Merge branch 'dev'

Critical (4)

C1 — udp_client.hpp / udp_client.cpp: Moved mStartReceive() out of the constructor into start(), after the socket is opened.
C2 — client/main.cpp:187: || → && in the main loop condition, so it exits when the connection drops instead of spinning forever.
C3 — tcp_connection.hpp: Added mConnectionAESKey{}, mConnectionSessionID(0), and mConnectionPublicKey{} to the constructor initializer list.
C4 — tcp_server.hpp / tcp_server.cpp: Added std::mutex mClientsMutex and locked it at all three mClients access sites (insert, erase callback, stop snapshot).
High (5)

H1 — tcp_connection.cpp:284: Replaced hardcoded htonl(0x0A0A0001) with htonl(baseIP + 1).
H2 — session_registry.hpp / session_registry.cpp / udp_server.cpp: Changed get() and getByIP() to return shared_ptr<SessionState> (non-const); removed all four const_cast usages.
H3 — session_registry.cpp:90: Guarded against mask == 0 || mask >= 32 (shift UB) and hostCount < 3 (unsigned underflow).
H4 — virtual_interface.cpp: Added runCommandWin32() using CreateProcess (no shell); replaced both system() calls in resetIP().
H5 — virtual_interface.cpp: Added close(mFd); mFd = -1; before both throw sites in the macOS constructor (ioctl failure and connect failure).
Medium (4)

M1 — tcp_connection.cpp:241: Added explicit find() + end-iterator check for NETWORK and SUBNET_MASK before dereferencing.
M2 — tcp_message_handler.cpp: Added an 8 KB (MAX_MSG_BODY = 8192) cap on incoming message body length; oversized messages close the connection.
M3 — tcp_connection.cpp:232: Capped the session ID generation loop at 16 attempts before disconnecting.
M4 — session_registry.cpp:8: put() now evicts the old IP→session mapping before replacing an entry, preventing stale mIPSessions entries.

.github/workflows/sanitizers.yml

@@ -0,0 +1,39 @@
+name: Sanitizers
+
+on:
+  push:
+    branches: [ main, master ]
+  pull_request:
+    branches: [ main, master ]
+
+jobs:
+  build-and-test:
+    runs-on: ubuntu-latest
+    env:
+      SANITIZERS: "-fsanitize=address,undefined -fno-omit-frame-pointer -g -O1"
+      ASAN_OPTIONS: "detect_leaks=1:abort_on_error=1"
+      UBSAN_OPTIONS: "print_stacktrace=1"
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Install dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y cmake build-essential clang
+
+      - name: Configure (CMake)
+        run: |
+          mkdir -p build-sanitizers
+          cd build-sanitizers
+          CC=clang CXX=clang++ cmake -DCMAKE_BUILD_TYPE=Debug -DCMAKE_CXX_FLAGS="$SANITIZERS" -DCMAKE_EXE_LINKER_FLAGS="$SANITIZERS" ..
+
+      - name: Build
+        run: |
+          cd build-sanitizers
+          cmake --build . -- -j
+
+      - name: Run tests
+        run: |
+          cd build-sanitizers
+          ctest --output-on-failure || (echo "ctest failed"; exit 1)

.gitignore

@@ -12,5 +12,6 @@ _deps
 CMakeUserPresets.json
 
 build/
+build*/
 .vscode/
 .DS_Store

CMakeLists.txt

@@ -6,7 +6,7 @@ cmake_minimum_required(VERSION 3.16)
 # If MAJOR is 0, and MINOR > 0, Version is BETA
 
 project(ColumnLynx
-    VERSION 1.1.0
+    VERSION 1.2.0
     LANGUAGES CXX
 )
 
@@ -173,3 +173,28 @@ install(FILES
 	LICENSES/GPL-2.0-only.txt
 	LICENSES/GPL-3.0.txt
         DESTINATION ${CMAKE_INSTALL_DATAROOTDIR}/licenses/${PROJECT_NAME})
+
+# ---------------------------------------------------------
+# Unit tests
+# ---------------------------------------------------------
+option(BUILD_TESTS "Build unit tests" ON)
+
+if(BUILD_TESTS)
+    enable_testing()
+    file(GLOB_RECURSE TEST_SRC CONFIGURE_DEPENDS tests/*.cpp)
+    if(TEST_SRC)
+        foreach(TEST_FILE IN LISTS TEST_SRC)
+            get_filename_component(TEST_NAME ${TEST_FILE} NAME_WE)
+            add_executable(${TEST_NAME} ${TEST_FILE})
+            target_link_libraries(${TEST_NAME} PRIVATE common sodium)
+            target_include_directories(${TEST_NAME} PRIVATE 
+                ${PROJECT_SOURCE_DIR}/include
+                ${asio_SOURCE_DIR}/asio/include
+                ${sodium_SOURCE_DIR}/src/libsodium/include
+                ${sodium_BINARY_DIR}/src/libsodium/include
+            )
+            add_test(NAME ${TEST_NAME} COMMAND ${TEST_NAME})
+            set_target_properties(${TEST_NAME} PROPERTIES OUTPUT_NAME "columnlynx_${TEST_NAME}")
+        endforeach()
+    endif()
+endif()

README.md

@@ -55,7 +55,22 @@ openssl pkey -in key.pem -pubout -outform DER | tail -c 32 | xxd -p -c 32
 # Output example: 1c9d4f7a3b2e8a6d0f5c9b1e4d8a7f3c6e2b1a9d5f4c8e0a7b3d6c9f2e
 ```
 
-You can then set these keys accordingly in the **server_config** and **client_config** files.
+Write the hex output into two separate files in the matching config directory:
+
+- `public.key` for the public key
+- `private.key` for the private key seed
+
+The files should contain only the hex ASCII characters, optionally followed by a trailing newline. Hex parsing is case-insensitive.
+
+For example:
+
+```bash
+printf '%s' '1c9d4f7a3b2e8a6d0f5c9b1e4d8a7f3c6e2b1a9d5f4c8e0a7b3d6c9f2e' > /etc/columnlynx/public.key
+printf '%s' '9f3a2b6c0f8e4d1a7c3e9a4b5d2f8c6e1a9d0b7e3f4c2a8e6d5b1f0a3c4e' > /etc/columnlynx/private.key
+chmod 600 /etc/columnlynx/private.key
+```
+
+On Unix-like systems, the software will warn if the private key file is too permissive and recommend tightening it with `chmod 600`.
 
 ### Server Setup (Linux Server ONLY)
 
@@ -157,20 +172,19 @@ sudo nft add rule nat postroute ip saddr 10.10.0.0/24 oifname "eth0" masquerade
  
 "**server_config**" is a file that contains the server configuration, **one variable per line**. These are the current configuration available variables:
 
-- **SERVER_PUBLIC_KEY** (Hex String): The public key to be used - Used for verification
-- **SERVER_PRIVATE_KEY** (Hex String): The private key seed to be used
 - **NETWORK** (IPv4 Format): The network IPv4 to be used (Server Interface still needs to be configured manually)
 - **SUBNET_MASK** (Integer): The subnet mask to be used (ensure proper length, it will not be checked)
 
 **Example:**
 
