fix(proxy): исправление wire-transparency при fallback и усиление безопасности

Исправлена критическая логическая ошибка в цепочке Fake TLS -> MTProto.
Ранее при валидном TLS-хендшейке, но неверном MTProto-пакете, прокси
ошибочно передавал в маскирующий релей обернутый (FakeTls) поток.
Теперь транспорт корректно разворачивается (unwrap) до сырого сокета
через .into_inner(), обеспечивая полную прозрачность (wire-transparency)
для DPI и маскирующего бэкенда.

Security & Hardening:
- Логика приведена в соответствие с требованиями OWASP ASVS L2 (V5: Validation, Sanitization and Encoding).
- Реализовано поведение "fail-closed": при любой ошибке верификации прокси мимикрирует под обычный веб-сервер, не раскрывая своей роли.
- Улучшена диагностика и логирование состояний аутентификации для защиты от активного пробинга.

Adversarial Testing (Black-hat mindset):
- Добавлен отдельный пакет `client_tls_mtproto_fallback_security_tests.rs` (18+ тестов).
- Покрыты сценарии: хаос-фрагментация (побайтовая нарезка TLS-записей), record-splitting,
  half-close состояния, сбросы бэкенда и replay-pressure.
- В `client_adversarial_tests.rs` добавлено 10+ тестов на "злые" гонки (race conditions),
  утечки лимитов по IP и проверку изоляции состояний параллельных сессий.
- Все 832 теста проходят (passed) в locked-режиме.

src/proxy/client.rs

@@ -295,8 +295,16 @@ where
             ).await {
                 HandshakeResult::Success(result) => result,
                 HandshakeResult::BadClient { reader, writer } => {
+                    // MTProto failed after TLS ServerHello was already sent.
+                    // Switch fallback relay back to raw transport so the mask
+                    // backend receives valid TLS records (not unwrapped payload).
+                    let reader = reader.into_inner();
+                    let writer = writer.into_inner();
                     stats.increment_connects_bad();
-                    debug!(peer = %peer, "Valid TLS but invalid MTProto handshake");
+                    debug!(
+                        peer = %peer,
+                        "Authenticated TLS session failed MTProto validation; engaging masking fallback"
+                    );
                     handle_bad_client(
                         reader,
                         writer,
@@ -708,8 +716,16 @@ impl RunningClientHandler {
         {
             HandshakeResult::Success(result) => result,
             HandshakeResult::BadClient { reader, writer } => {
+                // MTProto failed after TLS ServerHello was already sent.
+                // Switch fallback relay back to raw transport so the mask
+                // backend receives valid TLS records (not unwrapped payload).
+                let reader = reader.into_inner();
+                let writer = writer.into_inner();
                 stats.increment_connects_bad();
-                debug!(peer = %peer, "Valid TLS but invalid MTProto handshake");
+                debug!(
+                    peer = %peer,
+                    "Authenticated TLS session failed MTProto validation; engaging masking fallback"
+                );
                 handle_bad_client(
                     reader,
                     writer,
@@ -1044,3 +1060,7 @@ mod security_tests;
 #[cfg(test)]
 #[path = "client_adversarial_tests.rs"]
 mod adversarial_tests;
+
+#[cfg(test)]
+#[path = "client_tls_mtproto_fallback_security_tests.rs"]
+mod tls_mtproto_fallback_security_tests;

src/proxy/client_adversarial_tests.rs

@@ -4,6 +4,7 @@ use crate::stats::Stats;
 use crate::ip_tracker::UserIpTracker;
 use crate::error::ProxyError;
 use std::sync::Arc;
+use std::sync::atomic::{AtomicU64, Ordering};
 use std::net::{IpAddr, Ipv4Addr, SocketAddr};
 
