1#@!#!123s

: / lib / python3 / dist-packages / passlib /
Filename : pwd.py
back
import codecs
import contextlib
import os
from collections import defaultdict
from collections.abc import Hashable, MutableMapping
from importlib import resources
from math import ceil, log2

from passlib import exc
from passlib._logging import logger
from passlib.utils import getrandstr, rng, to_unicode
from passlib.utils.decor import memoized_property

# local
__all__ = [
    "genword",
    "default_charsets",
    "genphrase",
    "default_wordsets",
]

# XXX: rename / publically document this map?
entropy_aliases = dict(
    # barest protection from throttled online attack
    unsafe=12,
    # some protection from unthrottled online attack
    weak=24,
    # some protection from offline attacks
    fair=36,
    # reasonable protection from offline attacks
    strong=48,
    # very good protection from offline attacks
    secure=60,
)


def _superclasses(obj, cls):
    """return remaining classes in object's MRO after cls"""
    mro = type(obj).__mro__
    return mro[mro.index(cls) + 1 :]


def _self_info_rate(source):
    """
    returns 'rate of self-information' --
    i.e. average (per-symbol) entropy of the sequence **source**,
    where probability of a given symbol occurring is calculated based on
    the number of occurrences within the sequence itself.

    if all elements of the source are unique, this should equal ``log(len(source), 2)``.

    :arg source:
        iterable containing 0+ symbols
        (e.g. list of strings or ints, string of characters, etc).

    :returns:
        float bits of entropy
    """
    try:
        size = len(source)
    except TypeError:
        # if len() doesn't work, calculate size by summing counts later
        size = None
    counts = defaultdict(int)
    for char in source:
        counts[char] += 1
    if size is None:
        values = counts.values()
        size = sum(values)
    else:
        values = counts.values()
    if not size:
        return 0
    # NOTE: the following performs ``- sum(value / size * logf(value / size, 2) for value in values)``,
    #       it just does so with as much pulled out of the sum() loop as possible...
    return log2(size) - sum(value * log2(value) for value in values) / size


# def _total_self_info(source):
#     """
#     return total self-entropy of a sequence
#     (the average entropy per symbol * size of sequence)
#     """
#     return _self_info_rate(source) * len(source)


def _open_asset_path(path, encoding=None):
    """
    :param asset_path:
        string containing absolute path to file,
        or package-relative path using format
        ``"python.module:relative/file/path"``.

    :returns:
        filehandle opened in 'rb' mode
        (unless encoding explicitly specified)
    """
    if encoding:
        return codecs.getreader(encoding)(_open_asset_path(path))
    if os.path.isabs(path):
        return open(path, "rb")  # noqa: SIM115
    package, sep, subpath = path.partition(":")
    if not sep:
        raise ValueError(
            "asset path must be absolute file path "
            f"or use 'pkg.name:sub/path' format: {path!r}"
        )
    return resources.files(package).joinpath(subpath).open("rb")


#: type aliases
_sequence_types = (list, tuple)
_set_types = (set, frozenset)

#: set of elements that ensure_unique() has validated already.
_ensure_unique_cache: set[Hashable] = set()


def _ensure_unique(source, param="source"):
    """
    helper for generators --
    Throws ValueError if source elements aren't unique.
    Error message will display (abbreviated) repr of the duplicates in a string/list
    """
    # check cache to speed things up for frozensets / tuples / strings
    cache = _ensure_unique_cache
    hashable = True
    try:
        if source in cache:
            return True
    except TypeError:
        hashable = False

    # check if it has dup elements
    if isinstance(source, _set_types) or len(set(source)) == len(source):
        if hashable:
            with contextlib.suppress(TypeError):
                # XXX: under pypy, "list() in set()" above doesn't throw TypeError,
                #      but trying to add unhashable it to a set *does*.
                cache.add(source)
        return True

    # build list of duplicate values
    seen = set()
    dups = set()
    for elem in source:
        (dups if elem in seen else seen).add(elem)
    dups = sorted(dups)
    trunc = 8
    if len(dups) > trunc:
        trunc = 5
    dup_repr = ", ".join(repr(str(word)) for word in dups[:trunc])
    if len(dups) > trunc:
        dup_repr += ", ... plus %d others" % (len(dups) - trunc)

    # throw error
    raise ValueError(f"`{param}` cannot contain duplicate elements: {dup_repr}")


class SequenceGenerator:
    """
    Base class used by word & phrase generators.

