Decrypt passwords from asp.net membership framework in nodejs - asp.net

Question

I'm trying to decrypt passwords from membership framework in a node.js app.
They are able to be decrypted as I get get the plaintext version from the membership framework User.GetPassword().
I've tried the following, but this doesn't work:
let encryptedPassword = 'LqOz9My...';
let passwordSalt = 'JQ2...';
let validationKey = '0123456789ABCEF';
let decryptionKey = '0123456789ABCEF';
var algorithm = 'aes128';
var decipher = crypto.createDecipher(algorithm, decryptionKey);
var decryptedPassword = decipher.update(encryptedPassword, 'utf8', 'utf8') + decipher.final('utf8');

Answer 1

Here's the solution:
let salt = '<my base64 salt>';
let saltBuffer = Buffer.from(salt, 'base64'); // 16 bytes
let decryptionKey = '<my hex decryption key>';
let decryptionKeyBuffer = Buffer.from(decryptionKey, 'hex'); // 24 bytes
var algorithm = 'aes192';
let encryptedPassword = '<my base64 encoded, encrypted string>';
var decipher = crypto.createDecipheriv(algorithm, decryptionKeyBuffer, saltBuffer);
decipher.setAutoPadding(false);
var dec = decipher.update(encryptedPassword, 'base64', 'utf8');
dec += decipher.final('utf8');
console.log(dec);
The problem was that I was using the wrong encoding and wrong encryption. Here's how I figured it out.
Encryption
You can easily determine the encryption algorithm type via the length of your decryption key. In my case, once I converted the key to a Buffer, the length was 24, and because 24 * 8 = 192, my algo was aes192;
Encoding
In my original example, I had the encoding of the encrypted password as utf8. The encoding actually was base64. Not sure how to determine this other than trying the various accepted params.