Controlling Access to your Resources at the Best of re:Invent Tel Aviv 2015

1. © 2015, Amazon Web Services, Inc. or its Affiliates. All rights reserved.
IAM Best Practices to Live By
Ran Tessler, AWS Solutions Architect
November 2015

2. AWS Identity and Access Management (IAM)
Enables you to control who can do what in your AWS account
Users, groups, roles, and permissions
Control
– Centralized
– Fine-grained - APIs, resources, and AWS Management Console
Security
– Secure (deny) by default
– Multiple users, individual security credentials and permissions

3. What to expect from this session
We will look at:
• Best practices – To help you get started
• Versus – When to use one technology over another
• Demos – “Show and tell”

4. IAM Best Practices
• Basic user and permission management
• Credential management
• Delegation

5. Basic user and permission management
0. Create individual users Benefits
• Unique credentials
• Individual credential rotation
• Individual permissions

6. Basic user and permission management
0. Create individual users
1. Grant least privilege
Benefits
• Less chance of people making
mistakes
• Easier to relax than tighten up
• More granular control

7. Basic user and permission management
0. Create individual users
1. Grant least privilege
2. Manage permissions with groups
Benefits
• Easier to assign the same
permissions to multiple users
• Simpler to reassign permissions
based on change in
responsibilities
• Only one change to update
permissions for multiple users

8. Basic user and permission management
0. Create individual users
1. Grant least privilege
2. Manage permissions with groups
3. Restrict privileged access further with conditions
Benefits
• Additional granularity when
defining permissions
• Can be enabled for any AWS
service API
• Minimizes chances of
accidentally performing
privileged actions

9. Basic user and permission management
0. Create individual users
1. Grant least privilege
2. Manage permissions with groups
3. Restrict privileged access further with conditions
4. Enable AWS CloudTrail to get logs of API calls
Benefits
• Visibility into your user activity by
recording AWS API calls to an
Amazon S3 bucket

10. Credential management
5. Configure a strong password policy Benefits
• Ensures your users and your
data are protected

11. Credential management
5. Configure a strong password policy
6. Rotate security credentials regularly
Benefits
• Normal best practice

12. Credential management
5. Configure a strong password policy
6. Rotate security credentials regularly
7. Enable MFA for privileged users
Benefits
• Supplements user name and
password to require a one-time
code during authentication

13. Delegation
8. Use IAM roles to share access Benefits
• No need to share security
credentials
• No need to store long-term
credentials
• Use cases
- Cross-account access
- Intra-account delegation
- Federation

14. Delegation
8. Use IAM roles to share access
9. Use IAM roles for Amazon EC2 instances
Benefits
• Easy to manage access keys on
EC2 instances
• Automatic key rotation
• Assign least privilege to the
application
• AWS SDKs fully integrated
• AWS CLI fully integrated

15. Delegation
8. Use IAM roles to share access
9. Use IAM roles for Amazon EC2 instances
10. Reduce or remove use of root
Benefits
• Reduce potential for misuse of
credentials

16. Versus – When should I use…?

18. IAM users vs. federated users
• Depends on where you want to manage your users
– On-premises → Federated users (IAM roles)
– In your AWS account → IAM users
• Other important use cases
– Delegating access to your account → Federated users (IAM roles)
– Mobile application access → Should always be federated access
IMPORTANT: Never share security credentials.

19. prod@example.com
Acct ID: 111122223333
ddb-role
{ "Statement": [
{ "Action":
[
"dynamodb:GetItem",
"dynamodb:BatchGetItem",
"dynamodb:DescribeTable",
"dynamodb:ListTables"
],
"Effect": "Allow",
"Resource": "*“
}]}
dev@example.com
Acct ID: 123456789012
Authenticate with
Ran’s access keys
Get temporary
security credentials
for ddb-role
Call AWS APIs
using temporary
security credentials
of ddb-role
{ "Statement": [
{
"Effect": "Allow",
"Action": "sts:AssumeRole",
"Resource":
"arn:aws:iam::111122223333:role/ddb-role"
}]}
{ "Statement": [
{
"Effect":"Allow",
"Principal":{"AWS":"123456789012"},
"Action":"sts:AssumeRole"
}]}
How does federated access work?
ddb-role trusts IAM users from the AWS account
dev@example.com (123456789012)
Permissions assigned
to Ran granting him
permission to assume
ddb-role in account B
IAM user: Ran
Permissions assigned to ddb-role
STS

21. AWS access keys vs. passwords
• Depends on how your users will access AWS
– Console → Password
– API, CLI, SDK → Access keys
• In either case make sure to rotate credentials regularly
– Use Credential Report to audit credential rotation.
– Configure password policy.
– Configure policy to allow access key rotation.

