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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 Request reading and parsing.
// The http package implements parsing of HTTP requests, replies,
// and URLs and provides an extensible HTTP server and a basic
// HTTP client.
package http
import (
"bufio"
"bytes"
"container/vector"
"fmt"
"io"
"io/ioutil"
"os"
"strconv"
"strings"
)
const (
maxLineLength = 4096 // assumed <= bufio.defaultBufSize
maxValueLength = 4096
maxHeaderLines = 1024
chunkSize = 4 << 10 // 4 KB chunks
)
// HTTP request parsing errors.
type ProtocolError struct {
os.ErrorString
}
var (
ErrLineTooLong = &ProtocolError{"header line too long"}
ErrHeaderTooLong = &ProtocolError{"header too long"}
ErrShortBody = &ProtocolError{"entity body too short"}
ErrNotSupported = &ProtocolError{"feature not supported"}
ErrUnexpectedTrailer = &ProtocolError{"trailer header without chunked transfer encoding"}
ErrMissingContentLength = &ProtocolError{"missing ContentLength in HEAD response"}
)
type badStringError struct {
what string
str string
}
func (e *badStringError) String() string { return fmt.Sprintf("%s %q", e.what, e.str) }
var reqExcludeHeader = map[string]bool{
"Host": true,
"User-Agent": true,
"Referer": true,
"Content-Length": true,
"Transfer-Encoding": true,
"Trailer": true,
}
// A Request represents a parsed HTTP request header.
type Request struct {
Method string // GET, POST, PUT, etc.
RawURL string // The raw URL given in the request.
URL *URL // Parsed URL.
Proto string // "HTTP/1.0"
ProtoMajor int // 1
ProtoMinor int // 0
// A header mapping request lines to their values.
// If the header says
//
// accept-encoding: gzip, deflate
// Accept-Language: en-us
// Connection: keep-alive
//
// then
//
// Header = map[string]string{
// "Accept-Encoding": "gzip, deflate",
// "Accept-Language": "en-us",
// "Connection": "keep-alive",
// }
//
// HTTP defines that header names are case-insensitive.
// The request parser implements this by canonicalizing the
// name, making the first character and any characters
// following a hyphen uppercase and the rest lowercase.
Header map[string]string
// The message body.
Body io.ReadCloser
// ContentLength records the length of the associated content.
// The value -1 indicates that the length is unknown.
// Values >= 0 indicate that the given number of bytes may be read from Body.
ContentLength int64
// TransferEncoding lists the transfer encodings from outermost to innermost.
// An empty list denotes the "identity" encoding.
TransferEncoding []string
// Whether to close the connection after replying to this request.
Close bool
// The host on which the URL is sought.
// Per RFC 2616, this is either the value of the Host: header
// or the host name given in the URL itself.
Host string
// The referring URL, if sent in the request.
//
// Referer is misspelled as in the request itself,
// a mistake from the earliest days of HTTP.
// This value can also be fetched from the Header map
// as Header["Referer"]; the benefit of making it
// available as a structure field is that the compiler
// can diagnose programs that use the alternate
// (correct English) spelling req.Referrer but cannot
// diagnose programs that use Header["Referrer"].
Referer string
// The User-Agent: header string, if sent in the request.
UserAgent string
// The parsed form. Only available after ParseForm is called.
Form map[string][]string
// Trailer maps trailer keys to values. Like for Header, if the
// response has multiple trailer lines with the same key, they will be
// concatenated, delimited by commas.
Trailer map[string]string
}
// ProtoAtLeast returns whether the HTTP protocol used
// in the request is at least major.minor.
func (r *Request) ProtoAtLeast(major, minor int) bool {
return r.ProtoMajor > major ||
r.ProtoMajor == major && r.ProtoMinor >= minor
}
// Return value if nonempty, def otherwise.
func valueOrDefault(value, def string) string {
if value != "" {
return value
}
return def
}
const defaultUserAgent = "Go http package"
// Write writes an HTTP/1.1 request -- header and body -- in wire format.
