认证系统 | 博客

用户模型

认证包括验证和授权
这些操作都是围绕着用户表的操作，因此第一步是先确定用户表
默认的用户表一般满足不了实际的需求，这时我们可以

扩展，利用一对一关联 User 模型。
取代 User 表，User 表是继承自 AbstractUser，我们也可以直接继承来自定义我们的表字段，不过别忘记在设置里定义
完全自定义，AbstractUser 继承自 AbstractBaseUser 和 PermissionsMixin，而他们又都继承自 models.Model。因此我们完全可以直接自定义我们自己的用户表，不过这样会增加很多工作量。具体可参考官方的源码。

一般情况下可以使用第2种方式，可以复用框架大量的便利的实现。以下是按照 2 的情况。

认证后端

认证后端处理用户验证和权限验证。默认设置下 AUTHENTICATION_BACKENDS = ['django.contrib.auth.backends.ModelBackend'] ，认证后端可以有多个，当有多个认证后端时 django 会依次尝试验证直到所有后端都被尝试。
我们也可以自定义认证后端。认证代码类似下面这样

class MyBackend(django.contrib.auth.backends.ModelBackend):
    def authenticate(self, request, username=None, password=None):
        # Check the username/password and return a user.
        ...
    def has_perm(self, user_obj, perm, obj=None):
            return user_obj.username == settings.ADMIN_LOGIN

处理用户验证
authenticate 方法应该在验证通过后返回一个 user 对象，否则返回 None。
处理授权
用户模型会把权限查找函数(get_group_permissions(), get_all_permissions(), has_perm(), and has_module_perms()) 委托给任何实现了这些函数的验证后端。这些函数在 django.contrib.auth.backends.ModelBackend都已实现，我们只需继承就好了

分组和权限

对于 2 这种方式，AbstractUser 继承自 AbstractBaseUser 和 PermissionsMixin，我们的用户模型又继承自 AbstractUser，因此也会继承 AbstractBaseUser 和 PermissionsMixin。让我们看看在这三个类中发生了什么。首先 AbstractBaseUser 和 AbstractUser 定义了一些必须的字段，password、email 等；引入了 UserManager ;还有一些方法。而 PermissionsMixin 定义了两个多对多字段，一个是 groups 关联 Group 模型；另一个是 user_permissions 关联 Permission 模型。继续挖 Permission 模型，发现其和 ContentType 是多对一的关系，结合文档的一段话：

当 INSTALLED_APPS 设置了 django.contrib.auth 时，它将确保你的每个 Django 模型被创建时有四个默认权限：添加、修改、删除和查看。
运行 manage.py migrate 时将创建这些权限。当你添加 django.contrib.auth 到 INSTALLED_APPS 后第一次运行迁移，将会为所有只去已经安装过的模型以及现在正在安装的模型创建这些默认的权限。之后，每次你运行 manage.py migrate 都会为新模型创建默认权限 (创建权限的函数连接 post_migrate 信号)。

默认权限就是这么来的。
我们也可以自定义我们的权限，示例如下：

class Task(models.Model):
    ...
    class Meta:
        permissions = [
            ("change_task_status", "Can change the status of tasks"),
            ("close_task", "Can remove a task by setting its status as closed"),
        ]

这会在 migrate 时写到 Permission 表中。

详细实现可参考官方文档

主要涉及的代码文件：django.contrib.auth.backends.py 和 django.contrib.auth.models.py

#backends.py
class ModelBackend:

    def authenticate(self, request, username=None, password=None, **kwargs):
        if username is None:
            username = kwargs.get(UserModel.USERNAME_FIELD)
        try:
            user = UserModel._default_manager.get_by_natural_key(username)
        except UserModel.DoesNotExist:
            # Run the default password hasher once to reduce the timing
            # difference between an existing and a nonexistent user (#20760).
            UserModel().set_password(password)
        else:
            if user.check_password(password) and self.user_can_authenticate(user):
                return user

    def user_can_authenticate(self, user):
        """
        Reject users with is_active=False. Custom user models that don't have
        that attribute are allowed.
        """
        is_active = getattr(user, 'is_active', None)
        return is_active or is_active is None

    def _get_user_permissions(self, user_obj):
        return user_obj.user_permissions.all()

    def _get_group_permissions(self, user_obj):
        user_groups_field = get_user_model()._meta.get_field('groups')
        user_groups_query = 'group__%s' % user_groups_field.related_query_name()
        return Permission.objects.filter(**{user_groups_query: user_obj})

