I think it was 2008 when I was studying the second edition of “Writing Secure Code” by David LeBlanc and Michael Howard. It was there that I ran into the term “encraption” for the first time. Encraption refers, generally, to the bad practice of using poor encryption: old and deprecated algorithms, poor key complexities, storing the keys in plain sight, and other crap like that. Some of these bad practices can be fixed within a software development team by educating the members to ask for expertise in cryptography instead of just making assumptions. I have talked about this before, and yes, this aspect is critical.
I want to talk about a specific aspect of encraption: storing the keys in plain sight. I still encounter this situation so often, that I get physically ill when I am seeing it. If you claim to have never done it – store keys/sensitive information in plain sight – please think again, this time carefully. In fact, there is a secure coding principle stating that the source code of your application, in any configuration, should not be considered sensitive information. This, of course, has some very little exceptions.
Disclaimer! This article is just a summary of the reasons why you should consider using Azure Managed Service Identities, and does not describe the inner pluming of Managed Service Identities in Azure, nor does it provide examples. It would be stupid for me to claim that I can give more appropriate documentation than Microsoft already does on their platform. At the end of the article you will find links pointing you to those resources.
Let us imagine a classic situation here, for example a shared service that is required to store sensitive information that is generated by each of its users, and later make that data available ONLY to the user that generated it. Something like this:
Now, the trick is that any bug/quark that may appear inside the app will not allow for a user to obtain any key belonging to any other user. The cryptography behind this is not the scope of this article. Also, handling sensitive data while they are in memory is not the purpose of this article. So, in the end, how would you tackle this? Many of you would say, right away that key storage should be delegated to a dedicated service, let’s call it a HSM, like so:
Now, the problem is that you need to have an authenticated and secure communication channel with the HSM. If you are trying to accomplish this in your own infrastructure, then good luck. While it is possible to do it, it is most certainly expensive. If you are going to buy the HSM service from an external provider, then, most certainly you will have to obey a lot of security standards before obtaining it. Most of these so-called Key Vault services will allow access to them based on secret-based authentication (app id and secret) that your application, in turn will need to securely store. I hope you have spotted the loophole. The weakest link here is that your application will still have to manage a secret, a set of characters that is very, very sensitive information:
Of course, most teams will have a “rock-solid-secure-rocketscience-devops” that will protect this red key in the configuration management of the production environment. Someone will obey a very state of the art process to obtain and store the red key only in the production environment, and no one will ever get it. This is sarcasm in case you missed it. But why is it sarcasm? you may ask. Here are my reasons.
- In 15 years and probably hundreds of projects with a lot of people involved, I have maybe seen 3 – three – projects that have done this properly. Typical mistakes are ranging between
- the red key has changed, no one knew that it can change, the production halted, a SWAT team rushed to save the day and used their own machines for changing the key
- development team has access to production
- the “rock-solid-secure-rocketscience-devops” is ignored by the “experienced” developer that hard-codes the key
- no one really cares about that key. It is just “infrastructure”
- An attack can still target this red key. It is, in fact just another attack surface. Assuming the absurdity that all other parts of the system are secure, a system holding such a key will have at least two points of attack.
- The identity that has access to the production environment (this is very hard to eliminate)
- The red key itself
Why not eliminating this red key altogether? Why not going to a cloud provider where you can create an application (or any resource) and a Key Vault and then create a ‘trust relationship’ between those two that needs no other secrets in order to function. This way you will not have to manage yet another secret.
Please bear in mind, that if using an HSM or Key Vault, you can isolate all your sensitive information and keys at that level, so that you will never have to bother about the secure storage of those item ever. No more hard-coding, no more cumbersome dev-ops processes!
Managed Service Identities
This is possible in azure, using Managed Service Identities. As I have said before, the purpose of this article is not to replace the awesome documentation that Micro$oft has in place for MSI, but to encourage you to read it and use this magic feature in your applications. Current or future
Here is about Managed Service Identities:
Here is an example where you can use an Azure App Service together with an Key Vault