How can I encrypt a field of an embedded schema using Cloak?

Phoenix Forum Questions / Help
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1

Hi there,

How can I encrypt a specific field of an embedded schema in Ecto using Cloak.Ecto?

I have something like this:

defmodule MyApp.MySchema do 
  schema "my_schema" do
    embeds_many :my_embed, MyApp.MyEmbed
  end
end

defmodule MyApp.MyEmbed do 
  embedded_schema do 
    field :some_field 
    field :some_encrypted_field, MyApp.Encrypted.Binary
  end
end

However some_encrypted_field is in plain text.
I have setup Cloak correctly for other records/fields, but couldn’t get it to work with embedded schemas.

2

Looks to me that it’s not possible as the underlying map would need to be stored in the db as JSON but cannot be encoded as JSON:

iex(5)> map
%{
  "field" => <<1, 10, 65, 69, 83, 46, 71, 67, 77, 46, 86, 49, 77, 106, 7, 215,
    34, 88, 207, 175, 58, 88, 70, 232, 78, 230, 137, 18, 84, 54, 118, 166, 72,
    41, 72, 159, 20, 41, 218, 93, 76, 160, 88, 148, 123>>
}
iex(6)> Jason.encode!(map)
** (Jason.EncodeError) invalid byte 0xD7 in <<1, 10, 65, 69, 83, 46, 71, 67, 77, 46, 86, 49, 77, 106, 7, 215, 34, 88, 207, 175, 58, 88, 70, 232, 78, 230, 137, 18, 84, 54, 118, 166, 72, 41, 72, 159, 20, 41, 218, 93, 76, 160, 88, 148, 123>>
    (jason 1.4.4) lib/jason.ex:164: Jason.encode!/2
    iex:6: (file)
3

It can’t be encoded as the jsonb Postgres type. The json type should work though.