openwebrx-clone/owrx/receiverid.py

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import re
import logging
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import hashlib
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import hmac
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from datetime import datetime, timezone
from owrx.config import Config
logger = logging.getLogger(__name__)
keyRegex = re.compile("^([a-zA-Z]+)-([0-9a-f]{32})-([0-9a-f]{64})$")
keyChallengeRegex = re.compile("^([a-zA-Z]+)-([0-9a-f]{32})-([0-9a-f]{32})$")
headerRegex = re.compile("^ReceiverId (.*)$")
class KeyException(Exception):
pass
class Key(object):
def __init__(self, keyString):
matches = keyRegex.match(keyString)
if not matches:
raise KeyException("invalid key format")
self.source = matches.group(1)
self.id = matches.group(2)
self.secret = matches.group(3)
class KeyChallenge(object):
def __init__(self, challengeString):
matches = keyChallengeRegex.match(challengeString)
if not matches:
raise KeyException("invalid key challenge format")
self.source = matches.group(1)
self.id = matches.group(2)
self.challenge = matches.group(3)
class KeyResponse(object):
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def __init__(self, source, id, time, signature):
self.source = source
self.id = id
self.time = time
self.signature = signature
def __str__(self):
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return "{source}-{id}-{time}-{signature}".format(
source=self.source,
id=self.id,
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time=self.time,
signature=self.signature,
)
class ReceiverId(object):
@staticmethod
def getResponseHeader(requestHeader):
matches = headerRegex.match(requestHeader)
if not matches:
raise KeyException("invalid authorization header")
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challenges = [KeyChallenge(i) for i in matches.group(1).split(",")]
def signChallenge(challenge):
key = ReceiverId.findKey(challenge)
if key is None:
return
return ReceiverId.signChallenge(challenge, key)
responses = [signChallenge(c) for c in challenges]
return ",".join(str(r) for r in responses if r is not None)
@staticmethod
def findKey(challenge):
def parseKey(keyString):
try:
return Key(keyString)
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except KeyException as e:
logger.error(e)
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keys = [parseKey(keyString) for keyString in Config.get()['receiver_keys']]
keys = [key for key in keys if key is not None]
matching_keys = [key for key in keys if key.source == challenge.source and key.id == challenge.id]
if matching_keys:
return matching_keys[0]
return None
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@staticmethod
def signChallenge(challenge, key):
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now = datetime.utcnow().replace(microsecond=0, tzinfo=timezone.utc)
now_bytes = int(now.timestamp()).to_bytes(4, byteorder="big")
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m = hmac.new(bytes.fromhex(key.secret), digestmod=hashlib.sha256)
m.update(bytes.fromhex(challenge.challenge))
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m.update(now_bytes)
return KeyResponse(challenge.source, challenge.id, now_bytes.hex(), m.hexdigest())