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Remove use of BouncyCastle for HMAC key derivation #130
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171 changes: 171 additions & 0 deletions
171
src/main/java/com/amazonaws/encryptionsdk/internal/HmacKeyDerivationFunction.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,171 @@ | ||
| /* | ||
| * Copyright 2014 Amazon.com, Inc. or its affiliates. All Rights Reserved. | ||
| * | ||
| * Licensed under the Apache License, Version 2.0 (the "License"). | ||
| * You may not use this file except in compliance with the License. | ||
| * A copy of the License is located at | ||
| * | ||
| * http://aws.amazon.com/apache2.0 | ||
| * | ||
| * or in the "license" file accompanying this file. This file 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 com.amazonaws.encryptionsdk.internal; | ||
|
|
||
| import java.security.GeneralSecurityException; | ||
| import java.security.InvalidKeyException; | ||
| import java.security.NoSuchAlgorithmException; | ||
| import java.security.Provider; | ||
| import java.util.Arrays; | ||
|
|
||
| import javax.crypto.Mac; | ||
| import javax.crypto.SecretKey; | ||
| import javax.crypto.spec.SecretKeySpec; | ||
|
|
||
| import static org.apache.commons.lang3.Validate.isTrue; | ||
|
|
||
| /** | ||
| * HMAC-based Key Derivation Function. | ||
| * Adapted from Hkdf.java in aws-dynamodb-encryption-java | ||
| * | ||
| * @see <a href="http://tools.ietf.org/html/rfc5869">RFC 5869</a> | ||
| */ | ||
| public final class HmacKeyDerivationFunction { | ||
| private static final byte[] EMPTY_ARRAY = new byte[0]; | ||
| private final String algorithm; | ||
| private final Provider provider; | ||
| private SecretKey prk = null; | ||
|
|
||
| /** | ||
| * Returns an <code>Hkdf</code> object using the specified algorithm. | ||
| * | ||
| * @param algorithm the standard name of the requested MAC algorithm. See the Mac | ||
| * section in the <a href= | ||
| * "http://docs.oracle.com/javase/7/docs/technotes/guides/security/StandardNames.html#Mac" | ||
| * > Java Cryptography Architecture Standard Algorithm Name | ||
| * Documentation</a> for information about standard algorithm | ||
| * names. | ||
| * @return the new <code>Hkdf</code> object | ||
| * @throws NoSuchAlgorithmException if no Provider supports a MacSpi implementation for the | ||
| * specified algorithm. | ||
| */ | ||
| public static HmacKeyDerivationFunction getInstance(final String algorithm) | ||
| throws NoSuchAlgorithmException { | ||
| // Constructed specifically to sanity-test arguments. | ||
| Mac mac = Mac.getInstance(algorithm); | ||
| return new HmacKeyDerivationFunction(algorithm, mac.getProvider()); | ||
| } | ||
|
|
||
| /** | ||
| * Initializes this Hkdf with input keying material. A default salt of | ||
| * HashLen zeros will be used (where HashLen is the length of the return | ||
| * value of the supplied algorithm). | ||
| * | ||
| * @param ikm the Input Keying Material | ||
| */ | ||
| public void init(final byte[] ikm) { | ||
| init(ikm, null); | ||
| } | ||
|
|
||
| /** | ||
| * Initializes this Hkdf with input keying material and a salt. If <code> | ||
| * salt</code> is <code>null</code> or of length 0, then a default salt of | ||
| * HashLen zeros will be used (where HashLen is the length of the return | ||
| * value of the supplied algorithm). | ||
| * | ||
| * @param salt the salt used for key extraction (optional) | ||
| * @param ikm the Input Keying Material | ||
| */ | ||
| public void init(final byte[] ikm, final byte[] salt) { | ||
| byte[] realSalt = (salt == null) ? EMPTY_ARRAY : salt.clone(); | ||
| byte[] rawKeyMaterial = EMPTY_ARRAY; | ||
| try { | ||
| Mac extractionMac = Mac.getInstance(algorithm, provider); | ||
| if (realSalt.length == 0) { | ||
| realSalt = new byte[extractionMac.getMacLength()]; | ||
| Arrays.fill(realSalt, (byte) 0); | ||
| } | ||
| extractionMac.init(new SecretKeySpec(realSalt, algorithm)); | ||
| rawKeyMaterial = extractionMac.doFinal(ikm); | ||
| this.prk = new SecretKeySpec(rawKeyMaterial, algorithm); | ||
| } catch (GeneralSecurityException e) { | ||
| // We've already checked all of the parameters so no exceptions | ||
| // should be possible here. | ||
| throw new RuntimeException("Unexpected exception", e); | ||
| } finally { | ||
| Arrays.fill(rawKeyMaterial, (byte) 0); // Zeroize temporary array | ||
| } | ||
| } | ||
|
|
||
| private HmacKeyDerivationFunction(final String algorithm, final Provider provider) { | ||
| isTrue(algorithm.startsWith("Hmac"), "Invalid algorithm " + algorithm | ||
| + ". Hkdf may only be used with Hmac algorithms."); | ||
| this.algorithm = algorithm; | ||
| this.provider = provider; | ||
| } | ||
|
|
||
| /** | ||
| * Returns a pseudorandom key of <code>length</code> bytes. | ||
| * | ||
| * @param info optional context and application specific information (can be | ||
| * a zero-length array). | ||
| * @param length the length of the output key in bytes | ||
| * @return a pseudorandom key of <code>length</code> bytes. | ||
| * @throws IllegalStateException if this object has not been initialized | ||
| */ | ||
| public byte[] deriveKey(final byte[] info, final int length) throws IllegalStateException { | ||
| isTrue(length >= 0, "Length must be a non-negative value."); | ||
| assertInitialized(); | ||
| final byte[] result = new byte[length]; | ||
| Mac mac = createMac(); | ||
|
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| isTrue(length <= 255 * mac.getMacLength(), | ||
| "Requested keys may not be longer than 255 times the underlying HMAC length."); | ||
|
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| byte[] t = EMPTY_ARRAY; | ||
| try { | ||
| int loc = 0; | ||
| byte i = 1; | ||
| while (loc < length) { | ||
| mac.update(t); | ||
| mac.update(info); | ||
| mac.update(i); | ||
| t = mac.doFinal(); | ||
|
|
||
| for (int x = 0; x < t.length && loc < length; x++, loc++) { | ||
| result[loc] = t[x]; | ||
| } | ||
|
|
||
| i++; | ||
| } | ||
| } finally { | ||
| Arrays.fill(t, (byte) 0); // Zeroize temporary array | ||
| } | ||
| return result; | ||
| } | ||
|
|
||
| private Mac createMac() { | ||
| try { | ||
| Mac mac = Mac.getInstance(algorithm, provider); | ||
| mac.init(prk); | ||
| return mac; | ||
| } catch (NoSuchAlgorithmException | InvalidKeyException ex) { | ||
| // We've already validated that this algorithm/key is correct. | ||
| throw new RuntimeException(ex); | ||
| } | ||
| } | ||
|
|
||
| /** | ||
| * Throws an <code>IllegalStateException</code> if this object has not been | ||
| * initialized. | ||
| * | ||
| * @throws IllegalStateException if this object has not been initialized | ||
| */ | ||
| private void assertInitialized() throws IllegalStateException { | ||
| if (prk == null) { | ||
| throw new IllegalStateException("Hkdf has not been initialized"); | ||
| } | ||
| } | ||
| } | ||
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