cloudflared-mirror/h2mux/header.go

235 lines
7.8 KiB
Go

package h2mux
import (
"encoding/base64"
"fmt"
"net/http"
"net/url"
"strconv"
"strings"
"github.com/pkg/errors"
)
type Header struct {
Name, Value string
}
var headerEncoding = base64.RawStdEncoding
const (
RequestUserHeadersField = "cf-cloudflared-request-headers"
ResponseUserHeadersField = "cf-cloudflared-response-headers"
CFAccessTokenHeader = "cf-access-token"
CFJumpDestinationHeader = "CF-Access-Jump-Destination"
CFAccessClientIDHeader = "CF-Access-Client-Id"
CFAccessClientSecretHeader = "CF-Access-Client-Secret"
)
// 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 {
name := strings.ToLower(header.Name)
if !IsControlHeader(name) {
continue
}
switch 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
case RequestUserHeadersField:
// Do not forward the serialized headers to the origin -- deserialize them, and ditch the serialized version
// 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)
}
default:
// All other control headers shall just be proxied transparently
h1.Header.Add(http.CanonicalHeaderKey(header.Name), header.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 {
return headerName == "content-length" ||
headerName == "connection" || headerName == "upgrade" || // Websocket headers
strings.HasPrefix(headerName, ":") ||
strings.HasPrefix(headerName, "cf-")
}
// isWebsocketClientHeader returns true if the header name is required by the client to upgrade properly
func IsWebsocketClientHeader(headerName string) bool {
return headerName == "sec-websocket-accept" ||
headerName == "connection" ||
headerName == "upgrade"
}
func H1ResponseToH2ResponseHeaders(h1 *http.Response) (h2 []Header) {
h2 = []Header{
{Name: ":status", Value: strconv.Itoa(h1.StatusCode)},
}
userHeaders := make(http.Header, len(h1.Header))
for header, values := range h1.Header {
h2name := strings.ToLower(header)
if h2name == "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: "content-length", Value: values[0]})
} else if !IsControlHeader(h2name) || IsWebsocketClientHeader(h2name) {
// 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
userHeaders[header] = values
}
}
// Perform user header serialization and set them in the single header
h2 = append(h2, Header{ResponseUserHeadersField, SerializeHeaders(userHeaders)})
return h2
}
// Serialize HTTP1.x headers by base64-encoding each header name and value,
// and then joining them in the format of [key:value;]
func SerializeHeaders(h1Headers http.Header) string {
// compute size of the fully serialized value and largest temp buffer we will need
serializedLen := 0
maxTempLen := 0
for headerName, headerValues := range h1Headers {
for _, headerValue := range headerValues {
nameLen := headerEncoding.EncodedLen(len(headerName))
valueLen := headerEncoding.EncodedLen(len(headerValue))
const delims = 2
serializedLen += delims + nameLen + valueLen
if nameLen > maxTempLen {
maxTempLen = nameLen
}
if valueLen > maxTempLen {
maxTempLen = valueLen
}
}
}
var buf strings.Builder
buf.Grow(serializedLen)
temp := make([]byte, maxTempLen)
writeB64 := func(s string) {
n := headerEncoding.EncodedLen(len(s))
if n > len(temp) {
temp = make([]byte, n)
}
headerEncoding.Encode(temp[:n], []byte(s))
buf.Write(temp[:n])
}
for headerName, headerValues := range h1Headers {
for _, headerValue := range headerValues {
if buf.Len() > 0 {
buf.WriteByte(';')
}
writeB64(headerName)
buf.WriteByte(':')
writeB64(headerValue)
}
}
return buf.String()
}
// Deserialize headers serialized by `SerializeHeader`
func DeserializeHeaders(serializedHeaders string) ([]Header, error) {
const unableToDeserializeErr = "Unable to deserialize headers"
var deserialized []Header
for _, serializedPair := range strings.Split(serializedHeaders, ";") {
if len(serializedPair) == 0 {
continue
}
serializedHeaderParts := strings.Split(serializedPair, ":")
if len(serializedHeaderParts) != 2 {
return nil, errors.New(unableToDeserializeErr)
}
serializedName := serializedHeaderParts[0]
serializedValue := serializedHeaderParts[1]
deserializedName := make([]byte, headerEncoding.DecodedLen(len(serializedName)))
deserializedValue := make([]byte, headerEncoding.DecodedLen(len(serializedValue)))
if _, err := headerEncoding.Decode(deserializedName, []byte(serializedName)); err != nil {
return nil, errors.Wrap(err, unableToDeserializeErr)
}
if _, err := headerEncoding.Decode(deserializedValue, []byte(serializedValue)); err != nil {
return nil, errors.Wrap(err, unableToDeserializeErr)
}
deserialized = append(deserialized, Header{
Name: string(deserializedName),
Value: string(deserializedValue),
})
}
return deserialized, nil
}