AWS Identity and Access Management (IAM) Terraform module

Features

1. Cross-account access. Define IAM roles using iam_assumable_role or iam_assumable_roles submodules in "resource AWS accounts (prod, staging, dev)" and IAM groups and users using iam-group-with-assumable-roles-policy submodule in "IAM AWS Account" to setup access controls between accounts. See iam-group-with-assumable-roles-policy example for more details.
2. Individual IAM resources (users, roles, policies). See usage snippets and examples listed below.

Usage

iam-account:

module "iam_account" {
  source  = "terraform-aws-modules/iam/aws//modules/iam-account"
  version = "~> 4"

  account_alias = "awesome-company"

  minimum_password_length = 37
  require_numbers         = false
}

iam-assumable-role:

module "iam_assumable_role" {
  source  = "terraform-aws-modules/iam/aws//modules/iam-assumable-role"
  version = "~> 4"

  trusted_role_arns = [
    "arn:aws:iam::307990089504:root",
    "arn:aws:iam::835367859851:user/anton",
  ]

  create_role = true

  role_name         = "custom"
  role_requires_mfa = true

  custom_role_policy_arns = [
    "arn:aws:iam::aws:policy/AmazonCognitoReadOnly",
    "arn:aws:iam::aws:policy/AlexaForBusinessFullAccess",
  ]
  number_of_custom_role_policy_arns = 2
}

iam-assumable-role-with-oidc:

module "iam_assumable_role_with_oidc" {
  source  = "terraform-aws-modules/iam/aws//modules/iam-assumable-role-with-oidc"
  version = "~> 4"

  create_role = true

  role_name = "role-with-oidc"

  tags = {
    Role = "role-with-oidc"
  }

  provider_url = "oidc.eks.eu-west-1.amazonaws.com/id/BA9E170D464AF7B92084EF72A69B9DC8"

  role_policy_arns = [
    "arn:aws:iam::aws:policy/AmazonEKS_CNI_Policy",
  ]
  number_of_role_policy_arns = 1
}

iam-assumable-role-with-saml:

module "iam_assumable_role_with_saml" {
  source  = "terraform-aws-modules/iam/aws//modules/iam-assumable-role-with-saml"
  version = "~> 4"

  create_role = true

  role_name = "role-with-saml"

  tags = {
    Role = "role-with-saml"
  }

  provider_id = "arn:aws:iam::235367859851:saml-provider/idp_saml"

  role_policy_arns = [
    "arn:aws:iam::aws:policy/ReadOnlyAccess"
  ]
  number_of_role_policy_arns = 1
}

iam-assumable-roles:

module "iam_assumable_roles" {
  source  = "terraform-aws-modules/iam/aws//modules/iam-assumable-roles"
  version = "~> 4"

  trusted_role_arns = [
    "arn:aws:iam::307990089504:root",
    "arn:aws:iam::835367859851:user/anton",
  ]

  create_admin_role = true

  create_poweruser_role = true
  poweruser_role_name   = "developer"

  create_readonly_role       = true
  readonly_role_requires_mfa = false
}

iam-assumable-roles-with-saml:

module "iam_assumable_roles_with_saml" {
  source  = "terraform-aws-modules/iam/aws//modules/iam-assumable-roles-with-saml"
  version = "~> 4"

  create_admin_role = true

  create_poweruser_role = true
  poweruser_role_name   = "developer"

  create_readonly_role = true

  provider_id   = "arn:aws:iam::235367859851:saml-provider/idp_saml"
}

iam-user:

module "iam_user" {
  source  = "terraform-aws-modules/iam/aws//modules/iam-user"
  version = "~> 4"

  name          = "vasya.pupkin"
  force_destroy = true

  pgp_key = "keybase:test"

  password_reset_required = false
}

iam-policy:

module "iam_policy" {
  source  = "terraform-aws-modules/iam/aws//modules/iam-policy"
  version = "~> 4"

  name        = "example"
  path        = "/"
  description = "My example policy"

  policy = <<EOF
{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Action": [
        "ec2:Describe*"
      ],
      "Effect": "Allow",
      "Resource": "*"
    }
  ]
}
EOF
}

iam-read-only-policy:

module "iam_read_only_policy" {
  source  = "terraform-aws-modules/iam/aws//modules/iam-read-only-policy"
  version = "~> 4"

  name        = "example"
  path        = "/"
  description = "My example read-only policy"

