As per my understanding with out giving access, any IAM user can not access the S3 bucket/object. But in my use case I am able to access it.
Am I misunderstood the security policy in S3.
Here is my use case I have root account in AWS, say root user. And this user created two IAM users,say Admin and Test users. And root user given S3FullAccess permission to both IAM users.
Now I logged in as Admin and created one Bucket( say Test). And enabled "Block all public access ".
Now with another IAM user still I am able to access Test bucket, even though " Block all public access " enabled.
Ideally it should not right. The Test user should get access denied permission while accessing Test bucket.
Am I missing anything, any help would be highly appreciated
Thanks
AWS learner
The "block all public access" to the bucket is referring to outside your organization, not with the IAM users.
In other words, if your bucket is accessible to the public, then anyone who has access to the objects S3 URL can directly access that object.
You may restrict access to the bucket by using a bucket policy, but it would make more sense to remove the S3FullAdminAccess from the test user in IAM.
And root user given S3FullAccess permission to both IAM users
This is the reason why your both the users are able to see the bucket as they have the below policy attached with the user :
{
"Version": "2012-10-17",
"Statement": [
{
"Effect": "Allow",
"Action": "s3:*",
"Resource": "*"
}
]
}
You remove this policy from the user and you'll see below error :
Related
Scenario:
I have 3 AWS root accounts in the same organization.
admin#mydomain.com
user1#mydomain.com
user2#mydomain.com
user1 created an S3 bucket B1. I want user2 and admin to be able to see and browse B1 on their own S3 dashboard. Is this possible? What policy(policies) that I need to create? Where do I create these policies and how to create them?
**The original question has been edited. Some answers below might not be relevant any more
I believe all you need to do is add Principal: "*" to the policy. This opens access to anyone, but the condition will limit it to the org.
As far as I know, I cannot do the S3 bucket console sharing between root users. I've finally managed to share the bucket created by user1 with an IAM user.
Steps for Root User
Login into AWS console and go to IAM
Create group
Create IAM policy i.e. allowing S3 full access (see below)
Attach policy to group
Create IAM user
For Access type choose AWS Management Console access
Add user to the group you created in step 1
Follow through until you click on create user button
IAM Policy
{
"Version": "2012-10-17",
"Statement": [
{
"Effect": "Allow",
"Action": "s3:*",
"Resource": "*",
"Condition": {
"StringEquals": {
"aws:PrincipalOrgID": "o-xxxvvvwww8"
}
}
}
]
}
EDIT:
After rigorous trial & error testing, it seems that we don't even need bucket policy for this to work. I've removed the bucket policy and it all still works!
Steps for IAM User
Log into AWS console as IAM user
Go to S3 console. You should be able to see and browse all buckets and objects created by all organization members
Note
Your IAM user would not be able to see the bucket listed on its S3 console dashboard. That shared bucket can only be accessed through direct link. So your root user must provide the URL i.e. https://s3.console.aws.amazon.com/s3/buckets/bucket1/ to your IAM user
Is it possible to disable AWS S3 management console for the security reasons?
We don't want anyone including root/admin users to access customer files directly from the AWS S3. We should just have programmatic access to the files stored in S3.
If this is not possible, is it possible to stop listing the directories inside the bucket for all users ?
This is a tricky one to implement, however the following should be able to fulfill the requirements.
Programmatic Access Only
You need to define exactly which actions should be denied you would not want to block access completely otherwise you might lose the ability to do anything.
If you're in AWS you should use IAM roles, and a VPC endpoint to connect to the S3 service. Both of these support the ability to control access within your S3 buckets Bucket Policy.
You would use this to deny List* actions where the source is not the VPC endpoint. You could also deny where its not a specific subset of roles.
This works for all programmatic use cases and for people who login as an IAM user from the console, however this does not deny access to the root user.
Also bear in mind for any IAM user/IAM role that they do not have access unless you explicitly give it to them via an IAM policy.
Denying Access To The Root User
There is currently only one way to deny access to the root user of an AWS account (although you should share these credentials with anyone, even within your company) as that is using a Service Control Policy.
To do this the account would need to be part of an AWS organisation (as an organisational unit). If/once it is you would create a SCP that denies access to the root principal for the specific actions that you want.
An example of this policy for you would be
{
"Version": "2012-10-17",
"Statement": [
{
"Sid": "RestrictS3ForRoot",
"Effect": "Deny",
"Action": [
"s3:List*"
],
"Resource": [
"*"
],
"Condition": {
"StringLike": {
"aws:PrincipalArn": [
"arn:aws:iam::*:root"
]
}
}
}
]
}
Yes, it is possible to disable the Management Console: Don't give users a password.
When creating IAM Users, there are two ways to provide credentials:
Sign-in Credentials (for the Console)
Access Key (for API calls)
Only give users an Access Key and they won't be able to login to the console.
However, please note that when when using the Management Console, users have exactly the same permissions as using an Access Key. Thus, if they can do it in the console, then they can do it via an API call (if they have an Access Key).
If your goal is to prevent anyone from accessing customer files, then you can add a Bucket Policy with a Deny on s3:* for the bucket, where the Principal is not the customer.
Please note, however, that the Root login can remove such a policy.
If the customers really want to keep their own data private, then they would need to create their own AWS account and keep their files within it, without granting you access.
I'm developing a mobile application & i want to upload/get/delete a file in AWS S3 bucket.
But I'm very concern about the security problem.
S3 Bucket: It should not be public and only authorize IAM user can access who have the permission to access my bucket.
So, need help to configure permission of my S3 bucket & create an IAM user.
