init

.env

@@ -0,0 +1,6 @@
+NET_SUBNET=172.30.0.0/24
+SERVER_IP=172.30.0.10
+CLIENT_IP=172.30.0.11
+SERVER_PORT=3030
+INITIAL_VECTOR=807DEDFDE74B0C59
+SECRET_KEY=EA514659DC556DEECFFA5FD061363642

.gitignore

@@ -0,0 +1,9 @@
+# latex garbages
+*.aux
+*.fdb_latexmk
+*.fls
+*.log
+*.synctex.gz
+
+# vscode garbage
+.vscode

client-log.sh

@@ -0,0 +1 @@
+docker logs hw1-client

client-term.sh

@@ -0,0 +1 @@
+docker exec -it hw1-client sh

client.cpp

@@ -0,0 +1,146 @@
+#include <stdio.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <arpa/inet.h>
+
+// open ssl
+#include <openssl/conf.h>
+#include <openssl/evp.h>
+#include <openssl/err.h>
+
+#include <errno.h> // error handling
+#include <unistd.h> // for close()
+
+// load environment variables from .env file
+#include <fstream>
+#include <cstdlib>
+
+void load_env(const std::string& path) {
+    std::ifstream f(path);
+    std::string line;
+    while (std::getline(f, line)) {
+        if (line.empty() || line[0] == '#') continue;
+        auto pos = line.find('=');
+        if (pos == std::string::npos) continue;
+
+        std::string key = line.substr(0, pos);
+        std::string val = line.substr(pos + 1);
+
+        #ifdef _WIN32
+                _putenv_s(key.c_str(), val.c_str());
+        #else
+                setenv(key.c_str(), val.c_str(), 1);
+        #endif
+    }
+}
+
+// steam cipher encryption function
+int stream_encrypt(unsigned char *plaintext, int plaintext_len, unsigned char *key, unsigned char *iv, unsigned char *ciphertext) {
+    /* Declare cipher context */
+    EVP_CIPHER_CTX *ctx;
+
+    int len, ciphertext_len;
+
+    /* Create and initialise the context */
+    ctx = EVP_CIPHER_CTX_new();
+
+    /* Initialise the encryption operation. */
+    // choice for aes_256 ref: https://stackoverflow.com/questions/1220751/how-to-choose-an-aes-encryption-mode-cbc-ecb-ctr-ocb-cfb
+    EVP_EncryptInit_ex(ctx, EVP_aes_256_ctr(), NULL, key, iv);
+
+    /* Provide the message to be encrypted, and obtain the encrypted output. EVP_EncryptUpdate can be called multiple times if necessary */
+    EVP_EncryptUpdate(ctx, ciphertext, &len, plaintext, plaintext_len);
+
+    /* Finalize the encryption. Further cipher text bytes may be written at this stage. */
+    EVP_EncryptFinal_ex(ctx, ciphertext + len, &ciphertext_len);
+
+    /* Clean up */
+    EVP_CIPHER_CTX_free(ctx);
+
+    return ciphertext_len;
+}
+
+int main(void){
+    load_env(".env");
+    // Declare variables
+    const char *server_ip = std::getenv("SERVER_IP");
+    const int server_port = std::atoi(std::getenv("SERVER_PORT"));
+    printf("Connecting to server %s:%d\n", server_ip, server_port);
+    
+    char client_message[1024];
+    char server_message[1024];
+    const char * custom_message="Zheyuan Wu: ";
+
+    // encryption parameters
+    const char *inital_vector = std::getenv("INITIAL_VECTOR");
+    const char *secret_key = std::getenv("SECRET_KEY");
+    
+    // Create socket:
+    int client_socket = socket(AF_INET, SOCK_STREAM, 0);
+    if (client_socket == -1) {
+        perror("Failed to create socket");
+        return 1;
+    }else{
+        printf("Socket created successfully\n");
+    }
+
+    // Send connection request to server, be sure to set por tand IP the same as server-side
+    struct sockaddr_in server_addr;
+    server_addr.sin_family = AF_INET;
+    server_addr.sin_port = htons(server_port);
+    inet_pton(AF_INET, server_ip, &server_addr.sin_addr);
+
+    if (connect(client_socket, (struct sockaddr*)&server_addr, sizeof(server_addr)) == -1) {
+        perror("Failed to connect to server");
+        close(client_socket);
+        return 1;
+    }else{
+        printf("Connected to server successfully\n");
+    }
+
+    // Get input from the user:
+    printf("Enter message sent to the server (type \\quit to exit): ");
+    // clean the buffer
+    memset(client_message, 0, sizeof(client_message));
+    if (fgets(client_message, sizeof(client_message), stdin) == NULL) {
+        // EOF or error reading from stdin, exit the loop
+        perror("Error reading from stdin");
+        return 1;
+    }
+    
+    while (strcmp(client_message, "\\quit\n") != 0) {
+        
+        // Send the message to server:
+        // add my name in the front
+        char buffer[2048];
+        std::snprintf(buffer, sizeof(buffer), "%s%s", custom_message, client_message);
+
+        // encrypt message
+        char ciphertext[2048];
+        int ciphertext_len = stream_encrypt((unsigned char*)buffer, sizeof(buffer), (unsigned char*)secret_key, (unsigned char*)inital_vector, (unsigned char*)ciphertext);
+
+        send(client_socket, ciphertext, ciphertext_len, 0);
+
+        // Receive the server's response:
+        recv(client_socket, server_message, sizeof(server_message), 0);
+
+        printf("Server's response: %s\n", server_message);
+
+        printf("Enter message sent to the server (type \\quit to exit): ");
+
+        // clean the buffer
+        memset(client_message, 0, sizeof(client_message));
+        memset(server_message, 0, sizeof(server_message));
+        
+        if (fgets(client_message, sizeof(client_message), stdin) == NULL) {
+            // EOF or error reading from stdin, exit the loop
+            perror("Error reading from stdin");
+            break;
+        }
+    }
+
+    // Close the socket
+    close(client_socket);
+
+    return 0;
+}

