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https://github.com/nshafer/django-hashid-field

Django Model Field that uses Hashids to obscure the value
https://github.com/nshafer/django-hashid-field

django django-rest-framework hashid hashids

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Django Model Field that uses Hashids to obscure the value

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WARNING! This module is retired!

================================



**This library has been retired. It is no longer recommended for new projects. Existing projects do not require**

**changes, but should consider migrating to a different library. See the**

`RETIRED `_

**document for more information.**



Django Hashid Field

===================



A custom Model Field that uses the `Hashids `_ `library `_

to obfuscate an IntegerField or AutoField. It can be used in new models or dropped in place of an existing IntegerField,

explicit AutoField, or an automatically generated AutoField.



Features

--------



* Stores IDs as integers in the database

* Allows lookups and filtering by hashid string or Hashid object and (optionally) integer.

* Can enable integer lookups globally or per-field

* Can be used as sort key

* Allows specifying a salt, min_length and alphabet globally

* Supports custom *salt*, *min_length*, *alphabet*, *prefix* and *allow_int_lookup* settings per field

* Allows prefixing hashids with custom string, e.g. `prefix="user_"` for hashids like "user_h6ks82g"

* Can drop-in replace an existing IntegerField (HashidField) or AutoField (HashidAutoField)

* Supports "Big" variants for large integers: BigHashidField, BigHashidAutoField

* Supports Django 3.2 setting `DEFAULT_AUTO_FIELD = 'hashid_field.BigHashidAutoField'`

* Supports Django REST Framework Serializers

* Supports exact ID searches in Django Admin when field is specified in search_fields.

* Supports common filtering lookups, such as ``__iexact``, ``__contains``, ``__icontains``, though matching is the same as ``__exact``.

* Supports subquery lookups with ``field__in=queryset``

* Supports other lookups: `isnull`, `gt`, `gte`, `lt` and `lte`.

* Supports hashing operations so the fields can be used in Dictionaries and Sets.



Requirements

------------



This module is tested and known to work with:



* Python 3.7, 3.8, 3.9, 3.10, 3.11, 3.12

* Django 3.2, 4.2, 5.0

* Hashids 1.3

* Django REST Framework 3.14



*Please Note*: Python 2.x is at its end of life and is no longer supported.



Installation

------------



Install the package (preferably in a virtualenv):



.. code-block:: bash



    $ pip install django-hashid-field



Configure a global SALT for all HashidFields to use by default in your settings.py. (*Note*: Using a global salt for all

fields will result in IDs from different fields/models being the same. If you want to have unique hashid strings for the

same id, then also configure per-field salts as described in Field Parameters below.)



.. code-block:: python



    HASHID_FIELD_SALT = "a long and secure salt value that is not the same as SECRET_KEY"

    # Note: You can generate a secure key with:

    #     from django.core.management.utils import get_random_secret_key; print(get_random_secret_key())



Add it to your model



.. code-block:: python



    from hashid_field import HashidField



    class Book(models.Model):

        reference_id = HashidField()



Migrate your database



.. code-block:: bash



    $ ./manage.py makemigrations

    $ ./manage.py migrate



Basic Usage

-----------



Use your field like you would any other, for the most part. You can assign integers:



.. code-block:: python



    >>> b = Book()

    >>> b.reference_id = 123

    >>> b.reference_id

    Hashid(123): OwLxW8D



You can assign valid hashids. It's valid only if it can be decoded into an integer based on your settings:



.. code-block:: python



    >>> b.reference_id = 'r8636LO'

    >>> b.reference_id

    Hashid(456): r8636LO



You can access your field with either hashid strings or Hashid objects:



.. code-block:: python



    >>> Book.objects.filter(reference_id='OwLxW8D')

    ]>

    >>> b = Book.objects.get(reference_id='OwLxW8D')

    >>> b

    

    >>> h = b.reference_id

    >>> h

    Hashid(123): OwLxW8D

    >>> Book.objects.filter(reference_id=h)

    



You can lookup objects with integers if you set ``HASHID_FIELD_ALLOW_INT_LOOKUP = True`` or ``allow_int_lookup=True``

as a parameter to the field.



