I am looking for a bucket policy which allows only the root account user and the bucket creator to delete the bucket. something like below. Please suggest. How to restrict to only bucket creator and root?
{
"Version": "2012-10-17",
"Id": "PutObjBucketPolicy",
"Statement": [
{
"Sid": "Prevent bucket delete",
"Effect": "Allow",
"Principal": {
"AWS": "arn:aws:iam::xxxxxxx:root"
},
"Action": "s3:DeleteBucket",
"Resource": "arn:aws:s3:::test-bucket-s3"
},
{
"Sid": "Prevent bucket delete",
"Effect": "Deny",
"Principal": *,
"Action": "s3:DeleteBucket",
"Resource": "arn:aws:s3:::test-bucket-s3"
}
]
}
A Deny always beats an Allow. Therefore, with this policy, nobody would be allowed to delete the bucket. (I assume, however, that the root user would be able to do so, since it exists outside of IAM.)
There is no need to assign permissions to the root, since it can always do anything.
Also, there is no concept of the "bucket creator". It belongs to the account, not a user.
Therefore:
Remove the Allow section (it does nothing)
Test whether the policy prevents non-root users from deleting it
Test whether the policy still permits the root user to delete it
There are 2 different type of permission in S3.
Resource Based policies
User Policies
So Bucket policies and access control lists (ACLs) are part of Resource Based and which attached to the bucket.
if all users are in same aws account. you can consider user policy which is attached to user or role.
if you are dealing with multiple aws accounts, Bucket policies or ACL is better.
only different is, Bucket policies allows you grant or deny access and apply too all object in the bucket.
ACL is grant basic read or write permission and can't add conditional check.
Related
I am looking for a bucket policy which allows only the root account user and the bucket creator to delete the bucket. something like below. Please suggest. How to restrict to only bucket creator and root?
{
"Version": "2012-10-17",
"Id": "PutObjBucketPolicy",
"Statement": [
{
"Sid": "Prevent bucket delete",
"Effect": "Allow",
"Principal": {
"AWS": "arn:aws:iam::xxxxxxx:root"
},
"Action": "s3:DeleteBucket",
"Resource": "arn:aws:s3:::test-bucket-s3"
},
{
"Sid": "Prevent bucket delete",
"Effect": "Deny",
"Principal": *,
"Action": "s3:DeleteBucket",
"Resource": "arn:aws:s3:::test-bucket-s3"
}
]
}
A Deny always beats an Allow. Therefore, with this policy, nobody would be allowed to delete the bucket. (I assume, however, that the root user would be able to do so, since it exists outside of IAM.)
There is no need to assign permissions to the root, since it can always do anything.
Also, there is no concept of the "bucket creator". It belongs to the account, not a user.
Therefore:
Remove the Allow section (it does nothing)
Test whether the policy prevents non-root users from deleting it
Test whether the policy still permits the root user to delete it
There are 2 different type of permission in S3.
Resource Based policies
User Policies
So Bucket policies and access control lists (ACLs) are part of Resource Based and which attached to the bucket.
if all users are in same aws account. you can consider user policy which is attached to user or role.
if you are dealing with multiple aws accounts, Bucket policies or ACL is better.
only different is, Bucket policies allows you grant or deny access and apply too all object in the bucket.
ACL is grant basic read or write permission and can't add conditional check.
In our environment, all IAM user accounts are assigned a customer-managed policy that grants read-only access to a lot of AWS services. Here's what I want to do:
Migrate a sql server 2012 express database from on-prem to a RDS instance
Limit access to the S3 bucket containing the database files
Here's the requirements according to AWS:
A S3 bucket to store the .bak database file
A role with access to the bucket
SQLSERVER_BACKUP_RESTORE option attached to RDS instance
So far, I've done the following:
Created a bucket under the name "test-bucket" (and uploaded the .bak file here)
Created a role under the name "rds-s3-role"
Created a policy under the name "rds-s3-policy" with these settings:
{
"Version": "2012-10-17",
"Statement": [
{
"Effect": "Allow",
"Action": [
"s3:ListBucket",
"s3:GetBucketLocation"
],
"Resource": "arn:aws:s3:::test-bucket/"
},
{
"Effect": "Allow",
"Action": [
"s3:GetObjectMetaData",
"s3:GetObject",
"s3:PutObject",
"s3:ListMultipartUploadParts",
"s3:AbortMultipartUpload"
],
"Resource": "arn:aws:s3:::test-bucket/*"
}
]
}
Assigned the policy to the role
Gave the AssumeRole permissions to the RDS service to assume the role created above
Created a new option group in RDS with the SQLSERVER_BACKUP_RESTORE option and linked it to my RDS instance
With no restrictions on my S3 bucket, I can perform the restore just fine; however, I can't find a solid way of restricting access to the bucket without hindering the RDS service from doing the restore.
