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Amazon Web Services SDK for Android
/*
* Copyright 2013-2016 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.services.s3.internal.crypto;
import com.amazonaws.AmazonClientException;
import com.amazonaws.services.s3.Headers;
import com.amazonaws.services.s3.model.EncryptionMaterials;
import com.amazonaws.services.s3.model.EncryptionMaterialsAccessor;
import com.amazonaws.services.s3.model.ObjectMetadata;
import com.amazonaws.services.s3.model.S3Object;
import com.amazonaws.util.Base64;
import com.amazonaws.util.StringUtils;
import com.amazonaws.util.json.JsonUtils;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.security.Key;
import java.security.Provider;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
/**
* Cryptographic material used for client-side content encrypt/decryption in S3.
* This includes the randomly generated one-time secured CEK
* (content-encryption-key) and the respective key wrapping algorithm, if any,
* and the cryptographic scheme in use.
*/
final class ContentCryptoMaterial {
// null if cek is not secured via key wrapping
private final String keyWrappingAlgorithm;
private final CipherLite cipherLite;
private final Map kekMaterialsDescription;
private final byte[] encryptedCEK;
ContentCryptoMaterial(Map kekMaterialsDescription,
byte[] encryptedCEK,
String keyWrappingAlgorithm,
CipherLite cipherLite) {
this.cipherLite = cipherLite;
this.keyWrappingAlgorithm = keyWrappingAlgorithm;
this.encryptedCEK = encryptedCEK.clone();
this.kekMaterialsDescription = kekMaterialsDescription;
}
/**
* Returns the key wrapping algorithm, or null if the content key is not
* secured via a key wrapping algorithm.
*/
String getKeyWrappingAlgorithm() {
return keyWrappingAlgorithm;
}
/**
* Returns the content crypto scheme.
*/
ContentCryptoScheme getContentCryptoScheme() {
return cipherLite.getContentCryptoScheme();
}
/**
* Returns the given metadata updated with this content crypto material.
*/
ObjectMetadata toObjectMetadata(ObjectMetadata metadata) {
// If we generated a symmetric key to encrypt the data, store it in the
// object metadata.
byte[] encryptedCEK = getEncryptedCEK();
metadata.addUserMetadata(Headers.CRYPTO_KEY_V2,
Base64.encodeAsString(encryptedCEK));
// Put the cipher initialization vector (IV) into the object metadata
byte[] iv = cipherLite.getIV();
metadata.addUserMetadata(Headers.CRYPTO_IV, Base64.encodeAsString(iv));
// Put the materials description into the object metadata as JSON
metadata.addUserMetadata(Headers.MATERIALS_DESCRIPTION,
kekMaterialDescAsJson());
// The CRYPTO_CEK_ALGORITHM, CRYPTO_TAG_LENGTH and
// CRYPTO_KEYWRAP_ALGORITHM were not available in the Encryption Only
// (EO) implementation
ContentCryptoScheme scheme = getContentCryptoScheme();
metadata.addUserMetadata(Headers.CRYPTO_CEK_ALGORITHM,
scheme.getCipherAlgorithm());
int tagLen = scheme.getTagLengthInBits();
if (tagLen > 0)
metadata.addUserMetadata(Headers.CRYPTO_TAG_LENGTH,
String.valueOf(tagLen));
String keyWrapAlgo = getKeyWrappingAlgorithm();
if (keyWrapAlgo != null)
metadata.addUserMetadata(Headers.CRYPTO_KEYWRAP_ALGORITHM,
keyWrapAlgo);
return metadata;
}
String toJsonString() {
Map map = new HashMap();
byte[] encryptedCEK = getEncryptedCEK();
map.put(Headers.CRYPTO_KEY_V2, Base64.encodeAsString(encryptedCEK));
byte[] iv = cipherLite.getIV();
map.put(Headers.CRYPTO_IV, Base64.encodeAsString(iv));
map.put(Headers.MATERIALS_DESCRIPTION, kekMaterialDescAsJson());
// The CRYPTO_CEK_ALGORITHM, CRYPTO_TAG_LENGTH and
// CRYPTO_KEYWRAP_ALGORITHM were not available in the Encryption Only
// (EO) implementation
ContentCryptoScheme scheme = getContentCryptoScheme();
map.put(Headers.CRYPTO_CEK_ALGORITHM, scheme.getCipherAlgorithm());
int tagLen = scheme.getTagLengthInBits();
if (tagLen > 0)
map.put(Headers.CRYPTO_TAG_LENGTH, String.valueOf(tagLen));
String keyWrapAlgo = getKeyWrappingAlgorithm();
if (keyWrapAlgo != null)
map.put(Headers.CRYPTO_KEYWRAP_ALGORITHM, keyWrapAlgo);
return JsonUtils.mapToString(map);
}
/**
* Returns the key-encrypting-key material description as a non-null json
* string;
*/
private String kekMaterialDescAsJson() {
Map kekMaterialDesc = getKEKMaterialsDescription();
if (kekMaterialDesc == null)
kekMaterialDesc = Collections.emptyMap();
return JsonUtils.mapToString(kekMaterialDesc);
}
/**
* Returns the corresponding kek material description from the given json;
* or null if the input is null.
