sfm: fix reads,writes of the seed file, refactor

seed_file_management.cpp

@@ -6,10 +6,14 @@
 #include "util.h"
 
 #include <cryptopp/secblock.h>
+#include <cryptopp/secblockfwd.h>
 #include <fmt/core.h>
+#include <sys/stat.h>
 
+#include <cassert>
 #include <cstdint>
 #include <fstream>
+#include <memory>
 #include <stdexcept>
 #include <utility>
 
@@ -37,29 +41,54 @@ auto SeedFileManager::do_stuff() -> void {
 	do_task.thread_pls(config.write_interval, [this] { write_seed_file(); });
 }
 
+auto SeedFileManager::seed_file_exists() const -> bool {
+	// based on https://stackoverflow.com/a/6296808
+	struct stat buf;
+	if (stat(config.seed_f_path.c_str(), &buf) != -1) {
+		return true;
+	}
+	return false;
+}
+
 auto SeedFileManager::update_seed_file() -> void {
+	fortuna::SeedFileManager::RUNNING = true;
 	CryptoPP::SecByteBlock buff{config.seed_f_length};
 
 	{
-		std::ifstream f_stream{config.seed_f_path, std::ios::binary};
-		if (!f_stream) {
-			std::string msg{"error opening seed file"};
-			fmt::print("{} {}\n", msg, config.seed_f_path);
-			fortuna::SeedFileManager::RUNNING = false;
-			// FIXME: perhaps create a seed file instead of bailing...
-			throw std::runtime_error("error opening seed file");
+		if (!seed_file_exists()) {
+			fmt::print("\t[i] sfm: SEED FILE NOT PRESENT, creating...\n");
+			std::fstream f_stream;
+			f_stream.open(config.seed_f_path,
+						  std::fstream::out | std::fstream::trunc);
+			f_stream << "";
+			f_stream.close();
+			return;
+		}
+
+		std::ifstream f_stream{config.seed_f_path, std::ios::binary};
+
+		if (!f_stream.is_open()) {
+			const std::string msg{"\t[!] sfm: error opening seed file!\n"};
+			fmt::print("{} {}\n", msg, config.seed_f_path);
+
+			fortuna::SeedFileManager::RUNNING = false;
+			throw std::runtime_error(msg);
 		}
-		fortuna::SeedFileManager::RUNNING = true;
 
 		f_stream.read(reinterpret_cast<char*>(buff.BytePtr()),
 					  static_cast<int64_t>(config.seed_f_length));
+
 		if (static_cast<std::size_t>(f_stream.gcount()) !=
 			config.seed_f_length) {
-			std::string msg{"error reading seed from file"};
-			fmt::print("{} {}, length: {}\n",
+			const std::string msg{
+				"\t[!] sfm: error reading seed from file, length mismatch"};
+			fmt::print("{} {}, length: {} vs desired length: {}\n",
 					   msg,
 					   config.seed_f_path,
+					   f_stream.gcount(),
 					   config.seed_f_length);
+
+			fortuna::SeedFileManager::RUNNING = false;
 			throw std::runtime_error(msg);
 		}
 	}
@@ -68,21 +97,36 @@ auto SeedFileManager::update_seed_file() -> void {
 		std::string str_buff(reinterpret_cast<const char*>(&buff[0]),
 							 buff.SizeInBytes() *
 								 8); // we need the size in bits
+
 		accumulator.call_reseed(str_buff);
 		write_seed_file();
 	}
 	catch (std::exception& e) {
-		fmt::print("{}", e.what());
+		fmt::print("{}\n", e.what());
+		fortuna::SeedFileManager::RUNNING = false;
+		throw;
 	}
 }
 
 auto SeedFileManager::write_seed_file() -> void {
-	const std::size_t seed_file_length_blocks{
-		fortuna::Util::b2b(config.seed_f_length)};
-	CryptoPP::SecByteBlock buff{seed_file_length_blocks *
-								fortuna::Util::gen_block_size};
-	std::string da_buff{accumulator.get_random_data(
-		static_cast<unsigned int>(seed_file_length_blocks))};
+	fortuna::SeedFileManager::RUNNING = true;
+	CryptoPP::SecByteBlock buff{config.seed_f_length};
+	const std::string da_buff{accumulator.get_random_data(
+		static_cast<unsigned int>(config.seed_f_length))};
+
+	assert(da_buff.length() % 2 == 0);
+	assert(da_buff.size() == config.seed_f_length * 2); // da_buff is
+														// hex-encoded
+
+	// account for hex encoding that is returned from get_random_data(), i.e.
+	// the total length is half of the actual number of characters
+	const size_t length{da_buff.length() / 2};
+
+	CryptoPP::StringSource src(
+		da_buff.c_str(),
+		true /*pumpAll*/,
+		new CryptoPP::HexDecoder(new CryptoPP::ArraySink(&buff[0], length)));
+
 	fmt::print("[*] sfm: writing seed file\n");
 
 	try {
@@ -90,12 +134,12 @@ auto SeedFileManager::write_seed_file() -> void {
 							   std::ios::binary | std::ios::trunc};
 		f_stream.write(reinterpret_cast<const char*>(buff.BytePtr()),
 					   static_cast<int64_t>(config.seed_f_length));
-		fortuna::SeedFileManager::RUNNING = true;
 	}
 	catch (std::exception& e) {
 		fmt::print("[!] sfm: error writing to seed file!\n");
 		fmt::print("{}\n", e.what());
 		fortuna::SeedFileManager::RUNNING = false;
+		throw;
 	}
 }
 

seed_file_management.h

@@ -15,8 +15,8 @@ public:
 		// std::chrono::minutes write_interval{10};
 		// 10 minutes (as the standard recommends) is a lot, go with 120s
 		std::chrono::seconds write_interval{120};
-		std::string seed_f_path = "./.fortuna.seed";
-		std::size_t seed_f_length = 64;
+		std::string seed_f_path{"./.fortuna.seed"};
+		std::size_t seed_f_length{64};
 
 		conf(){};
 	};
@@ -37,6 +37,7 @@ private:
 	DoTask do_task;
 	fortuna::accumulator::Accumulator accumulator;
 
+	auto seed_file_exists() const -> bool;
 	auto write_seed_file() -> void;
 	auto update_seed_file() -> void;