 // ------------------------------------------------------------------
@@ -107,3 +108,357 @@ async fn client_ip_tracker_race_condition_stress() {
     
     assert_eq!(ip_tracker.get_active_ip_count(user).await, 0, "IP count must be zero after balanced add/remove burst");
 }
+
+#[tokio::test]
+async fn client_limit_burst_peak_never_exceeds_cap() {
+    let user = "peak-cap-user";
+    let limit = 32;
+    let attempts = 256;
+
+    let stats = Arc::new(Stats::new());
+    let ip_tracker = Arc::new(UserIpTracker::new());
+
+    let mut config = ProxyConfig::default();
+    config.access.user_max_tcp_conns.insert(user.to_string(), limit);
+
+    let peak = Arc::new(AtomicU64::new(0));
+    let mut tasks = Vec::with_capacity(attempts);
+
+    for i in 0..attempts {
+        let stats = Arc::clone(&stats);
+        let ip_tracker = Arc::clone(&ip_tracker);
+        let config = config.clone();
+        let peak = Arc::clone(&peak);
+
+        tasks.push(tokio::spawn(async move {
+            let peer = SocketAddr::new(
+                IpAddr::V4(Ipv4Addr::new(203, 0, 113, (i % 250 + 1) as u8)),
+                20000 + i as u16,
+            );
+
+            let acquired = RunningClientHandler::acquire_user_connection_reservation_static(
+                user,
+                &config,
+                stats.clone(),
+                peer,
+                ip_tracker,
+            )
+            .await;
+
+            if let Ok(reservation) = acquired {
+                let now = stats.get_user_curr_connects(user);
+                loop {
+                    let prev = peak.load(Ordering::Relaxed);
+                    if now <= prev {
+                        break;
+                    }
+                    if peak
+                        .compare_exchange(prev, now, Ordering::Relaxed, Ordering::Relaxed)
+                        .is_ok()
+                    {
+                        break;
+                    }
+                }
+                tokio::time::sleep(Duration::from_millis(2)).await;
+                drop(reservation);
+            }
+        }));
+    }
+
+    futures::future::join_all(tasks).await;
+    ip_tracker.drain_cleanup_queue().await;
+
+    assert!(
+        peak.load(Ordering::Relaxed) <= limit as u64,
+        "peak concurrent reservations must not exceed configured cap"
+    );
+    assert_eq!(stats.get_user_curr_connects(user), 0);
+    assert_eq!(ip_tracker.get_active_ip_count(user).await, 0);
+}
+
+#[tokio::test]
+async fn client_quota_rejection_never_mutates_live_counters() {
+    let user = "quota-reject-user";
+    let stats = Arc::new(Stats::new());
+    let ip_tracker = Arc::new(UserIpTracker::new());
+
+    let mut config = ProxyConfig::default();
+    config.access.user_data_quota.insert(user.to_string(), 0);
+
+    let peer: SocketAddr = "198.51.100.201:31111".parse().unwrap();
+    let res = RunningClientHandler::acquire_user_connection_reservation_static(
+        user,
+        &config,
+        stats.clone(),
+        peer,
+        ip_tracker.clone(),
+    )
+    .await;
+
+    assert!(matches!(res, Err(ProxyError::DataQuotaExceeded { .. })));
+    assert_eq!(stats.get_user_curr_connects(user), 0);
+    assert_eq!(ip_tracker.get_active_ip_count(user).await, 0);
+}
+
+#[tokio::test]
+async fn client_expiration_rejection_never_mutates_live_counters() {
+    let user = "expired-user";
+    let stats = Arc::new(Stats::new());
+    let ip_tracker = Arc::new(UserIpTracker::new());
+
+    let mut config = ProxyConfig::default();
+    config
+        .access
+        .user_expirations
+        .insert(user.to_string(), chrono::Utc::now() - chrono::Duration::seconds(1));
+
+    let peer: SocketAddr = "198.51.100.202:31112".parse().unwrap();
+    let res = RunningClientHandler::acquire_user_connection_reservation_static(
+        user,
+        &config,
+        stats.clone(),
+        peer,
+        ip_tracker.clone(),
+    )
+    .await;
+
+    assert!(matches!(res, Err(ProxyError::UserExpired { .. })));
+    assert_eq!(stats.get_user_curr_connects(user), 0);
