Unable to decrypt aes-128-cbc in Node when encrypted in Python

Question

I made the following MRE to illustrate my problem. My Python code is taking a string, encrypting it with an ad-hoc created key and posting it to a Node server that is supposed to use the provided key for decryption.

• Using the console output I can see that the Python output (key and encrypted message) are the same on both systems (after base64 conversion for transfer).
• Also from another post on stackoverflow, I understand that the key generated by Pyhon is already base64 encoded and the decoded value needs to be split to extract the iv and key respectively.

However, I get an error saying that the iv length is invalid. I am not sure what I am doing wrong. Thanks for your hints.

Python Code fernet.py (Python 3.10.5 on Windows 11)

import requests
import base64
from cryptography.fernet import Fernet

def get_key():
    key = Fernet.generate_key()
    return key

def enc(input, key):
    f = Fernet(key)
    encrypted = f.encrypt(input.encode())
    return encrypted

msg = "hello world"
key = get_key()
cypher = enc(msg, key)
print("msg: " + msg)
print("key: " + key.decode())
print("cyp: " + cypher.decode())

url='http://.../test'
headers = {'Content-type': 'application/json'}
r = requests.post(url, data={"key": key, "msg": base64.b64encode(cypher)})

Output:

msg: hello world
key: bOe3HCoveTPhHi04FvvG697O2rEkwF9vuXeZcGgbu9k=
cyp: gAAAAABi0WYLxwlMG7RGKqISZABsPlmenUmN8Ii81rJBIQdSPGzi1-IHss4atZuGp4eZIdaiR7mpBah6cQmlXxw2DzY3Ct9d7A==

Here is my node server (12.22.09 running on a Ubuntu 22.04 VM)

const express = require('express');
const url = require('url');
const crypto = require('crypto');

const app = express();
const port = 8088;

app.use(express.urlencoded({extended: true, limit:'100mb', parameterLimit:1000000}));
app.disable('x-powered-by');

function decrypt(message, fernet) {
    let iv = Buffer.from(fernet, 'base64').toString('binary', 0, 16)
    let key = Buffer.from(fernet, 'base64').toString('binary', 16,32);
    let decoded_msg = Buffer.from(message, 'base64').toString('utf8');

    let decipher = crypto.createDecipheriv('aes-128-cbc', key, iv);
    let decrypted = decipher.update(decoded_msg, 'binary', 'utf8') + decipher.final('utf8');
    console.log(decrypted);

    return decrypted
}

app.post("/test", function(req, res) {
    
    let fernet = req.body.key;
    let message = req.body.msg;
    console.log("key: " + fernet);
    console.log("msg: " + Buffer.from(message, 'base64').toString('utf8'));
    
    let dec = decrypt(message, fernet);
    console.log("dec: " + dec);
    
    res.writeHead(200, {"Content-Type": "application/json"});
    res.end(JSON.stringify({"status": "OK"}));
});

app.listen(port, () => {
    console.log("Listening on localhost:" + port);
});

Output:

key: bOe3HCoveTPhHi04FvvG697O2rEkwF9vuXeZcGgbu9k=
msg: gAAAAABi0WYLxwlMG7RGKqISZABsPlmenUmN8Ii81rJBIQdSPGzi1-IHss4atZuGp4eZIdaiR7mpBah6cQmlXxw2DzY3Ct9d7A==

Error: Invalid IV length

    at Decipheriv.createCipherBase (internal/crypto/cipher.js:103:19)

    at Decipheriv.createCipherWithIV (internal/crypto/cipher.js:121:20)

    at new Decipheriv (internal/crypto/cipher.js:262:22)

    at Object.createDecipheriv (crypto.js:131:10)

    at decrypt (/.../app.js:55:24)