Source file src/net/http/transfer.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  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 any) (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  		close(t.ByteReadCh)
   216  	}(t.Body)
   217  	timer := time.NewTimer(200 * time.Millisecond)
   218  	select {
   219  	case rres := <-t.ByteReadCh:
   220  		timer.Stop()
   221  		if rres.n == 0 && rres.err == io.EOF {
   222  			// It was empty.
   223  			t.Body = nil
   224  			t.ContentLength = 0
   225  		} else if rres.n == 1 {
   226  			if rres.err != nil {
   227  				t.Body = io.MultiReader(&byteReader{b: rres.b}, errorReader{rres.err})
   228  			} else {
   229  				t.Body = io.MultiReader(&byteReader{b: rres.b}, t.Body)
   230  			}
   231  		} else if rres.err != nil {
   232  			t.Body = errorReader{rres.err}
   233  		}
   234  	case <-timer.C:
   235  		// Too slow. Don't wait. Read it later, and keep
   236  		// assuming that this is ContentLength == -1
   237  		// (unknown), which means we'll send a
   238  		// "Transfer-Encoding: chunked" header.
   239  		t.Body = io.MultiReader(finishAsyncByteRead{t}, t.Body)
   240  		// Request that Request.Write flush the headers to the
   241  		// network before writing the body, since our body may not
   242  		// become readable until it's seen the response headers.
   243  		t.FlushHeaders = true
   244  	}
   245  }
   246  
   247  func noResponseBodyExpected(requestMethod string) bool {
   248  	return requestMethod == "HEAD"
   249  }
   250  
   251  func (t *transferWriter) shouldSendContentLength() bool {
   252  	if chunked(t.TransferEncoding) {
   253  		return false
   254  	}
   255  	if t.ContentLength > 0 {
   256  		return true
   257  	}
   258  	if t.ContentLength < 0 {
   259  		return false
   260  	}
   261  	// Many servers expect a Content-Length for these methods
   262  	if t.Method == "POST" || t.Method == "PUT" || t.Method == "PATCH" {
   263  		return true
   264  	}
   265  	if t.ContentLength == 0 && isIdentity(t.TransferEncoding) {
   266  		if t.Method == "GET" || t.Method == "HEAD" {
   267  			return false
   268  		}
   269  		return true
   270  	}
   271  
   272  	return false
   273  }
   274  
   275  func (t *transferWriter) writeHeader(w io.Writer, trace *httptrace.ClientTrace) error {
   276  	if t.Close && !hasToken(t.Header.get("Connection"), "close") {
   277  		if _, err := io.WriteString(w, "Connection: close\r\n"); err != nil {
   278  			return err
   279  		}
   280  		if trace != nil && trace.WroteHeaderField != nil {
   281  			trace.WroteHeaderField("Connection", []string{"close"})
   282  		}
   283  	}
   284  
   285  	// Write Content-Length and/or Transfer-Encoding whose values are a
   286  	// function of the sanitized field triple (Body, ContentLength,
   287  	// TransferEncoding)
   288  	if t.shouldSendContentLength() {
   289  		if _, err := io.WriteString(w, "Content-Length: "); err != nil {
   290  			return err
   291  		}
   292  		if _, err := io.WriteString(w, strconv.FormatInt(t.ContentLength, 10)+"\r\n"); err != nil {
   293  			return err
   294  		}
   295  		if trace != nil && trace.WroteHeaderField != nil {
   296  			trace.WroteHeaderField("Content-Length", []string{strconv.FormatInt(t.ContentLength, 10)})
   297  		}
   298  	} else if chunked(t.TransferEncoding) {
   299  		if _, err := io.WriteString(w, "Transfer-Encoding: chunked\r\n"); err != nil {
   300  			return err
   301  		}
   302  		if trace != nil && trace.WroteHeaderField != nil {
   303  			trace.WroteHeaderField("Transfer-Encoding", []string{"chunked"})
   304  		}
   305  	}
   306  
   307  	// Write Trailer header
   308  	if t.Trailer != nil {
   309  		keys := make([]string, 0, len(t.Trailer))
   310  		for k := range t.Trailer {
   311  			k = CanonicalHeaderKey(k)
   312  			switch k {
   313  			case "Transfer-Encoding", "Trailer", "Content-Length":
   314  				return badStringError("invalid Trailer key", k)
   315  			}
   316  			keys = append(keys, k)
   317  		}
   318  		if len(keys) > 0 {
   319  			sort.Strings(keys)
   320  			// TODO: could do better allocation-wise here, but trailers are rare,
   321  			// so being lazy for now.