 ```
-SERVER_PUBLIC_KEY=1c9d4f7a3b2e8a6d0f5c9b1e4d8a7f3c6e2b1a9d5f4c8e0a7b3d6c9f2e
-SERVER_PRIVATE_KEY=9f3a2b6c0f8e4d1a7c3e9a4b5d2f8c6e1a9d0b7e3f4c2a8e6d5b1f0a3c4e
 NETWORK=10.10.0.0
 SUBNET_MASK=24
 ```
 
+The server keypair must now live in the same directory as `server_config`, stored in `public.key` and `private.key`.
+`server_config` no longer stores key material.
+
 <hr></hr>
 
 "**whitelisted_keys**" is a file that **public keys of clients that are allowed to connect to the server, one key per line**.
@@ -184,17 +198,9 @@ SUBNET_MASK=24
 
 ### Client
  
-"**client_config**" is a file that contains the client configuration, **one variable per line**. These are the current configuration available variables:
+"**client_config**" is a file that contains the client configuration, **one variable per line**. Key material is no longer stored here; if you do not have any client-only settings yet, this file can stay empty.
 
-- **CLIENT_PUBLIC_KEY** (Hex String): The public key to be used - Used for verification
-- **CLIENT_PRIVATE_KEY** (Hex String): The private key seed to be used
-
-**Example:**
-
-```
-CLIENT_PUBLIC_KEY=1c9d4f7a3b2e8a6d0f5c9b1e4d8a7f3c6e2b1a9d5f4c8e0a7b3d6c9f2e
-CLIENT_PRIVATE_KEY=9f3a2b6c0f8e4d1a7c3e9a4b5d2f8c6e1a9d0b7e3f4c2a8e6d5b1f0a3c4e
-```
+The client keypair must now live in the same directory as `client_config`, stored in `public.key` and `private.key`.
 
 <hr></hr>
 

include/columnlynx/client/client_session.hpp

@@ -87,6 +87,10 @@ namespace ColumnLynx {
 
             void incrementSendCount() {
                 std::unique_lock lock(mMutex);
+                if (mClientState->send_cnt == std::numeric_limits<uint64_t>::max()) {
+                    Utils::error("ClientSession: send counter overflow detected");
+                    return;
+                }
                 mClientState->send_cnt++;
             }
 

include/columnlynx/client/net/tcp/tcp_client.hpp

@@ -11,9 +11,9 @@
 #include <columnlynx/common/utils.hpp>
 #include <columnlynx/common/libsodium_wrapper.hpp>
 #include <array>
+#include <atomic>
 #include <algorithm>
 #include <vector>
-#include <unordered_map>
 #include <string>
 #include <columnlynx/common/net/protocol_structs.hpp>
 #include <columnlynx/common/net/virtual_interface.hpp>
@@ -26,48 +26,7 @@ namespace ColumnLynx::Net::TCP {
         public:
             TCPClient(asio::io_context& ioContext,
                       const std::string& host,
-                      const std::string& port)
-                :
-                mResolver(ioContext),
-                mSocket(ioContext),
-                mHost(host),
-                mPort(port),
-                mHeartbeatTimer(mSocket.get_executor()),
-                mLastHeartbeatReceived(std::chrono::steady_clock::now()),
-                mLastHeartbeatSent(std::chrono::steady_clock::now())
-            {
-                // Get initial client config
-                std::string configPath = ClientSession::getInstance().getConfigPath();
-                std::shared_ptr<Utils::LibSodiumWrapper> mLibSodiumWrapper = ClientSession::getInstance().getSodiumWrapper();
-
-                // Preload the config map
-                mRawClientConfig = Utils::getConfigMap(configPath + "client_config");
-
-                auto itPubkey = mRawClientConfig.find("CLIENT_PUBLIC_KEY");
-                auto itPrivkey = mRawClientConfig.find("CLIENT_PRIVATE_KEY");
-
-                if (itPubkey != mRawClientConfig.end() && itPrivkey != mRawClientConfig.end()) {
-                    Utils::log("Loading keypair from config file.");
-                
-                    PublicKey pk;
-                    PrivateSeed seed;
-                
-                    std::copy_n(Utils::hexStringToBytes(itPrivkey->second).begin(), seed.size(), seed.begin()); // This is extremely stupid, but the C++ compiler has forced my hand (I would've just used to_array, but fucking asio decls)
-                    std::copy_n(Utils::hexStringToBytes(itPubkey->second).begin(), pk.size(), pk.begin());
-                
-                    if (!mLibSodiumWrapper->recomputeKeys(seed, pk)) {
-                        throw std::runtime_error("Failed to recompute keypair from config file values!");
-                    }
-
-                    Utils::debug("Newly-Loaded Public Key: " + Utils::bytesToHexString(mLibSodiumWrapper->getPublicKey(), 32));
-                } else {
-                    #if defined(DEBUG)
-                    Utils::warn("No keypair found in config file! Using random key.");
-                    #else
-                    throw std::runtime_error("No keypair found in config file! Cannot start client without keys.");
-                    #endif
-                }
-            }
+                      const std::string& port);
 
             // Starts the TCP Client and initiaties the handshake
             void start();
@@ -89,8 +48,8 @@ namespace ColumnLynx::Net::TCP {
 
             // TODO: Move ptrs to smart ptrs
 
-            bool mConnected = false;
-            bool mHandshakeComplete = false;
+            std::atomic<bool> mConnected{false};
+            std::atomic<bool> mHandshakeComplete{false};
             tcp::resolver mResolver;
             tcp::socket mSocket;
             std::shared_ptr<MessageHandler> mHandler;
@@ -105,6 +64,5 @@ namespace ColumnLynx::Net::TCP {
             int mMissedHeartbeats = 0;
             bool mIsHostDomain;
             Protocol::TunConfig mTunConfig;
-            std::unordered_map<std::string, std::string> mRawClientConfig;
     };
 }

include/columnlynx/client/net/udp/udp_client.hpp

@@ -20,7 +20,6 @@ namespace ColumnLynx::Net::UDP {
                       const std::string& port)
                 : mSocket(ioContext), mResolver(ioContext), mHost(host), mPort(port)
             {
-                mStartReceive(); 
             }
 
             // Start the UDP client

include/columnlynx/common/net/session_registry.hpp

@@ -61,10 +61,10 @@ namespace ColumnLynx::Net {
             void put(uint32_t sessionID, std::shared_ptr<SessionState> state);
 
             // Lookup a session entry by session ID
-            std::shared_ptr<const SessionState> get(uint32_t sessionID) const;
+            std::shared_ptr<SessionState> get(uint32_t sessionID) const;
 
             // Lookup a session entry by IPv4
-            std::shared_ptr<const SessionState> getByIP(uint32_t ip) const;
+            std::shared_ptr<SessionState> getByIP(uint32_t ip) const;
 
             // Get a snapshot of the Session Registry
             std::unordered_map<uint32_t, std::shared_ptr<SessionState>> snapshot() const;

include/columnlynx/common/net/tcp/tcp_message_handler.hpp

@@ -39,6 +39,6 @@ namespace ColumnLynx::Net::TCP {
             std::array<uint8_t, 3> mHeader{}; // [type][lenHigh][lenLow]
             std::vector<uint8_t> mBody;
             std::function<void(AnyMessageType, std::string)> mOnMessage;
-            std::function<void(asio::error_code&)> mOnDisconnect;
+            std::function<void(const asio::error_code&)> mOnDisconnect;
     };
 }

include/columnlynx/common/utils.hpp

@@ -15,7 +15,7 @@
 #include <unordered_map>
 #include <unordered_set>
 #include <algorithm>
-#include <bits/stdc++.h>
+
 
 #ifdef _WIN32
     #include <winsock2.h>
@@ -79,4 +79,15 @@ namespace ColumnLynx::Utils {
 
     // Returns the config file in an unordered_map format. This purely reads the config file, you still need to parse it manually.
     std::unordered_map<std::string, std::string> getConfigMap(std::string path, std::vector<std::string> requiredKeys = {});
+
+    // Load a hex-encoded file, validate its byte length, and return the decoded bytes.
+    std::vector<uint8_t> loadHexBytesFromFile(const std::string& path, size_t expectedBytes, const std::string& description = "key", bool warnOnInsecurePermissions = false);
+
+    template <size_t N>
+    inline std::array<uint8_t, N> loadHexArrayFromFile(const std::string& path, const std::string& description = "key", bool warnOnInsecurePermissions = false) {
+        auto bytes = loadHexBytesFromFile(path, N, description, warnOnInsecurePermissions);
+        std::array<uint8_t, N> out{};
+        std::copy_n(bytes.begin(), N, out.begin());
+        return out;
+    }
 };

include/columnlynx/server/net/tcp/tcp_connection.hpp

@@ -53,6 +53,9 @@ namespace ColumnLynx::Net::TCP {
                 :
                 mHandler(std::make_shared<MessageHandler>(std::move(socket))),
                 mHeartbeatTimer(mHandler->socket().get_executor()),
+                mConnectionAESKey{},
+                mConnectionSessionID(0),
+                mConnectionPublicKey{},
                 mLastHeartbeatReceived(std::chrono::steady_clock::now()),
                 mLastHeartbeatSent(std::chrono::steady_clock::now())
             {}

include/columnlynx/server/net/tcp/tcp_server.hpp

@@ -9,6 +9,7 @@
 #include <unordered_map>
 #include <vector>
 #include <memory>
+#include <mutex>
 #include <unordered_set>
 #include <new>
 #include <asio.hpp>
@@ -77,6 +78,7 @@ namespace ColumnLynx::Net::TCP {
             
             asio::io_context &mIoContext;
             asio::ip::tcp::acceptor mAcceptor;
+            std::mutex mClientsMutex;
             std::unordered_set<TCPConnection::pointer> mClients;
     };
 

src/client/main.cpp

@@ -5,6 +5,7 @@
 #include <asio.hpp>
 #include <csignal>
 #include <iostream>
+#include <filesystem>
 #include <columnlynx/common/utils.hpp>
 #include <columnlynx/common/panic_handler.hpp>
 #include <columnlynx/client/net/tcp/tcp_client.hpp>
@@ -90,7 +91,20 @@ int main(int argc, char** argv) {
         std::string configPath = optionsObj["config-dir"].as<std::string>();
         const char* envConfigPath = std::getenv("COLUMNLYNX_CONFIG_DIR");
         if (envConfigPath != nullptr) {
-            configPath = std::string(envConfigPath);
+            // Validate and canonicalize environment-provided path
+            try {
+                namespace fs = std::filesystem;
+                std::error_code ec;
+                fs::path candidate(envConfigPath);
+                fs::path abs = fs::absolute(candidate, ec);
+                if (!ec) {
+                    configPath = abs.string();
+                } else {
+                    warn(std::string("Invalid COLUMNLYNX_CONFIG_DIR value: ") + envConfigPath + " - using default");
+                }
+            } catch (const std::exception& e) {
+                warn(std::string("Failed to canonicalize COLUMNLYNX_CONFIG_DIR: ") + e.what());
+            }
         }
 
         if (configPath.back() != '/' && configPath.back() != '\\') {
@@ -113,6 +127,28 @@ int main(int argc, char** argv) {
