...
Run Format

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		"io/ioutil"
    14		"net/http/internal"
    15		"net/textproto"
    16		"sort"
    17		"strconv"
    18		"strings"
    19		"sync"
    20	)
    21	
    22	// ErrLineTooLong is returned when reading request or response bodies
    23	// with malformed chunked encoding.
    24	var ErrLineTooLong = internal.ErrLineTooLong
    25	
    26	type errorReader struct {
    27		err error
    28	}
    29	
    30	func (r errorReader) Read(p []byte) (n int, err error) {
    31		return 0, r.err
    32	}
    33	
    34	// transferWriter inspects the fields of a user-supplied Request or Response,
    35	// sanitizes them without changing the user object and provides methods for
    36	// writing the respective header, body and trailer in wire format.
    37	type transferWriter struct {
    38		Method           string
    39		Body             io.Reader
    40		BodyCloser       io.Closer
    41		ResponseToHEAD   bool
    42		ContentLength    int64 // -1 means unknown, 0 means exactly none
    43		Close            bool
    44		TransferEncoding []string
    45		Trailer          Header
    46		IsResponse       bool
    47	}
    48	
    49	func newTransferWriter(r interface{}) (t *transferWriter, err error) {
    50		t = &transferWriter{}
    51	
    52		// Extract relevant fields
    53		atLeastHTTP11 := false
    54		switch rr := r.(type) {
    55		case *Request:
    56			if rr.ContentLength != 0 && rr.Body == nil {
    57				return nil, fmt.Errorf("http: Request.ContentLength=%d with nil Body", rr.ContentLength)
    58			}
    59			t.Method = rr.Method
    60			t.Body = rr.Body
    61			t.BodyCloser = rr.Body
    62			t.ContentLength = rr.ContentLength
    63			t.Close = rr.Close
    64			t.TransferEncoding = rr.TransferEncoding
    65			t.Trailer = rr.Trailer
    66			atLeastHTTP11 = rr.ProtoAtLeast(1, 1)
    67			if t.Body != nil && len(t.TransferEncoding) == 0 && atLeastHTTP11 {
    68				if t.ContentLength == 0 {
    69					// Test to see if it's actually zero or just unset.
    70					var buf [1]byte
    71					n, rerr := io.ReadFull(t.Body, buf[:])
    72					if rerr != nil && rerr != io.EOF {
    73						t.ContentLength = -1
    74						t.Body = errorReader{rerr}
    75					} else if n == 1 {
    76						// Oh, guess there is data in this Body Reader after all.
    77						// The ContentLength field just wasn't set.
    78						// Stich the Body back together again, re-attaching our
    79						// consumed byte.
    80						t.ContentLength = -1
    81						t.Body = io.MultiReader(bytes.NewReader(buf[:]), t.Body)
    82					} else {
    83						// Body is actually empty.
    84						t.Body = nil
    85						t.BodyCloser = nil
    86					}
    87				}
    88				if t.ContentLength < 0 {
    89					t.TransferEncoding = []string{"chunked"}
    90				}
    91			}
    92		case *Response:
    93			t.IsResponse = true
    94			if rr.Request != nil {
    95				t.Method = rr.Request.Method
    96			}
    97			t.Body = rr.Body
    98			t.BodyCloser = rr.Body
    99			t.ContentLength = rr.ContentLength
   100			t.Close = rr.Close
   101			t.TransferEncoding = rr.TransferEncoding
   102			t.Trailer = rr.Trailer
   103			atLeastHTTP11 = rr.ProtoAtLeast(1, 1)
   104			t.ResponseToHEAD = noBodyExpected(t.Method)
   105		}
   106	
   107		// Sanitize Body,ContentLength,TransferEncoding
   108		if t.ResponseToHEAD {
   109			t.Body = nil
   110			if chunked(t.TransferEncoding) {
   111				t.ContentLength = -1
   112			}
   113		} else {
   114			if !atLeastHTTP11 || t.Body == nil {
   115				t.TransferEncoding = nil
   116			}
   117			if chunked(t.TransferEncoding) {
   118				t.ContentLength = -1
   119			} else if t.Body == nil { // no chunking, no body
   120				t.ContentLength = 0
   121			}
   122		}
   123	
   124		// Sanitize Trailer
   125		if !chunked(t.TransferEncoding) {
   126			t.Trailer = nil
   127		}
   128	
   129		return t, nil
   130	}
   131	
   132	func noBodyExpected(requestMethod string) bool {
   133		return requestMethod == "HEAD"
   134	}
   135	
   136	func (t *transferWriter) shouldSendContentLength() bool {
   137		if chunked(t.TransferEncoding) {
   138			return false