   322  			if _, err := io.WriteString(w, "Trailer: "+strings.Join(keys, ",")+"\r\n"); err != nil {
   323  				return err
   324  			}
   325  			if trace != nil && trace.WroteHeaderField != nil {
   326  				trace.WroteHeaderField("Trailer", keys)
   327  			}
   328  		}
   329  	}
   330  
   331  	return nil
   332  }
   333  
   334  // always closes t.BodyCloser
   335  func (t *transferWriter) writeBody(w io.Writer) (err error) {
   336  	var ncopy int64
   337  	closed := false
   338  	defer func() {
   339  		if closed || t.BodyCloser == nil {
   340  			return
   341  		}
   342  		if closeErr := t.BodyCloser.Close(); closeErr != nil && err == nil {
   343  			err = closeErr
   344  		}
   345  	}()
   346  
   347  	// Write body. We "unwrap" the body first if it was wrapped in a
   348  	// nopCloser or readTrackingBody. This is to ensure that we can take advantage of
   349  	// OS-level optimizations in the event that the body is an
   350  	// *os.File.
   351  	if t.Body != nil {
   352  		var body = t.unwrapBody()
   353  		if chunked(t.TransferEncoding) {
   354  			if bw, ok := w.(*bufio.Writer); ok && !t.IsResponse {
   355  				w = &internal.FlushAfterChunkWriter{Writer: bw}
   356  			}
   357  			cw := internal.NewChunkedWriter(w)
   358  			_, err = t.doBodyCopy(cw, body)
   359  			if err == nil {
   360  				err = cw.Close()
   361  			}
   362  		} else if t.ContentLength == -1 {
   363  			dst := w
   364  			if t.Method == "CONNECT" {
   365  				dst = bufioFlushWriter{dst}
   366  			}
   367  			ncopy, err = t.doBodyCopy(dst, body)
   368  		} else {
   369  			ncopy, err = t.doBodyCopy(w, io.LimitReader(body, t.ContentLength))
   370  			if err != nil {
   371  				return err
   372  			}
   373  			var nextra int64
   374  			nextra, err = t.doBodyCopy(io.Discard, body)
   375  			ncopy += nextra
   376  		}
   377  		if err != nil {
   378  			return err
   379  		}
   380  	}
   381  	if t.BodyCloser != nil {
   382  		closed = true
   383  		if err := t.BodyCloser.Close(); err != nil {
   384  			return err
   385  		}
   386  	}
   387  
   388  	if !t.ResponseToHEAD && t.ContentLength != -1 && t.ContentLength != ncopy {
   389  		return fmt.Errorf("http: ContentLength=%d with Body length %d",
   390  			t.ContentLength, ncopy)
   391  	}
   392  
   393  	if chunked(t.TransferEncoding) {
   394  		// Write Trailer header
   395  		if t.Trailer != nil {
   396  			if err := t.Trailer.Write(w); err != nil {
   397  				return err
   398  			}
   399  		}
   400  		// Last chunk, empty trailer
   401  		_, err = io.WriteString(w, "\r\n")
   402  	}
   403  	return err
   404  }
   405  
   406  // doBodyCopy wraps a copy operation, with any resulting error also
   407  // being saved in bodyReadError.
   408  //
   409  // This function is only intended for use in writeBody.
   410  func (t *transferWriter) doBodyCopy(dst io.Writer, src io.Reader) (n int64, err error) {
   411  	n, err = io.Copy(dst, src)
   412  	if err != nil && err != io.EOF {
   413  		t.bodyReadError = err
   414  	}
   415  	return
   416  }
   417  
   418  // unwrapBodyReader unwraps the body's inner reader if it's a
   419  // nopCloser. This is to ensure that body writes sourced from local
   420  // files (*os.File types) are properly optimized.
   421  //
   422  // This function is only intended for use in writeBody.
