Import Upstream version 4.12.4
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geos_one
247
ipaserver/custodia/message/kem.py
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247
ipaserver/custodia/message/kem.py
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# Copyright (C) 2015 Custodia Project Contributors - see LICENSE file
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from __future__ import absolute_import
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import os
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import time
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from jwcrypto.common import json_decode
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from jwcrypto.common import json_encode
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from jwcrypto.jwe import JWE
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from jwcrypto.jwk import JWK
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from jwcrypto.jws import JWS
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from jwcrypto.jwt import JWT
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from ipaserver.custodia.httpd.authorizers import SimplePathAuthz
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from ipaserver.custodia.log import getLogger
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from ipaserver.custodia.message.common import InvalidMessage
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from ipaserver.custodia.message.common import MessageHandler
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logger = getLogger(__name__)
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KEY_USAGE_SIG = 0
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KEY_USAGE_ENC = 1
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KEY_USAGE_MAP = {KEY_USAGE_SIG: 'sig', KEY_USAGE_ENC: 'enc'}
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class UnknownPublicKey(Exception):
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def __init__(self, message=None):
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logger.debug(message)
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super(UnknownPublicKey, self).__init__(message)
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class KEMKeysStore(SimplePathAuthz):
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"""A KEM Keys Store.
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This is a store that holds public keys of registered
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clients allowed to use KEM messages. It takes the form
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of an authorizer merely for the purpose of attaching
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itself to a 'request' so that later on the KEM Parser
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can fetch the appropriate key to verify/decrypt an
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incoming request and make the payload available.
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The KEM Parser will actually perform additional
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authorization checks in this case.
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SimplePathAuthz is extended here as we ant to attach the
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store only to requests on paths we are configured to
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manage.
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"""
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def __init__(self, config):
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super(KEMKeysStore, self).__init__(config)
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self._server_keys = None
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self._alg = None
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self._enc = None
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def _db_key(self, kid):
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return os.path.join('kemkeys', kid)
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def handle(self, request):
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inpath = super(KEMKeysStore, self).handle(request)
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if inpath:
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request['KEMKeysStore'] = self
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return inpath
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def find_key(self, kid, usage):
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dbkey = self._db_key('%s/%s' % (KEY_USAGE_MAP[usage], kid))
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pubkey = self.store.get(dbkey)
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if pubkey is None:
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raise UnknownPublicKey(kid)
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return pubkey
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@property
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def server_keys(self):
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if self._server_keys is None:
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if 'server_keys' not in self.config:
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raise UnknownPublicKey("Server Keys not defined")
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skey = self.find_key(self.config['server_keys'], KEY_USAGE_SIG)
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ekey = self.find_key(self.config['server_keys'], KEY_USAGE_ENC)
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self._server_keys = [JWK(**(json_decode(skey))),
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JWK(**(json_decode(ekey)))]
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return self._server_keys
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@property
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def alg(self):
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if self._alg is None:
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alg = self.config.get('signing_algorithm', None)
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if alg is None:
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ktype = self.server_keys[KEY_USAGE_SIG]['kty']
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if ktype == 'RSA':
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alg = 'RS256'
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elif ktype == 'EC':
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alg = 'ES256'
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else:
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raise ValueError('Key type unsupported for signing')
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self._alg = alg
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return self._alg
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def check_kem_claims(claims, name):
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if 'sub' not in claims:
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raise InvalidMessage('Missing subject in payload')
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if claims['sub'] != name:
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raise InvalidMessage('Key name %s does not match subject %s' % (
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name, claims['sub']))
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if 'exp' not in claims:
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raise InvalidMessage('Missing expiration time in payload')
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if claims['exp'] - (10 * 60) > int(time.time()):
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raise InvalidMessage('Message expiration too far in the future')
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if claims['exp'] < int(time.time()):
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raise InvalidMessage('Message Expired')
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class KEMHandler(MessageHandler):
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"""Handles 'kem' messages"""
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def __init__(self, request):
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super(KEMHandler, self).__init__(request)
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self.kkstore = self.req.get('KEMKeysStore', None)
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if self.kkstore is None:
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raise Exception('KEM KeyStore not configured')
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self.client_keys = None
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self.name = None
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def _get_key(self, header, usage):
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if 'kid' not in header:
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raise InvalidMessage("Missing key identifier")
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key = self.kkstore.find_key(header.get('kid'), usage)
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if key is None:
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raise UnknownPublicKey('Key found [kid:%s]' % header.get('kid'))
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return json_decode(key)
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def parse(self, msg, name):
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"""Parses the message.
