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lib/src/main/java/zeroecho/sdk/guard/UnlockMaterial.java

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+/*******************************************************************************
+ * Copyright (C) 2025, Leo Galambos
+ * All rights reserved.
+ * 
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ * 
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ * 
+ * 3. All advertising materials mentioning features or use of this software must
+ *    display the following acknowledgement:
+ *    This product includes software developed by the Egothor project.
+ * 
+ * 4. Neither the name of the copyright holder nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ ******************************************************************************/
+package zeroecho.sdk.guard;
+
+import zeroecho.core.annotation.Describable;
+
+/**
+ * UnlockMaterial represents the unlocking data supplied to a recipient opener
+ * to recover a content-encryption key (CEK).
+ *
+ * <h2>Overview</h2> The multi-recipient envelope scans recipient entries and
+ * delegates each attempt to a {@code RecipientOpener}. An opener may require
+ * either a private key or a password to unwrap or derive the CEK. This sealed
+ * interface defines the two supported kinds of unlocking material and
+ * centralizes their lifetime and handling.
+ *
+ * <h2>Usage</h2> <pre>{@code
+ * // Decrypt with a private key
+ * DataContent decRsa = new MultiRecipientDataSourceBuilder()
+ *     .withAes(AesDataContentBuilder.builder().modeGcm(128).withHeader())
+ *     .payloadKeyBytes(32)
+ *     .unlockWith(new UnlockMaterial.Private(rsaPrivateKey))
+ *     .build(false);
+ *
+ * // Decrypt with a password
+ * char[] pwd = "correct horse battery staple".toCharArray();
+ * DataContent decPwd = new MultiRecipientDataSourceBuilder()
+ *     .withAes(AesDataContentBuilder.builder().modeCbcPkcs7().withHeader())
+ *     .payloadKeyBytes(32)
+ *     .unlockWith(new UnlockMaterial.Password(pwd))
+ *     .build(false);
+ * // Clear the password when no longer needed
+ * java.util.Arrays.fill(pwd, '\0');
+ * }</pre>
+ *
+ * <h2>Security notes</h2>
+ * <ul>
+ * <li>{@link Password} stores a reference to the caller-provided {@code char[]}
+ * for performance and zeroization. The caller is responsible for clearing the
+ * array after use.</li>
+ * <li>{@link Private} holds a {@link java.security.PrivateKey}. Manage the
+ * key's lifetime outside the opener and avoid logging or copying it
+ * unnecessarily.</li>
+ * </ul>
+ */
+sealed public interface UnlockMaterial extends Describable {
+    /**
+     * Private holds a private key used to decrypt or decapsulate a recipient entry.
+     *
+     * <p>
+     * Typical uses include RSA-OAEP decryption, ElGamal decryption, or KEM
+     * decapsulation with a private KEM key.
+     * </p>
+     *
+     * @param key the private key used by a matching {@code RecipientOpener}; must
+     *            not be null
+     */
+    record Private(java.security.PrivateKey key) implements UnlockMaterial, Describable {
+
+        @Override
+        public String description() {
+            return "Unlock via key of " + key.getAlgorithm();
+        }
+    }
+
+    /**
+     * Password holds characters used to derive a key-encryption key (KEK) for
+     * unwrapping the CEK.
+     *
+     * <p>
+     * The array reference is stored as provided to allow the caller to clear it
+     * after use. If defensive copying is desired, the caller should provide a copy
+     * and clear both copies after decryption.
+     * </p>
+     *
+     * @param password the password characters; the caller should clear the array
+     *                 when no longer needed
+     */
+    record Password(char[] password) implements UnlockMaterial, Describable {
+
+        @Override
+        public String description() {
+            return "Unlock via password";
+        }
+    }
+}