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// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package http
import (
"bufio"
"bytes"
"errors"
"fmt"
"io"
"io/ioutil"
"net/http/internal"
"net/textproto"
"sort"
"strconv"
"strings"
"sync"
)
// ErrLineTooLong is returned when reading request or response bodies
// with malformed chunked encoding.
var ErrLineTooLong = internal.ErrLineTooLong
type errorReader struct {
err error
}
func (r *errorReader) Read(p []byte) (n int, err error) {
return 0, r.err
}
// transferWriter inspects the fields of a user-supplied Request or Response,
// sanitizes them without changing the user object and provides methods for
// writing the respective header, body and trailer in wire format.
type transferWriter struct {
Method string
Body io.Reader
BodyCloser io.Closer
ResponseToHEAD bool
ContentLength int64 // -1 means unknown, 0 means exactly none
Close bool
TransferEncoding []string
Trailer Header
}
func newTransferWriter(r interface{}) (t *transferWriter, err error) {
t = &transferWriter{}
// Extract relevant fields
atLeastHTTP11 := false
switch rr := r.(type) {
case *Request:
if rr.ContentLength != 0 && rr.Body == nil {
return nil, fmt.Errorf("http: Request.ContentLength=%d with nil Body", rr.ContentLength)
}
t.Method = rr.Method
t.Body = rr.Body
t.BodyCloser = rr.Body
t.ContentLength = rr.ContentLength
t.Close = rr.Close
t.TransferEncoding = rr.TransferEncoding
t.Trailer = rr.Trailer
atLeastHTTP11 = rr.ProtoAtLeast(1, 1)
if t.Body != nil && len(t.TransferEncoding) == 0 && atLeastHTTP11 {
if t.ContentLength == 0 {
// Test to see if it's actually zero or just unset.
var buf [1]byte
n, rerr := io.ReadFull(t.Body, buf[:])
if rerr != nil && rerr != io.EOF {
t.ContentLength = -1
t.Body = &errorReader{rerr}
} else if n == 1 {
// Oh, guess there is data in this Body Reader after all.
// The ContentLength field just wasn't set.
// Stich the Body back together again, re-attaching our
// consumed byte.
t.ContentLength = -1
t.Body = io.MultiReader(bytes.NewReader(buf[:]), t.Body)
} else {
// Body is actually empty.
t.Body = nil
t.BodyCloser = nil
}
}
if t.ContentLength < 0 {
t.TransferEncoding = []string{"chunked"}
}
}
case *Response:
if rr.Request != nil {
t.Method = rr.Request.Method
}
t.Body = rr.Body
t.BodyCloser = rr.Body
t.ContentLength = rr.ContentLength
t.Close = rr.Close
t.TransferEncoding = rr.TransferEncoding
t.Trailer = rr.Trailer
atLeastHTTP11 = rr.ProtoAtLeast(1, 1)
t.ResponseToHEAD = noBodyExpected(t.Method)
}
// Sanitize Body,ContentLength,TransferEncoding
if t.ResponseToHEAD {
t.Body = nil
if chunked(t.TransferEncoding) {
t.ContentLength = -1
}
} else {
if !atLeastHTTP11 || t.Body == nil {
t.TransferEncoding = nil
}
if chunked(t.TransferEncoding) {
t.ContentLength = -1
} else if t.Body == nil { // no chunking, no body
t.ContentLength = 0
}
}
// Sanitize Trailer
if !chunked(t.TransferEncoding) {
t.Trailer = nil
}
return t, nil
}
func noBodyExpected(requestMethod string) bool {
return requestMethod == "HEAD"
}
func (t *transferWriter) shouldSendContentLength() bool {
if chunked(t.TransferEncoding) {
return false
}
if t.ContentLength > 0 {
return true
}
// Many servers expect a Content-Length for these methods
if t.Method == "POST" || t.Method == "PUT" {
return true
}
if t.ContentLength == 0 && isIdentity(t.TransferEncoding) {
return true
}
return false
}
func (t *transferWriter) WriteHeader(w io.Writer) error {
if t.Close {
if _, err := io.WriteString(w, "Connection: close\r\n"); err != nil {
return err
}
}
// Write Content-Length and/or Transfer-Encoding whose values are a
// function of the sanitized field triple (Body, ContentLength,
// TransferEncoding)
if t.shouldSendContentLength() {
if _, err := io.WriteString(w, "Content-Length: "); err != nil {
return err
}
if _, err := io.WriteString(w, strconv.FormatInt(t.ContentLength, 10)+"\r\n"); err != nil {
return err
}
} else if chunked(t.TransferEncoding) {
if _, err := io.WriteString(w, "Transfer-Encoding: chunked\r\n"); err != nil {
return err
}
}
// Write Trailer header
if t.Trailer != nil {
keys := make([]string, 0, len(t.Trailer))
for k := range t.Trailer {
k = CanonicalHeaderKey(k)
switch k {
case "Transfer-Encoding", "Trailer", "Content-Length":
return &badStringError{"invalid Trailer key", k}
}
keys = append(keys, k)
}
if len(keys) > 0 {
sort.Strings(keys)
// TODO: could do better allocation-wise here, but trailers are rare,
// so being lazy for now.
