Restrict (Deny) Bucket List by IP - amazon-web-services

I have a bucket policy that works properly to restrict access to a bucket to certain IP's, but I actually want to deny listing the bucket itself or bucket(s) to only certain IP's.
I got it working with everything except the listing. I can deny listing the bucket contents, uploading, downloading, but can't deny doing a simple command like Get-S3Bucket -BucketName "bucket"
My current policy:
{
"Version": "2012-10-17",
"Id": "bucket-policy",
"Statement": [
{
"Sid": "IPDeny",
"Effect": "Deny",
"Principal": "*",
"Action": [
"s3:ListBucket",
"s3:GetBucketLocation",
"s3:PutObject",
"s3:GetObject",
"s3:GetObjectVersion"
],
"Resource": [
"arn:aws:s3:::bucketName/*",
"arn:aws:s3:::bucketName"
],
"Condition": {
"NotIpAddress": {
"aws:SourceIp": ["1.2.3.4.5","6.7.8.9"]
}
}
}
]
}

The issue was specific to PowerShell Toolkit. Which I learned the Get-S3Bucket actually runs an "s3 collection" which I believe to include the following:
s3:ListBucket,
s3:ListAllMyBuckets,
s3:HeadBucket
So the issue for me wasn't the bucket policy, it was the IAM user policy.
I solved it via the user policy like follows:
{
"Sid": "listBuckets",
"Effect": "Allow",
"Action": [
"s3:ListBucket",
"s3:ListAllMyBuckets",
"s3:HeadBucket"
],
"Resource": "*",
"Condition": {
"IpAddress": {
"aws:SourceIp": ["1.2.3.4","5.6.7.8"]
}
}
}

Related

AWS Transfer service - SFTP - deny ability to list directory is affecting ability to put file to the directory

I'm attempting to set up permissions for a user account on AWS Transfer Service with SFTP protocol. I have a use case where a user should be able to add a file to a directory but not list the files in it.
When I tweak the IAM role to deny 's3:ListBucket' for a specific subdirectory the put operation fails as well. Theoretically s3 does allow to Put object without having the ability to list the prefixes. AWS transfer service however seems to be implicitly using the list bucket operation before put. Has anyone managed to deny listing ability while still being able to upload.
IAM policy :
{
"Version": "2012-10-17",
"Statement": [
{
"Action": "s3:ListBucket",
"Effect": "Allow",
"Resource": [
"arn:aws:s3:::<my-bucket>"
],
"Sid": "AllowListDirectories",
"Condition": {
"StringLike": {
"s3:prefix": [
"data/partner_2/*"
]
}
}
},
{
"Sid": "DenyMkdir",
"Action": [
"s3:PutObject"
],
"Effect": "Deny",
"Resource": "arn:aws:s3:::<my-bucket>/*/"
},
{
"Sid": "DenyListFilesInSubDirectory",
"Action": [
"s3:ListBucket"
],
"Effect": "Deny",
"Resource": "arn:aws:s3:::<my-bucket>",
"Condition": {
"StringLike": {
"s3:prefix": [
"data/partner_2/data/incoming/*"
]
}
}
},
{
"Effect": "AllowReadWirteInSubDirectory",
"Action": [
"s3:GetObject",
"s3:GetObjectVersion",
"s3:PutObject",
"s3:PutObjectAcl",
"s3:PutObjectTagging",
"s3:PutObjectVersionAcl",
"s3:PutObjectVersionTagging"
],
"Resource": "arn:aws:s3:::<my-bucket>/data/partner_2/data/incoming/*"
},
{
"Effect": "AllowOnlyReadInADifferentDirectory",
"Action": [
"s3:GetObject",
"s3:GetObjectVersion"
],
"Resource": "arn:aws:s3:::<my-bucket>/data/partner_2/data/outgoing/*"
}
]
}
The output from SFTP client:
sftp> cd data/incoming
sftp> ls
Couldn't read directory: Permission denied
sftp> put /Users/foo/Downloads/test.log
Uploading /Users/foo/Downloads/test.log to /data/incoming/test.log
remote open("/data/incoming/test.log"): Permission denied
sftp> get test-one.txt
Fetching /data/incoming/test-one.txt to test-one.txt
sftp> exit
Since you will have to allow the upload to your s3 bucket through SFTP, this answer doesn't quite meet your requirements. If the SFTP requirement wasn't there, you may be able to provide pre-signed urls to the client to upload files securely.
I couldn't manage to find an exact solution, however, a workaround could be allowing list+upload permission to a directory in your bucket that is specific to the client/user. Got a helpful video here to share, and corresponding medium article.
Basically, the IAM policy the user is attached to will have the following permissions to a specific folder while you block all public access to your bucket.
{
"Version": "2023-02-16",
"Statement": [
{
"Sid": "AllowListingOfUserFolder",
"Action": [
"s3:ListBucket"
],
"Effect": "Allow",
"Resource": [
"arn:aws:s3:::<my-bucket>"
],
"Condition": {
"StringLike": {
"s3:prefix": [
"restricted-folder-user-1/*",
"restricted-folder-user-1"
]
}
}
},
{
"Sid": "HomeDirObjectAccess",
"Effect": "Allow",
"Action": [
"s3:PutObject",
"s3:GetObject",
"s3:GetObjectVersion"
],
"Resource": "arn:aws:s3:::<arn of restricted-folder-user-1>*"
}
]
}

