Source file src/net/http/transfer.go

Documentation: net/http

     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  package http
     6  
     7  import (
     8  	"bufio"
     9  	"bytes"
    10  	"errors"
    11  	"fmt"
    12  	"io"
    13  	"net/http/httptrace"
    14  	"net/http/internal"
    15  	"net/http/internal/ascii"
    16  	"net/textproto"
    17  	"reflect"
    18  	"sort"
    19  	"strconv"
    20  	"strings"
    21  	"sync"
    22  	"time"
    23  
    24  	"golang.org/x/net/http/httpguts"
    25  )
    26  
    27  // ErrLineTooLong is returned when reading request or response bodies
    28  // with malformed chunked encoding.
    29  var ErrLineTooLong = internal.ErrLineTooLong
    30  
    31  type errorReader struct {
    32  	err error
    33  }
    34  
    35  func (r errorReader) Read(p []byte) (n int, err error) {
    36  	return 0, r.err
    37  }
    38  
    39  type byteReader struct {
    40  	b    byte
    41  	done bool
    42  }
    43  
    44  func (br *byteReader) Read(p []byte) (n int, err error) {
    45  	if br.done {
    46  		return 0, io.EOF
    47  	}
    48  	if len(p) == 0 {
    49  		return 0, nil
    50  	}
    51  	br.done = true
    52  	p[0] = br.b
    53  	return 1, io.EOF
    54  }
    55  
    56  // transferWriter inspects the fields of a user-supplied Request or Response,
    57  // sanitizes them without changing the user object and provides methods for
    58  // writing the respective header, body and trailer in wire format.
    59  type transferWriter struct {
    60  	Method           string
    61  	Body             io.Reader
    62  	BodyCloser       io.Closer
    63  	ResponseToHEAD   bool
    64  	ContentLength    int64 // -1 means unknown, 0 means exactly none
    65  	Close            bool
    66  	TransferEncoding []string
    67  	Header           Header
    68  	Trailer          Header
    69  	IsResponse       bool
    70  	bodyReadError    error // any non-EOF error from reading Body
    71  
    72  	FlushHeaders bool            // flush headers to network before body
    73  	ByteReadCh   chan readResult // non-nil if probeRequestBody called
    74  }
    75  
    76  func newTransferWriter(r interface{}) (t *transferWriter, err error) {
    77  	t = &transferWriter{}
    78  
    79  	// Extract relevant fields
    80  	atLeastHTTP11 := false
    81  	switch rr := r.(type) {
    82  	case *Request:
    83  		if rr.ContentLength != 0 && rr.Body == nil {
    84  			return nil, fmt.Errorf("http: Request.ContentLength=%d with nil Body", rr.ContentLength)
    85  		}
    86  		t.Method = valueOrDefault(rr.Method, "GET")
    87  		t.Close = rr.Close
    88  		t.TransferEncoding = rr.TransferEncoding
    89  		t.Header = rr.Header
    90  		t.Trailer = rr.Trailer
    91  		t.Body = rr.Body
    92  		t.BodyCloser = rr.Body
    93  		t.ContentLength = rr.outgoingLength()
    94  		if t.ContentLength < 0 && len(t.TransferEncoding) == 0 && t.shouldSendChunkedRequestBody() {
    95  			t.TransferEncoding = []string{"chunked"}
    96  		}
    97  		// If there's a body, conservatively flush the headers
    98  		// to any bufio.Writer we're writing to, just in case
    99  		// the server needs the headers early, before we copy
   100  		// the body and possibly block. We make an exception
   101  		// for the common standard library in-memory types,
   102  		// though, to avoid unnecessary TCP packets on the
   103  		// wire. (Issue 22088.)
   104  		if t.ContentLength != 0 && !isKnownInMemoryReader(t.Body) {
   105  			t.FlushHeaders = true
   106  		}
   107  
   108  		atLeastHTTP11 = true // Transport requests are always 1.1 or 2.0
   109  	case *Response:
   110  		t.IsResponse = true
   111  		if rr.Request != nil {
   112  			t.Method = rr.Request.Method
   113  		}
   114  		t.Body = rr.Body
   115  		t.BodyCloser = rr.Body
   116  		t.ContentLength = rr.ContentLength
   117  		t.Close = rr.Close
   118  		t.TransferEncoding = rr.TransferEncoding
   119  		t.Header = rr.Header
   120  		t.Trailer = rr.Trailer
   121  		atLeastHTTP11 = rr.ProtoAtLeast(1, 1)
   122  		t.ResponseToHEAD = noResponseBodyExpected(t.Method)
   123  	}
   124  
   125  	// Sanitize Body,ContentLength,TransferEncoding
   126  	if t.ResponseToHEAD {
   127  		t.Body = nil
   128  		if chunked(t.TransferEncoding) {
   129  			t.ContentLength = -1
   130  		}
   131  	} else {
   132  		if !atLeastHTTP11 || t.Body == nil {
   133  			t.TransferEncoding = nil
   134  		}
   135  		if chunked(t.TransferEncoding) {
   136  			t.ContentLength = -1
   137  		} else if t.Body == nil { // no chunking, no body
   138  			t.ContentLength = 0
   139  		}
   140  	}
   141  
   142  	// Sanitize Trailer
   143  	if !chunked(t.TransferEncoding) {
   144  		t.Trailer = nil
   145  	}
   146  
   147  	return t, nil
   148  }
   149  
   150  // shouldSendChunkedRequestBody reports whether we should try to send a
   151  // chunked request body to the server. In particular, the case we really
   152  // want to prevent is sending a GET or other typically-bodyless request to a
   153  // server with a chunked body when the body has zero bytes, since GETs with
   154  // bodies (while acceptable according to specs), even zero-byte chunked
   155  // bodies, are approximately never seen in the wild and confuse most
   156  // servers. See Issue 18257, as one example.
