84 lines
2.8 KiB
Java
84 lines
2.8 KiB
Java
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/*
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* Copyright (C) 2019 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package android.content.integrity;
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import static com.android.internal.util.Preconditions.checkArgument;
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/**
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* Utils class for simple operations used in integrity module.
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*
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* @hide
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*/
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public class IntegrityUtils {
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private static final char[] HEX_CHARS = "0123456789ABCDEF".toCharArray();
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/**
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* Obtain the raw bytes from hex encoded string.
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*
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* @throws IllegalArgumentException if {@code hexDigest} is not a valid hex encoding of some
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* bytes
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*/
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public static byte[] getBytesFromHexDigest(String hexDigest) {
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checkArgument(
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hexDigest.length() % 2 == 0,
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"Invalid hex encoding %s: must have even length", hexDigest);
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byte[] rawBytes = new byte[hexDigest.length() / 2];
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for (int i = 0; i < rawBytes.length; i++) {
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int upperNibble = hexDigest.charAt(2 * i);
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int lowerNibble = hexDigest.charAt(2 * i + 1);
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rawBytes[i] = (byte) ((hexToDec(upperNibble) << 4) | hexToDec(lowerNibble));
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}
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return rawBytes;
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}
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/** Obtain hex encoded string from raw bytes. */
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public static String getHexDigest(byte[] rawBytes) {
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char[] hexChars = new char[rawBytes.length * 2];
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for (int i = 0; i < rawBytes.length; i++) {
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int upperNibble = (rawBytes[i] >>> 4) & 0xF;
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int lowerNibble = rawBytes[i] & 0xF;
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hexChars[i * 2] = decToHex(upperNibble);
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hexChars[i * 2 + 1] = decToHex(lowerNibble);
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}
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return new String(hexChars);
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}
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private static int hexToDec(int hexChar) {
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if (hexChar >= '0' && hexChar <= '9') {
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return hexChar - '0';
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}
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if (hexChar >= 'a' && hexChar <= 'f') {
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return hexChar - 'a' + 10;
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}
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if (hexChar >= 'A' && hexChar <= 'F') {
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return hexChar - 'A' + 10;
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}
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throw new IllegalArgumentException("Invalid hex char " + hexChar);
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}
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private static char decToHex(int dec) {
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if (dec >= 0 && dec < HEX_CHARS.length) {
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return HEX_CHARS[dec];
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}
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throw new IllegalArgumentException("Invalid dec value to be converted to hex digit " + dec);
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}
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}
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