250 lines
7.9 KiB
Python
250 lines
7.9 KiB
Python
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# -*- coding: utf-8 -*-
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"""
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werkzeug.security
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~~~~~~~~~~~~~~~~~
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Security related helpers such as secure password hashing tools.
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:copyright: 2007 Pallets
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:license: BSD-3-Clause
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"""
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import codecs
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import hashlib
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import hmac
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import os
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import posixpath
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from random import SystemRandom
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from struct import Struct
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from ._compat import izip
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from ._compat import PY2
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from ._compat import range_type
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from ._compat import text_type
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from ._compat import to_bytes
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from ._compat import to_native
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SALT_CHARS = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
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DEFAULT_PBKDF2_ITERATIONS = 150000
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_pack_int = Struct(">I").pack
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_builtin_safe_str_cmp = getattr(hmac, "compare_digest", None)
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_sys_rng = SystemRandom()
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_os_alt_seps = list(
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sep for sep in [os.path.sep, os.path.altsep] if sep not in (None, "/")
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)
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def pbkdf2_hex(
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data, salt, iterations=DEFAULT_PBKDF2_ITERATIONS, keylen=None, hashfunc=None
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):
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"""Like :func:`pbkdf2_bin`, but returns a hex-encoded string.
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.. versionadded:: 0.9
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:param data: the data to derive.
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:param salt: the salt for the derivation.
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:param iterations: the number of iterations.
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:param keylen: the length of the resulting key. If not provided,
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the digest size will be used.
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:param hashfunc: the hash function to use. This can either be the
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string name of a known hash function, or a function
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from the hashlib module. Defaults to sha256.
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"""
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rv = pbkdf2_bin(data, salt, iterations, keylen, hashfunc)
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return to_native(codecs.encode(rv, "hex_codec"))
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def pbkdf2_bin(
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data, salt, iterations=DEFAULT_PBKDF2_ITERATIONS, keylen=None, hashfunc=None
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):
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"""Returns a binary digest for the PBKDF2 hash algorithm of `data`
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with the given `salt`. It iterates `iterations` times and produces a
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key of `keylen` bytes. By default, SHA-256 is used as hash function;
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a different hashlib `hashfunc` can be provided.
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.. versionadded:: 0.9
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:param data: the data to derive.
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:param salt: the salt for the derivation.
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:param iterations: the number of iterations.
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:param keylen: the length of the resulting key. If not provided
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the digest size will be used.
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:param hashfunc: the hash function to use. This can either be the
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string name of a known hash function or a function
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from the hashlib module. Defaults to sha256.
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"""
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if not hashfunc:
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hashfunc = "sha256"
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data = to_bytes(data)
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salt = to_bytes(salt)
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if callable(hashfunc):
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_test_hash = hashfunc()
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hash_name = getattr(_test_hash, "name", None)
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else:
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hash_name = hashfunc
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return hashlib.pbkdf2_hmac(hash_name, data, salt, iterations, keylen)
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def safe_str_cmp(a, b):
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"""This function compares strings in somewhat constant time. This
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requires that the length of at least one string is known in advance.
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Returns `True` if the two strings are equal, or `False` if they are not.
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.. versionadded:: 0.7
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"""
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if isinstance(a, text_type):
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a = a.encode("utf-8")
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if isinstance(b, text_type):
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b = b.encode("utf-8")
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if _builtin_safe_str_cmp is not None:
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return _builtin_safe_str_cmp(a, b)
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if len(a) != len(b):
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return False
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rv = 0
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if PY2:
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for x, y in izip(a, b):
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rv |= ord(x) ^ ord(y)
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else:
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for x, y in izip(a, b):
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rv |= x ^ y
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return rv == 0
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def gen_salt(length):
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"""Generate a random string of SALT_CHARS with specified ``length``."""
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if length <= 0:
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raise ValueError("Salt length must be positive")
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return "".join(_sys_rng.choice(SALT_CHARS) for _ in range_type(length))
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def _hash_internal(method, salt, password):
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"""Internal password hash helper. Supports plaintext without salt,
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unsalted and salted passwords. In case salted passwords are used
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hmac is used.
