Replace privileged PSK with Ed25519 signature verification

common/lua/privileged.go

@@ -0,0 +1,80 @@
+package lua
+
+import (
+	"bytes"
+	"crypto/ed25519"
+	"crypto/sha256"
+	"encoding/base64"
+	"sync"
+
+	"github.com/xtls/xray-core/common/errors"
+)
+
+var privilegedKey struct {
+	sync.Once
+	publicKey ed25519.PublicKey
+}
+
+// SetPrivilegedPublicKey configures the trusted Ed25519 public key once at
+// startup, before compiling scripts. An empty value disables authorization.
+// Nonempty values must be unpadded Base64URL encodings of exactly 32 bytes.
+func SetPrivilegedPublicKey(value string) error {
+	var publicKey ed25519.PublicKey
+	if value != "" {
+		decoded, err := decodePrivilegedValue(value, ed25519.PublicKeySize)
+		if err != nil {
+			return errors.New("invalid Lua privileged public key").Base(err)
+		}
+		publicKey = ed25519.PublicKey(decoded)
+	}
+	privilegedKey.Do(func() {
+		privilegedKey.publicKey = publicKey
+	})
+	return nil
+}
+
+func decodePrivilegedValue(value string, size int) ([]byte, error) {
+	encoding := base64.RawURLEncoding.Strict()
+	if len(value) != encoding.EncodedLen(size) {
+		return nil, errors.New("expected an unpadded Base64URL encoding of ", size, " bytes")
+	}
+	decoded, err := encoding.DecodeString(value)
+	if err != nil || len(decoded) != size || encoding.EncodeToString(decoded) != value {
+		return nil, errors.New("expected an unpadded Base64URL encoding of ", size, " bytes")
+	}
+	return decoded, nil
+}
+
+func verifyPrivilegedSignature(code []byte) (bool, error) {
+	for len(code) != 0 {
+		line, rest, _ := bytes.Cut(code, []byte{'\n'})
+		code = rest
+		line = bytes.TrimSuffix(line, []byte{'\r'})
+		if len(bytes.TrimSpace(line)) == 0 {
+			continue
+		}
+		line, found := bytes.CutPrefix(bytes.TrimLeft(line, " \t"), []byte("--"))
+		if !found {
+			return false, nil
+		}
+		value, found := bytes.CutPrefix(bytes.TrimLeft(line, " \t"), []byte("@xray:privileged-signature="))
+		if !found {
+			return false, nil
+		}
+
+		publicKey := privilegedKey.publicKey
+		if len(publicKey) == 0 {
+			return false, errors.New("Lua privileged signature requires --lua-privileged-pubkey")
+		}
+		signature, err := decodePrivilegedValue(string(bytes.TrimSpace(value)), ed25519.SignatureSize)
+		if err != nil {
+			return false, errors.New("invalid Lua privileged signature").Base(err)
+		}
+		digest := sha256.Sum256(bytes.TrimSpace(rest))
+		if !ed25519.Verify(publicKey, digest[:], signature) {
+			return false, errors.New("Lua privileged signature verification failed")
+		}
+		return true, nil
+	}
+	return false, nil
+}