   157  //
   158  // The only reason we'd send such a request is if the user set the Body to a
   159  // non-nil value (say, io.NopCloser(bytes.NewReader(nil))) and didn't
   160  // set ContentLength, or NewRequest set it to -1 (unknown), so then we assume
   161  // there's bytes to send.
   162  //
   163  // This code tries to read a byte from the Request.Body in such cases to see
   164  // whether the body actually has content (super rare) or is actually just
   165  // a non-nil content-less ReadCloser (the more common case). In that more
   166  // common case, we act as if their Body were nil instead, and don't send
   167  // a body.
   168  func (t *transferWriter) shouldSendChunkedRequestBody() bool {
   169  	// Note that t.ContentLength is the corrected content length
   170  	// from rr.outgoingLength, so 0 actually means zero, not unknown.
   171  	if t.ContentLength >= 0 || t.Body == nil { // redundant checks; caller did them
   172  		return false
   173  	}
   174  	if t.Method == "CONNECT" {
   175  		return false
   176  	}
   177  	if requestMethodUsuallyLacksBody(t.Method) {
   178  		// Only probe the Request.Body for GET/HEAD/DELETE/etc
   179  		// requests, because it's only those types of requests
   180  		// that confuse servers.
   181  		t.probeRequestBody() // adjusts t.Body, t.ContentLength
   182  		return t.Body != nil
   183  	}
   184  	// For all other request types (PUT, POST, PATCH, or anything
   185  	// made-up we've never heard of), assume it's normal and the server
   186  	// can deal with a chunked request body. Maybe we'll adjust this
   187  	// later.
   188  	return true
   189  }
   190  
   191  // probeRequestBody reads a byte from t.Body to see whether it's empty
   192  // (returns io.EOF right away).
   193  //
   194  // But because we've had problems with this blocking users in the past
   195  // (issue 17480) when the body is a pipe (perhaps waiting on the response
   196  // headers before the pipe is fed data), we need to be careful and bound how
   197  // long we wait for it. This delay will only affect users if all the following
   198  // are true:
   199  //   * the request body blocks
   200  //   * the content length is not set (or set to -1)
   201  //   * the method doesn't usually have a body (GET, HEAD, DELETE, ...)
   202  //   * there is no transfer-encoding=chunked already set.
   203  // In other words, this delay will not normally affect anybody, and there
   204  // are workarounds if it does.
   205  func (t *transferWriter) probeRequestBody() {
   206  	t.ByteReadCh = make(chan readResult, 1)
   207  	go func(body io.Reader) {
   208  		var buf [1]byte
   209  		var rres readResult
   210  		rres.n, rres.err = body.Read(buf[:])
   211  		if rres.n == 1 {
   212  			rres.b = buf[0]
   213  		}
   214  		t.ByteReadCh <- rres
   215  	}(t.Body)
   216  	timer := time.NewTimer(200 * time.Millisecond)
   217  	select {
   218  	case rres := <-t.ByteReadCh:
   219  		timer.Stop()
   220  		if rres.n == 0 && rres.err == io.EOF {
   221  			// It was empty.
   222  			t.Body = nil
   223  			t.ContentLength = 0
   224  		} else if rres.n == 1 {
   225  			if rres.err != nil {
   226  				t.Body = io.MultiReader(&byteReader{b: rres.b}, errorReader{rres.err})
   227  			} else {
   228  				t.Body = io.MultiReader(&byteReader{b: rres.b}, t.Body)
   229  			}
   230  		} else if rres.err != nil {
   231  			t.Body = errorReader{rres.err}
   232  		}
   233  	case <-timer.C:
   234  		// Too slow. Don't wait. Read it later, and keep
   235  		// assuming that this is ContentLength == -1
   236  		// (unknown), which means we'll send a
   237  		// "Transfer-Encoding: chunked" header.
   238  		t.Body = io.MultiReader(finishAsyncByteRead{t}, t.Body)
   239  		// Request that Request.Write flush the headers to the
   240  		// network before writing the body, since our body may not
   241  		// become readable until it's seen the response headers.
