Review

class SecureMessagingWrapper {
   /*@ requires apdu != null && 4 <= len && len <= apdu.length;
    */
   private byte[] wrapCommandAPDU(byte[] capdu, int len)
   throws GeneralSecurityException, IOException {
      if (capdu == null || capdu.length < 4 || len < 4) {
         throw new IllegalArgumentException("Invalid type");
      }

      /* Determine lc and le... */
      int lc = 0;
      int le = capdu[len - 1] & 0x000000FF;
      if (len == 4) {
         lc = 0;
         le = 0;
      } else if (len == 5) {
         /* No command data, byte at index 5 is le. */
         lc = 0;
      } else if (len > 5) {
         /* Byte at index 5 is not le, so it must be lc. */
         lc = capdu[ISO7816.OFFSET_LC] & 0x000000FF;
      }
      if (4 + lc >= len) {
         /* Value of lc covers rest of apdu length, there is no le. */
         le = 0;
      }

      ByteArrayOutputStream out = new ByteArrayOutputStream();

      byte[] maskedHeader = new byte[4];
      System.arraycopy(capdu, 0, maskedHeader, 0, 4);
      maskedHeader[ISO7816.OFFSET_CLA] = (byte)0x0C;
      byte[] paddedHeader = Util.pad(maskedHeader);

      byte[] do87 = new byte[0];
      byte[] do8E = new byte[0];
      byte[] do97 = new byte[0];

      if (le > 0) {
         out.reset();
         out.write((byte)0x97);
         out.write((byte)0x01);
         out.write((byte)le);
         do97 = out.toByteArray();
      }

      if (lc > 0) {
         byte[] data = Util.pad(capdu, ISO7816.OFFSET_CDATA, lc);
         cipher.init(Cipher.ENCRYPT_MODE, ksEnc, ZERO_IV_PARAM_SPEC);
         byte[] ciphertext = cipher.doFinal(data);

         out.reset();
         out.write((byte)0x87);
         out.write((byte)(ciphertext.length + 1));
         out.write(0x01);
         out.write(ciphertext, 0, ciphertext.length);
         do87 = out.toByteArray();
      }

      out.reset();
      out.write(paddedHeader, 0, paddedHeader.length);
      out.write(do87, 0, do87.length);
      out.write(do97, 0, do97.length);
      byte[] m = out.toByteArray();

      out.reset();
      DataOutputStream dataOut = new DataOutputStream(out);
      ssc++;
      dataOut.writeLong(ssc);
      dataOut.write(m, 0, m.length);
      dataOut.flush();
      byte[] n = Util.pad(out.toByteArray());

      /* Compute cryptographic checksum... */
      mac.init(ksMac);
      byte[] cc = mac.doFinal(n);
      // ssc++; // TODO dit snappen

      out.reset();
      out.write((byte)0x8E);
      out.write(cc.length);
      out.write(cc, 0, cc.length);
      do8E = out.toByteArray();

      /* Construct protected apdu... */
      out.reset();
      out.write(maskedHeader, 0, 4);
      out.write((byte)(do87.length + do97.length + do8E.length));
      out.write(do87, 0, do87.length);
      out.write(do97, 0, do97.length);
      out.write(do8E, 0, do8E.length);
      out.write(0x00);

      return out.toByteArray();
   }

}