response to the user. The
// error details should not be sent to the client, as they may
// contain sensitive information. If the error is an
// HTTPError, though, callers should use the HTTP response
// code and message as the response to the client.
ServeHTTPReturn(http.ResponseWriter, *http.Request) error
}
// BucketedStatsOptions describes tsweb handler options surrounding
// the generation of metrics, grouped into buckets.
type BucketedStatsOptions struct {
// Bucket returns which bucket the given request is in.
// If nil, [NormalizedPath] is used to compute the bucket.
Bucket func(req *http.Request) string
// If non-nil, Started maintains a counter of all requests which
// have begun processing.
Started *metrics.LabelMap
// If non-nil, Finished maintains a counter of all requests which
// have finished processing with success (that is, the HTTP handler has
// returned).
Finished *metrics.LabelMap
}
// normalizePathRegex matches components in a HTTP request path
// that should be replaced.
//
// See: https://regex101.com/r/WIfpaR/3 for the explainer and test cases.
var normalizePathRegex = regexp.MustCompile("([a-fA-F0-9]{9,}|([^\\/])+\\.([^\\/]){2,}|((n|k|u|L|t|S)[a-zA-Z0-9]{5,}(CNTRL|Djz1H|LV5CY|mxgaY|jNy1b))|(([^\\/])+\\@passkey))")
// NormalizedPath returns the given path with the following modifications:
//
// - any query parameters are removed
// - any path component with a hex string of 9 or more characters is
// replaced by an ellipsis
// - any path component containing a period with at least two characters
// after the period (i.e. an email or domain)
// - any path component consisting of a common Tailscale Stable ID
// - any path segment *@passkey.
func NormalizedPath(p string) string {
// Fastpath: No hex sequences in there we might have to trim.
// Avoids allocating.
if normalizePathRegex.FindStringIndex(p) == nil {
b, _, _ := strings.Cut(p, "?")
return b
}
// If we got here, there's at least one hex sequences we need to
// replace with an ellipsis.
replaced := normalizePathRegex.ReplaceAllString(p, "…")
b, _, _ := strings.Cut(replaced, "?")
return b
}
func (o *BucketedStatsOptions) bucketForRequest(r *http.Request) string {
if o.Bucket != nil {
return o.Bucket(r)
}
return NormalizedPath(r.URL.Path)
}
type HandlerOptions struct {
QuietLoggingIfSuccessful bool // if set, do not log successfully handled HTTP requests (200 and 304 status codes)
Logf logger.Logf
Now func() time.Time // if nil, defaults to time.Now
// If non-nil, StatusCodeCounters maintains counters
// of status codes for handled responses.
// The keys are "1xx", "2xx", "3xx", "4xx", and "5xx".
StatusCodeCounters *expvar.Map
// If non-nil, StatusCodeCountersFull maintains counters of status
// codes for handled responses.
// The keys are HTTP numeric response codes e.g. 200, 404, ...
StatusCodeCountersFull *expvar.Map
// If non-nil, BucketedStats computes and exposes statistics
// for each bucket based on the contained parameters.
BucketedStats *BucketedStatsOptions
// OnError is called if the handler returned a HTTPError. This
// is intended to be used to present pretty error pages if
// the user agent is determined to be a browser.
OnError ErrorHandlerFunc
}
// ErrorHandlerFunc is called to present a error response.
type ErrorHandlerFunc func(http.ResponseWriter, *http.Request, HTTPError)
// ReturnHandlerFunc is an adapter to allow the use of ordinary
// functions as ReturnHandlers. If f is a function with the
// appropriate signature, ReturnHandlerFunc(f) is a ReturnHandler that
// calls f.
type ReturnHandlerFunc func(http.ResponseWriter, *http.Request) error
// A Middleware is a function that wraps an http.Handler to extend or modify
// its behaviour.
//
// The implementation of the wrapper is responsible for delegating its input
// request to the underlying handler, if appropriate.
type Middleware func(h http.Handler) http.Handler
// ServeHTTPReturn calls f(w, r).
func (f ReturnHandlerFunc) ServeHTTPReturn(w http.ResponseWriter, r *http.Request) error {
return f(w, r)
}
// StdHandler converts a ReturnHandler into a standard http.Handler.
// Handled requests are logged using opts.Logf, as are any errors.
