136 lines
5 KiB
Python
136 lines
5 KiB
Python
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# ===================================================================
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#
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# Copyright (c) 2019, Helder Eijs <helderijs@gmail.com>
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# All rights reserved.
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#
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# Redistribution and use in source and binary forms, with or without
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# modification, are permitted provided that the following conditions
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# are met:
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#
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# 1. Redistributions of source code must retain the above copyright
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# notice, this list of conditions and the following disclaimer.
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# 2. Redistributions in binary form must reproduce the above copyright
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# notice, this list of conditions and the following disclaimer in
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# the documentation and/or other materials provided with the
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# distribution.
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#
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# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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# COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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# POSSIBILITY OF SUCH DAMAGE.
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# ===================================================================
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import struct
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from Cryptodome.Cipher import AES
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from Cryptodome.Hash import SHA512
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from Cryptodome.Protocol.KDF import _bcrypt_hash
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from Cryptodome.Util.strxor import strxor
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from Cryptodome.Util.py3compat import tostr, bchr, bord
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def read_int4(data):
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if len(data) < 4:
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raise ValueError("Insufficient data")
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value = struct.unpack(">I", data[:4])[0]
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return value, data[4:]
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def read_bytes(data):
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size, data = read_int4(data)
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if len(data) < size:
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raise ValueError("Insufficient data (V)")
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return data[:size], data[size:]
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def read_string(data):
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s, d = read_bytes(data)
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return tostr(s), d
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def check_padding(pad):
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for v, x in enumerate(pad):
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if bord(x) != ((v + 1) & 0xFF):
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raise ValueError("Incorrect padding")
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def import_openssh_private_generic(data, password):
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# https://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/PROTOCOL.key?annotate=HEAD
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# https://github.com/openssh/openssh-portable/blob/master/sshkey.c
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# https://coolaj86.com/articles/the-openssh-private-key-format/
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# https://coolaj86.com/articles/the-ssh-public-key-format/
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if not data.startswith(b'openssh-key-v1\x00'):
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raise ValueError("Incorrect magic value")
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data = data[15:]
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ciphername, data = read_string(data)
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kdfname, data = read_string(data)
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kdfoptions, data = read_bytes(data)
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number_of_keys, data = read_int4(data)
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if number_of_keys != 1:
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raise ValueError("We only handle 1 key at a time")
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_, data = read_string(data) # Public key
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encrypted, data = read_bytes(data)
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if data:
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raise ValueError("Too much data")
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if len(encrypted) % 8 != 0:
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raise ValueError("Incorrect payload length")
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# Decrypt if necessary
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if ciphername == 'none':
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decrypted = encrypted
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else:
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if (ciphername, kdfname) != ('aes256-ctr', 'bcrypt'):
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raise ValueError("Unsupported encryption scheme %s/%s" % (ciphername, kdfname))
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salt, kdfoptions = read_bytes(kdfoptions)
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iterations, kdfoptions = read_int4(kdfoptions)
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if len(salt) != 16:
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raise ValueError("Incorrect salt length")
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if kdfoptions:
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raise ValueError("Too much data in kdfoptions")
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pwd_sha512 = SHA512.new(password).digest()
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# We need 32+16 = 48 bytes, therefore 2 bcrypt outputs are sufficient
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stripes = []
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constant = b"OxychromaticBlowfishSwatDynamite"
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for count in range(1, 3):
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salt_sha512 = SHA512.new(salt + struct.pack(">I", count)).digest()
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out_le = _bcrypt_hash(pwd_sha512, 6, salt_sha512, constant, False)
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out = struct.pack("<IIIIIIII", *struct.unpack(">IIIIIIII", out_le))
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acc = bytearray(out)
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for _ in range(1, iterations):
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out_le = _bcrypt_hash(pwd_sha512, 6, SHA512.new(out).digest(), constant, False)
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out = struct.pack("<IIIIIIII", *struct.unpack(">IIIIIIII", out_le))
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strxor(acc, out, output=acc)
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stripes.append(acc[:24])
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result = b"".join([bchr(a)+bchr(b) for (a, b) in zip(*stripes)])
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cipher = AES.new(result[:32],
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AES.MODE_CTR,
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nonce=b"",
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initial_value=result[32:32+16])
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decrypted = cipher.decrypt(encrypted)
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checkint1, decrypted = read_int4(decrypted)
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checkint2, decrypted = read_int4(decrypted)
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if checkint1 != checkint2:
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raise ValueError("Incorrect checksum")
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ssh_name, decrypted = read_string(decrypted)
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return ssh_name, decrypted
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