How do I prevent permission escalation in Django a

Question

I have a django site with a large customer base. I would like to give our customer service department the ability to alter normal user accounts, doing things like changing passwords, email addresses, etc. However, if I grant someone the built-in auth | user | Can change user permission, they gain the ability to set the is_superuser flag on any account, including their own. (!!!)

What's the best way to remove this option for non-superuser staff? I'm sure it involves subclassing django.contrib.auth.forms.UserChangeForm and hooking it into my already-custom UserAdmin object... somehow. But I can't find any documentation on how to do this, and I don't yet understand the internals well enough.

Answer 1

Full code for django 1.1 (limited to basic user information for staff (not superusers))

from django.contrib.auth.models import User
from django.utils.translation import ugettext_lazy as _


class MyUserAdmin(UserAdmin):
   my_fieldsets = (
       (None, {'fields': ('username', 'password')}),
       (_('Personal info'), {'fields': ('first_name', 'last_name', 'email')}),
   )

   def change_view(self, request, object_id, extra_context=None):
       # for non-superuser
       print 'test'
       if not request.user.is_superuser:
           self.fieldsets = self.my_fieldsets
           response = UserAdmin.change_view(self, request, object_id,
extra_context=None)
           return response
       else:
           return UserAdmin.change_view(self, request, object_id,
extra_context=None)


admin.site.unregister(User)
admin.site.register(User, MyUserAdmin)

Answer 2

This approach was put together from several helpful tips on the web. In this case we are modifying UserAdmin so that, for non-superuser staff with user add/change permission, the only permissions and groups they can grant another user are the ones the staff member already has.

(for Django 1.11)

from django.contrib.auth.admin import UserAdmin, User
from django.contrib import admin

class RestrictedUserAdmin(UserAdmin):
    model = User

    def formfield_for_dbfield(self, db_field, **kwargs):
        field = super(RestrictedUserAdmin, self).formfield_for_dbfield(db_field, **kwargs)
        user = kwargs['request'].user
        if not user.is_superuser:
            if db_field.name == 'groups':
                field.queryset = field.queryset.filter(id__in=[i.id for i in user.groups.all()])
            if db_field.name == 'user_permissions':
                field.queryset = field.queryset.filter(id__in=[i.id for i in user.user_permissions.all()])
            if db_field.name == 'is_superuser':
                field.widget.attrs['disabled'] = True
        return field

admin.site.unregister(User)
admin.site.register(User, RestrictedUserAdmin)

This should likewise be done for GroupAdmin if a user is given permission to change groups.

Answer 3

Great thanks to Clément. What I came up with when doing the same for my site is that I needed additionally to make all fields readonly for users you other than self. So basing on Clément's answer I addeed readonly fields and password field hiding when viewing not self

class MyUserAdmin(UserAdmin):
    model = User
    staff_self_fieldsets = (
        (None, {'fields': ('username', 'password')}),
        (_('Personal info'), {'fields': ('first_name', 'last_name', 'email')}),
        # No permissions
        (_('Important dates'), {'fields': ('last_login', 'date_joined')}),
    )

    staff_other_fieldsets = (
        (None, {'fields': ('username', )}),
        (_('Personal info'), {'fields': ('first_name', 'last_name', 'email')}),
        # No permissions
        (_('Important dates'), {'fields': ('last_login', 'date_joined')}),
    )

    staff_self_readonly_fields = ('last_login', 'date_joined')

    def change_view(self, request, object_id, form_url='', extra_context=None, *args, **kwargs):
        # for non-superuser
        if not request.user.is_superuser:
            try:
                if int(object_id) != request.user.id:
                    self.readonly_fields = User._meta.get_all_field_names()
                    self.fieldsets = self.staff_other_fieldsets
                else:
                    self.readonly_fields = self.staff_self_readonly_fields
                    self.fieldsets = self.staff_self_fieldsets

                response = super(MyUserAdmin, self).change_view(request, object_id, form_url, extra_context, *args, **kwargs)
            except:
                logger.error('Admin change view error. Returned all readonly fields')

                self.fieldsets = self.staff_other_fieldsets
                self.readonly_fields = ('first_name', 'last_name', 'email', 'username', 'password', 'last_login', 'date_joined')
                response = super(MyUserAdmin, self).change_view(request, object_id, form_url, extra_context, *args, **kwargs)
            finally:
                # Reset fieldsets to its original value
                self.fieldsets = UserAdmin.fieldsets
                self.readonly_fields = UserAdmin.readonly_fields
            return response
        else:
            return super(MyUserAdmin, self).change_view(request, object_id, form_url, extra_context, *args, **kwargs)

