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2 | 2 | // SPDX-License-Identifier: Apache-2.0 |
3 | 3 | package software.amazon.encryption.s3.internal; |
4 | 4 |
|
| 5 | +import software.amazon.awssdk.core.ResponseInputStream; |
| 6 | +import software.amazon.awssdk.core.async.AsyncResponseTransformer; |
| 7 | +import software.amazon.awssdk.protocols.jsoncore.JsonNode; |
| 8 | +import software.amazon.awssdk.protocols.jsoncore.JsonNodeParser; |
| 9 | +import software.amazon.awssdk.services.s3.S3AsyncClient; |
5 | 10 | import software.amazon.awssdk.services.s3.model.GetObjectRequest; |
6 | 11 | import software.amazon.awssdk.services.s3.model.GetObjectResponse; |
| 12 | +import software.amazon.awssdk.services.s3.model.NoSuchKeyException; |
| 13 | +import software.amazon.encryption.s3.S3EncryptionClientException; |
| 14 | +import software.amazon.encryption.s3.algorithms.AlgorithmSuite; |
| 15 | +import software.amazon.encryption.s3.materials.EncryptedDataKey; |
| 16 | +import software.amazon.encryption.s3.materials.S3Keyring; |
7 | 17 |
|
8 | | -@FunctionalInterface |
9 | | -public interface ContentMetadataDecodingStrategy { |
10 | | - ContentMetadata decodeMetadata(GetObjectRequest request, GetObjectResponse response); |
| 18 | +import java.nio.charset.StandardCharsets; |
| 19 | +import java.util.Base64; |
| 20 | +import java.util.HashMap; |
| 21 | +import java.util.Map; |
| 22 | + |
| 23 | +import static software.amazon.encryption.s3.S3EncryptionClientUtilities.INSTRUCTION_FILE_SUFFIX; |
| 24 | + |
| 25 | +public class ContentMetadataDecodingStrategy { |
| 26 | + |
| 27 | + private static final Base64.Decoder DECODER = Base64.getDecoder(); |
| 28 | + |
| 29 | + private final S3AsyncClient wrappedAsyncClient_; |
| 30 | + |
| 31 | + public ContentMetadataDecodingStrategy(S3AsyncClient s3AsyncClient) { |
| 32 | + if (s3AsyncClient == null) { |
| 33 | + throw new S3EncryptionClientException("ContentMetadataDecodingStrategy requires a non-null async client."); |
| 34 | + } |
| 35 | + wrappedAsyncClient_ = s3AsyncClient; |
| 36 | + } |
| 37 | + |
| 38 | + private ContentMetadata readFromMap(Map<String, String> metadata, GetObjectResponse response) { |
| 39 | + // Get algorithm suite |
| 40 | + final String contentEncryptionAlgorithm = metadata.get(MetadataKeyConstants.CONTENT_CIPHER); |
| 41 | + AlgorithmSuite algorithmSuite; |
| 42 | + String contentRange = response.contentRange(); |
| 43 | + if (contentEncryptionAlgorithm == null |
| 44 | + || contentEncryptionAlgorithm.equals(AlgorithmSuite.ALG_AES_256_CBC_IV16_NO_KDF.cipherName())) { |
| 45 | + algorithmSuite = AlgorithmSuite.ALG_AES_256_CBC_IV16_NO_KDF; |
| 46 | + } else if (contentEncryptionAlgorithm.equals(AlgorithmSuite.ALG_AES_256_GCM_IV12_TAG16_NO_KDF.cipherName())) { |
| 47 | + // If contentRange is provided, this is a ranged get. |
| 48 | + // ranged gets require legacy unauthenticated modes. |
| 49 | + // Change AES-GCM to AES-CTR to disable authentication when reading this message. |
| 50 | + algorithmSuite = (contentRange == null) |
| 51 | + ? AlgorithmSuite.ALG_AES_256_GCM_IV12_TAG16_NO_KDF |
| 52 | + : AlgorithmSuite.ALG_AES_256_CTR_IV16_TAG16_NO_KDF; |
| 53 | + } else { |
| 54 | + throw new S3EncryptionClientException( |
| 55 | + "Unknown content encryption algorithm: " + contentEncryptionAlgorithm); |
| 56 | + } |
| 57 | + |
| 58 | + // Do algorithm suite dependent decoding |
| 59 | + byte[] edkCiphertext; |
| 60 | + |
| 61 | + // Currently, this is not stored within the metadata, |
| 62 | + // signal to keyring(s) intended for S3EC |
