Ansible vault decryption in NodeJS

decrypt-ansible-vault.js

const crypto = require('crypto');

const password = "password";
const vault = `$ANSIBLE_VAULT;1.1;AES256
33343835306666636239373663396363643766613363343837646633343933376633323964663030
3134616235646661306436643134383333633730376233650a663466323032343633383061336461
36393261363338616337613039363435313631343437323164386661326633313339396238396236
3462393338636632650a653036663266373533343232393838343161396564333963643632653932
30386135636131656130346537356637396139323134386162306431376564346537633566666532
6331323061373237336639356165393563613765663864366231`;

const splitInput = (vault) => {

    const vaultNoHeader = vault.split("\n").slice(1).join("");
    const [salt, hmac, payload] = vaultNoHeader.split("0a").map(e => Buffer.from(e, "hex"));
    return [salt.toString(), hmac.toString(), payload.toString()];
}

const deriveKey = (password, salt, iterations = 10000, keyLen = 80, algo = "sha256") => {
    const saltBuffer = Buffer.from(salt.toString(), "hex")
    const derivedKey = crypto.pbkdf2Sync(password, saltBuffer, iterations, keyLen, algo);
    return derivedKey.toString("hex");
}

const checkHmac = (key, verify, algo = "sha256") => {
    const hmac = crypto.createHmac(algo, Buffer.from(key, "hex"));
    hmac.update(Buffer.from(payload, "hex"));

    const digest = hmac.digest().toString("hex")
    if (digest !== verify) {
        throw new Error("HMac invalid");
    }
}

const convert = (key, nonce, algo = 'aes-256-ctr') => {
    const decipher = crypto.createDecipheriv(algo, Buffer.from(key, "hex"), Buffer.from(nonce, "hex"));

    let decrypted = decipher.update(Buffer.from(payload, "hex"));
    decrypted = Buffer.concat([decrypted, decipher.final()]);

    return decrypted.toString("utf-8");
}

const [salt, hmac, payload] = splitInput(vault);
const derivedKey = deriveKey(password, salt);

const hmacKey = derivedKey.slice(64, 128);
const aesKey = derivedKey.slice(0, 64);
const nonce = derivedKey.slice(128);

checkHmac(hmacKey, hmac);

console.log(convert(aesKey, nonce));

This is basically a NodeJS version of what is described here: https://www.bloggingforlogging.com/2018/05/20/decrypting-the-secrets-of-ansible-vault-in-powershell/