Cross-service confused deputy prevention - AWS B2B Data Interchange
When AWS B2B Data Interchange accesses other services on your behalfImplementing confused deputy protectionExample policies

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.

When AWS B2B Data Interchange accesses other services on your behalf

AWS B2B Data Interchange accesses other services on your behalf in the following scenarios:

  • Amazon S3 access: AWS B2B Data Interchange reads input files from your Amazon S3 buckets and writes transformed output files to your Amazon S3 buckets. This occurs during EDI transformation workflows when processing documents through trading capabilities.

  • AWS KMS access: When your Amazon S3 buckets use AWS KMS encryption, AWS B2B Data Interchange accesses AWS KMS to decrypt input files and encrypt output files during transformation processes.

AWS B2B Data Interchange includes the appropriate aws:SourceArn and aws:SourceAccount condition context keys when making these cross-service calls, enabling you to implement confused deputy protection in your resource policies.

Note

AWS B2B Data Interchange uses Forward Access Sessions (FAS) when accessing for generative AI-assisted EDI mapping features, which provides built-in protection against the confused deputy problem. No additional confused deputy protection is needed for access.

Implementing confused deputy protection

We recommend using the aws:SourceArn and aws:SourceAccount global condition context keys in resource policies to limit the permissions that AWS B2B Data Interchange 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:b2bi:*: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 the AWS B2B Data Interchange resource (such as a profile, transformer, trading capability, or partnership) that is accessing the cross-service resource.

Example policies

The following examples show how you can use the aws:SourceArn and aws:SourceAccount global condition context keys to prevent the confused deputy problem when AWS B2B Data Interchange accesses your resources.

Amazon S3 bucket policy example

The following example shows an Amazon S3 bucket policy that allows AWS B2B Data Interchange to access your bucket while preventing the confused deputy problem:

{
  "Version": "2012-10-17",		 	 	 
  "Statement": [
    {
      "Sid": "AllowB2BIAccess",
      "Effect": "Allow",
      "Principal": {
        "Service": "b2bi.amazonaws.com"
      },
      "Action": [
        "s3:GetObject",
        "s3:PutObject",
        "s3:DeleteObject"
      ],
      "Resource": "arn:aws:s3:::your-bucket-name/*",
      "Condition": {
        "StringEquals": {
          "aws:SourceAccount": "123456789012"
        },
        "StringLike": {
          "aws:SourceArn": "arn:aws:b2bi:*:123456789012:*"
        }
      }
    }
  ]
}

AWS KMS key policy example

The following example shows a AWS KMS key policy that allows AWS B2B Data Interchange to use your key for encryption and decryption while preventing the confused deputy problem:

{
  "Version": "2012-10-17",		 	 	 
  "Statement": [
    {
      "Sid": "AllowB2BIKMSAccess",
      "Effect": "Allow",
      "Principal": {
        "Service": "b2bi.amazonaws.com"
      },
      "Action": [
        "kms:Decrypt",
        "kms:Encrypt",
        "kms:GenerateDataKey"
      ],
      "Resource": "*",
      "Condition": {
        "StringEquals": {
          "aws:SourceAccount": "123456789012"
        },
        "StringLike": {
          "aws:SourceArn": "arn:aws:b2bi:*:123456789012:*"
        }
      }
    }
  ]
}