【初心者向け】Django認証システムの要: auth.models.AbstractBaseUser.check_password() の仕組みと実装

Purpose

The check_password() method is an essential component of Django's authentication system, responsible for verifying the validity of a user's password against the stored hashed password. It plays a crucial role in ensuring secure user authentication and preventing unauthorized access.

Implementation

1. Retrieving Hashed Password
   

   The method begins by retrieving the hashed password associated with the provided user object. This hashed password is typically stored in the database as part of the user's profile.

2. Password Encoding
   

   Next, the provided password, which is assumed to be in plain text format, is encoded using the same hashing algorithm as the stored password. This ensures that both passwords are compared in a consistent and secure manner.

3. Password Comparison
   

   The core of the method lies in comparing the encoded plain-text password to the retrieved hashed password. Django utilizes a secure password comparison function that performs a constant-time comparison to prevent timing attacks.

4. Return Value
   

   If the comparison succeeds, indicating that the provided password matches the stored hashed password, the method returns True. Conversely, if the passwords do not match, the method returns False.

Significance

The check_password() method serves as a critical safeguard in Django's authentication process. By accurately verifying user passwords, it helps prevent unauthorized access to sensitive user accounts and data.

• Password Reset Mechanisms
  Django offers password reset features to assist users in recovering their accounts if they forget their passwords.

• Password Strength Requirements
  Django provides mechanisms to enforce password strength policies, ensuring users choose strong and secure passwords.

• Password Salt
  The hashing process typically incorporates a salt, a random value, to further enhance password security.

• Password Hashing Algorithm
  Django employs a robust password hashing algorithm to protect user passwords from being easily deciphered.

---

from django.contrib.auth.models import AbstractBaseUser, BaseUserManager


class MyUserManager(BaseUserManager):
    """
    Custom user manager for creating and managing users.
    """

    def create_user(self, email, password=None):
        """
        Create a new user with the given email and password.
        """
        if not email:
            raise ValueError('Users must have an email address')

        user = self.model(email=self.normalize_email(email))
        user.set_password(password)
        user.save(using=self._db)
        return user


class MyUser(AbstractBaseUser):
    """
    Custom user model that extends the base user model.
    """

    email = models.EmailField(unique=True, max_length=255)
    # Add other fields as needed

    objects = MyUserManager()

    USERNAME_FIELD = 'email'
    REQUIRED_FIELDS = ['email']

    def __str__(self):
        return self.email

    def check_password(self, password):
        """
        Check if the given password matches the stored password.
        """
        return self.set_password_hash(password) == self.password


# Usage example:

user = MyUser.objects.create_user(email='[email protected]', password='secret')

if user.check_password('secret'):
    print('Password is correct')
else:
    print('Password is incorrect')

1. • django.contrib.auth.models: Imports the AbstractBaseUser and BaseUserManager classes from Django's authentication framework.

2. Define Custom User Manager
   

   • MyUserManager: Creates a custom user manager class that inherits from BaseUserManager.
   • create_user(): This method is responsible for creating new user objects. It takes an email and an optional password as arguments.
     • Validates the provided email address.
     • Creates a new user object with the given email and sets the password using set_password().
     • Saves the user object to the database.
     • Returns the newly created user object.

3. Define Custom User Model
   

   • MyUser: Creates a custom user model class that inherits from AbstractBaseUser.
   • email: Defines an email field as the unique identifier for the user.
     • Sets unique=True to ensure that no two users can have the same email address.
     • Sets max_length=255 to specify the maximum length of the email address.
   • objects: Assigns the custom user manager to the user model.
   • USERNAME_FIELD: Specifies the field that will be used for user authentication. In this case, it's the email field.
   • REQUIRED_FIELDS: Defines the fields that are required when creating a user object. In this case, it's only the email field.
   • __str__(): Defines the string representation of the user object, returning the user's email address.
   • check_password(): This method is responsible for verifying the provided password against the stored hashed password.
     • Receives the plain-text password as an argument.
     • Hashes the plain-text password using set_password_hash().
     • Compares the generated hashed password to the stored hashed password (accessible through the password attribute).
     • Returns True if the passwords match, False otherwise.

4. Usage Example
   

   • Creates a new user object using the custom user manager's create_user() method.
   • Calls the check_password() method on the user object, passing the plain-text password ('secret').
   • Prints a message indicating whether the password is correct or incorrect based on the return value of check_password().

---

1. Custom Password Verification Function
   

For advanced password policies or custom hashing algorithms, you can create a custom password verification function that replicates the functionality of check_password(). This function would have access to the user object and the plain-text password, allowing you to implement your own password verification logic.

1. Third-Party Authentication Libraries
   

If you're integrating with external authentication providers or services, you may utilize their password verification APIs instead of Django's built-in method. This approach can simplify integration and leverage the expertise of the external provider.

1. Password Validation Framework
   

Consider using a password validation framework like django-password-validators to enforce complex password requirements and perform additional password checks. This can enhance password security and reduce the risk of weak passwords.

1. Two-Factor Authentication (2FA)
   

Implement two-factor authentication (2FA) to add an extra layer of security beyond password verification. This requires users to provide a second authentication factor, such as a code sent to their phone, in addition to their password.

1. Passwordless Authentication
   

Explore passwordless authentication mechanisms, such as magic links or biometrics, for a more user-friendly and secure authentication experience. These methods eliminate the need for passwords and rely on alternative verification techniques.