Accessing no-ingress EC2 instances with AWS Systems Manager

A "no-ingress EC2 instance" that's created for an EC2 environment enables AWS Cloud9 to connect to its Amazon EC2 instance without the need to open any inbound ports on that instance. You can select the no-ingress option when creating an EC2 environment using the console, the command line interface, or a AWS CloudFormation stack.

Important

There are no additional charges for using Systems Manager Session Manager to manage connections to your EC2 instance.

When selecting an environment type in the Create environment page of the console, you can choose a new EC2 instance that requires inbound connectivity or a new no-ingress EC2 instance that doesn't require the following:

• New EC2 instance – With this setup, the security group for the instance has a rule to allow incoming networking traffic. Incoming network traffic is restricted to IP addresses approved for AWS Cloud9 connections. An open inbound port enables AWS Cloud9 to connect over SSH to its instance. If you use AWS Systems Manager Session Manager, you can access your Amazon EC2 instance through SSM without opening inbound ports (no ingress). This method is only applicable for new Amazon EC2 instances. For more information, see Benefits of using Systems Manager for EC2 environments.

• Existing compute – With this setup, an existing Amazon EC2 instance is accessed that requires SSH login details that the instance must have an inbound security group rule for. If you select this option, a service role is automatically created. You can view the name of the service role in a note at the bottom of the setup screen.

If creating an environment using the AWS CLI, you can configure a no-ingress EC2 instance by setting the --connection-type CONNECT_SSM option when calling the create-environment-ec2 command. For more information about creating the required service role and instance profile, see Managing instance profiles for Systems Manager with the AWS CLI.

After you complete creating an environment that uses a no-ingress EC2 instance, confirm the following:

• Systems Manager Session Manager has permissions to perform actions on the EC2 instance on your behalf. For more information, see Managing Systems Manager permissions.

• AWS Cloud9 users can access the instance managed by Session Manager. For more information, see Giving users access to instances managed by Session Manager.

Benefits of using Systems Manager for EC2 environments

Allowing Session Manager to handle the secure connection between AWS Cloud9 and its EC2 instance offers two key benefits:

• No requirement to open inbound ports for the instance

• Option to launch the instance into a public or private subnet

No open inbound ports

Secure connections between AWS Cloud9 and its EC2 instance are handled by Session Manager. Session Manager is a fully managed Systems Manager capability that enables AWS Cloud9 to connect to its EC2 instance without the need to open inbound ports.

Important

The option to use Systems Manager for no-ingress connections is currently available only when creating new EC2 environments.

With the start of a Session Manager session, a connection is made to the target instance. With the connection in place, the environment can now interact with the instance through the Systems Manager service. The Systems Manager service communicates with the instance through the Systems Manager Agent (SSM Agent).

By default, SSM Agent is installed on all instances that are used by EC2 environments.

Private/public subnets

When selecting a subnet for your instance in the Network settings (advanced) section, you can select a private or public subnet if the instance for your environment is accessed through Systems Manager.

Private subnets

For a private subnet, ensure that the instance can still connect to the SSM service. This can be done by setting up a NAT gateway in a public subnet or configuring a VPC endpoint for Systems Manager.

The advantage of using the NAT gateway is that it prevents the internet from initiating a connection to the instance in the private subnet. The instance for your environment is assigned a private IP address instead of a public one. So, the NAT gateway forwards traffic from the instance to the internet or other AWS services, and then sends the response back to the instance.

For the VPC option, create at least three required interface endpoints for Systems Manager: com.amazonaws.region.ssm, com.amazonaws.region.ec2messages, and com.amazonaws.region.ssmmessages. For more information, see Creating VPC endpoints for Systems Manager in the AWS Systems Manager User Guide.

Important

Currently, if the EC2 instance for your environment is launched into a private subnet, you can't use AWS managed temporary credentials to allow the EC2 environment to access an AWS service on behalf of an AWS entity (an IAM user, for example).

