Source file src/net/http/client.go
1 // Copyright 2009 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 // HTTP client. See RFC 7230 through 7235. 6 // 7 // This is the high-level Client interface. 8 // The low-level implementation is in transport.go. 9 10 package http 11 12 import ( 13 "context" 14 "crypto/tls" 15 "encoding/base64" 16 "errors" 17 "fmt" 18 "io" 19 "log" 20 "net/http/internal/ascii" 21 "net/url" 22 "reflect" 23 "slices" 24 "strings" 25 "sync" 26 "sync/atomic" 27 "time" 28 29 "golang.org/x/net/http/httpguts" 30 ) 31 32 // A Client is an HTTP client. Its zero value ([DefaultClient]) is a 33 // usable client that uses [DefaultTransport]. 34 // 35 // The [Client.Transport] typically has internal state (cached TCP 36 // connections), so Clients should be reused instead of created as 37 // needed. Clients are safe for concurrent use by multiple goroutines. 38 // 39 // A Client is higher-level than a [RoundTripper] (such as [Transport]) 40 // and additionally handles HTTP details such as cookies and 41 // redirects. 42 // 43 // When following redirects, the Client will forward all headers set on the 44 // initial [Request] except: 45 // 46 // - when forwarding sensitive headers like "Authorization", 47 // "WWW-Authenticate", and "Cookie" to untrusted targets. 48 // These headers will be ignored when following a redirect to a domain 49 // that is not a subdomain match or exact match of the initial domain. 50 // For example, a redirect from "foo.com" to either "foo.com" or "sub.foo.com" 51 // will forward the sensitive headers, but a redirect to "bar.com" will not. 52 // - when forwarding the "Cookie" header with a non-nil cookie Jar. 53 // Since each redirect may mutate the state of the cookie jar, 54 // a redirect may possibly alter a cookie set in the initial request. 55 // When forwarding the "Cookie" header, any mutated cookies will be omitted, 56 // with the expectation that the Jar will insert those mutated cookies 57 // with the updated values (assuming the origin matches). 58 // If Jar is nil, the initial cookies are forwarded without change. 59 type Client struct { 60 // Transport specifies the mechanism by which individual 61 // HTTP requests are made. 62 // If nil, DefaultTransport is used. 63 Transport RoundTripper 64 65 // CheckRedirect specifies the policy for handling redirects. 66 // If CheckRedirect is not nil, the client calls it before 67 // following an HTTP redirect. The arguments req and via are 68 // the upcoming request and the requests made already, oldest 69 // first. If CheckRedirect returns an error, the Client's Get 70 // method returns both the previous Response (with its Body 71 // closed) and CheckRedirect's error (wrapped in a url.Error) 72 // instead of issuing the Request req. 73 // As a special case, if CheckRedirect returns ErrUseLastResponse, 74 // then the most recent response is returned with its body 75 // unclosed, along with a nil error. 76 // 77 // If CheckRedirect is nil, the Client uses its default policy, 78 // which is to stop after 10 consecutive requests. 79 CheckRedirect func(req *Request, via []*Request) error 80 81 // Jar specifies the cookie jar. 82 // 83 // The Jar is used to insert relevant cookies into every 84 // outbound Request and is updated with the cookie values 85 // of every inbound Response. The Jar is consulted for every 86 // redirect that the Client follows. 87 // 88 // If Jar is nil, cookies are only sent if they are explicitly 89 // set on the Request. 90 Jar CookieJar 91 92 // Timeout specifies a time limit for requests made by this 93 // Client. The timeout includes connection time, any 94 // redirects, and reading the response body. The timer remains 95 // running after Get, Head, Post, or Do return and will 96 // interrupt reading of the Response.Body. 97 // 98 // A Timeout of zero means no timeout. 99 // 100 // The Client cancels requests to the underlying Transport 101 // as if the Request's Context ended. 102 Timeout time.Duration 103 } 104 105 // DefaultClient is the default [Client] and is used by [Get], [Head], and [Post]. 106 var DefaultClient = &Client{} 107 108 // RoundTripper is an interface representing the ability to execute a 109 // single HTTP transaction, obtaining the [Response] for a given [Request]. 110 // 111 // A RoundTripper must be safe for concurrent use by multiple 112 // goroutines. 113 type RoundTripper interface { 114 // RoundTrip executes a single HTTP transaction, returning 115 // a Response for the provided Request. 116 // 117 // RoundTrip should not attempt to interpret the response. In 118 // particular, RoundTrip must return err == nil if it obtained 119 // a response, regardless of the response's HTTP status code. 120 // A non-nil err should be reserved for failure to obtain a 121 // response. Similarly, RoundTrip should not attempt to 122 // handle higher-level protocol details such as redirects, 123 // authentication, or cookies. 