   139		}
   140		if t.ContentLength > 0 {
   141			return true
   142		}
   143		if t.ContentLength < 0 {
   144			return false
   145		}
   146		// Many servers expect a Content-Length for these methods
   147		if t.Method == "POST" || t.Method == "PUT" {
   148			return true
   149		}
   150		if t.ContentLength == 0 && isIdentity(t.TransferEncoding) {
   151			if t.Method == "GET" || t.Method == "HEAD" {
   152				return false
   153			}
   154			return true
   155		}
   156	
   157		return false
   158	}
   159	
   160	func (t *transferWriter) WriteHeader(w io.Writer) error {
   161		if t.Close {
   162			if _, err := io.WriteString(w, "Connection: close\r\n"); err != nil {
   163				return err
   164			}
   165		}
   166	
   167		// Write Content-Length and/or Transfer-Encoding whose values are a
   168		// function of the sanitized field triple (Body, ContentLength,
   169		// TransferEncoding)
   170		if t.shouldSendContentLength() {
   171			if _, err := io.WriteString(w, "Content-Length: "); err != nil {
   172				return err
   173			}
   174			if _, err := io.WriteString(w, strconv.FormatInt(t.ContentLength, 10)+"\r\n"); err != nil {
   175				return err
   176			}
   177		} else if chunked(t.TransferEncoding) {
   178			if _, err := io.WriteString(w, "Transfer-Encoding: chunked\r\n"); err != nil {
   179				return err
   180			}
   181		}
   182	
   183		// Write Trailer header
   184		if t.Trailer != nil {
   185			keys := make([]string, 0, len(t.Trailer))
   186			for k := range t.Trailer {
   187				k = CanonicalHeaderKey(k)
   188				switch k {
   189				case "Transfer-Encoding", "Trailer", "Content-Length":
   190					return &badStringError{"invalid Trailer key", k}
   191				}
   192				keys = append(keys, k)
   193			}
   194			if len(keys) > 0 {
   195				sort.Strings(keys)
   196				// TODO: could do better allocation-wise here, but trailers are rare,
   197				// so being lazy for now.
   198				if _, err := io.WriteString(w, "Trailer: "+strings.Join(keys, ",")+"\r\n"); err != nil {
   199					return err
   200				}
   201			}
   202		}
   203	
   204		return nil
   205	}
   206	
   207	func (t *transferWriter) WriteBody(w io.Writer) error {
   208		var err error
   209		var ncopy int64
   210	
   211		// Write body
   212		if t.Body != nil {
   213			if chunked(t.TransferEncoding) {
   214				if bw, ok := w.(*bufio.Writer); ok && !t.IsResponse {
   215					w = &internal.FlushAfterChunkWriter{bw}
   216				}
   217				cw := internal.NewChunkedWriter(w)
   218				_, err = io.Copy(cw, t.Body)
   219				if err == nil {
   220					err = cw.Close()
   221				}
   222			} else if t.ContentLength == -1 {
   223				ncopy, err = io.Copy(w, t.Body)
   224			} else {
   225				ncopy, err = io.Copy(w, io.LimitReader(t.Body, t.ContentLength))
   226				if err != nil {
   227					return err
   228				}
   229				var nextra int64
   230				nextra, err = io.Copy(ioutil.Discard, t.Body)
   231				ncopy += nextra
   232			}
   233			if err != nil {
   234				return err
   235			}
   236			if err = t.BodyCloser.Close(); err != nil {
   237				return err
   238			}
   239		}
   240	
   241		if !t.ResponseToHEAD && t.ContentLength != -1 && t.ContentLength != ncopy {
   242			return fmt.Errorf("http: ContentLength=%d with Body length %d",
   243				t.ContentLength, ncopy)
   244		}
   245	
   246		if chunked(t.TransferEncoding) {
   247			// Write Trailer header
   248			if t.Trailer != nil {
   249				if err := t.Trailer.Write(w); err != nil {
   250					return err
   251				}
   252			}
   253			// Last chunk, empty trailer
   254			_, err = io.WriteString(w, "\r\n")
   255		}
   256		return err
   257	}
   258	
   259	type transferReader struct {
   260		// Input
   261		Header        Header
   262		StatusCode    int
   263		RequestMethod string
   264		ProtoMajor    int
   265		ProtoMinor    int
   266		// Output
   267		Body             io.ReadCloser
   268		ContentLength    int64
   269		TransferEncoding []string
   270		Close            bool
   271		Trailer          Header
   272	}
   273	
   274	// bodyAllowedForStatus reports whether a given response status code
   275	// permits a body.  See RFC2616, section 4.4.
