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A lexicon-driven AppView for ATProto.
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Rust
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use super::tid::generate_tid;
const INSTRUCTION_LIMIT: u32 = 1_000_000;
/// Create a fresh sandboxed Lua VM.////// - Dangerous globals (`io`, `debug`, `package`, `require`, `dofile`, `loadfile`, `load`) are removed./// - `os` is replaced with a safe subset exposing only `time`, `date`, `difftime`, and `clock`./// - An instruction-count hook prevents infinite loops./// - Utility globals `now()` and `log()` are injected.pub fn create_sandbox() -> LuaResult<Lua> { let lua = Lua::new();
// Preserve safe os functions before removing the full os table let globals = lua.globals(); let safe_os = lua.create_table()?; if let Ok(os_table) = globals.get::<mlua::Table>("os") { for name in &["time", "date", "difftime", "clock"] { if let Ok(func) = os_table.get::<mlua::Function>(*name) { safe_os.set(*name, func)?; } } }
// Remove dangerous globals for name in &[ "os", "io", "debug", "package", "require", "dofile", "loadfile", "load", "collectgarbage", ] { globals.raw_set(*name, mlua::Value::Nil)?; }
// Re-add os with only safe functions (time, date, difftime, clock) globals.set("os", safe_os)?;
// Instruction limit to prevent infinite loops lua.set_hook( mlua::HookTriggers::new().every_nth_instruction(INSTRUCTION_LIMIT), |_lua, _debug| Err(mlua::Error::runtime("script exceeded execution limit")), )?;
// Utility: now() returns UTC ISO 8601 string let now_fn = lua.create_function(|_, ()| Ok(chrono::Utc::now().to_rfc3339()))?; globals.set("now", now_fn)?;
// `log(message)` no-op stub. The real implementation lives in // `super::scripts::register_log_event_api` and is registered by // every runner so the trigger context can be threaded into each // `event_logs` row. The stub here exists only so paths that exec // a script body OUTSIDE a runner — namely `validate_script` // (admin write-time linting) and the in-process xrpc_api tests — // don't break on top-level `log("...")` calls in user scripts. // The runner-level registration always overrides this stub. let log_fn = lua.create_function(|_, _msg: String| Ok(()))?; globals.set("log", log_fn)?;
// Utility: TID() returns a fresh AT Protocol TID string let tid_fn = lua.create_function(|_, ()| Ok(generate_tid()))?; globals.set("TID", tid_fn)?;
// Utility: toarray(table) marks a table as a JSON array for serialization. // Ensures empty tables serialize as [] instead of {}. let toarray_fn = lua.create_function(|lua, table: mlua::Table| { let values: Vec<mlua::Value> = table.sequence_values().collect::<LuaResult<_>>()?; let seq = lua.create_sequence_from(values)?; seq.set_metatable(Some(lua.array_metatable()))?; Ok(seq) })?; globals.set("toarray", toarray_fn)?;
// JSON utilities: json.encode(table) -> string, json.decode(string) -> table let json_table = lua.create_table()?;
let encode_fn = lua.create_function(|lua, value: mlua::Value| { let json_value: serde_json::Value = lua .from_value(value) .map_err(|e| mlua::Error::runtime(format!("json.encode: {e}")))?; serde_json::to_string(&json_value) .map_err(|e| mlua::Error::runtime(format!("json.encode: {e}"))) })?; json_table.set("encode", encode_fn)?;
let decode_fn = lua.create_function(|lua, s: String| { let json_value: serde_json::Value = serde_json::from_str(&s) .map_err(|e| mlua::Error::runtime(format!("json.decode: {e}")))?; lua.to_value(&json_value) .map_err(|e| mlua::Error::runtime(format!("json.decode: {e}"))) })?; json_table.set("decode", decode_fn)?;
globals.set("json", json_table)?;
Ok(lua)}
/// Validate that a script compiles and defines a `handle` function.pub fn validate_script(source: &str) -> Result<(), String> { let lua = create_sandbox().map_err(|e| format!("failed to create Lua VM: {e}"))?; // Set a stub env table that returns "" for any missing key so scripts // that do top-level concatenation (e.g. `env.URL .. "/path"`) don't fail. let env_stub = lua.create_table().unwrap(); let meta = lua.create_table().unwrap(); meta.set( "__index", lua.create_function(|_, (_t, _k): (mlua::Value, mlua::Value)| Ok("".to_string())) .unwrap(), ) .unwrap(); let _ = env_stub.set_metatable(Some(meta)); lua.globals() .set("env", env_stub) .map_err(|e| format!("failed to set env stub: {e}"))?; lua.load(source) .exec() .map_err(|e| format!("script compilation failed: {e}"))?;
let globals = lua.globals(); match globals.get::<mlua::Function>("handle") { Ok(_) => Ok(()), Err(_) => Err("script must define a handle() function".into()), }}
