TUN-2746: Add the new header management functions

h2mux/header.go

@@ -1,7 +1,6 @@
 package h2mux
 
 import (
-	"bytes"
 	"encoding/base64"
 	"fmt"
 	"github.com/pkg/errors"
@@ -17,9 +16,130 @@ type Header struct {
 
 var headerEncoding = base64.RawStdEncoding
 
-// OldH2RequestHeadersToH1Request converts the HTTP/2 headers to an HTTP/1 Request
-// object. This includes conversion of the pseudo-headers into their closest
+const (
+	RequestUserHeadersField  = "cf-cloudflared-request-headers"
+	ResponseUserHeadersField = "cf-cloudflared-response-headers"
+)
+
+// H2RequestHeadersToH1Request converts the HTTP/2 headers coming from origintunneld
+// to an HTTP/1 Request object destined for the local origin web service.
+// This operation includes conversion of the pseudo-headers into their closest
 // HTTP/1 equivalents. See https://tools.ietf.org/html/rfc7540#section-8.1.2.3
+func H2RequestHeadersToH1Request(h2 []Header, h1 *http.Request) error {
+	for _, header := range h2 {
+		switch strings.ToLower(header.Name) {
+		case ":method":
+			h1.Method = header.Value
+		case ":scheme":
+			// noop - use the preexisting scheme from h1.URL
+		case ":authority":
+			// Otherwise the host header will be based on the origin URL
+			h1.Host = header.Value
+		case ":path":
+			// We don't want to be an "opinionated" proxy, so ideally we would use :path as-is.
+			// However, this HTTP/1 Request object belongs to the Go standard library,
+			// whose URL package makes some opinionated decisions about the encoding of
+			// URL characters: see the docs of https://godoc.org/net/url#URL,
+			// in particular the EscapedPath method https://godoc.org/net/url#URL.EscapedPath,
+			// which is always used when computing url.URL.String(), whether we'd like it or not.
+			//
+			// Well, not *always*. We could circumvent this by using url.URL.Opaque. But
+			// that would present unusual difficulties when using an HTTP proxy: url.URL.Opaque
+			// is treated differently when HTTP_PROXY is set!
+			// See https://github.com/golang/go/issues/5684#issuecomment-66080888
+			//
+			// This means we are subject to the behavior of net/url's function `shouldEscape`
+			// (as invoked with mode=encodePath): https://github.com/golang/go/blob/go1.12.7/src/net/url/url.go#L101
+
+			if header.Value == "*" {
+				h1.URL.Path = "*"
+				continue
+			}
+			// Due to the behavior of validation.ValidateUrl, h1.URL may
+			// already have a partial value, with or without a trailing slash.
+			base := h1.URL.String()
+			base = strings.TrimRight(base, "/")
+			// But we know :path begins with '/', because we handled '*' above - see RFC7540
+			requestURL, err := url.Parse(base + header.Value)
+			if err != nil {
+				return errors.Wrap(err, fmt.Sprintf("invalid path '%v'", header.Value))
+			}
+			h1.URL = requestURL
+		case "content-length":
+			contentLength, err := strconv.ParseInt(header.Value, 10, 64)
+			if err != nil {
+				return fmt.Errorf("unparseable content length")
+			}
+			h1.ContentLength = contentLength
+		default:
+			// Ignore any other header;
+			// User headers will be read from `RequestUserHeadersField`
+			continue
+		}
+	}
+
+	// Find and parse user headers serialized into a single one
+	userHeaders, err := ParseUserHeaders(RequestUserHeadersField, h2)
+	if err != nil {
+		return errors.Wrap(err, "Unable to parse user headers")
+	}
+	for _, userHeader := range userHeaders {
+		h1.Header.Add(http.CanonicalHeaderKey(userHeader.Name), userHeader.Value)
+	}
+
+	return nil
+}
+
+func ParseUserHeaders(headerNameToParseFrom string, headers []Header) ([]Header, error) {
+	for _, header := range headers {
+		if header.Name == headerNameToParseFrom {
+			return DeserializeHeaders(header.Value)
+		}
+	}
+
+	return nil, fmt.Errorf("%v header not found", RequestUserHeadersField)
+}
+
+func IsControlHeader(headerName string) bool {
+	headerName = strings.ToLower(headerName)
+
+	return strings.ToLower(headerName) == "content-length" ||
+		strings.HasPrefix(headerName, ":") ||
+		strings.HasPrefix(headerName, "cf-")
+}
+
+func H1ResponseToH2ResponseHeaders(h1 *http.Response) (h2 []Header) {
+	h2 = []Header{
+		{Name: ":status", Value: strconv.Itoa(h1.StatusCode)},
+	}
+	userHeaders := http.Header{}
+	for header, values := range h1.Header {
+		for _, value := range values {
+			if strings.ToLower(header) == "content-length" {
+				// This header has meaning in HTTP/2 and will be used by the edge,
+				// so it should be sent as an HTTP/2 response header.
+
+				// Since these are http2 headers, they're required to be lowercase
+				h2 = append(h2, Header{Name: strings.ToLower(header), Value: value})
+			} else if !IsControlHeader(header) {
+				// User headers, on the other hand, must all be serialized so that
+				// HTTP/2 header validation won't be applied to HTTP/1 header values
+				if _, ok := userHeaders[header]; ok {
+					userHeaders[header] = append(userHeaders[header], value)
+				} else {
+					userHeaders[header] = []string{value}
+				}
+			}
+		}
+	}
+
+	// Perform user header serialization and set them in the single header
+	h2 = append(h2, CreateSerializedHeaders(ResponseUserHeadersField, userHeaders)...)
+
+	return h2
+}
+
+// Obsolete version of H2RequestHeadersToH1Request
 func OldH2RequestHeadersToH1Request(h2 []Header, h1 *http.Request) error {
 	for _, header := range h2 {
 		switch header.Name {
@@ -73,6 +193,7 @@ func OldH2RequestHeadersToH1Request(h2 []Header, h1 *http.Request) error {
 	return nil
 }
 
