diff options
| -rw-r--r-- | synapse/crypto/event_signing.py | 99 | ||||
| -rw-r--r-- | synapse/events/utils.py | 47 |
2 files changed, 104 insertions, 42 deletions
diff --git a/synapse/crypto/event_signing.py b/synapse/crypto/event_signing.py index 8774b28967..d01ac5075c 100644 --- a/synapse/crypto/event_signing.py +++ b/synapse/crypto/event_signing.py @@ -23,14 +23,14 @@ from signedjson.sign import sign_json from unpaddedbase64 import decode_base64, encode_base64 from synapse.api.errors import Codes, SynapseError -from synapse.events.utils import prune_event +from synapse.events.utils import prune_event, prune_event_dict logger = logging.getLogger(__name__) def check_event_content_hash(event, hash_algorithm=hashlib.sha256): """Check whether the hash for this PDU matches the contents""" - name, expected_hash = compute_content_hash(event, hash_algorithm) + name, expected_hash = compute_content_hash(event.get_pdu_json(), hash_algorithm) logger.debug("Expecting hash: %s", encode_base64(expected_hash)) # some malformed events lack a 'hashes'. Protect against it being missing @@ -59,35 +59,70 @@ def check_event_content_hash(event, hash_algorithm=hashlib.sha256): return message_hash_bytes == expected_hash -def compute_content_hash(event, hash_algorithm): - event_json = event.get_pdu_json() - event_json.pop("age_ts", None) - event_json.pop("unsigned", None) - event_json.pop("signatures", None) - event_json.pop("hashes", None) - event_json.pop("outlier", None) - event_json.pop("destinations", None) +def compute_content_hash(event_dict, hash_algorithm): + """Compute the content hash of an event, which is the hash of the + unredacted event. - event_json_bytes = encode_canonical_json(event_json) + Args: + event_dict (dict): The unredacted event as a dict + hash_algorithm: A hasher from `hashlib`, e.g. hashlib.sha256, to use + to hash the event + + Returns: + tuple[str, bytes]: A tuple of the name of hash and the hash as raw + bytes. + """ + event_dict = dict(event_dict) + event_dict.pop("age_ts", None) + event_dict.pop("unsigned", None) + event_dict.pop("signatures", None) + event_dict.pop("hashes", None) + event_dict.pop("outlier", None) + event_dict.pop("destinations", None) + + event_json_bytes = encode_canonical_json(event_dict) hashed = hash_algorithm(event_json_bytes) return (hashed.name, hashed.digest()) def compute_event_reference_hash(event, hash_algorithm=hashlib.sha256): + """Computes the event reference hash. This is the hash of the redacted + event. + + Args: + event (FrozenEvent) + hash_algorithm: A hasher from `hashlib`, e.g. hashlib.sha256, to use + to hash the event + + Returns: + tuple[str, bytes]: A tuple of the name of hash and the hash as raw + bytes. + """ tmp_event = prune_event(event) - event_json = tmp_event.get_pdu_json() - event_json.pop("signatures", None) - event_json.pop("age_ts", None) - event_json.pop("unsigned", None) - event_json_bytes = encode_canonical_json(event_json) + event_dict = tmp_event.get_pdu_json() + event_dict.pop("signatures", None) + event_dict.pop("age_ts", None) + event_dict.pop("unsigned", None) + event_json_bytes = encode_canonical_json(event_dict) hashed = hash_algorithm(event_json_bytes) return (hashed.name, hashed.digest()) -def compute_event_signature(event, signature_name, signing_key): - tmp_event = prune_event(event) - redact_json = tmp_event.get_pdu_json() +def compute_event_signature(event_dict, signature_name, signing_key): + """Compute the signature of the event for the given name and key. + + Args: + event_dict (dict): The event as a dict + signature_name (str): The name of the entity signing the event + (typically the server's hostname). + signing_key (syutil.crypto.SigningKey): The key to sign with + + Returns: + dict[str, dict[str, str]]: Returns a dictionary in the same format of + an event's signatures field. + """ + redact_json = prune_event_dict(event_dict) redact_json.pop("age_ts", None) redact_json.pop("unsigned", None) logger.debug("Signing event: %s", encode_canonical_json(redact_json)) @@ -98,23 +133,27 @@ def compute_event_signature(event, signature_name, signing_key): def add_hashes_and_signatures(event, signature_name, signing_key, hash_algorithm=hashlib.sha256): - # if hasattr(event, "old_state_events"): - # state_json_bytes = encode_canonical_json( - # [e.event_id for e in event.old_state_events.values()] - # ) - # hashed = hash_algorithm(state_json_bytes) - # event.state_hash = { - # hashed.name: encode_base64(hashed.digest()) - # } - - name, digest = compute_content_hash(event, hash_algorithm=hash_algorithm) + """Add content hash and sign the event + + Args: + event_dict (EventBuilder): The event to add hashes to and sign + signature_name (str): The name of the entity signing the event + (typically the server's hostname). + signing_key (syutil.crypto.SigningKey): The key to sign with + hash_algorithm: A hasher from `hashlib`, e.g. hashlib.sha256, to use + to hash the event + """ + + name, digest = compute_content_hash( + event.get_pdu_json(), hash_algorithm=hash_algorithm, + ) if not hasattr(event, "hashes"): event.hashes = {} event.hashes[name] = encode_base64(digest) event.signatures = compute_event_signature( - event, + event.get_pdu_json(), signature_name=signature_name, signing_key=signing_key, ) diff --git a/synapse/events/utils.py b/synapse/events/utils.py index 652941ca0d..63f693f259 100644 --- a/synapse/events/utils.py +++ b/synapse/events/utils.py @@ -38,8 +38,31 @@ def prune_event(event): This is used when we "redact" an event. We want to remove all fields that the user has specified, but we do want to keep necessary information like type, state_key etc. + + Args: + event (FrozenEvent) + + Returns: + FrozenEvent + """ + pruned_event_dict = prune_event_dict(event.get_dict()) + + from . import event_type_from_format_version + return event_type_from_format_version(event.format_version)( + pruned_event_dict, event.internal_metadata.get_dict() + ) + + +def prune_event_dict(event_dict): + """Redacts the event_dict in the same way as `prune_event`, except it + operates on dicts rather than event objects + + Args: + event_dict (dict) + + Returns: + dict: A copy of the pruned event dict """ - event_type = event.type allowed_keys = [ "event_id", @@ -59,13 +82,13 @@ def prune_event(event): "membership", ] - event_dict = event.get_dict() + event_type = event_dict["type"] new_content = {} def add_fields(*fields): for field in fields: - if field in event.content: + if field in event_dict["content"]: new_content[field] = event_dict["content"][field] if event_type == EventTypes.Member: @@ -98,17 +121,17 @@ def prune_event(event): allowed_fields["content"] = new_content - allowed_fields["unsigned"] = {} + unsigned = {} + allowed_fields["unsigned"] = unsigned - if "age_ts" in event.unsigned: - allowed_fields["unsigned"]["age_ts"] = event.unsigned["age_ts"] - if "replaces_state" in event.unsigned: - allowed_fields["unsigned"]["replaces_state"] = event.unsigned["replaces_state"] + event_unsigned = event_dict.get("unsigned", {}) - return type(event)( - allowed_fields, - internal_metadata_dict=event.internal_metadata.get_dict() - ) + if "age_ts" in event_unsigned: + unsigned["age_ts"] = event_unsigned["age_ts"] + if "replaces_state" in event_unsigned: + unsigned["replaces_state"] = event_unsigned["replaces_state"] + + return allowed_fields def _copy_field(src, dst, field): |