How to Check PNG files for Malware in Node.js

Sophisticated threat actors can hide malware in just about any seemingly innocent file type — including PNG files.

They can also use intentionally malformed PNGs to trigger heap or stack buffer overflows in vulnerable PNG rendering and processing libraries.

Using Node.js code examples provided below, we can simultaneously scan PNG files for malware and check to make sure the file strictly adheres to PNG formatting standards. We can scan dozens of additional media files (and Office formats + PDFs) using this API, so it’s a great solution to incorporate in a Node.js form handling client-side file uploads.

To begin, let’s install the SDK via NPM install:

npm install cloudmersive-virus-api-client --save

Alternatively, we can add this snippet to our package.json:

  "dependencies": {
    "cloudmersive-virus-api-client": "^1.1.9"
  }

Next, let’s turn our attention to authorization. If we grab a free Cloudmersive API key, we’ll be able to make up to 800 API calls per month with zero commitments.

Lastly, let’s go ahead and call the function:

var CloudmersiveVirusApiClient = require('cloudmersive-virus-api-client');
var defaultClient = CloudmersiveVirusApiClient.ApiClient.instance;

// Configure API key authorization: Apikey
var Apikey = defaultClient.authentications['Apikey'];
Apikey.apiKey = 'YOUR API KEY';



var apiInstance = new CloudmersiveVirusApiClient.ScanApi();

var inputFile = Buffer.from(fs.readFileSync("C:\\temp\\inputfile").buffer); // File | Input file to perform the operation on.

var opts = { 
  'allowExecutables': true, // Boolean | Set to false to block executable files (program code) from being allowed in the input file.  Default is false (recommended).
  'allowInvalidFiles': true, // Boolean | Set to false to block invalid files, such as a PDF file that is not really a valid PDF file, or a Word Document that is not a valid Word Document.  Default is false (recommended).
  'allowScripts': true, // Boolean | Set to false to block script files, such as a PHP files, Python scripts, and other malicious content or security threats that can be embedded in the file.  Set to true to allow these file types.  Default is false (recommended).
  'allowPasswordProtectedFiles': true, // Boolean | Set to false to block password protected and encrypted files, such as encrypted zip and rar files, and other files that seek to circumvent scanning through passwords.  Set to true to allow these file types.  Default is false (recommended).
  'allowMacros': true, // Boolean | Set to false to block macros and other threats embedded in document files, such as Word, Excel and PowerPoint embedded Macros, and other files that contain embedded content threats.  Set to true to allow these file types.  Default is false (recommended).
  'allowXmlExternalEntities': true, // Boolean | Set to false to block XML External Entities and other threats embedded in XML files, and other files that contain embedded content threats.  Set to true to allow these file types.  Default is false (recommended).
  'allowInsecureDeserialization': true, // Boolean | Set to false to block Insecure Deserialization and other threats embedded in JSON and other object serialization files, and other files that contain embedded content threats.  Set to true to allow these file types.  Default is false (recommended).
  'allowHtml': true, // Boolean | Set to false to block HTML input in the top level file; HTML can contain XSS, scripts, local file accesses and other threats.  Set to true to allow these file types.  Default is false (recommended) [for API keys created prior to the release of this feature default is true for backward compatability].
  'restrictFileTypes': "restrictFileTypes_example" // String | Specify a restricted set of file formats to allow as clean as a comma-separated list of file formats, such as .pdf,.docx,.png would allow only PDF, PNG and Word document files.  All files must pass content verification against this list of file formats, if they do not, then the result will be returned as CleanResult=false.  Set restrictFileTypes parameter to null or empty string to disable; default is disabled.
};

var callback = function(error, data, response) {
  if (error) {
    console.error(error);
  } else {
    console.log('API called successfully. Returned data: ' + data);
  }
};
apiInstance.scanFileAdvanced(inputFile, opts, callback);

The underlying service will automatically check for viruses and malware, and we can set additional custom threat rules in our request body to block a wide range of other content threats (scripts, invalid files, etc.)

We could even use the ‘restrictFileTypes’ parameter to block PNG file uploads entirely if we’re only targeting other image formats. To do that, we would simply need to include a comma-separated list that specified the formats we wanted (e.g., ‘.gif,.jpg’), and any files that didn’t pass a verification check against those specific formats would receive a “CleanResult”: False response.