*/
private static Map matdescFromJson(String json) {
if (json == null) {
return null;
}
Map map = JsonUtils.jsonToMap(json);
return map == null ? null : Collections.unmodifiableMap(map);
}
/**
* Returns the content encrypting key unwrapped or decrypted.
*
* @param cekSecured the content encrypting key in wrapped or encrypted
* form; must not be null
* @param keyWrapAlgo key wrapping algorithm; or null if direct encryption
* instead of key wrapping is used
* @param materials the client key encrypting key material for the content
* encrypting key
* @param securityProvider security provider or null if the default security
* provider of the JCE is used
*/
private static SecretKey cek(byte[] cekSecured, String keyWrapAlgo,
EncryptionMaterials materials, Provider securityProvider) {
Key kek;
if (materials.getKeyPair() != null) {
// Do envelope decryption with private key from key pair
kek = materials.getKeyPair().getPrivate();
} else {
// Do envelope decryption with symmetric key
kek = materials.getSymmetricKey();
}
try {
if (keyWrapAlgo != null) {
// Key wrapping specified
Cipher cipher = securityProvider == null ? Cipher
.getInstance(keyWrapAlgo) : Cipher.getInstance(
keyWrapAlgo, securityProvider);
cipher.init(Cipher.UNWRAP_MODE, kek);
return (SecretKey) cipher.unwrap(cekSecured, keyWrapAlgo,
Cipher.SECRET_KEY);
}
// fall back to the Encryption Only (EO) key decrypting method
Cipher cipher;
if (securityProvider != null) {
cipher = Cipher.getInstance(kek.getAlgorithm(),
securityProvider);
} else {
cipher = Cipher.getInstance(kek.getAlgorithm());
}
cipher.init(Cipher.DECRYPT_MODE, kek);
byte[] decryptedSymmetricKeyBytes = cipher.doFinal(cekSecured);
return new SecretKeySpec(decryptedSymmetricKeyBytes,
JceEncryptionConstants.SYMMETRIC_KEY_ALGORITHM);
} catch (Exception e) {
throw new AmazonClientException(
"Unable to decrypt symmetric key from object metadata : "
+ e.getMessage(), e);
}
}
/**
* Factory method to return the content crypto material from the S3 object
* meta data, using the specified key encrypting key material accessor and
* an optional security provider.
*/
static ContentCryptoMaterial fromObjectMetadata(
ObjectMetadata metadata,
EncryptionMaterialsAccessor kekMaterialAccessor,
Provider securityProvider,
long[] range) {
// CEK and IV
Map userMeta = metadata.getUserMetadata();
String b64key = userMeta.get(Headers.CRYPTO_KEY_V2);
if (b64key == null) {
b64key = userMeta.get(Headers.CRYPTO_KEY);
if (b64key == null)
throw new AmazonClientException("Content encrypting key not found.");
}
byte[] cekWrapped = Base64.decode(b64key);
byte[] iv = Base64.decode(userMeta.get(Headers.CRYPTO_IV));
if (cekWrapped == null || iv == null) {
throw new AmazonClientException("Content encrypting key or IV not found.");
}
// Material description
String matdescStr = userMeta.get(Headers.MATERIALS_DESCRIPTION);
Map matdesc = matdescFromJson(matdescStr);
EncryptionMaterials materials = kekMaterialAccessor == null
? null
: kekMaterialAccessor.getEncryptionMaterials(matdesc);
if (materials == null) {
throw new AmazonClientException(
"Unable to retrieve the client encryption materials");
}
// CEK algorithm
String cekAlgo = userMeta.get(Headers.CRYPTO_CEK_ALGORITHM);
boolean isRangeGet = range != null;
// The content crypto scheme may vary depending on whether
// it is a range get operation
ContentCryptoScheme contentCryptoScheme = ContentCryptoScheme
.fromCEKAlgo(cekAlgo, isRangeGet);
if (isRangeGet) {
// Adjust the IV as needed
iv = contentCryptoScheme.adjustIV(iv, range[0]);
} else {
// Validate the tag length supported
int tagLenExpected = contentCryptoScheme.getTagLengthInBits();
if (tagLenExpected > 0) {
String s = userMeta.get(Headers.CRYPTO_TAG_LENGTH);
int tagLenActual = Integer.parseInt(s);
if (tagLenExpected != tagLenActual) {
throw new AmazonClientException("Unsupported tag length: "
+ tagLenActual + ", expected: " + tagLenExpected);
}
}
}
// Unwrap or decrypt the CEK
String keyWrapAlgo = userMeta.get(Headers.CRYPTO_KEYWRAP_ALGORITHM);
SecretKey cek = cek(cekWrapped, keyWrapAlgo, materials,
securityProvider);
return new ContentCryptoMaterial(matdesc, cekWrapped, keyWrapAlgo,
contentCryptoScheme.createCipherLite(cek, iv,
Cipher.DECRYPT_MODE, securityProvider));
}
/**
* Factory method to return the content crypto material from the S3
* instruction file, using the specified key encrypting key material
* accessor and an optional security provider.