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We check that the message is properly formatted.
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:param msg: a json-encoded value containing a JWS or JWE+JWS token
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:raises InvalidMessage: if the message cannot be parsed or validated
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:returns: A verified payload
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"""
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try:
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jtok = JWT(jwt=msg)
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except Exception as e:
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raise InvalidMessage('Failed to parse message: %s' % str(e))
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try:
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token = jtok.token
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if isinstance(token, JWE):
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token.decrypt(self.kkstore.server_keys[KEY_USAGE_ENC])
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# If an encrypted payload is received then there must be
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# a nested signed payload to verify the provenance.
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payload = token.payload.decode('utf-8')
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token = JWS()
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token.deserialize(payload)
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elif isinstance(token, JWS):
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pass
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else:
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raise TypeError("Invalid Token type: %s" % type(jtok))
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# Retrieve client keys for later use
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self.client_keys = [
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JWK(**self._get_key(token.jose_header, KEY_USAGE_SIG)),
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JWK(**self._get_key(token.jose_header, KEY_USAGE_ENC))]
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# verify token and get payload
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token.verify(self.client_keys[KEY_USAGE_SIG])
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claims = json_decode(token.payload)
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except Exception as e:
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logger.debug('Failed to validate message', exc_info=True)
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raise InvalidMessage('Failed to validate message: %s' % str(e))
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check_kem_claims(claims, name)
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self.name = name
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self.payload = claims.get('value')
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self.msg_type = 'kem'
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return {'type': self.msg_type,
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'value': {'kid': self.client_keys[KEY_USAGE_ENC].get('kid'),
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'claims': claims}}
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def reply(self, output):
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if self.client_keys is None:
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raise UnknownPublicKey("Peer key not defined")
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ktype = self.client_keys[KEY_USAGE_ENC]['kty']
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if ktype == 'RSA':
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enc = ('RSA-OAEP', 'A256CBC-HS512')
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else:
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raise ValueError("'%s' type not supported yet" % ktype)
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value = make_enc_kem(self.name, output,
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self.kkstore.server_keys[KEY_USAGE_SIG],
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self.kkstore.alg,
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self.client_keys[1], enc)
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return {'type': 'kem', 'value': value}
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class KEMClient:
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def __init__(self, server_keys, client_keys):
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self.server_keys = server_keys
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self.client_keys = client_keys
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def make_request(self, name, value=None, alg="RS256", encalg=None):
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if encalg is None:
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return make_sig_kem(name, value,
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self.client_keys[KEY_USAGE_SIG], alg)
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else:
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return make_enc_kem(name, value,
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self.client_keys[KEY_USAGE_SIG], alg,
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self.server_keys[KEY_USAGE_ENC], encalg)
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def parse_reply(self, name, message):
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claims = decode_enc_kem(message,
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self.client_keys[KEY_USAGE_ENC],
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self.server_keys[KEY_USAGE_SIG])
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check_kem_claims(claims, name)
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return claims['value']
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def make_sig_kem(name, value, key, alg):
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header = {'kid': key.get('kid'), 'alg': alg}
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claims = {'sub': name, 'exp': int(time.time() + (5 * 60))}
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if value is not None:
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claims['value'] = value
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jwt = JWT(header, claims)
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jwt.make_signed_token(key)
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return jwt.serialize(compact=True)
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def make_enc_kem(name, value, sig_key, alg, enc_key, enc):
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plaintext = make_sig_kem(name, value, sig_key, alg)
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eprot = {'kid': enc_key.get('kid'), 'alg': enc[0], 'enc': enc[1]}
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jwe = JWE(plaintext, json_encode(eprot))
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jwe.add_recipient(enc_key)
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return jwe.serialize(compact=True)
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def decode_enc_kem(message, enc_key, sig_key):
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jwe = JWT(jwt=message, key=enc_key)
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jws = JWT(jwt=jwe.claims, key=sig_key)
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return json_decode(jws.claims)
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