git » go-net » commit 5916dcb

diff --git a/http2/frame.go b/http2/frame.go
index 4badb9d..88067dc 100644
--- a/http2/frame.go
+++ b/http2/frame.go
@@ -15,6 +15,7 @@ import (
 	"sync"
 
 	"golang.org/x/net/http2/hpack"
+	"golang.org/x/net/lex/httplex"
 )
 
 const frameHeaderLen = 9
@@ -1395,7 +1396,7 @@ func (fr *Framer) readMetaFrame(hf *HeadersFrame) (*MetaHeadersFrame, error) {
 	hdec.SetEmitEnabled(true)
 	hdec.SetMaxStringLength(fr.maxHeaderStringLen())
 	hdec.SetEmitFunc(func(hf hpack.HeaderField) {
-		if !validHeaderFieldValue(hf.Value) {
+		if !httplex.ValidHeaderFieldValue(hf.Value) {
 			invalid = headerFieldValueError(hf.Value)
 		}
 		isPseudo := strings.HasPrefix(hf.Name, ":")
@@ -1405,7 +1406,7 @@ func (fr *Framer) readMetaFrame(hf *HeadersFrame) (*MetaHeadersFrame, error) {
 			}
 		} else {
 			sawRegular = true
-			if !validHeaderFieldName(hf.Name) {
+			if !validWireHeaderFieldName(hf.Name) {
 				invalid = headerFieldNameError(hf.Name)
 			}
 		}
diff --git a/http2/http2.go b/http2/http2.go
index 7b98e75..0173aed 100644
--- a/http2/http2.go
+++ b/http2/http2.go
@@ -27,6 +27,8 @@ import (
 	"strconv"
 	"strings"
 	"sync"
+
+	"golang.org/x/net/lex/httplex"
 )
 
 var (
@@ -166,58 +168,23 @@ var (
 	errInvalidHeaderFieldValue = errors.New("http2: invalid header field value")
 )
 
-// validHeaderFieldName reports whether v is a valid header field name (key).
-//  RFC 7230 says:
-//   header-field   = field-name ":" OWS field-value OWS
-//   field-name     = token
-//   token          = 1*tchar
-//   tchar = "!" / "#" / "$" / "%" / "&" / "'" / "*" / "+" / "-" / "." /
-//           "^" / "_" / "`" / "|" / "~" / DIGIT / ALPHA
+// validWireHeaderFieldName reports whether v is a valid header field
+// name (key). See httplex.ValidHeaderName for the base rules.
+//
 // Further, http2 says:
 //   "Just as in HTTP/1.x, header field names are strings of ASCII
 //   characters that are compared in a case-insensitive
 //   fashion. However, header field names MUST be converted to
 //   lowercase prior to their encoding in HTTP/2. "
-func validHeaderFieldName(v string) bool {
+func validWireHeaderFieldName(v string) bool {
 	if len(v) == 0 {
 		return false
 	}
 	for _, r := range v {
-		if int(r) >= len(isTokenTable) || ('A' <= r && r <= 'Z') {
+		if !httplex.IsTokenRune(r) {
 			return false
 		}
-		if !isTokenTable[byte(r)] {
-			return false
-		}
-	}
-	return true
-}
-
-// validHeaderFieldValue reports whether v is a valid header field value.
-//
-// 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++ {
-		if b := v[i]; b < ' ' && b != '\t' || b == 0x7f {
+		if 'A' <= r && r <= 'Z' {
 			return false
 		}
 	}
@@ -346,86 +313,6 @@ func (e *httpError) Temporary() bool { return true }
 
 var errTimeout error = &httpError{msg: "http2: timeout awaiting response headers", timeout: true}
 
-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,
-}
-
 type connectionStater interface {
 	ConnectionState() tls.ConnectionState
 }
diff --git a/http2/server_test.go b/http2/server_test.go
index 0907530..012bfd4 100644
--- a/http2/server_test.go
+++ b/http2/server_test.go
@@ -209,7 +209,9 @@ func (st *serverTester) Close() {
 		// unwindowing), force close the connection, so the
 		// httptest.Server doesn't wait forever for the conn
 		// to close.
-		st.cc.Close()
+		if st.cc != nil {
+			st.cc.Close()
+		}
 	}
 	st.ts.Close()
 	if st.cc != nil {
diff --git a/http2/transport.go b/http2/transport.go
index 4aa3b7b..5f1564a 100644
--- a/http2/transport.go
+++ b/http2/transport.go
@@ -25,6 +25,7 @@ import (
 	"time"
 
 	"golang.org/x/net/http2/hpack"
+	"golang.org/x/net/lex/httplex"
 )
 
 const (
@@ -632,12 +633,8 @@ func (cc *ClientConn) RoundTrip(req *http.Request) (*http.Response, error) {
 		return nil, errClientConnUnusable
 	}
 
