Table of Contents
How are S3 bucket policies evaluated?
Amazon S3 evaluates all the relevant access policies, user policies, and resource-based policies (bucket policy, bucket ACL, object ACL) in deciding whether to authorize the request. In each step, Amazon S3 evaluates a subset of policies in a specific context, based on the context authority.
How does AWS IAM evaluate a policy?
When an IAM entity (user or role) requests access to a resource within the same account, AWS evaluates all the permissions granted by the identity-based and resource-based policies. If an action is allowed by an identity-based policy, a resource-based policy, or both, then AWS allows the action.
How does an Amazon S3 bucket policy differ from and IAM identity policy?
IAM policies vs. In other words, IAM policies define what a principal can do in your AWS environment. S3 bucket policies specify what actions are allowed or denied for which principals on the bucket that the bucket policy is attached to (e.g. allow user Alice to PUT but not DELETE objects in the bucket).
Does S3 bucket policy override IAM policy?
Yes it can indeed override the policy, but only where it uses a Deny. If it includes an Allow but the IAM policy includes a Deny this will not evaluate as Allow.
How do I authenticate a S3 bucket?
The Amazon S3 REST API uses a custom HTTP scheme based on a keyed-HMAC (Hash Message Authentication Code) for authentication. To authenticate a request, you first concatenate selected elements of the request to form a string. You then use your AWS secret access key to calculate the HMAC of that string.
How do you test IAM policies?
You can access the IAM Policy Simulator Console at: https://policysim.aws.amazon.com/
- Test policies that are attached to IAM users, user groups, or roles in your AWS account.
- Test and troubleshoot the effect of permissions boundaries on IAM entities.
Which of the following can be found in an IAM policy?
IAM Policy Examples In this policy, there are four major JSON elements: Version, Effect, Action, and Resource. The Version element defines the version of the policy language.
What is the difference between bucket policy and ACL?
Bucket ACLs allow you to control access at a bucket level, while Object ACLs allow you to control access at the object level. For example, you could use S3 object ACLs if you need to manage permissions on individual objects within a bucket.
Is AWS Arns case sensitive?
Role names are case sensitive when you assume a role. When you assume a role using AWS STS API or AWS CLI, make sure to use the exact name of your role in the ARN. Role names are case sensitive when you assume a role.
What is the difference between S3 bucket policy and IAM policy?
The IAM user’s policy and the role’s user policy grant access to “s3:*”. The S3 bucket policy restricts access to only the role. Both the IAM user and the role can access buckets in the account. The role is able to access both buckets, but the user can access only the bucket without the bucket policy attached to it.
How do I restrict access to a specific AWS S3 bucket?
S3 bucket policies are usually used for cross-account access, but you can also use them to restrict access through an explicit Deny, which would be applied to all principals, whether they were in the same account as the bucket or within a different account. Each IAM entity (user or role) has a defined aws:userid variable.
What is AWS Identity and access management (IAM) user policy?
Short Description. You can use AWS Identity and Access Management (IAM) user policies to control who has access to specific folders in your Amazon Simple Storage Service (Amazon S3) buckets.
What should I look for in Arns for AWS resources?
Be aware that the ARNs for some resources omit the Region, the account ID, or both the Region and the account ID. The partition in which the resource is located. A partition is a group of AWS Regions. Each AWS account is scoped to one partition. The service namespace that identifies the AWS product. For example, s3 for Amazon S3.