Public subnets

If your development environment is using SSM to access an EC2 instance, ensure that the instance is assigned a public IP address by the public subnet it's launched into. To do so, you can specify your own IP address or enable the automatic assignment of a public IP address. For the steps involved in modifying auto-assign IP settings, see IP Addressing in your VPC in the Amazon VPC User Guide.

For more information on configuring private and public subnets for your environment instances, see Create a subnet for AWS Cloud9.

Managing Systems Manager permissions

By default, Systems Manager doesn't have permission to perform actions on EC2 instances. Access is provided through an AWS Identity and Access Management (IAM) instance profile. (An instance profile is a container that passes IAM role information to an EC2 instance at launch.)

When you create the no-ingress EC2 instance using the AWS Cloud9 console, both the service role (AWSCloud9SSMAccessRole) and the IAM instance profile (AWSCloud9SSMInstanceProfile) are created automatically for you. (You can view AWSCloud9SSMAccessRole in the IAM Management console. Instance profiles aren't displayed in the IAM console.)

Important

If you create a no-ingress EC2 environment for the first time with AWS CLI, you must explicitly define the required service role and instance profile. For more information, see Managing instance profiles for Systems Manager with the AWS CLI.

For additional security protection, the AWS Cloud9 service-linked role, AWSServiceRoleforAWSCloud9, features a PassRole restriction in its AWSCloud9ServiceRolePolicy policy. When you pass an IAM role to a service, it allows that service to assume the role and perform actions on your behalf. In this case, the PassRole permission ensures that AWS Cloud9 can pass only the AWSCloud9SSMAccessRole role (and its permission) to an EC2 instance. This restricts the actions that can be performed on the EC2 instance to only those required by AWS Cloud9.

Note

If you no longer need to use Systems Manager to access an instance, you can delete the AWSCloud9SSMAccessRole service role. For more information, see Deleting roles or instance profiles in the IAM User Guide.

Managing instance profiles for Systems Manager with the AWS CLI

You can also create a no-ingress EC2 environment with the AWS CLI. When you call create-environment-ec2, set the --connection-type option to CONNECT_SSM.

If you use this option, the AWSCloud9SSMAccessRole service role and AWSCloud9SSMInstanceProfile aren't automatically created. So, to create the required service profile and instance profile, do one of the following:

• Create an EC2 environment using the console once have the AWSCloud9SSMAccessRole service role and AWSCloud9SSMInstanceProfile created automatically afterward. After they're created, the service role and instance profile are available for any additional EC2 Environments created using the AWS CLI.

• Run the following AWS CLI commands to create the service role and instance profile.

  aws iam create-role --role-name AWSCloud9SSMAccessRole --path /service-role/ --assume-role-policy-document '{"Version": "2012-10-17","Statement": [{"Effect": "Allow","Principal": {"Service": ["ec2.amazonaws.com","cloud9.amazonaws.com"]      },"Action": "sts:AssumeRole"}]}'
  aws iam attach-role-policy --role-name AWSCloud9SSMAccessRole --policy-arn arn:aws:iam::aws:policy/AWSCloud9SSMInstanceProfile
  aws iam create-instance-profile --instance-profile-name AWSCloud9SSMInstanceProfile --path /cloud9/
  aws iam add-role-to-instance-profile --instance-profile-name AWSCloud9SSMInstanceProfile --role-name AWSCloud9SSMAccessRole

Giving users access to instances managed by Session Manager

To open an AWS Cloud9 environment that's connected to an EC2 instance through Systems Manager, a user must have permission for the API operation, StartSession. This operation initiates a connection to the managed EC2 instance for a Session Manager session. You can give users access by using an AWS Cloud9 specific managed policy (recommended) or by editing an IAM policy and adding the necessary permissions.

