When you audit an environment governed by AWS Control Tower, having visibility into the AWS Control Tower console allows you to collect important configuration information, but currently there isn’t a read-only role installed by AWS Control Tower. In this post, I will show you how to create a custom permission set by using both a managed AWS policy and a custom permissions policy. This custom permission set will allow you to get the visibility you need, while still enforcing the principle of least privilege. You will have access to the read-only information you need, without asking your administrator to provide the attestation.
AWS Control Tower sets up AWS Single Sign-On (AWS SSO) with a native default directory. AWS Control Tower comes with a set of preconfigured permission sets available out-of-the-box. A permission set is a collection of administrator-defined policies that AWS SSO uses to determine a user’s effective permissions to access a specific AWS account. Permission sets can contain an AWS inline policy and you can also attach AWS managed policies. When you assign a permission set to a user or group in an account, AWS SSO creates an IAM role in the AWS account, configures the inline and AWS managed policies, and creates the trust policies that allow the assigned users to assume the role through AWS SSO.
To create a custom permission set for AWS Control Tower
Log into your AWS Control Tower environment as an administrator.
Choose the AWS Single Sign-On service, then choose AWS accounts.
On the AWS Accounts pane, choose the Permission sets tab, then choose Create permission set, as shown in the following figure.
Figure 1: Permission sets tab in the SSO console
Select Create a custom permission set and enter a name in the Name field (in this example, I named mine Audit-enhanced), then enter text in the Description field, as shown in figure 2.
Figure 2: AWS Single Sign-On console – Create new permission set workflow
Choose a value for Session duration (in this example I set the duration to 1 hour). Optionally, you can set a relay state (in this example, I left it blank), and select both Attach AWS managed policies and Create a custom permissions policy, as shown in the following figure.
Figure 3: AWS Single Sign-On console – Setting additional permission set configurations
In the Attach AWS Managed policies dashboard, in the search bar, enter audit and select the SecurityAudit managed policy, as shown in figure 4.
This policy grants the following read-level permissions: Get, List, Describe API actions. This is the additional set of permissions necessary to enhance the SecurityAudit role, so that you can gain visibility into the AWS Control Tower console.
Scroll down to the Create a custom permissions policy dashboard, paste the policy you previously copied into the field, as shown in figure 5, then choose Create.
Figure 5: AWS Single Sign-On console – Entering JSON code for custom permission policy
Now, when you go to the Permission sets tab, you should see your newly created custom permission set.
To assign the newly created permission set access to your AWS Control Tower master account
On the AWS organization tab, select the box for your AWS Control Tower master account (in this example, the account newControlTower), then choose Assign users, as shown in figure 6.
On the Users tab, select your user (in this example, CT Tester) as shown in figure 7, and choose Next: Permission sets.
Figure 7: AWS Single Sign-On console – Users tab – Assigning access to your user
Select the box next to the custom permission set you created earlier (in this example, Audit-enhanced), and choose Finish, as shown in figure 8.
Figure 8: AWS Single Sign-On console – Select permission sets
You should see a Complete page, and the newControlTower account will show Status as Complete, as shown in figure 9.
Figure 9: AWS Single Sign-On console – Successful completion of permission set assignment
You now have a permission set that enhances your SecurityAuditor role and gives you read-only visibility into your AWS Control Tower environment.
Summary
In this post, we’ve detailed how to enhance an “audit-like” role to incorporate additional permissions by using a custom permission set in AWS SSO, while enforcing the principle of least privilege to gain read-only capabilities into the AWS Control Tower console.
For more information on the technologies mentioned in this post, see the following links:
To keep pace with AWS innovation, many customers allow their application teams to experiment with AWS services in sandbox environments as they move toward production-ready architecture. These teams need timely access to various sets of AWS services and resources, which means they also need a mechanism to help ensure least privilege is granted. In other words, your application team generally shouldn’t have access to administrative resources, such as an AWS Lambda function that takes periodic Amazon Elastic Block Store snapshot backups, or an Amazon CloudWatch Events rule that sends events to a centralized information security account managed by your security team.
In this blog post, I’ll show you how to create a centralized and automated workflow that creates and validates AWS Identity and Access Management (IAM) policies for application teams working in various sandbox, development, and test environments. Your security developers can customize this workflow according to the specific requirements of your security team. They can create logic to limit the allowed permission sets based on account type or owning team. I’ll use AWS CodePipeline to create and manage a workflow containing various stages and spanning multiple AWS accounts that I’ll describe in more detail in the next section.
Solution overview
I’ll start with this scenario: Alice is an administrator for an AWS sandbox account used by her organization’s data scientists to try out AWS analytics services such as Amazon Athena and Amazon EMR. The data scientists assess the suitability of these services for their production use cases by running sample analytics jobs on portions of real data sets after any sensitive information has been taken out. The data sets are stored in an existing Amazon Simple Storage Service (Amazon S3) bucket. For every new project, Alice authors a new IAM policy that allows the project team to access their requested Amazon S3 bucket and create their analytics clusters. However, Alice must follow a company guideline that sandbox accounts can only launch specific Amazon Elastic Compute Cloud (Amazon EC2) instance types. She must also restrict access to all administrative AWS Lambda functions and CloudWatch Events rules that the security team use to monitor sandbox account compliance. Below is the solution that meets these requirements and makes it easier for Alice and other administrators to perform their tasks.
Figure 1: Solution architecture
Alice uses the IAM visual editor to author a template that gives the data science team access to launch and manage EMR clusters that analyze S3-based data sets. She then uploads the IAM JSON policy document into an existing S3 bucket using an AWS Key Management Service (AWS KMS) key. The key and the S3 bucket are already created by the security team as part of account baselining, which I will detail later in this post.
AWS CodePipeline automatically fetches the IAM JSON policy document and invokes a sequence of validation checks that use a single and central Lambda function hosted in an AWS account managed by the security team.
If the IAM JSON policy adheres to all account and general security requirements coded by the security developers, the central Lambda function automatically creates the policy in Alice’s account and the pipeline will succeed. The central validation Lambda function will also attach a set of predefined explicit denies to the IAM policy to ensure that it limits undesired user capabilities in the sandbox account. If the IAM JSON policy fails the checks, the pipeline will fail and provide Alice the specific reason for non-compliance. Alice must then modify the policy and resubmit. When the policy has been successfully created, Alice will attach it to the right IAM user, group, or role.
As this solution manages permissions granted to AWS services or IAM entities, I highly recommend that you try the solution first in an isolated test environment to make sure it meets all your security requirements.
You’ll need administrator access in two AWS accounts to set up the solution. The deployment of this solution is typically done by one of your organization’s administrators while setting up new AWS accounts. These are the two account types you’ll need access to:
A sandbox account. This lets application teams experiment with various AWS architectures. This could be a development or test account, as mentioned earlier.
A central information security account. Typically, this is owned by an information security team who monitors and enforces security compliance within a multi-account structure.
Important: Because the Lambda function that you’ll create in the information security account has highly privileged permissions, it’s important to strictly follow best practices for securing the account. You need to limit account access to security team members. Sandbox account administrators should also not give this central Lambda function any IAM permissions in their sandbox account beyond IAM Policy creation.
Because you’ll use the AWS Management Console for both AWS accounts, I strongly recommended that you have roles in both AWS accounts and use the console’s Switch Role feature. You can attach an alias to each account and give each a different color code so that you always know which one you’re logged into.
Make sure to use the same AWS region for all the resources that you create for this solution.
Step 1: Deploy the solution prerequisites
Before building the pipeline across the two AWS accounts, you must first configure the required resources in both accounts, such as IAM roles and encryption keys. This configuration is typically done according to your security team’s guidelines when your organization first sets up the sandbox, development, or test environment.
Important
In addition to the initial setup you’ll create in this section, your security team must explicitly deny sandbox, development, or test account administrators from attaching IAM Policies that do not meet the allowed security policies for that account type, such as the AdministratorAccess IAM policy. Moreover, your security team must ensure any current or future users, groups, or roles in the account have no permissions to directly set or update IAM policies like (for example) CreatePolicy, CreatePolicyVersion, PutRolePolicy, PutUserPolicy, PutGroupPolicy, or UpdateAssumeRolePolicy. You want to ensure that creating permissions can only be done through the automation pipeline, which I’ll show you how to build shortly.
Because the solution I’ll be describing focuses on the creation of least privilege permissions, it’s highly advisable that your security team combines the solution with IAM permission boundaries to make sure that any permissions defined in this solution are scoped by a set of pre-defined permissions for every type of account in the organization. For example, your account administrators might only be allowed to create IAM users or roles with a pre-defined set of permission boundaries that limit the permissions attached to those principals. For more information about permission boundaries, please refer to this AWS Security blog post.
Create the sandbox account prerequisites
Follow the steps below to deploy an AWS CloudFormation template that will create the following resources in the sandbox account:
An S3 bucket where your sandbox administrators will upload IAM policies
An IAM role that your automated pipeline will use to access the S3 bucket that stores the IAM policies
An AWS KMS key that you will use to encrypt the IAM policies in your S3 bucket
Figure 2: CloudFormation console with prepopulated URL
Select Next and, optionally, provide a name for your stack. A suggested stack name, Sandbox-Prerequisites, should already be populated.
The template defines an input parameter called CentralAccount that you can populate with the AWS account ID of your security account. For more information on how to find the account ID of your security account, check here.
Select Next, and then select Next again.
To have the stack create the IAM roles that your pipeline will use, select the check box that says I acknowledge that AWS CloudFormation might create IAM resources with custom names, and then select Create Stack.
Select the Stack info tab and refresh periodically while watching the Stack Status field value. After your stack reaches the state CREATE_COMPLETE, navigate to the CloudFormation Outputs tab and copy the following output values to the text editor of your choice. You’ll use these values in subsequent CloudFormation stacks.
Figure 3: CloudFormation Outputs tab
Create the information security account prerequisites
Follow the steps below to deploy a CloudFormation template that will create the following resources in your information security account:
An IAM role used by your automated pipeline to invoke your central Lambda function and to provide access to the sandbox account KMS key
An IAM role used by the central Lambda function to assume a role in the sandbox account and manage IAM policies
Select Next and, optionally, provide a name for your stack. A suggested stack name, Sandbox-Prerequisites, should already be populated.
Populate the following input parameter fields:
SandboxAccount: The AWS account ID for the sandbox account.
ArtifactBucket: The bucket name that you noted in your text editor from the previous stack run in the sandbox account
CMKARN: The Amazon Resource Name (ARN) of the KMS key that you noted in your text editor from the previous stack run in the sandbox account
PolicyCheckerFunctionName: The name of the Lambda function to be created later. The default value is PolicyChecker
Select Next, and then select Next again.
To have the stack create the IAM roles used by your pipeline, select the box that reads I acknowledge that AWS CloudFormation might create IAM resources with custom names, and then select Create Stack.
Wait for your stack until it reaches the state CREATE_COMPLETE.
Create the sandbox account pipeline
Now, switch back to your sandbox account and deploy the CloudFormation template that will create the following resources in the sandbox account:
An AWS CodePipeline automation pipeline that fetches the IAM policy document from S3 and sends it to the security account for centralized validation. If valid, a Lambda function in the information security account will also create the IAM policy in the sandbox account.
An S3 bucket policy to allow your central Lambda function to fetch the IAM policy JSON document from your bucket
An IAM role that will be assumed by the Lambda function in the central information security account and used to create IAM policies in the sandbox account. Sandbox account administrator can then attach those IAM policies to the required entities, like an IAM user or role.
Click Next and, optionally, provide a name for your stack. A suggested stack name, Sandbox-Pipeline, should already be populated.
Populate the following input parameter fields:
CentralAccount: The AWS account ID of the information security account, without hyphens.
ArtifactBucket: The same bucket name that you noted in your text editor earlier and used in the previous stack in the information security account.
CMKARN: The ARN of the KMS key that you noted in your text editor earlier and used in the previous stack in the information security account.
PolicyCheckerFunctionName: Again, the name of the Lambda function to be created later. It must be the same value you provided to the information security account template.
Select Next, and then select Next again.
To have the stack create the required IAM roles, select the box that reads I acknowledge that AWS CloudFormation might create IAM resources with custom names, and then select Create Stack.
Wait for your stack until it reaches the state CREATE_COMPLETE.
Step 2: Set up the policy validation Lambda function in the central information security account
In the central information security account, create the Lambda function to validate the IAM policies created in sandbox environment.
In the AWS Lambda console, select Create Function and then select Author from scratch. Provide values for the following fields:
Name. This must be the same function name defined as input parameter PolicyCheckerFunctionName to CloudFormation in step 1, when you set up the information security account prerequisites. If you did not change the default value in step 1, the default is still PolicyChecker.
Runtime. Python 2.7.
Role. To set the role, select Choose an existing role, and then select the role named policy-checker-lambda-role. This is the role you created in step 1, when you set up the information security account prerequisites.
Choose Create Function, scroll down to Function Code, and then paste the following code into the editor (replacing the existing code):
# Copyright 2017 Amazon.com, Inc. or its affiliates. All Rights Reserved.
# Licensed under the Apache License, Version 2.0 (the "License"). You may not
# use this file except in compliance with
# the License. A copy of the License is located at
# http://aws.amazon.com/apache2.0/
# or in the "license" file accompanying this file. This file is distributed
# on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
# either express or implied. See the License for the
# specific language governing permissions and
# limitations under the License.
from __future__ import print_function
import json
import boto3
import zipfile
import tempfile
import os
print('Loading function')
PERMISSIVE_ERROR_MSG = """Policy creation request rejected: * permissions not
allowed in both actions and resources"""
GENERAL_ERROR_MSG = """An error has occurred while validating policy.
