Azure

Custom “Virtual Network Operator” Role in Azure

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We all know that cloud environments are different than on premises. Development environments can be even more difficult, the right cross between giving freedom to produce business value and enough security and controls to maintain a good security posture. Recently I came across a scenario where the design was that the networking components (Virtual Network, S2S VPN, Peerings, Service Endpoints, UDRs, Subnets, etc.) were all under the control of a Networking team so that the Azure environment would be an extension of their local network. From a permissions standpoint though this caused some problems. The goal would be to empower developers to build whatever they need and just attach it to the vNet when connectivity was needed, with the caveat that they shouldn’t be able to modify any of the network settings or configurations in the shared vNet. This however, turned out not to be possible with default IAM roles.

In my testing, even though you’re not “modifying” anything per se in the vNet – when attaching a network interface card to a Subnet it does require write access. Reader access will give the user this error.

 

After looking through the default IAM roles, there aren’t any that do what I need them to do. Alas, a custom role is needed. For reference, please checkout this docs page for custom roles – https://docs.microsoft.com/en-us/azure/role-based-access-control/custom-roles.

First, I need to see what actions are available to pack into the custom role so I run the following command in Azure Powershell and get these results.

Get-AzProviderOperation “Microsoft.Network/virtualNetworks/*” | FT OperationName, Operation, Description -AutoSize

Great, now I can see what is available. It looks like the actions that I need are the /subnet/join/action and /subnet/joinViaServiceEndpoint/Action. Based on the descriptions these two will essentially give “operator” role to the vnet. The assignee will be able to use the subnet(s) but not able to modify them.

Next, you can use one of the template references in the Microsoft Docs link (https://docs.microsoft.com/en-us/azure/role-based-access-control/custom-roles-powershell#create-a-custom-role-with-json-template) and modify the actions.

{
  “Name”: “Custom – Network Operator Role”,
  “Id”: null,
  “IsCustom”: true,
  “Description”: “Allows for read access to Azure network and join actions for service endpoints and subnets.”,
  “Actions”: [
  “Microsoft.Network/virtualNetworks/subnets/join/action”,
  “Microsoft.Network/virtualNetworks/subnets/joinViaServiceEndpoint/action”,
  “Microsoft.Network/virtualNetworks/subnets/read”
   ],
  “NotActions”: [],
  “AssignableScopes”: [
  “/subscriptions/00000000-0000-0000-0000-000000000000”,
  “/subscriptions/11111111-1111-1111-1111-111111111111”
  ]
}

 

After modifying the assignable subscription IDs, save that as a .json file and use it in the following command to import the custom role.

New-AzRoleDefinition -InputFile “C:\FileFolderLocationPath\CustomNetworkOperatorRole.json”

After a portal refresh you get the custom role available as an IAM role assignment.

 

There you go, after assigning this role the user was able to create VMs and attach them to the Virtual Network while still leaving control of the Network configuration to the Networking Team.

I hope I’ve made your day at least a little bit easier!

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Isolated Virtual Machines in Azure

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In a recent design session, I had someone mention how they wish that Azure had dedicated and/or isolated IaaS VMs like some of the other cloud providers. They were shocked with I said – they do! Azure has a number of isolated VM types that you can provision and leverage just the same as any other IaaS VM.

The link to Microsoft documentation below states that “Azure Compute offers virtual machine sizes that are Isolated to a specific hardware type and dedicated to a single customer. These virtual machine sizes are best suited for workloads that require a high degree of isolation from other customers for workloads involving elements like compliance and regulatory requirements.”

https://docs.microsoft.com/en-us/azure/security/azure-isolation#isolated-virtual-machine-sizes

Yup, you read that right, dedicated hardware. This means that using one of the isolated VM types (listed below) will guarantee that your virtual machine will be the only one running on that server instance (as of Nov. 1, 2018).

  • Standard_E64is_v3
  • Standard_E64i_v3
  • Standard_M128ms
  • Standard_GS5
  • Standard_G5
  • Standard_DS15_v2
  • Standard_D15_v2

 

If VM isolation is what you’re after, you can also consider Nested Virtualization in Azure (link below). A few VM types in Azure support Nested Hyper-V (not suitable for production, mind you) and Hyper-V Containers using Docker.

https://azure.microsoft.com/en-us/blog/nested-virtualization-in-azure/

https://docs.microsoft.com/en-us/virtualization/windowscontainers/manage-containers/hyperv-container

 

Lastly, there is a new feature that recently went GA that’s sort of in-line with VM isolation – Confidential Compute. While this isn’t VM isolation, it is an isolated enclave for executing code in TEEs (Trusted Execution Environments) using Intel’s SGX capabilities. This allows for code to be executed in an environment that, while it’s being executed, can not be accessed by any source outside of the enclave (see diagrams in the links below).

https://azure.microsoft.com/en-us/blog/introducing-azure-confidential-computing/

https://azure.microsoft.com/en-us/blog/azure-confidential-computing/

 

Using physical isolation techniques in the cloud can be very different than the way we’re used to doing it on-prem. Hopefully, though, this post and its associated links will get you thinking about different ways you can design for isolation in Azure. Feel free to comment, or reach out on Twitter @MattHansen0.

Thanks, and I hope I’ve made your day at least a little bit easier.