         initialState.virtualInterface = tun;
 
         std::shared_ptr<LibSodiumWrapper> sodiumWrapper = std::make_shared<LibSodiumWrapper>();
+        const std::string clientPublicKeyPath = configPath + "public.key";
+        const std::string clientPrivateKeyPath = configPath + "private.key";
+
+        namespace fs = std::filesystem;
+        bool clientKeyFilesPresent = fs::exists(clientPublicKeyPath) && fs::exists(clientPrivateKeyPath);
+        if (clientKeyFilesPresent) {
+            Utils::log("Loading client keypair from key files.");
+
+            PublicKey pk = Utils::loadHexArrayFromFile<crypto_sign_PUBLICKEYBYTES>(clientPublicKeyPath, "client public key");
+            PrivateSeed seed = Utils::loadHexArrayFromFile<crypto_sign_SEEDBYTES>(clientPrivateKeyPath, "client private key", true);
+
+            if (!sodiumWrapper->recomputeKeys(seed, pk)) {
+                throw std::runtime_error("Failed to recompute client keypair from key files!");
+            }
+        } else {
+#if defined(DEBUG)
+            Utils::warn("No client keypair files found! Using random key.");
+#else
+            throw std::runtime_error("No client keypair files found! Cannot start client without keys.");
+#endif
+        }
+
         debug("Public Key: " + Utils::bytesToHexString(sodiumWrapper->getPublicKey(), 32));
         debug("Private Key: " + Utils::bytesToHexString(sodiumWrapper->getPrivateKey(), 64));
         initialState.sodiumWrapper = sodiumWrapper;
@@ -148,7 +184,7 @@ int main(int argc, char** argv) {
         debug("isDone flag: " + std::to_string(done));
         
         // Client is running
-        while ((client->isConnected() || !client->isHandshakeComplete()) && !done) {
+        while (client->isConnected() && !done) {
             //debug("Client connection flag: " + std::to_string(client->isConnected()));
             auto packet = tun->readPacket();
             /*if (!client->isConnected() || done) {

src/client/net/tcp/tcp_client.cpp

@@ -6,6 +6,20 @@
 //#include <arpa/inet.h>
 
 namespace ColumnLynx::Net::TCP {
+    TCPClient::TCPClient(asio::io_context& ioContext, const std::string& host, const std::string& port)
+        : mResolver(ioContext),
+          mSocket(ioContext),
+          mHost(host),
+          mPort(port),
+          mHeartbeatTimer(mSocket.get_executor()),
+          mLastHeartbeatReceived(std::chrono::steady_clock::now()),
+          mLastHeartbeatSent(std::chrono::steady_clock::now())
+    {
+        if (!ClientSession::getInstance().getSodiumWrapper()) {
+            throw std::runtime_error("ClientSession sodium wrapper is not initialized");
+        }
+    }
+
     void TCPClient::start() {
         auto self = shared_from_this();
         mResolver.async_resolve(mHost, mPort,
@@ -14,19 +28,25 @@ namespace ColumnLynx::Net::TCP {
                     asio::async_connect(mSocket, endpoints,
                         [this, self](asio::error_code ec, const tcp::endpoint&) {
                             if (!ec) {
-                                mConnected = true;
+                                mConnected.store(true, std::memory_order_relaxed);
                                 Utils::log("Client connected.");
                                 mHandler = std::make_shared<MessageHandler>(std::move(mSocket));
-                                mHandler->onMessage([this](AnyMessageType type, const std::string& data) {
-                                    mHandleMessage(static_cast<ServerMessageType>(MessageHandler::toUint8(type)), data);
+                                mHandler->onMessage([weakSelf = weak_from_this()](AnyMessageType type, const std::string& data) {
+                                    if (auto self = weakSelf.lock()) {
+                                        self->mHandleMessage(static_cast<ServerMessageType>(MessageHandler::toUint8(type)), data);
+                                    }
                                 });
                                 // Close only after peer FIN to avoid RSTs
-                                mHandler->onDisconnect([this](const asio::error_code& ec) {
-                                    asio::error_code ec2;
-                                    if (mHandler) {
-                                        mHandler->socket().close(ec2);
+                                mHandler->onDisconnect([weakSelf = weak_from_this()](const asio::error_code& ec) {
+                                    auto self = weakSelf.lock();
+                                    if (!self) {
+                                        return;
                                     }
-                                    mConnected = false;
+                                    asio::error_code ec2;
+                                    if (self->mHandler) {
+                                        self->mHandler->socket().close(ec2);
+                                    }
+                                    self->mConnected.store(false, std::memory_order_relaxed);
                                     Utils::log(std::string("Server disconnected: ") + ec.message());
                                 });
                                 mHandler->start();
@@ -74,7 +94,7 @@ namespace ColumnLynx::Net::TCP {
     }
 
     void TCPClient::sendMessage(ClientMessageType type, const std::string& data) {
-        if (!mConnected) {
+        if (!mConnected.load(std::memory_order_relaxed)) {
             Utils::error("Cannot send message, client not connected.");
             return;
         }
@@ -87,7 +107,7 @@ namespace ColumnLynx::Net::TCP {
     }
 
     void TCPClient::disconnect(bool echo) {
-        if (mConnected && mHandler) {
+        if (mConnected.load(std::memory_order_relaxed) && mHandler) {
             if (echo) {
                 mHandler->sendMessage(ClientMessageType::GRACEFUL_DISCONNECT, "Goodbye");
             }
@@ -107,17 +127,17 @@ namespace ColumnLynx::Net::TCP {
     }
 
     bool TCPClient::isHandshakeComplete() const {
-        return mHandshakeComplete;
+        return mHandshakeComplete.load(std::memory_order_relaxed);
     }
 
     bool TCPClient::isConnected() const {
-        return mConnected;
+        return mConnected.load(std::memory_order_relaxed);
     }
 
     void TCPClient::mStartHeartbeat() {
         auto self = shared_from_this();
         mHeartbeatTimer.expires_after(std::chrono::seconds(5));
-        mHeartbeatTimer.async_wait([this, self](const asio::error_code& ec) {
+        mHeartbeatTimer.async_wait([self](const asio::error_code& ec) {
             if (ec == asio::error::operation_aborted) {
                 return; // Timer was cancelled
             }
@@ -130,9 +150,11 @@ namespace ColumnLynx::Net::TCP {
                 
                 // Close sockets forcefully, server is dead
                 asio::error_code ec;
-                mHandler->socket().shutdown(tcp::socket::shutdown_both, ec);
-                mHandler->socket().close(ec);
-                mConnected = false;
+                if (self->mHandler) {
+                    self->mHandler->socket().shutdown(tcp::socket::shutdown_both, ec);
+                    self->mHandler->socket().close(ec);
+                }
+                self->mConnected.store(false, std::memory_order_relaxed);
                 
                 ClientSession::getInstance().setAESKey({}); // Clear AES key with all zeros
                 ClientSession::getInstance().setSessionID(0);
@@ -151,7 +173,13 @@ namespace ColumnLynx::Net::TCP {
     void TCPClient::mHandleMessage(ServerMessageType type, const std::string& data) {
         switch (type) {
             case ServerMessageType::HANDSHAKE_IDENTIFY: {
-                    std::memcpy(mServerPublicKey, data.data(), std::min(data.size(), sizeof(mServerPublicKey)));
+                    if (data.size() != sizeof(mServerPublicKey)) {
+                        Utils::warn("HANDSHAKE_IDENTIFY has invalid size: " + std::to_string(data.size()));
+                        disconnect();
+                        return;
+                    }
+
+                    std::memcpy(mServerPublicKey, data.data(), sizeof(mServerPublicKey));
                     std::string hexServerPub = Utils::bytesToHexString(mServerPublicKey, 32);
                     Utils::log("Received server identity. Public Key: " + hexServerPub);
 
@@ -180,7 +208,13 @@ namespace ColumnLynx::Net::TCP {
                 {
                     // Verify the signature
                     Signature sig{};
-                    std::memcpy(sig.data(), data.data(), std::min(data.size(), sig.size()));
+                    if (data.size() != sig.size()) {
+                        Utils::warn("HANDSHAKE_CHALLENGE_RESPONSE has invalid size: " + std::to_string(data.size()));
+                        disconnect();
+                        return;
+                    }
+
+                    std::memcpy(sig.data(), data.data(), sig.size());
                     if (Utils::LibSodiumWrapper::verifyMessage(mSubmittedChallenge.data(), mSubmittedChallenge.size(), sig, mServerPublicKey)) {
                         Utils::log("Challenge response verified successfully.");
                         
@@ -261,7 +295,7 @@ namespace ColumnLynx::Net::TCP {
                         mTun->configureIP(clientIP, serverIP, prefixLen, mtu);
                     }
 
-                    mHandshakeComplete = true;
+                    mHandshakeComplete.store(true, std::memory_order_relaxed);
                 }
             
                 break;
@@ -276,13 +310,13 @@ namespace ColumnLynx::Net::TCP {
                 break;
             case ServerMessageType::GRACEFUL_DISCONNECT:
                 Utils::log("Server is disconnecting: " + data);
-                if (mConnected) { // Prevent Recursion
+                if (mConnected.load(std::memory_order_relaxed)) { // Prevent Recursion
                     disconnect(false);
                 }
                 break;
             case ServerMessageType::KILL_CONNECTION:
                 Utils::warn("Server is killing the connection: " + data);
-                if (mConnected) {
+                if (mConnected.load(std::memory_order_relaxed)) {
                     disconnect(false);
                 }
                 break;

src/client/net/udp/udp_client.cpp

@@ -3,6 +3,8 @@
 // Distributed under the terms of the GNU General Public License, either version 2 only or version 3. See LICENSES/ for details.
 
 #include <columnlynx/client/net/udp/udp_client.hpp>
+#include <thread>
+#include <chrono>
 
 namespace ColumnLynx::Net::UDP {
     void UDPClient::start() {
@@ -42,6 +44,7 @@ namespace ColumnLynx::Net::UDP {
         }
         
