fix(raw-aes-keyring-node): copy unencryptedMasterKey instead of consuming it

modules/raw-aes-keyring-node/src/raw_aes_keyring_node.ts

@@ -61,13 +61,17 @@ export class RawAesKeyringNode extends KeyringNode {
     } = input
     /* Precondition: AesKeyringNode needs identifying information for encrypt and decrypt. */
     needs(keyName && keyNamespace, 'Identifying information must be defined.')
+    /* The material takes ownership of the key it is given and zeros it once it is
+     * moved into a KeyObject, so the material is given a copy.
+     * The caller keeps ownership of unencryptedMasterKey and is responsible for zeroing it.
+     */
     /* Precondition: RawAesKeyringNode requires wrappingSuite to be a valid RawAesWrappingSuite. */
     const wrappingMaterial = new NodeRawAesMaterial(wrappingSuite)
       /* Precondition: unencryptedMasterKey must correspond to the NodeAlgorithmSuite specification.
        * Note: the KeyringTrace and flag are _only_ set because I am reusing an existing implementation.
        * See: raw_aes_material.ts in @aws-crypto/raw-keyring for details
        */
-      .setUnencryptedDataKey(unencryptedMasterKey, {
+      .setUnencryptedDataKey(copyOfMasterKey(unencryptedMasterKey), {
         keyNamespace,
         keyName,
         flags: KeyringTraceFlag.WRAPPING_KEY_GENERATED_DATA_KEY,
@@ -147,6 +151,21 @@ export class RawAesKeyringNode extends KeyringNode {
 }
 immutableClass(RawAesKeyringNode)
 
+/**
+ * Returns an isolated copy of the caller supplied master key.
+ * The isolation precondition is checked against the caller's buffer
+ * because the copy always starts at offset 0 of its own ArrayBuffer.
+ */
+function copyOfMasterKey(unencryptedMasterKey: Uint8Array): Uint8Array {
+  /* Precondition: The caller's master key must be an isolated buffer. */
+  needs(
+    unencryptedMasterKey instanceof Uint8Array &&
+      unencryptedMasterKey.byteOffset === 0,
+    'Unencrypted Master Key must be an isolated buffer.'
+  )
+  return new Uint8Array(unencryptedMasterKey)
+}
+
 const encryptFlags =
   KeyringTraceFlag.WRAPPING_KEY_ENCRYPTED_DATA_KEY |
   KeyringTraceFlag.WRAPPING_KEY_SIGNED_ENC_CTX

modules/raw-aes-keyring-node/test/raw_aes_keyring_node.test.ts

@@ -118,6 +118,89 @@ describe('RawAesKeyringNode::constructor', () => {
   })
 })
 
+describe('RawAesKeyringNode::constructor does not consume the caller key (#970)', () => {
+  const wrappingSuite =
+    RawAesWrappingSuiteIdentifier.AES128_GCM_IV12_TAG16_NO_PADDING
+  const keyNamespace = 'keyNamespace'
+  const keyName = 'keyName'
+  const suite = new NodeAlgorithmSuite(
+    AlgorithmSuiteIdentifier.ALG_AES256_GCM_IV12_TAG16_HKDF_SHA256
+  )
+
+  it('leaves the unencryptedMasterKey passed in by the caller intact', () => {
+    const unencryptedMasterKey = new Uint8Array(128 / 8).fill(7)
+    new RawAesKeyringNode({
+      keyName,
+      keyNamespace,
+      unencryptedMasterKey,
+      wrappingSuite,
+    })
+    expect(Array.from(unencryptedMasterKey)).to.deep.equal(
+      new Array(128 / 8).fill(7)
+    )
+  })
+
+  it('keeps working after the caller zeros its own unencryptedMasterKey', async () => {
+    const unencryptedMasterKey = new Uint8Array(128 / 8).fill(7)
+    const keyring = new RawAesKeyringNode({
+      keyName,
+      keyNamespace,
+      unencryptedMasterKey,
+      wrappingSuite,
+    })
+    unencryptedMasterKey.fill(0)
+
+    const encryptionMaterial = await keyring.onEncrypt(
+      new NodeEncryptionMaterial(suite, {})
+    )
+    const [edk] = encryptionMaterial.encryptedDataKeys
+    const decryptionMaterial = await keyring.onDecrypt(
+      new NodeDecryptionMaterial(suite, {}),
+      [edk]
+    )
+    expect(
+      unwrapDataKey(decryptionMaterial.getUnencryptedDataKey())
+    ).to.deep.equal(unwrapDataKey(encryptionMaterial.getUnencryptedDataKey()))
+  })
+
+  it('two keyrings can be built from the same unencryptedMasterKey', async () => {
+    const unencryptedMasterKey = new Uint8Array(128 / 8).fill(7)
+    const first = new RawAesKeyringNode({
+      keyName,
+      keyNamespace,
+      unencryptedMasterKey,
+      wrappingSuite,
+    })
+    const second = new RawAesKeyringNode({
+      keyName,
+      keyNamespace,
+      unencryptedMasterKey,
+      wrappingSuite,
+    })
+    const encryptionMaterial = await first.onEncrypt(
+      new NodeEncryptionMaterial(suite, {})
+    )
+    const decryptionMaterial = await second.onDecrypt(
+      new NodeDecryptionMaterial(suite, {}),
+      encryptionMaterial.encryptedDataKeys
+    )
+    expect(decryptionMaterial.hasValidKey()).to.equal(true)
+  })
+
+  it('Precondition: unencryptedMasterKey must be an isolated buffer.', () => {
+    const shared = new Uint8Array(new ArrayBuffer(64), 16, 128 / 8)
+    expect(
+      () =>
+        new RawAesKeyringNode({
+          keyName,
+          keyNamespace,
+          unencryptedMasterKey: shared,
+          wrappingSuite,
+        })
+    ).to.throw('Unencrypted Master Key must be an isolated buffer.')
+  })
+})
+
 describe('RawAesKeyringNode::_filter', () => {
   const wrappingSuite =
     RawAesWrappingSuiteIdentifier.AES128_GCM_IV12_TAG16_NO_PADDING