RCEoR Client

--[[
RCEoR: a secure protocol for remote code execution over rednet (ComputerCraft)

This is free and unencumbered software released into the public domain.

Anyone is free to copy, modify, publish, use, compile, sell, or
distribute this software, either in source code form or as a compiled
binary, for any purpose, commercial or non-commercial, and by any
means.

In jurisdictions that recognize copyright laws, the author or authors
of this software dedicate any and all copyright interest in the
software to the public domain. We make this dedication for the benefit
of the public at large and to the detriment of our heirs and
successors. We intend this dedication to be an overt act of
relinquishment in perpetuity of all present and future rights to this
software under copyright law.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
OTHER DEALINGS IN THE SOFTWARE.

For more information, please refer to <http://unlicense.org/>

RCEoR v1.1
Protocol: rednet protocol "rceor", messages of the format:
{code = [code to run], evil = [evilness of code]}
live is also accepted as an alias for evil.
]]

local secureEnv = {
    print = print,
    http = http,
    rednet = rednet,
    textutils = textutils,
    bit = bit,
    pcall = pcall,
    colors = colors,
    gps = gps,
    pairs = pairs,
    ipairs = ipairs,
    math = math,
    _HOST = _HOST .. " (RCEoR Sandbox)",
    string = string
}

function clone(x)
    local ty = type(x)
    if ty == "table" then
        local new = {}
        for k, v in pairs(x) do
            new[k] = clone(v)
        end
    elseif ty == "function" then
        return function(...) return x(...) end
    else
        return x
    end
end

secureEnv.rednet.close = nil

local argv = {...}
local secure = true

if argv[1] == "insecure" then
    secure = false
end

for _, n in pairs(peripheral.getNames()) do -- open modems
    if pcall(rednet.open, n) then
        print("Opened a modem")
    end
end

local coros = {}

local function safeish_serialize(x)
    local ok, res = pcall(textutils.serialize, x)
    if ok then return res
    else return tostring(x) end
end

function run(code)
    print("Executing", code)

    if secure then
        local f = load(code, "@<RCEoR input>", "t", clone(secureEnv))
        if f then
            table.insert(coros, coroutine.create(function()
                local result = {pcall(f)}
                print(safeish_serialise(result))
            end))
        else
            print "Invalid code: EVIL?!!?!?!?!?!"
        end
    else
        print(safeish_serialise(loadstring(code)()))
    end
end

function receiver()
    while true do
        local sender, message = rednet.receive "rceor"
        if message and message.code then
            if secure then
                if message.evil or message.live then
                    print "Evil message detected"
                else
                    print "Running securely"
                    run(message.code)
                end
            else
                print "Running"
                run(message.code)
            end
        end
    end
end

if not secure then receiver() end

table.insert(coros, coroutine.create(receiver))

while true do
    local ev = {os.pullEvent()}
    for k, c in pairs(coros) do
        if coroutine.status(c) == "dead" then coros[k] = nil end
        coroutine.resume(c, table.unpack(ev))
    end
end