awscli-plugin-execute-api

Plugin to configure a single AWS CLI operation to invoke an API Gateway / Lambda method

Quick Start

Install with pip

$ pip install awscli-plugin-execute-api

If you installed awscli with Homebrew, use its bundled Python:

$ /usr/local/opt/awscli/libexec/bin/pip install awscli-plugin-execute-api

Register the plugin

$ aws configure set plugins.execute-api awscli_plugin_execute_api

Configure an operation endpoint

First configure a profile for the IAM with execute-api:Invoke permission:

$ export AWS_PROFILE=myprofile

$ aws configure
AWS Access Key ID [None]: AKIA...
AWS Secret Access Key [None]: pWim...
Default region name [None]: us-east-1
Default output format [None]: json

Next configure the plugin for an operation and its API Gateway invocation URL:

$ aws configure set dynamodb.update-table https://m303r7o808.execute-api.us-east-1.amazonaws.com/Prod/update-table

[plugins]
execute-api = awscli_plugin_execute_api

[profile myprofile]
region = us-east-1
output = json
dynamodb =
    update-table = https://m303r7o808.execute-api.us-east-1.amazonaws.com/Prod/update-table

Run an operation

Now run a command:

$ aws dynamodb update-table --table-name $TABLE_NAME --sse-specification Enabled=false
An error occurred (ValidationException) when calling the UpdateTable operation: Custom error from Lambda handler

$ aws dynamodb update-table --debug --table-name $TABLE_NAME
Plugin awscli_plugin_execute_api: Config [myprofile] dynamodb.update-table => URL https://m303r7o808.execute-api.us-east-1.amazonaws.com/Prod/update-table
Plugin awscli_plugin_execute_api: renamed X-Amz-Target DynamoDB_20120810.UpdateTable

$ aws dynamodb describe-table --debug --table-name $TABLE_NAME
Plugin awscli_plugin_execute_api: Config [myprofile] dynamodb.describe-table not found

Motivation

For security reasons we'd like to give an IAM user access to a limited subset of an AWS API call functionality. For example on the dynamodb update-table operation we'd like to allow a user to modify:

• Global indexes

But disallow them to modify:

• Provisioned throughput
• Streams
• Server side encryption

A "serverless" solution includes:

• IAM User

  • Policy that disallows dynamodb:UpdateTable
  • Policy that allows execute-api:Invoke on an API Gateway resource
  • Access keys

• API Gateway Method

  • URL to POST an update-table request
  • AWS_IAM authorization

• Lambda Function

  • Policy that allows dynamodb:UpdateTable
  • Code that validates and performs update-table request

• AWS CLI

  • Custom endpoint URL for dynamodb update-table command
  • Request signature for API Gateway

This plugin registers a URL for a single CLI operation and automatically uses it.

$ aws configure set dynamodb.update-table https://m303r7o808.execute-api.us-east-1.amazonaws.com/Prod/update-table
$ aws dynamodb update-table --table-name $TABLE_NAME --sse-specification Enabled=false
An error occurred (ValidationException) when calling the UpdateTable operation: Modifying SSESpecification is not allowed

Troubleshooting

IAM

The CLI user needs API execution permissions:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": [
                "execute-api:Invoke"
            ],
            "Resource": [
                "arn:aws:execute-api:us-east-1:303718836660:m303r7o808/*/POST/update-table"
            ]
        }
    ]
}

Lambda

The CLI operation is in the X-Target header, since X-Amz-Target

Credits

• https://github.com/wbingli/awscli-plugin-endpoint