arti/Estonian-ID-card-mobile-authenticator-POC
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Merge pull request #6 from TanelOrumaa/nfc

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Adds a class for exchanging data with the ID-card over NFC.
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Lemmo Lavonen 2021-10-06 14:18:24 +03:00 committed by GitHub
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4
MobileAuthApp/app/build.gradle
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@ -55,4 +55,8 @@ dependencies {
//ViewModel
implementation "androidx.lifecycle:lifecycle-viewmodel-ktx:$lifecycle_version"
//For cryptography
implementation group: 'org.bouncycastle', name: 'bcprov-jdk15on', version: '1.69'
}

324
MobileAuthApp/app/src/main/java/com/tarkvaraprojekt/mobileauthapp/NFC/Comms.java Normal file
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@ -0,0 +1,324 @@
package com.tarkvaraprojekt.mobileauthapp.NFC;
import android.nfc.tech.IsoDep;
import android.util.Log;
import org.bouncycastle.crypto.BlockCipher;
import org.bouncycastle.crypto.engines.AESEngine;
import org.bouncycastle.crypto.macs.CMac;
import org.bouncycastle.crypto.params.KeyParameter;
import org.bouncycastle.jce.ECNamedCurveTable;
import org.bouncycastle.jce.spec.ECNamedCurveParameterSpec;
import org.bouncycastle.math.ec.ECPoint;
import org.bouncycastle.util.encoders.Hex;
import java.io.IOException;
import java.math.BigInteger;
import java.nio.charset.StandardCharsets;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.Arrays;
import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
public class Comms {
private static final byte[] master = { // select Main AID
0, -92, 4, 12, 16, -96, 0, 0, 0, 119, 1, 8, 0, 7, 0, 0, -2, 0, 0, 1, 0
};
private static final byte[] MSESetAT = { // manage security environment: set authentication template
0, 34, -63, -92, 15, -128, 10, 4, 0, 127, 0, 7, 2, 2, 4, 2, 4, -125, 1, 2, 0
};
private static final byte[] GAGetNonce = { // general authenticate: get nonce
16, -122, 0, 0, 2, 124, 0, 0
};
private static final byte[] GAMapNonceIncomplete = {
16, -122, 0, 0, 69, 124, 67, -127, 65
};
private static final byte[] GAKeyAgreementIncomplete = {
16, -122, 0, 0, 69, 124, 67, -125, 65
};
private static final byte[] GAMutualAuthenticationIncomplete = {
0, -122, 0, 0, 12, 124, 10, -123, 8
};
private static final byte[] dataForMACIncomplete = {
127, 73, 79, 6, 10, 4, 0, 127, 0, 7, 2, 2, 4, 2, 4, -122, 65
};
private static final byte[] masterSec = {
12, -92, 4, 12, 45, -121, 33, 1
};
private static final byte[] personal = { // select personal data DF
12, -92, 1, 12, 29, -121, 17, 1
};
private static final byte[] read = { // read binary
12, -80, 0, 0, 13, -105, 1, 0
};
private IsoDep idCard;
private final byte[] keyEnc;
private final byte[] keyMAC;
private byte ssc; // Send sequence counter.
/**
* The constructor performs PACE and stores the session keys
*
* @param idCard link to the card
* @param CAN the card authentication number
*/
public Comms(IsoDep idCard, String CAN) throws IOException, NoSuchPaddingException, InvalidKeyException, NoSuchAlgorithmException, IllegalBlockSizeException, BadPaddingException, InvalidAlgorithmParameterException {
idCard.connect();
this.idCard = idCard;
long start = System.currentTimeMillis();
byte[][] keys = PACE(CAN);
Log.i("Pace duration", String.valueOf(System.currentTimeMillis() - start));
keyEnc = keys[0];
keyMAC = keys[1];
}
/**
* Calculates the message authentication code
*
* @param APDU the byte array on which the CMAC algorithm is performed
* @param keyMAC the key for performing CMAC
* @return MAC
*/
private byte[] getMAC(byte[] APDU, byte[] keyMAC) {
BlockCipher blockCipher = new AESEngine();
CMac cmac = new CMac(blockCipher);
cmac.init(new KeyParameter(keyMAC));
cmac.update(APDU, 0, APDU.length);
byte[] MAC = new byte[cmac.getMacSize()];
cmac.doFinal(MAC, 0);
return Arrays.copyOf(MAC, 8);
}
/**
* Creates an application protocol data unit
*
* @param template the byte array to be used as a template
* @param data the data necessary for completing the APDU
* @param extra the missing length of the APDU being created
* @return the complete APDU
*/
private byte[] createAPDU(byte[] template, byte[] data, int extra) {
byte[] APDU = Arrays.copyOf(template, template.length + extra);
