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 // HTTP Response reading and parsing. 6 7 package http 8 9 import ( 10 "bufio" 11 "bytes" 12 "crypto/tls" 13 "errors" 14 "fmt" 15 "io" 16 "net/textproto" 17 "net/url" 18 "strconv" 19 "strings" 20 21 "golang.org/x/net/http/httpguts" 22 ) 23 24 var respExcludeHeader = map[string]bool{ 25 "Content-Length": true, 26 "Transfer-Encoding": true, 27 "Trailer": true, 28 } 29 30 // Response represents the response from an HTTP request. 31 // 32 // The Client and Transport return Responses from servers once 33 // the response headers have been received. The response body 34 // is streamed on demand as the Body field is read. 35 type Response struct { 36 Status string // e.g. "200 OK" 37 StatusCode int // e.g. 200 38 Proto string // e.g. "HTTP/1.0" 39 ProtoMajor int // e.g. 1 40 ProtoMinor int // e.g. 0 41 42 // Header maps header keys to values. If the response had multiple 43 // headers with the same key, they may be concatenated, with comma 44 // delimiters. (RFC 7230, section 3.2.2 requires that multiple headers 45 // be semantically equivalent to a comma-delimited sequence.) When 46 // Header values are duplicated by other fields in this struct (e.g., 47 // ContentLength, TransferEncoding, Trailer), the field values are 48 // authoritative. 49 // 50 // Keys in the map are canonicalized (see CanonicalHeaderKey). 51 Header Header 52 53 // Body represents the response body. 54 // 55 // The response body is streamed on demand as the Body field 56 // is read. If the network connection fails or the server 57 // terminates the response, Body.Read calls return an error. 58 // 59 // The http Client and Transport guarantee that Body is always 60 // non-nil, even on responses without a body or responses with 61 // a zero-length body. It is the caller's responsibility to 62 // close Body. The default HTTP client's Transport may not 63 // reuse HTTP/1.x "keep-alive" TCP connections if the Body is 64 // not read to completion and closed. 65 // 66 // The Body is automatically dechunked if the server replied 67 // with a "chunked" Transfer-Encoding. 68 // 69 // As of Go 1.12, the Body will also implement io.Writer 70 // on a successful "101 Switching Protocols" response, 71 // as used by WebSockets and HTTP/2's "h2c" mode. 72 Body io.ReadCloser 73 74 // ContentLength records the length of the associated content. The 75 // value -1 indicates that the length is unknown. Unless Request.Method 76 // is "HEAD", values >= 0 indicate that the given number of bytes may 77 // be read from Body. 78 ContentLength int64 79 80 // Contains transfer encodings from outer-most to inner-most. Value is 81 // nil, means that "identity" encoding is used. 82 TransferEncoding []string 83 84 // Close records whether the header directed that the connection be 85 // closed after reading Body. The value is advice for clients: neither 86 // ReadResponse nor Response.Write ever closes a connection. 87 Close bool 88 89 // Uncompressed reports whether the response was sent compressed but 90 // was decompressed by the http package. When true, reading from 91 // Body yields the uncompressed content instead of the compressed 92 // content actually set from the server, ContentLength is set to -1, 93 // and the "Content-Length" and "Content-Encoding" fields are deleted 94 // from the responseHeader. To get the original response from 95 // the server, set Transport.DisableCompression to true. 96 Uncompressed bool 97 98 // Trailer maps trailer keys to values in the same 99 // format as Header. 100 // 101 // The Trailer initially contains only nil values, one for 102 // each key specified in the server's "Trailer" header 103 // value. Those values are not added to Header. 104 // 105 // Trailer must not be accessed concurrently with Read calls 106 // on the Body. 107 // 108 // After Body.Read has returned io.EOF, Trailer will contain 109 // any trailer values sent by the server. 110 Trailer Header 111 112 // Request is the request that was sent to obtain this Response. 113 // Request's Body is nil (having already been consumed). 