   242  		t.FlushHeaders = true
   243  	}
   244  }
   245  
   246  func noResponseBodyExpected(requestMethod string) bool {
   247  	return requestMethod == "HEAD"
   248  }
   249  
   250  func (t *transferWriter) shouldSendContentLength() bool {
   251  	if chunked(t.TransferEncoding) {
   252  		return false
   253  	}
   254  	if t.ContentLength > 0 {
   255  		return true
   256  	}
   257  	if t.ContentLength < 0 {
   258  		return false
   259  	}
   260  	// Many servers expect a Content-Length for these methods
   261  	if t.Method == "POST" || t.Method == "PUT" || t.Method == "PATCH" {
   262  		return true
   263  	}
   264  	if t.ContentLength == 0 && isIdentity(t.TransferEncoding) {
   265  		if t.Method == "GET" || t.Method == "HEAD" {
   266  			return false
   267  		}
   268  		return true
   269  	}
   270  
   271  	return false
   272  }
   273  
   274  func (t *transferWriter) writeHeader(w io.Writer, trace *httptrace.ClientTrace) error {
   275  	if t.Close && !hasToken(t.Header.get("Connection"), "close") {
   276  		if _, err := io.WriteString(w, "Connection: close\r\n"); err != nil {
   277  			return err
   278  		}
   279  		if trace != nil && trace.WroteHeaderField != nil {
   280  			trace.WroteHeaderField("Connection", []string{"close"})
   281  		}
   282  	}
   283  
   284  	// Write Content-Length and/or Transfer-Encoding whose values are a
   285  	// function of the sanitized field triple (Body, ContentLength,
   286  	// TransferEncoding)
   287  	if t.shouldSendContentLength() {
   288  		if _, err := io.WriteString(w, "Content-Length: "); err != nil {
   289  			return err
   290  		}
   291  		if _, err := io.WriteString(w, strconv.FormatInt(t.ContentLength, 10)+"\r\n"); err != nil {
   292  			return err
   293  		}
   294  		if trace != nil && trace.WroteHeaderField != nil {
   295  			trace.WroteHeaderField("Content-Length", []string{strconv.FormatInt(t.ContentLength, 10)})
   296  		}
   297  	} else if chunked(t.TransferEncoding) {
   298  		if _, err := io.WriteString(w, "Transfer-Encoding: chunked\r\n"); err != nil {
   299  			return err
   300  		}
   301  		if trace != nil && trace.WroteHeaderField != nil {
   302  			trace.WroteHeaderField("Transfer-Encoding", []string{"chunked"})
   303  		}
   304  	}
   305  
   306  	// Write Trailer header
   307  	if t.Trailer != nil {
   308  		keys := make([]string, 0, len(t.Trailer))
   309  		for k := range t.Trailer {
   310  			k = CanonicalHeaderKey(k)
   311  			switch k {
   312  			case "Transfer-Encoding", "Trailer", "Content-Length":
   313  				return badStringError("invalid Trailer key", k)
   314  			}
   315  			keys = append(keys, k)
   316  		}
   317  		if len(keys) > 0 {
   318  			sort.Strings(keys)
   319  			// TODO: could do better allocation-wise here, but trailers are rare,
   320  			// so being lazy for now.
   321  			if _, err := io.WriteString(w, "Trailer: "+strings.Join(keys, ",")+"\r\n"); err != nil {
   322  				return err
   323  			}
   324  			if trace != nil && trace.WroteHeaderField != nil {
   325  				trace.WroteHeaderField("Trailer", keys)
   326  			}
   327  		}
   328  	}
   329  
   330  	return nil
   331  }
   332  
   333  // always closes t.BodyCloser
   334  func (t *transferWriter) writeBody(w io.Writer) (err error) {
   335  	var ncopy int64
   336  	closed := false
   337  	defer func() {
   338  		if closed || t.BodyCloser == nil {
   339  			return
   340  		}
   341  		if closeErr := t.BodyCloser.Close(); closeErr != nil && err == nil {
   342  			err = closeErr
   343  		}
   344  	}()
   345  
   346  	// Write body. We "unwrap" the body first if it was wrapped in a
   347  	// nopCloser or readTrackingBody. This is to ensure that we can take advantage of
   348  	// OS-level optimizations in the event that the body is an
   349  	// *os.File.
   350  	if t.Body != nil {
   351  		var body = t.unwrapBody()
   352  		if chunked(t.TransferEncoding) {
   353  			if bw, ok := w.(*bufio.Writer); ok && !t.IsResponse {
   354  				w = &internal.FlushAfterChunkWriter{Writer: bw}
   355  			}
   356  			cw := internal.NewChunkedWriter(w)
   357  			_, err = t.doBodyCopy(cw, body)
   358  			if err == nil {
   359  				err = cw.Close()
   360  			}
   361  		} else if t.ContentLength == -1 {
   362  			dst := w
   363  			if t.Method == "CONNECT" {
   364  				dst = bufioFlushWriter{dst}
   365  			}
   366  			ncopy, err = t.doBodyCopy(dst, body)
   367  		} else {
   368  			ncopy, err = t.doBodyCopy(w, io.LimitReader(body, t.ContentLength))
   369  			if err != nil {
   370  				return err
   371  			}
   372  			var nextra int64
   373  			nextra, err = t.doBodyCopy(io.Discard, body)
   374  			ncopy += nextra
   375  		}
   376  		if err != nil {
   377  			return err
   378  		}
   379  	}
   380  	if t.BodyCloser != nil {
   381  		closed = true
   382  		if err := t.BodyCloser.Close(); err != nil {
   383  			return err
   384  		}
   385  	}
   386  
   387  	if !t.ResponseToHEAD && t.ContentLength != -1 && t.ContentLength != ncopy {
   388  		return fmt.Errorf("http: ContentLength=%d with Body length %d",
   389  			t.ContentLength, ncopy)
   390  	}
   391  
   392  	if chunked(t.TransferEncoding) {
   393  		// Write Trailer header
   394  		if t.Trailer != nil {
   395  			if err := t.Trailer.Write(w); err != nil {
   396  				return err
   397  			}
   398  		}
   399  		// Last chunk, empty trailer
   400  		_, err = io.WriteString(w, "\r\n")
   401  	}
   402  	return err
   403  }
   404  
   405  // doBodyCopy wraps a copy operation, with any resulting error also
   406  // being saved in bodyReadError.
   407  //
   408  // This function is only intended for use in writeBody.
