update with end to end encryption

CMakeLists.txt

@@ -15,3 +15,4 @@ add_executable(
     schc
     ${SOURCES_CLIENT}
 )
+target_link_libraries(schc ssl crypto)

Makefile

@@ -2,6 +2,7 @@ CC = gcc
 CFLAGS = -Wall -g -std=gnu2x
 LDFLAGS =
 LIBS =
+CLIBS = -lcrypto -lssl
 INCLUDES = -I./src/lib -I./src
 SRCS = src/main.c
 CSRCS = src/client.c
@@ -17,7 +18,7 @@ $(TARGET): $(OBJS)
 	$(CROSS_COMPILE)$(CC) $(LDFLAGS) $^ -o $@ $(LIBS)
 
 $(CTARGET): $(COBJS)
-	$(CROSS_COMPILE)$(CC) $(LDFLAGS) $^ -o $@ $(LIBS)
+	$(CROSS_COMPILE)$(CC) $(LDFLAGS) $^ -o $@ $(CLIBS)
 
 %.o: %.c
 	$(CROSS_COMPILE)$(CC) $(CFLAGS) $(INCLUDES) -c $< -o $@

meson.build

@@ -1,4 +1,12 @@
 project('sch', 'c', default_options: ['cpp_std=c20'])
 include_dirs = include_directories('src')
+extra_c_args = ['-ffunction-sections', '-fdata-sections']
+deps = [dependency('openssl')]
 executable('sch', 'src/main.c', include_directories: include_dirs, install: true)
-executable('schc', 'src/client.c', include_directories: include_dirs, install: true)
+executable(
+  'schc',
+  'src/client.c',
+  include_directories: include_dirs,
+  dependencies: deps,
+  install: true,
+)

src/client.c

@@ -1,18 +1,537 @@
 #include <arpa/inet.h>
+#include <getopt.h>
+#include <openssl/evp.h>
+#include <openssl/rand.h>
+#include <signal.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
+#include <sys/ioctl.h>
 #include <sys/socket.h>
 #include <sys/wait.h>
+#include <termios.h>
 #include <unistd.h>
-#include "log.h"
 
 #define PORT 7777
-#define BUFFER_SIZE 1024
+#define BUFFER_SIZE 4096
+#define USERNAME_MAX 50
+#define INPUT_HEIGHT 3
+#define DEFAULT_MSG_BUFFER 100
+#define AES_KEY_SIZE 32
+#define AES_IV_SIZE 12
+#define AES_TAG_SIZE 16
 