// Errors are handled as specified by the Handler interface.
func StdHandler(h ReturnHandler, opts HandlerOptions) http.Handler {
if opts.Now == nil {
opts.Now = time.Now
}
if opts.Logf == nil {
opts.Logf = logger.Discard
}
return retHandler{h, opts}
}
// retHandler is an http.Handler that wraps a Handler and handles errors.
type retHandler struct {
rh ReturnHandler
opts HandlerOptions
}
// ServeHTTP implements the http.Handler interface.
func (h retHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
msg := AccessLogRecord{
When: h.opts.Now(),
RemoteAddr: r.RemoteAddr,
Proto: r.Proto,
TLS: r.TLS != nil,
Host: r.Host,
Method: r.Method,
RequestURI: r.URL.RequestURI(),
UserAgent: r.UserAgent(),
Referer: r.Referer(),
RequestID: RequestIDFromContext(r.Context()),
}
var bucket string
bumpStartIfNeeded := func() {}
if bs := h.opts.BucketedStats; bs != nil {
bucket = bs.bucketForRequest(r)
if bs.Started != nil {
switch v := bs.Started.Map.Get(bucket).(type) {
case *expvar.Int:
// If we've already seen this bucket for, count it immediately.
v.Add(1)
case nil:
// Otherwise, for newly seen paths, only count retroactively
// (so started-finished doesn't go negative) so we don't fill
// this LabelMap up with internet scanning spam.
bumpStartIfNeeded = func() { bs.Started.Add(bucket, 1) }
}
}
}
lw := &loggingResponseWriter{ResponseWriter: w, logf: h.opts.Logf}
// In case the handler panics, we want to recover and continue logging the
// error before raising the panic again for the server to handle.
var (
didPanic bool
panicRes any
)
defer func() {
if didPanic {
panic(panicRes)
}
}()
runWithPanicProtection := func() (err error) {
defer func() {
if r := recover(); r != nil {
didPanic = true
panicRes = r
// Even if r is an error, do not wrap it as an error here as
// that would allow things like panic(vizerror.New("foo")) which
// is really hard to define the behavior of.
err = fmt.Errorf("panic: %v", r)
}
}()
return h.rh.ServeHTTPReturn(lw, r)
}
err := runWithPanicProtection()
var hErr HTTPError
var hErrOK bool
if errors.As(err, &hErr) {
hErrOK = true
} else if vizErr, ok := vizerror.As(err); ok {
hErrOK = true
hErr = HTTPError{Msg: vizErr.Error()}
}
if lw.code == 0 && err == nil && !lw.hijacked {
// If the handler didn't write and didn't send a header, that still means 200.
// (See https://play.golang.org/p/4P7nx_Tap7p)
lw.code = 200
}
msg.Seconds = h.opts.Now().Sub(msg.When).Seconds()
msg.Code = lw.code
msg.Bytes = lw.bytes
switch {
case lw.hijacked:
// Connection no longer belongs to us, just log that we
// switched protocols away from HTTP.
if msg.Code == 0 {
msg.Code = http.StatusSwitchingProtocols
}
case err != nil && r.Context().Err() == context.Canceled:
msg.Code = 499 // nginx convention: Client Closed Request
msg.Err = context.Canceled.Error()
case hErrOK:
// Handler asked us to send an error. Do so, if we haven't
// already sent a response.
msg.Err = hErr.Msg
if hErr.Err != nil {
if msg.Err == "" {
msg.Err = hErr.Err.Error()
} else {
msg.Err = msg.Err + ": " + hErr.Err.Error()
}
}
if lw.code != 0 {
h.opts.Logf("[unexpected] handler returned HTTPError %v, but already sent a response with code %d", hErr, lw.code)
break
}
msg.Code = hErr.Code
if msg.Code == 0 {
h.opts.Logf("[unexpected] HTTPError %v did not contain an HTTP status code, sending internal server error", hErr)
msg.Code = http.StatusInternalServerError
}
if h.opts.OnError != nil {
h.opts.OnError(lw, r, hErr)
} else {
// Default headers set by http.Error.
lw.Header().Set("Content-Type", "text/plain; charset=utf-8")
lw.Header().Set("X-Content-Type-Options", "nosniff")
for k, vs := range hErr.Header {
lw.Header()[k] = vs
}
lw.WriteHeader(msg.Code)
fmt.Fprintln(lw, hErr.Msg)
if msg.RequestID != "" {
fmt.Fprintln(lw, msg.RequestID)
}
}
case err != nil:
const internalServerError = "internal server error"
errorMessage := internalServerError
if msg.RequestID != "" {
errorMessage += "\n" + string(msg.RequestID)
}
// Handler returned a generic error. Serve an internal server
// error, if necessary.
msg.Err = err.Error()
if lw.code == 0 {
msg.Code = http.StatusInternalServerError
http.Error(lw, errorMessage, msg.Code)
}
}
if bs := h.opts.BucketedStats; bs != nil && bs.Finished != nil {
// Only increment metrics for buckets that result in good HTTP statuses.
