Added iam-assumable-roles (#2)

README.md

-# terraform-aws-iam
-Terraform module which creates IAM resources on AWS
-
-- [ ] IAM account
-- [ ] IAM groups
-- [ ] IAM users
-- [ ] IAM assumable roles
-- [ ] IAM group with assumable roles policy
+# AWS Identity and Access Management (IAM) Terraform module
+
+These types of resources are supported:
+
+* [IAM account alias](https://www.terraform.io/docs/providers/aws/r/iam_account_alias.html)
+* [IAM password policy](https://www.terraform.io/docs/providers/aws/r/iam_account_password_policy.html)
+* [IAM user](https://www.terraform.io/docs/providers/aws/r/iam_user.html)
+* [IAM user login profile](https://www.terraform.io/docs/providers/aws/r/iam_user_login_profile.html)
+* [IAM group](https://www.terraform.io/docs/providers/aws/r/iam_group.html)
+* [IAM role](https://www.terraform.io/docs/providers/aws/r/iam_role.html)
+
+## Usage
+
+`iam-account`:
+
+```hcl
+module "iam_account" {
+  source = "terraform-aws-modules/iam/aws//modules/iam-account"
+
+  account_alias = "awesome-company"
+
+  minimum_password_length = 37
+  require_numbers         = false
+}
+```
+
+`iam-assumable-roles`:
+```hcl
+module "iam_assumable_roles" {
+  source = "terraform-aws-modules/iam/aws//modules/iam-assumable-roles"
+
+  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-user`:
+```hcl
+# todo
+```
+
+`iam-group-with-assumable-roles-policy`:
+```hcl
+# todo
+```
+
+## IAM Best Practices
+
+AWS published [IAM Best Practices](https://docs.aws.amazon.com/IAM/latest/UserGuide/best-practices.html) and this Terraform module was created to help with some of points listed there:
+
+### Create Individual IAM Users
+
+Use [iam-user module](https://github.com/terraform-aws-modules/terraform-aws-iam/tree/master/modules/iam-user) module to manage IAM users.
+
+### Use AWS Defined Policies to Assign Permissions Whenever Possible
+
+Use [iam-assumable-roles module](https://github.com/terraform-aws-modules/terraform-aws-iam/tree/master/modules/iam-assumable-roles) to create IAM roles with managed policies to support common tasks (admin, poweruser or readonly). 
+
+### Use Groups to Assign Permissions to IAM Users
+
+Use [iam-group-with-assumable-roles-policy module](https://github.com/terraform-aws-modules/terraform-aws-iam/tree/master/modules/iam-group-with-assumable-roles-policy) to manage IAM groups of users who can assume roles.
+
+### Configure a Strong Password Policy for Your Users
+
+Use [iam-account module](https://github.com/terraform-aws-modules/terraform-aws-iam/tree/master/modules/iam-account) to set password policy for your IAM users.
+
+### Enable MFA for Privileged Users
+
+Terraform can't configure MFA for the user. It is only possible via [AWS Console](https://docs.aws.amazon.com/IAM/latest/UserGuide/id_credentials_mfa.html) and [AWS CLI](https://docs.aws.amazon.com/cli/latest/reference/iam/enable-mfa-device.html).
+
+### Delegate by Using Roles Instead of by Sharing Credentials
+
+[iam-assumable-roles](https://github.com/terraform-aws-modules/terraform-aws-iam/tree/master/modules/iam-assumable-roles) and [iam-group-with-assumable-roles-policy](https://github.com/terraform-aws-modules/terraform-aws-iam/tree/master/modules/iam-group-with-assumable-roles-policy) modules provide complete set of functionality required for this.
+
+### Use Policy Conditions for Extra Security
+
+[iam-assumable-roles module](https://github.com/terraform-aws-modules/terraform-aws-iam/tree/master/modules/iam-assumable-roles) can be configured to require valid MFA token when different roles are assumed (for example, admin role requires MFA, but readonly - does not).
+
+
+## Examples
+
+* [complete](https://github.com/terraform-aws-modules/terraform-aws-iam/tree/master/modules/complete) - Create all required resources to allow one group of users to assume privileged role, while another group of users can only assume readonly role.
+* [iam-account](https://github.com/terraform-aws-modules/terraform-aws-iam/tree/master/modules/iam-account) - Set AWS account alias and password policy
+* [iam-assumable-roles](https://github.com/terraform-aws-modules/terraform-aws-iam/tree/master/modules/iam-assumable-roles) - Create IAM roles which can be assumed from specified ARNs (AWS accounts, IAM users, etc)
+
+
+## Authors
+
+Module managed by [Anton Babenko](https://github.com/antonbabenko).
+
+## License
+
+Apache 2 Licensed. See LICENSE for full details.