   409  func (t *transferWriter) doBodyCopy(dst io.Writer, src io.Reader) (n int64, err error) {
   410  	n, err = io.Copy(dst, src)
   411  	if err != nil && err != io.EOF {
   412  		t.bodyReadError = err
   413  	}
   414  	return
   415  }
   416  
   417  // unwrapBodyReader unwraps the body's inner reader if it's a
   418  // nopCloser. This is to ensure that body writes sourced from local
   419  // files (*os.File types) are properly optimized.
   420  //
   421  // This function is only intended for use in writeBody.
   422  func (t *transferWriter) unwrapBody() io.Reader {
   423  	if reflect.TypeOf(t.Body) == nopCloserType {
   424  		return reflect.ValueOf(t.Body).Field(0).Interface().(io.Reader)
   425  	}
   426  	if r, ok := t.Body.(*readTrackingBody); ok {
   427  		r.didRead = true
   428  		return r.ReadCloser
   429  	}
   430  	return t.Body
   431  }
   432  
   433  type transferReader struct {
   434  	// Input
   435  	Header        Header
   436  	StatusCode    int
   437  	RequestMethod string
   438  	ProtoMajor    int
   439  	ProtoMinor    int
   440  	// Output
   441  	Body          io.ReadCloser
   442  	ContentLength int64
   443  	Chunked       bool
   444  	Close         bool
   445  	Trailer       Header
   446  }
   447  
   448  func (t *transferReader) protoAtLeast(m, n int) bool {
   449  	return t.ProtoMajor > m || (t.ProtoMajor == m && t.ProtoMinor >= n)
   450  }
   451  
   452  // bodyAllowedForStatus reports whether a given response status code
   453  // permits a body. See RFC 7230, section 3.3.
   454  func bodyAllowedForStatus(status int) bool {
   455  	switch {
   456  	case status >= 100 && status <= 199:
   457  		return false
   458  	case status == 204:
   459  		return false
   460  	case status == 304:
   461  		return false
   462  	}
   463  	return true
   464  }
   465  
   466  var (
   467  	suppressedHeaders304    = []string{"Content-Type", "Content-Length", "Transfer-Encoding"}
   468  	suppressedHeadersNoBody = []string{"Content-Length", "Transfer-Encoding"}
   469  )
   470  
   471  func suppressedHeaders(status int) []string {
   472  	switch {
   473  	case status == 304:
   474  		// RFC 7232 section 4.1
   475  		return suppressedHeaders304
   476  	case !bodyAllowedForStatus(status):
   477  		return suppressedHeadersNoBody
   478  	}
   479  	return nil
   480  }
   481  
   482  // msg is *Request or *Response.
   483  func readTransfer(msg interface{}, r *bufio.Reader) (err error) {
   484  	t := &transferReader{RequestMethod: "GET"}
   485  
   486  	// Unify input
   487  	isResponse := false
   488  	switch rr := msg.(type) {
   489  	case *Response:
   490  		t.Header = rr.Header
   491  		t.StatusCode = rr.StatusCode
   492  		t.ProtoMajor = rr.ProtoMajor
   493  		t.ProtoMinor = rr.ProtoMinor
   494  		t.Close = shouldClose(t.ProtoMajor, t.ProtoMinor, t.Header, true)
   495  		isResponse = true
   496  		if rr.Request != nil {
   497  			t.RequestMethod = rr.Request.Method
   498  		}
   499  	case *Request:
   500  		t.Header = rr.Header
   501  		t.RequestMethod = rr.Method
   502  		t.ProtoMajor = rr.ProtoMajor
   503  		t.ProtoMinor = rr.ProtoMinor
   504  		// Transfer semantics for Requests are exactly like those for
   505  		// Responses with status code 200, responding to a GET method
   506  		t.StatusCode = 200
   507  		t.Close = rr.Close
   508  	default:
   509  		panic("unexpected type")
   510  	}
   511  
   512  	// Default to HTTP/1.1
   513  	if t.ProtoMajor == 0 && t.ProtoMinor == 0 {
   514  		t.ProtoMajor, t.ProtoMinor = 1, 1
   515  	}
   516  
   517  	// Transfer-Encoding: chunked, and overriding Content-Length.
   518  	if err := t.parseTransferEncoding(); err != nil {
   519  		return err
   520  	}
   521  
   522  	realLength, err := fixLength(isResponse, t.StatusCode, t.RequestMethod, t.Header, t.Chunked)
   523  	if err != nil {
   524  		return err
   525  	}
   526  	if isResponse && t.RequestMethod == "HEAD" {
   527  		if n, err := parseContentLength(t.Header.get("Content-Length")); err != nil {
   528  			return err
   529  		} else {
   530  			t.ContentLength = n
   531  		}
   532  	} else {
   533  		t.ContentLength = realLength
   534  	}
   535  
   536  	// Trailer
   537  	t.Trailer, err = fixTrailer(t.Header, t.Chunked)
   538  	if err != nil {
   539  		return err
   540  	}
   541  
   542  	// If there is no Content-Length or chunked Transfer-Encoding on a *Response
   543  	// and the status is not 1xx, 204 or 304, then the body is unbounded.
   544  	// See RFC 7230, section 3.3.
   545  	switch msg.(type) {
   546  	case *Response:
   547  		if realLength == -1 && !t.Chunked && bodyAllowedForStatus(t.StatusCode) {
   548  			// Unbounded body.