if _, err := io.WriteString(w, "Trailer: "+strings.Join(keys, ",")+"\r\n"); err != nil {
return err
}
}
}
return nil
}
func (t *transferWriter) WriteBody(w io.Writer) error {
var err error
var ncopy int64
// Write body
if t.Body != nil {
if chunked(t.TransferEncoding) {
cw := internal.NewChunkedWriter(w)
_, err = io.Copy(cw, t.Body)
if err == nil {
err = cw.Close()
}
} else if t.ContentLength == -1 {
ncopy, err = io.Copy(w, t.Body)
} else {
ncopy, err = io.Copy(w, io.LimitReader(t.Body, t.ContentLength))
if err != nil {
return err
}
var nextra int64
nextra, err = io.Copy(ioutil.Discard, t.Body)
ncopy += nextra
}
if err != nil {
return err
}
if err = t.BodyCloser.Close(); err != nil {
return err
}
}
if !t.ResponseToHEAD && t.ContentLength != -1 && t.ContentLength != ncopy {
return fmt.Errorf("http: ContentLength=%d with Body length %d",
t.ContentLength, ncopy)
}
if chunked(t.TransferEncoding) {
// Write Trailer header
if t.Trailer != nil {
if err := t.Trailer.Write(w); err != nil {
return err
}
}
// Last chunk, empty trailer
_, err = io.WriteString(w, "\r\n")
}
return err
}
type transferReader struct {
// Input
Header Header
StatusCode int
RequestMethod string
ProtoMajor int
ProtoMinor int
// Output
Body io.ReadCloser
ContentLength int64
TransferEncoding []string
Close bool
Trailer Header
}
// bodyAllowedForStatus reports whether a given response status code
// permits a body. See RFC2616, section 4.4.
func bodyAllowedForStatus(status int) bool {
switch {
case status >= 100 && status <= 199:
return false
case status == 204:
return false
case status == 304:
return false
}
return true
}
var (
suppressedHeaders304 = []string{"Content-Type", "Content-Length", "Transfer-Encoding"}
suppressedHeadersNoBody = []string{"Content-Length", "Transfer-Encoding"}
)
func suppressedHeaders(status int) []string {
switch {
case status == 304:
// RFC 2616 section 10.3.5: "the response MUST NOT include other entity-headers"
return suppressedHeaders304
case !bodyAllowedForStatus(status):
return suppressedHeadersNoBody
}
return nil
}
// msg is *Request or *Response.
