120 lines
4.3 KiB
Python
120 lines
4.3 KiB
Python
import base64
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import datetime
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import hashlib
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import hmac
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import random
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import secrets
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import urllib.parse
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from django.utils.encoding import smart_bytes
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from django.utils.http import quote, urlencode
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class SignatureError(Exception):
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pass
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def sign_url(url, key, algo='sha256', timestamp=None, nonce=None):
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parsed = urllib.parse.urlparse(url)
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new_query = sign_query(parsed.query, key, algo, timestamp, nonce)
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return urllib.parse.urlunparse(parsed[:4] + (new_query,) + parsed[5:])
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def sign_query(query, key, algo='sha256', timestamp=None, nonce=None):
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if timestamp is None:
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timestamp = datetime.datetime.utcnow()
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timestamp = timestamp.strftime('%Y-%m-%dT%H:%M:%SZ')
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if nonce is None:
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nonce = hex(random.getrandbits(128))[2:]
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new_query = query
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if new_query:
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new_query += '&'
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new_query += urlencode((('algo', algo), ('timestamp', timestamp)))
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if nonce: # we don't add nonce if it's an empty string
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new_query += '&nonce=' + quote(nonce)
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signature = base64.b64encode(sign_string(new_query, key, algo=algo))
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new_query += '&signature=' + quote(signature)
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return new_query
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def sign_string(s, key, algo='sha256'):
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digestmod = getattr(hashlib, algo)
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if isinstance(key, str):
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key = key.encode('utf-8')
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hash = hmac.HMAC(smart_bytes(key), digestmod=digestmod, msg=smart_bytes(s))
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return hash.digest()
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def check_url(url, key, known_nonce=None, timedelta=30, raise_on_error=False):
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parsed = urllib.parse.urlparse(url, 'https')
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return check_query(
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parsed.query, key, known_nonce=known_nonce, timedelta=timedelta, raise_on_error=raise_on_error
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)
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def check_query(query, key, known_nonce=None, timedelta=30, raise_on_error=False):
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parsed = urllib.parse.parse_qs(query)
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parsed = {key: value[0] if len(value) == 1 else value for key, value in parsed.items()}
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signature = parsed.get('signature')
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if not signature or not isinstance(signature, str):
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if raise_on_error:
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raise SignatureError('multiple/missing signature')
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return False
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algo = parsed.get('algo')
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if not algo or not isinstance(algo, str):
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if raise_on_error:
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raise SignatureError('multiple/missing algo')
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return False
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if algo != 'sha256':
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if raise_on_error:
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raise SignatureError('invalid algo, must be sha256')
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return False
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timestamp = parsed.get('timestamp')
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if not timestamp or not isinstance(timestamp, str):
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if raise_on_error:
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raise SignatureError('multiple/missing timestamp')
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return False
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if known_nonce is not None:
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nonce = parsed.get('nonce')
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if not nonce or not isinstance(nonce, str):
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if raise_on_error:
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raise SignatureError('multiple/missing nonce')
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return False
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if known_nonce(nonce):
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if raise_on_error:
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raise SignatureError('nonce replayed')
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return False
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unsigned_query, signature_content = query.split('&signature=', 1)
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if '&' in signature_content:
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if raise_on_error:
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raise SignatureError('signature is not the last parameter')
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return False # signature must be the last parameter
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try:
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signature = base64.b64decode(signature)
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except ValueError:
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if raise_on_error:
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raise SignatureError('signature is invalid base64')
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return False
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try:
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timestamp = datetime.datetime.strptime(timestamp, '%Y-%m-%dT%H:%M:%SZ')
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except ValueError as e:
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if raise_on_error:
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raise SignatureError('invalid timestamp, %s' % e)
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return False
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delta = abs(datetime.datetime.utcnow() - timestamp)
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if delta > datetime.timedelta(seconds=timedelta):
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if raise_on_error:
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raise SignatureError('timestamp delta is more than %s seconds: %s' % (timedelta, delta))
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return False
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return check_string(unsigned_query, signature, key, algo=algo, raise_on_error=raise_on_error)
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def check_string(s, signature, key, algo='sha256', raise_on_error=False):
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# constant time compare
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signature2 = sign_string(s, key, algo=algo)
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if not secrets.compare_digest(signature, signature2):
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if raise_on_error:
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raise SignatureError('HMAC hash is different')
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return False
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return True
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