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chore: clarify Key.getAlgorithm/Cipher.getInstance usage #455

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chore: clarify Key.getAlgorithm/Cipher.getInstance usage #455

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6144721
chore: clarify Key.getAlgorithm usage
alex-chew Jun 11, 2022
3a40c73
Merge branch 'master' into clarify-key-get-algorithm-usage
texastony Aug 16, 2022
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12 changes: 11 additions & 1 deletion .../amazonaws/services/dynamodbv2/datamodeling/encryption/materials/WrappedRawMaterials.java
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Original file line number Diff line number Diff line change
Expand Up @@ -40,6 +40,10 @@
* <p>Other possibly implementations might use a Key-Derivation Function to derive a unique key per
* record.
*
* <p>This class is only as strong as the security of the wrapping/unwrapping keys' underlying
* cryptographic algorithm. We recommend using an AES or RSA key, though other algorithms may also
* be used.
*
* @author Greg Rubin
*/
public class WrappedRawMaterials extends AbstractRawMaterials {
Expand Down Expand Up @@ -117,6 +121,7 @@ protected SecretKey initEnvelopeKey() throws GeneralSecurityException {
throw new IllegalStateException("No private decryption key provided.");
}
byte[] encryptedKey = Base64.decode(description.get(ENVELOPE_KEY));
// The wrapping/unwrapping keys can be of any algorithm of the user's choice, so no check is needed/possible here.
String wrappingAlgorithm = unwrappingKey.getAlgorithm();
if (description.containsKey(KEY_WRAPPING_ALGORITHM)) {
wrappingAlgorithm = description.get(KEY_WRAPPING_ALGORITHM);
Expand All @@ -128,13 +133,16 @@ protected SecretKey initEnvelopeKey() throws GeneralSecurityException {
? generateContentKey(description.get(CONTENT_KEY_ALGORITHM))
: generateContentKey(DEFAULT_ALGORITHM);

// The wrapping/unwrapping keys can be of any algorithm of the user's choice, so no check is needed/possible here.
String wrappingAlg =
description.containsKey(KEY_WRAPPING_ALGORITHM)
? description.get(KEY_WRAPPING_ALGORITHM)
: getTransformation(wrappingKey.getAlgorithm());
String contentKeyAlg = key.getAlgorithm();

byte[] encryptedKey = wrapKey(key, wrappingAlg);
description.put(ENVELOPE_KEY, Base64.encodeToString(encryptedKey));
description.put(CONTENT_KEY_ALGORITHM, key.getAlgorithm());
description.put(CONTENT_KEY_ALGORITHM, contentKeyAlg);
description.put(KEY_WRAPPING_ALGORITHM, wrappingAlg);
setMaterialDescription(description);
return key;
Expand All @@ -147,6 +155,7 @@ public byte[] wrapKey(SecretKey key, String wrappingAlg)
if (wrappingKey instanceof DelegatedKey) {
return ((DelegatedKey) wrappingKey).wrap(key, null, wrappingAlg);
} else {
// The wrapping key can be of any algorithm of the user's choice, so no check is needed/possible here.
Cipher cipher = Cipher.getInstance(wrappingAlg);
cipher.init(Cipher.WRAP_MODE, wrappingKey, Utils.getRng());
byte[] encryptedKey = cipher.wrap(key);
Expand All @@ -167,6 +176,7 @@ protected SecretKey unwrapKey(
null,
wrappingAlgorithm);
} else {
// The unwrapping key can be of any algorithm of the user's choice, so no check is needed/possible here.
Cipher cipher = Cipher.getInstance(wrappingAlgorithm);

// This can be of the form "AES/256" as well as "AES" e.g.,
Expand Down
4 changes: 4 additions & 0 deletions ...onaws/services/dynamodbv2/datamodeling/encryption/providers/WrappedMaterialsProvider.java
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Original file line number Diff line number Diff line change
Expand Up @@ -38,6 +38,10 @@
* <p>This is generally a more secure way of encrypting data than with the {@link
* SymmetricStaticProvider}.
*
* <p>This class is only as strong as the security of the wrapping/unwrapping keys' underlying
* cryptographic algorithm. We recommend using an AES or RSA key, though other algorithms may also
* be used.
*
* @see WrappedRawMaterials
* @author Greg Rubin
*/
Expand Down