    These objects take a series of options, corresponding
    to those of the :func:`generate` function.
    They act as callables which can be used to generate a password
    or a list of 1+ passwords. They also expose some read-only
    informational attributes.

    Parameters
    ----------
    :param entropy:
        Optionally specify the amount of entropy the resulting passwords
        should contain (as measured with respect to the generator itself).
        This will be used to auto-calculate the required password size.

    :param length:
        Optionally specify the length of password to generate,
        measured as count of whatever symbols the subclass uses (characters or words).
        Note if ``entropy`` requires a larger minimum length,
        that will be used instead.

    :param rng:
        Optionally provide a custom RNG source to use.
        Should be an instance of :class:`random.Random`,
        defaults to :class:`random.SystemRandom`.

    Attributes
    ----------
    .. autoattribute:: length
    .. autoattribute:: symbol_count
    .. autoattribute:: entropy_per_symbol
    .. autoattribute:: entropy

    Subclassing
    -----------
    Subclasses must implement the ``.__next__()`` method,
    and set ``.symbol_count`` before calling base ``__init__`` method.
    """

    #: requested size of final password
    length = None

    #: requested entropy of final password
    requested_entropy = "strong"

    #: random number source to use
    rng = rng

    #: number of potential symbols (must be filled in by subclass)
    symbol_count = None

    def __init__(self, entropy=None, length=None, rng=None, **kwds):
        # make sure subclass set things up correctly
        assert self.symbol_count is not None, "subclass must set .symbol_count"

        # init length & requested entropy
        if entropy is not None or length is None:
            if entropy is None:
                entropy = self.requested_entropy
            entropy = entropy_aliases.get(entropy, entropy)
            if entropy <= 0:
                raise ValueError("`entropy` must be positive number")
            min_length = int(ceil(entropy / self.entropy_per_symbol))
            if length is None or length < min_length:
                length = min_length

        self.requested_entropy = entropy

        if length < 1:
            raise ValueError("`length` must be positive integer")
        self.length = length

        # init other common options
        if rng is not None:
            self.rng = rng

        # hand off to parent
        if kwds and _superclasses(self, SequenceGenerator) == (object,):
            raise TypeError("Unexpected keyword(s): {}".format(", ".join(kwds.keys())))
        super().__init__(**kwds)

    @memoized_property
    def entropy_per_symbol(self):
        """
        Average entropy per symbol (assuming all symbols have equal probability)
        """
        return log2(self.symbol_count)

    @memoized_property
    def entropy(self):
        """
        Effective entropy of generated passwords.

        This value will always be a multiple of :attr:`entropy_per_symbol`.
        If entropy is specified in constructor, :attr:`length` will be chosen so
        so that this value is the smallest multiple >= :attr:`requested_entropy`.
        """
        return self.length * self.entropy_per_symbol

    def __next__(self):
        """main generation function, should create one password/phrase"""
        raise NotImplementedError("implement in subclass")

    def __call__(self, returns=None):
        """
        frontend used by genword() / genphrase() to create passwords
        """
        if returns is None:
            return next(self)
        if isinstance(returns, int):
            return [next(self) for _ in range(returns)]
        if returns is iter:
            return self
        raise exc.ExpectedTypeError(returns, "<None>, int, or <iter>", "returns")

    def __iter__(self):
        return self


#: global dict of predefined characters sets
default_charsets = dict(
    # ascii letters, digits, and some punctuation
    ascii_72="0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ!@#$%^&*?/",
    # ascii letters and digits
    ascii_62="0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ",
    # ascii_50, without visually similar '1IiLl', '0Oo', '5S', '8B'
    ascii_50="234679abcdefghjkmnpqrstuvwxyzACDEFGHJKMNPQRTUVWXYZ",
    # lower case hexadecimal
    hex="0123456789abcdef",
)


class WordGenerator(SequenceGenerator):
    """
    Class which generates passwords by randomly choosing from a string of unique characters.