// This method consults the following fields of req:
// Host
// RawURL, if non-empty, or else URL
// Method (defaults to "GET")
// UserAgent (defaults to defaultUserAgent)
// Referer
// Header
// Body
//
// If Body is present, Write forces "Transfer-Encoding: chunked" as a header
// and then closes Body when finished sending it.
func (req *Request) Write(w io.Writer) os.Error {
host := req.Host
if host == "" {
host = req.URL.Host
}
uri := req.RawURL
if uri == "" {
uri = valueOrDefault(urlEscape(req.URL.Path, false), "/")
if req.URL.RawQuery != "" {
uri += "?" + req.URL.RawQuery
}
}
fmt.Fprintf(w, "%s %s HTTP/1.1\r\n", valueOrDefault(req.Method, "GET"), uri)
// Header lines
fmt.Fprintf(w, "Host: %s\r\n", host)
fmt.Fprintf(w, "User-Agent: %s\r\n", valueOrDefault(req.UserAgent, defaultUserAgent))
if req.Referer != "" {
fmt.Fprintf(w, "Referer: %s\r\n", req.Referer)
}
// Process Body,ContentLength,Close,Trailer
tw, err := newTransferWriter(req)
if err != nil {
return err
}
err = tw.WriteHeader(w)
if err != nil {
return err
}
// TODO: split long values? (If so, should share code with Conn.Write)
// TODO: if Header includes values for Host, User-Agent, or Referer, this
// may conflict with the User-Agent or Referer headers we add manually.
// One solution would be to remove the Host, UserAgent, and Referer fields
// from Request, and introduce Request methods along the lines of
// Response.{GetHeader,AddHeader} and string constants for "Host",
// "User-Agent" and "Referer".
err = writeSortedKeyValue(w, req.Header, reqExcludeHeader)
if err != nil {
return err
}
io.WriteString(w, "\r\n")
// Write body and trailer
err = tw.WriteBody(w)
if err != nil {
return err
}
return nil
}
// Read a line of bytes (up to \n) from b.
// Give up if the line exceeds maxLineLength.
// The returned bytes are a pointer into storage in
// the bufio, so they are only valid until the next bufio read.
func readLineBytes(b *bufio.Reader) (p []byte, err os.Error) {
if p, err = b.ReadSlice('\n'); err != nil {
// We always know when EOF is coming.
// If the caller asked for a line, there should be a line.
if err == os.EOF {
err = io.ErrUnexpectedEOF
}
return nil, err
}
if len(p) >= maxLineLength {
return nil, ErrLineTooLong
}
// Chop off trailing white space.
var i int
for i = len(p); i > 0; i-- {
if c := p[i-1]; c != ' ' && c != '\r' && c != '\t' && c != '\n' {
break
}
}
return p[0:i], nil
}
// readLineBytes, but convert the bytes into a string.
func readLine(b *bufio.Reader) (s string, err os.Error) {
p, e := readLineBytes(b)
if e != nil {
return "", e
}
return string(p), nil
}
var colon = []byte{':'}
// Read a key/value pair from b.
// A key/value has the form Key: Value\r\n
// and the Value can continue on multiple lines if each continuation line
// starts with a space.
func readKeyValue(b *bufio.Reader) (key, value string, err os.Error) {
line, e := readLineBytes(b)
if e != nil {
return "", "", e
}
if len(line) == 0 {
return "", "", nil
}
// Scan first line for colon.
i := bytes.Index(line, colon)
if i < 0 {
goto Malformed
}
key = string(line[0:i])
if strings.Index(key, " ") >= 0 {
// Key field has space - no good.
goto Malformed
}
// Skip initial space before value.
for i++; i < len(line); i++ {
if line[i] != ' ' {
break
}
}
value = string(line[i:])
// Look for extension lines, which must begin with space.
for {
c, e := b.ReadByte()
if c != ' ' {
if e != os.EOF {
b.UnreadByte()
}
break
}
// Eat leading space.
for c == ' ' {
if c, e = b.ReadByte(); e != nil {
if e == os.EOF {
e = io.ErrUnexpectedEOF
}
return "", "", e
}
}
b.UnreadByte()
// Read the rest of the line and add to value.
