Can we define object level ACL having group in which I can club users from other AWS account. Idea is having a group to which I can add or remove users. I know ACL are maintained at object level and for every new grantee I have to add it in ACL. But having a group assigned to ACL and then modifying that group will be way easier approach. I know it supports predefined groups like authenticated user . Is there a way to create other predefined groups based on application need?
Don't use ACLs, they're a legacy access control mechanism and they're going to bite you.
According to the docs (emphasis mine):
Access control lists (ACLs) are one of the resource-based access
policy options (see Overview of managing access) that you can use to
manage access to your buckets and objects. You can use ACLs to grant
basic read/write permissions to other AWS accounts. There are limits
to managing permissions using ACLs.
For example, you can grant permissions only to other AWS accounts; you
cannot grant permissions to users in your account. You cannot grant
conditional permissions, nor can you explicitly deny permissions. ACLs
are suitable for specific scenarios. For example, if a bucket owner
allows other AWS accounts to upload objects, permissions to these
objects can only be managed using object ACL by the AWS account that
owns the object.
As you can see from the limitations, it doesn't seem suitable for your use case.
There is a better solution for resource-based access policies and it's called bucket policies. They allow you to grant access to prefixes in the bucket based on IAM principals such as users and roles or AWS services, even from other AWS accounts. (note, that IAM groups don't work).
I suggest you review the Access Policy Guidelines before making your decision.
Related
I have two IAM roles in AWS; A and B. In role A I have an explicit deny to prevent certain permissions from being performed in Elastic Map Reduce(EMR). How can I prevent a scenario where Role B could be updated to have an allow on the permissions that were denied in Role A?
I am not very familiar with our IAM federation but my understanding is that users access a federated portal URL and are presented with an initial role that they can select from a radial button based on the AD groups that they are in. From there users can change role/assume role if permissions are setup properly. Currently we have ~150 roles that I would need to ensure do not have the ability to circumvent the explicit deny in Role A.
If possible, it is always better to avoid Deny policies because they often do not work the way people expect. AWS has "deny by default" behaviour, so it is better to control access by limiting Allow permissions.
Unfortunately, many organisations use "Grant All" permissions, such as granting s3:* permissions and giving people Admin permissions. These examples grant too many permissions, which might then need a Deny to override.
Some services (eg Amazon S3, Amazon SQS) also have the ability to apply service-specific policies (eg S3 Bucket Policies) that can grant permissions in addition to IAM.
A good place to start is to strongly limit who has iam: permissions. Only admins should have the ability to use IAM (and that should only be granted via an IAM Role that the admins need to Assume). By controlling such access, it will avoid your scenario where you are worried that an IAM Role could be modified to permit unwanted access.
For worst-case situations where it is vital that access to certain resources are strictly controlled (eg S3 buckets with HR information), a common practice is to create a separate AWS Account and grant limited cross-account access. This way, access will not be granted via generic Admin policies.
For using s3 bucket which IAM policy need to be created AdministratorAccess or AmazonS3FullAccess or both together?
You can use amazons3full access but I would suggest you to create a custom Iam policy which gives access to just that particular bucket .
Refer: https://aws.amazon.com/blogs/security/writing-iam-policies-how-to-grant-access-to-an-amazon-s3-bucket/
If you are the only person using the AWS Account, then Administrator permissions are fine.
If, however, multiple people are using the account, then you should consider how to manage security of the AWS Account and the resources within the account.
Only grant Admin permissions to people who are responsible for all systems. It has "All Access" (including Amazon S3), so it can be quite dangerous.
Similarly, granting AmazonS3FullAccess is not necessarily a wise move. It allows the recipient all access to S3, including the ability to delete buckets and objects.
Preferably, only allocate the permissions that each user actually needs to perform their job.
I find myself using a lot roles/storage.legacyBucketWriter which has the following permissions:
storage.buckets.get
storage.objects.create
storage.objects.delete
storage.objects.list
May be it's okay but it feels odd to me to be using a role with legacy in its name ...
I don't want to create a custom role either because it seems overkill since there is this role fitting the need.
And yes there is a role roles/storage.objectAdmin but it lacks the storage.buckets.get permission.
What do you think ?
Remember legacy roles are related to primitive roles on GCP, It is 'Legacy' because it exactly matches the pre-IAM permissions granted via the legacy role on an Object. It all depends on your use case, the best recommended practice is to follow the principle of least privilege.
Keep in mind as is mentioned at the official documentation:
Legacy Bucket IAM roles work in tandem with bucket ACLs: when you add
or remove a Legacy Bucket role, the ACLs associated with the bucket
reflect your changes.
Also, consider the scope of the read/write legacy roles as is described on this table.
Finally take a look at the section of Security, ACLs, and access control for follow the best practices recommended for Cloud Storage service.
