IAM roles concept in AWS - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an IAM role in AWS?

An IAM role is like a set of permissions that you can give to AWS services or users to let them do specific tasks without sharing your personal credentials.

beginner

How is an IAM role different from an IAM user?

An IAM user is a person or service with long-term credentials, while an IAM role is a temporary set of permissions that can be assumed by users or services when needed.

beginner

What does it mean to 'assume' an IAM role?

To 'assume' a role means to temporarily take on the permissions defined by that role to perform tasks, like borrowing a key to access a room for a short time.

intermediate

Why use IAM roles instead of sharing access keys?

IAM roles improve security by avoiding sharing permanent keys. They provide temporary permissions that expire, reducing risk if credentials are exposed.

beginner

Give an example of when you would use an IAM role.

You use an IAM role when an EC2 instance needs to access S3 storage. Instead of storing keys on the instance, the EC2 assumes a role with permission to read S3.

What is the main purpose of an IAM role in AWS?

A To monitor AWS usage

B To create permanent user accounts

C To grant temporary permissions to users or services

D To store data securely

IAM roles provide temporary permissions that can be assumed by users or services.

Which of the following can assume an IAM role?

A Only root account

B Only AWS services

C Only IAM users

D Both IAM users and AWS services

Both IAM users and AWS services can assume roles to gain temporary permissions.

What happens when you assume an IAM role?

A You get permanent access keys

B You receive temporary security credentials

C Your user account is deleted

D You create a new IAM user

Assuming a role provides temporary security credentials for access.

Why is using IAM roles considered more secure than sharing access keys?

A Roles provide temporary credentials that reduce risk

B Roles allow unlimited access

C Roles never expire

D Roles are easier to remember

Temporary credentials from roles reduce the risk of long-term key exposure.

Which AWS service commonly uses IAM roles to access other services securely?

A Amazon EC2

B Amazon S3

C AWS Lambda

D Amazon RDS

Amazon EC2 instances often assume IAM roles to securely access other AWS services.

Explain what an IAM role is and how it helps improve security in AWS.

Think about borrowing permissions instead of sharing keys.

Describe a real-life scenario where you would use an IAM role in AWS.

Consider how an EC2 server accesses S3 without storing keys.

Practice

1. What is the main purpose of an IAM role in AWS?

easy

A. To monitor network traffic

B. To store user passwords securely

C. To create virtual machines

D. To grant permissions to entities without sharing long-term credentials

Solution

1. Step 1: Understand IAM role purpose

   An IAM role allows AWS entities to assume permissions temporarily without needing permanent credentials like passwords.

2. Step 2: Compare options

   Only To grant permissions to entities without sharing long-term credentials correctly describes this purpose. Options B, C, and D describe unrelated AWS features.

3. Final Answer:

   To grant permissions to entities without sharing long-term credentials -> Option D

4. Quick Check:

   IAM roles = temporary permissions without passwords [OK]

Hint: Roles give permissions without passwords or keys [OK]

Common Mistakes:

• Confusing roles with user accounts
• Thinking roles store passwords
• Mixing roles with AWS services like EC2

2. Which of the following is the correct way to specify a trust policy for an IAM role?

easy

A. { "Statement": [{ "Effect": "Allow", "Principal": { "Service": "lambda.amazonaws.com" }, "Action": "iam:PassRole" }] }

B. { "Statement": [{ "Effect": "Allow", "Principal": { "Service": "ec2.amazonaws.com" }, "Action": "sts:AssumeRole" }] }

C. { "Statement": [{ "Effect": "Allow", "Principal": { "User": "admin" }, "Action": "iam:CreateUser" }] }

D. { "Statement": [{ "Effect": "Deny", "Principal": { "AWS": "*" }, "Action": "sts:AssumeRole" }] }

Solution

1. Step 1: Identify trust policy structure

   A trust policy allows a trusted entity (like EC2) to assume the role using sts:AssumeRole action.

2. Step 2: Check each option

   { "Statement": [{ "Effect": "Allow", "Principal": { "Service": "ec2.amazonaws.com" }, "Action": "sts:AssumeRole" }] } correctly allows EC2 service to assume the role. { "Statement": [{ "Effect": "Deny", "Principal": { "AWS": "*" }, "Action": "sts:AssumeRole" }] } denies all, which is invalid for trust. { "Statement": [{ "Effect": "Allow", "Principal": { "User": "admin" }, "Action": "iam:CreateUser" }] } uses wrong action and principal. { "Statement": [{ "Effect": "Allow", "Principal": { "Service": "lambda.amazonaws.com" }, "Action": "iam:PassRole" }] } uses wrong action (iam:PassRole) for trust.

