getOwnPropertyDescriptor() can be used to get access to raw values

[ravijayaramappa]

Description

When an observable value has a configurable property, the reactive proxy and the readonly proxy can be bypassed to gain access to the underlying raw value.

This can be done using the getOwnPropertyDescriptor() to gain access to the raw descriptor of the raw value. In the case of the read-only proxy, the user can bypass the read only membrane and mutate the original object.

Further, the proxy implementation has to protection for descriptors that have a getter/setter.

Steps to Reproduce

const target = new ReactiveMembrane();
const todos = {};
const observable = {};
Object.defineProperty(todos, 'foo', {
    get() {
        return observable;
    },
    configurable: true
});

const proxy = target.getProxy(todos);
const desc = Object.getOwnPropertyDescriptor(proxy, 'foo');
const { get } = desc;
get(); // Will return the raw observable object. expected to see a reactive proxy
proxy.foo; // Will return a reactive proxy as expected

const target = new ReactiveMembrane();
const todos = {};
const observable = {};
Object.defineProperty(todos, 'foo', {
    value : observable,
    configurable: true
});

const proxy = target.getProxy(todos);

const desc = Object.getOwnPropertyDescriptor(proxy, 'foo');
const { value } = desc;
value; Will be the raw observable object, expected to be a proxy

Added tests as part of a PR: #21

Expected Results

Should not be able to evade the membrane containment using getOwnPropertyDescriptor()

Actual Results

Able to get out of the membrane

Browsers Affected

all

Version

0.25.0

Possible Solution

getOwnPropertyDescriptor(shadowTarget: ReactiveMembraneShadowTarget, key: PropertyKey): PropertyDescriptor | undefined {
    const { originalTarget, membrane, valueObserved } = this;

    // keys looked up via hasOwnProperty need to be reactive
    if (!isUndefined(valueObserved)) {
        valueObserved(originalTarget, key);
    }

    let desc = getOwnPropertyDescriptor(originalTarget, key);
    if (isUndefined(desc)) {
        return desc;
    }
    // Fix
    if(configurable) {
        return wrapDescriptor(membrane, desc);
    }
    // endFix
    const shadowDescriptor = getOwnPropertyDescriptor(shadowTarget, key);
    if (!desc.configurable && !shadowDescriptor) {
        // If descriptor from original target is not configurable,
        // We must copy the wrapped descriptor over to the shadow target.
        // Otherwise, proxy will throw an invariant error.
        // This is our last chance to lock the value.
        // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy/handler/getOwnPropertyDescriptor#Invariants
        desc = wrapDescriptor(membrane, desc);
        ObjectDefineProperty(shadowTarget, key, desc);
    }
    return shadowDescriptor || desc;
}

Additional context/Screenshots
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