add NullAEAD implementation

crypto/NullAEAD.go

@@ -0,0 +1,38 @@
+package crypto
+
+import (
+	"bytes"
+	"encoding/binary"
+	"errors"
+	"io"
+	"io/ioutil"
+)
+
+// NullAEAD handles not-yet encrypted packets
+type NullAEAD struct{}
+
+var _ AEAD = &NullAEAD{}
+
+// Open and verify the ciphertext
+func (*NullAEAD) Open(associatedData []byte, r io.Reader) (io.Reader, error) {
+	ciphertext, err := ioutil.ReadAll(r)
+	if err != nil {
+		return nil, err
+	}
+	if len(ciphertext) < 12 {
+		return nil, errors.New("NullAEAD: ciphertext cannot be less than 12 bytes long")
+	}
+
+	hash := New128a()
+	hash.Write(associatedData)
+	hash.Write(ciphertext[12:])
+	testHigh, testLow := hash.Sum128()
+
+	low := binary.LittleEndian.Uint64(ciphertext)
+	high := binary.LittleEndian.Uint32(ciphertext[8:])
+
+	if uint32(testHigh&0xffffffff) != high || testLow != low {
+		return nil, errors.New("NullAEAD: failed to authenticate received data")
+	}
+	return bytes.NewReader(ciphertext[12:]), nil
+}

crypto/NullAEAD_test.go

@@ -0,0 +1,25 @@
+package crypto_test
+
+import (
+	"bytes"
+	"io/ioutil"
+
+	"github.com/lucas-clemente/quic-go/crypto"
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+)
+
+var _ = Describe("Crypto/NullAEAD", func() {
+	It("opens", func() {
+		aad := []byte("All human beings are born free and equal in dignity and rights.")
+		plainText := []byte("They are endowed with reason and conscience and should act towards one another in a spirit of brotherhood.")
+		hash := []byte{0x98, 0x9b, 0x33, 0x3f, 0xe8, 0xde, 0x32, 0x5c, 0xa6, 0x7f, 0x9c, 0xf7}
+		cipherText := append(hash, plainText...)
+		aead := &crypto.NullAEAD{}
+		r, err := aead.Open(aad, bytes.NewReader(cipherText))
+		Expect(err).ToNot(HaveOccurred())
+		res, err := ioutil.ReadAll(r)
+		Expect(err).ToNot(HaveOccurred())
+		Expect(res).To(Equal([]byte("They are endowed with reason and conscience and should act towards one another in a spirit of brotherhood.")))
+	})
+})