diff options
Diffstat (limited to 'synapse/handlers/e2e_keys.py')
| -rw-r--r-- | synapse/handlers/e2e_keys.py | 391 |
1 files changed, 390 insertions, 1 deletions
diff --git a/synapse/handlers/e2e_keys.py b/synapse/handlers/e2e_keys.py index be675197f1..5ea54f60be 100644 --- a/synapse/handlers/e2e_keys.py +++ b/synapse/handlers/e2e_keys.py @@ -19,12 +19,15 @@ import logging from six import iteritems +import attr from canonicaljson import encode_canonical_json, json +from signedjson.key import decode_verify_key_bytes from signedjson.sign import SignatureVerifyException, verify_signed_json +from unpaddedbase64 import decode_base64 from twisted.internet import defer -from synapse.api.errors import CodeMessageException, Codes, SynapseError +from synapse.api.errors import CodeMessageException, Codes, NotFoundError, SynapseError from synapse.logging.context import make_deferred_yieldable, run_in_background from synapse.logging.opentracing import log_kv, set_tag, tag_args, trace from synapse.types import ( @@ -602,6 +605,339 @@ class E2eKeysHandler(object): return {} + @defer.inlineCallbacks + def upload_signatures_for_device_keys(self, user_id, signatures): + """Upload device signatures for cross-signing + + Args: + user_id (string): the user uploading the signatures + signatures (dict[string, dict[string, dict]]): map of users to + devices to signed keys. This is the submission from the user; an + exception will be raised if it is malformed. + Returns: + dict: response to be sent back to the client. The response will have + a "failures" key, which will be a dict mapping users to devices + to errors for the signatures that failed. + Raises: + SynapseError: if the signatures dict is not valid. + """ + failures = {} + + # signatures to be stored. Each item will be a SignatureListItem + signature_list = [] + + # split between checking signatures for own user and signatures for + # other users, since we verify them with different keys + self_signatures = signatures.get(user_id, {}) + other_signatures = {k: v for k, v in signatures.items() if k != user_id} + + self_signature_list, self_failures = yield self._process_self_signatures( + user_id, self_signatures + ) + signature_list.extend(self_signature_list) + failures.update(self_failures) + + other_signature_list, other_failures = yield self._process_other_signatures( + user_id, other_signatures + ) + signature_list.extend(other_signature_list) + failures.update(other_failures) + + # store the signature, and send the appropriate notifications for sync + logger.debug("upload signature failures: %r", failures) + yield self.store.store_e2e_cross_signing_signatures(user_id, signature_list) + + self_device_ids = [item.target_device_id for item in self_signature_list] + if self_device_ids: + yield self.device_handler.notify_device_update(user_id, self_device_ids) + signed_users = [item.target_user_id for item in other_signature_list] + if signed_users: + yield self.device_handler.notify_user_signature_update( + user_id, signed_users + ) + + return {"failures": failures} + + @defer.inlineCallbacks + def _process_self_signatures(self, user_id, signatures): + """Process uploaded signatures of the user's own keys. + + Signatures of the user's own keys from this API come in two forms: + - signatures of the user's devices by the user's self-signing key, + - signatures of the user's master key by the user's devices. + + Args: + user_id (string): the user uploading the keys + signatures (dict[string, dict]): map of devices to signed keys + + Returns: + (list[SignatureListItem], dict[string, dict[string, dict]]): + a list of signatures to store, and a map of users to devices to failure + reasons + + Raises: + SynapseError: if the input is malformed + """ + signature_list = [] + failures = {} + if not signatures: + return signature_list, failures + + if not isinstance(signatures, dict): + raise SynapseError(400, "Invalid parameter", Codes.INVALID_PARAM) + + try: + # get our self-signing key to verify the signatures + _, self_signing_key_id, self_signing_verify_key = yield self._get_e2e_cross_signing_verify_key( + user_id, "self_signing" + ) + + # get our master key, since we may have received a signature of it. + # We need to fetch it here so that we know what its key ID is, so + # that we can check if a signature that was sent is a signature of + # the master key or of a device + master_key, _, master_verify_key = yield self._get_e2e_cross_signing_verify_key( + user_id, "master" + ) + + # fetch our stored devices. This is used to 1. verify + # signatures on the master key, and 2. to compare with what + # was sent if the device was signed + devices = yield self.store.get_e2e_device_keys([(user_id, None)]) + + if user_id not in devices: + raise NotFoundError("No device keys found") + + devices = devices[user_id] + except SynapseError