Tag Archives: OAuth2

Speaking at Scottish Summit 2021!

I’m very much looking forward to speaking this Saturday 27th of February at the Virtual Scottish Summit 2021! This amazing Community conference will host 365 (!) virtual sessions from experts all over the world, ranging from first-time speakers to experienced community leaders.

Sessions will be delivered in a range of tracks covering Microsoft technologies and community topics, something to choose from for everyone.

My session will be about why it so important to have Zero Trust Admins with least privilege access, and why you start using Azure AD PIM (Privileged Identity Management) today!

I learned about the stereotype of cheap Scots from reading about Scrooge McDuck, I’ve no idea if this is true or not, probably not ;), but the thing that is true is that you should be really cheap when handing out admin privileges.

Today Microsoft 365 Global Administrators or Azure Subscription Owners are the new Domain/Enterprise Admins, in many organizations too many users have these roles. In the session I will show how by implementing just-in-time and just-enough-access (JIT/JEA) policies, we can reduce vulnerability and attack surface, and the right tool for the job is using Azure AD Privileged Identity Management (PIM).

I have been using AAD PIM for years, and in this session I will share my best practices and how to implement and use the right way.

Session details:

There is still time to register, but time and available tickets are running out fast. Go an register your free ticket for an awesome day of free community contents here:

Scottish Summit 2021 | Scottish Summit

Have a great conference and hope you visit my session if the topic is of your interest!

Speaking at Nordic Virtual Summit 2021!

I’m excited to announce that I’m speaking at the inaugural Nordic Virtual Summit 2021, from 10th to 11th February. Nordic Virtual Summit is a Microsoft IT Pro Community Event, organized by the people behind #SGUCSE #SCUGDK #SCUGFI #MMUGNO and #MSEndpointMgr communities!

Sessions will be delivered in 3 tracks:

  • Endpoint Management
  • Security & Compliance
  • Azure & Automation

Each day will start with a pre-conference talk, and then the sessions kick off each hour mark, 3 sessions before lunch and 3 after. There will be 15 minutes break and Q/A between sessions, so you can catch your breath, fill up your coffee or just wait in excitement for the next session πŸ™‚

My session will be about while Azure Serverless Automation solutions like Azure Functions & Logic Apps can be great for your automation scenarios, how can you secure access to sending requests and protect your serverless automation using Azure AD authentication and authorization.

Session details:

I’m hearing the number of registered attendees is now closing in on 2000, so make sure you register and secure your FREE ticket today:

Register – Nordic Virtual Summit

Hope to see you there!

Speaking at Global Automation Bootcamp 2021

I’m happy to announce that I’m part of the amazing global initiative of automation bootcamps in starting from February 5th to 20th 2021!

Update: The Azure Automation track has now been pushed back one week from February 20th to February 27th.

I will speak about how Azure Serverless Automation solutions like Azure Functions, Logic Apps and more can be protected by Azure AD and how Power Platform can securely send requests to trigger your automation scenarios. Session details:

You can register for FREE here at this link: Global Automation Bootcamp 2021 – Power Community

The agenda is very exciting with top speakers, and sessions will be delivered according to the following tracks and days:

  • Automation Summit Day 1, Fri 5th February
  • Power Automate Saturday Bootcamp, Sat 6th February
  • Power Automate Bootcamp Day 2, Sun 7th February
  • RPA & UI Test Automation Bootcamp, Sat 13th February
  • Azure Automation Bootcamp, Sat 27th February
  • Powershell Saturday Bootcamp, Sat 20th February

You can sign up anytime, hope to see you at my session and catch any of the other great sessions πŸ™‚

Protect Logic Apps with Azure AD OAuth – Part 3 Connect to API from Power Platform

In this article I’m going to build on my previous blog posts in this series where I have written about how to add Azure AD OAuth authentication and authorization to your Logic Apps and expose them as an API. For reference the links to these blog post articles are here:

If you want to connect to API’s using Power Platform (Power Automate Flows, PowerApps etc.), you can do this in two different ways:

  • Using HTTP action and send requests that use Azure AD OAuth authentication. This will use the “Client Credentials” OAuth flow, and is suitable for calling the API using application permissions and roles.
  • Setting up a Custom Connector for the API, and using the HTTP logic app trigger as operation. This will use the “Authorization Code” OAuth flow, and is suitable for using delegated permissions and scopes for the logged on user via connections.

So it depends on how you want your Power Platform users to be able to send requests your Logic App API. Should they do this as themselves with their logged on user, or should they use an application identity? There are use cases for both, so I will show both in this article.

Connect to Logic App API using Custom Connector

Using Custom Connectors is a great way to use your own identity for sending requests to an API. This way you can also securely share Custom Connectors, and Flows/PowerApps, using them in your organization, without needing to share sensitive credentials like client id and client secrets.

If you want to create a Custom Connector in Power Platform that triggers an HTTP request to a Logic App, you can currently do this in one of the following ways:

  1. Creating Custom Connector using Azure services and Logic App.
  2. Exporting the Logic App to a Power Platform environment.
  3. Creating the Custom Connector using an OpenAPI swagger definition file/url.
  4. Creating the Custom Connector from blank.

Lets take a quick look at each of these, but first we need to take care of some permissions in Azure for creating the Custom Connector automatically.

Azure Permissions for Logic Apps and listing swagger

There are some minimum permissions your user needs to be able to create a Custom Connector automatically by browsing the Azure Service.

A good starting point is using one of the built in Azure roles for Logic Apps:

But even these do not have the permissions necessary, if you try you will get an error similar to the following:

So we need to att this ../listSwagger/action for the scope, and you could give the user full Contributor access, but that seems rather excessive. Lets create a custom role instead. I will do this using Azure PowerShell, for reference please see the docs: Create or update Azure custom roles using Azure PowerShell – Azure RBAC | Microsoft Docs.

After connecting to Azure using an Azure account that can create custom roles for the scope (Owner or User Access Administrator), start by exporting an existing role as a starting point:

# 1. Export a JSON template as a reference based on an exisiting role
Get-AzRoleDefinition -Name "Logic App Operator" | ConvertTo-Json | Out-File .\LogicAppAPIOperator.json

Then edit this JSON file, by removing the Id parameter, defining a Name, setting the IsCustom to true, and Description to something descriptive like below. I have also set my Azure subscription id under assignable scopes, and added the required ../listSwagger/action:

{
  "Name": "Logic App API Operator",
  "IsCustom": true,
  "Description": "Lets you read, enable and disable logic app, and list swagger actions for API.",
  "Actions": [
    "Microsoft.Authorization/*/read",
    "Microsoft.Insights/alertRules/*/read",
    "Microsoft.Insights/metricAlerts/*/read",
    "Microsoft.Insights/diagnosticSettings/*/read",
    "Microsoft.Insights/metricDefinitions/*/read",
    "Microsoft.Logic/*/read",
    "Microsoft.Logic/workflows/disable/action",
    "Microsoft.Logic/workflows/enable/action",
    "Microsoft.Logic/workflows/validate/action",
    "Microsoft.Resources/deployments/operations/read",
    "Microsoft.Resources/subscriptions/operationresults/read",
    "Microsoft.Resources/subscriptions/resourceGroups/read",
    "Microsoft.Support/*",
    "Microsoft.Web/connectionGateways/*/read",
    "Microsoft.Web/connections/*/read",
    "Microsoft.Web/customApis/*/read",
    "Microsoft.Web/serverFarms/read",
    "Microsoft.Logic/workflows/listSwagger/action"
  ],
  "NotActions": [],
  "DataActions": [],
  "NotDataActions": [],
  "AssignableScopes": [
    "/subscriptions/<my azure sub id>"
  ]
}

After that you can create the custom role:

# 3. Create the new custom role:
New-AzRoleDefinition -InputFile .\LogicAppAPIOperator.json

This role can now be assigned to the Power Platform user(s) that need it, using the scope of your Logic Apps, for example the Resource Group. You can either add the role assignment to the user directly, or preferrably using Azure PIM:

With the correct permissions now in place, you can proceed to the next step.

Creating Custom Connector using Azure services and Logic App

Log in to Power Apps or Power Automate using your Power Platform user. Under Data and Custom Connectors, select to create a New custom connector. From there select “Create from Azure Service” (Preview as per now):

Next, type name for your Custom Connector, select which Azure subscription, and from which Azure service which in this case is Logic Apps. Note that you can create from Azure Functions and Azure API Management as well. Then select the Logic App name from the list:

If you don’t see or get any errors here, verify your permissions.

Click Continue, and you will see something like the following, where the Host and Base URL has automatically been set correctly for your Logic App HTTP trigger. If you want you can upload an icon, background color and desctription as well:

Click Next to go to Security. Here we need to change the Authentication to OAuth 2.0, as this is what we have implemented for authorizing requests to the Logic App. To authenticate and get the correct Access Token, we will reuse the LogicApp Client app registration that we created in the previous blog post. Copy the Application Client ID and Tenant ID:

And then create and copy a new secret for using in the Power Platform Custom Connector:

Fill in the rest of the OAuth 2.0 details for your environment like below:

Note from above that we need to specify the correct resource (the backend API) and scope. This is all very vell described in the previous blog post.

Click Create Connector to save the Connector details. Make sure that you copy the Redirect URL:

And add that to the App Registration redirect URLs:

Next, under the Custom Connector proceed to step 3. Definition. This is where the POST request trigger will be, and it should already be populated with an action:

We need to specify a value for Summary, in my case I will type “Get Managed Devices”:

Next, under Request Query, remove the “sp”, “sv” and “sig” parameters, as these will not be needed as long as we are using OAuth2 authorization scheme:

The Body parameter should be correctly specified, expecting an operatingSystem, osVersion and userUpn request body parameters:

Last, lets check the Responses from the Logic App. They have been successfully configured with status 200 (OK) and 403 (Not Authorized), as these two responses were defined in the Logic App.

If the Response body is empty like below, we would need to import from sample output from the Logic App (response body should have automatically been configured if the response action in Logic App had a response schema defined):

For response status 200, the sample import is:

[
  {
    "deviceName": "",
    "manufacturerer": "",
    "model": "",
    "operatingSystem": "",
    "osVersion": "",
    "userDisplayName": "",
    "userPrincipalName": ""
  }
]

Giving this response definition:

The sample response from the 403 not authorized should be:

{
  "Message": "",
  "Roles Required": "",
  "Roles in Token": "",
  "Scopes Required": "",
  "Scopes in Token": ""
}

Giving this response definition:

NB! It’s important to have correct responses defined like above, it will make it easier to consume those responses later in Power Automate Flows and Power Apps.

Click on Update Connector, and then go to next section 4. Test.

We can now test the Logic App trigger via the Custom Connector, first we need to create a new connection:

After logging in, and if needed consenting to the permissions scopes (se previous blog post for details), we should have a connection. We can now test the trigger by supplying the api-version (2016-10-01) and specify the operatingSystem, osVersion and userUpn parameters:

Click Test operation and verify a successful response like below:

Let’s try another test, this time leaving the userUpn blank (from the previous blog post this means that the Logic App tries to return all managed devices, if the user has the correct scope and/or roles). This time I get a 403 not authorized, which is expected as I don’t have the correct scope/role:

Checking the Logic App run history I can see that my Power Platform user triggered the Logic App and I can see the expected scp and roles claim:

Perfect so far! In the end of this blog post article I will show how we can get this response data to a Power App via a Flow and the Custom Connector, but first lets look into the other ways of creating a Custom Connector.

Exporting the Logic App to a Power Platform environment

In the previous example, I created the Custom Connector from my Power Platform environment, in this example I will do an Export from the Logic App. The user I will do this with needs to be a Power Platform licensed user and have access to the environments, or else I will get this:

To Export, click this button:

Then fill inn the name of the Custom Connector to create, I will call this ..v2, and select environment:

You might get another permission error:

If so, we need to update the Custom Role created earlier with this permission. Do the following:

# 3b. Update the custom role
$roleLogicAppAPIOperator = Get-AzRoleDefinition -Name "Logic App API Operator"
$roleLogicAppAPIOperator.Actions.Add("Microsoft.Logic/workflows/triggers/listCallbackUrl/action")
Set-AzRoleDefinition -Role $roleLogicAppAPIOperator

The role and the assignment should now be updated, so we can try again. You might need to refresh or log out and in again for the permission to be updated. After this the Export should be successful:

We can now find the Custom Connector right below the first we created:

We still need to edit the Custom Connector with the authentication details, adding the app/client id, secret etc. The export has also left out all the query parameters (sv, sp, sig) but also the required api-version. This must be fixed, the easiest way is to switch to Swagger Editor, and add the line 15 and 16 as shown below:

After this you should be able to Update the Connector, and the Test, Create a Connection and verify successful results.

Creating the Custom Connector using an OpenAPI swagger definition file/url

Both examples above, either importing a Custom Connector from Azure Service, or exporting the Logic App to a Custom Connector in a Power Platform environment, require that the user doing this both has:

  • Azure RBAC role assignment and permissions as detailed above.
  • Access to Power Platform environment and licensed for using Power Platform.

What if you as Azure administrator don’t want your Power Platform users to have access to Azure, but you still want to help them with creating Custom Connectors that send requests to selected Logic App workflow APIs?

Then you can provide them with an OpenAPI swagger definition file or url. You can get the swagger OpenAPI definition by running this Azure REST request: Workflows – List Swagger (Azure Logic Apps) | Microsoft Docs.

To get your swagger you can look at the first blog post in this series, where I showed how you could use Az PowerShell to get management access tokens using Get-AzAccessToken and running Invoke-RestMethod. In this example I’m just going to use the Try it button from the Docs link above, and then authenticate to my Azure subscription, and fill inn the required parameters:

Running this request should produce your requested swagger OpenAPI definition. You can now copy this to a file:

Before you share this OpenAPI file with your Power Platform developers, you should edit and remove the following request query parameters, as these are not needed when running the OAuth2 authorization scheme:

After this you can create a new Custom Connector, by specifying an OpenAPI file / url, depending on where you made the file available to your Power Platform Developers.