-int main() {
+int sock;
-  int sock;
+char username[USERNAME_MAX];
+int term_rows, term_cols;
+struct termios orig_termios;
+
+int msg_buffer_size = DEFAULT_MSG_BUFFER;
+char **message_history = NULL;
+int history_count = 0;
+int history_start = 0;
+int scroll_offset = 0;
+
+unsigned char aes_key[AES_KEY_SIZE];
+
+volatile int need_redraw = 0;
+volatile int running = 1;
+
+void get_terminal_size() {
+  struct winsize ws;
+  ioctl(STDOUT_FILENO, TIOCGWINSZ, &ws);
+  term_rows = ws.ws_row;
+  term_cols = ws.ws_col;
+}
+
+void enable_raw_mode() {
+  tcgetattr(STDIN_FILENO, &orig_termios);
+  struct termios raw = orig_termios;
+  raw.c_lflag &= ~(ECHO | ICANON);
+  raw.c_cc[VMIN] = 0;
+  raw.c_cc[VTIME] = 1;
+  tcsetattr(STDIN_FILENO, TCSAFLUSH, &raw);
+}
+
+void disable_raw_mode() {
+  tcsetattr(STDIN_FILENO, TCSAFLUSH, &orig_termios);
+}
+
+void clear_screen() {
+  printf("\033[2J\033[H");
+  fflush(stdout);
+}
+
+void move_cursor(int row, int col) {
+  printf("\033[%d;%dH", row, col);
+  fflush(stdout);
+}
+
+void clear_line() {
+  printf("\033[2K");
+  fflush(stdout);
+}
+
+void hide_cursor() {
+  printf("\033[?25l");
+  fflush(stdout);
+}
+
+void show_cursor() {
+  printf("\033[?25h");
+  fflush(stdout);
+}
+
+void derive_key_from_password(const char *password, unsigned char *key) {
+  unsigned char salt[16] = {0};
+  if (!PKCS5_PBKDF2_HMAC(password, strlen(password), salt, sizeof(salt), 100000,
+                         EVP_sha256(), AES_KEY_SIZE, key)) {
+    fprintf(stderr, "Failed to derive key\n");
+    exit(1);
+  }
+}
+
+int encrypt_message(const unsigned char *plaintext, int plaintext_len,
+                    const unsigned char *key, const unsigned char *iv,
+                    unsigned char *ciphertext, unsigned char *tag) {
+  EVP_CIPHER_CTX *ctx = EVP_CIPHER_CTX_new();
+  int len;
+  int ciphertext_len;
+
+  if (!ctx) return -1;
+
+  if (EVP_EncryptInit_ex(ctx, EVP_aes_256_gcm(), NULL, NULL, NULL) != 1)
+    return -1;
+  if (EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_SET_IVLEN, AES_IV_SIZE, NULL) != 1)
+    return -1;
+  if (EVP_EncryptInit_ex(ctx, NULL, NULL, key, iv) != 1) return -1;
+
+  if (EVP_EncryptUpdate(ctx, ciphertext, &len, plaintext, plaintext_len) != 1)
+    return -1;
+  ciphertext_len = len;
+
+  if (EVP_EncryptFinal_ex(ctx, ciphertext + len, &len) != 1) return -1;
+  ciphertext_len += len;
+
+  if (EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_GET_TAG, AES_TAG_SIZE, tag) != 1)
+    return -1;
+
+  EVP_CIPHER_CTX_free(ctx);
+  return ciphertext_len;
+}
+
+int decrypt_message(const unsigned char *ciphertext, int ciphertext_len,
+                    const unsigned char *key, const unsigned char *iv,
+                    const unsigned char *tag, unsigned char *plaintext) {
+  EVP_CIPHER_CTX *ctx = EVP_CIPHER_CTX_new();
+  int len;
+  int plaintext_len;
+  int ret;
+
+  if (!ctx) return -1;
+
+  if (!EVP_DecryptInit_ex(ctx, EVP_aes_256_gcm(), NULL, NULL, NULL)) {
+    EVP_CIPHER_CTX_free(ctx);
+    return -1;
+  }
+  if (!EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_SET_IVLEN, AES_IV_SIZE, NULL)) {
+    EVP_CIPHER_CTX_free(ctx);
+    return -1;
+  }
+  if (!EVP_DecryptInit_ex(ctx, NULL, NULL, key, iv)) {
+    EVP_CIPHER_CTX_free(ctx);
+    return -1;
+  }
+
+  if (!EVP_DecryptUpdate(ctx, plaintext, &len, ciphertext, ciphertext_len)) {
+    EVP_CIPHER_CTX_free(ctx);
+    return -1;
+  }