    Parameters
    ----------
    :param chars:
        custom character string to draw from.

    :param charset:
        predefined charset to draw from.

    :param \\*\\*kwds:
        all other keywords passed to the :class:`SequenceGenerator` parent class.

    Attributes
    ----------
    .. autoattribute:: chars
    .. autoattribute:: charset
    .. autoattribute:: default_charsets
    """

    #: Predefined character set in use (set to None for instances using custom 'chars')
    charset = "ascii_62"

    #: string of chars to draw from -- usually filled in from charset
    chars = None

    def __init__(self, chars=None, charset=None, **kwds):
        # init chars and charset
        if chars:
            if charset:
                raise TypeError("`chars` and `charset` are mutually exclusive")
        else:
            if not charset:
                charset = self.charset
                assert charset
            chars = default_charsets[charset]
        self.charset = charset
        chars = to_unicode(chars, param="chars")
        _ensure_unique(chars, param="chars")
        self.chars = chars

        # hand off to parent
        super().__init__(**kwds)
        # log.debug("WordGenerator(): entropy/char=%r", self.entropy_per_symbol)

    @memoized_property
    def symbol_count(self):
        return len(self.chars)

    def __next__(self):
        # XXX: could do things like optionally ensure certain character groups
        #      (e.g. letters & punctuation) are included
        return getrandstr(self.rng, self.chars, self.length)


def genword(entropy=None, length=None, returns=None, **kwds):
    """Generate one or more random passwords.

    This function uses :mod:`random.SystemRandom` to generate
    one or more passwords using various character sets.
    The complexity of the password can be specified
    by size, or by the desired amount of entropy.

    Usage Example::

        >>> # generate a random alphanumeric string with 48 bits of entropy (the default)
        >>> from passlib import pwd
        >>> pwd.genword()
        'DnBHvDjMK6'

        >>> # generate a random hexadecimal string with 52 bits of entropy
        >>> pwd.genword(entropy=52, charset="hex")
        '310f1a7ac793f'

    :param entropy:
        Strength of resulting password, measured in 'guessing entropy' bits.
        An appropriate **length** value will be calculated
        based on the requested entropy amount, and the size of the character set.

        This can be a positive integer, or one of the following preset
        strings: ``"weak"`` (24), ``"fair"`` (36),
        ``"strong"`` (48), and ``"secure"`` (56).

        If neither this or **length** is specified, **entropy** will default
        to ``"strong"`` (48).

    :param length:
        Size of resulting password, measured in characters.
        If omitted, the size is auto-calculated based on the **entropy** parameter.

        If both **entropy** and **length** are specified,
        the stronger value will be used.

    :param returns:
        Controls what this function returns:

        * If ``None`` (the default), this function will generate a single password.
        * If an integer, this function will return a list containing that many passwords.
        * If the ``iter`` constant, will return an iterator that yields passwords.

    :param chars:

        Optionally specify custom string of characters to use when randomly
        generating a password. This option cannot be combined with **charset**.

    :param charset:

        The predefined character set to draw from (if not specified by **chars**).
        There are currently four presets available:

        * ``"ascii_62"`` (the default) -- all digits and ascii upper & lowercase letters.
          Provides ~5.95 entropy per character.

        * ``"ascii_50"`` -- subset which excludes visually similar characters
          (``1IiLl0Oo5S8B``). Provides ~5.64 entropy per character.

        * ``"ascii_72"`` -- all digits and ascii upper & lowercase letters,
          as well as some punctuation. Provides ~6.17 entropy per character.

        * ``"hex"`` -- Lower case hexadecimal.  Providers 4 bits of entropy per character.

    :returns:
        :class:`!str` string containing randomly generated password;
        or list of 1+ passwords if :samp:`returns={int}` is specified.
    """
    gen = WordGenerator(length=length, entropy=entropy, **kwds)
    return gen(returns)


def _load_wordset(asset_path):
    """
    load wordset from compressed datafile within package data.
    file should be utf-8 encoded

    :param asset_path:
        string containing  absolute path to wordset file,
        or "python.module:relative/file/path".