124 // 125 // RoundTrip should not modify the request, except for 126 // consuming and closing the Request's Body. RoundTrip may 127 // read fields of the request in a separate goroutine. Callers 128 // should not mutate or reuse the request until the Response's 129 // Body has been closed. 130 // 131 // RoundTrip must always close the body, including on errors, 132 // but depending on the implementation may do so in a separate 133 // goroutine even after RoundTrip returns. This means that 134 // callers wanting to reuse the body for subsequent requests 135 // must arrange to wait for the Close call before doing so. 136 // 137 // The Request's URL and Header fields must be initialized. 138 RoundTrip(*Request) (*Response, error) 139 } 140 141 // refererForURL returns a referer without any authentication info or 142 // an empty string if lastReq scheme is https and newReq scheme is http. 143 // If the referer was explicitly set, then it will continue to be used. 144 func refererForURL(lastReq, newReq *url.URL, explicitRef string) string { 145 // https://tools.ietf.org/html/rfc7231#section-5.5.2 146 // "Clients SHOULD NOT include a Referer header field in a 147 // (non-secure) HTTP request if the referring page was 148 // transferred with a secure protocol." 149 if lastReq.Scheme == "https" && newReq.Scheme == "http" { 150 return "" 151 } 152 if explicitRef != "" { 153 return explicitRef 154 } 155 156 referer := lastReq.String() 157 if lastReq.User != nil { 158 // This is not very efficient, but is the best we can 159 // do without: 160 // - introducing a new method on URL 161 // - creating a race condition 162 // - copying the URL struct manually, which would cause 163 // maintenance problems down the line 164 auth := lastReq.User.String() + "@" 165 referer = strings.Replace(referer, auth, "", 1) 166 } 167 return referer 168 } 169 170 // didTimeout is non-nil only if err != nil. 171 func (c *Client) send(req *Request, deadline time.Time) (resp *Response, didTimeout func() bool, err error) { 172 cookieURL := req.URL 173 if req.Host != "" { 174 cookieURL = cloneURL(cookieURL) 175 cookieURL.Host = req.Host 176 } 177 if c.Jar != nil { 178 for _, cookie := range c.Jar.Cookies(cookieURL) { 179 req.AddCookie(cookie) 180 } 181 } 182 resp, didTimeout, err = send(req, c.transport(), deadline) 183 if err != nil { 184 return nil, didTimeout, err 185 } 186 if c.Jar != nil { 187 if rc := resp.Cookies(); len(rc) > 0 { 188 c.Jar.SetCookies(cookieURL, rc) 189 } 190 } 191 return resp, nil, nil 192 } 193 194 func (c *Client) deadline() time.Time { 195 if c.Timeout > 0 { 196 return time.Now().Add(c.Timeout) 197 } 198 return time.Time{} 199 } 200 201 func (c *Client) transport() RoundTripper { 202 if c.Transport != nil { 203 return c.Transport 204 } 205 return DefaultTransport 206 } 207 208 // ErrSchemeMismatch is returned when a server returns an HTTP response to an HTTPS client. 209 var ErrSchemeMismatch = errors.New("http: server gave HTTP response to HTTPS client") 210 211 // send issues an HTTP request. 212 // Caller should close resp.Body when done reading from it. 213 func send(ireq *Request, rt RoundTripper, deadline time.Time) (resp *Response, didTimeout func() bool, err error) { 214 req := ireq // req is either the original request, or a modified fork 215 216 if rt == nil { 217 req.closeBody() 218 return nil, alwaysFalse, errors.New("http: no Client.Transport or DefaultTransport") 219 } 220 221 if req.URL == nil { 222 req.closeBody() 223 return nil, alwaysFalse, errors.New("http: nil Request.URL") 224 } 225 226 if req.RequestURI != "" { 227 req.closeBody() 228 return nil, alwaysFalse, errors.New("http: Request.RequestURI can't be set in client requests") 229 } 230 231 // forkReq forks req into a shallow clone of ireq the first 232 // time it's called. 233 forkReq := func() { 234 if ireq == req { 235 req = new(Request) 236 *req = *ireq // shallow clone 237 } 238 } 239 240 // Most of the callers of send (Get, Post, et al) don't need 241 // Headers, leaving it uninitialized. We guarantee to the 242 // Transport that this has been initialized, though. 243 if req.Header == nil { 244 forkReq() 245 req.Header = make(Header) 246 } 247 248 if u := req.URL.User; u != nil && req.Header.Get("Authorization") == "" { 249 username := u.Username() 250 password, _ := u.Password() 251 forkReq() 252 req.Header = cloneOrMakeHeader(ireq.Header) 253 req.Header.Set("Authorization", "Basic "+basicAuth(username, password)) 254 } 255 256 if !deadline.IsZero() { 257 forkReq() 258 } 259 stopTimer, didTimeout := setRequestCancel(req, rt, deadline) 260 261 resp, err = rt.RoundTrip(req) 262 if err != nil { 263 stopTimer() 264 if resp != nil { 265 log.Printf("RoundTripper returned a response & error; ignoring response") 266 } 267 if tlsErr, ok := err.