| // Copyright 2021 Google LLC |
| // |
| // 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 com.google.crypto.tink.hybrid.internal; |
| |
| import static java.nio.charset.StandardCharsets.UTF_8; |
| |
| import com.google.crypto.tink.proto.HpkeAead; |
| import com.google.crypto.tink.proto.HpkeKdf; |
| import com.google.crypto.tink.proto.HpkeKem; |
| import com.google.crypto.tink.proto.HpkeParams; |
| import com.google.crypto.tink.subtle.Bytes; |
| import java.security.GeneralSecurityException; |
| |
| /** Collection of helper functions for HPKE. */ |
| public final class HpkeUtil { |
| // HPKE mode identifiers. |
| public static final byte[] BASE_MODE = intToByteArray(1, 0x0); |
| |
| // HPKE KEM algorithm identifiers. |
| public static final byte[] X25519_HKDF_SHA256_KEM_ID = intToByteArray(2, 0x20); |
| public static final byte[] P256_HKDF_SHA256_KEM_ID = intToByteArray(2, 0x10); |
| public static final byte[] P384_HKDF_SHA384_KEM_ID = intToByteArray(2, 0x11); |
| public static final byte[] P521_HKDF_SHA512_KEM_ID = intToByteArray(2, 0x12); |
| |
| // HPKE KDF algorithm identifiers. |
| public static final byte[] HKDF_SHA256_KDF_ID = intToByteArray(2, 0x1); |
| public static final byte[] HKDF_SHA384_KDF_ID = intToByteArray(2, 0x2); |
| public static final byte[] HKDF_SHA512_KDF_ID = intToByteArray(2, 0x3); |
| |
| // HPKE AEAD algorithm identifiers. |
| public static final byte[] AES_128_GCM_AEAD_ID = intToByteArray(2, 0x1); |
| public static final byte[] AES_256_GCM_AEAD_ID = intToByteArray(2, 0x2); |
| public static final byte[] CHACHA20_POLY1305_AEAD_ID = intToByteArray(2, 0x3); |
| |
| public static final byte[] EMPTY_SALT = new byte[0]; |
| |
| private static final byte[] KEM = "KEM".getBytes(UTF_8); |
| private static final byte[] HPKE = "HPKE".getBytes(UTF_8); |
| private static final byte[] HPKE_V1 = "HPKE-v1".getBytes(UTF_8); |
| |
| /** |
| * Transforms a passed value to an MSB first byte array with the size of the specified capacity. |
| * (i.e., {@link com.google.crypto.tink.subtle.Bytes#intToByteArray(int, int)} with MSB first |
| * instead of LSB first). |
| * |
| * <p>The HPKE standard defines this function as I2OSP(n, w) where w = capacity and n = value. |
| * |
| * <p>https://www.rfc-editor.org/rfc/rfc9180.html#name-notation |
| * |
| * @param capacity size of the resulting byte array |
| * @param value that should be represented as a byte array |
| */ |
| public static byte[] intToByteArray(int capacity, int value) { |
| final byte[] result = new byte[capacity]; |
| for (int i = 0; i < capacity; i++) { |
| result[i] = (byte) ((value >> (8 * (capacity - i - 1))) & 0xFF); |
| } |
| return result; |
| } |
| |
| /** |
| * Generates KEM suite id from {@code kemId} according to the definition in |
| * https://www.rfc-editor.org/rfc/rfc9180.html#section-4.1-5. Only used for KEM suite id. |
| * |
| * @throws GeneralSecurityException when byte concatenation fails. |
| */ |
| static byte[] kemSuiteId(byte[] kemId) throws GeneralSecurityException { |
| return Bytes.concat(KEM, kemId); |
| } |
| |
| /** |
| * Generates HPKE suite id from {@code kemId}, {@code kdfId}, and {@code aeadId} according to the |
| * definition in https://www.rfc-editor.org/rfc/rfc9180.html#section-5.1-8. Used for any non-KEM |
| * suite id. |
| * |
| * @throws GeneralSecurityException when byte concatenation fails. |
| */ |
| static byte[] hpkeSuiteId(byte[] kemId, byte[] kdfId, byte[] aeadId) |
| throws GeneralSecurityException { |
| return Bytes.concat(HPKE, kemId, kdfId, aeadId); |
| } |
| |
| /** |
| * Transforms {@code ikm} into labeled ikm using {@code label} and {@code suiteId} according to |
| * {@code LabeledExtract()} defined in https://www.rfc-editor.org/rfc/rfc9180.html#section-4. |
| * |
| * @throws GeneralSecurityException when byte concatenation fails. |
| */ |
| static byte[] labelIkm(String label, byte[] ikm, byte[] suiteId) throws GeneralSecurityException { |
| return Bytes.concat(HPKE_V1, suiteId, label.getBytes(UTF_8), ikm); |
| } |
| |
| /** |
| * Transforms {@code info} into labeled info using {@code label}, {@code suiteId}, and {@code |
| * length} according to {@code LabeledExpand()} defined in |
| * https://www.rfc-editor.org/rfc/rfc9180.html#section-4. |
| * |
| * @throws GeneralSecurityException when byte concatenation fails. |
| */ |
| static byte[] labelInfo(String label, byte[] info, byte[] suiteId, int length) |
| throws GeneralSecurityException { |
| return Bytes.concat(intToByteArray(2, length), HPKE_V1, suiteId, label.getBytes(UTF_8), info); |
| } |
| |
| static void validateParams(HpkeParams params) throws GeneralSecurityException { |
| if ((params.getKem() == HpkeKem.KEM_UNKNOWN) || (params.getKem() == HpkeKem.UNRECOGNIZED)) { |
| throw new GeneralSecurityException("Invalid KEM param: " + params.getKem().name()); |
| } |
| if ((params.getKdf() == HpkeKdf.KDF_UNKNOWN) || (params.getKdf() == HpkeKdf.UNRECOGNIZED)) { |
| throw new GeneralSecurityException("Invalid KDF param: " + params.getKdf().name()); |
| } |
| if ((params.getAead() == HpkeAead.AEAD_UNKNOWN) |
| || (params.getAead() == HpkeAead.UNRECOGNIZED)) { |
| throw new GeneralSecurityException("Invalid AEAD param: " + params.getAead().name()); |
| } |
| } |
| |
| private HpkeUtil() {} |
| } |