New Tools for Protection and Forensics by Unknown

Author:Unknown
Format: epub
Published: 0101-01-01T00:00:00+00:00

5.2. A practical example

Least privilege dictates the minimum set of system resources (network, file system, desktop) that a given task needs to function correctly, for example, in the context of the browser, a task is an application context defined by the top-level domain (the site top-level domain). What resources does Facebook.com, for example, really need? It needs its cookie and DOM storage, and access to the untrusted web. If the browser tab for Facebook.com is compromised (e.g., it delivers a poisoned advertisement), we can tolerate loss of the cookie (which compromises user privacy, but not system security). We can live with the fact that malware will have access to the untrusted internet. The system will still be safe if malware cannot:

• see any user keystrokes, mouse input, or gain access to the screen (to copy pixels from the display, or display any content to the user),

• access any other privileged data, for example, files other than the Facebook cookie, or registry entries that might leak valuable information

• gain access to valuable networks or sites (e.g., SaaS sites or the intranet),

• access any privileged devices (printers, webcam, the OS file system, or shares)

Least privilege dictates that the task must not have access to any other resources unless they are explicitly required, and then only under precise control, and only for the shortest possible duration. For example:

• If the user wants to upload a photo to Facebook, he/she can select the photo (in the usual way) on the desktop, and then (only) the selected file will be injected into the hardware-isolated task that is rendering the Facebook.com browser tab.

• If the user wants to download a file, it can be allowed to persist outside the confines of the isolated task, but only if we remember the fact that it is untrusted, so that it can only ever be opened in another hardware-isolated task.

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