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🌻 fields is a collection of useful field definitions (Custom Ecto Types) that helps you easily define an Ecto Schema with validation, encryption and hashing functions so that you can ship your Elixir/Phoenix App much faster!

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A **collection of frequently used `fields`**
implemented as custom **`Ecto` Types** 
with best-practice following
[validation](https://hexdocs.pm/fields/Fields.Validate.html),
[sanitising](https://hexdocs.pm/fields/Fields.HtmlBody.html),
transparent
[encryption](https://hexdocs.pm/fields/Fields.AES.html) /
[decryption](https://hexdocs.pm/fields/Fields.AES.html#decrypt/1)
&
[hashing](https://hexdocs.pm/fields/Fields.Password.html) 
functions to **build privacy compliant & security-focussed
`Phoenix` apps _much_ faster!** 🚀

![GitHub Workflow Status](https://img.shields.io/github/actions/workflow/status/dwyl/fields/ci.yml?label=build&style=flat-square&branch=main)
[![codecov.io](https://img.shields.io/codecov/c/github/dwyl/fields/master.svg?style=flat-square)](https://codecov.io/github/dwyl/fields?branch=master)
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</div>

# _Why_? 🤷‍♀️

We found ourselves repeating code
for commonly used fields on each new **`Phoenix`** project/App ... 
We wanted a **_much_ easier/faster** way of building apps
so we created a collection of pre-defined fields
with built-in validation, sanitising and security.
**`Fields`** makes defining `Ecto` Schemas faster
and more precise.

# _What_? 💭

An `Elixir` package that helps you add popular custom types
to your `Phoenix` / `Ecto` schemas so you can **build apps _faster_**!
All data is **automatically validated**
and
**securely encrypted** (or hashed)
before being **safely stored**.
e.g:

> The **data is illegible** to anyone
> who doesn't have the encryption keys. 
> So in the event of **database breach/compromise**
> the **data is still safe**.

> **@dwyl** we are firm believers that **personal data**
> (_Personally Identifiable Information_ (PII)) **should be encrypted**
> [at rest](https://en.wikipedia.org/wiki/Digital_data#Data_at_rest)
> i.e. all "user" data should be encrypted
> _before_ being stored in the database.
> This project makes hashing, encryption
> and _decryption_ for secure data storage
> **_much_ easier** for everyone.

> This package was born out of our research
> into the best/easiest way 
> to encrypt data in a **`Phoenix`** app:
> [dwyl/phoenix-ecto-encryption-example](https://github.com/dwyl/phoenix-ecto-encryption-example)

# _Who_? 👥

This module is for people building `Elixir` / `Phoenix` apps
who want to ship _simpler_ and more **maintainable code**.

> We've attempted to make **`Fields`**
> as **beginner-friendly** as possible. 
> If you get stuck using it or anything is unclear, please ask for
> [help!](https://github.com/dwyl/fields/issues)

# _How_? ✅

Start using **`Fields`** in your Phoenix App today
with these **3 easy steps**:

## 1. Add the `fields` hex package to `deps` in `mix.exs` 📦

Add the `fields` package to your list of dependencies in your `mix.exs` file:

```elixir
def deps do
  [
    {:fields, "~> 2.12"}
  ]
end
```

Once you have saved the `mix.exs` file,
run **`mix deps.get`** in your terminal
to download the package.

## 2. Ensure you have the necessary environment variables 🔑

In order to use **Encryption** and **Hashing**,
you will need to have environment variables
defined for `ENCRYPTION_KEYS` and `SECRET_KEY_BASE` respectively.

```yaml
export ENCRYPTION_KEYS=nMdayQpR0aoasLaq1g94FLba+A+wB44JLko47sVQXMg=
export SECRET_KEY_BASE=GLH2S6EU0eZt+GSEmb5wEtonWO847hsQ9fck0APr4VgXEdp9EKfni2WO61z0DMOF
```

If you need to create a secure `SECRET_KEY_BASE` value, 
please see:
[How to create Phoenix `secret_key_base`](https://github.com/dwyl/phoenix-ecto-encryption-example#generate-the-secret_key_base) 
And for `ENCRYPTION_KEYS`, see:
[How to create encryption keys](https://github.com/dwyl/phoenix-ecto-encryption-example#how-to-generate-aes-encryption-keys)

> In our case we use a **`.env`** file
> to manage our environment variables. 
> See:
> [github.com/dwyl/**learn-environment-variables**](https://git.io/JeMLg) 
> This allows us to **securely manage** our **secret keys** in dev
> without the risk of accidentally publishing them on Github. 
> When we _deploy_ our Apps, we use our service provider's
> built-in key management service to securely store Environment Variables.
> e.g:
> [Environment Variables on Heroku](https://github.com/dwyl/learn-environment-variables#environment-variables-on-heroku)

## 3. Apply the relevant field(s) to your schema 📝

Each field can be used in place of an Ecto type when defining your schema.

