From a3251a7c8b539dc19c21dfcb3245411962d75533 Mon Sep 17 00:00:00 2001
From: surtur <a_mirre@utb.cz>
Date: Mon, 24 Jan 2022 03:52:42 +0100
Subject: [PATCH] fix(pool): properly encode full event

---
 pool.cpp | 33 ++++++++++++++++++++++-----------
 1 file changed, 22 insertions(+), 11 deletions(-)

diff --git a/pool.cpp b/pool.cpp
index 388f4bd..be643cb 100644
--- a/pool.cpp
+++ b/pool.cpp
@@ -4,6 +4,7 @@
 #include "pool.h"
 
 #include <fmt/core.h>
+#include <fmt/ranges.h>
 
 #include <atomic>
 #include <climits>
@@ -67,20 +68,30 @@ auto Pool::add_entropy(const unsigned int& source,
 
 	if (all_ok) {
 		try {
-			// FIXME: check for overflow - std::string size bounding?
-			event_str.assign(event.begin(), event.end());
-
-			// FIXME: check size for overflow
-			// also, atm this counts event size but actually what gets appended
-			// are digests of 64 characters (hex-encoded 32 bytes)
-			size += event_size;
-
+			const std::string strsource{std::to_string(source)};
 			{
-				const std::string digest(fortuna::Util::do_sha(event));
+				// FIXME: check for overflow - std::string size bounding?
+				// event_str.assign(event.begin(), event.end());
 
-				fmt::print("\t[i] add_entropy(digest): {}\n", digest);
+				// as per Cryptography Engineering, p. 148 (180/385)
+				std::vector<char> fullevent{static_cast<char>(source)};
+				fullevent.push_back(static_cast<char>(event_size));
+				fullevent.insert(
+					std::end(fullevent), std::begin(event), std::end(event));
+				fmt::print("\t[i] add_entropy(fullevent): {}\n", fullevent);
 
-				append_s(digest);
+				// FIXME: check size for overflow
+				// also, atm this counts event size but actually what gets
+				// appended are digests of 64 characters (hex-encoded 32 bytes)
+				size += event_size;
+
+				{
+					const std::string digest(fortuna::Util::do_sha(fullevent));
+
+					fmt::print("\t[i] add_entropy(digest): {}\n", digest);
+
+					append_s(digest);
+				}
 			}
 
 			fmt::print("\t[i] s.length()  (simple char count): {}\n"