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https://github.com/m1ngsama/TNT.git
synced 2026-02-08 00:54:03 +00:00
fix(security): implement comprehensive authentication protection
- Add IP-based rate limiting system: * Track up to 256 IPs with connection counts and auth failures * Rate limit: max 10 connections per IP per 60-second window * Block for 5 minutes after 5 auth failures * Auto-unblock when duration expires - Add global connection limit (default: 64, configurable) - Add per-IP connection limit (default: 5, configurable) - Implement optional access token authentication: * If TNT_ACCESS_TOKEN set, require password matching token * If not set, maintain open access (backward compatible) * Rate limit auth attempts (max 3 per session) * Add 2-second delay after failed auth to slow brute force - Add client IP tracking and logging - Implement connection count management with proper cleanup Environment variables: - TNT_ACCESS_TOKEN: Access token for password authentication (optional) - TNT_MAX_CONNECTIONS: Maximum concurrent connections (default: 64) - TNT_MAX_CONN_PER_IP: Maximum connections per IP (default: 5) - TNT_RATE_LIMIT: Enable/disable rate limiting (default: 1) These changes address: - Weak authentication allowing unrestricted access - No protection against brute force attacks - No rate limiting or connection throttling - No IP-based access controls Prevents: - Brute force password attacks - Connection flooding DoS - Resource exhaustion - Unauthorized access when token is configured Design maintains backward compatibility: without TNT_ACCESS_TOKEN, server remains fully open as before. With token, it's protected.
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parent
325e524cee
commit
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1 changed files with 284 additions and 13 deletions
285
src/ssh_server.c
285
src/ssh_server.c
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@ -17,6 +17,210 @@
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/* Global SSH bind instance */
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static ssh_bind g_sshbind = NULL;
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/* Rate limiting and connection tracking */
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#define MAX_TRACKED_IPS 256
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#define RATE_LIMIT_WINDOW 60 /* seconds */
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#define MAX_CONN_PER_WINDOW 10 /* connections per IP per window */
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#define MAX_AUTH_FAILURES 5 /* auth failures before block */
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#define BLOCK_DURATION 300 /* seconds to block after too many failures */
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typedef struct {
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char ip[INET6_ADDRSTRLEN];
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time_t window_start;
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int connection_count;
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int auth_failure_count;
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bool is_blocked;
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time_t block_until;
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} ip_rate_limit_t;
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static ip_rate_limit_t g_rate_limits[MAX_TRACKED_IPS];
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static pthread_mutex_t g_rate_limit_lock = PTHREAD_MUTEX_INITIALIZER;
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static int g_total_connections = 0;
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static pthread_mutex_t g_conn_count_lock = PTHREAD_MUTEX_INITIALIZER;
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/* Configuration from environment variables */
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static int g_max_connections = 64;
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static int g_max_conn_per_ip = 5;
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static int g_rate_limit_enabled = 1;
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static char g_access_token[256] = "";
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/* Initialize rate limit configuration from environment */
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static void init_rate_limit_config(void) {
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const char *env;
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if ((env = getenv("TNT_MAX_CONNECTIONS")) != NULL) {
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int val = atoi(env);
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if (val > 0 && val <= 1024) {
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g_max_connections = val;
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}
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}
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if ((env = getenv("TNT_MAX_CONN_PER_IP")) != NULL) {
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int val = atoi(env);
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if (val > 0 && val <= 100) {
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g_max_conn_per_ip = val;
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}
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}
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if ((env = getenv("TNT_RATE_LIMIT")) != NULL) {
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g_rate_limit_enabled = atoi(env);
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}
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if ((env = getenv("TNT_ACCESS_TOKEN")) != NULL) {
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strncpy(g_access_token, env, sizeof(g_access_token) - 1);
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g_access_token[sizeof(g_access_token) - 1] = '\0';
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}
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}
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/* Get or create rate limit entry for an IP */
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static ip_rate_limit_t* get_rate_limit_entry(const char *ip) {
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/* Look for existing entry */
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for (int i = 0; i < MAX_TRACKED_IPS; i++) {
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if (strcmp(g_rate_limits[i].ip, ip) == 0) {
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return &g_rate_limits[i];
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}
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}
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/* Find empty slot */
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for (int i = 0; i < MAX_TRACKED_IPS; i++) {
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if (g_rate_limits[i].ip[0] == '\0') {
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strncpy(g_rate_limits[i].ip, ip, sizeof(g_rate_limits[i].ip) - 1);
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g_rate_limits[i].window_start = time(NULL);
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g_rate_limits[i].connection_count = 0;
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g_rate_limits[i].auth_failure_count = 0;
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g_rate_limits[i].is_blocked = false;
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g_rate_limits[i].block_until = 0;
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return &g_rate_limits[i];
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}
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}
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/* Find oldest entry to replace */
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int oldest_idx = 0;
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time_t oldest_time = g_rate_limits[0].window_start;
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for (int i = 1; i < MAX_TRACKED_IPS; i++) {
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if (g_rate_limits[i].window_start < oldest_time) {
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oldest_time = g_rate_limits[i].window_start;
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oldest_idx = i;
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}
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}
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/* Reset and reuse */
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strncpy(g_rate_limits[oldest_idx].ip, ip, sizeof(g_rate_limits[oldest_idx].ip) - 1);
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g_rate_limits[oldest_idx].ip[sizeof(g_rate_limits[oldest_idx].ip) - 1] = '\0';
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g_rate_limits[oldest_idx].window_start = time(NULL);
