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128 lines
4.2 KiB
Python
128 lines
4.2 KiB
Python
import base64
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import hashlib
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import logging
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from collections import namedtuple
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import six
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from cryptography.fernet import Fernet, InvalidToken
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from cryptography.hazmat.backends import default_backend
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from django.utils.encoding import smart_str
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__all__ = ['get_encryption_key', 'encrypt_value', 'encrypt_field',
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'decrypt_field', 'decrypt_value']
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logger = logging.getLogger('awx.main.utils.encryption')
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class Fernet256(Fernet):
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'''Not techincally Fernet, but uses the base of the Fernet spec and uses AES-256-CBC
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instead of AES-128-CBC. All other functionality remain identical.
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'''
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def __init__(self, key, backend=None):
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if backend is None:
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backend = default_backend()
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key = base64.urlsafe_b64decode(key)
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if len(key) != 64:
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raise ValueError(
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"Fernet key must be 64 url-safe base64-encoded bytes."
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)
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self._signing_key = key[:32]
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self._encryption_key = key[32:]
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self._backend = backend
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def get_encryption_key(field_name, pk=None):
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'''
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Generate key for encrypted password based on field name,
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``settings.SECRET_KEY``, and instance pk (if available).
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:param pk: (optional) the primary key of the model object;
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can be omitted in situations where you're encrypting a setting
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that is not database-persistent (like a read-only setting)
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'''
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from django.conf import settings
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h = hashlib.sha512()
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h.update(settings.SECRET_KEY)
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if pk is not None:
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h.update(str(pk))
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h.update(field_name)
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return base64.urlsafe_b64encode(h.digest())
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def encrypt_value(value, pk=None):
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TransientField = namedtuple('TransientField', ['pk', 'value'])
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return encrypt_field(TransientField(pk=pk, value=value), 'value')
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def encrypt_field(instance, field_name, ask=False, subfield=None, skip_utf8=False):
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'''
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Return content of the given instance and field name encrypted.
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'''
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value = getattr(instance, field_name)
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if isinstance(value, dict) and subfield is not None:
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value = value[subfield]
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if not value or value.startswith('$encrypted$') or (ask and value == 'ASK'):
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return value
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if skip_utf8:
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utf8 = False
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else:
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utf8 = type(value) == six.text_type
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value = smart_str(value)
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key = get_encryption_key(field_name, getattr(instance, 'pk', None))
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f = Fernet256(key)
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encrypted = f.encrypt(value)
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b64data = base64.b64encode(encrypted)
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tokens = ['$encrypted', 'AESCBC', b64data]
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if utf8:
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# If the value to encrypt is utf-8, we need to add a marker so we
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# know to decode the data when it's decrypted later
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tokens.insert(1, 'UTF8')
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return '$'.join(tokens)
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def decrypt_value(encryption_key, value):
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raw_data = value[len('$encrypted$'):]
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# If the encrypted string contains a UTF8 marker, discard it
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utf8 = raw_data.startswith('UTF8$')
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if utf8:
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raw_data = raw_data[len('UTF8$'):]
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algo, b64data = raw_data.split('$', 1)
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if algo != 'AESCBC':
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raise ValueError('unsupported algorithm: %s' % algo)
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encrypted = base64.b64decode(b64data)
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f = Fernet256(encryption_key)
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value = f.decrypt(encrypted)
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# If the encrypted string contained a UTF8 marker, decode the data
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if utf8:
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value = value.decode('utf-8')
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return value
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def decrypt_field(instance, field_name, subfield=None):
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'''
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Return content of the given instance and field name decrypted.
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'''
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value = getattr(instance, field_name)
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if isinstance(value, dict) and subfield is not None:
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value = value[subfield]
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if not value or not value.startswith('$encrypted$'):
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return value
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key = get_encryption_key(field_name, getattr(instance, 'pk', None))
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try:
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return decrypt_value(key, value)
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except InvalidToken:
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logger.exception(
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"Failed to decrypt `%s(pk=%s).%s`; if you've recently restored from "
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"a database backup or are running in a clustered environment, "
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"check that your `SECRET_KEY` value is correct",
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instance.__class__.__name__,
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getattr(instance, 'pk', None),
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field_name,
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exc_info=True
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)
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raise
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