How to pickle namedtuple subclass with RSAPublicKey field

Question

I'm trying to serialize objects that subclass namedtuple and hold references to RSAPublicKey objects.

• I subclass a namedtuple to create immutable object instances.

• One of the fields of my class holds a reference to an object of type RSAPublicKey.

• I define __setstate__(self) to serialize the RSAPublicKey object for pickling.

class implementation

from collections import namedtuple

class MyClass(namedtuple('MyTuple', ['pub_key', 'foo'])):
    def __getstate__(self):
        return {
            'pub_key': serialize(self.pub_key),
            'foo': self.foo
        }

    def __repr__(self):
        return f'MyClass({serialize(self.pub_key)}, {self.foo})'

in use

import pickle

pr, pu = generate_keys()
my_obj = MyClass(pu, 4)

key generation and serialization

from cryptography.hazmat.primitives.asymmetric import rsa
from cryptography.hazmat.primitives import serialization
from cryptography.hazmat.backends import default_backend

def generate_keys():
    priv = rsa.generate_private_key(
        public_exponent=65537,
        key_size=2048,
        backend=default_backend()
    )
    return priv, priv.public_key()

def serialize(key):
    return key.public_bytes(
        serialization.Encoding.PEM,
        serialization.PublicFormat.SubjectPublicKeyInfo
    )

I get the following error.

TypeError                                 Traceback (most recent call last)
<ipython-input-14-cb7f2cfd2a4d> in <module>
      1 with open('save.dat', 'wb') as f:
----> 2     pickle.dump(my_obj, f)

TypeError: can't pickle CompiledFFI objects

When I change my class to subclass object, the serialization works correctly.

class MyClass():
    def __init__(self, pub_key, foo):
        self.pub_key = pub_key
        self.foo = foo

    def __getstate__(self):
        return {
            'pub_key': serialize(self.pub_key),
            'foo': self.foo
        }

    def __repr__(self):
        return f'MyClass({serialize(self.pub_key)}, {self.foo})'

Answer 1

this will work:

from collections import namedtuple

class MyClass(namedtuple('MyTuple', ['pub_key', 'foo'])):
    def __getstate__(self):
        return {
            'pub_key': serialize(self.pub_key),
            'foo': self.foo
        }

    def __repr__(self):
        return f'MyClass({serialize(self.pub_key)}, {self.foo})'




#key generation and serialization

from cryptography.hazmat.primitives.asymmetric import rsa
from cryptography.hazmat.primitives import serialization
from cryptography.hazmat.backends import default_backend

def generate_keys():
    priv = rsa.generate_private_key(
        public_exponent=65537,
        key_size=2048,
        backend=default_backend()
    )
    return priv, priv.public_key()

def serialize(key):
    return key.public_bytes(
        serialization.Encoding.PEM,
        serialization.PublicFormat.SubjectPublicKeyInfo
    )
import pickle
#dumping
pr, pu = generate_keys()
my_obj = MyClass(pu, 4)

with open('save.dat', 'wb') as f:
    #getting the data from the class
    pickle.dump(my_obj.__getstate__(), f)

it is the same but i use getstate to get the data and not the whole class