1 /* 2 * Copyright (C) 2021 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package android.bluetooth; 18 19 import android.os.UserHandle; 20 import android.util.Log; 21 22 import java.time.Duration; 23 import java.util.ArrayList; 24 import java.util.Collections; 25 import java.util.List; 26 27 /** 28 * {@hide} 29 */ 30 public final class BluetoothUtils { 31 private static final String TAG = "BluetoothUtils"; 32 33 /** 34 * This utility class cannot be instantiated 35 */ BluetoothUtils()36 private BluetoothUtils() {} 37 38 /** 39 * Timeout value for synchronous binder call 40 */ 41 private static final Duration SYNC_CALLS_TIMEOUT = Duration.ofSeconds(5); 42 43 /** 44 * @return timeout value for synchronous binder call 45 */ getSyncTimeout()46 static Duration getSyncTimeout() { 47 return SYNC_CALLS_TIMEOUT; 48 } 49 50 /** 51 * Match with UserHandl.NULL but accessible inside bluetooth package 52 */ 53 public static final UserHandle USER_HANDLE_NULL = UserHandle.of(-10000); 54 55 static class TypeValueEntry { 56 private final int mType; 57 private final byte[] mValue; 58 TypeValueEntry(int type, byte[] value)59 TypeValueEntry(int type, byte[] value) { 60 mType = type; 61 mValue = value; 62 } 63 getType()64 public int getType() { 65 return mType; 66 } 67 getValue()68 public byte[] getValue() { 69 return mValue; 70 } 71 } 72 73 // Helper method to extract bytes from byte array. extractBytes(byte[] rawBytes, int start, int length)74 private static byte[] extractBytes(byte[] rawBytes, int start, int length) { 75 int remainingLength = rawBytes.length - start; 76 if (remainingLength < length) { 77 Log.w(TAG, "extractBytes() remaining length " + remainingLength 78 + " is less than copying length " + length + ", array length is " 79 + rawBytes.length + " start is " + start); 80 return null; 81 } 82 byte[] bytes = new byte[length]; 83 System.arraycopy(rawBytes, start, bytes, 0, length); 84 return bytes; 85 } 86 87 /** 88 * Parse Length Value Entry from raw bytes 89 * 90 * The format is defined in Bluetooth 4.1 specification, Volume 3, Part C, Section 11 and 18. 91 * 92 * @param rawBytes raw bytes of Length-Value-Entry array 93 * @hide 94 */ parseLengthTypeValueBytes(byte[] rawBytes)95 public static List<TypeValueEntry> parseLengthTypeValueBytes(byte[] rawBytes) { 96 if (rawBytes == null) { 97 return Collections.emptyList(); 98 } 99 if (rawBytes.length == 0) { 100 return Collections.emptyList(); 101 } 102 103 int currentPos = 0; 104 List<TypeValueEntry> result = new ArrayList<>(); 105 while (currentPos < rawBytes.length) { 106 // length is unsigned int. 107 int length = rawBytes[currentPos] & 0xFF; 108 if (length == 0) { 109 break; 110 } 111 currentPos++; 112 if (currentPos >= rawBytes.length) { 113 Log.w(TAG, "parseLtv() no type and value after length, rawBytes length = " 114 + rawBytes.length + ", currentPost = " + currentPos); 115 break; 116 } 117 // Note the length includes the length of the field type itself. 118 int dataLength = length - 1; 119 // fieldType is unsigned int. 120 int type = rawBytes[currentPos] & 0xFF; 121 currentPos++; 122 if (currentPos >= rawBytes.length) { 123 Log.w(TAG, "parseLtv() no value after length, rawBytes length = " 124 + rawBytes.length + ", currentPost = " + currentPos); 125 break; 126 } 127 byte[] value = extractBytes(rawBytes, currentPos, dataLength); 128 if (value == null) { 129 Log.w(TAG, "failed to extract bytes, currentPost = " + currentPos); 130 break; 131 } 132 result.add(new TypeValueEntry(type, value)); 133 currentPos += dataLength; 134 } 135 return result; 136 } 137 138 /** 139 * Serialize type value entries to bytes 140 * @param typeValueEntries type value entries 141 * @return serialized type value entries on success, null on failure 142 */ serializeTypeValue(List<TypeValueEntry> typeValueEntries)143 public static byte[] serializeTypeValue(List<TypeValueEntry> typeValueEntries) { 144 // Calculate length 145 int length = 0; 146 for (TypeValueEntry entry : typeValueEntries) { 147 // 1 for length and 1 for type 148 length += 2; 149 if ((entry.getType() - (entry.getType() & 0xFF)) != 0) { 150 Log.w(TAG, "serializeTypeValue() type " + entry.getType() 151 + " is out of range of 0-0xFF"); 152 return null; 153 } 154 if (entry.getValue() == null) { 155 Log.w(TAG, "serializeTypeValue() value is null"); 156 return null; 157 } 158 int lengthValue = entry.getValue().length + 1; 159 if ((lengthValue - (lengthValue & 0xFF)) != 0) { 160 Log.w(TAG, "serializeTypeValue() entry length " + entry.getValue().length 161 + " is not in range of 0 to 254"); 162 return null; 163 } 164 length += entry.getValue().length; 165 } 166 byte[] result = new byte[length]; 167 int currentPos = 0; 168 for (TypeValueEntry entry : typeValueEntries) { 169 result[currentPos] = (byte) ((entry.getValue().length + 1) & 0xFF); 170 currentPos++; 171 result[currentPos] = (byte) (entry.getType() & 0xFF); 172 currentPos++; 173 System.arraycopy(entry.getValue(), 0, result, currentPos, entry.getValue().length); 174 currentPos += entry.getValue().length; 175 } 176 return result; 177 } 178 179 /** 180 * Convert an address to an obfuscate one for logging purpose 181 * @param address Mac address to be log 182 * @return Loggable mac address 183 */ toAnonymizedAddress(String address)184 public static String toAnonymizedAddress(String address) { 185 if (address == null || address.length() != 17) { 186 return null; 187 } 188 return "XX:XX:XX" + address.substring(8); 189 } 190 } 191