    def _get_permissions(self, user_obj, obj, from_name):
        """
        Return the permissions of `user_obj` from `from_name`. `from_name` can
        be either "group" or "user" to return permissions from
        `_get_group_permissions` or `_get_user_permissions` respectively.
        """
        if not user_obj.is_active or user_obj.is_anonymous or obj is not None:
            return set()

        perm_cache_name = '_%s_perm_cache' % from_name
        if not hasattr(user_obj, perm_cache_name):
            if user_obj.is_superuser:
                perms = Permission.objects.all()
            else:
                perms = getattr(self, '_get_%s_permissions' % from_name)(user_obj)
            perms = perms.values_list('content_type__app_label', 'codename').order_by()
            setattr(user_obj, perm_cache_name, {"%s.%s" % (ct, name) for ct, name in perms})
        return getattr(user_obj, perm_cache_name)

    def get_user_permissions(self, user_obj, obj=None):
        """
        Return a set of permission strings the user `user_obj` has from their
        `user_permissions`.
        """
        return self._get_permissions(user_obj, obj, 'user')

    def get_group_permissions(self, user_obj, obj=None):
        """
        Return a set of permission strings the user `user_obj` has from the
        groups they belong.
        """
        return self._get_permissions(user_obj, obj, 'group')

    def get_all_permissions(self, user_obj, obj=None):
        if not user_obj.is_active or user_obj.is_anonymous or obj is not None:
            return set()
        if not hasattr(user_obj, '_perm_cache'):
            user_obj._perm_cache = {
                *self.get_user_permissions(user_obj),
                *self.get_group_permissions(user_obj),
            }
        return user_obj._perm_cache

    def has_perm(self, user_obj, perm, obj=None):
        return user_obj.is_active and perm in self.get_all_permissions(user_obj, obj)

    def has_module_perms(self, user_obj, app_label):
        """
        Return True if user_obj has any permissions in the given app_label.
        """
        return user_obj.is_active and any(
            perm[:perm.index('.')] == app_label
            for perm in self.get_all_permissions(user_obj)
        )

    def get_user(self, user_id):
        try:
            user = UserModel._default_manager.get(pk=user_id)
        except UserModel.DoesNotExist:
            return None
        return user if self.user_can_authenticate(user) else None

# models.py
from django.contrib import auth
from django.contrib.auth.base_user import AbstractBaseUser, BaseUserManager
from django.contrib.contenttypes.models import ContentType
from django.core.exceptions import PermissionDenied
from django.core.mail import send_mail
from django.db import models
from django.db.models.manager import EmptyManager
from django.utils import timezone
from django.utils.translation import gettext_lazy as _

from .validators import UnicodeUsernameValidator


def update_last_login(sender, user, **kwargs):
    """
    A signal receiver which updates the last_login date for
    the user logging in.
    """
    user.last_login = timezone.now()
    user.save(update_fields=['last_login'])


class PermissionManager(models.Manager):
    use_in_migrations = True

    def get_by_natural_key(self, codename, app_label, model):
        return self.get(
            codename=codename,
            content_type=ContentType.objects.db_manager(self.db).get_by_natural_key(app_label, model),
        )


class Permission(models.Model):
    """
    The permissions system provides a way to assign permissions to specific
    users and groups of users.

    The permission system is used by the Django admin site, but may also be
    useful in your own code. The Django admin site uses permissions as follows:

        - The "add" permission limits the user's ability to view the "add" form
          and add an object.
        - The "change" permission limits a user's ability to view the change
          list, view the "change" form and change an object.
        - The "delete" permission limits the ability to delete an object.
        - The "view" permission limits the ability to view an object.

    Permissions are set globally per type of object, not per specific object
    instance. It is possible to say "Mary may change news stories," but it's
    not currently possible to say "Mary may change news stories, but only the
    ones she created herself" or "Mary may only change news stories that have a
    certain status or publication date."

    The permissions listed above are automatically created for each model.
    """
    name = models.CharField(_('name'), max_length=255)
    content_type = models.ForeignKey(
        ContentType,
        models.CASCADE,
        verbose_name=_('content type'),
    )
    codename = models.CharField(_('codename'), max_length=100)

    objects = PermissionManager()

    class Meta:
        verbose_name = _('permission')
        verbose_name_plural = _('permissions')
        unique_together = (('content_type', 'codename'),)
        ordering = ('content_type__app_label', 'content_type__model',
                    'codename')

    def __str__(self):
        return "%s | %s | %s" % (
            self.content_type.app_label,
            self.content_type,
            self.name,
        )

    def natural_key(self):
        return (self.codename,) + self.content_type.natural_key()
    natural_key.dependencies = ['contenttypes.contenttype']


class GroupManager(models.Manager):
    """
    The manager for the auth's Group model.
    """
    use_in_migrations = True

    def get_by_natural_key(self, name):
        return self.get(name=name)


class Group(models.Model):
    """
    Groups are a generic way of categorizing users to apply permissions, or
    some other label, to those users. A user can belong to any number of
    groups.

