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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.
// HTTP Response reading and parsing.
package http
import (
"bufio"
"bytes"
"crypto/tls"
"errors"
"fmt"
"internal/x/net/http/httpguts"
"io"
"net/textproto"
"net/url"
"strconv"
"strings"
)
var respExcludeHeader = map[string]bool{
"Content-Length": true,
"Transfer-Encoding": true,
"Trailer": true,
}
// Response represents the response from an HTTP request.
//
// The Client and Transport return Responses from servers once
// the response headers have been received. The response body
// is streamed on demand as the Body field is read.
type Response struct {
Status string // e.g. "200 OK"
StatusCode int // e.g. 200
Proto string // e.g. "HTTP/1.0"
ProtoMajor int // e.g. 1
ProtoMinor int // e.g. 0
// Header maps header keys to values. If the response had multiple
// headers with the same key, they may be concatenated, with comma
// delimiters. (RFC 7230, section 3.2.2 requires that multiple headers
// be semantically equivalent to a comma-delimited sequence.) When
// Header values are duplicated by other fields in this struct (e.g.,
// ContentLength, TransferEncoding, Trailer), the field values are
// authoritative.
//
// Keys in the map are canonicalized (see CanonicalHeaderKey).
Header Header
// Body represents the response body.
//
// The response body is streamed on demand as the Body field
// is read. If the network connection fails or the server
// terminates the response, Body.Read calls return an error.
//
// The http Client and Transport guarantee that Body is always
// non-nil, even on responses without a body or responses with
// a zero-length body. It is the caller's responsibility to
// close Body. The default HTTP client's Transport may not
// reuse HTTP/1.x "keep-alive" TCP connections if the Body is
// not read to completion and closed.
//
// The Body is automatically dechunked if the server replied
// with a "chunked" Transfer-Encoding.
//
// As of Go 1.12, the Body will be also implement io.Writer
// on a successful "101 Switching Protocols" responses,
// as used by WebSockets and HTTP/2's "h2c" mode.
Body io.ReadCloser
// ContentLength records the length of the associated content. The
// value -1 indicates that the length is unknown. Unless Request.Method
// is "HEAD", values >= 0 indicate that the given number of bytes may
// be read from Body.
ContentLength int64
// Contains transfer encodings from outer-most to inner-most. Value is
// nil, means that "identity" encoding is used.
TransferEncoding []string
// Close records whether the header directed that the connection be
// closed after reading Body. The value is advice for clients: neither
// ReadResponse nor Response.Write ever closes a connection.
Close bool
// Uncompressed reports whether the response was sent compressed but
// was decompressed by the http package. When true, reading from
// Body yields the uncompressed content instead of the compressed
// content actually set from the server, ContentLength is set to -1,
// and the "Content-Length" and "Content-Encoding" fields are deleted
// from the responseHeader. To get the original response from
// the server, set Transport.DisableCompression to true.
Uncompressed bool
// Trailer maps trailer keys to values in the same
// format as Header.
//
// The Trailer initially contains only nil values, one for
// each key specified in the server's "Trailer" header
// value. Those values are not added to Header.
//
// Trailer must not be accessed concurrently with Read calls
// on the Body.
//
// After Body.Read has returned io.EOF, Trailer will contain
// any trailer values sent by the server.
Trailer Header
// Request is the request that was sent to obtain this Response.
// Request's Body is nil (having already been consumed).
// This is only populated for Client requests.
Request *Request
// TLS contains information about the TLS connection on which the
// response was received. It is nil for unencrypted responses.
// The pointer is shared between responses and should not be
// modified.
TLS *tls.ConnectionState
}
// Cookies parses and returns the cookies set in the Set-Cookie headers.
func (r *Response) Cookies() []*Cookie {
return readSetCookies(r.Header)
}
// ErrNoLocation is returned by Response's Location method
// when no Location header is present.
var ErrNoLocation = errors.New("http: no Location header in response")
// Location returns the URL of the response's "Location" header,
// if present. Relative redirects are resolved relative to
// the Response's Request. ErrNoLocation is returned if no
// Location header is present.
func (r *Response) Location() (*url.URL, error) {
lv := r.Header.Get("Location")
if lv == "" {
return nil, ErrNoLocation
}
if r.Request != nil && r.Request.URL != nil {
return r.Request.URL.Parse(lv)
}
return url.Parse(lv)
}
// ReadResponse reads and returns an HTTP response from r.
// The req parameter optionally specifies the Request that corresponds
// to this Response. If nil, a GET request is assumed.
// Clients must call resp.Body.Close when finished reading resp.Body.