         Utils::log("UDP Client ready to send to " + mRemoteEndpoint.address().to_string() + ":" + std::to_string(mRemoteEndpoint.port()));
+        mStartReceive();
     }
 
     void UDPClient::sendMessage(const std::string& data) {
@@ -73,7 +76,7 @@ namespace ColumnLynx::Net::UDP {
             reinterpret_cast<uint8_t*>(&hdr) + sizeof(UDPPacketHeader)
         );
         uint32_t sessionID = static_cast<uint32_t>(ClientSession::getInstance().getSessionID());
-        uint32_t sessionIDNet = sessionID;
+        uint32_t sessionIDNet = htonl(sessionID);
         packet.insert(packet.end(),
             reinterpret_cast<uint8_t*>(&sessionIDNet),
             reinterpret_cast<uint8_t*>(&sessionIDNet) + sizeof(uint32_t)
@@ -102,7 +105,12 @@ namespace ColumnLynx::Net::UDP {
                 if (ec) {
                     if (ec == asio::error::operation_aborted) return; // Socket closed
                     // Other recv error
-                    mStartReceive();
+                    Utils::warn("UDPClient receive error: " + ec.message());
+                    // Back off briefly before restarting receive to avoid busy error loops
+                    asio::post(mSocket.get_executor(), [this]() {
+                        std::this_thread::sleep_for(std::chrono::milliseconds(50));
+                        mStartReceive();
+                    });
                     return;
                 }
 
@@ -136,9 +144,24 @@ namespace ColumnLynx::Net::UDP {
         }
 
         // Decrypt payload
+        // Extract ciphertext safely
+        size_t headerLen = sizeof(UDPPacketHeader) + sizeof(uint32_t);
+        if (bytes < headerLen) {
+            Utils::warn("UDP Client received packet too small after header check.");
+            return;
+        }
+
+        size_t ciphertextLen = bytes - headerLen;
+        // Enforce reasonable maximum (UDP payload practical limit)
+        const size_t MAX_UDP_PAYLOAD = 65507; // 65535 - UDP/IP headers
+        if (ciphertextLen > MAX_UDP_PAYLOAD) {
+            Utils::warn("UDP Client received packet with excessive payload size: " + std::to_string(ciphertextLen));
+            return;
+        }
+
         std::vector<uint8_t> ciphertext(
-            mRecvBuffer.begin() + sizeof(UDPPacketHeader) + sizeof(uint32_t),
-            mRecvBuffer.begin() + bytes
+            mRecvBuffer.begin() + headerLen,
+            mRecvBuffer.begin() + headerLen + ciphertextLen
         );
 
         if (ClientSession::getInstance().getAESKey().empty()) {

src/common/session_registry.cpp

@@ -7,17 +7,22 @@
 namespace ColumnLynx::Net {
     void SessionRegistry::put(uint32_t sessionID, std::shared_ptr<SessionState> state) {
         std::unique_lock lock(mMutex);
+        // If replacing an existing entry, evict its old IP mapping first.
+        auto existing = mSessions.find(sessionID);
+        if (existing != mSessions.end() && existing->second) {
+            mIPSessions.erase(existing->second->clientTunIP);
+        }
         mSessions[sessionID] = std::move(state);
         mIPSessions[mSessions[sessionID]->clientTunIP] = mSessions[sessionID];
     }
 
-    std::shared_ptr<const SessionState> SessionRegistry::get(uint32_t sessionID) const {
+    std::shared_ptr<SessionState> SessionRegistry::get(uint32_t sessionID) const {
         std::shared_lock lock(mMutex);
         auto it = mSessions.find(sessionID);
         return (it == mSessions.end()) ? nullptr : it->second;
     }
 
-    std::shared_ptr<const SessionState> SessionRegistry::getByIP(uint32_t ip) const {
+    std::shared_ptr<SessionState> SessionRegistry::getByIP(uint32_t ip) const {
         std::shared_lock lock(mMutex);
         auto it = mIPSessions.find(ip);
         return (it == mIPSessions.end()) ? nullptr : it->second;
@@ -32,7 +37,26 @@ namespace ColumnLynx::Net {
 
     void SessionRegistry::erase(uint32_t sessionID) {
         std::unique_lock lock(mMutex);
-        mSessions.erase(sessionID);
+        auto it = mSessions.find(sessionID);
+        if (it != mSessions.end()) {
+            // If the session has a client IP mapping, remove it to avoid stale entries
+            if (it->second) {
+                uint32_t ip = it->second->clientTunIP;
+                auto ipIt = mIPSessions.find(ip);
+                if (ipIt != mIPSessions.end()) {
+                    // Only erase if it points to the same session
+                    if (ipIt->second == it->second) {
+                        mIPSessions.erase(ipIt);
+                    }
+                }
+            }
+
+            // Remove any session->ip bookkeeping
+            mSessionIPs.erase(sessionID);
+
+            // Finally erase the session
+            mSessions.erase(it);
+        }
     }
 
     void SessionRegistry::cleanupExpired() {
@@ -68,7 +92,9 @@ namespace ColumnLynx::Net {
     uint32_t SessionRegistry::getFirstAvailableIP(uint32_t baseIP, uint8_t mask) const {
         std::shared_lock lock(mMutex);
 
+        if (mask == 0 || mask >= 32) return 0; // degenerate subnet
         uint32_t hostCount = (1u << (32 - mask));
+        if (hostCount < 3) return 0; // no assignable host addresses
         uint32_t firstHost = 2;
         uint32_t lastHost  = hostCount - 2;
 
@@ -85,11 +111,15 @@ namespace ColumnLynx::Net {
     void SessionRegistry::lockIP(uint32_t sessionID, uint32_t ip) {
         std::unique_lock lock(mMutex);
         mSessionIPs[sessionID] = ip;
-        
-        /*if (mIPSessions.find(sessionID) == mIPSessions.end()) {
-            Utils::debug("yikes");
-        }*/
-        mIPSessions[ip] = mSessions.find(sessionID)->second;
+
+        auto it = mSessions.find(sessionID);
+        if (it == mSessions.end() || !it->second) {
+            Utils::warn("SessionRegistry::lockIP called for unknown session " + std::to_string(sessionID));
+            mSessionIPs.erase(sessionID);
+            return;
+        }
+
+        mIPSessions[ip] = it->second;
     }
 
     void SessionRegistry::deallocIP(uint32_t sessionID) {

src/common/tcp_message_handler.cpp

@@ -5,6 +5,7 @@
 #include <columnlynx/common/net/tcp/tcp_message_handler.hpp>
 #include <columnlynx/common/net/tcp/net_helper.hpp>
 #include <columnlynx/common/utils.hpp>
+#include <memory>
 
 namespace ColumnLynx::Net::TCP {
     void MessageHandler::start() {
@@ -17,17 +18,23 @@ namespace ColumnLynx::Net::TCP {
             return static_cast<uint8_t>(type);
         }, type);
 
-        std::vector<uint8_t> data;
-        data.push_back(typeByte);
-        uint16_t length = payload.size();
+        auto data = std::make_shared<std::vector<uint8_t>>();
+        data->push_back(typeByte);
+        // Ensure payload fits into protocol's 16-bit length field
+        if (payload.size() > static_cast<size_t>(std::numeric_limits<uint16_t>::max())) {
+            Utils::error("sendMessage(): payload too large (>65535 bytes)");
+            return;
+        }
 
-        data.push_back(length >> 8);
-        data.push_back(length & 0xFF);
+        uint16_t length = static_cast<uint16_t>(payload.size());
 
-        data.insert(data.end(), payload.begin(), payload.end());
+        data->push_back(static_cast<uint8_t>(length >> 8));
+        data->push_back(static_cast<uint8_t>(length & 0xFF));
+
+        data->insert(data->end(), payload.begin(), payload.end());
         auto self = shared_from_this();
-        asio::async_write(mSocket, asio::buffer(data),
-            [self](asio::error_code ec, std::size_t) {
+        asio::async_write(mSocket, asio::buffer(*data),
+            [self, data](asio::error_code ec, std::size_t) {
                 if (ec) {
                     Utils::error("Send failed: " + ec.message());
                 }
@@ -47,6 +54,12 @@ namespace ColumnLynx::Net::TCP {
                     mCurrentType = decodeMessageType(mHeader[0]);
 
                     uint16_t len = (mHeader[1] << 8) | mHeader[2];
+                    constexpr uint16_t MAX_MSG_BODY = 8192;
+                    if (len > MAX_MSG_BODY) {
+                        Utils::error("Incoming message body too large (" + std::to_string(len) + " > " + std::to_string(MAX_MSG_BODY) + "), closing connection.");
+                        if (mOnDisconnect) mOnDisconnect(asio::error::message_size);
+                        return;
+                    }
                     mReadBody(len);
                 } else {
                     if (!NetHelper::isExpectedDisconnect(ec)) {

src/common/utils.cpp

@@ -3,6 +3,8 @@
 // Distributed under the terms of the GNU General Public License, either version 2 only or version 3. See LICENSES/ for details.
 
 #include <columnlynx/common/utils.hpp>
+#include <filesystem>
+#include <cctype>
 
 namespace ColumnLynx::Utils {
     std::string unixMillisToISO8601(uint64_t unixMillis, bool local) {
@@ -85,7 +87,7 @@ namespace ColumnLynx::Utils {
     }
 
     std::string getVersion() {
-        return "1.1.0";
+        return "1.2.1";
     }
 
     unsigned short serverPort() {
@@ -144,19 +146,49 @@ namespace ColumnLynx::Utils {
 
         std::vector<std::string> out;
 
-        std::ifstream file(basePath + "whitelisted_keys");
+        namespace fs = std::filesystem;
+        std::error_code ec;
+
+        fs::path base(basePath);
+        fs::path absBase = fs::absolute(base, ec);
+        if (ec) {
+            warn("getWhitelistedKeys(): failed to resolve base path: " + basePath + " - " + ec.message());
+            return out;
+        }
+
+        fs::path whitelist = absBase / "whitelisted_keys";
+        if (!fs::exists(whitelist, ec) || ec) {
+            warn("getWhitelistedKeys(): whitelist file not found: " + whitelist.string());
+            return out;
+        }
+
+        // Canonicalize to avoid symlink tricks
+        fs::path canon = fs::canonical(whitelist, ec);
+        if (ec) {
+            warn("getWhitelistedKeys(): failed to canonicalize path: " + whitelist.string());
+            return out;
+        }
+
+        std::ifstream file(canon);
         if (!file.is_open()) {
-            warn("Failed to open whitelisted_keys file at path: " + basePath + "whitelisted_keys");
+            warn("getWhitelistedKeys(): failed to open whitelist file: " + canon.string());
             return out;
         }
 
         std::string line;
         while (std::getline(file, line)) {
+            // Trim whitespace
+            while (!line.empty() && isspace(static_cast<unsigned char>(line.back()))) line.pop_back();
+            size_t start = 0;
+            while (start < line.size() && isspace(static_cast<unsigned char>(line[start]))) ++start;
+            if (start >= line.size()) continue;
+            std::string key = line.substr(start);
+