compile.sh

@@ -0,0 +1,25 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+mkdir -p bin
+
+# add libssl-dev if needed
+
+# apt-get update && apt-get install -y --no-install-recommends libssl-dev
+
+# Adjust flags as you like
+CXXFLAGS="-std=c++17 -O2 -Wall -Wextra -pedantic"
+OPENSSL_LIBS="-lssl -lcrypto"
+
+g++ ${CXXFLAGS} server.cpp -o bin/server ${OPENSSL_LIBS}
+g++ ${CXXFLAGS} client.cpp -o bin/client ${OPENSSL_LIBS}
+
+echo "Built:"
+file bin/server bin/client || true
+
+chmod a+x bin/server bin/client
+
+docker compose up -d server
+docker compose run --rm -it client
+
+echo "Done."

docker-compose.yml

@@ -0,0 +1,38 @@
+services:
+  server:
+    image: debian:bookworm-slim
+    container_name: hw1-server
+    working_dir: /app
+    env_file:
+      - .env
+    networks:
+      net-hw1:
+        ipv4_address: ${SERVER_IP}
+    volumes:
+      - ./bin/server:/usr/local/bin/server:ro
+    entrypoint: ["bash", "-lc", "apt-get update && apt-get install -y --no-install-recommends libstdc++6 iproute2 libssl-dev; exec stdbuf -oL -eL /usr/local/bin/server"]
+
+  client:
+    image: debian:bookworm-slim
+    container_name: hw1-client
+    working_dir: /app
+    env_file:
+      - .env
+    networks:
+      net-hw1:
+        ipv4_address: ${CLIENT_IP}
+    depends_on:
+      - server
+    stdin_open: true
+    tty: true
+    volumes:
+      - ./bin/client:/usr/local/bin/client:ro
+    entrypoint: ["bash", "-lc", "apt-get update && apt-get install -y --no-install-recommends libstdc++6 iproute2 libssl-dev; exec stdbuf -oL -eL /usr/local/bin/client"]
+
+networks:
+  net-hw1:
+    name: net-hw1
+    driver: bridge
+    ipam:
+      config:
+        - subnet: ${NET_SUBNET}

