API HTTP Gateway lambda integration 'null' in Resource Path - amazon-web-services

Question

I am setting up an API HTTP Gateway (V2) with lambda integrations via Cloudformation, and everything has been working so far. I have 2 working integrations, but my third integration is not working: Everything looks fine from the API Gateway side (it lists the correct route with a link to the Lambda), but the API endpoint in the lambda is listed as "https://c59boisn2k.execute-api.eu-central-1.amazonaws.com/productionnull". When I try to call the route, it says "Not Found". The odd thing is that I am using the same template for all three integrations.
I was thinking it could be a "dependsOn" issue, but I think I have all the correct dependencies. I tried re-creating the stack from scratch and now two of the three functions say "null" in their URL while the API Gateway still states the correct routes. Can this be a 'dependsOn' problem?
Here's my template for a single integration:
{
"Resources": {
"api": {
"Type": "AWS::ApiGatewayV2::Api",
"Properties": {
"Name": { "Ref": "AWS::StackName" },
"ProtocolType": "HTTP",
"CorsConfiguration": {
"AllowMethods": ["*"],
"AllowOrigins": ["*"]
}
}
},
"stage": {
"Type": "AWS::ApiGatewayV2::Stage",
"Properties": {
"Description": { "Ref": "AWS::StackName" },
"StageName": "production",
"AutoDeploy": true,
"ApiId": { "Ref": "api" },
"AccessLogSettings": {
"DestinationArn": {
"Fn::GetAtt": ["stageLogGroup", "Arn"]
}
}
}
},
"getSignedS3LambdaRole": {
"Type": "AWS::IAM::Role",
"Properties": {
"RoleName": {
"Fn::Sub": "${AWS::StackName}-getSignedS3"
},
"AssumeRolePolicyDocument": {
"Version": "2012-10-17",
"Statement": [
{
"Effect": "Allow",
"Principal": {
"Service": ["lambda.amazonaws.com"]
},
"Action": ["sts:AssumeRole"]
}
]
},
"Policies": [
{
"PolicyName": "root",
"PolicyDocument": {
"Version": "2012-10-17",
"Statement": [
{
"Effect": "Allow",
"Resource": "arn:aws:logs:*:*:*",
"Action": "logs:*"
},
{
"Effect": "Allow",
"Action": ["s3:*"],
"Resource": ["arn:aws:s3:::euromomo.eu/uploads/*"]
}
]
}
}
]
}
},
"getSignedS3Lambda": {
"Type": "AWS::Lambda::Function",
"DependsOn": ["getSignedS3LambdaRole"],
"Properties": {
"FunctionName": {
"Fn::Sub": "${AWS::StackName}-getSignedS3"
},
"Code": {
"S3Bucket": { "Ref": "operationsS3Bucket" },
"S3Key": { "Ref": "getSignedS3S3Key" }
},
"Runtime": "nodejs10.x",
"Handler": "index.handler",
"Role": { "Fn::GetAtt": ["getSignedS3LambdaRole", "Arn"] }
}
},
"getSignedS3Permission": {
"Type": "AWS::Lambda::Permission",
"DependsOn": ["api", "getSignedS3Lambda"],
"Properties": {
"Action": "lambda:InvokeFunction",
"FunctionName": { "Ref": "getSignedS3Lambda" },
"Principal": "apigateway.amazonaws.com",
"SourceArn": {
"Fn::Sub": "arn:aws:execute-api:${AWS::Region}:${AWS::AccountId}:${api}/*/*"
}
}
},
"getSignedS3Integration": {
"Type": "AWS::ApiGatewayV2::Integration",
"DependsOn": ["getSignedS3Permission"],
"Properties": {
"ApiId": { "Ref": "api" },
"IntegrationType": "AWS_PROXY",
"IntegrationUri": {
"Fn::Sub": "arn:aws:apigateway:${AWS::Region}:lambda:path/2015-03-31/functions/${getSignedS3Lambda.Arn}/invocations"
},
"PayloadFormatVersion": "2.0"
}
},
"getSignedS3Route": {
"Type": "AWS::ApiGatewayV2::Route",
"DependsOn": ["getSignedS3Integration"],
"Properties": {
"ApiId": { "Ref": "api" },
"RouteKey": "POST /getSignedS3",
"AuthorizationType": "NONE",
"Target": { "Fn::Sub": "integrations/${getSignedS3Integration}" }
}
}
}
}

Answer 1

After spending hours debugging this, I found that the problem was in my Lambda permission. I need to use the correct path in the permission.
This does not work:
arn:aws:execute-api:${AWS::Region}:${AWS::AccountId}:${api}/*/*
This does work:
arn:aws:execute-api:${AWS::Region}:${AWS::AccountId}:${api}/*/*/getSignedS3
I believe I could scope it even more to this:
arn:aws:execute-api:${AWS::Region}:${AWS::AccountId}:${api}/*/POST/getSignedS3
This fixed all my problems and shows the correct path in the lambda web console.