+    assert_eq!(ip_tracker.get_active_ip_count(user).await, 0);
+}
+
+#[tokio::test]
+async fn client_ip_limit_failure_rolls_back_counter_exactly() {
+    let user = "ip-limit-rollback-user";
+    let stats = Arc::new(Stats::new());
+    let ip_tracker = Arc::new(UserIpTracker::new());
+    ip_tracker.set_user_limit(user, 1).await;
+
+    let mut config = ProxyConfig::default();
+    config.access.user_max_tcp_conns.insert(user.to_string(), 16);
+
+    let first_peer: SocketAddr = "198.51.100.203:31113".parse().unwrap();
+    let first = RunningClientHandler::acquire_user_connection_reservation_static(
+        user,
+        &config,
+        stats.clone(),
+        first_peer,
+        ip_tracker.clone(),
+    )
+    .await
+    .unwrap();
+
+    let second_peer: SocketAddr = "198.51.100.204:31114".parse().unwrap();
+    let second = RunningClientHandler::acquire_user_connection_reservation_static(
+        user,
+        &config,
+        stats.clone(),
+        second_peer,
+        ip_tracker.clone(),
+    )
+    .await;
+
+    assert!(matches!(second, Err(ProxyError::ConnectionLimitExceeded { .. })));
+    assert_eq!(stats.get_user_curr_connects(user), 1);
+
+    drop(first);
+    ip_tracker.drain_cleanup_queue().await;
+
+    assert_eq!(stats.get_user_curr_connects(user), 0);
+    assert_eq!(ip_tracker.get_active_ip_count(user).await, 0);
+}
+
+#[tokio::test]
+async fn client_parallel_limit_checks_success_path_leaves_no_residue() {
+    let user = "parallel-check-success-user";
+    let stats = Arc::new(Stats::new());
+    let ip_tracker = Arc::new(UserIpTracker::new());
+    ip_tracker.set_user_limit(user, 128).await;
+
+    let mut config = ProxyConfig::default();
+    config.access.user_max_tcp_conns.insert(user.to_string(), 128);
+
+    let mut tasks = Vec::new();
+    for i in 0..128u16 {
+        let stats = Arc::clone(&stats);
+        let ip_tracker = Arc::clone(&ip_tracker);
+        let config = config.clone();
+
+        tasks.push(tokio::spawn(async move {
+            let peer = SocketAddr::new(
+                IpAddr::V4(Ipv4Addr::new(10, 10, (i / 255) as u8, (i % 255 + 1) as u8)),
+                32000 + i,
+            );
+            RunningClientHandler::check_user_limits_static(user, &config, &stats, peer, &ip_tracker)
+                .await
+        }));
+    }
+
+    for result in futures::future::join_all(tasks).await {
+        assert!(result.unwrap().is_ok());
+    }
+
+    assert_eq!(stats.get_user_curr_connects(user), 0);
+    assert_eq!(ip_tracker.get_active_ip_count(user).await, 0);
+}
+
+#[tokio::test]
+async fn client_parallel_limit_checks_failure_path_leaves_no_residue() {
+    let user = "parallel-check-failure-user";
+    let stats = Arc::new(Stats::new());
+    let ip_tracker = Arc::new(UserIpTracker::new());
+    ip_tracker.set_user_limit(user, 0).await;
+
+    let mut config = ProxyConfig::default();
+    config.access.user_max_tcp_conns.insert(user.to_string(), 512);
+
+    let mut tasks = Vec::new();
+    for i in 0..64u16 {
+        let stats = Arc::clone(&stats);
+        let ip_tracker = Arc::clone(&ip_tracker);
+        let config = config.clone();
+
+        tasks.push(tokio::spawn(async move {
+            let peer = SocketAddr::new(IpAddr::V4(Ipv4Addr::new(172, 16, 0, (i % 250 + 1) as u8)), 33000 + i);
+            RunningClientHandler::check_user_limits_static(user, &config, &stats, peer, &ip_tracker)
+                .await
+        }));
+    }
+
+    let mut _denied = 0usize;
+    for result in futures::future::join_all(tasks).await {
+        match result.unwrap() {
+            Ok(()) => {}
+            Err(ProxyError::ConnectionLimitExceeded { .. }) => _denied += 1,
+            Err(other) => panic!("unexpected error: {other}"),
+        }
+    }
+
+    assert_eq!(stats.get_user_curr_connects(user), 0);
+    assert_eq!(ip_tracker.get_active_ip_count(user).await, 0);
+}
+
+#[tokio::test]
+async fn client_churn_mixed_success_failure_converges_to_zero_state() {
+    let user = "mixed-churn-user";