Please contact admin"""
def get_template(event, s3, artifact, file_in_zip):
tmp_file = tempfile.NamedTemporaryFile()
bucket = event['CodePipeline.job']['data']['inputArtifacts'][0]['location']['s3Location']['bucketName']
key = event['CodePipeline.job']['data']['inputArtifacts'][0]['location']['s3Location']['objectKey']
with tempfile.NamedTemporaryFile() as tmp_file:
s3.download_file(bucket, key, tmp_file.name)
with zipfile.ZipFile(tmp_file.name, 'r') as zip:
return zip.read(file_in_zip)
def get_sts_session(event, account, rolename):
sts = boto3.client("sts")
RoleArn = str("arn:aws:iam::" + account + ":role/" + rolename)
response = sts.assume_role(
RoleArn=RoleArn,
RoleSessionName='SecurityManageAccountPermissions',
DurationSeconds=900)
sts_session = boto3.Session(
aws_access_key_id=response['Credentials']['AccessKeyId'],
aws_secret_access_key=response['Credentials']['SecretAccessKey'],
aws_session_token=response['Credentials']['SessionToken'],
region_name=os.environ['AWS_REGION'],
botocore_session=None,
profile_name=None)
return (sts_session)
def ManagePolicy(event, context):
# Set boto session to get pipeline artifact from sandbox/dev/test account
artifact_session = boto3.Session(
aws_access_key_id=event['CodePipeline.job']['data']
['artifactCredentials']['accessKeyId'],
aws_secret_access_key=event['CodePipeline.job']['data']
['artifactCredentials']['secretAccessKey'],
aws_session_token=event['CodePipeline.job']['data']
['artifactCredentials']['sessionToken'],
region_name=os.environ['AWS_REGION'],
botocore_session=None,
profile_name=None)
# Fetch pipeline artifact from S3
s3 = artifact_session.client('s3')
permission_doc = get_template(event, s3, '', 'policy.json')
metadata_doc = json.loads(get_template(event, s3, '', 'metadata.json'))
permission_doc_json = json.loads(permission_doc)
# Assume the central account role in sandbox/dev/test account
global STS_SESSION
STS_SESSION = ''
STS_SESSION = get_sts_session(
event, event['CodePipeline.job']['accountId'], 'central-account-role')
iam = STS_SESSION.client('iam')
codepipeline = STS_SESSION.client('codepipeline')
policy_arn = 'arn:aws:iam::' + event['CodePipeline.job']['accountId'] + ':policy/' + metadata_doc['PolicyName']
try:
# 1.Sample code - Validate policy sent from sandbox/dev/test account:
# look for * actions and * resources
for statement in permission_doc_json['Statement']:
if statement['Action'] == '*' and statement['Resource'] == '*':
return codepipeline.put_job_failure_result(
jobId=event['CodePipeline.job']['id'],
failureDetails={
'type': 'JobFailed',
'message': PERMISSIVE_ERROR_MSG})
# 2.Sample code - Attach any required denies from central
# pre-defined policy
iam_local = boto3.client('iam')
account_id = context.invoked_function_arn.split(":")[4]
local_policy_arn = 'arn:aws:iam::' + account_id + ':policy/central-deny-policy-sandbox'
policy_response = iam_local.get_policy(PolicyArn=local_policy_arn)
policy_version_id = policy_response['Policy']['DefaultVersionId']
policy_version_doc = iam_local.get_policy_version(
PolicyArn=local_policy_arn,
VersionId=policy_version_id)
for statement in policy_version_doc['PolicyVersion']['Document']['Statement']:
permission_doc_json['Statement'].append(
statement
)
# 3. If validated successfully, create policy in
# sandbox/dev/test account
iam.create_policy(
PolicyName=metadata_doc['PolicyName'],
PolicyDocument=json.dumps(permission_doc_json),
Description=metadata_doc['PolicyDescription'])
# successful creation, put result back to
# sandbox/dev/test account pipeline
codepipeline.put_job_success_result(
jobId=event['CodePipeline.job']['id'])
except Exception as e:
print('Error: ' + str(e))
codepipeline.put_job_failure_result(
jobId=event['CodePipeline.job']['id'],
failureDetails={'type': 'JobFailed', 'message': GENERAL_ERROR_MSG})
def lambda_handler(event, context):
print(event)
ManagePolicy(event, context)
This sample code shows how the Lambda function checks the IAM JSON policy submitted by Alice for policies that are too permissive because they allow all IAM actions on all account resources. The sample code also shows an IAM Deny action that prevents the launch of Amazon EC2 instances that are not part of the T2 EC2 instance family. An explicit deny here ensures that only T2 instances can be launched. Your security developers should author code similar to this sample code, in order to meet the security policies of every account type and control the IAM policies created in various sandbox, development, and test environments.
Before saving your new Lambda function code, scroll further down to the Basic Settings section and increase the function timeout to 10 seconds.
Select Save.
Step 3: Test the sandbox account pipeline
Now it’s time to deploy the solution in your sandbox account.
Create the following files and compress them into an archive with the name policy.zip (this is the name expected by your created pipeline).
metadata.json: This file contains metadata like the name and description of the IAM policy to be created.
To upload your policy.zip file to the bucket you created earlier, go to the Amazon S3 console in the sandbox account and, in the search box at the top of the page, search for the bucket you noted in your text editor earlier as ArtifactBucket.
When you locate your bucket, select the bucket name, and then select Upload. The upload dialog will appear.
Select Add Files and navigate to the folder with the policy.zip file. Select the file, select Open, select Next, and then select Next again.
Figure 4: S3 upload dialog
Select the AWS KMS master-key radio button, and then select the KMS key that has the alias codepipeline-policy-crossaccounts.
Figure 5: Selecting the KMS key
Select Next, and then select Upload.
Go to AWS CodePipeline console, select your sandbox pipeline, and wait for the pipeline to start running. It can take up to a minute for it to start.
Figure 6: AWS CodePipeline console
Wait for your pipeline to complete. There should be no validation errors for the IAM policy you just uploaded and your IAM policy should be successfully created. To view the newly created IAM policy, open the AWS IAM console.
Select Policies on the left and search for the policy with the name defined in the metadata.json file.
Figure 7: Viewing your new policy
Select the policy name. Note the IAM deny that was automatically added to your defined policy.
If you’d like to test the pipeline further, you can modify the policy to permit all actions on all resources. When policy.zip is uploaded again, the pipeline should return the following error:
Policy creation request rejected: * permissions not allowed in both actions and resources
If you encounter any errors as you modify your Lambda function code, you can always go back to the Lambda function logs in the central information security account. For more information on how to access Lambda function logs, please refer to the documentation.
The same logic used here can be extended to other sandbox, development, or test environments. However, for the central information security account, the existing roles will need to be updated to trust and have access to the resources in the newly added sandbox, development, or test account.
Summary
In this blog post, I showed you how to centralize the validation and creation of IAM policies across various AWS accounts. This allows your security developers to start coding your security best practices; permitting automatic creation and validation of IAM policies across your various sandbox, development, and test accounts. Account administrators can then attach those validated IAM policies to the required IAM users, groups or roles. This process strikes the balance between agility and control. It empowers your account administrators to create compliant and least-privilege permission IAM policies, while also allowing your application teams to keep quickly experimenting and innovating. If you have feedback about this blog post, submit comments in the Comments section below.
Want more AWS Security how-to content, news, and feature announcements? Follow us on Twitter.
Previously, I showed you how to rotate Amazon RDS database credentials automatically with AWS Secrets Manager. In addition to database credentials, AWS Secrets Manager makes it easier to rotate, manage, and retrieve API keys, OAuth tokens, and other secrets throughout their lifecycle. You can configure Secrets Manager to rotate these secrets automatically, which can help you meet your compliance needs. You can also use Secrets Manager to rotate secrets on demand, which can help you respond quickly to security events. In this post, I show you how to store an API key in Secrets Manager and use a custom Lambda function to rotate the key automatically. I’ll use a Twitter API key and bearer token as an example; you can reference this example to rotate other types of API keys.
The instructions are divided into four main phases:
Store a Twitter API key and bearer token in Secrets Manager.
Create a custom Lambda function to rotate the bearer token.
Configure your application to retrieve the bearer token from Secrets Manager.
Configure Secrets Manager to use the custom Lambda function to rotate the bearer token automatically.
For the purpose of this post, I use the placeholder Demo/Twitter_Api_Key to denote the API key, the placeholder Demo/Twitter_bearer_token to denote the bearer token, and placeholder Lambda_Rotate_Bearer_Token to denote the custom Lambda function. Be sure to replace these placeholders with the resource names from your account.
Phase 1: Store a Twitter API key and bearer token in Secrets Manager
Twitter enables developers to register their applications and retrieve an API key, which includes a consumer_key and consumer_secret. Developers use these to generate a bearer token that applications can then use to authenticate and retrieve information from Twitter. At any given point of time, you can use an API key to create only one valid bearer token.
Start by storing the API key in Secrets Manager. Here’s how:
Figure 1: The “Store a new secret” button in the AWS Secrets Manager console
Select Other type of secrets (because you’re storing an API key).
Input the consumer_key and consumer_secret, and then select Next.
Figure 2: Select the consumer_key and the consumer_secret
Specify values for Secret Name and Description, then select Next. For this example, I use Demo/Twitter_API_Key.
Figure 3: Set values for “Secret Name” and “Description”
On the next screen, keep the default setting, Disable automatic rotation, because you’ll use the same API key to rotate bearer tokens programmatically and automatically. Applications and employees will not retrieve this API key. Select Next.
Figure 4: Keep the default “Disable automatic rotation” setting
Review the information on the next screen and, if everything looks correct, select Store. You’ve now successfully stored a Twitter API key in Secrets Manager.
Next, store the bearer token in Secrets Manager. Here’s how:
From the Secrets Manager console, select Store a new secret, select Other type of secrets, input details (access_token, token_type, and ARN of the API key) about the bearer token, and then select Next.
Figure 5: Add details about the bearer token
Specify values for Secret Name and Description, and then select Next. For this example, I use Demo/Twitter_bearer_token.
Figure 6: Again set values for “Secret Name” and “Description”
Keep the default rotation setting, Disable automatic rotation, and then select Next. You’ll enable rotation after you’ve updated the application to use Secrets Manager APIs to retrieve secrets.
Review the information and select Store. You’ve now completed storing the bearer token in Secrets Manager. I take note of the sample code provided on the review page. I’ll use this code to update my application to retrieve the bearer token using Secrets Manager APIs.
Figure 7: The sample code you can use in your app
Phase 2: Create a custom Lambda function to rotate the bearer token
While Secrets Manager supports rotating credentials for databases hosted on Amazon RDS natively, it also enables you to meet your unique rotation-related use cases by authoring custom Lambda functions. Now that you’ve stored the API key and bearer token, you’ll create a Lambda function to rotate the bearer token. For this example, I’ll create my Lambda function using Python 3.6.
Figure 8: In the Lambda console, select “Create function”
Select Author from scratch. For this example, I use the name Lambda_Rotate_Bearer_Token for my Lambda function. I also set the Runtime environment as Python 3.6.
Figure 9: Create a new function from scratch
This Lambda function requires permissions to call AWS resources on your behalf. To grant these permissions, select Create a custom role. This opens a console tab.
Select Create a new IAM Role and specify the value for Role Name. For this example, I use Role_Lambda_Rotate_Twitter_Bearer_Token.
Figure 10: For “IAM Role,” select “Create a new IAM role”
Next, to define the IAM permissions, copy and paste the following IAM policy in the View Policy Document text-entry field. Be sure to replace the placeholder ARN-OF-Demo/Twitter_API_Key with the ARN of your secret.
Figure 11: The IAM policy pasted in the “View Policy Document” text-entry field
Now, select Allow. This brings me back to the Lambda console with the appropriate Role selected.
Select Create function.
Figure 12: Select the “Create function” button in the lower-right corner
Copy the following Python code and paste it in the Function code section.
import base64
import json
import logging
import os
import boto3
from botocore.vendored import requests
logger = logging.getLogger()
logger.setLevel(logging.INFO)
def lambda_handler(event, context):
"""Secrets Manager Twitter Bearer Token Handler
This handler uses the master-user rotation scheme to rotate a bearer token of a Twitter app.
The Secret PlaintextString is expected to be a JSON string with the following format:
{
'access_token': ,
'token_type': ,
'masterarn':
}
Args:
event (dict): Lambda dictionary of event parameters. These keys must include the following:
- SecretId: The secret ARN or identifier
- ClientRequestToken: The ClientRequestToken of the secret version
- Step: The rotation step (one of createSecret, setSecret, testSecret, or finishSecret)
context (LambdaContext): The Lambda runtime information
Raises:
ResourceNotFoundException: If the secret with the specified arn and stage does not exist
ValueError: If the secret is not properly configured for rotation
KeyError: If the secret json does not contain the expected keys
"""
arn = event['SecretId']
token = event['ClientRequestToken']
step = event['Step']
# Setup the client and environment variables
service_client = boto3.client('secretsmanager', endpoint_url=os.environ['SECRETS_MANAGER_ENDPOINT'])
oauth2_token_url = os.environ['TWITTER_OAUTH2_TOKEN_URL']
oauth2_invalid_token_url = os.environ['TWITTER_OAUTH2_INVALID_TOKEN_URL']
tweet_search_url = os.environ['TWITTER_SEARCH_URL']
# Make sure the version is staged correctly
metadata = service_client.describe_secret(SecretId=arn)
if not metadata['RotationEnabled']:
logger.error("Secret %s is not enabled for rotation" % arn)
raise ValueError("Secret %s is not enabled for rotation" % arn)
versions = metadata['VersionIdsToStages']
if token not in versions:
logger.error("Secret version %s has no stage for rotation of secret %s." % (token, arn))
raise ValueError("Secret version %s has no stage for rotation of secret %s." % (token, arn))
if "AWSCURRENT" in versions[token]:
logger.info("Secret version %s already set as AWSCURRENT for secret %s." % (token, arn))
return
elif "AWSPENDING" not in versions[token]:
logger.error("Secret version %s not set as AWSPENDING for rotation of secret %s." % (token, arn))
raise ValueError("Secret version %s not set as AWSPENDING for rotation of secret %s." % (token, arn))
# Call the appropriate step
if step == "createSecret":
create_secret(service_client, arn, token, oauth2_token_url, oauth2_invalid_token_url)
elif step == "setSecret":
set_secret(service_client, arn, token, oauth2_token_url)
elif step == "testSecret":
test_secret(service_client, arn, token, tweet_search_url)
elif step == "finishSecret":
finish_secret(service_client, arn, token)
else:
logger.error("lambda_handler: Invalid step parameter %s for secret %s" % (step, arn))
raise ValueError("Invalid step parameter %s for secret %s" % (step, arn))
def create_secret(service_client, arn, token, oauth2_token_url, oauth2_invalid_token_url):
"""Get a new bearer token from Twitter
This method invalidates existing bearer token for the Twitter app and retrieves a new one from Twitter.