   549  			t.Close = true
   550  		}
   551  	}
   552  
   553  	// Prepare body reader. ContentLength < 0 means chunked encoding
   554  	// or close connection when finished, since multipart is not supported yet
   555  	switch {
   556  	case t.Chunked:
   557  		if noResponseBodyExpected(t.RequestMethod) || !bodyAllowedForStatus(t.StatusCode) {
   558  			t.Body = NoBody
   559  		} else {
   560  			t.Body = &body{src: internal.NewChunkedReader(r), hdr: msg, r: r, closing: t.Close}
   561  		}
   562  	case realLength == 0:
   563  		t.Body = NoBody
   564  	case realLength > 0:
   565  		t.Body = &body{src: io.LimitReader(r, realLength), closing: t.Close}
   566  	default:
   567  		// realLength < 0, i.e. "Content-Length" not mentioned in header
   568  		if t.Close {
   569  			// Close semantics (i.e. HTTP/1.0)
   570  			t.Body = &body{src: r, closing: t.Close}
   571  		} else {
   572  			// Persistent connection (i.e. HTTP/1.1)
   573  			t.Body = NoBody
   574  		}
   575  	}
   576  
   577  	// Unify output
   578  	switch rr := msg.(type) {
   579  	case *Request:
   580  		rr.Body = t.Body
   581  		rr.ContentLength = t.ContentLength
   582  		if t.Chunked {
   583  			rr.TransferEncoding = []string{"chunked"}
   584  		}
   585  		rr.Close = t.Close
   586  		rr.Trailer = t.Trailer
   587  	case *Response:
   588  		rr.Body = t.Body
   589  		rr.ContentLength = t.ContentLength
   590  		if t.Chunked {
   591  			rr.TransferEncoding = []string{"chunked"}
   592  		}
   593  		rr.Close = t.Close
   594  		rr.Trailer = t.Trailer
   595  	}
   596  
   597  	return nil
   598  }
   599  
   600  // Checks whether chunked is part of the encodings stack
   601  func chunked(te []string) bool { return len(te) > 0 && te[0] == "chunked" }
   602  
   603  // Checks whether the encoding is explicitly "identity".
   604  func isIdentity(te []string) bool { return len(te) == 1 && te[0] == "identity" }
   605  
   606  // unsupportedTEError reports unsupported transfer-encodings.
   607  type unsupportedTEError struct {
   608  	err string
   609  }
   610  
   611  func (uste *unsupportedTEError) Error() string {
   612  	return uste.err
   613  }
   614  
   615  // isUnsupportedTEError checks if the error is of type
   616  // unsupportedTEError. It is usually invoked with a non-nil err.
   617  func isUnsupportedTEError(err error) bool {
   618  	_, ok := err.(*unsupportedTEError)
   619  	return ok
   620  }
   621  
   622  // parseTransferEncoding sets t.Chunked based on the Transfer-Encoding header.
   623  func (t *transferReader) parseTransferEncoding() error {
   624  	raw, present := t.Header["Transfer-Encoding"]
   625  	if !present {
   626  		return nil
   627  	}
   628  	delete(t.Header, "Transfer-Encoding")
   629  
   630  	// Issue 12785; ignore Transfer-Encoding on HTTP/1.0 requests.
   631  	if !t.protoAtLeast(1, 1) {
   632  		return nil
   633  	}
   634  
   635  	// Like nginx, we only support a single Transfer-Encoding header field, and
   636  	// only if set to "chunked". This is one of the most security sensitive
   637  	// surfaces in HTTP/1.1 due to the risk of request smuggling, so we keep it
   638  	// strict and simple.
   639  	if len(raw) != 1 {
   640  		return &unsupportedTEError{fmt.Sprintf("too many transfer encodings: %q", raw)}
   641  	}
   642  	if !ascii.EqualFold(textproto.TrimString(raw[0]), "chunked") {
   643  		return &unsupportedTEError{fmt.Sprintf("unsupported transfer encoding: %q", raw[0])}
   644  	}
   645  
   646  	// RFC 7230 3.3.2 says "A sender MUST NOT send a Content-Length header field
   647  	// in any message that contains a Transfer-Encoding header field."
   648  	//
   649  	// but also: "If a message is received with both a Transfer-Encoding and a
   650  	// Content-Length header field, the Transfer-Encoding overrides the
   651  	// Content-Length. Such a message might indicate an attempt to perform
   652  	// request smuggling (Section 9.5) or response splitting (Section 9.4) and
   653  	// ought to be handled as an error. A sender MUST remove the received
   654  	// Content-Length field prior to forwarding such a message downstream."
   655  	//
   656  	// Reportedly, these appear in the wild.
   657  	delete(t.Header, "Content-Length")
   658  
   659  	t.Chunked = true
   660  	return nil
   661  }
   662  
   663  // Determine the expected body length, using RFC 7230 Section 3.3. This
   664  // function is not a method, because ultimately it should be shared by
   665  // ReadResponse and ReadRequest.
   666  func fixLength(isResponse bool, status int, requestMethod string, header Header, chunked bool) (int64, error) {
   667  	isRequest := !isResponse
   668  	contentLens := header["Content-Length"]
   669  
   670  	// Hardening against HTTP request smuggling
   671  	if len(contentLens) > 1 {
   672  		// Per RFC 7230 Section 3.3.2, prevent multiple
   673  		// Content-Length headers if they differ in value.
   674  		// If there are dups of the value, remove the dups.
   675  		// See Issue 16490.
