crypto: fix public PKCS8 export error

lib/internal/crypto/webcrypto.js

@@ -530,45 +530,51 @@ function exportKeySpki(key) {
 }
 
 function exportKeyPkcs8(key) {
+  let exporter;
   switch (getCryptoKeyAlgorithm(key).name) {
     case 'RSASSA-PKCS1-v1_5':
       // Fall through
     case 'RSA-PSS':
       // Fall through
     case 'RSA-OAEP':
-      return require('internal/crypto/rsa')
-        .rsaExportKey(key, kWebCryptoKeyFormatPKCS8);
+      exporter = require('internal/crypto/rsa').rsaExportKey;
+      break;
     case 'ECDSA':
       // Fall through
     case 'ECDH':
-      return require('internal/crypto/ec')
-        .ecExportKey(key, kWebCryptoKeyFormatPKCS8);
+      exporter = require('internal/crypto/ec').ecExportKey;
+      break;
     case 'Ed25519':
       // Fall through
     case 'Ed448':
       // Fall through
     case 'X25519':
       // Fall through
     case 'X448':
-      return require('internal/crypto/cfrg')
-        .cfrgExportKey(key, kWebCryptoKeyFormatPKCS8);
+      exporter = require('internal/crypto/cfrg').cfrgExportKey;
+      break;
     case 'ML-DSA-44':
       // Fall through
     case 'ML-DSA-65':
       // Fall through
     case 'ML-DSA-87':
-      return require('internal/crypto/ml_dsa')
-        .mlDsaExportKey(key, kWebCryptoKeyFormatPKCS8);
+      exporter = require('internal/crypto/ml_dsa').mlDsaExportKey;
+      break;
     case 'ML-KEM-512':
       // Fall through
     case 'ML-KEM-768':
       // Fall through
     case 'ML-KEM-1024':
-      return require('internal/crypto/ml_kem')
-        .mlKemExportKey(key, kWebCryptoKeyFormatPKCS8);
+      exporter = require('internal/crypto/ml_kem').mlKemExportKey;
+      break;
     default:
       return undefined;
   }
+
+  if (getCryptoKeyType(key) !== 'private')
+    throw lazyDOMException('Key must be a private key', 'InvalidAccessError');
+
+  return exporter(key, kWebCryptoKeyFormatPKCS8);
 }
 
 function exportKeyRawPublic(key, format) {
@@ -777,9 +783,7 @@ function exportKeySync(format, key) {
       break;
     }
     case 'pkcs8': {
-      if (type === 'private') {
-        result = exportKeyPkcs8(key);
-      }
+      result = exportKeyPkcs8(key);
       break;
     }
     case 'jwk': {

test/parallel/test-webcrypto-export-import-ec.js

@@ -120,6 +120,12 @@ async function testImportSpki({ name, publicUsages }, namedCurve, extractable) {
     assert.strictEqual(
       Buffer.from(spki).toString('hex'),
       keyData[namedCurve].spki.toString('hex'));
+
+    await assert.rejects(
+      subtle.exportKey('pkcs8', key), {
+        message: 'Key must be a private key',
+        name: 'InvalidAccessError',
+      });
   } else {
     await assert.rejects(
       subtle.exportKey('spki', key), {

test/parallel/test-webcrypto-wrap-unwrap.js

@@ -567,6 +567,17 @@ async function testNonByteLengthWrapUnwrap({
       name: 'InvalidAccessError',
     });
 
+  // Symmetric case: exporting a public key as 'pkcs8' must also fail with
+  // InvalidAccessError, not the generic NotSupportedError.
+  await assert.rejects(
+    subtle.wrapKey('pkcs8', ecKey.publicKey, wrapKey, {
+      name: 'AES-GCM',
+      iv: new Uint8Array(12),
+    }), {
+      message: 'Key must be a private key',
+      name: 'InvalidAccessError',
+    });
+
   // --- unwrapKey validation tests ---
 
   const ciphertext = new Uint8Array(32); // Dummy ciphertext