if line, e = readLineBytes(b); e != nil {
return "", "", e
}
value += " " + string(line)
if len(value) >= maxValueLength {
return "", "", &badStringError{"value too long for key", key}
}
}
return key, value, nil
Malformed:
return "", "", &badStringError{"malformed header line", string(line)}
}
// Convert decimal at s[i:len(s)] to integer,
// returning value, string position where the digits stopped,
// and whether there was a valid number (digits, not too big).
func atoi(s string, i int) (n, i1 int, ok bool) {
const Big = 1000000
if i >= len(s) || s[i] < '0' || s[i] > '9' {
return 0, 0, false
}
n = 0
for ; i < len(s) && '0' <= s[i] && s[i] <= '9'; i++ {
n = n*10 + int(s[i]-'0')
if n > Big {
return 0, 0, false
}
}
return n, i, true
}
// Parse HTTP version: "HTTP/1.2" -> (1, 2, true).
func parseHTTPVersion(vers string) (int, int, bool) {
if len(vers) < 5 || vers[0:5] != "HTTP/" {
return 0, 0, false
}
major, i, ok := atoi(vers, 5)
if !ok || i >= len(vers) || vers[i] != '.' {
return 0, 0, false
}
var minor int
minor, i, ok = atoi(vers, i+1)
if !ok || i != len(vers) {
return 0, 0, false
}
return major, minor, true
}
var cmap = make(map[string]string)
// CanonicalHeaderKey returns the canonical format of the
// HTTP header key s. The canonicalization converts the first
// letter and any letter following a hyphen to upper case;
// the rest are converted to lowercase. For example, the
// canonical key for "accept-encoding" is "Accept-Encoding".
func CanonicalHeaderKey(s string) string {
if t, ok := cmap[s]; ok {
return t
}
// canonicalize: first letter upper case
// and upper case after each dash.
// (Host, User-Agent, If-Modified-Since).
// HTTP headers are ASCII only, so no Unicode issues.
a := []byte(s)
upper := true
for i, v := range a {
if upper && 'a' <= v && v <= 'z' {
a[i] = v + 'A' - 'a'
}
if !upper && 'A' <= v && v <= 'Z' {
a[i] = v + 'a' - 'A'
}
upper = false
if v == '-' {
upper = true
}
}
t := string(a)
cmap[s] = t
return t
}
type chunkedReader struct {
r *bufio.Reader
n uint64 // unread bytes in chunk
err os.Error
}
func newChunkedReader(r *bufio.Reader) *chunkedReader {
return &chunkedReader{r: r}
}
func (cr *chunkedReader) beginChunk() {
// chunk-size CRLF
var line string
line, cr.err = readLine(cr.r)
if cr.err != nil {
return
}
cr.n, cr.err = strconv.Btoui64(line, 16)
if cr.err != nil {
return
}
if cr.n == 0 {
// trailer CRLF
for {
line, cr.err = readLine(cr.r)
if cr.err != nil {
return
}
if line == "" {
break
}
}
cr.err = os.EOF
}
}
func (cr *chunkedReader) Read(b []uint8) (n int, err os.Error) {
if cr.err != nil {
return 0, cr.err
}
if cr.n == 0 {
cr.beginChunk()
if cr.err != nil {
return 0, cr.err
}
}
if uint64(len(b)) > cr.n {
b = b[0:cr.n]
}
n, cr.err = cr.r.Read(b)
cr.n -= uint64(n)
if cr.n == 0 && cr.err == nil {
// end of chunk (CRLF)
b := make([]byte, 2)
if _, cr.err = io.ReadFull(cr.r, b); cr.err == nil {
if b[0] != '\r' || b[1] != '\n' {
cr.err = os.NewError("malformed chunked encoding")
}
}
}
return n, cr.err
}
// ReadRequest reads and parses a request from b.