   676  		first := textproto.TrimString(contentLens[0])
   677  		for _, ct := range contentLens[1:] {
   678  			if first != textproto.TrimString(ct) {
   679  				return 0, fmt.Errorf("http: message cannot contain multiple Content-Length headers; got %q", contentLens)
   680  			}
   681  		}
   682  
   683  		// deduplicate Content-Length
   684  		header.Del("Content-Length")
   685  		header.Add("Content-Length", first)
   686  
   687  		contentLens = header["Content-Length"]
   688  	}
   689  
   690  	// Logic based on response type or status
   691  	if noResponseBodyExpected(requestMethod) {
   692  		// For HTTP requests, as part of hardening against request
   693  		// smuggling (RFC 7230), don't allow a Content-Length header for
   694  		// methods which don't permit bodies. As an exception, allow
   695  		// exactly one Content-Length header if its value is "0".
   696  		if isRequest && len(contentLens) > 0 && !(len(contentLens) == 1 && contentLens[0] == "0") {
   697  			return 0, fmt.Errorf("http: method cannot contain a Content-Length; got %q", contentLens)
   698  		}
   699  		return 0, nil
   700  	}
   701  	if status/100 == 1 {
   702  		return 0, nil
   703  	}
   704  	switch status {
   705  	case 204, 304:
   706  		return 0, nil
   707  	}
   708  
   709  	// Logic based on Transfer-Encoding
   710  	if chunked {
   711  		return -1, nil
   712  	}
   713  
   714  	// Logic based on Content-Length
   715  	var cl string
   716  	if len(contentLens) == 1 {
   717  		cl = textproto.TrimString(contentLens[0])
   718  	}
   719  	if cl != "" {
   720  		n, err := parseContentLength(cl)
   721  		if err != nil {
   722  			return -1, err
   723  		}
   724  		return n, nil
   725  	}
   726  	header.Del("Content-Length")
   727  
   728  	if isRequest {
   729  		// RFC 7230 neither explicitly permits nor forbids an
   730  		// entity-body on a GET request so we permit one if
   731  		// declared, but we default to 0 here (not -1 below)
   732  		// if there's no mention of a body.
   733  		// Likewise, all other request methods are assumed to have
   734  		// no body if neither Transfer-Encoding chunked nor a
   735  		// Content-Length are set.
   736  		return 0, nil
   737  	}
   738  
   739  	// Body-EOF logic based on other methods (like closing, or chunked coding)
   740  	return -1, nil
   741  }
   742  
   743  // Determine whether to hang up after sending a request and body, or
   744  // receiving a response and body
   745  // 'header' is the request headers
   746  func shouldClose(major, minor int, header Header, removeCloseHeader bool) bool {
   747  	if major < 1 {
   748  		return true
   749  	}
   750  
   751  	conv := header["Connection"]
   752  	hasClose := httpguts.HeaderValuesContainsToken(conv, "close")
   753  	if major == 1 && minor == 0 {
   754  		return hasClose || !httpguts.HeaderValuesContainsToken(conv, "keep-alive")
   755  	}
   756  
   757  	if hasClose && removeCloseHeader {
   758  		header.Del("Connection")
   759  	}
   760  
   761  	return hasClose
   762  }
   763  
   764  // Parse the trailer header
   765  func fixTrailer(header Header, chunked bool) (Header, error) {
   766  	vv, ok := header["Trailer"]
   767  	if !ok {
   768  		return nil, nil
   769  	}
   770  	if !chunked {
   771  		// Trailer and no chunking:
   772  		// this is an invalid use case for trailer header.
   773  		// Nevertheless, no error will be returned and we
   774  		// let users decide if this is a valid HTTP message.
   775  		// The Trailer header will be kept in Response.Header
   776  		// but not populate Response.Trailer.
   777  		// See issue #27197.
   778  		return nil, nil
   779  	}
   780  	header.Del("Trailer")
   781  
   782  	trailer := make(Header)
   783  	var err error
   784  	for _, v := range vv {
   785  		foreachHeaderElement(v, func(key string) {
   786  			key = CanonicalHeaderKey(key)
   787  			switch key {
   788  			case "Transfer-Encoding", "Trailer", "Content-Length":
   789  				if err == nil {
   790  					err = badStringError("bad trailer key", key)
   791  					return
   792  				}
   793  			}
   794  			trailer[key] = nil
   795  		})
   796  	}
   797  	if err != nil {
   798  		return nil, err
   799  	}
   800  	if len(trailer) == 0 {
   801  		return nil, nil
   802  	}
   803  	return trailer, nil
   804  }
   805  
   806  // body turns a Reader into a ReadCloser.
   807  // Close ensures that the body has been fully read
   808  // and then reads the trailer if necessary.
   809  type body struct {
   810  	src          io.Reader
   811  	hdr          interface{}   // non-nil (Response or Request) value means read trailer
   812  	r            *bufio.Reader // underlying wire-format reader for the trailer
   813  	closing      bool          // is the connection to be closed after reading body?
   814  	doEarlyClose bool          // whether Close should stop early
   815  
   816  	mu         sync.Mutex // guards following, and calls to Read and Close
   817  	sawEOF     bool
   818  	closed     bool
   819  	earlyClose bool   // Close called and we didn't read to the end of src
   820  	onHitEOF   func() // if non-nil, func to call when EOF is Read
   821  }
   822  
   823  // ErrBodyReadAfterClose is returned when reading a Request or Response
   824  // Body after the body has been closed. This typically happens when the body is
   825  // read after an HTTP Handler calls WriteHeader or Write on its
   826  // ResponseWriter.
