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  	"internal/godebug"
    13  	"io"
    14  	"maps"
    15  	"net/http/httptrace"
    16  	"net/http/internal"
    17  	"net/http/internal/ascii"
    18  	"net/textproto"
    19  	"reflect"
    20  	"slices"
    21  	"strconv"
    22  	"strings"
    23  	"sync"
    24  	"time"
    25  
    26  	"golang.org/x/net/http/httpguts"
    27  )
    28  
    29  // ErrLineTooLong is returned when reading request or response bodies
    30  // with malformed chunked encoding.
    31  var ErrLineTooLong = internal.ErrLineTooLong
    32  
    33  type errorReader struct {
    34  	err error
    35  }
    36  
    37  func (r errorReader) Read(p []byte) (n int, err error) {
    38  	return 0, r.err
    39  }
    40  
    41  type byteReader struct {
    42  	b    byte
    43  	done bool
    44  }
    45  
    46  func (br *byteReader) Read(p []byte) (n int, err error) {
    47  	if br.done {
    48  		return 0, io.EOF
    49  	}
    50  	if len(p) == 0 {
    51  		return 0, nil
    52  	}
    53  	br.done = true
    54  	p[0] = br.b
    55  	return 1, io.EOF
    56  }
    57  
    58  // transferWriter inspects the fields of a user-supplied Request or Response,
    59  // sanitizes them without changing the user object and provides methods for
    60  // writing the respective header, body and trailer in wire format.
    61  type transferWriter struct {
    62  	Method           string
    63  	Body             io.Reader
    64  	BodyCloser       io.Closer
    65  	ResponseToHEAD   bool
    66  	ContentLength    int64 // -1 means unknown, 0 means exactly none
    67  	Close            bool
    68  	TransferEncoding []string
    69  	Header           Header
    70  	Trailer          Header
    71  	IsResponse       bool
    72  	bodyReadError    error // any non-EOF error from reading Body
    73  
    74  	FlushHeaders bool            // flush headers to network before body
    75  	ByteReadCh   chan readResult // non-nil if probeRequestBody called
    76  }
    77  
    78  func newTransferWriter(r any) (t *transferWriter, err error) {
    79  	t = &transferWriter{}
    80  
    81  	// Extract relevant fields
    82  	atLeastHTTP11 := false
    83  	switch rr := r.(type) {
    84  	case *Request:
    85  		if rr.ContentLength != 0 && rr.Body == nil {
    86  			return nil, fmt.Errorf("http: Request.ContentLength=%d with nil Body", rr.ContentLength)
    87  		}
    88  		t.Method = valueOrDefault(rr.Method, "GET")
    89  		t.Close = rr.Close
    90  		t.TransferEncoding = rr.TransferEncoding
    91  		t.Header = rr.Header
    92  		t.Trailer = rr.Trailer
    93  		t.Body = rr.Body
    94  		t.BodyCloser = rr.Body
    95  		t.ContentLength = rr.outgoingLength()
    96  		if t.ContentLength < 0 && len(t.TransferEncoding) == 0 && t.shouldSendChunkedRequestBody() {
    97  			t.TransferEncoding = []string{"chunked"}
    98  		}
    99  		// If there's a body, conservatively flush the headers
   100  		// to any bufio.Writer we're writing to, just in case
   101  		// the server needs the headers early, before we copy
   102  		// the body and possibly block. We make an exception
   103  		// for the common standard library in-memory types,
   104  		// though, to avoid unnecessary TCP packets on the
   105  		// wire. (Issue 22088.)
   106  		if t.ContentLength != 0 && !isKnownInMemoryReader(t.Body) {
   107  			t.FlushHeaders = true
   108  		}
   109  
   110  		atLeastHTTP11 = true // Transport requests are always 1.1 or 2.0
   111  	case *Response:
   112  		t.IsResponse = true
   113  		if rr.Request != nil {
   114  			t.Method = rr.Request.Method
   115  		}
   116  		t.Body = rr.Body
   117  		t.BodyCloser = rr.Body
   118  		t.ContentLength = rr.ContentLength
   119  		t.Close = rr.Close
   120  		t.TransferEncoding = rr.TransferEncoding
   121  		t.Header = rr.Header
   122  		t.Trailer = rr.Trailer
   123  		atLeastHTTP11 = rr.ProtoAtLeast(1, 1)
   124  		t.ResponseToHEAD = noResponseBodyExpected(t.Method)
   125  	}
   126  
   127  	// Sanitize Body,ContentLength,TransferEncoding
   128  	if t.ResponseToHEAD {
   129  		t.Body = nil
   130  		if chunked(t.TransferEncoding) {
   131  			t.ContentLength = -1
   132  		}
   133  	} else {
   134  		if !atLeastHTTP11 || t.Body == nil {
   135  			t.TransferEncoding = nil
   136  		}
   137  		if chunked(t.TransferEncoding) {
   138  			t.ContentLength = -1
   139  		} else if t.Body == nil { // no chunking, no body
   140  			t.ContentLength = 0
   141  		}
   142  	}
   143  
   144  	// Sanitize Trailer
   145  	if !chunked(t.TransferEncoding) {
   146  		t.Trailer = nil
   147  	}
   148  
   149  	return t, nil
   150  }
   151  
   152  // shouldSendChunkedRequestBody reports whether we should try to send a
   153  // chunked request body to the server. In particular, the case we really
   154  // want to prevent is sending a GET or other typically-bodyless request to a
   155  // server with a chunked body when the body has zero bytes, since GETs with
   156  // bodies (while acceptable according to specs), even zero-byte chunked
   157  // bodies, are approximately never seen in the wild and confuse most
   158  // servers. See Issue 18257, as one example.
