Terraform supports 12-factor style environment variables. Thus we prescribe using a combination of terraform environment variables and chamber.

Usage

First, review our documentation on using chamber to manage secrets.

Access Secrets from HCL

To access secrets within terraform code, simply refer to a variable. Do not set a default value to enforce that the value come from the environment.

variable "POSTGRES_PASSWORD" {
  description = "Master password for Postgres database"
}

Since chamber will export all environment variables as strictly upper case, make sure that you define all variables in terraform in upper case as well. This also serves as a nice convention to follow because it communicates which variables should come from the environment.

When setting the variables with chamber write, make sure you prefix all variables with TF_VAR_. This will ensure they are properly exported in a way that terraform will read them. For example, if you have a HCL variable called POSTGRES_PASSWORD, then the chamber environment variable should be named TF_VAR_POSTGRES_PASSWORD.

Use Chamber with terraform Commands

To use chamber with terraform, it’s pretty straightforward.

Manage the secrets in SSM using the standard chamber commands: chamber write, chamber list, chamber delete.

Execute all terraform commands with chamber exec ...

For example, to run terraform plan using chamber with the example namespace, you would run chamber exec example -- terraform plan (after replacing example with the actual SSM path).

It should also be noted that you can pass multiple namespaces. This provides a nice way of inheriting settings and scoping IAM permissions.