crypto: clear err stack after ECDH::BufferToPoint

Functions that call `ECDH::BufferToPoint` were not clearing the
error stack on failure, so an invalid key could leave leftover
error state and cause subsequent (unrelated) signing operations
to fail.

PR-URL: nodejs#13275
Backport-PR-URL: nodejs#13397
Reviewed-By: Fedor Indutny <fedor.indutny@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Sam Roberts <vieuxtech@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

src/node_crypto.cc

@@ -5011,6 +5011,8 @@ void ECDH::ComputeSecret(const FunctionCallbackInfo<Value>& args) {
   ECDH* ecdh;
   ASSIGN_OR_RETURN_UNWRAP(&ecdh, args.Holder());
 
+  MarkPopErrorOnReturn mark_pop_error_on_return;
+
   if (!ecdh->IsKeyPairValid())
     return env->ThrowError("Invalid key pair");
 
@@ -5160,6 +5162,8 @@ void ECDH::SetPublicKey(const FunctionCallbackInfo<Value>& args) {
 
   THROW_AND_RETURN_IF_NOT_BUFFER(args[0], "Public key");
 
+  MarkPopErrorOnReturn mark_pop_error_on_return;
+
   EC_POINT* pub = ecdh->BufferToPoint(Buffer::Data(args[0].As<Object>()),
                                       Buffer::Length(args[0].As<Object>()));
   if (pub == nullptr)

test/parallel/test-crypto-dh.js

@@ -270,6 +270,26 @@ ecdh5.setPrivateKey(cafebabeKey, 'hex');
   assert.strictEqual(ecdh5.getPrivateKey('hex'), cafebabeKey);
 });
 
+// Use of invalid keys was not cleaning up ERR stack, and was causing
+// unexpected failure in subsequent signing operations.
+const ecdh6 = crypto.createECDH('prime256v1');
+const invalidKey = Buffer.alloc(65);
+invalidKey.fill('\0');
+ecdh6.generateKeys();
+assert.throws(() => {
+  ecdh6.computeSecret(invalidKey);
+}, /^Error: Failed to translate Buffer to a EC_POINT$/);
+// Check that signing operations are not impacted by the above error.
+const ecPrivateKey =
+  '-----BEGIN EC PRIVATE KEY-----\n' +
+  'MHcCAQEEIF+jnWY1D5kbVYDNvxxo/Y+ku2uJPDwS0r/VuPZQrjjVoAoGCCqGSM49\n' +
+  'AwEHoUQDQgAEurOxfSxmqIRYzJVagdZfMMSjRNNhB8i3mXyIMq704m2m52FdfKZ2\n' +
+  'pQhByd5eyj3lgZ7m7jbchtdgyOF8Io/1ng==\n' +
+  '-----END EC PRIVATE KEY-----';
+assert.doesNotThrow(() => {
+  crypto.createSign('SHA256').sign(ecPrivateKey);
+});
+
 // invalid test: curve argument is undefined
 assert.throws(() => {
   crypto.createECDH();