(tls.RecordHeaderError); ok { 268 // If we get a bad TLS record header, check to see if the 269 // response looks like HTTP and give a more helpful error. 270 // See golang.org/issue/11111. 271 if string(tlsErr.RecordHeader[:]) == "HTTP/" { 272 err = ErrSchemeMismatch 273 } 274 } 275 return nil, didTimeout, err 276 } 277 if resp == nil { 278 return nil, didTimeout, fmt.Errorf("http: RoundTripper implementation (%T) returned a nil *Response with a nil error", rt) 279 } 280 if resp.Body == nil { 281 // The documentation on the Body field says “The http Client and Transport 282 // guarantee that Body is always non-nil, even on responses without a body 283 // or responses with a zero-length body.” Unfortunately, we didn't document 284 // that same constraint for arbitrary RoundTripper implementations, and 285 // RoundTripper implementations in the wild (mostly in tests) assume that 286 // they can use a nil Body to mean an empty one (similar to Request.Body). 287 // (See https://golang.org/issue/38095.) 288 // 289 // If the ContentLength allows the Body to be empty, fill in an empty one 290 // here to ensure that it is non-nil. 291 if resp.ContentLength > 0 && req.Method != "HEAD" { 292 return nil, didTimeout, fmt.Errorf("http: RoundTripper implementation (%T) returned a *Response with content length %d but a nil Body", rt, resp.ContentLength) 293 } 294 resp.Body = io.NopCloser(strings.NewReader("")) 295 } 296 if !deadline.IsZero() { 297 resp.Body = &cancelTimerBody{ 298 stop: stopTimer, 299 rc: resp.Body, 300 reqDidTimeout: didTimeout, 301 } 302 } 303 return resp, nil, nil 304 } 305 306 // timeBeforeContextDeadline reports whether the non-zero Time t is 307 // before ctx's deadline, if any. If ctx does not have a deadline, it 308 // always reports true (the deadline is considered infinite). 309 func timeBeforeContextDeadline(t time.Time, ctx context.Context) bool { 310 d, ok := ctx.Deadline() 311 if !ok { 312 return true 313 } 314 return t.Before(d) 315 } 316 317 // knownRoundTripperImpl reports whether rt is a RoundTripper that's 318 // maintained by the Go team and known to implement the latest 319 // optional semantics (notably contexts). The Request is used 320 // to check whether this particular request is using an alternate protocol, 321 // in which case we need to check the RoundTripper for that protocol. 322 func knownRoundTripperImpl(rt RoundTripper, req *Request) bool { 323 switch t := rt.(type) { 324 case *Transport: 325 if altRT := t.alternateRoundTripper(req); altRT != nil { 326 return knownRoundTripperImpl(altRT, req) 327 } 328 return true 329 case http2RoundTripper: 330 return true 331 } 332 // There's a very minor chance of a false positive with this. 333 // Instead of detecting our golang.org/x/net/http2.Transport, 334 // it might detect a Transport type in a different http2 335 // package. But I know of none, and the only problem would be 336 // some temporarily leaked goroutines if the transport didn't 337 // support contexts. So this is a good enough heuristic: 338 if reflect.TypeOf(rt).String() == "*http2.Transport" { 339 return true 340 } 341 return false 342 } 343 344 // setRequestCancel sets req.Cancel and adds a deadline context to req 345 // if deadline is non-zero. 346 // 347 // As background, there are (or were) three ways to cancel a request: 348 // First was Transport.CancelRequest. (deprecated, no longer supported) 349 // Second was Request.Cancel. 350 // Third was Request.Context. 351 // 352 // This function populates Request.Cancel and Request.Context. 353 func setRequestCancel(req *Request, rt RoundTripper, deadline time.Time) (stopTimer func(), didTimeout func() bool) { 354 if deadline.IsZero() { 355 return nop, alwaysFalse 356 } 357 knownTransport := knownRoundTripperImpl(rt, req) 358 oldCtx := req.Context() 359 360 if req.Cancel == nil && knownTransport { 361 // If they already had a Request.Context that's 362 // expiring sooner, do nothing: 363 if !timeBeforeContextDeadline(deadline, oldCtx) { 364 return nop, alwaysFalse 365 } 366 367 ctx, cancelCtx := context.WithDeadline(oldCtx, deadline) 368 req.ctx = ctx 369 return cancelCtx, func() bool { return ctx.Err() == context.DeadlineExceeded } 370 } 371 initialReqCancel := req.Cancel // the user's original Request.Cancel, if any 372 373 var cancelCtx func() 374 if timeBeforeContextDeadline(deadline, oldCtx) { 375 req.ctx, cancelCtx = context.WithDeadline(oldCtx, deadline) 376 } 377 378 cancel := make(chan struct{}) 379 req.Cancel = cancel 380 381 stopTimerCh := make(chan struct{}) 382 stopTimer = sync.OnceFunc(func() { 383 close(stopTimerCh) 384 if cancelCtx != nil { 385 cancelCtx() 386 } 387 }) 388 389 timer := time.NewTimer(time.Until(deadline)) 390 var timedOut atomic.Bool 391 392 go func() { 393 select { 394 case <-initialReqCancel: 395 close(cancel) 396 timer.Stop() 397 case <-timer.C: 398 timedOut.Store(true) 399 close(cancel) 400 case <-stopTimerCh: 401 timer.Stop() 402 } 403 }() 404 405 return stopTimer, timedOut.Load 406 } 407 408 // See 2 (end of page 4) https://www.ietf.org/rfc/rfc2617.txt 409 // "To receive authorization, the client sends the userid and password, 410 // separated by a single colon (":") character, within a base64 411 // encoded string in the credentials." 