func readTransfer(msg interface{}, r *bufio.Reader) (err error) {
t := &transferReader{RequestMethod: "GET"}
// Unify input
isResponse := false
switch rr := msg.(type) {
case *Response:
t.Header = rr.Header
t.StatusCode = rr.StatusCode
t.ProtoMajor = rr.ProtoMajor
t.ProtoMinor = rr.ProtoMinor
t.Close = shouldClose(t.ProtoMajor, t.ProtoMinor, t.Header, true)
isResponse = true
if rr.Request != nil {
t.RequestMethod = rr.Request.Method
}
case *Request:
t.Header = rr.Header
t.ProtoMajor = rr.ProtoMajor
t.ProtoMinor = rr.ProtoMinor
// Transfer semantics for Requests are exactly like those for
// Responses with status code 200, responding to a GET method
t.StatusCode = 200
default:
panic("unexpected type")
}
// Default to HTTP/1.1
if t.ProtoMajor == 0 && t.ProtoMinor == 0 {
t.ProtoMajor, t.ProtoMinor = 1, 1
}
// Transfer encoding, content length
t.TransferEncoding, err = fixTransferEncoding(t.RequestMethod, t.Header)
if err != nil {
return err
}
realLength, err := fixLength(isResponse, t.StatusCode, t.RequestMethod, t.Header, t.TransferEncoding)
if err != nil {
return err
}
if isResponse && t.RequestMethod == "HEAD" {
if n, err := parseContentLength(t.Header.get("Content-Length")); err != nil {
return err
} else {
t.ContentLength = n
}
} else {
t.ContentLength = realLength
}
// Trailer
t.Trailer, err = fixTrailer(t.Header, t.TransferEncoding)
if err != nil {
return err
}
// If there is no Content-Length or chunked Transfer-Encoding on a *Response
// and the status is not 1xx, 204 or 304, then the body is unbounded.
// See RFC2616, section 4.4.
switch msg.(type) {
case *Response:
if realLength == -1 &&
!chunked(t.TransferEncoding) &&
bodyAllowedForStatus(t.StatusCode) {
// Unbounded body.
t.Close = true
}
}
// Prepare body reader. ContentLength < 0 means chunked encoding
// or close connection when finished, since multipart is not supported yet
switch {
case chunked(t.TransferEncoding):
if noBodyExpected(t.RequestMethod) {
t.Body = eofReader
} else {
t.Body = &body{src: internal.NewChunkedReader(r), hdr: msg, r: r, closing: t.Close}
}
case realLength == 0:
t.Body = eofReader
case realLength > 0:
t.Body = &body{src: io.LimitReader(r, realLength), closing: t.Close}
default:
// realLength < 0, i.e. "Content-Length" not mentioned in header
if t.Close {
// Close semantics (i.e. HTTP/1.0)
t.Body = &body{src: r, closing: t.Close}
} else {
// Persistent connection (i.e. HTTP/1.1)
t.Body = eofReader
}
}
// Unify output
switch rr := msg.(type) {
case *Request:
rr.Body = t.Body
rr.ContentLength = t.ContentLength
rr.TransferEncoding = t.TransferEncoding
rr.Close = t.Close
rr.Trailer = t.Trailer
case *Response:
rr.Body = t.Body
rr.ContentLength = t.ContentLength
rr.TransferEncoding = t.TransferEncoding
rr.Close = t.Close
rr.Trailer = t.Trailer
}
return nil
}
// Checks whether chunked is part of the encodings stack
func chunked(te []string) bool { return len(te) > 0 && te[0] == "chunked" }
// Checks whether the encoding is explicitly "identity".
func isIdentity(te []string) bool { return len(te) == 1 && te[0] == "identity" }
// Sanitize transfer encoding
func fixTransferEncoding(requestMethod string, header Header) ([]string, error) {
raw, present := header["Transfer-Encoding"]
if !present {
return nil, nil
}
delete(header, "Transfer-Encoding")
encodings := strings.Split(raw[0], ",")
te := make([]string, 0, len(encodings))
// TODO: Even though we only support "identity" and "chunked"
// encodings, the loop below is designed with foresight. One
// invariant that must be maintained is that, if present,
// chunked encoding must always come first.
