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#!/usr/bin/env python
# -*-Python-*-
# Cipher 1.00
#
# Part of the Python Cryptography Toolkit
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
#
import sys, getopt, os
# Determine the name of this executable
executable = os.path.basename(sys.argv[0])
if executable=='': executable='cipher'
cipher = '' # Unknown ciphering algorithm
key = (0, '') # Empty key
magic = 'ctx\001' # Magic string prefixed to the data
NoInputFile = '' # Exceptions raised on file errors
NoOutputFile = ''
def PrintUsage():
print 'Usage: cipher [OPTIONS] file1 file2 ...'
print '\n -c ciphername Force use of ciphername to encrypt/decrypt'
print ' -k key Key to use for encryption/decryption'
print '\nThe default cipher algorithm is IDEA; if no key is set on the command'
print 'line, you will be prompted to enter a key.'
print 'Files are read completely into memory, so do not try to encrypt'
print 'very large files.'
def GenerateIV(length):
import whrandom
IV=''
for i in range(0, length):
IV=IV + chr(int(256*whrandom.random()))
return IV
def Encipher(filename, cipher, key):
if (cipher==''): cipher='IDEA'
try:
exec ('from Crypto.Cipher import '+cipher)
module=eval(cipher)
except ImportError:
print executable+ ':', cipher, ': Cipher does not exist.'
sys.exit(1)
import Crypto.Hash.MD5
try:
input=open(filename, 'r')
except IOError:
raise NoInputFile
try:
output=open(filename+'.cip', 'w')
except IOError:
raise NoOutputFile, filename+'.cip'
if (key[0]==0):
key=raw_input('Enter encryption key for '+ filename+ ':')
else: key=key[1]
key=Crypto.Hash.MD5.new(key).digest()
IV=''
for i in range(0, module.blocksize): IV=IV+'A'
if (module.keysize==0):
cipherobj=module.new(key, module.CBC, IV)
else:
cipherobj=module.new(key[0:module.keysize], module.CBC, IV)
output.write(magic+cipher+'\0')
data = GenerateIV(module.blocksize)
filedata=input.read()
data = data + magic + str(len(filedata))+'\0'+filename+'\0'
data = data + filedata
input.close()
padding=module.blocksize - (len(data) % module.blocksize)
for i in range(0, padding):
data = data + chr(i)
ciphertext=cipherobj.encrypt(data)
output.write(ciphertext)
output.close()
def Decipher(filename, cipher, key):
import Crypto.Hash.MD5, string
try:
input=open(filename, 'r')
except IOError:
raise NoInputFile
if (input.read(len(magic))!=magic):
print executable+':', filename+': Does not seem to be a ciphered file'
return
t=''
while (1):
c=input.read(1)
if (ord(c)==0): break
t=t+c
if (cipher==''): cipher=t
try:
from Crypto.Cipher import *
module=eval(cipher)
except ImportError:
print executable+ ':', cipher, ': Cipher does not exist.'
sys.exit(1)
if (key[0]==0):
key=raw_input('Enter encryption key for '+ filename+ ':')
else: key=key[1]
key=Crypto.Hash.MD5.new(key).digest()
IV = ''
for i in range(0, module.blocksize): IV=IV+'A'
data=input.read()
if (module.keysize==0):
cipherobj=module.new(key, module.CBC, IV)
else:
cipherobj=module.new(key[0:module.keysize], module.CBC, IV)
plain=cipherobj.decrypt(data) # Decrypt the data
plain=plain[module.blocksize:] # Discard first block of random data
if (plain[0:len(magic)]!=magic):
print executable+':', filename+': Incorrect key or cipher algorithm'
return
else: plain=plain[len(magic):]
i=string.find(plain, '\0')
length=string.atoi(plain[0:i])
j=string.find(plain, '\0', i+1)
newfilename=plain[i+1:j]
try:
output=open(newfilename, 'w')
except IOError:
raise NoOutputFile, newfilename
output.write(plain[j+1:j+1+length])
output.close()
if len(sys.argv)==1: PrintUsage() ; sys.exit(0)
options, args=getopt.getopt(sys.argv[1:], 'c:k:hH')
for opt in options:
letter, param = opt
if (letter=='-c'): cipher = param
if (letter=='-k'): key = (1, param)
if (letter=='-h' or letter=='-H'):
PrintUsage()
sys.exit(0)
for file in args:
try:
if (file[-4:]=='.cip'):
Decipher(file, cipher, key)
else:
Encipher(file, cipher, key)
except NoInputFile:
print executable+ ':', file+ ': No such file.'
except NoOutputFile, filename:
print executable+ ':', filename+ ': Cannot open file'
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