func ReadRequest(b *bufio.Reader) (req *Request, err os.Error) {
req = new(Request)
// First line: GET /index.html HTTP/1.0
var s string
if s, err = readLine(b); err != nil {
return nil, err
}
var f []string
if f = strings.Split(s, " ", 3); len(f) < 3 {
return nil, &badStringError{"malformed HTTP request", s}
}
req.Method, req.RawURL, req.Proto = f[0], f[1], f[2]
var ok bool
if req.ProtoMajor, req.ProtoMinor, ok = parseHTTPVersion(req.Proto); !ok {
return nil, &badStringError{"malformed HTTP version", req.Proto}
}
if req.URL, err = ParseURL(req.RawURL); err != nil {
return nil, err
}
// Subsequent lines: Key: value.
nheader := 0
req.Header = make(map[string]string)
for {
var key, value string
if key, value, err = readKeyValue(b); err != nil {
return nil, err
}
if key == "" {
break
}
if nheader++; nheader >= maxHeaderLines {
return nil, ErrHeaderTooLong
}
key = CanonicalHeaderKey(key)
// RFC 2616 says that if you send the same header key
// multiple times, it has to be semantically equivalent
// to concatenating the values separated by commas.
oldvalue, present := req.Header[key]
if present {
req.Header[key] = oldvalue + "," + value
} else {
req.Header[key] = value
}
}
// RFC2616: Must treat
// GET /index.html HTTP/1.1
// Host: www.google.com
// and
// GET http://www.google.com/index.html HTTP/1.1
// Host: doesntmatter
// the same. In the second case, any Host line is ignored.
req.Host = req.URL.Host
if req.Host == "" {
req.Host = req.Header["Host"]
}
req.Header["Host"] = "", false
fixPragmaCacheControl(req.Header)
// Pull out useful fields as a convenience to clients.
req.Referer = req.Header["Referer"]
req.Header["Referer"] = "", false
req.UserAgent = req.Header["User-Agent"]
req.Header["User-Agent"] = "", false
// TODO: Parse specific header values:
// Accept
// Accept-Encoding
// Accept-Language
// Authorization
// Cache-Control
// Connection
// Date
// Expect
// From
// If-Match
// If-Modified-Since
// If-None-Match
// If-Range
// If-Unmodified-Since
// Max-Forwards
// Proxy-Authorization
// Referer [sic]
// TE (transfer-codings)
// Trailer
// Transfer-Encoding
// Upgrade
// User-Agent
// Via
// Warning
err = readTransfer(req, b)
if err != nil {
return nil, err
}
return req, nil
}
func ParseQuery(query string) (m map[string][]string, err os.Error) {
m = make(map[string][]string)
for _, kv := range strings.Split(query, "&", -1) {
kvPair := strings.Split(kv, "=", 2)
var key, value string
var e os.Error
key, e = URLUnescape(kvPair[0])
if e == nil && len(kvPair) > 1 {
value, e = URLUnescape(kvPair[1])
}
if e != nil {
err = e
}
vec := vector.StringVector(m[key])
vec.Push(value)
m[key] = vec
}
return
}
// ParseForm parses the request body as a form for POST requests, or the raw query for GET requests.
// It is idempotent.
func (r *Request) ParseForm() (err os.Error) {
if r.Form != nil {
return
}
var query string
switch r.Method {
case "GET":
query = r.URL.RawQuery
case "POST":
if r.Body == nil {
r.Form = make(map[string][]string)
return os.ErrorString("missing form body")
}
ct := r.Header["Content-Type"]
switch strings.Split(ct, ";", 2)[0] {
case "text/plain", "application/x-www-form-urlencoded", "":
var b []byte
if b, err = ioutil.ReadAll(r.Body); err != nil {
r.Form = make(map[string][]string)
return err
}
query = string(b)
// TODO(dsymonds): Handle multipart/form-data
default:
r.Form = make(map[string][]string)
return &badStringError{"unknown Content-Type", ct}
}
}
r.Form, err = ParseQuery(query)
return
}
// FormValue returns the first value for the named component of the query.
// FormValue calls ParseForm if necessary.
func (r *Request) FormValue(key string) string {
if r.Form == nil {
r.ParseForm()
}
if vs := r.Form[key]; len(vs) > 0 {
return vs[0]
}
return ""
}
func (r *Request) expectsContinue() bool {
expectation, ok := r.Header["Expect"]
return ok && strings.ToLower(expectation) == "100-continue"
}