Merge pull request #6 from imabhichow/main

Add RSA/ECB Legacy Keyring

Author: imabhichow

src/main/java/software/amazon/encryption/s3/legacy/materials/RsaEcbKeyring.java

@@ -0,0 +1,86 @@
+package software.amazon.encryption.s3.legacy.materials;
+
+
+import software.amazon.encryption.s3.S3EncryptionClientException;
+import software.amazon.encryption.s3.materials.DecryptionMaterials;
+import software.amazon.encryption.s3.materials.EncryptedDataKey;
+import software.amazon.encryption.s3.materials.EncryptionMaterials;
+import software.amazon.encryption.s3.materials.Keyring;
+
+import javax.crypto.Cipher;
+import java.security.Key;
+import java.security.KeyPair;
+import java.util.List;
+
+/**
+ * RsaEcbKeyring is a legacy, decrypt-only keyring and will use an RSA Public key to unwrap the data key
+ * used to encrypt content.
+ */
+
+public class RsaEcbKeyring implements Keyring{
+
+    private static final String KEY_ALGORITHM = "RSA";
+    private static final String KEY_PROVIDER_ID = "RSA/ECB/OAEPWithSHA-256AndMGF1Padding";
+    private static final String CIPHER_ALGORITHM = "RSA/ECB/OAEPWithSHA-256AndMGF1Padding";
+
+    private final KeyPair _wrappingKeyPair;
+
+    private RsaEcbKeyring(RsaEcbKeyring.Builder builder) {
+        _wrappingKeyPair = builder._wrappingKeyPair;
+    }
+
+    public static RsaEcbKeyring.Builder builder() {
+        return new RsaEcbKeyring.Builder();
+    }
+
+    @Override
+    public EncryptionMaterials onEncrypt(EncryptionMaterials materials) {
+        throw new S3EncryptionClientException("Encrypt not supported for " + KEY_PROVIDER_ID);
+    }
+
+    @Override
+    public DecryptionMaterials onDecrypt(DecryptionMaterials materials, List<EncryptedDataKey> encryptedDataKeys) {
+        if (materials.plaintextDataKey() != null) {
+            throw new S3EncryptionClientException("Decryption materials already contains a plaintext data key.");
+        }
+
+        for (EncryptedDataKey encryptedDataKey : encryptedDataKeys) {
+            if (!encryptedDataKey.keyProviderId().equals(KEY_PROVIDER_ID)) {
+                continue;
+            }
+
+            try {
+                final Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM);
+                cipher.init(Cipher.UNWRAP_MODE, _wrappingKeyPair.getPrivate());
+
+                Key plaintextKey = cipher.unwrap(encryptedDataKey.ciphertext(), CIPHER_ALGORITHM, Cipher.SECRET_KEY);
+
+                return materials.toBuilder().plaintextDataKey(plaintextKey.getEncoded()).build();
+            } catch (Exception e) {
+                throw new S3EncryptionClientException("Unable to " + KEY_PROVIDER_ID + " unwrap", e);
+            }
+        }
+
+        return materials;
+    }
+
+    public static class Builder {
+        private KeyPair _wrappingKeyPair;
+
+        private Builder() {}
+
+        public RsaEcbKeyring.Builder wrappingKeyPair(KeyPair wrappingKeyPair) {
+            if (!wrappingKeyPair.getPublic().getAlgorithm().equals(KEY_ALGORITHM)) {
+                throw new S3EncryptionClientException("Invalid algorithm '" + wrappingKeyPair.getPublic().getAlgorithm() + "', expecting " + KEY_ALGORITHM);
+            }
+            _wrappingKeyPair = wrappingKeyPair;
+            return this;
+        }
+
+        public RsaEcbKeyring build() {
+            return new RsaEcbKeyring(this);
+        }
+    }
+}
+
+