【SaaS架构】使用AWS Lambda令牌自动售货机为Amazon S3实施SaaS租户隔离

Environment: PoC or pilot

Technologies: Modernization; SaaS

AWS services: AWS Identity and Access Management; AWS Lambda; Amazon S3; AWS STS

The implementation of this pattern requires includes several variable names that must be used consistently. Determine the values that should be used for each variable, and provide that value when requested in subsequent steps.

<AWS Account ID> ─ The 12-digit account ID that is associated with the AWS account you are implementing this pattern in. For information about how to find your AWS cccount ID, see Your AWS account ID and its alias in the IAM documentation.

<AWS Region> ─ The AWS Region that you are implementing this pattern in. For more information on AWS Regions, see Regions and Availability Zones on the AWS website.

<sample-tenant-name> ─ The name of a tenant to use in the application. We recommend that you use only alphanumeric characters in this value for simplicity, but you can use any valid name for an S3 object key.

<sample-tvm-role-name> ─ The name of the IAM role attached to the Lambda function that runs the TVM and sample application. The role name is a string that consists of uppercase and lowercase alphanumeric characters with no spaces. You can also include any of the following characters: underscore (_), plus sign (+), equal sign (=), comma (,), period (.), at sign (@), and hyphen (-). The role name must be unique within the account.

<sample-app-role-name> ─ The name of the IAM role that is assumed by the Lambda function when it generates scoped, temporary STS credentials. The role name is a string that consists of uppercase and lowercase alphanumeric characters with no spaces. You can also include any of the following characters: underscore (_), plus sign (+), equal sign (=), comma (,), period (.), at sign (@), and hyphen (-). The role name must be unique within the account.

<sample-app-function-name> ─ The name of the Lambda function. This is a string that’s up to 64 characters in length.

<sample-app-bucket-name> ─ The name of an S3 bucket that must be accessed with permissions that are scoped to a specific tenant. S3 bucket names:

• Must be between 3 and 63 characters long.

• Must consist of only lowercase letters, numbers, periods (.), and hyphens (-).

• Must begin and end with a letter or number.

• Must not be formatted as an IP address (for example, 192.168.5.4).

• Must be unique within a partition. A partition is a grouping of Regions. AWS currently has three partitions: aws (Standard Regions), aws-cn (China Regions), and aws-us-gov (AWS GovCloud [US] Regions).

Use the following AWS CLI command to create an S3 bucket. Provide the <sample-app-bucket-name> value in the code snippet:

The Lambda sample application uploads JSON files to this bucket.

Use one of the following AWS CLI commands to create an IAM role. Provide the <sample-tvm-role-name> value in the command.

For macOS or Linux shells:

For the Windows command line:

The Lambda sample application assumes this role when the application is invoked. The capability to assume the application role with a scoped policy gives the code broader permissions to access the S3 bucket.

Use one of the following AWS CLI commands to create an IAM policy. Provide the <sample-tvm-role-name>, <AWS Account ID>, and <sample-app-role-name> values in the command.

For macOS or Linux shells:  

For the Windows command line:

This policy is attached to the TVM role. It gives the code the capability to assume the application role, which has broader permissions to access the S3 bucket.

Use the following AWS CLI command to attach the AWSLambdaBasicExecutionRole IAM policy. Provide the <sample-tvm-role-name> value in the command:

This managed policy is attached to the TVM role to permit Lambda to send logs to Amazon CloudWatch.

Use one of the following AWS CLI commands to create an IAM role. Provide the <sample-app-role-name>, <AWS Account ID>, and <sample-tvm-role-name> values in the command.

For macOS or Linux shells:  

For the Windows command line:

The Lambda sample application assumes this role with a scoped policy to get tenant-based access to an S3 bucket.

Use one of the following AWS CLI commands to create an IAM policy. Provide the <sample-app-role-name> and <sample-app-bucket-name> values in the command.

For macOS or Linux shells:  

For the Windows command line:

This policy is attached to the application role. It provides broad access to objects in the S3 bucket. When the sample application assumes the role, these permissions are scoped to a specific tenant with the TVM's dynamically generated policy.

Download the s3UploadSample.jar and tvm-layer.zip files, which are included as attachments. The source code used to create these artifacts and compilation instuctions are provided in token-vending-machine-sample-app.zip.

Use the following AWS CLI command to create a Lambda layer, which makes the TVM accessible to Lambda. 

Note: If you aren’t running this command from the location where you downloaded tvm-layer.zip, provide the correct path to tvm-layer.zip in the --zip-file parameter. 

This command creates a Lambda layer that contains the reusable TVM library.

Use the following AWS CLI command to create a Lambda function. Provide the <sample-app-function-name>, <AWS Account ID>, <AWS Region>, <sample-tvm-role-name>, <sample-app-bucket-name>, and <sample-app-role-name> values in the command. 

Note: If you aren’t running this command from the location where you downloaded s3UploadSample.jar, provide the correct path to s3UploadSample.jar in the --zip-file parameter. 

This command creates a Lambda function with the sample application code and the TVM layer attached. It also sets two environment variables: S3_BUCKET and ROLE. The sample application uses these variables to determine the role to assume and the S3 bucket to upload JSON documents to.

Use one of the following AWS CLI commands to start the Lambda sample application with its expected payload. Provide the <sample-app-function-name> and <sample-tenant-name> values in the command.

For macOS and Linux shells:

For the Windows command line:  

This command calls the Lambda function and returns the result in a response.json document. On many Unix-based systems, you can change response.json to /dev/stdout to output the results directly to your shell without creating another file. 

Note: Changing the <sample-tenant-name> value in subsequent invocations of this Lambda function alters the location of the JSON document and the permissions the token provides.

Browse to the S3 bucket ( <sample-app-bucket-name>) that you created earlier. This  bucket contains an S3 object prefix with the value of <sample-tenant-name>. Under that prefix, you will find a JSON document named with a UUID. Invoking the sample application multiple times adds more JSON documents.

View the Cloudwatch logs associated with the Lambda function named <sample-app-function-name>. For instructions, see Accessing Amazon CloudWatch logs for AWS Lambda in the AWS Lambda documentation. You can view the tenant-scoped policy generated by the TVM in these logs. This tenant-scoped policy gives permissions for the sample application to the Amazon S3 PutObject, GetObject, DeleteObject, and ListBucket APIs, but only for the object prefix associated with <sample-tenant-name>. In subsequent invocations of the sample application, if you change the <sample-tenant-name>, the TVM updates the scoped policy to correspond to the tenant provided in the invocation payload. This dynamically generated policy shows how tenant-scoped access can be maintained with a TVM in SaaS applications. 

The TVM functionality is provided in a Lambda layer so that it can be attached to other Lambda functions used by an application without having to replicate the code.

For an illustration of the dynamically generated policy, see the Additional information section.