.. code-block:: python



    reference_id = HashidField(allow_int_lookup=True)



Now integer lookups are allowed. Useful if migrating an existing AutoField to a HashidAutoField, but you need to allow

lookups with older integers.



.. code-block:: python



    >>> Book.objects.filter(reference_id=123)

    ]>



By default, the objects returned from a HashidField are an instance of the class Hashid (this can be disabled globally

or per-field), and allow basic access to the original integer or the hashid:



.. code-block:: python



    >>> from hashid_field import Hashid

    >>> h = Hashid(123)

    >>> h.id

    123

    >>> h.hashid

    'Mj3'

    >>> print(h)

    Mj3

    >>> repr(h)

    'Hashid(123): Mj3'



Hashid Auto Field

-----------------



Along with ``HashidField`` there is also a ``HashidAutoField`` that works in the same way, but that auto-increments just

like an ``AutoField``.



.. code-block:: python



    from hashid_field import HashidAutoField



    class Book(models.Model):

        serial_id = HashidAutoField(primary_key=True)



The only difference is that if you don't assign a value to it when you save, it will auto-generate a value from your

database, just as an AutoField would do. Please note that ``HashidAutoField`` inherits from ``AutoField`` and there can

only be one ``AutoField`` on a model at a time.



.. code-block:: python



    >>> b = Book()

    >>> b.save()

    >>> b.serial_id

    Hashid(1): AJEM7LK



It can be dropped into an existing model that has an auto-created AutoField (all models do by default) as long as you

give it the same name and set ``primary_key=True``. So if you have this model:



.. code-block:: python



    class Author(models.Model):

        name = models.CharField(max_length=40)



Then Django has created a field for you called 'id' automatically. We just need to override that by specifying our own

field with *primary_key* set to True.



.. code-block:: python



    class Author(models.Model):

        id = HashidAutoField(primary_key=True)

        name = models.CharField(max_length=40)



And now you can use the 'id' or 'pk' attributes on your model instances:



.. code-block:: python



    >>> a = Author.objects.create(name="John Doe")

    >>> a.id

    Hashid(60): N8VNa8z

    >>> Author.objects.get(pk='N8VNa8z')

    



In Django 3.2 a new setting, "DEFAULT_AUTO_FIELD" was added to change all auto-generated AutoFields to a specific class.

This is fully supported with django-hashid-field, and can be enabled with:



.. code-block:: python



    DEFAULT_AUTO_FIELD = 'hashid_field.HashidAutoField'

    DEFAULT_AUTO_FIELD = 'hashid_field.BigHashidAutoField'



Care must be given, as this will alter ALL models in your project. Usually you would only set this in a new project.

Also, since this changes the auto-generated field, only global settings will be used for that field. If you desire

specific settings for different models, then using this setting is not advised.



Django may configure the per-app `default_auto_field` when a new app is created. This will prevent the global setting

from taking affect. If you are attempting to use the global setting, you should check your app configs in

`project/app_name/apps.py` to ensure they don't interfere.



.. code-block:: python



    from django.apps import AppConfig



    class ScheduleConfig(AppConfig):

        default_auto_field = 'django.db.models.BigAutoField'

        name = 'schedule'



Global Settings

---------------



HASHID_FIELD_SALT

~~~~~~~~~~~~~~~~~



You can optionally set a global Salt to be used by all HashFields and HashidAutoFields in your project. Do not use the

same string as your SECRET_KEY, as this could lead to your SECRET_KEY being exposed to an attacker.

Please note that changing this value will cause all HashidFields to change their values, and any previously published

IDs will become invalid.

Can be overridden by the field definition if you desire unique hashid strings for a given field, as described in

Field Parameters below.



:Type:    string

:Default: ""

:Note:    The upstream hashids-python library [only considers the first 43 characters of the salt](https://github.com/davidaurelio/hashids-python/issues/43).

:Example:

    .. code-block:: python



        HASHID_FIELD_SALT = "a long and secure salt value that is not the same as SECRET_KEY"



HASHID_FIELD_MIN_LENGTH

~~~~~~~~~~~~~~~~~~~~~~~



Default minimum length for (non-Big) HashidField and AutoHashidField.