    A user in a group automatically has all the permissions granted to that
    group. For example, if the group 'Site editors' has the permission
    can_edit_home_page, any user in that group will have that permission.

    Beyond permissions, groups are a convenient way to categorize users to
    apply some label, or extended functionality, to them. For example, you
    could create a group 'Special users', and you could write code that would
    do special things to those users -- such as giving them access to a
    members-only portion of your site, or sending them members-only email
    messages.
    """
    name = models.CharField(_('name'), max_length=150, unique=True)
    permissions = models.ManyToManyField(
        Permission,
        verbose_name=_('permissions'),
        blank=True,
    )

    objects = GroupManager()

    class Meta:
        verbose_name = _('group')
        verbose_name_plural = _('groups')

    def __str__(self):
        return self.name

    def natural_key(self):
        return (self.name,)


class UserManager(BaseUserManager):
    use_in_migrations = True

    def _create_user(self, username, email, password, **extra_fields):
        """
        Create and save a user with the given username, email, and password.
        """
        if not username:
            raise ValueError('The given username must be set')
        email = self.normalize_email(email)
        username = self.model.normalize_username(username)
        user = self.model(username=username, email=email, **extra_fields)
        user.set_password(password)
        user.save(using=self._db)
        return user

    def create_user(self, username, email=None, password=None, **extra_fields):
        extra_fields.setdefault('is_staff', False)
        extra_fields.setdefault('is_superuser', False)
        return self._create_user(username, email, password, **extra_fields)

    def create_superuser(self, username, email, password, **extra_fields):
        extra_fields.setdefault('is_staff', True)
        extra_fields.setdefault('is_superuser', True)

        if extra_fields.get('is_staff') is not True:
            raise ValueError('Superuser must have is_staff=True.')
        if extra_fields.get('is_superuser') is not True:
            raise ValueError('Superuser must have is_superuser=True.')

        return self._create_user(username, email, password, **extra_fields)


# A few helper functions for common logic between User and AnonymousUser.
def _user_get_all_permissions(user, obj):
    permissions = set()
    for backend in auth.get_backends():
        if hasattr(backend, "get_all_permissions"):
            permissions.update(backend.get_all_permissions(user, obj))
    return permissions


def _user_has_perm(user, perm, obj):
    """
    A backend can raise `PermissionDenied` to short-circuit permission checking.
    """
    for backend in auth.get_backends():
        if not hasattr(backend, 'has_perm'):
            continue
        try:
            if backend.has_perm(user, perm, obj):
                return True
        except PermissionDenied:
            return False
    return False


def _user_has_module_perms(user, app_label):
    """
    A backend can raise `PermissionDenied` to short-circuit permission checking.
    """
    for backend in auth.get_backends():
        if not hasattr(backend, 'has_module_perms'):
            continue
        try:
            if backend.has_module_perms(user, app_label):
                return True
        except PermissionDenied:
            return False
    return False


class PermissionsMixin(models.Model):
    """
    Add the fields and methods necessary to support the Group and Permission
    models using the ModelBackend.
    """
    is_superuser = models.BooleanField(
        _('superuser status'),
        default=False,
        help_text=_(
            'Designates that this user has all permissions without '
            'explicitly assigning them.'
        ),
    )
    groups = models.ManyToManyField(
        Group,
        verbose_name=_('groups'),
        blank=True,
        help_text=_(
            'The groups this user belongs to. A user will get all permissions '
            'granted to each of their groups.'
        ),
        related_name="user_set",
        related_query_name="user",
    )
    user_permissions = models.ManyToManyField(
        Permission,
        verbose_name=_('user permissions'),
        blank=True,
        help_text=_('Specific permissions for this user.'),
        related_name="user_set",
        related_query_name="user",
    )

    class Meta:
        abstract = True

    def get_group_permissions(self, obj=None):
        """
        Return a list of permission strings that this user has through their
        groups. Query all available auth backends. If an object is passed in,
        return only permissions matching this object.
        """
        permissions = set()
        for backend in auth.get_backends():
            if hasattr(backend, "get_group_permissions"):
                permissions.update(backend.get_group_permissions(self, obj))
        return permissions

    def get_all_permissions(self, obj=None):
        return _user_get_all_permissions(self, obj)

    def has_perm(self, perm, obj=None):
        """
        Return True if the user has the specified permission. Query all
        available auth backends, but return immediately if any backend returns
        True. Thus, a user who has permission from a single auth backend is
        assumed to have permission in general. If an object is provided, check
        permissions for that object.
        """
        # Active superusers have all permissions.
        if self.is_active and self.is_superuser:
            return True

