Tutorial / Cram Notes
Effective IAM usage ensures secure access control by employing different entities such as users, groups, roles, identity providers, and policies which include identity-based policies, resource-based policies, and session policies. Here, we will delve into the appropriate usage of these entities to facilitate both human and machine access.
IAM Users and Groups
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IAM Users: An IAM user is an identity that represents a person or service needing to interact with AWS services. Each IAM user can have specific permission sets that define what actions they are allowed to perform within AWS.
Usage Example:
An IAM user can be created for an employee who needs to access the AWS Management Console. You can assign permissions directly to this user which specifically align with their job responsibilities. -
IAM Groups: A group is a collection of IAM users. Groups allow you to specify permissions for multiple users, which can make it easier to manage the permissions for those users.
Usage Example:
You might create an IAM group called “Developers,” to which you add all user accounts for individuals in the development team, and attach policies that grant the necessary permissions for application development tasks.
IAM Roles
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IAM Roles: A role is a set of permissions that a user or AWS service assumes but is not uniquely associated with one person. It allows AWS service or a user to assume temporary security credentials.
Usage Example:
You might create an IAM role with permissions to access Amazon S3 and then assign that role to an application running on an EC2 instance. This allows the application to access the necessary resources without embedding credentials.
Identity Providers
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Identity Providers (IdP): Identity providers allow you to grant users access to AWS resources using their corporate credentials (e.g., Active Directory, LDAP).
Usage Example:
You can set up a third-party SAML 2.0 compliant IdP to federate Single Sign-On (SSO) allowing users to log in to the AWS Management Console without IAM user credentials.
Identity-Based Policies vs. Resource-Based Policies
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Identity-Based Policies: These are attached to an IAM entity (user, group, or role) and manage permissions across AWS resources.
Usage Example:
An identity-based policy could allow a user to perform actions like launching EC2 instances or reading data from an S3 bucket. -
Resource-Based Policies: These are attached directly to a resource (such as an S3 bucket or a KMS key) and specify who (which identities) can access that resource and what actions they can take.
Usage Example:
A resource-based policy on an S3 bucket might permit any user or role within your AWS account to read files from that bucket.
Session Policies
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Session Policies: These policies are passed when you assume a role or federated user session. They further restrict the permissions that the role or user’s security credentials provide for a session.
Usage Example:
When a developer assumes a role to perform a specific task, you can attach a session policy that restricts the actions the developer can take during that session to an even smaller subset of permissions.
Here’s a comparative outline of these IAM entities:
| Entity | Use Case | Example Usage |
| IAM User | Represent individual or service with permanent long-term credentials | Employee needing console access with specific permissions |
| IAM Group | Organize users with similar permissions | Grouping developers and assigning development-related policies |
| IAM Role | Provide temporary permissions to AWS services or users assuming the role | EC2 instances accessing S3 data |
| Identity Provider | Enable federation with external identity systems for single sign-on | Users signing in through corporate IdP to access AWS services |
| Identity-Based Policy | Attach policies to IAM users, groups, or roles to specify allowed or denied actions | Granting a user access to launch EC2 instances |
| Resource-Based Policy | Attach policies to AWS resources to define who can access this resource and what actions they can take | Allowing reading files from an S3 bucket to any entity in the AWS account |
| Session Policy | Provides stricter permissions during a given session when a role is assumed or federated | Restricting developer access to certain resources during assume role |
Employing these IAM entities in appropriate ways can help ensure that your AWS environment is secure, following the principle of least privilege – granting only the necessary permissions to perform a task. For the “AWS Certified DevOps Engineer – Professional (DOP-C02)” exam, understanding how and when to use each of these entities in a scalable and secure manner is essential.
Practice Test with Explanation
True or False: IAM roles can be used to provide temporary security credentials to grant access to AWS resources.
- A) True
- B) False
Answer: A) True
Explanation: IAM roles offer a way to provide temporary security credentials for temporary access to AWS resources.
Which IAM entity is recommended for a human user who needs to regularly interact with AWS services?
- A) IAM User
- B) IAM Role
- C) IAM Group
Answer: A) IAM User
Explanation: IAM Users are designed for human users who need to authenticate and interact with AWS services.
When should you use an IAM Group?
