feat: add ech-key for listeners

component/ech/key.go

@@ -0,0 +1,143 @@
+package ech
+
+import (
+	"crypto/ecdh"
+	"crypto/rand"
+	"encoding/base64"
+	"encoding/pem"
+	"errors"
+	"fmt"
+	"os"
+
+	"github.com/metacubex/mihomo/component/ca"
+	tlsC "github.com/metacubex/mihomo/component/tls"
+
+	"golang.org/x/crypto/cryptobyte"
+)
+
+const (
+	AEAD_AES_128_GCM      = 0x0001
+	AEAD_AES_256_GCM      = 0x0002
+	AEAD_ChaCha20Poly1305 = 0x0003
+)
+
+const extensionEncryptedClientHello = 0xfe0d
+const DHKEM_X25519_HKDF_SHA256 = 0x0020
+const KDF_HKDF_SHA256 = 0x0001
+
+// sortedSupportedAEADs is just a sorted version of hpke.SupportedAEADS.
+// We need this so that when we insert them into ECHConfigs the ordering
+// is stable.
+var sortedSupportedAEADs = []uint16{AEAD_AES_128_GCM, AEAD_AES_256_GCM, AEAD_ChaCha20Poly1305}
+
+func marshalECHConfig(id uint8, pubKey []byte, publicName string, maxNameLen uint8) []byte {
+	builder := cryptobyte.NewBuilder(nil)
+
+	builder.AddUint16(extensionEncryptedClientHello)
+	builder.AddUint16LengthPrefixed(func(builder *cryptobyte.Builder) {
+		builder.AddUint8(id)
+
+		builder.AddUint16(DHKEM_X25519_HKDF_SHA256) // The only DHKEM we support
+		builder.AddUint16LengthPrefixed(func(builder *cryptobyte.Builder) {
+			builder.AddBytes(pubKey)
+		})
+		builder.AddUint16LengthPrefixed(func(builder *cryptobyte.Builder) {
+			for _, aeadID := range sortedSupportedAEADs {
+				builder.AddUint16(KDF_HKDF_SHA256) // The only KDF we support
+				builder.AddUint16(aeadID)
+			}
+		})
+		builder.AddUint8(maxNameLen)
+		builder.AddUint8LengthPrefixed(func(builder *cryptobyte.Builder) {
+			builder.AddBytes([]byte(publicName))
+		})
+		builder.AddUint16(0) // extensions
+	})
+
+	return builder.BytesOrPanic()
+}
+
+func GenECHConfig(publicName string) (configBase64 string, keyPem string, err error) {
+	echKey, err := ecdh.X25519().GenerateKey(rand.Reader)
+	if err != nil {
+		return
+	}
+
+	echConfig := marshalECHConfig(0, echKey.PublicKey().Bytes(), publicName, 0)
+
+	builder := cryptobyte.NewBuilder(nil)
+	builder.AddUint16LengthPrefixed(func(builder *cryptobyte.Builder) {
+		builder.AddBytes(echConfig)
+	})
+	echConfigList := builder.BytesOrPanic()
+
+	builder2 := cryptobyte.NewBuilder(nil)
+	builder2.AddUint16LengthPrefixed(func(builder *cryptobyte.Builder) {
+		builder.AddBytes(echKey.Bytes())
+	})
+	builder2.AddUint16LengthPrefixed(func(builder *cryptobyte.Builder) {
+		builder.AddBytes(echConfig)
+	})
+	echConfigKeys := builder2.BytesOrPanic()
+
+	configBase64 = base64.StdEncoding.EncodeToString(echConfigList)
+	keyPem = string(pem.EncodeToMemory(&pem.Block{Type: "ECH KEYS", Bytes: echConfigKeys}))
+	return
+}
+
+func UnmarshalECHKeys(raw []byte) ([]tlsC.EncryptedClientHelloKey, error) {
+	var keys []tlsC.EncryptedClientHelloKey
+	rawString := cryptobyte.String(raw)
+	for !rawString.Empty() {
+		var key tlsC.EncryptedClientHelloKey
+		if !rawString.ReadUint16LengthPrefixed((*cryptobyte.String)(&key.PrivateKey)) {
+			return nil, errors.New("error parsing private key")
+		}
+		if !rawString.ReadUint16LengthPrefixed((*cryptobyte.String)(&key.Config)) {
+			return nil, errors.New("error parsing config")
+		}
+		keys = append(keys, key)
+	}
+	if len(keys) == 0 {
+		return nil, errors.New("empty ECH keys")
+	}
+	return keys, nil
+}
+
+func LoadECHKey(key string, tlsConfig *tlsC.Config, path ca.Path) error {
+	if key == "" {
+		return nil
+	}
+	painTextErr := loadECHKey([]byte(key), tlsConfig)
+	if painTextErr == nil {
+		return nil
+	}
+	key = path.Resolve(key)
+	var loadErr error
+	if !path.IsSafePath(key) {
+		loadErr = path.ErrNotSafePath(key)
+	} else {
+		var echKey []byte
+		echKey, loadErr = os.ReadFile(key)
+		if loadErr == nil {
+			loadErr = loadECHKey(echKey, tlsConfig)
+		}
+	}
+	if loadErr != nil {
+		return fmt.Errorf("parse ECH keys failed, maybe format error:%s, or path error: %s", painTextErr.Error(), loadErr.Error())
+	}
+	return nil
+}
+
+func loadECHKey(echKey []byte, tlsConfig *tlsC.Config) error {
+	block, rest := pem.Decode(echKey)
+	if block == nil || block.Type != "ECH KEYS" || len(rest) > 0 {
+		return errors.New("invalid ECH keys pem")
+	}
+	echKeys, err := UnmarshalECHKeys(block.Bytes)
+	if err != nil {
+		return fmt.Errorf("parse ECH keys: %w", err)
+	}
+	tlsConfig.EncryptedClientHelloKeys = echKeys
+	return nil
+}