Step 2: Create an IAM Policy and User

Security best practices for AWS dictate the use of fine-grained permissions to control access to different resources. AWS Identity and Access Management (IAM) allows you to manage users and user permissions in AWS. An IAM policy explicitly lists actions that are allowed and the resources on which the actions are applicable.

The following are the minimum permissions generally required for a Kinesis Data Streams producer and consumer.

Producer
Actions	Resource	Purpose
DescribeStream, DescribeStreamSummary, DescribeStreamConsumer	Kinesis data stream	Before attempting to write records, the producer checks if the stream exists and is active, and if the shards are contained in the stream, and if the stream has a consumer.
SubscribeToShard, RegisterStreamConsumer	Kinesis data stream	Subscribes and register a consumers to a Kinesis Data Stream shard.
PutRecord, PutRecords	Kinesis data stream	Write records to Kinesis Data Streams.

Consumer
Actions	Resource	Purpose
DescribeStream	Kinesis data stream	Before attempting to read records, the consumer checks if the stream exists and is active, and if the shards are contained in the stream.
GetRecords, GetShardIterator	Kinesis data stream	Read records from a Kinesis Data Streams shard.
CreateTable, DescribeTable, GetItem, PutItem, Scan, UpdateItem	Amazon DynamoDB table	If the consumer is developed using the Kinesis Client Library (KCL), it needs permissions to a DynamoDB table to track the processing state of the application. The first consumer started creates the table.
DeleteItem	Amazon DynamoDB table	For when the consumer performs split/merge operations on Kinesis Data Streams shards.
PutMetricData	Amazon CloudWatch log	The KCL also uploads metrics to CloudWatch, which are useful for monitoring the application.

For this application, you create a single IAM policy that grants all of the preceding permissions. In practice, you might want to consider creating two policies, one for producers and one for consumers.

To create an IAM policy

1. Locate the Amazon Resource Name (ARN) for the new stream. You can find this ARN listed as Stream ARN at the top of the Details tab. The ARN format is as follows:

   arn:aws:kinesis:region:account:stream/name

   region

   The Region code; for example, us-west-2. For more information, see Region and Availability Zone Concepts.

   account

   The AWS account ID, as shown in Account Settings.

   name

   The name of the stream from Step 1: Create a Data Stream, which is StockTradeStream.

2. Determine the ARN for the DynamoDB table to be used by the consumer (and created by the first consumer instance). It must be in the following format:

   arn:aws:dynamodb:region:account:table/name

   The Region and account are from the same place as the previous step, but this time name is the name of the table created and used by the consumer application. The KCL used by the consumer uses the application name as the table name. Use StockTradesProcessor, which is the application name used later.

3. In the IAM console, in Policies (https://console.aws.amazon.com/iam/home#policies), choose Create policy. If this is the first time that you have worked with IAM policies, choose Get Started, Create Policy.

4. Choose Select next to Policy Generator.

5. Choose Amazon Kinesis as the AWS service.

6. Select DescribeStream, GetShardIterator, GetRecords, PutRecord, and PutRecords as the allowed actions.

7. Enter the ARN that you created in Step 1.

8. Use Add Statement for each of the following:

   AWS Service	Actions	ARN
   Amazon DynamoDB	CreateTable, DeleteItem, DescribeTable, GetItem, PutItem, Scan, UpdateItem	The ARN you created in Step 2
   Amazon CloudWatch	PutMetricData	*

   The asterisk (*) that is used when specifying an ARN is not required. In this case, it's because there is no specific resource in CloudWatch on which the PutMetricData action is invoked.

9. Choose Next Step.

10. Change Policy Name to StockTradeStreamPolicy, review the code, and choose Create Policy.

The resulting policy document should look something like the following:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "Stmt123",
      "Effect": "Allow",
      "Action": [
        "kinesis:DescribeStream",
        "kinesis:PutRecord",
        "kinesis:PutRecords",
        "kinesis:GetShardIterator",
        "kinesis:GetRecords",
        "kinesis:ListShards",
        "kinesis:DescribeStreamSummary",
        "kinesis:RegisterStreamConsumer"
      ],
      "Resource": [
        "arn:aws:kinesis:us-west-2:123:stream/StockTradeStream"
      ]
    },
    {
      "Sid": "Stmt234",
      "Effect": "Allow",
      "Action": [
        "kinesis:SubscribeToShard",
        "kinesis:DescribeStreamConsumer"
      ],
      "Resource": [
        "arn:aws:kinesis:us-west-2:123:stream/StockTradeStream/*"
      ]
    },
    {
      "Sid": "Stmt456",
      "Effect": "Allow",
      "Action": [
        "dynamodb:*"
      ],
      "Resource": [
        "arn:aws:dynamodb:us-west-2:123:table/StockTradesProcessor"
      ]
    },
    {
      "Sid": "Stmt789",
      "Effect": "Allow",
      "Action": [
        "cloudwatch:PutMetricData"
      ],
      "Resource": [
        "*"
      ]
    }
  ]
}

To create an IAM user

1. Open the IAM console at https://console.aws.amazon.com/iam/.

2. On the Users page, choose Add user.

3. For User name, type StockTradeStreamUser.

4. For Access type, choose Programmatic access, and then choose Next: Permissions.

5. Choose Attach existing policies directly.

6. Search by name for the policy that you created. Select the box to the left of the policy name, and then choose Next: Review.

7. Review the details and summary, and then choose Create user.

8. Copy the Access key ID, and save it privately. Under Secret access key, choose Show, and save that key privately also.

9. Paste the access and secret keys to a local file in a safe place that only you can access. For this application, create a file named ~/.aws/credentials (with strict permissions). The file should be in the following format:

   [default]
   aws_access_key_id=access key
   aws_secret_access_key=secret access key

To attach an IAM policy to a user

1. In the IAM console, open Policies and choose Policy Actions.

2. Choose StockTradeStreamPolicy and Attach.

3. Choose StockTradeStreamUser and Attach Policy.

Next Steps

Step 3: Download and Build the Implementation Code