-	cs := cc.newStream()
-	cs.req = req
-	cs.trace = requestTrace(req)
-	hasBody := body != nil
-
 	// TODO(bradfitz): this is a copy of the logic in net/http. Unify somewhere?
+	var requestedGzip bool
 	if !cc.t.disableCompression() &&
 		req.Header.Get("Accept-Encoding") == "" &&
 		req.Header.Get("Range") == "" &&
@@ -654,13 +651,24 @@ func (cc *ClientConn) RoundTrip(req *http.Request) (*http.Response, error) {
 		// We don't request gzip if the request is for a range, since
 		// auto-decoding a portion of a gzipped document will just fail
 		// anyway. See https://golang.org/issue/8923
-		cs.requestedGzip = true
+		requestedGzip = true
 	}
 
 	// we send: HEADERS{1}, CONTINUATION{0,} + DATA{0,} (DATA is
 	// sent by writeRequestBody below, along with any Trailers,
 	// again in form HEADERS{1}, CONTINUATION{0,})
-	hdrs := cc.encodeHeaders(req, cs.requestedGzip, trailers, contentLen)
+	hdrs, err := cc.encodeHeaders(req, requestedGzip, trailers, contentLen)
+	if err != nil {
+		cc.mu.Unlock()
+		return nil, err
+	}
+
+	cs := cc.newStream()
+	cs.req = req
+	cs.trace = requestTrace(req)
+	hasBody := body != nil
+	cs.requestedGzip = requestedGzip
+
 	cc.wmu.Lock()
 	endStream := !hasBody && !hasTrailers
 	werr := cc.writeHeaders(cs.ID, endStream, hdrs)
@@ -936,7 +944,7 @@ type badStringError struct {
 func (e *badStringError) Error() string { return fmt.Sprintf("%s %q", e.what, e.str) }
 
 // requires cc.mu be held.
-func (cc *ClientConn) encodeHeaders(req *http.Request, addGzipHeader bool, trailers string, contentLength int64) []byte {
+func (cc *ClientConn) encodeHeaders(req *http.Request, addGzipHeader bool, trailers string, contentLength int64) ([]byte, error) {
 	cc.hbuf.Reset()
 
 	host := req.Host
@@ -944,6 +952,20 @@ func (cc *ClientConn) encodeHeaders(req *http.Request, addGzipHeader bool, trail
 		host = req.URL.Host
 	}
 
+	// Check for any invalid headers and return an error before we
+	// potentially pollute our hpack state. (We want to be able to
+	// continue to reuse the hpack encoder for future requests)
+	for k, vv := range req.Header {
+		if !httplex.ValidHeaderFieldName(k) {
+			return nil, fmt.Errorf("invalid HTTP header name %q", k)
+		}
+		for _, v := range vv {
+			if !httplex.ValidHeaderFieldValue(v) {
+				return nil, fmt.Errorf("invalid HTTP header value %q for header %q", v, k)
+			}
+		}
+	}
+
 	// 8.1.2.3 Request Pseudo-Header Fields
 	// The :path pseudo-header field includes the path and query parts of the
 	// target URI (the path-absolute production and optionally a '?' character
@@ -1000,7 +1022,7 @@ func (cc *ClientConn) encodeHeaders(req *http.Request, addGzipHeader bool, trail
 	if !didUA {
 		cc.writeHeader("user-agent", defaultUserAgent)
 	}
-	return cc.hbuf.Bytes()
+	return cc.hbuf.Bytes(), nil
 }
 
 // shouldSendReqContentLength reports whether the http2.Transport should send
diff --git a/http2/transport_test.go b/http2/transport_test.go
index bcc2a5f..bd07c93 100644
--- a/http2/transport_test.go
+++ b/http2/transport_test.go
@@ -1666,6 +1666,68 @@ func TestTransportRejectsConnHeaders(t *testing.T) {
 	}
 }
 
+// golang.org/issue/14048
+func TestTransportFailsOnInvalidHeaders(t *testing.T) {
+	st := newServerTester(t, func(w http.ResponseWriter, r *http.Request) {
+		var got []string
+		for k := range r.Header {
+			got = append(got, k)
+		}
+		sort.Strings(got)
+		w.Header().Set("Got-Header", strings.Join(got, ","))
+	}, optOnlyServer)
+	defer st.Close()
+
+	tests := [...]struct {
+		h       http.Header
+		wantErr string
+	}{
+		0: {
+			h:       http.Header{"with space": {"foo"}},
+			wantErr: `invalid HTTP header name "with space"`,
+		},
+		1: {
+			h:       http.Header{"name": {"Брэд"}},
+			wantErr: "", // okay
+		},
+		2: {
+			h:       http.Header{"имя": {"Brad"}},
+			wantErr: `invalid HTTP header name "имя"`,
+		},
+		3: {
+			h:       http.Header{"foo": {"foo\x01bar"}},
+			wantErr: `invalid HTTP header value "foo\x01bar" for header "foo"`,
+		},
+	}
+
+	tr := &Transport{TLSClientConfig: tlsConfigInsecure}
+	defer tr.CloseIdleConnections()
+
+	for i, tt := range tests {
+		req, _ := http.NewRequest("GET", st.ts.URL, nil)
+		req.Header = tt.h
+		res, err := tr.RoundTrip(req)
+		var bad bool
+		if tt.wantErr == "" {
+			if err != nil {
+				bad = true
+				t.Errorf("case %d: error = %v; want no error", i, err)
+			}
+		} else {
+			if !strings.Contains(fmt.Sprint(err), tt.wantErr) {
+				bad = true
+				t.Errorf("case %d: error = %v; want error %q", i, err, tt.wantErr)
+			}
+		}
+		if err == nil {
+			if bad {
+				t.Logf("case %d: server got headers %q", i, res.Header.Get("Got-Header"))
+			}
+			res.Body.Close()
+		}
+	}
+}
+
 // Tests that gzipReader doesn't crash on a second Read call following
 // the first Read call's gzip.NewReader returning an error.
 func TestGzipReader_DoubleReadCrash(t *testing.T) {
diff --git a/http2/write.go b/http2/write.go
index 0143b24..27ef0dd 100644
--- a/http2/write.go
+++ b/http2/write.go
@@ -12,6 +12,7 @@ import (
 	"time"
 
