Chore: embed shadowsocks2

transport/shadowsocks/shadowaead/cipher.go

@@ -0,0 +1,94 @@
+package shadowaead
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/sha1"
+	"io"
+	"strconv"
+
+	"golang.org/x/crypto/chacha20poly1305"
+	"golang.org/x/crypto/hkdf"
+)
+
+type Cipher interface {
+	KeySize() int
+	SaltSize() int
+	Encrypter(salt []byte) (cipher.AEAD, error)
+	Decrypter(salt []byte) (cipher.AEAD, error)
+}
+
+type KeySizeError int
+
+func (e KeySizeError) Error() string {
+	return "key size error: need " + strconv.Itoa(int(e)) + " bytes"
+}
+
+func hkdfSHA1(secret, salt, info, outkey []byte) {
+	r := hkdf.New(sha1.New, secret, salt, info)
+	if _, err := io.ReadFull(r, outkey); err != nil {
+		panic(err) // should never happen
+	}
+}
+
+type metaCipher struct {
+	psk      []byte
+	makeAEAD func(key []byte) (cipher.AEAD, error)
+}
+
+func (a *metaCipher) KeySize() int { return len(a.psk) }
+func (a *metaCipher) SaltSize() int {
+	if ks := a.KeySize(); ks > 16 {
+		return ks
+	}
+	return 16
+}
+
+func (a *metaCipher) Encrypter(salt []byte) (cipher.AEAD, error) {
+	subkey := make([]byte, a.KeySize())
+	hkdfSHA1(a.psk, salt, []byte("ss-subkey"), subkey)
+	return a.makeAEAD(subkey)
+}
+
+func (a *metaCipher) Decrypter(salt []byte) (cipher.AEAD, error) {
+	subkey := make([]byte, a.KeySize())
+	hkdfSHA1(a.psk, salt, []byte("ss-subkey"), subkey)
+	return a.makeAEAD(subkey)
+}
+
+func aesGCM(key []byte) (cipher.AEAD, error) {
+	blk, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+	return cipher.NewGCM(blk)
+}
+
+// AESGCM creates a new Cipher with a pre-shared key. len(psk) must be
+// one of 16, 24, or 32 to select AES-128/196/256-GCM.
+func AESGCM(psk []byte) (Cipher, error) {
+	switch l := len(psk); l {
+	case 16, 24, 32: // AES 128/196/256
+	default:
+		return nil, aes.KeySizeError(l)
+	}
+	return &metaCipher{psk: psk, makeAEAD: aesGCM}, nil
+}
+
+// Chacha20Poly1305 creates a new Cipher with a pre-shared key. len(psk)
+// must be 32.
+func Chacha20Poly1305(psk []byte) (Cipher, error) {
+	if len(psk) != chacha20poly1305.KeySize {
+		return nil, KeySizeError(chacha20poly1305.KeySize)
+	}
+	return &metaCipher{psk: psk, makeAEAD: chacha20poly1305.New}, nil
+}
+
+// XChacha20Poly1305 creates a new Cipher with a pre-shared key. len(psk)
+// must be 32.
+func XChacha20Poly1305(psk []byte) (Cipher, error) {
+	if len(psk) != chacha20poly1305.KeySize {
+		return nil, KeySizeError(chacha20poly1305.KeySize)
+	}
+	return &metaCipher{psk: psk, makeAEAD: chacha20poly1305.NewX}, nil
+}