Browse to the filename and type a Connector name:

After this you will have the basis of the Connector defined, where you can customize general settings etc:

You will now need to add the authentication for Azure AD OAuth2 with client id, secret etc under Security, as well as creating the connector, and under test create a connection and test the operations. This is the same as I showed earlier, so I don’t need to show tthe details here.

Creating the Custom Connector from blank

You can of course create Power Platform Custom Connectors from blank as well, this should be easy enough based on the details I have provided above, but basically you will need to make sure to set the correct Host and Base URL path for your Logic App here:

After adding the authentication details for Azure AD OAuth2 (same as before), you will need to manually add actions, and providing a request from sample, as well as defining the default responses for 200 and 403 status, as shown in the earlier steps.

With the Custom Connector now in place for sending Requests to the Logic App using delegated authentication, we can now start using this Connector in our Flows/Power Apps.

Lets build a quick sample of that.

Creating a Power Automate Flow that will trigger Logic App API

I’ll just assume readers of this blog post knows a thing or two about Power Automate and Cloud Flows, so I’ll try to keep this high level.

I’ve created a new instant Cloud Flow, using PowerApps as a trigger. Then I add three initialize variables actions, giving the variables and actions name like below, before I set “Ask in PowerApps” for values:

Next, add a Custom Connector action, selecting the Custom Connector we created earlier (I have 3 versions here, as I shown above with the alternative ways to set up a Custom Connector from Logic Apps:

Next, select the action from the chosen Custom Connector, and fill in the parameters like below:

Next, we need to check the response status code we get back from the Custom Connector. Add a Switch control action, where we will check against the outputs from the Get Managed Devices and statusCode:

Make sure that the Switch action should run either if the Get Managed Devices is successful or failed:

For each case of statusCode we will check against, we need a Response action to return data back to the PowerApp. For status code 200 OK, I’ll return the Status Code as shown below, adding Headers to be Content-Type application/json, and using the Body output from the Get Managed Devices custom connector action. The Response Body JSON schema is based on the sample output from the Logic App API.

PS! To get the Body output, you can use the following custom expression: outputs('Get_Managed_Devices')?['body']:

For status code 403 I have added the following Case and Response action, using the Body output again, but this time the schema is based on the 403 response from the Logic App API:

Last, as every case should have Response, I’ll add the following Default Case:

The whole Flow visualized:

PS! Instead of using the Response action, I could also have used the “Respond to PowerApps” action. However this action only let me return text strings, numbers, boolean etc, and I wanted to return native JSON response.

Make sure that you test and verify the Flow before you proceed.

Creating the Power App to connect to the Flow

With the Flow ready, lets quickly build a PowerApp. My PowerApp is a Canvas App, and I have been using the Phone layout.

You can build this any way you want, but I used a dark theme, added an Icon at the top screen, and the 3 labels and text inputs for the parameters needed for the Flow. I then added a button for triggering the Flow, and under the button I have added a (hidden now) text label, for showing any error messages from the Flow. And I have added a Gallery control under there again for showing the resulting devices:

For the Button, select it and click on the Action menu and the Power Automate to connect your Flow. Next, change the “OnSelect” event for the Button to the following command:

Set(wait,true);
Clear(MyManagedDevices);Set(MyErrorMessage,Blank());
Set(MyDeviceResponse,GetManagedDevices.Run(textOperatingSystem.Text,textOSVersion.Text,textUserUpn.Text));
If(IsBlank(MyDeviceResponse),Set(MyErrorMessage,"Authorization Error: Check Flow for details on missing scope or roles claims for querying organization devices."),ClearCollect(MyManagedDevices,MyDeviceResponse));
Set(wait,!true)

A quick explanation of the commands above:

  • Set(wait,true) and Set(wait,!true) is to make the PowerApp “busy” when clicking.
  • I then Clear my Collection and Variable used.
  • I then use Set to get a “MyDeviceResponse”, this will return a collection of items (devices) returned via a JSON array from the Flow, or if I’m not authorized, it will return a failed response (based on the 403) and a blank MyDeviceResponse.
  • Next I do a If test, if the MyDeviceResponse i Blank, I’ll set the MyErrorMessage variable, if it’s not blank I will run a ClearCollect and fill the Collection with returned devices.

I fully appreciate that there might be other ways to do this fail checking and error handling, please let me know in the comments if you have other suggestions πŸ™‚

For the Gallery I set the Data source to MyManagedDevices collection, and I have selected to use the layout of “Title, subtitle, and body”. You can change the device data that get filled in for these items in the Galleri, for example Manufacturer, Version, Name etc.

And last I set the Text property of my error message label to the MyErrorMessage variable:

Let’s Save, Publish and test this PowerApp!

First, I’ll try to add parameters for getting all Windows 10 devices, leaving user principal name blank. This will via the Custom Connector send a request to the Logic App API to return all devices, and in this case I’m not authorized to do so, so I’ll get an authorization error:

This is something I can verify in the Flow run history also:

Next, I’ll try to return my test users devices only, and this is successful and will fill the gallery:

We now have a working Flow and PowerApp connected to the Logic App API using the signed in users delegated permissions. If I want I can now share the PowerApp and Flow including the Custom Connector with other users in my organization, and they can use their own user identity for connections to the Logic App API.

In the next part of this blog post I will show how you can access the Logic App API using HTTP action and application permissions.

Connect to Logic App API using HTTP action

Sometimes you will have scenarios where you want to use an application identity to call an API like the Logic App I have used in this blog post article series. This is especially useful if you want to run a Power Automate Flow without a logged in user’s permissions.

I the previous blog post part 2 for exposing Logic App as an API, I created this App Registration to represent the Application Client scenarios and Application permissions:

In that App Registration, create a new Client Secret for using in Power Automate, and copy this to your clipboard:

Make sure to copy the Application (Client) ID and Tenant ID also:

Now let’s create a new Power Automate Flow to test this scenario. This type of Flow could use a range of different triggers based on your needs, but I’ll just use a Instant Cloud Flow as trigger where I have configured the following inputs:

Note that I have configured userUpn as an optional input.

Next add a “Compose” action for the Client Secret, give the action a name and paste in the Client Secret you created earlier. Note the Lock symbol:

Click on settings and select to Secure Inputs:

Next add a HTTP action, specifying the Method to POST and the URI to be the LogicApp API url, remember to not include the sv, sp and sig query parameters. Set Headers Content-Type to application/json, and under queries add the api-version. For body build the JSON request body using the inputs. We need to build a dynamic expression for userUpn, as this can be optional. I have used the following expression:

if(not(empty(triggerBody()?['text_2'])),triggerBody()?['text_2'],'')

Click to show advanced settings, and choose Authentication to use Azure AD OAuth. Add the authority, tenant id and set audience to the custom Logic App API URI. Then paste in the Application (Client) Id, and use the Outputs from the Compose Client Secret action:

This authentication above will use the Client Credentials Flow to get an access token that will be accepted by the Logic App API.

The remaining parts of this Flow can be exactly the same as the previous Flow we built, a Switch control that continiues on success/failure of the HTTP action:

And then returning Response objects from the HTTP action body for each case:

When testing the Flow now, I can see that the client secret is hidden from all relevant actions:

Summary and Next Steps

We are at the end of another extensive blog post. The focus for this article has been to show how you can use Power Automate to connect to your custom API, that we built in the previous blog post for exposing the Logic App as an API.

The community are increasingly creating Power Platform custom connectors and http actions that sends requests to API’s to Microsoft Graph directly, and that is great but it might result in too extensive permissions given to users and application clients. My focus has been to show how you can control authentication and authorization using on-behalf-of flows hidden behind a Logic App API where users and clients are allowed to send requests based on allowed permission scopes and/or roles, using the powers of Azure Active Directory and OAuth2.

There will be a later blog post in this series also, where I look into how Azure API Management can be used in these scenarios as well.

In the meantime, thanks for reading, hope it has been helpful!

How to Send Requests to GitHub API from Power Platform using Custom Connector

Recently I came across a personal scenario where I use Hugo and GitHub Pages as a team site for a Soccer team I’m coaching and wanted to automate some updates to the web site. I’ve written a blog post previously on how I organized trainings at home using Power Platform: How I as a Soccer Coach…. | GoToGuy Blog, and I am now using Github Pages and Hugo for publishing some statistics and more for that scenario.

In this blog post I will show how I:

  1. Created an OAuth Application for Github API.
  2. Created a Custom Connector in Power Platform for connections to that OAuth Application.
  3. Created Operations for getting content, updating content and triggering workflows for Github Actions.
  4. Connected to Github API using my Azure AD account and user impersonation.
  5. Created a Power Automate Cloud Flow for using the Custom Connector and the defined operations.

Lets get started!

Create OAuth Application for Github API

Start by logging in to your GitHub account and go to Settings. Under Settings you will find Developer Settings where you can access OAuth Apps. You can also go directly to the following URL https://github.com/settings/developers.

Click to Register a new application, and fill in something like the following:

As the above image shows, give the application a descriptive name for your scenario, you can type any homepage URL, this is not important in this scenario. The authorization callback URL is important though, as this will the callback to the Custom Connector we will create later. We can verify the URL later, but use https://global.consent.azure-apim.net/redirect.

Register the application. Next you can change the settings for the registered app. You will have to copy the Client ID, we will need that later. You also need to create Client Secret, make sure to copy that as well, you will only be able to see this once. You can also change some settings like name, logo and branding if you like. This is how my Github App registration looks like now:

We can now proceed to Power Platform to create the Custom Connector.

Create Custom Connector to Github API in Power Platform

Log in to your Power Platform environment, and go to Custom Connectors under Data. Click to create a New custom connector. You can select to create from blank if you want to follow along the steps in my blog post here, or you can select to import an OpenAPI for URL, as I will provide the swagger file at the end of this blog post.

Give the connector a name of your choice and continue:

Next you need to specify “api.github.com” as host. You can also optionally upload a connector icon, as I have done here:

(You can grab the mark logo used above from here, GitHub Logos and Usage, note the usage requirements).

Next, go to Security. Select OAuth 2.0 as authentication type, and then selec GitHub as Identity Provider.

(PS! You can select Generic OAuth 2 also, but it will fall back to GitHub as Identity Provider eventually after all).

Add your Client ID and Secret from the Github OAuth application registration:

It is important to configure the correct scope (or scopes) as this will authorize the client for accessing the API. If you leave the scope blank, you will only get public read only access. You can read more on available scopes here: Scopes for OAuth Apps – GitHub Docs

In my case I want to have full read and write access to public repositories, as well as read write to user profile, so I set the scope to “public_repo user” (use space delimiter for multiple scopes):

I can now click “Create connector”. After creating the security details are now hidden/disabled, and I can verify the Redirect URL to be the same as the Callback URL from the GitHub OAuth app registration:

We can now start defining the operations for the actions I want to do against the GitHub API.

Create Operations for sending requests to GitHub API

When querying and sending request to the GitHub API you need to know the API details and required parameters for what you want. The following link is for the official GitHub Rest API reference: Reference – GitHub Docs.

In my example I want to define the following 3 operations in my Custom Connector:

Under 3. Definition, select to create a New action, and call it something like “Get Repository Content” with the Operation ID set to “GetRepositoryContent”:

Then, under Request, click Import from sample. Select the Verb GET, and under URL type https://api.github.com. The rest of the query we will get from the GitHub API docs. Copy the following fra the REST API reference docs:

So that your sample request now looks like this, remember to add the recommended Accept header:

Click Import. The request will now ask for owner, repo and path as parameters:

Next, click the default response. Here you can copy the sample response from the REST API docs, I’ve copied the sample response for getting file contents:

After that click “Update connector” and we have the first action operation defined.

Click New action again, this time for updating file contents:

For the sample request the Verb is PUT, the URL is the same as when getting file content, but now we need to specify a request body as well:

I’ve created the sample request body based on the docs reference, with just empty placeholder values for the parameters needed. Some of these can be omitted, but message, contents, sha and branch is required for updating an existing file:

{
 "message": "",
 "content": "",
 "sha": "",
 "branch": "",
 "committer": {
  "name": "",
  "email": "",
  "author": {
   "name": "",
   "email": ""
  }
 }
}

After importing the sample request, you can click into the body parameter and change to required for the body itself, as well as the payload parameters that you always want to include from below:

Add a sample default response as well, I’ve copied the example response for updating a file from the docs.

Click “Update connector” again and we are ready to add the third action:

This will be a POST request, with the following URL and request body:

Note from above that “ref” needs to be referencing a branch or tag name as is a required parameter. “Inputs” is an object, depending on your GitHub Actions workflow if incoming parameters is defned, so in many cases this can be empty.

You can leave the default response as it is, as API will return 204 No Content if request is successful.

Click on “Update connector” again, and you should now have 3 actions successfully configured.

We can now proceed to create a connection and authenticate to GitHub API using this custom connector.

Connect to Github API using my Azure AD account and user impersonation

Go to “4. Test”, and click to create a “New connection”. This will create a new authentication popup, and if you’re not already logged in to GitHub you must log in first. Note the correct reference and branding to the “Elven Power Platform OAuth App”:

After logging in I’m prompted to authorize the OAuth app to access data in my account. Note that the scopes “public_repo” and “user” is shown in the authorization request:

If you own other organizations you can grant access to that as well. Click Authorize “OwnerName”: as shown below:

After authorizing you will be redirected back to the Connections, and you should be able to successfully get a new connection object.

Let’s take a look at GitHub settings again, under https://github.com/settings/applications. You should see the OAuth App and the correct permissions configured if you click into details. You can also revoke the access if you need to remove it or reconfigure the scopes for example:

Let’s do a test from the Custom Connector and see what we get. Click on the GetRepositoryContent, and provide the paramaters for “owner” (your GitHub account name), “repo” (any repository, I’m using my GitHub Pages repo here), and a “path” to an existing file in that repo (I’m just testing against my README.md at root, but this can be any subfolder\file also). Click Test operation and see:

This should be successful, note that the response contains a couple of important values for later, the “sha” for the existing file, and the “content” which is a base64 representation of the current contents of the README.md file.