If a secret version with AWSPENDING stage exists, updates it with the newly retrieved bearer token and if
the AWSPENDING stage does not exist, creates a new version of the secret with that stage label.
Args:
service_client (client): The secrets manager service client
arn (string): The secret ARN or other identifier
token (string): The ClientRequestToken associated with the secret version
oauth2_token_url (string): The Twitter API endpoint to request a bearer token
oauth2_invalid_token_url (string): The Twitter API endpoint to invalidate a bearer token
Raises:
ValueError: If the current secret is not valid JSON
KeyError: If the secret json does not contain the expected keys
ResourceNotFoundException: If the current secret is not found
"""
# Make sure the current secret exists and try to get the master arn from the secret
try:
current_secret_dict = get_secret_dict(service_client, arn, "AWSCURRENT")
master_arn = current_secret_dict['masterarn']
logger.info("createSecret: Successfully retrieved secret for %s." % arn)
except service_client.exceptions.ResourceNotFoundException:
return
# create bearer token credentials to be passed as authorization string to Twitter
bearer_token_credentials = encode_credentials(service_client, master_arn, "AWSCURRENT")
# get the bearer token from Twitter
bearer_token_from_twitter = get_bearer_token(bearer_token_credentials,oauth2_token_url)
# invalidate the current bearer token
invalidate_bearer_token(oauth2_invalid_token_url,bearer_token_credentials,bearer_token_from_twitter)
# get a new bearer token from Twitter
new_bearer_token = get_bearer_token(bearer_token_credentials, oauth2_token_url)
# if a secret version with AWSPENDING stage exists, update it with the lastest bearer token
# if the AWSPENDING stage does not exist, then create the version with AWSPENDING stage
try:
pending_secret_dict = get_secret_dict(service_client, arn, "AWSPENDING", token)
pending_secret_dict['access_token'] = new_bearer_token
service_client.put_secret_value(SecretId=arn, ClientRequestToken=token, SecretString=json.dumps(pending_secret_dict), VersionStages=['AWSPENDING'])
logger.info("createSecret: Successfully invalidated the bearer token of the secret %s and updated the pending version" % arn)
except service_client.exceptions.ResourceNotFoundException:
current_secret_dict['access_token'] = new_bearer_token
service_client.put_secret_value(SecretId=arn, ClientRequestToken=token, SecretString=json.dumps(current_secret_dict), VersionStages=['AWSPENDING'])
logger.info("createSecret: Successfully invalidated the bearer token of the secret %s and and created the pending version." % arn)
def set_secret(service_client, arn, token, oauth2_token_url):
"""Validate the pending secret with that in Twitter
This method checks wether the bearer token in Twitter is the same as the one in the version with AWSPENDING stage.
Args:
service_client (client): The secrets manager service client
arn (string): The secret ARN or other identifier
token (string): The ClientRequestToken associated with the secret version
oauth2_token_url (string): The Twitter API endopoint to get a bearer token
Raises:
ResourceNotFoundException: If the secret with the specified arn and stage does not exist
ValueError: If the secret is not valid JSON or master credentials could not be used to login to DB
KeyError: If the secret json does not contain the expected keys
"""
# First get the pending version of the bearer token and compare it with that in Twitter
pending_secret_dict = get_secret_dict(service_client, arn, "AWSPENDING")
master_arn = pending_secret_dict['masterarn']
# create bearer token credentials to be passed as authorization string to Twitter
bearer_token_credentials = encode_credentials(service_client, master_arn, "AWSCURRENT")
# get the bearer token from Twitter
bearer_token_from_twitter = get_bearer_token(bearer_token_credentials, oauth2_token_url)
# if the bearer tokens are same, invalidate the bearer token in Twitter
# if not, raise an exception that bearer token in Twitter was changed outside Secrets Manager
if pending_secret_dict['access_token'] == bearer_token_from_twitter:
logger.info("createSecret: Successfully verified the bearer token of arn %s" % arn)
else:
raise ValueError("The bearer token of the Twitter app was changed outside Secrets Manager. Please check.")
def test_secret(service_client, arn, token, tweet_search_url):
"""Test the pending secret by calling a Twitter API
This method tries to use the bearer token in the secret version with AWSPENDING stage and search for tweets
with 'aws secrets manager' string.
Args:
service_client (client): The secrets manager service client
arn (string): The secret ARN or other identifier
token (string): The ClientRequestToken associated with the secret version
Raises:
ResourceNotFoundException: If the secret with the specified arn and stage does not exist
ValueError: If the secret is not valid JSON or pending credentials could not be used to login to the database
KeyError: If the secret json does not contain the expected keys
"""
# First get the pending version of the bearer token and compare it with that in Twitter
pending_secret_dict = get_secret_dict(service_client, arn, "AWSPENDING", token)
# Now verify you can search for tweets using the bearer token
if verify_bearer_token(pending_secret_dict['access_token'], tweet_search_url):
logger.info("testSecret: Successfully authorized with the pending secret in %s." % arn)
return
else:
logger.error("testSecret: Unable to authorize with the pending secret of secret ARN %s" % arn)
raise ValueError("Unable to connect to Twitter with pending secret of secret ARN %s" % arn)
def finish_secret(service_client, arn, token):
"""Finish the rotation by marking the pending secret as current
This method moves the secret from the AWSPENDING stage to the AWSCURRENT stage.
Args:
service_client (client): The secrets manager service client
arn (string): The secret ARN or other identifier
token (string): The ClientRequestToken associated with the secret version
Raises:
ResourceNotFoundException: If the secret with the specified arn and stage does not exist
"""
# First describe the secret to get the current version
metadata = service_client.describe_secret(SecretId=arn)
current_version = None
for version in metadata["VersionIdsToStages"]:
if "AWSCURRENT" in metadata["VersionIdsToStages"][version]:
if version == token:
# The correct version is already marked as current, return
logger.info("finishSecret: Version %s already marked as AWSCURRENT for %s" % (version, arn))
return
current_version = version
break
# Finalize by staging the secret version current
service_client.update_secret_version_stage(SecretId=arn, VersionStage="AWSCURRENT", MoveToVersionId=token, RemoveFromVersionId=current_version)
logger.info("finishSecret: Successfully set AWSCURRENT stage to version %s for secret %s." % (version, arn))
def encode_credentials(service_client, arn, stage):
"""Encodes the Twitter credentials
This helper function encodes the Twitter credentials (consumer_key and consumer_secret)
Args:
service_client (client):The secrets manager service client
arn (string): The secret ARN or other identifier
stage (stage): The stage identifying the secret version
Returns:
encoded_credentials (string): base64 encoded authorization string for Twitter
Raises:
KeyError: If the secret json does not contain the expected keys
"""
required_fields = ['consumer_key','consumer_secret']
master_secret_dict = get_secret_dict(service_client, arn, stage)
for field in required_fields:
if field not in master_secret_dict:
raise KeyError("%s key is missing from the secret JSON" % field)
encoded_credentials = base64.urlsafe_b64encode(
'{}:{}'.format(master_secret_dict['consumer_key'], master_secret_dict['consumer_secret']).encode('ascii')).decode('ascii')
return encoded_credentials
def get_bearer_token(encoded_credentials, oauth2_token_url):
"""Gets a bearer token from Twitter
This helper function retrieves the current bearer token from Twitter, given a set of credentials.
Args:
encoded_credentials (string): Twitter credentials for authentication
oauth2_token_url (string): REST API endpoint to request a bearer token from Twitter
Raises:
KeyError: If the secret json does not contain the expected keys
"""
headers = {
'Authorization': 'Basic {}'.format(encoded_credentials),
'Content-Type': 'application/x-www-form-urlencoded;charset=UTF-8',
}
data = 'grant_type=client_credentials'
response = requests.post(oauth2_token_url, headers=headers, data=data)
response_data = response.json()
if response_data['token_type'] == 'bearer':
bearer_token = response_data['access_token']
return bearer_token
else:
raise RuntimeError('unexpected token type: {}'.format(response_data['token_type']))
def invalidate_bearer_token(oauth2_invalid_token_url, bearer_token_credentials, bearer_token):
"""Invalidates a Bearer Token of a Twitter App
This helper function invalidates a bearer token of a Twitter app.
If successful, it returns the invalidated bearer token, else None
Args:
oauth2_invalid_token_url (string): The Twitter API endpoint to invalidate a bearer token
bearer_token_credentials (string): encoded consumer key and consumer secret to authenticate with Twitter
bearer_token (string): The bearer token to be invalidated
Returns:
invalidated_bearer_token: The invalidated bearer token
Raises:
ResourceNotFoundException: If the secret with the specified arn and stage does not exist
ValueError: If the secret is not valid JSON
KeyError: If the secret json does not contain the expected keys
"""
headers = {
'Authorization': 'Basic {}'.format(bearer_token_credentials),
'Content-Type': 'application/x-www-form-urlencoded;charset=UTF-8',
}
data = 'access_token=' + bearer_token
invalidate_response = requests.post(oauth2_invalid_token_url, headers=headers, data=data)
invalidate_response_data = invalidate_response.json()
if invalidate_response_data:
return
else:
raise RuntimeError('Invalidate bearer token request failed')
def verify_bearer_token(bearer_token, tweet_search_url):
"""Verifies access to Twitter APIs using a bearer token
This helper function verifies that the bearer token is valid by calling Twitter's search/tweets API endpoint
Args:
bearer_token (string): The current bearer token for the application
Returns:
True or False
Raises:
KeyError: If the response of search tweets API call fails
"""
headers = {
'Authorization' : 'Bearer {}'.format(bearer_token),
'Content-Type': 'application/x-www-form-urlencoded;charset=UTF-8',
}
search_results = requests.get(tweet_search_url, headers=headers)
try:
search_results.json()['statuses']
return True
except:
return False
def get_secret_dict(service_client, arn, stage, token=None):
"""Gets the secret dictionary corresponding for the secret arn, stage, and token
This helper function gets credentials for the arn and stage passed in and returns the dictionary by parsing the JSON string
Args:
service_client (client): The secrets manager service client
arn (string): The secret ARN or other identifier
token (string): The ClientRequestToken associated with the secret version, or None if no validation is desired
stage (string): The stage identifying the secret version
Returns:
SecretDictionary: Secret dictionary
Raises:
ResourceNotFoundException: If the secret with the specified arn and stage does not exist
ValueError: If the secret is not valid JSON
"""
# Only do VersionId validation against the stage if a token is passed in
if token:
secret = service_client.get_secret_value(SecretId=arn, VersionId=token, VersionStage=stage)
else:
secret = service_client.get_secret_value(SecretId=arn, VersionStage=stage)
plaintext = secret['SecretString']
# Parse and return the secret JSON string
return json.loads(plaintext)
Here’s what it will look like:
Figure 13: The Python code pasted in the “Function code” section
On the same page, provide the following environment variables:
Note: Resources used in this example are in US East (Ohio) region. If you intend to use another AWS Region, change the SECRETS_MANAGER_ENDPOINT set in the Environment variables to the appropriate region.
You’ve now created a Lambda function that can rotate the bearer token:
Figure 15: The new Lambda function
Before you can configure Secrets Manager to use this Lambda function, you need to update the function policy of the Lambda function. A function policy permits AWS services, such as Secrets Manager, to invoke a Lambda function on behalf of your application. You can attach a Lambda function policy from the AWS Command Line Interface (AWS CLI) or SDK. To attach a function policy, call the add-permission Lambda API from the AWS CLI.
Phase 3: Configure your application to retrieve the bearer token from Secrets Manager
Now that you’ve stored the bearer token in Secrets Manager, update the application to retrieve the bearer token from Secrets Manager instead of hard-coding this information in a configuration file or source code. For this example, I show you how to configure a Python application to retrieve this secret from Secrets Manager.
import config
def no_secrets_manager_sample()
# Get the bearer token from a config file.
Bearer_token = config.bearer_token
# Use the bearer token to authenticate requests to Twitter
Use the sample code from section titled Phase 1 and update the application to retrieve the bearer token from Secrets Manager. The following code sets up the client and retrieves and decrypts the secret Demo/Twitter_bearer_token.
