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89 lines
2.9 KiB
Python
89 lines
2.9 KiB
Python
"""A thin ctypes based wrapper for OpenSSL 1.0
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"""
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import os
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from ctypes import cdll, c_char_p, c_int, c_uint, c_void_p, POINTER, create_string_buffer
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from ctypes.util import find_library
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import struct
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def _find_libcrypto():
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_possible_paths = [
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find_library('crypto'),
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os.environ.get('ATTIC_LIBCRYPTO_PATH'),
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'/usr/local/opt/openssl/lib/libcrypto.dylib', # OS X Brew
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'/usr/local/lib/libcrypto.so', # FreeBSD Ports
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'/usr/local/ssl/lib/libcrypto.so'
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]
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for path in _possible_paths:
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try:
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lib = cdll.LoadLibrary(path)
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if hasattr(lib, 'PKCS5_PBKDF2_HMAC'):
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return lib
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except OSError:
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pass
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raise Exception('Failed to find libcrypto version >= 1.0')
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libcrypto = _find_libcrypto()
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libcrypto.PKCS5_PBKDF2_HMAC.argtypes = (c_char_p, c_int, c_char_p, c_int, c_int, c_void_p, c_int, c_char_p)
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libcrypto.EVP_sha256.restype = c_void_p
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libcrypto.AES_set_encrypt_key.argtypes = (c_char_p, c_int, c_char_p)
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libcrypto.AES_ctr128_encrypt.argtypes = (c_char_p, c_char_p, c_int, c_char_p, c_char_p, c_char_p, POINTER(c_uint))
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libcrypto.RAND_bytes.argtypes = (c_char_p, c_int)
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libcrypto.RAND_bytes.restype = c_int
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_int = struct.Struct('>I')
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_long = struct.Struct('>Q')
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bytes_to_int = lambda x, offset=0: _int.unpack_from(x, offset)[0]
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bytes_to_long = lambda x, offset=0: _long.unpack_from(x, offset)[0]
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long_to_bytes = lambda x: _long.pack(x)
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def num_aes_blocks(length):
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"""Return the number of AES blocks required to encrypt/decrypt *length* bytes of data
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"""
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return (length + 15) // 16
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def pbkdf2_sha256(password, salt, iterations, size):
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"""Password based key derivation function 2 (RFC2898)
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"""
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key = create_string_buffer(size)
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rv = libcrypto.PKCS5_PBKDF2_HMAC(password, len(password), salt, len(salt), iterations, libcrypto.EVP_sha256(), size, key)
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if not rv:
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raise Exception('PKCS5_PBKDF2_HMAC failed')
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return key.raw
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def get_random_bytes(n):
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"""Return n cryptographically strong pseudo-random bytes
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"""
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buf = create_string_buffer(n)
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if libcrypto.RAND_bytes(buf, n) < 1:
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raise Exception('RAND_bytes failed')
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return buf.raw
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class AES:
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"""A thin wrapper around the OpenSSL AES CTR_MODE cipher
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"""
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def __init__(self, key, iv=None):
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self.key = create_string_buffer(2000)
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self.iv = create_string_buffer(16)
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self.buf = create_string_buffer(16)
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self.num = c_uint()
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self.reset(key, iv)
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def reset(self, key=None, iv=None):
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if key:
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libcrypto.AES_set_encrypt_key(key, len(key) * 8, self.key)
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if iv:
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self.iv.raw = iv
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self.num.value = 0
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def encrypt(self, data):
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out = create_string_buffer(len(data))
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libcrypto.AES_ctr128_encrypt(data, out, len(data), self.key, self.iv, self.buf, self.num)
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return out.raw
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decrypt = encrypt
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