   423  func (t *transferWriter) unwrapBody() io.Reader {
   424  	if reflect.TypeOf(t.Body) == nopCloserType {
   425  		return reflect.ValueOf(t.Body).Field(0).Interface().(io.Reader)
   426  	}
   427  	if r, ok := t.Body.(*readTrackingBody); ok {
   428  		r.didRead = true
   429  		return r.ReadCloser
   430  	}
   431  	return t.Body
   432  }
   433  
   434  type transferReader struct {
   435  	// Input
   436  	Header        Header
   437  	StatusCode    int
   438  	RequestMethod string
   439  	ProtoMajor    int
   440  	ProtoMinor    int
   441  	// Output
   442  	Body          io.ReadCloser
   443  	ContentLength int64
   444  	Chunked       bool
   445  	Close         bool
   446  	Trailer       Header
   447  }
   448  
   449  func (t *transferReader) protoAtLeast(m, n int) bool {
   450  	return t.ProtoMajor > m || (t.ProtoMajor == m && t.ProtoMinor >= n)
   451  }
   452  
   453  // bodyAllowedForStatus reports whether a given response status code
   454  // permits a body. See RFC 7230, section 3.3.
   455  func bodyAllowedForStatus(status int) bool {
   456  	switch {
   457  	case status >= 100 && status <= 199:
   458  		return false
   459  	case status == 204:
   460  		return false
   461  	case status == 304:
   462  		return false
   463  	}
   464  	return true
   465  }
   466  
   467  var (
   468  	suppressedHeaders304    = []string{"Content-Type", "Content-Length", "Transfer-Encoding"}
   469  	suppressedHeadersNoBody = []string{"Content-Length", "Transfer-Encoding"}
   470  )
   471  
   472  func suppressedHeaders(status int) []string {
   473  	switch {
   474  	case status == 304:
   475  		// RFC 7232 section 4.1
   476  		return suppressedHeaders304
   477  	case !bodyAllowedForStatus(status):
   478  		return suppressedHeadersNoBody
   479  	}
   480  	return nil
   481  }
   482  
   483  // msg is *Request or *Response.
   484  func readTransfer(msg any, r *bufio.Reader) (err error) {
   485  	t := &transferReader{RequestMethod: "GET"}
   486  
   487  	// Unify input
   488  	isResponse := false
   489  	switch rr := msg.(type) {
   490  	case *Response:
   491  		t.Header = rr.Header
   492  		t.StatusCode = rr.StatusCode
   493  		t.ProtoMajor = rr.ProtoMajor
   494  		t.ProtoMinor = rr.ProtoMinor
   495  		t.Close = shouldClose(t.ProtoMajor, t.ProtoMinor, t.Header, true)
   496  		isResponse = true
   497  		if rr.Request != nil {
   498  			t.RequestMethod = rr.Request.Method
   499  		}
   500  	case *Request:
   501  		t.Header = rr.Header
   502  		t.RequestMethod = rr.Method
   503  		t.ProtoMajor = rr.ProtoMajor
   504  		t.ProtoMinor = rr.ProtoMinor
   505  		// Transfer semantics for Requests are exactly like those for
   506  		// Responses with status code 200, responding to a GET method
   507  		t.StatusCode = 200
   508  		t.Close = rr.Close
   509  	default:
   510  		panic("unexpected type")
   511  	}
   512  
   513  	// Default to HTTP/1.1
   514  	if t.ProtoMajor == 0 && t.ProtoMinor == 0 {
   515  		t.ProtoMajor, t.ProtoMinor = 1, 1
   516  	}
   517  
   518  	// Transfer-Encoding: chunked, and overriding Content-Length.
   519  	if err := t.parseTransferEncoding(); err != nil {
   520  		return err
   521  	}
   522  
   523  	realLength, err := fixLength(isResponse, t.StatusCode, t.RequestMethod, t.Header, t.Chunked)
   524  	if err != nil {
   525  		return err
   526  	}
   527  	if isResponse && t.RequestMethod == "HEAD" {
   528  		if n, err := parseContentLength(t.Header.get("Content-Length")); err != nil {
   529  			return err
   530  		} else {
   531  			t.ContentLength = n
   532  		}
   533  	} else {
   534  		t.ContentLength = realLength
   535  	}
   536  
   537  	// Trailer
   538  	t.Trailer, err = fixTrailer(t.Header, t.Chunked)
   539  	if err != nil {
   540  		return err
   541  	}
   542  
   543  	// If there is no Content-Length or chunked Transfer-Encoding on a *Response
   544  	// and the status is not 1xx, 204 or 304, then the body is unbounded.
   545  	// See RFC 7230, section 3.3.
   546  	switch msg.(type) {
   547  	case *Response:
   548  		if realLength == -1 && !t.Chunked && bodyAllowedForStatus(t.StatusCode) {
   549  			// Unbounded body.
