87 lines
2.8 KiB
Python
87 lines
2.8 KiB
Python
# authentic2 - versatile identity manager
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# Copyright (C) 2010-2019 Entr'ouvert
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#
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# This program is free software: you can redistribute it and/or modify it
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# under the terms of the GNU Affero General Public License as published
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# by the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU Affero General Public License for more details.
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#
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# You should have received a copy of the GNU Affero General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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import hashlib
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import logging
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import time
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from django.core.cache import cache
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class ExponentialRetryTimeout:
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FACTOR = 1.8
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DURATION = 0.8
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MAX_DURATION = 3600 # max 1 hour
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KEY_PREFIX = 'exp-backoff-'
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CACHE_DURATION = 86400
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def __init__(
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self,
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factor=FACTOR,
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duration=DURATION,
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max_duration=MAX_DURATION,
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key_prefix=None,
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cache_duration=CACHE_DURATION,
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):
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self.factor = factor
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self.duration = duration
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self.max_duration = max_duration
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self.cache_duration = cache_duration
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self.logger = logging.getLogger(__name__)
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self.key_prefix = key_prefix
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def key(self, keys):
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key = '-'.join(str(key) for key in keys)
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key = key.encode('utf-8')
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return '%s%s' % (self.key_prefix or self.KEY_PREFIX, hashlib.md5(key).hexdigest())
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def seconds_to_wait(self, *keys):
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"""Return the duration in seconds until the next time when an action can be
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done.
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"""
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key = self.key(keys)
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if self.duration:
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now = time.time()
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what = cache.get(key)
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if what and what[1] > now:
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return what[1] - now
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return 0
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def success(self, *keys):
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"""Signal an action success, delete exponential backoff cache."""
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key = self.key(keys)
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if not self.duration:
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return
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cache.delete(key)
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self.logger.debug('success for %s', keys)
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def failure(self, *keys):
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"""Signal an action failure, augment the exponential backoff one level."""
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key = self.key(keys)
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if not self.duration:
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return
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what = cache.get(key)
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if not what:
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now = time.time()
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level, next_time = 0, now + self.duration
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else:
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level, next_time = what
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level += 1
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duration = min(self.duration * self.factor ** level, self.max_duration)
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next_time += duration
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cache.set(key, (level, next_time), self.cache_duration)
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self.logger.debug('failure for %s, level: %s, next_time: %s', keys, level, next_time)
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