*/
static ContentCryptoMaterial fromInstructionFile(Map instFile,
EncryptionMaterialsAccessor kekMaterialAccessor,
Provider securityProvider,
long[] range) {
return fromInstructionFile0(instFile, kekMaterialAccessor,
securityProvider, range);
}
private static ContentCryptoMaterial fromInstructionFile0(
Map map,
EncryptionMaterialsAccessor kekMaterialAccessor,
Provider securityProvider,
long[] range) {
// CEK and IV
String b64key = map.get(Headers.CRYPTO_KEY_V2);
if (b64key == null) {
b64key = map.get(Headers.CRYPTO_KEY);
if (b64key == null)
throw new AmazonClientException("Content encrypting key not found.");
}
byte[] cekWrapped = Base64.decode(b64key);
byte[] iv = Base64.decode(map.get(Headers.CRYPTO_IV));
if (cekWrapped == null || iv == null) {
throw new AmazonClientException(
"Necessary encryption info not found in the instruction file "
+ map);
}
// Material description
String matdescStr = map.get(Headers.MATERIALS_DESCRIPTION);
Map matdesc = matdescFromJson(matdescStr);
EncryptionMaterials materials = kekMaterialAccessor == null
? null
: kekMaterialAccessor.getEncryptionMaterials(matdesc);
if (materials == null) {
throw new AmazonClientException(
"Unable to retrieve the encryption materials that originally "
+ "encrypted object corresponding to instruction file " + map);
}
// CEK algorithm
String cekAlgo = map.get(Headers.CRYPTO_CEK_ALGORITHM);
boolean isRangeGet = range != null;
// The content crypto scheme may vary depending on whether
// it is a range get operation
ContentCryptoScheme contentCryptoScheme = ContentCryptoScheme
.fromCEKAlgo(cekAlgo, isRangeGet);
if (isRangeGet) {
// Adjust the IV as needed
iv = contentCryptoScheme.adjustIV(iv, range[0]);
} else {
// Validate the tag length supported
int tagLenExpected = contentCryptoScheme.getTagLengthInBits();
if (tagLenExpected > 0) {
String s = map.get(Headers.CRYPTO_TAG_LENGTH);
int tagLenActual = Integer.parseInt(s);
if (tagLenExpected != tagLenActual) {
throw new AmazonClientException("Unsupported tag length: "
+ tagLenActual + ", expected: " + tagLenExpected);
}
}
}
// Unwrap or decrypt the CEK
String keyWrapAlgo = map.get(Headers.CRYPTO_KEYWRAP_ALGORITHM);
SecretKey cek = cek(cekWrapped, keyWrapAlgo, materials, securityProvider);
return new ContentCryptoMaterial(matdesc, cekWrapped, keyWrapAlgo,
contentCryptoScheme.createCipherLite(cek, iv,
Cipher.DECRYPT_MODE, securityProvider));
}
/**
* Parses instruction data retrieved from S3 and returns a JSON string
* representing the instruction. Made for testing purposes.
*/
static String parseInstructionFile(S3Object instructionFile) {
try {
return convertStreamToString(instructionFile.getObjectContent());
} catch (Exception e) {
throw new AmazonClientException("Error parsing JSON instruction file: "
+ e.getMessage());
}
}
/**
* Converts the contents of an input stream to a String
*/
private static String convertStreamToString(InputStream inputStream) throws IOException {
if (inputStream == null) {
return "";
} else {
StringBuilder stringBuilder = new StringBuilder();
String line;
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream,
StringUtils.UTF8));
while ((line = reader.readLine()) != null) {
stringBuilder.append(line);
}
} finally {
inputStream.close();
}
return stringBuilder.toString();
}
}
/**
* Return the cipher lite used for content encryption/decryption purposes.
*/
CipherLite getCipherLite() {
return cipherLite;
}
/**
* Returns the description of the kek materials that were used to encrypt
* the cek.
*/
Map getKEKMaterialsDescription() {
return this.kekMaterialsDescription;
}
/**
* Returns an array of bytes representing the encrypted envelope symmetric
* key.
*
* @return an array of bytes representing the encrypted envelope symmetric
* key.
*/
byte[] getEncryptedCEK() {
return this.encryptedCEK.clone();
}
}
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