// Otherwise they get full of internet scanning noise. Only filtering 404
// gets most of the way there but there are also plenty of URLs that are
// almost right but result in 400s too. Seem easier to just only ignore
// all 4xx and 5xx.
if msg.Code < 400 {
bumpStartIfNeeded()
bs.Finished.Add(bucket, 1)
}
}
if !h.opts.QuietLoggingIfSuccessful || (msg.Code != http.StatusOK && msg.Code != http.StatusNotModified) {
h.opts.Logf("%s", msg)
}
if h.opts.StatusCodeCounters != nil {
h.opts.StatusCodeCounters.Add(responseCodeString(msg.Code/100), 1)
}
if h.opts.StatusCodeCountersFull != nil {
h.opts.StatusCodeCountersFull.Add(responseCodeString(msg.Code), 1)
}
}
func responseCodeString(code int) string {
if v, ok := responseCodeCache.Load(code); ok {
return v.(string)
}
var ret string
if code < 10 {
ret = fmt.Sprintf("%dxx", code)
} else {
ret = strconv.Itoa(code)
}
responseCodeCache.Store(code, ret)
return ret
}
// responseCodeCache memoizes the string form of HTTP response codes,
// so that the hot request-handling codepath doesn't have to allocate
// in strconv/fmt for every request.
//
// Keys are either full HTTP response code ints (200, 404) or "family"
// ints representing entire families (e.g. 2 for 2xx codes). Values
// are the string form of that code/family.
var responseCodeCache sync.Map
// loggingResponseWriter wraps a ResponseWriter and record the HTTP
// response code that gets sent, if any.
type loggingResponseWriter struct {
http.ResponseWriter
code int
bytes int
hijacked bool
logf logger.Logf
}
// WriteHeader implements http.Handler.
func (l *loggingResponseWriter) WriteHeader(statusCode int) {
if l.code != 0 {
l.logf("[unexpected] HTTP handler set statusCode twice (%d and %d)", l.code, statusCode)
return
}
l.code = statusCode
l.ResponseWriter.WriteHeader(statusCode)
}
// Write implements http.Handler.
func (l *loggingResponseWriter) Write(bs []byte) (int, error) {
if l.code == 0 {
l.code = 200
}
n, err := l.ResponseWriter.Write(bs)
l.bytes += n
return n, err
}
// Hijack implements http.Hijacker. Note that hijacking can still fail
// because the wrapped ResponseWriter is not required to implement
// Hijacker, as this breaks HTTP/2.
func (l *loggingResponseWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
h, ok := l.ResponseWriter.(http.Hijacker)
if !ok {
return nil, nil, errors.New("ResponseWriter is not a Hijacker")
}
conn, buf, err := h.Hijack()
if err == nil {
l.hijacked = true
}
return conn, buf, err
}
func (l loggingResponseWriter) Flush() {
f, _ := l.ResponseWriter.(http.Flusher)
if f == nil {
l.logf("[unexpected] tried to Flush a ResponseWriter that can't flush")
return
}
f.Flush()
}
// HTTPError is an error with embedded HTTP response information.
//
// It is the error type to be (optionally) used by Handler.ServeHTTPReturn.
type HTTPError struct {
Code int // HTTP response code to send to client; 0 means 500
Msg string // Response body to send to client
Err error // Detailed error to log on the server
Header http.Header // Optional set of HTTP headers to set in the response
}
// Error implements the error interface.
func (e HTTPError) Error() string { return fmt.Sprintf("httperror{%d, %q, %v}", e.Code, e.Msg, e.Err) }
func (e HTTPError) Unwrap() error { return e.Err }
// Error returns an HTTPError containing the given information.
func Error(code int, msg string, err error) HTTPError {
return HTTPError{Code: code, Msg: msg, Err: err}
}
// VarzHandler writes expvar values as Prometheus metrics.