Click on the Request tab, and you will see a preview of how the request was constructed. You will also see the Authorization Header with the Bearer Token:

A couple of important things to note:

  • The request uses an API gateway in Azure APIM, not GitHub directly.
  • The Bearer Token in the Authorization Header is for the Azure API GW audience, so it cannot be used directly against GitHub API.

Copy the entire token value, from after “Bearer <token……>”, and paste it into a JWT debugger like jwt.io. From there we can look at the decoded payload:

From that payload it’s clear that the Token has been issued by my Azure AD tenant and for my logged on user in Power Platform. The scope is user_impersonation, so this will be used in a on-behalf-of flow scenario via the audience defined as apihub.azure.com, which in turn will request from GitHub API resources on my behalf via the APIM gateway used by Power Platform.

You can also lookup the appid from the Token in the Azure AD tenant, and you will find the following Enterprise Application, from where you can enable or disable it on an organization level, or you can examine the sign in logs:

We can test the other operations as well, but let’s create a Flow for that scenario.

Create a Power Automate Cloud Flow for using the Custom Connector to Get and Update File Content

Create a new Cloud Flow, using an instant trigger for manually triggering a flow. Add some inputs like shown below:

Next, add a new action and from under Custom find the GitHub Custom Connector:

Add the “Get Repository Content” action and then fill in the inputs like below:

Next, add a Compose action, with the following dynamic expression:

base64ToString(outputs('Get_Repository_Content')?['body/content'])

This is just for checking what the existing file contents is:

We can do a quick Save and then Test Flow so far, from the Run history I should get the correct inputs, and when finding the existing file the outputs will include the sha value of the existing file, as well as the base64 encoded value of the content:

And when looking at the decoding of the content I can see that the readme.md file content is shown correctly:


Go into Flow edit mode again, and add another Compose action, this time we need to base64 encode the new content I want to update the file with:

Note that the base64 function uses for parameter the input trigger of base64(triggerBody()?['text']), as this is the first text parameter of the trigger.

Add a new action, this time for the Custom Connector again, and the Update File Contents. Specify the owner, repo and path as previously input values, type a custom message for the message, and select the outputs from the “Base64 Updated Content” action, and use the sha value from the “Get Repository Content”. The rest of the values (committer, author objects) are optional:

Save and then do another test, for example like the following to update the README.md file:

And the test should be successful:

I can also verify this at my repository and check the file has been updated. Note also the commit message:

Triggering a GitHub Actions Workflow

The last thing I wanted to go through in this blog post is using the Power Platform Custom Connector to trigger a GitHub Actions workflow. My use case for this is to start a Hugo build when I have dynamically updated files for my static website, but for now I will keep it simple.

I have via a basic template created a simple workflow like this:

This workflow can also be triggered manually using workflow_dispatch, so let’s use that to verify that I can call it from Power Platform.

Add a new action at the end of the Flow, adding the Custom Connector action for Dispatching Workflow event:

Specify Owner and Repo from inputs, and for workflow id either specify ID or the name of the workflow file, in this case blank.yml. The ref parameter is either a branch or tag name, so in my case I use main branch. I leave the other parameters blank as I don’t have any inputs to supply, and use the default Accept header.

Save and Test the Flow again, supplying an updated file content, owner, repo and path similar to what we did previously. When the Flow runs it should complete successfully:

If I go to my GitHub repository, and under Actions, I can see that this workflow has been triggered:

Actually it has been triggered twice, as the first trigger is automatic for the push commit on the file update, and the other (named “CI” in results) is the actual workflow dispatch from the Flow.

Basically this means that I can select some different logic to when my workflows will trigger, either as a push or pull trigger, or as a trigger event based on my Flows. But of course I won’t normally run both triggers πŸ˜‰

I now have what I need for working further with my personal Hugo and GitHub Pages project, my plan is to update data and assets files from my Power Platform environment, and then trigger a Hugo build for my website. I might blog more on that process later.

Summary and some last thoughts

In this blog post I wanted to show how you can work with the GitHub REST API via a Power Platform Custom Connector. This way you can basically achieve anything that the GitHub API has available, provided the correct scope/scopes has been authorized.

I do want to mention however that there is a GitHub Connector you can use directly in Power Automate, Logic Apps, or Power Apps also: GitHub – Connectors | Microsoft Docs, where you can create a direct connection to your GitHub account. You should take a look at that if that can server your needs.

In my case I needed the API to get or update file contents directly, as well as when using impersonation people in my organization can use their own Azure AD accounts if I share the Custom Connector with them, they don’t need their own GitHub accounts as long as the OAuth App has been authorized on my behalf.

If you want a quickstart on creating the Custom Connector your self, below is the Swagger definition. Thanks for reading, hope it has been useful!

swagger: '2.0'
info: {title: JanVidarElven Github Connector, description: GitHub API Connector for
JanVidarElven, version: '1.0'}
host: api.github.com
basePath: /
schemes: [https]
consumes: []
produces: []
paths:
/repos/{owner}/{repo}/contents/{path}:
get:
responses:
default:
description: default
schema:
type: object
properties:
type: {type: string, description: type}
encoding: {type: string, description: encoding}
size: {type: integer, format: int32, description: size}
name: {type: string, description: name}
path: {type: string, description: path}
content: {type: string, description: content}
sha: {type: string, description: sha}
url: {type: string, description: url}
git_url: {type: string, description: git_url}
html_url: {type: string, description: html_url}
download_url: {type: string, description: download_url}
_links:
type: object
properties:
git: {type: string, description: git}
self: {type: string, description: self}
html: {type: string, description: html}
description: _links
summary: Get Repository Content
operationId: GetRepositoryContent
description: Get File or Folder Content from Repository
parameters:
{name: owner, in: path, required: true, type: string}
{name: repo, in: path, required: true, type: string}
{name: path, in: path, required: true, type: string}
{name: Accept, in: header, required: false, type: string}
put:
responses:
default:
description: default
schema:
type: object
properties:
content:
type: object
properties:
name: {type: string, description: name}
path: {type: string, description: path}
sha: {type: string, description: sha}
size: {type: integer, format: int32, description: size}
url: {type: string, description: url}
html_url: {type: string, description: html_url}
git_url: {type: string, description: git_url}
download_url: {type: string, description: download_url}
type: {type: string, description: type}
_links:
type: object
properties:
self: {type: string, description: self}
git: {type: string, description: git}
html: {type: string, description: html}
description: _links
description: content
commit:
type: object
properties:
sha: {type: string, description: sha}
node_id: {type: string, description: node_id}
url: {type: string, description: url}
html_url: {type: string, description: html_url}
author:
type: object
properties:
date: {type: string, description: date}
name: {type: string, description: name}
email: {type: string, description: email}
description: author
committer:
type: object
properties:
date: {type: string, description: date}
name: {type: string, description: name}
email: {type: string, description: email}
description: committer
message: {type: string, description: message}
tree:
type: object
properties:
url: {type: string, description: url}
sha: {type: string, description: sha}
description: tree
parents:
type: array
items:
type: object
properties:
url: {type: string, description: url}
html_url: {type: string, description: html_url}
sha: {type: string, description: sha}
description: parents
verification:
type: object
properties:
verified: {type: boolean, description: verified}
reason: {type: string, description: reason}
signature: {type: string, description: signature}
payload: {type: string, description: payload}
description: verification
description: commit
summary: Update File Contents
description: Update existing file in repository
operationId: UpdateFileContents
parameters:
{name: owner, in: path, required: true, type: string}
{name: repo, in: path, required: true, type: string}
{name: path, in: path, required: true, type: string}
{name: Accept, in: header, required: false, type: string}
name: body
in: body
required: true
schema:
type: object
properties:
message: {type: string, description: message, title: ''}
content: {type: string, description: content, title: ''}
sha: {type: string, description: sha, title: ''}
branch: {type: string, description: branch, title: ''}
committer:
type: object
properties:
name: {type: string, description: name}
email: {type: string, description: email}
author:
type: object
properties:
name: {type: string, description: name}
email: {type: string, description: email}
description: author
description: committer
required: [branch, content, message, sha]
/repos/{owner}/{repo}/actions/workflows/{workflow_id}/dispatches:
post:
responses:
default:
description: default
schema: {}
summary: Dispatch Workflow Event
operationId: DispatchWorkflowEvent
description: Trigger a GitHub Actions Workflow by ID
parameters:
{name: owner, in: path, required: true, type: string}
{name: repo, in: path, required: true, type: string}
{name: workflow_id, in: path, required: true, type: string}
{name: Accept, in: header, required: false, type: string}
name: body
in: body
required: true
schema:
type: object
properties:
ref: {type: string, description: ref, title: ''}
inputs:
type: object
properties: {}
description: inputs
required: [ref]
definitions: {}
parameters: {}
responses: {}
securityDefinitions:
oauth2_auth:
type: oauth2
flow: accessCode
authorizationUrl: https://github.com/login/oauth/authorize
tokenUrl: https://login.windows.net/common/oauth2/authorize
scopes: {public_repo user: public_repo user}
security:
oauth2_auth: [public_repo user]
tags: []

Protect Logic Apps with Azure AD OAuth – Part 2 Expose Logic App as API

This blog article will build on the previous blog post published, Protect Logic Apps with Azure AD OAuth – Part 1 Management Access | GoToGuy Blog, which provided some basic understanding around authorizing to Logic Apps request triggers using OAuth and Access Tokens.

In this blog I will build on that, creating a scenario where a Logic App will be exposed as an API to end users. In this API, I will call another popular API: Microsoft Graph.

My scenario will use a case where end users does not have access themselves to certain Microsoft Graph requests, but where the Logic App does. Exposing the Logic App as an API will let users be able to authenticate and authorize, requesting and consenting to the custom Logic App API permissions I choose. Some of these permissions can users consent to themselves, while other must be admin consented. This way I can use some authorizing inside the Logic App, and only let the end users be able to request what they are permitted to.

I will also look into assigning users and groups, and using scopes and roles for additional fine graining end user and principal access to the Logic App.

A lot of topics to cover, so let’s get started by first creating the scenario for the Logic App.

Logic App calling Microsoft Graph API

A Logic App can run requests against the Microsoft Graph API using the HTTP action and specifying the method (GET, POST, etc) and resource URI. For authentication against Graph from the Logic App you can use either:

  • Using Azure Active Directory OAuth and Client Credentials Flow with Client Id and Secret.
  • Using System or User Assigned Managed Identity.

Permissions for Microsoft Graph API are either using “delegated” (in context of logged in user) or “application” (in context of application/deamon service). These scenarios using Logic App will use application permissions for Microsoft Graph.

PS! Using Logic Apps Custom Connectors (Custom connectors overview | Microsoft Docs) you can also use delegated permissions by creating a connection with a logged in user, but this outside of the scope of this article.

Scenario for using Microsoft Graph in Logic App

There are a variety of usage scenarios for Microsoft Graph, so for the purpose of this Logic App I will focus on one of the most popular: Device Management (Intune API) resources. This is what I want the Logic App to do in this first phase:

  • Listing a particular user’s managed devices.
  • Listing all of the organization’s managed devices.
  • Filtering managed devices based on operating system and version.

In addition to the above I want to implement the custom API such that any assigned user can list their own devices through end-user consent, but to be able to list all devices or any other user than your self you will need an admin consented permission for the custom API.

Creating the Logic App

In your Azure subscription, add a new Logic App to your chosen resource group and name it according to your naming standard. After the Logic App is created, you will need add the trigger. As this will be a custom API, you will need it to use HTTP as trigger, and you will also need a response back to the caller, so the easiest way is to use the template for HTTP Request-Response as shown below:

Your Logic App will now look like this:

Save the Logic App before proceeding.

Create a Managed Identity for the Logic App

Exit the designer and go to the Identity section of the Logic App. We need a managed identity, either system assigned or user assigned, to let the Logic App authenticate against Microsoft Graph.

A system assigned managed identity will follow the lifecycle of this Logic App, while a user assigned managed identity will have it’s own lifecycle, and can be used by other resources also. I want that flexibility, so I will create a user assigned managed identity for this scenario. In the Azure Portal, select to create a new resource and find User Assigned Managed Identity:

Create a new User Assigned Managed Identity in your selected resource group and give it a name based on your naming convention:

After creating the managed identity, go back to your Logic App, and then under Identity section, add the newly created managed identity under User Assigned Managed Identity:

Before we proceed with the Logic App, we need to give the Managed Identity the appropriate Microsoft Graph permissions.

Adding Microsoft Graph Permissions to the Managed Identity

Now, if we wanted the Logic App to have permissions to the Azure Rest API, we could have easily added Azure role assignments to the managed identity directly:

But, as we need permissions to Microsoft Graph, there are no GUI to do this for now. The permissions needed for listing managed devices are documented here: List managedDevices – Microsoft Graph v1.0 | Microsoft Docs.

So we need a minimum of: DeviceManagementManagedDevices.Read.All.

To add these permissions we need to run some PowerShell commands using the AzureAD module. If you have that installed locally, you can connect and proceed with the following commands, for easy of access you can also use the Cloud Shell in the Azure Portal, just run Connect-AzureAD first:

PS! You need to be a Global Admin to add Graph Permissions.

You can run each of these lines separately, or run it as a script:

# Microsoft Graph App Well Known App Id
$msGraphAppId = "00000003-0000-0000-c000-000000000000"

# Display Name if Managed Identity
$msiDisplayName="msi-ops-manageddevices" 

# Microsoft Graph Permission required
$msGraphPermission = "DeviceManagementManagedDevices.Read.All" 

# Get Managed Identity Service Principal Name
$msiSpn = (Get-AzureADServicePrincipal -Filter "displayName eq '$msiDisplayName'")

# Get Microsoft Graph Service Principal
$msGraphSpn = Get-AzureADServicePrincipal -Filter "appId eq '$msGraphAppId'"

# Get the Application Role for the Graph Permission
$appRole = $msGraphSpn.AppRoles | Where-Object {$_.Value -eq $msGraphPermission -and $_.AllowedMemberTypes -contains "Application"}

# Assign the Application Role to the Managed Identity
New-AzureAdServiceAppRoleAssignment -ObjectId $msiSpn.ObjectId -PrincipalId $msiSpn.ObjectId -ResourceId $msGraphSpn.ObjectId -Id $appRole.Id

Verify that it runs as expected:

As mentioned earlier, adding these permissions has to be done using script commands, but there is a way to verify the permissions by doing the following:

  1. Find the Managed Identity, and copy the Client ID:
  1. Under Azure Active Directory and Enterprise Applications, make sure you are in the Legacy Search Experience and paste in the Client ID:
  1. Which you then can click into, and under permissions you will see the admin has consented to Graph permissions:

The Logic App can now get Intune Managed Devices from Microsoft Graph API using the Managed Identity.