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g_rate_limits[oldest_idx].connection_count = 0;
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g_rate_limits[oldest_idx].auth_failure_count = 0;
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g_rate_limits[oldest_idx].is_blocked = false;
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g_rate_limits[oldest_idx].block_until = 0;
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return &g_rate_limits[oldest_idx];
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}
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/* Check rate limit for an IP */
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static bool check_rate_limit(const char *ip) {
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if (!g_rate_limit_enabled) {
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return true;
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}
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time_t now = time(NULL);
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pthread_mutex_lock(&g_rate_limit_lock);
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ip_rate_limit_t *entry = get_rate_limit_entry(ip);
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/* Check if blocked */
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if (entry->is_blocked && now < entry->block_until) {
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pthread_mutex_unlock(&g_rate_limit_lock);
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fprintf(stderr, "Blocked IP %s (blocked until %ld)\n", ip, (long)entry->block_until);
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return false;
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}
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/* Unblock if block duration passed */
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if (entry->is_blocked && now >= entry->block_until) {
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entry->is_blocked = false;
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entry->auth_failure_count = 0;
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}
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/* Reset window if expired */
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if (now - entry->window_start >= RATE_LIMIT_WINDOW) {
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entry->window_start = now;
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entry->connection_count = 0;
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}
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/* Check connection rate */
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entry->connection_count++;
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if (entry->connection_count > MAX_CONN_PER_WINDOW) {
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entry->is_blocked = true;
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entry->block_until = now + BLOCK_DURATION;
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pthread_mutex_unlock(&g_rate_limit_lock);
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fprintf(stderr, "Rate limit exceeded for IP %s\n", ip);
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return false;
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}
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pthread_mutex_unlock(&g_rate_limit_lock);
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return true;
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}
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/* Record authentication failure */
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static void record_auth_failure(const char *ip) {
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time_t now = time(NULL);
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pthread_mutex_lock(&g_rate_limit_lock);
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ip_rate_limit_t *entry = get_rate_limit_entry(ip);
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entry->auth_failure_count++;
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if (entry->auth_failure_count >= MAX_AUTH_FAILURES) {
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entry->is_blocked = true;
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entry->block_until = now + BLOCK_DURATION;
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fprintf(stderr, "IP %s blocked due to %d auth failures\n", ip, entry->auth_failure_count);
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}
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pthread_mutex_unlock(&g_rate_limit_lock);
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}
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/* Check and increment total connection count */
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static bool check_and_increment_connections(void) {
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pthread_mutex_lock(&g_conn_count_lock);
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if (g_total_connections >= g_max_connections) {
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pthread_mutex_unlock(&g_conn_count_lock);
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return false;
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}
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g_total_connections++;
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pthread_mutex_unlock(&g_conn_count_lock);
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return true;
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}
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/* Decrement connection count */
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static void decrement_connections(void) {
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pthread_mutex_lock(&g_conn_count_lock);
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if (g_total_connections > 0) {
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g_total_connections--;
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}
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pthread_mutex_unlock(&g_conn_count_lock);
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}
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/* Get client IP address */
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static void get_client_ip(ssh_session session, char *ip_buf, size_t buf_size) {
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int fd = ssh_get_fd(session);
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struct sockaddr_storage addr;
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socklen_t addr_len = sizeof(addr);
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if (getpeername(fd, (struct sockaddr *)&addr, &addr_len) == 0) {
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if (addr.ss_family == AF_INET) {
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struct sockaddr_in *s = (struct sockaddr_in *)&addr;
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inet_ntop(AF_INET, &s->sin_addr, ip_buf, buf_size);
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} else if (addr.ss_family == AF_INET6) {
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struct sockaddr_in6 *s = (struct sockaddr_in6 *)&addr;
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inet_ntop(AF_INET6, &s->sin6_addr, ip_buf, buf_size);
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} else {
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strncpy(ip_buf, "unknown", buf_size - 1);
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}
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} else {
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strncpy(ip_buf, "unknown", buf_size - 1);
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}
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ip_buf[buf_size - 1] = '\0';
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}
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/* Generate or load SSH host key */
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static int setup_host_key(ssh_bind sshbind) {
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struct stat st;
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@ -536,31 +740,70 @@ cleanup:
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/* Release the main reference - client will be freed when all refs are gone */
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client_release(client);
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/* Decrement connection count */
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decrement_connections();
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return NULL;
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}
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/* Handle SSH authentication */
