update demo_dynamic.py
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Larry Bugbee
Steffen Jaeckel
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122
demos/demo_dynamic.py
Executable file → Normal file
122
demos/demo_dynamic.py
Executable file → Normal file
@ -1,7 +1,7 @@
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"""
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demo_dynamic.py v1
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demo_dynamic.py v2
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This program demonstrates Python's use of the dynamic
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language support additions to LTC, namely access to LTC
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@ -19,26 +19,21 @@
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load multiple .dylibs, but it does not support this level
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of tight coupling between otherwise independent libraries.)
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My .dylib was created on OSX with the following steps:
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1- compile LTC to a .a static lib:
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CFLAGS="-DLTM_DESC -DUSE_LTM" make
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2- link LTC and LTM into a single .dylib:
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ar2dylib_with tomcrypt tommath
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where ar2dylib_with is a shell script that combines
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the LTC .a with the LTM .dylib
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My .dylib was created on OSX/macOS with the following:
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sudo make -j5 -f makefile.shared \
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CFLAGS="-DUSE_TFM -DTFM_DESC -I/usr/local/include" \
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EXTRALIBS=/usr/local/lib/libtfm.a install
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Reminder: you don't need to bind in a math library unless
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you are going to use LTC functions that depend
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on a mathlib. For example, public key crypto
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needs a mathlib; hashing and symmetric encryption
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do not.
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you are going to use LTC functions that need a
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mathlib. For example, public key crypto requires
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a mathlib; hashing and symmetric encryption do not.
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This code was written for Python 2.7.
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Larry Bugbee
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March 2014
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March 2014 v1
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August 2017 v2
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"""
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@ -46,15 +41,23 @@
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from ctypes import *
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from ctypes.util import find_library
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# switches to enable/disable selected output
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SHOW_ALL_CONSTANTS = True
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SHOW_ALL_SIZES = True
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SHOW_SELECTED_CONSTANTS = True
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SHOW_SELECTED_SIZES = True
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SHOW_BUILD_OPTIONS_ALGS = True
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SHOW_SHA256_EXAMPLE = True
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SHOW_CHACHA_EXAMPLE = True
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print
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print(' demo_dynamic.py')
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#---------------------------------------------------------------
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# load the .dylib
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libname = 'tomcrypt'
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libpath = find_library(libname)
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print
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print(' demo_dynamic.py')
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print
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print(' path to library %s: %s' % (libname, libpath))
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@ -69,7 +72,8 @@ print
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# supported sizes. One alternative: these lists may be parsed
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# and used as needed.
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if 1:
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if SHOW_ALL_CONSTANTS:
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print '-'*60
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print ' all supported constants and their values:'
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# get size to allocate for constants output list
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@ -85,7 +89,8 @@ if 1:
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print
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if 1:
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if SHOW_ALL_SIZES:
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print '-'*60
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print ' all supported sizes:'
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# get size to allocate for sizes output list
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@ -105,7 +110,8 @@ if 1:
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# get individually named constants and sizes
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# print selected constants
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if 1:
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if SHOW_SELECTED_CONSTANTS:
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print '-'*60
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print '\n selected constants:'
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names = [
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@ -122,7 +128,8 @@ if 1:
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print ' %-25s %d' % (name, value)
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# print selected sizes
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if 1:
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if SHOW_SELECTED_SIZES:
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print '-'*60
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print '\n selected sizes:'
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names = [
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@ -143,14 +150,18 @@ if 1:
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#---------------------------------------------------------------
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#---------------------------------------------------------------
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# ctypes getting a list of this build's supported algorithms
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# and compiler switches
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# LibTomCrypt exposes one interesting string that can be accessed
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# via Python's ctypes module, "crypt_build_settings", which
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# provides a list of this build's compiler switches and supported
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# algorithms. If someday LTC exposes other interesting strings,
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# they can be found with:
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# nm /usr/local/lib/libtomcrypt.dylib | grep " D "
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def get_named_string(lib, name):
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return c_char_p.in_dll(lib, name).value
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if 0:
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print '\n%s' % ('-'*60)
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if SHOW_BUILD_OPTIONS_ALGS:
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print '-'*60
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print 'This is a string compiled into LTC showing compile '
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print 'options and algorithms supported by this build \n'
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print get_named_string(LTC, 'crypt_build_settings')
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@ -160,23 +171,31 @@ if 0:
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#---------------------------------------------------------------
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#---------------------------------------------------------------
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# here is an example of how a wrapper can make Python access
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# more Pythonic
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# here is an example of how Python code can be written to access
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# LTC's implementation of SHA256 and ChaCha,
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# - - - - - - - - - - - - -
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# a wrapper fragment...