114 // This is only populated for Client requests. 115 Request *Request 116 117 // TLS contains information about the TLS connection on which the 118 // response was received. It is nil for unencrypted responses. 119 // The pointer is shared between responses and should not be 120 // modified. 121 TLS *tls.ConnectionState 122 } 123 124 // Cookies parses and returns the cookies set in the Set-Cookie headers. 125 func (r *Response) Cookies() []*Cookie { 126 return readSetCookies(r.Header) 127 } 128 129 // ErrNoLocation is returned by Response's Location method 130 // when no Location header is present. 131 var ErrNoLocation = errors.New("http: no Location header in response") 132 133 // Location returns the URL of the response's "Location" header, 134 // if present. Relative redirects are resolved relative to 135 // the Response's Request. ErrNoLocation is returned if no 136 // Location header is present. 137 func (r *Response) Location() (*url.URL, error) { 138 lv := r.Header.Get("Location") 139 if lv == "" { 140 return nil, ErrNoLocation 141 } 142 if r.Request != nil && r.Request.URL != nil { 143 return r.Request.URL.Parse(lv) 144 } 145 return url.Parse(lv) 146 } 147 148 // ReadResponse reads and returns an HTTP response from r. 149 // The req parameter optionally specifies the Request that corresponds 150 // to this Response. If nil, a GET request is assumed. 151 // Clients must call resp.Body.Close when finished reading resp.Body. 152 // After that call, clients can inspect resp.Trailer to find key/value 153 // pairs included in the response trailer. 154 func ReadResponse(r *bufio.Reader, req *Request) (*Response, error) { 155 tp := textproto.NewReader(r) 156 resp := &Response{ 157 Request: req, 158 } 159 160 // Parse the first line of the response. 161 line, err := tp.ReadLine() 162 if err != nil { 163 if err == io.EOF { 164 err = io.ErrUnexpectedEOF 165 } 166 return nil, err 167 } 168 if i := strings.IndexByte(line, ' '); i == -1 { 169 return nil, badStringError("malformed HTTP response", line) 170 } else { 171 resp.Proto = line[:i] 172 resp.Status = strings.TrimLeft(line[i+1:], " ") 173 } 174 statusCode := resp.Status 175 if i := strings.IndexByte(resp.Status, ' '); i != -1 { 176 statusCode = resp.Status[:i] 177 } 178 if len(statusCode) != 3 { 179 return nil, badStringError("malformed HTTP status code", statusCode) 180 } 181 resp.StatusCode, err = strconv.Atoi(statusCode) 182 if err != nil || resp.StatusCode < 0 { 183 return nil, badStringError("malformed HTTP status code", statusCode) 184 } 185 var ok bool 186 if resp.ProtoMajor, resp.ProtoMinor, ok = ParseHTTPVersion(resp.Proto); !ok { 187 return nil, badStringError("malformed HTTP version", resp.Proto) 188 } 189 190 // Parse the response headers. 191 mimeHeader, err := tp.ReadMIMEHeader() 192 if err != nil { 193 if err == io.EOF { 194 err = io.ErrUnexpectedEOF 195 } 196 return nil, err 197 } 198 resp.Header = Header(mimeHeader) 199 200 fixPragmaCacheControl(resp.Header) 201 202 err = readTransfer(resp, r) 203 if err != nil { 204 return nil, err 205 } 206 207 return resp, nil 208 } 209 210 // RFC 7234, section 5.4: Should treat 211 // Pragma: no-cache 212 // like 213 // Cache-Control: no-cache 214 func fixPragmaCacheControl(header Header) { 215 if hp, ok := header["Pragma"]; ok && len(hp) > 0 && hp[0] == "no-cache" { 216 if _, presentcc := header["Cache-Control"]; !presentcc { 217 header["Cache-Control"] = []string{"no-cache"} 218 } 219 } 220 } 221 222 // ProtoAtLeast reports whether the HTTP protocol used 223 // in the response is at least major.minor. 224 func (r *Response) ProtoAtLeast(major, minor int) bool { 225 return r.ProtoMajor > major || 226 r.ProtoMajor == major && r.ProtoMinor >= minor 227 } 228 229 // Write writes r to w in the HTTP/1.x server response format, 230 // including the status line, headers, body, and optional trailer. 