Просмотр исходного кода

simplify exceptions into four classes instead of eight; make error messages more verbose

tags/v0.1^2
Ben Kurtovic 13 лет назад
Родитель
Сommit
2c7b684fa0
1 измененных файлов: 20 добавлений и 34 удалений
  1. +20
    -34
      lib/blowfish.py

+ 20
- 34
lib/blowfish.py Просмотреть файл

@@ -33,16 +33,6 @@ The entire Blowfish() class (excluding verify_key()) is by Michael Gilfix

Blowfish.verify_key(), exception classes, encrypt() and decrypt() wrappers, and
interactive mode are by Ben Kurtovic <ben.kurtovic@verizon.net>.

Map of exceptions:
* BlowfishError
* BlockSizeError
* KeyLengthError
* KeyTooShortError
* KeyTooLongError
* DecryptionError
* IncorrectKeyError
* BadCyphertextError
"""

class BlowfishError(Exception):
@@ -53,22 +43,12 @@ class BlockSizeError(BlowfishError):
"""Attempted to handle a block not 8 bytes in length."""

class KeyLengthError(BlowfishError):
"""Base class for invalid key length exceptions."""

class KeyTooShortError(KeyLengthError):
"""The given key is too short: it is less than 8 bytes (64 bits)."""

class KeyTooLongError(KeyLengthError):
"""The given key is too long: it is more than 56 bytes (448 bits."""
"""Attempted to use a key that is either less than 8 bytes or more than 56
bytes in length."""

class DecryptionError(BlowfishError):
"""Base class for exceptions that occur during decryption only."""

class IncorrectKeyError(DecryptionError):
"""Attempted to decrypt something with the wrong key."""

class BadCyphertextError(DecryptionError):
"""The given cyphertext is malformed and cannot be decrypted."""
"""Attempted to decrypt malformed cyphertext (e.g., not evenly divisible
into 8-byte blocks) or attempted to decrypt using a bad key."""

class Blowfish(object):
"""Blowfish encryption Scheme
@@ -462,7 +442,8 @@ class Blowfish(object):

def encrypt(self, data):
if not len(data) == 8:
raise BlockSizeError("{0} != 8".format(len(data)))
raise BlockSizeError("blocks must be 8 bytes long, but tried to " +
"encrypt one {0} bytes long".format(len(data)))

# Use big endianess since that's what everyone else uses
xl = ord (data[3]) | (ord (data[2]) << 8) | (ord (data[1]) << 16) | (ord (data[0]) << 24)
@@ -477,7 +458,8 @@ class Blowfish(object):

def decrypt(self, data):
if not len(data) == 8:
raise BlockSizeError("{0} != 8".format(len(data)))
raise BlockSizeError("blocks must be 8 bytes long, but tried to " +
"decrypt one {0} bytes long".format(len(data)))

# Use big endianess since that's what everyone else uses
cl = ord (data[3]) | (ord (data[2]) << 8) | (ord (data[1]) << 16) | (ord (data[0]) << 24)
@@ -503,11 +485,13 @@ class Blowfish(object):
"""Make sure our key is not too short or too long; if there's a
problem, raise KeyTooShortError() or KeyTooLongError()."""
if not key:
raise KeyTooShortError("no key given")
raise KeyLengthError("no key given")
if len(key) < 8:
raise KeyTooShortError("{0} < 8".format(len(key)))
raise KeyLengthError(("key is {0} bytes long, but it must be at " +
"least 8").format(len(key)))
if len(key) > 56:
raise KeyTooLongError("{0} > 56".format(len(key)))
raise KeyLengthError(("key is {0} bytes long, but it must be " +
"less than 56").format(len(key)))

def encrypt(key, plaintext):
"""Encrypt any length of plaintext using a given key that must be between
@@ -534,18 +518,20 @@ def decrypt(key, cyphertext):

try:
cyphertext = cyphertext.decode("hex")
except TypeError as e:
raise BadCyphertextError(e)
except TypeError as error:
e = error.message
raise DecryptionError("cyphertext could not be decoded: " + e.lower())

if len(cyphertext) % 8 > 0:
raise BadCyphertextError("cyphertext cannot be broken into " +
"8-byte blocks evenly")
raise DecryptionError("cyphertext cannot be broken into " +
"8-byte blocks evenly")

blocks = [cyphertext[f:f+8] for f in range(0, len(cyphertext), 8)]
msg = ''.join(map(cypher.decrypt, blocks))

if not msg.startswith("TRUE"): # sanity check to ensure valid decryption
raise IncorrectKeyError()
raise DecryptionError("the given key is incorrect, or part of the " +
"cyphertext is malformed")

size, msg = msg[4:].split("|", 1)
while len(msg) > int(size):


Загрузка…
Отмена
Сохранить