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/**
 * Copyright Microsoft Corporation
 * 
 * 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.microsoft.azure.storage.blob;

import java.io.OutputStream;
import java.util.HashMap;
import java.util.Map;

import javax.crypto.Cipher;
import javax.crypto.CipherOutputStream;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

import org.apache.commons.lang3.tuple.Pair;

import com.microsoft.azure.keyvault.core.IKey;
import com.microsoft.azure.keyvault.core.IKeyResolver;
import com.microsoft.azure.storage.Constants;
import com.microsoft.azure.storage.StorageErrorCodeStrings;
import com.microsoft.azure.storage.StorageException;
import com.microsoft.azure.storage.core.EncryptionAgent;
import com.microsoft.azure.storage.core.EncryptionAlgorithm;
import com.microsoft.azure.storage.core.SR;
import com.microsoft.azure.storage.core.Utility;
import com.microsoft.azure.storage.core.WrappedContentKey;


/**
 * Represents a blob encryption policy that is used to perform envelope encryption/decryption of Azure blobs.
 */
public final class BlobEncryptionPolicy {

    /**
     * The {@link IKeyResolver} used to select the correct key for decrypting existing blobs.
     */
    public IKeyResolver keyResolver;

    /**
     * An object of type {@link IKey} that is used to wrap/unwrap the content key during encryption.
     */
    public IKey keyWrapper;

    /**
     * Initializes a new instance of the {@link BlobEncryptionPolicy} class with the specified key and resolver.
     * 