   159  //
   160  // The only reason we'd send such a request is if the user set the Body to a
   161  // non-nil value (say, io.NopCloser(bytes.NewReader(nil))) and didn't
   162  // set ContentLength, or NewRequest set it to -1 (unknown), so then we assume
   163  // there's bytes to send.
   164  //
   165  // This code tries to read a byte from the Request.Body in such cases to see
   166  // whether the body actually has content (super rare) or is actually just
   167  // a non-nil content-less ReadCloser (the more common case). In that more
   168  // common case, we act as if their Body were nil instead, and don't send
   169  // a body.
   170  func (t *transferWriter) shouldSendChunkedRequestBody() bool {
   171  	// Note that t.ContentLength is the corrected content length
   172  	// from rr.outgoingLength, so 0 actually means zero, not unknown.
   173  	if t.ContentLength >= 0 || t.Body == nil { // redundant checks; caller did them
   174  		return false
   175  	}
   176  	if t.Method == "CONNECT" {
   177  		return false
   178  	}
   179  	if requestMethodUsuallyLacksBody(t.Method) {
   180  		// Only probe the Request.Body for GET/HEAD/DELETE/etc
   181  		// requests, because it's only those types of requests
   182  		// that confuse servers.
   183  		t.probeRequestBody() // adjusts t.Body, t.ContentLength
   184  		return t.Body != nil
   185  	}
   186  	// For all other request types (PUT, POST, PATCH, or anything
   187  	// made-up we've never heard of), assume it's normal and the server
   188  	// can deal with a chunked request body. Maybe we'll adjust this
   189  	// later.
   190  	return true
   191  }
   192  
   193  // probeRequestBody reads a byte from t.Body to see whether it's empty
   194  // (returns io.EOF right away).
   195  //
   196  // But because we've had problems with this blocking users in the past
   197  // (issue 17480) when the body is a pipe (perhaps waiting on the response
   198  // headers before the pipe is fed data), we need to be careful and bound how
   199  // long we wait for it. This delay will only affect users if all the following
   200  // are true:
   201  //   - the request body blocks
   202  //   - the content length is not set (or set to -1)
   203  //   - the method doesn't usually have a body (GET, HEAD, DELETE, ...)
   204  //   - there is no transfer-encoding=chunked already set.
   205  //
   206  // In other words, this delay will not normally affect anybody, and there
   207  // are workarounds if it does.
   208  func (t *transferWriter) probeRequestBody() {
   209  	t.ByteReadCh = make(chan readResult, 1)
   210  	go func(body io.Reader) {
   211  		var buf [1]byte
   212  		var rres readResult
   213  		rres.n, rres.err = body.Read(buf[:])
   214  		if rres.n == 1 {
   215  			rres.b = buf[0]
   216  		}
   217  		t.ByteReadCh <- rres
   218  		close(t.ByteReadCh)
   219  	}(t.Body)
   220  	timer := time.NewTimer(200 * time.Millisecond)
   221  	select {
   222  	case rres := <-t.ByteReadCh:
   223  		timer.Stop()
   224  		if rres.n == 0 && rres.err == io.EOF {
   225  			// It was empty.
   226  			t.Body = nil
   227  			t.ContentLength = 0
   228  		} else if rres.n == 1 {
   229  			if rres.err != nil {
   230  				t.Body = io.MultiReader(&byteReader{b: rres.b}, errorReader{rres.err})
   231  			} else {
   232  				t.Body = io.MultiReader(&byteReader{b: rres.b}, t.Body)
   233  			}
   234  		} else if rres.err != nil {
   235  			t.Body = errorReader{rres.err}
   236  		}
   237  	case <-timer.C:
   238  		// Too slow. Don't wait. Read it later, and keep
   239  		// assuming that this is ContentLength == -1
   240  		// (unknown), which means we'll send a
   241  		// "Transfer-Encoding: chunked" header.
   242  		t.Body = io.MultiReader(finishAsyncByteRead{t}, t.Body)
   243  		// Request that Request.Write flush the headers to the
   244  		// network before writing the body, since our body may not
   245  		// become readable until it's seen the response headers.