It is suggested to use 7 for HashidField and HashidAutoField, so that all possible values

(up to 2147483647) are the same length.



:Type:    integer

:Default: 7

:Example:

    .. code-block:: python



        HASHID_FIELD_MIN_LENGTH = 20



HASHID_FIELD_BIG_MIN_LENGTH

~~~~~~~~~~~~~~~~~~~~~~~~~~~



Default minimum length for BigHashidField and BigHashidAutoField.

It is suggested to use 13 for BigHashidField and BigHashidAutoField, so that all possible values

(up to 9223372036854775807) are the same length.



:Type:    integer

:Default: 13

:Example:

    .. code-block:: python



        HASHID_FIELD_BIG_MIN_LENGTH = 30



HASHID_FIELD_ALPHABET

~~~~~~~~~~~~~~~~~~~~~~~



The default alphabet to use for characters in generated Hashids strings. Must be at least 16 unique characters.



:Type:    string

:Default: "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890"

:Example:

    .. code-block:: python



        HASHID_FIELD_ALPHABET = "0123456789abcdef"



HASHID_FIELD_ALLOW_INT_LOOKUP

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~



Allow lookups or fetches of fields using the underlying integer that's stored in the database.

Disabled by default to prevent users from being to do a sequential scan of objects by pulling objects by

integers (1, 2, 3) instead of Hashid strings ("Ba9p1AG", "7V9gk9Z", "wro12zm").

Can be overridden by the field definition.



:Type:    boolean

:Default: False

:Example:

    .. code-block:: python



        HASHID_FIELD_ALLOW_INT_LOOKUP = True



HASHID_FIELD_LOOKUP_EXCEPTION

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~



By default any invalid hashid strings or integer lookups when integer lookups are turned off will result in an

EmptyResultSet being returned. Enable this to instead throw a ValueError exception (similar to the behavior prior to 2.0).



:Type:    boolean

:Default: False

:Example:

    .. code-block:: python



        HASHID_FIELD_LOOKUP_EXCEPTION = True



HASHID_FIELD_ENABLE_HASHID_OBJECT

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~



The default behavior is to return an instance of the Hashid object (described below) in each instance of your Model.

This makes it possible to get both the integer and hashid version of the field. However, other django modules, serializers,

etc may be confused and not know how to handle a Hashid object, so you can turn them off here. Instead, a string

of the hashid will be returned, and a new attribute with the suffix `_hashid` will be created on each instance with the

Hashid object. So if you have `key = HashidField(...)` then `key_hashid` will be created on each instance.

Can be overriden by the field definition.



:Type:    boolean

:Default: True

:Example:

    .. code-block:: python



        HASHID_FIELD_ENABLE_HASHID_OBJECT = False



HASHID_FIELD_ENABLE_DESCRIPTOR

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~



By default a Hashid*Field on a model will replace the original value returned from the database with a Descriptor

that attempts to convert values that are set on that field of an instance with a new Hashid object (or string if

ENABLE_HASHID_OBJECT is False), regardless if you set an integer or a valid hashid. For the most part this is

completely invisible and benign, however if you have issues due to this descriptor, you can disable it here, or

on the field, and the raw value will not be replaced with the Descriptor.

Can be overriden by the field definition.



:Type:    boolean

:Default: True

:Example:

    .. code-block:: python



        HASHID_FIELD_ENABLE_DESCRIPTOR = False



Field Parameters

----------------



Besides the standard field options, there are settings you can tweak that are specific to HashidField and

AutoHashidField.



