Limiting Server Access to Authorized S3 Buckets using Role-Based Access Control
Question
A manufacturing firm is storing all project documents in various S3 buckets.
Application servers deployed within a VPC need to access these S3 buckets to fetch the latest files.
To limit servers with Internet access, the client has created Amazon S3 endpoint to have secure access to the S3 bucket.
The client needs to further enhance security by having control over individual Servers accessing only authorized S3 buckets (using role-based access on a bucket policy) and should be denied from accessing all other S3 buckets.
Which of the following can be used to meet this requirement?
Answers
Explanations
Click on the arrows to vote for the correct answer
A. B. C. D.Correct Answer - A.
A VPC endpoint policy is an IAM resource policy that you attach to an endpoint when creating or modifying the endpoint.
If you do not attach a policy when you create an endpoint, we attach a default policy for you that allows full access to the service.
If a service does not support endpoint policies, the endpoint allows full access to the service.
An endpoint policy does not override or replace IAM user policies or service-specific policies (such as S3 bucket policies)
It is a separate policy for controlling access from the endpoint to the specified service.
Option A is correct as the VPC endpoint policy can be used to limit all resources in a subnet to access a particular S3 bucket alone.
Refer link: https://docs.aws.amazon.com/vpc/latest/userguide/vpc-endpoints-access.html#vpc-endpoint-policies and https://docs.aws.amazon.com/vpc/latest/userguide/vpc-endpoints-s3.html#vpc-endpoints-policies-s3
Option B is incorrect as For Gateway VPC endpoint, S3 bucket policy cannot be configured for VPC endpoint, as a source IP address can be the same.
Option C is incorrect because access to specific S3 buckets cannot be handled by an "outbound security group rule."
Option D is incorrect as for Gateway VPC endpoint, the S3 prefix list cannot be specified with NACL.
For more information on controlling access to Gateway Endpoints, refer to the following URL.
https://docs.aws.amazon.com/vpc/latest/userguide/vpce-gateway.html![Using endpoint policies for Amazon $3
‘The following are example endpoint policies for accessing Amazon $3. For more information, see Using VPC endpoint policies. It is up to the user
‘to determine the policy restrictions that meet the business needs. For example, you can specify the Region ("packages.us-west-
‘Lamazonaws.com) to avoid an ambiguous $3 bucket name.
A Important
All types of policies — 1AM user policies, endpoint policies, $3 bucket policies, and Amazon $3 ACL policies (if any) — must grant the
necessary permissions for access to Amazon $3 to succeed.
Example: Restricting access to a specific bucket
You can create a policy that restricts access to specific $3 buckets only. This is useful if you have other AWS services in your VPC that use $3
buckets. The following is an example of a policy that restricts access to my_secure_bucket only.
{
statement": [
{
"sid": “Access-to-specific-bucket-only",
"principal": "*",
action’
ay_secure_bucket™,
‘my_secure_bucket/*"]](https://eaeastus2.blob.core.windows.net/optimizedimages/static/images/AWS-Certified-Advanced-Networking-Specialty/answer/imgckeditor_32602.png)
The requirement is to control access to specific S3 buckets from individual servers using role-based access on a bucket policy while denying access to all other S3 buckets. To achieve this, we need to ensure that only authorized servers can access the specified S3 buckets and all other servers are denied access.
A. Create a VPC endpoint policy that restricts access to specific S3 buckets only.
A VPC endpoint policy can be used to control access to S3 buckets through a VPC endpoint. However, this policy only applies to the VPC endpoint, and not to individual servers within the VPC. This means that all servers within the VPC that use the VPC endpoint will have access to the specified S3 buckets, and we cannot use role-based access on a bucket policy to further restrict access.
B. Create an S3 bucket policy with aws:SourceIp condition matching instance IP address to control access from each server to S3 bucket.
This option involves creating an S3 bucket policy that allows access to the specified S3 buckets only from specific IP addresses, i.e., the IP addresses of the individual servers that are authorized to access the S3 buckets. This can be achieved using the aws:SourceIp condition in the bucket policy. The IP addresses of the servers can be obtained from the VPC's subnet or instance metadata. This solution provides the required control over individual servers accessing authorized S3 buckets and denying access to all other S3 buckets.
C. Create an outbound security group rule which specifies a prefix list for the S3 bucket from each server.
This option involves creating an outbound security group rule that allows traffic to the specified S3 buckets only from servers with the required prefix list. However, this solution does not provide the required role-based access control to individual servers accessing authorized S3 buckets.
D. Create an outbound NACL that specifies a prefix list for the S3 bucket from each server.
This option involves creating an outbound NACL rule that allows traffic to the specified S3 buckets only from servers with the required prefix list. However, like the previous option, this solution does not provide the required role-based access control to individual servers accessing authorized S3 buckets.
Therefore, the correct answer is B. Create an S3 bucket policy with aws:SourceIp condition matching instance IP address to control access from each server to S3 bucket.