   276	func bodyAllowedForStatus(status int) bool {
   277		switch {
   278		case status >= 100 && status <= 199:
   279			return false
   280		case status == 204:
   281			return false
   282		case status == 304:
   283			return false
   284		}
   285		return true
   286	}
   287	
   288	var (
   289		suppressedHeaders304    = []string{"Content-Type", "Content-Length", "Transfer-Encoding"}
   290		suppressedHeadersNoBody = []string{"Content-Length", "Transfer-Encoding"}
   291	)
   292	
   293	func suppressedHeaders(status int) []string {
   294		switch {
   295		case status == 304:
   296			// RFC 2616 section 10.3.5: "the response MUST NOT include other entity-headers"
   297			return suppressedHeaders304
   298		case !bodyAllowedForStatus(status):
   299			return suppressedHeadersNoBody
   300		}
   301		return nil
   302	}
   303	
   304	// msg is *Request or *Response.
   305	func readTransfer(msg interface{}, r *bufio.Reader) (err error) {
   306		t := &transferReader{RequestMethod: "GET"}
   307	
   308		// Unify input
   309		isResponse := false
   310		switch rr := msg.(type) {
   311		case *Response:
   312			t.Header = rr.Header
   313			t.StatusCode = rr.StatusCode
   314			t.ProtoMajor = rr.ProtoMajor
   315			t.ProtoMinor = rr.ProtoMinor
   316			t.Close = shouldClose(t.ProtoMajor, t.ProtoMinor, t.Header, true)
   317			isResponse = true
   318			if rr.Request != nil {
   319				t.RequestMethod = rr.Request.Method
   320			}
   321		case *Request:
   322			t.Header = rr.Header
   323			t.RequestMethod = rr.Method
   324			t.ProtoMajor = rr.ProtoMajor
   325			t.ProtoMinor = rr.ProtoMinor
   326			// Transfer semantics for Requests are exactly like those for
   327			// Responses with status code 200, responding to a GET method
   328			t.StatusCode = 200
   329			t.Close = rr.Close
   330		default:
   331			panic("unexpected type")
   332		}
   333	
   334		// Default to HTTP/1.1
   335		if t.ProtoMajor == 0 && t.ProtoMinor == 0 {
   336			t.ProtoMajor, t.ProtoMinor = 1, 1
   337		}
   338	
   339		// Transfer encoding, content length
   340		t.TransferEncoding, err = fixTransferEncoding(isResponse, t.RequestMethod, t.Header)
   341		if err != nil {
   342			return err
   343		}
   344	
   345		realLength, err := fixLength(isResponse, t.StatusCode, t.RequestMethod, t.Header, t.TransferEncoding)
   346		if err != nil {
   347			return err
   348		}
   349		if isResponse && t.RequestMethod == "HEAD" {
   350			if n, err := parseContentLength(t.Header.get("Content-Length")); err != nil {
   351				return err
   352			} else {
   353				t.ContentLength = n
   354			}
   355		} else {
   356			t.ContentLength = realLength
   357		}
   358	
   359		// Trailer
   360		t.Trailer, err = fixTrailer(t.Header, t.TransferEncoding)
   361		if err != nil {
   362			return err
   363		}
   364	
   365		// If there is no Content-Length or chunked Transfer-Encoding on a *Response
   366		// and the status is not 1xx, 204 or 304, then the body is unbounded.
   367		// See RFC2616, section 4.4.