| 63 | + final String keyProviderId = S3Keyring.KEY_PROVIDER_ID; |
| 64 | + String keyProviderInfo; |
| 65 | + switch (algorithmSuite) { |
| 66 | + case ALG_AES_256_CBC_IV16_NO_KDF: |
| 67 | + // Extract encrypted data key ciphertext |
| 68 | + if (metadata.containsKey(MetadataKeyConstants.ENCRYPTED_DATA_KEY_V1)) { |
| 69 | + edkCiphertext = DECODER.decode(metadata.get(MetadataKeyConstants.ENCRYPTED_DATA_KEY_V1)); |
| 70 | + } else if (metadata.containsKey(MetadataKeyConstants.ENCRYPTED_DATA_KEY_V2)) { |
| 71 | + // when using v1 to encrypt in its default mode, it may use the v2 EDK key |
| 72 | + // despite also using CBC as the content encryption algorithm, presumably due |
| 73 | + // to how the v2 changes were backported to v1 |
| 74 | + edkCiphertext = DECODER.decode(metadata.get(MetadataKeyConstants.ENCRYPTED_DATA_KEY_V2)); |
| 75 | + } else { |
| 76 | + // this shouldn't happen under normal circumstances- only if out-of-band modification |
| 77 | + // to the metadata is performed. it is most likely that the data is unrecoverable in this case |
| 78 | + throw new S3EncryptionClientException("Malformed object metadata! Could not find the encrypted data key."); |
| 79 | + } |
| 80 | + |
| 81 | + if (!metadata.containsKey(MetadataKeyConstants.ENCRYPTED_DATA_KEY_ALGORITHM)) { |
| 82 | + /* |
| 83 | + For legacy v1 EncryptionOnly objects, |
| 84 | + there is no EDK algorithm given, it is either plain AES or RSA |
| 85 | + In v3, we infer AES vs. RSA based on the length of the ciphertext. |
| 86 | +
|
| 87 | + In v1, whichever key material is provided in its EncryptionMaterials |
| 88 | + is used to decrypt the EDK. |
| 89 | +
|
| 90 | + In v3, this is not possible as the keyring code is factored such that |
| 91 | + the keyProviderInfo is known before the keyring is known. |
| 92 | + Ciphertext size is expected to be reliable as no AES data key should |
| 93 | + exceed 256 bits (32 bytes) + 16 padding bytes. |
| 94 | +
|
| 95 | + In the unlikely event that this assumption is false, the fix would be |
| 96 | + to refactor the keyring to always use the material given instead of |
| 97 | + inferring it this way. |
| 98 | + */ |
| 99 | + if (edkCiphertext.length > 48) { |
| 100 | + keyProviderInfo = "RSA"; |
| 101 | + } else { |
| 102 | + keyProviderInfo = "AES"; |
| 103 | + } |
| 104 | + } else { |
| 105 | + keyProviderInfo = metadata.get(MetadataKeyConstants.ENCRYPTED_DATA_KEY_ALGORITHM); |
| 106 | + } |
| 107 | + break; |
| 108 | + case ALG_AES_256_GCM_IV12_TAG16_NO_KDF: |
| 109 | + case ALG_AES_256_CTR_IV16_TAG16_NO_KDF: |
| 110 | + // Check tag length |
| 111 | + final int tagLength = Integer.parseInt(metadata.get(MetadataKeyConstants.CONTENT_CIPHER_TAG_LENGTH)); |
| 112 | + if (tagLength != algorithmSuite.cipherTagLengthBits()) { |
| 113 | + throw new S3EncryptionClientException("Expected tag length (bits) of: " |
| 114 | + + algorithmSuite.cipherTagLengthBits() |
| 115 | + + ", got: " + tagLength); |
| 116 | + } |
| 117 | + |
| 118 | + // Extract encrypted data key ciphertext and provider id |
| 119 | + edkCiphertext = DECODER.decode(metadata.get(MetadataKeyConstants.ENCRYPTED_DATA_KEY_V2)); |
| 120 | + keyProviderInfo = metadata.get(MetadataKeyConstants.ENCRYPTED_DATA_KEY_ALGORITHM); |
| 121 | + |
| 122 | + break; |
| 123 | + default: |
| 124 | + throw new S3EncryptionClientException( |
| 125 | + "Unknown content encryption algorithm: " + algorithmSuite.id()); |
| 126 | + } |
| 127 | + |
| 128 | + // Build encrypted data key |
| 129 | + EncryptedDataKey edk = EncryptedDataKey.builder() |
| 130 | + .encryptedDataKey(edkCiphertext) |
| 131 | + .keyProviderId(keyProviderId) |