An example for defining a "user" schema using **Fields**:

```elixir
schema "users" do
  field :first_name, Fields.Name            # Length validated and encrypted
  field :email, Fields.EmailEncrypted       # Validates email then encrypts
  field :address, Fields.AddressEncrypted   # Trims address string then encrypts
  field :postcode, Fields.PostcodeEncrypted # Validates postcode then encrypts
  field :password, Fields.Password          # Hash password with argon2 industry standard

timestamps()
end
```

Each field is defined as an
[Ecto type](https://hexdocs.pm/ecto/Ecto.Type.html),
with the relevant callbacks.
So when you call `Ecto.Changeset.cast/4`
in your schema's changeset function,
the field will be correctly validated.
For example, calling cast on the `:email` field
will ensure it is a valid format for an email address
[RFC 5322](https://en.wikipedia.org/wiki/Email_address).

When you load one of the fields into your database,
the corresponding `dump/1` callback will be called,
ensuring it is inserted into the database in the correct format.
In the case of `Fields.EmailEncrypted`,
it will encrypt the email address
using a given encryption key
before inserting it.

Likewise, when you load a field from the database,
the `load/1` callback will be called,
giving you the data in the format you need.
`Fields.EmailEncrypted` will be decrypted back to plaintext.
This all happens 100% transparently to the developer.
It's _like_ magic. But the kind where you can
actually _understand_ how it works!
(_if you're curious, read the
[**`code`**](https://github.com/dwyl/fields/tree/master/lib)_)

Each Field optionally defines an `input_type/0` function.
This will return an atom
representing the `Phoenix.HTML.Form` input type to use for the Field.
For example: `Fields.DescriptionPlaintextUnlimited.input_type`
returns `:textarea` which helps us render the correct field in a form.

The fields `DescriptionPlaintextUnlimited`
and `HtmlBody` uses
[`html_sanitize_ex`](https://github.com/rrrene/html_sanitize_ex)
to remove scripts and help keep your project safe.
`HtmlBody` is able to display basic html elements
whilst `DescriptionPlaintextUnlimited` displays text.
Remember to use `raw` when rendering
the content of your `DescriptionPlaintextUnlimited`
and `HtmlBody` fields
so that symbols such as & (ampersand) and Html are rendered correctly.
e.g:
`<%= raw @product.description %>`

## Available `Fields` 📖

- [`Address`](lib/address.ex) - an address for a physical location.
  Validated and stored as a (`plaintext`) `String`.
- [`AddressEncrypted`](lib/address_encrypted.ex) - an address for a customer
  or user which should be stored encrypted for data protection.
- [`DescriptionPlaintextUnlimited`](lib/description_plaintext_unlimited.ex) -
  filters any HTML/JS to avoid security issues. Perfect for blog post comments.
- [`Encrypted`](lib/encrypted.ex) - a general purpose encrypted field.
  converts any type of data `to_string` and then encrypts it.
- [`EmailEncrypted`](lib/email_encrypted.ex) - validate and strongly encrypt
  email address to ensure they are kept private and secure.
- [`EmailHash`](lib/email_hash.ex) - when an email needs to be looked up fast
  without decrypting. Salted and hashed with `:sha256`.
- [`EmailPlaintext`](lib/email_plaintext.ex) - when an email address is `public`
  there's no advantage to encrypting it. e.g. a customer support email.
- [`Hash`](lib/hash.ex) - a general-purpose hash field using `:sha256`,
  useful if you need to store the hash of a value. (_one way_)
- [`HtmlBody`](lib/html-body.ex) - useful for storing HTML data e.g in a CMS.
- [`Name`](lib/html-body.ex) - used for personal names
  that need to be kept private/secure. Max length 35 characters. AES Encrypted.
- [`Password`](lib/password.ex) - passwords hashed using `argon2`.
- [`PhoneNumberEncrypted`](lib/phone_number_encrypted.ex) - a phone number that should be kept private gets validated and encrypted.
- [`PhoneNumber`](lib/phone_number.ex) - when a phone number is _not_
  sensitive information and can be stored in plaintext.
- [`Postcode`](lib/postcode.ex) - validated postcode stored as `plaintext`.
- [`PostcodeEncrypted`](lib/postcode_encrypted.ex) - validated and encrypted.
- [`Url`](lib/url.ex) - validate a URL and store as `plaintext`
  (_not encrypted_) `String`
- [`UrlEncrypted`](lib/url_encrypted.ex) - validate a URL and store as AES _encrypted_ `Binary`
- [`IpAddressPlaintext`](lib/ip_address_plaintext.ex) - validate an ipv4 and ipv6 address and store as `plaintext`
- [`IpAddressHash`](lib/ip_address_hash.ex) - hash for ipv4 or ipv6
- [`IpAddressEncrypted`](lib/ip_address_encrypted.ex) - validate an ipv4 and ipv6 address and store as AES _encrypted_ `Binary`

