The answer is that the resource ARN in the policy is missing the stage and method, so it should be formatted as `arn:aws:execute-api:us-east-1:123456789012:api-id/stage/GET/resource`. This is because API Gateway IAM authorization requires the resource ARN to include the specific stage, HTTP method, and resource path (or wildcards) to match the incoming request; using `api-id/*` alone is too broad and fails to grant permission for a particular invocation, resulting in a 403 Forbidden error even when the IP condition is correct. On the AWS Certified Security Specialty SCS-C02 exam, this question tests your understanding of how IAM policy resource ARNs interact with API Gateway’s hierarchical resource structure—a common trap is assuming `*` after the API ID covers everything, when in fact you must specify at least `*/*` for stage and method. A reliable memory tip is to think of the ARN as a URL path: just as you need the full route to reach a specific endpoint, the ARN must include stage, method, and resource to grant invoke access.
SCS-C02 Identity and Access Management Practice Question
This SCS-C02 practice question tests your understanding of identity and access management. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
A company is using Amazon API Gateway to expose a set of REST APIs. The APIs are backed by AWS Lambda functions. The security team wants to control access to the APIs using IAM authorization. The team has created an IAM policy for a group of developers that allows them to invoke the APIs only from within the corporate network (IP range 203.0.113.0/24). The policy is attached to an IAM group, and the developers are members of the group. However, when a developer tries to invoke the API from the corporate network, they receive a '403 Forbidden' error. The API Gateway endpoint is configured with IAM authorization. The IAM policy is as follows: {"Version":"2012-10-17","Statement":[{"Effect":"Allow","Action":"execute-api:Invoke","Resource":"arn:aws:execute-api:us-east-1:123456789012:api-id/*","Condition":{"IpAddress":{"aws:SourceIp":"203.0.113.0/24"}}}]}. What is the MOST likely reason for the failure?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
The resource ARN in the policy does not include the stage and method; it should be 'arn:aws:execute-api:us-east-1:123456789012:api-id/stage/GET/resource'.
The resource ARN must be more specific to match the API's resource hierarchy.
B
The IAM policy must be attached directly to the IAM user, not to a group.
Why wrong: Policies attached to a group affect all members.
C
The condition key aws:SourceIp does not work for API Gateway; you must use a custom header.
Why wrong: aws:SourceIp works with API Gateway IAM authorization.
D
API Gateway IAM authorization does not support resource-level conditions; you must use a Lambda authorizer.
Why wrong: IAM authorization does support resource-level conditions.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The resource ARN in the policy does not include the stage and method; it should be 'arn:aws:execute-api:us-east-1:123456789012:api-id/stage/GET/resource'.
Option B is correct. For API Gateway IAM authorization, the resource ARN must include the stage and method, or use wildcards. The policy uses 'api-id/*' which may not match the actual resource path. Option A is wrong because the condition is correct for IP restriction. Option C is wrong because the policy is attached to the group, so the developers should inherit it. Option D is wrong because API Gateway IAM authorization works with IAM policies; the issue is likely the resource ARN.
Key principle: Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
The resource ARN in the policy does not include the stage and method; it should be 'arn:aws:execute-api:us-east-1:123456789012:api-id/stage/GET/resource'.
Why this is correct
The resource ARN must be more specific to match the API's resource hierarchy.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Authentication checks who the user is.
✗
The IAM policy must be attached directly to the IAM user, not to a group.
Why it's wrong here
Policies attached to a group affect all members.
✗
The condition key aws:SourceIp does not work for API Gateway; you must use a custom header.
Why it's wrong here
aws:SourceIp works with API Gateway IAM authorization.
✗
API Gateway IAM authorization does not support resource-level conditions; you must use a Lambda authorizer.
Why it's wrong here
IAM authorization does support resource-level conditions.
Common exam traps
Common exam trap: authentication is not authorization
Logging in proves the user can authenticate. It does not automatically mean the user is allowed to enter privileged or configuration mode. Watch for AAA authorization, privilege level and command authorization details.
Detailed technical explanation
How to think about this question
This kind of question is testing the difference between identity and permission. A user may successfully log in to a router because authentication is working, but still fail to enter configuration mode because authorization is missing, misconfigured or mapped to a lower privilege level.
KKey Concepts to Remember
Authentication checks who the user is.
Authorization controls what the user is allowed to do after login.
Privilege levels affect access to EXEC and configuration commands.
AAA, TACACS+ and RADIUS can separate login success from command access.
TExam Day Tips
→Do not assume successful login means full administrative access.
→Look for words such as cannot enter configuration mode, privilege level, authorization or command access.
→Separate login problems from permission problems before choosing the answer.
Key takeaway
Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
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.
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related SCS-C02 questions on access control and AAA configuration.
Identity and Access Management — This question tests Identity and Access Management — Authentication checks who the user is..
What is the correct answer to this question?
The correct answer is: The resource ARN in the policy does not include the stage and method; it should be 'arn:aws:execute-api:us-east-1:123456789012:api-id/stage/GET/resource'. — Option B is correct. For API Gateway IAM authorization, the resource ARN must include the stage and method, or use wildcards. The policy uses 'api-id/*' which may not match the actual resource path. Option A is wrong because the condition is correct for IP restriction. Option C is wrong because the policy is attached to the group, so the developers should inherit it. Option D is wrong because API Gateway IAM authorization works with IAM policies; the issue is likely the resource ARN.
What should I do if I get this SCS-C02 question wrong?
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related SCS-C02 questions on access control and AAA configuration.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Authentication checks who the user is.
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Question Discussion
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