In terms of my attempts to restrict access to the S3 bucket, I found a few posts online recommending using an explicit Deny statement to deny access to all types of principals and grant access based on some conditional statements.
Here's the contents of my bucket policy:
{
"Version": "2012-10-17",
"Id": "Policy1486769843194",
"Statement": [
{
"Sid": "Stmt1486769841856",
"Effect": "Deny",
"Principal": "*",
"Action": "s3:*",
"Resource": [
"arn:aws:s3:::test-bucket",
"arn:aws:s3:::test-bucket/*"
],
"Condition": {
"StringNotLike": {
"aws:userid": [
"<root_id>",
"<user1_userid>",
"<user2_userid>",
"<user3_userid>",
"<role_roleid>:*"
]
}
}
}
]
}
I can confirm the bucket policy does restrict access to only the IAM users that I specified, but I am not sure how it treats IAM roles. I used the :* syntax above per a document I found on the aws forums where the author stated the ":*" is a catch-all for every principal that assumes the specified role.
The only thing I'm having a problem with is, with this bucket policy in place, when I attempt to do the database restore, I get an access denied error. Has anyone ever done something like this? I've been going at it all day and haven't been able to find a working solution.
The following, admittedly, is guesswork... but reading between the lines of the somewhat difficult to navigate IAM documentation and elsewhere, and taking into account the way I originally interpreted it (incorrectly), I suspect that you are using the role's name rather than the role's ID in the policy.
Role IDs look similar to AWSAccessKeyIds except that they begin with AROA....
For the given role, find RoleId in the output from this:
$ aws iam get-role --role-name ROLE-NAME
https://aws.amazon.com/blogs/security/how-to-restrict-amazon-s3-bucket-access-to-a-specific-iam-role/
Use caution when creating a broad Deny policy. You can end up denying s3:PutBucketPolicy to yourself, which leaves you in a situation where your policy prevents you from changing the policy... in which case, your only recourse is presumably to persuade AWS support to remove the bucket policy. A safer configuration would be to use this to deny only the object-level permissions.
I have created the following IAM policy:
{
"Version": "2012-10-17",
"Statement": [
{
"Effect": "Allow",
"Action": "s3:ListAllMyBuckets",
"Resource": "arn:aws:s3:::*"
},
{
"Effect": "Allow",
"Action": "s3:*",
"Resource": [
"arn:aws:s3:::bucketname",
"arn:aws:s3:::bucketname/*"
]
}
]
}
This works in that the only bucket they can access is the correct one, but what I want to do is set it so that the only bucket that shows when going to the bucket list is the one they have access to.
I tried changing the ARN in the listallmybuckets action to the ARN of the bucket itself, but this just gives a "no access" error when going to the bucket list
How do I change this to only list the bucket they have access to in the bucket list?
S3 buckets are owned by a specific canonical user ID that is tied to an AWS
account. When a principal is given s3:ListAllMyBuckets in an IAM policy, they
have access to enumerate all buckets owned by the canonical user ID that
provides their credential's arn (the account number that is the fifth segment
in the arn of the user or role bearing the permission).
This means that for a given account, all principals either have
ListAllMyBuckets for all buckets in the account or none at all.
With AWS Organizations, it's relatively easy to create a dedicated account and
then provide credentials (or cross account access) to a bucket (or set of buckets)
that are isolated from all others; this may simulate the limited listing behavior
the OP is asking for.
For security reasons, we have a pre-prod and a prod AWS account. We're now beginning to use IAM Roles for S3 access to js/css files through django-storage / boto.
While this is working correctly on a per account basis, now a need has risen where the QA instance needs to access one S3 bucket on a the prod account.
Is there a way to have one IAM role that can grant access to the pre-prod And prod S3 buckets? As I'm writing it seems impossible, but it never hearts to ask!
Here's the AWS doc on this: http://docs.aws.amazon.com/AmazonS3/latest/dev/example-walkthroughs-managing-access-example2.html
Essentially, you have to delegate permissions to one account from the other account using the Principal block of your Bucket's IAM policy, and then set up your IAM user in the second account as normal.