Answer 4

The below part of the accepted answer has a race condition where if two staff users try to access the admin form at the same time, one of them may get the superuser form.

try:
    self.readonly_fields = self.staff_self_readonly_fields
    response = super(MyUserAdmin, self).change_view(request, object_id, form_url, extra_context, *args, **kwargs)
finally:
    # Reset fieldsets to its original value
    self.fieldsets = UserAdmin.fieldsets

To avoid this race condition (and in my opinion improve the overall quality of the solution), we can override the get_fieldsets() and get_readonly_fields() methods directly:

class UserAdmin(BaseUserAdmin):
    staff_fieldsets = (
        (None, {'fields': ('username')}),
        ('Personal info', {'fields': ('first_name', 'last_name', 'email')}),
        # No permissions
        ('Important dates', {'fields': ('last_login', 'date_joined')}),
    )
    staff_readonly_fields = ('username', 'first_name', 'last_name', 'email', 'last_login', 'date_joined')

    def get_fieldsets(self, request, obj=None):
        if not request.user.is_superuser:
            return self.staff_fieldsets
        else:
            return super(UserAdmin, self).get_fieldsets(request, obj)

    def get_readonly_fields(self, request, obj=None):
        if not request.user.is_superuser:
            return self.staff_readonly_fields
        else:
            return super(UserAdmin, self).get_readonly_fields(request, obj)

Answer 5

they gain the ability to set the is_superuser flag on any account, including their own. (!!!)

Not only this, they also gain the ability to give themselves any permissions one-by-one, same effect...

I'm sure it involves subclassing django.contrib.auth.forms.UserChangeForm

Well, not necessarily. The form you see in the change page of django's admin is dynamically created by the admin application, and based on UserChangeForm, but this class barely adds regex validation to the username field.

and hooking it into my already-custom UserAdmin object...

A custom UserAdmin is the way to go here. Basically, you want to change the fieldsets property to something like that :

class MyUserAdmin(UserAdmin):
    fieldsets = (
        (None, {'fields': ('username', 'password')}),
        (_('Personal info'), {'fields': ('first_name', 'last_name', 'email')}),
        # Removing the permission part
        # (_('Permissions'), {'fields': ('is_staff', 'is_active', 'is_superuser', 'user_permissions')}),
        (_('Important dates'), {'fields': ('last_login', 'date_joined')}),
        # Keeping the group parts? Ok, but they shouldn't be able to define
        # their own groups, up to you...
        (_('Groups'), {'fields': ('groups',)}),
    )

But the problem here is that this restriction will apply to all users. If this is not what you want, you could for example override change_view to behave differently depending on the permission of the users. Code snippet :

class MyUserAdmin(UserAdmin):
    staff_fieldsets = (
        (None, {'fields': ('username', 'password')}),
        (_('Personal info'), {'fields': ('first_name', 'last_name', 'email')}),
        # No permissions
        (_('Important dates'), {'fields': ('last_login', 'date_joined')}),
        (_('Groups'), {'fields': ('groups',)}),
    )

    def change_view(self, request, *args, **kwargs):
        # for non-superuser
        if not request.user.is_superuser:
            try:
                self.fieldsets = self.staff_fieldsets
                response = super(MyUserAdmin, self).change_view(request, *args, **kwargs)
            finally:
                # Reset fieldsets to its original value
                self.fieldsets = UserAdmin.fieldsets
            return response
        else:
            return super(MyUserAdmin, self).change_view(request, *args, **kwargs)