# Use this code snippet in your app.
import boto3
from botocore.exceptions import ClientError
def get_secret():
secret_name = "Demo/Twitter_bearer_token"
endpoint_url = "https://secretsmanager.us-east-2.amazonaws.com"
region_name = "us-east-2"
session = boto3.session.Session()
client = session.client(
service_name='secretsmanager',
region_name=region_name,
endpoint_url=endpoint_url
)
try:
get_secret_value_response = client.get_secret_value(
SecretId=secret_name
)
except ClientError as e:
if e.response['Error']['Code'] == 'ResourceNotFoundException':
print("The requested secret " + secret_name + " was not found")
elif e.response['Error']['Code'] == 'InvalidRequestException':
print("The request was invalid due to:", e)
elif e.response['Error']['Code'] == 'InvalidParameterException':
print("The request had invalid params:", e)
else:
# Decrypted secret using the associated KMS CMK
# Depending on whether the secret was a string or binary, one of these fields will be populated
if 'SecretString' in get_secret_value_response:
secret = get_secret_value_response['SecretString']
else:
binary_secret_data = get_secret_value_response['SecretBinary']
# Your code goes here.
Applications require permissions to access Secrets Manager. My application runs on Amazon EC2 and uses an IAM role to get access to AWS services. I’ll attach the following policy to my IAM role, and you should take a similar action with your IAM role. This policy uses the GetSecretValue action to grant my application permissions to read secrets from Secrets Manager. This policy also uses the resource element to limit my application to read only the Demo/Twitter_bearer_token secret from Secrets Manager. Read the AWS Secrets Manager documentation to understand the minimum IAM permissions required to retrieve a secret.
{
"Version": "2012-10-17",
"Statement": {
"Sid": "RetrieveBearerToken",
"Effect": "Allow",
"Action": "secretsmanager:GetSecretValue",
"Resource": Input ARN of the secret Demo/Twitter_bearer_token here
}
}
Note: To improve the resiliency of your applications, associate your application with two API keys/bearer tokens. This is a higher availability option because you can continue to use one bearer token while Secrets Manager rotates the other token. Read the AWS documentation to learn how AWS Secrets Manager rotates your secrets.
Phase 4: Enable and verify rotation
Now that you’ve stored the secret in Secrets Manager and created a Lambda function to rotate this secret, configure Secrets Manager to rotate the secret Demo/Twitter_bearer_token.
From the Secrets Manager console, go to the list of secrets and choose the secret you created in the first step (in my example, this is named Demo/Twitter_bearer_token).
Scroll to Rotation configuration, and then select Edit rotation.
Figure 16: Select the “Edit rotation” button
To enable rotation, select Enable automatic rotation, and then choose how frequently you want Secrets Manager to rotate this secret. For this example, I set the rotation interval to 30 days. I also choose the rotation Lambda function, Lambda_Rotate_Bearer_Token, from the drop-down list.
Figure 17: “Edit rotation configuration” options
The banner on the next screen confirms that I have successfully configured rotation and the first rotation is in progress, which enables you to verify that rotation is functioning as expected. Secrets Manager will rotate this credential automatically every 30 days.
Figure 18: Confirmation notice
Summary
In this post, I showed you how to configure Secrets Manager to manage and rotate an API key and bearer token used by applications to authenticate and retrieve information from Twitter. You can use the steps described in this blog to manage and rotate other API keys, as well.
Secrets Manager helps you protect access to your applications, services, and IT resources without the upfront investment and on-going maintenance costs of operating your own secrets management infrastructure. To get started, open the Secrets Manager console. To learn more, read the Secrets Manager documentation.
If you have comments about this post, submit them in the Comments section below. If you have questions about anything in this post, start a new thread on the Secrets Manager forum or contact AWS Support.
Want more AWS Security news? Follow us on Twitter.
AWS Identity and Access Management (IAM) now makes it easier for you to control access to your AWS resources by using the AWS organization of IAM principals (users and roles). For some services, you grant permissions using resource-based policies to specify the accounts and principals that can access the resource and what actions they can perform on it. Now, you can use a new condition key, aws:PrincipalOrgID, in these policies to require all principals accessing the resource to be from an account in the organization. For example, let’s say you have an Amazon S3 bucket policy and you want to restrict access to only principals from AWS accounts inside of your organization. To accomplish this, you can define the aws:PrincipalOrgID condition and set the value to your organization ID in the bucket policy. Your organization ID is what sets the access control on the S3 bucket. Additionally, when you use this condition, policy permissions apply when you add new accounts to this organization without requiring an update to the policy.
In this post, I walk through the details of the new condition and show you how to restrict access to only principals in your organization using S3.
Condition concepts
Before I introduce the new condition, let’s review the condition element of an IAM policy. A condition is an optional IAM policy element you can use to specify special circumstances under which the policy grants or denies permission. A condition includes a condition key, operator, and value for the condition. There are two types of conditions: service-specific conditions and global conditions. Service-specific conditions are specific to certain actions in an AWS service. For example, the condition key ec2:InstanceType supports specific EC2 actions. Global conditions support all actions across all AWS services.
Now that I’ve reviewed the condition element in an IAM policy, let me introduce the new condition.
AWS:PrincipalOrgID Condition Key
You can use this condition key to apply a filter to the Principal element of a resource-based policy. You can use any string operator, such as StringLike, with this condition and specify the AWS organization ID for as its value.
Condition key
Description
Operator(s)
Value
aws:PrincipalOrgID
Validates if the principal accessing the resource belongs to an account in your organization.
Example: Restrict access to only principals from my organization
Let’s consider an example where I want to give specific IAM principals in my organization direct access to my S3 bucket, 2018-Financial-Data, that contains sensitive financial information. I have two accounts in my AWS organization with multiple account IDs, and only some IAM users from these accounts need access to this financial report.
To grant this access, I author a resource-based policy for my S3 bucket as shown below. In this policy, I list the individuals who I want to grant access. For the sake of this example, let’s say that while doing so, I accidentally specify an incorrect account ID. This means a user named Steve, who is not in an account in my organization, can now access my financial report. To require the principal account to be in my organization, I add a condition to my policy using the global condition key aws:PrincipalOrgID. This condition requires that only principals from accounts in my organization can access the S3 bucket. This means that although Steve is one of the principals in the policy, he can’t access the financial report because the account that he is a member of doesn’t belong to my organization.
In the policy above, I specify the principals that I grant access to using the principal element of the statement. Next, I add s3:GetObject as the action and 2018-Financial-Data/* as the resource to grant read access to my S3 bucket. Finally, I add the new condition key aws:PrincipalOrgID and specify my organization ID in the condition element of the statement to make sure only the principals from the accounts in my organization can access this bucket.
Summary
You can now use the aws:PrincipalOrgID condition key in your resource-based policies to more easily restrict access to IAM principals from accounts in your AWS organization. For more information about this global condition key and policy examples using aws:PrincipalOrgID, read the IAM documentation.
If you have comments about this post, submit them in the Comments section below. If you have questions about or suggestions for this solution, start a new thread on the IAM forum or contact AWS Support.
Want more AWS Security news? Follow us on Twitter.
Thanks to Susan Ferrell, Senior Technical Writer, for a great blog post on how to use CodeCommit branch-level permissions. —-
AWS CodeCommit users have been asking for a way to restrict commits to some repository branches to just a few people. In this blog post, we’re going to show you how to do that by creating and applying a conditional policy, an AWS Identity and Access Management (IAM) policy that contains a context key.
Why would I do this?
When you create a branch in an AWS CodeCommit repository, the branch is available, by default, to all repository users. Here are some scenarios in which refining access might help you:
You maintain a branch in a repository for production-ready code, and you don’t want to allow changes to this branch except from a select group of people.
You want to limit the number of people who can make changes to the default branch in a repository.
You want to ensure that pull requests cannot be merged to a branch except by an approved group of developers.
We’ll show you how to create a policy in IAM that prevents users from pushing commits to and merging pull requests to a branch named master. You’ll attach that policy to one group or role in IAM, and then test how users in that group are affected when that policy is applied. We’ll explain how it works, so you can create custom policies for your repositories.
What you need to get started
You’ll need to sign in to AWS with sufficient permissions to:
Create and apply policies in IAM.
Create groups in IAM.
Add users to those groups.
Apply policies to those groups.
You can use existing IAM groups, but because you’re going to be changing permissions, you might want to first test this out on groups and users you’ve created specifically for this purpose.
You’ll need a repository in AWS CodeCommit with at least two branches: master and test-branch. For information about how to create repositories, see Create a Repository. For information about how to create branches, see Create a Branch. In this blog post, we’ve named the repository MyDemoRepo. You can use an existing repository with branches of another name, if you prefer.
Let’s get started!
Create two groups in IAM
We’re going to set up two groups in IAM: Developers and Senior_Developers. To start, both groups will have the same managed policy, AWSCodeCommitPowerUsers, applied. Users in each group will have exactly the same permissions to perform actions in IAM.
Figure 1: Two example groups in IAM, with distinct users but the same managed policy applied to each group
In the navigation pane, choose Groups, and then choose Create New Group.
In the Group Name box, type Developers, and then choose Next Step.
In the list of policies, select the check box for AWSCodeCommitPowerUsers, then choose Next Step.
Choose Create Group.
Now, follow these steps to create the Senior_Developers group and attach the AWSCodeCommitPowerUsers managed policy. You now have two empty groups with the same policy attached.
Create users in IAM
Next, add at least one unique user to each group. You can use existing IAM users, but because you’ll be affecting their access to AWS CodeCommit, you might want to create two users just for testing purposes. Let’s go ahead and create Arnav and Mary.
In the navigation pane, choose Users, and then choose Add user.
For the new user, type Arnav_Desai.
Choose Add another user, and then type Mary_Major.
Select the type of access (programmatic access, access to the AWS Management Console, or both). In this blog post, we’ll be testing everything from the console, but if you want to test AWS CodeCommit using the AWS CLI, make sure you include programmatic access and console access.
For Console password type, choose Custom password. Each user is assigned the password that you type in the box. Write these down so you don’t forget them. You’ll need to sign in to the console using each of these accounts.
Choose Next: Permissions.
On the Set permissions page, choose Add user to group. Add Arnav to the Developers group. Add Mary to the Senior_Developers group.
Choose Next: Review to see all of the choices you made up to this point. When you are ready to proceed, choose Create user.
Sign in as Arnav, and then follow these steps to go to the master branch and add a file. Then sign in as Mary and follow the same steps.
On the Dashboard page, from the list of repositories, choose MyDemoRepo.
In the Code view, choose the branch named master.
Choose Add file, and then choose Create file. Type some text or code in the editor.
Provide information to other users about who added this file to the repository and why.
In Author name, type the name of the user (Arnav or Mary).
In Email address, type an email address so that other repository users can contact you about this change.
In Commit message, type a brief description to help you remember why you added this file or any other details you might find helpful.
Type a name for the file.
Choose Commit file.
Now follow the same steps to add a file in a different branch. (In our example repository, that’s the branch named test-branch.) You should be able to add a file to both branches regardless of whether you’re signed in as Arnav or Mary.
Let’s change that.
Create a conditional policy in IAM
You’re going to create a policy in IAM that will deny API actions if certain conditions are met. We want to prevent users with this policy applied from updating a branch named master, but we don’t want to prevent them from viewing the branch, cloning the repository, or creating pull requests that will merge to that branch. For this reason, we want to pick and choose our APIs carefully. Looking at the Permissions Reference, the logical permissions for this are:
GitPush
PutFile
MergePullRequestByFastForward
Now’s the time to think about what else you might want this policy to do. For example, because we don’t want users with this policy to make changes to this branch, we probably don’t want them to be able to delete it either, right? So let’s add one more permission:
DeleteBranch
The branch in which we want to deny these actions is master. The repository in which the branch resides is MyDemoRepo. We’re going to need more than just the repository name, though. We need the repository ARN. Fortunately, that’s easy to find. Just go to the AWS CodeCommit console, choose the repository, and choose Settings. The repository ARN is displayed on the General tab.
Now we’re ready to create a policy. 1. Open the IAM console at https://console.aws.amazon.com/iam/. Make sure you’re signed in with the account that has sufficient permissions to create policies, and not as Arnav or Mary. 2. In the navigation pane, choose Policies, and then choose Create policy. 3. Choose JSON, and then paste in the following:
You’ll notice a few things here. First, change the repository ARN to the ARN for your repository and include the repository name. Second, if you want to restrict access to a branch with a name different from our example, master, change that reference too.
Now let’s talk about this policy and what it does. You might be wondering why we’re using a Git reference (refs/heads) value instead of just the branch name. The answer lies in how Git references things, and how AWS CodeCommit, as a Git-based repository service, implements its APIs. A branch in Git is a simple pointer (reference) to the SHA-1 value of the head commit for that branch.
You might also be wondering about the second part of the condition, the nullification language. This is necessary because of the way git push and git-receive-pack work. Without going into too many technical details, when you attempt to push a change from a local repo to AWS CodeCommit, an initial reference call is made to AWS CodeCommit without any branch information. AWS CodeCommit evaluates that initial call to ensure that:
a) You’re authorized to make calls.
b) A repository exists with the name specified in the initial call. If you left that null out of the policy, users with that policy would be unable to complete any pushes from their local repos to the AWS CodeCommit remote repository at all, regardless of which branch they were trying to push their commits to.
Could you write a policy in such a way that the null is not required? Of course. IAM policy language is flexible. There’s an example of how to do this in the AWS CodeCommit User Guide, if you’re curious. But for the purposes of this blog post, let’s continue with this policy as written.
So what have we essentially said in this policy? We’ve asked IAM to deny the relevant CodeCommit permissions if the request is made to the resource MyDemoRepo and it meets the following condition: the reference is to refs/heads/master. Otherwise, the deny does not apply.
