implementation for Shadowsocks AEAD

common/crypto/auth.go

@@ -29,6 +29,26 @@ func (v StaticBytesGenerator) Next() []byte {
 	return v.Content
 }
 
+type IncreasingAEADNonceGenerator struct {
+	nonce []byte
+}
+
+func NewIncreasingAEADNonceGenerator() *IncreasingAEADNonceGenerator {
+	return &IncreasingAEADNonceGenerator{
+		nonce: []byte{0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF},
+	}
+}
+
+func (g *IncreasingAEADNonceGenerator) Next() []byte {
+	for i := range g.nonce {
+		g.nonce[i]++
+		if g.nonce[i] != 0 {
+			break
+		}
+	}
+	return g.nonce
+}
+
 type Authenticator interface {
 	NonceSize() int
 	Overhead() int

common/crypto/chunk.go

@@ -34,6 +34,29 @@ func (PlainChunkSizeParser) Decode(b []byte) (uint16, error) {
 	return serial.BytesToUint16(b), nil
 }
 
+type AEADChunkSizeParser struct {
+	Auth *AEADAuthenticator
+}
+
+func (p *AEADChunkSizeParser) SizeBytes() int {
+	return 2 + p.Auth.Overhead()
+}
+
+func (p *AEADChunkSizeParser) Encode(size uint16, b []byte) []byte {
+	b = serial.Uint16ToBytes(size, b)
+	b, err := p.Auth.Seal(b[:0], b)
+	common.Must(err)
+	return b
+}
+
+func (p *AEADChunkSizeParser) Decode(b []byte) (uint16, error) {
+	b, err := p.Auth.Open(b[:0], b)
+	if err != nil {
+		return 0, err
+	}
+	return serial.BytesToUint16(b), nil
+}
+
 type ChunkStreamReader struct {
 	sizeDecoder ChunkSizeDecoder
 	reader      buf.Reader