AppSec Function for Secrets and techniques Administration | by Teri Radichel | Cloud Safety | Oct, 2022 | Tech Aza

86. Design an structure that requires three-party collusion to entry secrets and techniques in Secrets and techniques Supervisor

It is a continuation of my sequence of posts on Automating Cybersecurity Metrics.

Within the final publish, we created an AppSec function.

I began refactoring the code to configure customers with their very own secrets and techniques. That is the place I bumped into a bit snag.

Suppose an IAM administrator needs to create a brand new person with an SSH key saved in a user-specific secret.

• We won’t create the SSH key till we now have a secret to place it in if another person is creating the key.
• The group liable for managing the secrets and techniques useful resource coverage wants the username earlier than they will create the user-specific secret.
• The KMS person, function, and group should be created earlier than they will deploy a KMS key.
• The Secrets and techniques Administration person, group, and function (what I am calling AppSec right here) should be created earlier than they will create a secret.
• The KMS key wants and the person should be created earlier than the key will be created with a correct coverage.
• We do not wish to put a price on the key till we now have a coverage (an issue with our earlier scripts).

The present deployment script has person creation in a single script. We have to separate the KMS customers from the deployment.sh script or separate the SSH key creation into its personal script, run in any case customers and the KMS script have been created, and after the key is deployed the place we are able to retailer the SSH key. The latter appears simpler to deal with.

Separate deployment script for SSH keys

In my IAM listing, I will create a separate deployment_ssh_keys.sh script and name the create_ssh_key perform instantly from that script for the developer person.

I will take away the y/n parameter that I actually did not like within the first place from the person creation code in my primary deployment.sh script. So this:

It turns into this:

We are going to take away the person creation logic to optionally create the SSH key:

At this level, I gave my deployment.sh person script a fast check to ensure I did not have any typos (and I did, so I mounted it).

I additionally check my ssh key creation script to ensure I am beginning with identified and dealing code.

Create an AppSec subfolder and secret administration code

Subsequent, we have to create the AppSec listing in our code base that matches the opposite subfolder hierarchies. We are going to create our customary deployment.sh file and an appsec_functions.sh file as in earlier posts for reusable features.

We will add a create_secret() perform to create a brand new secret within the secret supervisor. Since a secret should have a default worth, we’ll set a short lived worth that may be overridden when a secret worth is added. As famous, we do not wish to go delicate values ​​to the CloudFormation parameters anyway, as they’d be seen within the AWS console.

We are going to pull the CloudFormation templates from the IAM listing to create the key and secret coverage within the cfn folder within the AppSec listing in order that the paths within the code above level to the right recordsdata.

I eliminated all stacks associated to secrets and techniques to ensure my code would not simply skip a deployment as a result of the template hasn’t modified. I additionally do not need a stack to be created with a brand new identify and go away an outdated stack hanging round someway.

Be sure you have configured a CLI profile referred to as “AppSec” utilizing the AppSec function and person credentials described within the final publish.

It’s at this level that I noticed that I forgot so as to add the permission to make use of CloudFormation to the AppSec function within the final publish, so I added and carried out that change.

Oh sure, and that is the place we stumble as soon as once more.

Keep in mind how we have been attempting to guarantee that the one that creates the key coverage does not have entry to delete the key? Properly, we will not create a secret with no worth, so we now have to encrypt the worth so as to add the key.

It appears that evidently our plans have been annoyed. Till AWS permits us to create a secret and coverage, we will not do what we needed to do with this secret and coverage to create segregation of duties and non-repudiation.

To illustrate we create an unencrypted secret. So we would not want the KMS key, proper? So can we replace the important thing so as to add the KMS ID later? However who would implement and assure that the key was up to date with a KMS ID? All the things is getting very messy at this level.

One of the best answer can be for AWS to permit creation of a secret with a KMS key ID however not requirement so as to add or encrypt a price.The opposite a part of this answer is for AWS to repair KMS key insurance policies and IAM Permissions so a person will be supplied permissions to EITHER encrypt or decrypt however not each.