   246  		t.FlushHeaders = true
   247  	}
   248  }
   249  
   250  func noResponseBodyExpected(requestMethod string) bool {
   251  	return requestMethod == "HEAD"
   252  }
   253  
   254  func (t *transferWriter) shouldSendContentLength() bool {
   255  	if chunked(t.TransferEncoding) {
   256  		return false
   257  	}
   258  	if t.ContentLength > 0 {
   259  		return true
   260  	}
   261  	if t.ContentLength < 0 {
   262  		return false
   263  	}
   264  	// Many servers expect a Content-Length for these methods
   265  	if t.Method == "POST" || t.Method == "PUT" || t.Method == "PATCH" {
   266  		return true
   267  	}
   268  	if t.ContentLength == 0 && isIdentity(t.TransferEncoding) {
   269  		if t.Method == "GET" || t.Method == "HEAD" {
   270  			return false
   271  		}
   272  		return true
   273  	}
   274  
   275  	return false
   276  }
   277  
   278  func (t *transferWriter) writeHeader(w io.Writer, trace *httptrace.ClientTrace) error {
   279  	if t.Close && !hasToken(t.Header.get("Connection"), "close") {
   280  		if _, err := io.WriteString(w, "Connection: close\r\n"); err != nil {
   281  			return err
   282  		}
   283  		if trace != nil && trace.WroteHeaderField != nil {
   284  			trace.WroteHeaderField("Connection", []string{"close"})
   285  		}
   286  	}
   287  
   288  	// Write Content-Length and/or Transfer-Encoding whose values are a
   289  	// function of the sanitized field triple (Body, ContentLength,
   290  	// TransferEncoding)
   291  	if t.shouldSendContentLength() {
   292  		if _, err := io.WriteString(w, "Content-Length: "); err != nil {
   293  			return err
   294  		}
   295  		if _, err := io.WriteString(w, strconv.FormatInt(t.ContentLength, 10)+"\r\n"); err != nil {
   296  			return err
   297  		}
   298  		if trace != nil && trace.WroteHeaderField != nil {
   299  			trace.WroteHeaderField("Content-Length", []string{strconv.FormatInt(t.ContentLength, 10)})
   300  		}
   301  	} else if chunked(t.TransferEncoding) {
   302  		if _, err := io.WriteString(w, "Transfer-Encoding: chunked\r\n"); err != nil {
   303  			return err
   304  		}
   305  		if trace != nil && trace.WroteHeaderField != nil {
   306  			trace.WroteHeaderField("Transfer-Encoding", []string{"chunked"})
   307  		}
   308  	}
   309  
   310  	// Write Trailer header
   311  	if t.Trailer != nil {
   312  		keys := make([]string, 0, len(t.Trailer))
   313  		for k := range t.Trailer {
   314  			k = CanonicalHeaderKey(k)
   315  			switch k {
   316  			case "Transfer-Encoding", "Trailer", "Content-Length":
   317  				return badStringError("invalid Trailer key", k)
   318  			}
   319  			keys = append(keys, k)
   320  		}
   321  		if len(keys) > 0 {
   322  			slices.Sort(keys)
   323  			// TODO: could do better allocation-wise here, but trailers are rare,
   324  			// so being lazy for now.
   325  			if _, err := io.WriteString(w, "Trailer: "+strings.Join(keys, ",")+"\r\n"); err != nil {
   326  				return err
   327  			}
   328  			if trace != nil && trace.WroteHeaderField != nil {
   329  				trace.WroteHeaderField("Trailer", keys)
   330  			}
   331  		}
   332  	}
   333  
   334  	return nil
   335  }
   336  
   337  // always closes t.BodyCloser
   338  func (t *transferWriter) writeBody(w io.Writer) (err error) {
   339  	var ncopy int64
   340  	closed := false
   341  	defer func() {
   342  		if closed || t.BodyCloser == nil {
   343  			return
   344  		}
   345  		if closeErr := t.BodyCloser.Close(); closeErr != nil && err == nil {
   346  			err = closeErr
   347  		}
   348  	}()
   349  
   350  	// Write body. We "unwrap" the body first if it was wrapped in a
   351  	// nopCloser or readTrackingBody. This is to ensure that we can take advantage of
   352  	// OS-level optimizations in the event that the body is an
   353  	// *os.File.
   354  	if !t.ResponseToHEAD && t.Body != nil {
   355  		var body = t.unwrapBody()
   356  		if chunked(t.TransferEncoding) {
   357  			if bw, ok := w.(*bufio.Writer); ok && !t.IsResponse {
   358  				w = &internal.FlushAfterChunkWriter{Writer: bw}
   359  			}
   360  			cw := internal.NewChunkedWriter(w)
   361  			_, err = t.doBodyCopy(cw, body)
   362  			if err == nil {
   363  				err = cw.Close()
   364  			}
   365  		} else if t.ContentLength == -1 {
   366  			dst := w
   367  			if t.Method == "CONNECT" {
   368  				dst = bufioFlushWriter{dst}
   369  			}
   370  			ncopy, err = t.doBodyCopy(dst, body)
   371  		} else {
   372  			ncopy, err = t.doBodyCopy(w, io.LimitReader(body, t.ContentLength))
   373  			if err != nil {
   374  				return err
   375  			}
   376  			var nextra int64
   377  			nextra, err = t.doBodyCopy(io.Discard, body)
   378  			ncopy += nextra
   379  		}
   380  		if err != nil {
   381  			return err
   382  		}
   383  	}
   384  	if t.BodyCloser != nil {
   385  		closed = true
   386  		if err := t.BodyCloser.Close(); err != nil {
   387  			return err
   388  		}
   389  	}
   390  
   391  	if !t.ResponseToHEAD && t.ContentLength != -1 && t.ContentLength != ncopy {
   392  		return fmt.Errorf("http: ContentLength=%d with Body length %d",
   393  			t.ContentLength, ncopy)
   394  	}
   395  
   396  	if !t.ResponseToHEAD && chunked(t.TransferEncoding) {
   397  		// Write Trailer header
   398  		if t.Trailer != nil {
   399  			if err := t.Trailer.Write(w); err != nil {
   400  				return err
   401  			}
   402  		}
   403  		// Last chunk, empty trailer
   404  		_, err = io.WriteString(w, "\r\n")
   405  	}
   406  	return err
   407  }
   408  
   409  // doBodyCopy wraps a copy operation, with any resulting error also
   410  // being saved in bodyReadError.
