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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"
"io"
"io/ioutil"
"os"
"strconv"
"strings"
)
// 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 {
Body io.ReadCloser
ResponseToHEAD bool
ContentLength int64
Close bool
TransferEncoding []string
Trailer Header
}
func newTransferWriter(r interface{}) (t *transferWriter, err os.Error) {
t = &transferWriter{}
// Extract relevant fields
atLeastHTTP11 := false
switch rr := r.(type) {
case *Request:
t.Body = 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 && t.ContentLength <= 0 && len(t.TransferEncoding) == 0 && atLeastHTTP11 {
t.TransferEncoding = []string{"chunked"}
}
case *Response:
t.Body = 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(rr.Request.Method)
}
// Sanitize Body,ContentLength,TransferEncoding
if t.ResponseToHEAD {
t.Body = nil
t.TransferEncoding = nil
// ContentLength is expected to hold Content-Length
if t.ContentLength < 0 {
return nil, ErrMissingContentLength
}
} 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) WriteHeader(w io.Writer) (err os.Error) {
if t.Close {
_, err = io.WriteString(w, "Connection: close\r\n")
if err != nil {
return
}
}
// Write Content-Length and/or Transfer-Encoding whose values are a
// function of the sanitized field triple (Body, ContentLength,
// TransferEncoding)
if chunked(t.TransferEncoding) {
_, err = io.WriteString(w, "Transfer-Encoding: chunked\r\n")
if err != nil {
return
}
} else if t.ContentLength > 0 || t.ResponseToHEAD || (t.ContentLength == 0 && isIdentity(t.TransferEncoding)) {
io.WriteString(w, "Content-Length: ")
_, err = io.WriteString(w, strconv.Itoa64(t.ContentLength)+"\r\n")
if err != nil {
return
}
}
// Write Trailer header
if t.Trailer != nil {
// TODO: At some point, there should be a generic mechanism for
// writing long headers, using HTTP line splitting
io.WriteString(w, "Trailer: ")
needComma := false
for k := range t.Trailer {
k = CanonicalHeaderKey(k)
switch k {
case "Transfer-Encoding", "Trailer", "Content-Length":
return &badStringError{"invalid Trailer key", k}
}
if needComma {
io.WriteString(w, ",")
}
io.WriteString(w, k)
needComma = true
}
_, err = io.WriteString(w, "\r\n")
}
return
}
func (t *transferWriter) WriteBody(w io.Writer) (err os.Error) {
// Write body
if t.Body != nil {
if chunked(t.TransferEncoding) {
cw := NewChunkedWriter(w)
_, err = io.Copy(cw, t.Body)
if err == nil {
err = cw.Close()
}
} else if t.ContentLength == -1 {
_, err = io.Copy(w, t.Body)
} else {
_, err = io.Copy(w, io.LimitReader(t.Body, t.ContentLength))
}
if err != nil {
return err
}
if err = t.Body.Close(); err != nil {
return err
}
}
// TODO(petar): Place trailer writer code here.
if chunked(t.TransferEncoding) {
// Last chunk, empty trailer
_, err = io.WriteString(w, "\r\n")
}
return
}
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 returns 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
}
// msg is *Request or *Response.
func readTransfer(msg interface{}, r *bufio.Reader) (err os.Error) {
t := &transferReader{}
// Unify input
switch rr := msg.(type) {
case *Response:
t.Header = rr.Header
t.StatusCode = rr.StatusCode
t.RequestMethod = rr.Request.Method
t.ProtoMajor = rr.ProtoMajor
t.ProtoMinor = rr.ProtoMinor
t.Close = shouldClose(t.ProtoMajor, t.ProtoMinor, t.Header)
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
t.RequestMethod = "GET"
}
// 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
}
t.ContentLength, err = fixLength(t.StatusCode, t.RequestMethod, t.Header, t.TransferEncoding)
if err != nil {
return err
}
// 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 t.ContentLength == -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):
t.Body = &body{Reader: newChunkedReader(r), hdr: msg, r: r, closing: t.Close}
case t.ContentLength >= 0:
// TODO: limit the Content-Length. This is an easy DoS vector.
t.Body = &body{Reader: io.LimitReader(r, t.ContentLength), closing: t.Close}
default:
// t.ContentLength < 0, i.e. "Content-Length" not mentioned in header
if t.Close {
// Close semantics (i.e. HTTP/1.0)
t.Body = &body{Reader: r, closing: t.Close}
} else {
// Persistent connection (i.e. HTTP/1.1)
t.Body = &body{Reader: io.LimitReader(r, 0), closing: t.Close}
}
// TODO(petar): It may be a good idea, for extra robustness, to
// assume ContentLength=0 for GET requests (and other special
// cases?). This logic should be in fixLength().
}
// 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, os.Error) {
raw, present := header["Transfer-Encoding"]
if !present {
return nil, nil
}
header["Transfer-Encoding"] = nil, false
// Head responses have no bodies, so the transfer encoding
// should be ignored.
if requestMethod == "HEAD" {
return nil, nil
}
encodings := strings.Split(raw[0], ",", -1)
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 recored
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.
header["Content-Length"] = nil, false
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(status int, requestMethod string, header Header, te []string) (int64, os.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 := strconv.Atoi64(cl)
if err != nil || n < 0 {
return -1, &badStringError{"bad Content-Length", cl}
}
return n, nil
} else {
header.Del("Content-Length")
}
// Logic based on media type. The purpose of the following code is just
// to detect whether the unsupported "multipart/byteranges" is being
// used. A proper Content-Type parser is needed in the future.
if strings.Contains(strings.ToLower(header.Get("Content-Type")), "multipart/byteranges") {
return -1, ErrNotSupported
}
// 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) 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" {
header.Del("Connection")
return true
}
}
return false
}
// Parse the trailer header
func fixTrailer(header Header, te []string) (Header, os.Error) {
raw := header.Get("Trailer")
if raw == "" {
return nil, nil
}
header.Del("Trailer")
trailer := make(Header)
keys := strings.Split(raw, ",", -1)
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.Del(key)
}
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 {
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?
closed bool
}
// ErrBodyReadAfterClose is returned when reading a Request 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 = os.NewError("http: invalid Read on closed request Body")
func (b *body) Read(p []byte) (n int, err os.Error) {
if b.closed {
return 0, ErrBodyReadAfterClose
}
return b.Reader.Read(p)
}
func (b *body) Close() os.Error {
if b.closed {
return nil
}
defer func() {
b.closed = true
}()
if b.hdr == nil && b.closing {
// no trailer and closing the connection next.
// no point in reading to EOF.
return nil
}
if _, err := io.Copy(ioutil.Discard, b); err != nil {
return err
}
if b.hdr == nil { // not reading trailer
return nil
}
// TODO(petar): Put trailer reader code here
return nil
}