Assuming roles for temporary access in AWS - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ service_behavior

intermediate

What is the duration of temporary credentials when assuming a role with AWS STS by default?

When you use AWS Security Token Service (STS) to assume a role without specifying the duration, how long do the temporary credentials last by default?

A 12 hours

B 1 hour and 15 minutes

C 1 hour

D 15 minutes

💡 Hint

Think about the default session duration for AssumeRole API calls.

By default, AWS STS issues temporary credentials valid for 1 hour when assuming a role unless a different duration is specified.

❓ security

intermediate

Which AWS policy element allows a user to assume a specific role?

To allow a user to assume an IAM role, which policy action must be included in the user's permissions?

A "sts:AssumeRole"

B "iam:PassRole"

C "iam:AssumeRolePolicy"

D "sts:GetSessionToken"

💡 Hint

Look for the STS action that grants role assumption capability.

The action "sts:AssumeRole" is required to allow a user or service to assume an IAM role.

❓ Architecture

advanced

Which trust policy snippet correctly allows an EC2 instance to assume a role?

Given an IAM role trust policy, which snippet correctly allows EC2 instances to assume the role?

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

B { "Effect": "Allow", "Principal": { "AWS": "arn:aws:iam::123456789012:user/EC2User" }, "Action": "sts:AssumeRole" }

C { "Effect": "Allow", "Principal": { "Service": "ecs.amazonaws.com" }, "Action": "sts:AssumeRole" }

D { "Effect": "Allow", "Principal": { "Service": "ec2.amazonaws.com" }, "Action": "sts:AssumeRole" }

💡 Hint

Which AWS service represents EC2 in trust policies?

The service principal for EC2 is "ec2.amazonaws.com" in the trust policy to allow EC2 instances to assume the role.

✅ Best Practice

advanced

What is the recommended maximum session duration for an IAM role to minimize risk?

To reduce security risks, what is the best practice for setting the maximum session duration for an IAM role?

A Set maximum session duration to 1 hour or less to limit exposure of temporary credentials

B Set maximum session duration to 12 hours to reduce frequent re-authentication

C Set maximum session duration to 24 hours for convenience

D Set maximum session duration to 7 days to avoid interruptions

💡 Hint

Shorter sessions reduce the window for compromised credentials.

Short session durations limit the time temporary credentials are valid, reducing risk if credentials are exposed.

🧠 Conceptual

expert

What happens if you try to assume a role with an expired session token?

If you use AWS STS to assume a role but provide an expired session token, what is the expected behavior?

A The AssumeRole call succeeds but credentials are invalid when used

B The AssumeRole call fails with an "ExpiredToken" error

C The AssumeRole call succeeds and returns new credentials ignoring the expired token

D The AssumeRole call returns credentials with reduced permissions

💡 Hint

Expired tokens cannot be used to get new credentials.

AWS STS rejects AssumeRole calls with expired tokens and returns an "ExpiredToken" error.

Practice

1. What is the main benefit of assuming an AWS role for temporary access?

easy

A. It automatically deletes the AWS account after use.

B. It provides temporary, limited access without using permanent credentials.

C. It disables all access to AWS resources.

D. It creates a new permanent user with full permissions.

Solution

1. Step 1: Understand role assumption purpose

   Assuming a role grants temporary permissions without needing permanent credentials.

2. Step 2: Compare options

   Only 'It provides temporary, limited access without using permanent credentials.' correctly describes temporary, limited access. Others describe incorrect or unrelated actions.

3. Final Answer:

   It provides temporary, limited access without using permanent credentials. -> Option B

4. Quick Check:

   Temporary access = It provides temporary, limited access without using permanent credentials. [OK]

Hint: Temporary access means no permanent keys used [OK]

Common Mistakes:

• Thinking roles create permanent users
• Confusing role assumption with account deletion
• Believing role assumption disables access

2. Which AWS CLI command is used to assume a role for temporary access?

easy

A. aws sts assume-role

B. aws iam create-role

C. aws s3 ls

D. aws ec2 start-instances

Solution

1. Step 1: Identify the correct command for role assumption

   The AWS CLI command to assume a role is aws sts assume-role.