| 132 | + .keyProviderInfo(keyProviderInfo.getBytes(StandardCharsets.UTF_8)) |
| 133 | + .build(); |
| 134 | + |
| 135 | + // Get encrypted data key encryption context |
| 136 | + final Map<String, String> encryptionContext = new HashMap<>(); |
| 137 | + final String jsonEncryptionContext = metadata.get(MetadataKeyConstants.ENCRYPTED_DATA_KEY_CONTEXT); |
| 138 | + try { |
| 139 | + JsonNodeParser parser = JsonNodeParser.create(); |
| 140 | + JsonNode objectNode = parser.parse(jsonEncryptionContext); |
| 141 | + |
| 142 | + for (Map.Entry<String, JsonNode> entry : objectNode.asObject().entrySet()) { |
| 143 | + encryptionContext.put(entry.getKey(), entry.getValue().asString()); |
| 144 | + } |
| 145 | + } catch (Exception e) { |
| 146 | + throw new RuntimeException(e); |
| 147 | + } |
| 148 | + |
| 149 | + // Get content iv |
| 150 | + byte[] iv = DECODER.decode(metadata.get(MetadataKeyConstants.CONTENT_IV)); |
| 151 | + |
| 152 | + return ContentMetadata.builder() |
| 153 | + .algorithmSuite(algorithmSuite) |
| 154 | + .encryptedDataKey(edk) |
| 155 | + .encryptedDataKeyContext(encryptionContext) |
| 156 | + .contentIv(iv) |
| 157 | + .contentRange(contentRange) |
| 158 | + .build(); |
| 159 | + } |
| 160 | + |
| 161 | + public ContentMetadata decode(GetObjectRequest request, GetObjectResponse response) { |
| 162 | + Map<String, String> metadata = response.metadata(); |
| 163 | + ContentMetadataDecodingStrategy strategy; |
| 164 | + if (metadata != null |
| 165 | + && metadata.containsKey(MetadataKeyConstants.CONTENT_IV) |
| 166 | + && (metadata.containsKey(MetadataKeyConstants.ENCRYPTED_DATA_KEY_V1) |
| 167 | + || metadata.containsKey(MetadataKeyConstants.ENCRYPTED_DATA_KEY_V2))) { |
| 168 | + return decodeFromObjectMetadata(request, response); |
| 169 | + } else { |
| 170 | + return decodeFromInstructionFile(request, response); |
| 171 | + } |
| 172 | + } |
| 173 | + |
| 174 | + private ContentMetadata decodeFromObjectMetadata(GetObjectRequest request, GetObjectResponse response) { |
| 175 | + return readFromMap(response.metadata(), response); |
| 176 | + } |
| 177 | + |
| 178 | + private ContentMetadata decodeFromInstructionFile(GetObjectRequest request, GetObjectResponse response) { |
| 179 | + GetObjectRequest instructionGetObjectRequest = GetObjectRequest.builder() |
| 180 | + .bucket(request.bucket()) |
| 181 | + .key(request.key() + INSTRUCTION_FILE_SUFFIX) |
| 182 | + .build(); |
| 183 | + |
| 184 | + ResponseInputStream<GetObjectResponse> instruction; |
| 185 | + try { |
| 186 | + instruction = wrappedAsyncClient_.getObject(instructionGetObjectRequest, AsyncResponseTransformer.toBlockingInputStream()).join(); |
| 187 | + } catch (NoSuchKeyException exception) { |
| 188 | + // Most likely, the customer is attempting to decrypt an object |
| 189 | + // which is not encrypted with the S3 EC. |
| 190 | + throw new S3EncryptionClientException("Instruction file not found! Please ensure the object you are" + |
| 191 | + " attempting to decrypt has been encrypted using the S3 Encryption Client.", exception); |
| 192 | + } |
| 193 | + |
| 194 | + Map<String, String> metadata = new HashMap<>(); |
| 195 | + JsonNodeParser parser = JsonNodeParser.create(); |
| 196 | + JsonNode objectNode = parser.parse(instruction); |
| 197 | + for (Map.Entry<String, JsonNode> entry : objectNode.asObject().entrySet()) { |
| 198 | + metadata.put(entry.getKey(), entry.getValue().asString()); |
| 199 | + } |
| 200 | + return readFromMap(metadata, response); |
| 201 | + } |
11 | 202 | } |
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