latex/H1_CSE4303_ZheyuanWu.tex

@@ -0,0 +1,144 @@
+\documentclass[11pt]{article}
+\usepackage{amsmath, amsfonts, amsthm}
+\usepackage{amssymb}
+\usepackage{fancyhdr,parskip}
+\usepackage{fullpage}
+\usepackage{mathrsfs}
+\usepackage{mathtools}
+
+\usepackage{float}
+
+% code listing
+\usepackage{listings}
+\usepackage{xcolor}
+\lstset{%
+  language=c++,
+  breaklines=true,
+  commentstyle=\color{green},    % comment style
+  escapeinside={\%*}{*)},          % if you want to add LaTeX within your code
+  keywordstyle=\color{blue},       % keyword style
+  stringstyle=\color{purple},        % string literal style
+}
+
+%%
+%% Stuff above here is packages that will be used to compile your document.
+%% If you've used unusual LaTeX features, you may have to install extra packages by adding them to this list.
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+
+\setlength{\headheight}{15.2pt}
+\setlength{\headsep}{20pt}
+\pagestyle{fancyplain}
+
+%%
+%% Stuff above here is layout and formatting.  If you've never used LaTeX before, you probably don't need to change any of it.
+%% Later, you can learn how it all works and adjust it to your liking, or write your own formatting code.
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+%%%%%%%%%%%%%%%%%%%%%%
+% These commands create theorem-like environments.
+\newtheorem{theorem}{Theorem}
+\newtheorem{lemma}[theorem]{Lemma}
+\newtheorem{corollary}[theorem]{Corollary}
+\newtheorem{prop}[theorem]{Proposition}
+\newtheorem{defn}[theorem]{Definition}
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%% This section contains some useful macros that will save you time typing.
+%%
+
+% Using \displaystyle (or \ds) in a block of math has a number of effects, but most notably, it makes your fractions come out bigger.
+\newcommand{\ds}{\displaystyle}
+
+% These lines are for displaying integrals; typing \dx will make the dx at the end of the integral look better.
+\newcommand{\is}{\hspace{2pt}}
+\newcommand{\dx}{\is dx}
+
+% These commands produce the fancy Z (for the integers) and other letters conveniently.
+\newcommand{\Z}{\mathbb{Z}}
+\newcommand{\Q}{\mathbb{Q}}
+\newcommand{\R}{\mathbb{R}}
+\newcommand{\C}{\mathbb{C}}
+\newcommand{\F}{\mathbb{F}}
+\newcommand{\T}{\mathcal{T}}
+\newcommand{\B}{\mathcal{B}}
+
+% for fancy empty set char
+\renewcommand{\emptyset}{\varnothing}
+
+% customized commands for future assignements
+\newcommand{\imply}{\Rightarrow}
+\def\P{\mathscr{P}}
+\def\L{\mathscr{L}}
+\def\M{\mathscr{M}}
+\DeclarePairedDelimiterX{\inp}[2]{\langle}{\rangle}{#1, #2}
+
+% url embedding
+\usepackage{hyperref}
+
+\hypersetup{colorlinks=true,linkcolor=blue,urlcolor=blue}
+
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%% This is the header.  It will appear on every page, and it's a good place to put your name, the assignment title, and stuff like that.
+%% I usually leave the center header blank to avoid clutter.
+%%
+
+\fancyhead[L]{\textbf{CSE4303 Homework 1}}
+\fancyhead[C]{509191}
+\fancyhead[R]{Zheyuan Wu}
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+
+\begin{document}
+
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%% Actual math starts here!
+
+
+% Use an enumerated list to write up problems.  First we begin a list.
+
+\begin{enumerate}
+\item[1.] Description of experimental setup
+
+We use the same docker image and settings with environment files as last time.
+
+For encryption method, I checked some wikis on the internet and found aes seems to be the best practically safe algorithm I can found.
+
+For the detailed method and distinctions for different variations for aes, I checked the post on \href{stackoverflow.com/questions/1220751/how-to-choose-an-aes-encryption-mode-cbc-ecb-ctr-ocb-cfb}{stackoverflow} for steam cipher, seems that \texttt{NVP\_aes\_256\_ctr()} is the optimal choice for us.
+
+\newpage
+\item[2.] Server code
+
+\begin{enumerate}
+    \item Screenshot or well-formatted copy of code
+    \item Quick overview of what the code does in your own words.
+\end{enumerate}
+\newpage
+
+\item[3.] Client code
+
+\begin{enumerate}
+
+    \item Screenshot or well-formatted copy of code
+    \item Quick overview of what the code does in your own words.
+    
+\end{enumerate}
+\newpage
+
+
+\item[4.] Extra credits
+\newpage
+
+\end{enumerate}
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%% Actual math ends here.  Don't put any content below the \end{document} line.
+%%
+
+\end{document}

