Add Protocol::SignedMessage struct (not done)

CMakeLists.txt

@@ -4,12 +4,12 @@ project(Sabalty)
 set(CMAKE_CXX_STANDARD 23)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
+include(FetchContent)
 
 option(BUILD_TESTING "Build tests" OFF)
 if(BUILD_TESTING)
 	enable_testing()
 
-	include(FetchContent)
 	FetchContent_Declare(
 		Catch2
       		GIT_REPOSITORY https://github.com/catchorg/Catch2.git
@@ -21,5 +21,12 @@ if(BUILD_TESTING)
     	include(Catch)
 endif()
 
+FetchContent_Declare(Sodium
+	GIT_REPOSITORY https://github.com/robinlinden/libsodium-cmake.git
+    	GIT_TAG cfebfd3da486d5a86c644c8b47067e5411c7599c # HEAD, last updated at 2026-02-28
+)
+set(SODIUM_DISABLE_TESTS ON)
+FetchContent_MakeAvailable(Sodium)
+
 add_subdirectory(Server)
 add_subdirectory(Protocol)

Protocol/src/CMakeLists.txt

@@ -8,3 +8,8 @@ target_sources(Protocol
 		BASE_DIRS include
 		FILES include/protocol/protocol.hxx
 )
+
+target_link_libraries(Protocol
+	PRIVATE
+		sodium
+)

Protocol/src/include/protocol/protocol.hxx

@@ -0,0 +1,23 @@
+#pragma once
+
+#include "sodium/crypto_hash_sha256.h"
+#include "sodium/crypto_sign.h"
+#include <cstdint>
+#include <string>
+namespace Protocol {
+
+struct SignedMessage {
+      unsigned char sender_key_fingerprint[crypto_hash_sha256_BYTES];
+      std::string plaintext;
+      int64_t timestamp;
+      unsigned char sender_key_signature[crypto_sign_BYTES]; // signs fields 1-3
+
+      // Fills the fields and signs the plaintext
+      SignedMessage(unsigned char sender_pub_key[crypto_sign_PUBLICKEYBYTES],
+                    unsigned char sender_priv_key[crypto_sign_SECRETKEYBYTES],
+                    std::string plaintext);
+
+      // TODO: bool isMessageTrusted(std::string pub_key);
+};
+
+} // namespace Protocol

Protocol/src/protocol.cxx

@@ -0,0 +1,38 @@
+#include "sodium/crypto_sign_ed25519.h"
+#include <chrono>
+#include <protocol/protocol.hxx>
+#include <sodium.h>
+
+namespace Protocol {
+
+SignedMessage::SignedMessage(
+    unsigned char sender_pub_key[crypto_sign_PUBLICKEYBYTES],
+    unsigned char sender_priv_key[crypto_sign_SECRETKEYBYTES],
+    std::string plaintext)
+    : plaintext(plaintext) {
+      if (sodium_init() < 0) {
+            throw std::runtime_error("Failed to init sodium!");
+      }
+
+      timestamp = std::chrono::system_clock::now().time_since_epoch().count();
+      crypto_hash_sha256(sender_key_fingerprint, sender_pub_key,
+                         crypto_sign_PUBLICKEYBYTES);
+
+      std::vector<uint8_t> toBeSigned;
+      toBeSigned.reserve(sizeof(sender_key_fingerprint) + plaintext.size() +
+                         sizeof(timestamp));
+
+      toBeSigned.insert(toBeSigned.cend(), sender_key_fingerprint,
+                        sender_key_fingerprint +
+                            sizeof(sender_key_fingerprint));
+      toBeSigned.insert(toBeSigned.cend(), plaintext.data(),
+                        plaintext.data() + plaintext.length());
+      auto timestamp_bytes = reinterpret_cast<const uint8_t *>(&timestamp);
+      toBeSigned.insert(toBeSigned.cend(), timestamp_bytes,
+                        timestamp_bytes + sizeof(timestamp));
+
+      crypto_sign_detached(sender_key_signature, nullptr, toBeSigned.data(),
+                           toBeSigned.size(), sender_priv_key);
+}
+
+} // namespace Protocol

Protocol/tests/CMakeLists.txt

@@ -6,6 +6,7 @@ target_link_libraries(Protocol_tests
 	PRIVATE
 		Protocol
 		Catch2::Catch2WithMain
+		sodium
 )
 
 catch_discover_tests(Protocol_tests)

Protocol/tests/test_protocol.cxx

@@ -1,6 +1,32 @@
+#include "sodium/crypto_sign.h"
 #include <catch2/catch_test_macros.hpp>
 #include <protocol/protocol.hxx>
+#include <sodium.h>
 
-TEST_CASE("something", "[stun]") {
+TEST_CASE("SignedMessage", "[protocol]") {
-      SECTION("true") { REQUIRE(true); }
+      SECTION("sodium init") REQUIRE(sodium_init() >= 0);
+
+      unsigned char pub_key[crypto_sign_PUBLICKEYBYTES];
+      unsigned char priv_key[crypto_sign_SECRETKEYBYTES];
+      crypto_sign_keypair(pub_key, priv_key);
+
+      auto msg = Protocol::SignedMessage(pub_key, priv_key, "Hello, world!");
+      std::vector<uint8_t> toBeSigned;
+      toBeSigned.reserve(sizeof(msg.sender_key_fingerprint) +
+                         msg.plaintext.size() + sizeof(msg.timestamp));
+
+      toBeSigned.insert(toBeSigned.cend(), msg.sender_key_fingerprint,
+                        msg.sender_key_fingerprint +
+                            sizeof(msg.sender_key_fingerprint));
+      toBeSigned.insert(toBeSigned.cend(), msg.plaintext.data(),
+                        msg.plaintext.data() + msg.plaintext.length());
+      auto timestamp_bytes = reinterpret_cast<const uint8_t *>(&msg.timestamp);
+      toBeSigned.insert(toBeSigned.cend(), timestamp_bytes,
+                        timestamp_bytes + sizeof(msg.timestamp));
+
+      SECTION("signed message") {
+            REQUIRE(crypto_sign_verify_detached(
+                        msg.sender_key_signature, toBeSigned.data(),
+                        toBeSigned.size(), pub_key) == 0);
+      }
 }