+  plaintext_len = len;
+
+  if (!EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_SET_TAG, AES_TAG_SIZE,
+                           (void *) tag)) {
+    EVP_CIPHER_CTX_free(ctx);
+    return -1;
+  }
+
+  ret = EVP_DecryptFinal_ex(ctx, plaintext + len, &len);
+  EVP_CIPHER_CTX_free(ctx);
+
+  if (ret > 0) {
+    plaintext_len += len;
+    return plaintext_len;
+  } else {
+    return -1;
+  }
+}
+
+void init_message_buffer() {
+  message_history = calloc(msg_buffer_size, sizeof(char *));
+}
+
+void free_message_buffer() {
+  if (!message_history) return;
+  for (int i = 0; i < msg_buffer_size; i++) {
+    free(message_history[i]);
+  }
+  free(message_history);
+}
+
+void add_to_history(const char *msg) {
+  int idx = (history_start + history_count) % msg_buffer_size;
+
+  free(message_history[idx]);
+  message_history[idx] = strdup(msg);
+
+  if (history_count < msg_buffer_size) {
+    history_count++;
+  } else {
+    history_start = (history_start + 1) % msg_buffer_size;
+  }
+}
+
+char *get_message_by_index(int idx) {
+  if (idx < 0 || idx >= history_count) return NULL;
+  int real_idx = (history_start + idx) % msg_buffer_size;
+  return message_history[real_idx];
+}
+
+int get_last_visible_index() {
+  return history_count - 1 - scroll_offset;
+}
+
+void draw_input_frame() {
+  int input_row = term_rows - INPUT_HEIGHT + 1;
+
+  move_cursor(input_row, 1);
+  printf("+");
+  for (int i = 0; i < term_cols - 2; i++) printf("-");
+  printf("+");
+
+  move_cursor(input_row + 1, 1);
+  printf("| %s: ", username);
+  int username_len = strlen(username) + 4;
+  for (int i = username_len; i < term_cols - 1; i++) printf(" ");
+  printf("|");
+
+  move_cursor(input_row + 2, 1);
+  printf("+");
+  for (int i = 0; i < term_cols - 2; i++) printf("-");
+  printf("+");
+
+  if (scroll_offset > 0) {
+    move_cursor(input_row, term_cols - 10);
+    printf("[^%d]", scroll_offset);
+  }
+
+  fflush(stdout);
+}
+
+void redraw_chat() {
+  hide_cursor();
+
+  for (int i = 1; i <= term_rows - INPUT_HEIGHT; i++) {
+    move_cursor(i, 1);
+    clear_line();
+  }
+
+  int max_visible = term_rows - INPUT_HEIGHT;
+  int last_idx = get_last_visible_index();
+
+  int row = max_visible;
+  for (int i = 0; i < max_visible && (last_idx - i) >= 0; i++) {
+    char *msg = get_message_by_index(last_idx - i);
+    if (!msg) break;
+
+    move_cursor(row, 1);
+
+    int msg_len = strlen(msg);
+    if (msg_len > 0 && msg[msg_len - 1] == '\n') msg_len--;
+
+    int max_line = term_cols - 1;
+    if (msg_len > max_line) msg_len = max_line;
+
+    printf("%.*s", msg_len, msg);
+
+    row--;
+    if (row < 1) break;
+  }
+
+  draw_input_frame();
+  show_cursor();
+}
+
+void update_input_text(const char *text) {
+  int input_row = term_rows - INPUT_HEIGHT + 2;
+  move_cursor(input_row, strlen(username) + 5);
+  printf("%s", text);
+  int text_len = strlen(text);
+  int max_len = term_cols - strlen(username) - 6;
+  for (int i = text_len; i < max_len; i++) printf(" ");
+  move_cursor(input_row, strlen(username) + 5 + text_len);
+  fflush(stdout);
+}
+
+void add_chat_message(const char *msg) {
+  int was_at_bottom = (scroll_offset == 0);
+  add_to_history(msg);
+  if (was_at_bottom) {
+    scroll_offset = 0;
+  }
+  redraw_chat();
+}
+
+void scroll_up() {
+  int max_visible = term_rows - INPUT_HEIGHT;
+  int max_offset =
+      history_count > max_visible ? history_count - max_visible : 0;