as e: + failure = _exception_to_failure(e) + failures[user_id] = {device: failure for device in signatures.keys()} + return signature_list, failures + + for device_id, device in signatures.items(): + # make sure submitted data is in the right form + if not isinstance(device, dict): + raise SynapseError(400, "Invalid parameter", Codes.INVALID_PARAM) + + try: + if "signatures" not in device or user_id not in device["signatures"]: + # no signature was sent + raise SynapseError( + 400, "Invalid signature", Codes.INVALID_SIGNATURE + ) + + if device_id == master_verify_key.version: + # The signature is of the master key. This needs to be + # handled differently from signatures of normal devices. + master_key_signature_list = self._check_master_key_signature( + user_id, device_id, device, master_key, devices + ) + signature_list.extend(master_key_signature_list) + continue + + # at this point, we have a device that should be signed + # by the self-signing key + if self_signing_key_id not in device["signatures"][user_id]: + # no signature was sent + raise SynapseError( + 400, "Invalid signature", Codes.INVALID_SIGNATURE + ) + + try: + stored_device = devices[device_id] + except KeyError: + raise NotFoundError("Unknown device") + if self_signing_key_id in stored_device.get("signatures", {}).get( + user_id, {} + ): + # we already have a signature on this device, so we + # can skip it, since it should be exactly the same + continue + + _check_device_signature( + user_id, self_signing_verify_key, device, stored_device + ) + + signature = device["signatures"][user_id][self_signing_key_id] + signature_list.append( + SignatureListItem( + self_signing_key_id, user_id, device_id, signature + ) + ) + except SynapseError as e: + failures.setdefault(user_id, {})[device_id] = _exception_to_failure(e) + + return signature_list, failures + + def _check_master_key_signature( + self, user_id, master_key_id, signed_master_key, stored_master_key, devices + ): + """Check signatures of a user's master key made by their devices. + + Args: + user_id (string): the user whose master key is being checked + master_key_id (string): the ID of the user's master key + signed_master_key (dict): the user's signed master key that was uploaded + stored_master_key (dict): our previously-stored copy of the user's master key + devices (iterable(dict)): the user's devices + + Returns: + list[SignatureListItem]: a list of signatures to store + + Raises: + SynapseError: if a signature is invalid + """ + # for each device that signed the master key, check the signature. + master_key_signature_list = [] + sigs = signed_master_key["signatures"] + for signing_key_id, signature in sigs[user_id].items(): + _, signing_device_id = signing_key_id.split(":", 1) + if ( + signing_device_id not in devices + or signing_key_id not in devices[signing_device_id]["keys"] + ): + # signed by an unknown device, or the + # device does not have the key + raise SynapseError(400, "Invalid signature", Codes.INVALID_SIGNATURE) + + # get the key and check the signature + pubkey = devices[signing_device_id]["keys"][signing_key_id] + verify_key = decode_verify_key_bytes(signing_key_id, decode_base64(pubkey)) + _check_device_signature( + user_id, verify_key, signed_master_key, stored_master_key + ) + + master_key_signature_list.append( + SignatureListItem(signing_key_id, user_id, master_key_id, signature) + ) + + return master_key_signature_list + + @defer.inlineCallbacks + def _process_other_signatures(self, user_id, signatures): + """Process uploaded signatures of other users' keys. These will be the + target user's master keys, signed by the uploading user's user-signing + key. + + Args: + user_id (string): the user uploading the keys + signatures (dict[string, dict]): map of users to devices to signed keys + + Returns: + (list[SignatureListItem], dict[string, dict[string, dict]]): + a list of signatures to store, and a map of users to devices to failure + reasons + + Raises: + SynapseError: if the input is malformed + """ + signature_list = [] + failures = {} + if not signatures: + return signature_list, failures + + try: + # get our user-signing key to verify the signatures + user_signing_key, user_signing_key_id, user_signing_verify_key = yield self._get_e2e_cross_signing_verify_key( + user_id, "user_signing" + ) + except SynapseError as e: + failure = _exception_to_failure(e) + for user, devicemap in signatures.items(): + failures[user] = {device_id: failure for device_id in devicemap.keys()} + return signature_list, failures + + for target_user, devicemap in signatures.items(): + # make sure submitted data is in the right form + if not isinstance(devicemap, dict): + raise SynapseError(400, "Invalid parameter", Codes.INVALID_PARAM) + for device in devicemap.values(): + if not isinstance(device, dict): + raise SynapseError(400, "Invalid