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@kbn/safer-lodash-set

src/platform/packages/shared/kbn-safer-lodash-set/README.md

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@kbn/safer-lodash-set

This module adds protection against prototype pollution to the set and setWith functions from Lodash and are API compatible with Lodash v4.x.

Example Usage

js
const { set } = require('@kbn/safer-lodash-set');

const object = { a: [{ b: { c: 3 } }] };

set(object, 'a[0].b.c', 4);
console.log(object.a[0].b.c); // => 4

set(object, ['x', '0', 'y', 'z'], 5);
console.log(object.x[0].y.z); // => 5

API

The main module exposes two functions, set and setWith:

js
const { set, setWith } = require('@kbn/safer-lodash-set');

Besides the main module, it's also possible to require each function individually:

js
const set = require('@kbn/safer-lodash-set/set');
const setWith = require('@kbn/safer-lodash-set/setWith');

The APIs of these functions are identical to the equivalent Lodash set and setWith functions. Please refer to the Lodash documentation for the respective functions for details.

Functional Programming support (fp)

This module also supports the lodash/fp api and hence exposes the following fp compatible functions:

js
const { set, setWith } = require('@kbn/safer-lodash-set/fp');

Besides the main fp module, it's also possible to require each function individually:

js
const set = require('@kbn/safer-lodash-set/fp/set');
const setWith = require('@kbn/safer-lodash-set/fp/setWith');

Limitations

The safety improvements in this module is achieved by adding the following limitations to the algorithm used to walk the path given as the 2nd argument to the set and setWith functions:

Only own properties are followed when walking the path

js
const parent = { foo: 1 };
const child = { bar: 2 };

Object.setPrototypeOf(child, parent);

// Now `child` can access `foo` through prototype inheritance
console.log(child.foo); // 1

set(child, 'foo', 3);

// A different `foo` property has now been added directly to the `child`
// object and the `parent` object has not been modified:
console.log(child.foo); // 3
console.log(parent.foo); // 1
console.log(Object.hasOwn(child, 'foo')); // true

The path must not access function prototypes

js
const object = {
  fn1: function () {},
  fn2: () => {},
};

// Attempting to access any function prototype will result in an
// exception being thrown:
assert.throws(() => {
  // Throws: Illegal access of function prototype
  set(object, 'fn1.prototype.toString', 'bang!');
});

// This also goes for arrow functions even though they don't have a
// prototype property. This is just to keep things consistent:
assert.throws(() => {
  // Throws: Illegal access of function prototype
  set(object, 'fn2.prototype.toString', 'bang!');
});

License

MIT