**Please note** that changing any of the values for ``salt``, ``min_length``, ``alphabet`` or ``prefix`` *will* affect

the obfuscation of the integers that are stored in the database, and will change what are considered "valid" hashids.

If you have links or URLs that include your HashidField values, then they will stop working after changing any of these

values. It's highly advised that you don't change any of these settings once you publish any references to your field.



salt

~~~~



Local overridable salt for hashids generated specifically for this field.

Set this to a unique value for each field if you want the IDs for that field to be different to the same IDs

on another field. e.g. so that `book.id = Hashid(5): 0Q8Kg9r` and `author.id = Hashid(5): kp0eq0V`.

Suggestion: `fieldname = HashIdField(salt="modelname_fieldname_" + settings.HASHID_FIELD_SALT)`

See HASHID_FIELD_SALT above.



:Type:    string

:Default: settings.HASHID_FIELD_SALT, ""

:Note:    The upstream hashids-python library [only considers the first 43 characters of the salt](https://github.com/davidaurelio/hashids-python/issues/43).

:Example:

    .. code-block:: python



        reference_id = HashidField(salt="Some salt value")



min_length

~~~~~~~~~~



Generate hashid strings of this minimum length, regardless of the value of the integer that is being encoded.

This defaults to 7 for the field since the maximum IntegerField value can be encoded in 7 characters with

the default *alphabet* setting of 62 characters.



:Type:     int

:Default:  7

:Example:

    .. code-block:: python



        reference_id = HashidField(min_length=15)



alphabet

~~~~~~~~



The set of characters to generate hashids from. Must be at least 16 characters.



:Type:    string of characters

:Default: Hashids.ALPHABET, which is "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890"

:Example:

    .. code-block:: python



        # Only use numbers and lower-case letters

        reference_id = HashidField(alphabet="0123456789abcdefghijklmnopqrstuvwxyz")



prefix

~~~~~~



An optional string prefix that will be prepended to all generated hashids. Also affects validation, so only hashids

that have this prefix will be considered correct.



IMPORTANT: Do not end your prefix with an underscore, as this can cause issues with the Django admin. See Known Issues

below.



:Type:    String

:Default: ""

:Example:

    .. code-block:: python



        # Including the type of id in the id itself:

        reference_id = HashidField(prefix="order-")



allow_int_lookup

~~~~~~~~~~~~~~~~



Local field override for default global on whether or not integer lookups for this field should be allowed.

See HASHID_FIELD_ALLOW_INT_LOOKUP above.



:Type:    boolean

:Default: settings.HASHID_FIELD_ALLOW_INT_LOOKUP, False

:Example:

    .. code-block:: python



        reference_id = HashidField(allow_int_lookup=True)



enable_hashid_object

~~~~~~~~~~~~~~~~~~~~



Local field override for whether or not to return Hashid objects or plain strings.

Can be safely changed without affecting any existing hashids.

See HASHID_FIELD_ENABLE_HASHID_OBJECT above.



:Type:    boolean

:Default: settings.HASHID_FIELD_ENABLE_HASHID_OBJECT, True

:Example:

    .. code-block:: python



        reference_id = HashidField(enable_hashid_object=False)



enable_descriptor

~~~~~~~~~~~~~~~~~



Local field override for whether or not to use the Descriptor on instances of the field.

Can be safely changed without affecting any existing hashids.

See HASHID_FIELD_ENABLE_DESCRIPTOR above.



:Type:    boolean

:Default: settings.HASHID_FIELD_ENABLE_DESCRIPTOR, True

:Example:

    .. code-block:: python



        reference_id = HashidField(enable_descriptor=False)



Hashid Class

------------



Operations with a HashidField or HashidAutoField return a ``Hashid`` object (unless disabled).

This simple class does the heavy lifting of converting integers and hashid strings back and forth.

There shouldn't be any need to instantiate these manually.



Methods