AWS S3 Bucket Policy: How to grant access to EC2 instance?

I am really struggling with this and the AWS Official Docs simply does not help!
I have an S3 bucket set up and it is allowing public access from a few specified ip addresses. This is the custom policy that is working:
{
"Version": "2012-10-17",
"Id": "Policy1111111111",
"Statement": [
{
"Sid": "Stmt111111111",
"Effect": "Deny",
"Principal": "*",
"Action": "s3:*",
"Resource": "arn:aws:s3:::myapp-local-test/*",
"Condition": {
"NotIpAddress": {
"aws:SourceIp": [
"12.122.123.111",
"121.217.73.153"
]
}
}
},
{
"Sid": "Stmt1111111111",
"Effect": "Allow",
"Principal": "*",
"Action": [
"s3:GetObject",
"s3:PutObject"
],
"Resource": "arn:aws:s3:::myapp-local-test/*",
"Condition": {
"IpAddress": {
"aws:SourceIp": [
"12.122.123.111",
"121.217.73.153"
]
}
}
},
]
}
Now, instead of only allowing the above 2 ip addresses to access resources in the bucket, I also want my EC2 instance to access it.
I followed this doc: https://aws.amazon.com/premiumsupport/knowledge-center/ec2-instance-access-s3-bucket/
I followed the exact steps.
I have created a new IAM role, (arn: "arn:aws:iam::1223123156:role/EC2-to-S3")
I have also attached the role to my EC2 instance.
But in step 6:
6. In your bucket policy, edit or remove any Effect: Deny
statements that are denying the IAM instance profile access to
your bucket. For instructions on editing policies,
see Editing IAM policies.
How exactly do I do it? It directs me to another doc about Editing IAM policies, BUT IT DOES NOT HELP !!!
How do I remove any "Effect: Deny" statements that are denying the IAM instance profile access to my bucket?
What keyword should I use?
Here is what I tried:
{
"Version": "2012-10-17",
"Id": "Policy1111111111",
"Statement": [
{
"Sid": "Stmt111111111",
"Effect": "Deny",
"Principal": "*",
"Action": "s3:*",
"Resource": "arn:aws:s3:::myapp-local-test/*",
"Condition": {
"NotIpAddress": {
"aws:SourceIp": [
"12.122.123.111",
"121.217.73.153"
]
},
"StringNotEquals": {
"aws:SourceArn": "arn:aws:iam::1223123156:role/EC2-to-S3"
}
},
{
"Sid": "Stmt1111112222",
"Effect": "Allow",
"Principal": "*",
"Action": [
"s3:GetObject",
"s3:PutObject"
],
"Resource": "arn:aws:s3:::myapp-local-test/*",
"Condition": {
"IpAddress": {
"aws:SourceIp": [
"12.122.123.111",
"121.217.73.153"
]
}
}
},
{
"Sid": "Stmt1639460338435",
"Effect": "Allow",
"Principal": "*",
"Action": [
"s3:GetObject",
"s3:PutObject"
],
"Resource": "arn:aws:s3:::myapp-local-test/*",
"Condition": {
"StringEquals": {
"aws:SourceArn": "arn:aws:iam::1223123156:role/EC2-to-S3"
}
}
}
]
}
which does not work. I still had an "Access Denied" error.
Can the docs be a little bit more specific?
Why is it so hard to get such a basic task done with aws docs??
This finally worked:
{
"Version": "2012-10-17",
"Id": "Policy1111111",
"Statement": [
{
"Sid": "Stmt11111",
"Effect": "Allow",
"Principal": "*",
"Action": [
"s3:GetObject",
"s3:PutObject"
],
"Resource": "arn:aws:s3:::myapp-local-test/*",
"Condition": {
"IpAddress": {
"aws:SourceIp": [
"12.122.123.111",
"121.217.73.153"
]
}
}
},
{
"Sid": "Stmt1222222222",
"Effect": "Allow",
"Principal": {
"AWS": "arn:aws:iam::1234556:role/EC2-to-S3"
},
"Action": [
"s3:GetObject",
"s3:PutObject"
],
"Resource": "arn:aws:s3:::myapp-local-test/*"
}
]
}
So the trick is to drop the deny statement completely since by default everything is denied access.
And my edits earlier:
"Statement": [
{
"Sid": "Stmt111111111",
"Effect": "Deny",
"Principal": "*",
"Action": "s3:*",
"Resource": "arn:aws:s3:::myapp-local-test/*",
"Condition": {
"NotIpAddress": {
"aws:SourceIp": [
"12.122.123.111",
"121.217.73.153"
]
},
"StringNotEquals": {
"aws:SourceArn": "arn:aws:iam::1223123156:role/EC2-to-S3"
}
},
the StringNotEquals part does not drop the default deny for the iam role.
If possible, you should avoid using Deny statements, since they override any Allow statements.
Your first bucket policy is saying:
Deny access to the bucket if requests are not coming from the given IP addresses
Allow access to the bucket if requests are coming from the given IP addresses
Unfortunately, the Deny will prohibit access from the EC2 instance, since it is not one of the listed IP addresses.
Instead of using Deny, just grant Allow access when needed. Access to S3 is denied by default, so users can only gain access if there is an Allow policy that grants them access.
To grant access to instance create iam instance profile and attach it your EC2 instance.
https://aws.amazon.com/premiumsupport/knowledge-center/ec2-instance-access-s3-bucket/

