March 28, 2023

Slack launched GovSlack in July 2022. With GovSlack, authorities companies, and people they work with, can allow their groups to seamlessly collaborate of their digital headquarters, whereas preserving safety and compliance on the forefront. Utilizing GovSlack consists of the next advantages:

  • Helps key authorities safety requirements, akin to FedRAMP Excessive, DoD IL4, and ITAR
  • Runs in AWS GovCloud information facilities
  • Permits exterior collaboration with different GovSlack-using organizations via Slack Join
  • Offers entry to your individual set of encryption keys for superior auditing and logging controls
  • Permits permission and entry controls at scale via Slack’s enterprise-grade admin dashboard
  • Features a listing of curated purposes (together with DLP and eDiscovery apps) that may combine with Slack
  • Maintained and supported by US personnel

Earlier than the massive launch, the Cloud Foundations workforce spent nearly two quarters organising the infrastructure wanted to run GovSlack.

GovSlack is the very first service Slack launched on AWS Gov infrastructure. Subsequently we needed to spend a big period of time studying the variations between customary and Gov AWS and making adjustments to our tooling and the platform to have the ability to run on Gov AWS.

On this weblog put up, we’re going to take a look at how we constructed the AWS infrastructure wanted for GovSlack and challenges we confronted. In the event you’re eager about constructing a brand new service on AWS GovCloud, this put up is for you.

How are GovCloud accounts associated to industrial accounts?

Not way back, Slack began shifting from a single AWS account to youngster accounts. As a part of this challenge, we additionally made vital adjustments to our world community infrastructure. You may learn extra about this within the weblog posts Constructing the Subsequent Evolution of Cloud Networks at Slack and Constructing the Subsequent Evolution of Cloud Networks at Slack – A Retrospective. We have been capable of make the most of most of our learnings into constructing the GovSlack community infrastructure.

To start with, AWS Gov accounts would not have any billing functionality. The sources within the Gov accounts will propagate their billing right into a linked shell industrial AWS account. Whenever you request a Gov AWS account, a linked shell industrial AWS account is mechanically created. Subsequently the very first thing we needed to do was to request a Gov root AWS account utilizing our root payer industrial account. This was a prolonged course of, however not as a result of it was a technically tough factor to do—it was so simple as clicking a button on our root industrial AWS account. Nevertheless including the Gov Accounts to our current agreements with AWS did take a number of weeks. As soon as we had our Gov root account, we have been capable of request extra GovCloud accounts for our service groups. It’s value mentioning that GovCloud youngster accounts nonetheless must be requested utilizing the industrial AWS API utilizing the create-gov-cloud-account name.

When a brand new GovCloud youngster account is created, you’ll be able to assume the OrganizationAccountAccessRole within the youngster account by way of the GovCloud root account’s OrganizationAccountAccessRole (this function identify might differ if you happen to override the identify utilizing –role-name flag).

Let’s take a look at what are these hyperlinks appear to be in a diagram:

As we will see above, all our GovCloud sources prices are propagated to our root industrial AWS account.

How did we create GovCloud accounts?

As we mentioned above, we use the AWS organizations API and the create-gov-cloud-account name to request a brand new GovCloud youngster account. This course of creates two new accounts: the GovCloud account and the linked industrial AWS account. We use a pipeline on the industrial facet for this portion of the method. Then the linked industrial AWS account is moved to a extremely restricted OU, so it’s blocked from creating any AWS sources in it.

We use a Jenkins pipeline within the AWS Gov partition to configure the GovCloud youngster account. We are able to assume the OrganizationAccountAccessRole of the brand new youngster account from the GovCloud root account as quickly as it’s created. Nevertheless our Gov Jenkins providers are positioned in a devoted youngster account. Subsequently there’s a step on this pipeline that may replace the kid account’s OrganizationAccountAccessRole’s belief coverage, so it may be assumed by the Jenkins employees. This step should be accomplished first earlier than we will transfer on to different steps of the kid account configuration course of.

How can we separate GovDev and GovProd?

As talked about beforehand, one of many core compliance necessities for a GovCloud surroundings was that solely US individuals could be licensed to the manufacturing surroundings. With this requirement in thoughts we made the choice to face up two Gov environments, one being the manufacturing Gov surroundings, recognized internally as “GovProd”, and a second surroundings, often called “GovDev”. The GovDev surroundings could be accessed by anybody and check their providers earlier than being deployed to GovProd by US personnel.

To make sure now we have full isolation between these environments, now we have approached the construct out utilizing a full shared-nothing paradigm, which allows the environments to function in fully completely different AWS organizations. The layer 3 networking mesh we use (Nebula) is totally disconnected, which means the networks are solely segregated from each other.

To archive this, we created two AWS organizations in GovCloud, and underneath every of those organizations, an equivalent set of kid accounts to launch our providers within the Dev and Prod environments.

Is that this actually remoted?

When a brand new youngster account is created, we have to use the Gov root account for assuming the OrganizationAccountAccessRole’s into it for the primary portion of the provisioning as we mentioned here. Since solely US personnel can entry the Gov prod accounts, solely US personnel are capable of entry the Gov root account, as this account has entry to imagine the OrganizationAccountAccessRole within the youngster accounts. Subsequently the preliminary provisioning of dev accounts additionally should run on Gov prod Jenkins, and US personnel are required to be engaged to kick off the preliminary a part of GovDev accounts creation.

