Step 1: Create a destination - Amazon CloudWatch Logs

Step 1: Create a destination


All steps in this procedure are to be done in the log data recipient account.

For this example, the log data recipient account has an AWS account ID of 999999999999, while the log data sender AWS account ID is 111111111111.

This example creates a destination using a Kinesis Data Streams stream called RecipientStream, and a role that enables CloudWatch Logs to write data to it.

When the destination is created, CloudWatch Logs sends a test message to the destination on the recipient account’s behalf. When the subscription filter is active later, CloudWatch Logs sends log events to the destination on the source account’s behalf.

To create a destination
  1. In the recipient account, create a destination stream in Kinesis Data Streams. At a command prompt, type:

    aws kinesis create-stream --stream-name "RecipientStream" --shard-count 1
  2. Wait until the stream becomes active. You can use the aws kinesis describe-stream command to check the StreamDescription.StreamStatus property. In addition, take note of the StreamDescription.StreamARN value because you will pass it to CloudWatch Logs later:

    aws kinesis describe-stream --stream-name "RecipientStream" { "StreamDescription": { "StreamStatus": "ACTIVE", "StreamName": "RecipientStream", "StreamARN": "arn:aws:kinesis:us-east-1:999999999999:stream/RecipientStream", "Shards": [ { "ShardId": "shardId-000000000000", "HashKeyRange": { "EndingHashKey": "34028236692093846346337460743176EXAMPLE", "StartingHashKey": "0" }, "SequenceNumberRange": { "StartingSequenceNumber": "4955113521868881845667950383198145878459135270218EXAMPLE" } } ] } }

    It might take a minute or two for your stream to show up in the active state.

  3. Create the IAM role that grants CloudWatch Logs the permission to put data into your stream. First, you'll need to create a trust policy in a file ~/TrustPolicyForCWL.json. Use a text editor to create this policy file, do not use the IAM console.

    This policy includes a aws:SourceArn global condition context key that specifies the sourceAccountId to help prevent the confused deputy security problem. If you don't yet know the source account ID in the first call, we recommend that you put the destination ARN in the source ARN field. In the subsequent calls, you should set the source ARN to be the actual source ARN that you gathered from the first call. For more information, see Confused deputy prevention.

    { "Statement": { "Effect": "Allow", "Principal": { "Service": "" }, "Condition": { "StringLike": { "aws:SourceArn": [ "arn:aws:logs:region:sourceAccountId:*", "arn:aws:logs:region:recipientAccountId:*" ] } }, "Action": "sts:AssumeRole" } }
  4. Use the aws iam create-role command to create the IAM role, specifying the trust policy file. Take note of the returned Role.Arn value because it will also be passed to CloudWatch Logs later:

    aws iam create-role \ --role-name CWLtoKinesisRole \ --assume-role-policy-document file://~/TrustPolicyForCWL.json { "Role": { "AssumeRolePolicyDocument": { "Statement": { "Action": "sts:AssumeRole", "Effect": "Allow", "Condition": { "StringLike": { "aws:SourceArn": [ "arn:aws:logs:region:sourceAccountId:*", "arn:aws:logs:region:recipientAccountId:*" ] } }, "Principal": { "Service": "" } } }, "RoleId": "AAOIIAH450GAB4HC5F431", "CreateDate": "2015-05-29T13:46:29.431Z", "RoleName": "CWLtoKinesisRole", "Path": "/", "Arn": "arn:aws:iam::999999999999:role/CWLtoKinesisRole" } }
  5. Create a permissions policy to define which actions CloudWatch Logs can perform on your account. First, use a text editor to create a permissions policy in a file ~/PermissionsForCWL.json:

    { "Statement": [ { "Effect": "Allow", "Action": "kinesis:PutRecord", "Resource": "arn:aws:kinesis:region:999999999999:stream/RecipientStream" } ] }
  6. Associate the permissions policy with the role by using the aws iam put-role-policy command:

    aws iam put-role-policy \ --role-name CWLtoKinesisRole \ --policy-name Permissions-Policy-For-CWL \ --policy-document file://~/PermissionsForCWL.json
  7. After the stream is in the active state and you have created the IAM role, you can create the CloudWatch Logs destination.

    1. This step doesn't associate an access policy with your destination and is only the first step out of two that completes a destination creation. Make a note of the DestinationArn that is returned in the payload:

      aws logs put-destination \ --destination-name "testDestination" \ --target-arn "arn:aws:kinesis:region:999999999999:stream/RecipientStream" \ --role-arn "arn:aws:iam::999999999999:role/CWLtoKinesisRole" { "DestinationName" : "testDestination", "RoleArn" : "arn:aws:iam::999999999999:role/CWLtoKinesisRole", "DestinationArn" : "arn:aws:logs:us-east-1:999999999999:destination:testDestination", "TargetArn" : "arn:aws:kinesis:us-east-1:999999999999:stream/RecipientStream" }
    2. After step 7a is complete, in the log data recipient account, associate an access policy with the destination. This policy must specify the logs:PutSubscriptionFilter action and grants permission to the sender account to access the destination.

      The policy grants permission to the AWS account that sends logs. You can specify just this one account in the policy, or if the sender account is a member of an organization, the policy can specify the organization ID of the organization. This way, you can create just one policy to allow multiple accounts in one organization to send logs to this destination account.

      Use a text editor to create a file named ~/AccessPolicy.json with one of the following policy statements.

      This first example policy allows all accounts in the organization that have an ID of o-1234567890 to send logs to the recipient account.

      { "Version" : "2012-10-17", "Statement" : [ { "Sid" : "", "Effect" : "Allow", "Principal" : "*", "Action" : "logs:PutSubscriptionFilter", "Resource" : "arn:aws:logs:region:999999999999:destination:testDestination", "Condition": { "StringEquals" : { "aws:PrincipalOrgID" : ["o-1234567890"] } } } ] }

      This next example allows just the log data sender account (111111111111) to send logs to the log data recipient account.

      { "Version" : "2012-10-17", "Statement" : [ { "Sid" : "", "Effect" : "Allow", "Principal" : { "AWS" : "111111111111" }, "Action" : "logs:PutSubscriptionFilter", "Resource" : "arn:aws:logs:region:999999999999:destination:testDestination" } ] }
    3. Attach the policy you created in the previous step to the destination.

      aws logs put-destination-policy \ --destination-name "testDestination" \ --access-policy file://~/AccessPolicy.json

      This access policy enables users in the AWS Account with ID 111111111111 to call PutSubscriptionFilter against the destination with ARN arn:aws:logs:region:999999999999:destination:testDestination. Any other user's attempt to call PutSubscriptionFilter against this destination will be rejected.

      To validate a user's privileges against an access policy, see Using Policy Validator in the IAM User Guide.

When you have finished, if you're using AWS Organizations for your cross-account permissions, follow the steps in Step 2: (Only if using an organization) Create an IAM role. If you're granting permissions directly to the other account instead of using Organizations, you can skip that step and proceed to Step 4: Create a subscription filter.