binary responses with Serverless, Bref PHP, and Slim getting CORS or base64 encoded

Question

I have been setting up a Serverless(.com) setup with AWS, using Bref (PHP layer) to run MPDF to convert HTML to PDF using AWS Lambda and API Gateway. Following instructions,.. here is the setup.

After way to much debugging, it appears that either I can:

1. Add the apiGateway option in the serverless file, but I always get a CORS issue (i.e. the classic No 'Access-Control-Allow-Origin' header is present). I have tried every combination of headers from the client/request side and responses from the server side (see code below).

2. OR, I can not have the apiGateway option, as below, but then I have to base64encode my body (see $body = base64_encode($pdf);) or I get a Bref error stating The Lambda response cannot be encoded to JSON (...) saying one should use the apiGateway options.

Encoding the body is fine, but doesn't work well for direct download as I need to base64decode the data from the response in order to have the binary data.

Help.

serverless.yml: (notice the commented out apiGateway settings - read more for why)

 service: html2pdf
    
    provider:
        name: aws
        region: us-east-1
        runtime: provided
        stage: ${opt:stage, 'dev'}
        # apiGateway:    ## <======= We talk about this below
        #     binaryMediaTypes:
        #         - '*/*'
        # environment:
        #     BREF_BINARY_RESPONSES: 1
    
    plugins:
        - ./vendor/bref/bref
    
    functions:
        html2pdf:
            handler: index.php
            description: ''
            timeout: 28 # in seconds (API Gateway has a timeout of 29 seconds)
            layers:
                - ${bref:layer.php-73-fpm} #-fpm
            events:
                - http:
                    path: /html2pdf
                    method: post
                    cors: true
    
       
    
    # Exclude files from deployment
    package:
        exclude:
            - 'node_modules/**'
            - 'tests/**'

The index.php (mentioned in the yml file above):

 <?php
    
    require_once __DIR__ . '/../vendor/autoload.php';
    
    use App\JsonParserMiddleware;
    
    use Psr\Http\Message\ResponseInterface as Response;
    use Psr\Http\Message\ServerRequestInterface as Request;
    use Slim\Factory\AppFactory;
    
    $app = AppFactory::create();
    $app->addMiddleware(new JsonParserMiddleware());
    
    $app->post("/html2pdf", function (Request $request, Response $response) {
        
        $data = $request->getParsedBody();
        $payload = [];
        $statusCode = 200;
        if ($data['data'] == null) {
            $payload['error'] = "HTML 64-bit encoded string is required";
            return response($response, $payload, 422);
        }
        $mpdf = new \Mpdf\Mpdf(['tempDir' => '/tmp']);
        $mpdf->WriteHTML(base64_decode($data['data']));
        
        $pdf = $mpdf->Output(null,"S");
    
        $filename = $data['title'];
    
        $body = base64_encode($pdf);
    
        $response->getBody()->write($body);
    
        $response->isBase64Encoded = true;
        
        $response = $response 
                    ->withHeader("Access-Control-Allow-Origin", "*")
                    ->withHeader('Access-Control-Allow-Credentials', "true")  
                    ->withHeader('Content-Type','application/pdf')
                    ->withHeader('Content-Disposition', sprintf('attachment; filename="%s"', $filename))
                    ->withStatus($statusCode);
        
        return $response;
        
    });

And the client-side code, using axios, is:

let data = { data: <<some base64 encoded html string>>, title: "file.pdf" };

let options = {
              headers: {
                "Content-Type": "application/json",
                // "Accept": "*/*",
              },
             }
let payload = {data : btoa(data),title:"contract.pdf"};
let url = "https://oli9w0wghb.execute-api.us-east-1.amazonaws.com/dev/html2pdf";

axios.post(url, payload, options)
    .then(response => {
      console.log(response.data);
    });

Answer 1

Hi i had the same problem, and I fixed it:

The headers i used in the controller are (Im using SLIM4):

    $response->getBody()->write($pdfContent);
    $response = $response->withHeader('Content-type', 'application/pdf');
    $response->isBase64Encoded = true;

Then to configure the serverless.yml i need to add:

service: *****

provider:
    region: ****
    runtime: ***
    profile: ****
    apiGateway:
        binaryMediaTypes:
            - 'application/pdf'
    environment:
        BREF_BINARY_RESPONSES: '1'
       


plugins:
    - ./vendor/bref/bref

functions:
    api:
        handler: public/index.php
        description: ''
        timeout: 28 # in seconds (API Gateway has a timeout of 29 seconds)
        layers:
            - ${bref:layer.php-81-fpm}
        events:
            -   http: ANY /{proxy+}
        environment:
            BREF_BINARY_RESPONSE: '1'

I hope this helps you.