Standard Notes protocol v004 reference decryption demo

sn004-demo.py

# Standard Notes protocol v004 reference decryption demo
# by Tanner Collin, MIT license
#
# Install dependencies in your Python 3 environment:
# pip install argon2-cffi requests pycryptodome
#
# do not use your real account
# use a fresh account so there's no 003 items
# or use this test account
email = 'standardnotes-fs004@domain.com'
password = 'testaccount'

import argon2
import hashlib
import json
import requests

from binascii import hexlify, unhexlify
from base64 import b64decode
from Crypto.Cipher import ChaCha20_Poly1305

p = dict(email=email, api='20200115')
r = requests.get('https://sync.standardnotes.org/auth/params', params=p)
auth_params = r.json()

print('Auth params:', auth_params)

print()
string_to_hash = email + ':' + auth_params['pw_nonce']
print('Hashing:', string_to_hash)
salt = hashlib.sha256(string_to_hash.encode()).hexdigest()[:32]
print('Salt:', salt)

argon2_hash = argon2.low_level.hash_secret_raw(
        secret=password.encode(),
        salt=unhexlify(salt),
        time_cost=5,
        memory_cost=65536,
        parallelism=1,
        hash_len=64,
        type=argon2.Type.ID,
    )
derived_key = hexlify(argon2_hash).decode()

print('Derived key:', derived_key, 'Length:', len(derived_key))

master_key = derived_key[:64]
server_password = derived_key[64:]

print()
print('Master key:', master_key)
print('Server password:', server_password)

d = dict(
        email=email,
        api='20200115',
        ephemeral=False,
        password=server_password,
    )
r = requests.post('https://sync.standardnotes.org/auth/sign_in', data=d)
sign_in = r.json()
session = sign_in['session']
key_params = sign_in['key_params']
user = sign_in['user']

print()
print('Session:', session)
print('Key params:', key_params)
print('User:', user)

h = {'Authorization': 'Bearer ' + session['access_token']}
d = dict(items=[], compute_integrity=True, limit=150, api='20200115')
r = requests.post('https://sync.standardnotes.org/items/sync', headers=h, data=d)
sync = r.json()

print()
print('retrieved_items:', sync['retrieved_items'])
print('sync_token', sync['sync_token'])

default_items_key = None
notes = {}

for item in sync['retrieved_items']:
    uuid = item['uuid']
    content = item['content']
    content_type = item['content_type']
    enc_item_key = item['enc_item_key']

    print()
    print('Processing item', uuid)
    print('    content_type', content_type)
    print('    Decrypting enc_item_key')

    version, nonce, ciphertext, encoded_authenticated_data = enc_item_key.split(':')
    authenticated_data = json.loads(b64decode(encoded_authenticated_data).decode())

    print('        version:', version)
    print('        nonce:', nonce)
    print('        ciphertext:', ciphertext)
    print('        auth data:', authenticated_data)

    if content_type == 'SN|ItemsKey':
        key = master_key
    else:
        key = default_items_key

    cipher = ChaCha20_Poly1305.new(key=unhexlify(key), nonce=unhexlify(nonce))
    item_key = cipher.decrypt(b64decode(ciphertext))[:-16].decode()
    print('        item_key', item_key)

    print('    Decrypting content')

    version, nonce, ciphertext, encoded_authenticated_data = content.split(':')
    authenticated_data = json.loads(b64decode(encoded_authenticated_data).decode())

    print('        version:', version)
    print('        nonce:', nonce)
    print('        ciphertext:', ciphertext)
    print('        auth data:', authenticated_data)

    cipher = ChaCha20_Poly1305.new(key=unhexlify(item_key), nonce=unhexlify(nonce))
    plaintext = cipher.decrypt(b64decode(ciphertext))[:-16].decode()
    print('        plaintext', plaintext)

    plainjson = json.loads(plaintext)
    
    if plainjson.get('isDefault', False):
        default_items_key = plainjson['itemsKey']

    if content_type == 'Note':
        notes[plainjson['title']] = plainjson['text']

print()
print()
print('Here are your notes:')

for title, text in notes.items():
    print()
    print(title)
    print(text)