diff options
Diffstat (limited to 'synapse/federation/federation_base.py')
| -rw-r--r-- | synapse/federation/federation_base.py | 158 |
1 files changed, 136 insertions, 22 deletions
diff --git a/synapse/federation/federation_base.py b/synapse/federation/federation_base.py index c11798093d..b7ad729c63 100644 --- a/synapse/federation/federation_base.py +++ b/synapse/federation/federation_base.py @@ -13,17 +13,20 @@ # See the License for the specific language governing permissions and # limitations under the License. import logging +from collections import namedtuple import six from twisted.internet import defer +from twisted.internet.defer import DeferredList -from synapse.api.constants import MAX_DEPTH +from synapse.api.constants import MAX_DEPTH, EventTypes, Membership from synapse.api.errors import Codes, SynapseError from synapse.crypto.event_signing import check_event_content_hash from synapse.events import FrozenEvent from synapse.events.utils import prune_event from synapse.http.servlet import assert_params_in_dict +from synapse.types import get_domain_from_id from synapse.util import logcontext, unwrapFirstError logger = logging.getLogger(__name__) @@ -133,34 +136,45 @@ class FederationBase(object): * throws a SynapseError if the signature check failed. The deferreds run their callbacks in the sentinel logcontext. """ - - redacted_pdus = [ - prune_event(pdu) - for pdu in pdus - ] - - deferreds = self.keyring.verify_json_objects_for_server([ - (p.origin, p.get_pdu_json()) - for p in redacted_pdus - ]) + deferreds = _check_sigs_on_pdus(self.keyring, pdus) ctx = logcontext.LoggingContext.current_context() - def callback(_, pdu, redacted): + def callback(_, pdu): with logcontext.PreserveLoggingContext(ctx): if not check_event_content_hash(pdu): - logger.warn( - "Event content has been tampered, redacting %s: %s", - pdu.event_id, pdu.get_pdu_json() - ) - return redacted + # let's try to distinguish between failures because the event was + # redacted (which are somewhat expected) vs actual ball-tampering + # incidents. + # + # This is just a heuristic, so we just assume that if the keys are + # about the same between the redacted and received events, then the + # received event was probably a redacted copy (but we then use our + # *actual* redacted copy to be on the safe side.) + redacted_event = prune_event(pdu) + if ( + set(redacted_event.keys()) == set(pdu.keys()) and + set(six.iterkeys(redacted_event.content)) + == set(six.iterkeys(pdu.content)) + ): + logger.info( + "Event %s seems to have been redacted; using our redacted " + "copy", + pdu.event_id, + ) + else: + logger.warning( + "Event %s content has been tampered, redacting", + pdu.event_id, pdu.get_pdu_json(), + ) + return redacted_event if self.spam_checker.check_event_for_spam(pdu): logger.warn( "Event contains spam, redacting %s: %s", pdu.event_id, pdu.get_pdu_json() ) - return redacted + return prune_event(pdu) return pdu @@ -168,21 +182,121 @@ class FederationBase(object): failure.trap(SynapseError) with logcontext.PreserveLoggingContext(ctx): logger.warn( - "Signature check failed for %s", - pdu.event_id, + "Signature check failed for %s: %s", + pdu.event_id, failure.getErrorMessage(), ) return failure - for deferred, pdu, redacted in zip(deferreds, pdus, redacted_pdus): + for deferred, pdu in zip(deferreds, pdus): deferred.addCallbacks( callback, errback, - callbackArgs=[pdu, redacted], + callbackArgs=[pdu], errbackArgs=[pdu], ) return deferreds +class PduToCheckSig(namedtuple("PduToCheckSig", [ + "pdu", "redacted_pdu_json", "event_id_domain", "sender_domain", "deferreds", +])): + pass + + +def _check_sigs_on_pdus(keyring, pdus): + """Check that the given events are correctly signed + + Args: + keyring (synapse.crypto.Keyring): keyring object to do the checks + pdus (Collection[EventBase]): the events to be checked + + Returns: + List[Deferred]: a Deferred for each event in pdus, which will either succeed if + the signatures are valid, or fail (with a SynapseError) if not. + """ + + # (currently this is written assuming the v1 room structure; we'll probably want a + # separate function for checking v2 rooms) + + # we want to check that the event is signed by: + # + # (a) the server which created the event_id + # + # (b) the sender's server. + # + # - except in the case of invites created from a 3pid invite, which are exempt + # from this check, because the sender has to match that of the original 3pid + # invite, but the event may come from a different HS, for reasons that I don't + # entirely grok (why do the senders have to match? and if they do, why doesn't the + # joining server ask the inviting server to do the switcheroo with + # exchange_third_party_invite?). + # + # That's pretty awful, since redacting such an invite will render it invalid + # (because it will then look like a regular invite without a valid signature), + # and signatures are *supposed* to be valid whether or not an event has been + # redacted. But this isn't the worst of the ways that 3pid invites are broken. + # + # let's start by getting the domain for each pdu, and flattening the event back + # to JSON. + pdus_to_check = [ + PduToCheckSig( + pdu=p, + redacted_pdu_json=prune_event(p).get_pdu_json(), + event_id_domain=get_domain_from_id(p.event_id), + sender_domain=get_domain_from_id(p.sender), + deferreds=[], + ) + for p in pdus + ] + + # first make sure that the event is signed by the event_id's domain + deferreds = keyring.verify_json_objects_for_server([ + (p.event_id_domain, p.redacted_pdu_json) + for p in pdus_to_check + ]) + + for p, d in zip(pdus_to_check, deferreds): + p.deferreds.append(d) + + # now let's look for events where the sender's domain is different to the + # event id's domain (normally only the case for joins/leaves), and add additional + # checks. + pdus_to_check_sender = [ + p for p in pdus_to_check + if p.sender_domain != p.event_id_domain and not _is_invite_via_3pid(p.pdu) + ] + + more_deferreds = keyring.verify_json_objects_for_server([ + (p.sender_domain, p.redacted_pdu_json) + for p in pdus_to_check_sender + ]) + + for p, d in zip(pdus_to_check_sender, more_deferreds): + p.deferreds.append(d) + + # replace lists of deferreds with single Deferreds + return [_flatten_deferred_list(p.deferreds) for p in pdus_to_check] + + +def _flatten_deferred_list(deferreds): + """Given a list of one or more deferreds, either return the single deferred, or + combine into a DeferredList. + """ + if len(deferreds) > 1: + return DeferredList(deferreds, fireOnOneErrback=True, consumeErrors=True) + else: + assert len(deferreds) == 1 + return deferreds[0] + + +def _is_invite_via_3pid(event): + return ( + event.type == EventTypes.Member + and event.membership == Membership.INVITE + and "third_party_invite" in event.content + ) + + def event_from_pdu_json(pdu_json, outlier=False): """Construct a FrozenEvent from an event json received over federation |