// After that call, clients can inspect resp.Trailer to find key/value
// pairs included in the response trailer.
func ReadResponse(r *bufio.Reader, req *Request) (*Response, error) {
tp := textproto.NewReader(r)
resp := &Response{
Request: req,
}
// Parse the first line of the response.
line, err := tp.ReadLine()
if err != nil {
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
return nil, err
}
if i := strings.IndexByte(line, ' '); i == -1 {
return nil, &badStringError{"malformed HTTP response", line}
} else {
resp.Proto = line[:i]
resp.Status = strings.TrimLeft(line[i+1:], " ")
}
statusCode := resp.Status
if i := strings.IndexByte(resp.Status, ' '); i != -1 {
statusCode = resp.Status[:i]
}
if len(statusCode) != 3 {
return nil, &badStringError{"malformed HTTP status code", statusCode}
}
resp.StatusCode, err = strconv.Atoi(statusCode)
if err != nil || resp.StatusCode < 0 {
return nil, &badStringError{"malformed HTTP status code", statusCode}
}
var ok bool
if resp.ProtoMajor, resp.ProtoMinor, ok = ParseHTTPVersion(resp.Proto); !ok {
return nil, &badStringError{"malformed HTTP version", resp.Proto}
}
// Parse the response headers.
mimeHeader, err := tp.ReadMIMEHeader()
if err != nil {
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
return nil, err
}
resp.Header = Header(mimeHeader)
fixPragmaCacheControl(resp.Header)
err = readTransfer(resp, r)
if err != nil {
return nil, err
}
return resp, nil
}
// RFC 7234, section 5.4: Should treat
// Pragma: no-cache
// like
// Cache-Control: no-cache
func fixPragmaCacheControl(header Header) {
if hp, ok := header["Pragma"]; ok && len(hp) > 0 && hp[0] == "no-cache" {
if _, presentcc := header["Cache-Control"]; !presentcc {
header["Cache-Control"] = []string{"no-cache"}
}
}
}
// ProtoAtLeast reports whether the HTTP protocol used
// in the response is at least major.minor.
func (r *Response) ProtoAtLeast(major, minor int) bool {
return r.ProtoMajor > major ||
r.ProtoMajor == major && r.ProtoMinor >= minor
}
// Write writes r to w in the HTTP/1.x server response format,
// including the status line, headers, body, and optional trailer.
//
// This method consults the following fields of the response r:
//
// StatusCode
// ProtoMajor
// ProtoMinor
// Request.Method
// TransferEncoding
// Trailer
// Body
// ContentLength
// Header, values for non-canonical keys will have unpredictable behavior
//
// The Response Body is closed after it is sent.
func (r *Response) Write(w io.Writer) error {
// Status line
text := r.Status
if text == "" {
var ok bool
text, ok = statusText[r.StatusCode]
if !ok {
text = "status code " + strconv.Itoa(r.StatusCode)
}
} else {
// Just to reduce stutter, if user set r.Status to "200 OK" and StatusCode to 200.
// Not important.
text = strings.TrimPrefix(text, strconv.Itoa(r.StatusCode)+" ")
}
if _, err := fmt.Fprintf(w, "HTTP/%d.%d %03d %s\r\n", r.ProtoMajor, r.ProtoMinor, r.StatusCode, text); err != nil {
return err
}
// Clone it, so we can modify r1 as needed.
r1 := new(Response)
*r1 = *r
if r1.ContentLength == 0 && r1.Body != nil {
// Is it actually 0 length? Or just unknown?
var buf [1]byte
n, err := r1.Body.Read(buf[:])
if err != nil && err != io.EOF {
return err
}
if n == 0 {
// Reset it to a known zero reader, in case underlying one
// is unhappy being read repeatedly.
r1.Body = NoBody
} else {
r1.ContentLength = -1
r1.Body = struct {
io.Reader
io.Closer
}{
io.MultiReader(bytes.NewReader(buf[:1]), r.Body),
r.Body,
}
}
}
// If we're sending a non-chunked HTTP/1.1 response without a
// content-length, the only way to do that is the old HTTP/1.0
// way, by noting the EOF with a connection close, so we need
// to set Close.
if r1.ContentLength == -1 && !r1.Close && r1.ProtoAtLeast(1, 1) && !chunked(r1.TransferEncoding) && !r1.Uncompressed {
r1.Close = true
}
// Process Body,ContentLength,Close,Trailer
tw, err := newTransferWriter(r1)
if err != nil {
return err
}
err = tw.writeHeader(w, nil)
if err != nil {
return err
}
// Rest of header
err = r.Header.WriteSubset(w, respExcludeHeader)
if err != nil {
return err
}
// contentLengthAlreadySent may have been already sent for
// POST/PUT requests, even if zero length. See Issue 8180.
contentLengthAlreadySent := tw.shouldSendContentLength()
if r1.ContentLength == 0 && !chunked(r1.TransferEncoding) && !contentLengthAlreadySent && bodyAllowedForStatus(r.StatusCode) {
if _, err := io.WriteString(w, "Content-Length: 0\r\n"); err != nil {
return err
}
}
// End-of-header
if _, err := io.WriteString(w, "\r\n"); err != nil {
return err
}
// Write body and trailer
err = tw.writeBody(w)
if err != nil {
return err
}
// Success
return nil
}
func (r *Response) closeBody() {
if r.Body != nil {
r.Body.Close()
}
}
// bodyIsWritable reports whether the Body supports writing. The
// Transport returns Writable bodies for 101 Switching Protocols
// responses.
// The Transport uses this method to determine whether a persistent
// connection is done being managed from its perspective. Once we
// return a writable response body to a user, the net/http package is
// done managing that connection.
func (r *Response) bodyIsWritable() bool {
_, ok := r.Body.(io.Writer)
return ok
}
// isProtocolSwitch reports whether r is a response to a successful
// protocol upgrade.
func (r *Response) isProtocolSwitch() bool {
return r.StatusCode == StatusSwitchingProtocols &&
r.Header.Get("Upgrade") != "" &&
httpguts.HeaderValuesContainsToken(r.Header["Connection"], "Upgrade")
}