Calling Microsoft Graph from the Logic App

Let’s start by adding some inputs to the Logic App. I’m planning to trigger the Logic App using an http request body like the following:

{
 "userUpn": "[email protected]",
 "operatingSystem": "Windows",
 "osVersion": "10"
}

In the Logic App request trigger, paste as a sample JSON payload:

The request body schema will be updated accordingly, and the Logic App is prepared to receive inputs:

Next, add a Condition action, where we will check if we should get a users’ managed devices, or all. Use an expression with the empty function to check for userUpn, and another expression for the true value, like below:

We will add more logic and conditions later for the filtering of the operating system and version, but for now add an HTTP action under True like the following:

Note the use of the Managed Identity and Audience, which will have permission for querying for managed devices.

Under False, we will get the managed devices for a specific user. So add the following, using the userUpn input in the URI:

Both these actions should be able to run successfully now, but we will leave the testing for a bit later. First I want to return the managed devices found via the Response action.

Add an Initialize Variable action before the Condition action. Set the Name and Type to Array as shown below, but the value can be empty for now:

Next, under True and Get All Managed Devices, add a Parse JSON action, adding the output body from the http action and using either the sample response from the Microsoft Graph documentation, or your own to create the schema.

PS! Note that if you have over 1000 managed devices, Graph will page the output, so you should test for odata.nextLink to be present as well. You can use the following anonymized sample response for schema which should work in most cases:

{
     "@odata.context": "https://graph.microsoft.com/v1.0/$metadata#deviceManagement/managedDevices",
     "@odata.count": 1000,
     "@odata.nextLink": "https://graph.microsoft.com/v1.0/deviceManagement/managedDevices?$skiptoken=",
     "value": [
         {
             "id": "id Value",
             "userId": "User Id value",
             "deviceName": "Device Name value",
             "managedDeviceOwnerType": "company",
             "operatingSystem": "Operating System value",
             "complianceState": "compliant",
             "managementAgent": "mdm",
             "osVersion": "Os Version value",
             "azureADRegistered": true,
             "deviceEnrollmentType": "userEnrollment",
             "azureADDeviceId": "Azure ADDevice Id value",
             "deviceRegistrationState": "registered",
             "isEncrypted": true,
             "userPrincipalName": "User Principal Name Value ",
             "model": "Model Value",
             "manufacturer": "Manufacturer Value",
             "userDisplayName": "User Display Name Value",
             "managedDeviceName": "Managed Device Name Value"
         }
     ]
 }

PS! Remove any sample response output from schema if values will be null or missing from your output. For example I needed to remove the configurationManagerClientEnabledFeatures from my schema, as this is null in many cases.

Add another Parse JSON action under the get user managed devices action as well:

Now we will take that output and do a For Each loop for each value. On both sides of the conditon, add a For Each action, using the value from the previous HTTP action:

Inside that For Each loop, add an Append to Array variable action. In this action we will build a JSON object, returning our chosen attributes (you can change to whatever you want), and selecting the properties from the value that was parsed:

Do the exact same thing for the user devices:

Now, on each side of the condition, add a response action, that will return the ManagedDevices array variable, this will be returned as a JSON som set the Content-Type to application/json:

Finally, remove the default response action that is no longer needed:

The complete Logic App should look like the following now:

As I mentioned earlier, we’ll get to the filtering parts later, but now it’s time for some testing.

Testing the Logic App from Postman

In the first part of this blog post article series, Protect Logic Apps with Azure AD OAuth – Part 1 Management Access | GoToGuy Blog, I described how you could use Postman, PowerShell or Azure CLI to test against REST API’s.

Let’s test this Logic App now with Postman. Copy the HTTP POST URL:

And paste it to Postman, remember to change method to POST:

You can now click Send, and the Logic App will trigger, and should return all your managed devices.

If you want a specific users’ managed devices, then you need to go to the Body parameter, and add like the following with an existing user principal name in your organization:

You should then be able to get this users’ managed devices, for example for my test user this was just a virtual machine with Window 10:

And I can verify a successful run from the Logic App history:

Summary so far

We’ve built a Logic App that uses it’s own identity (User Assigned Managed Identity) to access the Microsoft Graph API using Application Permissions to get managed devices for all users or a selected user by UPN. Now it’s time to exposing this Logic App as an API son end users can call this securely using Azure AD OAuth.

Building the Logic App API

When exposing the Logic App as an API, this will be the resource that end users will access and call as a REST API. Consider the following diagram showing the flow for OpenID Connect and OAuth, where Azure AD will be the Authorization Server from where end users can request access tokens where the audience will be the Logic App resource:

Our next step will be to create Azure AD App Registrations, and we will start with the App Registration for the resource API.

Creating App Registration for Logic App API

In your Azure AD tenant, create a new App Registration, and call it something like (YourName) LogicApp API:

I will use single tenant for this scenario, leave the other settings as it is and create.

Next, go to Expose an API:

Click on Set right next to Application ID URI, and save the App ID URI to your choice. You can keep the GUID if you want, but you can also type any URI value you like here (using api:// or https://). I chose to set the api URI to this:

Next we need to add scopes that will be the permissions that delegated end users can consent to. This will be the basis of the authorization checks we can do in the Logic App later.

Add a scope with the details shown below. This will be a scope end users can consent to themselves, but it will only allow them to read their own managed devices:

Next, add another Scope, with the following details. This will be a scope that only Admins can consent to, and will be authorized to read all devices:

You should now have the following scopes defined:

Next, go to the Manifest and change the accessTokenAcceptedVersion from null to 2, this will configure so that Tokens will use the OAuth2 endpoints:

That should be sufficient for now. In the next section we will prepare for the OAuth client.

Create App Registration for the Logic App Client

I choose to create a separate App Registration in Azure AD for the Logic App Client. This will represent the OAuth client that end users will use for OAuth authentication flows and requesting permissions for the Logic App API. I could have configured this in the same App Registration as the API created in the previous section, but this will provide better flexibility and security if I want to share the API with other clients also later, or if I want to separate the permission grants between clients.

Go to App Registrations in Azure AD, and create a new registration calling it something like (yourname) LogicApp Client:

Choose single tenant and leave the other settings for now.

After registering, go to API permissions, and click on Add a permission. From there you can browse to “My APIs” and you should be able to locate the (yourname) Logic API. Select to add the delegated permissions as shown below:

These delegated permissions reflect the scopes we defined in the API earlier. Your App registration and API permission should now look like below. NB! Do NOT click to Grant admin consent for your Azure AD! This will grant consent on behalf of all your users, which will work against our intended scenario later.

Next, we need to provide a way for clients to authenticate using Oauth flows, so go to the Certificates & secrets section. Click to create a Client secret, I will name my secret after where I want to use it for testing later (Postman):

Make sure you copy the secret value for later:

(Don’t worry, I’ve already invalidated the secret above and created a new one).

Next, go to Authentication. We need to add a platform for authentication flows, so click Add a platform and choose Web. For using Postman later for testing, add the following as Redirect URI: https://oauth.pstmn.io/v1/callback

Next, we will also provide another test scenario using PowerShell or Azure CLI client, so click on Add a platform one more time, this time adding Mobile desktop and apps as platform and use the following redirect URI: urn:ietf:wg:oauth:2.0:oob

Your platform configuration should now look like this:

Finally, go to advanced and set yes to allow public client flows, as this will aid in testing from PowerShell or Azure CLI clients later:

Now that we have configured the necessary App registrations, we can set up the Azure AD OAuth Authorization Policy for the Logic App.

Configuring Azure AD OAuth Authorization Policy for Logic App

Back in the Logic App, create an Azure AD Authorization Policy with issuer and audience as shown below:

Note the Claims values:

We are using the v2.0 endpoint as we configured in the manifest of the App Registration that accessTokenAcceptedVersion should be 2. (as opposed to v1.0 issuer that would be in the format https://sts.windows.net/{tenantId}/). And the Audience claim would be our configured API App ID. (for v1.0 the audience would be the App ID URI, like api://elven-logicapp-api).

Save the Logic App, and we can now start to do some testing where we will use the client app registration to get an access token for the Logic App API resource.

Testing with Postman Client

The first test scenario we will explore is using Postman Client and the Authorization Code flow for getting the correct v2.0 Token.

A recommended practice when using Postman and reusing variable values is to create an Environment. I’ve created this Environment for storing my Tenant ID, Client ID (App ID for the Client App Registration) and Client Secret (the secret I created for using Postman):

Previously in this blog article, we tested the Logic App using Postman. On that request, select the Authorization tab, and set type to OAuth 2.0:

Next, under Token configuration add the values like the following. Give the Token a recognizable name, this is just for Postman internal refererence. Make sure that the Grant Type is Authorization Code. Note the Callback URL, this is the URL we configured for the App registration and Callback Url. In the Auth and Access Token URL, configure the use of the v2.0 endpoints, using TenantID from the environment variables. (Make sure to set the current environment top right). And for Client ID and Client Secret these will also refer to the environment variables:

One important step remains, and that is to correctly set the scope for the access token. Using something like user.read here will only produce an Access Token for Microsoft Graph as audience. So we need to change to the Logic App API, and the scope for ManagedDevices.Read in this case:

Let’s get the Access Token, click on the Get New Access Token button:

A browser window launches, and if you are not already logged in, you must log in first. Then you will be prompted to consent to the permission as shown below. The end user is prompted to consent for the LogicApp API, as well as basic OpenID Connect consents:

After accepting, a popup will try to redirect you to Postman, so make sure you don’t block that:

Back in Postman, you will see that we have got a new Access Token:

Copy that Access Token, and paste it into a JWT debugger like jwt.ms or jwt.io. You should see in the data payload that the claims for audience and issuer is the same values we configured in the Logic App Azure AD OAuth policy:

Note also the token version is 2.0.

Click to use the Token in the Postman request, it should populate this field:

Before testing the request, remember to remove the SAS query parameters from the request, so that sv, sp and sig are not used with the query for the Logic App:

Now, we can test. Click Send on the Request. It should complete successfully with at status of 200 OK, and return the managed device details:

Let’s add to the permission scopes, by adding the ManagedDevices.Read.All:

Remember just to have a blank space between the scopes, and then click Get New Access Token:

If I’m logged on with a normal end user, I will get the prompt above that I need admin privileges. If I log in with an admin account, this will be shown:

Note that I can now do one of two actions:

  1. I can consent only on behalf of myself (the logged in admin user), OR..
  2. I can consent on behalf of the organization, by selecting the check box. This way all users will get that permission as well.

Be very conscious when granting consents on behalf of your organization.

At this point the Logic App will authorize if the Token is from the correct issuer and for the correct audience, but the calling user can still request any managed device or all devices. Before we get to that, I will show another test scenario using a public client like PowerShell.

Testing with PowerShell and MSAL.PS

MSAL.PS is a perfect companion for using MSAL (Microsoft Authentication Library) to get Access Tokens in PowerShell. You can install MSAL.PS from PowerShellGallery using Install-Module MSAL.PS.

The following commands show how you can get an Access Token using MSAL.PS:

# Set Client and Tenant ID
$clientID = "cd5283d0-8613-446f-bfd7-8eb1c6c9ac19"
$tenantID = "104742fb-6225-439f-9540-60da5f0317dc"

# Get Access Token using Interactive Authentication for Specified Scope and Redirect URI (Windows PowerShell)
$tokenResponse = Get-MsalToken -ClientId $clientID -TenantId $tenantID -Interactive -Scope 'api://elven-logicapp-api/ManagedDevices.Read' -RedirectUri 'urn:ietf:wg:oauth:2.0:oob'

# Get Access Token using Interactive Authentication for Specified Scope and Redirect URI (PowerShell Core)
$tokenResponse = Get-MsalToken -ClientId $clientID -TenantId $tenantID -Interactive -Scope 'api://elven-logicapp-api/ManagedDevices.Read' -RedirectUri 'http://localhost'


MSAL.PS can be used both for Windows PowerShell, and for PowerShell Core, so in the above commands, I show both. Note that the redirect URI for MSAL.PS on PowerShell Core need to be http://localhost. You also need to add that redirect URI to the App Registration:

Running the above command will prompt an interactive logon, and should return a successful response saved in the $tokenResponse variable.

We can verify the response, for example checking scopes or copying the Access Token to the clipboard so that we can check the token in a JWT debugger:

# Check Token Scopes
$tokenResponse.Scopes

# Copy Access Token to Clipboard
$tokenResponse.AccessToken | Clip

In the first blog post of this article series I covered how you can use Windows PowerShell and Core to use Invoke-RestMethod for calling the Logic App, here is an example where I call my Logic App using the Access Token (in PowerShell Core):

# Set variable for Logic App URL
$logicAppUrl = "https://prod-05.westeurope.logic.azure.com:443/workflows/d429c07002b44d63a388a698c2cee4ec/triggers/request/paths/invoke?api-version=2016-10-01"

# Convert Access Token to a Secure String for Bearer Token
$bearerToken = ConvertTo-SecureString ($tokenResponse.AccessToken) -AsPlainText -Force

# Invoke Logic App using Bearer Token
Invoke-RestMethod -Method Post -Uri $logicAppUrl -Authentication OAuth -Token $bearerToken

And I can verify that it works:

Great. I now have a couple of alternatives for calling my Logic App securely using Azure AD OAuth. In the next section we will get into how we can do authorization checks inside the Logic App.