   368		switch msg.(type) {
   369		case *Response:
   370			if realLength == -1 &&
   371				!chunked(t.TransferEncoding) &&
   372				bodyAllowedForStatus(t.StatusCode) {
   373				// Unbounded body.
   374				t.Close = true
   375			}
   376		}
   377	
   378		// Prepare body reader.  ContentLength < 0 means chunked encoding
   379		// or close connection when finished, since multipart is not supported yet
   380		switch {
   381		case chunked(t.TransferEncoding):
   382			if noBodyExpected(t.RequestMethod) {
   383				t.Body = eofReader
   384			} else {
   385				t.Body = &body{src: internal.NewChunkedReader(r), hdr: msg, r: r, closing: t.Close}
   386			}
   387		case realLength == 0:
   388			t.Body = eofReader
   389		case realLength > 0:
   390			t.Body = &body{src: io.LimitReader(r, realLength), closing: t.Close}
   391		default:
   392			// realLength < 0, i.e. "Content-Length" not mentioned in header
   393			if t.Close {
   394				// Close semantics (i.e. HTTP/1.0)
   395				t.Body = &body{src: r, closing: t.Close}
   396			} else {
   397				// Persistent connection (i.e. HTTP/1.1)
   398				t.Body = eofReader
   399			}
   400		}
   401	
   402		// Unify output
   403		switch rr := msg.(type) {
   404		case *Request:
   405			rr.Body = t.Body
   406			rr.ContentLength = t.ContentLength
   407			rr.TransferEncoding = t.TransferEncoding
   408			rr.Close = t.Close
   409			rr.Trailer = t.Trailer
   410		case *Response:
   411			rr.Body = t.Body
   412			rr.ContentLength = t.ContentLength
   413			rr.TransferEncoding = t.TransferEncoding
   414			rr.Close = t.Close
   415			rr.Trailer = t.Trailer
   416		}
   417	
   418		return nil
   419	}
   420	
   421	// Checks whether chunked is part of the encodings stack
   422	func chunked(te []string) bool { return len(te) > 0 && te[0] == "chunked" }
   423	
   424	// Checks whether the encoding is explicitly "identity".
   425	func isIdentity(te []string) bool { return len(te) == 1 && te[0] == "identity" }
   426	
   427	// Sanitize transfer encoding
   428	func fixTransferEncoding(isResponse bool, requestMethod string, header Header) ([]string, error) {
   429		raw, present := header["Transfer-Encoding"]
   430		if !present {
   431			return nil, nil
   432		}
   433		delete(header, "Transfer-Encoding")
   434	
   435		encodings := strings.Split(raw[0], ",")
   436		te := make([]string, 0, len(encodings))
   437		// TODO: Even though we only support "identity" and "chunked"
   438		// encodings, the loop below is designed with foresight. One
   439		// invariant that must be maintained is that, if present,
   440		// chunked encoding must always come first.
   441		for _, encoding := range encodings {
   442			encoding = strings.ToLower(strings.TrimSpace(encoding))
   443			// "identity" encoding is not recorded
   444			if encoding == "identity" {
   445				break
   446			}
   447			if encoding != "chunked" {
   448				return nil, &badStringError{"unsupported transfer encoding", encoding}
   449			}
   450			te = te[0 : len(te)+1]
   451			te[len(te)-1] = encoding
   452		}
   453		if len(te) > 1 {
   454			return nil, &badStringError{"too many transfer encodings", strings.Join(te, ",")}
   455		}
   456		if len(te) > 0 {
   457			// RFC 7230 3.3.2 says "A sender MUST NOT send a
   458			// Content-Length header field in any message that
   459			// contains a Transfer-Encoding header field."
   460			//
   461			// but also:
   462			// "If a message is received with both a
   463			// Transfer-Encoding and a Content-Length header
   464			// field, the Transfer-Encoding overrides the
   465			// Content-Length. Such a message might indicate an
   466			// attempt to perform request smuggling (Section 9.5)
   467			// or response splitting (Section 9.4) and ought to be
   468			// handled as an error. A sender MUST remove the
   469			// received Content-Length field prior to forwarding
   470			// such a message downstream."
   471			//
   472			// Reportedly, these appear in the wild.
