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aws-iam.md

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aws (Amazon Web Services) iam (Identity Access Management)

Concepts in short

  • Policy
    • collection of allow/deny statements (n actions, m resources)
    • managed either by AWS or by the customer
  • Role
    • collection of managed/inline policies
    • a role can be assumed by a service/user/another role
  • Users
    • ~human being (should have multi factor authentication)
    • collection of managed/inline policies
    • part of groups
  • Groups
    • collection of managed/inline policies
    • collection of users

NOTE inline policies should be considered only for LAST-RESORT EMERGENCIES.

Setup

NOTE for security reasons, create a dev account and a prod account. Access to the prod account should be limited (mainly to a CI/CD user only).

NOTE a 3rd account, a user-only account, can be used to handle only users, while the dev and prod accounts handle anything but users. When working with many projects, each with their own dev and prod account, having a user-only account diminishes the duplication. Alternatively, the dev account can act as a user-only stand-in account.

All users are created in a user-only account (except CI/CD users that go in both dev and prod) and the only permission they have is to manage their own user resource, and to assume a role by getting a session token. See https://cloudonaut.io/improve-aws-security-protect-your-keys-with-ease/ .

These permissions are given by including the user in two groups

  • infra-AssumeRoleG-*
  • infra-ManageOwnUserG-*

Roles are created in both dev and prod accounts, and user-only users can assume roles in both.

Users/Groups are created in a CloudFormation stack called infra, thus the policies/roles/groups are prefixed with infra-.

Standardized Roles

  • infra-AdminR-* role has FULL power over all services, but this role is FOR EMERGENCIES ONLY.
  • infra-OpsR-* role has FULL power over specified services
    • this includes FULL IAM power, which means that an infra-OpsR-* user can actually assign higher permissions to themselves
    • this includes infra-ReadR-* role below
  • infra-ReadR-* role has READ-ONLY power over all services

A permission for a user to assume a role can be done on account-basis (for example, can be an AdminR on dev, but ReadR on prod).

NOTE for safety reasons, a selected few are in a special infra-PowerG-* group, which gives them FULL IAM power, without them needing to assume the infra-OpsR-* role.

Onboarding a new user

  • As an infra-OpsR-* (or infar-AdminR-* or infra-PowerG-*) user, create a user in the user-only account
    • with AWS console access (skip programmatic)
    • with temporary password
    • add them to the infra-AssumeRoleG-* and infra-ManageOwnUserG-* IAM groups
  • Have the user log in
    • Go to Services -> IAM
    • Go to Users -> their own user
    • Go to Security credentials
    • Set the Assigned MFA device
    • Create access key
  • Add the user to the infra stack by adding them to specific roles in cfn/infra/users.js part of the aws*-dev-prod repository, commit, create a release with make release, and promote the new release to infra with make promote/infra/v0.0.0.
  • The CI/CD build of that commit will update the role(s) and their Trust Relationships to allow the user to assume the role(s)
  • The user should now be able to
    • login in the AWS console
    • assume the role in the AWS console
    • assume a role in the CLI

How to support yplatform's aws-iam-bootstrap

If you own a repository that version controls the infra stack (with roles and policies), you may want to support aws-iam-bootstrap, and then you need the following in the root of the repository:

  • a CONST.inc file with environment variables
  • a aws-cli.config.tpl file with resembles ~/.aws/config but can make use of ${SOME_VAR} placeholder, where SOME_VAR is defined in CONST.inc
  • a aws-cli.credentials.tpl file with resembles ~/.aws/credentials but can make use of ${SOME_VAR} placeholder, where SOME_VAR is defined in CONST.inc

Example of a CONST.inc:

GLOBAL_AWS_REGION=eu-west-1

DEV_AWS_ACCOUNT_ID=1234567890
DEV_AWS_ACCOUNT_NAME=myawsaccount
DEV_IAM_READ_ROLE=infra-ReadR-1234567890

Example of a aws-cli.config.tpl:

[default]
region = ${GLOBAL_AWS_REGION}
s3 =
  signature_version = s3v4
  max_concurrent_requests = 100
  max_queue_size = 1000
  multipart_threshold = 64MB
  multipart_chunksize = 16MB

[profile ${AWS_ACCOUNT_NAME}]
region = ${GLOBAL_AWS_REGION}
source_profile = ${AWS_ACCOUNT_NAME}

[profile ${DEV_AWS_ACCOUNT_NAME}_read]
region = ${GLOBAL_AWS_REGION}
role_arn = arn:aws:iam::${DEV_AWS_ACCOUNT_ID}:role/${DEV_IAM_READ_ROLE}
source_profile = ${AWS_ACCOUNT_NAME}

Example of a aws-cli.credentials.tpl:

[${AWS_ACCOUNT_NAME}]
aws_access_key_id = ${AWS_ACCESS_KEY_ID}
aws_secret_access_key = ${AWS_SECRET_ACCESS_KEY}

[${DEV_AWS_ACCOUNT_NAME}_read]
aws_access_key_id = ${AWS_ACCESS_KEY_ID}
aws_secret_access_key = ${AWS_SECRET_ACCESS_KEY}