Incorrect endpoint used for AWS SSO when FIPS enabled

[abohne]

Describe the bug

We utilize AWS SSO in GovCloud for authentication. When our AWS profile has use_fips_endpoint = true, we see the following error when terragrunt is run.

11:54:53.360 ERROR  Error finding AWS credentials (did you set the AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY environment variables?): RequestError: send request failed
caused by: Get "https://portal.sso-fips.us-gov-west-1.amazonaws.com/federation/credentials?account_id=XXXXX&role_name=AdministratorAccess": dial tcp: lookup portal.sso-fips.us-gov-west-1.amazonaws.com: no such host

AWS FIPS Documentation states that the correct FIPS endpoints for SSO are sso.us-gov-west-1.amazonaws.com and sso.us-gov-east-1.amazonaws.com.

Steps To Reproduce

Either configure your AWS profile with use_fips_endpoint = true or export AWS_USE_FIPS_ENDPOINT=true

Login to SSO via cli
aws sso login

generate "provider" {
  path        = "provider.tf"
  if_exists   = "overwrite_terragrunt"
  if_disabled = "remove_terragrunt"
  contents    = <<EOF
provider "aws" {
  region = "us-gov-east-1"
}
EOF
}

remote_state {
  backend = "s3"
  config = {
    encrypt        = true
    bucket         = "mystatebucket"
    key            = "terraform.tfstate"
    region         = "us-gov-east-1"
    dynamodb_table = "mydynamotable"
  }
  generate = {
    path      = "backend.tf"
    if_exists = "overwrite_terragrunt"
  }
}

terragrunt plan

Expected behavior

Terragrunt is able to utilize the existing AWS credentials.

Nice to haves

• Terminal output
• Screenshots

Versions

• Terragrunt version: 0.72.0
• OpenTofu/Terraform version: Terraform 1.10.4
• Environment details (Ubuntu 20.04, Windows 10, etc.): MacOS Sequoia 15.0.1

Additional context

Add any other context about the problem here.