add key derivation and change AEAD in session, not working right now :(

crypto/key_derivation.go

@@ -0,0 +1,43 @@
+package crypto
+
+import (
+	"bytes"
+	"crypto/sha256"
+	"io"
+
+	"github.com/lucas-clemente/quic-go/protocol"
+	"github.com/lucas-clemente/quic-go/utils"
+
+	"golang.org/x/crypto/hkdf"
+)
+
+// DeriveKeysAESGCM derives the client and server keys and creates a matching AES-GCM instance
+func DeriveKeysAESGCM(sharedSecret, nonces []byte, connID protocol.ConnectionID, chlo []byte, scfg []byte) (AEAD, error) {
+	var info bytes.Buffer
+	info.Write([]byte("QUIC key expansion\x00"))
+	utils.WriteUint64(&info, uint64(connID))
+	info.Write(chlo)
+	info.Write(scfg)
+
+	r := hkdf.New(sha256.New, sharedSecret, nonces, info.Bytes())
+
+	otherKey := make([]byte, 16)
+	myKey := make([]byte, 16)
+	otherIV := make([]byte, 4)
+	myIV := make([]byte, 4)
+
+	if _, err := io.ReadFull(r, otherKey); err != nil {
+		return nil, err
+	}
+	if _, err := io.ReadFull(r, myKey); err != nil {
+		return nil, err
+	}
+	if _, err := io.ReadFull(r, otherIV); err != nil {
+		return nil, err
+	}
+	if _, err := io.ReadFull(r, myIV); err != nil {
+		return nil, err
+	}
+
+	return NewAEADAESGCM(otherKey, myKey, otherIV, myIV)
+}