"""passlib.handlers.md5_crypt - md5-crypt algorithm"""
#=============================================================================
# imports
#=============================================================================
# core
from hashlib import md5
import logging; log = logging.getLogger(__name__)
# site
# pkg
from passlib.utils import safe_crypt, test_crypt, repeat_string
from passlib.utils.binary import h64
from passlib.utils.compat import unicode, u
import passlib.utils.handlers as uh
# local
__all__ = [
"md5_crypt",
"apr_md5_crypt",
]
#=============================================================================
# pure-python backend
#=============================================================================
_BNULL = b"\x00"
_MD5_MAGIC = b"$1$"
_APR_MAGIC = b"$apr1$"
# pre-calculated offsets used to speed up C digest stage (see notes below).
# sequence generated using the following:
##perms_order = "p,pp,ps,psp,sp,spp".split(",")
##def offset(i):
## key = (("p" if i % 2 else "") + ("s" if i % 3 else "") +
## ("p" if i % 7 else "") + ("" if i % 2 else "p"))
## return perms_order.index(key)
##_c_digest_offsets = [(offset(i), offset(i+1)) for i in range(0,42,2)]
_c_digest_offsets = (
(0, 3), (5, 1), (5, 3), (1, 2), (5, 1), (5, 3), (1, 3),
(4, 1), (5, 3), (1, 3), (5, 0), (5, 3), (1, 3), (5, 1),
(4, 3), (1, 3), (5, 1), (5, 2), (1, 3), (5, 1), (5, 3),
)
# map used to transpose bytes when encoding final digest
_transpose_map = (12, 6, 0, 13, 7, 1, 14, 8, 2, 15, 9, 3, 5, 10, 4, 11)
def _raw_md5_crypt(pwd, salt, use_apr=False):
"""perform raw md5-crypt calculation
this function provides a pure-python implementation of the internals
for the MD5-Crypt algorithms; it doesn't handle any of the
parsing/validation of the hash strings themselves.
:arg pwd: password chars/bytes to hash
:arg salt: salt chars to use
:arg use_apr: use apache variant
:returns:
encoded checksum chars
"""
# NOTE: regarding 'apr' format:
# really, apache? you had to invent a whole new "$apr1$" format,
# when all you did was change the ident incorporated into the hash?
# would love to find webpage explaining why just using a portable
# implementation of $1$ wasn't sufficient. *nothing else* was changed.
#===================================================================
# init & validate inputs
#===================================================================
# validate secret
# XXX: not sure what official unicode policy is, using this as default
if isinstance(pwd, unicode):
pwd = pwd.encode("utf-8")
assert isinstance(pwd, bytes), "pwd not unicode or bytes"
if _BNULL in pwd:
raise uh.exc.NullPasswordError(md5_crypt)
pwd_len = len(pwd)
# validate salt - should have been taken care of by caller
assert isinstance(salt, unicode), "salt not unicode"
salt = salt.encode("ascii")
assert len(salt) < 9, "salt too large"
# NOTE: spec says salts larger than 8 bytes should be truncated,
# instead of causing an error. this function assumes that's been
# taken care of by the handler class.
# load APR specific constants
if use_apr:
magic = _APR_MAGIC
else:
magic = _MD5_MAGIC
#===================================================================
# digest B - used as subinput to digest A
#===================================================================
db = md5(pwd + salt + pwd).digest()
#===================================================================
# digest A - used to initialize first round of digest C
#===================================================================
# start out with pwd + magic + salt
a_ctx = md5(pwd + magic + salt)
a_ctx_update = a_ctx.update
# add pwd_len bytes of b, repeating b as many times as needed.
a_ctx_update(repeat_string(db, pwd_len))
# add null chars & first char of password
# NOTE: this may have historically been a bug,
# where they meant to use db[0] instead of B_NULL,
# but the original code memclear'ed db,
# and now all implementations have to use this.
i = pwd_len
evenchar = pwd[:1]
while i:
a_ctx_update(_BNULL if i & 1 else evenchar)
i >>= 1
# finish A
da = a_ctx.digest()
#===================================================================
# digest C - for a 1000 rounds, combine A, S, and P
# digests in various ways; in order to burn CPU time.
#===================================================================
# NOTE: the original MD5-Crypt implementation performs the C digest
# calculation using the following loop:
#
##dc = da
##i = 0
##while i < rounds:
## tmp_ctx = md5(pwd if i & 1 else dc)
## if i % 3:
## tmp_ctx.update(salt)
## if i % 7:
## tmp_ctx.update(pwd)
## tmp_ctx.update(dc if i & 1 else pwd)
## dc = tmp_ctx.digest()
## i += 1
#
# The code Passlib uses (below) implements an equivalent algorithm,
# it's just been heavily optimized to pre-calculate a large number
# of things beforehand. It works off of a couple of observations
# about the original algorithm:
#
# 1. each round is a combination of 'dc', 'salt', and 'pwd'; and the exact
# combination is determined by whether 'i' a multiple of 2,3, and/or 7.
# 2. since lcm(2,3,7)==42, the series of combinations will repeat
# every 42 rounds.
# 3. even rounds 0-40 consist of 'hash(dc + round-specific-constant)';
# while odd rounds 1-41 consist of hash(round-specific-constant + dc)
#
# Using these observations, the following code...
# * calculates the round-specific combination of salt & pwd for each round 0-41
# * runs through as many 42-round blocks as possible (23)
# * runs through as many pairs of rounds as needed for remaining rounds (17)
# * this results in the required 42*23+2*17=1000 rounds required by md5_crypt.
#
# this cuts out a lot of the control overhead incurred when running the
# original loop 1000 times in python, resulting in ~20% increase in
# speed under CPython (though still 2x slower than glibc crypt)
# prepare the 6 combinations of pwd & salt which are needed
# (order of 'perms' must match how _c_digest_offsets was generated)
pwd_pwd = pwd+pwd
pwd_salt = pwd+salt
perms = [pwd, pwd_pwd, pwd_salt, pwd_salt+pwd, salt+pwd, salt+pwd_pwd]
# build up list of even-round & odd-round constants,
# and store in 21-element list as (even,odd) pairs.
data = [ (perms[even], perms[odd]) for even, odd in _c_digest_offsets]
# perform 23 blocks of 42 rounds each (for a total of 966 rounds)
dc = da
blocks = 23
while blocks:
for even, odd in data:
dc = md5(odd + md5(dc + even).digest()).digest()
blocks -= 1
# perform 17 more pairs of rounds (34 more rounds, for a total of 1000)
for even, odd in data[:17]:
dc = md5(odd + md5(dc + even).digest()).digest()
#===================================================================
# encode digest using appropriate transpose map
#===================================================================
return h64.encode_transposed_bytes(dc, _transpose_map).decode("ascii")
#=============================================================================
# handler
#=============================================================================
class _MD5_Common(uh.HasSalt, uh.GenericHandler):
"""common code for md5_crypt and apr_md5_crypt"""
#===================================================================
# class attrs
#===================================================================
# name - set in subclass
setting_kwds = ("salt", "salt_size")
# ident - set in subclass
checksum_size = 22
checksum_chars = uh.HASH64_CHARS
max_salt_size = 8
salt_chars = uh.HASH64_CHARS
#===================================================================
# methods
#===================================================================
@classmethod
def from_string(cls, hash):
salt, chk = uh.parse_mc2(hash, cls.ident, handler=cls)
return cls(salt=salt, checksum=chk)
def to_string(self):
return uh.render_mc2(self.ident, self.salt, self.checksum)
# _calc_checksum() - provided by subclass
#===================================================================
# eoc
#===================================================================
class md5_crypt(uh.HasManyBackends, _MD5_Common):
"""This class implements the MD5-Crypt password hash, and follows the :ref:`password-hash-api`.
It supports a variable-length salt.
The :meth:`~passlib.ifc.PasswordHash.using` method accepts the following optional keywords:
:type salt: str
:param salt:
Optional salt string.
If not specified, one will be autogenerated (this is recommended).
If specified, it must be 0-8 characters, drawn from the regexp range ``[./0-9A-Za-z]``.
:type salt_size: int
:param salt_size:
Optional number of characters to use when autogenerating new salts.
Defaults to 8, but can be any value between 0 and 8.
(This is mainly needed when generating Cisco-compatible hashes,
which require ``salt_size=4``).
:type relaxed: bool
:param relaxed:
By default, providing an invalid value for one of the other
keywords will result in a :exc:`ValueError`. If ``relaxed=True``,
and the error can be corrected, a :exc:`~passlib.exc.PasslibHashWarning`
will be issued instead. Correctable errors include
``salt`` strings that are too long.
.. versionadded:: 1.6
"""
#===================================================================
# class attrs
#===================================================================
name = "md5_crypt"
ident = u("$1$")
#===================================================================
# methods
#===================================================================
# FIXME: can't find definitive policy on how md5-crypt handles non-ascii.
# all backends currently coerce -> utf-8
backends = ("os_crypt", "builtin")
#---------------------------------------------------------------
# os_crypt backend
#---------------------------------------------------------------
@classmethod
def _load_backend_os_crypt(cls):
if test_crypt("test", '$1$test$pi/xDtU5WFVRqYS6BMU8X/'):
cls._set_calc_checksum_backend(cls._calc_checksum_os_crypt)
return True
else:
return False
def _calc_checksum_os_crypt(self, secret):
config = self.ident + self.salt
hash = safe_crypt(secret, config)
if hash is None:
# py3's crypt.crypt() can't handle non-utf8 bytes.
# fallback to builtin alg, which is always available.
return self._calc_checksum_builtin(secret)
if not hash.startswith(config) or len(hash) != len(config) + 23:
raise uh.exc.CryptBackendError(self, config, hash)
return hash[-22:]
#---------------------------------------------------------------
# builtin backend
#---------------------------------------------------------------
@classmethod
def _load_backend_builtin(cls):
cls._set_calc_checksum_backend(cls._calc_checksum_builtin)
return True
def _calc_checksum_builtin(self, secret):
return _raw_md5_crypt(secret, self.salt)
#===================================================================
# eoc
#===================================================================
class apr_md5_crypt(_MD5_Common):
"""This class implements the Apr-MD5-Crypt password hash, and follows the :ref:`password-hash-api`.
It supports a variable-length salt.
The :meth:`~passlib.ifc.PasswordHash.using` method accepts the following optional keywords:
:type salt: str
:param salt:
Optional salt string.
If not specified, one will be autogenerated (this is recommended).
If specified, it must be 0-8 characters, drawn from the regexp range ``[./0-9A-Za-z]``.
:type relaxed: bool
:param relaxed:
By default, providing an invalid value for one of the other
keywords will result in a :exc:`ValueError`. If ``relaxed=True``,
and the error can be corrected, a :exc:`~passlib.exc.PasslibHashWarning`
will be issued instead. Correctable errors include
``salt`` strings that are too long.
.. versionadded:: 1.6
"""
#===================================================================
# class attrs
#===================================================================
name = "apr_md5_crypt"
ident = u("$apr1$")
#===================================================================
# methods
#===================================================================
def _calc_checksum(self, secret):
return _raw_md5_crypt(secret, self.salt, use_apr=True)
#===================================================================
# eoc
#===================================================================
#=============================================================================
# eof
#=============================================================================