+  if (scroll_offset < max_offset) {
+    scroll_offset++;
+    redraw_chat();
+  }
+}
+
+void scroll_down() {
+  if (scroll_offset > 0) {
+    scroll_offset--;
+    redraw_chat();
+  }
+}
+
+// Формат пакета: [total_len:4][iv:12][tag:16][ciphertext:N]
+void send_encrypted_message(int socket, const char *plaintext) {
+  unsigned char iv[AES_IV_SIZE];
+  RAND_bytes(iv, AES_IV_SIZE);
+
+  unsigned char ciphertext[BUFFER_SIZE];
+  unsigned char tag[AES_TAG_SIZE];
+
+  int ciphertext_len =
+      encrypt_message((unsigned char *) plaintext, strlen(plaintext), aes_key,
+                      iv, ciphertext, tag);
+  if (ciphertext_len < 0) {
+    fprintf(stderr, "Encryption failed\n");
+    return;
+  }
+
+  int total_len = AES_IV_SIZE + AES_TAG_SIZE + ciphertext_len;
+  int net_total_len = htonl(total_len);
+
+  send(socket, &net_total_len, sizeof(int), 0);
+  send(socket, iv, AES_IV_SIZE, 0);
+  send(socket, tag, AES_TAG_SIZE, 0);
+  send(socket, ciphertext, ciphertext_len, 0);
+}
+
+// Получить и расшифровать сообщение
+int receive_encrypted_message(int socket, char *plaintext, int max_len) {
+  int net_total_len;
+  int valread = read(socket, &net_total_len, sizeof(int));
+  if (valread <= 0) return -1;
+
+  int total_len = ntohl(net_total_len);
+  if (total_len <= AES_IV_SIZE + AES_TAG_SIZE || total_len > BUFFER_SIZE) {
+    fprintf(stderr, "Invalid total length: %d\n", total_len);
+    return -1;
+  }
+
+  unsigned char iv[AES_IV_SIZE];
+  unsigned char tag[AES_TAG_SIZE];
+  unsigned char ciphertext[BUFFER_SIZE];
+
+  valread = read(socket, iv, AES_IV_SIZE);
+  if (valread != AES_IV_SIZE) {
+    fprintf(stderr, "Failed to read IV: %d\n", valread);
+    return -1;
+  }
+
+  valread = read(socket, tag, AES_TAG_SIZE);
+  if (valread != AES_TAG_SIZE) {
+    fprintf(stderr, "Failed to read tag: %d\n", valread);
+    return -1;
+  }
+
+  int ciphertext_len = total_len - AES_IV_SIZE - AES_TAG_SIZE;
+  int total_read = 0;
+  while (total_read < ciphertext_len) {
+    valread =
+        read(socket, ciphertext + total_read, ciphertext_len - total_read);
+    if (valread <= 0) {
+      fprintf(stderr, "Failed to read ciphertext\n");
+      return -1;
+    }
+    total_read += valread;
+  }
+
+  int plaintext_len = decrypt_message(ciphertext, ciphertext_len, aes_key, iv,
+                                      tag, (unsigned char *) plaintext);
+
+  if (plaintext_len > 0) {
+    plaintext[plaintext_len] = '\0';
+  } else {
+    fprintf(stderr, "Decryption failed (ciphertext_len=%d)\n", ciphertext_len);
+  }
+
+  return plaintext_len;
+}
+
+void load_history_from_server() {
+  int net_count;
+  if (read(sock, &net_count, sizeof(int)) <= 0) return;
+  int count = ntohl(net_count);
+
+  printf("[INFO] Loading %d encrypted messages from history\n", count);
+
+  for (int i = 0; i < count && i < msg_buffer_size; i++) {
+    char plaintext[BUFFER_SIZE];
+    int len = receive_encrypted_message(sock, plaintext, BUFFER_SIZE);
+    if (len > 0) {
+      add_to_history(plaintext);
+    } else {
+      fprintf(stderr, "[DEBUG] Failed to decrypt history message %d\n", i);
+    }
+  }
+}
+
+void handle_input() {
+  char input_buffer[BUFFER_SIZE] = {0};
+  int pos = 0;
+  char c;
+
+  redraw_chat();
+  update_input_text("");
+
+  while (running) {
+    if (read(STDIN_FILENO, &c, 1) != 1) {
+      if (need_redraw) {
+        need_redraw = 0;
+        get_terminal_size();
