cdk-secret-manager-wrapper-layer

that Lambda layer uses a wrapper script to fetch information from Secrets Manager and create environmental variables.

idea from source

Example

import { App, Stack, CfnOutput, Duration } from 'aws-cdk-lib';
import { Effect, PolicyStatement } from 'aws-cdk-lib/aws-iam';
import { Function, Runtime, Code, FunctionUrlAuthType } from 'aws-cdk-lib/aws-lambda';
import { CfnSecret } from 'aws-cdk-lib/aws-secretsmanager';
import { SecretManagerWrapperLayer } from 'cdk-secret-manager-wrapper-layer';
const env = {
  region: process.env.CDK_DEFAULT_REGION,
  account: process.env.CDK_DEFAULT_ACCOUNT,
};
const app = new App();
const stack = new Stack(app, 'testing-stack', { env });

/**
 * Example create an Secret for testing.
 */
const secret = new CfnSecret(stack, 'Mysecret', {
  secretString: JSON.stringify({
    KEY1: 'VALUE1',
    KEY2: 'VALUE2',
    KEY3: 'VALUE3',
  }),
});

const layer = new SecretManagerWrapperLayer(stack, 'SecretManagerWrapperLayer');

const lambda = new Function(stack, 'fn', {
  runtime: Runtime.PYTHON_3_9,
  code: Code.fromInline(`
import os
def hander(events, contexts):
    env = {}
    env['KEY1'] = os.environ.get('KEY1', 'Not Found')
    env['KEY2'] = os.environ.get('KEY2', 'Not Found')
    env['KEY3'] = os.environ.get('KEY3', 'Not Found')
    return env
    `),
  handler: 'index.hander',
  layers: [layer],
  timeout: Duration.minutes(1),
  /**
   * you need to define this 4 environment various.
   */
  environment: {
    AWS_LAMBDA_EXEC_WRAPPER: '/opt/get-secrets-layer',
    SECRET_REGION: stack.region,
    SECRET_ARN: secret.ref,
    API_TIMEOUT: '5000',
  },
});

/**
 * Add Permission for lambda get secret value from secret manager.
 */
lambda.role!.addToPrincipalPolicy(
  new PolicyStatement({
    effect: Effect.ALLOW,
    actions: ['secretsmanager:GetSecretValue'],
    // Also you can use find from context.
    resources: [secret.ref],
  }),
);

/**
 * For Testing.
 */
const FnUrl = lambda.addFunctionUrl({
  authType: FunctionUrlAuthType.NONE,
});

new CfnOutput(stack, 'FnUrl', {
  value: FnUrl.url,
});

Testing

# ex: curl https://sdfghjklertyuioxcvbnmghj.lambda-url.us-east-1.on.aws/
curl ${FnUrl}
{"KEY2":"VALUE2","KEY1":"VALUE1","KEY3":"VALUE3"}