Mua

This is a mad-science project to turn Matrix rooms into a kind of distributed Lua environment. It's probably crazy and I don't really know why anyone would want to, but here we are.

Starting muac

The defaults will create a guest account on matrix.org and join you to #mua-test:matrix.org.

It'll load the Lua contents from the mua.source event with the state key main and run it.

Give it a go:

go run github.com/neilalexander/mua/cmd/muac

If all goes well, you should get an interactive prompt in which you can type Lua.

Loading Lua from the room

Using importstate(), you can import something from a specific event state key:

$ go run github.com/neilalexander/mua/cmd/muac
Using https://matrix.org
HELLO!
This code is running from the room state. Neat!
>> importstate("!TdSVXZoEcLugVpglQn:matrix.org", "mua.source", "main")
HELLO!
This is running from bytecodes stored in the room state.
>> 

... or the same event by event ID instead:

>> importevent("!TdSVXZoEcLugVpglQn:matrix.org", "$Z_brwOSlxvtgp24_g_N4QmzBQtSEtl7rI4IQIp02S94")
HELLO!
This is running from bytecodes stored in the room state.

Loading room events

You can load an event from the room:

>> ev = event.new("!TdSVXZoEcLugVpglQn:matrix.org", "$Z_brwOSlxvtgp24_g_N4QmzBQtSEtl7rI4IQIp02S94")
>> print(ev:json())
{"state_key":"main","sender":"@neilalexander:matrix.org","type":"mua.source","origin_server_ts":1589709947669,"event_id":"$Z_brwOSlxvtgp24_g_N4QmzBQtSEtl7rI4IQIp02S94","room_id":"!TdSVXZoEcLugVpglQn:matrix.org","unsigned":{"age":1079280},"content":{"source":"cHJpbnQoIkhFTExPISIpCnByaW50KCJUaGlzIGlzIHJ1bm5pbmcgZnJvbSBieXRlY29kZXMgc3RvcmVkIGluIHRoZSByb29tIHN0YXRlLiIpCmxvYWRlZCA9IHRydWUK","type":0}}
>> print(ev:type())
mua.source

Run local scripts

Run a local script, as compiled with luac:

$ go run github.com/neilalexander/mua/cmd/muac luac.out
HELLO!
This code is running from the room state. Neat!
m.room.member
{"avatar_url":"","displayname":"neilalexander (Dendrite)","membership":"join"}

You can importevent() or importstate() in your script as normal in order to import and run Lua bytecode from the room.

Encode some Lua

You can also take a compiled Lua file from luac, say luac.out, and encode it with the -encode luac.out command line parameters:

$ go run github.com/neilalexander/mua/cmd/muac -encode test.lua
{
  "type": 0,
  "source": "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"
}

You can now use your favourite client to send a custom event with this encoded blob as the content.

Is this safe?

You can't access the filesystem, sockets, system calls or such within the Lua environment. It should be reasonably self-contained as a result, although this may also make it a bit harder to do anything useful with.

Why would you do this?

No idea.