Unable to get access to Key Vault using Azure MSI on App Service

Question

I have enabled Managed Service Identities on an App Service. However, my WebJobs seem unable to access the keys.

They report:

Tried the following 3 methods to get an access token, but none of them worked. Parameters: Connectionstring: [No connection string specified], Resource: https://vault.azure.net, Authority: . Exception Message: Tried to get token using Managed Service Identity. Unable to connect to the Managed Service Identity (MSI) endpoint. Please check that you are running on an Azure resource that has MSI setup. Parameters: Connectionstring: [No connection string specified], Resource: https://vault.azure.net, Authority: https://login.microsoftonline.com/common. Exception Message: Tried to get token using Active Directory Integrated Authentication. Access token could not be acquired. password_required_for_managed_user: Password is required for managed user Parameters: Connectionstring: [No connection string specified], Resource: https://vault.azure.net, Authority: . Exception Message: Tried to get token using Azure CLI. Access token could not be acquired. 'az' is not recognized as an internal or external command,

Kudo does not show any MSI_ environmental variables.

How is this supposed to work? This is an existing App Service Plan.

Answer 1

Go to Tools->Options->Azure Services Authentication, and re-authenticate the account you want to use.

Answer 2

Might be unrelated to your issue but I was getting the same error message.

For me, the issue was using pip3's azure-cli. I was able to fix this issue by using brew packages for both azure-cli and azure-functions-core-tools.

Uninstall pip3 azure-cli

pip3 uninstall azure-cli

Install brew azure-cli

brew update
brew install azure-cli

Answer 3

For the folks that will come across these answers, I would like to share my experience.

I got this problem with Azure Synapse pipeline run. Essentially I added access policies properly to the KeyVault, and also I added a LinkedService to the Azure Synapse pointing to my KeyVault.

If I trigger the notebook manually it works, but in the pipeline, it fails.

Initially, I used the following statement:

url = TokenLibrary.getSecret("mykeyvault", "ConnectionString")

Then I added the name of the linked service as a third parameter, and the pipeline was able to leverage that linked service to obtain the MSI token for a Vault.

url = TokenLibrary.getSecret("mykeyvault", "ConnectionString", "AzureKeyVaultLinkedServiceName")

Answer 4

For the ones, like my self, wondering how to enable MSI.

My scenario: I have an App Service already deployed and running for a long time. In addition, on Azure DevOps I have my Pipeline configured to Auto-Swap my Deployment Slots (Staging/Production). Suddenly, after a normal push, Production starts failing because of the described issue.

So, in order to enable MSI again (I don't know why it has to be re-enabled but I believe this is only a workaround, not a solution, as it should be still enabled in the first place)

Go to your App Service. Then Under Settings --> Identity. Check the status: In my case, it was off

I have attached an image below to make it easier to follow.

Answer 5

Just switched ON the Status like @Sebastian Inones showed. Than add access policy for KeyVault like

This is resolved the issue!!

Answer 6

Enable the identity and give access to your azure function app in keyvault via access policy. You can find identity in platform feature tab These two steps works for me

Answer 7

In my case I had forgotten to add an Access Policy for the application in the Key Vault

Answer 8

I've found out that if you enable MSI and then swap out the slot, the functionality leaves with the slot change. You can re-enable it by switching it off and on again but that will create a new identity in AD and will require you to reset permissions on the key vault for it to work.

Answer 9

I just solved this issue when trying to use MSI with a Function app, though I already had the environment variables set. I tried restarting multiple times to no success. What I ended up doing was manually turning off MSI for the Function, then re-enabling it. This wasn't ideal, but it worked.

Hope it helps!

Answer 10

The AppAuthentication library leverages an internal endpoint in App Service that receives the tokens on your site's behalf. This endpoint is non-static and therefore is set to an environment variable. After activating MSI for your site through ARM, your site will need to be restarted to get two new Environment Variables set in it:

MSI_ENDPOINT and MSI_SECRET

The presence of these variables are essential to the MSI feature working properly during runtime as the AppAuthentication library uses them to get the authorization token. The error message reflects this:

Exception Message: Tried to get token using Managed Service Identity. Unable to connect to the Managed Service Identity (MSI) endpoint. Please check that you are running on an Azure resource that has MSI setup.

If these variables are absent, you might need to restart the site.

https://learn.microsoft.com/en-us/azure/app-service/app-service-managed-service-identity

If the environment variables are set and you still see the same error, the article above has a code sample showing how to send requests to that endpoint manually.

public static async Task<HttpResponseMessage> GetToken(string resource, string apiversion)  {
HttpClient client = new HttpClient();
client.DefaultRequestHeaders.Add("Secret", Environment.GetEnvironmentVariable("MSI_SECRET"));
return await client.GetAsync(String.Format("{0}/?resource={1}&api-version={2}", Environment.GetEnvironmentVariable("MSI_ENDPOINT"), resource, apiversion));

}

I would try that and see what kind of response I get back.