I understand that in AWS we can control access to AWS S3 bucket as well as to contained folders for each user by using username variable in the bucket IAM policy. I followed this blog:
Writing IAM Policies: Grant Access to User-Specific Folders in an Amazon S3 Buckete
The question is that I do not see how this can be possible also for groups. Because I want to create folders for groups rather than folders for users. According to this IAM Policy Elements: Variables and Tags I understand that there is NO variable group that I can use in the policy.
Any idea? thanks
I don't think this would be possible because an IAM User an be in multiple IAM Groups, so the name of the folder would not be predictable.
Instead, you would need to add a policy to each group that grants access to a specific bucket + path.
Related
I have an IAM user that has full S3 access (i.e. can perform any S3 actions on any S3 resource within the AWS account). This user has created a bucket and put some files in it. The bucket has a policy which just contains an Allow rule that grants access to a different IAM user, in the same AWS account. Public access is turned off for the bucket.
Should the first user be able to access objects in this bucket? If so, is that because they created the bucket, or because they're in the account that owns the bucket? Is it possible to limit access to a bucket for users within the same AWS account?
S3 is one of the few services with resource policies, in this case they are called bucket policies.
A user in the same account has access to a (S3) resource if
nothing explicitly denies the access AND
either the bucket policy grants access OR the user / entity has a policy attached that grants access
If you wanted to restrict a bucket to a single user / entity you would
need to write a bucket policy that specifies that using a Deny statement for every user except the target one AND
either add a statement to the bucket policy or a policy attached to the user / entity granting access to the bucket.
The standard doc for understanding policy evaluation logic is this. There are other, more complicated ways to achieve your goal using e.g. permission boundaries and SCPs but they are probably overkill in your situation.
I'm tasked with creating an IAM policy in AWS which grants a user access to all s3 objects in all s3 buckets within a specific account.
However, because s3 bucket names are globally unique, and there being no region or account element in an s3 ARN, it would appear that there's no way to grant access to all s3 objects in one specific account. I must grant it either to specific buckets, or all buckets in all accounts. Is that true? There must be a work around.
I want something like:
"Resource": "arn:aws:s3::<accountid>:*"
not:
"Resource": "arn:aws:s3:::*"
Anyone see any solution? I did already read this other related discussion
You can add conditions to S3 resource policies, one of them is s3:ResourceAccount which should allow you to use the ARN arn:aws:s3:::* but still restrict access to only buckets in your account.
https://aws.amazon.com/blogs/storage/limit-access-to-amazon-s3-buckets-owned-by-specific-aws-accounts/
Need to create S3 bucket and few objects which are intranet facing. But users may not be having AWS access.
How to restrict S3 access to users of my companies Active Directory.
You need to do two things,
Connective Active Directory to AWS IAM
Create Roles for users to whichever the way you want it to S3
AD to IAM:
https://aws.amazon.com/blogs/security/how-to-connect-your-on-premises-active-directory-to-aws-using-ad-connector/
S3 IAM Role based Access:
https://aws.amazon.com/blogs/security/writing-iam-policies-grant-access-to-user-specific-folders-in-an-amazon-s3-bucket/
Hope it helps.
I have been reading a number of docs and watched number of videos, but I am still very confused about IAM Roles and Bucket policies. Here is what confuses me:
1) I create a bucket. At that time I can make it public or keep it private. If I make it public, then anyone, or any Application, can "see" the objects in the bucket. I think the permissions can be set to add/delete/get/list objects in the bucket. If this is the case, then why do I ever need to add any IAM Role for S3 buckets, or, add any Bucket policy (???)
2) At the time I create a bucket, can I give very specific permissions to only certain users/applications/EC2 instances etc to all or part of the bucket? e.g. App1 on EC2-X can access subfolder A in bucket B1.
3) Coming to IAM Roles, an EC2 role that gives full S3 access- what does it mean? Full access to any bucket? How can I restrict an app running on an EC2 to only certain buckets, with only certain restricted permissions (see #2) above)? Do all Apps on the EC2 have full access to all buckets? At the time of creating a bucket, can the permissions be so set that an IAM Role can be overruled?
4) Finally, what do Bucket Policies do in addition to the above IAM Roles? e.g is 'AllowS3FullAccess' a "Bucket Policy", or an "IAM Policy"? Why differentiate between types of policies- policies are just that- they define some permissions/rules on some objects/resources,as I see it.
Thanks for any clarifications.
- a newcomer to AWS
I think you are confusing permissions for resources with IAM entities.
i) There are resources (S3 bucket, EC2 instances etc.) owned by the AWS account and these resources can be accessed by IAM users, IAM roles or other AWS Services (can be from same or different account)
ii) We manage who can access and their permission level with policies
iii) Policies can be identity based (attached to IAM user/group/role) or resource based (attached to S3 bucket, SNS topic)
iv) Resource based policy will have a Principal element but the identity based policies will not have that (because the attached IAM entity is the Principal)
v) Permissions start from default deny, allow overrides the default deny and an explicit deny overrides any allow
vi) Final access will be determined by combination of all policies
To answer your questions:
1> We cannot add (or attach) an IAM role with an S3 bucket. If you want your bucket should be public (which is not recommended but need to do it till some extent if it's in use for static website), then you can keep it public
2> It is not possible while creating the bucket. You have to do it after creating the bucket via IAM and/or S3 bucket policy
3> If an IAM role has AmazonS3FullAccess, the role can (Effect:Allow) call any S3 API (s3:) for any S3 resource (Resource:) in your account (provided they don't have cross account access).
If multiple applications run on an instance with an IAM role attached and are using credentials provided by the role, their permission will be same.
4> I don't know where you got the reference AllowS3FullAccess but we cannot confirm unless we know the exact JSON. If it is attached to a bucket or has the Principal element, it is a bucket policy.
You can use IAM and Bucket policies based on your need. Usually bucket policies are used for cross account access or if you want to manage S3 permission policies in a single place.
The goal
I have a few users I created from IAM > Users. I want these users, and only these users, to access my files in my s3 bucket.
The problem
I thought I can add these users to a group. After I created a group in IAM > Groups I expect it to show in list of grantee when I'm changing permissions of a file in my bucket.
Problem is, it doesn't. That means somewhere along the way my understanding might be wrong. But then again in official AWS S3 documentation there is no information about this (I can hardly believe!).
Please help.
Currently AWS doesn't support IAM group or role as Principal for S3 buckets. I had the same requirement and from this discussion it is clear there is no support for group ARN or role ARN in bucket policy.
The format and use of the IAM policies was brought over to s3 for the
bucket policies but as you have seen group are not valid within s3
bucket policy. I can also let you know that roles are also not
available within the s3 bucket policies.