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import express, { Request, Response } from 'express';
// Middleware for security
import csurf from 'csurf';
import cookieParser from 'cookie-parser';
import fileUpload, { UploadedFile } from 'express-fileupload';
// For executing the python scripts
import { access, stat } from 'fs/promises';
import { Stats } from 'fs';
import { quote } from 'shell-quote';
import { spawn } from 'child_process';
const api = express.Router();
// Use JSON parser for API requests and responses
api.use(express.json());
// CSRF protection
api.use(cookieParser());
const csrf = csurf({ cookie: true });
// For file uploads
api.use(fileUpload({
preserveExtension: true, // Preserve file extension on upload
safeFileNames: true, // Only allow alphanumeric characters in file names
limits: { fileSize: 1 * 1024 * 1024 }, // Limit file size to 1MB
useTempFiles: true, // Store files in temp instead of memory
tempFileDir: '/tmp/', // Store files in /tmp/
debug: false, // Log debug information
}));
/*
Upload a file to the server
POST /api/v1/upload
Parameters:
files: The file to upload
Returns:
201:
{
"message": "File uploaded successfully",
"file": {
"name": "file.py",
"path": "/tmp/file-538126",
}
}
400 when there is no file
413 when the file is too large
415 when the file's MIME type is not text/x-python
500 for any other errors
*/
api.route('/upload')
.post(csrf, (req: Request, res: Response) => {
try {
// Check if anything was actually uploaded
if (!req.files || Object.keys(req.files).length === 0)
return res.status(400).json({ error: 'No file uploaded.' });
const file: UploadedFile = req.files.file as UploadedFile; // Kludge to prevent a compiler error, only one file gets uploaded so this should be fine
// Check if the file is too large (see fileUpload.limits for the limit)
if (file.truncated)
return res.status(413).json({ error: 'File uploaded was too large.' });
// Check if the file is a python file
if (file.mimetype !== 'text/x-python')
return res.status(415).json({ error: 'File uploaded was not a Python file.' });
res.status(201).json({ file: file.name, path: file.tempFilePath, msg: 'File uploaded successfully.', csrf: req.csrfToken() });
} catch (err) {
// Generic error handler
res.status(500).json({ error: 'An unknown error occurred while uploading the file.', error_msg: err });
}
})
// Fallback
.all(csrf, (req: Request, res: Response) => {
res.set('Allow', 'POST');
res.status(405).json({ error: 'Method not allowed.' });
});
/*
Actuate the pendulum
POST /api/v1/actuate
Parameters:
name: The name of the file to run, currently unused
path: The path to the uploaded file on the server, passed in from /api/v1/upload on the website
Returns:
200:
{
"stdout": "Hello from Python!\n",
}
400 for when the file passed in is not a regular file
403 when the file is not accessible
500:
{
"error": "Program exited with error code 1.",
"error_msg": "NameError: name 'sleep' is not defined",
}
This route is probably a complete security nightmare. It allows anyone to run arbitrary Python code on the server.
Minimizing PE vectors like running this as an extremely low privilege user is a must.
*/
api.route('/actuate')
// Snyk error mitigation, should be fine since the rate limiting is already in place
// file deepcode ignore NoRateLimitingForExpensiveWebOperation: This is already rate limited by the website, so we don't need to do it again
.post(csrf, async (req: Request, res: Response) => {
// Make sure the file being requested to run exists
try {
await access(req.body.path);
} catch (err) {
return res.status(403).json({ error: 'File is not accessible or does not exist.' });
}
const stats: Stats = await stat(req.body.path);
// Make sure the file being requested to run is a regular file
if (!stats.isFile())
return res.status(400).json({ error: 'File is not a regular file.' });
// Make sure the file being requested to run is not a directory
if (stats.isDirectory())
return res.status(400).json({ error: 'File is a directory.' });
const escaped = quote( [ req.body.path ] );
// Run the code
/*
TODO:
- Potentially add the limiter to one-per-person here
- Add a timeout
- Communicate to the machine to give up (the user as well), maybe just kill the process?
- Make this more secure
- HOW?
*/
let output = '';
const actuation = spawn('python', escaped.split(' '));
actuation.stdout.on('data', (data: Buffer) => {
output += data.toString();
});
actuation.stderr.on('data', (data: Buffer) => {
output += `STDERR: ${data.toString()}`;
});
actuation.on('close', (code: number) => {
if (code !== 0)
res.status(500).json({ error: `Program exited with exit code ${code}`, error_msg: output });
res.status(200).json({ stdout: output });
});
})
// Fallback
.all(csrf, (req: Request, res: Response) => {
res.set('Allow', 'POST');
res.status(405).json({ error: 'Method not allowed.' });
});
export default api;
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