412 // It is not meant to be urlencoded. 413 func basicAuth(username, password string) string { 414 auth := username + ":" + password 415 return base64.StdEncoding.EncodeToString([]byte(auth)) 416 } 417 418 // Get issues a GET to the specified URL. If the response is one of 419 // the following redirect codes, Get follows the redirect, up to a 420 // maximum of 10 redirects: 421 // 422 // 301 (Moved Permanently) 423 // 302 (Found) 424 // 303 (See Other) 425 // 307 (Temporary Redirect) 426 // 308 (Permanent Redirect) 427 // 428 // An error is returned if there were too many redirects or if there 429 // was an HTTP protocol error. A non-2xx response doesn't cause an 430 // error. Any returned error will be of type [*url.Error]. The url.Error 431 // value's Timeout method will report true if the request timed out. 432 // 433 // When err is nil, resp always contains a non-nil resp.Body. 434 // Caller should close resp.Body when done reading from it. 435 // 436 // Get is a wrapper around DefaultClient.Get. 437 // 438 // To make a request with custom headers, use [NewRequest] and 439 // DefaultClient.Do. 440 // 441 // To make a request with a specified context.Context, use [NewRequestWithContext] 442 // and DefaultClient.Do. 443 func Get(url string) (resp *Response, err error) { 444 return DefaultClient.Get(url) 445 } 446 447 // Get issues a GET to the specified URL. If the response is one of the 448 // following redirect codes, Get follows the redirect after calling the 449 // [Client.CheckRedirect] function: 450 // 451 // 301 (Moved Permanently) 452 // 302 (Found) 453 // 303 (See Other) 454 // 307 (Temporary Redirect) 455 // 308 (Permanent Redirect) 456 // 457 // An error is returned if the [Client.CheckRedirect] function fails 458 // or if there was an HTTP protocol error. A non-2xx response doesn't 459 // cause an error. Any returned error will be of type [*url.Error]. The 460 // url.Error value's Timeout method will report true if the request 461 // timed out. 462 // 463 // When err is nil, resp always contains a non-nil resp.Body. 464 // Caller should close resp.Body when done reading from it. 465 // 466 // To make a request with custom headers, use [NewRequest] and [Client.Do]. 467 // 468 // To make a request with a specified context.Context, use [NewRequestWithContext] 469 // and Client.Do. 470 func (c *Client) Get(url string) (resp *Response, err error) { 471 req, err := NewRequest("GET", url, nil) 472 if err != nil { 473 return nil, err 474 } 475 return c.Do(req) 476 } 477 478 func alwaysFalse() bool { return false } 479 480 // ErrUseLastResponse can be returned by Client.CheckRedirect hooks to 481 // control how redirects are processed. If returned, the next request 482 // is not sent and the most recent response is returned with its body 483 // unclosed. 484 var ErrUseLastResponse = errors.New("net/http: use last response") 485 486 // checkRedirect calls either the user's configured CheckRedirect 487 // function, or the default. 488 func (c *Client) checkRedirect(req *Request, via []*Request) error { 489 fn := c.CheckRedirect 490 if fn == nil { 491 fn = defaultCheckRedirect 492 } 493 return fn(req, via) 494 } 495 496 // redirectBehavior describes what should happen when the 497 // client encounters a 3xx status code from the server. 498 func redirectBehavior(reqMethod string, resp *Response, ireq *Request) (redirectMethod string, shouldRedirect, includeBody bool) { 499 switch resp.StatusCode { 500 case 301, 302, 303: 501 redirectMethod = reqMethod 502 shouldRedirect = true 503 includeBody = false 504 505 // RFC 10008, Section 2.5: QUERY is safe and idempotent, so 301 506 // and 302 preserve the method and re-send the body (as 307 and 507 // 308 do); only 303 changes the method to GET. 508 if reqMethod == "QUERY" && resp.StatusCode != 303 { 509 includeBody = true 510 if ireq.GetBody == nil && ireq.outgoingLength() != 0 { 511 // We had a request body, and 301/302 require 512 // re-sending it, but GetBody is not defined. 513 shouldRedirect = false 514 } 515 } else if reqMethod != "GET" && reqMethod != "HEAD" { 516 // RFC 2616 allowed automatic redirection only with GET and 517 // HEAD requests. RFC 7231 lifts this restriction, but we still 518 // restrict other methods to GET to maintain compatibility. 