Store encrypted HTML

lib/wiki/content/page.ex

@@ -8,6 +8,9 @@ defmodule Wiki.Content.Page do
           encrypted_content_tag: binary(),
           content: String.t() | nil,
           content_encryption_key: String.t() | nil,
+          encrypted_html: binary(),
+          encrypted_html_iv: binary(),
+          encrypted_html_tag: binary(),
           html: String.t() | nil,
           title: String.t(),
           user: Wiki.Accounts.User.t(),
@@ -20,6 +23,9 @@ defmodule Wiki.Content.Page do
     field :encrypted_content_tag, :binary
     field :content, :string, virtual: true
     field :content_encryption_key, :string, virtual: true
+    field :encrypted_html, :binary
+    field :encrypted_html_iv, :binary
+    field :encrypted_html_tag, :binary
     field :html, :string, virtual: true
     field :title, :string
 
@@ -55,13 +61,21 @@ defmodule Wiki.Content.Page do
   defp encrypt_changeset(%Ecto.Changeset{changes: %{content: _}} = changeset) do
     content = get_change(changeset, :content)
     key = get_field(changeset, :content_encryption_key)
+
     {encrypted_content, tag, iv} = do_encrypt(content, key)
 
+    user_id = get_field(changeset, :user_id)
+    {html, _linked_pages} = Wiki.Content.Renderer.render(content, user_id)
+    {encrypted_html, html_tag, html_iv} = do_encrypt(html, key)
+
     changeset
     |> put_change(:encrypted_content, encrypted_content)
     |> put_change(:encrypted_content_tag, tag)
     |> put_change(:encrypted_content_iv, iv)
     |> delete_change(:content)
+    |> put_change(:encrypted_html, encrypted_html)
+    |> put_change(:encrypted_html_tag, html_tag)
+    |> put_change(:encrypted_html_iv, html_iv)
     |> delete_change(:content_encryption_key)
   end
 
@@ -74,29 +88,38 @@ defmodule Wiki.Content.Page do
     key = Base.decode16!(key, case: :lower)
     iv = :crypto.strong_rand_bytes(@iv_size)
 
-    {encrypted_text, tag} =
-      :crypto.crypto_one_time_aead(:aes_256_gcm, key, iv, text, <<>>, true)
-      |> IO.inspect()
+    {encrypted_text, tag} = :crypto.crypto_one_time_aead(:aes_256_gcm, key, iv, text, <<>>, true)
 
     {encrypted_text, tag, iv}
   end
 
   def decrypt_content(page) do
-    key = Base.decode16!(page.content_encryption_key, case: :lower)
-    iv = page.encrypted_content_iv
-    tag = page.encrypted_content_tag
+    key = page.content_encryption_key
 
     content =
+      do_decrypt(
+        page.encrypted_content,
+        page.encrypted_content_iv,
+        page.encrypted_content_tag,
+        key
+      )
+
+    html = do_decrypt(page.encrypted_html, page.encrypted_html_iv, page.encrypted_html_tag, key)
+
+    %__MODULE__{page | content: content, html: html}
+  end
+
+  defp do_decrypt(encrypted_text, iv, tag, key) do
+    key = Base.decode16!(key, case: :lower)
+
     :crypto.crypto_one_time_aead(
       :aes_256_gcm,
       key,
       iv,
-        page.encrypted_content,
+      encrypted_text,
       <<>>,
       tag,
       false
     )
-
-    %__MODULE__{page | content: content}
   end
 end

lib/wiki/content/renderer.ex

@@ -5,37 +5,61 @@ defmodule Wiki.Content.Renderer do
   alias WikiWeb.Endpoint
   import Ecto.Query
 
-  @spec render(Page.t()) :: String.t()
-  def render(page) do
-    page.content
-    |> replace_page_links(page)
-    |> render_markdown()
+  @spec render(String.t(), integer()) :: {String.t(), [integer()]}
+  def render(content, user_id) do
+    {content, linked_pages} = replace_page_links(content, user_id)
+
+    {
+      render_markdown(content),
+      Enum.uniq(linked_pages)
+    }
   end
 
   @page_link_regex ~r/\[\[.*?\]\]/
 
-  @spec replace_page_links(content :: String.t(), root_page :: Page.t()) :: String.t()
-  defp replace_page_links(content, root_page) do
-    String.replace(content, @page_link_regex, fn match ->
+  @spec replace_page_links(content :: String.t(), user_id :: integer()) ::
+          {String.t(), [integer()]}
+  defp replace_page_links(content, user_id) do
+    results = Regex.scan(@page_link_regex, content, return: :index)
+
+    results
+    |> Enum.reverse()
+    |> Enum.reduce({content, []}, fn [{start, length}], {str, acc} ->
+      # can't use String.slice here, because the indicies produced by Regex.scan are character indices, and slice operates on graphemes
+      match = :erlang.binary_part(str, start, length)
       title = String.slice(match, 2..-3)
       lower_title = String.downcase(title)
 
-      path =
+      str_before = :erlang.binary_part(str, 0, start)
+
+      str_after = :erlang.binary_part(str, start + length, byte_size(str) - start - length)
+
+      {path, acc} =
         from(p in Page)
-        |> where([p], p.user_id == ^root_page.user_id)
+        |> where([p], p.user_id == ^user_id)
         |> where([p], fragment("lower(?)", p.title) == ^lower_title)
         |> select([p], p.id)
         |> Repo.one()
         |> case do
           nil ->
-            Routes.page_path(Endpoint, :new, title: title)
+            {
+              Routes.page_path(Endpoint, :new, title: title),
+              acc
+            }
 
           linked_page_id ->
-            Routes.page_path(Endpoint, :show, linked_page_id)
+            {
+              Routes.page_path(Endpoint, :show, linked_page_id),
+              [linked_page_id | acc]
+            }
         end
 
-      # convert link to markdown, because [[title]] -> link transformation happens before markdown parsing
-      "[#{title}](#{path})"
+      page_link = "[#{title}](#{path})"
+
+      {
+        str_before <> page_link <> str_after,
+        acc
+      }
     end)
   end
 

lib/wiki_web/controllers/page_controller.ex

@@ -86,8 +86,7 @@ defmodule WikiWeb.PageController do
 
   def show(conn, _params) do
     page = Repo.preload(conn.assigns.page, :uploads)
-    rendered_content = Content.Renderer.render(page)
-    render(conn, "show.html", page: page, content: rendered_content)
+    render(conn, "show.html", page: page)
   end
 
   def edit(conn, _params) do

lib/wiki_web/templates/page/show.html.eex

@@ -3,7 +3,7 @@
 <span><%= link "Back", to: Routes.page_path(@conn, :index) %></span>
 
 <div>
-  <%= raw(@content) %>
+  <%= raw(@page.html) %>
 </div>
 
 <%= for upload <- @page.uploads do %>

priv/repo/migrations/20200726020001_create_pages.exs

@@ -7,12 +7,15 @@ defmodule Wiki.Repo.Migrations.CreatePages do
       add :encrypted_content, :binary
       add :encrypted_content_iv, :binary
       add :encrypted_content_tag, :binary
+      add :encrypted_html, :binary
+      add :encrypted_html_iv, :binary
+      add :encrypted_html_tag, :binary
       add :user_id, references(:users, on_delete: :delete_all)
 
       timestamps()
     end
 
     create index(:pages, [:user_id])
-    create index(:pages, ["(lower(title))"], name: :pages_lowercase_title_index)
+    create unique_index(:pages, ["(lower(title))"], name: :pages_lowercase_title_index)
   end
 end