diff --git a/include/ircd/util/blackwhite.h b/include/ircd/util/blackwhite.h
new file mode 100644
index 000000000..ccca77cbf
--- /dev/null
+++ b/include/ircd/util/blackwhite.h
@@ -0,0 +1,55 @@
+// Matrix Construct
+//
+// Copyright (C) Matrix Construct Developers, Authors & Contributors
+// Copyright (C) 2016-2023 Jason Volk <jason@zemos.net>
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice is present in all copies. The
+// full license for this software is available in the LICENSE file.
+
+#pragma once
+#define HAVE_IRCD_UTIL_BLACKWHITE_H
+
+namespace ircd { inline namespace util
+{
+	namespace blackwhite
+	{
+		struct list;
+	}
+}}
+
+class ircd::util::blackwhite::list
+{
+	string_view black;
+	string_view white;
+	char delim;
+
+	bool match(const string_view &) const;
+
+  public:
+	bool operator()(const string_view &) const;
+
+	list(const char delim          = ' ',
+	     const string_view &black  = {},
+	     const string_view &white  = {});
+};
+
+inline
+ircd::util::blackwhite::list::list(const char delim,
+	                               const string_view &black,
+	                               const string_view &white)
+:black{black}
+,white{white}
+,delim{delim}
+{}
+
+inline bool
+ircd::util::blackwhite::list::operator()(const string_view &s)
+const
+{
+	if(!this->black && !this->white)
+		return true;
+
+	return match(s);
+}
diff --git a/include/ircd/util/util.h b/include/ircd/util/util.h
index 633c2bdd3..dfd0229e1 100644
--- a/include/ircd/util/util.h
+++ b/include/ircd/util/util.h
@@ -67,6 +67,7 @@ namespace ircd
 #include "all.h"
 #include "compare_exchange.h"
 #include "bitset.h"
+#include "blackwhite.h"
 
 // Unsorted section
 namespace ircd {
diff --git a/ircd/util.cc b/ircd/util.cc
index 01ab8718c..07c5591c8 100644
--- a/ircd/util.cc
+++ b/ircd/util.cc
@@ -23,6 +23,40 @@ ircd::util::size(std::ostream &s)
 	return ret;
 }
 
+///////////////////////////////////////////////////////////////////////////////
+//
+// util/blackwhite.h
+//
+
+bool
+ircd::util::blackwhite::list::match(const string_view &a)
+const
+{
+	const auto matcher
+	{
+		[&a](const string_view &b) noexcept
+		{
+			return a != b;
+		}
+	};
+
+	const bool black
+	{
+		this->black && !this->white?
+			!tokens(this->black, delim, matcher):
+			false
+	};
+
+	const bool white
+	{
+		!black && this->white?
+			!tokens(this->white, delim, matcher):
+			false
+	};
+
+	return !black && (white || !this->white);
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 //
 // util/env.h