Execution failed due to configuration error: Inval

Question

I am building a serverless application using AWS Lambda and API Gateway via Visual Studio. I am working in C#, and using the serverless application model (SAM) in order to deploy my API. I build the code in Visual Studio, then deploy via publish to Lambda. This is working, except every time I do a new build, and try to execute an API call, I get this error:

Execution failed due to configuration error: Invalid permissions on Lambda function

Doing some research, I found this fix mentioned elsewhere (to be done via the AWS Console):

Fix: went to API Gateway > API name > Resources > Resource name > Method > Integration Request > Lambda Function and reselected my existing function, before "saving" it with the little checkmark.

Now this works for me, but it breaks the automation of using the serverless.template (JSON) to build out my API. Does anyone know how to fix this within the serverless.template file? So that I don't need to take action in the console to resolve? Here's a sample of one of my methods from the serverless.template file

{
  "AWSTemplateFormatVersion" : "2010-09-09",
  "Transform" : "AWS::Serverless-2016-10-31",
  "Description" : "An AWS Serverless Application.",

  "Resources" : {

    "Get" : {
      "Type" : "AWS::Serverless::Function",
      "Properties": {
        "VpcConfig":{
          "SecurityGroupIds" : ["sg-111a1476"],
          "SubnetIds" : [ "subnet-3029a769","subnet-5ec0b928"]
        },
        "Handler": "AWSServerlessInSiteDataGw::AWSServerlessInSiteDataGw.Functions::Get",
        "Runtime": "dotnetcore2.0",
        "CodeUri": "",
        "MemorySize": 256,
        "Timeout": 30,
        "Role": null,
        "Policies": [ "AWSLambdaBasicExecutionRole","AWSLambdaVPCAccessExecutionRole","AmazonSSMFullAccess"],
        "Events": {
          "PutResource": {
            "Type": "Api",
            "Properties": {
              "Path": "/",
              "Method": "GET"
            }
          }
        }
      }
    },

Answer 1

I was having the same issue but I was deploying through Terraform. After a suggestion from another user, I reselected my Lambda function in the Integration part of the API Gateway, and then checked what changed in my Lambda permissions. Turns out I needed to add a "*" where I was putting the stage name in the source_arn section of the API Gateway trigger in my Lambda resource. Not sure how SAM compares to Terraform but perhaps you can change the stage name or just try this troubleshooting technique that I tried.

My SO posting: AWS API Gateway and Lambda function deployed through terraform -- Execution failed due to configuration error: Invalid permissions on Lambda function