From bf4da27fc6042c9a0031fec0f587a095cf313969 Mon Sep 17 00:00:00 2001
From: Jason Volk <jason@zemos.net>
Date: Wed, 4 Apr 2018 14:52:12 -0700
Subject: [PATCH] ircd::m: Ensure X-Matrix content is properly excluded or
 included for verification.

---
 ircd/m/request.cc | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/ircd/m/request.cc b/ircd/m/request.cc
index 915b54122..d5535e097 100644
--- a/ircd/m/request.cc
+++ b/ircd/m/request.cc
@@ -199,9 +199,18 @@ const
 		1_MiB
 	};
 
+	// Matrix spec sez that an empty content object {} is excluded entirely
+	// from the verification. Our JSON only excludes members if they evaluate
+	// to undefined i.e json::object{}/string_view{} but not json::object{"{}"}
+	// or even json::object{""}; rather than burdening the caller with ensuring
+	// their assignment conforms perfectly, we ensure correctness manually.
+	auto _this(*this);
+	if(empty(json::get<"content"_>(*this)))
+		json::get<"content"_>(_this) = json::object{};
+
 	const size_t request_size
 	{
-		json::serialized(*this)
+		json::serialized(_this)
 	};
 
 	const ctx::critical_assertion ca;
@@ -217,7 +226,7 @@ const
 
 	const json::object object
 	{
-		stringify(mutable_buffer{buf}, *this)
+		stringify(mutable_buffer{buf}, _this)
 	};
 
 	return verify(pk, sig, object);