What We Realized from Constructing GovSlack

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 retaining safety and compliance on the forefront. Utilizing GovSlack consists of the next advantages:

  • Helps key authorities safety requirements, reminiscent of FedRAMP Excessive, DoD IL4, and ITAR
  • Runs in AWS GovCloud information facilities
  • Allows exterior collaboration with different GovSlack-using organizations by means of Slack Join
  • Supplies entry to your individual set of encryption keys for superior auditing and logging controls
  • Permits permission and entry controls at scale by means of Slack’s enterprise-grade admin dashboard
  • Features a listing of curated functions (together with DLP and eDiscovery apps) that may combine with Slack
  • Maintained and supported by US personnel
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Earlier than the massive launch, the Cloud Foundations group spent virtually two quarters organising the infrastructure wanted to run GovSlack.

GovSlack is the very first service Slack launched on AWS Gov infrastructure. Due to this fact we needed to spend a big period of time studying the variations between commonplace and Gov AWS and making modifications 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 enthusiastic about constructing a brand new service on AWS GovCloud, this put up is for you.

How are GovCloud accounts associated to business accounts?

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Not way back, Slack began shifting from a single AWS account to little one accounts. As a part of this challenge, we additionally made vital modifications to our international 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 in a position to make the most of most of our learnings into constructing the GovSlack community infrastructure.

Initially, AWS Gov accounts would not have any billing functionality. The sources within the Gov accounts will propagate their billing right into a linked shell business AWS account. If you request a Gov AWS account, a linked shell business AWS account is mechanically created. Due to this fact the very first thing we needed to do was to request a Gov root AWS account utilizing our root payer business 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 business AWS account. Nonetheless including the Gov Accounts to our present agreements with AWS did take just a few weeks. As soon as we had our Gov root account, we have been in a position to request extra GovCloud accounts for our service groups. It’s value mentioning that GovCloud little one accounts nonetheless must be requested utilizing the business AWS API utilizing the create-gov-cloud-account name.

When a brand new GovCloud little one account is created, you may assume the OrganizationAccountAccessRole within the little one account by way of the GovCloud root account’s OrganizationAccountAccessRole (this function title might differ if you happen to override the title 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 business AWS account.

How did we create GovCloud accounts?

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As we mentioned above, we use the AWS organizations API and the create-gov-cloud-account name to request a brand new GovCloud little one account. This course of creates two new accounts: the GovCloud account and the linked business AWS account. We use a pipeline on the business aspect for this portion of the method. Then the linked business 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 little one account. We are able to assume the OrganizationAccountAccessRole of the brand new little one account from the GovCloud root account as quickly as it’s created. Nonetheless our Gov Jenkins companies are positioned in a devoted little one account. Due to this fact there’s a step on this pipeline that can replace the kid account’s OrganizationAccountAccessRole’s belief coverage, so it may be assumed by the Jenkins staff. This step have to 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?

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As talked about beforehand, one of many core compliance necessities for a GovCloud surroundings was that solely US individuals can 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, identified internally as “GovProd”, and a second surroundings, often known as “GovDev”. The GovDev surroundings will be accessed by anybody and check their companies earlier than being deployed to GovProd by US personnel.

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

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

Is that this actually remoted?

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When a brand new little one 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 right here. Since solely US personnel can entry the Gov prod accounts, solely US personnel are in a position to entry the Gov root account, as this account has entry to imagine the OrganizationAccountAccessRole within the little one accounts. Due to this fact 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

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GovProd additionally lacks some AWS companies, reminiscent of CloudFront and public zones in Route53. Moreover, after we are utilizing the AWS CLI in GovCloud, we should go 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 business area for API calls.

Route53 and ACM

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A few of our Gov companies use AWS ACM for the load balancer SSL certifications. We keep away from utilizing electronic 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. Due to this fact, we use the identical devoted business DNS account for validating our ACM certificates as nicely. Entry to this business DNS account is restricted to US personnel.


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AWS GovCloud doesn’t assist public Route53 zones. Nonetheless non-public zones are allowed. We created a GovDev and Gov Prod DNS account for internet hosting non-public Route53 zones. The Cloud Foundations group 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 world community mesh. Lastly these VPCs are shared into little one 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 non-public Route53 zones we create are hooked up to the shared VPCs, in order quickly as a document is added to those zones, it may be resolved inside our VPCs.

Nonetheless since GovCloud doesn’t assist public DNS, we have to create these information on the business aspect. Due to this fact, we created a devoted business AWS account for internet hosting public GovSlack DNS information. Entry to this business DNS account is restricted to US personnel.

How can we switch artefacts between business and GovCloud?

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AWS doesn’t assist assuming roles between AWS commonplace and AWS GovCloud partitions. Due to this fact we created a mechanism to compliantly go 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

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We use Terraform modules for constructing our infrastructure as a group of interdependent sources reminiscent of 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 commonplace partitions. One key distinction between the business and Gov AWS sources are the sources ARNs. Business ARNs begin with arn:aws versus Gov ARNs begin with arn:aws-us-gov.

Due to this fact 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 = substitute(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" 
  depend = module.aws_partition.is_govcloud ? 1 : 0

  title = "example-rule"

	proprietor             = "AWS"

VPC endpoints

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Over the past three years Slack has been working very arduous to utilize AWS’ VPC endpoints for accessing native AWS companies in our business surroundings. They cut back the latency and improve the resiliency of our techniques, whereas additionally lowering our networking prices.

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

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


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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 resolution. AWS lately launched the AWS-SSO resolution into their business surroundings and much more lately of their Gov surroundings. As this was a whole greenfield buildout it was alternative to experiment with new applied sciences and enhance our present implementation.

Not like AWS’ commonplace IAM roles, AWS-SSO permission units are an org-wide international (throughout the complete org, versus an account) useful resource, and this modifications how we construct and deploy them.

Since deploying AWS-SSO within the GovCloud surroundings, we have now taken the learnings and back-ported it into our business surroundings. Whereas we already had an present SSO system in place for entry to everything of our business AWS surroundings, utilizing AWS-SSO has made this course of so much smoother and simpler.

So what have we realized?

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Rebuilding our complete 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 in a position to clear up a large number of hardcoded values and alter issues to be extra reusable. We have been additionally in a position to take a step again and have a deep dive into our processes, instruments, AWS footprint and achieve a higher understanding of our platform as this entire course of gave us a possibility to rebuild Slack from scratch.