519 // See Issue 18570. 520 redirectMethod = "GET" 521 } 522 case 307, 308: 523 redirectMethod = reqMethod 524 shouldRedirect = true 525 includeBody = true 526 527 if ireq.GetBody == nil && ireq.outgoingLength() != 0 { 528 // We had a request body, and 307/308 require 529 // re-sending it, but GetBody is not defined. So just 530 // return this response to the user instead of an 531 // error, like we did in Go 1.7 and earlier. 532 shouldRedirect = false 533 } 534 } 535 return redirectMethod, shouldRedirect, includeBody 536 } 537 538 // urlErrorOp returns the (*url.Error).Op value to use for the 539 // provided (*Request).Method value. 540 func urlErrorOp(method string) string { 541 if method == "" { 542 return "Get" 543 } 544 if lowerMethod, ok := ascii.ToLower(method); ok { 545 return method[:1] + lowerMethod[1:] 546 } 547 return method 548 } 549 550 // Do sends an HTTP request and returns an HTTP response, following 551 // policy (such as redirects, cookies, auth) as configured on the 552 // client. 553 // 554 // An error is returned if caused by client policy (such as 555 // CheckRedirect), or failure to speak HTTP (such as a network 556 // connectivity problem). A non-2xx status code doesn't cause an 557 // error. 558 // 559 // If the returned error is nil, the [Response] will contain a non-nil 560 // Body which the user is expected to close. If the Body is not both 561 // read to EOF and closed, the [Client]'s underlying [RoundTripper] 562 // (typically [Transport]) may not be able to re-use a persistent TCP 563 // connection to the server for a subsequent "keep-alive" request. 564 // Note, however, that [Transport] will automatically try to read a 565 // [Response] Body to EOF asynchronously up to a conservative limit 566 // when a Body is closed. 567 // 568 // The request Body, if non-nil, will be closed by the underlying 569 // Transport, even on errors. The Body may be closed asynchronously after 570 // Do returns. 571 // 572 // On error, any Response can be ignored. A non-nil Response with a 573 // non-nil error only occurs when CheckRedirect fails, and even then 574 // the returned [Response.Body] is already closed. 575 // 576 // Generally [Get], [Post], or [PostForm] will be used instead of Do. 577 // 578 // If the server replies with a redirect, the Client first uses the 579 // CheckRedirect function to determine whether the redirect should be 580 // followed. If permitted, a 301, 302, or 303 redirect causes 581 // subsequent requests to use HTTP method GET 582 // (or HEAD if the original request was HEAD), with no body. 583 // A 307 or 308 redirect preserves the original HTTP method and body, 584 // provided that the [Request.GetBody] function is defined. 585 // The [NewRequest] function automatically sets GetBody for common 586 // standard library body types. 587 // 588 // Note that the [Client] redirect behavior does not follow the WHATWG 589 // Fetch standard. This is because it was written before established 590 // standards existed. As such, by modern standards, [Client] has a 591 // rather permissive behavior. For example, sensitive headers are 592 // retained on redirect to a subdomain or to a different scheme on the 593 // same host. 594 // 595 // Any returned error will be of type [*url.Error]. The url.Error 596 // value's Timeout method will report true if the request timed out. 597 func (c *Client) Do(req *Request) (*Response, error) { 598 return c.do(req) 599 } 600 601 var testHookClientDoResult func(retres *Response, reterr error) 602 603 func (c *Client) do(req *Request) (retres *Response, reterr error) { 604 if testHookClientDoResult != nil { 605 defer func() { testHookClientDoResult(retres, reterr) }() 606 } 607 if req.URL == nil { 608 req.closeBody() 609 return nil, &url.Error{ 610 Op: urlErrorOp(req.Method), 611 Err: errors.New("http: nil Request.URL"), 612 } 613 } 614 _ = *c // panic early if c is nil; see go.dev/issue/53521 615 616 var ( 617 deadline = c.deadline() 618 reqs []*Request 619 resp *Response 620 copyHeaders = c.makeHeadersCopier(req) 621 reqBodyClosed = false // have we closed the current req.Body? 622 623 // Redirect behavior: 624 redirectMethod string 625 includeBody = true 626 stripSensitiveHeaders = false 627 ) 628 uerr := func(err error) error { 629 // the body may have been closed already by c.send() 630 if !reqBodyClosed { 631 req.closeBody() 632 } 633 var urlStr string 634 if resp != nil && resp.Request != nil { 635 urlStr = stripPassword(resp.Request.URL) 636 } else { 637 urlStr = stripPassword(req.URL) 638 } 639 return &url.Error{ 640 Op: urlErrorOp(reqs[0].Method), 641 URL: urlStr, 642 Err: err, 643 } 644 } 645 for { 646 // For all but the first request, create the next 647 // request hop and replace req. 648 if len(reqs) > 0 { 649 loc := resp.Header.Get("Location") 650 if loc == "" { 651 // While most 3xx responses include a Location, it is not 652 // required and 3xx responses without a Location have been 653 // observed in the wild. See issues #17773 and #49281. 