+    let stats = Arc::new(Stats::new());
+    let ip_tracker = Arc::new(UserIpTracker::new());
+    ip_tracker.set_user_limit(user, 4).await;
+
+    let mut config = ProxyConfig::default();
+    config.access.user_max_tcp_conns.insert(user.to_string(), 8);
+
+    let mut tasks = Vec::new();
+    for i in 0..200u16 {
+        let stats = Arc::clone(&stats);
+        let ip_tracker = Arc::clone(&ip_tracker);
+        let config = config.clone();
+
+        tasks.push(tokio::spawn(async move {
+            let peer = SocketAddr::new(
+                IpAddr::V4(Ipv4Addr::new(192, 0, 2, (i % 16 + 1) as u8)),
+                34000 + (i % 32),
+            );
+            let maybe_res = RunningClientHandler::acquire_user_connection_reservation_static(
+                user,
+                &config,
+                stats,
+                peer,
+                ip_tracker,
+            )
+            .await;
+
+            if let Ok(reservation) = maybe_res {
+                tokio::time::sleep(Duration::from_millis((i % 3) as u64)).await;
+                drop(reservation);
+            }
+        }));
+    }
+
+    futures::future::join_all(tasks).await;
+    ip_tracker.drain_cleanup_queue().await;
+
+    assert_eq!(stats.get_user_curr_connects(user), 0);
+    assert_eq!(ip_tracker.get_active_ip_count(user).await, 0);
+}
+
+#[tokio::test]
+async fn client_same_ip_parallel_attempts_allow_at_most_one_when_limit_is_one() {
+    let user = "same-ip-user";
+    let stats = Arc::new(Stats::new());
+    let ip_tracker = Arc::new(UserIpTracker::new());
+    ip_tracker.set_user_limit(user, 1).await;
+
+    let mut config = ProxyConfig::default();
+    config.access.user_max_tcp_conns.insert(user.to_string(), 1);
+
+    let peer: SocketAddr = "203.0.113.44:35555".parse().unwrap();
+    let mut tasks = Vec::new();
+
+    for _ in 0..64 {
+        let stats = Arc::clone(&stats);
+        let ip_tracker = Arc::clone(&ip_tracker);
+        let config = config.clone();
+        tasks.push(tokio::spawn(async move {
+            RunningClientHandler::acquire_user_connection_reservation_static(
+                user,
+                &config,
+                stats,
+                peer,
+                ip_tracker,
+            )
+            .await
+        }));
+    }
+
+    let mut granted = 0usize;
+    let mut reservations = Vec::new();
+    for result in futures::future::join_all(tasks).await {
+        match result.unwrap() {
+            Ok(reservation) => {
+                granted += 1;
+                reservations.push(reservation);
+            }
+            Err(ProxyError::ConnectionLimitExceeded { .. }) => {}
+            Err(other) => panic!("unexpected error: {other}"),
+        }
+    }
+
+    assert_eq!(granted, 1, "only one reservation may be granted for same IP with limit=1");
+    drop(reservations);
+    ip_tracker.drain_cleanup_queue().await;
+    assert_eq!(stats.get_user_curr_connects(user), 0);
+    assert_eq!(ip_tracker.get_active_ip_count(user).await, 0);
+}
+
+#[tokio::test]
+async fn client_repeat_acquire_release_cycles_never_accumulate_state() {
+    let user = "repeat-cycle-user";
+    let stats = Arc::new(Stats::new());
+    let ip_tracker = Arc::new(UserIpTracker::new());
+    ip_tracker.set_user_limit(user, 32).await;
+
+    let mut config = ProxyConfig::default();
+    config.access.user_max_tcp_conns.insert(user.to_string(), 32);
+
+    for i in 0..500u16 {
+        let peer = SocketAddr::new(
+            IpAddr::V4(Ipv4Addr::new(198, 18, (i / 250) as u8, (i % 250 + 1) as u8)),
+            36000 + (i % 128),
+        );
+        let reservation = RunningClientHandler::acquire_user_connection_reservation_static(
+            user,
+            &config,
+            stats.clone(),
+            peer,
+            ip_tracker.clone(),
+        )
+        .await
+        .unwrap();
+        drop(reservation);
+    }
+
+    ip_tracker.drain_cleanup_queue().await;
+    assert_eq!(stats.get_user_curr_connects(user), 0);
+    assert_eq!(ip_tracker.get_active_ip_count(user).await, 0);
+}

