commit 0d18570de51486ffa63ad0fe2f8b71be44b34f55 Author: Dave Rolek <dmr-x@riseup.net> Date: Wed Aug 8 17:31:29 2018 +0000 Refactor payload parsing (unpacking) into separate method Eventually, having this separated out will help during decryption of cells in multi-hop circuits - each layer of decryption must attempt to interpret the payload in order to ascertain whether it has been fully decrypted. --- stem/client/cell.py | 22 ++++++++++++++++++---- 1 file changed, 18 insertions(+), 4 deletions(-) diff --git a/stem/client/cell.py b/stem/client/cell.py index a7b57326..9194c29c 100644 --- a/stem/client/cell.py +++ b/stem/client/cell.py @@ -436,6 +436,23 @@ class RelayCell(CircuitCell): @classmethod def _unpack(cls, content, circ_id, link_protocol): + command, recognized, stream_id, digest, data_len, data, unused = RelayCell._unpack_payload(content) + + if len(data) != data_len: + raise ValueError('%s cell said it had %i bytes of data, but only had %i' % (cls.NAME, data_len, len(data))) + + return RelayCell(circ_id, command, data, digest, stream_id, recognized, unused) + + @staticmethod + def _unpack_payload(content): + """ + Directly interpret the payload without any validation. + + :param bytes content: cell payload + + :returns: (command, recognized, stream_id, digest, data_len, data, unused) tuple + """ + command, content = Size.CHAR.pop(content) recognized, content = Size.SHORT.pop(content) # 'recognized' field stream_id, content = Size.SHORT.pop(content) @@ -443,10 +460,7 @@ class RelayCell(CircuitCell): data_len, content = Size.SHORT.pop(content) data, unused = split(content, data_len) - if len(data) != data_len: - raise ValueError('%s cell said it had %i bytes of data, but only had %i' % (cls.NAME, data_len, len(data))) - - return RelayCell(circ_id, command, data, digest, stream_id, recognized, unused) + return command, recognized, stream_id, digest, data_len, data, unused def __hash__(self): return stem.util._hash_attr(self, 'command_int', 'stream_id', 'digest', 'data', cache = True)