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|
""" Bcfg2.Server.Encryption provides a number of convenience methods
for handling encryption in Bcfg2. See :ref:`server-encryption` for
more details. """
import os
import sys
import copy
import logging
import lxml.etree
import Bcfg2.Logger
import Bcfg2.Options
from M2Crypto import Rand
from M2Crypto.EVP import Cipher, EVPError
from Bcfg2.Utils import safe_input
from Bcfg2.Server import XMLParser
from Bcfg2.Compat import md5, b64encode, b64decode, StringIO
#: 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 = r'\0' * 16
class _OptionContainer(object):
options = [
Bcfg2.Options.BooleanOption(
cf=("encryption", "lax_decryption"),
help="Decryption failures should cause warnings, not errors"),
Bcfg2.Options.Option(
cf=("encryption", "algorithm"), default="aes_256_cbc",
type=lambda v: v.lower().replace("-", "_"),
help="The encryption algorithm to use"),
Bcfg2.Options.Option(
cf=("encryption", "*"), dest='passphrases', default=dict(),
help="Encryption passphrases")]
Bcfg2.Options.get_parser().add_component(_OptionContainer)
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=None, 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
"""
if algorithm is None:
algorithm = Bcfg2.Options.setup.algorithm
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=None):
""" 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
"""
if algorithm is None:
algorithm = Bcfg2.Options.setup.algorithm
cipher = Cipher(alg=algorithm, key=key, iv=iv, op=DECRYPT)
return _cipher_filter(cipher, crypted)
def ssl_decrypt(data, passwd, algorithm=None):
""" 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]
# pylint: disable=E1101,E1121
hashes = [md5(passwd + salt).digest()]
for i in range(1, 3):
hashes.append(md5(hashes[i - 1] + passwd + salt).digest())
# pylint: enable=E1101,E1121
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=None, 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)
# pylint: disable=E1101,E1121
hashes = [md5(passwd + salt).digest()]
for i in range(1, 3):
hashes.append(md5(hashes[i - 1] + passwd + salt).digest())
# pylint: enable=E1101,E1121
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 bruteforce_decrypt(crypted, passphrases=None, algorithm=None):
""" Convenience method to decrypt the given encrypted string by
trying the given passphrases or all 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 = Bcfg2.Options.setup.passphrases.values()
for passwd in passphrases:
try:
return ssl_decrypt(crypted, passwd, algorithm=algorithm)
except EVPError:
pass
raise EVPError("Failed to decrypt")
class EncryptionChunkingError(Exception):
""" error raised when Encryptor cannot break a file up into chunks
to be encrypted, or cannot reassemble the chunks """
pass
class Encryptor(object):
""" Generic encryptor for all files """
def __init__(self):
self.passphrase = None
self.pname = None
self.logger = logging.getLogger(self.__class__.__name__)
def get_encrypted_filename(self, plaintext_filename):
""" get the name of the file encrypted data should be written to """
return plaintext_filename
def get_plaintext_filename(self, encrypted_filename):
""" get the name of the file decrypted data should be written to """
return encrypted_filename
def chunk(self, data):
""" generator to break the file up into smaller chunks that
will each be individually encrypted or decrypted """
yield data
def unchunk(self, data, original): # pylint: disable=W0613
""" given chunks of a file, reassemble then into the whole file """
try:
return data[0]
except IndexError:
raise EncryptionChunkingError("No data to unchunk")
def set_passphrase(self):
""" set the passphrase for the current file """
if not Bcfg2.Options.setup.passphrases:
self.logger.error("No passphrases available in %s" %
Bcfg2.Options.setup.config)
return False
if self.passphrase:
self.logger.debug("Using previously determined passphrase %s" %