for _, encoding := range encodings {
encoding = strings.ToLower(strings.TrimSpace(encoding))
// "identity" encoding is not recorded
if encoding == "identity" {
break
}
if encoding != "chunked" {
return nil, &badStringError{"unsupported transfer encoding", encoding}
}
te = te[0 : len(te)+1]
te[len(te)-1] = encoding
}
if len(te) > 1 {
return nil, &badStringError{"too many transfer encodings", strings.Join(te, ",")}
}
if len(te) > 0 {
// Chunked encoding trumps Content-Length. See RFC 2616
// Section 4.4. Currently len(te) > 0 implies chunked
// encoding.
delete(header, "Content-Length")
return te, nil
}
return nil, nil
}
// Determine the expected body length, using RFC 2616 Section 4.4. This
// function is not a method, because ultimately it should be shared by
// ReadResponse and ReadRequest.
func fixLength(isResponse bool, status int, requestMethod string, header Header, te []string) (int64, error) {
// Logic based on response type or status
if noBodyExpected(requestMethod) {
return 0, nil
}
if status/100 == 1 {
return 0, nil
}
switch status {
case 204, 304:
return 0, nil
}
// Logic based on Transfer-Encoding
if chunked(te) {
return -1, nil
}
// Logic based on Content-Length
cl := strings.TrimSpace(header.get("Content-Length"))
if cl != "" {
n, err := parseContentLength(cl)
if err != nil {
return -1, err
}
return n, nil
} else {
header.Del("Content-Length")
}
if !isResponse && requestMethod == "GET" {
// RFC 2616 doesn't explicitly permit nor forbid an
// entity-body on a GET request so we permit one if
// declared, but we default to 0 here (not -1 below)
// if there's no mention of a body.
return 0, nil
}
// Body-EOF logic based on other methods (like closing, or chunked coding)
return -1, nil
}
// Determine whether to hang up after sending a request and body, or
// receiving a response and body
// 'header' is the request headers
func shouldClose(major, minor int, header Header, removeCloseHeader bool) bool {
if major < 1 {
return true
} else if major == 1 && minor == 0 {
if !strings.Contains(strings.ToLower(header.get("Connection")), "keep-alive") {
return true
}
return false
} else {
// TODO: Should split on commas, toss surrounding white space,
// and check each field.
if strings.ToLower(header.get("Connection")) == "close" {
if removeCloseHeader {
header.Del("Connection")
}
return true
}
}
return false
}
// Parse the trailer header
func fixTrailer(header Header, te []string) (Header, error) {
raw := header.get("Trailer")
if raw == "" {
return nil, nil
}
header.Del("Trailer")
trailer := make(Header)
keys := strings.Split(raw, ",")
for _, key := range keys {
key = CanonicalHeaderKey(strings.TrimSpace(key))
switch key {
case "Transfer-Encoding", "Trailer", "Content-Length":
return nil, &badStringError{"bad trailer key", key}
}
trailer[key] = nil
}
if len(trailer) == 0 {
return nil, nil
}
if !chunked(te) {
// Trailer and no chunking
return nil, ErrUnexpectedTrailer
}
return trailer, nil
}
// body turns a Reader into a ReadCloser.
// Close ensures that the body has been fully read
// and then reads the trailer if necessary.
type body struct {
src io.Reader
hdr interface{} // non-nil (Response or Request) value means read trailer
r *bufio.Reader // underlying wire-format reader for the trailer
closing bool // is the connection to be closed after reading body?
mu sync.Mutex // guards closed, and calls to Read and Close
closed bool
}
// ErrBodyReadAfterClose is returned when reading a Request or Response
// Body after the body has been closed. This typically happens when the body is
// read after an HTTP Handler calls WriteHeader or Write on its
// ResponseWriter.
var ErrBodyReadAfterClose = errors.New("http: invalid Read on closed Body")
func (b *body) Read(p []byte) (n int, err error) {
b.mu.Lock()
defer b.mu.Unlock()
if b.closed {
return 0, ErrBodyReadAfterClose
}
return b.readLocked(p)
}
// Must hold b.mu.
func (b *body) readLocked(p []byte) (n int, err error) {
n, err = b.src.Read(p)
if err == io.EOF {
// Chunked case. Read the trailer.
