Fix Command Injection in LoopBack
Command injection in LoopBack applications occurs when unsanitized user input is passed directly to system shell execution functions like child_process.exec. This allows attackers to execute arbitrary OS commands with the privileges of the Node.js process, leading to full system compromise.
The Vulnerable Pattern
const { exec } = require('child_process');
// In a LoopBack 4 Controller async runDiagnostic(@param.query.string(‘ip’) ip: string): Promise{ return new Promise((resolve, reject) => { // DANGER: String concatenation in exec() triggers a shell exec( ping -c 1 ${ip}, (error, stdout, stderr) => { if (error) return reject(error); resolve(stdout); }); }); }
The Secure Implementation
The vulnerability stems from 'child_process.exec', which spawns a /bin/sh (or cmd.exe) instance to parse the command string. Attackers can use shell metacharacters like ';', '&&', or '`' to inject their own commands. To remediate, use 'child_process.spawn' or 'child_process.execFile' which execute the binary directly without a shell, treating the input strictly as an argument. Additionally, implement strict allow-list regex validation on all parameters before they reach the process execution layer.
const { spawn } = require('child_process');// In a LoopBack 4 Controller async runDiagnostic(@param.query.string(‘ip’) ip: string): Promise
{ // 1. Strict input validation using regex if (!/^[a-zA-Z0-9.-]+$/.test(ip)) { throw new Error(‘Invalid input’); } return new Promise((resolve, reject) => { // 2. Use spawn or execFile with an arguments array to bypass shell interpretation const child = spawn(‘ping’, [‘-c’, ‘1’, ip]); let output = ”;
child.stdout.on('data', (data) => { output += data; }); child.stderr.on('data', (data) => { console.error(data.toString()); }); child.on('close', (code) => { if (code !== 0) reject(new Error('Process exited with code ' + code)); resolve(output); });
}); }
Your LoopBack API
might be exposed to Command Injection
74% of LoopBack apps fail this check. Hackers use automated scanners to find this specific flaw. Check your codebase before they do.
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