Manage Kubernetes running anywhere via Azure Arc

Azure Arc (currently in preview) allows attach and configure Kubernetes Clusters running anywhere (inside or outside of Azure). Once connected the clusters shows up in Azure portal and allows applying tags, policies like other resources. This brings simplicity and uniformity managing both cloud and on-premises resources in a single management pane (Azure Portal).

Azure Arc enabled Kubernetes is in preview. It’s NOT recommended for production workloads.

Following are the key scenarios where Azure Arc adds value:

  • Connect Kubernetes running outside of Azure for inventory, grouping, and tagging.
  • Apply policies by using Azure Policy for Kubernetes.
  • Deploy applications and apply configuration by using GitOps-based configuration management.
  • Use Azure Monitor for containers to view and monitor your clusters.

Connect an on-premises (or another cloud) clusters to Azure Arc

I have used the local Kubernetes (docker desktop) for this, however, the steps are identical for any other Kubernetes clusters. All you need is to run the following Azure CLI command from a machine where you can reach both the on-premises Kubernetes cluster and Azure.

az connectedk8s connect --name <ClusterName> --resource-group <ResourceGroup>

It will take moment and then the cluster is connected to Azure. We can see that in Azure portal:

Once we have the connected cluster to Azure – we can create/edit tags just like any other Azure resource. Which is awesome.

Same goes true for the Azure Policies – I can apply any compliance constraints to the cluster and monitor their compliance status in Azure Security center.

GitOps on Arc enabled Kubernetes cluster

The next piece of feature is interesting and can be very useful for many scenarios. This is much like infrastructure-as-code for your Kubernetes configuration (namespaces, deployments etc.). The idea is we define one or more git repository that keeps the desired state of the cluster (i.e. namespaces, deployments etc.) in Yaml files and Azure Resource Manager does the necessary actions to apply those desired state into the connected cluster. Microsoft Document describes how this works:

The connection between your cluster and one or more Git repositories is tracked in Azure Resource Manager as a sourceControlConfiguration extension resource. The sourceControlConfiguration resource properties represent where and how Kubernetes resources should flow from Git to your cluster. The sourceControlConfiguration data is stored encrypted at rest in an Azure Cosmos DB database to ensure data confidentiality.

The config-agent running in your cluster is responsible for watching for new or updated sourceControlConfiguration extension resources on the Azure Arc enabled Kubernetes resource, deploying a flux operator to watch the Git repository, and propagating any updates made to the sourceControlConfiguration. It is even possible to create multiple sourceControlConfiguration resources with namespace scope on the same Azure Arc enabled Kubernetes cluster to achieve multi-tenancy. In such a case, each operator can only deploy configurations to its respective namespace.

An example Git repository can be found in here: https://github.com/Azure/arc-k8s-demo. We can create the configuration from the Portal or via Azure CLI:

az k8sconfiguration create \
    --name cluster-config \
    --cluster-name AzureArcTest1 --resource-group AzureArcTest \
    --operator-instance-name cluster-config --operator-namespace cluster-config \
    --repository-url https://github.com/Azure/arc-k8s-demo \
    --scope cluster --cluster-type connectedClusters

That’s it, We can see that in Azure Portal:

With that setup committing changes to the Git repository will now reflect in connected cluster.

Monitoring

Connected clusters can also be monitored with Azure Monitor for containers. It’s as simple as creating a Log analytics workspace and configuring the cluster to push metrics to it. This document describes the steps to enable monitoring.

I have seen some scenarios where people running on-premises (or in other cloud) clusters heavily using Prometheus and Grafana for monitoring clusters. Good news, we can get the same on Azure Arc enabled clusters. Once we have the metrics available in Azure Log Analytics, we can use Grafana to point to the workspace – it takes less than a minute and few button clicks (no-code configuration required).

Isn’t it awesome? Go, checkout Azure Arc for Kubernetes today.

Restricting Unverified Kubernetes Content with Docker Content Trust

Docker Content Trust (DCT) provides the ability to use digital signatures for data sent to and received from remote Docker registries. These signatures allow client-side or runtime verification of the integrity and publisher of specific image tags.

Signed tags
Image source: Docker Content Trust


Through DCT, image publishers can sign their images and image consumers can ensure that the images they pull are signed. Publishers could be individuals or organizations manually signing their content or automated software supply chains signing content as part of their release process.


Azure Container Registry implements Docker’s content trust model, enabling pushing and pulling of signed images. Once Content Trust is enabled in Azure Container Registry, signing an image is extremely easy as below:

Signing an image from console

Problem statement

Now that we can have DCT enabled in Azure Container Registry (i.e. allows pushing signed images into the repository), we want to make sure Kubernetes Cluster would deny running any images that are not signed.

However, Azure Kubernetes Service doesn’t have the feature (as of the today while writing this article) to restrict only signed images to be executed in the cluster. This doesn’t mean we’re stuck until AKS releases the feature. We can implement the content trust restriction using a custom Admission controller. In this article I want to share how one can create their own custom Admission controller to achieve DCT in an AKS cluster.

What are Admission Controllers?

In a nutshell, Kubernetes admission controllers are plugins that govern and enforce how the cluster is used. They can be thought of as a gatekeeper that intercept (authenticated) API requests and may change the request object or deny the request altogether.

Admission Controller Phases
Image source: Kubernetes Documentations

The admission control process has two phases: the mutating phase is executed first, followed by the validating phase. Consequently, admission controllers can act as mutating or validating controllers or as a combination of both.

In this article we will create a validation controller that would check if the docker image signature and will disallow Kubernetes to run any unsigned image for a selected Azure Container Registry. And we will create our Admission controller in .net core.

Writing a custom Admission Controller

Writing Admission Controller is fairly easy and straightforward – they’re just web APIs (Webhook) get invoked by API server while a resource is about to be created/updated/deleted etc. Webhook can respond to that request with an Allowed or Disallowed flag.

Kubernetes uses mutual TLS for all the communication with Admission controllers hence, we would need to create self-signed certificate for our Admission controller service.

Creating Self Signed Certificates

Following is a bash script that would generate a custom CA (certificate authority) and a pair of certificates for our web hook API.

#!/usr/bin/env bash

# Generate the CA cert and private key
openssl req -nodes -new -x509 -keyout ca.key -out ca.crt -subj "/CN=TailSpin CA"
# Generate the private key for the tailspin server
openssl genrsa -out tailspin-server-tls.key 2048
# Generate a Certificate Signing Request (CSR) for the private key, and sign it with the private key of the CA.

