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Quick start#

In this page a high-level overview of the flow development process is presented. Readers will be able to take a peep at the overall experience through a simple "hello world" example.

The basics#

These are key concepts to keep in mind before starting.

Enable the engine#

Ensure the Agama engine is enabled in your installation. Do the following:

  • Enable Agama bridge script. You can find details on how to manage custom scripts in this page. Here, set property enabled to true and increase revision value by one
  • Set enabled property in Agama configuration to true. This is located in the agamaConfiguration section of the auth server configuration

Flow data#

Every flow has some associated information. At minimum this is required:

  • Qualified name: The flow identifer. This is normally expressed using an Internet domain reverse notation, e.g. co.acme.SmsOTP
  • Source code: The flow implementation using Agama DSL

Optional details include:

  • Enabled status: Determines if the flow can be launched directly from a web browser
  • Display name: A short descriptive name of the flow intended for humans, e.g. "passwordless authentication"
  • Description
  • Flow author
  • Properties: A JSON document often used to supply configuration parameters

More on how to supply this data later.

Assets#

These are elements used to build the user interface such as templates, images, stylesheets, and javascript code.

Templates are written using FreeMarker Template Language (FTL). This is a simple and highly productive language to produce HTML and other forms of output. By convention templates generating HTML markup in Agama have the extension ftlh.

In Agama, templates must reside in the filesystem under /opt/jans/jetty/jans-auth/agama/ftl directory.

All the other assets (CSS, JS, etc.) are expected to be under /opt/jans/jetty/jans-auth/agama/fl.

Java classes#

Agama DSL supports calling Java code - it is designed to force developers use Java when tasks cannot be implemented by simple data manipulation or comparison of values. Any public class or interface in the classpath of jans-auth webapp can be used for this purpose. Additionally the classpath can be augmented by uploaded source files on the fly. Click here to learn more.

Client application#

This is the target application that end-users will get access to after a successful authentication. In OpenId Connect terms, a "Relying Party" or RP. It is advisable to have this application ready before proceeding to the next section of this document.

Depending on the tools and acquaintance with OpenId Connect protocol, this may take some time for developers. Note it may also require to apply configurations in the (Janssen) server for this purpose.

A low resistance path we recommend is trying the stripped down Javascript client example by Nat Sakimura. Here, the discovery URL is your server's URL.

Another alternative is trying mod_auth_openidc, an Apache 2 server module that implements RP functionality.

Hello world sample flow#

Your first taste of Agama will be through a dummy "hello world" flow. Here, the end-user will be presented a salutation page with a submit button which once pressed, will finish the process. For the sake of simplicity, the user to be authenticated will be a hardcoded one. This way we avoid gathering data at the browser and any other further processing in order to keep the example as short and simple as possible.

Note

While in most cases flows need to externally "receive" data and configuration parameters to properly drive their behavior, this is not the case here. The flow will only show a static salutation message and will terminate logging in a certain user, if existing.

Flow code#

The source code (written in agama DSL dialect) is shown below. Note the absence of parenthesis and semicolons - in general the syntax is very lightweight.

hello world flow

A line-by-line description follows:

  • Line 2: every flow starts with the Flow keyword followed by a qualified name (think of it as the flow identifier)

  • Line 3: Basepath specifies the directory where the assets of this flow reside. Note this is part of an indented block. There are more directives that may go here but they are beyond scope right now. Basepath is always mandatory.

  • Line 4: empty. There can be any number of empty lines in a source file

  • Line 5: an assignment to a variable. Agama is dynamically typed and variables are not declared. Here in is a map (a collection of key/value pairs). Note its resemblance to JSON. in has no special meaning, we could have used x, Soup, or whatever_123.

  • Line 6: RRF is used to send a response to the user's browser: it takes the path to a template (hello/index.ftlh) and injects a value into it (in in this case). The produced (Rendered) markup is sent (Replied) to the browser. Finally, the result of the interaction of the user with the page can be retrieved (Fetched), however, this is skipped here because we are no capturing anything at the client side.

  • The contents of index.ftlh should be familiar to web developers. The ${...} notation is used to dynamically insert values in the markup: the text John in this case. Expressions like this are integral part of Freemarker. Once form submission occurs, flow execution continues at line 8.

  • Line 8: a logging statement. This appends the text Done! to the flow's log. The Log instruction is pretty versatile; it is used in its simplest form here.

  • Line 9: marks the flow ending. Finish has several forms but here a shorthand notation is used where we always report a positive success and supply the identifier of a user. If it turns out your local user database contains a user identified by john_doe, this will be the subject that will get authenticated by the server, otherwise an error page will be shown.

This flow is extremely static and unrealistic but showcases minimal key elements for flow building. Please do not try this flow in any of your production servers.

Getting an access token#

In order to add/modify flows, you will interact with a small REST API which is protected by bearer token. To be able to get tokens, SSH to your server and perform the following steps:

  • Run python3 /opt/jans/jans-cli/config-cli.py
  • In the menu enter to OAuth > OIDC clients > Get list of clients
  • Accept the default parameters, for pattern enter config
  • Follow the instructions (in a web browser) to get authorized access
  • A list of results will be shown, pick the value in the inum column for the client with display name Jans Config Api Client
  • Choose back, and enter to Get client by inum
  • Enter the collected inum and grab the value of clientSecret in the resulting JSON document
  • Finally, choose logout and quit

The collected secret is encoded, run python3 /opt/jans/bin/encode.py -D <clientSecret> to decode it.