654 return resp, nil 655 } 656 u, err := req.URL.Parse(loc) 657 if err != nil { 658 resp.closeBody() 659 return nil, uerr(fmt.Errorf("failed to parse Location header %q: %v", loc, err)) 660 } 661 host := "" 662 if req.Host != "" && req.Host != req.URL.Host { 663 // If the caller specified a custom Host header and the 664 // redirect location is relative, preserve the Host header 665 // through the redirect. See issue #22233. 666 if u, _ := url.Parse(loc); u != nil && !u.IsAbs() { 667 host = req.Host 668 } 669 } 670 ireq := reqs[0] 671 req = &Request{ 672 Method: redirectMethod, 673 Response: resp, 674 URL: u, 675 Header: make(Header), 676 Host: host, 677 Cancel: ireq.Cancel, 678 ctx: ireq.ctx, 679 } 680 if includeBody && ireq.GetBody != nil { 681 req.Body, err = ireq.GetBody() 682 if err != nil { 683 resp.closeBody() 684 return nil, uerr(err) 685 } 686 req.GetBody = ireq.GetBody 687 req.ContentLength = ireq.ContentLength 688 } 689 690 // Copy original headers before setting the Referer, 691 // in case the user set Referer on their first request. 692 // If they really want to override, they can do it in 693 // their CheckRedirect func. 694 if !stripSensitiveHeaders && reqs[0].URL.Host != req.URL.Host { 695 if !shouldCopyHeaderOnRedirect(reqs[0].URL, req.URL) { 696 stripSensitiveHeaders = true 697 } 698 } 699 copyHeaders(req, stripSensitiveHeaders, !includeBody) 700 // Add the Referer header from the most recent 701 // request URL to the new one, if it's not https->http: 702 if ref := refererForURL(reqs[len(reqs)-1].URL, req.URL, req.Header.Get("Referer")); ref != "" { 703 req.Header.Set("Referer", ref) 704 } 705 err = c.checkRedirect(req, reqs) 706 707 // Sentinel error to let users select the 708 // previous response, without closing its 709 // body. See Issue 10069. 710 if err == ErrUseLastResponse { 711 return resp, nil 712 } 713 714 // Close the previous response's body. But 715 // read at least some of the body so if it's 716 // small the underlying TCP connection will be 717 // re-used. No need to check for errors: if it 718 // fails, the Transport won't reuse it anyway. 719 const maxBodySlurpSize = 2 << 10 720 if resp.ContentLength == -1 || resp.ContentLength <= maxBodySlurpSize { 721 io.CopyN(io.Discard, resp.Body, maxBodySlurpSize) 722 } 723 resp.Body.Close() 724 725 if err != nil { 726 // Special case for Go 1 compatibility: return both the response 727 // and an error if the CheckRedirect function failed. 728 // See https://golang.org/issue/3795 729 // The resp.Body has already been closed. 730 ue := uerr(err) 731 ue.(*url.Error).URL = loc 732 return resp, ue 733 } 734 } 735 736 reqs = append(reqs, req) 737 var err error 738 var didTimeout func() bool 739 if resp, didTimeout, err = c.send(req, deadline); err != nil { 740 // c.send() always closes req.Body 741 reqBodyClosed = true 742 if !deadline.IsZero() && didTimeout() { 743 err = &timeoutError{err.Error() + " (Client.Timeout exceeded while awaiting headers)"} 744 } 745 return nil, uerr(err) 746 } 747 748 var shouldRedirect, includeBodyOnHop bool 749 redirectMethod, shouldRedirect, includeBodyOnHop = redirectBehavior(req.Method, resp, reqs[0]) 750 if !shouldRedirect { 751 return resp, nil 752 } 753 if !includeBodyOnHop { 754 // Once a hop drops the body, we never send it again 755 // (because we're now handling a redirect for a request with no body). 756 includeBody = false 757 } 758 759 req.closeBody() 760 } 761 } 762 763 // makeHeadersCopier makes a function that copies headers from the 764 // initial Request, ireq. For every redirect, this function must be called 765 // so that it can copy headers into the upcoming Request. 766 func (c *Client) makeHeadersCopier(ireq *Request) func(req *Request, stripSensitiveHeaders, stripBodyHeaders bool) { 767 // The headers to copy are from the very initial request. 768 // We use a closured callback to keep a reference to these original headers. 769 var ( 770 ireqhdr = cloneOrMakeHeader(ireq.Header) 771 icookies map[string][]*Cookie 772 ) 773 if c.Jar != nil && ireq.Header.Get("Cookie") != "" { 774 icookies = make(map[string][]*Cookie) 775 for _, c := range ireq.Cookies() { 776 icookies[c.Name] = append(icookies[c.Name], c) 777 } 778 } 779 780 return func(req *Request, stripSensitiveHeaders, stripBodyHeaders bool) { 781 // If Jar is present and there was some initial cookies provided 782 // via the request header, then we may need to alter the initial 783 // cookies as we follow redirects since each redirect may end up 784 // modifying a pre-existing cookie. 