1/* 2 * Copyright (C) 2016 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 17package android.util; 18 19import android.annotation.NonNull; 20import android.annotation.Nullable; 21import android.content.pm.PackageInfo; 22import android.content.pm.PackageManager; 23import android.content.pm.Signature; 24 25import java.security.MessageDigest; 26import java.security.NoSuchAlgorithmException; 27 28/** 29 * Helper functions applicable to packages. 30 * @hide 31 */ 32public final class PackageUtils { 33 private final static char[] HEX_ARRAY = "0123456789ABCDEF".toCharArray(); 34 35 private PackageUtils() { 36 /* hide constructor */ 37 } 38 39 /** 40 * Computes the SHA256 digest of the signing cert for a package. 41 * @param packageManager The package manager. 42 * @param packageName The package for which to generate the digest. 43 * @param userId The user for which to generate the digest. 44 * @return The digest or null if the package does not exist for this user. 45 */ 46 public static @Nullable String computePackageCertSha256Digest( 47 @NonNull PackageManager packageManager, 48 @NonNull String packageName, int userId) { 49 final PackageInfo packageInfo; 50 try { 51 packageInfo = packageManager.getPackageInfoAsUser(packageName, 52 PackageManager.GET_SIGNATURES, userId); 53 } catch (PackageManager.NameNotFoundException e) { 54 return null; 55 } 56 return computeCertSha256Digest(packageInfo.signatures[0]); 57 } 58 59 /** 60 * Computes the SHA256 digest of a cert. 61 * @param signature The signature. 62 * @return The digest or null if an error occurs. 63 */ 64 public static @Nullable String computeCertSha256Digest(@NonNull Signature signature) { 65 return computeSha256Digest(signature.toByteArray()); 66 } 67 68 /** 69 * Computes the SHA256 digest of some data. 70 * @param data The data. 71 * @return The digest or null if an error occurs. 72 */ 73 public static @Nullable String computeSha256Digest(@NonNull byte[] data) { 74 MessageDigest messageDigest; 75 try { 76 messageDigest = MessageDigest.getInstance("SHA256"); 77 } catch (NoSuchAlgorithmException e) { 78 /* can't happen */ 79 return null; 80 } 81 82 messageDigest.update(data); 83 84 final byte[] digest = messageDigest.digest(); 85 final int digestLength = digest.length; 86 final int charCount = 2 * digestLength; 87 88 final char[] chars = new char[charCount]; 89 for (int i = 0; i < digestLength; i++) { 90 final int byteHex = digest[i] & 0xFF; 91 chars[i * 2] = HEX_ARRAY[byteHex >>> 4]; 92 chars[i * 2 + 1] = HEX_ARRAY[byteHex & 0x0F]; 93 } 94 return new String(chars); 95 } 96} 97