""" 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
[docs]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)
[docs]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)
[docs]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)
[docs]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"
[docs]def is_encrypted(val):
""" Make a best guess if the value is encrypted or not. This just
checks to see if ``val`` is a base64-encoded string whose content
starts with "Salted__", so it may have (rare) false positives. It
will not have false negatives. """
try:
return b64decode(val).startswith("Salted__")
except: # pylint: disable=W0702
return False
[docs]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")
[docs]def print_xml(element, keep_text=False):
""" Render an XML element for error output. This prefixes the
line number and removes children for nicer display.
:param element: The element to render
:type element: lxml.etree._Element
:param keep_text: Do not discard text content from the element for
display
:type keep_text: boolean
"""
xml = None
if len(element) or element.text:
el = copy.copy(element)
if el.text and not keep_text:
el.text = '...'
for child in el.iterchildren():
el.remove(child)
xml = lxml.etree.tostring(
el,
xml_declaration=False).decode("UTF-8").strip()
else:
xml = lxml.etree.tostring(
element,
xml_declaration=False).decode("UTF-8").strip()
return "%s (line %s)" % (xml, element.sourceline)
[docs]class PassphraseError(Exception):
""" Exception raised when there's a problem determining the
passphrase to encrypt or decrypt with """
[docs]class DecryptError(Exception):
""" Exception raised when decryption fails. """
[docs]class EncryptError(Exception):
""" Exception raised when encryption fails. """
[docs]class Decryptor(CryptoTool):
""" Decryptor interface """
[docs] def decrypt(self):
""" decrypt the file, returning the encrypted data """
raise NotImplementedError
[docs]class Encryptor(CryptoTool):
""" encryptor interface """
[docs] def encrypt(self):
""" encrypt the file, returning the encrypted data """
raise NotImplementedError
[docs]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.config)
def encrypt(self):
if is_encrypted(self.data):
raise EncryptError("Data is alraedy encrypted")
return ssl_encrypt(self.data, self.passphrase)
def get_destination_filename(self, original_filename):
return original_filename + ".crypt"
[docs]class CfgDecryptor(Decryptor):
""" Decrypt Cfg files """
[docs] def decrypt(self):
""" decrypt the given file, returning the plaintext data """
if self.passphrase:
try:
return ssl_decrypt(self.data, self.passphrase)
except EVPError:
raise DecryptError("Could not decrypt %s with the "
"specified passphrase" % self.filename)
except:
raise DecryptError("Error decrypting %s: %s" %
(self.filename, sys.exc_info()[1]))
else: # no passphrase given, brute force
try:
return bruteforce_decrypt(self.data)
except EVPError:
raise DecryptError("Could not decrypt %s with any passphrase" %
self.filename)
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)
[docs]class PropertiesCryptoMixin(object):
""" Mixin to provide some common methods for Properties crypto """
default_xpath = '//*[@encrypted]'
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 Bcfg2.Options.setup.passphrases:
passphrase = Bcfg2.Options.setup.passphrases[pname]
else:
if pname:
self.logger.warning("Passphrase %s not found in %s, "
"using passphrase given on command line" %
(pname, Bcfg2.Options.setup.config))
if self.passphrase:
passphrase = self.passphrase
pname = self.pname
else:
self.logger.warning("No passphrase specified for %s element" %
element.tag)
raise PassphraseError("Multiple passphrases found in %s, "
"specify one on the command line with "
"-p" % Bcfg2.Options.setup.config)
return (pname, passphrase)
def _write(self, filename, data):
""" Write the data """
data.getroottree().write(filename,
xml_declaration=False,
pretty_print=True)
[docs]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):
if is_encrypted(elt.text):
raise EncryptError("Element is already encrypted: %s" %
print_xml(elt))
try:
pname, passphrase = self._get_element_passphrase(elt)
except PassphraseError:
raise EncryptError(str(sys.exc_info()[1]))
self.logger.debug("Encrypting %s" % print_xml(elt))
elt.text = ssl_encrypt(elt.text, passphrase).strip()
elt.set("encrypted", pname)
return xdata
def _write(self, filename, data):
PropertiesCryptoMixin._write(self, filename, data)
[docs]class PropertiesDecryptor(Decryptor, PropertiesCryptoMixin):
""" decryptor class for Properties files """
def decrypt(self):
decrypted_any = False
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:
raise DecryptError(str(sys.exc_info()[1]))
self.logger.debug("Decrypting %s" % print_xml(elt))
try:
decrypted = ssl_decrypt(elt.text, passphrase).strip()
elt.text = decrypted.encode('ascii', 'xmlcharrefreplace')
elt.set("encrypted", pname)
decrypted_any = True
except (EVPError, TypeError):
self.logger.error("Could not decrypt %s, skipping" %
print_xml(elt))
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)
if decrypted_any:
return xdata
else:
raise DecryptError("Failed to decrypt any data in %s" %
self.filename)
def _write(self, filename, data):
PropertiesCryptoMixin._write(self, filename, data)
[docs]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, argv=None):
parser = Bcfg2.Options.get_parser(
description="Encrypt and decrypt Bcfg2 data",
components=[self, _OptionContainer])
parser.parse(argv=argv)
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
[docs] 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:
ftype = "Properties"
if Bcfg2.Options.setup.remove:
self.logger.info("Cannot use --remove with Properties "
"file %s, ignoring for this file" % fname)
tools = (PropertiesEncryptor, PropertiesDecryptor)
else:
ftype = "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
tools = (CfgEncryptor, CfgDecryptor)
data = None
mode = None
if Bcfg2.Options.setup.encrypt:
try:
tool = tools[0](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
mode = "encrypt"
self.logger.debug("Encrypting %s file %s" % (ftype, fname))
elif Bcfg2.Options.setup.decrypt:
try:
tool = tools[1](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
mode = "decrypt"
self.logger.debug("Decrypting %s file %s" % (ftype, fname))
else:
self.logger.info("Neither --encrypt nor --decrypt specified, "
"determining mode")
try:
tool = tools[1](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
try:
self.logger.debug("Trying to decrypt %s file %s" % (ftype,
fname))
data = tool.decrypt()
mode = "decrypt"
self.logger.debug("Decrypted %s file %s" % (ftype, fname))
except DecryptError:
self.logger.info("Failed to decrypt %s, trying encryption"
% fname)
try:
tool = tools[0](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
mode = "encrypt"
self.logger.debug("Encrypting %s file %s" % (ftype, fname))
if data is None:
try:
data = getattr(tool, mode)()
except (EncryptError, DecryptError):
self.logger.error("Failed to %s %s, skipping: %s" %
(mode, fname, sys.exc_info()[1]))
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
