crypto: allow promisifying generateKeyPair

PR-URL: #22660
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ujjwal Sharma <usharma1998@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

Author: tniessen

doc/api/crypto.md

@@ -1753,6 +1753,9 @@ buffer containing the data encoded as DER. Note that Node.js itself does not
 accept DER, it is supported for interoperability with other libraries such as
 WebCrypto only.
 
+If this method is invoked as its [`util.promisify()`][]ed version, it returns
+a `Promise` for an `Object` with `publicKey` and `privateKey` properties.
+
 ### crypto.generateKeyPairSync(type, options)
 <!-- YAML
 added: REPLACEME
@@ -2907,6 +2910,7 @@ the `crypto`, `tls`, and `https` modules and are generally specific to OpenSSL.
 [`stream.transform` options]: stream.html#stream_new_stream_transform_options
 [`stream.Writable` options]: stream.html#stream_constructor_new_stream_writable_options
 [`tls.createSecureContext()`]: tls.html#tls_tls_createsecurecontext_options
+[`util.promisify()`]: util.html#util_util_promisify_original
 [`verify.update()`]: #crypto_verify_update_data_inputencoding
 [`verify.verify()`]: #crypto_verify_verify_object_signature_signatureformat
 [AEAD algorithms]: https://en.wikipedia.org/wiki/Authenticated_encryption

lib/internal/crypto/keygen.js

@@ -14,6 +14,7 @@ const {
   PK_FORMAT_DER,
   PK_FORMAT_PEM
 } = process.binding('crypto');
+const { customPromisifyArgs } = require('internal/util');
 const { isUint32 } = require('internal/validators');
 const {
   ERR_CRYPTO_INCOMPATIBLE_KEY_OPTIONS,
@@ -43,6 +44,11 @@ function generateKeyPair(type, options, callback) {
   handleError(impl, wrap);
 }
 
+Object.defineProperty(generateKeyPair, customPromisifyArgs, {
+  value: ['publicKey', 'privateKey'],
+  enumerable: false
+});
+
 function generateKeyPairSync(type, options) {
   const impl = check(type, options);
   return handleError(impl);

test/parallel/test-crypto-keygen.js

@@ -13,6 +13,7 @@ const {
   publicEncrypt,
   privateDecrypt
 } = require('crypto');
+const { promisify } = require('util');
 
 // Asserts that the size of the given key (in chars or bytes) is within 10% of
 // the expected size.
@@ -240,6 +241,34 @@ function convertDERToPEM(label, der) {
   }));
 }
 
+{
+  // Test the util.promisified API with async RSA key generation.
+  promisify(generateKeyPair)('rsa', {
+    publicExponent: 0x10001,
+    modulusLength: 3072,
+    publicKeyEncoding: {
+      type: 'pkcs1',
+      format: 'pem'
+    },
+    privateKeyEncoding: {
+      type: 'pkcs1',
+      format: 'pem'
+    }
+  }).then(common.mustCall((keys) => {
+    const { publicKey, privateKey } = keys;
+    assert.strictEqual(typeof publicKey, 'string');
+    assert(pkcs1PubExp.test(publicKey));
+    assertApproximateSize(publicKey, 600);
+
+    assert.strictEqual(typeof privateKey, 'string');
+    assert(pkcs1PrivExp.test(privateKey));
+    assertApproximateSize(privateKey, 2455);
+
+    testEncryptDecrypt(publicKey, privateKey);
+    testSignVerify(publicKey, privateKey);
+  })).catch(common.mustNotCall());
+}
+
 {
   // Test invalid key types.
   for (const type of [undefined, null, 0]) {