Vault and IAM integration

[psibi]

---

name: Pull request template
about: Make a PR to terraform-aws-foundation

Please include the following in your PR:

Please also note that these are not hard requirements, but merely serve to define
what maintainers are looking for in PR's. Including these will more likely lead
to your PR being reviewed and accepted.

• Update the changelog
• Make sure that modules and files are documented. This can be done inside the module and files.
• Make sure that new modules directories contain a basic README.md file.
• Make sure that the module is added to tests/main.tf
• Make sure that the linting passes on CI.
• Make sure that there is an up to date example for your code:
  - For new modules this would entail example code for how to use the module or some explanation in the module readme.
  - For new examples please provide a README explaining how to run the example. It's also ideal to provide a basic makefile to use the example as well.
• Make sure that there is a manual CI trigger that can test the deployment.

[ketzacoatl]

I'd like to make the following changes before merging:

• make vault-iam a module
• use a data source for the policy JSON
• parametize the vtest in arn:aws:iam::${data.aws_caller_identity.current.account_id}:user/vtest-* with a variable that defaults to vault
• update the vault-s3-private example to use the vault-iam module
• drop the aws provider from the vault-aws-backend module
• consider dropping the vault_aws_secret_backend resource and use a make target (this resource would include admin secrets in Terraform's state file)
• fixup commits

[psibi]

@ketzacoatl On further thought, I think we should remove the entire vault-aws-backend module itself from terraform (because we don't want admin secret in Terraform's state file and just having vault_aws_secret_backend_role resource isn't useful).

Also, I don't think it is useful for us to make vault-s3-private use vault-iam module, because they are not dependent. Only the running vault server's secret engine needs the access keys from the vault-iam module. No other output from vault-iam is actually needed for it in vault-s3-private. I think the right way for us to proceed would be:

• Have make target step for the vault-iam module. This step will create access keys which has to exposed via environment variables by us manully for the next step.
• Have another make target step (like what you have suggested) to create AWS secret engine path and create an appropriate role for this. (This step will completely replace the vault-aws-backend module). This step will require proper environment variable for access keys to be present for it to work.

What do you think ?

[ketzacoatl]

Yes, that sounds good.

I would comment though, that if there are no secrets, and we can do it in Terraform, we ought to. Some of the vault configuration can be done in Terraform and doesn't include secrets. Those should stay in Terraform. IDK if that is relevant to the vault-aws-backend module, I haven't reviewed the code in a few days.

[ketzacoatl]

@psibi are these updates WIP or is it ok to have one of our engineers make those updates?