#[cfg(test)]mod tests { use super::*;
#[test] fn sandbox_removes_dangerous_globals() { let lua = create_sandbox().unwrap(); let globals = lua.globals(); assert!(globals.get::<mlua::Value>("io").unwrap().is_nil()); assert!(globals.get::<mlua::Value>("debug").unwrap().is_nil()); assert!(globals.get::<mlua::Value>("package").unwrap().is_nil()); assert!(globals.get::<mlua::Value>("require").unwrap().is_nil()); }
#[test] fn sandbox_provides_safe_os_subset() { let lua = create_sandbox().unwrap(); let os_table: mlua::Table = lua.globals().get("os").unwrap(); assert!(os_table.get::<mlua::Function>("time").is_ok()); assert!(os_table.get::<mlua::Function>("date").is_ok()); assert!(os_table.get::<mlua::Function>("difftime").is_ok()); assert!(os_table.get::<mlua::Function>("clock").is_ok()); // Dangerous os functions should not be present assert!(os_table.get::<mlua::Value>("execute").unwrap().is_nil()); assert!(os_table.get::<mlua::Value>("remove").unwrap().is_nil()); assert!(os_table.get::<mlua::Value>("rename").unwrap().is_nil()); assert!(os_table.get::<mlua::Value>("exit").unwrap().is_nil()); }
#[test] fn sandbox_provides_now() { let lua = create_sandbox().unwrap(); let result: String = lua.load("return now()").eval().unwrap(); assert!(result.contains("T")); // ISO 8601 format }
#[test] fn sandbox_provides_log() { let lua = create_sandbox().unwrap(); lua.load(r#"log("test message")"#).exec().unwrap(); }
#[test] fn sandbox_provides_tid() { let lua = create_sandbox().unwrap(); let result: String = lua.load("return TID()").eval().unwrap(); assert_eq!(result.len(), 13); let valid = "234567abcdefghijklmnopqrstuvwxyz"; for ch in result.chars() { assert!(valid.contains(ch), "invalid char '{ch}' in TID"); } }
#[test] fn sandbox_tid_returns_unique_values() { let lua = create_sandbox().unwrap(); let a: String = lua.load("return TID()").eval().unwrap(); let b: String = lua.load("return TID()").eval().unwrap(); assert_ne!(a, b); }
#[test] fn sandbox_kills_infinite_loop() { let lua = create_sandbox().unwrap(); let result = lua.load("while true do end").exec(); assert!(result.is_err()); let err = result.unwrap_err().to_string(); assert!( err.contains("execution limit"), "expected execution limit error, got: {err}" ); }
#[test] fn validate_script_accepts_valid() { let result = validate_script("function handle() return {} end"); assert!(result.is_ok()); }
#[test] fn validate_script_rejects_missing_handle() { let result = validate_script("function other() return {} end"); assert!(result.is_err()); assert!(result.unwrap_err().contains("handle")); }
#[test] fn validate_script_rejects_syntax_error() { let result = validate_script("function handle("); assert!(result.is_err()); }
#[test] fn sandbox_provides_toarray() { let lua = create_sandbox().unwrap(); lua.load(r#"result = toarray({})"#).exec().unwrap(); }
#[test] fn sandbox_toarray_preserves_values() { let lua = create_sandbox().unwrap(); let result: Vec<i64> = lua .load(r#"return toarray({10, 20, 30})"#) .eval::<mlua::Table>() .unwrap() .sequence_values() .collect::<LuaResult<_>>() .unwrap(); assert_eq!(result, vec![10, 20, 30]); }
#[test] fn sandbox_toarray_empty_serializes_as_array() { use mlua::LuaSerdeExt; let lua = create_sandbox().unwrap(); let table: mlua::Table = lua.load(r#"return toarray({})"#).eval().unwrap(); let json: serde_json::Value = lua.from_value(mlua::Value::Table(table)).unwrap(); assert!(json.is_array(), "expected JSON array, got: {json}"); }
#[test] fn sandbox_provides_json_encode() { let lua = create_sandbox().unwrap(); let result: String = lua .load(r#"return json.encode({name = "test", count = 42})"#) .eval() .unwrap(); let parsed: serde_json::Value = serde_json::from_str(&result).unwrap(); assert_eq!(parsed["name"], "test"); assert_eq!(parsed["count"], 42); }
#[test] fn sandbox_provides_json_decode() { let lua = create_sandbox().unwrap(); let result: mlua::Table = lua .load(r#"return json.decode('{"name":"test","count":42}')"#) .eval() .unwrap(); assert_eq!(result.get::<String>("name").unwrap(), "test"); assert_eq!(result.get::<i64>("count").unwrap(), 42); }
#[test] fn sandbox_json_encode_array() { let lua = create_sandbox().unwrap(); let result: String = lua .load(r#"return json.encode(toarray({1, 2, 3}))"#) .eval() .unwrap(); assert_eq!(result, "[1,2,3]"); }
#[test] fn sandbox_json_decode_invalid_returns_error() { let lua = create_sandbox().unwrap(); let result: Result<mlua::Value, _> = lua.load(r#"return json.decode("not valid json")"#).eval(); assert!(result.is_err()); }}