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# definitions
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def _get_size(name):
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size = c_int(0)
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rc = LTC.crypt_get_size(name, byref(size))
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if rc != 0:
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raise Exception('LTC.crypt_get_size(%s) rc = %d' % (name, rc))
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return size.value
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sha256_state_struct_size = _get_size('sha256_state')
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sha512_state_struct_size = _get_size('sha512_state')
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def _get_constant(name):
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constant = c_int(0)
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rc = LTC.crypt_get_constant(name, byref(constant))
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if rc != 0:
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raise Exception('LTC.crypt_get_constant(%s) rc = %d' % (name, rc))
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return constant.value
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CRYPT_OK = _get_constant('CRYPT_OK')
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class SHA256(object):
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def __init__(self):
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self.state = c_buffer(sha256_state_struct_size)
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self.state = c_buffer(_get_size('sha256_state'))
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LTC.sha256_init(byref(self.state))
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def update(self, data):
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LTC.sha256_process(byref(self.state), data, len(data))
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@ -185,20 +204,55 @@ class SHA256(object):
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LTC.sha256_done(byref(self.state), byref(md))
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return md.raw
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class ChaCha(object):
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def __init__(self, key, rounds):
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self.state = c_buffer(_get_size('chacha_state'))
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self.counter = c_int(1)
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err = LTC.chacha_setup(byref(self.state), key, len(key), rounds)
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def set_iv32(self, iv):
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err = LTC.chacha_ivctr32(byref(self.state), iv, len(iv), byref(self.counter))
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if err != CRYPT_OK:
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raise Exception('LTC.chacha_ivctr32() err = %d' % err)
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def crypt(self, datain):
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dataout = c_buffer(len(datain))
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err = LTC.chacha_crypt(byref(self.state), datain, len(datain), byref(dataout))
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if err != CRYPT_OK:
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raise Exception('LTC.chacha_crypt() err = %d' % err)
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return dataout.raw
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# - - - - - - - - - - - - -
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# an app fragment...
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# a SHA256 app fragment...
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# from wrapper import * # uncomment in real life
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if SHOW_SHA256_EXAMPLE:
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print '-'*60
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data = 'hello world'
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sha256 = SHA256()
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sha256.update(data)
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md = sha256.digest()
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template = '\n\n the SHA256 digest for "%s" is %s \n'
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template = '\n the SHA256 digest for "%s" is %s \n'
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print template % (data, md.encode('hex'))
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# - - - - - - - - - - - - -
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# a ChaCha app fragment...
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if SHOW_CHACHA_EXAMPLE:
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print '-'*60
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key = 'hownowbrowncow\x00\x00' # exactly 16 or 32 bytes
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rounds = 12 # common values: 8, 12, 20
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iv = '123456789012' # exactly 12 bytes
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plain = 'Kilroy was here, there, and everywhere!'
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cha = ChaCha(key, rounds)
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cha.set_iv32(iv)
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cipher = cha.crypt(plain)
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template = '\n ChaCha%d ciphertext for "%s" is "%s" \n'
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print template % (rounds, plain, cipher.encode('hex'))
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#---------------------------------------------------------------
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