785 // 786 // Since cookies already set in the request header do not contain 787 // information about the original domain and path, the logic below 788 // assumes any new set cookies override the original cookie 789 // regardless of domain or path. 790 // 791 // See https://golang.org/issue/17494 792 if c.Jar != nil && icookies != nil { 793 var changed bool 794 resp := req.Response // The response that caused the upcoming redirect 795 for _, c := range resp.Cookies() { 796 if _, ok := icookies[c.Name]; ok { 797 delete(icookies, c.Name) 798 changed = true 799 } 800 } 801 if changed { 802 ireqhdr.Del("Cookie") 803 var ss []string 804 for _, cs := range icookies { 805 for _, c := range cs { 806 ss = append(ss, c.Name+"="+c.Value) 807 } 808 } 809 slices.Sort(ss) // Ensure deterministic headers 810 ireqhdr.Set("Cookie", strings.Join(ss, "; ")) 811 } 812 } 813 814 // Copy the initial request's Header values 815 // (at least the safe ones). 816 for k, vv := range ireqhdr { 817 sensitive := false 818 body := false 819 switch CanonicalHeaderKey(k) { 820 case "Authorization", "Www-Authenticate", "Cookie", "Cookie2", 821 "Proxy-Authorization", "Proxy-Authenticate": 822 sensitive = true 823 824 case "Content-Encoding", "Content-Language", "Content-Location", 825 "Content-Type": 826 // Headers relating to the body which is removed for 827 // POST to GET redirects 828 // https://fetch.spec.whatwg.org/#http-redirect-fetch 829 body = true 830 831 } 832 if !(sensitive && stripSensitiveHeaders) && !(body && stripBodyHeaders) { 833 req.Header[k] = vv 834 } 835 } 836 } 837 } 838 839 func defaultCheckRedirect(req *Request, via []*Request) error { 840 if len(via) >= 10 { 841 return errors.New("stopped after 10 redirects") 842 } 843 return nil 844 } 845 846 // Post issues a POST to the specified URL. 847 // 848 // Caller should close resp.Body when done reading from it. 849 // 850 // If the provided body is an [io.Closer], it is closed after the 851 // request. 852 // 853 // Post is a wrapper around DefaultClient.Post. 854 // 855 // To set custom headers, use [NewRequest] and DefaultClient.Do. 856 // 857 // See the [Client.Do] method documentation for details on how redirects 858 // are handled. 859 // 860 // To make a request with a specified context.Context, use [NewRequestWithContext] 861 // and DefaultClient.Do. 862 func Post(url, contentType string, body io.Reader) (resp *Response, err error) { 863 return DefaultClient.Post(url, contentType, body) 864 } 865 866 // Post issues a POST to the specified URL. 867 // 868 // Caller should close resp.Body when done reading from it. 869 // 870 // If the provided body is an [io.Closer], it is closed after the 871 // request. 872 // 873 // To set custom headers, use [NewRequest] and [Client.Do]. 874 // 875 // To make a request with a specified context.Context, use [NewRequestWithContext] 876 // and [Client.Do]. 877 // 878 // See the [Client.Do] method documentation for details on how redirects 879 // are handled. 880 func (c *Client) Post(url, contentType string, body io.Reader) (resp *Response, err error) { 881 req, err := NewRequest("POST", url, body) 882 if err != nil { 883 return nil, err 884 } 885 req.Header.Set("Content-Type", contentType) 886 return c.Do(req) 887 } 888 889 // PostForm issues a POST to the specified URL, with data's keys and 890 // values URL-encoded as the request body. 891 // 892 // The Content-Type header is set to application/x-www-form-urlencoded. 893 // To set other headers, use [NewRequest] and DefaultClient.Do. 894 // 895 // When err is nil, resp always contains a non-nil resp.Body. 896 // Caller should close resp.Body when done reading from it. 897 // 898 // PostForm is a wrapper around DefaultClient.PostForm. 899 // 900 // See the [Client.Do] method documentation for details on how redirects 901 // are handled. 902 // 903 // To make a request with a specified [context.Context], use [NewRequestWithContext] 904 // and DefaultClient.Do. 905 func PostForm(url string, data url.Values) (resp *Response, err error) { 906 return DefaultClient.PostForm(url, data) 907 } 908 909 // PostForm issues a POST to the specified URL, 910 // with data's keys and values URL-encoded as the request body. 911 // 912 // The Content-Type header is set to application/x-www-form-urlencoded. 913 // To set other headers, use [NewRequest] and [Client.Do]. 914 // 915 // When err is nil, resp always contains a non-nil resp.Body. 916 // Caller should close resp.Body when done reading from it. 917 // 918 // See the [Client.Do] method documentation for details on how redirects 919 // are handled. 