I’m sure you’re wondering if this policy has to be constrained to a specific repository resource like MyDemoRepo. After all, it would be awfully convenient if a single policy could apply to all branches in any repository in an AWS account, particularly since the default branch in any repository is initially the master branch. Good news! Simply replace the ARN with an *, and your policy will affect ALL branches named master in every AWS CodeCommit repository in your AWS account. Make sure that this is really what you want, though. We suggest you start by limiting the scope to just one repository, and then changing things when you’ve tested it and are happy with how it works.
When you’re sure you’ve modified the policy for your environment, choose Review policy to validate it. Give this policy a name, such as DenyChangesToMaster, provide a description of its purpose, and then choose Create policy.
Now that you have a policy, it’s time to apply and test it.
Apply the policy to a group
In theory, you could apply the policy you just created directly to any IAM user, but that really doesn’t scale well. You should apply this policy to a group, if you use IAM groups to manage users, or to a role, if your users assume a role when interacting with AWS resources.
In the IAM console, choose Groups, and then choose Developers.
On the Permissions tab, choose Attach Policy.
Choose DenyChangesToMaster, and then choose Attach policy.
Your groups now have a critical difference: users in the Developers group have an additional policy applied that restricts their actions in the master branch. In other words, Mary can continue to add files, push commits, and merge pull requests in the master branch, but Arnav cannot.
Figure 2: Two example groups in IAM, one with an additional policy applied that will prevent users in this group from making changes to the master branch
Test it out. Sign in as Arnav, and do the following:
On the Dashboard page, from the list of repositories, choose MyDemoRepo.
In the Code view, choose the branch named master.
Choose Add file, and then choose Create file, just as you did before. Provide some text, and then add the file name and your user information.
Choose Commit file.
This time you’ll see an error after choosing Commit file. It’s not a pretty message, but at the very end, you’ll see a telling phrase: “explicit deny”. That’s the policy in action. You, as Arnav, are explicitly denied PutFile, which prevents you from adding a file to the master branch. You’ll see similar results if you try other actions denied by that policy, such as deleting the master branch.
Stay signed in as Arnav, but this time add a file to test-branch. You should be able to add a file without seeing any errors. You can create a branch based on the master branch, add a file to it, and create a pull request that will merge to the master branch, all just as before. However, you cannot perform denied actions on that master branch.
Sign out as Arnav and sign in as Mary. You’ll see that as that IAM user, you can add and edit files in the master branch, merge pull requests to it, and even, although we don’t recommend this, delete it.
Conclusion
You can use conditional statements in policies in IAM to refine how users interact with your AWS CodeCommit repositories. This blog post showed how to use such a policy to prevent users from making changes to a branch named master. There are many other options. We hope this blog post will encourage you to experiment with AWS CodeCommit, IAM policies, and permissions. If you have any questions or suggestions, we’d love to hear from you.
We made it easier for you to comply with regulatory standards by controlling access to AWS Regions using IAM policies. For example, if your company requires users to create resources in a specific AWS region, you can now add a new condition to the IAM policies you attach to your IAM principal (user or role) to enforce this for all AWS services. In this post, I review conditions in policies, introduce the new condition, and review a policy example to demonstrate how you can control access across multiple AWS services to a specific region.
Condition concepts
Before I introduce the new condition, let’s review the condition element of an IAM policy. A condition is an optional IAM policy element that lets you specify special circumstances under which the policy grants or denies permission. A condition includes a condition key, operator, and value for the condition. There are two types of conditions: service-specific conditions and global conditions. Service-specific conditions are specific to certain actions in an AWS service. For example, the condition key ec2:InstanceType supports specific EC2 actions. Global conditions support all actions across all AWS services.
Now that I’ve reviewed the condition element in an IAM policy, let me introduce the new condition.
AWS:RequestedRegion condition key
The new global condition key, , supports all actions across all AWS services. You can use any string operator and specify any AWS region for its value.
Condition key
Description
Operator(s)
Value
aws:RequestedRegion
Allows you to specify the region to which the IAM principal (user or role) can make API calls
I’ll now demonstrate the use of the new global condition key.
Example: Policy with region-level control
Let’s say a group of software developers in my organization is working on a project using Amazon EC2 and Amazon RDS. The project requires a web server running on an EC2 instance using Amazon Linux and a MySQL database instance in RDS. The developers also want to test Amazon Lambda, an event-driven platform, to retrieve data from the MySQL DB instance in RDS for future use.
My organization requires all the AWS resources to remain in the Frankfurt, eu-central-1, region. To make sure this project follows these guidelines, I create a single IAM policy for all the AWS services that this group is going to use and apply the new global condition key aws:RequestedRegion for all the services. This way I can ensure that any new EC2 instances launched or any database instances created using RDS are in Frankfurt. This policy also ensures that any Lambda functions this group creates for testing are also in the Frankfurt region.
The first statement in the above example contains all the read-only actions that let my developers use the console for EC2, RDS, and Lambda. The permissions for IAM-related actions are required to launch EC2 instances with a role, enable enhanced monitoring in RDS, and for AWS Lambda to assume the IAM execution role to execute the Lambda function. I’ve combined all the read-only actions into a single statement for simplicity. The second statement is where I give write access to my developers for the three services and restrict the write access to the Frankfurt region using the aws:RequestedRegion condition key. You can also list multiple AWS regions with the new condition key if your developers are allowed to create resources in multiple regions. The third statement grants permissions for the IAM action iam:PassRole required by AWS Lambda. For more information on allowing users to create a Lambda function, see Using Identity-Based Policies for AWS Lambda.
Summary
You can now use the aws:RequestedRegion global condition key in your IAM policies to specify the region to which the IAM principal (user or role) can invoke an API call. This capability makes it easier for you to restrict the AWS regions your IAM principals can use to comply with regulatory standards and improve account security. For more information about this global condition key and policy examples using aws:RequestedRegion, see the IAM documentation.
If you have comments about this post, submit them in the Comments section below. If you have questions about or suggestions for this solution, start a new thread on the IAM forum.
Want more AWS Security news? Follow us on Twitter.
This post courtesy of Paul Johnston, AWS Senior Developer Advocate – Serverless
Welcome to the first edition of the AWS Serverless ICYMI (In case you missed it) quarterly recap! Every quarter we’ll share all of the most recent product launches, feature enhancements, blog posts, webinars, Twitch live streams, and other interesting things that you might have missed!
Alexa Random Restaurant – Python-based backend for an Alexa skill that returns an open restaurant in a specified city using the Yelp API. Published by: Harsha Warrdhan Sharma
Podless – A serverless application that downloads podcasts to an S3 bucket. Published by: Stilvoid
Crypto-monitor – Collect and store crypto currency prices and send yourself an alert if one changes significantly. Published by: Drew Dresser
DailyDoggo – Send a daily link to a random dog picture to a phone number, via AWS Lambda and SNS. Published by: Kevin McCandless
These runtimes give Lambda developers and development teams even greater options for coding serverless, on-demand, compute solutions.
The AWS SAM 1.4.0 release was one of its biggest. The release added features for configuring many aspects of Amazon API Gateway, including CORS support, regional endpoints, binary media types, and stage settings. It also included per function concurrency support, tags and TableName for SimpleTable, and many documentation updates. Check out the release notes for the full list!
AppSync came out of the whitelisted preview and added a whole bunch of new features:
Here are the three webinars we delivered in Q1. We hold several Serverless webinars throughout the year, so look out for them in the Serverless section of the AWS Online Tech Talks page:
Keep an eye on AWS on Twitch for more Serverless videos and on the Join us on the Twitch AWS page for information about upcoming broadcasts and recent live streams.
Case studies
We’ve published several new case studies this quarter to help you with understanding how other organizations are using serverless technologies:
If you haven’t read the AWS Well Architected Framework Serverless Application Lens document, then it’s worth taking the time to do so. The document covers common serverless applications scenarios and identifies key elements to ensure that your workloads are architected according to best practices.
From now on, if you find issues with documentation we have open-sourced, you can tell us via a Pull Request rather than tweeting or emailing us. The current available serverless repositories are here:
We’re always looking to help people start learning how to build serverless applications. Our serverless web application workshops are online and you can do the hands-on labs yourself: Build a Serverless web application
Still looking for more?
The Serverless landing page has lots of information including a resources page containing case studies, webinars, whitepapers, customer stories, reference architectures, and even more Getting Started tutorials. Check it out!
This post was contributed by Christoph Kassen, AWS Solutions Architect
With the emergence of microservices architectures, the number of services that are part of a web application has increased a lot. It’s not unusual anymore to build and operate hundreds of separate microservices, all as part of the same application.
Think of a typical e-commerce application that displays products, recommends related items, provides search and faceting capabilities, and maintains a shopping cart. Behind the scenes, many more services are involved, such as clickstream tracking, ad display, targeting, and logging. When handling a single user request, many of these microservices are involved in responding. Understanding, analyzing, and debugging the landscape is becoming complex.
AWS X-Ray provides application-tracing functionality, giving deep insights into all microservices deployed. With X-Ray, every request can be traced as it flows through the involved microservices. This provides your DevOps teams the insights they need to understand how your services interact with their peers and enables them to analyze and debug issues much faster.
With microservices architectures, every service should be self-contained and use the technologies best suited for the problem domain. Depending on how the service is built, it is deployed and hosted differently.
One of the most popular choices for packaging and deploying microservices at the moment is containers. The application and its dependencies are clearly defined, the container can be built on CI infrastructure, and the deployment is simplified greatly. Container schedulers, such as Kubernetes and Amazon Elastic Container Service (Amazon ECS), greatly simplify deploying and running containers at scale.
Running X-Ray on Kubernetes
Kubernetes is an open-source container management platform that automates deployment, scaling, and management of containerized applications.
This post shows you how to run X-Ray on top of Kubernetes to provide application tracing capabilities to services hosted on a Kubernetes cluster. Additionally, X-Ray also works for applications hosted on Amazon ECS, AWS Elastic Beanstalk, Amazon EC2, and even when building services with AWS Lambda functions. This flexibility helps you pick the technology you need while still being able to trace requests through all of the services running within your AWS environment.
The complete code, including a simple Node.js based demo application is available in the corresponding aws-xray-kubernetes GitHub repository, so you can quickly get started with X-Ray.
The sample application within the repository consists of two simple microservices, Service-A and Service-B. The following architecture diagram shows how each service is deployed with two Pods on the Kubernetes cluster:
Requests are sent to the Service-A from clients.
Service-A then contacts Service-B.
The requests are serviced by Service-B.
Service-B adds a random delay to each request to show different response times in X-Ray.
To test out the sample applications on your own Kubernetes cluster use the Dockerfiles provided in the GitHub repository, build the two containers, push them to a container registry and apply the yaml configuration with kubectl to your Kubernetes cluster.
Prerequisites
If you currently do not have a cluster running within your AWS environment, take a look at Amazon Elastic Container Service for Kubernetes (Amazon EKS), or use the instructions from the Manage Kubernetes Clusters on AWS Using Kops blog post to spin up a self-managed Kubernetes cluster.
Security Setup for X-Ray
The nodes in the Kubernetes cluster hosting web application Pods need IAM permissions so that the Pods hosting the X-Ray daemon can send traces to the X-Ray service backend.
The easiest way is to set up a new IAM policy allowing all worker nodes within your Kubernetes cluster to write data to X-Ray. In the IAM console or AWS CLI, create a new policy like the following:
Adjust the AWS account ID within the resource. Give the policy a descriptive name, such as k8s-nodes-XrayWriteAccess.
Next, attach the policy to the instance profile for the Kubernetes worker nodes. Therefore, select the IAM role assigned to your worker instances (check the EC2 console if you are unsure) and attach the IAM policy created earlier to it. You can attach the IAM permissions directly from the command line with the following command:
aws iam attach-role-policy --role-name k8s-nodes --policy-arn arn:aws:iam::000000000000:policy/k8s-nodes-XrayWriteAccess
Build the X-Ray daemon Docker image
The X-Ray daemon is available as a single, statically compiled binary that can be downloaded directly from the AWS website.
The first step is to create a Docker container hosting the X-Ray daemon binary and exposing port 2000 via UDP. The daemon is either configured via command line parameters or a configuration file. The most important option is to set the listen port to the correct IP address so that tracing requests from application Pods can be accepted.
To build your own Docker image containing the X-Ray daemon, use the Dockerfile shown below.
# Use Amazon Linux Version 1
FROM amazonlinux:1
# Download latest 2.x release of X-Ray daemon
RUN yum install -y unzip && \
cd /tmp/ && \
curl https://s3.dualstack.us-east-2.amazonaws.com/aws-xray-assets.us-east-2/xray-daemon/aws-xray-daemon-linux-2.x.zip > aws-xray-daemon-linux-2.x.zip && \
unzip aws-xray-daemon-linux-2.x.zip && \
cp xray /usr/bin/xray && \
rm aws-xray-daemon-linux-2.x.zip && \
rm cfg.yaml
# Expose port 2000 on udp
EXPOSE 2000/udp
ENTRYPOINT ["/usr/bin/xray"]
# No cmd line parameters, use default configuration
CMD ['']
This container image is based on Amazon Linux which results in a small container image. To build and tag the container image run docker build -t xray:latest.
Create an Amazon ECR repository
Create a repository in Amazon Elastic Container Registry (Amazon ECR) to hold your X-Ray Docker image. Your Kubernetes cluster uses this repository to pull the image from upon deployment of the X-Ray Pods.
Use the following CLI command to create your repository or alternatively the AWS Management Console:
Make sure that you configure the kubectl tool properly for your cluster to be able to deploy the X-Ray Pod onto your Kubernetes cluster. After the X-Ray Pods are deployed to your Kubernetes cluster, applications can send tracing information to the X-Ray daemon on their host. The biggest advantage is that you do not need to provide X-Ray as a sidecar container alongside your application. This simplifies the configuration and deployment of your applications and overall saves resources on your cluster.
