241 lines
7.0 KiB
Go
241 lines
7.0 KiB
Go
// Copyright 2018 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 h2c implements the unencrypted "h2c" form of HTTP/2.
|
|
//
|
|
// The h2c protocol is the non-TLS version of HTTP/2 which is not available from
|
|
// net/http or golang.org/x/net/http2.
|
|
package h2c
|
|
|
|
import (
|
|
"bufio"
|
|
"bytes"
|
|
"encoding/base64"
|
|
"errors"
|
|
"fmt"
|
|
"io"
|
|
"log"
|
|
"net"
|
|
"net/http"
|
|
"net/textproto"
|
|
"os"
|
|
"strings"
|
|
|
|
"golang.org/x/net/http/httpguts"
|
|
"golang.org/x/net/http2"
|
|
)
|
|
|
|
var (
|
|
http2VerboseLogs bool
|
|
)
|
|
|
|
func init() {
|
|
e := os.Getenv("GODEBUG")
|
|
if strings.Contains(e, "http2debug=1") || strings.Contains(e, "http2debug=2") {
|
|
http2VerboseLogs = true
|
|
}
|
|
}
|
|
|
|
// h2cHandler is a Handler which implements h2c by hijacking the HTTP/1 traffic
|
|
// that should be h2c traffic. There are two ways to begin a h2c connection
|
|
// (RFC 7540 Section 3.2 and 3.4): (1) Starting with Prior Knowledge - this
|
|
// works by starting an h2c connection with a string of bytes that is valid
|
|
// HTTP/1, but unlikely to occur in practice and (2) Upgrading from HTTP/1 to
|
|
// h2c - this works by using the HTTP/1 Upgrade header to request an upgrade to
|
|
// h2c. When either of those situations occur we hijack the HTTP/1 connection,
|
|
// convert it to an HTTP/2 connection and pass the net.Conn to http2.ServeConn.
|
|
type h2cHandler struct {
|
|
Handler http.Handler
|
|
s *http2.Server
|
|
}
|
|
|
|
// NewHandler returns an http.Handler that wraps h, intercepting any h2c
|
|
// traffic. If a request is an h2c connection, it's hijacked and redirected to
|
|
// s.ServeConn. Otherwise the returned Handler just forwards requests to h. This
|
|
// works because h2c is designed to be parseable as valid HTTP/1, but ignored by
|
|
// any HTTP server that does not handle h2c. Therefore we leverage the HTTP/1
|
|
// compatible parts of the Go http library to parse and recognize h2c requests.
|
|
// Once a request is recognized as h2c, we hijack the connection and convert it
|
|
// to an HTTP/2 connection which is understandable to s.ServeConn. (s.ServeConn
|
|
// understands HTTP/2 except for the h2c part of it.)
|
|
//
|
|
// The first request on an h2c connection is read entirely into memory before
|
|
// the Handler is called. To limit the memory consumed by this request, wrap
|
|
// the result of NewHandler in an http.MaxBytesHandler.
|
|
func NewHandler(h http.Handler, s *http2.Server) http.Handler {
|
|
return &h2cHandler{
|
|
Handler: h,
|
|
s: s,
|
|
}
|
|
}
|
|
|
|
// extractServer extracts existing http.Server instance from http.Request or create an empty http.Server
|
|
func extractServer(r *http.Request) *http.Server {
|
|
server, ok := r.Context().Value(http.ServerContextKey).(*http.Server)
|
|
if ok {
|
|
return server
|
|
}
|
|
return new(http.Server)
|
|
}
|
|
|
|
// ServeHTTP implement the h2c support that is enabled by h2c.GetH2CHandler.
|
|
func (s h2cHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
|
|
// Handle h2c with prior knowledge (RFC 7540 Section 3.4)
|
|
if r.Method == "PRI" && len(r.Header) == 0 && r.URL.Path == "*" && r.Proto == "HTTP/2.0" {
|
|
if http2VerboseLogs {
|
|
log.Print("h2c: attempting h2c with prior knowledge.")
|
|
}
|
|
conn, err := initH2CWithPriorKnowledge(w)
|
|
if err != nil {
|
|
if http2VerboseLogs {
|
|
log.Printf("h2c: error h2c with prior knowledge: %v", err)
|
|
}
|
|
return
|
|
}
|
|
defer conn.Close()
|
|
s.s.ServeConn(conn, &http2.ServeConnOpts{
|
|
Context: r.Context(),
|
|
BaseConfig: extractServer(r),
|
|
Handler: s.Handler,
|
|
SawClientPreface: true,
|
|
})
|
|
return
|
|
}
|
|
// Handle Upgrade to h2c (RFC 7540 Section 3.2)
|
|
if isH2CUpgrade(r.Header) {
|
|
conn, settings, err := h2cUpgrade(w, r)
|
|
if err != nil {
|
|
if http2VerboseLogs {
|
|
log.Printf("h2c: error h2c upgrade: %v", err)
|
|
}
|
|
w.WriteHeader(http.StatusInternalServerError)
|
|
return
|
|
}
|
|
defer conn.Close()
|
|
s.s.ServeConn(conn, &http2.ServeConnOpts{
|
|
Context: r.Context(),
|
|
BaseConfig: extractServer(r),
|
|
Handler: s.Handler,
|
|
UpgradeRequest: r,
|
|
Settings: settings,
|
|
})
|
|
return
|
|
}
|
|
s.Handler.ServeHTTP(w, r)
|
|
return
|
|
}
|
|
|
|
// initH2CWithPriorKnowledge implements creating a h2c connection with prior
|
|
// knowledge (Section 3.4) and creates a net.Conn suitable for http2.ServeConn.
