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 AWS, 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, AWS 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
or aws:SourceAccount
global condition context keys in resource
policies to limit the permissions that Amazon ECR 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:
. servicename
:region
:123456789012
:*
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 ResourceDescription.
The following example shows how you can use the aws:SourceArn
and
aws:SourceAccount
global condition context keys in an Amazon ECR repository
policy to allow AWS CodeBuild access to the Amazon ECR API actions necessary for integration with
that service while also preventing the confused deputy problem.
{ "Version":"2012-10-17", "Statement":[ { "Sid":"CodeBuildAccess", "Effect":"Allow", "Principal":{ "Service":"codebuild.amazonaws.com" }, "Action":[ "ecr:BatchGetImage", "ecr:GetDownloadUrlForLayer" ], "Condition":{ "ArnLike":{ "aws:SourceArn":"arn:aws:codebuild:
region
:123456789012
:project/project-name
" }, "StringEquals":{ "aws:SourceAccount":"123456789012
" } } } ] }