+        redraw_chat();
+        update_input_text(input_buffer);
+      }
+      continue;
+    }
+
+    if (c == '\n') {
+      if (pos == 0) continue;
+
+      input_buffer[pos] = '\0';
+
+      if (strcmp(input_buffer, "/exit") == 0) {
+        printf("[INFO] Client is exiting\n");
+        running = 0;
+        return;
+      }
+
+      // Форматируем и отправляем на сервер, НЕ добавляем локально!
+      char full_msg[BUFFER_SIZE];
+      int written = snprintf(full_msg, sizeof(full_msg), "[%s]: %s", username,
+                             input_buffer);
+
+      // Если truncation произошёл, ensure null-termination
+      if (written >= (int) sizeof(full_msg)) {
+        full_msg[sizeof(full_msg) - 1] = '\0';
+      }
+
+      send_encrypted_message(sock, full_msg);
+      // Сообщение появится когда придёт от сервера в receive_messages()
+
+      pos = 0;
+      input_buffer[0] = '\0';
+      update_input_text("");
+
+    } else if (c == 127 || c == '\b') {
+      if (pos > 0) {
+        pos--;
+        input_buffer[pos] = '\0';
+        update_input_text(input_buffer);
+      }
+
+    } else if (c == 27) {
+      char seq[2];
+      if (read(STDIN_FILENO, &seq[0], 1) != 1) continue;
+      if (read(STDIN_FILENO, &seq[1], 1) != 1) continue;
+
+      if (seq[0] == '[') {
+        if (seq[1] == 'A') {
+          scroll_up();
+        } else if (seq[1] == 'B') {
+          scroll_down();
+        } else if (seq[1] == '3') {
+          read(STDIN_FILENO, &c, 1);
+        }
+      }
+
+    } else if (c == 21) {
+      pos = 0;
+      input_buffer[0] = '\0';
+      update_input_text("");
+
+    } else if (pos < BUFFER_SIZE - 1 && c >= 32 && c < 127) {
+      input_buffer[pos++] = c;
+      input_buffer[pos] = '\0';
+      update_input_text(input_buffer);
+    }
+  }
+}
+
+void receive_messages() {
+  while (running) {
+    char plaintext[BUFFER_SIZE];
+    int len = receive_encrypted_message(sock, plaintext, BUFFER_SIZE);
+    if (len > 0) {
+      // ВСЕ сообщения приходят через сервер — и свои, и чужие
+      add_chat_message(plaintext);
+    } else if (len < 0) {
+      add_chat_message("*** Ошибка расшифровки сообщения ***");
+    } else {
+      add_chat_message("*** Соединение закрыто сервером ***");
+      break;
+    }
+  }
+}
+
+void sigwinch_handler(int sig) {
+  need_redraw = 1;
+}
+
+void parse_args(int argc, char *argv[]) {
+  static struct option long_options[] = {
+      {"messagebuffer", required_argument, 0, 'm'}, {0, 0, 0, 0}};
+
+  int opt;
+  while ((opt = getopt_long(argc, argv, "m:", long_options, NULL)) != -1) {
+    switch (opt) {
+      case 'm':
+        msg_buffer_size = atoi(optarg);
+        if (msg_buffer_size < 10) msg_buffer_size = 10;
+        if (msg_buffer_size > 10000) msg_buffer_size = 10000;
+        break;
+      default:
+        fprintf(stderr, "Usage: %s [-m N|--messagebuffer=N]\n", argv[0]);
+        exit(1);
+    }
+  }
+}
+
+int main(int argc, char *argv[]) {
   struct sockaddr_in server_addr;
-  char buffer[BUFFER_SIZE];
+
+  parse_args(argc, argv);
+
+  printf("Enter encryption password: ");
+  fflush(stdout);
+  char password[256];
+  fgets(password, sizeof(password), stdin);
+  password[strcspn(password, "\n")] = '\0';
+
+  derive_key_from_password(password, aes_key);
+
+  printf("Enter your username: ");
+  fflush(stdout);
+  fgets(username, USERNAME_MAX, stdin);
+  username[strcspn(username, "\n")] = '\0';
 
