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/*
* Copyright (C) 2016 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 android.util;
import android.annotation.NonNull;
import android.annotation.Nullable;
import android.content.pm.Signature;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Arrays;
/**
* Helper functions applicable to packages.
* @hide
*/
public final class PackageUtils {
private PackageUtils() {
/* hide constructor */
}
/**
* Computes the SHA256 digests of a list of signatures. Items in the
* resulting array of hashes correspond to the signatures in the
* input array.
* @param signatures The signatures.
* @return The digest array.
*/
public static @NonNull String[] computeSignaturesSha256Digests(
@NonNull Signature[] signatures) {
final int signatureCount = signatures.length;
final String[] digests = new String[signatureCount];
for (int i = 0; i < signatureCount; i++) {
digests[i] = computeSha256Digest(signatures[i].toByteArray());
}
return digests;
}
/**
* Computes a SHA256 digest of the signatures' SHA256 digests. First,
* individual hashes for each signature is derived in a hexademical
* form, then these strings are sorted based the natural ordering, and
* finally a hash is derived from these strings' bytes.
* @param signatures The signatures.
* @return The digest.
*/
public static @NonNull String computeSignaturesSha256Digest(
@NonNull Signature[] signatures) {
// Shortcut for optimization - most apps singed by a single cert
if (signatures.length == 1) {
return computeSha256Digest(signatures[0].toByteArray());
}
// Make sure these are sorted to handle reversed certificates
final String[] sha256Digests = computeSignaturesSha256Digests(signatures);
return computeSignaturesSha256Digest(sha256Digests);
}
/**
* Computes a SHA256 digest in of the signatures SHA256 digests. First,
* the strings are sorted based the natural ordering, and then a hash is
* derived from these strings' bytes.
* @param sha256Digests Signature SHA256 hashes in hexademical form.
* @return The digest.
*/
public static @NonNull String computeSignaturesSha256Digest(
@NonNull String[] sha256Digests) {
// Shortcut for optimization - most apps singed by a single cert
if (sha256Digests.length == 1) {
return sha256Digests[0];
}
// Make sure these are sorted to handle reversed certificates
Arrays.sort(sha256Digests);
final ByteArrayOutputStream bytes = new ByteArrayOutputStream();
for (String sha256Digest : sha256Digests) {
try {
bytes.write(sha256Digest.getBytes());
} catch (IOException e) {
/* ignore - can't happen */
}
}
return computeSha256Digest(bytes.toByteArray());
}
/**
* Computes the SHA256 digest of some data.
* @param data The data.
* @return The digest or null if an error occurs.
*/
public static @Nullable String computeSha256Digest(@NonNull byte[] data) {
MessageDigest messageDigest;
try {
messageDigest = MessageDigest.getInstance("SHA256");
} catch (NoSuchAlgorithmException e) {
/* can't happen */
return null;
}
messageDigest.update(data);
return ByteStringUtils.toHexString(messageDigest.digest());
}
}
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