django/contrib/auth/password_validation.py
import functools
import gzip
import re
from difflib import SequenceMatcher
from pathlib import Path
from django.conf import settings
from django.core.exceptions import (
FieldDoesNotExist,
ImproperlyConfigured,
ValidationError,
)
from django.utils.functional import cached_property, lazy
from django.utils.html import format_html, format_html_join
from django.utils.module_loading import import_string
from django.utils.translation import gettext as _
from django.utils.translation import ngettext
@functools.cache
def get_default_password_validators():
return get_password_validators(settings.AUTH_PASSWORD_VALIDATORS)
def get_password_validators(validator_config):
validators = []
for validator in validator_config:
try:
klass = import_string(validator["NAME"])
except ImportError:
msg = (
"The module in NAME could not be imported: %s. Check your "
"AUTH_PASSWORD_VALIDATORS setting."
)
raise ImproperlyConfigured(msg % validator["NAME"])
validators.append(klass(**validator.get("OPTIONS", {})))
return validators
def validate_password(password, user=None, password_validators=None):
"""
Validate that the password meets all validator requirements.
If the password is valid, return ``None``.
If the password is invalid, raise ValidationError with all error messages.
"""
errors = []
if password_validators is None:
password_validators = get_default_password_validators()
for validator in password_validators:
try:
validator.validate(password, user)
except ValidationError as error:
errors.append(error)
if errors:
raise ValidationError(errors)
def password_changed(password, user=None, password_validators=None):
"""
Inform all validators that have implemented a password_changed() method
that the password has been changed.
"""
if password_validators is None:
password_validators = get_default_password_validators()
for validator in password_validators:
password_changed = getattr(validator, "password_changed", lambda *a: None)
password_changed(password, user)
def password_validators_help_texts(password_validators=None):
"""
Return a list of all help texts of all configured validators.
"""
help_texts = []
if password_validators is None:
password_validators = get_default_password_validators()
for validator in password_validators:
help_texts.append(validator.get_help_text())
return help_texts
def _password_validators_help_text_html(password_validators=None):
"""
Return an HTML string with all help texts of all configured validators
in an <ul>.
"""
help_texts = password_validators_help_texts(password_validators)
help_items = format_html_join(
"", "<li>{}</li>", ((help_text,) for help_text in help_texts)
)
return format_html("<ul>{}</ul>", help_items) if help_items else ""
password_validators_help_text_html = lazy(_password_validators_help_text_html, str)
class MinimumLengthValidator:
"""
Validate that the password is of a minimum length.
"""
def __init__(self, min_length=8):
self.min_length = min_length
def validate(self, password, user=None):
if len(password) < self.min_length:
raise ValidationError(
ngettext(
"This password is too short. It must contain at least "
"%(min_length)d character.",
"This password is too short. It must contain at least "
"%(min_length)d characters.",
self.min_length,
),
code="password_too_short",
params={"min_length": self.min_length},
)
def get_help_text(self):
return ngettext(
"Your password must contain at least %(min_length)d character.",
"Your password must contain at least %(min_length)d characters.",
self.min_length,
) % {"min_length": self.min_length}
def exceeds_maximum_length_ratio(password, max_similarity, value):
"""
Test that value is within a reasonable range of password.
The following ratio calculations are based on testing SequenceMatcher like
this:
for i in range(0,6):
print(10**i, SequenceMatcher(a='A', b='A'*(10**i)).quick_ratio())
which yields:
1 1.0
10 0.18181818181818182
100 0.019801980198019802
1000 0.001998001998001998
10000 0.00019998000199980003
100000 1.999980000199998e-05
This means a length_ratio of 10 should never yield a similarity higher than
0.2, for 100 this is down to 0.02 and for 1000 it is 0.002. This can be
calculated via 2 / length_ratio. As a result we avoid the potentially
expensive sequence matching.
"""
pwd_len = len(password)
length_bound_similarity = max_similarity / 2 * pwd_len
value_len = len(value)
return pwd_len >= 10 * value_len and value_len < length_bound_similarity
class UserAttributeSimilarityValidator:
"""
Validate that the password is sufficiently different from the user's
attributes.
If no specific attributes are provided, look at a sensible list of
defaults. Attributes that don't exist are ignored. Comparison is made to
not only the full attribute value, but also its components, so that, for
example, a password is validated against either part of an email address,
as well as the full address.
"""
DEFAULT_USER_ATTRIBUTES = ("username", "first_name", "last_name", "email")
def __init__(self, user_attributes=DEFAULT_USER_ATTRIBUTES, max_similarity=0.7):
self.user_attributes = user_attributes
if max_similarity < 0.1:
raise ValueError("max_similarity must be at least 0.1")
self.max_similarity = max_similarity
def validate(self, password, user=None):
if not user:
return
password = password.lower()
for attribute_name in self.user_attributes:
value = getattr(user, attribute_name, None)
if not value or not isinstance(value, str):
continue
value_lower = value.lower()
value_parts = re.split(r"\W+", value_lower) + [value_lower]
for value_part in value_parts:
if exceeds_maximum_length_ratio(
password, self.max_similarity, value_part
):
continue
if (
SequenceMatcher(a=password, b=value_part).quick_ratio()
>= self.max_similarity
):
try:
verbose_name = str(
user._meta.get_field(attribute_name).verbose_name
)
except FieldDoesNotExist:
verbose_name = attribute_name
raise ValidationError(
_("The password is too similar to the %(verbose_name)s."),
code="password_too_similar",
params={"verbose_name": verbose_name},
)
def get_help_text(self):
return _(
"Your password can’t be too similar to your other personal information."
)
class CommonPasswordValidator:
"""
Validate that the password is not a common password.
The password is rejected if it occurs in a provided list of passwords,
which may be gzipped. The list Django ships with contains 20000 common
passwords (lowercased and deduplicated), created by Royce Williams:
https://gist.github.com/roycewilliams/226886fd01572964e1431ac8afc999ce
The password list must be lowercased to match the comparison in validate().
"""
@cached_property
def DEFAULT_PASSWORD_LIST_PATH(self):
return Path(__file__).resolve().parent / "common-passwords.txt.gz"
def __init__(self, password_list_path=DEFAULT_PASSWORD_LIST_PATH):
if password_list_path is CommonPasswordValidator.DEFAULT_PASSWORD_LIST_PATH:
password_list_path = self.DEFAULT_PASSWORD_LIST_PATH
try:
with gzip.open(password_list_path, "rt", encoding="utf-8") as f:
self.passwords = {x.strip() for x in f}
except OSError:
with open(password_list_path) as f:
self.passwords = {x.strip() for x in f}
def validate(self, password, user=None):
if password.lower().strip() in self.passwords:
raise ValidationError(
_("This password is too common."),
code="password_too_common",
)
def get_help_text(self):
return _("Your password can’t be a commonly used password.")
class NumericPasswordValidator:
"""
Validate that the password is not entirely numeric.
"""
def validate(self, password, user=None):
if password.isdigit():
raise ValidationError(
_("This password is entirely numeric."),
code="password_entirely_numeric",
)
def get_help_text(self):
return _("Your password can’t be entirely numeric.")