src/net/http/response.go - go - Git at Google

 // 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"
 	"io"
 	"net/textproto"
 	"net/url"
 	"strconv"
 	"strings"

 	"golang.org/x/net/http/httpguts"
 )

 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 also implement io.Writer
 	// on a successful "101 Switching Protocols" response,
 	// 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
 	}
 	proto, status, ok := strings.Cut(line, " ")
 	if !ok {
 		return nil, badStringError("malformed HTTP response", line)
 	}
 	resp.Proto = proto
 	resp.Status = strings.TrimLeft(status, " ")

 	statusCode, _, _ := strings.Cut(resp.Status, " ")
 	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)
 	}
 	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 == "" {
 		text = StatusText(r.StatusCode)
 		if text == "" {
 			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 the response code and header
 // indicate a successful protocol upgrade response.
 func (r *Response) isProtocolSwitch() bool {
 	return isProtocolSwitchResponse(r.StatusCode, r.Header)
 }

 // isProtocolSwitchResponse reports whether the response code and
 // response header indicate a successful protocol upgrade response.
 func isProtocolSwitchResponse(code int, h Header) bool {
 	return code == StatusSwitchingProtocols && isProtocolSwitchHeader(h)
 }

 // isProtocolSwitchHeader reports whether the request or response header
 // is for a protocol switch.
 func isProtocolSwitchHeader(h Header) bool {
 	return h.Get("Upgrade") != "" &&
 		httpguts.HeaderValuesContainsToken(h["Connection"], "Upgrade")
 }
	// 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"
	"io"
	"net/textproto"
	"net/url"
	"strconv"
	"strings"

	"golang.org/x/net/http/httpguts"
	)

	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 also implement io.Writer
	// on a successful "101 Switching Protocols" response,
	// 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
	}
	proto, status, ok := strings.Cut(line, " ")
	if !ok {
	return nil, badStringError("malformed HTTP response", line)
	}
	resp.Proto = proto
	resp.Status = strings.TrimLeft(status, " ")

	statusCode, _, _ := strings.Cut(resp.Status, " ")
	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)
	}
	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 == "" {
	text = StatusText(r.StatusCode)
	if text == "" {
	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 the response code and header
	// indicate a successful protocol upgrade response.
	func (r *Response) isProtocolSwitch() bool {
	return isProtocolSwitchResponse(r.StatusCode, r.Header)
	}

	// isProtocolSwitchResponse reports whether the response code and
	// response header indicate a successful protocol upgrade response.
	func isProtocolSwitchResponse(code int, h Header) bool {
	return code == StatusSwitchingProtocols && isProtocolSwitchHeader(h)
	}

	// isProtocolSwitchHeader reports whether the request or response header
	// is for a protocol switch.
	func isProtocolSwitchHeader(h Header) bool {
	return h.Get("Upgrade") != "" &&
	httpguts.HeaderValuesContainsToken(h["Connection"], "Upgrade")
	}