Trying to understand why my Genesys Cloud Architect Data Action returns a 403 Forbidden error when invoking an AWS Lambda function via the HTTP POST target.
I have configured the IAM role with the correct lambda:InvokeFunction permission and verified the endpoint URL.
{
“error”: “403 Forbidden”,
“message”: “User: arn:aws:iam::123456789:role/GC-Lambda-Role is not authorized to perform: lambda:InvokeFunction on resource: arn:aws:lambda:us-east-1:123456789:function:MyFunction”
}
Is there a specific VPC endpoint or security group configuration required for the Genesys Cloud platform to successfully authenticate this request?
It depends, but typically the issue is AWS-side authentication, not GC permissions.
- Check if your Lambda is public; GC needs an unauthenticated URL or API Gateway authorizer.
- Verify the IAM role attached to the Lambda execution context allows
lambda:InvokeFunction from the specific source IP or via API Gateway.
- Inspect the CloudWatch logs for the Lambda to see if it’s a cold start timeout masquerading as a 403.
It depends, but generally…
- The 403 indicates AWS rejected the request before it hit your Lambda logic, meaning your IAM role lacks
lambda:InvokeFunction or the resource ARN is malformed.
- Check CloudWatch logs for the exact denial reason and ensure the role attached to the execution context has the correct trust policy.
- If using API Gateway, verify the authorizer isn’t blocking the Genesys Cloud IP range.
It depends, but generally… the 403 is strictly an AWS IAM issue, not a Genesys Cloud permission glitch. The suggestion above about checking the trust policy is spot on. In my Laravel projects, when I hit external endpoints, I always verify the signature matches the expected IAM policy. Genesys Cloud sends a standard HTTP POST; it doesn’t sign requests with AWS credentials by default. You need an API Gateway in front of your Lambda to handle the auth, or use a Lambda@Edge function that validates a shared secret or JWT from Genesys. Direct invocation without API Gateway usually fails because Genesys isn’t in the Principal of your IAM role’s trust policy. Check your API Gateway logs. They show the actual rejection reason before it hits the Lambda.
Warning: Ensure your API Gateway stage variables are set correctly if you are routing through it. A missing header often causes a 403 instead of a 404.
If you check the docs, they mention that Genesys Cloud Architect does not natively support AWS SigV4 signing for direct Lambda invocations. Error: 403 Forbidden. Message: User is not authorized to perform lambda:InvokeFunction. This happens because the HTTP POST from GC is unauthenticated in the context of AWS IAM. I was trying to replicate my Terraform module for API Gateway, but I missed the trust policy requirement. If you call the Lambda ARN directly, AWS rejects it because GC isn’t in the allowed principals. You cannot just put the Lambda URL in the Data Action target without an intermediary. The suggestion above about API Gateway is correct, but you must ensure the Gateway stage is set to ANY or specific POST methods are allowed without Lambda authorizer if you want a quick test, or better, use a custom authorizer that validates the request source. My Terraform state drifted when I tried to hardcode the IP ranges for GC, which is a bad practice anyway since GC IPs change.
Here is the minimal IAM policy snippet you need for the API Gateway execution role, not the Lambda role itself, if you are using a custom authorizer. The Lambda role needs lambda:InvokeFunction but the Gateway needs apigateway:Invoke.
{
"Version": "2012-10-17",
"Statement": [
{
"Effect": "Allow",
"Action": "lambda:InvokeFunction",
"Resource": "arn:aws:lambda:us-east-1:123456789:func:MyGCFunction"
}
]
}
Wait, that’s for the Lambda. For the API Gateway, you need to ensure the method request is configured to pass headers if you are using a custom auth. If you skip API Gateway and use Lambda Function URLs, you must set the Auth type to NONE in the URL settings, otherwise it returns 403. I learned this the hard way when my Terraform apply succeeded but the flow failed. Check the Lambda Function URL configuration in AWS Console, not just the IAM role. The GC Data Action sends a plain POST. If the Lambda Function URL expects SigV4, it will fail. Set it to NONE for testing, then secure it properly. This saves hours of debugging CloudWatch logs.