Authorization inside Logic App

While the Logic App can have an authorization policy that verifies any claims like issuer and audience, or other custom claims, we cannot use that if we want to authorize inside the logic app based on scopes, roles etc.

In this section we will look into how we can do that.

Include Authorization Header in Logic Apps

First we need to include the Authorization header from the OAuth access token in the Logic App. To do this, open the Logic App in code view, and add the operationOptions to IncludeAuthorizationHeadersInOutputs for the trigger like this:

        "triggers": {
            "manual": {
                "inputs": {
                    "schema": {}
                },
                "kind": "Http",
                "type": "Request",
                "operationOptions": "IncludeAuthorizationHeadersInOutputs"
            }
        }

This will make the Bearer Token accessible inside the Logic App, as explained in detail in my previous post: Protect Logic Apps with Azure AD OAuth – Part 1 Management Access | GoToGuy Blog. There I also showed how to decode the token to get the readable JSON payload, so I need to apply the same steps here:

After applying the above steps, I can test the Logic App again, and get the details of the decoded JWT token, for example of interest will be to check the scopes:

Implement Logic to check the Scopes

When I created the LogicApp API app registration, I added two scopes: ManagedDevices.Read and ManagedDevices.Read.All. The authorization logic I want to implement now is to only let users calling the Logic App and that has the scope ManagedDevices.Read.All to be able to get ALL managed devices, or to get managed devices other than their own devices.

The first step will be to check if the JWT payload for scope “scp” contains the ManagedDevices.Read.All. Add a Compose action with the following expression:

contains(outputs('Base64_to_String_Json').scp,'ManagedDevices.Read.All')

This expression will return either true or false depending on the scp value.

Next after this action, add a Condition action, where we will do some authorization checks. I have created two groups of checks, where one OR the other needs to be true.

Here are the details for these two groups:

  • Group 1 (checks if scp does not contain ManagedDevices.Read.All and calling user tries to get All managed devices):
    • Outputs('Check_Scopes') = false
    • empty(triggerBody()?['userUpn']) = true
  • Group 2 (checks if scp does not contain ManagedDevices.Read.All, and tries to get managed devices for another user than users’ own upn):
    • Outputs('Check_Scopes') = false
    • triggerBody()?['userUpn'] != Outputs('Base64_to_String_Json')['preferred_username']

If either of those two groups is True, then we know that the calling user tries to do something the user is not authorized to do. This is something we need to give a customized response for. So inside the True condition, add a new Response action with something like the following:

I’m using a status code of 403, meaning that the request was successfully authenticated but was missing the required authorization for the resource.

Next, add a Terminate action, so that the Logic App stops with a successful status. Note also that on the False side of the condition, I leave it blank because I want it to proceed with the next steps in the Logic Apps.

Test the Authorization Scope Logic

We can now test the authorization scopes logic implemented above. In Postman, either use an existing Access Token or get a new Token that only include the ManagedDevices.Read scope.

Then, send a request with an empty request body. You should get the following response:

Then, try another test, this time specifying another user principal name than your own, which also should fail:

And then test with your own user principal name, which will match the ‘preferred_username’ claim in the Access Token, this should be successful and return your devices:

Perfect! It works as intended, normal end users can now only request their own managed devices.

Let’s test with an admin account and the ManagedDevices.Read.All scope. In Postman, add that scope, and get a new Access Token:

When logging in with a user that has admin privileges you will now get a Token that has the scope for getting all devices, for which your testing should return 200 OK for all or any users devices:

Adding Custom Claims to Access Token

In addition to the default claims and scopes in the Access Token, you can customize a select set of additional claims to be included in the JWT data payload. Since the Access Token is for the resource, you will need to customize this on the App Registration for the LogicApp API.

In Azure AD, select the App Registration for the API, and go to API permissions first. You need to add the OpenID scopes first. Add the following OpenID permissions:

Your API App Registration should look like this:

Next, go to Token configuration. Click Add optional claim, and select Access Token. For example you can add the ipaddr and upn claims as I have done below:

Note the optional claims listed for the resource API registration:

Next time I get a new access token, I can see that the claims are there:

Summary of User Authorization so far

What we have accomplished now is that users can get an Access Token for the Logic App API resource. This is the first requirement for users to be able to call the Logic App, that they indeed have a Bearer Token in the Authorization Header that includes the configured issuer and audience.

In my demos I have shown how to get an access token using Postman (Authorization Code Flow) and a Public Client using MSAL.PS. But you can use any kind of Web application, browser/SPA or, Client App, using any programming libraries that either support MSAL or OpenID Connect and OAuth2. Your solution, your choice πŸ˜‰

After that I showed how you can use scopes for delegated permissions, and how you can do internal authorization logic in the Logic App depending on what scope the user has consented to/allowed to.

We will now build on this, by looking into controlling access and using application roles for principals.

Assigning Users and Restricting Access

One of the most powerful aspects of exposing your API using Microsoft Identity Platform and Azure AD is that you now can control who can access your solution, in this case call the Logic App.

Better yet, you can use Azure AD Conditional Access to apply policies for requiring MFA, devices to be compliant, require locations or that sign-ins are under a certain risk level, to name a few.

Let’s see a couple of examples of that.

Require User Assignment

The first thing we need to do is to change the settings for the Enterprise Application. We created an App registration for the LogicApp Client, for users to able to authenticate and access the API. From that LogicApp Client, you can get to the Enterprise Application by clicking on the link for Managed application:

In the Enterprise App, go to Properties, and select User assignment required:

We can now control which users, or groups, that can authenticate to and get access to the Logic App API via the Client:

If I try to log in with a user that is not listed under Users and groups, I will get an error message that the “signed in user is not assigned to a role for the application”:

PS! The above error will show itself a little different based on how you authenticate, the above image is using a public client, if you use Postman, the error will be in the postman console log, if you use a web application you will get the error in the browser etc.

Configuring Conditional Access for the Logic App

In addition to controlling which users and groups that can access the Logic App, I can configure a Conditional Access policy in Azure AD for more fine grained access and security controls.

In your Azure AD blade, go to Security and Conditional Access. If you already have a CA policy that affects all Applications and Users, for example requiring MFA, your LogicApp API would already be affected by that.

Note that as we are protecting the resource here, your Conditional Access policy must be targeted to the LogicApp API Enterprise App.

Click to create a new policy specific for the Logic App API, as shown below:

For example I can require that my Logic App API only can be called from a managed and compliant device, or a Hybrid Azure AD Joined device as shown below:

If I create that policy, and then tries to get an access token using a device that are not registered or compliant with my organization, I will get this error:

Summary of Restricting Access for Users and Groups

With the above steps we can see that by adding an Azure AD OAuth authorization policy to the Logic App, we can control which users and groups that can authenticate to and get an Access Token required for calling the Logic App, and we can use Conditional Access for applying additional fine grained access control and security policies.

So far we have tested with interactive users and delegated permission acccess scenarios, in the next section we will dive into using application access and roles for authorization scenarios.

Adding Application Access and Roles

Sometimes you will have scenarios that will let application run as itself, like a deamon or service, without requiring an interactive user present.

Comparing that to the OIDC and OAuth flow from earlier the Client will access the Resource directly, by using an Access Token aquired from Azure AD using the Client Credentials Flow:

Using the Client Credentials Flow from Postman

Back in the Postman client, under the Authorization tab, just change the Grant Type to Client Credentials like the following. NB! When using application access, there are no spesific delegated scopes, so you need to change the scope so that it refers to .default after the scope URI:

Click Get New Access Token, and after successfully authenticating click to Use Token. Copy the Token to the Clipboard, and paste to a JWT debugger. Let’s examine the JWT payload:

Note that the audience and issuer is the same as when we got an access token for an end user, but also that the JWT payload does not contain any scopes (scp) or any other user identifiable claims.

Using the Client Credentials Flow from MSAL.PS

To get an Access Token for an application client in MSAL.PS, run the following commands:

# Set Client and Tenant ID
$clientID = "cd5283d0-8613-446f-bfd7-8eb1c6c9ac19"
$tenantID = "104742fb-6225-439f-9540-60da5f0317dc"
# Set Client Secret as Secure String (keep private)
$clientSecret = ConvertTo-SecureString ("<your secret in plain text") -AsPlainText -Force

# Get Access Token using Client Credentials Flow and Default Scope
$tokenResponse = Get-MsalToken -ClientId $clientID -ClientSecret $clientSecret -TenantId $tenantID -Scopes 'api://elven-logicapp-api/.default'

You can then validate this Token and copy it to a JWT debugger:

# Copy Access Token to Clipboard
$tokenResponse.AccessToken | Clip

Calling the Logic App using Client Application

We can send requests to the Logic App using an Access Token in an application by including it as a Bearer Token in the Authorization Header exactly the same way we did previously, however it might fail internally if the Logic App processing of the access token fails because it now contains a different payload with claims:

Looking into the run history of the Logic App I can see that the reason it fails is that it is missing scp (scopes) in the token.

This is expected when authenticating as an application, so we will fix that a little later.

A few words on Scopes vs. Roles

In delegated users scenarios, permissions are defined as Scopes. When using application permissions, we will be using Roles. Role permissions will always be granted by an admin, and every role permission granted for the application will be included in the token, and they will be provided by the .default scope for the API.

Adding Application Roles for Applications

Now, let’s look into adding Roles to our LogicApp API. Locate the App registration for the API, and go to the App roles | Preview blade. (this new preview let us define roles in the GUI, where until recently you had to go to the manifest to edit).

Next, click on Create app role. Give the app role a display name and value. PS! The value must be unique, so if you already have that value as a scope name, then you need to distinguish it eg. by using Role in the value as I have here:

The allowed member types give you a choice over who/what can be assigned the role. You can select either application or user/groups, or both.

Add another App Role as shown below:

You should now have the following two roles:

Assigning Roles to Application

I recommend that you create a new App Registration for application access scenarios. This way you can avoid mixing delegated and application permissions in the same app registration, it will make it easier to differentiate user and admins consents, and secret credentials will be easier to separate, and you can use different settings for restricting access using Azure AD Users/Groups and Conditional Access.

So create a new App registration, call it something like (Yourname) LogicApp Application Client:

Choose single tenant and leave the other settings as default. Click Register and copy the Application (Client ID) and store it for later:

Next, go to Certificates & secrets, and create a new Client secret:

Copy the secret and store it for later.

Go to API permissions, click Add a permission, and from My APIs, find the LogicApp API. Add the Application permissions as shown below, these are the App Roles we added to the API earlier:

Under API permissions you can remove the Microsoft Graph user.read permission, it won’t be needed here, the two remaining permissions should be:

These you NEED to grant admin consent for, as no interactive user will be involved in consent prompt:

The admin consent are granted as shown below:

Now we can test getting access token via this new app registration, either use Postman or MSAL.PS , remember to use the new app (client) id and app (client) secret. I chose to add the two values to my Postman environment like this:

Next, change the token settings for Client Credentials flow so that the Client ID and Secret use the new variable names. Click to Get New Access Token:

After successfully getting the access token, click Use Token and copy it to clipboard so we can analyze it in the JWT debugger. From there we can indeed see that the roles claims has been added:

We will look for these roles claims in the Logic App later. But first we will take a look at how we can add these roles to users as well.

Assigning Roles to Users/Groups

Adding roles to users or groups can be used for authorizing access based on the roles claim. Go to the Enterprise App for the Logic App API registration, you can get to the Enterprise App by clicking on the Managed application link:

In the Enterprise App, under Users and Groups, you will already see the ServicePrincipal’s for the LogicApp Application Client with the Roles assigned. This is because these role permissions were granted by admin consent:

Click on Add user/group, add for a user in your organization the selected role:

You can add more users or groups to assigned roles:

Lets do a test for this user scenario. We need to do an interactive user login again, so change to using Authorization Code Flow in Postman, and change to the originial ClientID and ClientSecret:

Click to Get New Access Token, authenticate with your user in the browser (the user you assigned a role to), and then use the token and copy it to clipboard. If we now examine that token and look at the JWT data payload, we can see that the user has now a role claim, as well as the scope claim:

We can now proceed to adjust the authorization checks in the Logic App.

Customizing Logic App to handle Roles Claims

Previously in the Logic App we did checks against the scopes (scp claim). We need to do some adjustment to this steps, as it will fail if there are no scp claim in the Token:

Change to the following expression, with a if test that returns false if no scp claim, in addition to the original check for scope to be ManagedDevices.Read.All:

This is the expression used above:

if(empty(outputs('Base64_to_String_Json')?['scp']),false,contains(outputs('Base64_to_String_Json').scp,'ManagedDevices.Read.All'))

Similary, add a new Compose action, where we will check for any Roles claim.

This expression will also return false if either the roles claim is empty, or does not contain the ManagedDevices.Role.Read.All:

if(empty(outputs('Base64_to_String_Json')?['roles']),false,contains(outputs('Base64_to_String_Json').roles,'ManagedDevices.Role.Read.All'))

Next we need to add more checks to the authorization logic. Add a new line to the first group, where we also check the output of the Check Roles action to be false:

In the above image I’ve also updated the action name and comment to reflect new checks.