self.pname)
return True
if Bcfg2.Options.setup.passphrase:
self.pname = Bcfg2.Options.setup.passphrase
if self.pname:
try:
self.passphrase = Bcfg2.Options.setup.passphrases[self.pname]
self.logger.debug("Using passphrase %s specified on command "
"line" % self.pname)
return True
except KeyError:
self.logger.error("Could not find passphrase %s in %s" %
(self.pname, Bcfg2.Options.setup.config))
return False
else:
pnames = Bcfg2.Options.setup.passphrases
if len(pnames) == 1:
self.pname = pnames.keys()[0]
self.passphrase = pnames[self.pname]
self.logger.info("Using passphrase %s" % self.pname)
return True
elif len(pnames) > 1:
self.logger.warning("Multiple passphrases found in %s, "
"specify one on the command line with -p" %
Bcfg2.Options.setup.config)
self.logger.info("No passphrase could be determined")
return False
def encrypt(self, fname):
""" encrypt the given file, returning the encrypted data """
try:
plaintext = open(fname).read()
except IOError:
err = sys.exc_info()[1]
self.logger.error("Error reading %s, skipping: %s" % (fname, err))
return False
if not self.set_passphrase():
return False
crypted = []
try:
for chunk in self.chunk(plaintext):
try:
passphrase, pname = self.get_passphrase(chunk)
except TypeError:
return False
crypted.append(self._encrypt(chunk, passphrase, name=pname))
except EncryptionChunkingError:
err = sys.exc_info()[1]
self.logger.error("Error getting data to encrypt from %s: %s" %
(fname, err))
return False
return self.unchunk(crypted, plaintext)
# pylint: disable=W0613
def _encrypt(self, plaintext, passphrase, name=None):
""" encrypt a single chunk of a file """
return ssl_encrypt(plaintext, passphrase)
# pylint: enable=W0613
def decrypt(self, fname):
""" decrypt the given file, returning the plaintext data """
try:
crypted = open(fname).read()
except IOError:
err = sys.exc_info()[1]
self.logger.error("Error reading %s, skipping: %s" % (fname, err))
return False
self.set_passphrase()
plaintext = []
try:
for chunk in self.chunk(crypted):
try:
passphrase, pname = self.get_passphrase(chunk)
try:
plaintext.append(self._decrypt(chunk, passphrase))
except EVPError:
self.logger.info("Could not decrypt %s with the "
"specified passphrase" % fname)
continue
except:
err = sys.exc_info()[1]
self.logger.error("Error decrypting %s: %s" %
(fname, err))
continue
except TypeError:
pchunk = None
for pname, passphrase in \
Bcfg2.Options.setup.passphrases.items():
self.logger.debug("Trying passphrase %s" % pname)
try:
pchunk = self._decrypt(chunk, passphrase)
break
except EVPError:
pass
except:
err = sys.exc_info()[1]
self.logger.error("Error decrypting %s: %s" %
(fname, err))
if pchunk is not None:
plaintext.append(pchunk)
else:
self.logger.error("Could not decrypt %s with any "
"passphrase in %s" %
(fname, Bcfg2.Options.setup.config))
continue
except EncryptionChunkingError:
err = sys.exc_info()[1]
self.logger.error("Error getting encrypted data from %s: %s" %
(fname, err))
return False
try:
return self.unchunk(plaintext, crypted)
except EncryptionChunkingError:
err = sys.exc_info()[1]
self.logger.error("Error assembling plaintext data from %s: %s" %
(fname, err))
return False
def _decrypt(self, crypted, passphrase):
""" decrypt a single chunk """
return ssl_decrypt(crypted, passphrase)
def write_encrypted(self, fname, data=None):
""" write encrypted data to disk """
if data is None:
data = self.decrypt(fname)
new_fname = self.get_encrypted_filename(fname)
try:
open(new_fname, "wb").write(data)
self.logger.info("Wrote encrypted data to %s" % new_fname)
return True
except IOError:
err = sys.exc_info()[1]
self.logger.error("Error writing encrypted data from %s to %s: %s"
% (fname, new_fname, err))
return False
except EncryptionChunkingError:
err = sys.exc_info()[1]
self.logger.error("Error assembling encrypted data from %s: %s" %
(fname, err))
return False
