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platform-iam-configs.md

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AWS IAM User/Group/Role/Account Configurations
Detailed information about our IAM configurations, and how to add/alter IAM components within our infrastructure.
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Platform

Overview

A set of modules in identity-terraform are used to create the full mappings between the users, groups, roles, and accounts across the org. Please refer to the [AWS Accounts and IAM Groups/Roles]({% link _articles/platform-aws-accounts-and-roles.md %}) page for specific data about our existing AWS accounts/groups/roles/etc.

Terraform Configuration

terraform/master/global/main.tf

The main module within main.tf contains all of the variable values used to build each configuration:

  1. aws_account_types
    • What It Is: Mapping of account types and ID numbers, with comments included to specify which account is which.
    • Module Used: identity-terraform/iam_masterassume
    • What It Does: Along with the role_list variable, generates IAM "AssumeRole" policies for each account type.
    • How It Fits: Allows (if desired) a lower number of individual AssumeRole policies to be created.
  2. role_list
    • What It Is: List of IAM roles available within all AWS accounts.
    • Module Used: identity-terraform/iam_masterassume
    • What It Does: Along with the aws_account_types variable, generates IAM "AssumeRole" policies for each account type.
    • How It Fits: Specifies all available roles, allowing for easier templating of AssumeRole policies.
  3. group_role_map
    • What It Is: Mapping of IAM groups, their available roles, and which account types they can Assume those roles in.
    • Module Used: identity-terraform/iam_assumegroup
    • What It Does: Generates IAM Groups and attaches existing IAM policies (i.e. those generated by iam_masterassume above) to them.
    • How It Fits: Creates the actual groups and provides per-role per-account access to users within the groups.
  4. user_map
    • What It Is: Mapping of IAM users to their respective groups.
    • Module Used: identity-terraform/iam_masterusers
    • What It Does: Generates IAM users and their group memberships, and attaches a "ManageYourAccount" IAM policy to each user, which allows them to log in and reset their password, Access/Secret Keys, and MFA device(s).
    • How It Fits: Used to generate/manage the actual IAM login profiles for each user, and sets their permissions via which group(s) they are added to.

terraform/all/

Within all are two components used to create the IAM roles available within each account, via the identity-terraform/iam_assumerole module:

  1. module/: contains all .tf template files which generate the IAM Role and Policy, along with any optionally-specified custom policies to attach to the role.

    • Each IAM resource set should be in a file named iam-role-<CLI POSTFIX>.tf as from the list above.
    • Each file should specify the role Name, which *_enabled variable is used to toggle its creation, and the two local variables master_assumerole_policy and custom_policy_arns, which permit AssumeRole access from a human user's central AWS account and attach the rds_delete_prevent and region_restriction policies to the role.
    • The actual IAM permissions granted by a role's Policy should also be included in the file, in a list named iam_policies. Each list item should include a policy_name, policy_description, and the actual policy_document as a list of the Statements for a policy. Most files will only contain 1 item in the iam_policies list; however, since AWS restricts the size of an individual IAM policy, longer policies (i.e. with more granular permission specs) will often be broken into multiple items.

    Aside from the above files, the variables.tf file should include each *_enabled variable which will enable/disable creation of the associated role, i.e.:

     variable "iam_power_enabled" {
   description = "Enable power role in this account."
   type        = bool
   default     = true
 }

  2. <CLI_PREFIX>/main.tf: Each directory named by one of the account-based CLI Prefixes above should contain a main.tf file which specifies, within a main module, if there are any *_enabled values which differ from the defaults specified in module/variables.tf. Example:

    module "main" {
  source = "../module"

  iam_account_alias            = "some-account-name"
  iam_kmsadmin_enabled         = true
  dashboard_logos_bucket_write = true
}

    The KMSAdministrator role is disabled by default (iam_kmsadmin_enabled is set to false in module/variables.tf), so setting iam_kmsadmin_enabled = true overrides the default and will cause the role/policy/attachments to be created.

Making Changes to Access

Any of the changes listed below will require a pull request in identity-devops, and a tf-deploy run of master/global successfully applied, before they are live.

IAM Users

To create a new IAM user profile, make changes to:

  1. Variable: user_map
  2. Format: "first.last" = ["group1", "group2", ...],.

User permissions are set on an additive basis, via their group(s). Add a user to multiple groups if a single group does not provide sufficient permissions for their work.