## NOTE
## The CN should be in this format: <service name>.<namespace>.svc
openssl req -new -key tailspin-server-tls.key -subj "/CN=tailspin-admission.tailspin.svc" \
    | openssl x509 -req -CA ca.crt -CAkey ca.key -CAcreateserial -out tailspin-server-tls.crt

We will create a simple asp.net core web api project. It’s as simple as a File->New asp.net web API project. Except, we would configure Kestrel to use the TLS certificates (created above) while listening by modifying the Program.cs as below.

public static IHostBuilder CreateHostBuilder(string[] args) =>
  Host.CreateDefaultBuilder(args)
      .ConfigureWebHostDefaults(webBuilder => {
        webBuilder
         .UseStartup<Startup>()
         .UseKestrel(options => {                        
 options.ConfigureHttpsDefaults(connectionOptions => 
     {                                    connectionOptions.AllowAnyClientCertificate();
connectionOptions.OnAuthenticate = (context, options) => {                                        Console.WriteLine($"OnAuthenticate:: TLS Connection ID: {context.ConnectionId}");
     };
   });
   options.ListenAnyIP(443, async listenOptions => {
     var certificate = await ResourceReader.GetEmbeddedStreamAsync(ResourceReader.Certificates.TLS_CERT);
     var privateKey = await ResourceReader.GetEmbeddedStreamAsync(ResourceReader.Certificates.TLS_KEY);

      Console.WriteLine("Certificate and Key received...creating PFX..");
      var pfxCertificate = CertificateHelper.GetPfxCertificate(
                certificate,
                privateKey);
      listenOptions.UseHttps(pfxCertificate);
      Console.WriteLine("Service is listening to TLS port");
      });
   });
});

Next, we will create a middle-ware/handler in Startup.cs to handle the Admission Validation requests.

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            app.Use(GetAdminissionMiddleware());

The implementation of the middleware looks as following:

public Func<HttpContext, Func<Task>, Task> GetAdminissionMiddleware()
        {            
            var acrName = Environment.GetEnvironmentVariable("RegistryFullName"); // "/subscriptions/XX/resourceGroups/YY/providers/Microsoft.ContainerRegistry/registries/ZZ";
            return async (context, next) =>
            {
                if (context.Request.Path.HasValue && context.Request.Path.Value.Equals("/admission"))
                {
                    using var streamReader = new StreamReader(context.Request.Body);
                    var body = await streamReader.ReadToEndAsync();
                    var payload = JsonConvert.DeserializeObject<AdmissionRequest>(body);

                    var allowed = true;
                    if (payload.Request.Operation.Equals("CREATE") || payload.Request.Operation.Equals("UPDATE"))
                    {                        
                        foreach(var container in payload.Request.Object.Spec.Containers)
                        {
                            allowed = (await RegistryHelper.VerifyAsync(acrName, container.Image)) && allowed;
                        }
                    }
                    await GenerateResponseAsync(context, payload, allowed);
                }
                await next();
            };
        }

What we are doing here is, once we receive a request from API server about a POD to be created or updated, we intercept the request, validate if the image has Digital Signature in place (DCT) and reply to API server accordingly. Here’s the response to API server:

private static async Task GenerateResponseAsync(HttpContext context, AdmissionRequest payload, bool allowed)
        {
            context.Response.Headers.Add("content-type", "application/json");
            await context
                .Response
                .WriteAsync(JsonConvert.SerializeObject(new AdmissionReviewResponse
                {
                    ApiVersion = payload.ApiVersion,
                    Kind = payload.Kind,
                    Response = new ResponsePayload
                    {
                        Uid = payload.Request.Uid,
                        Allowed = allowed
                    }
                }));
        }

Now let’s see how we can verify the image has a signed tag in Azure Container Registry.

public class RegistryHelper
    {
        private static HttpClient http = new HttpClient();

        public async static Task<bool> VerifyAsync(string acrName, string imageWithTag)
        {
            var imageNameWithTag = imageWithTag.Split(":".ToCharArray());
            var credentials = SdkContext
                .AzureCredentialsFactory
                .FromServicePrincipal(Environment.GetEnvironmentVariable("ADClientID"),
                Environment.GetEnvironmentVariable("ADClientSecret"),
                Environment.GetEnvironmentVariable("ADTenantID"),
                AzureEnvironment.AzureGlobalCloud);

            var azure = Azure
                .Configure()
                .WithLogLevel(HttpLoggingDelegatingHandler.Level.Basic)
                .Authenticate(credentials)
                .WithSubscription(Environment.GetEnvironmentVariable("ADSubscriptionID"));
           
            var azureRegistry = await azure.ContainerRegistries.GetByIdAsync(acrName);
            var creds = await azureRegistry.GetCredentialsAsync();           

            var authenticationString = $"{creds.Username}:{creds.AccessKeys[AccessKeyType.Primary]}";
            var base64EncodedAuthenticationString = 
                Convert.ToBase64String(ASCIIEncoding.UTF8.GetBytes(authenticationString));
            http.DefaultRequestHeaders.Add("Authorization", "Basic " + base64EncodedAuthenticationString);

            var response = await http.GetAsync($"https://{azureRegistry.Name}.azurecr.io/acr/v1/{imageNameWithTag[0]}/_tags/{imageNameWithTag[1]}");
            var repository = JsonConvert.DeserializeObject<RepositoryTag>(await response.Content.ReadAsStringAsync());

            return repository.Tag.Signed;
        }
    }

This class uses Azure REST API for Azure Container Registry to check if the image tag was digitally signed. That’s all. We would create a docker image (tailspin-admission:latest) for this application and deploy it to Kubernetes with the following manifest:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: tailspin-admission
  namespace: tailspin
spec:
  replicas: 1
  selector:
    matchLabels:
      app: tailspin-admission
  template:
    metadata:
      labels:
        app: tailspin-admission
    spec:
      nodeSelector:
        "beta.kubernetes.io/os": linux
      containers:
      - name: tailspin-admission
        image: "acr.io/tailspin-admission:latest"
        ports:
        - containerPort: 443
---
apiVersion: v1
kind: Service
metadata:
  name: tailspin-admission
  namespace: tailspin
spec:
  type: LoadBalancer
  selector:
    app: tailspin-admission
  ports:
    - port: 443
      targetPort: 443

Now our Admission Controller is running, we need to register this as a validation web hook with the following manifest:

apiVersion: admissionregistration.k8s.io/v1beta1
kind: ValidatingWebhookConfiguration
metadata:
  name: tailspin-admission-controller
webhooks:
  - name: tailspin-admission.tailspin.svc
    admissionReviewVersions: ["v1", "v1beta1"]
    failurePolicy: Fail
    clientConfig:
      service:
        name: tailspin-admission
        namespace: tailspin
        path: "/admission"
      caBundle: ${CA_PEM_B64}
    rules:
      - operations: [ "*" ]
        apiGroups: [""]
        apiVersions: ["*"]
        resources: ["*"]

Here the ${CA_PEM_B64} needs to be filled with the base64 of our CA certificate that we generated above. The following bash script can do that:

# Read the PEM-encoded CA certificate, base64 encode it, and replace the `${CA_PEM_B64}` placeholder in the YAML
# template with it. Then, create the Kubernetes resources.
ca_pem_b64="$(openssl base64 -A <"../certs/ca.crt")"
(sed -e 's@${CA_PEM_B64}@'"$ca_pem_b64"'@g' <"./manifests/webhook-deployment.template.yaml") > "./manifests/webhook-deployment.yaml"

We can now deploy this manifest (KubeCtl) to our AKS cluster. And we are done! The cluster will now prevent running any unsigned images coming from our Azure Container Registry.

Summary

A critical aspect for DCT feature on AKS is enabling a solution which can satisfy all requirements such as content moving repositories or across registries which may extend beyond the current scope of the Azure Container Registry content trust feature as seen today. And enabling DCT on each AKS node is not a feasible solution as many Kubernetes images are not signed.

A custom Admission controller allow you to avoid these limitations and complexity today still being able to enforce Content Trust specific to your own ACR and images only. This article shows a very quick and simple way to create a custom Admission Controller – in .net core and how easy it is to create your own security policy for your AKS cluster.

