Cross-service confused deputy prevention
The confused deputy problem is a security issue where an entity that doesn't have permission to perform an action can coerce a more-privileged entity to perform the action. In Amazon, cross-service impersonation can result in the confused deputy problem. Cross-service impersonation can occur when one service (the calling service) calls another service (the called service). The calling service can be manipulated to use its permissions to act on another customer's resources in a way it should not otherwise have permission to access. To prevent this, Amazon provides tools that help you protect your data for all services with service principals that have been given access to resources in your account.
We recommend using the aws:SourceArn
and aws:SourceAccount
global condition context keys in resource
policies to limit the permissions that Amazon Firewall Manager gives another service to the
resource. Use aws:SourceArn
if you want only one resource to be associated with
the cross-service access. Use aws:SourceAccount
if you want to allow any
resource in that account to be associated with the cross-service use.
The most effective way to protect against the confused deputy problem is to use the
aws:SourceArn
global condition context key with the full ARN of the
resource. If you don't know the full ARN of the resource or if you are specifying multiple
resources, use the aws:SourceArn
global context condition key with wildcard
characters (*
) for the unknown portions of the ARN. For example,
arn:aws-cn:fms:*:
. account-id
:*
If the aws:SourceArn
value does not contain the account ID, such as an Amazon S3
bucket ARN, you must use both global condition context keys to limit permissions.
The value of aws:SourceArn
must be the Amazon Firewall Manager administrator's Amazon account.
The following examples show how you can use the aws:SourceArn
global condition context key in Firewall Manager to prevent
the confused deputy problem.
The following example shows how to prevent the confused deputy problem by using the aws:SourceArn
global condition context key in the Firewall Manager role trust policy. Replace Region
and account-id
with your own information.
{ "Version": "2012-10-17", "Statement": { "Sid": "ConfusedDeputyPreventionExamplePolicy", "Effect": "Allow", "Principal": { "Service": "
servicename
.amazonaws.com" }, "Action": "sts:AssumeRole", "Condition": { "ArnLike": { "aws:SourceArn": [ "arn:aws-cn:fms:Region
:account-id
:${*}", "arn:aws-cn:fms:Region
:account-id
:policy/*"] }, "StringEquals": { "aws:SourceAccount": "account-id
" } } } }