Most Secure Methods for Granting Partner Account Access to Your S3 Bucket

Answer: A, C, and D.

Option A is CORRECT because a cross-account assume role has to be created for the requesting AWS account to access the services in your account.

Option B is incorrect because IAM roles are assumed and not IAM users to allow cross-account service access.

Option C is CORRECT because a cross-account assume role requires an external ID to be provided for the requesting AWS account to access the services in your account.

Option D is CORRECT because a cross-account assume role requires an ARN to be provided for the requesting AWS account to access the services in your account.

Option E is incorrect because the account ID is already available through ARN shared with the cross-account who wants to make a request.

Option F is incorrect because access keys are not required to assume a role for the requesting AWS account.

For more information on cross-account S3 access, refer to the URLs provided below:

When granting access to resources in your AWS account to a partner account, it is important to ensure that the access is secure and restricted to only what is necessary. Here are the most secure ways to allow the partner account to access your S3 bucket:

A. Ensure an IAM role is created which can be assumed by the partner account: You can create an IAM role in your account that allows the partner account to assume the role. You can then grant the necessary permissions to the role to access the S3 bucket. This approach is secure because it allows the partner account to access the resources using their own IAM credentials without exposing your AWS account access keys. Additionally, you can set permissions for the IAM role to restrict access to only the resources that the partner account requires.

C. Ensure the partner uses an external ID when making the request: When the partner account assumes the IAM role created in your account, they can specify an external ID. This external ID is then included in the API call to assume the role, and you can use it to further restrict access to the resources. This approach is secure because it helps prevent unauthorized access to the resources by ensuring that the request is coming from a trusted partner account.

D. Provide the ARN for the role to the partner account: When granting access to an IAM role, it is important to ensure that the role is uniquely identified. You can provide the Amazon Resource Name (ARN) for the IAM role to the partner account. The partner account can then use this ARN to assume the role and access the S3 bucket. This approach is secure because it ensures that the partner account is accessing the correct resources and is not inadvertently granted access to other resources in your AWS account.

It is important to note that options B, E, and F are not secure ways to allow the partner account to access the S3 bucket. Option B requires creating an IAM user which would need to be shared with the partner account, and this would not be secure because it exposes your AWS account access keys. Option E requires sharing your AWS account ID with the partner account, which is not secure because it could be used to gain unauthorized access to your AWS resources. Option F requires sharing your AWS account access keys with the partner account, which is not secure because it could be used to gain unauthorized access to your AWS resources.