Usei para baixar os arquivos fora do navegado do WhatsApp Web, quando usava https://github.com/mukulhase/WebWhatsapp-Wrapper

downloader.py

import os, sys, time, json
from base64 import b64decode, b64encode
from io import BytesIO
from axolotl.kdf.hkdfv3 import HKDFv3
from axolotl.util.byteutil import ByteUtil
import binascii
from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
from cryptography.hazmat.backends import default_backend
import mimetypes

import requests
class media_msg: pass
media_msg.content = ''
media_msg.client_url = 'https://mmg.whatsapp.net/d/f/Akj16wBZXU4Lz7ptWZwK-w4MD4CCnYp1dQJEHqgXrpC5.enc'
media_msg.media_key = 'B59MDEx062iyLoYYGCvVeNWcwILD2m+FFkCaYLgfkuc='
media_msg.crypt_keys = {'document': '576861747341707020446f63756d656e74204b657973',
                  'image'   : '576861747341707020496d616765204b657973',
                  'video'   : '576861747341707020566964656f204b657973',
                  'ptt'     : '576861747341707020417564696f204b657973',
                  'audio'   : '576861747341707020417564696f204b657973'}
media_msg.type = 'ptt'
media_msg.filename = ''
media_msg.mime = 'audio/ogg; codecs=opus'

if (media_msg.mime.find(";")==-1):
    extension = mimetypes.guess_extension(media_msg.mime)
else:
    extension = mimetypes.guess_extension(media_msg.mime[:media_msg.mime.find(";")])

media_msg.filename = ''.join([str(id(media_msg)), extension or ''])

def download_file(url):
    return requests.get(url).content

def download_media(media_msg, force_download=False):
    if not force_download:
        try:
            if media_msg.content:
                return BytesIO(b64decode(media_msg.content))
        except AttributeError:
            pass

    file_data = download_file(media_msg.client_url)

    if not file_data:
        raise Exception('Impossible to download file')

    media_key = b64decode(media_msg.media_key)
    derivative = HKDFv3().deriveSecrets(media_key,
                                        binascii.unhexlify(media_msg.crypt_keys[media_msg.type]),
                                        112)

    parts = ByteUtil.split(derivative, 16, 32)
    iv = parts[0]
    cipher_key = parts[1]
    e_file = file_data[:-10]

    cr_obj = Cipher(algorithms.AES(cipher_key), modes.CBC(iv), backend=default_backend())
    decryptor = cr_obj.decryptor()
    return BytesIO( decryptor.update(e_file) + decryptor.finalize())

def save_media(media_msg, path, force_download=False):
    # gets full media
    filename = os.path.join(path, media_msg.filename)
    ioobj = download_media(media_msg, force_download)
    with open(filename, "wb") as f:
        f.write(ioobj.getvalue())
    return filename

print(save_media(media_msg,'.',force_download=True))