   411  //
   412  // This function is only intended for use in writeBody.
   413  func (t *transferWriter) doBodyCopy(dst io.Writer, src io.Reader) (n int64, err error) {
   414  	buf := getCopyBuf()
   415  	defer putCopyBuf(buf)
   416  
   417  	n, err = io.CopyBuffer(dst, src, buf)
   418  	if err != nil && err != io.EOF {
   419  		t.bodyReadError = err
   420  	}
   421  	return
   422  }
   423  
   424  // unwrapBody unwraps the body's inner reader if it's a
   425  // nopCloser. This is to ensure that body writes sourced from local
   426  // files (*os.File types) are properly optimized.
   427  //
   428  // This function is only intended for use in writeBody.
   429  func (t *transferWriter) unwrapBody() io.Reader {
   430  	if r, ok := unwrapNopCloser(t.Body); ok {
   431  		return r
   432  	}
   433  	if r, ok := t.Body.(*readTrackingBody); ok {
   434  		r.didRead = true
   435  		return r.ReadCloser
   436  	}
   437  	return t.Body
   438  }
   439  
   440  type transferReader struct {
   441  	// Input
   442  	Header        Header
   443  	StatusCode    int
   444  	RequestMethod string
   445  	ProtoMajor    int
   446  	ProtoMinor    int
   447  	// Output
   448  	Body          io.ReadCloser
   449  	ContentLength int64
   450  	Chunked       bool
   451  	Close         bool
   452  	Trailer       Header
   453  }
   454  
   455  func (t *transferReader) protoAtLeast(m, n int) bool {
   456  	return t.ProtoMajor > m || (t.ProtoMajor == m && t.ProtoMinor >= n)
   457  }
   458  
   459  // bodyAllowedForStatus reports whether a given response status code
   460  // permits a body. See RFC 7230, section 3.3.
   461  func bodyAllowedForStatus(status int) bool {
   462  	switch {
   463  	case status >= 100 && status <= 199:
   464  		return false
   465  	case status == 204:
   466  		return false
   467  	case status == 304:
   468  		return false
   469  	}
   470  	return true
   471  }
   472  
   473  var (
   474  	suppressedHeaders304    = []string{"Content-Type", "Content-Length", "Transfer-Encoding"}
   475  	suppressedHeadersNoBody = []string{"Content-Length", "Transfer-Encoding"}
   476  	excludedHeadersNoBody   = map[string]bool{"Content-Length": true, "Transfer-Encoding": true}
   477  )
   478  
   479  func suppressedHeaders(status int) []string {
   480  	switch {
   481  	case status == 304:
   482  		// RFC 7232 section 4.1
   483  		return suppressedHeaders304
   484  	case !bodyAllowedForStatus(status):
   485  		return suppressedHeadersNoBody
   486  	}
   487  	return nil
   488  }
   489  
   490  // msg is *Request or *Response.
   491  func readTransfer(msg any, r *bufio.Reader) (err error) {
   492  	t := &transferReader{RequestMethod: "GET"}
   493  
   494  	// Unify input
   495  	isResponse := false
   496  	switch rr := msg.(type) {
   497  	case *Response:
   498  		t.Header = rr.Header
   499  		t.StatusCode = rr.StatusCode
   500  		t.ProtoMajor = rr.ProtoMajor
   501  		t.ProtoMinor = rr.ProtoMinor
   502  		t.Close = shouldClose(t.ProtoMajor, t.ProtoMinor, t.Header, true)
   503  		isResponse = true
   504  		if rr.Request != nil {
   505  			t.RequestMethod = rr.Request.Method
   506  		}
   507  	case *Request:
   508  		t.Header = rr.Header
   509  		t.RequestMethod = rr.Method
   510  		t.ProtoMajor = rr.ProtoMajor
   511  		t.ProtoMinor = rr.ProtoMinor
   512  		// Transfer semantics for Requests are exactly like those for
   513  		// Responses with status code 200, responding to a GET method
   514  		t.StatusCode = 200
   515  		t.Close = rr.Close
   516  	default:
   517  		panic("unexpected type")
   518  	}
   519  
   520  	// Default to HTTP/1.1
   521  	if t.ProtoMajor == 0 && t.ProtoMinor == 0 {
   522  		t.ProtoMajor, t.ProtoMinor = 1, 1
   523  	}
   524  
   525  	// Transfer-Encoding: chunked, and overriding Content-Length.