examples/iam-account/README.md

-HTTP Security Group example
-===========================
+# IAM account example
 
-Configuration in this directory creates set of Security Group and Security Group Rules resources in various combination.
+Configuration in this directory sets [AWS account alias](https://docs.aws.amazon.com/IAM/latest/UserGuide/console_account-alias.html) (also known as Console Account alias) and configures password policy.
 
-Data sources are used to discover existing VPC resources (VPC and default security group).
-
-Usage
-=====
+# Usage
 
 To run this example you need to execute:
 
@@ -16,4 +12,4 @@ $ terraform plan
 $ terraform apply
 ```
 
-Note that this example may create resources which cost money. Run `terraform destroy` when you don't need these resources.
+Run `terraform destroy` when you don't need these resources.

examples/iam-assumable-roles/README.md

+# IAM assumable roles example
+
+Configuration in this directory creates several IAM roles which can be assumed from a defined list of [IAM ARNs](https://docs.aws.amazon.com/IAM/latest/UserGuide/reference_identifiers.html#identifiers-arns).
+
+# Usage
+
+To run this example you need to execute:
+
+```bash
+$ terraform init
+$ terraform plan
+$ terraform apply
+```
+
+Run `terraform destroy` when you don't need these resources.

examples/iam-assumable-roles/main.tf

+provider "aws" {
+  region = "eu-west-1"
+}
+
+######################
+# IAM assumable roles
+######################
+module "iam_assumable_roles" {
+  source = "../../modules/iam-assumable-roles"
+
+  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
+}

examples/iam-assumable-roles/outputs.tf

+# Admin
+output "admin_iam_role_arn" {
+  description = "ARN of admin IAM role"
+  value       = "${module.iam_assumable_roles.admin_iam_role_arn}"
+}
+
+output "admin_iam_role_name" {
+  description = "Name of admin IAM role"
+  value       = "${module.iam_assumable_roles.admin_iam_role_name}"
+}
+
+output "admin_iam_role_requires_mfa" {
+  description = "Whether admin IAM role requires MFA"
+  value       = "${module.iam_assumable_roles.admin_iam_role_requires_mfa}"
+}
+
+output "admin_iam_role_path" {
+  description = "Path of admin IAM role"
+  value       = "${module.iam_assumable_roles.admin_iam_role_path}"
+}
+
+# Poweruser
+output "poweruser_iam_role_arn" {
+  description = "ARN of poweruser IAM role"
+  value       = "${module.iam_assumable_roles.poweruser_iam_role_arn}"
+}
+
+output "poweruser_iam_role_name" {
+  description = "Name of poweruser IAM role"
+  value       = "${module.iam_assumable_roles.poweruser_iam_role_name}"
+}
+
+output "poweruser_iam_role_requires_mfa" {
+  description = "Whether poweruser IAM role requires MFA"
+  value       = "${module.iam_assumable_roles.poweruser_iam_role_requires_mfa}"
+}
+
+output "poweruser_iam_role_path" {
+  description = "Path of poweruser IAM role"
+  value       = "${module.iam_assumable_roles.poweruser_iam_role_path}"
+}
+
+# Readonly
+output "readonly_iam_role_arn" {
+  description = "ARN of readonly IAM role"
+  value       = "${module.iam_assumable_roles.readonly_iam_role_arn}"
+}
+
+output "readonly_iam_role_name" {
+  description = "Name of readonly IAM role"
+  value       = "${module.iam_assumable_roles.readonly_iam_role_name}"
+}
+
+output "readonly_iam_role_path" {
+  description = "Path of readonly IAM role"
+  value       = "${module.iam_assumable_roles.readonly_iam_role_path}"