- A) To define permissions for an AWS service
- B) To organize IAM users with similar permissions
- C) To provide access to external users
Answer: B) To organize IAM users with similar permissions
Explanation: IAM Groups are used for managing sets of IAM users who need the same permissions.
For an application running on an EC2 instance which requires access to S3, which IAM entity should be used?
- A) IAM User
- B) IAM Role
- C) IAM Group
Answer: B) IAM Role
Explanation: An IAM Role can be attached to the EC2 instance to provide the necessary permissions for the application to access S
True or False: An IAM policy can only be associated with IAM users, not roles or groups.
- A) True
- B) False
Answer: B) False
Explanation: IAM policies can be attached to users, roles, and groups within AWS IAM.
What should be used to grant access to an AWS account to a trusted business partner without creating an IAM user?
- A) Identity Providers
- B) Resource-based policies
- C) IAM Group
Answer: A) Identity Providers
Explanation: Identity Providers can be used to establish trust and grant external users access to an AWS account without creating IAM users.
True or False: Resource-based policies can be used to directly grant permissions to resources such as S3 buckets or KMS keys.
- A) True
- B) False
Answer: A) True
Explanation: Resource-based policies are attached directly to an AWS resource to define who has what permissions.
Which IAM entity is most suitable for granting a third-party application access to AWS resources?
- A) IAM User
- B) IAM Role
- C) IAM Group
Answer: B) IAM Role
Explanation: IAM Roles are suitable for allowing third-party applications to assume the role and access resources without using access keys.
In what scenario are session policies useful?
- A) When you need to set long-term permissions for an IAM user
- B) When you want to restrict the permissions that a role or user’s security credentials can have during a session
- C) When managing permissions across multiple AWS accounts
Answer: B) When you want to restrict the permissions that a role or user’s security credentials can have during a session
Explanation: Session policies are used to limit permissions within an existing IAM role/user session.
True or False: Users within an IAM Group automatically inherit the permissions assigned to the group.
- A) True
- B) False
Answer: A) True
Explanation: IAM Groups are a way to manage permissions for multiple users, and any permissions assigned to the group are inherited by its members.
Which of the following is NOT a best practice for using IAM roles?
- A) Use roles for EC2 instances to interact with AWS resources.
- B) Assign one role to multiple EC2 instances that perform the same task.
- C) Attach policies with admin privileges to roles for broad access.
Answer: C) Attach policies with admin privileges to roles for broad access
Explanation: It’s not recommended to attach admin privileges unless absolutely necessary; the principle of least privilege should be followed.
Which IAM feature allows you to establish a trust relationship between your AWS account and another identity provider?
- A) IAM Role
- B) IAM User
- C) IAM Identity Providers
Answer: C) IAM Identity Providers
Explanation: IAM Identity Providers enable you to establish a trust relationship between your AWS account and a separate identity provider.
Interview Questions
Can you explain when to use IAM Users versus IAM Roles for human access to AWS resources?
IAM Users represent individual people or services that need to interact with AWS resources, while IAM Roles are used to grant specific permissions for specific tasks to users, services, or applications without using permanent credentials. IAM Users are ideal for human access when each person requires a unique set of credentials. IAM Roles are best for human access when users already have identities defined outside of AWS (like in corporate directories) or for temporary access. When launching an EC2 instance that requires access to certain AWS services, it is more secure to use an IAM Role rather than embedding static IAM User credentials within the instance.
Describe a scenario in which you would use a resource-based policy instead of an identity-based policy.
A resource-based policy is attached directly to the AWS resource for which you want to control access, in contrast to identity-based policies which are attached to IAM users, groups, or roles. You would use a resource-based policy when you want to allow users from different AWS accounts to access a resource in your account without having to create IAM users for them in your account (e.g., a bucket policy that allows other accounts to access an S3 bucket).
Great post! Quick question: For managing machine access, should I use IAM roles or IAM users?
This blog was really helpful. Thanks for sharing!
Is it possible to attach both identity-based and resource-based policies to an IAM role?
Can someone explain the difference between identity providers and federated users?
I think the blog could have included more examples for resource-based policies.
For human access, would you recommend IAM users or groups?
How effective are session policies for controlling temporary access?
This was exactly what I needed! Appreciate the depth in IAM roles.