crypto: allow zero-length secret KeyObject

doc/api/crypto.md

@@ -3539,6 +3539,9 @@ and it will be impossible to extract the private key from the returned object.
 <!-- YAML
 added: v11.6.0
 changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/44201
+    description: The key can now be zero-length.
   - version: v15.0.0
     pr-url: https://github.com/nodejs/node/pull/35093
     description: The key can also be an ArrayBuffer or string. The encoding

lib/internal/crypto/keys.js

@@ -38,7 +38,6 @@ const {
     ERR_ILLEGAL_CONSTRUCTOR,
     ERR_INVALID_ARG_TYPE,
     ERR_INVALID_ARG_VALUE,
-    ERR_OUT_OF_RANGE,
   }
 } = require('internal/errors');
 
@@ -588,8 +587,6 @@ function prepareSecretKey(key, encoding, bufferOnly = false) {
 
 function createSecretKey(key, encoding) {
   key = prepareSecretKey(key, encoding, true);
-  if (key.byteLength === 0)
-    throw new ERR_OUT_OF_RANGE('key.byteLength', '> 0', key.byteLength);
   const handle = new KeyObjectHandle();
   handle.init(kKeyTypeSecret, key);
   return new SecretKeyObject(handle);

src/crypto/crypto_keys.cc

@@ -872,7 +872,6 @@ void KeyObjectData::MemoryInfo(MemoryTracker* tracker) const {
 }
 
 std::shared_ptr<KeyObjectData> KeyObjectData::CreateSecret(ByteSource key) {
-  CHECK(key);
   return std::shared_ptr<KeyObjectData>(new KeyObjectData(std::move(key)));
 }
 

test/parallel/test-crypto-hmac.js

@@ -450,3 +450,12 @@ assert.strictEqual(
     () => crypto.createHmac('sha7', 'key'),
     /Invalid digest/);
 }
+
+{
+  const buf = Buffer.alloc(0);
+  const keyObject = crypto.createSecretKey(Buffer.alloc(0));
+  assert.deepStrictEqual(
+    crypto.createHmac('sha256', buf).update('foo').digest(),
+    crypto.createHmac('sha256', keyObject).update('foo').digest(),
+  );
+}

test/parallel/test-crypto-key-objects.js

@@ -33,18 +33,6 @@ const publicDsa = fixtures.readKey('dsa_public_1025.pem', 'ascii');
 const privateDsa = fixtures.readKey('dsa_private_encrypted_1025.pem',
                                     'ascii');
 
-{
-  // Attempting to create an empty key should throw.
-  assert.throws(() => {
-    createSecretKey(Buffer.alloc(0));
-  }, {
-    name: 'RangeError',
-    code: 'ERR_OUT_OF_RANGE',
-    message: 'The value of "key.byteLength" is out of range. ' +
-             'It must be > 0. Received 0'
-  });
-}
-
 {
   // Attempting to create a key of a wrong type should throw
   const TYPE = 'wrong_type';
@@ -870,3 +858,13 @@ const privateDsa = fixtures.readKey('dsa_private_encrypted_1025.pem',
   assert(!first.privateKey.equals(second.privateKey));
   assert(!first.privateKey.equals(second.publicKey));
 }
+
+{
+  const first = createSecretKey(Buffer.alloc(0));
+  const second = createSecretKey(new ArrayBuffer(0));
+  const third = createSecretKey(Buffer.alloc(1));
+  assert(first.equals(first));
+  assert(first.equals(second));
+  assert(!first.equals(third));
+  assert(!third.equals(first));
+}