Implement automatic drift remediation for AWS CloudFormation using Amazon CloudWatch and AWS Lambda

“Stack waft” is a common prevalence drift watch   for companies the use of AWS CloudFormation, and remediating stack waft represents a persistent and tedious mission for businesses dealing with essential infrastructure with CloudFormation stacks. Stack drift takes place while the actual configuration of an infrastructure useful resource differs from its anticipated configuration. Typically, this is as a result of users enhancing assets without delay by means of using the underlying carrier that created the resource. Changes that cause stack waft can be accidental, or can be made deliberately to reply to time-touchy operational occasions. For example, you can manually add greater capacity to a DynamoDB desk to reply to accelerated call for. Regardless of the starting place, minimizing stack go with the flow facilitates to make certain configuration consistency and a success stack operations.

When resources are created as a part of a CloudFormation stack, they are created in line with the specifications within the stack template. However, once created, those assets can be edited without delay, inflicting their specification to no longer in shape the specification outlined within the template. For example, an IAM function created in a CloudFormation stack can be modified with extra rules after creation. Although this IAM role continues to be part of the CloudFormation stack (and would be deleted if the CloudFormation stack had been deleted), the specifications of the IAM position now not healthy the ones laid out within the template.

AWS CloudFormation offers a “float detection” feature to mechanically locate unmanaged configuration modifications to stacks and sources. With this feature, AWS CloudFormation analyzes the modern-day specifications of assets in a stack towards the specs described inside the stack template, and reports the difference. To return a useful resource to compliance with the specifications in the stack template, the aid can be edited at once, manually imported into a new stack, or the stack may be destroyed and recreated with new sources.

In this submit, I reveal how your organization that is the use of AWS CloudFormation for undertaking-essential aid control can use a custom AWS Lambda characteristic and Amazon CloudWatch to put into effect automatic glide remediation and return assets created in a CloudFormation stack to compliance with the stack template. Using a custom Lambda feature for remediating stack drift offers a acquainted, automated, scalable, and customizable alternative to manually resolving stack flow.

Prerequisites
To construct the solution mentioned in this put up, you want:

An AWS account
Access to the AWS Management Console with permissions to create assets and control applications
Basic expertise of AWS CloudFormation, AWS Lambda, and Python three.7
Benefits of imposing glide remediation
Implementing automated flow remediation can offer the subsequent advantages:

Simplify stack operations and upkeep competencies: modifications to sources outdoor of AWS CloudFormation can complicate stack operations. Changes also can complicate troubleshooting and replication procedures for complicated resource configurations, as it is tough to realize the precise nation of resources at a given time. Automatically remediating configuration drifts can make sure that sources are usually running consistent with their stack template specs, and stack operations proceed easily.
Reduce danger to sensitive assets: prevent resources that are notably touchy (as an instance, IAM roles, S3 bucket guidelines, safety agencies) from being accidentally changed. This can ensure that all packages stay cozy, and simplify audit and compliance strategies.
Define custom remediation and notification good judgment: the technique used in this record to put into effect drift remediation lets in for the definition of custom code to outline which assets are robotically returned to compliance and which assets can, optionally, continue to be out of compliance. Drift notifications to services together with Amazon SNS can without difficulty be added as properly, if preferred.
For organizations using big groups to operate agile, touchy programs, imposing computerized flow remediation may be a precious addition to make sure that resources stay in compliance with stack templates.

Solution review
The following diagram shows that the high-stage structure you operate to enforce automated glide remediation.

Automatic flow remediation answer architecture
Automatic go with the flow remediation solution architecture

To screen the resources within the CloudFormation stack, you create a Lambda feature this is triggered on a schedule by way of a CloudWatch Events rule. This Lambda function tests if any resource in the stack has drifted, and if so, returns the resource to compliance.

Getting started out
To build the structure defined inside the solution overview, you want a CloudFormation stack to reveal, hit upon configuration go with the flow, and put in force useful resource compliance. The following AWS CloudFormation template defines several resources which are used on this submit to demonstrate implementation of automatic go with the flow remediation:

an IAM position, “AutomaticDriftRemediationRole.” This function includes AWS controlled rules blended with the purchaser controlled regulations described as follows.
A patron-managed IAM coverage, “AutomaticDriftRemediationPolicyOne”. This policy includes study-best access to Amazon S3 and Amazon S3 Glacier.
A consumer managed IAM policy, “AutomaticDriftRemediationPolicyTwo”. This policy consists of required permissions for operating with unique Amazon ECS clusters.
The sources described in this template are not meant to be taken as an example of realistic security policies, but as an alternative for instance of styles of assets that may be used with the automated float remediation patterns defined on this submit.

AWSTemplateFormatVersion: “2010-09-09”
Description: Contains IAM Role and rules to aid glide remediation demo
Resources:
AutomaticDriftRemediationRole:
Type: AWS::IAM::Role
Properties:
RoleName: ‘AutomaticDriftRemediationRole’
Path: /
AssumeRolePolicyDocument:
Version: 2012-10-17
Statement:
– Effect: Allow
Principal:
Service:
– ec2.Amazonaws.Com
Action:
– ‘sts:AssumeRole’
ManagedPolicyArns:
– arn:aws:iam::aws:coverage/AmazonEC2ReadOnlyAccess
– arn:aws:iam::aws:coverage/AmazonDynamoDBReadOnlyAccess
Policies:
– PolicyDocument:
Statement:
– Action:
– s3:Get*
– s3:List*
Effect: Allow
Resource: ‘*’
– Action:
– glacier:DescribeJob
– glacier:DescribeVault
– glacier:GetDataRetrievalPolicy
– glacier:GetJobOutput
– glacier:GetVaultAccessPolicy
– glacier:GetVaultLock
– glacier:GetVaultNotifications
– glacier:ListJobs
– glacier:ListMultipartUploads
– glacier:ListParts
– glacier:ListTagsForVault
– glacier:ListVaults
Effect: Allow
Resource: ‘*’
PolicyName: ‘AutomaticDriftRemediationPolicyOne’
– PolicyDocument:
Statement:
– Action:
– ecs:ListClusters
– ecs:DescribeContainerInstances
Effect: Allow
Resource:
– arn:aws:ecs:us-east-1:<YOUR_AWS_ACCOUNT>:carrier/exampleClusterOne*
– arn:aws:ecs:us-east-1:<YOUR_AWS_ACCOUNT>:provider/exampleClusterTwo*
PolicyName: ‘AutomaticDriftRemediationPolicyTwo’
YAML
To create this CloudFormation stack, down load this template and run the command under after replacing the placeholder values:

<YOUR_AWS_REGION>: AWS place wherein to create sources.
<YOUR_TEMPLATE_LOCATION>: nearby deal with of saved CloudFormation template.
Be certain to configure your AWS CLI with an IAM person that has permissions to create the assets defined inside the template. Refer to dealing with IAM permissions for extra info on creating custom IAM customers and rules.

Aws cloudformation create-stack
–location <YOUR_AWS_REGION>
–competencies CAPABILITY_NAMED_IAM

Bash
This command creates a CloudFormation stack, flow-remediation-demo, that consists of the IAM position and guidelines that we use to test our answer structure.

Sample CloudFormation stack
Sample CloudFormation stack

You must discover that your IAM function has been created and the rules defined within the template had been created and attached.

IAM role created by using CloudFormation stack
IAM function created through CloudFormation stack

Lambda go with the flow remediation a laugh

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