   sock = socket(AF_INET, SOCK_STREAM, 0);
   if (sock < 0) {
@@ -30,33 +549,36 @@ int main() {
     return 1;
   }
 
+  send(sock, username, USERNAME_MAX, 0);
+  printf("[INFO] username = %s, buffer_size = %d\n", username, msg_buffer_size);
+
+  init_message_buffer();
+  load_history_from_server();
+
+  get_terminal_size();
+  enable_raw_mode();
+  clear_screen();
+  hide_cursor();
+
+  signal(SIGWINCH, sigwinch_handler);
+
   pid_t child_pid = fork();
   if (child_pid == 0) {
-    while (1) {
+    receive_messages();
-      int valread = read(sock, buffer, BUFFER_SIZE);
+    exit(0);
-      if (valread > 0) {
-        buffer[valread] = '\0';
-        printf("%s", buffer);
-      }
-    }
   } else {
-    char username[50];
+    handle_input();
-    printf("Enter your username: ");
+    kill(child_pid, SIGKILL);
-    fgets(username, 50, stdin);
+    wait(NULL);
-    username[strlen(username) - 1] = '\0';
-    send(sock, username, 50, 0);
-    log_info("username = %s\n", username);
-    while (1) {
-      fgets(buffer, BUFFER_SIZE, stdin);
-      if (strcmp(buffer, "/exit\n") == 0) {
-        log_info("Client is exiting\n");
-        kill(child_pid, SIGKILL);
-        close(sock);
-        break;
-      }
-      send(sock, buffer, strlen(buffer), 0);
-    }
   }
 