Consider using the Storage Admin Role (roles/storage.admin) instead of a legacy role. This role grants both storage.buckets.* and storage.objects.* permissions, making it a suitable match for your requirements.
According to the Storage Admin Role description, this role
grants full control over buckets and objects. When applied to an individual bucket, control is limited to that specific bucket and its associated objects.
This role is particularly useful when utilizing the gsutil rsync command targeting a bucket.
I read https://aws.amazon.com/blogs/security/iam-policies-and-bucket-policies-and-acls-oh-my-controlling-access-to-s3-resources/, which to me answered the what and when, but not why.
I’m new to AWS and trying to learning it.
Why create two methods, and not just one? Based on the example in the article, why not just have IAM policy to handle both use cases, example like having IAM policy JSON include the ‘Principal’ entry as “base on association” or “??”, then it work like the Bucket policy. It look like for any services which require policy control will have another type of policy created. Example; YYY service policy will have a Principal and Action “YYY:”.
Reason I can think of is, S3 is where require lot of access control (like fine grain, grouping, etc..) and having a policy created specific S3 can ease management, and take less back-end resources?
S3 authorizes requests by testing all applicable authorities, in the "context" of user, bucket, and object.
See How Amazon S3 Authorizes a Request.
This document is confusing on first read, but it does give a better sense of what's happening with the multiple policies.
A few points to keep in mind:
Users do not own buckets. Accounts own buckets, and accounts own users.
If a user creates a bucket, the account that owns that user always owns that bucket.
If a user creates an object, the account that owns that user always owns that object -- even if the bucket where the object was created is owned by a different account.
Wait, what?
If my account gives your user permission to create an object in my bucket, you would actually own the object. Unless you give me permission to read it, I can't read it. Since it's in my bucket, and I am paying to store it, I can delete it, but that's absolutely all I can do to that object unless you give me access to it.
So there are three levels of permissions at play -- things users are allowed to do (IAM policies), things accounts allow to be done to their bucket and their objects in that bucket (bucket policies and ACLs) and things accounts allow to be done to objects they own (object ACLs).
The default action is implicit deny, but anything my account has the authority to allow can be allowed by allowing it in any one place, as long as it isn't explicitly denied, elsewhere. Explicit deny will always deny, without exception.
Implications of the model:
my user, my bucket, my object requires only one grant; access can be granted in any of the three places and only needs to be granted in one place, because my account owns all the resources... so I can do this in IAM policy, or bucket policy, or on the object.
my user, your bucket requires two grants -- I allow my user in IAM policy, and you must allow my user in yout bucket policy. I don't have authority to do things to your bucket without your consent, and you don't have authority to allow my user to do things without my consent.
it is possible to make my object in my bucket publicly readable via either the object ACL or via bucket policy, but not IAM policy, because IAM policies apply to users, and "everybody" is not one of my IAM users.
So, S3 needs multiple sources of grants becase of the permissions model. If you aren't doing anything cross-account, some of this would not be obvious since you would be unaware of some of the possible combinations.
My preference is for my bucket policies to require little attention. Users are given access in IAM, public objects are made public at the object level (you can do this in bucket policy, but I prefer it to be explicit at the object level), and so bucket policies have limited purpose -- sometimes there are bucket policy rules that deny access for all IP addresses except a list, usually the bucket policy denies uploads without AES-256 (so you can't "forget" to encrypt objects), and sometimes there are origin access identity rules for interoperating with CloudFront... but I do very little customization of bucket policies, because that's my design philosophy.
There are various reasons why there is IAM permission policy and resource-based policy such as S3 bucket policy.
Let's say you have a S3 bucket and you want to grant access to other account. It is not possible only using IAM policy. Hence you need the bucket policy to include the account or IAM entity as Principal.
Also, you cannot use Principal in the IAM permission policy since when you attach the policy to an IAM user, when the user makes request, it becomes the Principal.
Please have a look into the following for more details:
http://docs.aws.amazon.com/IAM/latest/UserGuide/reference_policies_elements.html#Principal
http://docs.aws.amazon.com/AmazonS3/latest/dev/access-control-overview.html
The AWS official site reads role as a collection of permissions and group as a collection of users. But still they look the same to me. You attach policies to groups or roles, and then assign groups or roles to a user. What exactly are the differences between role and group?
Short answer for googlers: you can't assign role to user.
group is a bunch of users with the same policies
role is a preset of policies for service(s)
Users can asume roles according to AWS docs:
Assuming a Role
AWS Groups are the standard groups which you can consider as collection of several users and a user can belong to multiple groups.
AWS IAM Roles are all together different species; they operate like individual users except that they work mostly towards the impersonation style and perform communication with AWS API calls without specifying the credentials.