~~~~~~~



\__init__(value, salt="", min_length=0, alphabet=Hashids.ALPHABET, prefix="", hashids=None):

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^



:value: **REQUIRED** Integer you wish to *encode* or hashid you wish to *decode*

:salt: Salt to use. **Default**: "" (empty string)

:min_length: Minimum length of encoded hashid string. **Default**: 0

:alphabet: The characters to use in the encoded hashid string. **Default**: Hashids.ALPHABET

:prefix: String prefix prepended to hashid strings. **Default**: "" (empty string)

:hashids: Instance of hashids.Hashids to use for encoding/decoding instead of instantiating another.



Read-Only Properties

~~~~~~~~~~~~~~~~~~~~



id

^^



:type: Int

:value: The *decoded* integer



hashid

^^^^^^



:type: String

:value: The *encoded* hashid string



hashids

^^^^^^^



:type: Hashids()

:value: The instance of the Hashids class that is used to *encode* and *decode*



prefix

^^^^^^



:type: String

:value: The prefix prepended to hashid strings



Django REST Framework Integration

=================================



If you wish to use a HashidField or HashidAutoField with a DRF ModelSerializer, there is one extra step that you must

take. Automatic declaration of any Hashid*Fields will result in an ImproperlyConfigured exception being thrown. You

must explicitly declare them in your Serializer, as there is no way for the generated field to know how to work with

a Hashid*Field, specifically what 'salt', 'min_length' and 'alphabet' to use, and can lead to very difficult errors or

behavior to debug, or in the worst case, corruption of your data. Here is an example:



.. code-block:: python



    from rest_framework import serializers

    from hashid_field.rest import HashidSerializerCharField



    class BookSerializer(serializers.ModelSerializer):

        reference_id = HashidSerializerCharField(source_field='library.Book.reference_id')



        class Meta:

            model = Book

            fields = ('id', 'reference_id')



    class AuthorSerializer(serializers.ModelSerializer):

        id = HashidSerializerCharField(source_field='library.Author.id', read_only=True)



        class Meta:

            model = Author

            fields = ('id', 'name')



The ``source_field`` allows the HashidSerializerCharField to copy the 'salt', 'min_length' and 'alphabet' settings from

the given field at ``app_name.model_name.field_name`` so that it can be defined in just one place. Explicit settings are

also possible:



.. code-block:: python



    reference_id = HashidSerializerCharField(salt="a different salt", min_length=10, alphabet="ABCDEFGHIJKLMNOPQRSTUVWXYZ")



If nothing is given, then the field will use the same global settings as a Hashid*Field. It is very important that the

options for the serializer field matches the model field, or else strange errors or data corruption can occur.



HashidSerializerCharField will serialize the value into a Hashids string, but will deserialize either a Hashids string or

integer and save it into the underlying Hashid*Field properly. There is also a HashidSerializerIntegerField that will

serialize the Hashids into an un-encoded integer as well.



Primary Key Related Fields

--------------------------



Any models that have a ForeignKey to another model that uses a Hashid*Field as its Primary Key will need to explicitly

define how the

`PrimaryKeyRelatedField `_

should serialize and deserialize the resulting value using the ``pk_field`` argument. If you don't you will get an error

such as "Hashid(60): N8VNa8z is not JSON serializable". We have to tell DRF how to serialize/deserialize Hashid*Fields.



For the given ``Author`` model defined

above that has an ``id = HashidAutoField(primary_key=True)`` set, your BookSerializer should look like the following.



.. code-block:: python



    from rest_framework import serializers

    from hashid_field.rest import HashidSerializerCharField



    class BookSerializer(serializers.ModelSerializer):

        author = serializers.PrimaryKeyRelatedField(

            pk_field=HashidSerializerCharField(source_field='library.Author.id'),

            read_only=True)



        class Meta:

            model = Book

            fields = ('id', 'author')



Make sure you pass the source field to the HashidSerializer*Field so that it can copy the 'salt', 'min_length' and 'alphabet'

as described above.



This example sets ``read_only=True`` but you can explicitly define a ``queryset`` or override ``get_queryset(self)`` to allow

read-write behavior.



.. code-block:: python



    author = serializers.PrimaryKeyRelatedField(

        pk_field=HashidSerializerCharField(source_field='library.Author.id'),

        queryset=Author.objects.all())



For a ManyToManyField, you must also remember to pass ``many=True`` to the ``PrimaryKeyRelatedField``.



HashidSerializerCharField

-------------------------



Serialize a Hashid\*Field to a Hashids string, de-serialize either a valid Hashids string or integer into a

Hashid\*Field (if allow_int_lookup is enabled.)



Parameters

