CloudTrail S3 Bucket Policy: Allowing the CloudTrail Service Principal
This SAP-C02 practice question tests your understanding of design solutions for organizational complexity. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 security engineer created the above bucket policy on the central-logging-bucket in account 111111111111. They want account 222222222222 to deliver CloudTrail logs to this bucket. What is missing?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The bucket policy must grant s3:PutObject to the CloudTrail service principal, not to a role.
CloudTrail delivers logs to S3 buckets by assuming a service-linked role, but the bucket policy must explicitly grant the `s3:PutObject` permission to the CloudTrail service principal (`cloudtrail.amazonaws.com`) rather than to an IAM role in the target account. This is because CloudTrail uses its own service principal to write logs, not a cross-account IAM role. Without this permission, the CloudTrail delivery will fail with an access denied error.
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.
✗
The prefix AWSLogs/111111111111 is incorrect; it should use the source account ID 222222222222.
Why it's wrong here
The prefix should be the source account ID.
✗
The role CrossAccountRole does not exist in account 222222222222.
Why it's wrong here
The policy references the role ARN; it must exist.
✓
The bucket policy must grant s3:PutObject to the CloudTrail service principal, not to a role.
Why this is correct
CloudTrail uses its own service principal to write logs.
Related concept
Read the scenario before looking for a memorised answer.
✗
The bucket must be in the same account as CloudTrail.
Why it's wrong here
Cross-account delivery is supported.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume cross-account access requires an IAM role, but CloudTrail uses a service principal instead, making the role-based option (B) a distractor.
Detailed technical explanation
How to think about this question
When CloudTrail delivers logs to a cross-account S3 bucket, it authenticates as the `cloudtrail.amazonaws.com` service principal, which must be granted `s3:PutObject` and `s3:GetBucketAcl` (for bucket ownership verification) in the bucket policy. The service principal operates independently of any IAM role in the source or destination account, and the bucket policy must include a condition like `aws:SourceArn` or `aws:SourceAccount` to prevent confused deputy attacks. This is defined in the AWS CloudTrail documentation for cross-account log delivery.
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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
Quick reference
AWS S3 Storage Class Comparison
Storage Class
Min Duration
Retrieval
Use Case
S3 Standard
None
Immediate
Frequently accessed data
S3 Standard-IA
30 days
Immediate
Infrequent access, rapid retrieval
S3 One Zone-IA
30 days
Immediate
Non-critical infrequent data
S3 Intelligent-Tiering
None
Immediate–hours
Unknown or changing access patterns
S3 Glacier Instant
90 days
Milliseconds
Archive with instant retrieval
S3 Glacier Flexible
90 days
Minutes–hours
Archive, flexible retrieval
S3 Glacier Deep Archive
180 days
Hours
Long-term compliance archive
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.
Design Solutions for Organizational Complexity — This question tests Design Solutions for Organizational Complexity — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The bucket policy must grant s3:PutObject to the CloudTrail service principal, not to a role. — CloudTrail delivers logs to S3 buckets by assuming a service-linked role, but the bucket policy must explicitly grant the `s3:PutObject` permission to the CloudTrail service principal (`cloudtrail.amazonaws.com`) rather than to an IAM role in the target account. This is because CloudTrail uses its own service principal to write logs, not a cross-account IAM role. Without this permission, the CloudTrail delivery will fail with an access denied error.
What should I do if I get this SAP-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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