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Using scopes for elegant JAMStack permissions

About a month ago I wrote about Adding granular role-based access to your JAMStack app. That worked okay.

Use something like useAuth to authenticate users, add some roles, then check those roles in your app. Often at the main <Layout> level.

You get an app that sometimes asks for additional permissions.

But this approach had 2 warts:

  1. Lots of people mentioned that scopes in practice scale better than roles
  2. You needed this gnarly code somewhere in your app

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Click through for source

fillion giphy

Scopes bring more elegance

Wanted to use this approach for my React for Dataviz course, which has 3 tiers on top of free stuff, and my head began to spin. No way this was gonna work. ๐Ÿ˜…

I set out to find a better way:

Click through for source
Click through for source

And I found one! Scopes.

A scope is no different than a role โ€“ a string attached to the user. The semantics of scopes are different though.

Instead of answering "Who is this user?" a scope answers "What can this user do?". Small difference, big impact.

And when you move permission checking to the router-level, the result is quite elegant. I think.

Haven't tried it with NextJS, with Gatsby you'd do something like this ๐Ÿ‘‡

1. wrap the root of your tree

Permission-checking happens as high up in your component tree as possible. For Gatsby that's the wrapPageElement method. I use the same method for gatsby-ssr and gatsby-browser.

Click through for source
Click through for source

Wrap everything in useAuth's <AuthProvider> then render the <MyRouter> component making sure to pass the element and all props.

2. a simple router

Next you need a router to map paths to components. Gatsby comes with reach/router built-in so that seems like a good choice.

Unfortunately I couldn't get it to work reliably. Kept matching incorrect routes. The integration isn't as tight as I hoped.

Click through for source
Click through for source

Click through for source
Click through for source

But that's okay. Turns out building your own basic router isn't so hard.

Here's mine:

Click through for source
Click through for source

We use a SCOPE_PAGE_MAP that maps glob'd locations to their scopes. Use the minimatch library to find a matching path.

If path is found, render <ScopedRoute>, otherwise render <Default>.

The SCOPE_PAGE_MAP is a long list like this:

Click through for source
Click through for source

This part is tedious. Thinking of ways to move this info into MDX frontmatter that you can query with GraphQL.

Perhaps an idea for a Gatsby plugin ๐Ÿค”

3. Default route

Now that you're mapping routes to components, you need those components :)

The <Default> component/route can be simple:

Click through for source
Click through for source

Tells the layout that you're not authenticated, not authorized, and in my case to render the page fullwidth without the sidebar.

The <Layout> could check for this stuff with useAuth but it's cleaner to just tell it. "Hey, show extra buttons for authorized users"

4. scoped route

<ScopedRoute> is the bread and butter of this approach. And unlike my previous attempt, it's not gnarly at all โœŒ๏ธ

Click through for source
Click through for source

Hook into user state with useAuth and render different pages when they're authenticated, authorized, or unknown.

Flags in <Layout> change some UI features and the child element being {element} โ€“ the MDX content โ€“ or purchase/login specifies the core of the page.

And that's how you get elegant scope-based permissions in your JAMStack app โœŒ๏ธ

Happy Monday

Cheers, ~Swizec

PS: scopes get into your users the same way roles do. You add them through the Auth0 API or UI and use a bit of Auth0 JavaScript to inject it into user properties on every request.

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Published on June 15th, 2020 in Front End, Technical

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