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James Harton
bc1e590bca
* docs: Update README to new format. * docs: tidy up docus some more. * docs: More documentation tweaks. * docs: Tweak readme.
139 lines
4.7 KiB
Markdown
139 lines
4.7 KiB
Markdown
# GitHub Tutorial
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This is a quick tutorial on how to configure your application to use GitHub for authentication.
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First you need to configure an application in your [GitHub developer settings](https://github.com/settings/developers):
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1. Click the "New OAuth App" button.
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2. Set your application name to something that identifies it. You will likely
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need separate applications for development and production environments, so
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keep that in mind.
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3. Set "Homepage URL" appropriately for your application and environment.
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4. In the "Authorization callback URL" section, add your callback URL. The
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callback URL is generated from the following information:
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- The base URL of the application - in development that would be
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`http://localhost:4000/` but in production will be your application's
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URL.
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- The mount point of the auth routes in your router - we'll assume
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`/auth`.
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- The "subject name" of the resource being authenticated - we'll assume `user`.
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- The name of the strategy in your configuration. By default this is
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`github`.
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This means that the callback URL should look something like
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`http://localhost:4000/auth/user/github/callback`.
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5. Do not set "Enable Device Flow" unless you know why you want this.
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6. Click "Register application".
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7. Click "Generate a new client secret".
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8. Copy the "Client ID" and "Client secret" somewhere safe, we'll need them
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soon.
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9. Click "Update application".
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Next we can configure our resource (assuming you already have everything else
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set up):
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```elixir
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defmodule MyApp.Accounts.User do
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use Ash.Resource,
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extensions: [AshAuthentication],
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domain: MyApp.Accounts
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authentication do
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strategies do
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github do
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client_id MyApp.Secrets
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redirect_uri MyApp.Secrets
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client_secret MyApp.Secrets
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end
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end
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end
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end
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```
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Because all the configuration values should be kept secret (ie the
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`client_secret`) or are likely to be different for each environment we use the
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`AshAuthentication.Secret` behaviour to provide them. In this case we're
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delegating to the OTP application environment, however you may want to use a
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system environment variable or some other secret store (eg Vault).
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```elixir
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defmodule MyApp.Secrets do
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use AshAuthentication.Secret
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def secret_for([:authentication, :strategies, :github, :client_id], MyApp.Accounts.User, _) do
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get_config(:client_id)
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end
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def secret_for([:authentication, :strategies, :github, :redirect_uri], MyApp.Accounts.User, _) do
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get_config(:redirect_uri)
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end
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def secret_for([:authentication, :strategies, :github, :client_secret], MyApp.Accounts.User, _) do
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get_config(:client_secret)
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end
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defp get_config(key) do
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:my_app
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|> Application.get_env(:github, [])
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|> Keyword.fetch(key)
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end
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end
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```
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The values for this configuration should be:
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- `client_id` - the client ID copied from the GitHub settings page.
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- `redirect_uri` - the URL to the generated auth routes in your application
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(eg `http://localhost:4000/auth`).
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- `client_secret` the client secret copied from the GitHub settings page.
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Lastly, we need to add a register action to your user resource. This is defined
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as an upsert so that it can register new users, or update information for
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returning users. The default name of the action is `register_with_` followed by
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the strategy name. In our case that is `register_with_github`.
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The register action takes two arguments, `user_info` and the `oauth_tokens`.
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- `user_info` contains the [`GET /user` response from
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GitHub](https://docs.github.com/en/rest/users/users?apiVersion=2022-11-28#get-the-authenticated-user)
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which you can use to populate your user attributes as needed.
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- `oauth_tokens` contains the [`POST /login/oauth/access_token` response from
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GitHub](https://docs.github.com/en/developers/apps/building-oauth-apps/authorizing-oauth-apps#response)
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- you may want to store these if you intend to call the GitHub API on behalf
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of the user.
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```elixir
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defmodule MyApp.Accounts.User do
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use Ash.Resource,
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extensions: [AshAuthentication],
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domain: MyApp.Accounts
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# ...
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actions do
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create :register_with_github do
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argument :user_info, :map, allow_nil?: false
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argument :oauth_tokens, :map, allow_nil?: false
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upsert? true
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upsert_identity :email
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# Required if you have token generation enabled.
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change AshAuthentication.GenerateTokenChange
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# Required if you have the `identity_resource` configuration enabled.
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change AshAuthentication.Strategy.OAuth2.IdentityChange
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change fn changeset, _ ->
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user_info = Ash.Changeset.get_argument(changeset, :user_info)
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Ash.Changeset.change_attributes(changeset, Map.take(user_info, ["email"]))
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end
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end
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end
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# ...
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end
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```
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