SOA-C02 Practice Question: S3 bucket policy for cross-account read access…
Account A owns an S3 bucket containing shared artifacts. Account B needs to read objects from the bucket. The Account A team wants to grant access without creating IAM users, sharing access keys, or creating a role in Account A that Account B assumes. How should the bucket be configured to allow Account B's IAM roles to read objects?
⚠ Common exam trap
The SOA-C02 exam often tests the misconception that a bucket policy with a cross-account Principal automatically grants access to all IAM roles in that account, but candidates forget that the roles must also have an explicit allow in their identity policies for the action to succeed.
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
✓
Add an S3 bucket policy on Account A's bucket with Principal set to Account B's account ID and s3:GetObject permission; ensure Account B's roles have s3:GetObject in their identity policies
It uses an S3 bucket policy with a Principal set to Account B's account ID, which grants cross-account access to all IAM principals (users and roles) in Account B. Account B's IAM roles must also have an identity policy that allows s3:GetObject, ensuring that the effective permissions require both the bucket policy and the role's policy to allow the action. This approach avoids creating IAM users, sharing access keys, or setting up a role in Account A for Account B to assume.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Add an S3 bucket policy on Account A's bucket with Principal set to Account B's account ID and s3:GetObject permission; ensure Account B's roles have s3:GetObject in their identity policies
Why this is correct
Cross-account S3 access requires both a resource-based policy (bucket policy) that grants Account B access, and identity-based policies in Account B that allow the action. The bucket policy's Principal field specifies Account B's account root ARN or specific role ARNs. When both sides allow, the call succeeds without any role chaining or credential sharing.
- ✗
Create an IAM role in Account A with s3:GetObject permission and a trust policy allowing Account B's roles to assume it
Why it's wrong here
This approach works (role chaining) but requires Account B's services to call sts:AssumeRole before each S3 operation, adding latency and complexity. The question asks for access without requiring Account B to assume a role in Account A.
- ✗
Generate a presigned URL for each object in Account A and share the URLs with Account B's services
Why it's wrong here
Presigned URLs expire and must be regenerated regularly. They are appropriate for temporary, unauthenticated object access (e.g., browser downloads) but are not suitable for an ongoing programmatic access pattern where Account B's services read many objects on demand.
- ✗
Enable S3 Access Points on the bucket and create an access point that allows Account B's VPC to connect via PrivateLink
Why it's wrong here
S3 Access Points simplify access management for large shared datasets and can restrict access to specific VPCs. However, cross-account access through an access point still requires a bucket policy delegation to the access point and a VPC endpoint setup — more configuration than a direct bucket policy grant, and PrivateLink is not strictly required for cross-account S3 access.
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 |
Go deeper
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This SOA-C02 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 SOA-C02 exam.