init

client.cpp

@@ -0,0 +1,192 @@
+#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
+    }
+}
+
+// hex to byte helper function
+int hex_to_bytes_upper(const char* hex, unsigned char* out, size_t out_size)
+{
+    size_t i = 0;
+    while (hex[0] && hex[1]) {
+        if (i >= out_size) return -1;
+        unsigned char h = hex[0];
+        unsigned char l = hex[1];
+        int hi = (h <= '9') ? (h - '0') : (h - 'A' + 10);
+        int lo = (l <= '9') ? (l - '0') : (l - 'A' + 10);
+        // minimal sanity check
+        if (hi < 0 || hi > 15 || lo < 0 || lo > 15)
+            return -1;
+        out[i++] = (unsigned char)((hi << 4) | lo);
+        hex += 2;
+    }
+    return (int)i;
+}
+
+// block cipher encryption function
+int block_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();
+    if (!ctx) {
+        ERR_print_errors_fp(stderr);
+    }
+
+    /* 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
+    if (EVP_EncryptInit_ex(ctx, EVP_aes_256_cbc(), NULL, key, iv) != 1){
+        ERR_print_errors_fp(stderr);
+    }
+
+    /* Provide the message to be encrypted, and obtain the encrypted output. EVP_EncryptUpdate can be called multiple times if necessary */
+    if (EVP_EncryptUpdate(ctx, ciphertext, &len, plaintext, plaintext_len) != 1) {
+        ERR_print_errors_fp(stderr);
+    }
+
+    /* Finalize the encryption. Further cipher text bytes may be written at this stage. */
+    if (EVP_EncryptFinal_ex(ctx, ciphertext + len, &ciphertext_len) != 1) {
+        ERR_print_errors_fp(stderr);
+    }
+
+    /* 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");
+    unsigned char key_bytes[32], iv_bytes[16];
+    
+    int key_len = hex_to_bytes_upper(secret_key, key_bytes, sizeof(key_bytes));
+    int iv_len  = hex_to_bytes_upper(inital_vector, iv_bytes, sizeof(iv_bytes));
+
+    if (key_len != 32 || iv_len != 16) {
+        fprintf(stderr, "Invalid key/IV size for AES-256\n");
+        return 1;
+    }
+
+    // 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);
+
+        unsigned char ciphertext[2048];
+
+        int plaintext_len = (int)strlen(buffer);
+        int ciphertext_len = stream_encrypt((unsigned char*)buffer, plaintext_len, key_bytes, iv_bytes, ciphertext);
+        if (ciphertext_len <= 0) {
+            printf("encrypt failed or produced empty ciphertext_len=%d\n", ciphertext_len);
+            break;
+        }
+
+        ssize_t sent = send(client_socket, ciphertext, (size_t)ciphertext_len, 0);
+        if (sent <= 0) { perror("No message sent to server"); break; }
+
+        // Receive the server's response:
+        // add terminator for string
+        ssize_t recvd = recv(client_socket, server_message, sizeof(server_message) - 1, 0);
+        if (recvd <= 0) { perror("No message received from server"); break; }
+        server_message[recvd] = '\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;
+}