Example bucket policy:
{
"Version": "2012-10-17",
"Statement": [
{
"Sid": "Example permissions",
"Effect": "Allow",
"Principal": {
"AWS": "arn:aws:iam::<Account-ID>:root"
},
"Action": [
"s3:GetBucketLocation",
"s3:ListBucket"
],
"Resource": [
"arn:aws:s3:::<bucket-name>"
]
}
]
}
This works well for read-only access, but there can be issues with write access. Primarily, the account writing the object will still be the owner of that object. When dealing with Write permissions, you'll usually want to make sure the account owning the bucket still has the ability to access objects written by the other account, which requires the object to be written with a particular header: x-amz-grant-full-control
You can set up your bucket policy so that the bucket will not accept cross-account objects that do not supply this header. There's an example of that at the bottom of this page: http://docs.aws.amazon.com/AmazonS3/latest/dev/example-bucket-policies.html (under "Granting Cross-Account Permissions to Upload Objects While Ensuring the Bucket Owner Has Full Control")
This makes use of a conditional Deny clause in the bucket policy, like so:
{
"Sid":"112",
"Effect":"Deny",
"Principal":{"AWS":"1111111111" },
"Action":"s3:PutObject",
"Resource":"arn:aws:s3:::examplebucket/*",
"Condition": {
"StringNotEquals": {"s3:x-amz-grant-full-control":["emailAddress=xyz#amazon.com"]}
}
}
I generally avoid cross-account object writes, myself...they are quite fiddly to set up.
We need to create an IAM user that is allowed to access buckets in our client's S3 accounts (provided that they have allowed us access to those buckets as well).
We have created an IAM user in our account with the following inline policy:
{
"Statement": [
{
"Effect": "Allow",
"Action": [
"s3:AbortMultipartUpload",
"s3:PutObjectAcl",
"s3:ListMultipartUploadParts",
"s3:PutObject",
"s3:ListBucketMultipartUploads",
"s3:GetBucketLocation"
],
"Resource": "arn:aws:s3:::*"
}
]
}
In addition to this, we will request that our clients use the following policy and apply it to their relevant bucket:
{
"Version": "2008-10-17",
"Id": "Policy1416999097026",
"Statement": [
{
"Sid": "Stmt1416998971331",
"Effect": "Allow",
"Principal": {
"AWS": "arn:aws:iam::229569340673:user/our-iam-user"
},
"Action": [
"s3:AbortMultipartUpload",
"s3:PutObjectAcl",
"s3:ListMultipartUploadParts",
"s3:PutObject"
],
"Resource": "arn:aws:s3:::client-bucket-name/*"
},
{
"Sid": "Stmt1416999025675",
"Effect": "Allow",
"Principal": {
"AWS": "arn:aws:iam::229569340673:user/our-iam-user"
},
"Action": [
"s3:ListBucketMultipartUploads",
"s3:GetBucketLocation"
],
"Resource": "arn:aws:s3:::client-bucket-name"
}
]
}
Whilst this all seems to work fine, the one major issue that we have discovered is our own internal inline policy seems to give full access to our-iam-user to all of our own internal buckets.
Have we mis-configured something, or are we missing something else obvious here?
According to AWS support, this is not the right way to approach the problem:
https://forums.aws.amazon.com/message.jspa?messageID=618606
I am copying the answer from them here.
AWS:
The policy you're using with your IAM user grants access to any Amazon S3 bucket. In this case this will include any S3 bucket in your account and any bucket in any other account, where the account owner has granted your user access. You'll want to be more specific with the policy of your IAM user. For example, the following policy will limit your IAM user access to a single bucket.
You can also grant access to an array of buckets, if the user requires access to more than one.
Me
Unfortunately, we don't know beforehand all of our client's bucket names when we create the inline policy. As we get more and more clients to our service, it would be impractical to keep adding new client bucket names to the inline policy.
I guess another option is to create a new AWS account used solely for the above purpose - i.e. this account will not itself own anything, and will only ever be used for uploading to client buckets.
Is this acceptable, or are there any other alternatives options open to us?
AWS
Having a separate AWS account would provide clear security boundaries. Keep in mind that if you ever create a bucket in that other account, the user would inherit access to any bucket if you grant access to "arn:aws:s3:::*".
Another approach would be to use blacklisting (note whitelisting as suggested above is a better practice).
As you can see, the 2nd statement explicitly denies access to an array of buckets. This will override the allow in the first statment. The disadvantage here is that by default the user will inherit access to any new bucket. Therefore, you'd need to be diligent about adding new buckets to the blacklist. Either approach will require you to maintain changes to the policy. Therefore, I recommend my previous policy (aka whitelisting) where you only grant access to the S3 buckets that the user requires.
Conclusion
For our purposes, the white listing/blacklisting approach is not acceptable because we don't know before all the buckets that will be supplied by our clients. In the end, we went the route of creating a new AWS account with a single user, and that user does not have of its own s3 buckets
The policy you grant to your internal user gives this user access to all S3 bucket for the API listed (the first policy in your question). This is unnecessary as your client's bucket policies will grant your user required privileges to access to client's bucket.
To solve your problem, remove the user policy - or - explicitly your client's bucket in the list of allowed [Resources] instead of using "*"