   827  var ErrBodyReadAfterClose = errors.New("http: invalid Read on closed Body")
   828  
   829  func (b *body) Read(p []byte) (n int, err error) {
   830  	b.mu.Lock()
   831  	defer b.mu.Unlock()
   832  	if b.closed {
   833  		return 0, ErrBodyReadAfterClose
   834  	}
   835  	return b.readLocked(p)
   836  }
   837  
   838  // Must hold b.mu.
   839  func (b *body) readLocked(p []byte) (n int, err error) {
   840  	if b.sawEOF {
   841  		return 0, io.EOF
   842  	}
   843  	n, err = b.src.Read(p)
   844  
   845  	if err == io.EOF {
   846  		b.sawEOF = true
   847  		// Chunked case. Read the trailer.
   848  		if b.hdr != nil {
   849  			if e := b.readTrailer(); e != nil {
   850  				err = e
   851  				// Something went wrong in the trailer, we must not allow any
   852  				// further reads of any kind to succeed from body, nor any
   853  				// subsequent requests on the server connection. See
   854  				// golang.org/issue/12027
   855  				b.sawEOF = false
   856  				b.closed = true
   857  			}
   858  			b.hdr = nil
   859  		} else {
   860  			// If the server declared the Content-Length, our body is a LimitedReader
   861  			// and we need to check whether this EOF arrived early.
   862  			if lr, ok := b.src.(*io.LimitedReader); ok && lr.N > 0 {
   863  				err = io.ErrUnexpectedEOF
   864  			}
   865  		}
   866  	}
   867  
   868  	// If we can return an EOF here along with the read data, do
   869  	// so. This is optional per the io.Reader contract, but doing
   870  	// so helps the HTTP transport code recycle its connection
   871  	// earlier (since it will see this EOF itself), even if the
   872  	// client doesn't do future reads or Close.
   873  	if err == nil && n > 0 {
   874  		if lr, ok := b.src.(*io.LimitedReader); ok && lr.N == 0 {
   875  			err = io.EOF
   876  			b.sawEOF = true
   877  		}
   878  	}
   879  
   880  	if b.sawEOF && b.onHitEOF != nil {
   881  		b.onHitEOF()
   882  	}
   883  
   884  	return n, err
   885  }
   886  
   887  var (
   888  	singleCRLF = []byte("\r\n")
   889  	doubleCRLF = []byte("\r\n\r\n")
   890  )
   891  
   892  func seeUpcomingDoubleCRLF(r *bufio.Reader) bool {
   893  	for peekSize := 4; ; peekSize++ {
   894  		// This loop stops when Peek returns an error,
   895  		// which it does when r's buffer has been filled.
   896  		buf, err := r.Peek(peekSize)
   897  		if bytes.HasSuffix(buf, doubleCRLF) {
   898  			return true
   899  		}
   900  		if err != nil {
   901  			break
   902  		}
   903  	}
   904  	return false
   905  }
   906  
   907  var errTrailerEOF = errors.New("http: unexpected EOF reading trailer")
   908  
   909  func (b *body) readTrailer() error {
   910  	// The common case, since nobody uses trailers.
   911  	buf, err := b.r.Peek(2)
   912  	if bytes.Equal(buf, singleCRLF) {
   913  		b.r.Discard(2)
   914  		return nil
   915  	}
   916  	if len(buf) < 2 {
   917  		return errTrailerEOF
   918  	}
   919  	if err != nil {
   920  		return err
   921  	}
   922  
   923  	// Make sure there's a header terminator coming up, to prevent
   924  	// a DoS with an unbounded size Trailer. It's not easy to
   925  	// slip in a LimitReader here, as textproto.NewReader requires
   926  	// a concrete *bufio.Reader. Also, we can't get all the way
   927  	// back up to our conn's LimitedReader that *might* be backing
   928  	// this bufio.Reader. Instead, a hack: we iteratively Peek up
   929  	// to the bufio.Reader's max size, looking for a double CRLF.
   930  	// This limits the trailer to the underlying buffer size, typically 4kB.
   931  	if !seeUpcomingDoubleCRLF(b.r) {
   932  		return errors.New("http: suspiciously long trailer after chunked body")
   933  	}
   934  
   935  	hdr, err := textproto.NewReader(b.r).ReadMIMEHeader()
   936  	if err != nil {
   937  		if err == io.EOF {
   938  			return errTrailerEOF
   939  		}
   940  		return err
   941  	}
   942  	switch rr := b.hdr.(type) {
   943  	case *Request:
   944  		mergeSetHeader(&rr.Trailer, Header(hdr))
   945  	case *Response:
   946  		mergeSetHeader(&rr.Trailer, Header(hdr))
   947  	}
   948  	return nil
   949  }
   950  
   951  func mergeSetHeader(dst *Header, src Header) {
   952  	if *dst == nil {
   953  		*dst = src
   954  		return
   955  	}
   956  	for k, vv := range src {
   957  		(*dst)[k] = vv
   958  	}
   959  }
   960  
   961  // unreadDataSizeLocked returns the number of bytes of unread input.
   962  // It returns -1 if unknown.
   963  // b.mu must be held.
   964  func (b *body) unreadDataSizeLocked() int64 {
   965  	if lr, ok := b.src.(*io.LimitedReader); ok {
   966  		return lr.N
   967  	}
   968  	return -1
   969  }
   970  
   971  func (b *body) Close() error {
   972  	b.mu.Lock()
   973  	defer b.mu.Unlock()
   974  	if b.closed {
   975  		return nil
   976  	}
   977  	var err error
   978  	switch {
   979  	case b.sawEOF:
   980  		// Already saw EOF, so no need going to look for it.
