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import hashlib
import hmac
import os
import posixpath
import secrets
import typing as t
if t.TYPE_CHECKING:
pass
SALT_CHARS = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
DEFAULT_PBKDF2_ITERATIONS = 260000
_os_alt_seps: t.List[str] = list(
sep for sep in [os.sep, os.path.altsep] if sep is not None and sep != "/"
)
def gen_salt(length: int) -> str:
"""Generate a random string of SALT_CHARS with specified ``length``."""
if length <= 0:
raise ValueError("Salt length must be positive")
return "".join(secrets.choice(SALT_CHARS) for _ in range(length))
def _hash_internal(method: str, salt: str, password: str) -> t.Tuple[str, str]:
"""Internal password hash helper. Supports plaintext without salt,
unsalted and salted passwords. In case salted passwords are used
hmac is used.
"""
if method == "plain":
return password, method
salt = salt.encode("utf-8")
password = password.encode("utf-8")
if method.startswith("pbkdf2:"):
if not salt:
raise ValueError("Salt is required for PBKDF2")
args = method[7:].split(":")
if len(args) not in (1, 2):
raise ValueError("Invalid number of arguments for PBKDF2")
method = args.pop(0)
iterations = int(args[0] or 0) if args else DEFAULT_PBKDF2_ITERATIONS
return (
hashlib.pbkdf2_hmac(method, password, salt, iterations).hex(),
f"pbkdf2:{method}:{iterations}",
)
if salt:
return hmac.new(salt, password, method).hexdigest(), method
return hashlib.new(method, password).hexdigest(), method
def generate_password_hash(
password: str, method: str = "pbkdf2:sha256", salt_length: int = 16
) -> str:
"""Hash a password with the given method and salt with a string of
the given length. The format of the string returned includes the method
that was used so that :func:`check_password_hash` can check the hash.
The format for the hashed string looks like this::
method$salt$hash
This method can **not** generate unsalted passwords but it is possible
to set param method='plain' in order to enforce plaintext passwords.
If a salt is used, hmac is used internally to salt the password.
If PBKDF2 is wanted it can be enabled by setting the method to
``pbkdf2:method:iterations`` where iterations is optional::
pbkdf2:sha256:80000$salt$hash
pbkdf2:sha256$salt$hash
:param password: the password to hash.
:param method: the hash method to use (one that hashlib supports). Can
optionally be in the format ``pbkdf2:method:iterations``
to enable PBKDF2.
:param salt_length: the length of the salt in letters.
"""
salt = gen_salt(salt_length) if method != "plain" else ""
h, actual_method = _hash_internal(method, salt, password)
return f"{actual_method}${salt}${h}"
def check_password_hash(pwhash: str, password: str) -> bool:
"""Check a password against a given salted and hashed password value.
In order to support unsalted legacy passwords this method supports
plain text passwords, md5 and sha1 hashes (both salted and unsalted).
Returns `True` if the password matched, `False` otherwise.
:param pwhash: a hashed string like returned by
:func:`generate_password_hash`.
:param password: the plaintext password to compare against the hash.
"""
if pwhash.count("$") < 2:
return False
method, salt, hashval = pwhash.split("$", 2)
return hmac.compare_digest(_hash_internal(method, salt, password)[0], hashval)
def safe_join(directory: str, *pathnames: str) -> t.Optional[str]:
"""Safely join zero or more untrusted path components to a base
directory to avoid escaping the base directory.
:param directory: The trusted base directory.
:param pathnames: The untrusted path components relative to the
base directory.
:return: A safe path, otherwise ``None``.
"""
if not directory:
# Ensure we end up with ./path if directory="" is given,
# otherwise the first untrusted part could become trusted.
directory = "."
parts = [directory]
for filename in pathnames:
if filename != "":
filename = posixpath.normpath(filename)
if (
any(sep in filename for sep in _os_alt_seps)
or os.path.isabs(filename)
or filename == ".."
or filename.startswith("../")
):
return None
parts.append(filename)
return posixpath.join(*parts)
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