Permissions for the Amazon S3 Bucket - Amazon Config
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Permissions for the Amazon S3 Bucket

By default, all Amazon S3 buckets and objects are private. Only the resource owner which is the Amazon account that created the bucket can access that bucket. The resource owner can, however, choose to grant access permissions to other resources and users. One way to do this is to write an access policy.

If Amazon Config creates an Amazon S3 bucket for you automatically (for example, if you use Amazon Config console to set up your delivery channel), these permissions are automatically added to Amazon S3 bucket. However, if you specify an existing Amazon S3 bucket, you must ensure that the S3 bucket has the correct permissions.

Note

An object does not inherit the permissions from its bucket. For example, if you create a bucket and grant write access to a user, you can't access that user’s objects unless the user explicitly grants you access.

Required Permissions for the Amazon S3 Bucket When Using IAM Roles

When Amazon Config sends configuration information (history files and snapshots) to Amazon S3 bucket in your account, it assumes the IAM role that you assigned when you set up Amazon Config. When Amazon Config sends configuration information to an Amazon S3 bucket in another account, it first attempts to use the IAM role, but this attempt fails if the access policy for the bucket does not grant WRITE access to the IAM role. In this event, Amazon Config sends the information again, this time as the Amazon Config service principal. Before the delivery can succeed, the access policy must grant WRITE access to the config.amazonaws.com principal name. Amazon Config is then the owner of the objects it delivers to the S3 bucket. You must attach an access policy, mentioned in step 6 below to the Amazon S3 bucket in another account to grant Amazon Config access to the Amazon S3 bucket.

Before Amazon Config can deliver logs to your Amazon S3 bucket Amazon Config checks whether the bucket exists and in which Amazon region the bucket is located. Amazon Config attempts to call Amazon S3 HeadBucket API to check whether the bucket exists and to get the bucket region. If permissions are not provided to locate the bucket when the location check is performed, you see AccessDenied error in Amazon CloudTrail logs. However, the log delivery to your Amazon S3 bucket succeeds if you do not provide bucket location permissions.

Required Permissions for the Amazon S3 Bucket When Using Service-Linked Roles

The Amazon Config service-linked role does not have permission to put objects to Amazon S3 buckets. So, if you set up Amazon Config using a service-linked role, Amazon Config will send configuration items as the Amazon Config service principal instead. You will need to attach an access policy, mentioned in step 6 below, to the Amazon S3 bucket in your own account or another account to grant Amazon Config access to the Amazon S3 bucket.

Granting Amazon Config access to the Amazon S3 Bucket

Follow these steps to add an access policy to the Amazon S3 bucket in your own account or another account. The access policy allows Amazon Config to send configuration information to the Amazon S3 bucket.

  1. Sign in to the Amazon Web Services Management Console using the account that has the S3 bucket.

  2. Open the Amazon S3 console at https://console.amazonaws.cn/s3/.

  3. Select the bucket that you want Amazon Config to use to deliver configuration items, and then choose Properties.

  4. Choose Permissions.

  5. Choose Edit Bucket Policy.

  6. Copy the following policy into the Bucket Policy Editor window:

    Important

    As a security best practice when allowing Amazon Config access to an Amazon S3 bucket, we strongly recommend that you restrict access in the bucket policy with the AWS:SourceAccount condition. If your existing bucket policy does not follow this security best practice, we strongly recommened you edit that bucket policy to include this protection. This makes sure that Amazon Config is granted access on behalf of expected users only.

    { "Version": "2012-10-17", "Statement": [ { "Sid": "AWSConfigBucketPermissionsCheck", "Effect": "Allow", "Principal": { "Service": "config.amazonaws.com" }, "Action": "s3:GetBucketAcl", "Resource": "arn:aws:s3:::targetBucketName", "Condition": { "StringEquals": { "AWS:SourceAccount": "sourceAccountID" } } }, { "Sid": "AWSConfigBucketExistenceCheck", "Effect": "Allow", "Principal": { "Service": "config.amazonaws.com" }, "Action": "s3:ListBucket", "Resource": "arn:aws:s3:::targetBucketName", "Condition": { "StringEquals": { "AWS:SourceAccount": "sourceAccountID" } } }, { "Sid": "AWSConfigBucketDelivery", "Effect": "Allow", "Principal": { "Service": "config.amazonaws.com" }, "Action": "s3:PutObject", "Resource": "arn:aws:s3:::targetBucketName/[optional] prefix/AWSLogs/sourceAccountID/Config/*", "Condition": { "StringEquals": { "s3:x-amz-acl": "bucket-owner-full-control", "AWS:SourceAccount": "sourceAccountID" } } } ] }
    Note

    Amazon Config is owned by Amazon and does not belong specifically to one of your Amazon accounts or linked accounts within your Amazon Organization. This means that when Amazon Config is sending configuration items as the Amazon Config service principal (such as when the IAM role that you assigned when you set up Amazon Config doesn’t have WRITE access to the bucket or when you setup Amazon Config to use a service-linked role), the service won't work with organization ID or organization units based conditions.

    Note

    When granting permissions to your IAM role instead of Amazon Config service principal name (SPN), ensure that your IAM role has PutObjectACL permission on cross-account bucket to avoid insufficient permission error. See sample IAM role policy at IAM Role Policy for Amazon S3 Bucket.

  7. Substitute the following values in the bucket policy:

    • targetBucketName – The name of the Amazon S3 bucket to which Amazon Config will deliver configuration items.

    • [optional] prefix – An optional addition to the Amazon S3 object key that helps create a folder-like organization in the bucket.

    • sourceAccountID – The ID of the account for which Amazon Config will deliver configuration items to the target bucket.

  8. Choose Save and then Close.

You can use the AWS:SourceAccount condition in the Amazon S3 bucket policy above to restrict the Config service principal to only interact with the Amazon S3 bucket when performing operations on behalf of specific accounts. If you plan to set up Amazon Config in many accounts from the same organization to deliver configuration items to a single Amazon S3 bucket, we recommend using IAM roles instead of service-linked roles so you can use Amazon Organizations conditions keys such as AWS:PrincipalOrgID. For more information on managing access permissions for an IAM role to use with Amazon Config, see Permissions for the IAM Role Assigned to Amazon Config. For more information about managing access permissions for Amazon Organizations, see Managing access permissions for your Amazon organization.

Amazon Config also supports the AWS:SourceArn condition which restricts the Config service principal to only interact with the Amazon S3 bucket when performing operations on behalf of specific Amazon Config delivery channels. When using the Amazon Config service principal, the AWS:SourceArn property will always be set to arn:aws:config:sourceRegion:sourceAccountID:* where sourceRegion is the region of the delivery channel and sourceAccountID is the ID of the account containing the delivery channel. For more information on Amazon Config delivery channels, see Managing the Delivery Channel. For example, add the following condition to restrict the Config service principal to interact with your Amazon S3 bucket only on behalf of a delivery channel in the us-east-1 region in the account 123456789012: "ArnLike": {"AWS:SourceArn": "arn:aws:config:us-east-1:123456789012:*"}.