   550  			t.Close = true
   551  		}
   552  	}
   553  
   554  	// Prepare body reader. ContentLength < 0 means chunked encoding
   555  	// or close connection when finished, since multipart is not supported yet
   556  	switch {
   557  	case t.Chunked:
   558  		if noResponseBodyExpected(t.RequestMethod) || !bodyAllowedForStatus(t.StatusCode) {
   559  			t.Body = NoBody
   560  		} else {
   561  			t.Body = &body{src: internal.NewChunkedReader(r), hdr: msg, r: r, closing: t.Close}
   562  		}
   563  	case realLength == 0:
   564  		t.Body = NoBody
   565  	case realLength > 0:
   566  		t.Body = &body{src: io.LimitReader(r, realLength), closing: t.Close}
   567  	default:
   568  		// realLength < 0, i.e. "Content-Length" not mentioned in header
   569  		if t.Close {
   570  			// Close semantics (i.e. HTTP/1.0)
   571  			t.Body = &body{src: r, closing: t.Close}
   572  		} else {
   573  			// Persistent connection (i.e. HTTP/1.1)
   574  			t.Body = NoBody
   575  		}
   576  	}
   577  
   578  	// Unify output
   579  	switch rr := msg.(type) {
   580  	case *Request:
   581  		rr.Body = t.Body
   582  		rr.ContentLength = t.ContentLength
   583  		if t.Chunked {
   584  			rr.TransferEncoding = []string{"chunked"}
   585  		}
   586  		rr.Close = t.Close
   587  		rr.Trailer = t.Trailer
   588  	case *Response:
   589  		rr.Body = t.Body
   590  		rr.ContentLength = t.ContentLength
   591  		if t.Chunked {
   592  			rr.TransferEncoding = []string{"chunked"}
   593  		}
   594  		rr.Close = t.Close
   595  		rr.Trailer = t.Trailer
   596  	}
   597  
   598  	return nil
   599  }
   600  
   601  // Checks whether chunked is part of the encodings stack
   602  func chunked(te []string) bool { return len(te) > 0 && te[0] == "chunked" }
   603  
   604  // Checks whether the encoding is explicitly "identity".
   605  func isIdentity(te []string) bool { return len(te) == 1 && te[0] == "identity" }
   606  
   607  // unsupportedTEError reports unsupported transfer-encodings.
   608  type unsupportedTEError struct {
   609  	err string
   610  }
   611  
   612  func (uste *unsupportedTEError) Error() string {
   613  	return uste.err
   614  }
   615  
   616  // isUnsupportedTEError checks if the error is of type
   617  // unsupportedTEError. It is usually invoked with a non-nil err.
   618  func isUnsupportedTEError(err error) bool {
   619  	_, ok := err.(*unsupportedTEError)
   620  	return ok
   621  }
   622  
   623  // parseTransferEncoding sets t.Chunked based on the Transfer-Encoding header.
   624  func (t *transferReader) parseTransferEncoding() error {
   625  	raw, present := t.Header["Transfer-Encoding"]
   626  	if !present {
   627  		return nil
   628  	}
   629  	delete(t.Header, "Transfer-Encoding")
   630  
   631  	// Issue 12785; ignore Transfer-Encoding on HTTP/1.0 requests.
   632  	if !t.protoAtLeast(1, 1) {
   633  		return nil
   634  	}
   635  
   636  	// Like nginx, we only support a single Transfer-Encoding header field, and
   637  	// only if set to "chunked". This is one of the most security sensitive
   638  	// surfaces in HTTP/1.1 due to the risk of request smuggling, so we keep it
   639  	// strict and simple.
   640  	if len(raw) != 1 {
   641  		return &unsupportedTEError{fmt.Sprintf("too many transfer encodings: %q", raw)}
   642  	}
   643  	if !ascii.EqualFold(textproto.TrimString(raw[0]), "chunked") {
   644  		return &unsupportedTEError{fmt.Sprintf("unsupported transfer encoding: %q", raw[0])}
   645  	}
   646  
   647  	// RFC 7230 3.3.2 says "A sender MUST NOT send a Content-Length header field
   648  	// in any message that contains a Transfer-Encoding header field."
   649  	//
   650  	// but also: "If a message is received with both a Transfer-Encoding and a
   651  	// Content-Length header field, the Transfer-Encoding overrides the
   652  	// Content-Length. Such a message might indicate an attempt to perform
   653  	// request smuggling (Section 9.5) or response splitting (Section 9.4) and
   654  	// ought to be handled as an error. A sender MUST remove the received
   655  	// Content-Length field prior to forwarding such a message downstream."
