MSI or Managed Service Identity that it stands for has been around for some time but quite recently a new set of resources has been integrated in to this and we need to start thinking of using MSI alot more. Since this will increase security and streamline the authorization process, one place to grant access, same account and authorization process. Sadly most of Microsoft’s documentation around this is still for Virtual Machines and I want to enlighten this alot more for IPaaS services like Logic Apps, Functions, API Management, Web Apps, DataFactory Service Bus and Event Grid.
So MSI is an identity of a resource just like any other user in Azure AD. The beauty of this is that with this we can assign access rights to that identity and the resource now authenticates by itself (with credentials no one else nows) and with those credentials it can use the resource. I usually like to discribe it as a virtualization of the service and used for authorization purposes, in the image bellow we can see that an Azure Function are making requests to Cosmos. This is allowed since we have assigned the role Cosmos DB Built-in Data Contributor to the identity of the function in a scope containing the Cosmos resource (could be on resource itself, a resource group that grants access to all cosmos resources in the resource group, or subscription granting access to all cosmos resources in that subscription).
What Resources can use MSI: (there are more but these are Integration focused)
What resources can we use authenticate to with MSI.
No before we created a SQL account, took keys from Cosmos, Service Bus etc, create a service principal or a service user in AD to accomplish other acesses. All of these could potentially be simplified and changed to only give the resource the appropiate access rights. Note not all resources is supporting this yet, but this is an area where Microsoft has done some great gains last 6 months.
No on the contrary, you as a developer don’t need to gather all these credentials either, development and testing can be used with your own account. Making it easier to get started and another great benefit is that you cannot accidently keep credentials and access after an completed assignement or project. With good documentation it’s also easier to get a new teammate up to speed. Another good thing is that we know that credentials are not wandering away when members leave the team.
As a developer you could usually grant yourself access to diffrent resources. When using MSI this is no longer the case, since the access is now granted by Azure AD and Azure AD access is often prohibited for developers. Authroization now need’s to be given by a user with Owner or User Access Administrator, to overcome this you need to create a plan for your team how this should be done.
A tip here is to create a Azure AD Group and add all developers to it that need specific access, remove them when they don’t need it. An extra step would be creating a PIM group for it.