That is not how you authorize access for mobile applications. Yes, you can create IAM user, generate access key and secret access key, store those keys in the application code and configure right permissions for the IAM user. Then you don't even need to configure bucket policy. By default, bucket is private and only IAM users in your account with appropriate permissions are able to access it. If you allow IAM user to access specific S3 bucket then you would need to configure explicit deny on bucket policy to override it.
But the above approach is against every security good practice. What you really want to do is to create IAM role that allows access to the bucket and assume that role from within the application. You can set up Cognito + web federation (or some other web federation provider) for your users and ask STS service to generate short lived credentials using sts:assumeRoleWithWebIdentity command.
As for the IAM permissions, you will need to allow s3:PutObject, s3:GetObject and s3:DeleteObject so the policy can look something like this.
{
"Version": "2012-10-17",
"Statement": [
{
"Sid": "VisualEditor0",
"Effect": "Allow",
"Action": [
"s3:PutObject",
"s3:GetObject",
"s3:DeleteObject"
],
"Resource": "<arn-of-your-bucket>"
}
]
}
You can be even more granular and allow Cognito users to access only "their" folder inside of a bucket if you need to.
As for the role, you just need to attach the above policy to it and configure trust relationship between the role and web identity provider (as mentioned above, this can be Cognito or any OpenID provider).
While writing S3 server implementation, ran into question I can't really find answer anywhere.
For example I'm the bucket owner, and as well owner of uploaded object.
In case I revoke "full_control" permission from object owner (myself), will I be able to access and modify that object?
What's the expected behaviour in following example:
s3cmd setacl --acl-grant full_control:ownerID s3://bucket/object
s3cmd setacl --acl-revoke full_control:ownerID s3://bucket/object
s3cmd setacl --acl-grant read:ownerID s3://bucket/object
Thanks
So there's the official answer from AWS support:
The short answer for that question would be yes, the bucket/object
owner has permission to read and update the bucket/object ACL,
provided that there is no bucket policy attached that explicitly
removes these permissions from the owner. For example, the following
policy would prevent the owner from doing anything on the bucket,
including changing the bucket's ACL:
{
"Id": "Policy1531126735810",
"Version": "2012-10-17",
"Statement": [
{
"Sid": "Example bucket policy",
"Action": "s3:*",
"Effect": "Deny",
"Resource": "arn:aws:s3:::<bucket>",
"Principal": "*"
}
]
}
However, as root (bucket owner) you'd still have permission to delete
that policy, which would then restore your permissions as bucket owner
to update the ACL.
By default, all S3 resources, buckets, objects and subresources, are
private; only the resource owner, which is the AWS account that
created it, can access the resource[1]. As the resource owner (AWS
account), you can optionally grant permission to other users by
attaching an access policy to the users.
Example: let's say you created an IAM user called -S3User1-, and gave
it permission to create buckets in S3 and update its ACLs. The user in
question then goes ahead and create a bucket and name it
"s3user1-bucket". After that, he goes further and remove List objects,
Write objects, Read bucket permission and Write bucket permissions
from the root account on the ACL section. At this point, if you log in
as root and attempt to read the objects in that bucket, an "Access
Denied" error will be thrown. However, as root you'll be able to go to
the "Permissions" section of the bucket and add these permissions
back.
These days it is recommended to use the official AWS Command-Line Interface (CLI) rather than s3cmd.
You should typically avoid using object-level permissions to control access. It is best to make them all "bucket-owner full control" and then use Bucket Policies to grant access to the bucket or a path.
If you wish to provide per-object access, it is recommended to use Amazon S3 pre-signed URLs, which give time-limited access to a private object. Once the time expires, the URL no longer works. Your application would be responsible for determining whether a user is permitted to access an object, and then generates the pre-signed URL (eg as a link or href on an HTML page).
I've created a s3 server which contain a large number of images. I'm now trying to create a bucket policy, which fits my needs. First of all i want everybody to have read permission, so they can see the images. However i also want to give a specific website the permission to upload and delete images. this website is not stored on a amazon server? how can i achieve this? so far i've created an bucket policy which enables everybody to see the images
{
"Version": "2012-10-17",
"Statement": [
{
"Sid": "AddPerm",
"Effect": "Allow",
"Principal": "*",
"Action": "s3:GetObject",
"Resource": "arn:aws:s3:::examplebucket/*"
}
]
}
You can delegate access to your bucket. To do this, the other server will need AWS credentials.
If the other server were an EC2 instance that you owned then you could do this easily by launching it with an IAM role. If the other server were an EC2 instance that someone else owned, then you could delegate access to them by allowing them to assume an appropriate IAM role in your account. But for a non-EC2 server, as seems to be the case here, you will have to provide AWS credentials in some other fashion.
One way to do this is by adding an IAM user with a policy allowing s3:PutObject and s3:DeleteObject on resource "arn:aws:s3:::examplebucket/*", and then give the other server those credentials.
A better way would be to create an IAM role that has the same policy and then have the other server assume that role. The upside is that the credentials must be rotated periodically so if they are leaked then the window of exposure is smaller. To assume a role, however, the other server will still need to authenticate so will need some base IAM user credentials (unless you have some way to get credentials via identity federation). You could add a base IAM user who has permissions to assume the aforementioned role (but has no other permissions) and supply the base IAM user credentials to the other server. When using AssumeRole in this fashion you should require an external ID. You may also be able to restrict the entity assuming this role to the specific IP address(es) of the other server using a policy condition (not 100% sure if this is possible).
The Bucket Policy will work nicely to give everybody read-only access.
To give specific permissions to an application:
Create an IAM User for the application (this also creates access credentials)
Assign a policy to the IAM User that gives the desired permissions (very similar to a Bucket Policy)
The application then makes API calls to Amazon S3 using the supplied access credentials
See also: Amazon S3 Developer Guide