920 // 921 // To make a request with a specified context.Context, use [NewRequestWithContext] 922 // and Client.Do. 923 func (c *Client) PostForm(url string, data url.Values) (resp *Response, err error) { 924 return c.Post(url, "application/x-www-form-urlencoded", strings.NewReader(data.Encode())) 925 } 926 927 // Head issues a HEAD to the specified URL. If the response is one of 928 // the following redirect codes, Head follows the redirect, up to a 929 // maximum of 10 redirects: 930 // 931 // 301 (Moved Permanently) 932 // 302 (Found) 933 // 303 (See Other) 934 // 307 (Temporary Redirect) 935 // 308 (Permanent Redirect) 936 // 937 // Head is a wrapper around DefaultClient.Head. 938 // 939 // To make a request with a specified [context.Context], use [NewRequestWithContext] 940 // and DefaultClient.Do. 941 func Head(url string) (resp *Response, err error) { 942 return DefaultClient.Head(url) 943 } 944 945 // Head issues a HEAD to the specified URL. If the response is one of the 946 // following redirect codes, Head follows the redirect after calling the 947 // [Client.CheckRedirect] function: 948 // 949 // 301 (Moved Permanently) 950 // 302 (Found) 951 // 303 (See Other) 952 // 307 (Temporary Redirect) 953 // 308 (Permanent Redirect) 954 // 955 // To make a request with a specified [context.Context], use [NewRequestWithContext] 956 // and [Client.Do]. 957 func (c *Client) Head(url string) (resp *Response, err error) { 958 req, err := NewRequest("HEAD", url, nil) 959 if err != nil { 960 return nil, err 961 } 962 return c.Do(req) 963 } 964 965 // CloseIdleConnections closes any connections on its [Transport] which 966 // were previously connected from previous requests but are now 967 // sitting idle in a "keep-alive" state. It does not interrupt any 968 // connections currently in use. 969 // 970 // If [Client.Transport] does not have a [Client.CloseIdleConnections] method 971 // then this method does nothing. 972 func (c *Client) CloseIdleConnections() { 973 type closeIdler interface { 974 CloseIdleConnections() 975 } 976 if tr, ok := c.transport().(closeIdler); ok { 977 tr.CloseIdleConnections() 978 } 979 } 980 981 // cancelTimerBody is an io.ReadCloser that wraps rc with two features: 982 // 1. On Close, the stop func is called. 983 // 2. On Read failure, if reqDidTimeout is true, the error is wrapped and 984 // marked as net.Error that hit its timeout. 985 type cancelTimerBody struct { 986 stop func() // stops the time.Timer waiting to cancel the request 987 rc io.ReadCloser 988 reqDidTimeout func() bool 989 } 990 991 func (b *cancelTimerBody) Read(p []byte) (n int, err error) { 992 n, err = b.rc.Read(p) 993 if err == nil { 994 return n, nil 995 } 996 if err == io.EOF { 997 return n, err 998 } 999 if b.reqDidTimeout() { 1000 err = &timeoutError{err.Error() + " (Client.Timeout or context cancellation while reading body)"} 1001 } 1002 return n, err 1003 } 1004 1005 func (b *cancelTimerBody) Close() error { 1006 err := b.rc.Close() 1007 b.stop() 1008 return err 1009 } 1010 1011 func shouldCopyHeaderOnRedirect(initial, dest *url.URL) bool { 1012 // Permit sending auth/cookie headers from "foo.com" 1013 // to "sub.foo.com". 1014 1015 // Note that we don't send all cookies to subdomains 1016 // automatically. This function is only used for 1017 // Cookies set explicitly on the initial outgoing 1018 // client request. Cookies automatically added via the 1019 // CookieJar mechanism continue to follow each 1020 // cookie's scope as set by Set-Cookie. But for 1021 // outgoing requests with the Cookie header set 1022 // directly, we don't know their scope, so we assume 1023 // it's for *.domain.com. 1024 1025 ihost, err1 := httpguts.PunycodeHostPort(initial.Hostname()) 1026 dhost, err2 := httpguts.PunycodeHostPort(dest.Hostname()) 1027 if err1 != nil || err2 != nil { 1028 return false 1029 } 1030 ihost, ok1 := ascii.ToLower(ihost) 1031 dhost, ok2 := ascii.ToLower(dhost) 1032 return ok1 && ok2 && isDomainOrSubdomain(dhost, ihost) 1033 } 1034 1035 // isDomainOrSubdomain reports whether sub is a subdomain (or exact 1036 // match) of the parent domain. 1037 // 1038 // Both domains must already be in canonical form. 1039 func isDomainOrSubdomain(sub, parent string) bool { 1040 if sub == parent { 1041 return true 1042 } 1043 // If sub contains a :, it's probably an IPv6 address (and is definitely not a hostname). 1044 // Don't check the suffix in this case, to avoid matching the contents of a IPv6 zone. 1045 // For example, "::1%.www.example.com" is not a subdomain of "www.example.com". 1046 if strings.ContainsAny(sub, ":%") { 1047 return false 1048 } 1049 // If sub is "foo.example.com" and parent is "example.com", 1050 // that means sub must end in "."+parent. 1051 // Do it without allocating. 1052 if !strings.HasSuffix(sub, parent) { 1053 return false 1054 } 1055 return sub[len(sub)-len(parent)-1] == '.' 1056 } 1057 1058 func stripPassword(u *url.URL) string { 1059 _, passSet := u.User.Password() 1060 if passSet { 1061 return strings.Replace(u.String(), u.User.String()+"@", u.User.Username()+":***@", 1) 1062 } 1063 return u.String() 1064 } 1065