2. Step 2: Eliminate unrelated commands

   Commands like aws iam create-role create roles but do not assume them; others manage services unrelated to role assumption.

3. Final Answer:

   aws sts assume-role -> Option A

4. Quick Check:

   Assume role command = aws sts assume-role [OK]

Hint: Assume role uses 'sts' service in CLI [OK]

Common Mistakes:

• Using 'iam create-role' instead of 'sts assume-role'
• Confusing service commands like s3 or ec2
• Typing incorrect command syntax

3. What is the expected output when running this command?

aws sts assume-role --role-arn arn:aws:iam::123456789012:role/demo --role-session-name testSession

medium

A. A JSON with temporary security credentials including AccessKeyId, SecretAccessKey, and SessionToken.

B. An error saying 'role not found' because the ARN is invalid.

C. A list of all IAM users in the account.

D. A confirmation message that the role was created.

Solution

1. Step 1: Understand the command output

   The aws sts assume-role command returns temporary credentials in JSON format.

2. Step 2: Analyze options

   Only 'A JSON with temporary security credentials including AccessKeyId, SecretAccessKey, and SessionToken.' correctly describes the expected JSON output with temporary keys. Others describe errors or unrelated outputs.

3. Final Answer:

   A JSON with temporary security credentials including AccessKeyId, SecretAccessKey, and SessionToken. -> Option A

4. Quick Check:

   Assume-role output = temporary credentials JSON [OK]

Hint: Assume-role returns temporary keys in JSON [OK]

Common Mistakes:

• Expecting role creation confirmation instead of credentials
• Confusing assume-role output with user listing
• Assuming error without verifying ARN

4. You run aws sts assume-role but get an 'AccessDenied' error. What is the most likely cause?

medium

A. The AWS CLI is not installed on your machine.

B. The AWS account is suspended.

C. The role session name is missing from the command.

D. The IAM user or role does not have permission to assume the specified role.

Solution

1. Step 1: Understand 'AccessDenied' meaning

   This error means the caller lacks permission to perform the action.

2. Step 2: Identify permission requirements for assume-role

   The IAM user or role must have explicit permission to assume the target role.

3. Final Answer:

   The IAM user or role does not have permission to assume the specified role. -> Option D

4. Quick Check:

   AccessDenied = missing assume-role permission [OK]

Hint: AccessDenied usually means missing assume-role permission [OK]

Common Mistakes:

• Assuming CLI installation causes AccessDenied
• Ignoring required role session name
• Blaming account suspension without checking permissions

5. You want to allow an EC2 instance to assume a role temporarily to access S3 buckets. Which combination is correct?

hard

A. Manually run aws sts assume-role on the EC2 instance without any IAM role attached.

B. Create an IAM user with S3 permissions and store its permanent keys on the EC2 instance.

C. Attach an IAM role with S3 permissions to the EC2 instance and use the instance profile to assume the role automatically.

D. Attach a security group to the EC2 instance that allows S3 access.

Solution

1. Step 1: Understand EC2 role usage

   Attaching an IAM role to EC2 via instance profile allows automatic temporary credentials for S3 access.

2. Step 2: Evaluate other options

   Manually running aws sts assume-role without an attached IAM role fails due to lack of initial credentials. Using permanent IAM user keys is less secure. Security groups control network access, not IAM permissions.

3. Final Answer:

   Attach an IAM role with S3 permissions to the EC2 instance and use the instance profile to assume the role automatically. -> Option C

4. Quick Check:

   EC2 uses instance profile role for temporary access [OK]

Hint: Use instance profile roles for EC2 temporary access [OK]

Common Mistakes:

• Using permanent keys on EC2 instead of roles
• Trying to assume role without attached IAM role
• Confusing security groups with permissions