   473			delete(header, "Content-Length")
   474			return te, nil
   475		}
   476	
   477		return nil, nil
   478	}
   479	
   480	// Determine the expected body length, using RFC 2616 Section 4.4. This
   481	// function is not a method, because ultimately it should be shared by
   482	// ReadResponse and ReadRequest.
   483	func fixLength(isResponse bool, status int, requestMethod string, header Header, te []string) (int64, error) {
   484		contentLens := header["Content-Length"]
   485		isRequest := !isResponse
   486		// Logic based on response type or status
   487		if noBodyExpected(requestMethod) {
   488			// For HTTP requests, as part of hardening against request
   489			// smuggling (RFC 7230), don't allow a Content-Length header for
   490			// methods which don't permit bodies. As an exception, allow
   491			// exactly one Content-Length header if its value is "0".
   492			if isRequest && len(contentLens) > 0 && !(len(contentLens) == 1 && contentLens[0] == "0") {
   493				return 0, fmt.Errorf("http: method cannot contain a Content-Length; got %q", contentLens)
   494			}
   495			return 0, nil
   496		}
   497		if status/100 == 1 {
   498			return 0, nil
   499		}
   500		switch status {
   501		case 204, 304:
   502			return 0, nil
   503		}
   504	
   505		if len(contentLens) > 1 {
   506			// harden against HTTP request smuggling. See RFC 7230.
   507			return 0, errors.New("http: message cannot contain multiple Content-Length headers")
   508		}
   509	
   510		// Logic based on Transfer-Encoding
   511		if chunked(te) {
   512			return -1, nil
   513		}
   514	
   515		// Logic based on Content-Length
   516		var cl string
   517		if len(contentLens) == 1 {
   518			cl = strings.TrimSpace(contentLens[0])
   519		}
   520		if cl != "" {
   521			n, err := parseContentLength(cl)
   522			if err != nil {
   523				return -1, err
   524			}
   525			return n, nil
   526		} else {
   527			header.Del("Content-Length")
   528		}
   529	
   530		if !isResponse {
   531			// RFC 2616 neither explicitly permits nor forbids an
   532			// entity-body on a GET request so we permit one if
   533			// declared, but we default to 0 here (not -1 below)
   534			// if there's no mention of a body.
   535			// Likewise, all other request methods are assumed to have
   536			// no body if neither Transfer-Encoding chunked nor a
   537			// Content-Length are set.
   538			return 0, nil
   539		}
   540	
   541		// Body-EOF logic based on other methods (like closing, or chunked coding)
   542		return -1, nil
   543	}
   544	
   545	// Determine whether to hang up after sending a request and body, or
   546	// receiving a response and body
   547	// 'header' is the request headers
   548	func shouldClose(major, minor int, header Header, removeCloseHeader bool) bool {
   549		if major < 1 {
   550			return true
   551		} else if major == 1 && minor == 0 {
   552			vv := header["Connection"]
   553			if headerValuesContainsToken(vv, "close") || !headerValuesContainsToken(vv, "keep-alive") {
   554				return true
   555			}
   556			return false
   557		} else {
   558			if headerValuesContainsToken(header["Connection"], "close") {
   559				if removeCloseHeader {
   560					header.Del("Connection")
   561				}
   562				return true
   563			}
   564		}
   565		return false
   566	}
   567	
   568	// Parse the trailer header
   569	func fixTrailer(header Header, te []string) (Header, error) {
   570		raw := header.get("Trailer")
   571		if raw == "" {
   572			return nil, nil
   573		}
   574	
   575		header.Del("Trailer")
   576		trailer := make(Header)
   577		keys := strings.Split(raw, ",")
   578		for _, key := range keys {
   579			key = CanonicalHeaderKey(strings.TrimSpace(key))
   580			switch key {
   581			case "Transfer-Encoding", "Trailer", "Content-Length":
   582				return nil, &badStringError{"bad trailer key", key}
   583			}
   584			trailer[key] = nil
   585		}
   586		if len(trailer) == 0 {
   587			return nil, nil
   588		}
   589		if !chunked(te) {
   590			// Trailer and no chunking
   591			return nil, ErrUnexpectedTrailer
   592		}
   593		return trailer, nil
   594	}
   595	
   596	// body turns a Reader into a ReadCloser.
   597	// Close ensures that the body has been fully read
   598	// and then reads the trailer if necessary.
