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
34    private PackageUtils() {
35        /* hide constructor */
36    }
37
38    /**
39     * Computes the SHA256 digest of the signing cert for a package.
40     * @param packageManager The package manager.
41     * @param packageName The package for which to generate the digest.
42     * @param userId The user for which to generate the digest.
43     * @return The digest or null if the package does not exist for this user.
44     */
45    public static @Nullable String computePackageCertSha256Digest(
46            @NonNull PackageManager packageManager,
47            @NonNull String packageName, int userId) {
48        final PackageInfo packageInfo;
49        try {
50            packageInfo = packageManager.getPackageInfoAsUser(packageName,
51                    PackageManager.GET_SIGNATURES, userId);
52        } catch (PackageManager.NameNotFoundException e) {
53            return null;
54        }
55        return computeCertSha256Digest(packageInfo.signatures[0]);
56    }
57
58    /**
59     * Computes the SHA256 digest of a cert.
60     * @param signature The signature.
61     * @return The digest or null if an error occurs.
62     */
63    public static @Nullable String computeCertSha256Digest(@NonNull Signature signature) {
64        return computeSha256Digest(signature.toByteArray());
65    }
66
67    /**
68     * Computes the SHA256 digest of some data.
69     * @param data The data.
70     * @return The digest or null if an error occurs.
71     */
72    public static @Nullable String computeSha256Digest(@NonNull byte[] data) {
73        MessageDigest messageDigest;
74        try {
75            messageDigest = MessageDigest.getInstance("SHA256");
76        } catch (NoSuchAlgorithmException e) {
77            /* can't happen */
78            return null;
79        }
80
81        messageDigest.update(data);
82
83        return ByteStringUtils.toHexString(messageDigest.digest());
84    }
85}
86