Architect Data Action calling AWS Lambda returns 403 Forbidden - IAM Policy Issue?

Architect & Flows
1

The documentation actually says that AWS Lambda URLs require specific authorization types, and the default is often AWS_IAM. This explains the 403 Forbidden error you are seeing. Your Genesys Cloud Data Action needs to send the correct headers.

Could someone explain how to configure the Lambda function URL to allow Invoke permissions from any origin for testing purposes?

2

Yep, this is a known issue… The Lambda function URL must be configured with NONE authorization to accept unauthenticated requests from Genesys Cloud Data Actions. Update the AWS console settings for that specific Function URL to allow invocations without IAM verification.

Note: Ensure the Genesys Cloud Data Action uses the Function URL endpoint, not the standard Invoke path, as they require different IAM policies.

3

You need to switch the authorization type to NONE. The current IAM setup blocks unauthenticated requests from Genesys Cloud. Here is the Python snippet to patch the config:

client.update_function_url_config(FunctionName="my-lambda", AuthType="NONE")

This resolves the 403 immediately.

4

Have you tried verifying the exact HTTP method and header requirements for the Function URL? The suggestion above regarding setting AuthType to “NONE” is correct for basic connectivity, but it introduces a significant security risk that is often overlooked in initial deployments.

The documentation for AWS Lambda Function URLs states: “When you set the authorization type to NONE, any caller can invoke the function.” In a Genesys Cloud context, this means any external actor who discovers your Function URL endpoint can trigger your Lambda function. This is not ideal for production environments handling PII or sensitive CRM data.

Instead of disabling authentication entirely, consider using a custom authorization header generated by Genesys Cloud Architect. You can inject a static secret key into the Data Action request headers and validate it within your Lambda function. This approach avoids the 403 Forbidden error while maintaining a basic layer of security.

Here is a C# example of how you might validate this header in your Lambda entry point, assuming you are using the .NET SDK for AWS Lambda:

public string FunctionHandler(APIGatewayProxyRequest request, ILambdaContext context)
{
 var authHeader = request.Headers["X-Custom-Auth-Token"];
 
 // Validate against a secret stored in AWS Secrets Manager or Environment Variables
 if (authHeader != Environment.GetEnvironmentVariable("GENESYS_SECRET_KEY"))
 {
 return new APIGatewayProxyResponse
 {
 StatusCode = (int)HttpStatusCode.Forbidden,
 Body = "Unauthorized"
 };
 }

 // Process request
 return new APIGatewayProxyResponse
 {
 StatusCode = (int)HttpStatusCode.OK,
 Body = "Success"
 };
}

Ensure your Genesys Cloud Data Action includes the X-Custom-Auth-Token header with the matching value. This prevents the 403 from IAM while keeping the endpoint protected from arbitrary public invocations.

5

I normally fix this by swapping to a CloudFront distribution with Lambda@Edge instead of exposing the Function URL directly, which lets me enforce strict API key validation in the origin-request phase before the payload ever hits your compute layer. Here is the basic CloudFormation snippet for that edge function to validate the key header.

EdgeFunction:
 Type: AWS::Lambda::Function
 Properties:
 Runtime: nodejs18.x
 Handler: index.handler
 Code:
 ZipFile: |
 exports.handler = (event, context, callback) => {
 const request = event.Records[0].cf.request;
 const apiKey = request.headers['x-api-key'][0].value;
 if (apiKey !== 'SECRET_KEY') {
 return { status: '403', statusDescription: 'Forbidden' };
 }
 return request;
 };