onprem-sa-key-management

Managing on-prem service account keys by uploading public keys

When managing GCP Service Accounts with terraform, it's often a question on how to avoid Service Account Key in the terraform state?

This example shows how to manage IAM Service Account Keys by manually generating a key pair and uploading the public part of the key to GCP. It has the following benefits:

• no passing keys between users or systems
• no private keys stored in the terraform state (only public part of the key is in the state)
• let keys expire automatically

Running the example

Clone this repository or open it in cloud shell, then go through the following steps to create resources:

Cleaning up example keys

rm -f /public-keys/data-uploader/
rm -f /public-keys/prisma-security/

Generate keys for service accounts

mkdir keys && cd keys
openssl req -x509 -nodes -newkey rsa:2048 -days 30 \
    -keyout data_uploader_private_key.pem \
    -out ../public-keys/data-uploader/public_key.pem \
    -subj "/CN=unused"
openssl req -x509 -nodes -newkey rsa:2048 -days 30 \
    -keyout prisma_security_private_key.pem \
    -out ../public-keys/prisma-security/public_key.pem \
    -subj "/CN=unused"

Deploy service accounts and keys

cd ..
terraform init
terraform apply -var project_id=$GOOGLE_CLOUD_PROJECT

Extract JSON credentials templates from terraform output and put the private part of the keys into templates

terraform show -json | jq '.values.outputs."sa-credentials".value."data-uploader"."public_key.pem" | fromjson' > data-uploader.json
terraform show -json | jq '.values.outputs."sa-credentials".value."prisma-security"."public_key.pem" | fromjson' > prisma-security.json

contents=$(jq --arg key "$(cat keys/data_uploader_private_key.pem)" '.private_key=$key' data-uploader.json) && echo "$contents" > data-uploader.json
contents=$(jq --arg key "$(cat keys/prisma_security_private_key.pem)" '.private_key=$key' prisma-security.json) && echo "$contents" > prisma-security.json

Testing the example

Validate that service accounts json credentials are valid

gcloud auth activate-service-account --key-file prisma-security.json
gcloud auth activate-service-account --key-file data-uploader.json

Cleaning up

terraform destroy -var project_id=$GOOGLE_CLOUD_PROJECT

Variables

name	description	type	required	default
project_id	Project id.	string	✓
project_create	Create project instead of using an existing one.	bool		false
service_accounts	List of service accounts.	list(object({…}))		[…]
services	Service APIs to enable.	list(string)		[]

Outputs

name	description	sensitive
sa-credentials	SA json key templates.