System.arraycopy(data, 0, APDU, template.length, data.length);
return APDU;
}
/**
* Creates a cipher key
*
* @param unpadded the array to be used as the basis for the key
* @param last the last byte in the appended padding
* @return the constructed key
*/
private byte[] createKey(byte[] unpadded, byte last) throws NoSuchAlgorithmException {
byte[] padded = Arrays.copyOf(unpadded, unpadded.length + 4);
padded[padded.length - 1] = last;
MessageDigest messageDigest = MessageDigest.getInstance("SHA-256");
return messageDigest.digest(padded);
}
/**
* Decrypts the nonce
*
* @param encryptedNonce the encrypted nonce received from the chip
* @param CAN the card access number provided by the user
* @return the decrypted nonce
*/
private byte[] decryptNonce(byte[] encryptedNonce, String CAN) throws NoSuchPaddingException, InvalidKeyException, NoSuchAlgorithmException, IllegalBlockSizeException, BadPaddingException, InvalidAlgorithmParameterException {
byte[] decryptionKey = createKey(CAN.getBytes(StandardCharsets.UTF_8), (byte) 3);
Cipher cipher = Cipher.getInstance("AES/CBC/NoPadding");
cipher.init(Cipher.DECRYPT_MODE, new SecretKeySpec(decryptionKey, "AES"), new IvParameterSpec(new byte[16]));
return cipher.doFinal(encryptedNonce);
}
/**
* Attempts to use the PACE protocol to create a secure channel with an Estonian ID-card
*
* @param CAN the card access number
*/
private byte[][] PACE(String CAN) throws IOException, NoSuchPaddingException, InvalidAlgorithmParameterException, NoSuchAlgorithmException, IllegalBlockSizeException, BadPaddingException, InvalidKeyException {
// select the ECC applet on the chip
byte[] response = idCard.transceive(master);
Log.i("Select applet", Hex.toHexString(response));
// initiate PACE
response = idCard.transceive(MSESetAT);
Log.i("Authentication template", Hex.toHexString(response));
// get nonce
response = idCard.transceive(GAGetNonce);
Log.i("Get nonce", Hex.toHexString(response));
byte[] decryptedNonce = decryptNonce(Arrays.copyOfRange(response, 4, response.length - 2), CAN);
// generate an EC keypair and exchange public keys with the chip
ECNamedCurveParameterSpec spec = ECNamedCurveTable.getParameterSpec("secp256r1");
BigInteger privateKey = new BigInteger(255, new SecureRandom()).add(BigInteger.ONE); // should be in [1, spec.getN()-1], but this is good enough for this application
ECPoint publicKey = spec.getG().multiply(privateKey).normalize();
byte[] APDU = createAPDU(GAMapNonceIncomplete, publicKey.getEncoded(false), 66);
response = idCard.transceive(APDU);
Log.i("Map nonce", Hex.toHexString(response));
ECPoint cardPublicKey = spec.getCurve().decodePoint(Arrays.copyOfRange(response, 4, 69));
// calculate the new base point, use it to generate a new keypair, and exchange public keys
ECPoint sharedSecret = cardPublicKey.multiply(privateKey);
ECPoint mappedECBasePoint = spec.getG().multiply(new BigInteger(1, decryptedNonce)).add(sharedSecret).normalize();
privateKey = new BigInteger(255, new SecureRandom()).add(BigInteger.ONE);
publicKey = mappedECBasePoint.multiply(privateKey).normalize();
APDU = createAPDU(GAKeyAgreementIncomplete, publicKey.getEncoded(false), 66);
response = idCard.transceive(APDU);
Log.i("Key agreement", Hex.toHexString(response));
cardPublicKey = spec.getCurve().decodePoint(Arrays.copyOfRange(response, 4, 69));
// generate the session keys and exchange MACs to verify them
sharedSecret = cardPublicKey.multiply(privateKey).normalize();
byte[] encodedSecret = sharedSecret.getAffineXCoord().getEncoded();
byte[] keyEnc = createKey(encodedSecret, (byte) 1);
byte[] keyMAC = createKey(encodedSecret, (byte) 2);
APDU = createAPDU(dataForMACIncomplete, cardPublicKey.getEncoded(false), 65);
byte[] MAC = getMAC(APDU, keyMAC);
APDU = createAPDU(GAMutualAuthenticationIncomplete, MAC, 9);
response = idCard.transceive(APDU);
Log.i("Mutual authentication", Hex.toHexString(response));
// if the chip-side verification fails, crash and burn
if (response.length == 2) throw new RuntimeException("Invalid CAN.");
// otherwise verify chip's MAC and return session keys
APDU = createAPDU(dataForMACIncomplete, publicKey.getEncoded(false), 65);
MAC = getMAC(APDU, keyMAC);
if (!Hex.toHexString(response, 4, 8).equals(Hex.toHexString(MAC))) {
throw new RuntimeException("Could not verify chip's MAC."); // Should never happen.
