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// Copyright 2013 The Gorilla WebSocket 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 websocket
import (
"crypto/rand"
"crypto/sha1"
"encoding/base64"
"io"
"net/http"
"strings"
"unicode/utf8"
)
var keyGUID = []byte("258EAFA5-E914-47DA-95CA-C5AB0DC85B11")
func computeAcceptKey(challengeKey string) string {
h := sha1.New()
h.Write([]byte(challengeKey))
h.Write(keyGUID)
return base64.StdEncoding.EncodeToString(h.Sum(nil))
}
func generateChallengeKey() (string, error) {
p := make([]byte, 16)
if _, err := io.ReadFull(rand.Reader, p); err != nil {
return "", err
}
return base64.StdEncoding.EncodeToString(p), nil
}
// Token octets per RFC 2616.
var isTokenOctet = [256]bool{
'!': true,
'#': true,
'$': true,
'%': true,
'&': true,
'\'': true,
'*': true,
'+': true,
'-': true,
'.': true,
'0': true,
'1': true,
'2': true,
'3': true,
'4': true,
'5': true,
'6': true,
'7': true,
'8': true,
'9': true,
'A': true,
'B': true,
'C': true,
'D': true,
'E': true,
'F': true,
'G': true,
'H': true,
'I': true,
'J': true,
'K': true,
'L': true,
'M': true,
'N': true,
'O': true,
'P': true,
'Q': true,
'R': true,
'S': true,
'T': true,
'U': true,
'W': true,
'V': true,
'X': true,
'Y': true,
'Z': true,
'^': true,
'_': true,
'`': true,
'a': true,
'b': true,
'c': true,
'd': true,
'e': true,
'f': true,
'g': true,
'h': true,
'i': true,
'j': true,
'k': true,
'l': true,
'm': true,
'n': true,
'o': true,
'p': true,
'q': true,
'r': true,
's': true,
't': true,
'u': true,
'v': true,
'w': true,
'x': true,
'y': true,
'z': true,
'|': true,
'~': true,
}
// skipSpace returns a slice of the string s with all leading RFC 2616 linear
// whitespace removed.
func skipSpace(s string) (rest string) {
i := 0
for ; i < len(s); i++ {
if b := s[i]; b != ' ' && b != '\t' {
break
}
}
return s[i:]
}
// nextToken returns the leading RFC 2616 token of s and the string following
// the token.
func nextToken(s string) (token, rest string) {
i := 0
for ; i < len(s); i++ {
if !isTokenOctet[s[i]] {
break
}
}
return s[:i], s[i:]
}
// nextTokenOrQuoted returns the leading token or quoted string per RFC 2616
// and the string following the token or quoted string.
func nextTokenOrQuoted(s string) (value string, rest string) {
if !strings.HasPrefix(s, "\"") {
return nextToken(s)
}
s = s[1:]
for i := 0; i < len(s); i++ {
switch s[i] {
case '"':
return s[:i], s[i+1:]
case '\\':
p := make([]byte, len(s)-1)
j := copy(p, s[:i])
escape := true
for i = i + 1; i < len(s); i++ {
b := s[i]
switch {
case escape:
escape = false
p[j] = b
j++
case b == '\\':
escape = true
case b == '"':
return string(p[:j]), s[i+1:]
default:
p[j] = b
j++
}
}
return "", ""
}
}
return "", ""
}
// equalASCIIFold returns true if s is equal to t with ASCII case folding as
// defined in RFC 4790.
func equalASCIIFold(s, t string) bool {
for s != "" && t != "" {
sr, size := utf8.DecodeRuneInString(s)
s = s[size:]
tr, size := utf8.DecodeRuneInString(t)
t = t[size:]
if sr == tr {
continue
}
if 'A' <= sr && sr <= 'Z' {
sr = sr + 'a' - 'A'
}
if 'A' <= tr && tr <= 'Z' {
tr = tr + 'a' - 'A'
}
if sr != tr {
return false
}
}
return s == t
}
// tokenListContainsValue returns true if the 1#token header with the given
// name contains a token equal to value with ASCII case folding.
func tokenListContainsValue(header http.Header, name string, value string) bool {
headers:
for _, s := range header[name] {
for {
var t string
t, s = nextToken(skipSpace(s))
if t == "" {
continue headers
}
s = skipSpace(s)
if s != "" && s[0] != ',' {
continue headers
}
if equalASCIIFold(t, value) {
return true
}
if s == "" {
continue headers
}
s = s[1:]
}
}
return false
}
// parseExtensions parses WebSocket extensions from a header.
func parseExtensions(header http.Header) []map[string]string {
// From RFC 6455:
//
// Sec-WebSocket-Extensions = extension-list
// extension-list = 1#extension
// extension = extension-token *( ";" extension-param )
// extension-token = registered-token
// registered-token = token
// extension-param = token [ "=" (token | quoted-string) ]
// ;When using the quoted-string syntax variant, the value
// ;after quoted-string unescaping MUST conform to the
// ;'token' ABNF.
var result []map[string]string
headers:
for _, s := range header["Sec-Websocket-Extensions"] {
for {
var t string
t, s = nextToken(skipSpace(s))
if t == "" {
continue headers
}
ext := map[string]string{"": t}
for {
s = skipSpace(s)
if !strings.HasPrefix(s, ";") {
break
}
var k string
k, s = nextToken(skipSpace(s[1:]))
if k == "" {
continue headers
}
s = skipSpace(s)
var v string
if strings.HasPrefix(s, "=") {
v, s = nextTokenOrQuoted(skipSpace(s[1:]))
s = skipSpace(s)
}
if s != "" && s[0] != ',' && s[0] != ';' {
continue headers
}
ext[k] = v
}
if s != "" && s[0] != ',' {
continue headers
}
result = append(result, ext)
if s == "" {
continue headers
}
s = s[1:]
}
}
return result
}