        # Otherwise we need to check the backends.
        return _user_has_perm(self, perm, obj)

    def has_perms(self, perm_list, obj=None):
        """
        Return True if the user has each of the specified permissions. If
        object is passed, check if the user has all required perms for it.
        """
        return all(self.has_perm(perm, obj) for perm in perm_list)

    def has_module_perms(self, app_label):
        """
        Return True if the user has any permissions in the given app label.
        Use similar logic as has_perm(), above.
        """
        # Active superusers have all permissions.
        if self.is_active and self.is_superuser:
            return True

        return _user_has_module_perms(self, app_label)


class AbstractUser(AbstractBaseUser, PermissionsMixin):
    """
    An abstract base class implementing a fully featured User model with
    admin-compliant permissions.

    Username and password are required. Other fields are optional.
    """
    username_validator = UnicodeUsernameValidator()

    username = models.CharField(
        _('username'),
        max_length=150,
        unique=True,
        help_text=_('Required. 150 characters or fewer. Letters, digits and @/./+/-/_ only.'),
        validators=[username_validator],
        error_messages={
            'unique': _("A user with that username already exists."),
        },
    )
    first_name = models.CharField(_('first name'), max_length=30, blank=True)
    last_name = models.CharField(_('last name'), max_length=150, blank=True)
    email = models.EmailField(_('email address'), blank=True)
    is_staff = models.BooleanField(
        _('staff status'),
        default=False,
        help_text=_('Designates whether the user can log into this admin site.'),
    )
    is_active = models.BooleanField(
        _('active'),
        default=True,
        help_text=_(
            'Designates whether this user should be treated as active. '
            'Unselect this instead of deleting accounts.'
        ),
    )
    date_joined = models.DateTimeField(_('date joined'), default=timezone.now)

    objects = UserManager()

    EMAIL_FIELD = 'email'
    USERNAME_FIELD = 'username'
    REQUIRED_FIELDS = ['email']

    class Meta:
        verbose_name = _('user')
        verbose_name_plural = _('users')
        abstract = True

    def clean(self):
        super().clean()
        self.email = self.__class__.objects.normalize_email(self.email)

    def get_full_name(self):
        """
        Return the first_name plus the last_name, with a space in between.
        """
        full_name = '%s %s' % (self.first_name, self.last_name)
        return full_name.strip()

    def get_short_name(self):
        """Return the short name for the user."""
        return self.first_name

    def email_user(self, subject, message, from_email=None, **kwargs):
        """Send an email to this user."""
        send_mail(subject, message, from_email, [self.email], **kwargs)


class User(AbstractUser):
    """
    Users within the Django authentication system are represented by this
    model.

    Username and password are required. Other fields are optional.
    """
    class Meta(AbstractUser.Meta):
        swappable = 'AUTH_USER_MODEL'


class AnonymousUser:
    id = None
    pk = None
    username = ''
    is_staff = False
    is_active = False
    is_superuser = False
    _groups = EmptyManager(Group)
    _user_permissions = EmptyManager(Permission)

    def __str__(self):
        return 'AnonymousUser'

    def __eq__(self, other):
        return isinstance(other, self.__class__)

    def __hash__(self):
        return 1  # instances always return the same hash value

    def __int__(self):
        raise TypeError('Cannot cast AnonymousUser to int. Are you trying to use it in place of User?')

    def save(self):
        raise NotImplementedError("Django doesn't provide a DB representation for AnonymousUser.")

    def delete(self):
        raise NotImplementedError("Django doesn't provide a DB representation for AnonymousUser.")

    def set_password(self, raw_password):
        raise NotImplementedError("Django doesn't provide a DB representation for AnonymousUser.")

    def check_password(self, raw_password):
        raise NotImplementedError("Django doesn't provide a DB representation for AnonymousUser.")

    @property
    def groups(self):
        return self._groups

    @property
    def user_permissions(self):
        return self._user_permissions

    def get_group_permissions(self, obj=None):
        return set()

    def get_all_permissions(self, obj=None):
        return _user_get_all_permissions(self, obj=obj)

    def has_perm(self, perm, obj=None):
        return _user_has_perm(self, perm, obj=obj)

    def has_perms(self, perm_list, obj=None):
        return all(self.has_perm(perm, obj) for perm in perm_list)

    def has_module_perms(self, module):
        return _user_has_module_perms(self, module)

    @property
    def is_anonymous(self):
        return True

    @property
    def is_authenticated(self):
        return False

    def get_username(self):
        return self.username