From 8a06c7d07485973541ef0b189c99708ac4270056 Mon Sep 17 00:00:00 2001
From: Michele Balistreri <opensource@bitgamma.com>
Date: Wed, 27 Sep 2017 15:22:34 +0300
Subject: [PATCH] implement CHANGE PIN

---
 .../java/im/status/wallet/SecureChannel.java  |  6 ++-
 .../java/im/status/wallet/WalletApplet.java   | 28 ++++++++++++-
 .../status/wallet/WalletAppletCommandSet.java |  5 +++
 .../im/status/wallet/WalletAppletTest.java    | 40 +++++++++++++++++++
 4 files changed, 75 insertions(+), 4 deletions(-)

diff --git a/src/main/java/im/status/wallet/SecureChannel.java b/src/main/java/im/status/wallet/SecureChannel.java
index bcd10d9..e7b98dc 100644
--- a/src/main/java/im/status/wallet/SecureChannel.java
+++ b/src/main/java/im/status/wallet/SecureChannel.java
@@ -53,7 +53,7 @@ public class SecureChannel {
     apdu.setOutgoingAndSend((short) 0, SC_SECRET_LENGTH);
   }
 
-  public short decryptAPDU(byte[] apduBuffer) {
+  public byte decryptAPDU(byte[] apduBuffer) {
     scCipher.init(scKey, Cipher.MODE_DECRYPT, apduBuffer, ISO7816.OFFSET_CDATA, SC_BLOCK_SIZE);
     short len = scCipher.doFinal(apduBuffer, (short)(ISO7816.OFFSET_CDATA + SC_BLOCK_SIZE), (short) (apduBuffer[ISO7816.OFFSET_LC] - SC_BLOCK_SIZE), apduBuffer, ISO7816.OFFSET_CDATA);
 
@@ -61,7 +61,9 @@ public class SecureChannel {
       len--;
     }
 
-    return (short) (len - 1);
+    apduBuffer[ISO7816.OFFSET_LC] = (byte) (len - 1);
+
+    return apduBuffer[ISO7816.OFFSET_LC];
   }
 
   public short encryptAPDU(byte[] apduBuffer, short len) {
diff --git a/src/main/java/im/status/wallet/WalletApplet.java b/src/main/java/im/status/wallet/WalletApplet.java
index 703e6a1..d020aff 100644
--- a/src/main/java/im/status/wallet/WalletApplet.java
+++ b/src/main/java/im/status/wallet/WalletApplet.java
@@ -88,9 +88,9 @@ public class WalletApplet extends Applet {
     }
 
     byte[] apduBuffer = apdu.getBuffer();
-    short len = secureChannel.decryptAPDU(apduBuffer);
+    byte len = secureChannel.decryptAPDU(apduBuffer);
 
-    if (!ownerPIN.check(apduBuffer, ISO7816.OFFSET_CDATA, (byte) len)) {
+    if (!ownerPIN.check(apduBuffer, ISO7816.OFFSET_CDATA, len)) {
       ISOException.throwIt((short)((short) 0x63c0 | (short) ownerPIN.getTriesRemaining()));
     }
   }
@@ -101,6 +101,16 @@ public class WalletApplet extends Applet {
     if (!(secureChannel.isOpen() && ownerPIN.isValidated())) {
       ISOException.throwIt(ISO7816.SW_CONDITIONS_NOT_SATISFIED);
     }
+
+    byte[] apduBuffer = apdu.getBuffer();
+    byte len = secureChannel.decryptAPDU(apduBuffer);
+
+    if (!(len == 6 && allDigits(apduBuffer, ISO7816.OFFSET_CDATA, len))) {
+      ISOException.throwIt(ISO7816.SW_WRONG_DATA);
+    }
+
+    ownerPIN.update(apduBuffer, ISO7816.OFFSET_CDATA, len);
+    ownerPIN.check(apduBuffer, ISO7816.OFFSET_CDATA, len);
   }
 
   private void unblockPIN(APDU apdu) {
@@ -126,4 +136,18 @@ public class WalletApplet extends Applet {
       ISOException.throwIt(ISO7816.SW_CONDITIONS_NOT_SATISFIED);
     }
   }
+
+  private boolean allDigits(byte[] buffer, short off, short len) {
+    while(len > 0) {
+      len--;
+
+      byte c = buffer[(short)(off+len)];
+
+      if (c < 0x30 || c > 0x39) {
+        return false;
+      }
+    }
+
+    return true;
+  }
 }
diff --git a/src/test/java/im/status/wallet/WalletAppletCommandSet.java b/src/test/java/im/status/wallet/WalletAppletCommandSet.java
index ac064fe..877692c 100644
--- a/src/test/java/im/status/wallet/WalletAppletCommandSet.java
+++ b/src/test/java/im/status/wallet/WalletAppletCommandSet.java
@@ -35,4 +35,9 @@ public class WalletAppletCommandSet {
     CommandAPDU verifyPIN = new CommandAPDU(0x80, WalletApplet.INS_VERIFY_PIN, 0, 0, secureChannel.encryptAPDU(pin.getBytes()));
     return apduChannel.transmit(verifyPIN);
   }
+
+  public ResponseAPDU changePIN(String pin) throws CardException {
+    CommandAPDU changePIN = new CommandAPDU(0x80, WalletApplet.INS_CHANGE_PIN, 0, 0, secureChannel.encryptAPDU(pin.getBytes()));
+    return apduChannel.transmit(changePIN);
+  }
 }
diff --git a/src/test/java/im/status/wallet/WalletAppletTest.java b/src/test/java/im/status/wallet/WalletAppletTest.java
index 236e66c..76b2f4d 100644
--- a/src/test/java/im/status/wallet/WalletAppletTest.java
+++ b/src/test/java/im/status/wallet/WalletAppletTest.java
@@ -95,4 +95,44 @@ public class WalletAppletTest {
 
     //TODO: Unblock PIN to make the test non-destructive
   }
+
+  @Test
+  @DisplayName("CHANGE PIN command")
+  void changePinTest() throws CardException {
+    ResponseAPDU response = cmdSet.changePIN("123456");
+    assertEquals(0x6985, response.getSW());
+
+    cmdSet.openSecureChannel();
+
+    response = cmdSet.changePIN("123456");
+    assertEquals(0x6985, response.getSW());
+
+    response = cmdSet.verifyPIN("000000");
+    assertEquals(0x9000, response.getSW());
+
+    response = cmdSet.changePIN("123456");
+    assertEquals(0x9000, response.getSW());
+
+    response = cmdSet.changePIN("654321");
+    assertEquals(0x9000, response.getSW());
+
+    apduChannel.getCard().getATR();
+    cmdSet.select();
+    cmdSet.openSecureChannel();
+
+    response = cmdSet.verifyPIN("654321");
+    assertEquals(0x9000, response.getSW());
+
+    response = cmdSet.changePIN("654a21");
+    assertEquals(0x6A80, response.getSW());
+
+    response = cmdSet.changePIN("54321");
+    assertEquals(0x6A80, response.getSW());
+
+    response = cmdSet.changePIN("7654321");
+    assertEquals(0x6A80, response.getSW());
+
+    response = cmdSet.changePIN("000000");
+    assertEquals(0x9000, response.getSW());
+  }
 }