if b.hdr != nil {
if e := b.readTrailer(); e != nil {
err = e
}
b.hdr = nil
} else {
// If the server declared the Content-Length, our body is a LimitedReader
// and we need to check whether this EOF arrived early.
if lr, ok := b.src.(*io.LimitedReader); ok && lr.N > 0 {
err = io.ErrUnexpectedEOF
}
}
}
// If we can return an EOF here along with the read data, do
// so. This is optional per the io.Reader contract, but doing
// so helps the HTTP transport code recycle its connection
// earlier (since it will see this EOF itself), even if the
// client doesn't do future reads or Close.
if err == nil && n > 0 {
if lr, ok := b.src.(*io.LimitedReader); ok && lr.N == 0 {
err = io.EOF
}
}
return n, err
}
var (
singleCRLF = []byte("\r\n")
doubleCRLF = []byte("\r\n\r\n")
)
func seeUpcomingDoubleCRLF(r *bufio.Reader) bool {
for peekSize := 4; ; peekSize++ {
// This loop stops when Peek returns an error,
// which it does when r's buffer has been filled.
buf, err := r.Peek(peekSize)
if bytes.HasSuffix(buf, doubleCRLF) {
return true
}
if err != nil {
break
}
}
return false
}
var errTrailerEOF = errors.New("http: unexpected EOF reading trailer")
func (b *body) readTrailer() error {
// The common case, since nobody uses trailers.
buf, err := b.r.Peek(2)
if bytes.Equal(buf, singleCRLF) {
b.r.Discard(2)
return nil
}
if len(buf) < 2 {
return errTrailerEOF
}
if err != nil {
return err
}
// Make sure there's a header terminator coming up, to prevent
// a DoS with an unbounded size Trailer. It's not easy to
// slip in a LimitReader here, as textproto.NewReader requires
// a concrete *bufio.Reader. Also, we can't get all the way
// back up to our conn's LimitedReader that *might* be backing
// this bufio.Reader. Instead, a hack: we iteratively Peek up
// to the bufio.Reader's max size, looking for a double CRLF.
// This limits the trailer to the underlying buffer size, typically 4kB.
if !seeUpcomingDoubleCRLF(b.r) {
return errors.New("http: suspiciously long trailer after chunked body")
}
hdr, err := textproto.NewReader(b.r).ReadMIMEHeader()
if err != nil {
if err == io.EOF {
return errTrailerEOF
}
return err
}
switch rr := b.hdr.(type) {
case *Request:
mergeSetHeader(&rr.Trailer, Header(hdr))
case *Response:
mergeSetHeader(&rr.Trailer, Header(hdr))
}
return nil
}
func mergeSetHeader(dst *Header, src Header) {
if *dst == nil {
*dst = src
return
}
for k, vv := range src {
(*dst)[k] = vv
}
}
func (b *body) Close() error {
b.mu.Lock()
defer b.mu.Unlock()
if b.closed {
return nil
}
var err error
switch {
case b.hdr == nil && b.closing:
// no trailer and closing the connection next.
// no point in reading to EOF.
default:
// Fully consume the body, which will also lead to us reading
// the trailer headers after the body, if present.
_, err = io.Copy(ioutil.Discard, bodyLocked{b})
}
b.closed = true
return err
}
// bodyLocked is a io.Reader reading from a *body when its mutex is
// already held.
type bodyLocked struct {
b *body
}
func (bl bodyLocked) Read(p []byte) (n int, err error) {
if bl.b.closed {
return 0, ErrBodyReadAfterClose
}
return bl.b.readLocked(p)
}
// parseContentLength trims whitespace from s and returns -1 if no value
// is set, or the value if it's >= 0.
func parseContentLength(cl string) (int64, error) {
cl = strings.TrimSpace(cl)
if cl == "" {
return -1, nil
}
n, err := strconv.ParseInt(cl, 10, 64)
if err != nil || n < 0 {
return 0, &badStringError{"bad Content-Length", cl}
}
return n, nil
}