cloudflared-mirror/h2mux/header.go

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package h2mux
import (
"encoding/base64"
"fmt"
"github.com/pkg/errors"
"net/http"
"net/url"
"strconv"
"strings"
)
type Header struct {
Name, Value string
}
var headerEncoding = base64.RawStdEncoding
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
}
// 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 {
var serializedHeaders []string
for headerName, headerValues := range h1Headers {
for _, headerValue := range headerValues {
encodedName := make([]byte, headerEncoding.EncodedLen(len(headerName)))
headerEncoding.Encode(encodedName, []byte(headerName))
encodedValue := make([]byte, headerEncoding.EncodedLen(len(headerValue)))
headerEncoding.Encode(encodedValue, []byte(headerValue))
serializedHeaders = append(
serializedHeaders,
strings.Join(
[]string{string(encodedName), string(encodedValue)},
":",
),
)
}
}
return strings.Join(serializedHeaders, ";")
}
// 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
}
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, ";"),
}}
}