scratch/test_decrypt.js

const crypto = require('crypto');

function deriveKeyAndIv(password, salt) {
    const passwordBuf = Buffer.from(password, 'utf8');
    let key = Buffer.alloc(0);
    let iv = Buffer.alloc(0);
    let lastHash = Buffer.alloc(0);

    while (key.length + iv.length < 48) {
        const hash = crypto.createHash('md5');
        hash.update(lastHash);
        hash.update(passwordBuf);
        hash.update(salt);
        lastHash = hash.digest();

        let remaining = lastHash;
        if (key.length < 32) {
            const keyToCopy = Math.min(32 - key.length, remaining.length);
            key = Buffer.concat([key, remaining.slice(0, keyToCopy)]);
            remaining = remaining.slice(keyToCopy);
        }

        if (remaining.length > 0 && iv.length < 16) {
            const ivToCopy = Math.min(16 - iv.length, remaining.length);
            iv = Buffer.concat([iv, remaining.slice(0, ivToCopy)]);
        }
    }

    return { key, iv };
}

function decrypt(ciphertext, password) {
    try {
        const buffer = Buffer.from(ciphertext, 'base64');

        if (buffer.slice(0, 8).toString('utf8') !== 'Salted__') {
            console.log('Invalid prefix');
            return null;
        }

        const salt = buffer.slice(8, 16);
        const encryptedData = buffer.slice(16);

        const keyIv = deriveKeyAndIv(password, salt);

        const decipher = crypto.createDecipheriv('aes-256-cbc', keyIv.key, keyIv.iv);
        let decrypted = decipher.update(encryptedData);
        decrypted = Buffer.concat([decrypted, decipher.final()]);

        return decrypted.toString('utf8');
    } catch (e) {
        console.log('Error:', e.message);
        return null;
    }
}

const key = "jb%!SZfM%AwwS7JmdM!";
const raw = "U2FsdGVkX19FssG+jADYfE/OYAT3jc+GMe+0/PII+aocWAvEBLte2kN5BTeLZ5+Xk3Tuo/H+6tSqMn49Juxdsg==";

console.log('Decrypted:', decrypt(raw, key));