   656  	//
   657  	// Reportedly, these appear in the wild.
   658  	delete(t.Header, "Content-Length")
   659  
   660  	t.Chunked = true
   661  	return nil
   662  }
   663  
   664  // Determine the expected body length, using RFC 7230 Section 3.3. This
   665  // function is not a method, because ultimately it should be shared by
   666  // ReadResponse and ReadRequest.
   667  func fixLength(isResponse bool, status int, requestMethod string, header Header, chunked bool) (int64, error) {
   668  	isRequest := !isResponse
   669  	contentLens := header["Content-Length"]
   670  
   671  	// Hardening against HTTP request smuggling
   672  	if len(contentLens) > 1 {
   673  		// Per RFC 7230 Section 3.3.2, prevent multiple
   674  		// Content-Length headers if they differ in value.
   675  		// If there are dups of the value, remove the dups.
   676  		// See Issue 16490.
   677  		first := textproto.TrimString(contentLens[0])
   678  		for _, ct := range contentLens[1:] {
   679  			if first != textproto.TrimString(ct) {
   680  				return 0, fmt.Errorf("http: message cannot contain multiple Content-Length headers; got %q", contentLens)
   681  			}
   682  		}
   683  
   684  		// deduplicate Content-Length
   685  		header.Del("Content-Length")
   686  		header.Add("Content-Length", first)
   687  
   688  		contentLens = header["Content-Length"]
   689  	}
   690  
   691  	// Logic based on response type or status
   692  	if noResponseBodyExpected(requestMethod) {
   693  		// For HTTP requests, as part of hardening against request
   694  		// smuggling (RFC 7230), don't allow a Content-Length header for
   695  		// methods which don't permit bodies. As an exception, allow
   696  		// exactly one Content-Length header if its value is "0".
   697  		if isRequest && len(contentLens) > 0 && !(len(contentLens) == 1 && contentLens[0] == "0") {
   698  			return 0, fmt.Errorf("http: method cannot contain a Content-Length; got %q", contentLens)
   699  		}
   700  		return 0, nil
   701  	}
   702  	if status/100 == 1 {
   703  		return 0, nil
   704  	}
   705  	switch status {
   706  	case 204, 304:
   707  		return 0, nil
   708  	}
   709  
   710  	// Logic based on Transfer-Encoding
   711  	if chunked {
   712  		return -1, nil
   713  	}
   714  
   715  	// Logic based on Content-Length
   716  	var cl string
   717  	if len(contentLens) == 1 {
   718  		cl = textproto.TrimString(contentLens[0])
   719  	}
   720  	if cl != "" {
   721  		n, err := parseContentLength(cl)
   722  		if err != nil {
   723  			return -1, err
   724  		}
   725  		return n, nil
   726  	}
   727  	header.Del("Content-Length")
   728  
   729  	if isRequest {
   730  		// RFC 7230 neither explicitly permits nor forbids an
   731  		// entity-body on a GET request so we permit one if
   732  		// declared, but we default to 0 here (not -1 below)
   733  		// if there's no mention of a body.
   734  		// Likewise, all other request methods are assumed to have
   735  		// no body if neither Transfer-Encoding chunked nor a
   736  		// Content-Length are set.
   737  		return 0, nil
   738  	}
   739  
   740  	// Body-EOF logic based on other methods (like closing, or chunked coding)
   741  	return -1, nil
   742  }
   743  
   744  // Determine whether to hang up after sending a request and body, or
   745  // receiving a response and body
   746  // 'header' is the request headers
   747  func shouldClose(major, minor int, header Header, removeCloseHeader bool) bool {
   748  	if major < 1 {
   749  		return true
   750  	}
   751  
   752  	conv := header["Connection"]
   753  	hasClose := httpguts.HeaderValuesContainsToken(conv, "close")
   754  	if major == 1 && minor == 0 {
   755  		return hasClose || !httpguts.HeaderValuesContainsToken(conv, "keep-alive")
   756  	}
   757  
   758  	if hasClose && removeCloseHeader {
   759  		header.Del("Connection")
   760  	}
   761  
   762  	return hasClose
   763  }
   764  
   765  // Parse the trailer header
   766  func fixTrailer(header Header, chunked bool) (Header, error) {
   767  	vv, ok := header["Trailer"]
   768  	if !ok {
   769  		return nil, nil
   770  	}
   771  	if !chunked {
   772  		// Trailer and no chunking:
   773  		// this is an invalid use case for trailer header.
