crypto: return a clearer error when loading an unsupported pkcs12

src/crypto/crypto_context.cc

@@ -1148,6 +1148,14 @@ void SecureContext::LoadPKCS12(const FunctionCallbackInfo<Value>& args) {
   if (!ret) {
     // TODO(@jasnell): Should this use ThrowCryptoError?
     unsigned long err = ERR_get_error();  // NOLINT(runtime/int)
+
+    if (ERR_GET_REASON(err) == ERR_R_UNSUPPORTED) {
+      // OpenSSL's "unsupported" error without any context is very
+      // common and not very helpful, so we override it:
+      return THROW_ERR_CRYPTO_UNSUPPORTED_OPERATION(
+          env, "Unsupported PKCS12 PFX data");
+    }
+
     const char* str = ERR_reason_error_string(err);
     str = str != nullptr ? str : "Unknown error";
 

test/parallel/test-tls-legacy-pfx.js

@@ -0,0 +1,24 @@
+'use strict';
+const common = require('../common');
+if (!common.hasCrypto)
+  common.skip('missing crypto');
+const fixtures = require('../common/fixtures');
+
+const {
+  assert, connect, keys
+} = require(fixtures.path('tls-connect'));
+
+const legacyPfx = fixtures.readKey('legacy.pfx');
+
+connect({
+  client: {
+    pfx: legacyPfx,
+    passphrase: 'legacy',
+    rejectUnauthorized: false
+  },
+  server: keys.agent1
+}, common.mustCall((e, pair, cleanup) => {
+  assert.strictEqual(e.code, 'ERR_CRYPTO_UNSUPPORTED_OPERATION');
+  assert.strictEqual(e.message, 'Unsupported PKCS12 PFX data');
+  cleanup();
+}));