Attach IAM Policy to SNS Topic - amazon-web-services

Question

I am trying deliver a message from an unencrypted SNS topic to an encrypted SQS queue following this guide. I was able to complete the "Configure KMS permissions for AWS services" step, but I am having trouble with the "Configure KMS permissions for producers
" step. I have created the IAM role, however attaching this role to my SNS topic is where I am specifically confused. Here are some questions I have which my own research was unable to answer:
Can an IAM role be attached to a specific item (SNS topic, SQS queue, etc...)? If not, what other way is there to grant permissions to a specific item?
When the instructions mention "producer", is this referring to the SNS topic or the AWS account which owns the SNS topic?
Any and all help is greatly appreciated.
Edit:
Here is my current AWS KMS key policy:
{
"Version": "2012-10-17",
"Id": "key-consolepolicy-3",
"Statement": [
{
"Sid": "Allow administration of the key",
"Effect": "Allow",
"Principal": {
"AWS": "arn:aws:iam::${aws_account_id}:root"
},
"Action": "kms:*",
"Resource": "*"
},
{
"Sid": "Allow SNS to use KMS",
"Effect": "Allow",
"Principal": {
"Service": "sns.amazonaws.com"
},
"Action": [
"kms:GenerateDataKey",
"kms:Decrypt"
],
"Resource": "*"
}
]
}
Whenever I add the following statements to my KMS key policy in the Statement list, I get the error "MalformedPolicyDocumentException - Policy contains a statement with no principal":
{
"Effect": "Allow",
"Action": [
"kms:GenerateDataKey",
"kms:Decrypt"
],
"Resource": "${kms_customer_managed_key_arn}"
},
{
"Effect": "Allow",
"Action": [
"sqs:SendMessage"
],
"Resource": "${sqs_queue_arn}"
}

Answer 1

If not, what other way is there to grant permissions to a specific item?
The permissons from the link are attached to your KMS CMK key policy.
When the instructions mention "producer", is this referring to the SNS topic or the AWS account which owns the SNS topic?
The producer is anyone or anything that sends messages. It can be a lambda function, an ec2 instance or IAM user/role. In that case you give the producer permissions to sendMessage and use the KMS key. For lambda it would be in lambda execution role, for instance it would be in an instance role.