bridgedb/parse/fingerprint.py

   1 # -*- coding: utf-8 ; test-case-name: bridgedb.test.test_parse_fingerprint ; -*-
   2 #_____________________________________________________________________________
   3 #
   4 # This file is part of BridgeDB, a Tor bridge distribution system.
   5 #
   6 # :authors: Isis Lovecruft 0xA3ADB67A2CDB8B35 <isis@torproject.org>
   7 #           please also see AUTHORS file
   8 # :copyright: (c) 2007-2017, The Tor Project, Inc.
   9 #             (c) 2014-2017, Isis Lovecruft
  10 # :license: see LICENSE for licensing information
  11 #_____________________________________________________________________________
  12
  13 """
  14 .. py:module:: bridgedb.parse.fingerprint
  15     :synopsis: Parsers for Tor Bridge fingerprints.
  16
  17 .. todo: This module is very small; it could possibly be combined with another
  18     module, e.g. :mod:`bridgedb.parse.descriptors`.
  19
  20 bridgedb.parse.fingerprint
  21 ============================
  22
  23 Utility functions for converting between various relay fingerprint formats,
  24 and checking their validity.
  25
  26 ::
  27
  28  toHex - Convert a fingerprint from its binary representation to hexadecimal.
  29  fromHex - Convert a fingerprint from hexadecimal to binary.
  30  isValidFingerprint - Validate a fingerprint.
  31 ..
  32 """
  33
  34 import binascii
  35 import logging
  36
  37
  38 #: The required length for hexidecimal representations of hash digest of a
  39 #: Tor relay's public identity key (a.k.a. its fingerprint).
  40 HEX_FINGERPRINT_LEN = 40
  41
  42
  43 #: (callable) Convert a value from binary to hexidecimal representation.
  44 toHex = binascii.b2a_hex
  45
  46 #: (callable) Convert a value from hexidecimal to binary representation.
  47 fromHex = binascii.a2b_hex
  48
  49 def isValidFingerprint(fingerprint):
  50     """Determine if a Tor relay fingerprint is valid.
  51
  52     :param str fingerprint: The hex-encoded hash digest of the relay's
  53         public identity key, a.k.a. its fingerprint.
  54     :rtype: bool
  55     :returns: ``True`` if the **fingerprint** was valid, ``False`` otherwise.
  56     """
  57     try:
  58         if len(fingerprint) != HEX_FINGERPRINT_LEN:
  59             raise ValueError("Fingerprint has incorrect length: %r"
  60                              % repr(fingerprint))
  61         fromHex(fingerprint)
  62     except (TypeError, ValueError):
  63         logging.debug("Invalid hex fingerprint: %r" % repr(fingerprint))
  64     else:
  65         return True
  66     return False