Properly that was enjoyable. We spend plenty of time for nothing, since we have not actually achieved our aim of non-repudiation, have we? The AppSec person wants permission to encrypt and decrypt the worth and desires permission to replace the key coverage. So what’s stopping them from updating the coverage to allow them to get the worth and decrypt it?

Do not forget that we denied the “get-secret-value” permission within the AppSec IAM coverage. The AppSec person is aware of the preliminary worth you set (a dummy worth), however can’t get the later up to date worth as a result of IAM restrictions.

So a extra exact diagram of our segregation of duties from our earlier publish would look extra like this to be exact if we contemplate who has permission to vary a coverage to have entry to the encrypted secret, with builders being granted entry by three completely different directors in order that have entry to their very own credentials (ssh key):

In different phrases, it will take three-party collusion for somebody to achieve entry to a secret they should not have if we be certain that IAM directors cannot grant themselves permissions they should not have. As talked about earlier than, there may be all the time a set of tremendous admin credentials that may change all of this and that needs to be used for preliminary setup after which locked out.

So let’s go forward and provides our AppSec person permission to encrypt and decrypt the identical method we did our IAM person in each the KMS coverage and their IAM function coverage.

Updating the function coverage is easy. Copy the IAM administrator function permissions:

Redeploy the roles to replace the coverage.

Move a number of ARNs to encrypt and decrypt with our KMS key

However wait, how can we add two ARNs to permit encryption and decryption? We will go a listing of ARNs to the important thing coverage for IAM and AppSec roles in the identical method that we go a listing of customers within the Developer group.

It seems like we’re already accepting a comma-separated record as a parameter:

Get our first identify and output identify to make use of with our frequent perform to get the output worth of a CloudFormation stack:

Get the ARN for the AppSec function, create a comma separated record, and go it in to create our key coverage.

Redeploy the keys to replace the DeveloperResources key coverage.

Properly, you could or could not have realized it, however I misspelled encryptarn2 above, so I needed to repair that. The code on GitHub ought to work. 🙂

Examine the important thing coverage to ensure the ARN for each roles has the mandatory permissions.

We will now attempt to implement the key once more as a result of our AppSec person ought to have entry to implement the key.

Success.

The IAM administrator updates the key with the SSH key

Now that the key exists, return to our create ssh key script and run it from the IAM listing.

./deploy_ssh_keys.sh

I needed to right some typos:

Success:

Now show that the developer can nonetheless get your secret worth (see earlier posts):

aws secretsmanager get-secret-value --secret-id Developer --profile developeruser

Once more, success.

Some remaining points

There are a number of remaining points to think about with our code above. Are you aware what they’re? What occurs if our key creation fails in the midst of a deployment? A brand new SSH key may be created if the key nonetheless accommodates the outdated SSH key. The important thing could also be created within the secret, however the person coverage will not be up to date and factors to no secret or the flawed secret if it was deleted and up to date.

This will or could not create a safety subject as a result of for essentially the most half pointing to one thing that was deleted and the truth that you may’t create a particular secret with a reputation you management means somebody can not directly level somebody to the flawed secret. There may be some difficult strategy to do it if there’s a helpful secret current in some unspecified time in the future, however I am not going to enter that now. In my case the danger appears extraordinarily low.

However extra hermetic code would be sure that if a set of operations which are supposed to finish collectively fail, the unfinished operations are rolled again or another operation happens to take away probably invalid pointers within the insurance policies. For instance, if one thing goes flawed, you may delete the key, the key coverage, and the person coverage. We cannot take these steps right here, however contemplate the risk mannequin in your personal surroundings and whether or not you wish to take these extra steps.

Actually, I plan to utterly change implementations sooner or later if my plan works out. I will do away with all of the bash for essentially the most half and use the CloudFormation templates, so I am not going to deal with this proper now. Bash will not be a super programming language by any means, so that is all proof of idea code at this level.

Now I wish to use this key for an EC2 occasion…keep tuned…

Teri Radichel

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