   774  		// Nevertheless, no error will be returned and we
   775  		// let users decide if this is a valid HTTP message.
   776  		// The Trailer header will be kept in Response.Header
   777  		// but not populate Response.Trailer.
   778  		// See issue #27197.
   779  		return nil, nil
   780  	}
   781  	header.Del("Trailer")
   782  
   783  	trailer := make(Header)
   784  	var err error
   785  	for _, v := range vv {
   786  		foreachHeaderElement(v, func(key string) {
   787  			key = CanonicalHeaderKey(key)
   788  			switch key {
   789  			case "Transfer-Encoding", "Trailer", "Content-Length":
   790  				if err == nil {
   791  					err = badStringError("bad trailer key", key)
   792  					return
   793  				}
   794  			}
   795  			trailer[key] = nil
   796  		})
   797  	}
   798  	if err != nil {
   799  		return nil, err
   800  	}
   801  	if len(trailer) == 0 {
   802  		return nil, nil
   803  	}
   804  	return trailer, nil
   805  }
   806  
   807  // body turns a Reader into a ReadCloser.
   808  // Close ensures that the body has been fully read
   809  // and then reads the trailer if necessary.
   810  type body struct {
   811  	src          io.Reader
   812  	hdr          any           // non-nil (Response or Request) value means read trailer
   813  	r            *bufio.Reader // underlying wire-format reader for the trailer
   814  	closing      bool          // is the connection to be closed after reading body?
   815  	doEarlyClose bool          // whether Close should stop early
   816  
   817  	mu         sync.Mutex // guards following, and calls to Read and Close
   818  	sawEOF     bool
   819  	closed     bool
   820  	earlyClose bool   // Close called and we didn't read to the end of src
   821  	onHitEOF   func() // if non-nil, func to call when EOF is Read
   822  }
   823  
   824  // ErrBodyReadAfterClose is returned when reading a Request or Response
   825  // Body after the body has been closed. This typically happens when the body is
   826  // read after an HTTP Handler calls WriteHeader or Write on its
   827  // ResponseWriter.
   828  var ErrBodyReadAfterClose = errors.New("http: invalid Read on closed Body")
   829  
   830  func (b *body) Read(p []byte) (n int, err error) {
   831  	b.mu.Lock()
   832  	defer b.mu.Unlock()
   833  	if b.closed {
   834  		return 0, ErrBodyReadAfterClose
   835  	}
   836  	return b.readLocked(p)
   837  }
   838  
   839  // Must hold b.mu.
   840  func (b *body) readLocked(p []byte) (n int, err error) {
   841  	if b.sawEOF {
   842  		return 0, io.EOF
   843  	}
   844  	n, err = b.src.Read(p)
   845  
   846  	if err == io.EOF {
   847  		b.sawEOF = true
   848  		// Chunked case. Read the trailer.
   849  		if b.hdr != nil {
   850  			if e := b.readTrailer(); e != nil {
   851  				err = e
   852  				// Something went wrong in the trailer, we must not allow any
   853  				// further reads of any kind to succeed from body, nor any
   854  				// subsequent requests on the server connection. See
   855  				// golang.org/issue/12027
   856  				b.sawEOF = false
   857  				b.closed = true
   858  			}
   859  			b.hdr = nil
   860  		} else {
   861  			// If the server declared the Content-Length, our body is a LimitedReader
   862  			// and we need to check whether this EOF arrived early.
   863  			if lr, ok := b.src.(*io.LimitedReader); ok && lr.N > 0 {
   864  				err = io.ErrUnexpectedEOF
   865  			}
   866  		}
   867  	}
   868  
   869  	// If we can return an EOF here along with the read data, do
   870  	// so. This is optional per the io.Reader contract, but doing
   871  	// so helps the HTTP transport code recycle its connection
   872  	// earlier (since it will see this EOF itself), even if the
   873  	// client doesn't do future reads or Close.
   874  	if err == nil && n > 0 {
   875  		if lr, ok := b.src.(*io.LimitedReader); ok && lr.N == 0 {
   876  			err = io.EOF
   877  			b.sawEOF = true
   878  		}
   879  	}
   880  
   881  	if b.sawEOF && b.onHitEOF != nil {
   882  		b.onHitEOF()
   883  	}
   884  
   885  	return n, err
   886  }
   887  
   888  var (
   889  	singleCRLF = []byte("\r\n")
   890  	doubleCRLF = []byte("\r\n\r\n")
   891  )
   892  
   893  func seeUpcomingDoubleCRLF(r *bufio.Reader) bool {
   894  	for peekSize := 4; ; peekSize++ {
   895  		// This loop stops when Peek returns an error,
   896  		// which it does when r's buffer has been filled.