message.txt

@@ -0,0 +1 @@
+My password is EA514659DC556DEECFFA5FD061363642

server-log.sh

@@ -0,0 +1 @@
+docker logs hw1-server --tail=50

server.cpp

@@ -0,0 +1,162 @@
+#include <stdio.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <arpa/inet.h>
+
+// open ssl
+#include <openssl/conf.h>
+#include <openssl/evp.h>
+#include <openssl/err.h>
+
+#include <errno.h> // for perror()
+#include <unistd.h> // for close()
+
+// load environment variables from .env file
+#include <fstream>
+#include <cstdlib>
+
+void load_env(const std::string& path) {
+    std::ifstream f(path);
+    std::string line;
+    while (std::getline(f, line)) {
+        if (line.empty() || line[0] == '#') continue;
+        auto pos = line.find('=');
+        if (pos == std::string::npos) continue;
+
+        std::string key = line.substr(0, pos);
+        std::string val = line.substr(pos + 1);
+
+        #ifdef _WIN32
+                _putenv_s(key.c_str(), val.c_str());
+        #else
+                setenv(key.c_str(), val.c_str(), 1);
+        #endif
+    }
+}
+
+// Define the decryption function
+int stream_decrypt(unsigned char *ciphertext, int ciphertext_len, unsigned char *key, unsigned char *iv, unsigned char *plaintext) {
+    /* Declare cipher context */
+    EVP_CIPHER_CTX *ctx;
+
+    int len, plaintext_len;
+
+    /* Create and initialise the context */
+    ctx = EVP_CIPHER_CTX_new();
+
+    /* Initialise the decryption operation. */
+    EVP_DecryptInit_ex(ctx, EVP_aes_256_ctr(), NULL, key, iv);
+
+    /* Provide the message to be decrypted, and obtain the plaintext output. EVP_DecryptUpdate can be called multiple times if necessary */
+    EVP_DecryptUpdate(ctx, plaintext, &len, ciphertext, ciphertext_len);
+
+    /* Finalize the decryption. Further plaintext bytes may be written at this stage. */
+    EVP_DecryptFinal_ex(ctx, plaintext + len, &plaintext_len);
+
+    /* Clean up */
+    EVP_CIPHER_CTX_free(ctx);
+
+    return plaintext_len;
+}
+
+int main(void){
+    printf("Server starting...\n");
+    load_env(".env");
+
+    // Declare variables
+    const char *server_ip = std::getenv("SERVER_IP");
+    const int server_port = std::atoi(std::getenv("SERVER_PORT"));
+    char client_message[2048];
+    char server_message[2048];
+    const char * custom_message="Server: Hello from server, ";
+
+    // decryption parameters
+    const char *inital_vector = std::getenv("INITIAL_VECTOR");
+    const char *secret_key = std::getenv("SECRET_KEY");
+
+    // debug
+    printf("Server starting at IP: %s, Port: %d\n", server_ip, server_port);
+
+    // Create socket
+    const int server_socket = socket(AF_INET, SOCK_STREAM, 0);
+    if (server_socket == -1) {
+        perror("Failed to create socket");
+        return 1;
+    }
+
+    // Bind to the set port and IP
+    struct sockaddr_in server_addr;
+    server_addr.sin_family = AF_INET;
+    server_addr.sin_port = htons(server_port);
+    inet_pton(AF_INET, server_ip, &server_addr.sin_addr);
+
+    if (bind(server_socket, (struct sockaddr*)&server_addr, sizeof(server_addr)) == -1) {
+        perror("Failed to bind socket");
+        close(server_socket);
+        return 1;
+    }
+    printf("Done with binding with IP: %s, Port: %d\n", server_ip, server_port);
+
+    // Listen for clients:
+    const char *client_ip = std::getenv("CLIENT_IP");
+    if (listen(server_socket, 1) == -1) {
+        perror("Failed to listen on socket");
+        close(server_socket);
+        return 1;
+    }
+    printf("Listening for incoming connections...\n");
+
+    // Accept an incoming connection
+    struct sockaddr_in client_addr;
+    socklen_t client_addr_len = sizeof(client_addr);
+    int client_socket = accept(server_socket, (struct sockaddr*)&client_addr, &client_addr_len);
+    if (client_socket == -1) {
+        perror("Failed to accept connection");
+        close(server_socket);
+        return 1;
+    }
+    printf("Client connected at IP: %s \n", client_ip);
+
+    // clean exising buffer
+    memset(client_message, 0, sizeof(client_message));
+
+    // Receive client's message
+    while (strcmp(client_message, "\\exit\n") != 0) {
+        
+        // clean exising buffer
+        memset(client_message, 0, sizeof(client_message));
+
+        recv(client_socket, client_message, sizeof(client_message), 0);
+
+        // decrypt client message
+        char plaintext[2048];
+        int plaintext_len = stream_decrypt((unsigned char*)client_message, strlen(client_message), (unsigned char*)secret_key, (unsigned char*)inital_vector, (unsigned char*)plaintext);
+
+        printf("Msg from client: %.*s", plaintext_len, plaintext);
+
+        // assign client message to plaintext
+        memcpy(client_message, plaintext, plaintext_len);
+
+        // Respond to client
+        // prepare server message
+        memset(server_message, 0, sizeof(server_message));
+        ;
+
+        // add my name in the back as response.
+        std::snprintf(server_message, sizeof(server_message), "%s%s", custom_message, strtok(client_message, ":"));
+        
+        if (send(client_socket, server_message, sizeof(server_message), 0) == -1) {
+            perror("Failed to send message");
+            close(client_socket);
+            close(server_socket);
+            return 1;
+        }
+        printf("Response sent to client: %s\n", server_message);
+
+    }
+    // Close the socket
+    close(client_socket);
+    close(server_socket);
+
+    return 0;
+}