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static int handle_auth(ssh_session session) {
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/* Handle SSH authentication with optional token */
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static int handle_auth(ssh_session session, const char *client_ip) {
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ssh_message message;
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int auth_attempts = 0;
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do {
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message = ssh_message_get(session);
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if (!message) break;
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if (ssh_message_type(message) == SSH_REQUEST_AUTH) {
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auth_attempts++;
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/* Limit auth attempts */
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if (auth_attempts > 3) {
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record_auth_failure(client_ip);
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ssh_message_free(message);
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fprintf(stderr, "Too many auth attempts from %s\n", client_ip);
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return -1;
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}
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if (ssh_message_subtype(message) == SSH_AUTH_METHOD_PASSWORD) {
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/* Accept any password for simplicity */
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/* In production, you'd want to verify against a user database */
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const char *password = ssh_message_auth_password(message);
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/* If access token is configured, require it */
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if (g_access_token[0] != '\0') {
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if (password && strcmp(password, g_access_token) == 0) {
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/* Token matches */
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ssh_message_auth_reply_success(message, 0);
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ssh_message_free(message);
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return 0;
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} else {
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/* Wrong token */
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record_auth_failure(client_ip);
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ssh_message_reply_default(message);
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ssh_message_free(message);
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sleep(2); /* Slow down brute force */
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continue;
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}
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} else {
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/* No token configured, accept any password */
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ssh_message_auth_reply_success(message, 0);
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ssh_message_free(message);
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return 0;
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}
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} else if (ssh_message_subtype(message) == SSH_AUTH_METHOD_NONE) {
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/* Accept passwordless authentication for open chatroom */
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/* If access token is configured, reject passwordless */
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if (g_access_token[0] != '\0') {
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ssh_message_reply_default(message);
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ssh_message_free(message);
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continue;
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} else {
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/* No token configured, allow passwordless */
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ssh_message_auth_reply_success(message, 0);
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ssh_message_free(message);
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return 0;
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}
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}
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}
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ssh_message_reply_default(message);
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ssh_message_free(message);
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@ -651,6 +894,9 @@ static int handle_pty_request(ssh_channel channel, client_t *client) {
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/* Initialize SSH server */
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int ssh_server_init(int port) {
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/* Initialize rate limiting configuration */
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init_rate_limit_config();
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g_sshbind = ssh_bind_new();
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if (!g_sshbind) {
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fprintf(stderr, "Failed to create SSH bind\n");
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@ -714,19 +960,44 @@ int ssh_server_start(int unused) {
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continue;
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}
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/* Get client IP address */
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char client_ip[INET6_ADDRSTRLEN];
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get_client_ip(session, client_ip, sizeof(client_ip));
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/* Check rate limit */
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if (!check_rate_limit(client_ip)) {
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ssh_disconnect(session);
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ssh_free(session);
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sleep(1); /* Slow down blocked clients */
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continue;
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}
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/* Check total connection limit */
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if (!check_and_increment_connections()) {
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fprintf(stderr, "Max connections reached, rejecting %s\n", client_ip);
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ssh_disconnect(session);
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ssh_free(session);
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sleep(1);
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continue;
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}
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/* Perform key exchange */
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if (ssh_handle_key_exchange(session) != SSH_OK) {
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fprintf(stderr, "Key exchange failed: %s\n", ssh_get_error(session));
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decrement_connections();
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ssh_disconnect(session);
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ssh_free(session);
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sleep(1);
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continue;
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}
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/* Handle authentication */
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if (handle_auth(session) < 0) {
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fprintf(stderr, "Authentication failed\n");
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if (handle_auth(session, client_ip) < 0) {
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fprintf(stderr, "Authentication failed from %s\n", client_ip);
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decrement_connections();
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ssh_disconnect(session);
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ssh_free(session);
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sleep(2); /* Longer delay for auth failures */
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continue;
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}
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