Receiving CloudTrail log files from multiple accounts - AWS CloudTrail
Redacting bucket owner account IDs for data events called by other accounts

Receiving CloudTrail log files from multiple accounts

You can have CloudTrail deliver log files from multiple AWS accounts into a single Amazon S3 bucket. For example, you have four AWS accounts with account IDs 111111111111, 222222222222, 333333333333, and 444444444444, and you want to configure CloudTrail to deliver log files from all four of these accounts to a bucket belonging to account 111111111111. To accomplish this, complete the following steps in order:

  1. Create a trail in the account where the destination bucket will belong (111111111111 in this example). Do not create a trail for any other accounts yet.

    For instructions, see Creating a trail in the console.

  2. Update the bucket policy on your destination bucket to grant cross-account permissions to CloudTrail.

    For instructions, see Setting bucket policy for multiple accounts.

  3. Create a trail in the other accounts (222222222222, 333333333333, and 444444444444 in this example) for which you want to log activity. When you create the trail in each account, specify the Amazon S3 bucket belonging to the account that you specified in step 1 (111111111111 in this example). For instructions, see Create trails in additional accounts.

    Note

    If you choose to enable SSE-KMS encryption, the KMS key policy must allow CloudTrail to use the key to encrypt your log files, and allow the users you specify to read log files in unencrypted form. For information about manually editing the key policy, see Configure AWS KMS key policies for CloudTrail.

Redacting bucket owner account IDs for data events called by other accounts

Historically, if CloudTrail data events were enabled in the AWS account of an Amazon S3 data event API caller, CloudTrail showed the account ID of the S3 bucket owner in the data event (such as PutObject). This occurred even if the bucket owner account did not have S3 data events enabled.

Now, CloudTrail removes the account ID of the S3 bucket owner in the resources block if both of the following conditions are met:

  • The data event API call is from a different AWS account than the Amazon S3 bucket owner.

  • The API caller received an AccessDenied error that was only for the caller account.

The owner of the resource on which the API call was made still receives the full event.

The following event record snippets are an example of the expected behavior. In the Historic snippet, the account ID 123456789012 of the S3 bucket owner is shown to an API caller from a different account. In the example of current behavior, the account ID of the bucket owner is not shown.

# Historic

"resources": [
    {
        "type": "AWS::S3::Object",
        "ARNPrefix": "arn:aws:s3:::amzn-s3-demo-bucket2/"
    },
    {
        "accountId": "123456789012",
        "type": "AWS::S3::Bucket",
        "ARN": "arn:aws:s3:::amzn-s3-demo-bucket2"
    }
]

The following is the current behavior.

# Current

"resources": [
    {
        "type": "AWS::S3::Object",
        "ARNPrefix": "arn:aws:s3:::amzn-s3-demo-bucket2/"
    },
    {
        "accountId": "",
        "type": "AWS::S3::Bucket",
        "ARN": "arn:aws:s3:::amzn-s3-demo-bucket2"
    }
]
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