}
return new byte[][]{keyEnc, keyMAC};
}
/**
* Encrypts or decrypts the APDU data
*
* @param data the array containing the data to be processed
* @param mode indicates whether to en- or decrypt the data
* @return the result of encryption or decryption
*/
private byte[] encryptDecryptData(byte[] data, int mode) throws NoSuchPaddingException, NoSuchAlgorithmException, InvalidKeyException, BadPaddingException, IllegalBlockSizeException, InvalidAlgorithmParameterException {
SecretKeySpec secretKeySpec = new SecretKeySpec(keyEnc, "AES");
Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec);
byte[] iv = Arrays.copyOf(cipher.doFinal(new byte[]{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, ssc}), 16);
cipher = Cipher.getInstance("AES/CBC/NoPadding");
cipher.init(mode, secretKeySpec, new IvParameterSpec(iv));
return cipher.doFinal(data);
}
/**
* Constructs APDUs suitable for the secure channel.
*
* @param data the data to be encrypted
* @param incomplete the array to be used as a template
* @return the constructed APDU
*/
private byte[] createSecureAPDU(byte[] data, byte[] incomplete) throws NoSuchPaddingException, InvalidAlgorithmParameterException, NoSuchAlgorithmException, IllegalBlockSizeException, BadPaddingException, InvalidKeyException {
ssc++;
byte[] encryptedData = new byte[0];
int length = 16 * (1 + data.length / 16);
// construct the required array and calculate the MAC based on it
byte[] macData = new byte[data.length > 0 ? 48 + length : 48];
macData[15] = ssc; // first block contains the ssc
System.arraycopy(incomplete, 0, macData, 16, 4); // second block has the command
macData[20] = -128; // elements are terminated by 0x80 and zero-padded to the next block
System.arraycopy(incomplete, 5, macData, 32, 3); // third block contains appropriately encapsulated data/Le
if (data.length > 0) { // if the APDU has data, add padding and encrypt it
byte[] paddedData = Arrays.copyOf(data, length);
paddedData[data.length] = -128;
encryptedData = encryptDecryptData(paddedData, Cipher.ENCRYPT_MODE);
System.arraycopy(encryptedData, 0, macData, 35, encryptedData.length);
}
macData[35 + encryptedData.length] = -128;
byte[] MAC = getMAC(macData, keyMAC);
// construct the APDU using the encrypted data and the MAC
byte[] APDU = new byte[incomplete.length + encryptedData.length + MAC.length + 3];
System.arraycopy(incomplete, 0, APDU, 0, incomplete.length);
if (encryptedData.length > 0) {
System.arraycopy(encryptedData, 0, APDU, incomplete.length, encryptedData.length);
}
System.arraycopy(new byte[]{-114, 8}, 0, APDU, incomplete.length + encryptedData.length, 2); // MAC is encapsulated using the tag 0x8E
System.arraycopy(MAC, 0, APDU, incomplete.length + encryptedData.length + 2, MAC.length);
ssc++;
return APDU;
}
/**
* Gets the contents of the personal data dedicated file
*
* @param FID the last bytes of file identifiers being requested
* @return array containing the data strings
*
*/
public String[] readPersonalData(byte[] FID) throws NoSuchPaddingException, InvalidKeyException, NoSuchAlgorithmException, IllegalBlockSizeException, BadPaddingException, InvalidAlgorithmParameterException, IOException {
String[] personalData = new String[FID.length];
byte[] data;
byte[] APDU;
byte[] response;
// select the personal data dedicated file
data = new byte[]{80, 0}; // personal data DF FID
APDU = createSecureAPDU(data, personal);
response = idCard.transceive(APDU);
Log.i("Select personal data DF", Hex.toHexString(response));
// select and read the first 8 elementary files in the DF
for (int i = 0; i < FID.length; i++) {
byte index = FID[i];
if (index > 15 || index < 1) throw new RuntimeException("Invalid personal data FID.");
data[1] = index;
APDU = createSecureAPDU(data, personal);
response = idCard.transceive(APDU);
Log.i(String.format("Select EF 500%d", index), Hex.toHexString(response));
APDU = createSecureAPDU(new byte[0], read);
response = idCard.transceive(APDU);
Log.i(String.format("Read binary EF 500%d", index), Hex.toHexString(response));
// store the decrypted datum
byte[] raw = encryptDecryptData(Arrays.copyOfRange(response, 3, 19), Cipher.DECRYPT_MODE);
int indexOfTerminator = Hex.toHexString(raw).lastIndexOf("80") / 2;
personalData[i] = new String(Arrays.copyOfRange(raw, 0, indexOfTerminator));
}
return personalData;
}
}

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gradle.properties Normal file
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