The following is an example of how to get a token using curl. Replace data in the placeholders appropriately:

curl -u '<client-inum:client-secret-decoded>'
     -d scope='https://jans.io/oauth/config/agama.write'
     -d grant_type=client_credentials https://<your-host>/jans-auth/restv1/token

You can extract the token from the (JSON) response obtained which is a self-explanatory. Add the -k switch if your server uses a self-signed certificate.

Tokens are required to have the right scopes depending on the operation to invoke, the following table summarizes this aspect:

scope permission allowed
https://jans.io/oauth/config/agama.readonly Retrieve flow data
https://jans.io/oauth/config/agama.write Create or modify a flow
https://jans.io/oauth/config/agama.delete Remove a flow

You can find here the open API definition of the REST API - locate the endpoints starting with /jans-config-api/api/v1/agama.

Notes:

  • Tokens have expiration time measured in seconds. When expired, you'll have to re-request
  • To get a token with more than one scope, supply the required scopes separated by whitespace in the scope parameter of the request above
  • You don't have to necessarily use the jans-config-api client to get your tokens. Any client, including one registered yourself can be used here as long as it can provide the needed scopes

Add the flow to the server#

The easiest way to create a flow is issuing a POST passing the source code in the payload. For our example, if the flow's source code resides in a file named flow.txt, the request would look this way:

curl -k -i -H 'Authorization: Bearer <token>' -H 'Content-Type: text/plain'
     --data-binary @flow.txt https://<your-host>/jans-config-api/api/v1/agama/test

(the -i switch is useful to check the HTTP headers sent with the response).

Notes:

  • test (the qualified named) was supplied as the last component of the URL to send the POST to
  • The expected status code of the response is 201 (i.e. created) unless there was some problem to process the request. Particularly, if 401 (unauthorized) was obtained, it means your token is no longer valid
  • A successful response contains a summary (in JSON format) of the flow created

If we had to modify the code of this flow, a similar operation could be used:

curl -k -i -H 'Authorization: Bearer <token>' -H 'Content-Type: text/plain'
     -X PUT --data-binary @flow.txt
     https://<your-host>/jans-config-api/api/v1/agama/source/test

/jans-config-api/api/v1/agama/source is a dedicated endpoint that replaces a flow's code whose name is supplied in the end of the URL.

If things went wrong and you want to start all over again, you can easily remove the flow like this (ensuring the token has the right scope):

curl -k -i -H 'Authorization: Bearer <token>' -X DELETE
     https://<your-host>/jans-config-api/api/v1/agama/test

The status code of a successful removal is 204 (empty).

To retrieve the flow's data, a request like the below can be used:

curl -k -i -H 'Authorization: Bearer <token>'
     https://<your-host>/jans-config-api/api/v1/agama/test

Note the source code is not part of the response by default. Append ?includeSource=true to the URL for the source to be included.

Important

There are different, more detailed ways to retrieve, create and update flows but they are regarded in the Development lifecycle doc page.

Finally the flow assets must be uploaded. You can SFTP/SCP or use other means to do so. In our example, only two steps are required:

  • Create a directory hello under /opt/jans/jetty/jans-auth/agama/ftl
  • Upload the template there

Craft an authentication request#

This section assumes your client application is ready, or at least you have made the configurations required so that you can trigger an (OpendId Connect) authentication request.

This usually boils down to create and launch a URL looking like https://<your-host>/jans-auth/restv1/authorize?acr_values=agama&customParam1=flow-qname&scope=...&response_type=...&redirect_uri=https...&client_id=...&state=.... You may like to check the spec for more details, however, keep in mind that:

  • To trigger an Agama flow, the acr_values parameter must be equal to agama

  • The qualified name (identifier) of the flow to trigger is passed using the parameter referenced in property cust_param_name of the Agama bridge script. customParam1 will work in most cases since this is the default value employed by the Jans installer. For the current example customParam1=test should be fine

Note

To use a different parameter name ensure to register the given parameter in the server configuration (property authorizationRequestCustomAllowedParameters) and update the bridge accordingly

  • If the flow to call receives input parameters, their values can be passed in the custom parameter as well. Use a hyphen to separate the flow name and the parameters expressed in JSON object format. For example, if the flow had inputs height and color, you can use test-{"height": 190, "color": "blue"} for the value of customParam1. Ensure to apply proper URL-encoding beforehand. In this case, the actual value would be test-%7B%22height%22%3A+190%2C+%22color%22%3A+%22blue%22%7D. If certain inputs are not provided, null values will be assigned for them

Testing#

Launch the authentication request in a web browser - preferably in a private window, a.k.a. incognito. You will be taken to a plain HTML page with a salutation and a "continue" button. After submission, a quick "Redirecting you" page will be shown and you will be taken probably to an error page showing "Unable to determine identity of user". That's expected.

Let's start by changing the salutation. Download the source code and template. In a text editor, modify line 5 of the source by changing the name surrounded by double quotes to a different word. Save the file and send the update as regarded in Add the flow to the server.

Wait for one minute. Generate an authentication request again and launch it. You will be able to see the changes. Feel free to edit index.ftlh and re-upload - templates changes are picked up immediately.

Now pick an existing username from your user base and alter the flow's code so that such user gets authenticated. Edit line 9 for this purpose, for example, Finish "admin".

If things went fine, after the form submission your browser should have been taken to the redirect_uri defined for the authentication request. Depending on how evolved your client application is, it may have created a session for such user and obtained profile data already!.

Logs often bring useful information while testing or troubleshooting. Check this page to learn how check the logs.

Next steps#

We have barely scratched the surface so far. There is lots more to learn in order to unveil the real power of Agama. The following topics may be of your interest:


Last update: 2022-09-27
Created: 2022-06-24