 	"golang.org/x/net/http2/hpack"
+	"golang.org/x/net/lex/httplex"
 )
 
 // writeFramer is implemented by any type that is used to write frames.
@@ -240,14 +241,15 @@ func encodeHeaders(enc *hpack.Encoder, h http.Header, keys []string) {
 	for _, k := range keys {
 		vv := h[k]
 		k = lowerHeader(k)
-		if !validHeaderFieldName(k) {
-			// TODO: return an error? golang.org/issue/14048
-			// For now just omit it.
+		if !validWireHeaderFieldName(k) {
+			// Skip it as backup paranoia. Per
+			// golang.org/issue/14048, these should
+			// already be rejected at a higher level.
 			continue
 		}
 		isTE := k == "transfer-encoding"
 		for _, v := range vv {
-			if !validHeaderFieldValue(v) {
+			if !httplex.ValidHeaderFieldValue(v) {
 				// TODO: return an error? golang.org/issue/14048
 				// For now just omit it.
 				continue
diff --git a/lex/httplex/httplex.go b/lex/httplex/httplex.go
new file mode 100644
index 0000000..bd0ec24
--- /dev/null
+++ b/lex/httplex/httplex.go
@@ -0,0 +1,312 @@
+// 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 (
+	"strings"
+	"unicode/utf8"
+)
+
+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
+}
diff --git a/lex/httplex/httplex_test.go b/lex/httplex/httplex_test.go
new file mode 100644
index 0000000..c4ace19
--- /dev/null
+++ b/lex/httplex/httplex_test.go
@@ -0,0 +1,101 @@
+// 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.
+
+package httplex
+
+import (
+	"testing"
+)
+
+func isChar(c rune) bool { return c <= 127 }
+
+func isCtl(c rune) bool { return c <= 31 || c == 127 }
+
+func isSeparator(c rune) bool {
+	switch c {
+	case '(', ')', '<', '>', '@', ',', ';', ':', '\\', '"', '/', '[', ']', '?', '=', '{', '}', ' ', '\t':
+		return true
+	}
+	return false
+}
+
+func TestIsToken(t *testing.T) {
+	for i := 0; i <= 130; i++ {
+		r := rune(i)
+		expected := isChar(r) && !isCtl(r) && !isSeparator(r)
+		if IsTokenRune(r) != expected {
+			t.Errorf("isToken(0x%x) = %v", r, !expected)
+		}
+	}
+}
+
+func TestHeaderValuesContainsToken(t *testing.T) {
+	tests := []struct {
+		vals  []string
+		token string
+		want  bool
+	}{
+		{
+			vals:  []string{"foo"},
+			token: "foo",
+			want:  true,
+		},
+		{
+			vals:  []string{"bar", "foo"},
+			token: "foo",
+			want:  true,
+		},
+		{
+			vals:  []string{"foo"},
+			token: "FOO",
+			want:  true,
+		},
+		{
+			vals:  []string{"foo"},
+			token: "bar",
+			want:  false,
+		},
+		{
+			vals:  []string{" foo "},
+			token: "FOO",
+			want:  true,
+		},
+		{
+			vals:  []string{"foo,bar"},
+			token: "FOO",
+			want:  true,
+		},
+		{
+			vals:  []string{"bar,foo,bar"},
+			token: "FOO",
+			want:  true,
+		},
+		{
+			vals:  []string{"bar , foo"},
+			token: "FOO",
+			want:  true,
+		},
+		{
+			vals:  []string{"foo ,bar "},
+			token: "FOO",
+			want:  true,
+		},
+		{
+			vals:  []string{"bar, foo ,bar"},
+			token: "FOO",
+			want:  true,
+		},
+		{
+			vals:  []string{"bar , foo"},
+			token: "FOO",
+			want:  true,
+		},
+	}
+	for _, tt := range tests {
+		got := HeaderValuesContainsToken(tt.vals, tt.token)
+		if got != tt.want {
+			t.Errorf("headerValuesContainsToken(%q, %q) = %v; want %v", tt.vals, tt.token, got, tt.want)
+		}
+	}
+}