To the second group, add two more lines, where line number 3 is checking outputs from Check Roles to be false (same as above), and line 4 do a check if the roles claim contains the role ManagedDevices.Role.Read:

The complete authorization checks logic should now be:

And this is the summary of conditions:

  • Group 1 (checks if scp does not contain ManagedDevices.Read.All and roles does not contain ManagedDevices.Role.Read.All and calling user tries to get All managed devices):
    • Outputs('Check_Scopes') = false
    • empty(triggerBody()?['userUpn']) = true
    • Outputs('Check_Roles') = false
  • Group 2 (checks if scp does not contain ManagedDevices.Read.All and roles does not contain ManagedDevices.Role.Read.All, and tries to get managed devices for another user than users’ own upn, and roles does not contain ManagedDevices.Role.Read):
    • Outputs('Check_Scopes') = false
    • triggerBody()?['userUpn'] != Outputs('Base64_to_String_Json')['preferred_username']
    • Outputs('Check_Roles') = false
    • contains(outputs('Base64_to_String_Json')?['roles'],'ManagedDevices.Role.Read') = false

If any of the two groups of checks above returns true, then it means that the request was not authorized. To give a more customized response, change the response action like the following:

In the above action I have changed that response is returned as a JSON object, and then changed the body so that it returns JSON data. I have also listed the values from the token that the user/application use when calling the Logic App. The dynamic expression for getting roles claim (for which will be in an array if there are any roles claim) is:
if(empty(outputs('Base64_to_String_Json')?['roles']),'',join(outputs('Base64_to_String_Json')?['roles'],' '))
And for getting any scopes claim, which will be a text string or null:
outputs('Base64_to_String_Json')?['scp']

Test Scenario Summary

I’ll leave the testing over to you, but if you have followed along and customized the Logic App as I described above, you should now be able to verify the following test scenarios:

User/AppScopeRolesResult
UserManagedDevices.ReadCan get own managed devices.
Not authorized to get all devices or other users’ managed devices.
User (Admin)ManagedDevices.Read.AllCan get any or all devices.
UserManagedDevices,ReadManagedDevices.Role.ReadCan get own managed devices.
Can get other users’ managed devices by userUpn.
Not authorized to get all devices.
UserManagedDevices.ReadManagedDevices.Role.Read.AllCan get any or all devices.
ApplicationManagedDevices.Role.ReadCan any users’ managed devices by userUpn.
Not authorized to get all devices.
ApplicationManagedDevices.Role.Read.AllCan get any or all devices.

When testing the above scenarios, you need a new access token using either authorization code flow (user) or client credentials (application). For testing with roles and user scenarios, you can change the role assignments for the user at the Enterprise Application for the LogicAPI API. For testing with roles with application scenarios, make sure that you only grant admin consent for the applicable roles you want to test.

Final Steps and Summary

This has been quite the long read. The goal of this blog post was to show how your Logic App workflows can be exposed as an API, and how Azure AD OAuth Authorization Policies can control who can send requests to the Logic App as well as how you can use scopes and roles in the Access Token to make authorization decisions inside the Logic App. And even of more importance, integrating with Azure AD let’s you control user/group access, as well as adding additional security layer with Conditional Access policies!

My demo scenario was to let the Logic App call Microsoft Graph and return managed devices, which require privileged access to Graph API, and by exposing the Logic App as an API I can now let end users/principals call that Logic App as long as they are authorized to do so using my defined scopes and/or roles. I can easily see several other Microsoft Graph API (or Azure Management APIs, etc) scenarios using Logic App where I can control user access similarly.

Note also that any callers of the Logic App that now will try to call the Logic App using SAS access scheme will fail, as a Bearer Token is expected in the Authorization Header and the custom authorization actions that has been implemented. You might want to implement some better error handling if you like.

There’s an added bonus at the end of this article, where I add the filters for getting managed devices. But for now I want to thank you for reading and more article in this series will come later, including:

  • Calling Logic Apps protected by Azure AD from Power Platform
  • Protecting Logic App APIs using Azure API Management (APIM)

Bonus read

To complete the filtering of Managed Devices from Microsoft Graph, the Logic App prepared inputs of operatingSystem and osVersion in addition to userUpn. Let’s how we can implement that support as well.

After the initialize variable ManagedDevices action, add a Compose action. In this action, which I rename to operatingSystemFilter, I add a long dynamic expression:

This expression will check if the request trigger has an operatingSystem value, it not this value will be a empty string, but if not empty the I start building a text string using concat function where I build the filter string. There are some complexities here, amongs others using escaping of single apostroph, by adding another single apostroph etc. But this expression works:

if(empty(triggerBody()?['operatingSystem']),'',concat('/?$filter=operatingSystem eq ''',triggerBody()?['operatingSystem'],''''))

Next, add another Compose action and name it operatingSystemVersionFilter. This expression is even longer, checking the request trigger for osVersion, and if empty, it just returns the operatingSystemFilter from the previos action, but if present another string concat where I ‘and’ with the previous filter:

The expression from above image:

if(empty(triggerBody()?['osVersion']),outputs('operatingSystemFilter'),concat(outputs('operatingSystemFilter'),' and startswith(osVersion,''',triggerBody()?['osVersion'],''')'))

We can now add that output to the Graph queries, both when getting all or a specific user’s devices:

I can now add operatingSystem and osVersion to the request body when calling the Logic App:

And if I check the run history when testing the Logic App, I can see that the filter has been appended to the Graph query:

You can if you want also build more error handling logic for when if users specify the wrong user principalname, or any other filtering errors that may occur because of syntax etc.

That concludes the bonus tip, thanks again for reading πŸ™‚

Protect Logic Apps with Azure AD OAuth – Part 1 Management Access

Azure Logic Apps are great for creating workflows for your IT automation scenarios. Logic App workflows can be triggered using a variety of sources and events, including schedules, but a popular trigger is using a HTTP trigger for starting the Logic App workflow interactively or on-demand from outside the Logic App.

To trigger a Logic App using a HTTP trigger, you need to know the endpoint URL, for example:

This URL consist of the endpoint address of the Logic App and workflow trigger, and with the following query parameters:

  • api-version
  • sp (specifies permissions for permitted HTTP methods to use)
  • sv (SAS version to use)
  • sig (shared access signature)

Anyone with access to this URL and query parameters kan trigger the Logic App, so it’s very important to protect it from unauthorized access and use.

In this multi part blog post series we will look into how Logic Apps can be protected by Azure AD.

Scenarios this multi-part blog post articles will cover:

  • Provide Management Access Tokens and Restrict Issuer and Audience via OAuth
  • Restrict External Guest User Access
  • Expose Logic App as API
  • Restrict permitted Enterprise Application Users and Groups and Conditional Access policies.
  • Scopes and Roles Authorization in Logic Apps.
  • Logic Apps and APIM (Azure API Management).

Lets first look at the other methods for protecting Logic Apps you should be aware of.

Protect Logic Apps Keys and URLs

Before we move on to protecting Logic Apps with Azure AD Open Authentication (OAuth), lets take a quick summary of other protections you should be aware of:

  • Regenerate access keys. If you have reason to think SAS keys are shared outside your control, you can regenerate and thus making previous SAS keys invalid.
  • Create expiring Callback URLs. If you need to share URLs with people outside your organization or team, you can limit exposure by creating a Callback URL that expire on a certain date and time.
  • Create Callback URL with primary or secondary key. You can select to create the Callback URL with the specified primary or secondary SAS key.

The above methods should be part of any governance and security strategy for protecting Logic Apps that perform privilieged actions or might return sensitive data.

Protect Logic Apps via restricting inbound IP address

Another way to protect Logic Apps is to restrict from where the Logic App can be triggered via inbound IP address restrictions.

This opens up scenarios where you can specify your datacenter IP ranges, or only let other Logic Apps outbound IP addresses call nested Logic Apps, or only allow Azure API management to call Logic App.

Protect Logic Apps with Azure AD OAuth

By creating an Authtorization Policy for your Logic App you can use a Authorization header with a Bearer Token and require that the token contains the specified issuer, audience or other claims. Showing how that works in detail, and usable scenarios will be the main focus for this blog post.

Let’s start by building a basic Logic App we can use for demo purpose.

Creating a basic Logic App with HTTP Trigger and Response

In you Azure Subcription, create a new Logic App, specifying to use a HTTP trigger. In my example below I have named my Logic App “logicapp-test-auth”:

Next, add a Parse JSON action, where the Content is set to the trigger headers, as shown below. I’ve just specified a simple schema output, this can be customized later if needed:

After that activity, add a Response action to return data to the caller. In my example below I return a Status Code of 200 (OK), and set the Content-Type to application/json, and return a simple JSON body of UserAgent where the value is set to the parsed header output from the trigger, using dynamic expression:
body('Parse_JSON_Headers')?['User-Agent']

Testing Logic App with Postman

A great way to test and explore HTTP and REST API calls from your client is to use Postman (Download Postman | Try Postman for Free). When testing the above Logic App, paste in the HTTP POST URL for your trigger, and set the method to POST as shown below:

From the above image, you can see the URL, and also the query parameters listed (api-version, sp, sv, and sig, remember that these should be shared publicly).

When I send the request, it will trigger the Logic App, and should response back:

We can also verify the run history for the Logic App:

We have now successfully tested the Logic App using SAS authentication scheme, and can proceed to adding Azure AD OAuth. First we need to create an Authorization Policy.

Creating an Azure AD Authorization Policy

Under Settings and Authorization for your Logic App, add a new Authorization Policy with your name, and add the Issuer claim for your tenant. Issuer will be either https://sts.windows.net/{your-tenant-id}/ or https://login.microsoftonline.com/{your-tenant-id}/ depending on the version of the Access Token:

We will add more Claims later, but for now we will just test against the Issuer. Before we can test however, we need to get an Access Token. There are several ways to easily get an access token, basically we can consider one of the following two scenarios:

  1. Aquire an Access Token for well known Azure Management Resource Endpoints.
  2. Create an App Registration in Azure AD exposing an API.

We’ll cover App Registration and more advanced scenarios later, but for now we will get an Access Token using well known resource endpoints for Azure management.

PS! Just a quick note on Access Tokens aquired for Microsoft Graph resources: These cannot be used for Logic Apps Azure AD OAuth authorization policies, because Graph access tokens does not allow for signature validation.

Management Access Tokens

The following examples require that you either have installed Azure CLI (Install the Azure CLI | Microsoft Docs) or Az PowerShell (Install Azure PowerShell with PowerShellGet | Microsoft Docs).

Azure CLI

If you haven’t already, you will first need to login to Azure using az login. You can login interactively using default browser which supports modern authentication, including MFA, but if you are running multiple browsers and profiles it might be easier to use the device code flow:

az login --use-device-code

You will be prompted to open the microsoft.com/devicelogin page and enter the supplied device code, and after authentication with your Azure AD account, you will get a list of all subscriptions you have access to.

PS! If your account has access to subscriptions in multiple tenants, you can also specify which tenant to log into using:

az login --tenant elven.onmicrosoft.com --use-device-code

To get an Access Token you can just run az account get-access-token, like the following:

Let’s save that into a variable and get the token:

$accessToken = az account get-access-token | ConvertFrom-Json
$accessToken.accessToken | Clip

The above command copies the Access Token to the Clipboard. Let’s take a look at the token. Open the website jwt.ms or jwt.io, and paste in the token. From the debugger you can look at the decoded token payload. The most interesting part for now is the issuer (iss) and audience (aud), which tells us where the token has been issued from, and to which audience:

As we can see from above, the audience for the token is “management.core.windows.net”. You can also get an access token for a specific resource endpoint using:

$accessToken = az account get-access-token --resource-type arm | ConvertFrom-Json

To show all available resource endpoints use:

az cloud show --query endpoints

Now that we have the method to get the access token using Az Cli, lets take a look at Az PowerShell as well. For reference for az account command and parameters, see docs here: az account | Microsoft Docs

Azure PowerShell

First you need to login to your Azure Subscription by using:

Connect-AzAccount

If your account has access to multiple subscriptions in multiple tenant, you can use the following command to specify tenant:

Connect-AzAccount -Tenant elven.onmicrosoft.com

If there are multiple subscriptions, you might need to specify which subscription to access using Set-AzContext -Subscription <Subscription>. Tip, use Get-AzContext -ListAvailable for listing available subscriptions.

To get an access token using Az PowerShell, use the following command to save to variable and copy to clipboard:

$accessToken = Get-AzAccessToken
$accessToken.Token | Clip

We can once again look at the JWT debugger to verify the token:

As with Az CLI, you can also specify resource endpoint by using the following command in Az PowerShell specifying the resource Url:

$accessToken = Get-AzAccessToken -ResourceUrl 'https://management.core.windows.net'

Now that we have the Access Token for an Azure Management resource endpoint, let’s see how we can use that against the Logic App.

Use Bearer Token in Postman

From the previous test using Postman earlier in this article, go to the Authorization section, and specify Bearer Token, and then Paste the management access token you should still have in your clipboard like the following:

When clicking Send request, observe the following error:

We cannot combine both SAS (Shared Access Signature) and Bearer Token, so we need to adjust the POST URL to the Logic Apps. In Postman, this can be easily done in Postman under Params. Deselect the sp, sv and sig query parameters like the following, which will remove these from the POST URL:

When you now click Send request, you should get a successful response again, provided that tha access token is valid:

Perfect! We have now authorized triggering the Logic App using Azure AD OAuth, based on the Authorization policy:

And the Access Token that match that Issuer:

I will now add the audience to the Authorization Policy as well, so that only Access Tokens for the management endpoint resource can be used:

Any HTTP requests to the Logic App that has a Bearer Token that does not comply with the above Authorization Policy, will received this 403 – Forbidden error:

Test using Bearer Token in Azure CLI

You can trigger HTTP REST methods in Azure CLI using az rest --method .. --url ...

When using az rest an authorization header with bearer token will be automatically added, trying to use the url as resource endpoint (if url is one of the well known resource endpoints). As we will be triggering the Logic App endpoint as url, we need to specify the resource endpoint as well. In my example, I will run the following command for my Logic App:

az rest --method POST --resource 'https://management.core.windows.net/' --url 'https://prod-72.we
steurope.logic.azure.com:443/workflows/2fa8c6d0ed894b50b8aa5af7abc0f08b/triggers/manual/paths/invoke?api-
version=2016-10-01'

From above, I specify the resource endpoint of management.core.windows.net, from which the access token will be aquired for, and for url I specify my Logic App endpoint url, without the sp, sv and sig query parameters. This results in the following response:

So the Logic App triggered successfully, this time returning my console (Windows Terminal using Azure CLI).

Test using Bearer Token in Azure PowerShell

I will also show you how you can do a test using Az PowerShell. Make sure that you get an access token and saving the bearer token to a variable using this command first:

$accessToken = Get-AzAccessToken
$bearerToken = $accessToken.Token

I will also set the Logic App url to a variable for easier access:

$logicAppUrl = 'https://prod-72.westeurope.logic.azure.com:443/workflows/2fa8c6d0ed894b50b8aa5af7abc0f08b/triggers/manual/paths/invoke?api-version=2016-10-01'

There are 2 ways you can use Az PowerShell, either using Windows PowerShell or PowerShell Core.