   526  	if err := t.parseTransferEncoding(); err != nil {
   527  		return err
   528  	}
   529  
   530  	realLength, err := fixLength(isResponse, t.StatusCode, t.RequestMethod, t.Header, t.Chunked)
   531  	if err != nil {
   532  		return err
   533  	}
   534  	if isResponse && t.RequestMethod == "HEAD" {
   535  		if n, err := parseContentLength(t.Header["Content-Length"]); err != nil {
   536  			return err
   537  		} else {
   538  			t.ContentLength = n
   539  		}
   540  	} else {
   541  		t.ContentLength = realLength
   542  	}
   543  
   544  	// Trailer
   545  	t.Trailer, err = fixTrailer(t.Header, t.Chunked)
   546  	if err != nil {
   547  		return err
   548  	}
   549  
   550  	// If there is no Content-Length or chunked Transfer-Encoding on a *Response
   551  	// and the status is not 1xx, 204 or 304, then the body is unbounded.
   552  	// See RFC 7230, section 3.3.
   553  	switch msg.(type) {
   554  	case *Response:
   555  		if realLength == -1 && !t.Chunked && bodyAllowedForStatus(t.StatusCode) {
   556  			// Unbounded body.
   557  			t.Close = true
   558  		}
   559  	}
   560  
   561  	// Prepare body reader. ContentLength < 0 means chunked encoding
   562  	// or close connection when finished, since multipart is not supported yet
   563  	switch {
   564  	case t.Chunked:
   565  		if isResponse && (noResponseBodyExpected(t.RequestMethod) || !bodyAllowedForStatus(t.StatusCode)) {
   566  			t.Body = NoBody
   567  		} else {
   568  			t.Body = &body{src: internal.NewChunkedReader(r), hdr: msg, r: r, closing: t.Close}
   569  		}
   570  	case realLength == 0:
   571  		t.Body = NoBody
   572  	case realLength > 0:
   573  		t.Body = &body{src: io.LimitReader(r, realLength), closing: t.Close}
   574  	default:
   575  		// realLength < 0, i.e. "Content-Length" not mentioned in header
   576  		if t.Close {
   577  			// Close semantics (i.e. HTTP/1.0)
   578  			t.Body = &body{src: r, closing: t.Close}
   579  		} else {
   580  			// Persistent connection (i.e. HTTP/1.1)
   581  			t.Body = NoBody
   582  		}
   583  	}
   584  
   585  	// Unify output
   586  	switch rr := msg.(type) {
   587  	case *Request:
   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  	case *Response:
   596  		rr.Body = t.Body
   597  		rr.ContentLength = t.ContentLength
   598  		if t.Chunked {
   599  			rr.TransferEncoding = []string{"chunked"}
   600  		}
   601  		rr.Close = t.Close
   602  		rr.Trailer = t.Trailer
   603  	}
   604  
   605  	return nil
   606  }
   607  
   608  // Checks whether chunked is part of the encodings stack.
   609  func chunked(te []string) bool { return len(te) > 0 && te[0] == "chunked" }
   610  
   611  // Checks whether the encoding is explicitly "identity".
   612  func isIdentity(te []string) bool { return len(te) == 1 && te[0] == "identity" }
   613  
   614  // unsupportedTEError reports unsupported transfer-encodings.
   615  type unsupportedTEError struct {
   616  	err string
   617  }
   618  
   619  func (uste *unsupportedTEError) Error() string {
   620  	return uste.err
   621  }
   622  
   623  // isUnsupportedTEError checks if the error is of type
   624  // unsupportedTEError. It is usually invoked with a non-nil err.
   625  func isUnsupportedTEError(err error) bool {
   626  	_, ok := err.(*unsupportedTEError)
   627  	return ok
   628  }
   629  
   630  // parseTransferEncoding sets t.Chunked based on the Transfer-Encoding header.
   631  func (t *transferReader) parseTransferEncoding() error {
   632  	raw, present := t.Header["Transfer-Encoding"]
   633  	if !present {
   634  		return nil
   635  	}
   636  	delete(t.Header, "Transfer-Encoding")
   637  
   638  	// Issue 12785; ignore Transfer-Encoding on HTTP/1.0 requests.
   639  	if !t.protoAtLeast(1, 1) {
   640  		return nil
   641  	}
   642  
   643  	// Like nginx, we only support a single Transfer-Encoding header field, and
   644  	// only if set to "chunked". This is one of the most security sensitive
   645  	// surfaces in HTTP/1.1 due to the risk of request smuggling, so we keep it
   646  	// strict and simple.
   647  	if len(raw) != 1 {
   648  		return &unsupportedTEError{fmt.Sprintf("too many transfer encodings: %q", raw)}
   649  	}
   650  	if !ascii.EqualFold(raw[0], "chunked") {
   651  		return &unsupportedTEError{fmt.Sprintf("unsupported transfer encoding: %q", raw[0])}
   652  	}
   653  
   654  	t.Chunked = true
   655  	return nil
   656  }
   657  
   658  // Determine the expected body length, using RFC 7230 Section 3.3. This
   659  // function is not a method, because ultimately it should be shared by
   660  // ReadResponse and ReadRequest.