To deploy the X-Ray daemon as Pods onto your Kubernetes cluster, run the following from the cloned GitHub repository:
kubectl apply -f xray-k8s-daemonset.yaml
This deploys and maintains an X-Ray Pod on each worker node, which is accepting tracing data from your microservices and routing it to one of the X-Ray pods. When deploying the container using a DaemonSet, the X-Ray port is also exposed directly on the host. This way, clients can connect directly to the daemon on your node. This avoids unnecessary network traffic going across your cluster.
Connecting to the X-Ray daemon
To integrate application tracing with your applications, use the X-Ray SDK for one of the supported programming languages:
Java
Node.js
.NET (Framework and Core)
Go
Python
The SDKs provide classes and methods for generating and sending trace data to the X-Ray daemon. Trace data includes information about incoming HTTP requests served by the application, and calls that the application makes to downstream services using the AWS SDK or HTTP clients.
By default, the X-Ray SDK expects the daemon to be available on 127.0.0.1:2000. This needs to be changed in this setup, as the daemon is not part of each Pod but hosted within its own Pod.
The deployed X-Ray DaemonSet exposes all Pods via the Kubernetes service discovery, so applications can use this endpoint to discover the X-Ray daemon. If you deployed to the default namespace, the endpoint is:
xray-service.default
Applications now need to set the daemon address either with the AWS_XRAY_DAEMON_ADDRESS environment variable (preferred) or directly within the SDK setup code:
To set up the environment variable, include the following information in your Kubernetes application deployment description YAML. That exposes the X-Ray service address via the environment variable, where it is picked up automatically by the SDK.
Sending tracing information from your application is straightforward with the X-Ray SDKs. The example code below serves as a starting point to instrument your application with traces. Take a look at the two sample applications in the GitHub repository to see how to send traces from Service A to Service B. The diagram below visualizes the flow of requests between the services.
Because your application is running within containers, enable both the EC2Plugin and ECSPlugin, which gives you information about the Kubernetes node hosting the Pod as well as the container name. Despite the name ECSPlugin, this plugin gives you additional information about your container when running your application on Kubernetes.
var app = express();
//...
var AWSXRay = require('aws-xray-sdk');
AWSXRay.config([XRay.plugins.EC2Plugin, XRay.plugins.ECSPlugin]);
app.use(AWSXRay.express.openSegment('defaultName')); //required at the start of your routes
app.get('/', function (req, res) {
res.render('index');
});
app.use(AWSXRay.express.closeSegment()); //required at the end of your routes / first in error handling routes
For more information about all options and possibilities to instrument your application code, see the X-Ray documentation page for the corresponding SDK information.
The picture below shows the resulting service map that provides insights into the flow of requests through the microservice landscape. You can drill down here into individual traces and see which path each request has taken.
From the service map, you can drill down into individual requests and see where they originated from and how much time was spent in each service processing the request.
You can also view details about every individual segment of the trace by clicking on it. This displays more details.
On the Resources tab, you will see the Kubernetes Pod picked up by the ECSPlugin, which handled the request, as well as the instance that Pod was running on.
Summary
In this post, I shared how to deploy and run X-Ray on an existing Kubernetes cluster. Using tracing gives you deep insights into your applications to ease analysis and spot potential problems early. With X-Ray, you get these insights for all your applications running on AWS, no matter if they are hosted on Amazon ECS, AWS Lambda, or a Kubernetes cluster.
Most malware tries to compromise your systems by using a known vulnerability that the operating system maker has already patched. As best practices to help prevent malware from affecting your systems, you should apply all operating system patches and actively monitor your systems for missing patches.
Launch an Amazon EC2 instance for use with Systems Manager.
Configure Systems Manager to patch your Amazon EC2 Linux instances.
In two previous blog posts (Part 1 and Part 2), I showed how to use the AWS Management Console to perform the necessary steps to patch, inspect, and protect Microsoft Windows workloads. You can implement those same processes for your Linux instances running in AWS by changing the instance tags and types shown in the previous blog posts.
Because most Linux system administrators are more familiar with using a command line, I show how to patch Linux workloads by using the AWS CLI in this blog post. The steps to use the Amazon EBS Snapshot Scheduler and Amazon Inspector are identical for both Microsoft Windows and Linux.
What you should know first
To follow along with the solution in this post, you need one or more Amazon EC2 instances. You may use existing instances or create new instances. For this post, I assume this is an Amazon EC2 for Amazon Linux instance installed from Amazon Machine Images (AMIs).
Systems Manager is a collection of capabilities that helps you automate management tasks for AWS-hosted instances on Amazon EC2 and your on-premises servers. In this post, I use Systems Manager for two purposes: to run remote commands and apply operating system patches. To learn about the full capabilities of Systems Manager, see What Is AWS Systems Manager?
If you are not familiar with how to launch an Amazon EC2 instance, see Launching an Instance. I also assume you launched or will launch your instance in a private subnet. You must make sure that the Amazon EC2 instance can connect to the internet using a network address translation (NAT) instance or NAT gateway to communicate with Systems Manager. The following diagram shows how you should structure your VPC.
Later in this post, you will assign tasks to a maintenance window to patch your instances with Systems Manager. To do this, the IAM user you are using for this post must have the iam:PassRole permission. This permission allows the IAM user assigning tasks to pass his own IAM permissions to the AWS service. In this example, when you assign a task to a maintenance window, IAM passes your credentials to Systems Manager. You also should authorize your IAM user to use Amazon EC2 and Systems Manager. As mentioned before, you will be using the AWS CLI for most of the steps in this blog post. Our documentation shows you how to get started with the AWS CLI. Make sure you have the AWS CLI installed and configured with an AWS access key and secret access key that belong to an IAM user that have the following AWS managed policies attached to the IAM user you are using for this example: AmazonEC2FullAccess and AmazonSSMFullAccess.
Step 1: Launch an Amazon EC2 Linux instance
In this section, I show you how to launch an Amazon EC2 instance so that you can use Systems Manager with the instance. This step requires you to do three things:
Create an IAM role for Systems Manager before launching your Amazon EC2 instance.
Launch your Amazon EC2 instance with Amazon EBS and the IAM role for Systems Manager.
Add tags to the instances so that you can add your instances to a Systems Manager maintenance window based on tags.
A. Create an IAM role for Systems Manager
Before launching an Amazon EC2 instance, I recommend that you first create an IAM role for Systems Manager, which you will use to update the Amazon EC2 instance. AWS already provides a preconfigured policy that you can use for the new role and it is called AmazonEC2RoleforSSM.
Create a JSON file named trustpolicy-ec2ssm.json that contains the following trust policy. This policy describes which principal (an entity that can take action on an AWS resource) is allowed to assume the role we are going to create. In this example, the principal is the Amazon EC2 service.
Use the following command to create a role named EC2SSM that has the AWS managed policy AmazonEC2RoleforSSM attached to it. This generates JSON-based output that describes the role and its parameters, if the command is successful.
$ aws iam create-role --role-name EC2SSM --assume-role-policy-document file://trustpolicy-ec2ssm.json
Use the following command to attach the AWS managed IAM policy (AmazonEC2RoleforSSM) to your newly created role.
$ aws iam attach-role-policy --role-name EC2SSM --policy-arn arn:aws:iam::aws:policy/service-role/AmazonEC2RoleforSSM
Use the following commands to create the IAM instance profile and add the role to the instance profile. The instance profile is needed to attach the role we created earlier to your Amazon EC2 instance.
$ aws iam create-instance-profile --instance-profile-name EC2SSM-IP
$ aws iam add-role-to-instance-profile --instance-profile-name EC2SSM-IP --role-name EC2SSM
B. Launch your Amazon EC2 instance
To follow along, you need an Amazon EC2 instance that is running Amazon Linux. You can use any existing instance you may have or create a new instance.
When launching a new Amazon EC2 instance, be sure that:
Use the following command to launch a new Amazon EC2 instance using an Amazon Linux AMI available in the US East (N. Virginia) Region (also known as us-east-1). Replace YourKeyPair and YourSubnetId with your information. For more information about creating a key pair, see the create-key-pair documentation. Write down the InstanceId that is in the output because you will need it later in this post.
If you are using an existing Amazon EC2 instance, you can use the following command to attach the instance profile you created earlier to your instance.
The final step of configuring your Amazon EC2 instances is to add tags. You will use these tags to configure Systems Manager in Step 2 of this post. For this example, I add a tag named Patch Group and set the value to Linux Servers. I could have other groups of Amazon EC2 instances that I treat differently by having the same tag name but a different tag value. For example, I might have a collection of other servers with the tag name Patch Group with a value of Web Servers.
Use the following command to add the Patch Group tag to your Amazon EC2 instance.
Note: You must wait a few minutes until the Amazon EC2 instance is available before you can proceed to the next section. To make sure your Amazon EC2 instance is online and ready, you can use the following AWS CLI command:
At this point, you now have at least one Amazon EC2 instance you can use to configure Systems Manager.
Step 2: Configure Systems Manager
In this section, I show you how to configure and use Systems Manager to apply operating system patches to your Amazon EC2 instances, and how to manage patch compliance.
To start, I provide some background information about Systems Manager. Then, I cover how to:
Create the Systems Manager IAM role so that Systems Manager is able to perform patch operations.
Create a Systems Manager patch baseline and associate it with your instance to define which patches Systems Manager should apply.
Define a maintenance window to make sure Systems Manager patches your instance when you tell it to.
Monitor patch compliance to verify the patch state of your instances.
You must meet two prerequisites to use Systems Manager to apply operating system patches. First, you must attach the IAM role you created in the previous section, EC2SSM, to your Amazon EC2 instance. Second, you must install the Systems Manager agent on your Amazon EC2 instance. If you have used a recent Amazon Linux AMI, Amazon has already installed the Systems Manager agent on your Amazon EC2 instance. You can confirm this by logging in to an Amazon EC2 instance and checking the Systems Manager agent log files that are located at /var/log/amazon/ssm/.
For a maintenance window to be able to run any tasks, you must create a new role for Systems Manager. This role is a different kind of role than the one you created earlier: this role will be used by Systems Manager instead of Amazon EC2. Earlier, you created the role, EC2SSM, with the policy, AmazonEC2RoleforSSM, which allowed the Systems Manager agent on your instance to communicate with Systems Manager. In this section, you need a new role with the policy, AmazonSSMMaintenanceWindowRole, so that the Systems Manager service can execute commands on your instance.
To create the new IAM role for Systems Manager:
Create a JSON file named trustpolicy-maintenancewindowrole.json that contains the following trust policy. This policy describes which principal is allowed to assume the role you are going to create. This trust policy allows not only Amazon EC2 to assume this role, but also Systems Manager.
Use the following command to create a role named MaintenanceWindowRole that has the AWS managed policy, AmazonSSMMaintenanceWindowRole, attached to it. This command generates JSON-based output that describes the role and its parameters, if the command is successful.
$ aws iam create-role --role-name MaintenanceWindowRole --assume-role-policy-document file://trustpolicy-maintenancewindowrole.json
Use the following command to attach the AWS managed IAM policy (AmazonEC2RoleforSSM) to your newly created role.
$ aws iam attach-role-policy --role-name MaintenanceWindowRole --policy-arn arn:aws:iam::aws:policy/service-role/AmazonSSMMaintenanceWindowRole
B. Create a Systems Manager patch baseline and associate it with your instance
Next, you will create a Systems Manager patch baseline and associate it with your Amazon EC2 instance. A patch baseline defines which patches Systems Manager should apply to your instance. Before you can associate the patch baseline with your instance, though, you must determine if Systems Manager recognizes your Amazon EC2 instance. Use the following command to list all instances managed by Systems Manager. The --filters option ensures you look only for your newly created Amazon EC2 instance.
If your instance is missing from the list, verify that:
Your instance is running.
You attached the Systems Manager IAM role, EC2SSM.
You deployed a NAT gateway in your public subnet to ensure your VPC reflects the diagram shown earlier in this post so that the Systems Manager agent can connect to the Systems Manager internet endpoint.
Now that you have checked that Systems Manager can manage your Amazon EC2 instance, it is time to create a patch baseline. With a patch baseline, you define which patches are approved to be installed on all Amazon EC2 instances associated with the patch baseline. The Patch Group resource tag you defined earlier will determine to which patch group an instance belongs. If you do not specifically define a patch baseline, the default AWS-managed patch baseline is used.
To create a patch baseline:
Use the following command to create a patch baseline named AmazonLinuxServers. With approval rules, you can determine the approved patches that will be included in your patch baseline. In this example, you add all Critical severity patches to the patch baseline as soon as they are released, by setting the Auto approval delay to 0 days. By setting the Auto approval delay to 2 days, you add to this patch baseline the Important, Medium, and Low severity patches two days after they are released.
Use the following command to register the patch baseline you created with your instance. To do so, you use the Patch Group tag that you added to your Amazon EC2 instance.
Now that you have successfully set up a role, created a patch baseline, and registered your Amazon EC2 instance with your patch baseline, you will define a maintenance window so that you can control when your Amazon EC2 instances will receive patches. By creating multiple maintenance windows and assigning them to different patch groups, you can make sure your Amazon EC2 instances do not all reboot at the same time.
To define a maintenance window:
Use the following command to define a maintenance window. In this example command, the maintenance window will start every Saturday at 10:00 P.M. UTC. It will have a duration of 4 hours and will not start any new tasks 1 hour before the end of the maintenance window.