3. Final Answer:

   { "Statement": [{ "Effect": "Allow", "Principal": { "Service": "ec2.amazonaws.com" }, "Action": "sts:AssumeRole" }] } -> Option B

4. Quick Check:

   Trust policy must allow sts:AssumeRole to a service [OK]

Hint: Trust policy uses sts:AssumeRole with service principal [OK]

Common Mistakes:

• Using iam:PassRole instead of sts:AssumeRole
• Denying all principals in trust policy
• Specifying user instead of service in Principal

3. Given this IAM role trust policy snippet:

{ "Statement": [{ "Effect": "Allow", "Principal": { "Service": "lambda.amazonaws.com" }, "Action": "sts:AssumeRole" }] }

Which AWS service can assume this role?

medium

A. AWS Lambda functions

B. Amazon EC2 instances

C. Amazon S3 buckets

D. AWS IAM users

Solution

1. Step 1: Read the Principal service

   The Principal is "lambda.amazonaws.com", which means AWS Lambda service is trusted.

2. Step 2: Match service to options

   AWS Lambda functions matches AWS Lambda functions. EC2, S3, and IAM users are different entities and not trusted here.

3. Final Answer:

   AWS Lambda functions -> Option A

4. Quick Check:

   Principal service = lambda.amazonaws.com means Lambda [OK]

Hint: Principal service name shows who can assume role [OK]

Common Mistakes:

• Confusing service names like ec2.amazonaws.com vs lambda.amazonaws.com
• Thinking S3 buckets can assume roles
• Assuming IAM users are trusted by default

4. You created an IAM role with this trust policy:

{ "Statement": [{ "Effect": "Allow", "Principal": { "Service": "ec2.amazonaws.com" }, "Action": "iam:PassRole" }] }

Why can't EC2 instances assume this role?

medium

A. Because the Effect should be Deny

B. Because the Principal service is incorrect

C. Because the action should be sts:AssumeRole, not iam:PassRole

D. Because EC2 instances cannot assume roles

Solution

1. Step 1: Identify the required action in trust policy

   The trust policy must allow the action sts:AssumeRole for the trusted entity to assume the role.

2. Step 2: Analyze the given policy

   The policy uses iam:PassRole, which is incorrect for trust. This prevents EC2 from assuming the role.

3. Final Answer:

   Because the action should be sts:AssumeRole, not iam:PassRole -> Option C

4. Quick Check:

   Trust policy action must be sts:AssumeRole [OK]

Hint: Trust policy action must be sts:AssumeRole [OK]

Common Mistakes:

• Using iam:PassRole instead of sts:AssumeRole
• Changing Effect to Deny by mistake
• Believing EC2 cannot assume roles

5. You want to allow an AWS Lambda function to assume an IAM role that grants access to S3 buckets. Which two policies must you configure correctly to make this work?

hard

A. A trust policy allowing lambda.amazonaws.com to assume the role and an IAM permissions policy granting S3 access

B. A trust policy allowing s3.amazonaws.com to assume the role and an IAM permissions policy granting Lambda execution

C. An IAM user policy granting Lambda permissions and a trust policy allowing EC2 to assume the role

D. A permissions policy granting S3 access and a trust policy denying all principals

Solution

1. Step 1: Identify trust policy requirements

   The trust policy must allow the Lambda service (lambda.amazonaws.com) to assume the role.

2. Step 2: Identify permissions policy requirements

   The role's permissions policy must grant access to S3 buckets for the Lambda function.

3. Step 3: Evaluate options

   A trust policy allowing lambda.amazonaws.com to assume the role and an IAM permissions policy granting S3 access correctly pairs the trust policy for Lambda and permissions for S3. Other options have incorrect principals or deny access.

4. Final Answer:

   A trust policy allowing lambda.amazonaws.com to assume the role and an IAM permissions policy granting S3 access -> Option A

5. Quick Check:

   Trust policy + permissions policy = role works [OK]

Hint: Trust policy for who assumes; permissions policy for what they can do [OK]

Common Mistakes:

• Allowing wrong service in trust policy
• Confusing permissions policy with trust policy
• Denying all principals in trust policy