From 80fcb13e8b545447f6a4da2adc4714d5a5badbff Mon Sep 17 00:00:00 2001
From: surtur <a_mirre@utb.cz>
Date: Sun, 30 Jan 2022 22:56:08 +0100
Subject: [PATCH] generator: use least-significant-byte-first ctr

---
 generator.cpp | 25 +++++++++++--------------
 generator.h   | 29 ++++++++++++++++++++++-------
 2 files changed, 33 insertions(+), 21 deletions(-)

diff --git a/generator.cpp b/generator.cpp
index a9d774c..997349a 100644
--- a/generator.cpp
+++ b/generator.cpp
@@ -38,7 +38,7 @@ void Generator::initialize_generator() {
 
 	try {
 		std::memset(G.k, 0x00, G.k.size());
-		G.ctr = 0;
+		std::memset(G.ctr.begin(), 0x00, this->ctr_len);
 		fmt::print("Generator initialized\n");
 	}
 	catch (CryptoPP::Exception& e) {
@@ -74,7 +74,7 @@ auto Generator::reseed(const std::string& s) -> void {
 	try {
 		std::string a{fortuna::Util::do_sha(da_key + s)};
 		std::memmove(G.k, fortuna::Util::de_hex(a).c_str(), G.k_length);
-		++G.ctr;
+		Generator::ctr_inc();
 		fmt::print("[i] generator: reseeded\n");
 	}
 	catch (std::exception& e) {
@@ -97,12 +97,8 @@ auto Generator::do_crypto() -> std::string {
 	const std::string plain{"Oh, I am fortune's fool!"};
 	std::string cipher, encoded_c;
 	std::unique_lock<std::mutex> ul(crypt_mtx);
-	// in case we need to convert counter to string
-	const std::string str_ctr{reinterpret_cast<const char*>(&G.ctr)};
-	// 16 bytes --> 128bit
-	static constexpr const std::size_t ctr_length{16};
-	CryptoPP::FixedSizeSecBlock<CryptoPP::byte, ctr_length> ctr;
-	std::memmove(ctr, str_ctr.c_str(), ctr_length);
+	CryptoPP::FixedSizeSecBlock<CryptoPP::byte, Generator::ctr_len> ctr;
+	std::memmove(ctr, G.ctr.data(), Generator::ctr_len);
 
 	try {
 		this->enc.SetKeyWithIV(G.k, G.k.size(), ctr);
@@ -139,7 +135,8 @@ auto Generator::do_crypto() -> std::string {
 auto Generator::generate_blocks(unsigned int k_blocks) -> std::string {
 	std::lock_guard<std::recursive_mutex> lg(mtx);
 
-	assert((G.ctr != 0) && "Counter is not 0, generator has been seeded");
+	assert((G.ctr != this->null_blk) &&
+		   "Counter is not 0, generator has been seeded");
 	if (!this->is_seeded()) {
 		throw std::logic_error("G.ctr == 0, generator has not been seeded!");
 	}
@@ -147,7 +144,7 @@ auto Generator::generate_blocks(unsigned int k_blocks) -> std::string {
 	std::string r{""};
 	while (k_blocks--) {
 		r += Generator::do_crypto();
-		++G.ctr;
+		Generator::ctr_inc();
 	}
 	return r;
 }
@@ -215,11 +212,11 @@ auto Generator::ctr_inc() -> void {
 
 	std::atomic<uint8_t> i{0};
 	while (true) {
-		this->G.counter.at(i) = static_cast<std::byte>(
-			static_cast<uint8_t>(this->G.counter.at(i)) + 0x01);
+		this->G.ctr.at(i) = static_cast<std::byte>(
+			static_cast<uint8_t>(this->G.ctr.at(i)) + 0x01);
 
-		if (this->G.counter.at(i) == static_cast<std::byte>(0x00) &&
-			++i < this->G.counter.size()) {
+		if (this->G.ctr.at(i) == static_cast<std::byte>(0x00) &&
+			++i < this->G.ctr.size()) {
 			continue;
 		}
 		break;
diff --git a/generator.h b/generator.h
index 545f754..81b3bd9 100644
--- a/generator.h
+++ b/generator.h
@@ -40,23 +40,38 @@ public:
 
 	auto is_seeded() const -> bool {
 		std::lock_guard<std::recursive_mutex> lg(mtx);
-		return !(this->G.ctr == 0x00);
+		return !(this->G.ctr == this->null_blk);
 	}
 
 
 private:
+	static constexpr const std::size_t ctr_len{16};
+	static constexpr const std::array<std::byte, ctr_len> null_blk{
+		std::byte{0x00},
+		std::byte{0x00},
+		std::byte{0x00},
+		std::byte{0x00},
+		std::byte{0x00},
+		std::byte{0x00},
+		std::byte{0x00},
+		std::byte{0x00},
+		std::byte{0x00},
+		std::byte{0x00},
+		std::byte{0x00},
+		std::byte{0x00},
+		std::byte{0x00},
+		std::byte{0x00},
+		std::byte{0x00},
+		std::byte{0x00},
+	}; // used for comparison with G.ctr in is_seeded() and generate_blocks()
 	CryptoPP::CTR_Mode<CryptoPP::Serpent>::Encryption enc;
+
 	struct G_state {
 		// 32*8
 		static constexpr const std::size_t k_length{32};
-		static constexpr const std::size_t ctr_len{16};
 
 		CryptoPP::FixedSizeSecBlock<CryptoPP::byte, k_length> k;
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wpedantic"
-		unsigned __int128 ctr;
-#pragma GCC diagnostic pop
-		std::array<std::byte, ctr_len> counter;
+		std::array<std::byte, ctr_len> ctr;
 	};
 	G_state G;