             // Convert to upper case to align with the bytesToHexString() output
-            for (int i = 0; i < line.length(); i++) {
-                line[i] = toupper(line[i]);
+            for (size_t i = 0; i < key.length(); ++i) {
+                key[i] = static_cast<char>(toupper(static_cast<unsigned char>(key[i])));
             }
-            out.push_back(line);
+            out.push_back(key);
         }
 
         return out;
@@ -166,9 +198,26 @@ namespace ColumnLynx::Utils {
         // TODO: Currently re-reads every time.
         std::vector<std::string> readLines;
 
-        std::ifstream file(path);
+        namespace fs = std::filesystem;
+        std::error_code ec;
+        fs::path p(path);
+        fs::path abs = fs::absolute(p, ec);
+        if (ec) {
+            throw std::runtime_error("getConfigMap(): failed to resolve path: " + path + " - " + ec.message());
+        }
+
+        if (!fs::exists(abs, ec) || ec) {
+            throw std::runtime_error("getConfigMap(): config file does not exist: " + abs.string());
+        }
+
+        fs::path canon = fs::canonical(abs, ec);
+        if (ec) {
+            throw std::runtime_error("getConfigMap(): failed to canonicalize config path: " + abs.string());
+        }
+
+        std::ifstream file(canon);
         if (!file.is_open()) {
-            throw std::runtime_error("Failed to open config file at path: " + path);
+            throw std::runtime_error("Failed to open config file at path: " + canon.string());
         }
 
         std::string line;
@@ -203,4 +252,78 @@ namespace ColumnLynx::Utils {
 
         return config;
     }
+
+    std::vector<uint8_t> loadHexBytesFromFile(const std::string& path, size_t expectedBytes, const std::string& description, bool warnOnInsecurePermissions) {
+        namespace fs = std::filesystem;
+        std::error_code ec;
+
+        fs::path p(path);
+        fs::path abs = fs::absolute(p, ec);
+        if (ec) {
+            throw std::runtime_error("loadHexBytesFromFile(): failed to resolve path: " + path + " - " + ec.message());
+        }
+
+        if (!fs::exists(abs, ec) || ec) {
+            throw std::runtime_error("loadHexBytesFromFile(): file does not exist: " + abs.string());
+        }
+
+        fs::path canon = fs::canonical(abs, ec);
+        if (ec) {
+            throw std::runtime_error("loadHexBytesFromFile(): failed to canonicalize path: " + abs.string());
+        }
+
+#ifndef _WIN32
+        if (warnOnInsecurePermissions) {
+            ec.clear();
+            fs::file_status status = fs::status(canon, ec);
+            if (ec) {
+                warn("loadHexBytesFromFile(): failed to inspect permissions for " + canon.string() + " - " + ec.message());
+            } else {
+                auto perms = status.permissions();
+                if ((perms & (fs::perms::group_all | fs::perms::others_all)) != fs::perms::none) {
+                    warn(description + " file permissions are too permissive: " + canon.string() + " (recommend chmod 600)");
+                }
+
+                if (!fs::is_regular_file(status)) {
+                    warn(description + " path is not a regular file: " + canon.string());
+                }
+            }
+        }
+#endif
+
+        std::ifstream file(canon);
+        if (!file.is_open()) {
+            throw std::runtime_error("Failed to open " + description + " file at path: " + canon.string());
+        }
+
+        std::string hex((std::istreambuf_iterator<char>(file)), std::istreambuf_iterator<char>());
+
+        auto trim = [](std::string& s) {
+            while (!s.empty() && std::isspace(static_cast<unsigned char>(s.back()))) {
+                s.pop_back();
+            }
+
+            size_t start = 0;
+            while (start < s.size() && std::isspace(static_cast<unsigned char>(s[start]))) {
+                ++start;
+            }
+
+            if (start > 0) {
+                s.erase(0, start);
+            }
+        };
+
+        trim(hex);
+
+        if (hex.empty()) {
+            throw std::runtime_error(description + " file is empty: " + canon.string());
+        }
+
+        std::vector<uint8_t> bytes = hexStringToBytes(hex);
+        if (bytes.size() != expectedBytes) {
+            throw std::runtime_error(description + " file must contain exactly " + std::to_string(expectedBytes * 2) + " hex characters (" + std::to_string(expectedBytes) + " bytes), got " + std::to_string(bytes.size()) + " bytes");
+        }
+
+        return bytes;
+    }
 }

src/common/virtual_interface.cpp

@@ -4,6 +4,11 @@
 
 #include <columnlynx/common/net/virtual_interface.hpp>
 
+#include <spawn.h>
+#include <sys/wait.h>
+
+extern char **environ;
+
 // This is all fucking voodoo dark magic.
 
 #if defined(_WIN32)
@@ -53,9 +58,74 @@ static void InitializeWintun()
 #undef RESOLVE
 }
 
+// Run a command on Windows via CreateProcess (no shell — shell metacharacters in
+// arguments are not interpreted by cmd.exe).
+static bool runCommandWin32(const std::vector<std::string>& args) {
+    if (args.empty()) return false;
+
+    // Build a properly-quoted command line using Windows quoting rules.
+    std::string cmdLine;
+    for (size_t i = 0; i < args.size(); i++) {
+        if (i > 0) cmdLine += ' ';
+        bool needsQuote = args[i].find_first_of(" \t\"") != std::string::npos || args[i].empty();
+        if (needsQuote) {
+            cmdLine += '"';
+            for (char c : args[i]) {
+                if (c == '"') cmdLine += '\\';
+                cmdLine += c;
+            }
+            cmdLine += '"';
+        } else {
+            cmdLine += args[i];
+        }
+    }
+
+    STARTUPINFOA si{};
+    si.cb = sizeof(si);
+    PROCESS_INFORMATION pi{};
+
+    if (!CreateProcessA(nullptr, cmdLine.data(), nullptr, nullptr,
+                        FALSE, CREATE_NO_WINDOW, nullptr, nullptr, &si, &pi))
+        return false;
+
+    WaitForSingleObject(pi.hProcess, INFINITE);
+    DWORD exitCode = 1;
+    GetExitCodeProcess(pi.hProcess, &exitCode);
+    CloseHandle(pi.hProcess);
+    CloseHandle(pi.hThread);
+    return exitCode == 0;
+}
+
 #endif // _WIN32
 
 namespace ColumnLynx::Net {
+
+// Run a command without invoking a shell. Arguments are passed directly
+// to the underlying process to avoid shell injection vulnerabilities.
+static bool runCommand(const std::vector<std::string>& args) {
+    if (args.empty()) return false;
+
+    std::vector<char*> argv;
+    argv.reserve(args.size() + 1);
+    for (const auto &s : args) {
+        argv.push_back(const_cast<char*>(s.c_str()));
+    }
+    argv.push_back(nullptr);
+
+    pid_t pid;
+    int rc = posix_spawnp(&pid, argv[0], nullptr, nullptr, argv.data(), environ);
+    if (rc != 0) {
+        return false;
+    }
+
+    int status = 0;
+    if (waitpid(pid, &status, 0) == -1) {
+        return false;
+    }
+
+    return WIFEXITED(status) && WEXITSTATUS(status) == 0;
+}
+
     // ------------------------------ Constructor ------------------------------
     VirtualInterface::VirtualInterface(const std::string& ifName)
         : mIfName(ifName), mFd(-1)
@@ -84,8 +154,10 @@ namespace ColumnLynx::Net {
 
         struct ctl_info ctlInfo {};
         std::strncpy(ctlInfo.ctl_name, UTUN_CONTROL_NAME, sizeof(ctlInfo.ctl_name));
-        if (ioctl(mFd, CTLIOCGINFO, &ctlInfo) == -1)
+        if (ioctl(mFd, CTLIOCGINFO, &ctlInfo) == -1) {
+            close(mFd); mFd = -1;
             throw std::runtime_error("ioctl(CTLIOCGINFO) failed: " + std::string(strerror(errno)));
+        }
 
         struct sockaddr_ctl sc {};
         sc.sc_len = sizeof(sc);
@@ -95,9 +167,11 @@ namespace ColumnLynx::Net {
         sc.sc_unit = 0; // 0 = auto-assign next utunX
 
         if (connect(mFd, (struct sockaddr*)&sc, sizeof(sc)) < 0) {
-            if (errno == EPERM)
+            int savedErrno = errno;
+            close(mFd); mFd = -1;
+            if (savedErrno == EPERM)
                 throw std::runtime_error("connect(AF_SYS_CONTROL) failed: Insufficient permissions (try running with sudo)");
-            throw std::runtime_error("connect(AF_SYS_CONTROL) failed: " + std::string(strerror(errno)));
+            throw std::runtime_error("connect(AF_SYS_CONTROL) failed: " + std::string(strerror(savedErrno)));
         }
 
         // Retrieve actual utun device name via UTUN_OPT_IFNAME
@@ -181,8 +255,8 @@ namespace ColumnLynx::Net {
         pfd.fd = mFd;
         pfd.events = POLLIN;
 
-        // timeout in ms; keep it small so shutdown is responsive
-        int ret = poll(&pfd, 1, 200);
+        // timeout in ms; keep it small so shutdown is responsive. Reduced for lower latency.
+        int ret = poll(&pfd, 1, 50);
 
         if (ret == 0) {
             // No data yet
@@ -307,25 +381,10 @@ namespace ColumnLynx::Net {
 
     void VirtualInterface::resetIP() {
     #if defined(__linux__)
-        char cmd[512];
-        snprintf(cmd, sizeof(cmd),
-                 "ip addr flush dev %s",
-                 mIfName.c_str()
-        );
-        system(cmd);
+        runCommand({"ip", "addr", "flush", "dev", mIfName});
     #elif defined(__APPLE__)
-        char cmd[512];
-        snprintf(cmd, sizeof(cmd),
-                 "ifconfig %s inet 0.0.0.0 delete",
-                 mIfName.c_str()
-        );
-        system(cmd);
-
-        snprintf(cmd, sizeof(cmd),
-                 "ifconfig %s inet6 :: delete",
-                 mIfName.c_str()
-        );
-        system(cmd);
+        runCommand({"ifconfig", mIfName, "inet", "0.0.0.0", "delete"});
+        runCommand({"ifconfig", mIfName, "inet6", "::", "delete"});
 
         // Wipe old routes
         //snprintf(cmd, sizeof(cmd),
@@ -334,20 +393,10 @@ namespace ColumnLynx::Net {
         //);
         //system(cmd);
     #elif defined(_WIN32)
-        char cmd[512];
         // Remove any persistent routes associated with this interface
-        snprintf(cmd, sizeof(cmd),
-            "netsh routing ip delete persistentroute all name=\"%s\"",
-            mIfName.c_str()
-        );
-        system(cmd);
-        
+        runCommandWin32({"netsh", "routing", "ip", "delete", "persistentroute", "all", "name=" + mIfName});
         // Reset to DHCP
-        snprintf(cmd, sizeof(cmd),
-            "netsh interface ip set address name=\"%s\" dhcp",
-            mIfName.c_str()
-        );
-        system(cmd);
+        runCommandWin32({"netsh", "interface", "ip", "set", "address", "name=" + mIfName, "dhcp"});
     #endif
     }
 
@@ -357,26 +406,19 @@ namespace ColumnLynx::Net {
     bool VirtualInterface::mApplyLinuxIP(uint32_t clientIP, uint32_t serverIP,
                                         uint8_t prefixLen, uint16_t mtu)
