From c4b0da3703a28dd4a4aeecaf7a14ec835ac8bcfb Mon Sep 17 00:00:00 2001
From: Michele Balistreri <opensource@bitgamma.com>
Date: Wed, 18 Oct 2017 15:51:03 +0300
Subject: [PATCH] fix DERIVE KEY

---
 src/main/java/im/status/wallet/Crypto.java           | 8 ++++----
 src/main/java/im/status/wallet/WalletApplet.java     | 9 +++++----
 src/test/java/im/status/wallet/WalletAppletTest.java | 9 +++++++--
 3 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/src/main/java/im/status/wallet/Crypto.java b/src/main/java/im/status/wallet/Crypto.java
index 059648a..9ee0b1b 100644
--- a/src/main/java/im/status/wallet/Crypto.java
+++ b/src/main/java/im/status/wallet/Crypto.java
@@ -34,6 +34,7 @@ public class Crypto {
       hmacSHA512 = Signature.getInstance(Signature.ALG_HMAC_SHA_512, false);
       hmacKey = (HMACKey) KeyBuilder.buildKey(KeyBuilder.TYPE_HMAC_TRANSIENT_DESELECT, KEY_SECRET_SIZE, false);
     } catch (CryptoException e) {
+      hmacSHA512 = null;
       sha512 = MessageDigest.getInstance(MessageDigest.ALG_SHA_512, false);
       blockSize = HMAC_BLOCK_SIZE;
     }
@@ -49,7 +50,7 @@ public class Crypto {
       off += privateKey.getS(tmp, off);
     } else {
       off = (short) (publicKey.getW(tmp, (short) 0) - 1);
-      tmp[0] = ((tmp[(short) off] & 1) != 0 ? (byte) 0x03 : (byte) 0x02);
+      tmp[0] = ((tmp[off] & 1) != 0 ? (byte) 0x03 : (byte) 0x02);
       off = (short) ((short) (off / 2) + 1);
     }
 
@@ -63,7 +64,7 @@ public class Crypto {
 
     privateKey.getS(tmp, (short) 0);
 
-    addm256(tmp, off, tmp, (short) 0, SECP256k1.SECP256K1_R, (short)0, tmp, off);
+    addm256(tmp, off, tmp, (short) 0, SECP256k1.SECP256K1_R, (short) 0, tmp, off);
 
     if (isZero256(tmp, off)) {
       return false;
@@ -135,10 +136,9 @@ public class Crypto {
   }
 
   private static short add256(byte[] a, short aOff,  byte[] b, short bOff, byte[] out, short outOff) {
-
     short outI = 0;
     for (short i = 31 ; i >= 0 ; i--) {
-      outI = (short) ((short)(a[(short)(aOff + i)] & 0x00FF) + (short)(b[(short)(bOff + i)] & 0xFF) + outI);
+      outI = (short) ((short)(a[(short)(aOff + i)] & 0xFF) + (short)(b[(short)(bOff + i)] & 0xFF) + outI);
       out[(short)(outOff + i)] = (byte)outI ;
       outI = (short)(outI >> 8);
     }
diff --git a/src/main/java/im/status/wallet/WalletApplet.java b/src/main/java/im/status/wallet/WalletApplet.java
index 1fef6cc..227da5a 100644
--- a/src/main/java/im/status/wallet/WalletApplet.java
+++ b/src/main/java/im/status/wallet/WalletApplet.java
@@ -357,12 +357,13 @@ public class WalletApplet extends Applet {
       ISOException.throwIt(ISO7816.SW_WRONG_DATA);
     }
 
-    resetKeys(apduBuffer, len);
+    short chainEnd = (short) (ISO7816.OFFSET_CDATA + len);
+    resetKeys(apduBuffer, chainEnd);
 
-    for (short i = 0; i < len; i += 4) {
+    for (short i = ISO7816.OFFSET_CDATA; i < chainEnd; i += 4) {
       Crypto.bip32CKDPriv(apduBuffer, i, privateKey, publicKey, chainCode, (short) 0);
-      short pubLen = SECP256k1.derivePublicKey(privateKey, apduBuffer, (short) 0);
-      publicKey.setW(apduBuffer, (short) 0, pubLen);
+      short pubLen = SECP256k1.derivePublicKey(privateKey, apduBuffer, chainEnd);
+      publicKey.setW(apduBuffer, chainEnd, pubLen);
     }
   }
 
diff --git a/src/test/java/im/status/wallet/WalletAppletTest.java b/src/test/java/im/status/wallet/WalletAppletTest.java
index e23b136..4dd0766 100644
--- a/src/test/java/im/status/wallet/WalletAppletTest.java
+++ b/src/test/java/im/status/wallet/WalletAppletTest.java
@@ -399,10 +399,15 @@ public class WalletAppletTest {
     response = cmdSet.deriveKey(new byte[] {0x00, 0x00, 0x00});
     assertEquals(0x6A80, response.getSW());
 
-    // Correct example
-    response = cmdSet.deriveKey(new byte[] {0x00, 0x00, 0x00, 0x00});
+    // Correct
+    response = cmdSet.deriveKey(new byte[] {0x00, 0x00, 0x00, 0x01});
     assertEquals(0x9000, response.getSW());
     verifyKeyDerivation(keyPair, chainCode, new int[] { 1 });
+
+    // 3 level with hardned key
+    response = cmdSet.deriveKey(new byte[] {0x00, 0x00, 0x00, 0x01, (byte) 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02});
+    assertEquals(0x9000, response.getSW());
+    verifyKeyDerivation(keyPair, chainCode, new int[] { 1, 0x80000000, 2});
   }
 
   @Test