147 lines
2.9 KiB
Python
147 lines
2.9 KiB
Python
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from time import time
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from base64 import b16encode
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import os.path
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import libnacl.utils, libnacl.sign
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from transaction_const import *
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from io import BytesIO
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from hashlib import sha3_256
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import logging
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from random import randint
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logging.basicConfig(level='DEBUG')
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log = logging.getLogger('tx')
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'''
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[ CA$H ]
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[signature ] * 16
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[load][used]
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[keyi][txid]
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[timestamp ]
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[ uuid ]
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[ F0X0 ]
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21*4 = 84bytes
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76 bytes
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'''
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FIELDS = {
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'signature': (0, 63),
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'enc_key': 64,
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'key_id': 65,
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'load_amt': (66, 67),
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'used_amt': (68, 69),
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'tx_id': (70, 71),
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'ts': (72, 75),
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'uuid': (76, 79)
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}
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class Transaction:
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def __init__(self, tag_id, nfc_bytes=None):
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# These are needed for proper randomness
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self.tag_id = tag_id
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self.data = bytearray(max([(x[1] if isinstance(x, tuple) else x) for x in FIELDS.values()])+1)
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self.set_field('key_id', KEY_ID)
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self.set_field('ts', time())
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self.set_field('uuid', libnacl.randombytes(4))
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if nfc_bytes:
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self.load(nfc_bytes)
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def set_field(self, fid, val):
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if isinstance(FIELDS[fid], int):
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flen = 1
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sbyte = FIELDS[fid]
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else:
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flen = 1 + FIELDS[fid][1] - FIELDS[fid][0]
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sbyte = FIELDS[fid][0]
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if isinstance(val, float):
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val = int(val)
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if isinstance(val, int):
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val = val.to_bytes(flen)
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assert len(val) <= flen
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if flen > 1:
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log.info(f"Writing {fid} at bytes {sbyte}:{sbyte+flen-1}: 0x{b16encode(val).decode()}")
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self.data[sbyte:sbyte+flen] = val
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else:
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log.info(f"Writing {fid} at byte {sbyte}: 0x{b16encode(val).decode()}")
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self.data[sbyte] = val[0]
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def get_field(self, fid):
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if isinstance(FIELDS[fid], int):
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flen = 1
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sbyte = FIELDS[fid]
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else:
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flen = 1 + FIELDS[fid][1] - FIELDS[fid][0]
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sbyte = FIELDS[fid][0]
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if flen > 1:
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val = bytes(self.data[sbyte:sbyte+flen])
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else:
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val = self.data[sbyte]
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return val
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def load(self, data):
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if data.startswith(HEADER):
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data = data[len(HEADER):]
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if data.find(FOOTER):
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data = data[:-data.find(FOOTER)]
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self.data = data
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def sign(self):
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self.set_field('key_id', KEY_ID)
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signer = libnacl.sign.Signer(KEY_SEED)
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signature = signer.signature(bytes(self.data[FIELDS['signature'][1]+1:]+self.tag_id))
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self.set_field('signature', signature)
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log.info("Signed message with success!")
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self.verify()
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def get_bytes(self):
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return HEADER + self.data + FOOTER
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# TODO: implement these
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def topup(self, amt):
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self.load_amount += amt
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self.tx_bytes
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def spend(self, amt):
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self.used_amount += amt
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def verify(self):
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verifier = libnacl.sign.Verifier(KEYS[self.get_field('key_id')])
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verifier.verify(bytes(self.data + self.tag_id))
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log.info("Signature has passed!")
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if __name__ == '__main__':
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print("Testing transaction.")
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tx = Transaction(tag_id=bytes(8))
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tx.sign()
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#for fname in FIELDS:
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# print(' ', fname, tx.get_field(fname), 'len')
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#res = tx.get_bytes()
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#tx.verify()
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#tx = Transaction(tag_id=bytes(8), nfc_bytes=res)
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#res2 = tx.get_bytes()
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