Month: August 2023

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How to find custom defined values in helm charts

I was trying to validate if a custom value that I overrode on a helm deployment was correct. In order to override a value in values.yaml you will need to pass the set flag as shown below.

helm upgrade --install -n sonarqube sonarqube sonarqube/sonarqube --set persistence.enabled=true

In the above installation command I override the persistence.enabled value to true instead of false that is by default.

First of all you will need to get the release name of the helm chart that you deployed. You can find this information by 

helm list --all -n namespace

After finding the name of the release you will need to use the get command in order to get values.

 helm -n sonarqube get values sonarqube -n sonarqube

This option will persist the Elasticsearch indexes in a Persistent Volume, but with regular killing operations by the Kubernetes Cluster, these indexes can be corrupted. By default, persistency is disabled in the Helm chart.

Deploy SonarQube on Kubernetes (sonarsource.com)

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How to implement Managed Identity on Service Fabric

Workloads deployed in Service Fabric clusters require Azure AD application credentials or managed identities to access Azure AD protected resources, such as Azure Key Vault and storage accounts. In case of Azure AD applications one can create a new app registration then assign permissions from Access control and finally use the client secret of this application inside the service fabric service.

If you need to enhance security and built based on well architected framework principles you can integrate managed identity authentication inside service fabric applications. Typically when you need to deploy an application on service fabric you should connect to the cluster and deploy using powershell commands. If you want to use managed identity it’s a whole different procedure and the first thing that needs to be changed is the deployment of the service inside the sf cluster.

The high level diagram can be found below.

It is mandatory to deploy the service fabric application as an arm template in order to enable managed identity. There is no other way to implement managed identity authentication except from arm templates.

In more detail there are some steps that need to be performed for the deployment:

  • some references for the user assigned managed identity should be added inside service fabric application in ServiceManifest.xml and ApplicationManifest.xml
  • the output package after the build should be bundled in a sfpkg zip format
  • the package should be uploaded in a storage account and it should be accessible from service fabric cluster (sas token)
  • an arm template should be created with some necessary information for the deployment such as application type and version, packageUrl, cluster name, managed identity name etc.
  • arm template should be applied in service fabric cluster resource group

Service fabric cluster configuration

ManagedIdentityTokenService should be enabled on Service Fabric cluster.

https://learn.microsoft.com/en-us/azure/service-fabric/configure-existing-cluster-enable-managed-identity-token-service

Azure configuration

  • Given that you have already created a user assigned Managed Identity you will need to add some references inside the service fabric application.

ApplicationManifest.xml

 <Principals>
    <ManagedIdentities>
      <ManagedIdentity Name="userassignedMI" />
    </ManagedIdentities>
  </Principals>
    <Policies>
      <IdentityBindingPolicy ServiceIdentityRef="SFServiceUser" ApplicationIdentityRef="userassignedMI" />
    </Policies>

ServiceManifest.xml

<ManagedIdentities DefaultIdentity="SFServiceUser">
    <ManagedIdentity Name="SFServiceUser" />
</ManagedIdentities>

https://learn.microsoft.com/en-us/azure/service-fabric/how-to-deploy-service-fabric-application-user-assigned-managed-identity

  • Then the appropriate RBAC should be assigned on the user assigned managed identity which is referenced inside service fabric application.

Code

In our code we can authenticate using Managed Identity instead of a connection string (DefaultAzureCredential class will automatically locate the managed identity configuration and use it).

var blobServiceClient = new BlobServiceClient( new Uri("https://storage.blob.core.windows.net"), new DefaultAzureCredential());

Deployment

The final step would be to deploy the application. Apply arm-template.json to create the SF service.

 az deployment group create --name sfdeployment --resource-group rgofsfcluster --template-file servicefabric-arm.json

Finally application will be created on service fabric cluster using arm templates supporting managed identity authentication.

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Enforce Azure policy on virtual machines

On previous articles I have used Azure policy to enforce and inherit tags on azure resources.

Azure policy require specific tags on resources
Inherit tags on Azure resources

However sometimes you need to enforce Azure policy only on specific resources. For this purpose you can use logical expression. Lets examine how we can apply an azure policy only on virtual machine resources. Under the policy rule, you will need to search for the field that equals Microsoft.Compute/virtualMachines. By doing so you can target only the specific resource and then based on your logic you can perform actions.

    "policyRule": {
      "if": {
        "allOf": [
          {
            "field": "type",
            "equals": "Microsoft.Compute/virtualMachines"
          },
          {
            "field": "[concat('tags[', parameters('something'), ']')]",
            "exists": "false"
          }
        ]
      },
      "then": {
        "effect": "audit"
      }
    }
  },

In the above scenario the policy rule evaluates to true and audits when a tag named something does not exist and the resource is a virtual machine.