forked from s434650/CatOrNot
72 lines
2.6 KiB
Python
72 lines
2.6 KiB
Python
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"""
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A provided CSRF implementation which puts CSRF data in a session.
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This can be used fairly comfortably with many `request.session` type
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objects, including the Werkzeug/Flask session store, Django sessions, and
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potentially other similar objects which use a dict-like API for storing
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session keys.
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The basic concept is a randomly generated value is stored in the user's
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session, and an hmac-sha1 of it (along with an optional expiration time,
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for extra security) is used as the value of the csrf_token. If this token
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validates with the hmac of the random value + expiration time, and the
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expiration time is not passed, the CSRF validation will pass.
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"""
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from __future__ import unicode_literals
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import hmac
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import os
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from hashlib import sha1
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from datetime import datetime, timedelta
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from ...validators import ValidationError
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from .form import SecureForm
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__all__ = ('SessionSecureForm', )
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class SessionSecureForm(SecureForm):
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TIME_FORMAT = '%Y%m%d%H%M%S'
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TIME_LIMIT = timedelta(minutes=30)
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SECRET_KEY = None
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def generate_csrf_token(self, csrf_context):
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if self.SECRET_KEY is None:
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raise Exception('must set SECRET_KEY in a subclass of this form for it to work')
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if csrf_context is None:
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raise TypeError('Must provide a session-like object as csrf context')
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session = getattr(csrf_context, 'session', csrf_context)
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if 'csrf' not in session:
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session['csrf'] = sha1(os.urandom(64)).hexdigest()
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self.csrf_token.csrf_key = session['csrf']
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if self.TIME_LIMIT:
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expires = (datetime.now() + self.TIME_LIMIT).strftime(self.TIME_FORMAT)
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csrf_build = '%s%s' % (session['csrf'], expires)
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else:
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expires = ''
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csrf_build = session['csrf']
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hmac_csrf = hmac.new(self.SECRET_KEY, csrf_build.encode('utf8'), digestmod=sha1)
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return '%s##%s' % (expires, hmac_csrf.hexdigest())
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def validate_csrf_token(self, field):
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if not field.data or '##' not in field.data:
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raise ValidationError(field.gettext('CSRF token missing'))
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expires, hmac_csrf = field.data.split('##')
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check_val = (field.csrf_key + expires).encode('utf8')
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hmac_compare = hmac.new(self.SECRET_KEY, check_val, digestmod=sha1)
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if hmac_compare.hexdigest() != hmac_csrf:
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raise ValidationError(field.gettext('CSRF failed'))
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if self.TIME_LIMIT:
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now_formatted = datetime.now().strftime(self.TIME_FORMAT)
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if now_formatted > expires:
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raise ValidationError(field.gettext('CSRF token expired'))
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