**_Detailed documentation_** available on **HexDocs**:
[hexdocs.pm/**fields**](https://hexdocs.pm/fields)

## Testing ![GitHub Workflow Status](https://img.shields.io/github/actions/workflow/status/dwyl/fields/ci.yml?label=build&style=flat-square&branch=main)

```sh
mix t
```

### _Coverage_ [![codecov.io](https://img.shields.io/codecov/c/github/dwyl/fields/master.svg?style=flat-square)](https://codecov.io/github/dwyl/fields?branch=master)

```sh
mix c
```

## Contributing ➕

[Contributions](https://github.com/dwyl/fields/graphs/contributors?all=1)
are always welcome!
If there is a `field` that you need in your app
that is not already in the **`Fields`** package,
[please open an issue](https://github.com/dwyl/fields/issues)
so we can add it!

## Background / Further Reading 🔗

If you want an in-depth understanding of how automatic/transparent
encryption/decryption works using Ecto Types, see:
[github.com/dwyl/**phoenix-ecto-encryption-example**](https://github.com/dwyl/phoenix-ecto-encryption-example)

If you are rusty/new on Binaries in Elixir,
take a look at this post by @blackode: 
https://medium.com/blackode/playing-with-elixir-binaries-strings-dd01a40039d5

# Questions? 🤔

If you have questions, please open an issue:
[github.com/dwyl/fields/issues](https://github.com/dwyl/fields/issues)

A recent/good example is: [issues/169](https://github.com/dwyl/auth/issues/169)

### Why do we have _both_ `EmailEncrypted` and `EmailHash` ? ✌️

[`EmailEncrypted`](https://github.com/dwyl/fields/blob/main/lib/email_encrypted.ex)
and
[`EmailHash`](https://github.com/dwyl/fields/blob/main/lib/email_hash.ex)
serve very different purposes.
Briefly:
with
[**encryption**](https://en.wikipedia.org/wiki/Encryption)
the output is **_always_ different**
is meant for safely storing sensitive data
that we want to **_decrypt_** later
whereas with
[**hash**](https://en.wikipedia.org/wiki/Hash_function)
the output is **_always_ the same**
it cannot be "unhashed" but
can be used to
[**_check_**](https://en.wikipedia.org/wiki/Checksum) a value,
i.e. you can lookup a _hashed_ value in a database.

The best way to understand how these work
is to see it for yourself.
Start an
[`IEx`](https://hexdocs.pm/iex/1.1.1/IEx.html)
session in your terminal:

```sh
iex -S mix
```

You should see output similar to the following:

```sh
Erlang/OTP 24 [erts-12.0.3] [source] [64-bit] [smp:8:8] [ds:8:8:10] [async-threads:1] [jit] [dtrace]

Compiling 23 files (.ex)
Generated fields app
Interactive Elixir (1.12.3) - press Ctrl+C to exit (type h() ENTER for help)
```

That confirms the `fields` module has compiled.