     {
-        char cmd[512];
     
         std::string ipStr = ipv4ToString(clientIP);
         std::string peerStr = ipv4ToString(serverIP);
     
         // Wipe the current config
-        snprintf(cmd, sizeof(cmd),
-                 "ip addr flush dev %s",
-                 mIfName.c_str()
-        );
-        system(cmd);
+        runCommand({"ip", "addr", "flush", "dev", mIfName});
 
-        snprintf(cmd, sizeof(cmd),
-                 "ip addr add %s/%d peer %s dev %s",
-                 ipStr.c_str(), prefixLen, peerStr.c_str(), mIfName.c_str());
-        system(cmd);
-    
-        snprintf(cmd, sizeof(cmd),
-                 "ip link set dev %s up mtu %d", mIfName.c_str(), mtu);
-        system(cmd);
+        // Add address with peer
+        std::string addrArg = ipStr + "/" + std::to_string(prefixLen);
+        runCommand({"ip", "addr", "add", addrArg, "peer", peerStr, "dev", mIfName});
+
+        // Bring link up and set MTU
+        runCommand({"ip", "link", "set", "dev", mIfName, "up", "mtu", std::to_string(mtu)});
     
         return true;
     }
@@ -387,39 +429,23 @@ namespace ColumnLynx::Net {
     bool VirtualInterface::mApplyMacOSIP(uint32_t clientIP, uint32_t serverIP,
                                         uint8_t prefixLen, uint16_t mtu)
     {
-        char cmd[512];
     
         std::string ipStr = ipv4ToString(clientIP);
         std::string peerStr = ipv4ToString(serverIP);
         std::string prefixStr = ipv4ToString(prefixLengthToNetmask(prefixLen), false);
         Utils::debug("Prefix string: " + prefixStr);
     
-        // Reset
-        snprintf(cmd, sizeof(cmd),
-                 "ifconfig %s inet 0.0.0.0 delete",
-                mIfName.c_str()
-        );
-        system(cmd);
+        // Reset IPv4 and IPv6 addresses
+        runCommand({"ifconfig", mIfName, "inet", "0.0.0.0", "delete"});
+        runCommand({"ifconfig", mIfName, "inet6", "::", "delete"});
 
-        snprintf(cmd, sizeof(cmd),
-                 "ifconfig %s inet6 :: delete",
-                mIfName.c_str()
-        );
-        system(cmd);
+        // Set address and netmask
+        std::string netArg = ipStr + " " + peerStr; // ifconfig expects ip peer
+        runCommand({"ifconfig", mIfName, "inet", ipStr, peerStr, "mtu", std::to_string(mtu), "netmask", prefixStr, "up"});
 
-        // Set
-        snprintf(cmd, sizeof(cmd),
-                "ifconfig %s inet %s %s mtu %d netmask %s up",
-                 mIfName.c_str(), ipStr.c_str(), peerStr.c_str(), mtu, prefixStr.c_str());
-        system(cmd);
-
-        // Host bits are auto-normalized by the kernel on macOS, so we don't need to worry about them not being zeroed out.
-        snprintf(cmd, sizeof(cmd),
-                 "route -n add -net %s/%d -interface %s",
-                 ipStr.c_str(), prefixLen, mIfName.c_str());
-        system(cmd);
-
-        Utils::log("Executed command: " + std::string(cmd));
+        // Add route for the network
+        std::string networkArg = ipStr + "/" + std::to_string(prefixLen);
+        runCommand({"route", "-n", "add", "-net", networkArg, "-interface", mIfName});
     
         return true;
     }

src/server/main.cpp

@@ -6,6 +6,8 @@
 #include <iostream>
 #include <thread>
 #include <chrono>
+#include <filesystem>
+#include <cstring>
 #include <columnlynx/common/utils.hpp>
 #include <columnlynx/common/panic_handler.hpp>
 #include <columnlynx/server/net/tcp/tcp_server.hpp>
@@ -90,10 +92,9 @@ int main(int argc, char** argv) {
         serverState.configPath = configPath;
 
 #if defined(DEBUG)
-        std::unordered_map<std::string, std::string> config = Utils::getConfigMap(configPath + "server_config", { "NETWORK", "SUBNET_MASK" });
+    std::unordered_map<std::string, std::string> config = Utils::getConfigMap(configPath + "server_config", { "NETWORK", "SUBNET_MASK" });
 #else
-        // A production server should never use random keys. If the config file cannot be read or does not contain keys, the server will fail to start.
-        std::unordered_map<std::string, std::string> config = Utils::getConfigMap(configPath + "server_config", { "NETWORK", "SUBNET_MASK", "SERVER_PUBLIC_KEY", "SERVER_PRIVATE_KEY" });
+    std::unordered_map<std::string, std::string> config = Utils::getConfigMap(configPath + "server_config", { "NETWORK", "SUBNET_MASK" });
 #endif
 
         serverState.serverConfig = config;
@@ -104,30 +105,28 @@ int main(int argc, char** argv) {
         // Store a reference to the tun in the serverState, it will increment and keep a safe reference (we love shared_ptrs)
         serverState.virtualInterface = tun;
 
-        // Generate a temporary keypair, replace with actual CA signed keys later (Note, these are stored in memory)
         std::shared_ptr<LibSodiumWrapper> sodiumWrapper = std::make_shared<LibSodiumWrapper>();
 
-        auto itPubkey = config.find("SERVER_PUBLIC_KEY");
-        auto itPrivkey = config.find("SERVER_PRIVATE_KEY");
+        const std::string serverPublicKeyPath = configPath + "public.key";
+        const std::string serverPrivateKeyPath = configPath + "private.key";
 
-        if (itPubkey != config.end() && itPrivkey != config.end()) {
-            log("Loading keypair from config file.");
+        namespace fs = std::filesystem;
+        bool serverKeyFilesPresent = fs::exists(serverPublicKeyPath) && fs::exists(serverPrivateKeyPath);
+        if (serverKeyFilesPresent) {
+            log("Loading server keypair from key files.");
 
-            PublicKey pk;
-            PrivateSeed seed;
-
-            std::copy_n(Utils::hexStringToBytes(itPrivkey->second).begin(), seed.size(), seed.begin());
-            std::copy_n(Utils::hexStringToBytes(itPubkey->second).begin(), pk.size(), pk.begin());
+            PublicKey pk = Utils::loadHexArrayFromFile<crypto_sign_PUBLICKEYBYTES>(serverPublicKeyPath, "server public key");
+            PrivateSeed seed = Utils::loadHexArrayFromFile<crypto_sign_SEEDBYTES>(serverPrivateKeyPath, "server private key", true);
 
             if (!sodiumWrapper->recomputeKeys(seed, pk)) {
-                throw std::runtime_error("Failed to recompute keypair from config file values!");
+                throw std::runtime_error("Failed to recompute keypair from key files!");
             }
         } else {
-            #if defined(DEBUG)
-            warn("No keypair found in config file! Using random key.");
-            #else
-            throw std::runtime_error("No keypair found in config file! Cannot start server without keys.");
-            #endif
+#if defined(DEBUG)
+            warn("No server keypair files found! Using random key.");
+#else
+            throw std::runtime_error("No server keypair files found! Cannot start server without keys.");
+#endif
         }
 
         log("Server public key: " + bytesToHexString(sodiumWrapper->getPublicKey(), crypto_sign_PUBLICKEYBYTES));
@@ -144,6 +143,22 @@ int main(int argc, char** argv) {
         auto server = std::make_shared<TCPServer>(io, serverPort());
         auto udpServer = std::make_shared<UDPServer>(io, serverPort());
 
+        // Schedule periodic cleanup of expired sessions every 5 minutes
+        auto cleanupTimer = std::make_shared<asio::steady_timer>(io);
+        auto cleanupHandler = std::make_shared<std::function<void(const asio::error_code&)>>();
+        *cleanupHandler = [cleanupTimer, cleanupHandler](const asio::error_code& ec) {
+            if (ec == asio::error::operation_aborted) return; // Timer cancelled
+            try {
+                SessionRegistry::getInstance().cleanupExpired();
+            } catch (const std::exception& e) {
+                Utils::warn(std::string("SessionRegistry::cleanupExpired() threw: ") + e.what());
+            }
+            cleanupTimer->expires_after(std::chrono::minutes(5));
+            cleanupTimer->async_wait(*cleanupHandler);
+        };
+        cleanupTimer->expires_after(std::chrono::minutes(5));
+        cleanupTimer->async_wait(*cleanupHandler);
+
         asio::signal_set signals(io, SIGINT, SIGTERM);
         signals.async_wait([&](const std::error_code&, int) {
             log("Received termination signal. Shutting down server gracefully.");
@@ -152,6 +167,8 @@ int main(int argc, char** argv) {
                 ServerSession::getInstance().setHostRunning(false);
                 server->stop();
                 udpServer->stop();
+                // Cancel cleanup timer
+                cleanupTimer->cancel();
             });
         });
 
@@ -172,15 +189,35 @@ int main(int argc, char** argv) {
                 continue;
             }
 
+            if (packet.size() < 20) {
+                Utils::warn("TUN: Dropping packet smaller than IPv4 header (" + std::to_string(packet.size()) + " bytes)");
+                continue;
+            }
+
             const uint8_t* ip = packet.data();
-            uint32_t srcIP = ntohl(*(uint32_t*)(ip + 12)); // IPv4 source address offset
-            uint32_t dstIP = ntohl(*(uint32_t*)(ip + 16)); // IPv4 destination address offset
+            uint8_t ipVersion = (ip[0] >> 4);
+            if (ipVersion != 4) {
+                Utils::debug("TUN: Non-IPv4 packet received (version=" + std::to_string(ipVersion) + "), skipping server IPv4 routing path.");
+                continue;
+            }
+
+            uint32_t srcIPNet = 0;
+            uint32_t dstIPNet = 0;
+            std::memcpy(&srcIPNet, ip + 12, sizeof(srcIPNet)); // IPv4 source address offset
+            std::memcpy(&dstIPNet, ip + 16, sizeof(dstIPNet)); // IPv4 destination address offset
+            uint32_t srcIP = ntohl(srcIPNet);
+            uint32_t dstIP = ntohl(dstIPNet);
         
             // First, check if destination IP is a registered client (e.g., server responding to client or client-to-client)
             auto dstSession = SessionRegistry::getInstance().getByIP(dstIP);
             if (dstSession) {
-                // Destination is a registered client, forward to that client's session
-                udpServer->sendData(dstSession->sessionID, std::string(packet.begin(), packet.end()));
+                // Destination is a registered client, enforce MTU and forward to that client's session
+                const size_t MTU = 1420; // Enforce configured MTU; TODO: read from server config
+                if (packet.size() > MTU) {
+                    Utils::warn("TUN: Dropping oversized packet (" + std::to_string(packet.size()) + " > MTU " + std::to_string(MTU) + ")");
+                } else {
+                    udpServer->sendData(dstSession->sessionID, std::string(packet.begin(), packet.end()));
+                }
                 continue;