After defining the maintenance window, you must register the Amazon EC2 instance with the maintenance window so that Systems Manager knows which Amazon EC2 instance it should patch in this maintenance window. You can register the instance by using the same Patch Group tag you used to associate the Amazon EC2 instance with the AWS-provided patch baseline, as shown in the following command.
Assign a task to the maintenance window that will install the operating system patches on your Amazon EC2 instance. The following command includes the following options.
name is the name of your task and is optional. I named mine Patching.
task-arn is the name of the task document you want to run.
max-concurrency allows you to specify how many of your Amazon EC2 instances Systems Manager should patch at the same time. max-errors determines when Systems Manager should abort the task. For patching, this number should not be too low, because you do not want your entire patch task to stop on all instances if one instance fails. You can set this, for example, to 20%.
service-role-arn is the Amazon Resource Name (ARN) of the AmazonSSMMaintenanceWindowRole role you created earlier in this blog post.
task-invocation-parameters defines the parameters that are specific to the AWS-RunPatchBaseline task document and tells Systems Manager that you want to install patches with a timeout of 600 seconds (10 minutes).
Now, you must wait for the maintenance window to run at least once according to the schedule you defined earlier. If your maintenance window has expired, you can check the status of any maintenance tasks Systems Manager has performed by using the following command.
You also can see the overall patch compliance of all Amazon EC2 instances using the following command in the AWS CLI.
$ aws ssm list-compliance-summaries
This command shows you the number of instances that are compliant with each category and the number of instances that are not in JSON format.
You also can see overall patch compliance by choosing Compliance under Insights in the navigation pane of the Systems Manager console. You will see a visual representation of how many Amazon EC2 instances are up to date, how many Amazon EC2 instances are noncompliant, and how many Amazon EC2 instances are compliant in relation to the earlier defined patch baseline.
In this section, you have set everything up for patch management on your instance. Now you know how to patch your Amazon EC2 instance in a controlled manner and how to check if your Amazon EC2 instance is compliant with the patch baseline you have defined. Of course, I recommend that you apply these steps to all Amazon EC2 instances you manage.
Summary
In this blog post, I showed how to use Systems Manager to create a patch baseline and maintenance window to keep your Amazon EC2 Linux instances up to date with the latest security patches. Remember that by creating multiple maintenance windows and assigning them to different patch groups, you can make sure your Amazon EC2 instances do not all reboot at the same time.
If you have comments about this post, submit them in the “Comments” section below. If you have questions about or issues implementing any part of this solution, start a new thread on the Amazon EC2 forum or contact AWS Support.
Amazon EMR enables data analysts and scientists to deploy a cluster running popular frameworks such as Spark, HBase, Presto, and Flink of any size in minutes. When you launch a cluster, Amazon EMR automatically configures the underlying Amazon EC2 instances with the frameworks and applications that you choose for your cluster. This can include popular web interfaces such as Hue workbench, Zeppelin notebook, and Ganglia monitoring dashboards and tools.
These web interfaces are hosted on the EMR master node and must be accessed using the public DNS name of the master node (master public DNS value). The master public DNS value is dynamically created, not very user friendly and is hard to remember— it looks something like ip-###-###-###-###.us-west-2.compute.internal. Not having a friendly URL to connect to the popular workbench or notebook interfaces may impact the workflow and hinder your gained agility.
Some customers have addressed this challenge through custom bootstrap actions, steps, or external scripts that periodically check for new clusters and register a friendlier name in DNS. These approaches either put additional burden on the data practitioners or require additional resources to execute the scripts. In addition, there is typically some lag time associated with such scripts. They often don’t do a great job cleaning up the DNS records after the cluster has terminated, potentially resulting in a security risk.
The solution in this post provides an automated, serverless approach to registering a friendly master node name for easy access to the web interfaces.
Before I dive deeper, I review these key services and how they are part of this solution.
CloudWatch Events
CloudWatch Events delivers a near real-time stream of system events that describe changes in AWS resources. Using simple rules, you can match events and route them to one or more target functions or streams. An event can be generated in one of four ways:
From an AWS service when resources change state
From API calls that are delivered via AWS CloudTrail
From your own code that can generate application-level events
In this solution, I cover the first type of event, which is automatically emitted by EMR when the cluster state changes. Based on the state of this event, either create or update the DNS record in Route 53 when the cluster state changes to STARTING, or delete the DNS record when the cluster is no longer needed and the state changes to TERMINATED. For more information about all EMR event details, see Monitor CloudWatch Events.
Route 53 private hosted zones
A private hosted zone is a container that holds information about how to route traffic for a domain and its subdomains within one or more VPCs. Private hosted zones enable you to use custom DNS names for your internal resources without exposing the names or IP addresses to the internet.
Route 53 supports resource record sets with a wide range of record types. In this solution, you use a CNAME record that is used to specify a domain name as an alias for another domain (the ‘canonical’ domain). You use a friendly name of the cluster as the CNAME for the EMR master public DNS value.
You are using private hosted zones because an EMR cluster is typically deployed within a private subnet and is accessed either from within the VPC or from on-premises resources over VPN or AWS Direct Connect. To resolve domain names in private hosted zones from your on-premises network, configure a DNS forwarder, as described in How can I resolve Route 53 private hosted zones from an on-premises network via an Ubuntu instance?.
Lambda
Lambda is a compute service that lets you run code without provisioning or managing servers. Lambda executes your code only when needed and scales automatically to thousands of requests per second. Lambda takes care of high availability, and server and OS maintenance and patching. You pay only for the consumed compute time. There is no charge when your code is not running.
Lambda provides the ability to invoke your code in response to events, such as when an object is put to an Amazon S3 bucket or as in this case, when a CloudWatch event is emitted. As part of this solution, you deploy a Lambda function as a target that is invoked by CloudWatch Events when the event matches your rule. You also configure the necessary permissions based on the Lambda permissions model, including a Lambda function policy and Lambda execution role.
Putting it all together
Now that you have all of the pieces, you can put together a complete solution. The following diagram illustrates how the solution works:
Start with a user activity such as launching or terminating an EMR cluster.
EMR automatically sends events to the CloudWatch Events stream.
A CloudWatch Events rule matches the specified event, and routes it to a target, which in this case is a Lambda function. In this case, you are using the EMR Cluster State Change
The Lambda function performs the following key steps:
Get the clusterId value from the event detail and use it to call EMR. DescribeCluster API to retrieve the following data points:
MasterPublicDnsName – public DNS name of the master node
Locate the tag containing the friendly name to use as the CNAME for the cluster. The key name containing the friendly name should be The value should be specified as host.domain.com, where domain is the private hosted zone in which to update the DNS record.
Update DNS based on the state in the event detail.
If the state is STARTING, the function calls the Route 53 API to create or update a resource record set in the private hosted zone specified by the domain tag. This is a CNAME record mapped to MasterPublicDnsName.
Conversely, if the state is TERMINATED, the function calls the Route 53 API to delete the associated resource record set from the private hosted zone.
Deploying the solution
Because all of the components of this solution are serverless, use the AWS Serverless Application Model (AWS SAM) template to deploy the solution. AWS SAM is natively supported by AWS CloudFormation and provides a simplified syntax for expressing serverless resources, resulting in fewer lines of code.
Overview of the SAM template
For this solution, the SAM template has 76 lines of text as compared to 142 lines without SAM resources (and writing the template in YAML would be even slightly smaller). The solution can be deployed using the AWS Management Console, AWS Command Line Interface (AWS CLI), or AWS SAM Local.
CloudFormation transforms help simplify template authoring by condensing a multiple-line resource declaration into a single line in your template. To inform CloudFormation that your template defines a serverless application, add a line under the template format version as follows:
Before SAM, you would use the AWS::Lambda::Function resource type to define your Lambda function. You would then need a resource to define the permissions for the function (AWS::Lambda::Permission), another resource to define a Lambda execution role (AWS::IAM::Role), and finally a CloudWatch Events resource (Events::Rule) that triggers this function.
With SAM, you need to define just a single resource for your function, AWS::Serverless::Function. Using this single resource type, you can define everything that you need, including function properties such as function handler, runtime, and code URI, as well as the required IAM policies and the CloudWatch event.
A few additional things to note in the code example:
CodeUri – Before you can deploy a SAM template, first upload your Lambda function code zip to S3. You can do this manually or use the aws cloudformation package CLI command to automate the task of uploading local artifacts to a S3 bucket, as shown later.
Lambda execution role and permissions – You are not specifying a Lambda execution role in the template. Rather, you are providing the required permissions as IAM policy documents. When the template is submitted, CloudFormation expands the AWS::Serverless::Function resource, declaring a Lambda function and an execution role. The created role has two attached policies: a default AWSLambdaBasicExecutionRole and the inline policy specified in the template.
CloudWatch Events rule – Instead of specifying a CloudWatch Events resource type, you are defining an event source object as a property of the function itself. When the template is submitted, CloudFormation expands this into a CloudWatch Events rule resource and automatically creates the Lambda resource-based permissions to allow the CloudWatch Events rule to trigger the function.
NOTE: If you are trying this solution outside of us-east-1, then you should download the necessary files, upload them to the buckets in your region, edit the script as appropriate and then run it or use the CLI deployment method below.
3.) Choose Next.
4.) On the Specify Details page, keep or modify the stack name and choose Next.
5.) On the Options page, choose Next.
6.) On the Review page, take the following steps:
Acknowledge the two Transform access capabilities. This allows the CloudFormation transform to create the required IAM resources with custom names.
Under Transforms, choose Create Change Set.
Wait a few seconds for the change set to be created before proceeding. The change set should look as follows:
7.) Choose Execute to deploy the template.
After the template is deployed, you should see four resources created:
After the package is successfully uploaded, the output should look as follows:
Uploading to 0f6d12c7872b50b37dbfd5a60385b854 1872 / 1872.0 (100.00%)
Successfully packaged artifacts and wrote output template to file serverless-output.template.
The CodeUri property in serverless-output.template is now referencing the packaged artifacts in the S3 bucket that you specified:
s3://<bucket>/0f6d12c7872b50b37dbfd5a60385b854
Use the aws cloudformation deploy CLI command to deploy the stack:
You should see the following output after the stack has been successfully created:
Waiting for changeset to be created...
Waiting for stack create/update to complete
Successfully created/updated stack – EmrDnsSetterCli
Validating results
To test the solution, launch an EMR cluster. The Lambda function looks for the cluster_name tag associated with the EMR cluster. Make sure to specify the friendly name of your cluster as host.domain.com where the domain is the private hosted zone in which to create the CNAME record.
Here is a sample CLI command to launch a cluster within a specific subnet in a VPC with the required tag cluster_name.
After the cluster is launched, log in to the Route 53 console. In the left navigation pane, choose Hosted Zones to view the list of private and public zones currently configured in Route 53. Select the hosted zone that you specified in the ZONE tag when you launched the cluster. Verify that the resource records were created.
You can also monitor the CloudWatch Events metrics that are published to CloudWatch every minute, such as the number of TriggeredRules and Invocations.
Now that you’ve verified that the Lambda function successfully updated the Route 53 resource records in the zone file, terminate the EMR cluster and verify that the records are removed by the same function.
Conclusion
This solution provides a serverless approach to automatically assigning a friendly name for your EMR cluster for easy access to popular notebooks and other web interfaces. CloudWatch Events also supports cross-account event delivery, so if you are running EMR clusters in multiple AWS accounts, all cluster state events across accounts can be consolidated into a single account.
I hope that this solution provides a small glimpse into the power of CloudWatch Events and Lambda and how they can be leveraged with EMR and other AWS big data services. For example, by using the EMR step state change event, you can chain various pieces of your analytics pipeline. You may have a transient cluster perform data ingest and, when the task successfully completes, spin up an ETL cluster for transformation and upload to Amazon Redshift. The possibilities are truly endless.
So, what’s Amazon Elastic Container Service (ECS)? ECS is a managed service for running containers on AWS, designed to make it easy to run applications in the cloud without worrying about configuring the environment for your code to run in. Using ECS, you can easily deploy containers to host a simple website or run complex distributed microservices using thousands of containers.
Getting started with ECS isn’t too difficult. To fully understand how it works and how you can use it, it helps to understand the basic building blocks of ECS and how they fit together!
Let’s begin with an analogy
Imagine you’re in a virtual reality game with blocks and portals, in which your task is to build kingdoms.
In your spaceship, you pull up a holographic map of your upcoming destination: Nozama, a golden-orange planet. Looking at its various regions, you see that the nearest one is za-southwest-1 (SWNozama). You set your destination, and use your jump drive to jump to the outer atmosphere of za-southwest-1.
As you approach SW Nozama, you see three portals, 1a, 1b, and 1c. Each portal lets you transport directly to an isolated zone (Availability Zone), where you can start construction on your new kingdom (cluster), Royaume.
With your supply of blocks, you take the portal to 1b, and erect the surrounding walls of your first territory (instance)*.
Before you get ahead of yourself, there are some rules to keep in mind. For your territory to be a part of Royaume, the land ordinance requires construction of a building (container), specifically a castle, from which your territory’s lord (agent)* rules.
You can then create architectural plans (task definitions) to build your developments (tasks), consisting of up to 10 buildings per plan. A development can be built now within this or any territory, or multiple territories.
If you do decide to create more territories, you can either stay here in 1b or take a portal to another location in SW Nozama and start building there.
Amazon EC2 building blocks
We currently provide two launch types: EC2 and Fargate. With Fargate, the Amazon EC2 instances are abstracted away and managed for you. Instead of worrying about ECS container instances, you can just worry about tasks. In this post, the infrastructure components used by ECS that are handled by Fargate are marked with a *.