For Windows PowerShell, use Invoke-RestMethod and add a Headers parameter specifying the Authorization header to use Bearer token:

Invoke-RestMethod -Method Post -Uri $logicAppUrl -Headers @{"Authorization"="Bearer $bearerToken"}

Running this should return this successfully, specifying my Windows PowerShell version (5.1) as User Agent:

For PowerShell Core, Invoke-RestMethod has now support for using OAuth as authentication, but I first need to convert the Bearer Token to a Secure String:

$accessToken = Get-AzAccessToken
$bearerToken = ConvertTo-SecureString ($accessToken.Token) -AsPlainText -Force

Then I can call the Logic App url using:

Invoke-RestMethod -Method Post -Uri $logicAppUrl -Authentication OAuth -Token $bearerToken

This should successfully return the following response, this time the User Agent is my PowerShell Core version (7.1):

Summary so far of Management Access Tokens and Logic Apps

At this point we can summarize the following:

  1. You can trigger your Logic App either by using SAS URL or using Bearer Token in Authorization Header, but not both at the same time.
  2. You can add an Azure AD Authorization Policy to your Logic App that specifies the Issuer and Audience, so that calling clients only can use Bearer Tokens from the specified issuer (tenant id), and audience (resource endpoint).
  3. While you cannot disable use of SAS signatures altogether, you can keep them secret, and periodically rollover, and only share the Logic App url endpoint and trigger path with clients.
  4. This is especially great for automation scenarios where users can use CLI or Azure PowerShell and call your Logic Apps securely using OAuth and Access Tokens.

In the next part we will look more into how we can customize the Logic App to get the details of the Access Token so we can use that in the actions.

Include Authorization Header in Logic Apps

You can include the Authorization header from the OAuth access token in the Logic App. To do this, open the Logic App in code view, and add the operationOptions to IncludeAuthorizatioNHeadersInOutputs for the trigger like this:

        "triggers": {
            "manual": {
                "inputs": {
                    "schema": {}
                },
                "kind": "Http",
                "type": "Request",
                "operationOptions": "IncludeAuthorizationHeadersInOutputs"
            }
        }

For subsequent runs of the Logic App, we can now see that the Authorization Header has been included:

And if we parse the headers output, we can access the Bearer Token:

If we want to decode that Bearer token to get a look into the payload claims, we can achieve that with some custom expression magic. Add a Compose action to the Logic App and use the following custom expression:

Let’s break it down:

  • The Replace function replaces the string ‘Bearer ‘ with blank (including the space after)
  • The Split function splits the token into the header, payload data, and signature parts of the JWT. We are interested in the payload, so refers to that with index [1]
split(replace(body('Parse_JSON_Headers')?['Authorization'], 'Bearer ',''), '.')[1]

Now it becomes a little tricky. We will have to use the base64ToString function to get the payload into readable string, but if the length of the payload isn’t dividable by 4 we will get an error. Therefore we need to see if we need to add padding (=), as explained here: (Base64 – Wikipedia).

First I get the length of the payload data, and then use modulo function to see if there are any remaining data after dividing by 4:

mod(length(outputs('Get_JWT_Payload')),4)

Then I can do a conditional logic, where I use concat to add padding (=) to make it dividable by 4:

if(equals(outputs('Length_and_Modulo'),1),concat(outputs('Get_JWT_Payload'),'==='),if(equals(outputs('Length_and_Modulo'),2),concat(outputs('Get_JWT_Payload'),'=='),if(equals(outputs('Length_and_Modulo'),3),concat(outputs('Get_JWT_Payload'),'='),outputs('Get_JWT_Payload'))))

After this I can use base64ToString to convert to a readable string object and format to JSON object:

json(base64ToString(outputs('Padded_JWT_Payload')))

Now that we have access to the claims, we can later be able to do some authorization in the Logic Apps, for example based on roles or scopes, but we can also get some information on which user that has called the Logic App.

In the Response action, add the following to return the Name claim:

And if I test the Logic App http request again, I can see at it indeed returns my name based on the claims from the access token:

We now have a way to identify users or principals calling the Logic App. The Authorization Policy for the Logic App now permits users and principals from my own organization (based on the issuer claim) and as long as the audience is for management.core.windows.net. But what if I want external access as well? Let’s add to the authorization policies next.

Add OAuth Authorization Policy for Guests

A logic app can have several Azure AD Authorization Policies, so if I want to let external guest users to be allowed to trigger the logic app, I will need to create another authorization policy that allows that issuer:

Lets also add the upn claim to the response, so it is easier to see which user from which tenant that triggered the Logic App:

When I now test with different users, internal to my tenant and external, I can see that it works and the response output is as expected:

Summary of Management Access Scenarios

The purpose of the above steps has been to provide a way for management scenarios, where users and principals can get an Access Token using one of the Azure Management well known endpoints, and provide that when calling the Logic App. The access token is validated using OAuth Authorization Policies, requiring specific issuer (tenant id) and audience (management endpoint). This way we can make sure that we don’t have to share the SAS details which lets users that have access to this URL call the Logic App without authentication.

In the next parts of this blog post articles, we will look into more advanced scenarios where we will expose the Logic App as an API and more.

Blog Series – Power’ing up your Home Office Lights: Part 10 – Subscribe to Graph and Teams Presence to automatically set Hue Lights based on my Teams Presence!

This blog post is part of the Blog Series: Power’ing up your Home Office Lights with Power Platform. See introduction post for links to the other articles in the series:
https://gotoguy.blog/2020/12/02/blog-series—powering-up-your-home-office-lights-using-power-platform—introduction/

In this last part of the blog series, we will build on the previous blog post where we could get the presence status from Teams to the Hue Power App. Now we will use Microsoft Graph and subscribe to change notifications for presence, so that both the Power App and my Hue Lights will automatically change status based on the presence.

In this blog post I will reuse the Custom Connector I created for managing Microsoft Graph Subscriptions in this previous blog post: Managing Microsoft Graph Change Notifications Subscriptions with Power Platform | GoToGuy Blog

To follow along, you will need at least to create the App Registration and the Custom Connector referred to in that blog post. You can also import the Custom Connector OpenAPI Swagger from this link: <MY GITHUB URL TO HERE>

Adding the Custom Connector to the PowerApp

In the Hue Power App, go to the View menu, and under Data click to “+ Add data source”. Add the MSGraph Subscription Connector as shown below. This way we can refer to this in the Hue Power App.

We are going to add the logic to creating the subscription based on this toggle button and the selected light source:

But before that we have somethings to prepare first. When creating a Graph Subscription, we will need to prepare a Webhook Url for where Graph will send its notifcations when the Teams presence changes. This will be handled in a Power Automate Flow, so lets create that first.

Creating the Flow for Graph Notifications and Hue Lights changes

Since I have built this all before, ref. https://gotoguy.blog/2020/10/24/managing-microsoft-graph-change-notifications-subscriptions-with-power-platform/, I will make a copy of the “Graph Notification – Presence Change” flow for this use case.

If you want to follow along, you will need to follow the instructions in that blog post first. After saving a copy, or if you created a new flow from blank using HTTP request webhook, you will need to copy the HTTP POST URL shown below, as that will be the “notification url” we will refer to later:

Next set some value that only you know for the secret client state:

The next part of the Flow are used to do a first-time validation of adding the change subscription, with Content-Type text/plain and request query containing a validation token. Microsoft Graph expects a response of status code 200 with the validation token back. If that is returned, Microsoft Graph will successfully create the subscription.

For subsequent requests, we must return a 202 Accepted response, and in the next step I parse the notification request body, so that we can look into what change we have been notified for:

Following the change notification, we can start looking into the change value. Firstly, I have added a verification of the secret client state I specified earlier, this is prevent misuse of the notification Url if that become known by others or used in the wrong context. After doing a simple test of the client state, where I do nothing if the client state don’t match, I can start building the logic behind the changes in presence status:

Inside the Switch Presence Status action, I will based on the availability status change, do a different case for each of the possible Teams Presence status values (see blog series post part 9 for explaining the different presence availability values):

Inside each of these cases I will define the light settings and colors, and after that call the Remote Hue API for setting the light. As you saw in part 8 of this blog series, in order to access the Hue API remotely I will need the following:

  • An Access Token to be included as a Bearer token in the Authorization Header
  • A username/whitelist identifier
  • The actual lightnumber to set the state for
  • A request body containing the light state, for example colors, brightness, on/off etc.

Remember, this Flow will be triggered from Microsoft Graph whenever there is a presence state change in Teams. So I need to be able to access/retreive the access token, username and for which lightnumber I created the subscription. This is how I will get it:

  • Access Token will be retreived via the Logic App I created in part 4 of the blog series.
  • Username/whitelist identifier will be retrieved via the SharePoint List i created in part 6, see below image.
  • However, I do need to store the lightnumber I will create the change notification for, and for this I will add a couple more columns in this list:

Customize the Configuration List for storing Subscription Details

I add the following two single-line-of-text columns to my List:

  • Subscribe Presence LightNumber. This will be the chosen Hue light I want to change when change notifications occur for Teams presence status.
  • Change Notification Subscription Id. This will be the Id I can refer back to when adding and removing the subscription when needed.

Customize the Flow for getting User Configuration and preparing Light States

Back to the Flow again, we need to add some actions. First, add a initialize variable action after the initialize SecretClientState action like here:

I set the type to Object and using the json function to create an empty json object. This variable will later be used for changing the light state.

Next, in the Flow after the “Parse Notification Body” action, add a “Get Items” action from SharePoint connector, and configure it to your site, list name and the following Filter Query:

My filter query:
first(body('Parse_Notification_Body')?['value'])?['subscriptionId']
will be used to find what username and light that have been set up for presence changes.

Next, lets set the variable for LigthState. Inside each of the Switch Cases, add the action Set Variable, and then set the variable to the chosen xy color code, as a json object like the following. This is for the color green:

Do the same for all of the other case, these are the values I have been using:

STATECOLORJSON VARIABLE
AwayYellowjson(‘{
“on”: true,
“bri”: 254,
“xy”: [ 0.517102, 0.474840 ],
“transitiontime”: 0
}’)
AvailableGreenjson(‘{
“on”: true,
“bri”: 254,
“xy”: [ 0.358189, 0.556853 ],
“transitiontime”: 0
}’)
AvailableIdleGreen (10% bright)json(‘{
“on”: true,
“bri”: 25,
“xy”: [ 0.358189, 0.556853 ],
“transitiontime”: 0
}’)
BusyRedjson(‘{
“on”: true,
“bri”: 254,
“xy”: [ 0.626564, 0.256591 ],
“transitiontime”: 0
}’)
BusyIdleRed (10% bright)json(‘{
“on”: true,
“bri”: 25,
“xy”: [ 0.626564, 0.256591 ],
“transitiontime”: 0
}’)
BeRightBackYellowjson(‘{
“on”: true,
“bri”: 254,
“xy”: [ 0.517102, 0.474840 ],
“transitiontime”: 0
}’)
DoNotDisturbRedjson(‘{
“on”: true,
“bri”: 254,
“xy”: [ 0.626564, 0.256591 ],
“transitiontime”: 0
}’)
OfflineGrey (10% bright)json(‘{
“on”: true,
“bri”: 25,
“xy”: [ 0.3146, 0.3303 ],
“transitiontime”: 0
}’)
PresenceUnknownWhitejson(‘{
“on”: true,
“bri”: 254,
“xy”: [ 0.3146, 0.3303 ],
“transitiontime”: 0
}’)

PS! The transitiontime is to get as close to realtime updates as possible. Add the colors similarly for rest of the states:

Get the Access Token and call Hue Remote API

Now we are ready to get the Access Token, and call the Hue Remote API with the selected light state.

First, add a HTTP action below the Switch Presence Status action, calling the Logic App previously created in part 4 of the blog series:

Next, add another HTTP request after, and this will call the Hue Remote API to set the lights:

When constructing Hue API URI above, I retreive the whitelist identifier for username with the following expression:

first(body('Get_My_Hue_User_Subscription')?['Value'])?['WhitelistIdentifier']

And then which light number with this expression:

first(body('Get_My_Hue_User_Subscription')?['Value'])?['SubscribePresenceLightNumber']

That should be the completion of this Flow. Remember to turn it on if needed. We are now ready for the last step.

Adding the Flow for Creating the Graph Subscription

In the beginning of this blog post I referred to the toggle “Sync Hue Lights with Teams” in the Power App. Now that we have prepared the Flow handling the notification Url, we need to add a new Flow that would handle the creating, or deletion, of Graph Subscriptions. As this is a toggle control, setting it to “On” should create a Graph subscription for the selected lights, and setting it to “Off” should remove that subscription again.

Create a new instant Flow with PowerApps as trigger:

Next, add an action for initialize variable for getting the UserDisplayName:

Use the following expression for getting the user display name:

triggerOutputs()['headers']['x-ms-user-name']

Next, add another initialize variable for getting the light number. After renaming the action, click on “Ask in PowerApps”:

Add another initialize variable, this time a boolean value, and for getting the value of the toggle sync control:

Next, we will retrieve our user config source from the SharePoint list again, this time filtered by the UserDisplayName variable:

We now need some logic to the next steps for the flow, lets start by the toogle button which will be either true or false:

If yes, that should mean that we either should create a new graph subscription, or update any exisiting ones.

Under Yes, add a new action. This action will call the Custom Connector I created in another blog post (https://gotoguy.blog/2020/10/24/managing-microsoft-graph-change-notifications-subscriptions-with-power-platform/). This Custom Connector should have the following actions:

Click on the Get Subscription action to add that. For the subscriptionId parameter I will refer to the first returned instance of any exisiting Graph Subscriptions I have in the SharePoint list returned earlier.

