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// Copyright Amazon.com Inc. or its affiliates. All Rights Reserved.
// SPDX-License-Identifier: Apache-2.0
package com.amazonaws.encryptionsdk.internal;
import java.io.Serializable;
import java.math.BigInteger;
import java.nio.Buffer;
import java.nio.ByteBuffer;
import java.nio.charset.StandardCharsets;
import java.security.SecureRandom;
import java.util.Arrays;
import java.util.Comparator;
import java.util.WeakHashMap;
import java.util.concurrent.atomic.AtomicLong;
import org.apache.commons.lang3.ArrayUtils;
import org.bouncycastle.util.encoders.Base64;
/** Internal utility methods. */
public final class Utils {
// SecureRandom objects can both be expensive to initialize and incur synchronization costs.
// This allows us to minimize both initializations and keep SecureRandom usage thread local
// to avoid lock contention.
private static final ThreadLocal LOCAL_RANDOM =
new ThreadLocal() {
@Override
protected SecureRandom initialValue() {
final SecureRandom rnd = new SecureRandom();
rnd.nextBoolean(); // Force seeding
return rnd;
}
};
private Utils() {
// Prevent instantiation
}
/*
* In some areas we need to be able to assign a total order over Java objects - generally with some primary sort,
* but we need a fallback sort that always works in order to ensure that we don't falsely claim objects A and B
* are equal just because the primary sort declares them to have equal rank.
*
* To do this, we'll define a fallback sort that assigns an arbitrary order to all objects. This order is
* implemented by first comparing hashcode, and in the rare case where we are asked to compare two objects with
* equal hashcode, we explicitly assign an index to them - using a WeakHashMap to track this index - and sort
* based on this index.
*/
private static AtomicLong FALLBACK_COUNTER = new AtomicLong(0);
private static WeakHashMap FALLBACK_COMPARATOR_MAP = new WeakHashMap<>();
private static synchronized long getFallbackObjectId(Object object) {
return FALLBACK_COMPARATOR_MAP.computeIfAbsent(
object, ignored -> FALLBACK_COUNTER.incrementAndGet());
}
/**
* Provides an arbitrary but consistent total ordering over all objects. This comparison
* function will return 0 if and only if a == b, and otherwise will return arbitrarily either -1
* or 1, but will do so in a way that results in a consistent total order.
*
* @param a
* @param b
* @return -1 or 1 (consistently) if a != b; 0 if a == b.
*/
public static int compareObjectIdentity(Object a, Object b) {
if (a == b) {
return 0;
}
if (a == null) {
return -1;
}
if (b == null) {
return 1;
}
int hashCompare = Integer.compare(System.identityHashCode(a), System.identityHashCode(b));
if (hashCompare != 0) {
return hashCompare;
}
// Unfortunately these objects have identical hashcodes, so we need to find some other way to
// compare them.
// We'll do this by mapping them to an incrementing counter, and comparing their assigned IDs
// instead.
int fallbackCompare = Long.compare(getFallbackObjectId(a), getFallbackObjectId(b));
if (fallbackCompare == 0) {
throw new AssertionError("Failed to assign unique order to objects");
}
return fallbackCompare;
}
public static long saturatingAdd(long a, long b) {
long r = a + b;
if (a > 0 && b > 0 && r < a) {
return Long.MAX_VALUE;
}
if (a < 0 && b < 0 && r > a) {
return Long.MIN_VALUE;
}
// If the signs between a and b differ, overflow is impossible.
return r;
}
/**
* Comparator that performs a lexicographical comparison of byte arrays, treating them as
* unsigned.
*/
public static class ComparingByteArrays implements Comparator, Serializable {
// We don't really need to be serializable, but it doesn't hurt, and FindBugs gets annoyed if
// we're not.
private static final long serialVersionUID = 0xdf641037ffe509e2L;
@Override
public int compare(byte[] o1, byte[] o2) {
return new ComparingByteBuffers().compare(ByteBuffer.wrap(o1), ByteBuffer.wrap(o2));
}
}
public static class ComparingByteBuffers implements Comparator, Serializable {
private static final long serialVersionUID = 0xa3c4a7300fbbf043L;
@Override
public int compare(ByteBuffer o1, ByteBuffer o2) {
o1 = o1.slice();
o2 = o2.slice();
int commonLength = Math.min(o1.remaining(), o2.remaining());
for (int i = 0; i < commonLength; i++) {
// Perform zero-extension as we want to treat the bytes as unsigned
int v1 = o1.get(i) & 0xFF;
int v2 = o2.get(i) & 0xFF;
if (v1 != v2) {
return v1 - v2;
}
}
// The longer buffer is bigger (0x00 comes after end-of-buffer)
return o1.remaining() - o2.remaining();
}
}
/**
* Throws {@link NullPointerException} with message {@code paramName} if {@code object} is null.
*
* @param object value to be null-checked
* @param paramName message for the potential {@link NullPointerException}
* @return {@code object}
* @throws NullPointerException if {@code object} is null
*/
public static T assertNonNull(final T object, final String paramName)
throws NullPointerException {
if (object == null) {
throw new NullPointerException(paramName + " must not be null");
}
return object;
}
/**
* Returns a possibly truncated version of {@code arr} which is guaranteed to be exactly {@code
* len} elements long. If {@code arr} is already exactly {@code len} elements long, then {@code
* arr} is returned without copy or modification. If {@code arr} is longer than {@code len}, then
* a truncated copy is returned. If {@code arr} is shorter than {@code len} then this throws an
* {@link IllegalArgumentException}.