IAM Groups

To create a new IAM group, make changes to:

  1. Variable: group_role_map
  2. Format:
"name" = [
  { "RoleOne"         = [ "AccountType1", "AccountType2", ... ] },
  { "RoleTwo"         = [ "AccountType1", "AccountType2", ... ] },
  { ... }
],

Group permissions are set on a whitelist basis, as per the mappings specified here. If a group has role access for a specific AccountType, they do NOT have access to that role in other AccountTypes, unless those AccountTypes are ALSO specified.

IAM Roles

To create a new IAM role, make changes to the following:

  • In terraform/all:

    1. Create a new iam-role-<CLI POSTFIX>.tf file in module/. (You may base it off one of the other template files for the sake of formatting, if desired.)
    2. Follow the requirements specified in the terraform/all section above when configuring the role template file.
    3. Add the new <CLI POSTFIX>_enabled variable to module/variables.tf. Most of the time, you will want to set the default value to true for a new role.
    4. If any specific AWS account(s) should not follow the default enabled value specified, add the necessary logic to the account's respective <CLI_PREFIX>/main.tf file. After this, run tf-deploy all/<CLI_PREFIX> for each account to add the role (or, in the case of disabled roles, to keep Terraform's state up to date).

  • In terraform/master/main.tf:

    1. Add the new role name to the role_list.
    2. For each group and account type mapping that needs access to the role, update group_role_map accordingly:
    "group1" = [
  { "Role" = [ "AccountType1", "AccountType2", ... ] },
],
"group2" = [
  { "Role" = [ "AccountType1", "AccountType2", ... ] },
],
...

Role permissions, like group permissions, are set on a whitelist basis. If a group has role access for a specific AccountType, they do NOT have access to that role in other AccountTypes, unless those AccountTypes are ALSO specified.

AWS Account Types

To create a new category of AWS account(s), make the following changes:

  1. Add the category as an AccountType to aws_account_types in the format of: 
    "AccountType" = [
  "111122223333", # <ACCOUNT NAME> alias
  "444455556666", # <ACCOUNT NAME> alias
  ...
],
    Each line should include the AWS Account ID number, as well as the precise AWS account alias (as specified in terraform/all/<CLI PREFIX>/main.tf), of all AWS accounts within the AccountType.
  2. For each group and role mapping that the new AccountType should support, update group_role_map accordingly: 
    "group1" = [
  { "RoleOne"         = [ "AccountType" ] },
  { "RoleTwo"         = [ "AccountType" ] },
  { ... }
],
"group2" = [
  { "RoleOne"         = [ "AccountType" ] },
  { "RoleTwo"         = [ "AccountType" ] },
  { ... }
],
...

An individual AWS IAM account can only be part of one AccountType. If you require more granular permission control, you will need to create additional AccountTypes.

Adding IAM Permissions To A New AWS Account

If a new AWS account is added to the Login.gov organization, the following changes will be needed to provide IAM permissions/access to it.

Prerequisites:

  • Determine the Friendly Name, Alias, CLI Prefix, AWS Account ID, and Account Type as per the other examples in [the AWS Accounts matrix]({% link _articles/platform-aws-accounts-and-roles.md %}). Add a new line with those values to the matrix as part of a PR update to this document.
  • Verify that there is at least one NON-Terraform-managed IAM user profile with the equivalent of FullAdministrator permissions within the account. This user will perform the initial run of terraform/all to create the Roles in the account, allowing users within terraform/master to Assume these Roles.

Steps:

  1. Create a new directory in terraform/all named with the CLI Prefix of the account.
  2. Copy over the env-vars.sh and main.tf files from another account's directory, and update the various values within the new files (i.e. AWS account ID number, AWS_PROFILE value, account alias, and any enabled values requiring non-default specification).
  3. Run tf-deploy all/<CLI_PREFIX> as the non-managed admin user in order to create the IAM roles in terraform/all/module within the account.
  4. Add the account to its appropriate Account Type list in aws_account_types, or create a new AccountType if the available options are too broad.
  5. Verify the groups, roles and AccountTypes in the group_role_map, and update them if necessary.
  6. Do the same for user_map if any user(s) need(s) to have their group-based permissions changed.
  7. Run tf-deploy global/master apply to create the AssumeRole policies and attachments as specified.