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metamask-extension/app/scripts/lockdown-more.js

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// Make all "object" and "function" own properties of globalThis
// non-configurable and non-writable, when possible.
// We call a property that is non-configurable and non-writable,
// "non-modifiable".
try {
/**
* `lockdown` only hardens the properties enumerated by the
* universalPropertyNames constant specified in 'ses/src/whitelist'. This
* function makes all function and object properties on the start compartment
* global non-configurable and non-writable, unless they are already
* non-configurable, or they were scuttled by LavaMoat runtime (LavaMoat#360).
*
* It is critical that this function runs at the right time during
* initialization, which should always be immediately after `lockdown` has been
* called. At the time of writing, the modifications this function makes to the
* runtime environment appear to be non-breaking, but that could change with
* the addition of dependencies, or the order of our scripts in our HTML files.
* Exercise caution.
*
* See inline comments for implementation details.
*
* We write this function in IIFE format to avoid polluting global scope.
*/
(function protectIntrinsics() {
const lmre = // regex expression for LavaMoat scuttling error message
/LavaMoat - property "[A-Za-z0-9]*" of globalThis is inaccessible under scuttling mode/u;
const namedIntrinsics = Reflect.ownKeys(new Compartment().globalThis);
// These named intrinsics are not automatically hardened by `lockdown`
const shouldHardenManually = new Set(['eval', 'Function']);
const globalProperties = new Set([
// universalPropertyNames is a constant added by lockdown to global scope
// at the time of writing, it is initialized in 'ses/src/whitelist'.
// These properties tend to be non-enumerable.
...namedIntrinsics,
// TODO: Also include the named platform globals
// This grabs every enumerable property on globalThis.
// ...Object.keys(globalThis),
]);
globalProperties.forEach((propertyName) => {
const descriptor = Reflect.getOwnPropertyDescriptor(
globalThis,
propertyName,
);
if (descriptor) {
if (descriptor.configurable) {
// If the property on globalThis is configurable, make it
// non-configurable. If it has no accessor properties, also make it
// non-writable.
if (hasAccessor(descriptor)) {
Object.defineProperty(globalThis, propertyName, {
configurable: false,
});
} else {
Object.defineProperty(globalThis, propertyName, {
configurable: false,
writable: false,
});
}
}
if (shouldHardenManually.has(propertyName)) {
try {
harden(globalThis[propertyName]);
} catch (err) {
if (!lmre.test(err.message)) {
throw err;
}
console.warn(
`Property ${propertyName} will not be hardened`,
`because it is scuttled by LavaMoat protection.`,
`Visit https://github.com/LavaMoat/LavaMoat/pull/360 to learn more.`,
);
}
}
}
});
/**
* Checks whether the given propertyName descriptor has any accessors, i.e. the
* properties `get` or `set`.
*
* We want to make globals non-writable, and we can't set the `writable`
* property and accessor properties at the same time.
*
* @param {object} descriptor - The propertyName descriptor to check.
* @returns {boolean} Whether the propertyName descriptor has any accessors.
*/
function hasAccessor(descriptor) {
return 'set' in descriptor || 'get' in descriptor;
}
})();
} catch (error) {
console.error('Protecting intrinsics failed:', error);
if (globalThis.sentry && globalThis.sentry.captureException) {
globalThis.sentry.captureException(
new Error(`Protecting intrinsics failed: ${error.message}`),
);
}
}