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"""
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if method == "plain":
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return password, method
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if isinstance(password, text_type):
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password = password.encode("utf-8")
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if method.startswith("pbkdf2:"):
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args = method[7:].split(":")
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if len(args) not in (1, 2):
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raise ValueError("Invalid number of arguments for PBKDF2")
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method = args.pop(0)
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iterations = args and int(args[0] or 0) or DEFAULT_PBKDF2_ITERATIONS
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is_pbkdf2 = True
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actual_method = "pbkdf2:%s:%d" % (method, iterations)
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else:
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is_pbkdf2 = False
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actual_method = method
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if is_pbkdf2:
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if not salt:
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raise ValueError("Salt is required for PBKDF2")
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rv = pbkdf2_hex(password, salt, iterations, hashfunc=method)
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elif salt:
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if isinstance(salt, text_type):
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salt = salt.encode("utf-8")
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mac = _create_mac(salt, password, method)
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rv = mac.hexdigest()
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else:
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rv = hashlib.new(method, password).hexdigest()
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return rv, actual_method
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def _create_mac(key, msg, method):
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if callable(method):
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return hmac.HMAC(key, msg, method)
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def hashfunc(d=b""):
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return hashlib.new(method, d)
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# Python 2.7 used ``hasattr(digestmod, '__call__')``
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# to detect if hashfunc is callable
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hashfunc.__call__ = hashfunc
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return hmac.HMAC(key, msg, hashfunc)
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def generate_password_hash(password, method="pbkdf2:sha256", salt_length=8):
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"""Hash a password with the given method and salt with a string of
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the given length. The format of the string returned includes the method
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that was used so that :func:`check_password_hash` can check the hash.
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The format for the hashed string looks like this::
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method$salt$hash
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This method can **not** generate unsalted passwords but it is possible
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to set param method='plain' in order to enforce plaintext passwords.
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If a salt is used, hmac is used internally to salt the password.
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If PBKDF2 is wanted it can be enabled by setting the method to
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``pbkdf2:method:iterations`` where iterations is optional::
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pbkdf2:sha256:80000$salt$hash
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pbkdf2:sha256$salt$hash
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:param password: the password to hash.
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:param method: the hash method to use (one that hashlib supports). Can
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optionally be in the format ``pbkdf2:<method>[:iterations]``
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to enable PBKDF2.
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:param salt_length: the length of the salt in letters.
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"""
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salt = gen_salt(salt_length) if method != "plain" else ""
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h, actual_method = _hash_internal(method, salt, password)
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return "%s$%s$%s" % (actual_method, salt, h)
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def check_password_hash(pwhash, password):
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"""check a password against a given salted and hashed password value.
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In order to support unsalted legacy passwords this method supports
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plain text passwords, md5 and sha1 hashes (both salted and unsalted).
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Returns `True` if the password matched, `False` otherwise.
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:param pwhash: a hashed string like returned by
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:func:`generate_password_hash`.
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:param password: the plaintext password to compare against the hash.
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"""
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if pwhash.count("$") < 2:
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return False
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method, salt, hashval = pwhash.split("$", 2)
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return safe_str_cmp(_hash_internal(method, salt, password)[0], hashval)
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def safe_join(directory, *pathnames):
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"""Safely join zero or more untrusted path components to a base
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directory to avoid escaping the base directory.
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:param directory: The trusted base directory.
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:param pathnames: The untrusted path components relative to the
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base directory.
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:return: A safe path, otherwise ``None``.
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"""
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parts = [directory]
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for filename in pathnames:
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if filename != "":
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filename = posixpath.normpath(filename)
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if (
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any(sep in filename for sep in _os_alt_seps)
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or os.path.isabs(filename)
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or filename == ".."
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or filename.startswith("../")
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):
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return None
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parts.append(filename)
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return posixpath.join(*parts)
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