* If the generated policy is intended to be used for encryption, users are expected to provide a key at the * minimum. The absence of key will cause an exception to be thrown during encryption. If the generated policy is * intended to be used for decryption, users can provide a keyResolver. The client library will - 1. Invoke the key * resolver if specified to get the key. 2. If resolver is not specified but a key is specified, match the key id on * the key and use it. * * @param key * An object of type {@link IKey} that is used to wrap/unwrap the content encryption key. * @param keyResolver * The key resolver used to select the correct key for decrypting existing blobs. */ public BlobEncryptionPolicy(IKey key, IKeyResolver keyResolver) { this.keyWrapper = key; this.keyResolver = keyResolver; } /** * Gets the {@link IKey} that is used to wrap/unwrap the content key during encryption. * * @return An {@link IKey} object. */ public IKey getKey() { return this.keyWrapper; } /** * Gets the key resolver used to select the correct key for decrypting existing blobs. * * @return A resolver that returns an {@link IKey} given a keyId. */ public IKeyResolver getKeyResolver() { return this.keyResolver; } /** * Sets the {@link IKey} that is used to wrap/unwrap the content key during encryption. * * @param key * An {@link IKey} object. */ public void setKey(IKey key) { this.keyWrapper = key; } /** * Sets the key resolver used to select the correct key for decrypting existing blobs. * * @param keyResolver * A resolver that returns an {@link IKey} given a keyId. */ public void setKeyResolver(IKeyResolver keyResolver) { this.keyResolver = keyResolver; } /** * Return a reference to a {@link OutputStream} given a user stream. This method is used for decrypting blobs. * @param userProvidedStream * The output stream provided by the user. * @param metadata * Reference to blob metadata object that is used to get the encryption materials. * @param requireEncryption * A value to indicate that the data read from the server should be encrypted. * @param iv * The iv to use if pre-buffered. Used only for range reads. * @param noPadding * Value indicating if the padding mode should be set or not. * @return A reference to a {@link OutputStream} that will be written to. * @throws StorageException * An exception representing any error which occurred during the operation. */ OutputStream decryptBlob(OutputStream userProvidedStream, Map metadata, Boolean requireEncryption, byte[] iv, boolean noPadding) throws StorageException { Utility.assertNotNull("metadata", metadata); String encryptionDataString = metadata.get("encryptiondata"); try { if (encryptionDataString != null) { BlobEncryptionData encryptionData = BlobEncryptionData.deserialize(encryptionDataString); Utility.assertNotNull("encryptionData", encryptionData); Utility.assertNotNull("contentEncryptionIV", encryptionData.getContentEncryptionIV()); Utility.assertNotNull("encryptedKey", encryptionData.getWrappedContentKey().getEncryptedKey()); // Throw if the encryption protocol on the message doesn't match the version that this client library understands // and is able to decrypt. if (!Constants.EncryptionConstants.ENCRYPTION_PROTOCOL_V1.equals(encryptionData.getEncryptionAgent() .getProtocol())) { throw new StorageException(StorageErrorCodeStrings.DECRYPTION_ERROR, SR.ENCRYPTION_PROTOCOL_VERSION_INVALID, null); } // Throw if neither the key nor the key resolver are set. if (this.keyWrapper == null && this.keyResolver == null) { throw new StorageException(StorageErrorCodeStrings.DECRYPTION_ERROR, SR.KEY_AND_RESOLVER_MISSING, null); } byte[] contentEncryptionKey = null; // 1. Invoke the key resolver if specified to get the key. If the resolver is specified but does not have a // mapping for the key id, an error should be thrown. This is important for key rotation scenario. // 2. If resolver is not specified but a key is specified, match the key id on the key and and use it. // Calling UnwrapKeyAsync synchronously is fine because for the storage client scenario, unwrap happens // locally. No service call is made. if (this.keyResolver != null) { IKey keyEncryptionKey = this.keyResolver.resolveKeyAsync(encryptionData.getWrappedContentKey() .getKeyId()).get(); Utility.assertNotNull("keyEncryptionKey", keyEncryptionKey); contentEncryptionKey = keyEncryptionKey.unwrapKeyAsync( encryptionData.getWrappedContentKey().getEncryptedKey(), encryptionData.getWrappedContentKey().getAlgorithm()).get(); } else { if (encryptionData.getWrappedContentKey().getKeyId().equals(this.keyWrapper.getKid())) { contentEncryptionKey = this.keyWrapper.unwrapKeyAsync( encryptionData.getWrappedContentKey().getEncryptedKey(), encryptionData.getWrappedContentKey().getAlgorithm()).get(); } else { throw new StorageException(StorageErrorCodeStrings.DECRYPTION_ERROR, SR.KEY_MISMATCH, null); } } switch (encryptionData.getEncryptionAgent().getEncryptionAlgorithm()) { case AES_CBC_256: Cipher myAes; if (noPadding) { myAes = Cipher.getInstance("AES/CBC/NoPadding"); } else { myAes = Cipher.getInstance("AES/CBC/PKCS5Padding"); } IvParameterSpec ivParameterSpec = new IvParameterSpec(iv != null ? iv : encryptionData.getContentEncryptionIV()); SecretKey keySpec = new SecretKeySpec(contentEncryptionKey, 0, contentEncryptionKey.length, "AES"); myAes.init(Cipher.DECRYPT_MODE, keySpec, ivParameterSpec); return new CipherOutputStream(userProvidedStream, myAes); default: throw new StorageException(StorageErrorCodeStrings.DECRYPTION_ERROR, SR.INVALID_ENCRYPTION_ALGORITHM, null); } } else { return userProvidedStream; } } catch (StorageException ex) { throw ex; } catch (Exception ex) { throw new StorageException(StorageErrorCodeStrings.DECRYPTION_ERROR, SR.DECRYPTION_LOGIC_ERROR, ex); } } /** * Internal helper method to wrap a user provided stream with the appropriate crypto stream. */ static OutputStream wrapUserStreamWithDecryptStream(CloudBlob blob, OutputStream userProvidedStream, BlobRequestOptions options, Map metadata, long blobLength, boolean rangeRead, Long endOffset, Long userSpecifiedLength, int discardFirst, boolean bufferIV) throws StorageException { // If encryption policy is set but the encryption metadata is absent, throw // an exception. String encryptionDataString = metadata.get("encryptiondata"); if (options.requireEncryption() != null && options.requireEncryption() && encryptionDataString == null) { throw new StorageException(StorageErrorCodeStrings.DECRYPTION_ERROR, SR.ENCRYPTION_DATA_NOT_PRESENT_ERROR, null); } if (!rangeRead) { // The user provided stream should be wrapped in a TruncatingNonCloseableStream in order to // avoid closing the user stream when the crypto stream is closed to flush the final decrypted // block of data. OutputStream decryptStream = options.getEncryptionPolicy().decryptBlob(userProvidedStream, metadata, options.requireEncryption(), null, blob.getProperties().getBlobType() == BlobType.PAGE_BLOB); return decryptStream; } else { // Check if end offset lies in the last AES block and send this information over to set the correct padding mode. boolean noPadding = blob.getProperties().getBlobType() == BlobType.PAGE_BLOB || endOffset != null && endOffset < blobLength - 16; return new BlobDecryptStream(userProvidedStream, metadata, userSpecifiedLength, discardFirst, bufferIV, noPadding, options.getEncryptionPolicy(), options.requireEncryption()); } } /** * Set up the encryption context required for encrypting blobs. * @param metadata * Reference to blob metadata object that is used to set the encryption materials. * @param noPadding * Value indicating if the padding mode should be set or not. * @return The Cipher to use to decrypt the blob. * @throws StorageException * An exception representing any error which occurred during the operation. */ Cipher createAndSetEncryptionContext(Map metadata, boolean noPadding) throws StorageException { Utility.assertNotNull("metadata", metadata); // The Key should be set on the policy for encryption. Otherwise, throw an error. if (this.keyWrapper == null) { throw new IllegalArgumentException(SR.KEY_MISSING); } try { KeyGenerator keyGen = KeyGenerator.getInstance("AES"); keyGen.init(256); Cipher myAes; if (noPadding) { myAes = Cipher.getInstance("AES/CBC/NoPadding"); } else { myAes = Cipher.getInstance("AES/CBC/PKCS5Padding"); } SecretKey aesKey = keyGen.generateKey(); myAes.init(Cipher.ENCRYPT_MODE, aesKey); BlobEncryptionData encryptionData = new BlobEncryptionData(); if (encryptionData.getKeyWrappingMetadata() == null) { encryptionData.setKeyWrappingMetadata(new HashMap()); } encryptionData.getKeyWrappingMetadata().put(Constants.EncryptionConstants.ENCRYPTION_LIBRARY, "Java " + Constants.HeaderConstants.USER_AGENT_VERSION); encryptionData.setEncryptionAgent(new EncryptionAgent(Constants.EncryptionConstants.ENCRYPTION_PROTOCOL_V1, EncryptionAlgorithm.AES_CBC_256)); // Wrap key Pair encryptedKey = this.keyWrapper.wrapKeyAsync(aesKey.getEncoded(), null /* algorithm */).get(); encryptionData.setWrappedContentKey(new WrappedContentKey(this.keyWrapper.getKid(), encryptedKey.getKey(), encryptedKey.getValue())); encryptionData.setContentEncryptionIV(myAes.getIV()); metadata.put(Constants.EncryptionConstants.BLOB_ENCRYPTION_DATA, encryptionData.serialize()); return myAes; } catch (Exception e) { throw StorageException.translateClientException(e); } } }





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