fernet_inspector 0.1.6

inspect fernet tokens generated by keystone

A tool for inspecting the contents of a Keystone Fernet token, with respect to the server it was generated from. The contents of a token can then be unpacked and mapped using the appropriate token format. This tool is designed to be an inspection tool and does not guarantee consistent format of the token payload.

Installation

$ pip install fernet-inspector

Usage

>>> fernet-inspector -h
usage: fernet-inspector [-h] [-k KEY_REPOSITORY] token

Inspect the contents of a Keystone Fernet token from the host it was issued
from.

positional arguments:
  token                 token to decrypt

optional arguments:
  -h, --help            show this help message and exit
  -k KEY_REPOSITORY, --key-repository KEY_REPOSITORY
                        location of Fernet key repository.

You should be able to decrypt a Fernet token and get the resulting payload:

>>> fernet-inspector <token-to-decrypt>
[2, '\xb0>\xd9\x14\x03kF\xb3\x94\xc9@A\x9e\x12\xda\x0f', 1, 'Z\xce\xd8U5ZH\xf6\xae\xd8n@;\x9a\x98`', 1442338543.238753, ['\xf0\xa8\x03T\x07\xbaJk\x8c;G\x9cG\xab\xdfX']]

This tool is only meant to supply information about a token. It’s not intended to make assumptions about a particular token format, or assertions about the order in which the data was packed.

Warning

The order and contents of any particular token format are subject to change at any time.

Now you can map to the appropriate payload based on the first element of the payload, which is the token version. In this case, the first element is 2, which means we are dealing with a ProjectScopedPayload of the keystone.token.providers.fernet.token_formatter.py:TokenFormatter class.

Handling Audit IDs

Audit IDs can be converted to their base64 representation with the following:

>>> import base64
>>> base64.urlsafe_b64encode('\xf0\xa8\x03T\x07\xbaJk\x8c;G\x9cG\xab\xdfX')
'8KgDVAe6SmuMOecR6vfWA=='

Handling UUIDs

Most unique identifiers packed into the token are converted from UUID.hex to their respective UUID.bytes representation. This results in a shorter overall token. The UUID.bytes representation of the token can be converted back to UUID.hex with the following:

>>> import uuid
>>> uuid.UUID(bytes='\xb0>\xd9\x14\x03kF\xb3\x94\xc9@A\x9e\x12\xda\x0f').hex
'b03ed914036b46b394c940419e12da0f'

Handling Timestamps

The expiration of a token is converted to an integer because it saves space in the token. The integer can be converted back to the original datetime object with the following:

>>> import datetime
>>> datetime.datetime.utcfromtimestamp(1442338543.238753)
datetime.datetime(2015, 9, 15, 17, 35, 43, 238753)