Method	Description
Use AWS Cloud9-specific managed policy	We recommend using AWS managed policies to allow users to access EC2 instances managed by Systems Manager. Managed policies provide a set of permissions for standard AWS Cloud9 use cases and can be easily attached to an IAM entity. All the managed policies also include the permissions to run the StartSession API operation. The following are managed policies specific to AWS Cloud9: AWSCloud9Administrator (arn:aws:iam::aws:policy/AWSCloud9Administrator) AWSCloud9User (arn:aws:iam::aws:policy/AWSCloud9User) AWSCloud9EnvironmentMember (arn:aws:iam::aws:policy/AWSCloud9EnvironmentMember) For more information, see AWS managed policies for AWS Cloud9.
Edit an IAM policy and add required policy statements	To edit an existing policy, you can add permissions for the StartSession API. To edit a policy using the AWS Management Console or AWS CLI, follow the instructions that are provided by Editing IAM policies in the IAM User Guide. When editing the policy, add the policy statement (see the following) that allows the ssm:startSession API operation to run.

You can use the following permissions to run the StartSession API operation. The ssm:resourceTag condition key specifies that a Session Manager session can be started for any instance (Resource: arn:aws:ec2:*:*:instance/*) on the condition that the instance is an AWS Cloud9 EC2 development environment (aws:cloud9:environment).

Note

The following managed policies also include these policy statements: AWSCloud9Administrator, AWSCloud9User, and AWSCloud9EnvironmentMember.

{
            "Effect": "Allow",
            "Action": "ssm:StartSession",
            "Resource": "arn:aws:ec2:*:*:instance/*",
            "Condition": {
                "StringLike": {
                    "ssm:resourceTag/aws:cloud9:environment": "*"
                },
                "StringEquals": {
                    "aws:CalledViaFirst": "cloud9.amazonaws.com"
                }
            }
        },
        {
            "Effect": "Allow",
            "Action": [
                "ssm:StartSession"
            ],
            "Resource": [
                "arn:aws:ssm:*:*:document/*"
            ]
        } 

Using AWS CloudFormation to create no-ingress EC2 environments

When using an AWS CloudFormation template to define a no-ingress Amazon EC2 development environment, do the following before creating the stack:

1. Create the AWSCloud9SSMAccessRole service role and AWSCloud9SSMInstanceProfile instance profile. For more information, see Creating service role and instance profile with an AWS CloudFormation template.

2. Update the policy for the IAM entity calling AWS CloudFormation. This way, the entity can start a Session Manager session that connects to the EC2 instance. For more information, see Adding Systems Manager permissions to an IAM policy.

Creating service role and instance profile with an AWS CloudFormation template

You need to create the service role AWSCloud9SSMAccessRole and the instance profile AWSCloud9SSMInstanceProfile to enable Systems Manager to manage the EC2 instance that backs your development environment.

If you previously created AWSCloud9SSMAccessRole and AWSCloud9SSMInstanceProfile by creating a no-ingress EC2 environment with the console or running AWS CLI commands, the service role and instance profile are already available for use.

Note

Suppose that you attempt to create an AWS CloudFormation stack for a no-ingress EC2 environment but you didn't first create the required service role and instance profile. Then, the stack isn't created and the following error message is displayed:

Instance profile AWSCloud9SSMInstanceProfile does not exist in account.

When creating a no-ingress EC2 environment for the first time using AWS CloudFormation, you can define the AWSCloud9SSMAccessRole and AWSCloud9SSMInstanceProfile as IAM resources in the template.

This excerpt from a sample template shows how to define these resources. The AssumeRole action returns security credentials that provide access to both the AWS Cloud9 environment and its EC2 instance.