   661  func fixLength(isResponse bool, status int, requestMethod string, header Header, chunked bool) (n int64, err error) {
   662  	isRequest := !isResponse
   663  	contentLens := header["Content-Length"]
   664  
   665  	// Hardening against HTTP request smuggling
   666  	if len(contentLens) > 1 {
   667  		// Per RFC 7230 Section 3.3.2, prevent multiple
   668  		// Content-Length headers if they differ in value.
   669  		// If there are dups of the value, remove the dups.
   670  		// See Issue 16490.
   671  		first := textproto.TrimString(contentLens[0])
   672  		for _, ct := range contentLens[1:] {
   673  			if first != textproto.TrimString(ct) {
   674  				return 0, fmt.Errorf("http: message cannot contain multiple Content-Length headers; got %q", contentLens)
   675  			}
   676  		}
   677  
   678  		// deduplicate Content-Length
   679  		header.Del("Content-Length")
   680  		header.Add("Content-Length", first)
   681  
   682  		contentLens = header["Content-Length"]
   683  	}
   684  
   685  	// Reject requests with invalid Content-Length headers.
   686  	if len(contentLens) > 0 {
   687  		n, err = parseContentLength(contentLens)
   688  		if err != nil {
   689  			return -1, err
   690  		}
   691  	}
   692  
   693  	// Logic based on response type or status
   694  	if isResponse && noResponseBodyExpected(requestMethod) {
   695  		return 0, nil
   696  	}
   697  	if status/100 == 1 {
   698  		return 0, nil
   699  	}
   700  	switch status {
   701  	case 204, 304:
   702  		return 0, nil
   703  	}
   704  
   705  	// According to RFC 9112, "If a message is received with both a
   706  	// Transfer-Encoding and a Content-Length header field, the Transfer-Encoding
   707  	// overrides the Content-Length. Such a message might indicate an attempt to
   708  	// perform request smuggling (Section 11.2) or response splitting (Section 11.1)
   709  	// and ought to be handled as an error. An intermediary that chooses to forward
   710  	// the message MUST first remove the received Content-Length field and process
   711  	// the Transfer-Encoding (as described below) prior to forwarding the message downstream."
   712  	//
   713  	// Chunked-encoding requests with either valid Content-Length
   714  	// headers or no Content-Length headers are accepted after removing
   715  	// the Content-Length field from header.
   716  	//
   717  	// Logic based on Transfer-Encoding
   718  	if chunked {
   719  		header.Del("Content-Length")
   720  		return -1, nil
   721  	}
   722  
   723  	// Logic based on Content-Length
   724  	if len(contentLens) > 0 {
   725  		return n, nil
   726  	}
   727  
   728  	header.Del("Content-Length")
   729  
   730  	if isRequest {
   731  		// RFC 7230 neither explicitly permits nor forbids an
   732  		// entity-body on a GET request so we permit one if
   733  		// declared, but we default to 0 here (not -1 below)
   734  		// if there's no mention of a body.
   735  		// Likewise, all other request methods are assumed to have
   736  		// no body if neither Transfer-Encoding chunked nor a
   737  		// Content-Length are set.
   738  		return 0, nil
   739  	}
   740  
   741  	// Body-EOF logic based on other methods (like closing, or chunked coding)
   742  	return -1, nil
   743  }
   744  
   745  // Determine whether to hang up after sending a request and body, or
   746  // receiving a response and body
   747  // 'header' is the request headers.
   748  func shouldClose(major, minor int, header Header, removeCloseHeader bool) bool {
   749  	if major < 1 {
   750  		return true
   751  	}
   752  
   753  	conv := header["Connection"]
   754  	hasClose := httpguts.HeaderValuesContainsToken(conv, "close")
   755  	if major == 1 && minor == 0 {
   756  		return hasClose || !httpguts.HeaderValuesContainsToken(conv, "keep-alive")
   757  	}
   758  
   759  	if hasClose && removeCloseHeader {
   760  		header.Del("Connection")
   761  	}
   762  
   763  	return hasClose
   764  }
   765  
   766  // Parse the trailer header.
   767  func fixTrailer(header Header, chunked bool) (Header, error) {
   768  	vv, ok := header["Trailer"]
   769  	if !ok {
   770  		return nil, nil
   771  	}
   772  	if !chunked {
   773  		// Trailer and no chunking:
   774  		// this is an invalid use case for trailer header.
   775  		// Nevertheless, no error will be returned and we
   776  		// let users decide if this is a valid HTTP message.
   777  		// The Trailer header will be kept in Response.Header
   778  		// but not populate Response.Trailer.
   779  		// See issue #27197.
   780  		return nil, nil
   781  	}
   782  	header.Del("Trailer")
   783  
   784  	trailer := make(Header)
   785  	var err error
   786  	for _, v := range vv {
   787  		foreachHeaderElement(v, func(key string) {
   788  			key = CanonicalHeaderKey(key)
   789  			switch key {
   790  			case "Transfer-Encoding", "Trailer", "Content-Length":
   791  				if err == nil {
   792  					err = badStringError("bad trailer key", key)
   793  					return
   794  				}
   795  			}
   796  			trailer[key] = nil
   797  		})
   798  	}
   799  	if err != nil {
   800  		return nil, err
   801  	}
   802  	if len(trailer) == 0 {
   803  		return nil, nil
   804  	}
   805  	return trailer, nil
   806  }
   807  
   808  // body turns a Reader into a ReadCloser.
