How do I allow base64 svg in img src?

Question

I'm using HTMLPurifier to make sure there is no malicious user input.

I'm having a hard time with base64 images. The regular one is already solved.
$config->set('URI.AllowedSchemes', ['data' => true]);

But how about the following?
<img src="data:image/svg+xml;base64,PHN2Zy...4MTEpIi8+PC9zdmc+Cg==" />

Answer 1

For everyone looking for a solution.. there is no built in way to allow base64 svg images. But there is a way to solve it.

I could not find an official documentation, but you can write custom validations.

<?php

namespace App\Services\HTMLPurifier;

use HTMLPurifier_AttrDef_URI;

/**
 * Class ParameterURIDef
 * @author Artem Schander
 */
class ParameterURIDef extends HTMLPurifier_AttrDef_URI
{
    public function validate($uri, $config, $context)
    {
        if (preg_match('/^data:image\/svg\+xml;base64,([^\"]*)$/', $uri)) {
            return true;
        }

        return parent::validate($uri, $config, $context);
    }
}

$config = HTMLPurifier_Config::createDefault();
$config->set('URI.AllowedSchemes', ['data' => true]);
$definition = $config->getHTMLDefinition(true);
$definition->addAttribute('img', 'src', new \App\Services\HTMLPurifier\ParameterURIDef());

$HTMLPurifier = new HTMLPurifier($config);