simplify PIN verification

lib/src/main/java/im/status/keycard/applet/KeycardCommandSet.java

@@ -1,9 +1,6 @@
 package im.status.keycard.applet;
 
-import im.status.keycard.io.APDUCommand;
-import im.status.keycard.io.APDUException;
-import im.status.keycard.io.APDUResponse;
-import im.status.keycard.io.CardChannel;
+import im.status.keycard.io.*;
 import org.bouncycastle.jce.interfaces.ECPrivateKey;
 import org.bouncycastle.jce.interfaces.ECPublicKey;
 
@@ -74,11 +71,19 @@ public class KeycardCommandSet {
   private final CardChannel apduChannel;
   private SecureChannelSession secureChannel;
 
+  /**
+   * Creates a KeycardCommandSet using the given APDU Channel
+   * @param apduChannel APDU channel
+   */
   public KeycardCommandSet(CardChannel apduChannel) {
     this.apduChannel = apduChannel;
     this.secureChannel = new SecureChannelSession();
   }
 
+  /**
+   * Set the SecureChannel object
+   * @param secureChannel secure channel
+   */
   protected void setSecureChannel(SecureChannelSession secureChannel) {
     this.secureChannel = secureChannel;
   }
@@ -257,7 +262,7 @@ public class KeycardCommandSet {
    * Sends a VERIFY PIN APDU. The raw bytes of the given string are encrypted using the secure channel and used as APDU
    * data.
    *
-   * @param pin the pin
+   * @param pin the PIN
    * @return the raw card response
    * @throws IOException communication error
    */

lib/src/main/java/im/status/keycard/io/APDUResponse.java

@@ -10,6 +10,7 @@ public class APDUResponse {
   public static final int SW_CARD_LOCKED = 0x6283;
   public static final int SW_REFERENCED_DATA_NOT_FOUND = 0x6A88;
   public static final int SW_CONDITIONS_OF_USE_NOT_SATISFIED = 0x6985; // applet may be already installed
+  public static final int SW_WRONG_PIN_MASK = 0x63C0;
 
   private byte[] apdu;
   private byte[] data;
@@ -87,6 +88,20 @@ public class APDUResponse {
     }
   }
 
+  /**
+   * Checks response from an authentication command (VERIFY PIN, UNBLOCK PUK)
+   *
+   * @throws WrongPINException wrong PIN
+   * @throws APDUException unexpected response
+   */
+  public APDUResponse checkAuthOK() throws WrongPINException, APDUException {
+    if ((this.sw & SW_WRONG_PIN_MASK) == SW_WRONG_PIN_MASK) {
+      throw new WrongPINException(sw2 & 0x0F);
+    } else {
+      return checkOK();
+    }
+  }
+
   /**
    * Returns the data field of this APDU.
    *

lib/src/main/java/im/status/keycard/io/WrongPINException.java

@@ -0,0 +1,27 @@
+package im.status.keycard.io;
+
+/**
+ * Exception thrown when checking PIN/PUK
+ */
+public class WrongPINException extends APDUException {
+  private int retryAttempts;
+
+  /**
+   * Construct an exception with the given number of retry attempts.
+   *
+   * @param retryAttempts the number of retry attempts
+   */
+  public WrongPINException(int retryAttempts) {
+    super("Wrong PIN");
+    this.retryAttempts = retryAttempts;
+  }
+
+  /**
+   * Returns the number of available retry attempts.
+   *
+   * @return the number of retry attempts
+   */
+  public int getRetryAttempts() {
+    return retryAttempts;
+  }
+}