| // Copyright 2022 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; |
| |
| import com.google.crypto.tink.annotations.Alpha; |
| import com.google.errorprone.annotations.CanIgnoreReturnValue; |
| import com.google.errorprone.annotations.CheckReturnValue; |
| import com.google.errorprone.annotations.Immutable; |
| import java.security.GeneralSecurityException; |
| import javax.annotation.Nullable; |
| |
| /** |
| * Represents access to secret key material. |
| * |
| * <p>Tink restricts access to secret key material, and users who require such access need to have |
| * an object of the class {@code SecretKeyAccess} to do this. For example, a function that outputs |
| * individiual key bytes might look like this: |
| * |
| * <pre> |
| * class HmacKey { |
| * ... |
| * public byte[] getKeyMaterial(SecretKeyAccess access) { |
| * checkNotNull(access); |
| * return keyMaterial; |
| * } |
| * } |
| * </pre> |
| * |
| * Users who want to call {@code getKeyMaterial} then need to get a {@code SecretKeyAccess} object |
| * via {@code InsecureSecretKeyAccess.get()}. |
| */ |
| @CheckReturnValue |
| @Alpha |
| @Immutable |
| public final class SecretKeyAccess { |
| private SecretKeyAccess() {} |
| |
| private static final SecretKeyAccess INSTANCE = new SecretKeyAccess(); |
| |
| /** Package visibility restricted for {@link InsecureSecretKeyAccess}. */ |
| static SecretKeyAccess instance() { |
| return INSTANCE; |
| } |
| |
| /** Throws an exception if the passed in SecretKeyAccess is null, otherwise returns it. */ |
| @CanIgnoreReturnValue |
| public static SecretKeyAccess requireAccess(@Nullable SecretKeyAccess access) |
| throws GeneralSecurityException { |
| if (access == null) { |
| throw new GeneralSecurityException("SecretKeyAccess is required"); |
| } |
| return access; |
| } |
| } |