    :returns:
        tuple of words, as loaded from specified words file.
    """
    # open resource file, convert to tuple of words (strip blank lines & ws)
    with _open_asset_path(asset_path, "utf-8") as fh:
        gen = (word.strip() for word in fh)
        words = tuple(word for word in gen if word)

    # NOTE: works but not used
    # # detect if file uses "<int> <word>" format, and strip numeric prefix
    # def extract(row):
    #     idx, word = row.replace("\t", " ").split(" ", 1)
    #     if not idx.isdigit():
    #         raise ValueError("row is not dice index + word")
    #     return word
    # try:
    #     extract(words[-1])
    # except ValueError:
    #     pass
    # else:
    #     words = tuple(extract(word) for word in words)

    logger.debug("loaded %d-element wordset from %r", len(words), asset_path)
    return words


class WordsetDict(MutableMapping):
    """
    Special mapping used to store dictionary of wordsets.
    Different from a regular dict in that some wordsets
    may be lazy-loaded from an asset path.
    """

    #: dict of key -> asset path
    paths = None

    #: dict of key -> value
    _loaded = None

    def __init__(self, *args, **kwds):
        self.paths = {}
        self._loaded = {}
        super().__init__(*args, **kwds)

    def __getitem__(self, key):
        try:
            return self._loaded[key]
        except KeyError:
            pass
        path = self.paths[key]
        value = self._loaded[key] = _load_wordset(path)
        return value

    def set_path(self, key, path):
        """
        set asset path to lazy-load wordset from.
        """
        self.paths[key] = path

    def __setitem__(self, key, value):
        self._loaded[key] = value

    def __delitem__(self, key):
        if key in self:
            del self._loaded[key]
            self.paths.pop(key, None)
        else:
            del self.paths[key]

    @property
    def _keyset(self):
        keys = set(self._loaded)
        keys.update(self.paths)
        return keys

    def __iter__(self):
        return iter(self._keyset)

    def __len__(self):
        return len(self._keyset)

    # NOTE: speeds things up, and prevents contains from lazy-loading
    def __contains__(self, key):
        return key in self._loaded or key in self.paths


#: dict of predefined word sets.
#: key is name of wordset, value should be sequence of words.
default_wordsets = WordsetDict()

# register the wordsets built into passlib
for name in ["eff_long", "eff_short", "eff_prefixed", "bip39"]:
    default_wordsets.set_path(name, f"passlib:_data/wordsets/{name}.txt")


class PhraseGenerator(SequenceGenerator):
    """class which generates passphrases by randomly choosing
    from a list of unique words.

    :param wordset:
        wordset to draw from.
    :param preset:
        name of preset wordlist to use instead of ``wordset``.
    :param spaces:
        whether to insert spaces between words in output (defaults to ``True``).
    :param \\*\\*kwds:
        all other keywords passed to the :class:`SequenceGenerator` parent class.

    .. autoattribute:: wordset
    """

    #: predefined wordset to use
    wordset = "eff_long"

    #: list of words to draw from
    words = None

    #: separator to use when joining words
    sep = " "

    def __init__(self, wordset=None, words=None, sep=None, **kwds):
        # load wordset
        if words is not None:
            if wordset is not None:
                raise TypeError("`words` and `wordset` are mutually exclusive")
        else:
            if wordset is None:
                wordset = self.wordset
                assert wordset
            words = default_wordsets[wordset]
        self.wordset = wordset

        # init words
        if not isinstance(words, _sequence_types):
            words = tuple(words)
        _ensure_unique(words, param="words")
        self.words = words

        # init separator
        if sep is None:
            sep = self.sep
        sep = to_unicode(sep, param="sep")
        self.sep = sep

        # hand off to parent
        super().__init__(**kwds)
        ##log.debug("PhraseGenerator(): entropy/word=%r entropy/char=%r min_chars=%r",
        ##          self.entropy_per_symbol, self.entropy_per_char, self.min_chars)

    @memoized_property
    def symbol_count(self):
        return len(self.words)

    def __next__(self):
        words = (self.rng.choice(self.words) for _ in range(self.length))
        return self.sep.join(words)


def genphrase(entropy=None, length=None, returns=None, **kwds):
    """Generate one or more random password / passphrases.

