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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):
""" Container for options loaded at import-time to configure
encryption """
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 PassphraseError(Exception):
""" Exception raised when there's a problem determining the
passphrase to encrypt or decrypt with """
class CryptoTool(object):
""" Generic decryption/encryption interface base object """
def __init__(self, filename):
self.logger = logging.getLogger(self.__class__.__name__)
self.filename = filename
self.data = open(self.filename).read()
self.pname, self.passphrase = self._get_passphrase()
def _get_passphrase(self):
""" get the passphrase for the current file """
if not Bcfg2.Options.setup.passphrases:
raise PassphraseError("No passphrases available in %s" %
Bcfg2.Options.setup.configfile)
pname = None
if Bcfg2.Options.setup.passphrase:
pname = Bcfg2.Options.setup.passphrase
if pname:
try:
passphrase = Bcfg2.Options.setup.passphrases[pname]
self.logger.debug("Using passphrase %s specified on command "
"line" % pname)
return (pname, passphrase)
except KeyError:
raise PassphraseError("Could not find passphrase %s in %s" %
(pname, Bcfg2.Options.setup.configfile))
else:
if len(Bcfg2.Options.setup.passphrases) == 1:
pname, passphrase = Bcfg2.Options.setup.passphrases.items()[0]
self.logger.info("Using passphrase %s" % pname)
return (pname, passphrase)
elif len(Bcfg2.Options.setup.passphrases) > 1:
return (None, None)
raise PassphraseError("No passphrase could be determined")
def get_destination_filename(self, original_filename):
""" Get the filename where data should be written """
return original_filename
def write(self, data):
""" write data to disk """
new_fname = self.get_destination_filename(self.filename)
try:
self._write(new_fname, data)
self.logger.info("Wrote data to %s" % new_fname)
return True
except IOError:
err = sys.exc_info()[1]
self.logger.error("Error writing data from %s to %s: %s" %
(self.filename, new_fname, err))
return False
def _write(self, filename, data):
""" Perform the actual write of data. This is separate from
:func:`CryptoTool.write` so it can be easily
overridden. """
open(filename, "wb").write(data)
class Decryptor(CryptoTool):
""" Decryptor interface """
def decrypt(self):
""" decrypt the file, returning the encrypted data """
raise NotImplementedError
class Encryptor(CryptoTool):
""" encryptor interface """
def encrypt(self):
""" encrypt the file, returning the encrypted data """
raise NotImplementedError
class CfgEncryptor(Encryptor):
""" encryptor class for Cfg files """
def __init__(self, filename):
Encryptor.__init__(self, filename)
if self.passphrase is None:
raise PassphraseError("Multiple passphrases found in %s, "
"specify one on the command line with -p" %
Bcfg2.Options.setup.configfile)
def encrypt(self):
return ssl_encrypt(self.data, self.passphrase)
def get_destination_filename(self, original_filename):
return original_filename + ".crypt"
class CfgDecryptor(Decryptor):
""" Decrypt Cfg files """
def decrypt(self):
""" decrypt the given file, returning the plaintext data """
if self.passphrase:
try:
return ssl_decrypt(self.data, self.passphrase)
except EVPError:
self.logger.info("Could not decrypt %s with the "
"specified passphrase" % self.filename)
return False
except:
err = sys.exc_info()[1]
self.logger.error("Error decrypting %s: %s" %
(self.filename, err))
return False
else: # no passphrase given, brute force
try:
return bruteforce_decrypt(self.data)
except EVPError:
self.logger.info("Could not decrypt %s with any passphrase" %
self.filename)
return False
def get_destination_filename(self, original_filename):
if original_filename.endswith(".crypt"):
return original_filename[:-6]
else:
return Decryptor.get_destination_filename(self, original_filename)
class PropertiesCryptoMixin(object):
""" Mixin to provide some common methods for Properties crypto """
default_xpath = '//*'
def _get_elements(self, xdata):
""" Get the list of elements to encrypt or decrypt """
if Bcfg2.Options.setup.xpath:
elements = xdata.xpath(Bcfg2.Options.setup.xpath)