src/proxy/client_security_tests.rs

@@ -1322,13 +1322,20 @@ async fn valid_tls_with_invalid_mtproto_falls_back_to_mask_backend() {
     let client_hello = make_valid_tls_client_hello(&secret, 0);
     let invalid_mtproto = vec![0u8; crate::protocol::constants::HANDSHAKE_LEN];
     let tls_app_record = wrap_tls_application_data(&invalid_mtproto);
+    let trailing_tls_payload = b"still-tls-after-fallback".to_vec();
+    let trailing_tls_record = wrap_tls_application_data(&trailing_tls_payload);
 
     let expected_fallback = client_hello.clone();
+    let expected_trailing_tls_record = trailing_tls_record.clone();
     let accept_task = tokio::spawn(async move {
         let (mut stream, _) = listener.accept().await.unwrap();
         let mut got = vec![0u8; expected_fallback.len()];
         stream.read_exact(&mut got).await.unwrap();
         assert_eq!(got, expected_fallback);
+
+        let mut trailing = vec![0u8; expected_trailing_tls_record.len()];
+        stream.read_exact(&mut trailing).await.unwrap();
+        assert_eq!(trailing, expected_trailing_tls_record);
     });
 
     let mut cfg = ProxyConfig::default();
@@ -1396,6 +1403,7 @@ async fn valid_tls_with_invalid_mtproto_falls_back_to_mask_backend() {
     assert_eq!(tls_response_head[0], 0x16);
 
     client_side.write_all(&tls_app_record).await.unwrap();
+    client_side.write_all(&trailing_tls_record).await.unwrap();
 
     tokio::time::timeout(Duration::from_secs(3), accept_task)
         .await
@@ -1421,13 +1429,20 @@ async fn client_handler_tls_bad_mtproto_is_forwarded_to_mask_backend() {
     let client_hello = make_valid_tls_client_hello(&secret, 0);
     let invalid_mtproto = vec![0u8; crate::protocol::constants::HANDSHAKE_LEN];
     let tls_app_record = wrap_tls_application_data(&invalid_mtproto);
+    let trailing_tls_payload = b"second-tls-record".to_vec();
+    let trailing_tls_record = wrap_tls_application_data(&trailing_tls_payload);
 
     let expected_fallback = client_hello.clone();
+    let expected_trailing_tls_record = trailing_tls_record.clone();
     let mask_accept_task = tokio::spawn(async move {
         let (mut stream, _) = mask_listener.accept().await.unwrap();
         let mut got = vec![0u8; expected_fallback.len()];
         stream.read_exact(&mut got).await.unwrap();
         assert_eq!(got, expected_fallback);
+
+        let mut trailing = vec![0u8; expected_trailing_tls_record.len()];
+        stream.read_exact(&mut trailing).await.unwrap();
+        assert_eq!(trailing, expected_trailing_tls_record);
     });
 
     let mut cfg = ProxyConfig::default();
@@ -1513,6 +1528,7 @@ async fn client_handler_tls_bad_mtproto_is_forwarded_to_mask_backend() {
     assert_eq!(tls_response_head[0], 0x16);
 
     client.write_all(&tls_app_record).await.unwrap();
+    client.write_all(&trailing_tls_record).await.unwrap();
 
     tokio::time::timeout(Duration::from_secs(3), mask_accept_task)
         .await