Example of API Gateway + S3 proxy

apigatewayS3serverless.yml

service: fileStorageServices
custom:
  accountId: <your acc id>
  bucketName: <your bucket name>
  HostedZoneId: <hosted zone id>
  authFunctionName: <auth fn name>
provider:
  name: aws
  runtime: dotnetcore1.0
  stage: ${opt:stage} #read from console input
  region: us-east-1
  role: arn:aws:iam::${self:custom.accountId}:role/s3ProxyRole
  versionFunctions: false
  custom:
    setup: ${file(vars.js):setup} #initializes the variables which adds to environment variables
  stackTags:
   Environment: ${opt:stage}
  stackPolicy: # Optional CF stack policy. The example below allows updates to all resources except deleting/replacing EC2 instances (use with caution!)
    - Effect: Allow
      Principal: "*"
      Action: "Update:*"
      Resource: "*"
    - Effect: Deny
      Principal: "*"
      Action:
        - Update:Replace
        - Update:Delete
      Condition:
        StringEquals:
          ResourceType:
            - AWS::EC2::Instance
resources:
  Resources:
    s3filesbucket:
      Type: 'AWS::S3::Bucket'
      Properties:
        AccessControl: PublicReadWrite
        BucketName: ${env:bucketNamePrefix}${self:custom.bucketName}
        VersioningConfiguration:
          Status: Suspended
        Tags:
          - Key: Environment
            Value: ${opt:stage}
        WebsiteConfiguration:
          IndexDocument: index.html
    route53BucketDNS: #this adds a DNS recordset which can be used for public viewing of objects
      Type: "AWS::Route53::RecordSet"
      Properties: 
        HostedZoneId: ${self:custom.HostedZoneId}
        Name: ${env:bucketNamePrefix}${self:custom.bucketName}
        ResourceRecords:
          - ${env:bucketNamePrefix}${self:custom.bucketName}.s3-website-us-east-1.amazonaws.com
        TTL: 300
        Type: CNAME
    s3Proxy:
      Type: "AWS::ApiGateway::RestApi"
      Properties:
        BinaryMediaTypes: #add or substract MIME types here
          - image/png
          - image/jpg
          - image/gif
          - image/x-icon
          - application/octet-stream
        Description: Storage service for ${opt:stage} environment
        FailOnWarnings: false
        Name: ${env:apiGatewayPrefix}fileStorage #api gateway name
    s3ProxyAuthorizer: #custom authorizer for the API gateway which adds stuff to the bucket
      Type: "AWS::ApiGateway::Authorizer"
      Properties:
        AuthorizerResultTtlInSeconds: 300
        AuthorizerUri: arn:aws:apigateway:us-east-1:lambda:path//2015-03-31/functions/arn:aws:lambda:us-east-1:${self:custom.accountId}:function:${opt:stage}${self:custom.authFunctionName}/invocations
        IdentitySource: method.request.header.Authorization
        IdentityValidationExpression: ^Bearer.+
        Name: CommonAuthorizer
        RestApiId:
          Ref: "s3Proxy"
        Type: TOKEN
    s3ProxyAnyMethod:
      Type: "AWS::ApiGateway::Method"
      Properties:
        ApiKeyRequired: false
        AuthorizationType: CUSTOM
        AuthorizerId:
          Ref: "s3ProxyAuthorizer"
        HttpMethod: ANY
        Integration:
          Credentials: arn:aws:iam::${self:custom.accountId}:role/s3ProxyRole
          IntegrationHttpMethod: ANY
          IntegrationResponses:
              - StatusCode: 200
                ResponseParameters:
                  method.response.header.Content-Type: integration.response.header.Content-Type
                  method.response.header.Content-Disposition: integration.response.header.Content-Disposition
              - StatusCode: 400
                SelectionPattern: "400"
                ResponseParameters:
                  method.response.header.Content-Type: integration.response.header.Content-Type
                  method.response.header.Content-Disposition: integration.response.header.Content-Disposition
              - StatusCode: 404
                SelectionPattern: "404"
                ResponseParameters:
                  method.response.header.Content-Type: integration.response.header.Content-Type
                  method.response.header.Content-Disposition: integration.response.header.Content-Disposition
              - StatusCode: 500
                SelectionPattern: '5\d{2}'
                ResponseParameters:
                  method.response.header.Content-Type: integration.response.header.Content-Type
                  method.response.header.Content-Disposition: integration.response.header.Content-Disposition
          PassthroughBehavior: WHEN_NO_MATCH
          RequestParameters:
            integration.request.header.Content-Disposition: method.request.header.Content-Disposition
            integration.request.header.Content-Type: method.request.header.Content-Type
            integration.request.header.x-amz-acl: method.request.header.x-amz-acl
            integration.request.path.key: method.request.querystring.key
          Type: AWS
          Uri: arn:aws:apigateway:us-east-1:s3:path/${env:bucketNamePrefix}${self:custom.bucketName}/{key}
        MethodResponses:
          - StatusCode: 200
            ResponseParameters:
              method.response.header.Content-Type: integration.response.header.Content-Type
              method.response.header.Content-Disposition: integration.response.header.Content-Disposition
          - StatusCode: 400
            ResponseParameters:
              method.response.header.Content-Type: integration.response.header.Content-Type
              method.response.header.Content-Disposition: integration.response.header.Content-Disposition
          - StatusCode: 404
            ResponseParameters:
              method.response.header.Content-Type: integration.response.header.Content-Type
              method.response.header.Content-Disposition: integration.response.header.Content-Disposition
          - StatusCode: 500
            ResponseParameters:
              method.response.header.Content-Type: integration.response.header.Content-Type
              method.response.header.Content-Disposition: integration.response.header.Content-Disposition
        RequestParameters:
          method.request.header.Content-Disposition: false
          method.request.header.Content-Type: false
          method.request.header.x-amz-acl: false
          method.request.querystring.key: false
        ResourceId:
          Fn::GetAtt: 
            - "s3Proxy"
            - "RootResourceId"
        RestApiId:
          Ref: "s3Proxy"
    ApiGatewayDeploymentthisiswhatiwillreplace:
      Type: 'AWS::ApiGateway::Deployment'
      Properties:
        RestApiId:
          Ref: "s3Proxy"
        StageName: ${opt:stage}
      DependsOn:
        - s3ProxyAnyMethod