#### Encryption 🙈

Now that you've initialized `IEx`,
issue the following commands:

```sh
iex> email = "alex@gmail.com"

"alex@gmail.com"

iex(2)> encrypted = Fields.AES.encrypt(email)

<<48, 48, 48, 49, 20, 6, 117, 239, 107, 251, 80, 156, 109, 46, 6, 75, 119, 89,
 72, 163, 156, 243, 60, 6, 17, 166, 130, 239, 93, 222, 65, 186, 185, 78, 77, 2,
 80, 194, 241, 31, 28, 24, 155, 172, 208, 185, 142, 64, 65, 127>>
```

> **Note**: the `Fields.EmailEncrypted`
> uses the `AES.encrypt/1` behind the scenes,
> that's why we are using it here directly.
> You could just as easily have written:
> `{:ok, encrypted} = Fields.EmailEncrypted.dump(email)`
> this is just a shorthand.

That output `<<48, 48, 48 ... 64, 65, 127>>` is a
[**bitstring**](https://elixir-lang.org/getting-started/binaries-strings-and-char-lists.html#bitstrings)
which is the sequence of bits in memory.
The encrypted data - usually called
["ciphertext"](https://en.wikipedia.org/wiki/Ciphertext) -
is not human readable, that's a feature.
But if you want to _decrypt_ it back to its human-readable form,
simply run:

```
iex(3)> decrypted = Fields.AES.decrypt(encrypted)

"alex@gmail.com"
```

So we know that an encrypted value can be decrypted.
In the case of `EmailEncrypted` this is useful
when we want to send someone an email message.
For security/privacy,
we want their sensitive personal data to be stored
_encrypted_ in the Database,
but when we need to decrypt it to send them a message,
it's easy enough.

If you run the `Fields.AES.encrypt/1` function
multiple times in your terminal,
you will _always_ see different output:

```elixir
iex(4)> Fields.AES.encrypt(email)
 <<48, 48, 48, 49, 168, 212, 210, 53, 233, 104, 27, 235, 199, 43, 87, 74, 3, 2,
 211, 114, 187, 229, 157, 182, 37, 34, 209, 37, 66, 160, 30, 126, 238, 180,
 146, 133, 227, 53, 245, 228, 119, 191, 117, 247, 37, 176, 130, 110, ...>>
iex(5)> Fields.AES.encrypt(email)
 <<48, 48, 48, 49, 196, 170, 48, 97, 75, 206, 148, 204, 41, 149, 64, 50, 27, 56,
 112, 19, 53, 108, 86, 153, 154, 53, 53, 97, 232, 133, 97, 88, 214, 254, 40,
 84, 65, 227, 75, 123, 212, 222, 63, 221, 176, 130, 11, 173, ...>>
iex(6)> Fields.AES.encrypt(email)
 <<48, 48, 48, 49, 201, 239, 104, 101, 140, 232, 0, 216, 183, 168, 220, 130, 24,
 236, 205, 220, 239, 112, 112, 168, 86, 235, 84, 115, 108, 116, 16, 234, 184,
 72, 111, 144, 245, 1, 125, 207, 230, 68, 126, 111, 84, 83, 23, 90, ...>>
iex(7)> Fields.AES.encrypt(email)
 <<48, 48, 48, 49, 176, 131, 145, 182, 128, 43, 11, 100, 253, 73, 179, 144, 139,
 45, 211, 156, 155, 117, 119, 59, 152, 148, 45, 36, 95, 141, 35, 242, 182, 51,
 235, 162, 186, 132, 23, 34, 174, 171, 157, 115, 54, 211, 124, 247, ...>>
```

The first 4 bytes `<<48, 48, 48, 49,` are the same
because we are using the same encryption key.
But the rest is _always_ different.

#### Hashing #️⃣

A `hash` function
can be used to map data of arbitrary size
to fixed-size values.
i.e. _any_ length of `plaintext` will
result in the _same_ length `hash` _value_.
A `hash` function is _one-way_,
it cannot be reversed or "un-hashed".
The `hash` _value_ is _always_ the same
for a given string of plaintext.