// TODO: migrate all users to varz.Handler or promvarz.Handler and remove this.
func VarzHandler(w http.ResponseWriter, r *http.Request) {
varz.Handler(w, r)
}
// CleanRedirectURL ensures that urlStr is a valid redirect URL to the
// current server, or one of allowedHosts. Returns the cleaned URL or
// a validation error.
func CleanRedirectURL(urlStr string, allowedHosts []string) (*url.URL, error) {
if urlStr == "" {
return &url.URL{}, nil
}
// In some places, we unfortunately query-escape the redirect URL
// too many times, and end up needing to redirect to a URL that's
// still escaped by one level. Try to unescape the input.
unescaped, err := url.QueryUnescape(urlStr)
if err == nil && unescaped != urlStr {
urlStr = unescaped
}
// Go's URL parser and browser URL parsers disagree on the meaning
// of malformed HTTP URLs. Given the input https:/evil.com, Go
// parses it as hostname="", path="/evil.com". Browsers parse it
// as hostname="evil.com", path="". This means that, using
// malformed URLs, an attacker could trick us into approving of a
// "local" redirect that in fact sends people elsewhere.
//
// This very blunt check enforces that we'll only process
// redirects that are definitely well-formed URLs.
//
// Note that the check for just / also allows URLs of the form
// "//foo.com/bar", which are scheme-relative redirects. These
// must be handled with care below when determining whether a
// redirect is relative to the current host. Notably,
// url.URL.IsAbs reports // URLs as relative, whereas we want to
// treat them as absolute redirects and verify the target host.
if !hasSafeRedirectPrefix(urlStr) {
return nil, fmt.Errorf("invalid redirect URL %q", urlStr)
}
url, err := url.Parse(urlStr)
if err != nil {
return nil, fmt.Errorf("invalid redirect URL %q: %w", urlStr, err)
}
// Redirects to self are always allowed. A self redirect must
// start with url.Path, all prior URL sections must be empty.
isSelfRedirect := url.Scheme == "" && url.Opaque == "" && url.User == nil && url.Host == ""
if isSelfRedirect {
return url, nil
}
for _, allowed := range allowedHosts {
if strings.EqualFold(allowed, url.Hostname()) {
return url, nil
}
}
return nil, fmt.Errorf("disallowed target host %q in redirect URL %q", url.Hostname(), urlStr)
}
// hasSafeRedirectPrefix reports whether url starts with a slash, or
// one of the case-insensitive strings "http://" or "https://".
func hasSafeRedirectPrefix(url string) bool {
if len(url) >= 1 && url[0] == '/' {
return true
}
const http = "http://"
if len(url) >= len(http) && strings.EqualFold(url[:len(http)], http) {
return true
}
const https = "https://"
if len(url) >= len(https) && strings.EqualFold(url[:len(https)], https) {
return true
}
return false
}
// AddBrowserHeaders sets various HTTP security headers for browser-facing endpoints.
//
// The specific headers:
// - require HTTPS access (HSTS)
// - disallow iframe embedding
// - mitigate MIME confusion attacks
//
// These headers are based on
// https://infosec.mozilla.org/guidelines/web_security
func AddBrowserHeaders(w http.ResponseWriter) {
w.Header().Set("Strict-Transport-Security", "max-age=63072000; includeSubDomains")
w.Header().Set("Content-Security-Policy", "default-src 'self'; frame-ancestors 'none'; form-action 'self'; base-uri 'self'; block-all-mixed-content; object-src 'none'")
w.Header().Set("X-Frame-Options", "DENY")
w.Header().Set("X-Content-Type-Options", "nosniff")
}
// BrowserHeaderHandler wraps the provided http.Handler with a call to
// AddBrowserHeaders.
func BrowserHeaderHandler(h http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
AddBrowserHeaders(w)
h.ServeHTTP(w, r)
})
}
// BrowserHeaderHandlerFunc wraps the provided http.HandlerFunc with a call to
// AddBrowserHeaders.
func BrowserHeaderHandlerFunc(h http.HandlerFunc) http.HandlerFunc {
return func(w http.ResponseWriter, r *http.Request) {
AddBrowserHeaders(w)
h.ServeHTTP(w, r)
}
}