Add Device info validator to oemcrypto util and unit tests

Validator that can parse and validate device info Cbor object.
This is to support better prov40 unit tests regarding
OEMCrypto_GetDeviceInformation() later.

Test: opk_ta_p40
Bug: 300304834
Change-Id: Ic260a6626dffcbef5d6b386263839499f83a69db

libwvdrmengine/oemcrypto/util/src/cbor_validator.cpp

@@ -109,5 +109,32 @@ void CborValidator::AddValidationMessage(CborMessageStatus status,
   validate_messages_.push_back({status, msg});
   if (status > message_status_) message_status_ = status;
 }
+
+// TODO(b/314141962): Replace this with the map lookup function in cppbor
+// library
+const cppbor::Item* CborValidator::GetMapEntry(const cppbor::Map& map,
+                                               const std::string& entry_name) {
+  for (auto const& entry : map) {
+    if (!entry.first->asTstr()) continue;
+    const std::string& name = entry.first->asTstr()->value();
+    if (name == entry_name) return entry.second.get();
+  }
+  return nullptr;
+}
+
+std::string CborValidator::CheckMapEntry(const cppbor::Map& map,
+                                         cppbor::MajorType major_type,
+                                         const std::string& entry_name) {
+  const cppbor::Item* value = GetMapEntry(map, entry_name);
+  if (!value) {
+    return entry_name + " is missing.";
+  }
+  if (value->type() != major_type) {
+    return entry_name + " has the wrong type. Expect: " +
+           CppborMajorTypeToString(major_type) +
+           ", actual: " + CppborMajorTypeToString(value->type());
+  }
+  return "";
+}
 }  // namespace util
 }  // namespace wvoec