+  close(sock);
+  show_cursor();
+  disable_raw_mode();
+  clear_screen();
+  printf("Goodbye, %s!\n", username);
+
+  free_message_buffer();
+
   return 0;
 }

src/main.c

@@ -1,129 +1,211 @@
 #include <arpa/inet.h>
-#include <asm-generic/socket.h>
+#include <pthread.h>
-#include <colors.h>
-#include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#include <sys/select.h>
 #include <sys/socket.h>
 #include <unistd.h>
-#include "log.h"
 
 #define PORT 7777
-#define MAX_CLIENTS 10
+#define BUFFER_SIZE 8192
-#define BUFFER_SIZE 1024
+#define MAX_CLIENTS 100
+#define HISTORY_SIZE 1000
+#define USERNAME_MAX 50
+#define AES_IV_SIZE 12
+#define AES_TAG_SIZE 16
 
-struct client_t {
+typedef struct {
-  int sock;
+    int socket;
-  char username[50];
+    char username[USERNAME_MAX];
-};
+} client_t;
+
+client_t *clients[MAX_CLIENTS];
+pthread_mutex_t clients_mutex = PTHREAD_MUTEX_INITIALIZER;
+
+typedef struct {
+    int data_len;
+    unsigned char *data;
+} encrypted_message_t;
+
+encrypted_message_t message_history[HISTORY_SIZE];
+int history_count = 0;
+int history_start = 0;
+pthread_mutex_t history_mutex = PTHREAD_MUTEX_INITIALIZER;
+
+void add_to_history(const unsigned char *data, int len) {
+    pthread_mutex_lock(&history_mutex);
+    int idx = (history_start + history_count) % HISTORY_SIZE;
+
+    free(message_history[idx].data);
+    message_history[idx].data = malloc(len);
+    memcpy(message_history[idx].data, data, len);
+    message_history[idx].data_len = len;
+
+    if (history_count < HISTORY_SIZE) {
+        history_count++;
+    } else {
+        history_start = (history_start + 1) % HISTORY_SIZE;
+    }
+    pthread_mutex_unlock(&history_mutex);
+}
+
+void send_history(int socket) {
+    pthread_mutex_lock(&history_mutex);
+
+    int net_count = htonl(history_count);
+    write(socket, &net_count, sizeof(int));
+
+    for (int i = 0; i < history_count; i++) {
+        int idx = (history_start + i) % HISTORY_SIZE;
+        int net_len = htonl(message_history[idx].data_len);
+        write(socket, &net_len, sizeof(int));
+        write(socket, message_history[idx].data, message_history[idx].data_len);
+    }
+
+    pthread_mutex_unlock(&history_mutex);
+}
+
+// Рассылка ВСЕМ клиентам включая отправителя (-1 = всем)
+void broadcast_to_all(const unsigned char *data, int len) {
+    pthread_mutex_lock(&clients_mutex);
+    for (int i = 0; i < MAX_CLIENTS; i++) {
+        if (clients[i]) {
+            int net_len = htonl(len);
+            send(clients[i]->socket, &net_len, sizeof(int), 0);
+            send(clients[i]->socket, data, len, 0);
+        }
+    }
+    pthread_mutex_unlock(&clients_mutex);
+}
+
+void *handle_client(void *arg) {
+    client_t *cli = (client_t *)arg;
+
+    int valread = read(cli->socket, cli->username, USERNAME_MAX);
+    if (valread <= 0) goto cleanup;
+    cli->username[valread] = '\0';
+    cli->username[strcspn(cli->username, "\n")] = '\0';
+
+    printf("User '%s' connected\n", cli->username);
+
+    send_history(cli->socket);
+
+    while (1) {
+        int net_total_len;
+        valread = read(cli->socket, &net_total_len, sizeof(int));
+        if (valread <= 0) break;
+
+        int total_len = ntohl(net_total_len);
+        if (total_len <= 0 || total_len > BUFFER_SIZE) {
+            printf("Invalid length from %s: %d\n", cli->username, total_len);
+            break;
+        }
+
+        unsigned char *data = malloc(total_len);
+        int total_read = 0;
+        while (total_read < total_len) {
+            valread = read(cli->socket, data + total_read, total_len - total_read);
+            if (valread <= 0) {
+                free(data);
+                goto cleanup;
+            }
+            total_read += valread;
+        }
+
+        // Сохраняем
+        add_to_history(data, total_len);
+
+        // Рассылаем ВСЕМ включая отправителя
+        broadcast_to_all(data, total_len);
+
+        free(data);
+    }
+
+cleanup:
+    printf("User '%s' disconnected\n", cli->username);
+    close(cli->socket);
+
+    pthread_mutex_lock(&clients_mutex);
+    for (int i = 0; i < MAX_CLIENTS; i++) {
+        if (clients[i] == cli) {
+            clients[i] = NULL;
+            break;
+        }
+    }
+    pthread_mutex_unlock(&clients_mutex);
+
+    free(cli);
+    pthread_exit(NULL);
+}
 
 int main() {
-  int server_fd;
+    int server_fd, new_socket;
-  struct client_t clients[MAX_CLIENTS];
+    struct sockaddr_in address;
-  struct sockaddr_in address;
+    int opt = 1;
-  int addrlen = sizeof(address);
+    int addrlen = sizeof(address);
-  fd_set readfds;
-  char buffer[BUFFER_SIZE];
 
-  for (int i = 0; i < MAX_CLIENTS; i++) {
+    for (int i = 0; i < HISTORY_SIZE; i++) {
-    clients[i].sock = 0;
+        message_history[i].data = NULL;
-    bzero(clients[i].username, sizeof(clients[i].username));
+        message_history[i].data_len = 0;
-  }
-
-  server_fd = socket(AF_INET, SOCK_STREAM, 0);
-  if (server_fd < 0) {
-    log_error("socket");
-    exit(EXIT_FAILURE);
-  }
-
-  int opt = 1;
-  if (setsockopt(server_fd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt)) < 0) {
-    log_error("setsockopt");
-    exit(EXIT_FAILURE);
-  }
-
-  address.sin_family = AF_INET;
-  address.sin_addr.s_addr = INADDR_ANY;
-  address.sin_port = htons(PORT);
-
-  if (bind(server_fd, (struct sockaddr *) &address, sizeof(address)) < 0) {
-    log_error("bind");
-    exit(EXIT_FAILURE);
-  }
-
-  if (listen(server_fd, 5) < 0) {
-    log_error("listen");
-    exit(EXIT_FAILURE);
-  }
-
-  printf("Chat server started on port %d\n", PORT);
-
-  while (1) {
-    FD_ZERO(&readfds);
-    FD_SET(server_fd, &readfds);
-    int max_sd = server_fd;
-
-    for (int i = 0; i < MAX_CLIENTS; i++) {
-      int sd = clients[i].sock;
-      if (sd > 0) FD_SET(sd, &readfds);
-      if (sd > max_sd) max_sd = sd;
     }
 