Here is the expression for your reference:

first(body('Get_My_Hue_User')?['Value'])?['ChangeNotificationSubscriptionId']

When running the Flow this action will either:

  • Return a 200 OK if the subscription is found, or if the SharePoint List has a blank value for ChangeNotificationSubscriptionId.
  • Return a 404 ResourceNotFound if the subscription is not found, this will happen if the subscription is expired. This is an error that will halt the Flow, so we need to handle it.

So lets start by getting the Status Code. I’ll do that by adding a compose action with the following expression:

outputs('Get_Graph_Subscription')['statusCode']

It’s also important to set that this action should run even if the Get Graph Subscription action fails:

Lets add another condition, where the outputs of the status code should be 200 (OK):

A status code of 200 will either indicate that either we found an existing Graph Subscription matching the configured subscription id from the SharePoint List, or that the list is blank and the Get Graph Subscription will return an empty array or any other Graph Subscriptions you might have. In the first case, we will just update the existing subscription, in the latter case we will create a new subscription. Lets start by adding another compose action:

Adding the Flow to the Hue Power App

Back in the Hue Power App, we can now link this Flow to the toggle control. With the sync toggle control selected, go to the Action menu, and then click on Power Automate. From there you should see the “Hue – Create Update Remove Graph Subscription” Flow, click to add it. On the OnChange event, add the Run parameters where the lightnumber value is read from the dropdown list and selected items lightnumber, and the toggle button value like this:

Blog Series – Power’ing up your Home Office Lights: Part 4 – Using Logic Apps to Get Access Token and Renew Access Token if needed

This blog post is part of the Blog Series: Power’ing up your Home Office Lights with Power Platform. See introduction post for links to the other articles in the series:
https://gotoguy.blog/2020/12/02/blog-series—powering-up-your-home-office-lights-using-power-platform—introduction/

After building the Logic App in part 3 that will authorize and get access token via Oauth2, we will now create another Logic App that will retrieve the Bearer Token from the Key Vault secret, and renew the Token using Refresh Token whenever it is expired.

Here is a short video where I walk through that Logic App scenario:

Create the Logic App and HTTP Trigger

The first thing you need to do, is to create a new Logic App in your Azure subscription. Select the Resource Group you have contributor access to, and give the Logic App a suitable name, as per your naming guidelines. This is the Logic App I created in my environment:

Add a HTTP request trigger for this Logic App as well:

In the Logic App Designer, make sure you hit Save on the Logic App before the next step. You will now be shown the URL, but first go down to the β€œAdd new parameter” and select Method and GET for method. This way your Logic App will trigger on HTTP GET requests.

Adding Logic App Identity and Key Vault Access

As this Logic App also will request secrets from Key Vault, we will need to add a Managed Service Identity and add that to the Key Vault access policy.

Go to Identity settings, and set the System assigned Identity to On:

Next, go to your Key Vault and under Access policies, add the the newly created Logic App with the following Secret permissions (Get, Set, List):

Add Actions for Getting or Renewing Bearer Token

The actions in this Logic App will retrieve the Bearer Token from the Key Vault and return the Access Token as a Response. If Token is expired, it will be renewed using the Refresh token.

Start by adding a HTTP request, and get the Secret for the Bearer Token like the following:

Next, add a Compose action, getting the outputs from the Get KV Secret Bearer Token action. This secret was stored as a Json Object, but will be returned as a String, so I have used the following custom expression to convert to Json:

json(outputs('Get_KV_Secret_Bearer_Token')?['body/value'])

Next, add the following Compose actions for getting the timestamps in Ticks, and converting to Epoch. See the previous blog post for explanation of why this is necessary, but we need to do this to be able to calculate wether the secret is expired or not:

For your convenience, I’ve added the custom expressions as comments to the actions above, or you can copy it from below:

ticks(utcNow())

ticks('1970-01-01T00:00:00Z')

div(sub(outputs('GetNowTimeStampInTicks'), outputs('Get1970TimestampInTicks')), 10000000)

Next, add a Condition action. Here we will check if the expiry date time of the secret is greater than the current calculated timestamp in Epoch:

Use the following custom expression for getting the “exp” attribute from Key Vault Secret:

outputs('Get_KV_Secret_Bearer_Token')?['body/attributes/exp']

If the secret hasn’t expired, we will return the access token as a Response action as shown below. Note that I will only return the access_token, not the complete Bearer Token stored in the Key Vault secret, as this also contains the refresh_token. The reasoning behind this is that the calling clients (users from PowerApps/Automate) only need the access_token.

As you see from above, I’ve built a Json body and schema for the response, and the custom expression returing the value of access_token is outputs('Compose_Bearer_Token')?['access_token'].

On the False side of the Condition, meaning that the Secret is expired, we will have the logic that renews the Bearer Token. First add two HTTP actions, for getting the Client Id and Client Secret from Key Vault:

Next, add another HTTP action, using Method POST we will send a request to the oauth2/refresh endpoint at Hue Remote API:

The refresh_token need to be sent in a Request Body, using the expression: outputs('Compose_Bearer_Token')?['refresh_token']

Remember to set Content-Type: application/x-www-form-urlencoded. And Authentication Type should be set to Basic, using the retrieved Client Id and Secret from Key Vault as username and password.

Refreshing the Token correctly will return a new Bearer Token. We now need to get and convert the time stamps to Epoch integer, to calulate when the Access Token expires. This is the same process as we used in the Logic App “logicapp-hue-authorize” in part 3 of this blog series. Add 3 new Compose actions like below:

For your convenience, here are the custom expressions used for the above actions:

addSeconds(utcNow(), int(body('Post_Refresh_Code_with_Basic_Auth_to_Update_Access_Token')?['access_token_expires_in']))

ticks(outputs('AccessToken_Expires_Utc'))

div(sub(outputs('GetTimestampInTicks'), outputs('Get1970TimestampInTicks')), 10000000)

Next step is to update the Bearer Token Secret in Key Vault with the new Token we received now and the new expiry date. Add a HTTP action like below:

We can now return the access_token using the HTTP action like below:

The last action we need to add is a default response if any accest_token could not be returned. This is important as we are going to call this Logic App using Power Automate Flows, and we need to have a response for any scenario. Add this after the condition action like below:

For the Null Response action, change the Configure run after setting like the following:

That should be it. Remember to secure outputs for any actions that return credential information:

Verify Logic App

We can now test the Logic App. You can use Postman, Invoke-RestMethod in PowerShell, or just run in the Browser your Logic App Http Trigger Url:

This should return your Access Token:

Looking at the Run History for the Logic App, we should see a sucessful run:

Summary and Next Steps

That should conclude this blog post. In this post, and the previous, we have built the logic behind authorizing and getting the Bearer Token for Philips Hue Remote API, as well as providing and refresh the Token when needed.

In the next part we are going to start building the solution in Power Automate. Thanks for reading, see you in the next part!

Blog Series – Power’ing up your Home Office Lights: Part 3 – Using Logic Apps to Authorize and Get Access Token using Oauth and Hue Remote API

This blog post is part of the Blog Series: Power’ing up your Home Office Lights with Power Platform. See introduction post for links to the other articles in the series:
https://gotoguy.blog/2020/12/02/blog-series—powering-up-your-home-office-lights-using-power-platform—introduction/

Now that we have registered the application for Hue Remote API, and stored the client Id and Secret in Azure Key Vault, we can start build the Logic App that will authorize and get access token via Oauth2.

Here is a short video where I introduce the concept:

Create the Logic App and HTTP Trigger

The first thing you need to do, is to create a new Logic App in your Azure subscription. Select the Resource Group you have contributor access to, and give the Logic App a suitable name, as per your naming guidelines:

Next, select HTTP request to be the trigger for the Logic App:

After that you will see the following in the Logic App designer:

Make sure you hit Save on the Logic App before the next step. You will now be shown the URL, but first go down to the “Add new parameter” and select Method and GET for method. This way your Logic App will trigger on HTTP GET requests, which is required for the Authorization Code flow with Hue:

Now copy this URL, and make sure that no one but you can access this URL, as this is a SAS (Shared Access Signature) URL that anyone in the world can send requests to if they know the URL. Save the Logic App.

Go back to your App Registration in the Hue Developers Portal, and change your temporary http://localhost/logicapp Callback URL to your Logic App URL:

This means that from now on, the Logic App will handle the authorization code for the Hue App. But first we will need to let the Logic App access the Key Vault.

Adding Logic App Identity and Key Vault Access

For the Logic App, under Settings and Identity, set system assigned managed identity to On:

After this setting is saved, you can later see the status and the object id of the service principal.

Next, under your Key Vault, click on Access Policies and Add Access Policy, from there selec the Get, Set and List Secret Management operations, and for principal search for and add the Logic App. This should look like this after adding:

With permissions in place, we are now ready to add actions to the Logic App.

Add Actions for getting Access Token

The first ting we need to do is to get the authorization code after the Hue App registration redirects back to the callback URL. This is returned as a querystring appended to the URL. Add a “Compose” action and use the following expression for getting the request queries:

(I’ve added the custom expression to comments for better visibility).

Then we need to get the Client Id and Secret from the Kay Vault. Add a HTTP action next, where we will use the Azure Rest API for getting the secret, and authenticate with the Managed Service Identity:

The URI above points to my Azure Key Vault URI, and the specified secret. The documentation for getting secrets can be seen here: Get Secret – Get Secret (Azure Key Vault) | Microsoft Docs.

The same applies to getting the Client Secret, add another HTTP action:

The get an access token from Hue Remote API we must either use Basic Authentication or Digest Authentication. Since I’m running this as a Logic App in a controlled environment and trusting the SSL encryption I will use Basic Authentication. In addition, I will secure the outputs from getting Client Id and Secret from Key Vault, so that other users cannot see those values from the run history:

This setting has been enabled for both the actions getting KV Secret Client Id and Client Secret:

For obtaining an Access Token with Basic Authentication the following header is required: Authorization: Basic <base64(clientid:clientsecret)>

This means that we need to base64 encode the clientid + “:” + clientsecret. This can be done using this lengthy expression, here in a “initialize variable” action:

This above action is just for reference though, as the HTTP action supports base64 encoding out of the box. So when posting to the token endpoint, the best way is to use the following:

(PS! Another way to do Basic Authentication in a HTTP action would be to add the Authorization header manually in the Action above with: “Basic <your calculated base64>” as value, and leaving the Authentication type to None.)

From the above settings, in the URI add the authorization code we got from the request queries earlier, using the expression:

outputs('Compose_Authorization_Code')?['code']

When selecting Authentication type to Basic, the username (client id) and password (secret) will automatically be base64 encoded. The values for username and password are the valies from the Get KV Secret Client actions earlier, in the following format:

body('Get_KV_Secret_Client_Id')?['value']

And this action will return the Bearer Token from Hue Remote API if everything is correctly inputted.

I also make sure that the output of this action is secured from viewing:

With the Bearer Token now retrieved, the next actions is to calculate the expiry time and write the Token back to the Key Vault secret.

Add Actions for getting expiry time and write Token to Key Vault

The Bearer Token returned by Hue Remote API will be in the format of the following masked response:

The _expires_in values are in seconds, so that means that the Access Token is valid for 7 days, and the Refresh Token about 112 days. It would then make sense to only refresh the token when needed.

Lets start by calculating when the access_token expires, with the following expression in a Compose action:

addSeconds(utcNow(), int(body('Post_Auth_Code_with_Basic_Auth_to_Get_Access_Token')?['access_token_expires_in']))

The above expression takes the current time and add the number of seconds for when the access token expires.

This will return a new datetime 7 days ahead. This value will be used to set the expiry time on the Key Vault secret for Bearer Token. By setting an expiry time I can later calculate if I need to refresh the Access Token or not.

But it’s not that easy.. The calculated time above will need to be converted to Epoch (32-bit “Unix”) integer format to be able to set the Key Vault secret “exp” attribute. This isn’t so clear when seeing the API docs, Set Secret – Set Secret (Azure Key Vault) | Microsoft Docs, so took me a little trial and error. And I found great help in this blog article: https://devkimchi.com/2018/11/04/converting-tick-or-epoch-to-timestamp-in-logic-app/.

Based on this I need to convert the timestamp to Ticks (64-bit). Ticks is a built in function in Logic Apps, but to be able to convert to Epoch I will need to calculate the difference in ticks between when the Access Token expire, and the first value of Epoch which is 1970-01-01T00:00:00Z. This is well explained in the above reference blog, but here are my resulting actions.

After calculating the Access Token expiry, I add a compose action which converts this to Ticks:

Using the following expression: ticks(outputs('AccessToken_Expires_Utc'))

Then I need to find the 1970-01-01T00:00:00Z value in Ticks:

Using this expression: ticks('1970-01-01T00:00:00Z')

Then we can convert this to Epoch by subtracting the two Ticks values calculated above, and divide by 1 million:

This is the expression used above: div(sub(outputs('GetTimestampInTicks'), outputs('Get1970TimestampInTicks')), 10000000)

We now have the correct format for the “exp” attribute to update the Key Vault secret. Add a new HTTP action and configure like below:

Remember to secure the Output for this action also:

Finally we can finish this Logic App by adding a Response action and do a quick test to verify that everything works as expected.

Adding Response action and verify Logic App

Add a Response action with status code 200 and a body like below:

Tips: It can be difficult to troubleshoot the Logic App when securing outputs, so you might hold back in that when testing. It will show your secrets in the run history though, so it might be best to do this in a test enviroment depending on your needs.

Now we can test. Construct the URL for authorizing the App again, like we did in Part 1:

https://api.meethue.com/oauth2/auth?clientid=&response_type=code&state=elvenanystring&appid=elven_demo_hue_app&deviceid=elven_demo&devicename=Elven Demo

Paste it in the Browser, and after granting access to the App in Hue Developer portal:

You should be redirected to the Logic App:

.. and with a respons success!

Looking at the Run history, we can verify the steps were successful:

You can also look into the inputs and outputs of the actions, except the actions where we secured the output:

We can also verify that the Key Vault secret storing the Bearer Token has been updated and have an Expiration Date one week forward:

Summary and next steps

That concludes this blog post. Thanks for reading this far, in the next part we will build the Logic App that will respond back the Access Token and renew using Refresh Token if needed.