A company uses identity federation to authenticate users into an identity account (987654321987), where they assume an IAM role named IdentityRole. They then assume an IAM role named JobFunctionRole in the target AWS account (123456789123) to perform their duties. A user cannot assume the role in the target account. The role in the identity account has an attached IAM policy (not shown). What change is required to allow the user to assume the appropriate role in the target account?

The issue lies in the ability to assume the JobFunctionRole in the target account. Assuming a role across accounts requires the target role's trust policy to explicitly allow the source role (or principal) to assume it. Therefore, the trust policy of JobFunctionRole in account 123456789123 must be updated to permit IdentityRole from account 987654321987 to assume it. Updating the IAM policy attached to IdentityRole in the identity account would control what actions IdentityRole itself can perform, but not whether another role can be assumed. Updating the trust policy on IdentityRole would control who can assume IdentityRole, which is not the current problem. Updating the IAM policy attached to JobFunctionRole would define what actions JobFunctionRole can perform once assumed, not who can assume it.