init.lua

-- allay-server: serve allay packages over rednet.
--
-- Run on a CC computer with a wireless modem. Other computers can then
-- `allay source add rednet://<this-station>` and install packages from
-- this host.
--
-- Files served from a configurable directory (default /home/allay-source/).

local PROTOCOL = "allay-source"
local DEFAULT_DIR = "/home/allay-source"
local STATION = os.getComputerLabel() or ("allay-" .. os.getComputerID())

local function find_modem()
  for _, side in ipairs(peripheral.getNames()) do
    if peripheral.getType(side) == "modem"
       and peripheral.call(side, "isWireless") then
      return side
    end
  end
  return nil
end

local function read_file(path)
  if not fs.exists(path) then return nil, "not found: " .. path end
  local f = fs.open(path, "r")
  if not f then return nil, "cannot open: " .. path end
  local content = f.readAll()
  f.close()
  return content
end

local function safe_path(root, requested)
  -- Reject paths with .. or null bytes.
  if requested:find("%.%.") or requested:find("\0") then
    return nil
  end
  if requested:sub(1, 1) == "/" then requested = requested:sub(2) end
  return root .. "/" .. requested
end

local function main(argv)
  argv = argv or {}
  local root = argv[1] or DEFAULT_DIR

  if not fs.exists(root) then
    print("error: source directory does not exist: " .. root)
    print("usage: allay-server <directory>")
    return
  end

  local side = find_modem()
  if not side then
    print("error: no wireless modem attached")
    return
  end
  rednet.open(side)
  rednet.host(PROTOCOL, STATION)

  print(string.format("allay-server serving %s as rednet station '%s'", root, STATION))
  print("(press Ctrl+T to stop)")

  while true do
    local sender, msg = rednet.receive(PROTOCOL)
    if type(msg) == "table" and type(msg.action) == "string" then
      if msg.action == "get" and type(msg.path) == "string" then
        local full = safe_path(root, msg.path)
        if not full then
          rednet.send(sender, { ok = false, err = "invalid path" }, PROTOCOL)
        else
          local content, err = read_file(full)
          if content then
            rednet.send(sender, { ok = true, content = content }, PROTOCOL)
          else
            rednet.send(sender, { ok = false, err = err }, PROTOCOL)
          end
        end
      else
        rednet.send(sender, { ok = false, err = "unknown action" }, PROTOCOL)
      end
    end
  end
end

main({...})