Instance*
EC2 instances are good ol’ virtual machines (VMs). And yes, don’t worry, you can connect to them (via SSH). Because customers have varying needs in memory, storage, and computing power, many different instance types are offered. Just want to run a small application or try a free trial? Try t2.micro. Want to run memory-optimized workloads? R3 and X1 instances are a couple options. There are many more instance types as well, which cater to various use cases.
AMI*
Sorry if you wanted to immediately march forward, but before you create your instance, you need to choose an AMI. An AMI stands for Amazon Machine Image. What does that mean? Basically, an AMI provides the information required to launch an instance: root volume, launch permissions, and volume-attachment specifications. You can find and choose a Linux or Windows AMI provided by AWS, the user community, the AWS Marketplace (for example, the Amazon ECS-Optimized AMI), or you can create your own.
Region
AWS is divided into regions that are geographic areas around the world (for now it’s just Earth, but maybe someday…). These regions have semi-evocative names such as us-east-1 (N. Virginia), us-west-2 (Oregon), eu-central-1 (Frankfurt), ap-northeast-1 (Tokyo), etc.
Each region is designed to be completely isolated from the others, and consists of multiple, distinct data centers. This creates a “blast radius” for failure so that even if an entire region goes down, the others aren’t affected. Like many AWS services, to start using ECS, you first need to decide the region in which to operate. Typically, this is the region nearest to you or your users.
Availability Zone
AWS regions are subdivided into Availability Zones. A region has at minimum two zones, and up to a handful. Zones are physically isolated from each other, spanning one or more different data centers, but are connected through low-latency, fiber-optic networking, and share some common facilities. EC2 is designed so that the most common failures only affect a single zone to prevent region-wide outages. This means you can achieve high availability in a region by spanning your services across multiple zones and distributing across hosts.
Are containers virtual machines? Nope! Virtual machines virtualize the hardware (benefits), while containers virtualize the operating system (even more benefits!). If you look inside a container, you would see that it is made by processes running on the host, and tied together by kernel constructs like namespaces, cgroups, etc. But you don’t need to bother about that level of detail, at least not in this post!
Why containers? Containers give you the ability to build, ship, and run your code anywhere!
Before the cloud, you needed to self-host and therefore had to buy machines in addition to setting up and configuring the operating system (OS), and running your code. In the cloud, with virtualization, you can just skip to setting up the OS and running your code. Containers make the process even easier—you can just run your code.
Additionally, all of the dependencies travel in a package with the code, which is called an image. This allows containers to be deployed on any host machine. From the outside, it looks like a host is just holding a bunch of containers. They all look the same, in the sense that they are generic enough to be deployed on any host.
With ECS, you can easily run your containerized code and applications across a managed cluster of EC2 instances.
Are containers a fairly new technology? The concept of containerization is not new. Its origins date back to 1979 with the creation of chroot. However, it wasn’t until the early 2000s that containers became a major technology. The most significant milestone to date was the release of Docker in 2013, which led to the popularization and widespread adoption of containers.
What does ECS use? While other container technologies exist (LXC, rkt, etc.), because of its massive adoption and use by our customers, ECS was designed first to work natively with Docker containers.
Container instance*
Yep, you are back to instances. An instance is just slightly more complex in the ECS realm though. Here, it is an ECS container instance that is an EC2 instance running the agent, has a specifically definedIAM policy and role, and has been registered into your cluster.
And as you probably guessed, in these instances, you are running containers.
AMI*
These container instances can use any AMI as long as it has the following specifications: a modern Linux distribution with the agent and the Docker Daemon with any Docker runtime dependencies running on it.
Want it more simplified? Well, AWS created the Amazon ECS-Optimized AMI for just that. Not only does that AMI come preconfigured with all of the previously mentioned specifications, it’s tested and includes the recommended ecs-init upstart process to run and monitor the agent.
Cluster
An ECS cluster is a grouping of (container) instances* (or tasks in Fargate) that lie within a single region, but can span multiple Availability Zones – it’s even a good idea for redundancy. When launching an instance (or tasks in Fargate), unless specified, it registers with the cluster named “default”. If “default” doesn’t exist, it is created. You can also scale and delete your clusters.
Agent*
The Amazon ECS container agent is a Go program that runs in its own container within each EC2 instance that you use with ECS. (It’s also available open source on GitHub!) The agent is the intermediary component that takes care of the communication between the scheduler and your instances. Want to register your instance into a cluster? (Why wouldn’t you? A cluster is both a logical boundary and provider of pool of resources!) Then you need to run the agent on it.
Task
When you want to start a container, it has to be part of a task. Therefore, you have to create a task first. Succinctly, tasks are a logical grouping of 1 to N containers that run together on the same instance, with N defined by you, up to 10. Let’s say you want to run a custom blog engine. You could put together a web server, an application server, and an in-memory cache, each in their own container. Together, they form a basic frontend unit.
Task definition
Ah, but you cannot create a task directly. You have to create a task definition that tells ECS that “task definition X is composed of this container (and maybe that other container and that other container too!).” It’s kind of like an architectural plan for a city. Some other details it can include are how the containers interact, container CPU and memory constraints, and task permissions using IAM roles.
Then you can tell ECS, “start one task using task definition X.” It might sound like unnecessary planning at first. As soon as you start to deal with multiple tasks, scaling, upgrades, and other “real life” scenarios, you’ll be glad that you have task definitions to keep track of things!
Scheduler*
So, the scheduler schedules… sorry, this should be more helpful, huh? The scheduler is part of the “hosted orchestration layer” provided by ECS. Wait a minute, what do I mean by “hosted orchestration”? Simply put, hosted means that it’s operated by ECS on your behalf, without you having to care about it. Your applications are deployed in containers running on your instances, but the managing of tasks is taken care of by ECS. One less thing to worry about!
Also, the scheduler is the component that decides what (which containers) gets to run where (on which instances), according to a number of constraints. Say that you have a custom blog engine to scale for high availability. You could create a service, which by default, spreads tasks across all zones in the chosen region. And if you want each task to be on a different instance, you can use the distinctInstancetask placement constraint. ECS makes sure that not only this happens, but if a task fails, it starts again.
Service
To ensure that you always have your task running without managing it yourself, you can create a service based on the task that you defined and ECS ensures that it stays running. A service is a special construct that says, “at any given time, I want to make sure that N tasks using task definition X1 are running.” If N=1, it just means “make sure that this task is running, and restart it if needed!” And with N>1, you’re basically scaling your application until you hit N, while also ensuring each task is running.
So, what now?
Hopefully you, at the very least, learned a tiny something. All comments are very welcome!
Want to discuss ECS with others? Join the amazon-ecs slack group, which members of the community created and manage.
Also, if you’re interested in learning more about the core concepts of ECS and its relation to EC2, here are some resources:
When managing your AWS resources, you often need to grant one AWS service access to another to accomplish tasks. For example, you could use an AWS Lambdafunction to resize, watermark, and postprocess images, for which you would need to store the associated metadata in Amazon DynamoDB. You also could use Lambda, Amazon S3, and Amazon CloudFront to build a serverless website that uses a DynamoDB table as a session store, with Lambda updating the information in the table. In both these examples, you need to grant Lambda functions permissions to write to DynamoDB.
In this post, I demonstrate how to create an AWS Identity and Access Management (IAM) policy that will be attached to an IAM role. The role is then used to grant a Lambda function access to a DynamoDB table. By using an IAM policy and role to control access, I don’t need to embed credentials in code and can tightly control which services the Lambda function can access. The policy also includes permissions to allow the Lambda function to write log files to Amazon CloudWatch Logs. This allows me to view utilization statistics for your Lambda functions and to have access to additional logging for troubleshooting issues.
Solution overview
The following architecture diagram presents an overview of the solution in this post.
The architecture of this post’s solution uses a Lambda function (1 in the preceding diagram) to make read API calls such as GET or SCAN and write API calls such as PUT or UPDATE to a DynamoDB table (2). The Lambda function also writes log files to CloudWatch Logs (3). The Lambda function uses an IAM role (4) that has an IAM policy attached (5) that grants access to DynamoDB and CloudWatch.
Overview of the AWS services used in this post
I use the following AWS services in this post’s solution:
IAM – For securely controlling access to AWS services. With IAM, you can centrally manage users, security credentials such as access keys, and permissions that control which AWS resources users and applications can access.
DynamoDB – A fast and flexible NoSQL database service for all applications that need consistent, single-digit-millisecond latency at any scale.
Lambda – Run code without provisioning or managing servers. You pay only for the compute time you consume—there is no charge when your code is not running.
CloudWatch Logs– For monitoring, storing, and accessing log files generated by AWS resources, including Lambda.
IAM access policies
I have authored an IAM access policy with JSON to grant the required permissions to the DynamoDB table and CloudWatch Logs. I will attach this policy to a role, and this role will then be attached to a Lambda function, which will assume the required access to DynamoDB and CloudWatch Logs
I will walk through this policy, and explain its elements and how to create the policy in the IAM console.
The following policy grants a Lambda function read and write access to a DynamoDB table and writes log files to CloudWatch Logs. This policy is called MyLambdaPolicy. The following is the full JSON document of this policy (the AWS account ID is a placeholder value that you would replace with your own account ID).
The first element in this policy is the Version, which defines the JSON version. At the time of this post’s publication, the most recent version of JSON is 2012-10-17.
The next element in this first policy is a Statement. This is the main section of the policy and includes multiple elements. This first statement is to Allow access to DynamoDB, and in this example, the elements I use are:
An Effect element – Specifies whether the statement results in an Allow or an explicit Deny. By default, access to resources is implicitly denied. In this example, I have used Allow because I want to allow the actions.
An Action element – Describes the specific actions for this statement. Each AWS service has its own set of actions that describe tasks that you can perform with that service. I have used the DynamoDB actions that I want to allow. For the definitions of all available actions for DynamoDB, see the DynamoDB API Reference.
A Resource element – Specifies the object or objects for this statement using Amazon Resource Names (ARNs). You use an ARN to uniquely identify an AWS resource. All Resource elements start with arn:aws and then define the object or objects for the statement. I use this to specify the DynamoDB table to which I want to allow access. To build the Resource element for DynamoDB, I have to specify:
The AWS service (dynamodb)
The AWS Region (eu-west-1)
The AWS account ID (123456789012)
The table (table/SampleTable)
The complete Resource element of the first statement is: arn:aws:dynamodb:eu-west-1:123456789012:table/SampleTable
In this policy, I created a second statement to allow access to CloudWatch Logs so that the Lambda function can write log files for troubleshooting and analysis. I have used the same elements as for the DynamoDB statement, but have changed the following values:
For the Action element, I used the CloudWatch actions that I want to allow. Definitions of all the available actions for CloudWatch are provided in the CloudWatch API Reference.
For the Resource element, I specified the AWS account to which I want to allow my Lambda function to write its log files. As in the preceding example for DynamoDB, you have to use the ARN for CloudWatch Logs to specify where access should be granted. To build the Resource element for CloudWatch Logs, I have to specify:
The AWS service (logs)
The AWS region (eu-west-1)
The AWS account ID (123456789012)
All log groups in this account (*)
The complete Resource element of the second statement is: arn:aws:logs:eu-west-1:123456789012:*
Create the IAM policy in your account
Before you can apply MyLambdaPolicy to a Lambda function, you have to create the policy in your own account and then apply it to an IAM role.
To create an IAM policy:
Navigate to the IAM console and choose Policies in the navigation pane. Choose Create policy.
Because I have already written the policy in JSON, you don’t need to use the Visual Editor, so you can choose the JSON tab and paste the content of the JSON policy document shown earlier in this post (remember to replace the placeholder account IDswith your own account ID). Choose Review policy.
Name the policy MyLambdaPolicy and give it a description that will help you remember the policy’s purpose. You also can view a summary of the policy’s permissions. Choose Create policy.
You have created the IAM policy that you will apply to the Lambda function.
Attach the IAM policy to an IAM role
To apply MyLambdaPolicy to a Lambda function, you first have to attach the policy to an IAM role.
To create a new role and attach MyLambdaPolicy to the role:
Navigate to the IAM console and choose Roles in the navigation pane. Choose Create role.
Choose AWS service and then choose Lambda. Choose Next: Permissions.
On the Attach permissions policies page, type MyLambdaPolicy in the Search box. Choose MyLambdaPolicy from the list of returned search results, and then choose Next: Review.
On the Review page, type MyLambdaRole in the Role name box and an appropriate description, and then choose Create role.
You have attached the policy you created earlier to a new IAM role, which in turn can be used by a Lambda function.
Apply the IAM role to a Lambda function
You have created an IAM role that has an attached IAM policy that grants both read and write access to DynamoDB and write access to CloudWatch Logs. The next step is to apply the IAM role to a Lambda function.
To apply the IAM role to a Lambda function:
Navigate to the Lambda console and choose Create function.
On the Create function page under Author from scratch, name the function MyLambdaFunction, and choose the runtime you want to use based on your application requirements. Lambda currently supports Node.js, Java, Python, Go, and .NET Core. From the Role dropdown, choose Choose an existing role, and from the Existing role dropdown, choose MyLambdaRole. Then choose Create function.
MyLambdaFunction now has access to CloudWatch Logs and DynamoDB. You can choose either of these services to see the details of which permissions the function has.
If you have any comments about this blog post, submit them in the “Comments” section below. If you have any questions about the services used, start a new thread in the applicable AWS forum: IAM, Lambda, DynamoDB, or CloudWatch.
– Andrew
The collective thoughts of the interwebz
By continuing to use the site, you agree to the use of cookies. more information
The cookie settings on this website are set to "allow cookies" to give you the best browsing experience possible. If you continue to use this website without changing your cookie settings or you click "Accept" below then you are consenting to this.