Given that IAM Roles are little different, I am emphasizing only that. There are several types of IAM Roles like EC2 IAM Roles, Lambda etc. If you consider, you can launch an EC2 instance with an EC2 IAM Role; hence forth any AWS API related communication wouldn't require any AWS Access Key or Secret key for authentication rather can call the APIs directly (however the long answer is - it uses STS and continuously recycles the credentials behind the scenes); the privileges or permissions of what it can do is determined by the IAM Policies attached to the IAM Role.
Lambda IAM Role works exactly the same, except that only Lambda function can use the Lambda IAM Role etc.
Users: End User (Think People).
Groups: A collection of users under one set of permissions (permission as policy). As per IAM standards we create groups with permissions and then assign user to that group.
Role: you create roles and assign them to AWS resource (AWS resource example can be a customer, supplier, contractor, employee, an EC2 instance, some external application outside AWS) but remember you can't assign role to user.
It’s not only users who will login, sometimes applications need access to AWS resources. For example, an EC2 instance might need to access one or more S3 buckets. Then, an IAM role needs to be created and attached to the EC2 instance. That role can be re-used by different EC2 instances.
Remember : Groups are for living. Roles are for non-living.
I think of an AWS Role as a kind of 'sudo', where each AWS Role can temporarily provide a very specific set of elevated privileges, but without needing the elevated credentials. I get the impression that like sudo, AWS Roles try to prevent privileged actions being used accidentally.
I'd be interested to hear if others agree with this analogy.
Please note that Groups are specific to local IAM users, which are not federated, and local IAM user logs do not show who has done the actions (i.e.., multiple people or applications could use the same long-term secret/access keys, and there is no record of which entity used them). If you must use local IAM users, you can place them into IAM Groups. Where this can be especially useful is to serve as a boundary -- you could place a deny policy on the group, restricting access to specific services or actions, and that deny policy will be applied to all users in the Group.
Conversely, roles can be federated, whereas local IAM users are not. You might create an on-premises AD group that serves as a member container, for example, and then the members of that AD group (and only they) can use the role that the AD group correlates to, with whatever allow or deny policies and/or permissions boundaries you've applied to the role. (Here is a link explaining the AWS ADFS federation.)
Importantly, roles allow for temporary session credentials (which is a best security practice), as their session tokens expire after a maximum of 12 hours. Equally importantly, roles do show in the logs which of the AD members with access to use the role actually did the action. You'll find this tacked to the end of the role ARN in the logs (e.g., a user ID). CloudTrail would be one of several services that indicate user activity. This is important from a logging standpoint.
Understanding IAM roles vs IAM groups (IAM indentities) is very important foundational concept . Its important to look at difference between IAM role and IAM user as essentially group is just a bunch of users performing similar functions (eg. group of developers, QA's etc.) Roles are not uniquely associated with one person (user), they can be assumed by user,resource or service who needs it to perform task at that point of time (session). Roles do not provide long-term credentials like password or access keys.
Best practice recommendation is to require workloads to use temporary credentials with IAM roles to access AWS
Please refer to link below for more clarity:
https://docs.aws.amazon.com/IAM/latest/UserGuide/id.html
I was confused all the time about the difference between these two functions.
In short,
Role is like a tag with all the preset policies that can attach on IAM users/groups or AWS services. IAM users share the same account with the account root user (Admin) but with assigned permissions by the root user to use AWS resources within that account.
Therefore, IAM users can directly interact with AWS services; whereas IAM roles cannot make direct requests to AWS services, they are meant to be assumed by authorised entities like an IAM user or an instance. https://aws.amazon.com/iam/faqs/
I had a hard time deciphering the spirit of the given answers..
Here's what I've found:
Groups:
Intended to represent human users created within IAM who need identical policies.
Ex. Dev 1 - Dev 8 are all developers, and all need access to create dev servers.
This is similar to traditional desktop users/groups, but for HUMAN users only.
Roles:
Roles rotate automatic credentials, meaning password input isn't needed for accessing policies.
This makes it good for two things:
Giving permissions to non-humans, such as services / applications.
Ex. EC2 of type A needs access to S3 of type B.
Giving permissions to federated / outside users & groups.
Ex. Contractor A # Outside Company A needs access to your Server A.
Authentication of users & groups are handled by some service, like Azure AD.
Authorizations are then mapped to your IAM role(s), NOT users or groups.
Note: I've used Jumpcloud's Article & AWS's Documentation to gather this information. The terms "Group", "Role", and "User" become overloaded in context to SSO+IdP, and IAM.
Here's an image showing how they map roles. !Need 10 Reputation :(
Aside: There is a way of assigning Roles to normal IAM Users & Groups, but it appears to be bad practice.
Hopefully this provides clarity to the answers above.
Only one IAM Role can be assumed at a time! And there are several
situations which fits exactly this kind of permission.
Read the faq about: How many IAM roles can I assume?
The underlaying tool in use is "Permission" in both of the use cases namely: Group and IAM Role.
Group or IAM Role --> Has Policy --> Policy defines permisions --> Permissions are assigned to a Group or IAM Role.