             }
 

src/server/net/tcp/tcp_connection.cpp

@@ -14,23 +14,31 @@ namespace ColumnLynx::Net::TCP {
             Utils::warn("Failed to get remote endpoint: " + std::string(e.what()));
         }
 
-        mHandler->onMessage([this](AnyMessageType type, const std::string& data) {
-            mHandleMessage(static_cast<ClientMessageType>(MessageHandler::toUint8(type)), data);
+        mHandler->onMessage([weakSelf = weak_from_this()](AnyMessageType type, const std::string& data) {
+            if (auto self = weakSelf.lock()) {
+                self->mHandleMessage(static_cast<ClientMessageType>(MessageHandler::toUint8(type)), data);
+            }
         });
 
-        mHandler->onDisconnect([this](const asio::error_code& ec) {
+        mHandler->onDisconnect([weakSelf = weak_from_this()](const asio::error_code& ec) {
+            auto self = weakSelf.lock();
+            if (!self) {
+                return;
+            }
             // Peer has closed; finalize locally without sending RST
-            Utils::log("Client disconnected: " + mRemoteIP + " - " + ec.message());
+            Utils::log("Client disconnected: " + self->mRemoteIP + " - " + ec.message());
             asio::error_code ec2;
-            mHandler->socket().close(ec2);
+            if (self->mHandler) {
+                self->mHandler->socket().close(ec2);
+            }
 
-            SessionRegistry::getInstance().erase(mConnectionSessionID);
-            SessionRegistry::getInstance().deallocIP(mConnectionSessionID);
+            SessionRegistry::getInstance().erase(self->mConnectionSessionID);
+            SessionRegistry::getInstance().deallocIP(self->mConnectionSessionID);
 
-            Utils::log("Closed connection to " + mRemoteIP);
+            Utils::log("Closed connection to " + self->mRemoteIP);
 
-            if (mOnDisconnect) {
-                mOnDisconnect(shared_from_this());
+            if (self->mOnDisconnect) {
+                self->mOnDisconnect(self);
             }
         });
 
@@ -77,7 +85,7 @@ namespace ColumnLynx::Net::TCP {
     void TCPConnection::mStartHeartbeat() {
         auto self = shared_from_this();
         mHeartbeatTimer.expires_after(std::chrono::seconds(5));
-        mHeartbeatTimer.async_wait([this, self](const asio::error_code& ec) {
+        mHeartbeatTimer.async_wait([self](const asio::error_code& ec) {
             if (ec == asio::error::operation_aborted) {
                 return; // Timer was cancelled
             }
@@ -90,10 +98,13 @@ namespace ColumnLynx::Net::TCP {
                 
                 // Remove socket forcefully, client is dead
                 asio::error_code ec;
-                mHandler->socket().shutdown(asio::ip::tcp::socket::shutdown_both, ec);
-                mHandler->socket().close(ec);
+                if (self->mHandler) {
+                    self->mHandler->socket().shutdown(asio::ip::tcp::socket::shutdown_both, ec);
+                    self->mHandler->socket().close(ec);
+                }
 
                 SessionRegistry::getInstance().erase(self->mConnectionSessionID);
+                SessionRegistry::getInstance().deallocIP(self->mConnectionSessionID);
 
                 return;
             }
@@ -113,8 +124,8 @@ namespace ColumnLynx::Net::TCP {
             case ClientMessageType::HANDSHAKE_INIT: {
                 Utils::log("Received HANDSHAKE_INIT from " + reqAddr);
 
-                if (data.size() < 1 + crypto_box_PUBLICKEYBYTES) {
-                    Utils::warn("HANDSHAKE_INIT from " + reqAddr + " is too short.");
+                if (data.size() != 1 + crypto_sign_PUBLICKEYBYTES) {
+                    Utils::warn("HANDSHAKE_INIT from " + reqAddr + " has invalid size: " + std::to_string(data.size()));
                     disconnect();
                     return;
                 }
@@ -130,7 +141,7 @@ namespace ColumnLynx::Net::TCP {
                 Utils::log("Client protocol version " + std::to_string(clientProtoVer) + " accepted from " + reqAddr + ".");
 
                 PublicKey signPk;
-                std::memcpy(signPk.data(), data.data() + 1, std::min(data.size() - 1, sizeof(signPk)));
+                std::memcpy(signPk.data(), data.data() + 1, sizeof(signPk));
 
                 // We can safely store this without further checking, the client will need to send the encrypted AES key in a way where they must possess the corresponding private key anyways.
                 int r = crypto_sign_ed25519_pk_to_curve25519(mConnectionPublicKey.data(), signPk.data()); // Store the client's public encryption key key (for identification)
@@ -162,9 +173,15 @@ namespace ColumnLynx::Net::TCP {
             case ClientMessageType::HANDSHAKE_CHALLENGE: {
                 Utils::log("Received HANDSHAKE_CHALLENGE from " + reqAddr);
                 
-                // Convert to byte array
+                // Convert to byte array - require exact size
+                if (data.size() != 32) {
+                    Utils::warn("HANDSHAKE_CHALLENGE has invalid size: " + std::to_string(data.size()));
+                    disconnect();
+                    return;
+                }
+
                 uint8_t challengeData[32];
-                std::memcpy(challengeData, data.data(), std::min(data.size(), sizeof(challengeData)));
+                std::memcpy(challengeData, data.data(), sizeof(challengeData));
 
                 // Sign the challenge
                 Signature sig = Utils::LibSodiumWrapper::signMessage(
@@ -212,17 +229,32 @@ namespace ColumnLynx::Net::TCP {
                     std::memcpy(mConnectionAESKey.data(), decrypted.data(), decrypted.size());
 
                     // Make a Session ID - unique and not zero (zero is reserved for invalid sessions)
-                    do {
-                        randombytes_buf(&mConnectionSessionID, sizeof(mConnectionSessionID));
-                    } while (SessionRegistry::getInstance().exists(mConnectionSessionID) || mConnectionSessionID == 0); // Regenerate if it already exists or is zero (zero is reserved for invalid sessions)
+                    {
+                        int idAttempts = 0;
+                        do {
+                            if (++idAttempts > 16) {
+                                Utils::error("Failed to generate unique session ID after 16 attempts. Killing connection from " + reqAddr);
+                                disconnect();
+                                return;
+                            }
+                            randombytes_buf(&mConnectionSessionID, sizeof(mConnectionSessionID));
+                        } while (SessionRegistry::getInstance().exists(mConnectionSessionID) || mConnectionSessionID == 0);
+                    }
 
                     // Encrypt the Session ID with the established AES key (using symmetric encryption, nonce can be all zeros for this purpose)
                     Nonce symNonce{}; // All zeros
 
                     const auto& serverConfig = ServerSession::getInstance().getRawServerConfig();
 
-                    std::string networkString = serverConfig.find("NETWORK")->second; // The load check guarantees that this value exists
-                    uint8_t configMask = std::stoi(serverConfig.find("SUBNET_MASK")->second); // Same deal here
+                    auto netIt  = serverConfig.find("NETWORK");
+                    auto maskIt = serverConfig.find("SUBNET_MASK");
+                    if (netIt == serverConfig.end() || maskIt == serverConfig.end()) {
+                        Utils::error("Server config is missing NETWORK or SUBNET_MASK. Killing connection from " + reqAddr);
+                        disconnect();
+                        return;
+                    }
+                    std::string networkString = netIt->second;
+                    uint8_t configMask = static_cast<uint8_t>(std::stoi(maskIt->second));
 
                     uint32_t baseIP = Net::VirtualInterface::stringToIpv4(networkString);
 
@@ -264,7 +296,7 @@ namespace ColumnLynx::Net::TCP {
 
                     // Add to session registry
                     Utils::log("Handshake with " + reqAddr + " completed successfully. Session ID assigned (" + std::to_string(mConnectionSessionID) + ").");
-                    auto session = std::make_shared<SessionState>(mConnectionAESKey, std::chrono::hours(12), clientIP, htonl(0x0A0A0001), mConnectionSessionID);
+                    auto session = std::make_shared<SessionState>(mConnectionAESKey, std::chrono::hours(12), clientIP, htonl(baseIP + 1), mConnectionSessionID);
                     session->setBaseNonce(); // Set it
                     SessionRegistry::getInstance().put(mConnectionSessionID, std::move(session));
                     SessionRegistry::getInstance().lockIP(mConnectionSessionID, clientIP);

src/server/net/tcp/tcp_server.cpp

@@ -35,11 +35,15 @@ namespace ColumnLynx::Net::TCP {
                 auto client = TCPConnection::create(
                     std::move(socket),
                     [this](std::shared_ptr<TCPConnection> c) {
+                        std::lock_guard<std::mutex> lock(mClientsMutex);
                         mClients.erase(c);
                         Utils::log("Client removed.");
                     }
                 );
-                mClients.insert(client);
+                {
+                    std::lock_guard<std::mutex> lock(mClientsMutex);
+                    mClients.insert(client);
+                }
                 client->start();
                 Utils::log("Accepted new client connection.");
             
@@ -59,7 +63,11 @@ namespace ColumnLynx::Net::TCP {
         }
 
         // Snapshot to avoid iterator invalidation while callbacks erase()
-        std::vector<std::shared_ptr<TCPConnection>> snapshot(mClients.begin(), mClients.end());
+        std::vector<std::shared_ptr<TCPConnection>> snapshot;
+        {
+            std::lock_guard<std::mutex> lock(mClientsMutex);
+            snapshot.assign(mClients.begin(), mClients.end());
+        }
         for (auto &client : snapshot) {
             try {
                 client->disconnect(); // should shutdown+close the socket

src/server/net/udp/udp_server.cpp

@@ -40,7 +40,7 @@ namespace ColumnLynx::Net::UDP {
         std::vector<uint8_t> encryptedPayload(it, mRecvBuffer.begin() + bytes);
 
         // Get associated session state
-        std::shared_ptr<const SessionState> session = SessionRegistry::getInstance().get(sessionID);
+        std::shared_ptr<SessionState> session = SessionRegistry::getInstance().get(sessionID);
 
         if (!session) {
             Utils::warn("UDP: Unknown or invalid session from " + mRemoteEndpoint.address().to_string());
