From 1cdee35414aca2d55a892a1af6ba7dc9af623232 Mon Sep 17 00:00:00 2001
From: Andrea Franz <andrea@gravityblast.com>
Date: Sat, 27 Oct 2018 18:52:39 +0200
Subject: [PATCH] open secure channel

---
 lightwallet/actions/actions.go | 22 ++++++++++++++++++----
 lightwallet/secure_channel.go  | 13 +++++++++++++
 2 files changed, 31 insertions(+), 4 deletions(-)

diff --git a/lightwallet/actions/actions.go b/lightwallet/actions/actions.go
index 13d41b1..ce4b246 100644
--- a/lightwallet/actions/actions.go
+++ b/lightwallet/actions/actions.go
@@ -3,6 +3,7 @@ package actions
 import (
 	"crypto/rand"
 	"crypto/sha256"
+	"crypto/sha512"
 	"errors"
 	"fmt"
 
@@ -105,16 +106,29 @@ func Pair(c globalplatform.Channel, pairingPass string, pin string) (*lightwalle
 	}, nil
 }
 
-func OpenSecureChannel(c globalplatform.Channel, appInfo *lightwallet.ApplicationInfo, pairingIndex uint8, pairingKey []byte) error {
+func OpenSecureChannel(c globalplatform.Channel, appInfo *lightwallet.ApplicationInfo, pairingIndex uint8, pairingKey []byte) (*lightwallet.SecureChannel, error) {
 	sc, err := lightwallet.NewSecureChannel(c, appInfo.PublicKey)
-
 	cmd := lightwallet.NewCommandOpenSecureChannel(pairingIndex, sc.RawPublicKey())
 	resp, err := c.Send(cmd)
 	if err = checkOKResponse(err, resp); err != nil {
-		return err
+		return nil, err
 	}
 
-	return nil
+	salt := resp.Data[:32]
+	iv := resp.Data[32:]
+
+	h := sha512.New()
+	h.Write(sc.Secret())
+	h.Write(pairingKey)
+	h.Write(salt)
+	data := h.Sum(nil)
+
+	encKey := data[:32]
+	macKey := data[32:]
+
+	sc.Init(iv, encKey, macKey)
+
+	return sc, nil
 }
 
 func parseApplicationInfo(resp *apdu.Response) (*lightwallet.ApplicationInfo, error) {
diff --git a/lightwallet/secure_channel.go b/lightwallet/secure_channel.go
index 04bc3ba..c46b9ad 100644
--- a/lightwallet/secure_channel.go
+++ b/lightwallet/secure_channel.go
@@ -13,6 +13,9 @@ type SecureChannel struct {
 	c         globalplatform.Channel
 	secret    []byte
 	publicKey *ecdsa.PublicKey
+	encKey    []byte
+	macKey    []byte
+	iv        []byte
 }
 
 func NewSecureChannel(c globalplatform.Channel, cardKeyData []byte) (*SecureChannel, error) {
@@ -35,6 +38,16 @@ func NewSecureChannel(c globalplatform.Channel, cardKeyData []byte) (*SecureChan
 	}, nil
 }
 
+func (sc *SecureChannel) Init(iv, encKey, macKey []byte) {
+	sc.iv = iv
+	sc.encKey = encKey
+	sc.macKey = macKey
+}
+
+func (sc *SecureChannel) Secret() []byte {
+	return sc.secret
+}
+
 func (sc *SecureChannel) PublicKey() *ecdsa.PublicKey {
 	return sc.publicKey
 }