+}
+
+output "readonly_iam_role_requires_mfa" {
+  description = "Whether readonly IAM role requires MFA"
+  value       = "${module.iam_assumable_roles.readonly_iam_role_requires_mfa}"
+}

modules/iam-assumable-roles/README.md

+# iam-assumable-roles
+
+Creates predefined IAM roles (admin, poweruser and readonly) which can be assumed by trusted resources.
+
+Trusted resources can be any [IAM ARNs](https://docs.aws.amazon.com/IAM/latest/UserGuide/reference_identifiers.html#identifiers-arns) - typically, AWS accounts and users.

modules/iam-assumable-roles/main.tf

+data "aws_iam_policy_document" "assume_role" {
+  statement {
+    effect = "Allow"
+
+    actions = ["sts:AssumeRole"]
+
+    principals {
+      type        = "AWS"
+      identifiers = ["${var.trusted_role_arns}"]
+    }
+  }
+}
+
+data "aws_iam_policy_document" "assume_role_with_mfa" {
+  statement {
+    effect = "Allow"
+
+    actions = ["sts:AssumeRole"]
+
+    principals {
+      type        = "AWS"
+      identifiers = ["${var.trusted_role_arns}"]
+    }
+
+    condition {
+      test     = "Bool"
+      variable = "aws:MultiFactorAuthPresent"
+      values   = ["true"]
+    }
+
+    condition {
+      test     = "NumericLessThan"
+      variable = "aws:MultiFactorAuthAge"
+      values   = ["${var.mfa_age}"]
+    }
+  }
+}
+
+# Admin
+resource "aws_iam_role" "admin" {
+  name = "${var.admin_role_name}"
+  path = "${var.admin_role_path}"
+
+  assume_role_policy = "${var.admin_role_requires_mfa ? data.aws_iam_policy_document.assume_role_with_mfa.json : data.aws_iam_policy_document.assume_role.json}"
+}
+
+resource "aws_iam_role_policy_attachment" "admin" {
+  role       = "${aws_iam_role.admin.name}"
+  policy_arn = "${var.admin_role_policy_arn}"
+}
+
+# Poweruser
+resource "aws_iam_role_policy_attachment" "poweruser" {
+  role       = "${aws_iam_role.poweruser.name}"
+  policy_arn = "${var.poweruser_role_policy_arn}"
+}
+
+resource "aws_iam_role" "poweruser" {
+  name = "${var.poweruser_role_name}"
+  path = "${var.poweruser_role_path}"
+
+  assume_role_policy = "${var.poweruser_role_requires_mfa ? data.aws_iam_policy_document.assume_role_with_mfa.json : data.aws_iam_policy_document.assume_role.json}"
+}
+
+# Readonly
+resource "aws_iam_role_policy_attachment" "readonly" {
+  role       = "${aws_iam_role.readonly.name}"
+  policy_arn = "${var.readonly_role_policy_arn}"
+}
+
+resource "aws_iam_role" "readonly" {
+  name = "${var.readonly_role_name}"
+  path = "${var.readonly_role_path}"
+
+  assume_role_policy = "${var.readonly_role_requires_mfa ?  data.aws_iam_policy_document.assume_role_with_mfa.json : data.aws_iam_policy_document.assume_role.json}"
+}

modules/iam-assumable-roles/outputs.tf

+#Admin
+output "admin_iam_role_arn" {
+  description = "ARN of admin IAM role"
+  value       = "${element(concat(aws_iam_role.admin.*.arn, list()), 0)}"
+}
+
+output "admin_iam_role_name" {
+  description = "Name of admin IAM role"
+  value       = "${element(concat(aws_iam_role.admin.*.name, list()), 0)}"
+}
+
+output "admin_iam_role_path" {
+  description = "Path of admin IAM role"
+  value       = "${element(concat(aws_iam_role.admin.*.path, list()), 0)}"
+}
+
+output "admin_iam_role_requires_mfa" {
+  description = "Whether admin IAM role requires MFA"
+  value       = "${var.admin_role_requires_mfa}"
+}
+
+# Poweruser
+output "poweruser_iam_role_arn" {
