A Serverless plugin which encrypts Lambda environment variables using an KMS key which is automatically generated for each stage.

An alternative approach is to use AWS Secrets Manager

environment: #${ssm:/aws/reference/secretsmanager/${self:custom.stage}/config~true}

yarn add -D serverless-plugin-encrypted

or

npm install --save-dev serverless-plugin-encrypted

service: my-service
provider:
  name: aws
  runtime: nodejs6.10
  role: lambda-role
  stage: DEV
  region: ap-southeast-2
  
plugins:
  - serverless-plugin-encrypted
    
custom:
  kmsKeyId: ${self:provider.stage}-my-service
  encrypted:
    SECRET_PASSWORD: ${env:MY_SECRET_PASSWORD}
        
functions:
  my-function:
    handler: index.handler
    environment:
      NOT_SECRET: ${env:NOT_SECRET}
      SECRET_PASSWORD: ${self:custom.encrypted.SECRET_PASSWORD}

$ serverless deploy

The plugin will look for a KMS key with alias DEV-my-service, and create it if it does not exist. Then it will go through all environment variables within provider and each function.
If it finds an entry in custom.encrypted with a matching name it will use the KMS key to encrypt the value (eg: custom.encrypted.SECRET_PASSWORD) and update the provider and function values.

Note: The original values in the provider and functions will be discarded. ie functions.my-function.environment.SECRET_PASSWORD has been set to ${self:custom.encrypted.SECRET_PASSWORD} in the example above, but it could be anything really, although it is a recommended convention.

When the plugin creates the KMS key, a policy will be created for it which allows:

• the account root user to manage the key
• anybody to encrypt