Allow comparisons of empty ObjectIds to succeed

Prior to this change if an ObjectId with no value is compared, a
null pointer dereference occurs. This allows empty ObjectIds to
be compared with operator==.

PiperOrigin-RevId: 290114531
Change-Id: I1fa9a31e7b2702b83e53631966fcc68a0519c30f

Author: sethmoo

asylo/crypto/asn1.cc

@@ -310,6 +310,9 @@ ObjectId::ObjectId(bssl::UniquePtr<ASN1_OBJECT> object)
     : object_(std::move(object)) {}
 
 bool operator==(const ObjectId &lhs, const ObjectId &rhs) {
+  if (lhs.object_ == nullptr || rhs.object_ == nullptr) {
+    return lhs.object_ == rhs.object_;
+  }
   return OBJ_cmp(lhs.object_.get(), rhs.object_.get()) == 0;
 }
 

asylo/crypto/asn1_test.cc

@@ -251,6 +251,21 @@ TEST(Asn1Test, ObjectIdEquality) {
   }
 }
 
+TEST(Asn1Test, ObjectIdEqualityWithEmptyOid) {
+  ObjectId cn;
+  ASYLO_ASSERT_OK_AND_ASSIGN(cn, ObjectId::CreateFromShortName("CN"));
+  ObjectId empty;
+
+  EXPECT_THAT(cn, Not(Eq(empty)));
+  EXPECT_THAT(cn, Ne(empty));
+
+  EXPECT_THAT(empty, Ne(cn));
+  EXPECT_THAT(empty, Not(Eq(cn)));
+
+  EXPECT_THAT(empty, Eq(empty));
+  EXPECT_THAT(empty, Not(Ne(empty)));
+}
+
 TEST(Asn1Test, ObjectIdCopyConstructionPreservesEquality) {
   for (const auto &ids : kShortLongNidOids) {
     ObjectId oid;