src/org/average/nfcauthcr/YkNeo.java

   1 package org.average.nfcauthcr;
   2
   3 import java.io.IOException;
   4 import java.lang.String;
   5 import java.util.ArrayList;
   6 import java.util.Arrays;
   7
   8 import android.nfc.NfcAdapter;
   9 import android.nfc.Tag;
  10 import android.nfc.tech.IsoDep;
  11
  12 import org.average.nfcauthcr.CRException;
  13
  14 public class YkNeo {
  15
  16         // http://forum.yubico.com/viewtopic.php?\
  17         //              f=26&t=1053&sid=2a11c0f97306e4b699bf67502b7a754a
  18         // CCID APDU, ISO 7816-4.
  19
  20         // Start with Select APDU:
  21         // CLA INS P1 P2 Lc AID Le
  22         //  00  A4 04 00                - GlobalPlatform - Application Select
  23         // Lc = 07
  24         //   A0 00 00 05 27
  25         //      Yubico's RID (Registered application provider IDentifier)
  26         //   20 01
  27         //      PIX (Proprietary application Identifier eXtension)
  28         //      for the Yubikey2 applet
  29         // Le = 00
  30         private static final byte[] selectApdu =
  31                 {0x00, (byte) 0xA4, 0x04, 0x00, 0x07, (byte) 0xA0,
  32                  0x00, 0x00, 0x05, 0x27, 0x20, 0x01, 0x00};
  33
  34         // Application APDUs:
  35         // CLA INS P1 P2
  36         //  00  01 YK 00
  37         //   YK is the one-byte command&slot code as in the USB interface
  38         //   Lc + data bytes follow
  39         //   Le is optional
  40         private static final byte SLOT_CHAL_HMAC1 = 0x30;
  41         private static final byte SLOT_CHAL_HMAC2 = 0x38;
  42
  43         public static ArrayList<String> doChalResp(IsoDep isoTag, int slot,
  44                                         ArrayList<String> cset)
  45                         throws IOException, CRException {
  46                 byte[] challenge = unhex(cset.get(0));
  47                 if (challenge.length > 127) {
  48                         throw new CRException(String.format(
  49                         "NFC challenge size too big: %d",
  50                         challenge.length));
  51                 }
  52                 if (slot != 1 && slot != 2) {
  53                         throw new CRException(String.format(
  54                         "NFC Yubikey slot is %d, can be 1 or 2",
  55                         slot));
  56                 }
  57                 byte[] resp = isoTag.transceive(selectApdu);
  58                 int length = resp.length;
  59                 if (resp[length - 2] != (byte)0x90 ||
  60                     resp[length - 1] != 0x00) {
  61                         throw new CRException(String.format(
  62                         "NFC select error code: %02x:%02x",
  63                         resp[length - 2], resp[length - 1]));
  64                 }
  65                 byte[] crApdu = new byte[6+challenge.length];
  66                 crApdu[0] = 0x00; // CLA
  67                 crApdu[1] = 0x01; // INS
  68                 switch (slot) {
  69                 case 1: crApdu[2] = SLOT_CHAL_HMAC1; break; // P1
  70                 case 2: crApdu[2] = SLOT_CHAL_HMAC2; break; // P1
  71                 }
  72                 crApdu[3] = 0x00; // P2
  73                 crApdu[4] = (byte)challenge.length; // Lc
  74                 System.arraycopy(challenge, 0, crApdu, 5,
  75                                         challenge.length); // Payload
  76                 crApdu[5+challenge.length] = 22; // Le
  77                 resp = isoTag.transceive(crApdu);
  78                 length = resp.length;
  79                 if (resp[length - 2] != (byte)0x90 ||
  80                     resp[length - 1] != 0x00) {
  81                         throw new CRException(String.format(
  82                         "NFC CR error code: %02x:%02x",
  83                         resp[length - 2], resp[length - 1]));
  84                 }
  85                 if (length <= 2) {
  86                         throw new CRException(String.format(
  87                         "NFC wrong response size: only %d bytes",
  88                         length-2));
  89                 }
  90                 ArrayList<String> rset = new ArrayList<String>();
  91                 rset.add(hex(Arrays.copyOf(resp, length-2)));
  92                 return rset;
  93         }
  94
  95         private static String hex(byte[] a) {
  96                 StringBuilder sb = new StringBuilder();
  97                 if (a == null) return "<null>";
  98                 for (byte b: a) sb.append(String.format("%02x", b&0xff));
  99                 return sb.toString();
 100         }
 101
 102         private static byte[] unhex(String s) {
 103                 int len = s.length();
 104                 if ((len % 2) != 0) return null;
 105                 byte[] b = new byte[len / 2];
 106                 for (int i = 0; i < len; i += 2) {
 107                         b[i / 2] = (byte)Integer.parseInt(
 108                                                 s.substring(i,i+2), 16);
 109                 }
 110                 return b;
 111         }
 112 }