Hope you find it useful and interesting.

Azure AD Pod Identity – password-less app-containers in AKS

Background

I like Azure Managed Identity since its advent. The concept behind Managed Identity is clever, and it adds observable value to any DevOps team. All concerns with password configurations in multiple places, life cycle management of secrets, certificates, and rotation policies suddenly irrelevant (OK, most of the cases).
Leveraging managed identity for application hosted in Azure Virtual machine, Azure web apps, Function apps etc. was straightforward. The Managed Identity sits on top of Azure Instance Metadata Service technology. Azure’s Instance Metadata Service is a REST Endpoint accessible to all IaaS VMs created via the Azure Resource Manager. The endpoint is available at a well-known non-routable IP address (169.254.169.254) that can be accessed only from within the VM. Under the hood Azure VMs, VMSS and Azure PaaS resources (i.e. Web Apps, Function Apps etc.) leverage metadata service to retrieve Azure AD token. Thus VM, Web App kind of establishes their own “Application Identity” (what Managed Identity essentially is) that Azure AD authenticates.

Managed Identity in Azure Kubernetes Service

Managed Identity in Kubernetes, however, is a different ballgame. Typically, multiple applications (often developed by different teams in an organization) running in a single cluster, pods are launching, exiting frequently in different nodes. Hence, Managed Identity associating with VM/VMSS are not sufficient, we needed a way to assign identity to every pods in an application. If pods move to different nodes, the identity must somehow move with them in the new node (VM).

Azure Pod Identity

Good news is Azure Pod Identity offers that capability. Azure Pod Identity is an Open source project in GitHub.

Note: Managed pod identities is an open source project and is not supported by Azure technical support.

An application can use Azure Pod Identity to access Azure resources (i.e. Key Vault, Storage, Azure SQL database etc.) via Managed Identity hence, there’s no secret/password involved anywhere in the process. Pods can directly fetch access tokens scoped to resources directly from Azure Active Directory.

Concept

The following two components are installed in cluster to achieve the pod identity.

1. The Node Management Identity (NMI)

AKS cluster runs this Daemon Set in every node. This intercepts outbound calls from pods requesting access tokens and proxies those calls with predefined Managed Identity.

2. The Managed Identity Controller (MIC)

MIC is a central pod with permissions to query the Kubernetes API server and checks for an Azure identity mapping that corresponds to a pod.

Source: GitHub Project – Azure Pod Identity

When pods request access to an Azure service, network rules redirect the traffic to the Node Management Identity (NMI) server. The NMI server identifies pods that request access to Azure services based on their remote address and queries the Managed Identity Controller (MIC). The MIC checks for Azure identity mappings in the AKS cluster, and the NMI server then requests an access token from Azure Active Directory (AD) based on the pod’s identity mapping. Azure AD provides access to the NMI server, which is returned to the pod. This access token can be used by the pod to then request access to services in Azure.

Microsoft

Azure Pipeline to Bootstrap pod Identity

I have started with an existing rbac-enabled Kubernetes cluster – that I have created before. Azure AD pod identity would setup “Service Account”, “custom resource definitions (CRD)”, Cluster Roles and bindings, DaemonSet for NMI etc. I wanted to do it via Pipeline, so I can repeat the process on-demand. Here are the interesting part of the azure-pod-identity-setup-pipeline.yaml

trigger:
- master
variables:
  tag: '$(Build.BuildId)'
  containerRegistry: $(acr-name).azurecr.io
  vmImageName: 'ubuntu-latest'
stages:
- stage: Build
  displayName: Aad-Pod-Identity-Setup
  jobs:  
  - job: Build
    displayName: Setup Aad-Pod-Identity.
    pool:
      vmImage: $(vmImageName)
    environment: 'Kubernetes-Cluster-Environment.default'
    steps:
      - bash: |
          kubectl apply -f https://raw.githubusercontent.com/Azure/aad-pod-identity/master/deploy/infra/deployment-rbac.yaml
        displayName: 'Setup Service Account, CRD, DaemonSet etc'


I will be using a “User assigned identity” for my sample application. I have written a basic .net app with SQL back-end for this purpose. My end goal is to allow the .net app talk to SQL server with pod identity.
Following instruction Aad-pod-identity project instruction, I have created the user assigned identity.

      - task: AzureCLI@2
        inputs:
          scriptType: 'bash'
          scriptLocation: 'inlineScript'
          inlineScript: 'az identity create -g $(rgp) -n $(uaiName) -o json'

In my repository, created the Azure Identity definition in a file named: aad-pod-identity.yaml

apiVersion: "aadpodidentity.k8s.io/v1"
kind: AzureIdentity
metadata:
  name: <a-idname>
spec:
  type: 0
  ResourceID: /subscriptions/<sub>/resourcegroups/<resourcegroup>/providers/Microsoft.ManagedIdentity/userAssignedIdentities/<name>
  ClientID: <clientId>
---
apiVersion: "aadpodidentity.k8s.io/v1"
kind: AzureIdentityBinding
metadata:
  name: demo1-azure-identity-binding
spec:
  AzureIdentity: <a-idname>
  Selector: managed-identity


And added a task to deploy that too.

      - bash: |
          kubectl apply -f manifests/ aad-pod-identity.yaml
        displayName: 'Setup Azure Identity

Triggered the pipeline and Azure pod Identity was ready to roll.

Deploying application

I have a .net core web app (Razor application) which I would configure to run with pod identity to connect to Azure SQL (a back-end) with Azure Active directory authentication – with no password configured at the application level.
Here’s the manifest file (front-end.yaml) for the application, the crucial part is to define the label (aadpodidbinding: managed-identity) match for binding the pod identity we have defined before:

        apiVersion:apps/v1
	kind: Deployment
	metadata:
	  name: dysnomia-frontend
	spec:
	  replicas: 6
	  selector:
	    matchLabels:
	      app: dysnomia-frontend      
	  strategy:
	    rollingUpdate:
	      maxSurge: 1
	      maxUnavailable: 1
	  minReadySeconds: 5 
	  template:
	    metadata:
	      labels:
	        app: dysnomia-frontend
                aadpodidbinding: managed-identity
	    spec:
	      nodeSelector:
	        "beta.kubernetes.io/os": linux
	      containers:
	      - name: dysnomia-frontend
	        image: #{containerRegistry}#/dysnomia-frontend:#{Build.BuildId}#
	        imagePullPolicy: "Always"

That’s pretty much it, once I have created my application pipeline with the above manifest deployed, the .net application can connect to Azure SQL database with the assigned pod identity.

      - bash: |
          kubectl apply -f manifests/front-end.yaml
        displayName: 'Deploy Front-end'


Of course, I needed to do Role assignment for User Assigned Identity and enable Azure AD authentication in my SQL server, but not describing those steps, I have written about that before.

What about non-Azure resources?

The above holds true for all Azure Resources that supports Managed Identity. That means, our application can connect to Cosmos DB, Storage Account, Service Bus, Key Vaults, and many other Azure resources without configuring any password and secrets anywhere in Kubernetes.
However, there are scenarios where we might want to run a Redis container or a SQL server container in our Kubernetes cluster. And cost wise, it might make sense to run it in Kubernetes (as you already have a cluster) instead of Azure PaaS (i.e. Azure SQL or Azure Redis) for many use-cases. In those cases, we must create the SQL password and configure into our .net app (using Kubernetes Secrets).
I was wondering if I could store my SQL password in an Azure Key Vault and let my SQL container and .net app both collect the password from key vault during launch using Azure pod identity. Kubernetes has a first-class option to handle such scenarios- Kubernetes secrets.

