TNT/docs/CHANGELOG.md

# Changelog

## 2026-05-16 - Internal cleanup

### Fixed
- `message_load()` now holds `g_message_file_lock` for the duration of the read.
  Previously `:last [N]` could race with `message_save()` and observe a
  half-written line.
- `constant_time_strcmp()` accumulates the length difference in `size_t` instead
  of `unsigned char`. The old code lost the length-mismatch signal when the
  two lengths differed by a multiple of 256.

### Changed
- `buffer_appendf()` and `buffer_append_bytes()` moved to `common.c`; the two
  identical copies in `ssh_server.c` and `tui.c` have been removed.
- Removed `TODO.md` (both items completed) and `docs/README.old` (superseded by
  the root `README.md`).
- Trimmed the auto-generated 2025 entry block from this changelog.

## 2026-04-23 - Chat UX Commands and MOTD

### Added
- **`:last [N]`** — show last N messages retrieved directly from the log file (1–50, default 10), bypassing the 100-message in-memory ring buffer limit
- **`:search <keyword>`** — case-insensitive full-text search across the entire message history on disk; returns the most recent 15 matches
- **`:mute-joins`** — per-client toggle to silence join/leave system notifications; title bar shows `[静音]` when active
- **MOTD support** — place `motd.txt` in the state directory; users see it on connect and press any key to enter chat
- **`message_search()`** — new function in `message.c` / `message.h` for log file keyword search with rolling result collection
- Updated in-TUI help screens (English and Chinese) with new commands

## 2026-03-10 - SSH Runtime & Unix Interface Update

### Fixed
- moved SSH handshake/auth/channel setup out of the main accept loop
- replaced synchronous room-wide fan-out with room update sequencing and per-client refresh
- switched idle session handling to `ssh_channel_poll_timeout()` plus blocking reads so quiet sessions are not dropped incorrectly
- made `-d/--state-dir` create the runtime state directory automatically

### Added
- SSH exec commands: `help`, `health`, `users`, `stats --json`, `tail`, `post`
- PTY window-change handling for terminal resize
- `TNT_MAX_CONN_RATE_PER_IP` for per-IP connection-rate control
- `tests/test_exec_mode.sh`
- `tests/test_connection_limits.sh`

### Changed
- `TNT_MAX_CONN_PER_IP` now means concurrent sessions per IP
- stress tests now disable rate-based blocking so they exercise concurrency instead of self-throttling

## 2026-01-22 - Security Audit Fixes

Comprehensive security hardening addressing 23 identified vulnerabilities across 6 categories.

### Critical

- **[AUTH]** Add optional access token authentication (`TNT_ACCESS_TOKEN`)
- **[AUTH]** Implement IP-based rate limiting (10 conn/IP/60s, 5-min block after 5 auth failures)
- **[AUTH]** Add global connection limits (default: 64, configurable via `TNT_MAX_CONNECTIONS`)

### High Priority

- **[BUFFER]** Replace all `strcpy()` with `strncpy()` (3 locations)
- **[BUFFER]** Add buffer overflow checking in `client_printf()`
- **[BUFFER]** Implement UTF-8 validation to prevent malformed input and overlong encodings
- **[SSH]** Upgrade RSA key from 2048 to 4096 bits
- **[SSH]** Fix key file permission race with atomic generation (umask + temp file + rename)
- **[SSH]** Add configurable bind address (`TNT_BIND_ADDR`) and log level (`TNT_SSH_LOG_LEVEL`)
- **[CONCURRENCY]** Fix `room_broadcast()` reference counting race
- **[CONCURRENCY]** Fix `tui_render_screen()` message array TOCTOU via snapshot approach
- **[CONCURRENCY]** Fix `handle_key()` scroll position TOCTOU

### Medium Priority

- **[INPUT]** Add username validation rejecting shell metacharacters and control chars
- **[INPUT]** Sanitize message content to prevent log injection attacks
- **[INPUT]** Enhance `message_load()` with field length and timestamp validation
- **[RESOURCE]** Convert message position array from fixed 1000 to dynamic allocation
- **[RESOURCE]** Enhance `setup_host_key()` validation (size, permissions, auto-regeneration)
- **[RESOURCE]** Improve thread cleanup with proper pthread_attr and error handling

### New Environment Variables

- `TNT_ACCESS_TOKEN` - Optional password for authentication (backward compatible)
- `TNT_BIND_ADDR` - Bind address (default: 0.0.0.0)
- `TNT_SSH_LOG_LEVEL` - SSH logging verbosity 0-4 (default: 1)
- `TNT_RATE_LIMIT` - Enable/disable rate limiting (default: 1)
- `TNT_MAX_CONNECTIONS` - Max concurrent connections (default: 64)
- `TNT_MAX_CONN_PER_IP` - Max connections per IP (default: 5)

### Security Summary

| Category | Fixes | Impact |
|----------|-------|--------|
| Buffer Security | 3 | Prevents overflows, malformed UTF-8 |
| SSH Hardening | 4 | Stronger crypto, no races |
| Input Validation | 3 | Prevents injection, log poisoning |
| Resource Management | 3 | Handles large logs, prevents DoS |
| Authentication | 3 | Optional protection, rate limiting |
| Concurrency Safety | 3 | Eliminates races, crashes |
| **TOTAL** | **19** | **23 vulnerabilities fixed** |

All changes maintain backward compatibility. Server remains open by default.

---

## 2025-12-02 - Stability & Testing Update

### Fixed
- Double colon bug in vim command mode (`:` key consumed properly)
- strtok data corruption in command output rendering
- Use-after-free race condition (added reference counting)
- SSH read blocking issues (added timeouts)
- PTY request infinite loop
- Message history memory waste (optimized loading)

### Added
- Reference counting for thread-safe client cleanup
- SSH read timeout (30s) and error handling
- UTF-8 incomplete sequence detection
- AddressSanitizer build target (`make asan`)
- Basic functional tests (`test_basic.sh`)
- Stress testing script (`test_stress.sh`)
- Static analysis target (`make check`)
- Developer documentation (HACKING)

### Changed
- Improved error handling throughout
- Better memory management in message loading