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# ===================================================================
#
# Copyright (c) 2019, Helder Eijs <[email protected]>
# 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.
# ===================================================================
import struct
from Cryptodome.Cipher import AES
from Cryptodome.Hash import SHA512
from Cryptodome.Protocol.KDF import _bcrypt_hash
from Cryptodome.Util.strxor import strxor
from Cryptodome.Util.py3compat import tostr, bchr, bord
def read_int4(data):
if len(data) < 4:
raise ValueError("Insufficient data")
value = struct.unpack(">I", data[:4])[0]
return value, data[4:]
def read_bytes(data):
size, data = read_int4(data)
if len(data) < size:
raise ValueError("Insufficient data (V)")
return data[:size], data[size:]
def read_string(data):
s, d = read_bytes(data)
return tostr(s), d
def check_padding(pad):
for v, x in enumerate(pad):
if bord(x) != ((v + 1) & 0xFF):
raise ValueError("Incorrect padding")
def import_openssh_private_generic(data, password):
# https://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/PROTOCOL.key?annotate=HEAD
# https://github.com/openssh/openssh-portable/blob/master/sshkey.c
# https://coolaj86.com/articles/the-openssh-private-key-format/
# https://coolaj86.com/articles/the-ssh-public-key-format/
if not data.startswith(b'openssh-key-v1\x00'):
raise ValueError("Incorrect magic value")
data = data[15:]
ciphername, data = read_string(data)
kdfname, data = read_string(data)
kdfoptions, data = read_bytes(data)
number_of_keys, data = read_int4(data)
if number_of_keys != 1:
raise ValueError("We only handle 1 key at a time")
_, data = read_string(data) # Public key
encrypted, data = read_bytes(data)
if data:
raise ValueError("Too much data")
if len(encrypted) % 8 != 0:
raise ValueError("Incorrect payload length")
# Decrypt if necessary
if ciphername == 'none':
decrypted = encrypted
else:
if (ciphername, kdfname) != ('aes256-ctr', 'bcrypt'):
raise ValueError("Unsupported encryption scheme %s/%s" % (ciphername, kdfname))
salt, kdfoptions = read_bytes(kdfoptions)
iterations, kdfoptions = read_int4(kdfoptions)
if len(salt) != 16:
raise ValueError("Incorrect salt length")
if kdfoptions:
raise ValueError("Too much data in kdfoptions")
pwd_sha512 = SHA512.new(password).digest()
# We need 32+16 = 48 bytes, therefore 2 bcrypt outputs are sufficient
stripes = []
constant = b"OxychromaticBlowfishSwatDynamite"
for count in range(1, 3):
salt_sha512 = SHA512.new(salt + struct.pack(">I", count)).digest()
out_le = _bcrypt_hash(pwd_sha512, 6, salt_sha512, constant, False)
out = struct.pack("<IIIIIIII", *struct.unpack(">IIIIIIII", out_le))
acc = bytearray(out)
for _ in range(1, iterations):
out_le = _bcrypt_hash(pwd_sha512, 6, SHA512.new(out).digest(), constant, False)
out = struct.pack("<IIIIIIII", *struct.unpack(">IIIIIIII", out_le))
strxor(acc, out, output=acc)
stripes.append(acc[:24])
result = b"".join([bchr(a)+bchr(b) for (a, b) in zip(*stripes)])
cipher = AES.new(result[:32],
AES.MODE_CTR,
nonce=b"",
initial_value=result[32:32+16])
decrypted = cipher.decrypt(encrypted)
checkint1, decrypted = read_int4(decrypted)
checkint2, decrypted = read_int4(decrypted)
if checkint1 != checkint2:
raise ValueError("Incorrect checksum")
ssh_name, decrypted = read_string(decrypted)
return ssh_name, decrypted
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