Prototype pollution fix - checking magic attributes

[d3v53c]

📊 Metadata *

js-data is vulnerable to Prototype Pollution.

Bounty URL: https://www.huntr.dev/bounties/2-npm-js-data/

⚙️ Description *

Prototype Pollution refers to the ability to inject properties into existing JavaScript language construct prototypes, such as objects.
JavaScript allows all Object attributes to be altered, including their magical attributes such as proto, constructor and prototype.
An attacker manipulates these attributes to overwrite, or pollute, a JavaScript application object prototype of the base object by injecting other values.
Properties on the Object.prototype are then inherited by all the JavaScript objects through the prototype chain.

💻 Technical Description *

Fixed by avoiding setting magical attributes. The bug is fixed by validating the input strArray to check for prototypes. It is implemented by a simple validation to check for prototype keywords (proto, constructor and prototype), where if it exists, the function returns the object without modifying it, thus fixing the Prototype Pollution Vulnerability.

🐛 Proof of Concept (PoC) *

Create the following PoC file:

// poc.js
const js = require("js-data");
const payload = JSON.parse('{"__proto__":{"polluted":"Yes! Its Polluted"}}');
var obj = {}
console.log("Before : " + {}.polluted);
js.utils.deepMixIn(obj, payload);
console.log("After : " + {}.polluted);

Execute the following commands in terminal:

npm i js-data # Install affected module
node poc.js #  Run the PoC

Check the Output:

Before : undefined
After : Yes! Its Polluted

🔥 Proof of Fix (PoF) *

Before:

After:

👍 User Acceptance Testing (UAT)

After applying the fix, functionality is unaffected.

🔗 Relates to...

418sec/huntr#1794

[huntr-helper]

👋 Hello, @jmdobry - @d3v53c has opened a PR to us with a fix for a potential vulnerability in your repository. To view the vulnerability, please refer to the bounty URL in the first comment, above.

Ultimately, you get to decide if the fix is 👍 or 👎. If you are happy with the fix, please write a new comment (@huntr-helper - LGTM) and we will open a PR to your repository with the fix. All remaining PRs for this vulnerability will be automatically closed.

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@jmdobry & @d3v53c - thank you for your efforts in securing the world’s open source code! 🎉