@@ -60,9 +60,9 @@ namespace ColumnLynx::Net::UDP {
 
             Utils::debug("Passed decryption");
 
-            const_cast<SessionState*>(session.get())->setUDPEndpoint(mRemoteEndpoint); // Update endpoint after confirming decryption
+            session->setUDPEndpoint(mRemoteEndpoint); // Update endpoint after confirming decryption
             // Update recv counter
-            const_cast<SessionState*>(session.get())->recv_ctr.fetch_add(1, std::memory_order_relaxed);
+            session->recv_ctr.fetch_add(1, std::memory_order_relaxed);
 
             // For now, just log the decrypted payload
             std::string payloadStr(plaintext.begin(), plaintext.end());
@@ -79,7 +79,7 @@ namespace ColumnLynx::Net::UDP {
 
     void UDPServer::sendData(uint32_t sessionID, const std::string& data) {
         // Find the IPv4/IPv6 endpoint for the session
-        std::shared_ptr<const SessionState> session = SessionRegistry::getInstance().get(sessionID);
+        std::shared_ptr<SessionState> session = SessionRegistry::getInstance().get(sessionID);
         if (!session) {
             Utils::warn("UDP: Cannot send data, unknown session ID " + std::to_string(sessionID));
             return;
@@ -95,7 +95,22 @@ namespace ColumnLynx::Net::UDP {
         UDPPacketHeader hdr{};
         uint8_t nonce[12];
         uint32_t prefix = session->noncePrefix;
-        uint64_t sendCount = const_cast<SessionState*>(session.get())->send_ctr.fetch_add(1, std::memory_order_relaxed);
+            // Increment send counter with overflow protection
+            uint64_t sendCount = 0;
+            {
+                uint64_t old = session->send_ctr.load(std::memory_order_relaxed);
+                for (;;) {
+                    if (old == std::numeric_limits<uint64_t>::max()) {
+                        Utils::error("UDP: send counter overflow for session " + std::to_string(sessionID));
+                        return;
+                    }
+                    if (session->send_ctr.compare_exchange_weak(old, old + 1, std::memory_order_relaxed)) {
+                        sendCount = old;
+                        break;
+                    }
+                    // old updated by compare_exchange_weak, loop
+                }
+            }
         memcpy(nonce, &prefix, sizeof(uint32_t)); // Prefix nonce
         memcpy(nonce + sizeof(uint32_t), &sendCount, sizeof(uint64_t)); // Use send count as nonce suffix to ensure uniqueness
         std::copy_n(nonce, 12, hdr.nonce.data());

tests/test_key_file_loading.cpp

@@ -0,0 +1,62 @@
+// Tests for hex key file loading helpers
+#include <cassert>
+#include <filesystem>
+#include <fstream>
+#include <iostream>
+
+#include <columnlynx/common/utils.hpp>
+#include <sodium.h>
+
+int main() {
+    namespace fs = std::filesystem;
+    using namespace ColumnLynx::Utils;
+
+    fs::path tempDir = fs::temp_directory_path() / "columnlynx_key_loader_test";
+    fs::remove_all(tempDir);
+    fs::create_directories(tempDir);
+
+    auto publicKeyPath = tempDir / "public.key";
+    auto privateKeyPath = tempDir / "private.key";
+
+    {
+        std::ofstream pub(publicKeyPath);
+        pub << "00112233445566778899aabbccddeeff00112233445566778899AABBCCDDEEFF";
+    }
+
+    {
+        std::ofstream priv(privateKeyPath);
+        priv << "ffeeddccbbaa99887766554433221100ffeeddccbbaa99887766554433221100\n";
+    }
+
+    auto pk = loadHexArrayFromFile<crypto_sign_PUBLICKEYBYTES>(publicKeyPath.string(), "public key");
+    auto sk = loadHexArrayFromFile<crypto_sign_SEEDBYTES>(privateKeyPath.string(), "private key", true);
+
+    assert(pk[0] == 0x00 && pk[1] == 0x11 && pk.back() == 0xFF);
+    assert(sk[0] == 0xFF && sk[1] == 0xEE && sk.back() == 0x00);
+
+    bool threwMissing = false;
+    try {
+        (void)loadHexArrayFromFile<crypto_sign_PUBLICKEYBYTES>((tempDir / "missing.key").string(), "missing key");
+    } catch (const std::exception&) {
+        threwMissing = true;
+    }
+    assert(threwMissing && "Missing key file should throw");
+
+    auto badLengthPath = tempDir / "bad-length.key";
+    {
+        std::ofstream bad(badLengthPath);
+        bad << "abcd";
+    }
+
+    bool threwBadLength = false;
+    try {
+        (void)loadHexArrayFromFile<crypto_sign_PUBLICKEYBYTES>(badLengthPath.string(), "bad length key");
+    } catch (const std::exception&) {
+        threwBadLength = true;
+    }
+    assert(threwBadLength && "Wrong-length key file should throw");
+
+    std::cout << "Key file loader tests passed\n";
+    fs::remove_all(tempDir);
+    return 0;
+}

tests/test_libsodium_wrapper.cpp

@@ -0,0 +1,42 @@
+// Tests for LibSodiumWrapper: random, symmetric encrypt/decrypt, sign/verify
+#include <iostream>
+#include <cassert>
+
+#include <columnlynx/common/libsodium_wrapper.hpp>
+
+int main() {
+    using namespace ColumnLynx::Utils;
+
+    // Random bytes uniqueness
+    auto a = LibSodiumWrapper::generateRandom256Bit();
+    auto b = LibSodiumWrapper::generateRandom256Bit();
+    assert(a != b && "generateRandom256Bit() should produce different outputs (very likely)");
+
+    // Symmetric encrypt/decrypt roundtrip
+    ColumnLynx::SymmetricKey key = {};
+    for (size_t i = 0; i < key.size(); ++i) key[i] = static_cast<uint8_t>(i);
+    auto nonce = LibSodiumWrapper::generateNonce();
+
+    std::string plaintext = "The quick brown fox jumps over the lazy dog";
+    auto ct = LibSodiumWrapper::encryptMessage(reinterpret_cast<const uint8_t*>(plaintext.data()), plaintext.size(), key, nonce, "aad");
+    auto pt = LibSodiumWrapper::decryptMessage(ct.data(), ct.size(), key, nonce, "aad");
+    std::string recovered(pt.begin(), pt.end());
+    assert(recovered == plaintext && "decrypt should recover original plaintext");
+
+    // Sign and verify
+    ColumnLynx::PrivateKey sk{}; ColumnLynx::PublicKey pk{};
+    randombytes_buf(sk.data(), sk.size());
+    // naive keypair generation for test purposes: use libsodium functions via wrapper
+    // generate a real keypair using crypto_sign
+    if (crypto_sign_keypair(pk.data(), sk.data()) != 0) {
+        std::cerr << "Failed to generate keypair\n";
+        return 2;
+    }
+
+    auto sig = LibSodiumWrapper::signMessage(plaintext, sk);
+    bool ok = LibSodiumWrapper::verifyMessage(plaintext, sig, pk);
+    assert(ok && "Signature should verify");
+
+    std::cout << "LibSodiumWrapper tests passed\n";
+    return 0;
+}

tests/test_session_registry.cpp

@@ -0,0 +1,49 @@
+// Simple unit tests for SessionRegistry
+#include <cassert>
+#include <iostream>
+#include <chrono>
+
+#include <columnlynx/common/net/session_registry.hpp>
+#include <columnlynx/common/libsodium_wrapper.hpp>
+
+int main() {
+    using namespace ColumnLynx::Net;
+    using namespace ColumnLynx::Utils;
+
+    auto &reg = SessionRegistry::getInstance();
+
+    // Use a unique session id to avoid colliding with any running instance
+    const uint32_t sid = 0xDEADBEEF;
+    // ensure clean state
+    reg.erase(sid);
+
+    auto key = LibSodiumWrapper::generateRandom256Bit();
+    auto state = std::make_shared<SessionState>(key, std::chrono::hours(24), 0xC0A80101 /*192.168.1.1*/, 0, sid);
+
+    reg.put(sid, state);
+
+    assert(reg.exists(sid) && "Session should exist after put()");
+
+    auto got = reg.get(sid);
+    assert(got && got->sessionID == sid && "get() should return stored session");
+
+    auto byip = reg.getByIP(0xC0A80101);
+    assert(byip && byip->sessionID == sid && "getByIP() should find session by client IP");
+
+    // Erase and verify removed
+    reg.erase(sid);
+    assert(!reg.exists(sid) && "Session should not exist after erase()");
+    assert(reg.getByIP(0xC0A80101) == nullptr && "getByIP() should return nullptr after erase");
+
+    // Test cleanupExpired: insert an already-expired session
+    const uint32_t sid2 = 0xFEEDBEEF;
+    reg.erase(sid2);
+    auto expiredState = std::make_shared<SessionState>(key, std::chrono::seconds(0), 0xC0A80102, 0, sid2);
+    reg.put(sid2, expiredState);
+    // Force cleanup
+    reg.cleanupExpired();
+    assert(!reg.exists(sid2) && "Expired session should be removed by cleanupExpired()");
+
+    std::cout << "SessionRegistry tests passed\n";
+    return 0;
+}

tests/test_session_registry_ip.cpp

@@ -0,0 +1,43 @@
+// Tests for SessionRegistry IP allocation and lock/dealloc
+#include <iostream>
+#include <cassert>
+
+#include <columnlynx/common/net/session_registry.hpp>
+#include <columnlynx/common/libsodium_wrapper.hpp>
+
+int main() {
+    using namespace ColumnLynx::Net;
+    using namespace ColumnLynx::Utils;
+
+    auto &reg = SessionRegistry::getInstance();
+
+    const uint32_t sid = 0xABCDEF01;
+    reg.erase(sid);
+
+    auto key = LibSodiumWrapper::generateRandom256Bit();
+    auto state = std::make_shared<SessionState>(key, std::chrono::hours(24), 0, 0, sid);
+    reg.put(sid, state);
+
+    // Lock IP
+    uint32_t ip = 0xC0A80201; // 192.168.2.1
+    reg.lockIP(sid, ip);
+
+    auto byip = reg.getByIP(ip);
+    assert(byip && byip->sessionID == sid && "lockIP should populate mIPSessions");
+
+    // deallocIP
+    reg.deallocIP(sid);
+    assert(reg.getByIP(ip) == nullptr && "deallocIP should remove mapping");
+
+    // getFirstAvailableIP: choose a small /30 range to limit hosts
+    uint32_t base = 0x0A000000; // 10.0.0.0
+    uint8_t mask = 30; // 2 usable hosts
+    uint32_t first = reg.getFirstAvailableIP(base, mask);
+    assert(first != 0 && "Should find available IP in empty registry");
+
+    // cleanup
+    reg.erase(sid);
+
+    std::cout << "SessionRegistry IP tests passed\n";
+    return 0;
+}

tests/test_tcp_message_handler_static.cpp

@@ -0,0 +1,30 @@
+// Tests for TCP MessageHandler static helpers
+#include <cassert>
+#include <iostream>
+
+#include <columnlynx/common/net/tcp/tcp_message_handler.hpp>
+#include <columnlynx/common/net/tcp/tcp_message_type.hpp>
+
+int main() {
+    using namespace ColumnLynx::Net::TCP;
+
+    // server message special codes
+    auto t1 = MessageHandler::decodeMessageType(0xFE);
+    // Expect GRACEFUL_DISCONNECT mapped
+    // Compare by converting back to uint8
+    assert(MessageHandler::toUint8(t1) == 0xFE);
+
+    auto t2 = MessageHandler::decodeMessageType(0xFF);
+    assert(MessageHandler::toUint8(t2) == 0xFF);
+
+    // Client message range (>= 0xA0)
+    auto t3 = MessageHandler::decodeMessageType(0xA5);
+    assert(MessageHandler::toUint8(t3) == 0xA5);
+
+    // Server message range (< 0xA0) and not special
+    auto t4 = MessageHandler::decodeMessageType(0x10);
+    assert(MessageHandler::toUint8(t4) == 0x10);
+
+    std::cout << "TCP MessageHandler static helpers tests passed\n";
+    return 0;
+}