However, today I am playing with Azure AD pod Identity – therefore, I really wanted to use pod identity – for fun ;-). Here’s how I managed to make it work.

SQL container, pod identity and Azure Key vault

I’ve created Key vault and defined SQL server password as a secret there. Configured my .net app to use pod identity to talk to key vault and configured key vault access policy so user-assigned identity created above can grab the SQL password. So far so good.

Now, I wanted to run a SQL server instance in my cluster which should also collect the password from Key vault – same way as it did for .net app. Turned out, SQL 2019 image (mcr.microsoft.com/mssql/server:2019-latest) expects the password as an environment variable during container launch.

docker run -d -p 1433:1433 `
           -e "ACCEPT_EULA=Y" `
           -e "SA_PASSWORD=P@ssw0rD" `
           mcr.microsoft.com/mssql/server:2019-latest

Initially, I thought it would be easy to use an init-container to grab the password from Azure Key vault and then pass it through the application container (SQL) as environment variable. After some failed attempts realized that isn’t trivial. I can of course create volume mounts (e.g. EmptyDir) to convey the password from init-container to application container – but that rather dirty – isn’t it?
Secondly I thought of creating my own Docker image based on the SQL container, then I could run a piece of script that will grab the password form Key vault and set it as environment variable. A simple script with a few curl commands would do the trick – you might think. Well, few small issues. SQL container images are striped down ubuntu core – which do not have apt, curl etc. also not running as root either – for all good reasons.


So, I have written a small program in Go and compiled it to a binary.

package main
import (
    "encoding/json"
    "fmt"
    "io/ioutil"
    "net/http"
    "os"
)
type TokenResponse struct {
    Token_type   string `json:"token_type"`
    Access_token string `json:"access_token"`
}
type SecretResponse struct {
    Value string `json:"value"`
    Id    string `json:"id"`
}
func main() {
    var p TokenResponse
    var s SecretResponse
    imds := "http://169.254.169.254/metadata/identity/oauth2/token" +
            "?api-version=2018-02-01&resource=https%3A%2F%2Fvault.azure.net"
    kvUrl := "https://" + os.Args[1] + "/secrets/" + os.Args[2] + 
             "?api-version=2016-10-01"

    client := &http.Client{}
    req, _ := http.NewRequest("GET", imds , nil)
    req.Header.Set("Metadata", "True")
    res, _ := client.Do(req)
    b, _ := ioutil.ReadAll(res.Body)
    json.Unmarshal(b, &p)

    req, _ = http.NewRequest("GET", kvUrl , nil)
    req.Header.Set("Authorization", p.Token_type+" "+p.Access_token)
    res, _ = client.Do(req)
    b, _ = ioutil.ReadAll(res.Body)
    json.Unmarshal(b, &s)
    fmt.Println(s.Value)
}

This program simply grabs the secret from Azure Key vault using Managed Identity. Created a binary out of it:

Go build -o aadtoken


Next, I have created my SQL container image with following docker file:

FROM mcr.microsoft.com/mssql/server:2019-latest

ENV ACCEPT_EULA=Y
ENV MSSQL_PID=Developer
ENV MSSQL_TCP_PORT=1433 
COPY ./aadtoken /
COPY ./startup.sh /
CMD [ "/bin/bash", "./startup.sh" ] 

You see, I am relying on “startup.sh” bash-script. Here’s it:

echo "Retrieving AAD Token with Managed Identity..."
export SA_PASSWORD=$(./aadtoken $KeyVault $SecretName)
echo "SQL password received and cofigured successfully"
/opt/mssql/bin/sqlservr --accept-eula

Created the image and here’s my SQL manifest to deploy in Kubernetes:

apiVersion: apps/v1beta1
kind: Deployment
metadata:
  name: mssql-deployment
spec:
  replicas: 1
  template:
    metadata:
      labels:
        app: mssql
        aadpodidbinding: managed-identity
    spec:
      terminationGracePeriodSeconds: 10
      containers:
      - name: mssql
        image: #{ACR.Name}#/sql-server:2019-latest
        ports:
        - containerPort: 1433
        env:
        - name: KeyVault
          value: "#{KeyVault.Name}#"
        - name: SecretName
          value: "SQL_PASSWORD"
        volumeMounts:
        - name: mssqldb
          mountPath: /var/opt/mssql
      volumes:
      - name: mssqldb
        persistentVolumeClaim:
          claimName: mssql-data

Deployed the manifest and voila! All works. SQL pods and .net app pods all are using Managed Identity to connect to Key vault and retrieving the secret, stored centrally in one place and management of the password nice & tidy.

Conclusion

I find Azure pod identity a neat feature and security best practice. Especially when you are using Azure Kubernetes and some Azure Resources (i.e. Cosmos DB, Azure SQL, Key vault, Storage Account, Service Bus etc.). If you didn’t know, hope this makes you more enthusiast to investigate further.

Disclaimer 1: It’s an open source project – so the Azure technical support doesn’t apply.

Disclaimer 2: The SQL container part with Go script is totally a fun learning attempt, don’t take it too seriously!

Azure AD App via ARM Template Deployment Scripts

Background

ARM templates offer a great way to define resources and deploy them. However, ARM templates didn’t have any support to invoke or run scripts. If we wanted to carry out some operations as part of the deployment (Azure AD app registrations, Certificate generations, copy data to/from another system etc.) we had to create pre or post deployment scripts (using Azure PowerShell or Azure CLI). Microsoft recently announced the preview of Deployment Scripts (new resource type Microsoft.Resources/deploymentScripts) – which brings a way to run a script as part of ARM template deployment.

I have few web apps using Open ID connect for user authentication and they’re running as Azure App services. I always wanted to automate (preferably in a declarative and idempotent way) the required app registrations in Azure AD and deploy them together with the ARM templates of web apps.

Since we now have deployment script capability, I wanted to leverage it for Azure AD app registrations. In this article I will share my experience doing exactly that.

What are deployment scripts?

Deployment scripts allows running custom scripts (can be either Azure PowerShell or Azure CLI) as part of an ARM template deployment. It can be used to perform custom steps that can’t be done by ARM templates.


A simple deployment template that runs a bash command (echo) looks like below:

Figure: Simple example of Deployment Scripts

Microsoft described the benefits of deployment scripts as following:

– Easy to code, use, and debug. You can develop deployment scripts in your favorite development environments. The scripts can be embedded in templates or in external script files.


– You can specify the script language and platform. Currently, Azure PowerShell and Azure CLI deployment scripts on the Linux environment are supported.


– Allow specifying the identities that are used to execute the scripts. Currently, only Azure user-assigned managed identity is supported.


– Allow passing command-line arguments to the script.
Can specify script outputs and pass them back to the deployment.

Source

Registering Azure AD app

We can write a small script (with Azure CLI) like above sample, that registers the Azure AD app – that’s quite straightforward. However, first we need to address the Identity aspect, what account would run the script and how app-registration permission can be granted to that account. The answer is using Managed Identity.