AWSTemplateFormatVersion: 2010-09-09
Resources: 
  AWSCloud9SSMAccessRole:
    Type: AWS::IAM::Role
    Properties: 
      AssumeRolePolicyDocument:
        Version: 2012-10-17
        Statement:
          - Effect: Allow
            Principal:
              Service:
              - cloud9.amazonaws.com
              - ec2.amazonaws.com
            Action:
              - 'sts:AssumeRole'
      Description: 'Service linked role for AWS Cloud9'
      Path: '/service-role/'
      ManagedPolicyArns: 
        - arn:aws:iam::aws:policy/AWSCloud9SSMInstanceProfile
      RoleName: 'AWSCloud9SSMAccessRole'

  AWSCloud9SSMInstanceProfile:
    Type: "AWS::IAM::InstanceProfile"
    Properties: 
      InstanceProfileName: AWSCloud9SSMInstanceProfile
      Path: "/cloud9/"
      Roles: 
        - 
          Ref: AWSCloud9SSMAccessRole
 

Adding Systems Manager permissions to an IAM policy

After defining a service role and instance profile in the AWS CloudFormation template, ensure that the IAM entity creating the stack has permission to start a Session Manager session. A session is a connection made to the EC2 instance using Session Manager.

Note

If you don't add permissions to start a Session Manager session before creating a stack for a no-ingress EC2 environment, an AccessDeniedException error is returned.

Add the following permissions to the policy for the IAM entity by calling AWS CloudFormation.

{
            "Effect": "Allow",
            "Action": "ssm:StartSession",
            "Resource": "arn:aws:ec2:*:*:instance/*",
            "Condition": {
                "StringLike": {
                    "ssm:resourceTag/aws:cloud9:environment": "*"
                },
                "StringEquals": {
                    "aws:CalledViaFirst": "cloudformation.amazonaws.com"
                }
            }
        },
        {
            "Effect": "Allow",
            "Action": [
                "ssm:StartSession"
            ],
            "Resource": [
                "arn:aws:ssm:*:*:document/*"
            ]
        } 

Configuring VPC endpoints for Amazon S3 to download dependencies

If your AWS Cloud9 environment’s EC2 instance doesn't have access to the internet, create a VPC endpoint for a specified Amazon S3 bucket. This bucket contains the dependencies that are required to keep your IDE up-to-date.

Setting up a VPC endpoint for Amazon S3 also involves customizing the access policy. You want the access policy to allow access to only the trusted S3 bucket that contains the dependencies to be downloaded.

Note

You can create and configure VPC endpoints using the AWS Management Console, AWS CLI, or Amazon VPC API. The following procedure shows how to create a VPC endpoint by using the console interface.

Create and configure a VPC endpoint for Amazon S3

1. In the AWS Management Console, go to the console page for Amazon VPC.

2. Choose Endpoints in the navigation bar.

3. In the Endpoints page, choose Create Endpoint.

4. In the Create Endpoint page, enter "s3" in the search field and press Return to list available endpoints for Amazon S3 in the current AWS Region.

5. From the list of returned Amazon S3 endpoints, select the Gateway type.

6. Next, choose the VPC that contains your environment's EC2 instance.

7. Now choose the VPC's route table. This way, the associated subnets can access the endpoint. Your environment's EC2 instance is in one of these subnets.

8. In the Policy section, choose the Custom option, and replace the standard policy with the following.

   {
     "Version": "2008-10-17",
     "Statement": [
         {
             "Sid": "Access-to-C9-bucket-only",
             "Effect": "Allow",
             "Principal": "*",
             "Action": "s3:GetObject",
             "Resource": "arn:aws:s3:::{bucket_name}/content/dependencies/*"
         }
     ]
   }

   For the Resource element, replace {bucket_name} with the actual name of the bucket that's available in your AWS Region. For example, if you're using AWS Cloud9 in the Europe (Ireland) Region, you specify the following: "Resource": "arn:aws:s3:::static-eu-west-1-prod-static-hld3vzaf7c4h/content/dependencies/.

   The following table lists the bucket names for the AWS Regions where AWS Cloud9 is available.