   897  		buf, err := r.Peek(peekSize)
   898  		if bytes.HasSuffix(buf, doubleCRLF) {
   899  			return true
   900  		}
   901  		if err != nil {
   902  			break
   903  		}
   904  	}
   905  	return false
   906  }
   907  
   908  var errTrailerEOF = errors.New("http: unexpected EOF reading trailer")
   909  
   910  func (b *body) readTrailer() error {
   911  	// The common case, since nobody uses trailers.
   912  	buf, err := b.r.Peek(2)
   913  	if bytes.Equal(buf, singleCRLF) {
   914  		b.r.Discard(2)
   915  		return nil
   916  	}
   917  	if len(buf) < 2 {
   918  		return errTrailerEOF
   919  	}
   920  	if err != nil {
   921  		return err
   922  	}
   923  
   924  	// Make sure there's a header terminator coming up, to prevent
   925  	// a DoS with an unbounded size Trailer. It's not easy to
   926  	// slip in a LimitReader here, as textproto.NewReader requires
   927  	// a concrete *bufio.Reader. Also, we can't get all the way
   928  	// back up to our conn's LimitedReader that *might* be backing
   929  	// this bufio.Reader. Instead, a hack: we iteratively Peek up
   930  	// to the bufio.Reader's max size, looking for a double CRLF.
   931  	// This limits the trailer to the underlying buffer size, typically 4kB.
   932  	if !seeUpcomingDoubleCRLF(b.r) {
   933  		return errors.New("http: suspiciously long trailer after chunked body")
   934  	}
   935  
   936  	hdr, err := textproto.NewReader(b.r).ReadMIMEHeader()
   937  	if err != nil {
   938  		if err == io.EOF {
   939  			return errTrailerEOF
   940  		}
   941  		return err
   942  	}
   943  	switch rr := b.hdr.(type) {
   944  	case *Request:
   945  		mergeSetHeader(&rr.Trailer, Header(hdr))
   946  	case *Response:
   947  		mergeSetHeader(&rr.Trailer, Header(hdr))
   948  	}
   949  	return nil
   950  }
   951  
   952  func mergeSetHeader(dst *Header, src Header) {
   953  	if *dst == nil {
   954  		*dst = src
   955  		return
   956  	}
   957  	for k, vv := range src {
   958  		(*dst)[k] = vv
   959  	}
   960  }
   961  
   962  // unreadDataSizeLocked returns the number of bytes of unread input.
   963  // It returns -1 if unknown.
   964  // b.mu must be held.
   965  func (b *body) unreadDataSizeLocked() int64 {
   966  	if lr, ok := b.src.(*io.LimitedReader); ok {
   967  		return lr.N
   968  	}
   969  	return -1
   970  }
   971  
   972  func (b *body) Close() error {
   973  	b.mu.Lock()
   974  	defer b.mu.Unlock()
   975  	if b.closed {
   976  		return nil
   977  	}
   978  	var err error
   979  	switch {
   980  	case b.sawEOF:
   981  		// Already saw EOF, so no need going to look for it.
   982  	case b.hdr == nil && b.closing:
   983  		// no trailer and closing the connection next.
   984  		// no point in reading to EOF.
   985  	case b.doEarlyClose:
   986  		// Read up to maxPostHandlerReadBytes bytes of the body, looking
   987  		// for EOF (and trailers), so we can re-use this connection.
   988  		if lr, ok := b.src.(*io.LimitedReader); ok && lr.N > maxPostHandlerReadBytes {
   989  			// There was a declared Content-Length, and we have more bytes remaining
   990  			// than our maxPostHandlerReadBytes tolerance. So, give up.
   991  			b.earlyClose = true
   992  		} else {
   993  			var n int64
   994  			// Consume the body, or, which will also lead to us reading
   995  			// the trailer headers after the body, if present.
   996  			n, err = io.CopyN(io.Discard, bodyLocked{b}, maxPostHandlerReadBytes)
   997  			if err == io.EOF {
   998  				err = nil
   999  			}
  1000  			if n == maxPostHandlerReadBytes {
  1001  				b.earlyClose = true
  1002  			}
  1003  		}
  1004  	default:
  1005  		// Fully consume the body, which will also lead to us reading
  1006  		// the trailer headers after the body, if present.