User Assigned Managed Identity

Managed identities for Azure resources provide Azure services with a managed identity in Azure Active Directory. We can use this identity to authenticate to services that support Azure AD authentication, without needing credentials in your code. There are two types of Managed Identity, System assigned and User Assigned.

Deployment Scripts currently supports User Assigned Identities only, hence, we need to create a User Assigned Managed Identity that would run the CLI script. This identity is used to execute deployment scripts. We would also grant Azure AD app registration permissions to this identity. Creating User Assigned Identity is straightforward and the steps are nicely described here.

Figure: User Assigned Managed Identity in Azure Portal

Next to that, we will have to grant permissions to the identity. Following PowerShell script grants the required permissions to the Managed Identity.

Figure: Grant permissions (Click to Open in window to copy)

ARM template

We will now write the ARM template that will leverage the deployment scripts to register our app in Azure AD.

Figure: Deployment Script (Click to Open in window to copy)

I wouldn’t explain each of the settings/config options in here. Most important part here is the scriptContent property – which can have a string value of any scripts (PowerShell or Bash). You can also point to an external script file instead of embedded script.

Another important property is cleanupPreference. It specifies the preference of cleaning up deployment resources when the script execution gets in a terminal state. Default setting is Always, which means deleting the resources despite the terminal state (Succeeded, Failed, Canceled).

You can find more details on each of the configuration properties for Deployment Script in this document.

I have used some variable references that are defined in the same template json file.

Figure: Variables (Click to open new window to copy)

Notice here the cliArg variable. This would be the argument that we are passing as inputs to our CLI/bash script. The catch here is, the arguments need to be separated by white-spaces.

Finally, we would love to grab the newly registered app id and configure an entry into the App Settings in our web app – so the web app Open ID authentication can work right after the deployment.

Figure: Variables (Click to open new window to copy)

At this point we will deploy the template and after the deployment completed, we will see the app has been registered in Azure AD:

Figure: Azure AD App

Also, we can verify that the newly created App ID is nicely configured into the web app’s app-settings.

Figure: App settings configured

That’s all there is to it!

I haven’t defined any API permission scopes for the app registrations in this example, however, having the Azure CLI script in place, defining further API scopes are trivial.

How it worked?

If we login to the Azure Portal we will see the following:

Figure: Azure Portal resources

We see a new resource of type Deployment Script besides our Web App (and it’s Service Plan) that is obvious. However, we also see Container Instance and a Storage Account. Where they came from?

Well, Azure RM deployment created them while deploying the Deployment scripts. The storage account and a container instance, are created in the same resource group for script execution and troubleshooting. These resources are usually deleted by the script service when the script execution gets in a terminal state. Important to know, we are billed for the resources until the resources are deleted.

The container instance runs a Docker image as a Sandbox for our Deployment Script. You can see the image name form the portal that Microsoft is using for execution. This can come handy to try out the script locally – for development purposes.

Conclusion

I have a mixed feeling about the deployment script in ARM templates. It obviously has some benefits. But this shouldn’t replace all pre or post deployment script. Because sometimes it might be cleaner and easier to create a pre- or post-script task in continuous delivery pipeline than composing all in ARM templates.

Terraforming Azure DevOps

Background

In many organizations, specially in large enterprises there’s a need to automate Azure DevOps projects and Teams members. Manually managing large number of Azure DevOps projects, Teams for these projects and users to the teams, on-boarding and off-boarding team members are not trivial.

Besides managing the users sometimes, we just need to have an overview (a documentation?) of users and Teams of Projects. Terraform is a great tool for Infrastructure as Code – which not only allows providing infrastructure on demand, but also gives us nice documentation which can be versioned control in a source control system. The workflow kind of looks like following:

GitOps

I am developing a Terraform Provider for Azure DevOps that helps me use Terraform for provisioning Azure DevOps projects, Teams and members. In this article I will share how I am building it.

Note
This provider doesn't implement the complete set of 
Azure DevOps REST APIs. 
Its limited to only projects, teams and member associations. 
It's not recommended to use it in production scenarios.

Terraform Provider

Terrafom is an amazing tool that lets you define your infrastructure as code. Under the hood it’s an incredibly powerful state machine that makes API requests and marshals resources. Terraform has lots of providers – almost for every major cloud – out there. Including many other systems – like Kubernetes, Palo-Alto Networks etc.

In nutshell if any system has REST API that can be manipulated with Terraform Provider. Azure DevOps also has a terraform provider – which doesn’t currently provide resources to create Teams and members. Hence, I am writing my own – shamelessly using/stealing the Microsoft’s Terraform provider (referenced above) for project creation.

Setting up GO Environment

Terraform Providers and plugins are binaries that Terraform communicates during runtime via RPC. It’s theoretically possible to write a provider in any language, but to be honest, I haven’t come across any providers that were written other languages than GO. Terraform provide helper libraries in Go to aid in writing and testing providers.

I am developing in Windows 10 and didn’t want to install GO on my local machine. Containers come to rescue of course. I am using the “Remote development” extension in VS Code. This extension allows me to keep the source code in local machine and compile, build the source code in a container like Magic!

remote

Figure: Remote Development extension in VSCode – running container to build local repository.

Creating the provider

To create a Terraform provider we need to write the logic for managing the Creation, Reading, Updating and Deletion (CRUD) of a resource (i.e. Azure DevOps project, Team and members in this scenario) and Terraform will take care of the rest; state, locking, templating language and managing the lifecycle of the resources. Here in this repository I have a minimum implementation that supports creating Azure DevOps projects, Teams and its members.

First of all we define our provider and resources in main.go file.

Next to that, we will define the provider schema (the attributes it supports as input and outputs, resources etc.)

We are using Azure DevOps personal Access token to communicate to the Azure DevOps REST API. The GO client for Azure DevOps from Microsoft – which is used as dependency, immensely simplified the implementation and also helped learning the flow.

Now defining the “team” resource as following:

That’s all for declaring, now implementing the CRUD methods in resource providers. The full source code is in GitHub.

We can compile the provider application using following command:

> GOOS=windows GOARCH=amd64 go build -o terraform-provider-azuredevops.exe

As I am using Dabian docker image for GoLang I need to specify my target OS (GOOS=windows) and CPU Architecture (GOARCH=amd64) when I build the provider. This will produce the terraform provider for Azure DevOps executable.

Although it’s executable, it’s not meant to launch directly from command prompt. Instead, I will copy it to “%APPDATA%\ terraform.d\plugins\windows_amd64” folder of my machine.

Terraform Script for Azrue DevOps

Now we can write the Terraform file (.tf) that will describe the Azure DevOps Project, Team and members etc.

Terraform

With this terraform file, we can now launch the following command to initialize our terraform environment.

init

The terraform init command is used to initialize a working directory containing Terraform configuration files. This is the first command that should be run after writing a new Terraform configuration or cloning an existing one from version control.

Terraform plan

The terraform plan command is used to create an execution plan. Terraform performs a refresh, and then determines what actions are necessary to achieve the desired state specified in the configuration files. This command is a convenient way to check whether the execution plan for a set of changes matches your expectations without making any changes to real resources or to the state. For example, terraform plan might be run before committing a change to version control, to create confidence that it will behave as expected.

