Migrate to stdlib ECH support

common/tls/ech.go

@@ -0,0 +1,174 @@
+//go:build go1.24
+
+package tls
+
+import (
+	"context"
+	"crypto/tls"
+	"encoding/base64"
+	"encoding/pem"
+	"net"
+	"os"
+	"strings"
+
+	"github.com/sagernet/sing-box/adapter"
+	"github.com/sagernet/sing-box/dns"
+	"github.com/sagernet/sing-box/experimental/deprecated"
+	"github.com/sagernet/sing-box/option"
+	E "github.com/sagernet/sing/common/exceptions"
+	aTLS "github.com/sagernet/sing/common/tls"
+	"github.com/sagernet/sing/service"
+
+	mDNS "github.com/miekg/dns"
+	"golang.org/x/crypto/cryptobyte"
+)
+
+func parseECHClientConfig(ctx context.Context, options option.OutboundTLSOptions, tlsConfig *tls.Config) (Config, error) {
+	var echConfig []byte
+	if len(options.ECH.Config) > 0 {
+		echConfig = []byte(strings.Join(options.ECH.Config, "\n"))
+	} else if options.ECH.ConfigPath != "" {
+		content, err := os.ReadFile(options.ECH.ConfigPath)
+		if err != nil {
+			return nil, E.Cause(err, "read ECH config")
+		}
+		echConfig = content
+	}
+	//nolint:staticcheck
+	if options.ECH.PQSignatureSchemesEnabled || options.ECH.DynamicRecordSizingDisabled {
+		deprecated.Report(ctx, deprecated.OptionLegacyECHOptions)
+	}
+	if len(echConfig) > 0 {
+		block, rest := pem.Decode(echConfig)
+		if block == nil || block.Type != "ECH CONFIGS" || len(rest) > 0 {
+			return nil, E.New("invalid ECH configs pem")
+		}
+		tlsConfig.EncryptedClientHelloConfigList = block.Bytes
+		return &STDClientConfig{tlsConfig}, nil
+	} else {
+		return &STDECHClientConfig{STDClientConfig{tlsConfig}, service.FromContext[adapter.DNSRouter](ctx)}, nil
+	}
+}
+
+func parseECHServerConfig(ctx context.Context, options option.InboundTLSOptions, tlsConfig *tls.Config, echKeyPath *string) error {
+	var echKey []byte
+	if len(options.ECH.Key) > 0 {
+		echKey = []byte(strings.Join(options.ECH.Key, "\n"))
+	} else if options.ECH.KeyPath != "" {
+		content, err := os.ReadFile(options.ECH.KeyPath)
+		if err != nil {
+			return E.Cause(err, "read ECH keys")
+		}
+		echKey = content
+		*echKeyPath = options.ECH.KeyPath
+	} else {
+		return E.New("missing ECH keys")
+	}
+	block, rest := pem.Decode(echKey)
+	if block == nil || block.Type != "ECH KEYS" || len(rest) > 0 {
+		return E.New("invalid ECH keys pem")
+	}
+	echKeys, err := UnmarshalECHKeys(block.Bytes)
+	if err != nil {
+		return E.Cause(err, "parse ECH keys")
+	}
+	tlsConfig.EncryptedClientHelloKeys = echKeys
+	//nolint:staticcheck
+	if options.ECH.PQSignatureSchemesEnabled || options.ECH.DynamicRecordSizingDisabled {
+		deprecated.Report(ctx, deprecated.OptionLegacyECHOptions)
+	}
+	return nil
+}
+
+func reloadECHKeys(echKeyPath string, tlsConfig *tls.Config) error {
+	echKey, err := os.ReadFile(echKeyPath)
+	if err != nil {
+		return E.Cause(err, "reload ECH keys from ", echKeyPath)
+	}
+	block, _ := pem.Decode(echKey)
+	if block == nil || block.Type != "ECH KEYS" {
+		return E.New("invalid ECH keys pem")
+	}
+	echKeys, err := UnmarshalECHKeys(block.Bytes)
+	if err != nil {
+		return E.Cause(err, "parse ECH keys")
+	}
+	tlsConfig.EncryptedClientHelloKeys = echKeys
+	return nil
+}
+
+type STDECHClientConfig struct {
+	STDClientConfig
+	dnsRouter adapter.DNSRouter
+}
+
+func (s *STDECHClientConfig) ClientHandshake(ctx context.Context, conn net.Conn) (aTLS.Conn, error) {
+	if len(s.config.EncryptedClientHelloConfigList) == 0 {
+		message := &mDNS.Msg{
+			MsgHdr: mDNS.MsgHdr{
+				RecursionDesired: true,
+			},
+			Question: []mDNS.Question{
+				{
+					Name:   mDNS.Fqdn(s.config.ServerName),
+					Qtype:  mDNS.TypeHTTPS,
+					Qclass: mDNS.ClassINET,
+				},
+			},
+		}
+		response, err := s.dnsRouter.Exchange(ctx, message, adapter.DNSQueryOptions{})
+		if err != nil {
+			return nil, E.Cause(err, "fetch ECH config list")
+		}
+		if response.Rcode != mDNS.RcodeSuccess {
+			return nil, E.Cause(dns.RcodeError(response.Rcode), "fetch ECH config list")
+		}
+		for _, rr := range response.Answer {
+			switch resource := rr.(type) {
+			case *mDNS.HTTPS:
+				for _, value := range resource.Value {
+					if value.Key().String() == "ech" {
+						echConfigList, err := base64.StdEncoding.DecodeString(value.String())
+						if err != nil {
+							return nil, E.Cause(err, "decode ECH config")
+						}
+						s.config.EncryptedClientHelloConfigList = echConfigList
+					}
+				}
+			}
+		}
+		return nil, E.New("no ECH config found in DNS records")
+	}
+	tlsConn, err := s.Client(conn)
+	if err != nil {
+		return nil, err
+	}
+	err = tlsConn.HandshakeContext(ctx)
+	if err != nil {
+		return nil, err
+	}
+	return tlsConn, nil
+}
+
+func (s *STDECHClientConfig) Clone() Config {
+	return &STDECHClientConfig{STDClientConfig{s.config.Clone()}, s.dnsRouter}
+}
+
+func UnmarshalECHKeys(raw []byte) ([]tls.EncryptedClientHelloKey, error) {
+	var keys []tls.EncryptedClientHelloKey
+	rawString := cryptobyte.String(raw)
+	for !rawString.Empty() {
+		var key tls.EncryptedClientHelloKey
+		if !rawString.ReadUint16LengthPrefixed((*cryptobyte.String)(&key.PrivateKey)) {
+			return nil, E.New("error parsing private key")
+		}
+		if !rawString.ReadUint16LengthPrefixed((*cryptobyte.String)(&key.Config)) {
+			return nil, E.New("error parsing config")
+		}
+		keys = append(keys, key)
+	}
+	if len(keys) == 0 {
+		return nil, E.New("empty ECH keys")
+	}
+	return keys, nil
+}