// Copyright 2016 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.
// Package httplex contains rules around lexical matters of various
// HTTP-related specifications.
//
// This package is shared by the standard library (which vendors it)
// and x/net/http2. It comes with no API stability promise.
package httplex
import (
"net"
"strings"
"unicode/utf8"
"golang.org/x/net/idna"
)
var isTokenTable = [127]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,
}
func IsTokenRune(r rune) bool {
i := int(r)
return i < len(isTokenTable) && isTokenTable[i]
}
func isNotToken(r rune) bool {
return !IsTokenRune(r)
}
// HeaderValuesContainsToken reports whether any string in values
// contains the provided token, ASCII case-insensitively.
func HeaderValuesContainsToken(values []string, token string) bool {
for _, v := range values {
if headerValueContainsToken(v, token) {
return true
}
}
return false
}
// isOWS reports whether b is an optional whitespace byte, as defined
// by RFC 7230 section 3.2.3.
func isOWS(b byte) bool { return b == ' ' || b == '\t' }
// trimOWS returns x with all optional whitespace removes from the
// beginning and end.
func trimOWS(x string) string {
// TODO: consider using strings.Trim(x, " \t") instead,
// if and when it's fast enough. See issue 10292.
// But this ASCII-only code will probably always beat UTF-8
// aware code.
for len(x) > 0 && isOWS(x[0]) {
x = x[1:]
}
for len(x) > 0 && isOWS(x[len(x)-1]) {
x = x[:len(x)-1]
}
return x
}
// headerValueContainsToken reports whether v (assumed to be a
// 0#element, in the ABNF extension described in RFC 7230 section 7)
// contains token amongst its comma-separated tokens, ASCII
// case-insensitively.
func headerValueContainsToken(v string, token string) bool {
v = trimOWS(v)
if comma := strings.IndexByte(v, ','); comma != -1 {
return tokenEqual(trimOWS(v[:comma]), token) || headerValueContainsToken(v[comma+1:], token)
}
return tokenEqual(v, token)
}
// lowerASCII returns the ASCII lowercase version of b.
func lowerASCII(b byte) byte {
if 'A' <= b && b <= 'Z' {
return b + ('a' - 'A')
}
return b
}
// tokenEqual reports whether t1 and t2 are equal, ASCII case-insensitively.
func tokenEqual(t1, t2 string) bool {
if len(t1) != len(t2) {
return false
}
for i, b := range t1 {
if b >= utf8.RuneSelf {
// No UTF-8 or non-ASCII allowed in tokens.
return false
}
if lowerASCII(byte(b)) != lowerASCII(t2[i]) {
return false
}
}
return true
}
// isLWS reports whether b is linear white space, according
// to http://www.w3.org/Protocols/rfc2616/rfc2616-sec2.html#sec2.2
// LWS = [CRLF] 1*( SP | HT )
func isLWS(b byte) bool { return b == ' ' || b == '\t' }
// isCTL reports whether b is a control byte, according
// to http://www.w3.org/Protocols/rfc2616/rfc2616-sec2.html#sec2.2
// CTL = <any US-ASCII control character
// (octets 0 - 31) and DEL (127)>
func isCTL(b byte) bool {
const del = 0x7f // a CTL
return b < ' ' || b == del
}
// ValidHeaderFieldName reports whether v is a valid HTTP/1.x header name.
// HTTP/2 imposes the additional restriction that uppercase ASCII
// letters are not allowed.