PLan

Figure: terraform plan output – shows exactly what is going to happen if we apply these changes to Azure DevOps

Terraform apply

The terraform apply command is used to apply the changes required to reach the desired state of the configuration, or the pre-determined set of actions generated by a terraform plan execution plan. We will launch it with an “-auto-approve” flag to assert the approval prompt.

apply

Now we can go to our Azure DevOps and sure enough there’s a new project created with the configuration as we scripted in Terraform file.

Taking it further

Now we can check in the terraform file (main.tf above) into an Azure DevOps repository and put a Branch policy to it. That will force any changes (such as creating new projects, adding removing team members) would requrie a Pull-Request and needs to be reviewed by peers (four-eyes principles). Once Pull-Requests are approved, a simple Azure Pipeline can trigger that does the terraform apply. And I have my workflow automated  and I also have nice histories in GIT – which records the purpose of any changes made in past.

Thanks for reading!

Inter-process communication on Windows Containers

Background

Legacy monolith applications that are built to run on single beefy server can take advantage of containers to simplify the deployment model and also potentially opens possibility to re-architect piece by piece without triggering a complete rewrite. I ran into a scenario where I am considering wrap up a large monolith (with many threads in it) into multiple containers and introduce some mode of execution. Therefore, each container instance runs a specific mode of operations and leads to a micro-service-based architecture in future. Splitting into containers is rather easier, but then I needed to introduce an IPC mechanism to enable communication between these container instances. In this post, I will write some IPC options that I have exercised in these scenarios.

The application is written in .net framework; therefore, I couldn’t use .net core and Linux machines. I have only investigated windows containers. I have tried following technologies for IPC and did some bench marking on latency.

Environment and Hardware specs

Most of these IPC technologies (e.g. TCP, gRPC, Web Sockets) also allow remote invocations, but I have only tried on single machine- as that’s what I wanted to investigate. I have run these benchmarks on windows 10 client machine with following configuration:

BenchmarkDotNet=v0.11.5, OS=Windows 10.0.18362

Intel Core i7-8650U CPU 1.90GHz (Kaby Lake R), 1 CPU, 8 logical and 4 physical cores

[Host]: .NET Framework 4.7.2 (CLR 4.0.30319.42000), 32bit LegacyJIT-v4.8.3815.0

Windows Container: Quick refresh

Windows Server containers provide application isolation through process and namespace isolation technology. That is often referred to as process-isolated containers. A Windows Server container shares a kernel with the container host and all containers running on the host. These process-isolated containers don’t provide a hostile security boundary and shouldn’t be used to isolate untrusted code. Because of the shared kernel space, these containers require the same kernel version and configuration.

However, windows containers also provide a different type of isolation – called Hyper-V isolation. Hyper-V isolation expands on the isolation provided by Windows Server containers by running each container in a highly optimized virtual machine.

HyperV conainers
Windows Container Hyper-V isolation

In this configuration, the container host doesn’t share its kernel with other containers on the same host. These containers are designed for hostile multi-tenant hosting with the same security assurances of a virtual machine. Since these containers don’t share the kernel with the host or other containers on the host, they can run kernels with different versions and configurations (within supported versions). For example, all Windows containers on Windows 10 use Hyper-V isolation to utilize the Windows Server kernel version and configuration.

Running a container on Windows with or without Hyper-V isolation is a runtime decision. We can initially create the container with Hyper-V isolation, and then later at runtime choose to run it as a Windows Server container instead.

I have run the IPC stack for each technology in three different setups.

  • Bare metal (running on my windows 10 client)
  • Two containers (server and client) running in Hyper-V isolation (–isolation=hyperv)
  • Two containers (server and client) running in Process isolation (–isolation=process)

Measure/benchmark

IPC – by its nature is a non-deterministic operation. Hence, I wanted to measure and focus on latencies in my investigation instead of throughputs. I created some IPC handshake applications that exchanges approximately 1 KB of message from client to server. I ran it in different frequencies (>10000 times) and measured the percentiles.

And of course, I am running Docker for Windows with following version:

docker-version

WCF TCP/IP Channel

TCP channel is probably the most commonly used binding in WCF applications. Here I have the simple WCF server and client that sends some bytes over the wire. TCP is a connection-based, stream-oriented delivery service with end-to-end error detection and correction. Connection-based means that a communication session between hosts is established before exchanging data. A host is any device on a TCP/IP network identified by a logical IP address.

The sample hosts a TCP server and waits for clients to connect. Once the client is connected, client sends 1KB bytes to the server for a n number of times.

WCF server

WCF Client

Running it on bare-metal:

TCP bare-metal

Now running it inside two containers (server and client) in Hyper-V isolation:

TCP-HyperV

We can see that it adds latency compare to Bare-metal. Let’s run it on process isolation mode:

TCP-Process

That improved a lot, almost as bare-metal.

gRPC

Like many RPC systems, gRPC is based around the idea of defining a service, specifying the methods that can be called remotely with their parameters and return types. By default, gRPC uses protocol buffers as the Interface Definition Language (IDL) for describing both the service interface and the structure of the payload messages. It is possible to use other alternatives if desired.

I have written a similar sample project as I did for TCP channel above but this time both the server and client uses gRPC for messaging.

Lets run the same exercise with gRPC.

gRPC

What I see is, the process isolation is pretty darn good compare to Hyper-V isolation.

Web Sockets

Web Sockets (over HTTPS) gives a easy programming model for network communication.  The WebSocket API is an advanced technology that makes it possible to open a two-way interactive communication session between the user’s browser and a server. With this API, you can send messages to a server and receive event-driven responses without having to poll the server for a reply.

I didn’t write or programmed web socket API directly though, I have used the SignalR self-hosting to do that.

In this exercise I created the same messaging with web sockets.

Web-socket

Unix Domain Sockets

Like I have mentioned above, Linux and .net core was not my option for this exercise. However, I couldn’t resist give it a shot running the same messaging over an Unix-domain-socket on Linux kernel.

Unix domain socket or IPC socket is a data communications endpoint for exchanging data between processes executing on the same host operating system. Valid socket types in the UNIX domain are: SOCK_STREAM (compare to TCP), for a stream-oriented socket; SOCK_DGRAM (compare to UDP), for a datagram-oriented socket that preserves message boundaries (as on most UNIX implementations, UNIX domain datagram sockets are always reliable and don’t reorder datagrams); and SOCK_SEQPACKET (compare to SCTP), for a sequenced-packet socket that is connection-oriented, preserves message boundaries, and delivers messages in the order that they were sent. The Unix domain socket facility is a standard component of POSIX operating systems.

Here’s what I get when running the similar messaging that leverages Unix domain sockets:

UDS

That’s blazing fast! Sadly I couldn’t use it for my purpose.

Summary

Putting all the numbers into a chart, I get this:

Graph

Disclaimer 1: Bench marking is difficult – it has so many moving factors to get everything right. I wouldn’t put any conclusive statement on it, like certain IPC technique is faster than other. But the source codes are included and you can run it on your environment and make your one judgement.

Disclaimer 2: Another interesting technology I needed to try out was windows named-pipes. The source code is in the same repository, but I couldn’t get it to work while sharing between containers. I will update the post once I have some progress there.

All remarks/questions are always welcome, Thanks for reading.

Linkerd in Azure Kubernetes Service cluster

In this article I would document my journey on setting up Linkerd Service Mesh on Azure Kubernetes service.

