174 lines
6.5 KiB
Python
174 lines
6.5 KiB
Python
#
|
|
# Util/PEM.py : Privacy Enhanced Mail utilities
|
|
#
|
|
# ===================================================================
|
|
#
|
|
# Copyright (c) 2014, Legrandin <helderijs@gmail.com>
|
|
# All rights reserved.
|
|
#
|
|
# Redistribution and use in source and binary forms, with or without
|
|
# modification, are permitted provided that the following conditions
|
|
# are met:
|
|
#
|
|
# 1. Redistributions of source code must retain the above copyright
|
|
# notice, this list of conditions and the following disclaimer.
|
|
# 2. Redistributions in binary form must reproduce the above copyright
|
|
# notice, this list of conditions and the following disclaimer in
|
|
# the documentation and/or other materials provided with the
|
|
# distribution.
|
|
#
|
|
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
|
|
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
|
|
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
|
|
# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
|
|
# COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
|
|
# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
|
|
# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
|
|
# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
|
|
# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
|
|
# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
|
|
# POSSIBILITY OF SUCH DAMAGE.
|
|
# ===================================================================
|
|
|
|
"""Set of functions for encapsulating data according to the PEM format.
|
|
|
|
PEM (Privacy Enhanced Mail) was an IETF standard for securing emails via a
|
|
Public Key Infrastructure. It is specified in RFC 1421-1424.
|
|
|
|
Even though it has been abandoned, the simple message encapsulation it defined
|
|
is still widely used today for encoding *binary* cryptographic objects like
|
|
keys and certificates into text.
|
|
"""
|
|
|
|
__all__ = ['encode', 'decode']
|
|
|
|
from Crypto.Util.py3compat import b, hexlify, unhexlify, tobytes, tostr
|
|
|
|
import re
|
|
from binascii import a2b_base64, b2a_base64
|
|
|
|
from Crypto.Hash import MD5
|
|
from Crypto.Util.Padding import pad, unpad
|
|
from Crypto.Cipher import DES, DES3, AES
|
|
from Crypto.Protocol.KDF import PBKDF1
|
|
from Crypto.Random import get_random_bytes
|
|
|
|
|
|
def encode(data, marker, passphrase=None, randfunc=None):
|
|
"""Encode a piece of binary data into PEM format.
|
|
|
|
:Parameters:
|
|
data : byte string
|
|
The piece of binary data to encode.
|
|
marker : string
|
|
The marker for the PEM block (e.g. "PUBLIC KEY").
|
|
Note that there is no official master list for all allowed markers.
|
|
Still, you can refer to the OpenSSL_ source code.
|
|
passphrase : byte string
|
|
If given, the PEM block will be encrypted. The key is derived from
|
|
the passphrase.
|
|
randfunc : callable
|
|
Random number generation function; it accepts an integer N and returns
|
|
a byte string of random data, N bytes long. If not given, a new one is
|
|
instantiated.
|
|
:Returns:
|
|
The PEM block, as a string.
|
|
|
|
.. _OpenSSL: http://cvs.openssl.org/fileview?f=openssl/crypto/pem/pem.h&v=1.66.2.1.4.2
|
|
"""
|
|
|
|
if randfunc is None:
|
|
randfunc = get_random_bytes
|
|
|
|
out = "-----BEGIN %s-----\n" % marker
|
|
if passphrase:
|
|
# We only support 3DES for encryption
|
|
salt = randfunc(8)
|
|
key = PBKDF1(passphrase, salt, 16, 1, MD5)
|
|
key += PBKDF1(key + passphrase, salt, 8, 1, MD5)
|
|
objenc = DES3.new(key, DES3.MODE_CBC, salt)
|
|
out += "Proc-Type: 4,ENCRYPTED\nDEK-Info: DES-EDE3-CBC,%s\n\n" %\
|
|
tostr(hexlify(salt).upper())
|
|
# Encrypt with PKCS#7 padding
|
|
data = objenc.encrypt(pad(data, objenc.block_size))
|
|
elif passphrase is not None:
|
|
raise ValueError("Empty password")
|
|
|
|
# Each BASE64 line can take up to 64 characters (=48 bytes of data)
|
|
# b2a_base64 adds a new line character!
|
|
chunks = [tostr(b2a_base64(data[i:i + 48]))
|
|
for i in range(0, len(data), 48)]
|
|
out += "".join(chunks)
|
|
out += "-----END %s-----" % marker
|
|
return out
|
|
|
|
|
|
def decode(pem_data, passphrase=None):
|
|
"""Decode a PEM block into binary.
|
|
|
|
:Parameters:
|
|
pem_data : string
|
|
The PEM block.
|
|
passphrase : byte string
|
|
If given and the PEM block is encrypted,
|
|
the key will be derived from the passphrase.
|
|
:Returns:
|
|
A tuple with the binary data, the marker string, and a boolean to
|
|
indicate if decryption was performed.
|
|
:Raises ValueError:
|
|
If decoding fails, if the PEM file is encrypted and no passphrase has
|
|
been provided or if the passphrase is incorrect.
|
|
"""
|
|
|
|
# Verify Pre-Encapsulation Boundary
|
|
r = re.compile("\s*-----BEGIN (.*)-----\s+")
|
|
m = r.match(pem_data)
|
|
if not m:
|
|
raise ValueError("Not a valid PEM pre boundary")
|
|
marker = m.group(1)
|
|
|
|
# Verify Post-Encapsulation Boundary
|
|
r = re.compile("-----END (.*)-----\s*$")
|
|
m = r.search(pem_data)
|
|
if not m or m.group(1) != marker:
|
|
raise ValueError("Not a valid PEM post boundary")
|
|
|
|
# Removes spaces and slit on lines
|
|
lines = pem_data.replace(" ", '').split()
|
|
|
|
# Decrypts, if necessary
|
|
if lines[1].startswith('Proc-Type:4,ENCRYPTED'):
|
|
if not passphrase:
|
|
raise ValueError("PEM is encrypted, but no passphrase available")
|
|
DEK = lines[2].split(':')
|
|
if len(DEK) != 2 or DEK[0] != 'DEK-Info':
|
|
raise ValueError("PEM encryption format not supported.")
|
|
algo, salt = DEK[1].split(',')
|
|
salt = unhexlify(tobytes(salt))
|
|
if algo == "DES-CBC":
|
|
# This is EVP_BytesToKey in OpenSSL
|
|
key = PBKDF1(passphrase, salt, 8, 1, MD5)
|
|
objdec = DES.new(key, DES.MODE_CBC, salt)
|
|
elif algo == "DES-EDE3-CBC":
|
|
# Note that EVP_BytesToKey is note exactly the same as PBKDF1
|
|
key = PBKDF1(passphrase, salt, 16, 1, MD5)
|
|
key += PBKDF1(key + passphrase, salt, 8, 1, MD5)
|
|
objdec = DES3.new(key, DES3.MODE_CBC, salt)
|
|
elif algo == "AES-128-CBC":
|
|
key = PBKDF1(passphrase, salt[:8], 16, 1, MD5)
|
|
objdec = AES.new(key, AES.MODE_CBC, salt)
|
|
else:
|
|
raise ValueError("Unsupport PEM encryption algorithm (%s)." % algo)
|
|
lines = lines[2:]
|
|
else:
|
|
objdec = None
|
|
|
|
# Decode body
|
|
data = a2b_base64(b(''.join(lines[1:-1])))
|
|
enc_flag = False
|
|
if objdec:
|
|
data = unpad(objdec.decrypt(data), objdec.block_size)
|
|
enc_flag = True
|
|
|
|
return (data, marker, enc_flag)
|