   981  	case b.hdr == nil && b.closing:
   982  		// no trailer and closing the connection next.
   983  		// no point in reading to EOF.
   984  	case b.doEarlyClose:
   985  		// Read up to maxPostHandlerReadBytes bytes of the body, looking
   986  		// for EOF (and trailers), so we can re-use this connection.
   987  		if lr, ok := b.src.(*io.LimitedReader); ok && lr.N > maxPostHandlerReadBytes {
   988  			// There was a declared Content-Length, and we have more bytes remaining
   989  			// than our maxPostHandlerReadBytes tolerance. So, give up.
   990  			b.earlyClose = true
   991  		} else {
   992  			var n int64
   993  			// Consume the body, or, which will also lead to us reading
   994  			// the trailer headers after the body, if present.
   995  			n, err = io.CopyN(io.Discard, bodyLocked{b}, maxPostHandlerReadBytes)
   996  			if err == io.EOF {
   997  				err = nil
   998  			}
   999  			if n == maxPostHandlerReadBytes {
  1000  				b.earlyClose = true
  1001  			}
  1002  		}
  1003  	default:
  1004  		// Fully consume the body, which will also lead to us reading
  1005  		// the trailer headers after the body, if present.
  1006  		_, err = io.Copy(io.Discard, bodyLocked{b})
  1007  	}
  1008  	b.closed = true
  1009  	return err
  1010  }
  1011  
  1012  func (b *body) didEarlyClose() bool {
  1013  	b.mu.Lock()
  1014  	defer b.mu.Unlock()
  1015  	return b.earlyClose
  1016  }
  1017  
  1018  // bodyRemains reports whether future Read calls might
  1019  // yield data.
  1020  func (b *body) bodyRemains() bool {
  1021  	b.mu.Lock()
  1022  	defer b.mu.Unlock()
  1023  	return !b.sawEOF
  1024  }
  1025  
  1026  func (b *body) registerOnHitEOF(fn func()) {
  1027  	b.mu.Lock()
  1028  	defer b.mu.Unlock()
  1029  	b.onHitEOF = fn
  1030  }
  1031  
  1032  // bodyLocked is a io.Reader reading from a *body when its mutex is
  1033  // already held.
  1034  type bodyLocked struct {
  1035  	b *body
  1036  }
  1037  
  1038  func (bl bodyLocked) Read(p []byte) (n int, err error) {
  1039  	if bl.b.closed {
  1040  		return 0, ErrBodyReadAfterClose
  1041  	}
  1042  	return bl.b.readLocked(p)
  1043  }
  1044  
  1045  // parseContentLength trims whitespace from s and returns -1 if no value
  1046  // is set, or the value if it's >= 0.
  1047  func parseContentLength(cl string) (int64, error) {
  1048  	cl = textproto.TrimString(cl)
  1049  	if cl == "" {
  1050  		return -1, nil
  1051  	}
  1052  	n, err := strconv.ParseUint(cl, 10, 63)
  1053  	if err != nil {
  1054  		return 0, badStringError("bad Content-Length", cl)
  1055  	}
  1056  	return int64(n), nil
  1057  
  1058  }
  1059  
  1060  // finishAsyncByteRead finishes reading the 1-byte sniff
  1061  // from the ContentLength==0, Body!=nil case.
  1062  type finishAsyncByteRead struct {
  1063  	tw *transferWriter
  1064  }
  1065  
  1066  func (fr finishAsyncByteRead) Read(p []byte) (n int, err error) {
  1067  	if len(p) == 0 {
  1068  		return
  1069  	}
  1070  	rres := <-fr.tw.ByteReadCh
  1071  	n, err = rres.n, rres.err
  1072  	if n == 1 {
  1073  		p[0] = rres.b
  1074  	}
  1075  	return
  1076  }
  1077  
  1078  var nopCloserType = reflect.TypeOf(io.NopCloser(nil))
  1079  
  1080  // isKnownInMemoryReader reports whether r is a type known to not
  1081  // block on Read. Its caller uses this as an optional optimization to
  1082  // send fewer TCP packets.
  1083  func isKnownInMemoryReader(r io.Reader) bool {
  1084  	switch r.(type) {
  1085  	case *bytes.Reader, *bytes.Buffer, *strings.Reader:
  1086  		return true
  1087  	}
  1088  	if reflect.TypeOf(r) == nopCloserType {
  1089  		return isKnownInMemoryReader(reflect.ValueOf(r).Field(0).Interface().(io.Reader))
  1090  	}
  1091  	if r, ok := r.(*readTrackingBody); ok {
  1092  		return isKnownInMemoryReader(r.ReadCloser)
  1093  	}
  1094  	return false
  1095  }
  1096  
  1097  // bufioFlushWriter is an io.Writer wrapper that flushes all writes
  1098  // on its wrapped writer if it's a *bufio.Writer.
  1099  type bufioFlushWriter struct{ w io.Writer }
  1100  
  1101  func (fw bufioFlushWriter) Write(p []byte) (n int, err error) {
  1102  	n, err = fw.w.Write(p)
  1103  	if bw, ok := fw.w.(*bufio.Writer); n > 0 && ok {
  1104  		ferr := bw.Flush()
  1105  		if ferr != nil && err == nil {
  1106  			err = ferr
  1107  		}
  1108  	}
  1109  	return
  1110  }
  1111  

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