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Does my application fit the Auth0 version of SPA?

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#1

What type is my client? I think it is an SPA, but the advice I’m seeing for SPA includes decoding the token there.

I’m writing a client with Angular. It gets all of its data from a server (RESTful API). With each API call the server will decode an authorization JWT, match the token with a user record, and have the user data define just what data the user is entitled to.

I want to install an Auth0 authorization onto the client, and think I’ve a SPA. However, the advice I’m seeing on the “Learn the Basics” lead me to think it wants me to decode the JWT on the client. That doesn’t sound right.

Is there other advice in the Auth0 tutorials that show using the Auth0 service for authorization and then having my server use a passed-in JWT?


#2

The main issue you’re facing and something that our documentation may also contribute to although we’ve been trying to make things more explicit is the overloaded use of JWT.

The reality is that when it comes to authentication and authorization the tokens/assertions passed from one entity to the other cannot be reduced to just the format used to represent them.

In the situation I believe you are, you have a client application (SPA) that performs the business logic by invoking a resource server (API) and wants to do so on behalf of an end-user. This is the textbook example for the use of OAuth 2.0 as the means for the client application to obtain an access token (forget about the format used for the representation of that access token) that it can then use to call the resource server. The resource server will validate the access token and through that validation process obtain the end-user that originally granted this access token.

In the above scenario there is absolutely no processing of the access token by the client application; it’s treated as an opaque token that gets received from the authorization server (in this case Auth0 service) and then sent to the resource server (your API).

Having said that, as part of the process to obtain the access token it’s highly likely that the end-user had to complete an authentication step so that the authorization server knows for whom to associate the access token. However, your client application can also express the desire to know about this end-user (this is where the OpenID Connect specification comes in) and in this case the identity provider/authorization server can issue not just an access token, but also an ID token that contains information about the completed authentication process. By specification the ID token will always be a JWT so here’s where both terms can start to get used interchangeably when they should not.

In summary:

  • an ID token is meant to be consumed/decoded and validated by the client application and it will always be represented using the JWT format.
  • an access token is delivered to a client application, but the client application must treat it as an opaque value. In addition, the format used to represent access tokens is an implementation detail between the authorization server and the resource server to which they are meant to.

Sidenote: When you configure your own resource server in the APIs section of the dashboard and then request an access token for that resource server then currently the format being used is also a JWT, but have in mind that other formats may be supported in the future.

Further relevant reading:


#3

It appears that my combination of client and server want to use the access token.

  • The user clicks on a link in my web page to call the Auth0 lock page.

  • The user satisfies the Auth0 lock page and given at least the access token and is also redirected back to my web page.

  • On future web page calls to my server the web page includes the access token in the request header.

I should then assume that I must use the Auth0 SPA model, and not the “Regular Web Application” model. Correct?

Jerome.


#4

It appears that my combination of client and server want to use the access token.

  • The user clicks on a link in my web page to call the Auth0 lock page.

  • The user satisfies the Auth0 lock page and given at least the access token and is also redirected back to my web page.

  • On future web page calls to my server the web page includes the access token in the request header.

I should then assume that I must use the Auth0 SPA model, and not the “Regular Web Application” model. Correct?

Jerome.


#5

Given you mention Angular you should follow the SPA model because with Angular the code performing the request to the API/resource server is located in the browser and hence the access token also needs to be available there.

The regular web application model would be for applications where the code that performs the calls to the API/resource server is located server-side. An example would be a PHP application calling an API (the PHP code that makes the request is run server-side).


#6