def write_decrypted(self, fname, data=None):
""" write decrypted data to disk """
if data is None:
data = self.decrypt(fname)
new_fname = self.get_plaintext_filename(fname)
try:
open(new_fname, "wb").write(data)
self.logger.info("Wrote decrypted data to %s" % new_fname)
return True
except IOError:
err = sys.exc_info()[1]
self.logger.error("Error writing encrypted data from %s to %s: %s"
% (fname, new_fname, err))
return False
def get_passphrase(self, chunk):
""" get the passphrase for a chunk of a file """
pname = self._get_passphrase(chunk)
if not self.pname:
if not pname:
self.logger.info("No passphrase given on command line or "
"found in file")
return False
elif pname in Bcfg2.Options.setup.passphrases:
passphrase = Bcfg2.Options.setup.passphrases[pname]
else:
self.logger.error("Could not find passphrase %s in %s" %
(pname, Bcfg2.Options.setup.config))
return False
else:
pname = self.pname
passphrase = self.passphrase
if self.pname != pname:
self.logger.warning("Passphrase given on command line (%s) "
"differs from passphrase embedded in "
"file (%s), using command-line option" %
(self.pname, pname))
return (passphrase, pname)
def _get_passphrase(self, chunk): # pylint: disable=W0613
""" get the passphrase for a chunk of a file """
return None
class CfgEncryptor(Encryptor):
""" encryptor class for Cfg files """
def get_encrypted_filename(self, plaintext_filename):
return plaintext_filename + ".crypt"
def get_plaintext_filename(self, encrypted_filename):
if encrypted_filename.endswith(".crypt"):
return encrypted_filename[:-6]
else:
return Encryptor.get_plaintext_filename(self, encrypted_filename)
class PropertiesEncryptor(Encryptor):
""" encryptor class for Properties files """
def _encrypt(self, plaintext, passphrase, name=None):
# plaintext is an lxml.etree._Element
if name is None:
name = "true"
if plaintext.text and plaintext.text.strip():
plaintext.text = ssl_encrypt(plaintext.text, passphrase).strip()
plaintext.set("encrypted", name)
return plaintext
def chunk(self, data):
xdata = lxml.etree.XML(data, parser=XMLParser)
if Bcfg2.Options.setup.xpath:
elements = xdata.xpath(Bcfg2.Options.setup.xpath)
if not elements:
raise EncryptionChunkingError(
"XPath expression %s matched no elements" %
Bcfg2.Options.setup.xpath)
else:
elements = xdata.xpath('//*[@encrypted]')
if not elements:
elements = list(xdata.getiterator(tag=lxml.etree.Element))
# filter out elements without text data
for el in elements[:]:
if not el.text:
elements.remove(el)
if Bcfg2.Options.setup.interactive:
for element in elements[:]:
if len(element):
elt = copy.copy(element)
for child in elt.iterchildren():
elt.remove(child)
else:
elt = element
print(lxml.etree.tostring(
elt,
xml_declaration=False).decode("UTF-8").strip())
ans = safe_input("Encrypt this element? [y/N] ")
if not ans.lower().startswith("y"):
elements.remove(element)
# this is not a good use of a generator, but we need to
# generate the full list of elements in order to ensure that
# some exist before we know what to return
for elt in elements:
yield elt
def unchunk(self, data, original):
# Properties elements are modified in-place, so we don't
# actually need to unchunk anything
xdata = Encryptor.unchunk(self, data, original)
# find root element
while xdata.getparent() is not None:
xdata = xdata.getparent()
return lxml.etree.tostring(xdata,
xml_declaration=False,
pretty_print=True).decode('UTF-8')
def _get_passphrase(self, chunk):
pname = chunk.get("encrypted")
if pname and pname.lower() != "true":
return pname
return None
def _decrypt(self, crypted, passphrase):
# crypted is in lxml.etree._Element
if not crypted.text or not crypted.text.strip():
self.logger.warning("Skipping empty element %s" % crypted.tag)
return crypted
decrypted = ssl_decrypt(crypted.text, passphrase).strip()
try:
crypted.text = decrypted.encode('ascii', 'xmlcharrefreplace')
except UnicodeDecodeError:
