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Diffstat (limited to 'samples/browseable/CardEmulation/src/com.example.android.cardemulation/CardService.java')
| -rw-r--r-- | samples/browseable/CardEmulation/src/com.example.android.cardemulation/CardService.java | 173 |
1 files changed, 173 insertions, 0 deletions
diff --git a/samples/browseable/CardEmulation/src/com.example.android.cardemulation/CardService.java b/samples/browseable/CardEmulation/src/com.example.android.cardemulation/CardService.java new file mode 100644 index 000000000..a409d28f4 --- /dev/null +++ b/samples/browseable/CardEmulation/src/com.example.android.cardemulation/CardService.java @@ -0,0 +1,173 @@ +/* + * Copyright (C) 2013 The Android Open Source Project + * + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +package com.example.android.cardemulation; + +import android.nfc.cardemulation.HostApduService; +import android.os.Bundle; +import com.example.android.common.logger.Log; + +import java.util.Arrays; + +/** + * This is a sample APDU Service which demonstrates how to interface with the card emulation support + * added in Android 4.4, KitKat. + * + * <p>This sample replies to any requests sent with the string "Hello World". In real-world + * situations, you would need to modify this code to implement your desired communication + * protocol. + * + * <p>This sample will be invoked for any terminals selecting AIDs of 0xF11111111, 0xF22222222, or + * 0xF33333333. See src/main/res/xml/aid_list.xml for more details. + * + * <p class="note">Note: This is a low-level interface. Unlike the NdefMessage many developers + * are familiar with for implementing Android Beam in apps, card emulation only provides a + * byte-array based communication channel. It is left to developers to implement higher level + * protocol support as needed. + */ +public class CardService extends HostApduService { + private static final String TAG = "CardService"; + // AID for our loyalty card service. + private static final String SAMPLE_LOYALTY_CARD_AID = "F222222222"; + // ISO-DEP command HEADER for selecting an AID. + // Format: [Class | Instruction | Parameter 1 | Parameter 2] + private static final String SELECT_APDU_HEADER = "00A40400"; + // "OK" status word sent in response to SELECT AID command (0x9000) + private static final byte[] SELECT_OK_SW = HexStringToByteArray("9000"); + // "UNKNOWN" status word sent in response to invalid APDU command (0x0000) + private static final byte[] UNKNOWN_CMD_SW = HexStringToByteArray("0000"); + private static final byte[] SELECT_APDU = BuildSelectApdu(SAMPLE_LOYALTY_CARD_AID); + + /** + * Called if the connection to the NFC card is lost, in order to let the application know the + * cause for the disconnection (either a lost link, or another AID being selected by the + * reader). + * + * @param reason Either DEACTIVATION_LINK_LOSS or DEACTIVATION_DESELECTED + */ + @Override + public void onDeactivated(int reason) { } + + /** + * This method will be called when a command APDU has been received from a remote device. A + * response APDU can be provided directly by returning a byte-array in this method. In general + * response APDUs must be sent as quickly as possible, given the fact that the user is likely + * holding his device over an NFC reader when this method is called. + * + * <p class="note">If there are multiple services that have registered for the same AIDs in + * their meta-data entry, you will only get called if the user has explicitly selected your + * service, either as a default or just for the next tap. + * + * <p class="note">This method is running on the main thread of your application. If you + * cannot return a response APDU immediately, return null and use the {@link + * #sendResponseApdu(byte[])} method later. + * + * @param commandApdu The APDU that received from the remote device + * @param extras A bundle containing extra data. May be null. + * @return a byte-array containing the response APDU, or null if no response APDU can be sent + * at this point. + */ + // BEGIN_INCLUDE(processCommandApdu) + @Override + public byte[] processCommandApdu(byte[] commandApdu, Bundle extras) { + Log.i(TAG, "Received APDU: " + ByteArrayToHexString(commandApdu)); + // If the APDU matches the SELECT AID command for this service, + // send the loyalty card account number, followed by a SELECT_OK status trailer (0x9000). + if (Arrays.equals(SELECT_APDU, commandApdu)) { + String account = AccountStorage.GetAccount(this); + byte[] accountBytes = account.getBytes(); + Log.i(TAG, "Sending account number: " + account); + return ConcatArrays(accountBytes, SELECT_OK_SW); + } else { + return UNKNOWN_CMD_SW; + } + } + // END_INCLUDE(processCommandApdu) + + /** + * Build APDU for SELECT AID command. This command indicates which service a reader is + * interested in communicating with. See ISO 7816-4. + * + * @param aid Application ID (AID) to select + * @return APDU for SELECT AID command + */ + public static byte[] BuildSelectApdu(String aid) { + // Format: [CLASS | INSTRUCTION | PARAMETER 1 | PARAMETER 2 | LENGTH | DATA] + return HexStringToByteArray(SELECT_APDU_HEADER + String.format("%02X", + aid.length() / 2) + aid); + } + + /** + * Utility method to convert a byte array to a hexadecimal string. + * + * @param bytes Bytes to convert + * @return String, containing hexadecimal representation. + */ + public static String ByteArrayToHexString(byte[] bytes) { + final char[] hexArray = {'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'}; + char[] hexChars = new char[bytes.length * 2]; // Each byte has two hex characters (nibbles) + int v; + for (int j = 0; j < bytes.length; j++) { + v = bytes[j] & 0xFF; // Cast bytes[j] to int, treating as unsigned value + hexChars[j * 2] = hexArray[v >>> 4]; // Select hex character from upper nibble + hexChars[j * 2 + 1] = hexArray[v & 0x0F]; // Select hex character from lower nibble + } + return new String(hexChars); + } + + /** + * Utility method to convert a hexadecimal string to a byte string. + * + * <p>Behavior with input strings containing non-hexadecimal characters is undefined. + * + * @param s String containing hexadecimal characters to convert + * @return Byte array generated from input + * @throws java.lang.IllegalArgumentException if input length is incorrect + */ + public static byte[] HexStringToByteArray(String s) throws IllegalArgumentException { + int len = s.length(); + if (len % 2 == 1) { + throw new IllegalArgumentException("Hex string must have even number of characters"); + } + byte[] data = new byte[len / 2]; // Allocate 1 byte per 2 hex characters + for (int i = 0; i < len; i += 2) { + // Convert each character into a integer (base-16), then bit-shift into place + data[i / 2] = (byte) ((Character.digit(s.charAt(i), 16) << 4) + + Character.digit(s.charAt(i+1), 16)); + } + return data; + } + + /** + * Utility method to concatenate two byte arrays. + * @param first First array + * @param rest Any remaining arrays + * @return Concatenated copy of input arrays + */ + public static byte[] ConcatArrays(byte[] first, byte[]... rest) { + int totalLength = first.length; + for (byte[] array : rest) { + totalLength += array.length; + } + byte[] result = Arrays.copyOf(first, totalLength); + int offset = first.length; + for (byte[] array : rest) { + System.arraycopy(array, 0, result, offset, array.length); + offset += array.length; + } + return result; + } +} |