1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
|
""" Bcfg2.Server.Encryption provides a number of convenience methods
for handling encryption in Bcfg2. See :ref:`server-encryption` for
more details. """
import os
import Bcfg2.Options
from M2Crypto import Rand
from M2Crypto.EVP import Cipher, EVPError
from Bcfg2.Compat import StringIO, md5, b64encode, b64decode
#: Constant representing the encryption operation for
#: :class:`M2Crypto.EVP.Cipher`, which uses a simple integer. This
#: makes our code more readable.
ENCRYPT = 1
#: Constant representing the decryption operation for
#: :class:`M2Crypto.EVP.Cipher`, which uses a simple integer. This
#: makes our code more readable.
DECRYPT = 0
#: Default initialization vector. For best security, you should use a
#: unique IV for each message. :func:`ssl_encrypt` does this in an
#: automated fashion.
IV = '\0' * 16
#: The config file section encryption options and passphrases are
#: stored in
CFG_SECTION = "encryption"
#: The config option used to store the algorithm
CFG_ALGORITHM = "algorithm"
#: The config option used to store the decryption strictness
CFG_DECRYPT = "decrypt"
#: Default cipher algorithm. To get a full list of valid algorithms,
#: you can run::
#:
#: openssl list-cipher-algorithms | grep -v ' => ' | \
#: tr 'A-Z-' 'a-z_' | sort -u
ALGORITHM = Bcfg2.Options.get_option_parser().cfp.get( # pylint: disable=E1103
CFG_SECTION,
CFG_ALGORITHM,
default="aes_256_cbc").lower().replace("-", "_")
Rand.rand_seed(os.urandom(1024))
def _cipher_filter(cipher, instr):
""" M2Crypto reads and writes file-like objects, so this uses
StringIO to pass data through it """
inbuf = StringIO(instr)
outbuf = StringIO()
while 1:
buf = inbuf.read()
if not buf:
break
outbuf.write(cipher.update(buf))
outbuf.write(cipher.final())
rv = outbuf.getvalue()
inbuf.close()
outbuf.close()
return rv
def str_encrypt(plaintext, key, iv=IV, algorithm=ALGORITHM, salt=None):
""" Encrypt a string with a key. For a higher-level encryption
interface, see :func:`ssl_encrypt`.
:param plaintext: The plaintext data to encrypt
:type plaintext: string
:param key: The key to encrypt the data with
:type key: string
:param iv: The initialization vector
:type iv: string
:param algorithm: The cipher algorithm to use
:type algorithm: string
:param salt: The salt to use
:type salt: string
:returns: string - The decrypted data
"""
cipher = Cipher(alg=algorithm, key=key, iv=iv, op=ENCRYPT, salt=salt)
return _cipher_filter(cipher, plaintext)
def str_decrypt(crypted, key, iv=IV, algorithm=ALGORITHM):
""" Decrypt a string with a key. For a higher-level decryption
interface, see :func:`ssl_decrypt`.
:param crypted: The raw binary encrypted data
:type crypted: string
:param key: The encryption key to decrypt with
:type key: string
:param iv: The initialization vector
:type iv: string
:param algorithm: The cipher algorithm to use
:type algorithm: string
:returns: string - The decrypted data
"""
cipher = Cipher(alg=algorithm, key=key, iv=iv, op=DECRYPT)
return _cipher_filter(cipher, crypted)
def ssl_decrypt(data, passwd, algorithm=ALGORITHM):
""" Decrypt openssl-encrypted data. This can decrypt data
encrypted by :func:`ssl_encrypt`, or ``openssl enc``. It performs
a base64 decode first if the data is base64 encoded, and
automatically determines the salt and initialization vector (both
of which are embedded in the encrypted data).
:param data: The encrypted data (either base64-encoded or raw
binary) to decrypt
:type data: string
:param passwd: The password to use to decrypt the data
:type passwd: string
:param algorithm: The cipher algorithm to use
:type algorithm: string
:returns: string - The decrypted data
"""
# base64-decode the data
data = b64decode(data)
salt = data[8:16]
hashes = [md5(passwd + salt).digest()]
for i in range(1, 3):
hashes.append(md5(hashes[i - 1] + passwd + salt).digest())
key = hashes[0] + hashes[1]
iv = hashes[2]
return str_decrypt(data[16:], key=key, iv=iv, algorithm=algorithm)
def ssl_encrypt(plaintext, passwd, algorithm=ALGORITHM, salt=None):
""" Encrypt data in a format that is openssl compatible.
:param plaintext: The plaintext data to encrypt
:type plaintext: string
:param passwd: The password to use to encrypt the data
:type passwd: string
:param algorithm: The cipher algorithm to use
:type algorithm: string
:param salt: The salt to use. If none is provided, one will be
randomly generated.
:type salt: bytes
:returns: string - The base64-encoded, salted, encrypted string.
The string includes a trailing newline to make it fully
compatible with openssl command-line tools.
"""
if salt is None:
salt = Rand.rand_bytes(8)
hashes = [md5(passwd + salt).digest()]
for i in range(1, 3):
hashes.append(md5(hashes[i - 1] + passwd + salt).digest())
key = hashes[0] + hashes[1]
iv = hashes[2]
crypted = str_encrypt(plaintext, key=key, salt=salt, iv=iv,
algorithm=algorithm)
return b64encode("Salted__" + salt + crypted) + "\n"
def get_passphrases():
""" Get all candidate encryption passphrases from the config file.
:returns: dict - a dict of ``<passphrase name>``: ``<passphrase>``
"""
setup = Bcfg2.Options.get_option_parser()
if setup.cfp.has_section(CFG_SECTION):
return dict([(o, setup.cfp.get(CFG_SECTION, o))
for o in setup.cfp.options(CFG_SECTION)
if o not in [CFG_ALGORITHM, CFG_DECRYPT]])
else:
return dict()
def bruteforce_decrypt(crypted, passphrases=None, algorithm=ALGORITHM):
""" Convenience method to decrypt the given encrypted string by
trying the given passphrases or all passphrases (as returned by
:func:`get_passphrases`) sequentially until one is found that
works.
:param crypted: The data to decrypt
:type crypted: string
:param passphrases: The passphrases to try.
:type passphrases: list
:param algorithm: The cipher algorithm to use
:type algorithm: string
:returns: string - The decrypted data
:raises: :class:`M2Crypto.EVP.EVPError`, if the data cannot be decrypted
"""
if passphrases is None:
passphrases = get_passphrases().values()
for passwd in passphrases:
try:
return ssl_decrypt(crypted, passwd, algorithm=algorithm)
except EVPError:
pass
raise EVPError("Failed to decrypt")
|