# we managed to decrypt the value, but it contains content
# that can't even be encoded into xml entities. what
# probably happened here is that we coincidentally could
# decrypt a value encrypted with a different key, and
# wound up with gibberish.
self.logger.warning("Decrypted %s to gibberish, skipping" %
crypted.tag)
return crypted
class CLI(object):
""" The bcfg2-crypt CLI """
options = [
Bcfg2.Options.ExclusiveOptionGroup(
Bcfg2.Options.BooleanOption(
"--encrypt", help='Encrypt the specified file'),
Bcfg2.Options.BooleanOption(
"--decrypt", help='Decrypt the specified file')),
Bcfg2.Options.BooleanOption(
"--stdout",
help='Decrypt or encrypt the specified file to stdout'),
Bcfg2.Options.Option(
"-p", "--passphrase", metavar="NAME",
help='Encryption passphrase name'),
Bcfg2.Options.ExclusiveOptionGroup(
Bcfg2.Options.BooleanOption(
"--properties",
help='Encrypt the specified file as a Properties file'),
Bcfg2.Options.BooleanOption(
"--cfg", help='Encrypt the specified file as a Cfg file')),
Bcfg2.Options.OptionGroup(
Bcfg2.Options.Common.interactive,
Bcfg2.Options.Option(
"--xpath",
help='XPath expression to select elements to encrypt'),
title="Options for handling Properties files"),
Bcfg2.Options.OptionGroup(
Bcfg2.Options.BooleanOption(
"--remove", help='Remove the plaintext file after encrypting'),
title="Options for handling Cfg files"),
Bcfg2.Options.PathOption(
"files", help="File(s) to encrypt or decrypt", nargs='+')]
def __init__(self):
parser = Bcfg2.Options.get_parser(
description="Encrypt and decrypt Bcfg2 data",
components=[self, OptionContainer])
parser.parse()
self.logger = logging.getLogger(parser.prog)
if Bcfg2.Options.setup.decrypt:
if Bcfg2.Options.setup.remove:
self.logger.error("--remove cannot be used with --decrypt, "
"ignoring --remove")
Bcfg2.Options.setup.remove = False
elif Bcfg2.Options.setup.interactive:
self.logger.error("Cannot decrypt interactively")
Bcfg2.Options.setup.interactive = False
if Bcfg2.Options.setup.cfg:
if Bcfg2.Options.setup.xpath:
self.logger.error("Specifying --xpath with --cfg is "
"nonsensical, ignoring --xpath")
Bcfg2.Options.setup.xpath = None
if Bcfg2.Options.setup.interactive:
self.logger.error("Cannot use interactive mode with --cfg, "
"ignoring --interactive")
Bcfg2.Options.setup.interactive = False
elif Bcfg2.Options.setup.properties:
if Bcfg2.Options.setup.remove:
self.logger.error("--remove cannot be used with --properties, "
"ignoring --remove")
Bcfg2.Options.setup.remove = False
self.props_crypt = PropertiesEncryptor()
self.cfg_crypt = CfgEncryptor()
def _is_properties(self, filename):
""" Determine if a given file is a Properties file or not """
if Bcfg2.Options.setup.properties:
return True
elif Bcfg2.Options.setup.cfg:
return False
elif fname.endswith(".xml"):
try:
xroot = lxml.etree.parse(fname).getroot()
return xroot.tag == "Properties"
except lxml.etree.XMLSyntaxError:
return False
else:
return False
def run(self): # pylint: disable=R0912,R0915
for fname in Bcfg2.Options.setup.files:
if not os.path.exists(fname):
self.logger.error("%s does not exist, skipping" % fname)
continue
# figure out if we need to encrypt this as a Properties file
# or as a Cfg file
try:
props = self._is_properties(fname)
except IOError:
err = sys.exc_info()[1]
self.logger.error("Error reading %s, skipping: %s" %
(fname, err))
continue
if props:
encryptor = self.props_crypt
if Bcfg2.Options.setup.remove:
self.logger.warning("Cannot use --remove with Properties "
"file %s, ignoring for this file" %
fname)
else:
if Bcfg2.Options.setup.xpath:
self.logger.warning("Cannot use xpath with Cfg file %s, "
"ignoring xpath for this file" % fname)
if Bcfg2.Options.setup.interactive:
self.logger.warning("Cannot use interactive mode with Cfg "
"file %s, ignoring --interactive for "
"this file" % fname)
encryptor = self.cfg_crypt
data = None
if Bcfg2.Options.setup.encrypt:
xform = encryptor.encrypt
write = encryptor.write_encrypted
elif Bcfg2.Options.setup.decrypt:
xform = encryptor.decrypt
write = encryptor.write_decrypted
else:
self.logger.warning("Neither --encrypt nor --decrypt "
"specified, determining mode")
data = encryptor.decrypt(fname)
if data:
write = encryptor.write_decrypted
else:
self.logger.warning("Failed to decrypt %s, trying "
"encryption" % fname)
data = None
xform = encryptor.encrypt
write = encryptor.write_encrypted
if data is None:
data = xform(fname)
if not data:
self.logger.error("Failed to %s %s, skipping" %
(xform.__name__, fname))
continue
if Bcfg2.Options.setup.stdout:
if len(Bcfg2.Options.setup.files) > 1:
print("----- %s -----" % fname)
print(data)
if len(Bcfg2.Options.setup.files) > 1:
print("")
else:
write(fname, data=data)
if (Bcfg2.Options.setup.remove and
encryptor.get_encrypted_filename(fname) != fname):
try:
os.unlink(fname)
except IOError:
err = sys.exc_info()[1]
self.logger.error("Error removing %s: %s" % (fname, err))
continue
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