+// Obsolete version of H1ResponseToH2ResponseHeaders
 func OldH1ResponseToH2ResponseHeaders(h1 *http.Response) (h2 []Header) {
 	h2 = []Header{{Name: ":status", Value: fmt.Sprintf("%d", h1.StatusCode)}}
 	for headerName, headerValues := range h1.Header {
@@ -86,9 +207,9 @@ func OldH1ResponseToH2ResponseHeaders(h1 *http.Response) (h2 []Header) {
 
 // Serialize HTTP1.x headers by base64-encoding each header name and value,
 // and then joining them in the format of [key:value;]
-func SerializeHeaders(h1 *http.Request) []byte {
-	var serializedHeaders [][]byte
-	for headerName, headerValues := range h1.Header {
+func SerializeHeaders(h1Headers http.Header) string {
+	var serializedHeaders []string
+	for headerName, headerValues := range h1Headers {
 		for _, headerValue := range headerValues {
 			encodedName := make([]byte, headerEncoding.EncodedLen(len(headerName)))
 			headerEncoding.Encode(encodedName, []byte(headerName))
@@ -98,28 +219,28 @@ func SerializeHeaders(h1 *http.Request) []byte {
 
 			serializedHeaders = append(
 				serializedHeaders,
-				bytes.Join(
-					[][]byte{encodedName, encodedValue},
-					[]byte(":"),
+				strings.Join(
+					[]string{string(encodedName), string(encodedValue)},
+					":",
 				),
 			)
 		}
 	}
 
-	return bytes.Join(serializedHeaders, []byte(";"))
+	return strings.Join(serializedHeaders, ";")
 }
 
 // Deserialize headers serialized by `SerializeHeader`
-func DeserializeHeaders(serializedHeaders []byte) (http.Header, error) {
+func DeserializeHeaders(serializedHeaders string) ([]Header, error) {
 	const unableToDeserializeErr = "Unable to deserialize headers"
 
-	deserialized := http.Header{}
-	for _, serializedPair := range bytes.Split(serializedHeaders, []byte(";")) {
+	var deserialized []Header
+	for _, serializedPair := range strings.Split(serializedHeaders, ";") {
 		if len(serializedPair) == 0 {
 			continue
 		}
 
-		serializedHeaderParts := bytes.Split(serializedPair, []byte(":"))
+		serializedHeaderParts := strings.Split(serializedPair, ":")
 		if len(serializedHeaderParts) != 2 {
 			return nil, errors.New(unableToDeserializeErr)
 		}
@@ -129,15 +250,30 @@ func DeserializeHeaders(serializedHeaders []byte) (http.Header, error) {
 		deserializedName := make([]byte, headerEncoding.DecodedLen(len(serializedName)))
 		deserializedValue := make([]byte, headerEncoding.DecodedLen(len(serializedValue)))
 
-		if _, err := headerEncoding.Decode(deserializedName, serializedName); err != nil {
+		if _, err := headerEncoding.Decode(deserializedName, []byte(serializedName)); err != nil {
 			return nil, errors.Wrap(err, unableToDeserializeErr)
 		}
-		if _, err := headerEncoding.Decode(deserializedValue, serializedValue); err != nil {
+		if _, err := headerEncoding.Decode(deserializedValue, []byte(serializedValue)); err != nil {
 			return nil, errors.Wrap(err, unableToDeserializeErr)
 		}
 
-		deserialized.Add(string(deserializedName), string(deserializedValue))
+		deserialized = append(deserialized, Header{
+			Name:  string(deserializedName),
+			Value: string(deserializedValue),
+		})
 	}
 
 	return deserialized, nil
 }
+
+func CreateSerializedHeaders(headersField string, headers ...http.Header) []Header {
+	var serializedHeaderChunks []string
+	for _, headerChunk := range headers {
+		serializedHeaderChunks = append(serializedHeaderChunks, SerializeHeaders(headerChunk))
+	}
+
+	return []Header{{
+		headersField,
+		strings.Join(serializedHeaderChunks, ";"),
+	}}
+}