Different challenges

GovProd additionally lacks some AWS providers, akin to CloudFront and public zones in Route53. Moreover, after we are utilizing the AWS CLI in GovCloud, we should move within the –area flag or set the AWS_DEFAULT_REGION surroundings variable with a Gov area because the AWS CLI at all times defaults to a industrial area for API calls.

Route53 and ACM

A few of our Gov providers use AWS ACM for the load balancer SSL certifications. We keep away from utilizing e mail certificates validation as this doesn’t enable us to auto-renew expiring certificates. ACM DNS helps auto-renewal however requires public DNS information to take action. Subsequently, we use the identical devoted industrial DNS account for validating our ACM certificates as effectively. Entry to this industrial DNS account is restricted to US personnel.


AWS GovCloud doesn’t assist public Route53 zones. Nevertheless personal zones are allowed. We created a GovDev and Gov Prod DNS account for internet hosting personal Route53 zones. The Cloud Foundations workforce creates VPCs in a set of accounts managed by us, then we use AWS Transit gateways to attach completely different areas collectively and construct a worldwide community mesh. Lastly these VPCs are shared into youngster accounts to summary the complexity of organising networks from software groups. You may learn extra about how we do that in our different two weblog posts Constructing the Subsequent Evolution of Cloud Networks at Slack and Constructing the Subsequent Evolution of Cloud Networks at Slack – A Retrospective

The personal Route53 zones we create are connected to the shared VPCs, in order quickly as a file is added to those zones, it may be resolved inside our VPCs.

Nevertheless since GovCloud doesn’t assist public DNS, we have to create these information on the industrial facet. Subsequently, we created a devoted industrial AWS account for internet hosting public GovSlack DNS information. Entry to this industrial DNS account is restricted to US personnel.

How can we switch artifacts between industrial and GovCloud?

AWS doesn’t assist assuming roles between AWS customary and AWS GovCloud partitions. Subsequently we created a mechanism to compliantly move objects to GovCloud.

This mechanism ensures the objects are pulled into AWS GovCloud partition from the usual partition utilizing AWS IAM credentials. Credentials to entry the usual partition for pulling these objects are saved securely on the AWS GovCloud partition.

Terraform modules

We use Terraform modules for constructing our infrastructure as a group of interdependent sources akin to VPCs, Web Gateways, Transit Gateways, and route tables. We needed to make use of the identical modules for constructing our Gov infrastructure so we will maintain these patterns constant between AWS Gov and customary partitions. One key distinction between the industrial and Gov AWS sources are the sources ARNs. Business ARNs begin with arn:aws versus Gov ARNs begin with arn:aws-us-gov.

Subsequently we needed to construct a quite simple Terraform module referred to as aws_partition. Utilizing outputs of this module, we will programmatically construct ARNs and uncover which AWS partition we’re in.

Let’s take a look at the aws_partition module,

information "aws_caller_identity" "present" 

information "aws_arn" "arn_details" 
  arn = information.aws_caller_identity.present.arn

output "partition" 
  worth = information.aws_arn.arn_details.partition

output "is_govcloud" 
  worth = exchange(information.aws_arn.arn_details.partition, "gov", "") != information.aws_arn.arn_details.partition ? true : false

Now let’s take a look at a instance utilization,

module "aws_partition" 
  supply = "../modules/aws/aws_partition"

information "aws_iam_policy_document" "instance" 
	impact = "Enable"

	actions = [

	sources = [

useful resource "aws_config_config_rule" "instance" 
  rely = module.aws_partition.is_govcloud ? 1 : 0

  identify = "example-rule"

	proprietor             = "AWS"

VPC endpoints

During the last three years Slack has been working very laborious to utilize AWS’ VPC endpoints for accessing native AWS providers in our industrial surroundings. They cut back the latency and improve the resiliency of our methods, whereas additionally lowering our networking prices.

With all these benefits, it’s very simple to imagine that it’s a easy transfer, however one obvious challenge that now we have present in each the industrial and GovCloud transfer to VPC endpoints is that AWS doesn’t at all times assist all providers in all AZs. Very often now we have discovered that we have to assist the flexibility for methods to entry AWS providers each with and with out VPC endpoints, which at instances can create summary edge circumstances that may be laborious to account for.

Whereas AWS is consistently releasing these VPC endpoints at a AZ stage, we nonetheless haven’t reached 100% of providers enabled for 100% of the areas/AZs we run our service in.


Whereas we have been constructing out the Gov surroundings, we began through the use of IAM customers to bootstrap the Gov surroundings, however this was solely ever going to be a short-term answer. AWS just lately launched the AWS-SSO answer into their industrial surroundings and much more just lately of their Gov surroundings. As this was an entire greenfield buildout it was a very good alternative to experiment with new applied sciences and enhance our current implementation.

In contrast to AWS’ customary IAM roles, AWS-SSO permission units are an org-wide world (throughout the complete org, versus an account) useful resource, and this adjustments how we construct and deploy them.

Since deploying AWS-SSO within the GovCloud surroundings, now we have taken the learnings and back-ported it into our industrial surroundings. Whereas we already had an current SSO system in place for entry to the whole thing of our industrial AWS surroundings, utilizing AWS-SSO has made this course of quite a bit smoother and simpler.

So what have we discovered?

Rebuilding our whole community infrastructure gave us the flexibility to check our tooling, processes,  and Terraform modules, and gave us the chance to make enhancements. We have been capable of clear up a large number of hardcoded values and alter issues to be extra reusable. We have been additionally capable of take a step again and have a deep dive into our processes, instruments, AWS footprint and acquire a higher understanding of our platform as this entire course of gave us a chance to rebuild Slack from scratch.