com.amazonaws.encryptionsdk.MasterKeyProvider Maven / Gradle / Ivy

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/*
 * Copyright 2016 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;

import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Map;

import com.amazonaws.encryptionsdk.exception.AwsCryptoException;
import com.amazonaws.encryptionsdk.exception.CannotUnwrapDataKeyException;
import com.amazonaws.encryptionsdk.exception.NoSuchMasterKeyException;
import com.amazonaws.encryptionsdk.exception.UnsupportedProviderException;

/**
 * Represents the logic necessary to select and construct {@link MasterKey}s for encrypting and
 * decrypting messages. This is an abstract class.
 *
 * @param 
 *            the type of {@link MasterKey} returned by this provider
 */
public abstract class MasterKeyProvider> {
    /**
     * ProviderId used by this instance when no other is specified.
     */
    public abstract String getDefaultProviderId();

    /**
     * Returns true if this MasterKeyProvider can provide keys from the specified @{code provider}.
     *
     * @param provider
     * @return
     */
    public boolean canProvide(final String provider) {
        return getDefaultProviderId().equals(provider);
    }

    /**
     * Equivalent to calling {@link #getMasterKey(String, String)} using
     * {@link #getDefaultProviderId()} as the provider.
     */
    public K getMasterKey(final String keyId) throws UnsupportedProviderException, NoSuchMasterKeyException {
        return getMasterKey(getDefaultProviderId(), keyId);
    }

    /**
     * Returns the specified {@link MasterKey} if possible.
     *
     * @param provider
     * @param keyId
     * @return
     * @throws UnsupportedProviderException
     *             if this object cannot return {@link MasterKeys} associated with the given
     *             provider
     * @throws NoSuchMasterKeyException
     *             if this object cannot find (and thus construct) the {@link MasterKey} associated
     *             with {@code keyId}
     */
    public abstract K getMasterKey(String provider, String keyId) throws UnsupportedProviderException,
    NoSuchMasterKeyException;

    /**
     * Returns all {@link MasterKey}s which should be used to protect the plaintext described by
     * {@code request}.
     */
    public abstract List getMasterKeysForEncryption(MasterKeyRequest request);

    /**
     * Iterates through {@code encryptedDataKeys} and returns the first one which can be
     * successfully decrypted.
     *
     * @return a DataKey if one can be decrypted, otherwise returns {@code null}
     * @throws UnsupportedProviderException
     *             if the {@code encryptedDataKey} is associated with an unsupported provider
     * @throws CannotUnwrapDataKeyException
     *             if the {@code encryptedDataKey} cannot be decrypted
     */
    public abstract DataKey decryptDataKey(CryptoAlgorithm algorithm,
            Collection encryptedDataKeys, Map encryptionContext)
            throws UnsupportedProviderException, AwsCryptoException;

    protected AwsCryptoException buildCannotDecryptDksException() {
        return buildCannotDecryptDksException(Collections. emptyList());
    }

    protected AwsCryptoException buildCannotDecryptDksException(Throwable t) {
        return buildCannotDecryptDksException(Collections.singletonList(t));
    }

    protected AwsCryptoException buildCannotDecryptDksException(List t) {
        if (t == null || t.isEmpty()) {
            return new CannotUnwrapDataKeyException("Unable to decrypt any data keys");
        } else {
            final CannotUnwrapDataKeyException ex = new CannotUnwrapDataKeyException("Unable to decrypt any data keys",
                    t.get(0));
            for (final Throwable e : t) {
                ex.addSuppressed(e);
            }
            return ex;
        }
    }
}