Password validations: Add two new validators

Add two new custom password validators. One ensures
passwords have a minimum number of uppercase letters and the
other ensures passwords have a minimum amount of numbers.

Signed-off-by: Roberto Rosario <roberto.rosario.gonzalez@gmail.com>

HISTORY.rst

@@ -85,6 +85,9 @@
   to a document's OCR content for indexing and other purposes.
 - Add the 'content' attribute to documents to allow access
   to a document's parsed content for indexing and other purposes.
+- Two new custom password validators added. One ensures
+  passwords have a minimum number of uppercase letters and the
+  other ensures passwords have a minimum amount of numbers.
 
 3.1.9 (2018-11-01)
 ==================

docs/chapters/password_validation.rst

@@ -0,0 +1,48 @@
+*******************
+Password validation
+*******************
+
+To help reduce the use of weak passwords, Mayan EDMS includes support for
+password validators. Password validator enforce policies by rejecting
+password that don't conform with the validator's logic.
+
+By default, Mayan EDMS sets this password validation setup:
+
+- That the password is not similar no any user attributes.
+- A minimum password size of 8 characters.
+- The password is not one of the 20,000 commonly used weak password.
+- That the password is not entirely numeric.
+
+This default is coded in the following manner by the default Python setup file::
+
+    AUTH_PASSWORD_VALIDATORS = [
+        {
+            'NAME': 'django.contrib.auth.password_validation.UserAttributeSimilarityValidator',
+        },
+        {
+            'NAME': 'django.contrib.auth.password_validation.MinimumLengthValidator',
+        },
+        {
+            'NAME': 'django.contrib.auth.password_validation.CommonPasswordValidator',
+        },
+        {
+            'NAME': 'django.contrib.auth.password_validation.NumericPasswordValidator',
+        },
+    ]
+
+If using the YAML configuration file the same setup would be coded in the
+following manner::
+
+    AUTH_PASSWORD_VALIDATORS:
+    - NAME: django.contrib.auth.password_validation.UserAttributeSimilarityValidator
+    - NAME: django.contrib.auth.password_validation.MinimumLengthValidator
+    - NAME: django.contrib.auth.password_validation.CommonPasswordValidator
+    - NAME: django.contrib.auth.password_validation.NumericPasswordValidator
+
+In addition to the password validators provided by Django
+:django-docs:`validators provided by Django <topics/auth/passwords/#included-validators>`,
+Mayan EDMS adds the following validators:
+
+.. autoclass:: mayan.apps.authentication.validators.MinimumCapitalLettersContentValidator
+
+.. autoclass:: mayan.apps.authentication.validators.MinimumNumberContentValidator

docs/topics/advanced.rst

@@ -8,3 +8,4 @@ Advanced topics
 .. include:: ../chapters/metadata.rst
 .. include:: ../chapters/transformations.rst
 .. include:: ../chapters/versioning.rst
+.. include:: ../chapters/password_validation.rst

mayan/apps/authentication/validators.py

@@ -0,0 +1,56 @@
+from __future__ import unicode_literals
+
+from django.core.exceptions import ValidationError
+from django.utils.translation import gettext as _
+
+
+class MinimumCapitalLettersContentValidator(object):
+    """
+    Validate whether the password contains a minimum number of uppercase
+    letters.
+    """
+    def __init__(self, minimum_capital_letters=1):
+        self.minimum_capital_letters = minimum_capital_letters
+
+    def validate(self, password, user=None):
+        if sum([1 for letter in password if letter.isupper()]) < self.minimum_capital_letters:  # NOQA
+            raise ValidationError(
+                _(
+                    'This password must contain at least '
+                    '%(minimum_capital_letters)d capital letters.'
+                ), code='password_not_enough_capital_letters',
+                params={
+                    'minimum_capital_letters': self.minimum_capital_letters
+                },
+            )
+
+    def get_help_text(self):
+        return _(
+            'Your password must contain at least %(minimum_capital_letters)d '
+            'capital letters.'
+            % {'minimum_capital_letters': self.minimum_capital_letters}
+        )
+
+
+class MinimumNumberContentValidator(object):
+    """
+    Validate whether the password contains a minimum number digits.
+    """
+    def __init__(self, minimum_numbers=1):
+        self.minimum_numbers = minimum_numbers
+
+    def validate(self, password, user=None):
+        if sum([1 for letter in password if letter.isdigit()]) < self.minimum_numbers:  # NOQA
+            raise ValidationError(
+                _(
+                    'This password must contain at least %(minimum_numbers)d '
+                    'numbers.'
+                ), code='password_not_enough_numbers',
+                params={'minimum_numbers': self.minimum_numbers},
+            )
+
+    def get_help_text(self):
+        return _(
+            'Your password must contain at least %(minimum_numbers)d numbers.'
+            % {'minimum_numbers': self.minimum_numbers}
+        )