crypto: throw on uninitialized DH computeSecret

Reject DiffieHellman computeSecret() when the instance does not
have private key material instead of returning an empty buffer.

Fixes: #63674

Signed-off-by: Filip Skokan <panva.ip@gmail.com>
PR-URL: #63922
Fixes: #63674
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Yagiz Nizipli <yagiz@nizipli.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

Author: panva

deps/ncrypto/ncrypto.cc

@@ -1710,6 +1710,13 @@ DataPointer DHPointer::getPrivateKey() const {
   return BignumPointer::Encode(pvt_key);
 }
 
+bool DHPointer::hasPrivateKey() const {
+  if (!dh_) return false;
+  const BIGNUM* pvt_key = nullptr;
+  DH_get0_key(dh_.get(), nullptr, &pvt_key);
+  return pvt_key != nullptr;
+}
+
 DataPointer DHPointer::generateKeys() const {
   ClearErrorOnReturn clearErrorOnReturn;
   if (!dh_) return {};

deps/ncrypto/ncrypto.h

@@ -1116,6 +1116,7 @@ class DHPointer final {
   DataPointer getGenerator() const;
   DataPointer getPublicKey() const;
   DataPointer getPrivateKey() const;
+  bool hasPrivateKey() const;
   DataPointer generateKeys() const;
   DataPointer computeSecret(const BignumPointer& peer) const;
 

src/crypto/crypto_dh.cc

@@ -324,6 +324,11 @@ void ComputeSecret(const FunctionCallbackInfo<Value>& args) {
       break;
   }
 
+  if (!dh.hasPrivateKey()) {
+    return THROW_ERR_CRYPTO_INVALID_STATE(
+        env, "Cannot compute shared secret without a private key");
+  }
+
   auto dp = dh.computeSecret(key);
 
   Local<Value> buffer;

test/parallel/test-crypto-dh-errors.js

@@ -100,6 +100,28 @@ assert.throws(
   'failed to throw the expected error.'
 );
 
+{
+  const group = crypto.getDiffieHellman('modp14');
+  const alice = crypto.createDiffieHellman(
+    group.getPrime(), group.getGenerator());
+  const bob = crypto.createDiffieHellman(
+    group.getPrime(), group.getGenerator());
+  bob.generateKeys();
+
+  assert.throws(
+    () => alice.computeSecret(bob.getPublicKey()),
+    {
+      name: 'Error',
+      code: 'ERR_CRYPTO_INVALID_STATE',
+      message: 'Cannot compute shared secret without a private key'
+    });
+
+  alice.generateKeys();
+  assert.deepStrictEqual(
+    alice.computeSecret(bob.getPublicKey()),
+    bob.computeSecret(alice.getPublicKey()));
+}
+
 assert.throws(
   () => crypto.createDiffieHellman('', true),
   {