Deny access to AWS S3 to all IPs except specific ranges

I hava an S3 Bucket ("myBucket"), to which only a user has access, let's call it "s3user". I have an IAM policy attached to this user as follows:
{
"Version": "2012-10-17",
"Statement": [
{
"Sid": "VisualEditor0",
"Effect": "Allow",
"Action": [
"s3:ListBucket",
"s3:GetBucketLocation"
],
"Resource": "arn:aws:s3:::myBucket"
},
{
"Sid": "VisualEditor1",
"Effect": "Allow",
"Action": [
"s3:PutObject",
"s3:GetObject",
"s3:ListBucket",
"s3:GetObjectVersion"
],
"Resource": "*"
}
]
}
I attached this IAM Policy to user "s3User", granting read-only access to "myBucket". So far so good.
Now, I added a second policy, but now not an IAM policy but an S3 Bucket Policy, as follows:
{
"Version": "2012-10-17",
"Id": "S3PolicyId1",
"Statement": [
{
"Sid": "IPAllow",
"Effect": "Deny",
"Principal": "*",
"Action": "s3:*",
"Resource": "arn:aws:s3:::myBucket/*",
"Condition": {
"NotIpAddress": {
"aws:SourceIp": [
"1.2.3.4/27",
"2.3.4.1/28",
"5.6.7.8/29"
]
}
}
}
]
}
I expected that this explicit deny will deny all requests not coming from the specified source IP ranges. But, it is still letting me list the contents of the bucket from other IPs. It seems as if the bucket policy had no effect at all.
According to this AWS S3 article, when you have multiple policies, they are all applied and explicit denies have precedence over explicit allows, so I think this should be working, but it isn't.
Any ideas why I'm not able to deny requests to a bucket based on sourceIP addresses?
Thanks!
You should update your Deny policy to include operations that are performed on the bucket itself, rather than its content (/*):
{
"Version": "2012-10-17",
"Id": "S3PolicyId1",
"Statement": [
{
"Sid": "DenyOutsideIPfromBucket",
"Effect": "Deny",
"Principal": "*",
"Action": [
"s3:ListBucket",
"s3:GetBucketLocation",
"s3:PutObject",
"s3:GetObject",
"s3:ListBucket",
"s3:GetObjectVersion"
],
"Resource": ["arn:aws:s3:::myBucket/*", "arn:aws:s3:::myBucket"],
"Condition": {
"NotIpAddress": {
"aws:SourceIp": [
"1.2.3.4/27",
"2.3.4.1/28",
"5.6.7.8/29"
]
}
}
}
]
}
Of course, if the only users with access to the bucket are the ones with the IAM policy, you could simply add a IpAddress condition on the original IAM policy, so they can only use the bucket from the given set of IP addresses. This would avoid the need for a Deny policy.

