The answer is that the Deny statement with the `aws:SourceAccount` condition denies access when the condition key is absent from the request. This occurs because IAM evaluates a `StringNotEquals` condition as false if the key is missing, causing the Deny to apply even when the request originates from the correct account. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this tests your understanding of how IAM handles absent condition keys—a common trap where candidates assume a missing key simply means the condition is ignored. The key insight is that `aws:SourceAccount` is not automatically included in all API calls; it must be explicitly passed by the calling service or principal. If the CI/CD system’s role does not include this key in its request, the Deny blocks all CodePipeline actions, overriding the Allow statement. Memory tip: “Missing key = Deny applied” — always verify that the condition key is actually present in the request, not just that the account matches.
DOP-C02 SDLC Automation Practice Question
This DOP-C02 practice question tests your understanding of sdlc automation. 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.
Refer to the exhibit. An IAM policy is attached to a role used by a CI/CD system. The policy is intended to allow starting the pipeline 'MyPipeline' from the same account. However, the CI/CD system receives an 'AccessDenied' error when trying to start the pipeline. What is the problem?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The Deny statement with the 'aws:SourceAccount' condition denies access if the condition key is not present in the request.
Option B is correct. The Deny statement with a condition denies all codepipeline actions if the source account is not 123456789012. However, the Allow statement allows StartPipelineExecution for the specific pipeline. But the Deny statement with a condition that does not match (i.e., if the source account is exactly 123456789012, the condition is false, so the Deny does not apply). Wait, let's analyze: The Deny statement applies when the source account is NOT 123456789012. So if the source account IS 123456789012, the Deny does not apply, and the Allow should work. But the error suggests AccessDenied. The issue could be that the policy also needs to allow other actions? Actually, looking closely: The Allow only allows StartPipelineExecution, but maybe the pipeline execution requires other actions? No, StartPipelineExecution should be sufficient. Another possibility: The Deny statement with condition might be interpreted incorrectly. Actually, the Deny with StringNotEquals will deny if the source account is not equal to the specified account. So if the source account is 123456789012, the condition is false, so the Deny does not apply. So the Allow should work. But the error persists. Perhaps the issue is that the policy also needs to allow 'codepipeline:GetPipeline' or something? However, the most likely cause is that the Deny statement is too broad: it denies all codepipeline actions for any resource, but only if the source account is not the one specified. If the source account is correct, the Deny doesn't apply. So why denial? Maybe the condition key 'aws:SourceAccount' is not set for the request? If the condition key is not present, then StringNotEquals evaluates to false (since not present is not equal), so the Deny would apply. That is a common pitfall: when the condition key is absent, the condition evaluates to false, causing the Deny to apply. So Option B is correct: the condition key 'aws:SourceAccount' may not be present in the request, causing the Deny to apply. Option A is wrong because the Allow is not blocked by Deny if condition met. Option C is wrong because there is no explicit deny for GetPipeline. Option D is wrong because the policy is attached to the role, not user.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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 Allow statement does not specify the correct pipeline ARN.
Why it's wrong here
The ARN is correct.
✗
The policy needs an additional Allow for 'codepipeline:GetPipeline' to start the pipeline.
Why it's wrong here
StartPipelineExecution alone is sufficient.
✗
The role does not have permission to pass the policy to the CI/CD system.
Why it's wrong here
Policy is attached to role, not passed.
✓
The Deny statement with the 'aws:SourceAccount' condition denies access if the condition key is not present in the request.
Why this is correct
If the condition key is absent, the Deny applies, causing AccessDenied.
Related concept
Standard ACLs match source addresses.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
How to think about this question
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
KKey Concepts to Remember
Standard ACLs match source addresses.
Extended ACLs can match source, destination, protocol and ports.
The first matching ACL entry is used.
There is usually an implicit deny at the end.
TExam Day Tips
→Check inbound versus outbound direction.
→Read the ACL from top to bottom.
→Look for a broader permit or deny above the intended line.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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 ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related DOP-C02 ACL questions on filtering logic and placement.
SDLC Automation — This question tests SDLC Automation — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: The Deny statement with the 'aws:SourceAccount' condition denies access if the condition key is not present in the request. — Option B is correct. The Deny statement with a condition denies all codepipeline actions if the source account is not 123456789012. However, the Allow statement allows StartPipelineExecution for the specific pipeline. But the Deny statement with a condition that does not match (i.e., if the source account is exactly 123456789012, the condition is false, so the Deny does not apply). Wait, let's analyze: The Deny statement applies when the source account is NOT 123456789012. So if the source account IS 123456789012, the Deny does not apply, and the Allow should work. But the error suggests AccessDenied. The issue could be that the policy also needs to allow other actions? Actually, looking closely: The Allow only allows StartPipelineExecution, but maybe the pipeline execution requires other actions? No, StartPipelineExecution should be sufficient. Another possibility: The Deny statement with condition might be interpreted incorrectly. Actually, the Deny with StringNotEquals will deny if the source account is not equal to the specified account. So if the source account is 123456789012, the condition is false, so the Deny does not apply. So the Allow should work. But the error persists. Perhaps the issue is that the policy also needs to allow 'codepipeline:GetPipeline' or something? However, the most likely cause is that the Deny statement is too broad: it denies all codepipeline actions for any resource, but only if the source account is not the one specified. If the source account is correct, the Deny doesn't apply. So why denial? Maybe the condition key 'aws:SourceAccount' is not set for the request? If the condition key is not present, then StringNotEquals evaluates to false (since not present is not equal), so the Deny would apply. That is a common pitfall: when the condition key is absent, the condition evaluates to false, causing the Deny to apply. So Option B is correct: the condition key 'aws:SourceAccount' may not be present in the request, causing the Deny to apply. Option A is wrong because the Allow is not blocked by Deny if condition met. Option C is wrong because there is no explicit deny for GetPipeline. Option D is wrong because the policy is attached to the role, not user.
What should I do if I get this DOP-C02 question wrong?
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related DOP-C02 ACL questions on filtering logic and placement.
What is the key concept behind this question?
Standard ACLs match source addresses.
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