crypto: optimize private EC JWK import

Avoid creating temporary EVP objects and repeating key validation while
retaining the private scalar range and public/private consistency
checks.

Assisted-by: GitHub Copilot
Signed-off-by: Filip Skokan <panva.ip@gmail.com>

Author: panva

deps/ncrypto/ncrypto.cc

@@ -5348,6 +5348,24 @@ bool ECPointPointer::mul(const EC_GROUP* group, const BIGNUM* priv_key) {
 
 // ============================================================================
 
+bool ECKeyPointer::checkPrivateKey() const {
+  const auto group = getGroup();
+  const auto priv = getPrivateKey();
+  const auto pub = getPublicKey();
+  if (group == nullptr || priv == nullptr || pub == nullptr) return false;
+
+  auto order = BignumPointer::New();
+  if (!order || !EC_GROUP_get_order(group, order.get(), nullptr) ||
+      BN_is_zero(priv) || BN_is_negative(priv) ||
+      BN_cmp(priv, order.get()) >= 0) {
+    return false;
+  }
+
+  auto expected = ECPointPointer::New(group);
+  return expected && expected.mul(group, priv) &&
+         EC_POINT_cmp(group, expected.get(), pub, nullptr) == 0;
+}
+
 #if NCRYPTO_USE_LEGACY_KEY_TYPES
 ECKeyPointer::ECKeyPointer() : key_(nullptr) {}
 

deps/ncrypto/ncrypto.h

@@ -1764,6 +1764,7 @@ class ECKeyPointer final {
   bool setPublicKeyRaw(const BignumPointer& x, const BignumPointer& y);
   bool generate();
   bool checkKey() const;
+  bool checkPrivateKey() const;
   DataPointer computeSecret(const ECPointPointer& peer) const;
 
   const EC_GROUP* getGroup() const;

src/crypto/crypto_ec.cc

@@ -756,7 +756,7 @@ KeyObjectData ImportJWKEcKey(Environment* env, Local<Object> jwk) {
       return {};
     }
     // Verify that the public point matches the private scalar (d*G == (x,y)).
-    if (!ec.checkKey()) {
+    if (!ec.checkPrivateKey()) {
       THROW_ERR_CRYPTO_INVALID_JWK(env, "Invalid JWK EC key");
       return {};
     }

test/parallel/test-crypto-key-objects-ec-jwk-private.js

@@ -0,0 +1,78 @@
+'use strict';
+
+const common = require('../common');
+if (!common.hasCrypto)
+  common.skip('missing crypto');
+
+const assert = require('assert');
+const {
+  createECDH,
+  createPrivateKey,
+  createPublicKey,
+  getFips,
+  sign,
+  verify,
+} = require('crypto');
+
+const curves = [
+  ['prime256v1', 'P-256', 32,
+   'ffffffff00000000ffffffffffffffffbce6faada7179e84f3b9cac2fc632551'],
+  ['secp384r1', 'P-384', 48,
+   'ffffffffffffffffffffffffffffffffffffffffffffffffc7634d81f4372ddf' +
+   '581a0db248b0a77aecec196accc52973'],
+  ['secp521r1', 'P-521', 66,
+   '01ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff' +
+   'fa51868783bf2f966b7fcc0148f709a5d03bb5c9b8899c47aebb6fb71e91386409'],
+];
+if (!getFips()) {
+  curves.push(['secp256k1', 'secp256k1', 32,
+               'fffffffffffffffffffffffffffffffebaaedce6af48a03bbfd25e8cd0364141']);
+}
+
+for (const [namedCurve, crv, width, orderHex] of curves) {
+  const order = BigInt(`0x${orderHex}`);
+  const encode = (scalar) => Buffer.from(
+    scalar.toString(16).padStart(width * 2, '0'), 'hex');
+  const makeJwk = (scalar) => {
+    const ecdh = createECDH(namedCurve);
+    ecdh.setPrivateKey(encode(scalar));
+    const point = ecdh.getPublicKey();
+    return {
+      kty: 'EC',
+      crv,
+      x: point.subarray(1, 1 + width).toString('base64url'),
+      y: point.subarray(1 + width).toString('base64url'),
+      d: encode(scalar).toString('base64url'),
+    };
+  };
+  const generator = makeJwk(1n);
+  const other = makeJwk(2n);
+  const message = Buffer.from('EC JWK private key consistency');
+
+  for (const jwk of [generator, other, makeJwk(order - 1n)]) {
+    const key = createPrivateKey({ format: 'jwk', key: jwk });
+    assert.deepStrictEqual(key.export({ format: 'jwk' }), jwk);
+    const publicJwk = { kty: jwk.kty, crv, x: jwk.x, y: jwk.y };
+    const publicKey = createPublicKey({ format: 'jwk', key: publicJwk });
+    assert(verify('sha256', message, publicKey, sign('sha256', message, key)));
+  }
+
+  const invalid = [
+    { ...generator, d: other.d },
+    { ...generator, x: other.x, y: other.y },
+    ...[0n, order, order + 1n].map((scalar) => ({
+      ...generator, d: encode(scalar).toString('base64url'),
+    })),
+    { ...generator, d: '' },
+    {
+      ...generator,
+      x: Buffer.alloc(width).toString('base64url'),
+      y: Buffer.alloc(width).toString('base64url'),
+    },
+  ];
+  for (const jwk of invalid) {
+    assert.throws(() => createPrivateKey({ format: 'jwk', key: jwk }), {
+      code: 'ERR_CRYPTO_INVALID_JWK',
+    });
+  }
+}