ircd::json: Add a preliminary suite of sign()/verify()/hash() for tuple.

include/ircd/json/tuple.h

@@ -64,6 +64,7 @@ struct tuple
 	using super_type = tuple<T...>;
 
 	operator json::value() const;
+	operator crh::sha256::buf() const;
 
 	static constexpr size_t size();
 
@@ -995,6 +996,97 @@ operator<<(std::ostream &s, const tuple<T...> &t)
     return s;
 }
 
+template<class... T>
+tuple<T...>::operator
+crh::sha256::buf()
+const
+{
+	//TODO: XXX
+	const auto preimage
+	{
+		json::strung(*this)
+	};
+
+	return crh::sha256::buf
+	{
+		[&preimage](auto &buf)
+		{
+			sha256{buf, const_raw_buffer{preimage}};
+		}
+	};
+}
+
+template<class tuple>
+enable_if_tuple<tuple, ed25519::sig>
+sign(const tuple &t,
+     const ed25519::sk &sk)
+{
+	//TODO: XXX
+	const auto preimage
+	{
+		json::strung(t)
+	};
+
+	return ed25519::sig
+	{
+		[&sk, &preimage](auto &buf)
+		{
+			sk.sign(buf, const_raw_buffer{preimage});
+		}
+	};
+}
+
+template<class tuple>
+enable_if_tuple<tuple, bool>
+verify(const tuple &t,
+       const ed25519::pk &pk,
+       const ed25519::sig &sig,
+       std::nothrow_t)
+noexcept try
+{
+	//TODO: XXX
+	const auto preimage
+	{
+		json::strung(t)
+	};
+
+	return pk.verify(const_raw_buffer{preimage}, sig);
+}
+catch(const std::exception &e)
+{
+	log::error("Verification of json::tuple unexpected failure: %s", e.what());
+	return false;
+}
+
+template<class tuple>
+enable_if_tuple<tuple, void>
+verify(const tuple &t,
+       const ed25519::pk &pk,
+       const ed25519::sig &sig)
+{
+	if(!verify(t, pk, sig, std::nothrow))
+		throw ed25519::bad_sig{"Verification failed"};
+}
+
+template<class tuple>
+enable_if_tuple<tuple, void>
+verify(const tuple &t,
+       const ed25519::pk &pk)
+{
+	const ed25519::sig sig
+	{
+		[&t](auto &buf)
+		{
+			b64decode(buf, at<"signatures"_>(t));
+		}
+	};
+
+	auto copy(t);
+	at<"signatures"_>(copy) = string_view{};
+	if(!verify(copy, pk, sig, std::nothrow))
+		throw ed25519::bad_sig{"Verification failed"};
+}
+
 template<class... T>
 tuple<T...>::operator
 json::value()