Setting bucket policy for multiple accounts

For a bucket to receive log files from multiple accounts, its bucket policy must grant CloudTrail permission to write log files from all the accounts you specify. This means that you must modify the bucket policy on your destination bucket to grant CloudTrail permission to write log files from each specified account.

Note

For security reasons, unauthorized users cannot create a trail that includes AWSLogs/ as the S3KeyPrefix parameter.

To modify bucket permissions so that files can be received from multiple accounts

1. Sign in to the AWS Management Console using the account that owns the bucket (111111111111 in this example) and open the Amazon S3 console.

2. Choose the bucket where CloudTrail delivers your log files and then choose Permissions.

3. For Bucket policy, choose Edit.

4. Modify the existing policy to add a line for each additional account whose log files you want delivered to this bucket. See the following example policy and note the underlined Resource line specifying a second account ID. As a security best practice, add an aws:SourceArn condition key to the Amazon S3 bucket policy. This helps prevent unauthorized access to your S3 bucket. If you have existing trails, be sure to add one or more condition keys.

   Note

   An AWS account ID is a twelve-digit number, including leading zeros.

   {
     "Version": "2012-10-17",
     "Statement": [
       {
         "Sid": "AWSCloudTrailAclCheck20131101",
         "Effect": "Allow",
         "Principal": {
           "Service": "cloudtrail.amazonaws.com"
         },
         "Action": "s3:GetBucketAcl",
         "Resource": "arn:aws:s3:::amzn-s3-demo-bucket",
         "Condition": { 
             "StringEquals": { 
               "aws:SourceArn": [ 
                 "arn:aws:cloudtrail:region:111111111111:trail/primaryTrailName",
                 "arn:aws:cloudtrail:region:222222222222:trail/secondaryTrailName"
               ]
             }
          }
       },
       {
         "Sid": "AWSCloudTrailWrite20131101",
         "Effect": "Allow",
         "Principal": {
           "Service": "cloudtrail.amazonaws.com"
         },
         "Action": "s3:PutObject",
         "Resource": [
           "arn:aws:s3:::amzn-s3-demo-bucket/optionalLogFilePrefix/AWSLogs/111111111111/*",
           "arn:aws:s3:::amzn-s3-demo-bucket/optionalLogFilePrefix/AWSLogs/222222222222/*"
         ],
         "Condition": { 
           "StringEquals": { 
             "aws:SourceArn": [ 
               "arn:aws:cloudtrail:region:111111111111:trail/primaryTrailName",
               "arn:aws:cloudtrail:region:222222222222:trail/secondaryTrailName"
             ],
             "s3:x-amz-acl": "bucket-owner-full-control"
           }
         }
       }
     ]
   }