*/
public static byte[] truncate(final byte[] arr, final int len) throws IllegalArgumentException {
if (arr.length == len) {
return arr;
} else if (arr.length > len) {
return Arrays.copyOf(arr, len);
} else {
throw new IllegalArgumentException("arr is not at least " + len + " elements long");
}
}
public static SecureRandom getSecureRandom() {
return LOCAL_RANDOM.get();
}
/**
* Generate the AAD bytes to use when encrypting/decrypting content. The generated AAD is a block
* of bytes containing the provided message identifier, the string identifier, the sequence
* number, and the length of the content.
*
* @param messageId the unique message identifier for the ciphertext.
* @param idString the string describing the type of content processed.
* @param seqNum the sequence number.
* @param len the length of the content.
* @return the bytes containing the generated AAD.
*/
static byte[] generateContentAad(
final byte[] messageId, final String idString, final int seqNum, final long len) {
final byte[] idBytes = idString.getBytes(StandardCharsets.UTF_8);
final int aadLen =
messageId.length + idBytes.length + Integer.SIZE / Byte.SIZE + Long.SIZE / Byte.SIZE;
final ByteBuffer aad = ByteBuffer.allocate(aadLen);
aad.put(messageId);
aad.put(idBytes);
aad.putInt(seqNum);
aad.putLong(len);
return aad.array();
}
static IllegalArgumentException cannotBeNegative(String field) {
return new IllegalArgumentException(field + " cannot be negative");
}
/**
* Equivalent to calling {@link ByteBuffer#flip()} but in a manner which is safe when compiled on
* Java 9 or newer but used on Java 8 or older.
*/
public static ByteBuffer flip(final ByteBuffer buff) {
((Buffer) buff).flip();
return buff;
}
/**
* Equivalent to calling {@link ByteBuffer#clear()} but in a manner which is safe when compiled on
* Java 9 or newer but used on Java 8 or older.
*/
public static ByteBuffer clear(final ByteBuffer buff) {
((Buffer) buff).clear();
return buff;
}
/**
* Equivalent to calling {@link ByteBuffer#position(int)} but in a manner which is safe when
* compiled on Java 9 or newer but used on Java 8 or older.
*/
public static ByteBuffer position(final ByteBuffer buff, final int newPosition) {
((Buffer) buff).position(newPosition);
return buff;
}
/**
* Equivalent to calling {@link ByteBuffer#limit(int)} but in a manner which is safe when compiled
* on Java 9 or newer but used on Java 8 or older.
*/
public static ByteBuffer limit(final ByteBuffer buff, final int newLimit) {
((Buffer) buff).limit(newLimit);
return buff;
}
/**
* Takes a Base64-encoded String, decodes it, and returns contents as a byte array.
*
* @param encoded Base64 encoded String
* @return decoded data as a byte array
*/
public static byte[] decodeBase64String(final String encoded) {
return encoded.isEmpty() ? ArrayUtils.EMPTY_BYTE_ARRAY : Base64.decode(encoded);
}
/**
* Takes data in a byte array, encodes them in Base64, and returns the result as a String.
*
* @param data The data to encode.
* @return Base64 string that encodes the {@code data}.
*/
public static String encodeBase64String(final byte[] data) {
return Base64.toBase64String(data);
}
/**
* Removes the leading zero sign byte from the byte array representation of a BigInteger (if
* present) and left pads with zeroes to produce a byte array of the given length.
*
* @param bigInteger The BigInteger to convert to a byte array
* @param length The length of the byte array, must be at least as long as the BigInteger byte
* array without the sign byte
* @return The byte array
*/
public static byte[] bigIntegerToByteArray(final BigInteger bigInteger, final int length) {
byte[] rawBytes = bigInteger.toByteArray();
// If rawBytes is already the correct length, return it.
if (rawBytes.length == length) {
return rawBytes;
}
// If we're exactly one byte too large, but we have a leading zero byte, remove it and return.
if (rawBytes.length == length + 1 && rawBytes[0] == 0) {
return Arrays.copyOfRange(rawBytes, 1, rawBytes.length);
}
if (rawBytes.length > length) {
throw new IllegalArgumentException(
"Length must be at least as long as the BigInteger byte array "
+ "without the sign byte");
}
final byte[] paddedResult = new byte[length];
System.arraycopy(rawBytes, 0, paddedResult, length - rawBytes.length, rawBytes.length);
return paddedResult;
}
/**
* Returns true if the prefix of the given length for the input arrays are equal. This method will
* return as soon as the first difference is found, and is thus not constant-time.
*
* @param a The first array.
* @param b The second array.
* @param length The length of the prefix to compare.
* @return True if the prefixes are equal, false otherwise.
*/
public static boolean arrayPrefixEquals(final byte[] a, final byte[] b, final int length) {
if (a == null || b == null || a.length < length || b.length < length) {
return false;
}
for (int x = 0; x < length; x++) {
if (a[x] != b[x]) {
return false;
}
}
return true;
}
}