    This function uses :mod:`random.SystemRandom` to generate
    one or more passwords; it can be configured to generate
    alphanumeric passwords, or full english phrases.
    The complexity of the password can be specified
    by size, or by the desired amount of entropy.

    Usage Example::

        >>> # generate random phrase with 48 bits of entropy
        >>> from passlib import pwd
        >>> pwd.genphrase()
        'gangly robbing salt shove'

        >>> # generate a random phrase with 52 bits of entropy
        >>> # using a particular wordset
        >>> pwd.genword(entropy=52, wordset="bip39")
        'wheat dilemma reward rescue diary'

    :param entropy:
        Strength of resulting password, measured in 'guessing entropy' bits.
        An appropriate **length** value will be calculated
        based on the requested entropy amount, and the size of the word set.

        This can be a positive integer, or one of the following preset
        strings: ``"weak"`` (24), ``"fair"`` (36),
        ``"strong"`` (48), and ``"secure"`` (56).

        If neither this or **length** is specified, **entropy** will default
        to ``"strong"`` (48).

    :param length:
        Length of resulting password, measured in words.
        If omitted, the size is auto-calculated based on the **entropy** parameter.

        If both **entropy** and **length** are specified,
        the stronger value will be used.

    :param returns:
        Controls what this function returns:

        * If ``None`` (the default), this function will generate a single password.
        * If an integer, this function will return a list containing that many passwords.
        * If the ``iter`` builtin, will return an iterator that yields passwords.

    :param words:

        Optionally specifies a list/set of words to use when randomly generating a passphrase.
        This option cannot be combined with **wordset**.

    :param wordset:

        The predefined word set to draw from (if not specified by **words**).
        There are currently four presets available:

        ``"eff_long"`` (the default)

            Wordset containing 7776 english words of ~7 letters.
            Constructed by the EFF, it offers ~12.9 bits of entropy per word.

            This wordset (and the other ``"eff_"`` wordsets)
            were `created by the EFF <https://www.eff.org/deeplinks/2016/07/new-wordlists-random-passphrases>`_
            to aid in generating passwords.  See their announcement page
            for more details about the design & properties of these wordsets.

        ``"eff_short"``

            Wordset containing 1296 english words of ~4.5 letters.
            Constructed by the EFF, it offers ~10.3 bits of entropy per word.

        ``"eff_prefixed"``

            Wordset containing 1296 english words of ~8 letters,
            selected so that they each have a unique 3-character prefix.
            Constructed by the EFF, it offers ~10.3 bits of entropy per word.

        ``"bip39"``

            Wordset of 2048 english words of ~5 letters,
            selected so that they each have a unique 4-character prefix.
            Published as part of Bitcoin's `BIP 39 <https://github.com/bitcoin/bips/blob/master/bip-0039/english.txt>`_,
            this wordset has exactly 11 bits of entropy per word.

            This list offers words that are typically shorter than ``"eff_long"``
            (at the cost of slightly less entropy); and much shorter than
            ``"eff_prefixed"`` (at the cost of a longer unique prefix).

    :param sep:
        Optional separator to use when joining words.
        Defaults to ``" "`` (a space), but can be an empty string, a hyphen, etc.

    :returns:
        :class:`!str` containing randomly generated passphrase;
        or list of 1+ passphrases if :samp:`returns={int}` is specified.
    """
    gen = PhraseGenerator(entropy=entropy, length=length, **kwds)
    return gen(returns)


# =============================================================================
# strength measurement
#
# NOTE:
# for a little while, had rough draft of password strength measurement alg here.
# but not sure if there's value in yet another measurement algorithm,
# that's not just duplicating the effort of libraries like zxcbn.
# may revive it later, but for now, leaving some refs to others out there:
#    * NIST 800-63 has simple alg
#    * zxcvbn (https://tech.dropbox.com/2012/04/zxcvbn-realistic-password-strength-estimation/)
#      might also be good, and has approach similar to composite approach i was already thinking about,
#      but much more well thought out.
#    * passfault (https://github.com/c-a-m/passfault) looks thorough,
#      but may have licensing issues, plus porting to python looks like very big job :(
#    * give a look at running things through zlib - might be able to cheaply
#      catch extra redundancies.
# =============================================================================