Protect secrets from __repr__

[webknjaz]

Looking at https://github.com/hynek/environ_config and my internal attrs classes representing a token response from GitHub API etc.

I know about repr=False (and I saw this hack) but in my case I don't want to "hide" the attr existence. I want to be able to sanitize it's value.
At @ansible we have this feature where we can mark vars at different levels as no_log and they appeared as censored. I assume it's a quite widely used practice.

With that in mind I'm currently thinking of these few ways:

1. full protection

>>> repr(AttrsClass(secret='value'))
AttrsClass(secret=attr.CENSORED_VAL)  # hide everything

2. partially sanitized

>>> repr(AttrsClass(secret='value'))
AttrsClass(secret=attr.CENSORED_VAL('va...e'))  # show some helper parts usually sufficient to recognize that token is smth odd when debugging things

3. could be also useful to preserve a pattern

>>> repr(AttrsClass(secret='DFJ-3E3-DF83'))
AttrsClass(secret=attr.CENSORED_VAL('XXX-XXX-XXXX'))

P.S. I saw #212 and #453 but I believe this use-case should get a first-class support separately from those.

[wsanchez]

My feeling is that this feature is too specific to be in attrs proper, especially the partially sanitized and pattern aspects.

[RonnyPfannschmidt]

@webknjaz wouldn't this better be served by having a very specific string class and using it to encode secrets? then this would just be a converter as far as attrs is concerned

[webknjaz]

Maybe, yes. Just like this hack: https://github.com/hynek/environ_config/blob/69b1c8a/src/environ/secrets.py#L114-L124

[droserasprout]

A bunch of dirty hacks to mask secret values conditionally at the runtime:

from inspect import isclass

from attr import dataclass
from attr._make import _add_repr
from typing import NewType, Optional


class Secret:
    def __new__(cls, typ):
        return NewType('Secret', typ)(cls)


@dataclass(kw_only=True)
class SecretClass:
    top_secret: Secret(Optional[str])

    def mask_secrets(self):
        for attrib in self.__class__.__attrs_attrs__:
            if isclass(attrib.type) and issubclass(attrib.type, Secret):
                object.__setattr__(attrib, 'repr', lambda _: '[MASKED]')
        self.__class__ = _add_repr(self.__class__)

[hynek]

You can pass a callable for repr since 19.2 – should't that solve your problem?

[webknjaz]

I guess. It may take some time to actually try it out, though. I'll close this issue for now and will get back or create a new one if something won't satisfy my expectations. Thanks :)