Читать книгу Security Engineering - Ross Anderson - Страница 219

The late 1990s saw the emergence of yet another type of access control: the software sandbox, introduced by Sun with its Java programming language. The model is that a user wants to run some code that she has downloaded as an applet, but is concerned that the applet might do something nasty, such as stealing her address book and mailing it off to a marketing company, or just hogging the CPU and running down the battery.

The designers of Java tackled this problem by providing a ‘sandbox’ – a restricted environment in which the code has no access to the local hard disk (or at most only temporary access to a restricted directory), and is only allowed to communicate with the host it came from (the same-origin policy). This is enforced by having the code executed by an interpreter – the Java Virtual Machine (JVM) – with only limited access rights [784]. This idea was adapted to JavaScript, the main scripting language used in web pages, though it's actually a different language; and other active content too. A version of Java is also used on smartcards so they can support applets written by different firms.