Service Principal in block

To authenticate Terraform to Azure in a secure, automated, and cloud-agnostic way, use a Service Principal and reference its credentials in your provider block. This is the recommended approach for CI/CD pipelines and IaC workflows.

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Step-by-Step Example

1. Store your Service Principal credentials securely (e.g., as environment variables or in your CI/CD secret manager):
   • ARM_SUBSCRIPTION_ID
   • ARM_TENANT_ID
   • ARM_CLIENT_ID
   • ARM_CLIENT_SECRET
2. Reference these variables in your Terraform provider block:

terraform {
  required_providers {
    azurerm = {
      source  = "hashicorp/azurerm"
      version = "~>3.0"
    }
  }
}

provider "azurerm" {
  features {}

  subscription_id = var.subscription_id
  tenant_id       = var.tenant_id
  client_id       = var.client_id
  client_secret   = var.client_secret
}

variable "subscription_id" {}
variable "tenant_id" {}
variable "client_id" {}
variable "client_secret" {}

1. Set the variables using environment variables or a terraform.tfvars file:

export TF_VAR_subscription_id=$ARM_SUBSCRIPTION_ID
export TF_VAR_tenant_id=$ARM_TENANT_ID
export TF_VAR_client_id=$ARM_CLIENT_ID
export TF_VAR_client_secret=$ARM_CLIENT_SECRET

Or in terraform.tfvars (not recommended for production):

subscription_id = "..."
tenant_id       = "..."
client_id       = "..."
client_secret   = "..."

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Real-Life DevOps Example: GitHub Actions

jobs:
  terraform:
    runs-on: ubuntu-latest
    env:
      ARM_SUBSCRIPTION_ID: ${{ secrets.AZURE_SUBSCRIPTION_ID }}
      ARM_TENANT_ID: ${{ secrets.AZURE_TENANT_ID }}
      ARM_CLIENT_ID: ${{ secrets.AZURE_CLIENT_ID }}
      ARM_CLIENT_SECRET: ${{ secrets.AZURE_CLIENT_SECRET }}
    steps:
      - uses: actions/checkout@v4
      - uses: hashicorp/setup-terraform@v3
      - run: terraform init
      - run: terraform apply -auto-approve

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Best Practices

• Never hardcode credentials in your Terraform code or repository
• Use environment variables or secret managers for sensitive values
• Rotate Service Principal credentials regularly
• Grant only the minimum RBAC permissions needed

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References

• Terraform Azure Provider: Authenticating via Service Principal
• Azure CLI: az ad sp create-for-rbac

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Tip: For passwordless authentication in CI/CD, consider using OIDC with GitHub Actions or Azure Pipelines.

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Add to SUMMARY.md

- [Specify Service Principal Credentials in a Terraform Provider Block](pages/terraform/authenticate-terraform-to-azure/specify-service-principal-credentials-in-a-terraform-provider-block.md)