   809  // Close ensures that the body has been fully read
   810  // and then reads the trailer if necessary.
   811  type body struct {
   812  	src          io.Reader
   813  	hdr          any           // non-nil (Response or Request) value means read trailer
   814  	r            *bufio.Reader // underlying wire-format reader for the trailer
   815  	closing      bool          // is the connection to be closed after reading body?
   816  	doEarlyClose bool          // whether Close should stop early
   817  
   818  	mu         sync.Mutex // guards following, and calls to Read and Close
   819  	sawEOF     bool
   820  	closed     bool
   821  	earlyClose bool   // Close called and we didn't read to the end of src
   822  	onHitEOF   func() // if non-nil, func to call when EOF is Read
   823  }
   824  
   825  // ErrBodyReadAfterClose is returned when reading a [Request] or [Response]
   826  // Body after the body has been closed. This typically happens when the body is
   827  // read after an HTTP [Handler] calls WriteHeader or Write on its
   828  // [ResponseWriter].
   829  var ErrBodyReadAfterClose = errors.New("http: invalid Read on closed Body")
   830  
   831  func (b *body) Read(p []byte) (n int, err error) {
   832  	b.mu.Lock()
   833  	defer b.mu.Unlock()
   834  	if b.closed {
   835  		return 0, ErrBodyReadAfterClose
   836  	}
   837  	return b.readLocked(p)
   838  }
   839  
   840  // Must hold b.mu.
   841  func (b *body) readLocked(p []byte) (n int, err error) {
   842  	if b.sawEOF {
   843  		return 0, io.EOF
   844  	}
   845  	n, err = b.src.Read(p)
   846  
   847  	if err == io.EOF {
   848  		b.sawEOF = true
   849  		// Chunked case. Read the trailer.
   850  		if b.hdr != nil {
   851  			if e := b.readTrailer(); e != nil {
   852  				err = e
   853  				// Something went wrong in the trailer, we must not allow any
   854  				// further reads of any kind to succeed from body, nor any
   855  				// subsequent requests on the server connection. See
   856  				// golang.org/issue/12027
   857  				b.sawEOF = false
   858  				b.closed = true
   859  			}
   860  			b.hdr = nil
   861  		} else {
   862  			// If the server declared the Content-Length, our body is a LimitedReader
   863  			// and we need to check whether this EOF arrived early.
   864  			if lr, ok := b.src.(*io.LimitedReader); ok && lr.N > 0 {
   865  				err = io.ErrUnexpectedEOF
   866  			}
   867  		}
   868  	}
   869  
   870  	// If we can return an EOF here along with the read data, do
   871  	// so. This is optional per the io.Reader contract, but doing
   872  	// so helps the HTTP transport code recycle its connection
   873  	// earlier (since it will see this EOF itself), even if the
   874  	// client doesn't do future reads or Close.
   875  	if err == nil && n > 0 {
   876  		if lr, ok := b.src.(*io.LimitedReader); ok && lr.N == 0 {
   877  			err = io.EOF
   878  			b.sawEOF = true
   879  		}
   880  	}
   881  
   882  	if b.sawEOF && b.onHitEOF != nil {
   883  		b.onHitEOF()
   884  	}
   885  
   886  	return n, err
   887  }
   888  
   889  var (
   890  	singleCRLF = []byte("\r\n")
   891  	doubleCRLF = []byte("\r\n\r\n")
   892  )
   893  
   894  func seeUpcomingDoubleCRLF(r *bufio.Reader) bool {
   895  	for peekSize := 4; ; peekSize++ {
   896  		// This loop stops when Peek returns an error,
   897  		// which it does when r's buffer has been filled.
   898  		buf, err := r.Peek(peekSize)
   899  		if bytes.HasSuffix(buf, doubleCRLF) {
   900  			return true
   901  		}
   902  		if err != nil {
   903  			break
   904  		}
   905  	}
   906  	return false
   907  }
   908  
   909  var errTrailerEOF = errors.New("http: unexpected EOF reading trailer")
   910  
   911  func (b *body) readTrailer() error {
   912  	// The common case, since nobody uses trailers.
   913  	buf, err := b.r.Peek(2)
   914  	if bytes.Equal(buf, singleCRLF) {
   915  		b.r.Discard(2)
   916  		return nil
   917  	}
   918  	if len(buf) < 2 {
   919  		return errTrailerEOF
   920  	}
   921  	if err != nil {
   922  		return err
   923  	}
   924  
   925  	// Make sure there's a header terminator coming up, to prevent
   926  	// a DoS with an unbounded size Trailer. It's not easy to
   927  	// slip in a LimitReader here, as textproto.NewReader requires
   928  	// a concrete *bufio.Reader. Also, we can't get all the way
   929  	// back up to our conn's LimitedReader that *might* be backing
   930  	// this bufio.Reader. Instead, a hack: we iteratively Peek up
   931  	// to the bufio.Reader's max size, looking for a double CRLF.