Try it in `IEx`:

```elixir
iex(1)> email = "alex@gmail.com"
"alex@gmail.com"

iex(2)> Fields.Helpers.hash(:sha256, email)
<<95, 251, 251, 204, 181, 59, 239, 4, 218, 193, 35, 20, 223, 131, 219, 101, 30,
 17, 97, 146, 103, 115, 3, 185, 230, 137, 218, 137, 209, 111, 48, 236>>
iex(3)> Fields.Helpers.hash(:sha256, email)
<<95, 251, 251, 204, 181, 59, 239, 4, 218, 193, 35, 20, 223, 131, 219, 101, 30,
 17, 97, 146, 103, 115, 3, 185, 230, 137, 218, 137, 209, 111, 48, 236>>
iex(4)> Fields.Helpers.hash(:sha256, email)
<<95, 251, 251, 204, 181, 59, 239, 4, 218, 193, 35, 20, 223, 131, 219, 101, 30,
 17, 97, 146, 103, 115, 3, 185, 230, 137, 218, 137, 209, 111, 48, 236>>
```

The hash _value_ is identical for the given input text
in this case the email address `"alex@gmail.com"`.

If you use the `Fields.EmailHash.dump/1` function,
you will see the same hash value
(_because the same helper function is invoked_):

```elixir
iex(5)> Fields.EmailHash.dump(email)
{:ok,
 <<95, 251, 251, 204, 181, 59, 239, 4, 218, 193, 35, 20, 223, 131, 219, 101, 30,
 17, 97, 146, 103, 115, 3, 185, 230, 137, 218, 137, 209, 111, 48, 236>>}
iex(6)> Fields.EmailHash.dump(email)
{:ok,
 <<95, 251, 251, 204, 181, 59, 239, 4, 218, 193, 35, 20, 223, 131, 219, 101, 30,
 17, 97, 146, 103, 115, 3, 185, 230, 137, 218, 137, 209, 111, 48, 236>>}
```

When the `EmailHash` is stored in a database
we can lookup an email address by hashing it
and comparing it to the list.

The best way of _visualizing_ this
is to convert the hash value (bitstring)
to `base64` so that it is _human-readable_:

```elixir
iex(1)> email = "alex@gmail.com"
"alex@gmail.com"

iex(2)> Fields.Helpers.hash(:sha256, email) |> :base64.encode
"X/v7zLU77wTawSMU34PbZR4RYZJncwO55onaidFvMOw="

iex(3)> Fields.Helpers.hash(:sha256, email) |> :base64.encode
"X/v7zLU77wTawSMU34PbZR4RYZJncwO55onaidFvMOw="
```

Imagine you have a database table called `people` that has just 3 columns: `id`, `email_hash` and `email_encrypted`

| `id` | `email_hash`                                 | `email_encrypted`                      |
| :--: | -------------------------------------------- | -------------------------------------- |
|  1   | X/v7zLU77wTawSMU34PbZR4RYZJncwO55onaidFvMOw= | MDAwMc57Y1j0nhwOdw7EvNeUVEfYQoAr7aT6oX |
|  2   | +zXMhia/Z2I64nul6pqoDZTVM1q2K21Pby6GtPcm9iE= | MDAwMXnS1uwGN/cZRFkQgArm2Sbj9y+hnUJIS7 |
|  3   | maY4IxoRSOSqm6qyJDrnEN1JQssJRqRGhzwOown4DPU= | MDAwMa4v0FBko++zqfAkfisXOLosQfrDLAdPax |

With this "database" table,
we can now _lookup_ an email address to find out their `id`:

```elixir
iex(4)> Fields.Helpers.hash(:sha256, "alice@gmail.com") |> :base64.encode
"+zXMhia/Z2I64nul6pqoDZTVM1q2K21Pby6GtPcm9iE="
```

This matches the `email_hash` in the second row of our table,
therefore **Alice's** `id` is `2` in the database.

### `AES` Encryption 🔐

[AES.encrypt/1](https://github.com/dwyl/fields/blob/519f2e9da9c6267e9b9b5359370b21a78390d020/lib/aes.ex#L30)
has an
[Initialization Vector](https://en.wikipedia.org/wiki/Initialization_vector) 
(**`IV`**)
which is a random set of bytes
prepended to the data each time it gets encrypted.
This increases the randomness of the **`ciphertext`**
and thus makes it more difficult to `decrypt`
in the event an attacker accesses the DB.

The `IV` is included in the `bitstring` returned by `AES.encrypt/1`
which could be split and stored separately in a high security system.
We are storing them together as we feel that having a **unique key**
stored in a Key Management System (KMS) is adequate for our needs.

<hr />

If you found this repository useful,
**please star** it
so we (and others) know you liked it. Thanks! ⭐️

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