  allowed_services = ["rds", "dynamo", "health"]
}

iam-group-with-assumable-roles-policy:

module "iam_group_with_assumable_roles_policy" {
  source  = "terraform-aws-modules/iam/aws//modules/iam-group-with-assumable-roles-policy"
  version = "~> 4"

  name = "production-readonly"

  assumable_roles = [
    "arn:aws:iam::835367859855:role/readonly"  # these roles can be created using `iam_assumable_roles` submodule
  ]

  group_users = [
    "user1",
    "user2"
  ]
}

iam-group-with-policies:

module "iam_group_with_policies" {
  source  = "terraform-aws-modules/iam/aws//modules/iam-group-with-policies"
  version = "~> 4"

  name = "superadmins"

  group_users = [
    "user1",
    "user2"
  ]

  attach_iam_self_management_policy = true

  custom_group_policy_arns = [
    "arn:aws:iam::aws:policy/AdministratorAccess",
  ]

  custom_group_policies = [
    {
      name   = "AllowS3Listing"
      policy = data.aws_iam_policy_document.sample.json
    }
  ]
}

iam-eks-role:

module "iam_eks_role" {
  source      = "terraform-aws-modules/iam/aws//modules/iam-eks-role"
  version     = "~> 4"

  role_name   = "my-app"

  cluster_service_accounts = {
    "cluster1" = ["default:my-app"]
    "cluster2" = [
      "default:my-app",
      "canary:my-app",
    ]
  }

  tags = {
    Name = "eks-role"
  }

  role_policy_arns = [
    "arn:aws:iam::aws:policy/AmazonEKS_CNI_Policy",
  ]
}

IAM Best Practices

AWS published IAM Best Practices and this Terraform module was created to help with some of points listed there:

1. Create Individual IAM Users

Use iam-user module module to manage IAM users.

2. Use AWS Defined Policies to Assign Permissions Whenever Possible

Use iam-assumable-roles module to create IAM roles with managed policies to support common tasks (admin, poweruser or readonly).

3. Use Groups to Assign Permissions to IAM Users

Use iam-group-with-assumable-roles-policy module to manage IAM groups of users who can assume roles.

Use iam-group-with-policies module to manage IAM groups of users where specified IAM policies are allowed.

4. Configure a Strong Password Policy for Your Users

Use iam-account module to set password policy for your IAM users.

5. Enable MFA for Privileged Users

Terraform can't configure MFA for the user. It is only possible via AWS Console and AWS CLI.

6. Delegate by Using Roles Instead of by Sharing Credentials

iam-assumable-role, iam-assumable-roles, iam-assumable-roles-with-saml and iam-group-with-assumable-roles-policy modules provide complete set of functionality required for this.

7. Use Policy Conditions for Extra Security

iam-assumable-roles module can be configured to require valid MFA token when different roles are assumed (for example, admin role requires MFA, but readonly - does not).

8. Create IAM Policies

Use iam-policy module module to manage IAM policy.

Use iam-read-only-policy module module to manage IAM read-only policies.

Examples

• iam-account - Set AWS account alias and password policy
• iam-assumable-role - Create individual IAM role which can be assumed from specified ARNs (AWS accounts, IAM users, etc)
• iam-assumable-role-with-oidc - Create individual IAM role which can be assumed from specified subjects federated with a OIDC Identity Provider
• iam-assumable-role-with-saml - Create individual IAM role which can be assumed by users with a SAML Identity Provider
• iam-assumable-roles - Create several IAM roles which can be assumed from specified ARNs (AWS accounts, IAM users, etc)
• iam-assumable-roles-with-saml - Create several IAM roles which can be assumed by users with a SAML Identity Provider
• iam-eks-role - Create an IAM role which can be assumed by one or more EKS ServiceAccount
• iam-group-with-assumable-roles-policy - IAM group with users who are allowed to assume IAM roles in the same or in separate AWS account
• iam-group-with-policies - IAM group with users who are allowed specified IAM policies (eg, "manage their own IAM user")
• iam-group-complete - IAM group with users who are allowed to assume IAM roles in another AWS account and have access to specified IAM policies
• iam-user - Add IAM user, login profile and access keys (with PGP enabled or disabled)
• iam-policy - Create IAM policy
• iam-read-only-policy - Create IAM read-only policy

Authors

Module is maintained by Anton Babenko with help from these awesome contributors.

License

Apache 2 Licensed. See LICENSE for full details.