-    if (select(max_sd + 1, &readfds, NULL, NULL, NULL) < 0) {
+    if ((server_fd = socket(AF_INET, SOCK_STREAM, 0)) == 0) {
-      log_error("select");
+        perror("socket failed");
-      exit(EXIT_FAILURE);
+        exit(EXIT_FAILURE);
     }
 
-    // Новое подключение
+    if (setsockopt(server_fd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt))) {
-    if (FD_ISSET(server_fd, &readfds)) {
+        perror("setsockopt");
-      int new_socket = accept(server_fd, (struct sockaddr *) &address,
+        exit(EXIT_FAILURE);
-                              (socklen_t *) &addrlen);
+    }
 
-      log_info("New connection: socket %d\n", new_socket);
+    address.sin_family = AF_INET;
-      read(new_socket, buffer, BUFFER_SIZE);
+    address.sin_addr.s_addr = INADDR_ANY;
+    address.sin_port = htons(PORT);
 
-      for (int i = 0; i < MAX_CLIENTS; i++) {
+    if (bind(server_fd, (struct sockaddr *)&address, sizeof(address)) < 0) {
-        if (clients[i].sock == 0) {
+        perror("bind failed");
-          clients[i].sock = new_socket;
+        exit(EXIT_FAILURE);
-          strcpy(clients[i].username, buffer);
+    }
-          break;
+
+    if (listen(server_fd, 3) < 0) {
+        perror("listen");
+        exit(EXIT_FAILURE);
+    }
+
+    printf("E2E Encrypted Server listening on port %d\n", PORT);
+
+    while (1) {
+        if ((new_socket = accept(server_fd, (struct sockaddr *)&address, (socklen_t*)&addrlen)) < 0) {
+            perror("accept");
+            continue;
         }
-      }
-    }
 
-    // Сообщения от клиентов
+        client_t *cli = malloc(sizeof(client_t));
-    for (int i = 0; i < MAX_CLIENTS; i++) {
+        cli->socket = new_socket;
-      int sd = clients[i].sock;
-      char sd_username[50];
-      bzero(sd_username, sizeof(sd_username));
-      strcpy(sd_username, clients[i].username);
 
-      if (FD_ISSET(sd, &readfds)) {
+        pthread_mutex_lock(&clients_mutex);
-        int valread = read(sd, buffer, BUFFER_SIZE);
+        int added = 0;
-
+        for (int i = 0; i < MAX_CLIENTS; i++) {
-        if (valread == 0) {
+            if (!clients[i]) {
-          log_info("Client disconnected: socket %d\n", sd);
+                clients[i] = cli;
-          close(sd);
+                added = 1;
-          clients[i].sock = 0;
+                break;
-          bzero(clients[i].username, sizeof(clients[i].username));
-        } else {
-          buffer[valread] = '\0';
-          log_info("[%s]: %s", sd_username, buffer);
-          char *message = malloc(strlen(buffer) + strlen(sd_username) + 5);
-          sprintf(message, "[%s]: %s", sd_username, buffer);
-          // Рассылка всем другим
-          for (int j = 0; j < MAX_CLIENTS; j++) {
-            if (clients[j].sock != 0 && clients[j].sock != sd) {
-              send(clients[j].sock, message, strlen(message), 0);
-              free(message);
             }
-          }
         }
-      }
+        pthread_mutex_unlock(&clients_mutex);
-    }
-  }
 
-  return 0;
+        if (!added) {
+            printf("Max clients reached\n");
+            close(new_socket);
+            free(cli);
+            continue;
+        }
+
+        pthread_t tid;
+        pthread_create(&tid, NULL, handle_client, cli);
+        pthread_detach(tid);
+    }
+
+    return 0;
 }