piston/api/src/job.js

const logger = require('logplease').create('job');
const { v4: uuidv4 } = require('uuid');
const cp = require('child_process');
const path = require('path');
const config = require('./config');
const globals = require('./globals');
const fs = require('fs/promises');
const wait_pid = require('waitpid');

const job_states = {
    READY: Symbol('Ready to be primed'),
    PRIMED: Symbol('Primed and ready for execution'),
    EXECUTED: Symbol('Executed and ready for cleanup'),
};

let uid = 0;
let gid = 0;

class Job {
    constructor({ runtime, files, args, stdin, timeouts, memory_limits }) {
        this.uuid = uuidv4();
        this.runtime = runtime;
        this.files = files.map((file, i) => ({
            name: file.name || `file${i}.code`,
            content: file.content,
        }));

        this.args = args;
        this.stdin = stdin;
        this.timeouts = timeouts;
        this.memory_limits = memory_limits;

        this.uid = config.runner_uid_min + uid;
        this.gid = config.runner_gid_min + gid;

        uid++;
        gid++;

        uid %= config.runner_uid_max - config.runner_uid_min + 1;
        gid %= config.runner_gid_max - config.runner_gid_min + 1;

        this.state = job_states.READY;
        this.dir = path.join(
            config.data_directory,
            globals.data_directories.jobs,
            this.uuid
        );
    }

    async prime() {
        logger.info(`Priming job uuid=${this.uuid}`);

        logger.debug('Writing files to job cache');

        logger.debug(`Transfering ownership uid=${this.uid} gid=${this.gid}`);

        await fs.mkdir(this.dir, { mode: 0o700 });
        await fs.chown(this.dir, this.uid, this.gid);

        for (const file of this.files) {
            let file_path = path.join(this.dir, file.name);
            const rel = path.relative(this.dir, file_path);

            if(rel.startsWith(".."))
                throw Error(`File path "${file.name}" tries to escape parent directory: ${rel}`)

            await fs.mkdir(path.dirname(file_path), {recursive: true,  mode: 0o700})
            await fs.chown(path.dirname(file_path), this.uid, this.gid);

            await fs.write_file(file_path, file.content);
            await fs.chown(file_path, this.uid, this.gid);
        }

        this.state = job_states.PRIMED;

        logger.debug('Primed job');
    }

    async safe_call(file, args, timeout, memory_limit) {
        return new Promise((resolve, reject) => {
            const nonetwork = config.disable_networking ? ['nosocket'] : [];

            const prlimit = [
                'prlimit',
                '--nproc=' + config.max_process_count,
                '--nofile=' + config.max_open_files,
                '--fsize=' + config.max_file_size,
            ];

            if (memory_limit >= 0) {
                prlimit.push('--as=' + memory_limit);
            }

            const proc_call = [...prlimit, ...nonetwork, 'bash', file, ...args];

            var stdout = '';
            var stderr = '';
            var output = '';

            const proc = cp.spawn(proc_call[0], proc_call.splice(1), {
                env: {
                    ...this.runtime.env_vars,
                    PISTON_LANGUAGE: this.runtime.language,
                },
                stdio: 'pipe',
                cwd: this.dir,
                uid: this.uid,
                gid: this.gid,
                detached: true, //give this process its own process group
            });

            proc.stdin.write(this.stdin);
            proc.stdin.end();
            proc.stdin.destroy();

            const kill_timeout = set_timeout(
                _ => proc.kill('SIGKILL'),
                timeout
            );

            proc.stderr.on('data', data => {
                if (stderr.length > config.output_max_size) {
                    proc.kill('SIGKILL');
                } else {
                    stderr += data;
                    output += data;
                }
            });

            proc.stdout.on('data', data => {
                if (stdout.length > config.output_max_size) {
                    proc.kill('SIGKILL');
                } else {
                    stdout += data;
                    output += data;
                }
            });

            const exit_cleanup = () => {
                clear_timeout(kill_timeout);

                proc.stderr.destroy();
                proc.stdout.destroy();
            };

            proc.on('exit', (code, signal) => {
                exit_cleanup();

                resolve({stdout, stderr, code, signal, output });
            });

            proc.on('error', err => {
                exit_cleanup();

                reject({ error: err, stdout, stderr, output });
            });
        });
    }

    async execute() {
        if (this.state !== job_states.PRIMED) {
            throw new Error(
                'Job must be in primed state, current state: ' +
                    this.state.toString()
            );
        }

        logger.info(
            `Executing job uuid=${this.uuid} uid=${this.uid} gid=${
                this.gid
            } runtime=${this.runtime.toString()}`
        );

        logger.debug('Compiling');

        let compile;

        if (this.runtime.compiled) {
            compile = await this.safe_call(
                path.join(this.runtime.pkgdir, 'compile'),
                this.files.map(x => x.name),
                this.timeouts.compile,
                this.memory_limits.compile
            );
        }

        logger.debug('Running');

        const run = await this.safe_call(
            path.join(this.runtime.pkgdir, 'run'),
            [this.files[0].name, ...this.args],
            this.timeouts.run,
            this.memory_limits.run
        );

        this.state = job_states.EXECUTED;

        return {
            compile,
            run,
            language: this.runtime.language,
            version: this.runtime.version.raw,
        };
    }

    async cleanup_processes() {
        let processes = [1];

        while (processes.length > 0) {
            processes = await new Promise((resolve, reject) =>
                cp.execFile('ps', ['awwxo', 'pid,ruid'], (err, stdout) => {
                    if (err === null) {
                        const lines = stdout.split('\n').slice(1); //Remove header with slice
                        const procs = lines.map(line => {
                            const [pid, ruid] = line
                                .trim()
                                .split(/\s+/)
                                .map(n => parseInt(n));

                            return { pid, ruid };
                        });

                        resolve(procs);
                    } else {
                        reject(error);
                    }
                })
            );

            processes = processes.filter(proc => proc.ruid === this.uid);

            for (const proc of processes) {
                // First stop the processes, but keep their resources allocated so they cant re-fork
                try {
                    process.kill(proc.pid, 'SIGSTOP');
                } catch {
                    // Could already be dead
                }
            }

            for (const proc of processes) {
                // Then clear them out of the process tree
                try {
                    process.kill(proc.pid, 'SIGKILL');
                } catch {
                    // Could already be dead and just needs to be waited on
                }

                wait_pid(proc.pid);
            }
        }
    }

    async cleanup_filesystem() {
        for (const clean_path of globals.clean_directories) {
            const contents = await fs.readdir(clean_path);

            for (const file of contents) {
                const file_path = path.join(clean_path, file);

                try {
                    const stat = await fs.stat(file_path);

                    if (stat.uid === this.uid) {
                        await fs.rm(file_path, {
                            recursive: true,
                            force: true,
                        });
                    }
                } catch (e) {
                    // File was somehow deleted in the time that we read the dir to when we checked the file
                    logger.warn(`Error removing file ${file_path}: ${e}`);
                }
            }
        }

        await fs.rm(this.dir, { recursive: true, force: true });
    }

    async cleanup() {
        logger.info(`Cleaning up job uuid=${this.uuid}`);

        await this.cleanup_processes();
        await this.cleanup_filesystem();
    }
}

module.exports = {
    Job,
};