   599	type body struct {
   600		src          io.Reader
   601		hdr          interface{}   // non-nil (Response or Request) value means read trailer
   602		r            *bufio.Reader // underlying wire-format reader for the trailer
   603		closing      bool          // is the connection to be closed after reading body?
   604		doEarlyClose bool          // whether Close should stop early
   605	
   606		mu         sync.Mutex // guards closed, and calls to Read and Close
   607		sawEOF     bool
   608		closed     bool
   609		earlyClose bool // Close called and we didn't read to the end of src
   610	}
   611	
   612	// ErrBodyReadAfterClose is returned when reading a Request or Response
   613	// Body after the body has been closed. This typically happens when the body is
   614	// read after an HTTP Handler calls WriteHeader or Write on its
   615	// ResponseWriter.
   616	var ErrBodyReadAfterClose = errors.New("http: invalid Read on closed Body")
   617	
   618	func (b *body) Read(p []byte) (n int, err error) {
   619		b.mu.Lock()
   620		defer b.mu.Unlock()
   621		if b.closed {
   622			return 0, ErrBodyReadAfterClose
   623		}
   624		return b.readLocked(p)
   625	}
   626	
   627	// Must hold b.mu.
   628	func (b *body) readLocked(p []byte) (n int, err error) {
   629		if b.sawEOF {
   630			return 0, io.EOF
   631		}
   632		n, err = b.src.Read(p)
   633	
   634		if err == io.EOF {
   635			b.sawEOF = true
   636			// Chunked case. Read the trailer.
   637			if b.hdr != nil {
   638				if e := b.readTrailer(); e != nil {
   639					err = e
   640					// Something went wrong in the trailer, we must not allow any
   641					// further reads of any kind to succeed from body, nor any
   642					// subsequent requests on the server connection. See
   643					// golang.org/issue/12027
   644					b.sawEOF = false
   645					b.closed = true
   646				}
   647				b.hdr = nil
   648			} else {
   649				// If the server declared the Content-Length, our body is a LimitedReader
   650				// and we need to check whether this EOF arrived early.
   651				if lr, ok := b.src.(*io.LimitedReader); ok && lr.N > 0 {
   652					err = io.ErrUnexpectedEOF
   653				}
   654			}
   655		}
   656	
   657		// If we can return an EOF here along with the read data, do
   658		// so. This is optional per the io.Reader contract, but doing
   659		// so helps the HTTP transport code recycle its connection
   660		// earlier (since it will see this EOF itself), even if the
   661		// client doesn't do future reads or Close.
   662		if err == nil && n > 0 {
   663			if lr, ok := b.src.(*io.LimitedReader); ok && lr.N == 0 {
   664				err = io.EOF
   665				b.sawEOF = true
   666			}
   667		}
   668	
   669		return n, err
   670	}
   671	
   672	var (
   673		singleCRLF = []byte("\r\n")
   674		doubleCRLF = []byte("\r\n\r\n")
   675	)
   676	
   677	func seeUpcomingDoubleCRLF(r *bufio.Reader) bool {
   678		for peekSize := 4; ; peekSize++ {
   679			// This loop stops when Peek returns an error,
   680			// which it does when r's buffer has been filled.
   681			buf, err := r.Peek(peekSize)
   682			if bytes.HasSuffix(buf, doubleCRLF) {
   683				return true
   684			}
   685			if err != nil {
   686				break
   687			}
   688		}
   689		return false
   690	}
   691	
   692	var errTrailerEOF = errors.New("http: unexpected EOF reading trailer")
   693	
   694	func (b *body) readTrailer() error {
   695		// The common case, since nobody uses trailers.
   696		buf, err := b.r.Peek(2)
   697		if bytes.Equal(buf, singleCRLF) {
   698			b.r.Discard(2)
   699			return nil
   700		}
   701		if len(buf) < 2 {
   702			return errTrailerEOF
   703		}
   704		if err != nil {
   705			return err
   706		}
   707	
   708		// Make sure there's a header terminator coming up, to prevent
   709		// a DoS with an unbounded size Trailer.  It's not easy to
   710		// slip in a LimitReader here, as textproto.NewReader requires
   711		// a concrete *bufio.Reader.  Also, we can't get all the way
   712		// back up to our conn's LimitedReader that *might* be backing
   713		// this bufio.Reader.  Instead, a hack: we iteratively Peek up
   714		// to the bufio.Reader's max size, looking for a double CRLF.