//
// RFC 7230 says:
// header-field = field-name ":" OWS field-value OWS
// field-name = token
// token = 1*tchar
// tchar = "!" / "#" / "$" / "%" / "&" / "'" / "*" / "+" / "-" / "." /
// "^" / "_" / "`" / "|" / "~" / DIGIT / ALPHA
func ValidHeaderFieldName(v string) bool {
if len(v) == 0 {
return false
}
for _, r := range v {
if !IsTokenRune(r) {
return false
}
}
return true
}
// ValidHostHeader reports whether h is a valid host header.
func ValidHostHeader(h string) bool {
// The latest spec is actually this:
//
// http://tools.ietf.org/html/rfc7230#section-5.4
// Host = uri-host [ ":" port ]
//
// Where uri-host is:
// http://tools.ietf.org/html/rfc3986#section-3.2.2
//
// But we're going to be much more lenient for now and just
// search for any byte that's not a valid byte in any of those
// expressions.
for i := 0; i < len(h); i++ {
if !validHostByte[h[i]] {
return false
}
}
return true
}
// See the validHostHeader comment.
var validHostByte = [256]bool{
'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, 'v': true, 'w': true, 'x': true,
'y': true, 'z': 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, // sub-delims
'$': true, // sub-delims
'%': true, // pct-encoded (and used in IPv6 zones)
'&': true, // sub-delims
'(': true, // sub-delims
')': true, // sub-delims
'*': true, // sub-delims
'+': true, // sub-delims
',': true, // sub-delims
'-': true, // unreserved
'.': true, // unreserved
':': true, // IPv6address + Host expression's optional port
';': true, // sub-delims
'=': true, // sub-delims
'[': true,
'\'': true, // sub-delims
']': true,
'_': true, // unreserved
'~': true, // unreserved
}
// ValidHeaderFieldValue reports whether v is a valid "field-value" according to
// http://www.w3.org/Protocols/rfc2616/rfc2616-sec4.html#sec4.2 :
//
// message-header = field-name ":" [ field-value ]
// field-value = *( field-content | LWS )
// field-content = <the OCTETs making up the field-value
// and consisting of either *TEXT or combinations
// of token, separators, and quoted-string>
//
// http://www.w3.org/Protocols/rfc2616/rfc2616-sec2.html#sec2.2 :
//
// TEXT = <any OCTET except CTLs,
// but including LWS>
// LWS = [CRLF] 1*( SP | HT )
// CTL = <any US-ASCII control character
// (octets 0 - 31) and DEL (127)>
//
// RFC 7230 says:
// field-value = *( field-content / obs-fold )
// obj-fold = N/A to http2, and deprecated
// field-content = field-vchar [ 1*( SP / HTAB ) field-vchar ]
// field-vchar = VCHAR / obs-text
// obs-text = %x80-FF
// VCHAR = "any visible [USASCII] character"
//
// http2 further says: "Similarly, HTTP/2 allows header field values
// that are not valid. While most of the values that can be encoded
// will not alter header field parsing, carriage return (CR, ASCII
// 0xd), line feed (LF, ASCII 0xa), and the zero character (NUL, ASCII
// 0x0) might be exploited by an attacker if they are translated
// verbatim. Any request or response that contains a character not
// permitted in a header field value MUST be treated as malformed
// (Section 8.1.2.6). Valid characters are defined by the
// field-content ABNF rule in Section 3.2 of [RFC7230]."
//
// This function does not (yet?) properly handle the rejection of
// strings that begin or end with SP or HTAB.
func ValidHeaderFieldValue(v string) bool {
for i := 0; i < len(v); i++ {
b := v[i]
if isCTL(b) && !isLWS(b) {
return false
}
}
return true
}
func isASCII(s string) bool {
for i := 0; i < len(s); i++ {
if s[i] >= utf8.RuneSelf {
return false
}
}
return true
}
// PunycodeHostPort returns the IDNA Punycode version
// of the provided "host" or "host:port" string.
func PunycodeHostPort(v string) (string, error) {
if isASCII(v) {
return v, nil
}
host, port, err := net.SplitHostPort(v)
if err != nil {
// The input 'v' argument was just a "host" argument,
// without a port. This error should not be returned
// to the caller.
host = v
port = ""
}
host, err = idna.ToASCII(host)
if err != nil {
// Non-UTF-8? Not representable in Punycode, in any
// case.
return "", err
}
if port == "" {
return host, nil
}
return net.JoinHostPort(host, port), nil
}