Slopdrop - Multi-Frontend TCL Eval Bot

A modern rewrite of the TCL eval bot in Rust, providing safe TCL code evaluation through multiple interfaces: IRC, CLI, TUI, and Web.

Features

Multiple Frontends

• IRC: Traditional IRC bot interface
• CLI: Interactive command-line REPL
• TUI: Full-screen terminal UI with split panes
• Web: Browser interface + REST API

All frontends share the same TCL interpreter and git-backed state.

Core Features

• Safe TCL Interpreter: Sandboxed TCL 8.6 with dangerous commands disabled
• Git State Persistence: All changes versioned with author attribution
• Async Architecture: Built on Tokio for high-performance
• Security Features:
  • Bracket balancing validation
  • Privileged user authentication (hostmask-based)
  • Command sandboxing (exec, file, socket disabled)
  • Memory limits (Unix): Configurable per-evaluation caps
  • Timeout protection: 30s default with automatic thread restart
  • Crash recovery: Automatic restart on OOM/panic

Building

Prerequisites

• Rust 1.70+
• TCL 8.6 development headers
• pkg-config

On Ubuntu/Debian:

apt-get install tcl8.6-dev pkg-config

Build

# Build with all frontends
cargo build --release --features all-frontends

# Or build specific frontends
cargo build --release --features cli
cargo build --release --features tui
cargo build --release --features web

Usage

IRC Bot (Default)

./target/release/slopdrop config.toml

CLI REPL

./target/release/slopdrop --cli
# Commands: .help, .history, .rollback, .more, .quit

TUI (Full-screen Terminal UI)

./target/release/slopdrop --tui
# Ctrl+Enter: Evaluate | F2: More output | F3: Refresh history | Ctrl+C: Quit

Web Server

./target/release/slopdrop --web
# Open http://127.0.0.1:8080

Multiple Frontends

./target/release/slopdrop --irc --web  # Run both IRC and Web

Configuration

Create a config.toml file (see config.toml.example):

[server]
hostname = "irc.libera.chat"
port = 6697
use_tls = true
nickname = "slopdrop"
channels = ["#bottest"]

[security]
privileged_users = ["admin!*@trusted.example.com"]
blacklisted_users = []
eval_timeout_ms = 30000
memory_limit_mb = 256
max_recursion_depth = 1000

[tcl]
state_path = "./state"
state_repo = "git@github.com:user/state.git"  # Optional: remote git sync
ssh_key = "/path/to/key"  # Optional: SSH key for git push
max_output_lines = 10

IRC Commands

• tcl <code> - Evaluate TCL code in sandboxed mode
• tcl more - Show more output from previous command (pagination)
• tclAdmin <code> - Evaluate with admin privileges (privileged users only)
• tclAdmin history [n] - View recent git commit history
• tclAdmin rollback <commit> - Revert state to a specific commit
• tclAdmin blacklist list - Show blacklisted users
• tclAdmin blacklist add <hostmask> - Block a user
• tclAdmin blacklist remove <hostmask> - Unblock a user

Example

<user> tcl expr {1 + 1}
<bot> 2

<user> tcl set myvar "hello world"
<bot> hello world

<user> tcl proc greet {} { return "hi there!" }
<bot>

<user> tcl greet
<bot> hi there!

Architecture

The bot uses a modular frontend architecture:

1. Frontend Layer: IRC, CLI, TUI, Web interfaces
2. TCL Service (tcl_service.rs): Frontend-agnostic evaluation service
3. TCL Thread (tcl_thread.rs): Thread-based execution with timeout
4. State Persistence (state.rs): Git-backed state storage

Communication uses Tokio mpsc channels for efficient async message passing.

Security

The bot implements defense-in-depth security for safe public deployment:

Execution Protection

• Timeout: 30s default (configurable)
• Memory limit: 256 MB on Unix (configurable)
• Recursion limit: 1000 levels (configurable)
• Auto-restart: Thread recovers from crashes/OOM

Network Protection (SSRF Prevention)

• URL validation: Blocks localhost, private IPs, link-local addresses
• Rate limiting: Per-eval (5), per-user (10/min), per-channel (25/min)
• Transfer limits: 150KB per-request, 500KB cumulative per-eval
• Redirect limit: Maximum 5 redirects

Access Control

• User blacklist: Block abusive users by hostmask pattern
• Admin authentication: Hostmask-based privilege checking
• Input validation: Bracket balancing, error sanitization

Resource Limits

• Cache limits: 1000 keys, 100KB per value, 1MB total per bucket
• Output pagination: Configurable line limits
• Sandbox: Dangerous commands disabled (exec, open, file, socket, source)

State Protection

• Git versioning: All changes tracked with author attribution
• Rollback: Admin command to revert malicious changes
• Auto GC: Repository garbage collection every 100 commits

For complete security documentation, see: PUBLIC_DEPLOYMENT_SECURITY.md

Implemented Features

State Persistence

• Git-based versioned state storage
• Automatic commits with IRC user as author
• SHA1 content-addressable files
• Proc and variable tracking
• Bootstrap loading (stolen-treasure.tcl, restore_missing_vars.tcl)
• Lazy-loaded english word list

Commands

• history - View git commit history
• rollback - Revert to previous state (admin only)
• chanlist - List channel members
• name/names - Random/all channel members
• cache::* - Persistent key-value storage
• http::* - HTTP operations with rate limiting
• encoding::* - Base64 and URL encoding
• sha1 - SHA1 hashing (requires tcllib)
• linkresolver - Auto-resolve URLs with extensible resolver API
• Utility commands - pick, choose, ??, first, last, rest, upper, lower
• get_english_words, random_word, word_count - English word list

IRC Features

• Auto-rejoin on kick (10s delay)
• Thread-based timeout with automatic restart
• IRC color/formatting code stripping
• Smart message splitting on word boundaries
• Channel member tracking (JOIN, PART, QUIT, KICK, NICK)
• PM notifications to admins on commits

Testing

• Comprehensive test suite (all passing)
• Integration tests with Ergo IRC server
• Automated test scripts

See TODO.md for implementation history and TEST_COVERAGE_REPORT.md for test details.

Container Deployment

A Containerfile is provided for secure deployment:

# Build container
./container-build.sh

# Run with security options
./container-run.sh --config /path/to/config.toml --state /path/to/state

See container-run.sh for all options including memory limits and state reset.

Documentation

• QUICKSTART.md - Quick start guide
• FRONTEND_GUIDE.md - Frontend usage details
• LINKRESOLVER.md - Link auto-resolver with custom resolver API
• PUBLIC_DEPLOYMENT_SECURITY.md - Security documentation
• HTTP_LIMITS.md - HTTP rate limiting details
• OOM_PROTECTION.md - Memory protection details
• TESTING_GUIDE.md - Testing guide
• tests/README.md - Test suite documentation

License

AGPL-3 (matching original)

Credits

Original bot: https://github.com/pillowtrucker/old-tcl-evalbot TCL bindings: https://github.com/oooutlk/tcltk