   Amazon S3 buckets in AWS Cloud9 Regions
   AWS Region	Bucket name
   US East (Ohio)	static-us-east-2-prod-static-1c3sfcvf9hy4m
   US East (N. Virginia)	static-us-east-1-prod-static-mft1klnkc4hl
   US West (Oregon)	static-us-west-2-prod-static-p21mksqx9zlr
   US West (N. California)	static-us-west-1-prod-static-16d59zrrp01z0
   Africa (Cape Town)	static-af-south-1-prod-static-v6v7i5ypdppv
   Asia Pacific (Hong Kong)	static-ap-east-1-prod-static-171xhpfkrorh6
   Asia Pacific (Mumbai)	static-ap-south-1-prod-static-ykocre202i9d
   Asia Pacific (Osaka)	static-ap-northeast-3-prod-static-ivmxqzrx2ioi
   Asia Pacific (Seoul)	static-ap-northeast-2-prod-static-1wxyctlhwiajm
   Asia Pacific (Singapore)	static-ap-southeast-1-prod-static-13ibpyrx4vk6d
   Asia Pacific (Sydney)	static-ap-southeast-2-prod-static-1cjsl8bx27rfu
   Asia Pacific (Tokyo)	static-ap-northeast-1-prod-static-4fwvbdisquj8
   Canada (Central)	static-ca-central-1-prod-static-g80lpejy486c
   Europe (Frankfurt)	static-eu-central-1-prod-static-14lbgls2vrkh
   Europe (Ireland)	static-eu-west-1-prod-static-hld3vzaf7c4h
   Europe (London)	static-eu-west-2-prod-static-36lbg202837x
   Europe (Milan)	static-eu-south-1-prod-static-1379tzkd3ni7d
   Europe (Paris)	static-eu-west-3-prod-static-1rwpkf766ke58
   Europe (Stockholm)	static-eu-north-1-prod-static-1qzw982y7yu7e
   Middle East (Bahrain)	static-me-south-1-prod-static-gmljex38qtqx
   South America (São Paulo)	static-sa-east-1-prod-static-1cl8k0y7opidt

9. Choose Create Endpoint.

   If you provided the correct configuration information, a message displays the ID of the endpoint that's created.

10. To check that your IDE can access the Amazon S3 bucket, start a terminal session by choosing Window, New Terminal on the menu bar. Then run the following command, replacing {bucket_name} with the actual name of the bucket for your Region.

    ping {bucket_name}.s3.{region}.amazonaws.com.

    For example, if you created an endpoint for an S3 bucket in the US East (N. Virginia) Region, run the following command.

    ping static-us-east-1-prod-static-mft1klnkc4hl.s3.us-east-1.amazonaws.com

    If the ping gets a response, this confirms that your IDE can access the bucket and its dependencies.

For more information about this feature, see Endpoints for Amazon S3 in the AWS PrivateLink Guide.

Configuring VPC endpoints for private connectivity

When you launch an instance into a subnet with the access using Systems Manager option, its security group doesn't have an inbound rule to allow incoming network traffic. But, the security group has an outbound rule that permits outbound traffic from the instance. This is required to download packages and libraries required to keep the AWS Cloud9 IDE up to date.

To prevent outbound and inbound traffic for the instance, create and configure Amazon VPC endpoints for Systems Manager. With an interface VPC endpoint (interface endpoint), you can connect to services powered by AWS PrivateLink. AWS PrivateLink is a technology that can be used to privately access Amazon EC2 and Systems Manager APIs by using private IP addresses. To configure VPC endpoints to use Systems Manager, follow the instructions provided by this Knowledge Center resource.

Warning

Assume that you configure a security group that doesn't permit inbound or outbound networking traffic. Then, the EC2 instance that supports your AWS Cloud9 IDE doesn't have internet access. You need to create an Amazon S3 endpoint for your VPC to allow access to the dependencies that are contained in a trusted S3 bucket. In addition, some AWS services, such as AWS Lambda, might not work as intended without internet access.

With AWS PrivateLink, there are data processing charges for each gigabyte processed through the VPC endpoint. This is regardless of the traffic’s source or destination. For more information, see AWS PrivateLink pricing.