|
|
// All we have to do is look for the client preface that is suppose to be part
|
|
// of the body, and reforward the client preface on the net.Conn this function
|
|
// creates.
|
|
func initH2CWithPriorKnowledge(w http.ResponseWriter) (net.Conn, error) {
|
|
hijacker, ok := w.(http.Hijacker)
|
|
if !ok {
|
|
return nil, errors.New("h2c: connection does not support Hijack")
|
|
}
|
|
conn, rw, err := hijacker.Hijack()
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
const expectedBody = "SM\r\n\r\n"
|
|
|
|
buf := make([]byte, len(expectedBody))
|
|
n, err := io.ReadFull(rw, buf)
|
|
if err != nil {
|
|
return nil, fmt.Errorf("h2c: error reading client preface: %s", err)
|
|
}
|
|
|
|
if string(buf[:n]) == expectedBody {
|
|
return newBufConn(conn, rw), nil
|
|
}
|
|
|
|
conn.Close()
|
|
return nil, errors.New("h2c: invalid client preface")
|
|
}
|
|
|
|
// h2cUpgrade establishes a h2c connection using the HTTP/1 upgrade (Section 3.2).
|
|
func h2cUpgrade(w http.ResponseWriter, r *http.Request) (_ net.Conn, settings []byte, err error) {
|
|
settings, err = getH2Settings(r.Header)
|
|
if err != nil {
|
|
return nil, nil, err
|
|
}
|
|
hijacker, ok := w.(http.Hijacker)
|
|
if !ok {
|
|
return nil, nil, errors.New("h2c: connection does not support Hijack")
|
|
}
|
|
|
|
body, err := io.ReadAll(r.Body)
|
|
if err != nil {
|
|
return nil, nil, err
|
|
}
|
|
r.Body = io.NopCloser(bytes.NewBuffer(body))
|
|
|
|
conn, rw, err := hijacker.Hijack()
|
|
if err != nil {
|
|
return nil, nil, err
|
|
}
|
|
|
|
rw.Write([]byte("HTTP/1.1 101 Switching Protocols\r\n" +
|
|
"Connection: Upgrade\r\n" +
|
|
"Upgrade: h2c\r\n\r\n"))
|
|
return newBufConn(conn, rw), settings, nil
|
|
}
|
|
|
|
// isH2CUpgrade returns true if the header properly request an upgrade to h2c
|
|
// as specified by Section 3.2.
|
|
func isH2CUpgrade(h http.Header) bool {
|
|
return httpguts.HeaderValuesContainsToken(h[textproto.CanonicalMIMEHeaderKey("Upgrade")], "h2c") &&
|
|
httpguts.HeaderValuesContainsToken(h[textproto.CanonicalMIMEHeaderKey("Connection")], "HTTP2-Settings")
|
|
}
|
|
|
|
// getH2Settings returns the settings in the HTTP2-Settings header.
|
|
func getH2Settings(h http.Header) ([]byte, error) {
|
|
vals, ok := h[textproto.CanonicalMIMEHeaderKey("HTTP2-Settings")]
|
|
if !ok {
|
|
return nil, errors.New("missing HTTP2-Settings header")
|
|
}
|
|
if len(vals) != 1 {
|
|
return nil, fmt.Errorf("expected 1 HTTP2-Settings. Got: %v", vals)
|
|
}
|
|
settings, err := base64.RawURLEncoding.DecodeString(vals[0])
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
return settings, nil
|
|
}
|
|
|
|
func newBufConn(conn net.Conn, rw *bufio.ReadWriter) net.Conn {
|
|
rw.Flush()
|
|
if rw.Reader.Buffered() == 0 {
|
|
// If there's no buffered data to be read,
|
|
// we can just discard the bufio.ReadWriter.
|
|
return conn
|
|
}
|
|
return &bufConn{conn, rw.Reader}
|
|
}
|
|
|
|
// bufConn wraps a net.Conn, but reads drain the bufio.Reader first.
|
|
type bufConn struct {
|
|
net.Conn
|
|
*bufio.Reader
|
|
}
|
|
|
|
func (c *bufConn) Read(p []byte) (int, error) {
|
|
if c.Reader == nil {
|
|
return c.Conn.Read(p)
|
|
}
|
|
n := c.Reader.Buffered()
|
|
if n == 0 {
|
|
c.Reader = nil
|
|
return c.Conn.Read(p)
|
|
}
|
|
if n < len(p) {
|
|
p = p[:n]
|
|
}
|
|
return c.Reader.Read(p)
|
|
}
|