+  description = "ARN of poweruser IAM role"
+  value       = "${element(concat(aws_iam_role.poweruser.*.arn, list()), 0)}"
+}
+
+output "poweruser_iam_role_name" {
+  description = "Name of poweruser IAM role"
+  value       = "${element(concat(aws_iam_role.poweruser.*.name, list()), 0)}"
+}
+
+output "poweruser_iam_role_path" {
+  description = "Path of poweruser IAM role"
+  value       = "${element(concat(aws_iam_role.poweruser.*.path, list()), 0)}"
+}
+
+output "poweruser_iam_role_requires_mfa" {
+  description = "Whether poweruser IAM role requires MFA"
+  value       = "${var.poweruser_role_requires_mfa}"
+}
+
+# Readonly
+output "readonly_iam_role_arn" {
+  description = "ARN of readonly IAM role"
+  value       = "${element(concat(aws_iam_role.readonly.*.arn, list()), 0)}"
+}
+
+output "readonly_iam_role_name" {
+  description = "Name of readonly IAM role"
+  value       = "${element(concat(aws_iam_role.readonly.*.name, list()), 0)}"
+}
+
+output "readonly_iam_role_path" {
+  description = "Path of readonly IAM role"
+  value       = "${element(concat(aws_iam_role.readonly.*.path, list()), 0)}"
+}
+
+output "readonly_iam_role_requires_mfa" {
+  description = "Whether readonly IAM role requires MFA"
+  value       = "${var.readonly_role_requires_mfa}"
+}

modules/iam-assumable-roles/variables.tf

+variable "trusted_role_arns" {
+  description = "ARNs of AWS entities who can assume these roles"
+  default     = []
+}
+
+variable "mfa_age" {
+  description = "Max age of valid MFA (in seconds) for roles which require MFA"
+  default     = 86400
+}
+
+# Admin
+variable "create_admin_role" {
+  description = "Whether to create admin role"
+  default     = false
+}
+
+variable "admin_role_name" {
+  description = "IAM role with admin access"
+  default     = "admin"
+}
+
+variable "admin_role_path" {
+  description = "Path of admin IAM role"
+  default     = "/"
+}
+
+variable "admin_role_requires_mfa" {
+  description = "Whether admin role requires MFA"
+  default     = true
+}
+
+variable "admin_role_policy_arn" {
+  description = "Policy ARN to use for admin role"
+  default     = "arn:aws:iam::aws:policy/AdministratorAccess"
+}
+
+# Poweruser
+variable "create_poweruser_role" {
+  description = "Whether to create poweruser role"
+  default     = false
+}
+
+variable "poweruser_role_name" {
+  description = "IAM role with poweruser access"
+  default     = "poweruser"
+}
+
+variable "poweruser_role_path" {
+  description = "Path of poweruser IAM role"
+  default     = "/"
+}
+
+variable "poweruser_role_requires_mfa" {
+  description = "Whether poweruser role requires MFA"
+  default     = true
+}
+
+variable "poweruser_role_policy_arn" {
+  description = "Policy ARN to use for admin role"
+  default     = "arn:aws:iam::aws:policy/PowerUserAccess"
+}
+
+# Readonly
+variable "create_readonly_role" {
+  description = "Whether to create poweruser role"
+  default     = false
+}
+
+variable "readonly_role_name" {
+  description = "IAM role with readonly access"
+  default     = "readonly"
+}
+
+variable "readonly_role_path" {
+  description = "Path of poweruser IAM role"
+  default     = "/"
+}
+
+variable "readonly_role_requires_mfa" {
+  description = "Whether readonly role requires MFA"
+  default     = true
+}
+
+variable "readonly_role_policy_arn" {
+  description = "Policy ARN to use for admin role"
+  default     = "arn:aws:iam::aws:policy/ReadOnlyAccess"
+}