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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.app.ActivityManager;
import android.content.pm.Signature;
import android.text.TextUtils;
import libcore.util.HexEncoding;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.security.DigestInputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Arrays;
/**
* Helper functions applicable to packages.
* @hide
*/
public final class PackageUtils {
private static final int LOW_RAM_BUFFER_SIZE_BYTES = 1 * 1000; // 1 kB
private static final int HIGH_RAM_BUFFER_SIZE_BYTES = 1 * 1000 * 1000; // 1 MB
private PackageUtils() {
/* hide constructor */
}
/**
* @see #computeSignaturesSha256Digests(Signature[], String)
*/
public static @NonNull String[] computeSignaturesSha256Digests(
@NonNull Signature[] signatures) {
return computeSignaturesSha256Digests(signatures, null);
}
/**
* 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.
* @param separator Separator between each pair of characters, such as a colon, or null to omit.
* @return The digest array.
*/
public static @NonNull String[] computeSignaturesSha256Digests(
@NonNull Signature[] signatures, @Nullable String separator) {
final int signatureCount = signatures.length;
final String[] digests = new String[signatureCount];
for (int i = 0; i < signatureCount; i++) {
digests[i] = computeSha256Digest(signatures[i].toByteArray(), separator);
}
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(), null);
}
// Make sure these are sorted to handle reversed certificates
final String[] sha256Digests = computeSignaturesSha256Digests(signatures, null);
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(), null);
}
/**
* Computes the SHA256 digest of some data.
* @param data The data.
* @return The digest or null if an error occurs.
*/
public static @Nullable byte[] computeSha256DigestBytes(@NonNull byte[] data) {
MessageDigest messageDigest;
try {
messageDigest = MessageDigest.getInstance("SHA256");
} catch (NoSuchAlgorithmException e) {
/* can't happen */
return null;
}
messageDigest.update(data);
return messageDigest.digest();
}
/**
* @see #computeSha256Digest(byte[], String)
*/
public static @Nullable String computeSha256Digest(@NonNull byte[] data) {
return computeSha256Digest(data, null);
}
/**
* Computes the SHA256 digest of some data.
* @param data The data.
* @param separator Separator between each pair of characters, such as a colon, or null to omit.
* @return The digest or null if an error occurs.
*/
public static @Nullable String computeSha256Digest(@NonNull byte[] data,
@Nullable String separator) {
byte[] sha256DigestBytes = computeSha256DigestBytes(data);
if (sha256DigestBytes == null) {
return null;
}
if (separator == null) {
return HexEncoding.encodeToString(sha256DigestBytes, true /* uppercase */);
}
int length = sha256DigestBytes.length;
String[] pieces = new String[length];
for (int index = 0; index < length; index++) {
pieces[index] = HexEncoding.encodeToString(sha256DigestBytes[index], true);
}
return TextUtils.join(separator, pieces);
}
/**
* Creates a fixed size buffer based on whether the device is low ram or not. This is to be used
* with the {@link #computeSha256DigestForLargeFile(String, byte[])} and
* {@link #computeSha256DigestForLargeFile(String, byte[], String)} methods.
* @return a byte array of size {@link #LOW_RAM_BUFFER_SIZE_BYTES} if the device is a low RAM
* device, otherwise a byte array of size {@link #HIGH_RAM_BUFFER_SIZE_BYTES}
*/
public static @NonNull byte[] createLargeFileBuffer() {
int bufferSize = ActivityManager.isLowRamDeviceStatic()
? LOW_RAM_BUFFER_SIZE_BYTES : HIGH_RAM_BUFFER_SIZE_BYTES;
return new byte[bufferSize];
}
/**
* @see #computeSha256DigestForLargeFile(String, byte[], String)
*/
public static @Nullable String computeSha256DigestForLargeFile(@NonNull String filePath,
@NonNull byte[] fileBuffer) {
return computeSha256DigestForLargeFile(filePath, fileBuffer, null);
}
/**
* Computes the SHA256 digest of large files. This is typically useful for large APEXs.
* @param filePath The path to which the file's content is to be hashed.
* @param fileBuffer A buffer to read file's content into memory. It is strongly recommended to
* make use of the {@link #createLargeFileBuffer()} method to create this
* buffer.
* @param separator Separator between each pair of characters, such as colon, or null to omit.
* @return The SHA256 digest or null if an error occurs.
*/
public static @Nullable String computeSha256DigestForLargeFile(@NonNull String filePath,
@NonNull byte[] fileBuffer, @Nullable String separator) {
MessageDigest messageDigest;
try {
messageDigest = MessageDigest.getInstance("SHA256");
messageDigest.reset();
} catch (NoSuchAlgorithmException e) {
// this really shouldn't happen!
return null;
}
File f = new File(filePath);
try {
DigestInputStream digestInputStream = new DigestInputStream(new FileInputStream(f),
messageDigest);
while (digestInputStream.read(fileBuffer) != -1);
} catch (IOException e) {
e.printStackTrace();
return null;
}
byte[] resultBytes = messageDigest.digest();
if (separator == null) {
return HexEncoding.encodeToString(resultBytes, true);
}
int length = resultBytes.length;
String[] pieces = new String[length];
for (int index = 0; index < length; index++) {
pieces[index] = HexEncoding.encodeToString(resultBytes[index], true);
}
return TextUtils.join(separator, pieces);
}
}
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