Background

I have a tiny Kubernetes cluster. I run some workload there, some are useful, others are just try-out, fun stuffs. I have few services that need to talk to each other. I do not have a lot of traffic to be honest, but I sometimes curiously run Apache ab to simulate load and see how my services perform under stress. Until very recently I was using a messaging (basically a pub-sub) pattern to create reactive service-to-service communication. Which works great, but often comes with a latency. I can only imagine, if I were to run these service to service communication for a mission critical high-traffic performance-driven scenario (an online game for instance), this model won’t fly well. There comes the need for a service-to-service communication pattern in cluster.

What’s big deal? We can have REST calls between services, even can implement gRPC for that matter. The issue is things behaves different at scale. When many services talks to many others, nodes fail in between, network address of PODs changes, new PODs show up, some goes down, figuring out where the service sits becomes quite a challenging task.

Then Kubernetes comes to rescue, Kubernetes provides “service”, that gives us service discovery out of the box. Which is awesome. Not all issues disappeared though. Services in a cluster need fault-tolerances, traceability and most importantly, “observability”.  Circuit-breakers, retry-logics etc. implementing them for each service is again a challenge. This is exactly the Service Mesh addresses.

Service mesh

From thoughtworks radar:

Service mesh is an approach to operating a secure, fast and reliable microservices ecosystem. It has been an important steppingstone in making it easier to adopt microservices at scale. It offers discovery, security, tracing, monitoring and failure handling. It provides these cross-functional capabilities without the need for a shared asset such as an API gateway or baking libraries into each service. A typical implementation involves lightweight reverse-proxy processes, aka sidecars, deployed alongside each service process in a separate container. Sidecars intercept the inbound and outbound traffic of each service and provide cross-functional capabilities mentioned above.

Some of us might remember Aspect Oriented programming (AOP) – where we used to separate cross cutting concerns from our core-business-concerns. Service mesh is no different. They isolate (in a separate container) these networking and fault-tolerance concerns from the core-capabilities (also running in container).

Linkerd

There are quite several service mesh solutions out there – all suitable to run in Kubernetes. I have used earlier Envoy and Istio. They work great in Kubernetes as well as VM hosted clusters. However, I must admit, I developed a preference for Linkerd since I discovered it. Let’s briefly look at how Linkerd works. Imagine the following two services, Service A and Service B. Service A talks to Service B.

service-2-service

When Linkerd installed, it works like an interceptor between all the communication between services. Linkerd uses sidecar pattern to proxy the communication by updating the KubeProxy IP Table.

Linkerd-architecture.png

Linkerd implants two sidecar containers in our PODs. The init container configures the IP table so the incoming and outgoing TCP traffics flow through the Linkerd Proxy container. The proxy container is the data plane that does the actual interception and all the other fault-tolerance goodies.

Primary reason behind my Linkerd preferences are performance and simplicity. Ivan Sim has done performance benchmarking with Linkerd and Istio:

Both the Linkerd2-meshed setup and Istio-meshed setup experienced higher latency and lower throughput, when compared with the baseline setup. The latency incurred in the Istio-meshed setup was higher than that observed in the Linkerd2-meshed setup. The Linkerd2-meshed setup was able to handle higher HTTP and GRPC ping throughput than the Istio-meshed setup.

Cluster provision

Spinning up AKS is easy as pie these days. We can use Azure Resource Manager Template or Terraform for that. I have used Terraform to generate that.

Service deployment

This is going to take few minutes and then we have a cluster. We will use the canonical emojivoto app (“buoyantio/emojivoto-emoji-svc:v8”) to test our Linkerd installation. Here’s the Kubernetes manifest file for that.

With this IaC – we can run Terraform apply to provision our AKS cluster in Azure.

Azure Pipeline

Let’s create a pipeline for the service deployment. The easiest way to do that is to create a service connection to our AKS cluster. We go to the project settings in Azure DevOps project, pick Service connections and create a new service connection of type “Kubernetes connection”.

Azure DevOps connection

Installing Linkerd

We will create a pipeline that installs Linkerd into the AKS cluster. Azure Pipeline now offers “pipeline-as-code” – which is just an YAML file that describes the steps need to be performed when the pipeline is triggered. We will use the following pipeline-as-code:

We can at this point trigger the pipeline to install Linkerd into the AKS cluster.

Linkerd installation (2)

Deployment of PODs and services

Let’s create another pipeline as code that deploys all the services and deployment resources to AKS using the following Kubernetes manifest file:

In Azure Portal we can already see our services running:

Azure KS

Also in Kubernetes Dashboard:

Kub1

We have got our services running – but they are not really affected by Linkerd yet. We will add another step into the build pipeline to tell Linkerd to do its magic.

Next thing, we trigger the pipeline and put some traffic into the service that we have just deployed. The emoji service is simulating some service to service invocation scenarios and now it’s time for us to open the Linkerd dashboard to inspect all the distributed traces and many other useful matrix to look at.

linkerd-censored

We can also see kind of an application map – in a graphical way to understand which service is calling who and what is request latencies etc.

linkerd-graph

Even fascinating, Linkerd provides some drill-down to the communications in Grafana Dashboard.

ezgif.com-gif-maker.gif

Conclusion

I have enjoyed a lot setting it up and see the outcome and wanted to share my experience with it. If you are looking into Service Mesh and read this post, I strongly encourage to give Linkerd a go, it’s awesome!

Thanks for reading.

Continuously deploy Blazor SPA to Azure Storage static web site

Lately I am learning ASP.net Blazor – the relatively new UI framework from Microsoft. Blazor is just awesome – the ability to write c# code both in server and client side is extremely productive for .net developers. From Blazor documentations:

Blazor lets you build interactive web UIs using C# instead of JavaScript. Blazor apps are composed of reusable web UI components implemented using C#, HTML, and CSS. Both client and server code is written in C#, allowing you to share code and libraries.

I wanted to write a simple SPA (Single Page Application) and run it as server-less. Azure Storage offers hosting static web sites for quite a while now. Which seems like a very nice option to run a Blazor SPA which executes into the user’s browser (within the same Sandbox as JavaScript does). It also a cheap way to run a Single Page application in Cloud.

I am using GitHub as my source repository for free (in a private repository). Today wanted to create a pipeline that will continuously deploy my Blazor app to the storage account. Azure Pipelines seems to have pretty nice integration with GitHub and it’s has a free tier as well . If either our GitHub repository or pipeline is private, Azure Pipeline still provide a free tier. In this tier, one can run one free parallel job that can run up to 60 minutes each time until we’ve used 1800 minutes per month. That’s pretty darn good for my use case.

I also wanted to build the project many times in my local machine (while developing) in the same way it gets built in the pipeline. Being a docker fan myself, that’s quite no-brainer. Let’s get started.

Pre-requisite

I have performed few steps before I ran after the pipeline – that are beyond the scope of this post.

  • I have created an Azure Subscription
  • Provisioned resource groups and storage account
  • I have created a Service Principal and granted Contributor role to the storage account

Publishing in Docker

I have created a docker file that will build the app, run unit tests and if all goes well, it will publish the app in a folder. All of these are standard dotnet commands.
Once, we have the application published in a folder, I have taken the content of that folder to a Azure CLI docker base image (where CLI is pre-installed) and thrown away the rest of the intermediate containers.