231 // 232 // This method consults the following fields of the response r: 233 // 234 // StatusCode 235 // ProtoMajor 236 // ProtoMinor 237 // Request.Method 238 // TransferEncoding 239 // Trailer 240 // Body 241 // ContentLength 242 // Header, values for non-canonical keys will have unpredictable behavior 243 // 244 // The Response Body is closed after it is sent. 245 func (r *Response) Write(w io.Writer) error { 246 // Status line 247 text := r.Status 248 if text == "" { 249 var ok bool 250 text, ok = statusText[r.StatusCode] 251 if !ok { 252 text = "status code " + strconv.Itoa(r.StatusCode) 253 } 254 } else { 255 // Just to reduce stutter, if user set r.Status to "200 OK" and StatusCode to 200. 256 // Not important. 257 text = strings.TrimPrefix(text, strconv.Itoa(r.StatusCode)+" ") 258 } 259 260 if _, err := fmt.Fprintf(w, "HTTP/%d.%d %03d %s\r\n", r.ProtoMajor, r.ProtoMinor, r.StatusCode, text); err != nil { 261 return err 262 } 263 264 // Clone it, so we can modify r1 as needed. 265 r1 := new(Response) 266 *r1 = *r 267 if r1.ContentLength == 0 && r1.Body != nil { 268 // Is it actually 0 length? Or just unknown? 269 var buf [1]byte 270 n, err := r1.Body.Read(buf[:]) 271 if err != nil && err != io.EOF { 272 return err 273 } 274 if n == 0 { 275 // Reset it to a known zero reader, in case underlying one 276 // is unhappy being read repeatedly. 277 r1.Body = NoBody 278 } else { 279 r1.ContentLength = -1 280 r1.Body = struct { 281 io.Reader 282 io.Closer 283 }{ 284 io.MultiReader(bytes.NewReader(buf[:1]), r.Body), 285 r.Body, 286 } 287 } 288 } 289 // If we're sending a non-chunked HTTP/1.1 response without a 290 // content-length, the only way to do that is the old HTTP/1.0 291 // way, by noting the EOF with a connection close, so we need 292 // to set Close. 293 if r1.ContentLength == -1 && !r1.Close && r1.ProtoAtLeast(1, 1) && !chunked(r1.TransferEncoding) && !r1.Uncompressed { 294 r1.Close = true 295 } 296 297 // Process Body,ContentLength,Close,Trailer 298 tw, err := newTransferWriter(r1) 299 if err != nil { 300 return err 301 } 302 err = tw.writeHeader(w, nil) 303 if err != nil { 304 return err 305 } 306 307 // Rest of header 308 err = r.Header.WriteSubset(w, respExcludeHeader) 309 if err != nil { 310 return err 311 } 312 313 // contentLengthAlreadySent may have been already sent for 314 // POST/PUT requests, even if zero length. See Issue 8180. 315 contentLengthAlreadySent := tw.shouldSendContentLength() 316 if r1.ContentLength == 0 && !chunked(r1.TransferEncoding) && !contentLengthAlreadySent && bodyAllowedForStatus(r.StatusCode) { 317 if _, err := io.WriteString(w, "Content-Length: 0\r\n"); err != nil { 318 return err 319 } 320 } 321 322 // End-of-header 323 if _, err := io.WriteString(w, "\r\n"); err != nil { 324 return err 325 } 326 327 // Write body and trailer 328 err = tw.writeBody(w) 329 if err != nil { 330 return err 331 } 332 333 // Success 334 return nil 335 } 336 337 func (r *Response) closeBody() { 338 if r.Body != nil { 339 r.Body.Close() 340 } 341 } 342 343 // bodyIsWritable reports whether the Body supports writing. The 344 // Transport returns Writable bodies for 101 Switching Protocols 345 // responses. 346 // The Transport uses this method to determine whether a persistent 347 // connection is done being managed from its perspective. Once we 348 // return a writable response body to a user, the net/http package is 349 // done managing that connection. 350 func (r *Response) bodyIsWritable() bool { 351 _, ok := r.Body.(io.Writer) 352 return ok 353 } 354 355 // isProtocolSwitch reports whether the response code and header 356 // indicate a successful protocol upgrade response. 357 func (r *Response) isProtocolSwitch() bool { 358 return isProtocolSwitchResponse(r.StatusCode, r.Header) 359 } 360 361 // isProtocolSwitchResponse reports whether the response code and 362 // response header indicate a successful protocol upgrade response. 363 func isProtocolSwitchResponse(code int, h Header) bool { 364 return code == StatusSwitchingProtocols && isProtocolSwitchHeader(h) 365 } 366 367 // isProtocolSwitchHeader reports whether the request or response header 368 // is for a protocol switch. 369 func isProtocolSwitchHeader(h Header) bool { 370 return h.Get("Upgrade") != "" && 371 httpguts.HeaderValuesContainsToken(h["Connection"], "Upgrade") 372 } 373