22. Enabling credential rotation for IAM users
(Enable access key rotation sample policy)
Access keys
{
"Version":"2012-10-17",
"Statement": [{
"Effect": "Allow",
"Action": [
"iam:CreateAccessKey",
"iam:DeleteAccessKey",
"iam:ListAccessKeys",
"iam:UpdateAccessKey"],
"Resource":
"arn:aws:iam::123456789012:
user/${aws:username}"
}]}
1. While the first set of credentials is still
active, create a second set of credentials,
which will also be active by default.
2. Update all applications to use the new
credentials.
3. Change the state of the first set of
credentials to Inactive.
4. Using only the new credentials, confirm
that your applications are working well.
5. Delete the first set of credentials.
Steps to rotate access keys

24. Inline policies vs. managed policies
• Use inline policies when you need to:
– Enforce a strict one-to-one relationship between policy and principal.
– Avoid the wrong policy being attached to a principal.
– Ensure the policy is deleted when deleting the principal.
• Use managed policies when you need:
– Reusability.
– Central change management.
– Versioning and rollback.
– Delegation of permissions management.
– Automatic updates for AWS managed policies.
– Larger policy size.

26. Groups vs. managed policies
• Provide similar benefits
– Can be used to assign the same permission to many users.
– Central location to manage permissions.
– Policy updates affect multiple users.
• Use groups when you need to
– Logically group and manage IAM users .
• Use managed policies when you need to
– Assign the same policy to users, groups, and roles.

27. Combine the power of groups AND managed policies
• Use groups to organize your users into logical clusters.
• Attach managed policies to those groups with the permissions those groups
need.
• Pro tip: Create managed policies based on logically separated permissions
such as AWS service or project, and attach managed policies mix-and-
match style to your groups.

29. How does tag-based access control work?
{
"Version": "2012-10-17",
"Statement": [
{
"Effect": "Allow",
"Action": "ec2:*",
"Resource": "*",
"Condition": {
"StringEquals": {
"ec2:ResourceTag/Project" : "Blue"
}
}
}
]
}
Permissions assigned to Bob granting him permission to
perform any EC2 action on resources tagged with
Project=Blue
IAM user: Bob
i-a1234b12
Project=Blue
i-a4321b12
Project=Blue
Project=Blue
i-a4321b12
Project=Green

30. Resource-specific policy vs. tag-based access control
• Use resource-specific policy when you need to:
• Control access to a specific resource.
• Control access to most AWS service resources.
• Use tag-based access control when you need to:
• Treat resources as a unit, such as a project.
• Automatically enforce permissions when new resources are created.
NOTE: The following services currently support tag-based access control:
Amazon EC2, Amazon VPC, Amazon EBS, Amazon RDS, Amazon Simple
Workflow Service, and AWS Data Pipeline

32. One AWS account vs. multiple AWS accounts?
Use a single AWS account when you:
• Want simpler control of who does what in your AWS environment.
• Have no need to isolate projects/products/teams.
• Have no need for breaking up the cost.
Use multiple AWS accounts when you:
• Need full isolation between projects/teams/environments.
• Want to isolate recovery data and/or auditing data (e.g., writing your
CloudTrail logs to a different account).
• Need a single bill, but want to break out the cost and usage.

33. Cross-account access with IAM roles
External identity
provider
acme@example.com
Acct ID: 123456789012
dev@example.com
Acct ID: 123456123456
proj2@example.com
Acct ID: 111222333444
proj1@example.com
Acct ID: 112233445566
IAM user: Alice
IAM user: Bob

34. What did we cover?
1. Top 11 best practices.
2. IAM users vs. federated users.
3. Access keys vs. passwords.
4. Inline policies vs. managed policies.
5. Groups vs. managed policies.
6. Resource-specific policy vs. tag-based access control.
7. One AWS account vs. multiple AWS accounts.

35. Thank you!