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Design Secure Architectures →easyMultiple ChoiceObjective-mapped

Quick Answer

The correct answer is to configure the trust policy in Company A to allow `sts:AssumeRole` only for the principal `arn:aws:iam::<company-b-account-id>:role/<specific-role-in-b>` and require a condition where `sts:ExternalId` equals the expected External ID value. This configuration is technically sound because it uses a resource-based policy to lock down the principal to a specific IAM role in Company B, while the `sts:ExternalId` condition key acts as a shared secret that prevents a confused deputy attack—without it, a malicious third party could trick Company A into granting access to an unintended role. On the SAA-C03 exam, this scenario tests your understanding of cross-account IAM role trust policies and the confused deputy problem, often appearing as a distractor where candidates mistakenly use a wildcard principal or omit the External ID. A common trap is thinking an account-level principal is sufficient, but the exam requires role-level specificity plus the External ID condition. Memory tip: think "Role + ID" — lock the role ARN and require the secret handshake.

SAA-C03 Design Secure Architectures Practice Question

This SAA-C03 practice question tests your understanding of design secure architectures. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.

Company A must allow workloads in Company B to assume an IAM role in Company A (RoleInA). To mitigate confused-deputy attacks, a Security requirement is to use an External ID. Company A should restrict who can assume RoleInA. Which trust-policy configuration is the best choice?

Clue words in this question

Noticing these words before you look at the options changes how you read each choice.

  • Clue: "best"

    Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.

Question 1easymultiple choice
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Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

✓

In Company A role trust policy, allow sts:AssumeRole only for principal "arn:aws:iam::<company-b-account-id>:role/<specific-role-in-b>" and require a condition where sts:ExternalId equals the expected External ID value.

Option B is correct because it restricts the trust policy to a specific IAM role in Company B (using the principal ARN) and requires the `sts:ExternalId` condition to match a predefined value. This ensures only the intended role in Company B can assume RoleInA, and the External ID prevents a confused-deputy attack by requiring the third party to provide a unique identifier that only the legitimate service knows.

Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

  • ✗

    In Company A role trust policy, allow sts:AssumeRole for principal "arn:aws:iam::<company-b-account-id>:root" with no sts:ExternalId condition.

    Why it's wrong here

    Allowing the entire Company B account root is broader than necessary, and omitting the sts:ExternalId condition does not provide confused-deputy protection.

  • ✓

    In Company A role trust policy, allow sts:AssumeRole only for principal "arn:aws:iam::<company-b-account-id>:role/<specific-role-in-b>" and require a condition where sts:ExternalId equals the expected External ID value.

    Why this is correct

    Restricting the principal to the specific intended role limits who can assume RoleInA. Requiring the correct sts:ExternalId in the trust policy mitigates confused-deputy attacks.

    Clue confirmation

    The clue word "best" in the question point toward this answer.

    Related concept

    Read the scenario before looking for a memorised answer.

  • ✗

    In the trust policy, allow iam:PassRole for the Company B principal and include an sts:ExternalId condition.

    Why it's wrong here

    Trust policies for role assumption use sts:AssumeRole. iam:PassRole is unrelated to establishing temporary credentials via STS AssumeRole.

  • ✗

    In Company A, grant Company B access using an IAM permissions policy attached to RoleInA instead of using a trust policy.

    Why it's wrong here

    Cross-account role assumption requires a trust policy that allows sts:AssumeRole. Identity permission policies alone do not permit assuming the role.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates often confuse `iam:PassRole` with `sts:AssumeRole` or think that a permissions policy can restrict who assumes a role, but only the trust policy defines the trusted principals and conditions for role assumption.

Trap categories for this question

  • Similar concept trap

    Allowing the entire Company B account root is broader than necessary, and omitting the sts:ExternalId condition does not provide confused-deputy protection.

Detailed technical explanation

How to think about this question

The `sts:ExternalId` condition key is a string that the calling service must include in the `AssumeRole` API request; it is commonly used when a third party (like Company B) needs to access resources in your account, ensuring that the request originates from an authorized client. Under the hood, the External ID is passed as a parameter in the `AssumeRole` call and must match the value in the trust policy, preventing a malicious actor from tricking the role into being assumed by a different principal. In real-world scenarios, this is critical for cross-account access in SaaS integrations or partner workflows where the external ID is a unique identifier generated by the account owner.

KKey Concepts to Remember

  • Read the scenario before looking for a memorised answer.
  • Find the constraint that changes the correct option.
  • Eliminate answers that are true in general but not in this case.

TExam Day Tips

  • Watch for words such as best, first, most likely and least administrative effort.
  • Review why wrong options are wrong, not only why the correct option is correct.

Key takeaway

Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.

Real-world example

How this comes up in practice

A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.

What to study next

Got this wrong? Here's your next step.

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

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FAQ

Questions learners often ask

What does this SAA-C03 question test?

Design Secure Architectures — This question tests Design Secure Architectures — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: In Company A role trust policy, allow sts:AssumeRole only for principal "arn:aws:iam::<company-b-account-id>:role/<specific-role-in-b>" and require a condition where sts:ExternalId equals the expected External ID value. — Option B is correct because it restricts the trust policy to a specific IAM role in Company B (using the principal ARN) and requires the `sts:ExternalId` condition to match a predefined value. This ensures only the intended role in Company B can assume RoleInA, and the External ID prevents a confused-deputy attack by requiring the third party to provide a unique identifier that only the legitimate service knows.

What should I do if I get this SAA-C03 question wrong?

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

Are there clue words in this question I should notice?

Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

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Last reviewed: Jun 11, 2026

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This SAA-C03 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the SAA-C03 exam.