if not elements:
self.logger.warning("XPath expression %s matched no elements" %
Bcfg2.Options.setup.xpath)
else:
elements = xdata.xpath(self.default_xpath)
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)
return elements
def _get_element_passphrase(self, element):
""" Get the passphrase to use to encrypt or decrypt a given
element """
pname = element.get("encrypted")
if pname in self.passphrases:
passphrase = self.passphrases[pname]
elif self.passphrase:
if pname:
self.logger.warning("Passphrase %s not found in %s, "
"using passphrase given on command line" %
(pname, Bcfg2.Options.setup.configfile))
passphrase = self.passphrase
pname = self.pname
else:
raise PassphraseError("Multiple passphrases found in %s, "
"specify one on the command line with -p" %
Bcfg2.Options.setup.configfile)
return (pname, passphrase)
def _write(self, filename, data):
""" Write the data """
data.getroottree().write(filename,
xml_declaration=False,
pretty_print=True)
class PropertiesEncryptor(Encryptor, PropertiesCryptoMixin):
""" encryptor class for Properties files """
def encrypt(self):
xdata = lxml.etree.XML(self.data, parser=XMLParser)
for elt in self._get_elements(xdata):
try:
pname, passphrase = self._get_element_passphrase(elt)
except PassphraseError:
self.logger.error(str(sys.exc_info()[1]))
return False
elt.text = ssl_encrypt(elt.text, passphrase).strip()
elt.set("encrypted", pname)
return xdata
def _write(self, filename, data):
PropertiesCryptoMixin._write(self, filename, data)
class PropertiesDecryptor(Decryptor, PropertiesCryptoMixin):
""" decryptor class for Properties files """
default_xpath = '//*[@encrypted]'
def decrypt(self):
xdata = lxml.etree.XML(self.data, parser=XMLParser)
for elt in self._get_elements(xdata):
try:
pname, passphrase = self._get_element_passphrase(elt)
except PassphraseError:
self.logger.error(str(sys.exc_info()[1]))
return False
decrypted = ssl_decrypt(elt.text, passphrase).strip()
try:
elt.text = decrypted.encode('ascii', 'xmlcharrefreplace')
elt.set("encrypted", pname)
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" %
elt.tag)
return xdata
def _write(self, filename, data):
PropertiesCryptoMixin._write(self, filename, data)
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
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 filename.endswith(".xml"):
try:
xroot = lxml.etree.parse(filename).getroot()
return xroot.tag == "Properties"
except lxml.etree.XMLSyntaxError:
return False
else:
return False
def run(self): # pylint: disable=R0912,R0915
""" Run bcfg2-crypt """
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:
if Bcfg2.Options.setup.remove:
self.logger.info("Cannot use --remove with Properties "
"file %s, ignoring for this file" % fname)
try:
tools = (PropertiesEncryptor(fname),
PropertiesDecryptor(fname))
except PassphraseError:
self.logger.error(str(sys.exc_info()[1]))
continue
except IOError:
self.logger.error("Error reading %s, skipping: %s" %
(fname, err))
continue
else:
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
try:
tools = (CfgEncryptor(fname), CfgDecryptor(fname))
except PassphraseError:
self.logger.error(str(sys.exc_info()[1]))
continue
except IOError:
self.logger.error("Error reading %s, skipping: %s" %
(fname, err))
continue
data = None
mode = None
if Bcfg2.Options.setup.encrypt:
tool = tools[0]
mode = "encrypt"
elif Bcfg2.Options.setup.decrypt:
tool = tools[1]
mode = "decrypt"
else:
self.logger.info("Neither --encrypt nor --decrypt specified, "
"determining mode")
tool = tools[1]
try:
data = tool.decrypt()
mode = "decrypt"
except: # pylint: disable=W0702
pass
if data is False:
data = None
self.logger.info("Failed to decrypt %s, trying encryption"
% fname)
tool = tools[0]
mode = "encrypt"
if data is None:
data = getattr(tool, mode)()
if not data:
self.logger.error("Failed to %s %s, skipping" % (mode, 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:
tool.write(data)
if (Bcfg2.Options.setup.remove and
tool.get_destination_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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