How to limit access to an S3 bucket to a specific VPC while allowing console access

I am setting up a selection of S3 buckets and wish to restrict access to them to a VPC while still allowing access to the buckets from the AWS console.
As proposed here I have created an S3 endpoint and also added it to the main routing table. The policy on the endpoint allows full access to all resources.
I have created an S3 policy (see below) and added it to the bucket. As soon as I save the policy, access to the bucket from the console is no longer possible.
I have also tried to specifically add a user to the condition "StringNotEquals" in the form of "aws:username": "user1", to no avail.
{
"Version": "2012-10-17",
"Id": "Policy-S3-Bucket-myBucket",
"Statement": [
{
"Sid": "Access-via-VPC-only",
"Principal": "*",
"Action": "s3:*",
"Effect": "Deny",
"Resource": [
"arn:aws:s3:::myBucket",
"arn:aws:s3:::myBucket/*"
],
"Condition": {
"StringNotEquals": {
"aws:sourceVpc": "vpc-01c9d66c12345"
}
}
},
{
"Sid": "Allow-console-access",
"Action": [
"s3:*"
],
"Effect": "Allow",
"Resource": [
"arn:aws:s3:::myBucket",
"arn:aws:s3:::myBucket/*"
],
"Principal": {
"AWS": [
"arn:aws:iam::<account-id>:user/user1", "arn:aws:iam::<account-id>:user/user2"
]
}
}
]
}
The expected result would be that the S3 bucket is only accessible by the aforementioned VPC and via the AWS console.
The actual result is:
The bucket overview shows an "Error: Access Denied" and the permissions page(public access settings) shows: "You don't have access to view this configuration. Contact your account administrator to request access."
I have to login using the root user and delete the policy to regain access to the bucket.
I found a solution which seems to work. I have tested it in the policy simulator and it also appears to work correctly in the live environment. The following policy does the trick:
{
"Version": "2012-10-17",
"Id": "Policy-S3-Bucket-myBucket",
"Statement": [
{
"Effect": "Allow",
"Action": [
"s3:GetBucketLocation",
"s3:ListAllMyBuckets"
],
"Resource": "*",
"Condition": {
"StringEquals": {
"aws:username": ["user1", "user2"]
}
}
},
{
"Effect": "Allow",
"Action": ["s3:ListBucket"],
"Resource": ["arn:aws:s3:::myBucket"],
"Condition": {
"StringEquals": {
"aws:sourceVpc": "vpc-01c9d66c12345"
}
}
},
{
"Effect": "Allow",
"Action": ["s3:ListBucket"],
"Resource": ["arn:aws:s3:::myBucket"],
"Condition": {
"StringEquals": {
"aws:username": ["user1", "user2"]
}
}
},
{
"Effect": "Allow",
"Action": [
"s3:PutObject",
"s3:GetObject"
],
"Resource": ["arn:aws:s3:::myBucket/*"],
"Condition": {
"StringEquals": {
"aws:sourceVpc": "vpc-01c9d66c12345"
}
}
},
{
"Effect": "Allow",
"Action": [
"s3:PutObject",
"s3:GetObject"
],
"Resource": ["arn:aws:s3:::myBucket/*"],
"Condition": {
"StringEquals": {
"aws:username": ["user1", "user2"]
}
}
}
]
}
The policy requires for either the sourceVpc string OR the username to be as listed in the condition.
Admittedly, the policy is verbose and there is a substantial amount of replication. If anyone has an idea to solve this more efficiently, I'm all ears.
This policy was tested and gives exactly what you need:
Statement": {
"Sid": "Allow-anonymous-access-from-specific-VPC",
"Effect": "Allow",
"Principal": "*",
"Action": "s3:GetObject",
"Resource": "arn:aws:s3:::bucket_name/*",
"Condition": {
"StringEquals": {
"aws:SourceVpc": "some-vpc-id"
}
}
}
This will allow anonymous access from requests coming from "some-vpc-id", while yet allowing access from AWS console.
Your VPC has to have S3 endpoint configured for it to work.
The trick seems to be on denying everything except if it comes from the user or from the VPC but it has to be in the same condition. The way policies work is that Deny rules precede over every other rule, so if you deny, you can't then allow on a subsequent rule; it's already denied and that's it.
By the way, the aws:userid of the root user is the Account Id. Probably a bad practice to use this user but oh well :P
So my bucket now only accepts traffic from the VPC and from the user I log into via the AWS web console (so I don't get access denied errors in the web console)
{
"Version": "2012-10-17",
"Id": "Policy154336817545456388",
"Statement": [
{
"Sid": "Block-if-not-from-VPC-or-Me",
"Effect": "Deny",
"Principal": "*",
"Action": "s3:*",
"Resource": [
"arn:aws:s3:::bucket-name",
"arn:aws:s3:::bucket-name/*"
],
"Condition": {
"StringNotEquals": {
"aws:SourceVpce": "vpce-4598ujfjrhc",
"aws:userid": "576767373466"
}
}
}
]
}

