ComputerCraft program to download files from a password-protected server

index.js

const express = require('express')
const app = express()
const fs = require('fs')
const path = require('path')
const port = 80
const secret = 'testing'
const safeDir = 'E:/Programming/Lua'

app.use('/luasync', (req, res) => {
    if (req.headers.authorization == null) {
        console.log('No secret')
        res.status(400)
        res.send('No secret given')
        return
    }
    if (req.headers.authorization != secret) {
        console.log('Invalid secret')
        res.status(401)
        res.send('Invalid secret')
        return
    }
    if (!('file' in req.query)) {
        console.log('No file')
        res.status(400)
        res.send('No file requested')
        return
    }

    try {
        const filePath = path.join(safeDir, req.query['file'])
        console.log(filePath)
        if (!fs.statSync(filePath).isFile()) {
            console.log('Invalid path')
            res.status(400)
            res.send('Invalid path')
            return
        }
        const file = fs.readFileSync(filePath)
        res.download(filePath)
        return
    } catch (e) {
        console.log(e)
        res.status(404)
        return
    }
})

app.listen(port)

sync.lua

local target, key, target_file, local_file = ...

if target == nil or key == nil or target_file == nil then
    print('Usage: sync <url> <key> <remote file> <local file>')
    return
end

print('Attempting connection to ' .. target)
local res, err = http.checkURL(target)
if not res then
    error(err)
end

print('Valid connection found. Sending sync request...')

res = http.get(target .. '/luasync?file=' .. target_file, {['Authorization'] = key})
if type(res) == 'string' then
    error(res)
elseif res == nil then
    error('Nil response')
end

print('Received response, writing file...')

-- Write file
local dir = shell.dir()
local file = fs.open(dir .. '/' .. local_file, 'w')
file.write(res.readAll())
file.close()
print('File written')