  1007  		_, err = io.Copy(io.Discard, bodyLocked{b})
  1008  	}
  1009  	b.closed = true
  1010  	return err
  1011  }
  1012  
  1013  func (b *body) didEarlyClose() bool {
  1014  	b.mu.Lock()
  1015  	defer b.mu.Unlock()
  1016  	return b.earlyClose
  1017  }
  1018  
  1019  // bodyRemains reports whether future Read calls might
  1020  // yield data.
  1021  func (b *body) bodyRemains() bool {
  1022  	b.mu.Lock()
  1023  	defer b.mu.Unlock()
  1024  	return !b.sawEOF
  1025  }
  1026  
  1027  func (b *body) registerOnHitEOF(fn func()) {
  1028  	b.mu.Lock()
  1029  	defer b.mu.Unlock()
  1030  	b.onHitEOF = fn
  1031  }
  1032  
  1033  // bodyLocked is an io.Reader reading from a *body when its mutex is
  1034  // already held.
  1035  type bodyLocked struct {
  1036  	b *body
  1037  }
  1038  
  1039  func (bl bodyLocked) Read(p []byte) (n int, err error) {
  1040  	if bl.b.closed {
  1041  		return 0, ErrBodyReadAfterClose
  1042  	}
  1043  	return bl.b.readLocked(p)
  1044  }
  1045  
  1046  // parseContentLength trims whitespace from s and returns -1 if no value
  1047  // is set, or the value if it's >= 0.
  1048  func parseContentLength(cl string) (int64, error) {
  1049  	cl = textproto.TrimString(cl)
  1050  	if cl == "" {
  1051  		return -1, nil
  1052  	}
  1053  	n, err := strconv.ParseUint(cl, 10, 63)
  1054  	if err != nil {
  1055  		return 0, badStringError("bad Content-Length", cl)
  1056  	}
  1057  	return int64(n), nil
  1058  
  1059  }
  1060  
  1061  // finishAsyncByteRead finishes reading the 1-byte sniff
  1062  // from the ContentLength==0, Body!=nil case.
  1063  type finishAsyncByteRead struct {
  1064  	tw *transferWriter
  1065  }
  1066  
  1067  func (fr finishAsyncByteRead) Read(p []byte) (n int, err error) {
  1068  	if len(p) == 0 {
  1069  		return
  1070  	}
  1071  	rres := <-fr.tw.ByteReadCh
  1072  	n, err = rres.n, rres.err
  1073  	if n == 1 {
  1074  		p[0] = rres.b
  1075  	}
  1076  	if err == nil {
  1077  		err = io.EOF
  1078  	}
  1079  	return
  1080  }
  1081  
  1082  var nopCloserType = reflect.TypeOf(io.NopCloser(nil))
  1083  
  1084  // isKnownInMemoryReader reports whether r is a type known to not
  1085  // block on Read. Its caller uses this as an optional optimization to
  1086  // send fewer TCP packets.
  1087  func isKnownInMemoryReader(r io.Reader) bool {
  1088  	switch r.(type) {
  1089  	case *bytes.Reader, *bytes.Buffer, *strings.Reader:
  1090  		return true
  1091  	}
  1092  	if reflect.TypeOf(r) == nopCloserType {
  1093  		return isKnownInMemoryReader(reflect.ValueOf(r).Field(0).Interface().(io.Reader))
  1094  	}
  1095  	if r, ok := r.(*readTrackingBody); ok {
  1096  		return isKnownInMemoryReader(r.ReadCloser)
  1097  	}
  1098  	return false
  1099  }
  1100  
  1101  // bufioFlushWriter is an io.Writer wrapper that flushes all writes
  1102  // on its wrapped writer if it's a *bufio.Writer.
  1103  type bufioFlushWriter struct{ w io.Writer }
  1104  
  1105  func (fw bufioFlushWriter) Write(p []byte) (n int, err error) {
  1106  	n, err = fw.w.Write(p)
  1107  	if bw, ok := fw.w.(*bufio.Writer); n > 0 && ok {
  1108  		ferr := bw.Flush()
  1109  		if ferr != nil && err == nil {
  1110  			err = ferr
  1111  		}
  1112  	}
  1113  	return
  1114  }
  1115  

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