Here’s our docker file:

The docker file expects few arguments (basically the service principal ID, the password of the service principal and the Azure AD tenant ID – these are required for Azure CLI to sign-in to my Azure subscription). Here’s how we can build this image now:

Azure Pipeline as code

We have now the container, time to run it every time a commit has been made to the GitHub repository. Azure Pipeline has a yaml format to define pipeline-as-code – which is another neat feature of Azure Pipelines.

Let’s see how the pipeline-as-code looks like:

I have committed this to the same repository into the root folder.

Creating the pipeline

We need to login to Azure DevOps and create a project (if there’s none). From the build option we can create a new build definition.

ado

The steps to create build definition is very straightforward. It allows us to directly point to a GitHub repository that we want to build.
Almost there. We need to supply the service principal ID, password, tenant ID and storage account names to this pipeline – because both our docker file and the pipeline-as-code expected them as dependencies. However, we can’t just put their values and commit them to GitHub. They should be kept secret.

Azure Pipeline Secret variables

Azure Pipeline allows us to define secret variable for a pipeline. We need to open the build definition in “edit” mode and then go to the top-right ellipses button as below:

ado1

Now we can define the values of these secret and keep them hidden (there’s a lock icon there).

ad02

That’s all what we need. Ready to deploy the code to Azure storage via this pipeline. If we now go an make a change in our repository it will trigger the pipeline and sure enough it will build-test-publish-deploy to Azure storage as a Static SPA.

Thanks for reading!

OpenSSL as Service

OpenSSL is awesome! Though, requires little manual work to remember all the commands, executing them in a machine that has OpenSSL installed. In this post, I’m about to build an HTTP API over OpenSSL, with the most commonly used commands (and the possibility to extend it further – as required). This will help folks who wants to run OpenSSL in a private network but wants to orchestrate it in their automation workflows.

Background

Ever wanted to automate the TLS (also known as SSL) configuration process for your web application? You know, the sites that served via HTTPS and Chrome shows a green “secure” mark in address bar. Serving site over HTTP is insecure (even for static contents) and major browsers will mark those sites as not secure, Chrome already does that today.

Serving contents via HTTPS involves buying a digital certificate (aka SSL/TLS certificate) from certificate authorities (CA). The process seemed complicated (sometimes expensive too) by many average site owners or developers. Let’s encrypt addressed this hardship and made it painless. It’s an open certificate authority that provides free TLS certificates in an automated and elegant way.

However, free certificates might not be ideal for enterprise scenarios. Enterprise might have a requirement to buy certificate from a specific CA. In many cases, that process is manual and often complicated and slow. Typically, the workflow starts by generating a Certificate Signing request (also known as CSR) which requires generating asymmetric key pair (a public and private key pair). Which is then sent to CA to get a Digital Identity certificate. This doesn’t stop here. Once the certificate is provided by the CA, sometimes (Specially if you are in IIS, .net or Azure world) it’s needed to be converted to a PFX (Personal Information Exchange) file to deploy the certificate to the web server.

PFX (aka PKCS #12) is a file format defines an archive file format for storing many cryptography objects as a single file. It’s used to bundle a private key with it’s X.509 certificate or bundling all the members of a chain of trust. This file may be encrypted and signed. The internal storage containers (aka SafeBags), may also be encrypted and signed.

Generating CSR, converting a Digital Identity certificate to PFX format are often done manually. There are some online services that allows you generating CSRs – via an API or an UI. These are very useful and handy, but not the best fit for an enterprise. Because the private keys need to be shared with the online provider – to generate the CSR. Which leads people to use the vastly popular utility – OpenSSL in their local workstation – generating CSRs. In this article, this is exactly what I am trying to avoid. I wanted to have an API over OpenSSL – so that I can invoke it from my other automation workflow running in the Cloud.

Next, we will see how we can expose the OpenSSL over HTTP API in a Docker container, so we can run the container in our private enterprise network and orchestrate this in our certificate automation workflows.

The Solution Design

We will write a .net core web app, exposing the OpenSSL command via web API. Web API requests will fork OpenSSL process with the command and will return the outcome as web API response.

OpenSSL behind .net core Web API

We are using System.Diagnostics.Process to lunch OpenSSL in our code. This is assuming we will have OpenSSL executable present in our path. Which we will ensure soon with Docker.

        private static StringBuilder ExecuteOpenSsl(string command)
        {
            var logs = new StringBuilder();
            var executableName = "openssl";
            var processInfo = new ProcessStartInfo(executableName)
            {
                Arguments = command,
                UseShellExecute = false,
                RedirectStandardError = true,
                RedirectStandardOutput = true,
                CreateNoWindow = true
            };

            var process = Process.Start(processInfo);
            while (!process.StandardOutput.EndOfStream)
            {
                logs.AppendLine(process.StandardOutput.ReadLine());
            }
            logs.AppendLine(process.StandardError.ReadToEnd());
            return logs;
        }

This is simply kicking off OpenSSL executable with a command and capturing the output (or errors). We can now use this in our Web API controller.

    /// <summary>
    /// The Open SSL API
    /// </summary>
    [Produces("application/json")]
    [Route("api/OpenSsl")]
    public class OpenSslController : Controller
    {
        /// <summary>
        /// Creates a new CSR
        /// </summary>
        /// Payload info
        /// The CSR with private key
        [HttpPost("CSR")]
        public async Task Csr([FromBody] CsrRequestPayload payload)
        {
            var response = await CertificateManager.GenerateCSRAsync(payload);
            return new JsonResult(response);
        }

This snippet only shows one example, where we are receiving a CSR generation request and using the OpenSSL to generate, returning the CSR details (in a base64 encoded string format) as API response.

Other commands are following the same model, so skipping them here.

Building Docker Image

Above snippet assumes that we have OpenSSL installed in the machine and the executable’s path is registered in our system’s path. We will turn that assumption to a fact by installing OpenSSL in our Docker image.

FROM microsoft/aspnetcore:2.0 AS base

RUN apt-get update -y
RUN apt-get install openssl

Here we are using aspnetcore:2.0 as our base image (which is a Linux distribution) and installing OpenSSL right after.

Let’s Run it!

I have built the docker image and published it to Docker Hub. All we need is to run it:

Untitled-1

The default port of the web API is 80, though in this example we will run it on 8080. Let’s open a browser pointing to:

http:localhost:8080/ 

Voila! We have our API’s. Here’s the Swagger UI for the web API.

swagger

And we can test our CSR generation API via Postman:

Postman

The complete code for this web app with Docker file can be found in this GitHub Repository. The Docker image is in Docker Hub.

Thanks for reading.

3D Docker Swarm visualizer with ThreeJS

Few days before I wrote about creating a Docker Swarm Visualizer here. I have enjoyed very much writing that peice of software. However, I wanted to have a more funny way to look at the cluster. Therefore, last weekend I thought of creating a 3D viewer of the cluster that might run on a large screen, realtime showing up the machines and their workloads.

After hacking a little bit, I ended up creating a 3D perspective of the Docker swarm cluster, that shows the nodes (workers in green, managers in blue and drained nodes in red colors and micro service containers in blue small cubes, all in real-time and by leveraging the ThreeJS library. It was just an added funny view to the existing visualizer. Hope you will like it!

You need to rebuild the docker image from the docker file in order to have the 3d view enabled. I didn’t want to include this into the moimhossain/viswarm image.