   715		// This limits the trailer to the underlying buffer size, typically 4kB.
   716		if !seeUpcomingDoubleCRLF(b.r) {
   717			return errors.New("http: suspiciously long trailer after chunked body")
   718		}
   719	
   720		hdr, err := textproto.NewReader(b.r).ReadMIMEHeader()
   721		if err != nil {
   722			if err == io.EOF {
   723				return errTrailerEOF
   724			}
   725			return err
   726		}
   727		switch rr := b.hdr.(type) {
   728		case *Request:
   729			mergeSetHeader(&rr.Trailer, Header(hdr))
   730		case *Response:
   731			mergeSetHeader(&rr.Trailer, Header(hdr))
   732		}
   733		return nil
   734	}
   735	
   736	func mergeSetHeader(dst *Header, src Header) {
   737		if *dst == nil {
   738			*dst = src
   739			return
   740		}
   741		for k, vv := range src {
   742			(*dst)[k] = vv
   743		}
   744	}
   745	
   746	// unreadDataSizeLocked returns the number of bytes of unread input.
   747	// It returns -1 if unknown.
   748	// b.mu must be held.
   749	func (b *body) unreadDataSizeLocked() int64 {
   750		if lr, ok := b.src.(*io.LimitedReader); ok {
   751			return lr.N
   752		}
   753		return -1
   754	}
   755	
   756	func (b *body) Close() error {
   757		b.mu.Lock()
   758		defer b.mu.Unlock()
   759		if b.closed {
   760			return nil
   761		}
   762		var err error
   763		switch {
   764		case b.sawEOF:
   765			// Already saw EOF, so no need going to look for it.
   766		case b.hdr == nil && b.closing:
   767			// no trailer and closing the connection next.
   768			// no point in reading to EOF.
   769		case b.doEarlyClose:
   770			// Read up to maxPostHandlerReadBytes bytes of the body, looking for
   771			// for EOF (and trailers), so we can re-use this connection.
   772			if lr, ok := b.src.(*io.LimitedReader); ok && lr.N > maxPostHandlerReadBytes {
   773				// There was a declared Content-Length, and we have more bytes remaining
   774				// than our maxPostHandlerReadBytes tolerance. So, give up.
   775				b.earlyClose = true
   776			} else {
   777				var n int64
   778				// Consume the body, or, which will also lead to us reading
   779				// the trailer headers after the body, if present.
   780				n, err = io.CopyN(ioutil.Discard, bodyLocked{b}, maxPostHandlerReadBytes)
   781				if err == io.EOF {
   782					err = nil
   783				}
   784				if n == maxPostHandlerReadBytes {
   785					b.earlyClose = true
   786				}
   787			}
   788		default:
   789			// Fully consume the body, which will also lead to us reading
   790			// the trailer headers after the body, if present.
   791			_, err = io.Copy(ioutil.Discard, bodyLocked{b})
   792		}
   793		b.closed = true
   794		return err
   795	}
   796	
   797	func (b *body) didEarlyClose() bool {
   798		b.mu.Lock()
   799		defer b.mu.Unlock()
   800		return b.earlyClose
   801	}
   802	
   803	// bodyLocked is a io.Reader reading from a *body when its mutex is
   804	// already held.
   805	type bodyLocked struct {
   806		b *body
   807	}
   808	
   809	func (bl bodyLocked) Read(p []byte) (n int, err error) {
   810		if bl.b.closed {
   811			return 0, ErrBodyReadAfterClose
   812		}
   813		return bl.b.readLocked(p)
   814	}
   815	
   816	// parseContentLength trims whitespace from s and returns -1 if no value
   817	// is set, or the value if it's >= 0.
   818	func parseContentLength(cl string) (int64, error) {
   819		cl = strings.TrimSpace(cl)
   820		if cl == "" {
   821			return -1, nil
   822		}
   823		n, err := strconv.ParseInt(cl, 10, 64)
   824		if err != nil || n < 0 {
   825			return 0, &badStringError{"bad Content-Length", cl}
   826		}
   827		return n, nil
   828	
   829	}
   830	

View as plain text