ECH: client support TLS Encrypted Client Hello

transport/internet/tls/ech.go

@@ -0,0 +1,137 @@
+package tls
+
+import (
+	"bytes"
+	"context"
+	"crypto/tls"
+	"io"
+	"net/http"
+	"sync"
+	"time"
+
+	"github.com/miekg/dns"
+	"github.com/xtls/xray-core/common/errors"
+	"github.com/xtls/xray-core/common/net"
+	"github.com/xtls/xray-core/transport/internet"
+)
+
+func ApplyECH(c *Config, config *tls.Config) error {
+	var ECHConfig []byte
+	var err error
+
+	if len(c.EchConfig) > 0 {
+		ECHConfig = c.EchConfig
+	} else { // ECH config > DOH lookup
+		if config.ServerName == "" {
+			return errors.New("Using DOH for ECH needs serverName")
+		}
+		ECHConfig, err = QueryRecord(c.ServerName, c.Ech_DOHserver)
+		if err != nil {
+			return err
+		}
+	}
+
+	config.EncryptedClientHelloConfigList = ECHConfig
+	return nil
+}
+
+type record struct {
+	record []byte
+	expire time.Time
+}
+
+var (
+	dnsCache = make(map[string]record)
+	mutex    sync.RWMutex
+)
+
+func QueryRecord(domain string, server string) ([]byte, error) {
+    mutex.Lock()
+    rec, found := dnsCache[domain]
+    if found && rec.expire.After(time.Now()) {
+        mutex.Unlock()
+        return rec.record, nil
+    }
+    mutex.Unlock()
+
+    errors.LogDebug(context.Background(), "Trying to query ECH config for domain: ", domain, " with ECH server: ", server)
+    record, ttl, err := dohQuery(server, domain)
+    if err != nil {
+        return []byte{}, err
+    }
+
+    if ttl < 600 {
+        ttl = 600
+    }
+
+    mutex.Lock()
+    defer mutex.Unlock()
+    rec.record = record
+    rec.expire = time.Now().Add(time.Second * time.Duration(ttl))
+    dnsCache[domain] = rec
+    return record, nil
+}
+
+func dohQuery(server string, domain string) ([]byte, uint32, error) {
+	m := new(dns.Msg)
+	m.SetQuestion(dns.Fqdn(domain), dns.TypeHTTPS)
+	m.Id = 0
+	msg, err := m.Pack()
+	if err != nil {
+		return []byte{}, 0, err
+	}
+	tr := &http.Transport{
+		IdleConnTimeout:   90 * time.Second,
+		ForceAttemptHTTP2: true,
+		DialContext: func(ctx context.Context, network, addr string) (net.Conn, error) {
+			dest, err := net.ParseDestination(network + ":" + addr)
+			if err != nil {
+				return nil, err
+			}
+			conn, err := internet.DialSystem(ctx, dest, nil)
+			if err != nil {
+				return nil, err
+			}
+			return conn, nil
+		},
+	}
+	client := &http.Client{
+		Timeout:   5 * time.Second,
+		Transport: tr,
+	}
+	req, err := http.NewRequest("POST", server, bytes.NewReader(msg))
+	if err != nil {
+		return []byte{}, 0, err
+	}
+	req.Header.Set("Content-Type", "application/dns-message")
+	resp, err := client.Do(req)
+	if err != nil {
+		return []byte{}, 0, err
+	}
+	defer resp.Body.Close()
+	respBody, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return []byte{}, 0, err
+	}
+	if resp.StatusCode != http.StatusOK {
+		return []byte{}, 0, errors.New("query failed with response code:", resp.StatusCode)
+	}
+	respMsg := new(dns.Msg)
+	err = respMsg.Unpack(respBody)
+	if err != nil {
+		return []byte{}, 0, err
+	}
+	if len(respMsg.Answer) > 0 {
+		for _, answer := range respMsg.Answer {
+			if https, ok := answer.(*dns.HTTPS); ok && https.Hdr.Name == dns.Fqdn(domain) {
+				for _, v := range https.Value {
+					if echConfig, ok := v.(*dns.SVCBECHConfig); ok {
+						errors.LogDebug(context.Background(), "Get ECH config:", echConfig.String(), " TTL:", respMsg.Answer[0].Header().Ttl)
+						return echConfig.ECH, answer.Header().Ttl, nil
+					}
+				}
+			}
+		}
+	}
+	return []byte{}, 0, errors.New("no ech record found")
+}