~~~~~~~~~~



source_field

^^^^^^^^^^^^



A 3-field dotted notation of the source field to load matching 'salt', 'min_length' and 'alphabet' settings from. Must

be in the format of "app_name.model_name.field_name". Example: "library.Book.reference_id".



salt, min_length, alphabet, prefix, allow_int_lookup

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^



See `Field Parameters`_



HashidSerializerIntegerField

----------------------------



Serialize a Hashid\*Field to an integer, de-serialize either a valid Hashids string or integer into a

Hashid\*Field. See `HashidSerializerCharField`_ for parameters.



*Please Note*: This field will always serialize to an integer and thus will also de-serialize integers into valid

objects, regardless of the `allow_int_lookup` setting.



Known Issues

============



'Hashid' object is not iterable

-------------------------------



With Django 5.0, attempting to filter on a field that is a ForeignKey to another model that uses a Hashid*Field as its

primary key will result in an error such as "'Hashid' object is not iterable". The workaround is to specify the exact

field of the related model to filter on. e.g. instead of `list_filter = ['author']` use `list_filter = ['author__name']`.



Admin can't find objects with a prefix that ends in an underscore

-----------------------------------------------------------------



The Django admin has a `quote` and `unquote` function that attempts to encode non-alphanumeric characters in primary

keys using the format of `_xx` where `xx` is the hex value of the character. This can be a problem if you are using

a prefix that ends in an underscore, as there's a chance that your Hashid primary key will be something like,

"user_3Ej8Kjm". The Django admin will attempt to `unquote` that to "user>j8Kjm" by swapping the "_3E" with a ">"

character, but that isn't valid and so it can't find the object. It will throw an error like, "Admin Object with id

'prefix<2345678' doesn't exist. Perhaps it was deleted?"



The workaround is to not use a prefix that ends in an underscore. You can end it with a character right after the

underscore that can't be used in hexidecimal, though, so it still looks right. e.g. `prefix="user_g"` so that the above

example would actually be "user_g3Ej8Kjm", and "_3E" can't be matched. Or you can use any other character, such as

a hyphen, .e.g `prefix="user-"`.



Development

===========



Here are some rough instructions on how to set up a dev environment to develop this module. Modify as needed. The

sandbox is a django project that uses django-hashid-id, and is useful for developing features with.



- ``git clone https://github.com/nshafer/django-hashid-field.git && cd django-hashid-field``

- ``mkvirtualenv -a . -p /usr/bin/python3 -r sandbox/requirements.txt django-hashid-field``

- ``python setup.py develop``

- ``sandbox/manage.py migrate``

- ``sandbox/manage.py createsuperuser``

- ``sandbox/manage.py loaddata authors books editors``

- ``sandbox/manage.py runserver``

- ``python runtests.py``



For any pull requests, clone the repo and push to it, then create the PR.



To install the latest development version, use:



```

pip install git+https://github.com/nshafer/django-hashid-field.git

```



LICENSE

=======



MIT License. You may use this in commercial and non-commercial projects with proper attribution.

Please see the `LICENSE `_