Restrict access to a single folder in S3 bucket

I want to restrict the access to a single folder in S3 bucket.
I have written a IAM role for the same. Somehow I am not upload/sync the files to this folder. Here, bucket is the bucket name and folder is the folder where I want to give access.
{
"Version": "2012-10-17",
"Statement": [
{
"Sid": "AllowUserToSeeBucketListInTheConsole",
"Action": [
"s3:ListAllMyBuckets",
"s3:GetBucketLocation"
],
"Effect": "Allow",
"Resource": [
"arn:aws:s3:::*"
]
},
{
"Sid": "AllowRootAndHomeListingOfBucket",
"Action": [
"s3:ListBucket"
],
"Effect": "Allow",
"Resource": [
"arn:aws:s3:::bucket"
],
"Condition": {
"StringEquals": {
"s3:prefix": [
""
],
"s3:delimiter": [
"/"
]
}
}
},
{
"Sid": "AllowListingOfUserFolder",
"Action": [
"s3:ListBucket",
"s3:PutObject",
"s3:PutObjectAcl",
"s3:GetObject",
"s3:GetObjectAcl",
"s3:HeadObject"
],
"Effect": "Allow",
"Resource": [
"arn:aws:s3:::bucket"
],
"Condition": {
"StringLike": {
"s3:prefix": [
"folder/*"
]
}
}
}
]
}
Please suggest where I am wrong.
This restrictive IAM policy grants only list and upload access to a particular prefix in a particular bucket. It also intends to allow multipart uploads.
References:
https://docs.aws.amazon.com/AmazonS3/latest/API/API_Operations.html
https://docs.aws.amazon.com/AmazonS3/latest/dev/mpuAndPermissions.html
{
"Version": "2012-10-17",
"Statement": [
{
"Sid": "ListBucket",
"Effect": "Allow",
"Action": "s3:ListBucket",
"Resource": "arn:aws:s3:::mybucket",
"Condition": {
"StringLike": {
"s3:prefix": "my/prefix/is/this/*"
}
}
},
{
"Sid": "UploadObject",
"Effect": "Allow",
"Action": [
"s3:PutObject",
"s3:AbortMultipartUpload",
"s3:ListMultipartUploadParts"
],
"Resource": [
"arn:aws:s3:::mybucket/my/prefix/is/this/*",
]
}
]
}
Note that specifying the s3:ListBucket resource compactly as "arn:aws:s3:::mybucket/my/prefix/is/this/*" didn't work.
Since you have requested to suggest, where you are wrong:
1> In AllowListingOfUserFolder, you have used the object as resource but you have used bucket level operations and "s3:prefix" will not work with object level APIs.
Please refer to the sample policies listed here:
http://docs.aws.amazon.com/AmazonS3/latest/dev/example-policies-s3.html#iam-policy-ex1
https://aws.amazon.com/blogs/security/writing-iam-policies-grant-access-to-user-specific-folders-in-an-amazon-s3-bucket/
{
"Version": "2012-10-17",
"Statement": [
{
"Sid": "ListObjectsInBucket",
"Effect": "Allow",
"Action": ["s3:ListBucket"],
"Resource": ["arn:aws:s3:::bucket-name"]
},
{
"Sid": "AllObjectActions",
"Effect": "Allow",
"Action": "s3:*Object",
"Resource": ["arn:aws:s3:::bucket-name/*"]
}
]
}
https://docs.aws.amazon.com/IAM/latest/UserGuide/reference_policies_examples_s3_rw-bucket.html
I believe for the scenario you're describing AWS recommends Bucket Policies. AWS IAM should be used to secure AWS resources such as S3 itself, whereas Bucket policies can be used to secure S3 buckets and documents.
Check out this AWS blog post on the subject:
https://aws.amazon.com/blogs/security/iam-policies-and-bucket-policies-and-acls-oh-my-controlling-access-to-s3-resources/