   932  	// This limits the trailer to the underlying buffer size, typically 4kB.
   933  	if !seeUpcomingDoubleCRLF(b.r) {
   934  		return errors.New("http: suspiciously long trailer after chunked body")
   935  	}
   936  
   937  	hdr, err := textproto.NewReader(b.r).ReadMIMEHeader()
   938  	if err != nil {
   939  		if err == io.EOF {
   940  			return errTrailerEOF
   941  		}
   942  		return err
   943  	}
   944  	switch rr := b.hdr.(type) {
   945  	case *Request:
   946  		mergeSetHeader(&rr.Trailer, Header(hdr))
   947  	case *Response:
   948  		mergeSetHeader(&rr.Trailer, Header(hdr))
   949  	}
   950  	return nil
   951  }
   952  
   953  func mergeSetHeader(dst *Header, src Header) {
   954  	if *dst == nil {
   955  		*dst = src
   956  		return
   957  	}
   958  	maps.Copy(*dst, src)
   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 an 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  var httplaxcontentlength = godebug.New("httplaxcontentlength")
  1046  
  1047  // parseContentLength checks that the header is valid and then trims
  1048  // whitespace. It returns -1 if no value is set otherwise the value
  1049  // if it's >= 0.
  1050  func parseContentLength(clHeaders []string) (int64, error) {
  1051  	if len(clHeaders) == 0 {
  1052  		return -1, nil
  1053  	}
  1054  	cl := textproto.TrimString(clHeaders[0])
  1055  
  1056  	// The Content-Length must be a valid numeric value.
  1057  	// See: https://datatracker.ietf.org/doc/html/rfc2616/#section-14.13
  1058  	if cl == "" {
  1059  		if httplaxcontentlength.Value() == "1" {
  1060  			httplaxcontentlength.IncNonDefault()
  1061  			return -1, nil
  1062  		}
  1063  		return 0, badStringError("invalid empty Content-Length", cl)
  1064  	}
  1065  	n, err := strconv.ParseUint(cl, 10, 63)
  1066  	if err != nil {
  1067  		return 0, badStringError("bad Content-Length", cl)
  1068  	}
  1069  	return int64(n), nil
  1070  }
  1071  
  1072  // finishAsyncByteRead finishes reading the 1-byte sniff
  1073  // from the ContentLength==0, Body!=nil case.
  1074  type finishAsyncByteRead struct {
  1075  	tw *transferWriter
  1076  }
  1077  
  1078  func (fr finishAsyncByteRead) Read(p []byte) (n int, err error) {
  1079  	if len(p) == 0 {
  1080  		return
  1081  	}
  1082  	rres := <-fr.tw.ByteReadCh
  1083  	n, err = rres.n, rres.err
  1084  	if n == 1 {
  1085  		p[0] = rres.b
  1086  	}
  1087  	if err == nil {
  1088  		err = io.EOF
  1089  	}
  1090  	return
  1091  }
  1092  
  1093  var nopCloserType = reflect.TypeOf(io.NopCloser(nil))
  1094  var nopCloserWriterToType = reflect.TypeOf(io.NopCloser(struct {
  1095  	io.Reader
  1096  	io.WriterTo
  1097  }{}))
  1098  
  1099  // unwrapNopCloser return the underlying reader and true if r is a NopCloser
  1100  // else it return false.
  1101  func unwrapNopCloser(r io.Reader) (underlyingReader io.Reader, isNopCloser bool) {
  1102  	switch reflect.TypeOf(r) {
  1103  	case nopCloserType, nopCloserWriterToType:
  1104  		return reflect.ValueOf(r).Field(0).Interface().(io.Reader), true
  1105  	default:
  1106  		return nil, false
  1107  	}
  1108  }
  1109  
  1110  // isKnownInMemoryReader reports whether r is a type known to not
  1111  // block on Read. Its caller uses this as an optional optimization to
  1112  // send fewer TCP packets.
  1113  func isKnownInMemoryReader(r io.Reader) bool {
  1114  	switch r.(type) {
  1115  	case *bytes.Reader, *bytes.Buffer, *strings.Reader:
  1116  		return true
  1117  	}
  1118  	if r, ok := unwrapNopCloser(r); ok {
  1119  		return isKnownInMemoryReader(r)
  1120  	}
  1121  	if r, ok := r.(*readTrackingBody); ok {
  1122  		return isKnownInMemoryReader(r.ReadCloser)
  1123  	}
  1124  	return false
  1125  }
  1126  
  1127  // bufioFlushWriter is an io.Writer wrapper that flushes all writes
  1128  // on its wrapped writer if it's a *bufio.Writer.
  1129  type bufioFlushWriter struct{ w io.Writer }
  1130  
  1131  func (fw bufioFlushWriter) Write(p []byte) (n int, err error) {
  1132  	n, err = fw.w.Write(p)
  1133  	if bw, ok := fw.w.(*bufio.Writer); n > 0 && ok {
  1134  		ferr := bw.Flush()
  1135  		if ferr != nil && err == nil {
  1136  			err = ferr
  1137  		}
  1138  	}
  1139  	return
  1140  }
  1141  

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