parameter", Codes.INVALID_PARAM) + + device_id = None + try: + # get the target user's master key, to make sure it matches + # what was sent + master_key, master_key_id, _ = yield self._get_e2e_cross_signing_verify_key( + target_user, "master", user_id + ) + + # make sure that the target user's master key is the one that + # was signed (and no others) + device_id = master_key_id.split(":", 1)[1] + if device_id not in devicemap: + logger.debug( + "upload signature: could not find signature for device %s", + device_id, + ) + # set device to None so that the failure gets + # marked on all the signatures + device_id = None + raise NotFoundError("Unknown device") + key = devicemap[device_id] + other_devices = [k for k in devicemap.keys() if k != device_id] + if other_devices: + # other devices were signed -- mark those as failures + logger.debug("upload signature: too many devices specified") + failure = _exception_to_failure(NotFoundError("Unknown device")) + failures[target_user] = { + device: failure for device in other_devices + } + + if user_signing_key_id in master_key.get("signatures", {}).get( + user_id, {} + ): + # we already have the signature, so we can skip it + continue + + _check_device_signature( + user_id, user_signing_verify_key, key, master_key + ) + + signature = key["signatures"][user_id][user_signing_key_id] + signature_list.append( + SignatureListItem( + user_signing_key_id, target_user, device_id, signature + ) + ) + except SynapseError as e: + failure = _exception_to_failure(e) + if device_id is None: + failures[target_user] = { + device_id: failure for device_id in devicemap.keys() + } + else: + failures.setdefault(target_user, {})[device_id] = failure + + return signature_list, failures + + @defer.inlineCallbacks + def _get_e2e_cross_signing_verify_key(self, user_id, key_type, from_user_id=None): + """Fetch the cross-signing public key from storage and interpret it. + + Args: + user_id (str): the user whose key should be fetched + key_type (str): the type of key to fetch + from_user_id (str): the user that we are fetching the keys for. + This affects what signatures are fetched. + + Returns: + dict, str, VerifyKey: the raw key data, the key ID, and the + signedjson verify key + + Raises: + NotFoundError: if the key is not found + """ + key = yield self.store.get_e2e_cross_signing_key( + user_id, key_type, from_user_id + ) + if key is None: + logger.debug("no %s key found for %s", key_type, user_id) + raise NotFoundError("No %s key found for %s" % (key_type, user_id)) + key_id, verify_key = get_verify_key_from_cross_signing_key(key) + return key, key_id, verify_key + def _check_cross_signing_key(key, user_id, key_type, signing_key=None): """Check a cross-signing key uploaded by a user. Performs some basic sanity @@ -630,7 +966,49 @@ def _check_cross_signing_key(key, user_id, key_type, signing_key=None): ) +def _check_device_signature(user_id, verify_key, signed_device, stored_device): + """Check that a signature on a device or cross-signing key is correct and + matches the copy of the device/key that we have stored. Throws an + exception if an error is detected. + + Args: + user_id (str): the user ID whose signature is being checked + verify_key (VerifyKey): the key to verify the device with + signed_device (dict): the uploaded signed device data + stored_device (dict): our previously stored copy of the device + + Raises: + SynapseError: if the signature was invalid or the sent device is not the + same as the stored device + + """ + + # make sure that the device submitted matches what we have stored + stripped_signed_device = { + k: v for k, v in signed_device.items() if k not in ["signatures", "unsigned"] + } + stripped_stored_device = { + k: v for k, v in stored_device.items() if k not in ["signatures", "unsigned"] + } + if stripped_signed_device != stripped_stored_device: + logger.debug( + "upload signatures: key does not match %s vs %s", + signed_device, + stored_device, + ) + raise SynapseError(400, "Key does not match") + + try: + verify_signed_json(signed_device, user_id, verify_key) + except SignatureVerifyException: + logger.debug("invalid signature on key") + raise SynapseError(400, "Invalid signature", Codes.INVALID_SIGNATURE) + + def _exception_to_failure(e): + if isinstance(e, SynapseError): + return {"status": e.code, "errcode": e.errcode, "message": str(e)} + if isinstance(e, CodeMessageException): return {"status": e.code, "message": str(e)} @@ -658,3 +1036,14 @@ def _one_time_keys_match(old_key_json, new_key): new_key_copy.pop("signatures", None) return old_key == new_key_copy + + +@attr.s +class SignatureListItem: + """An item in the signature list as used by upload_signatures_for_device_keys. + """ + + signing_key_id = attr.ib() + target_user_id = attr.ib() + target_device_id = attr.ib() + signature = attr.ib() |