* frameworks/base/core/java/android/os/PowerManager.java * The interface that applications use to talk to the global power manager Request to the PowerManager to acquire (and later release) a wake lock: Let’s see how this works through a simple example. The client’s requests without there being anyway for others to spoof it. Use as a token that can be shared with a server process, and the server can use it to validate Secure interaction between cooperating processes: a client can create a Binder object to Unique, which means if you create one, nobody else can create one that appears equal to it.įor this reason, the application framework uses Binder tokens extensively in order to ensure The Binder’s unique object identity rules allow them to be used for a special purpose: as Its appropriate value to ensure that equality will behave as expected even in remote (and vice versa) for each Binder it sees, and assigns each Binder’s object reference The Binder kernel driver maintains a mapping of local addresses to remote Binder handles A unique 32-bit handle (as assigned by the Binder kernel driver) pointing to theīinder’s virtual memory address in a different process.A virtual memory address pointing to a Binder object in the same process, or.Is treated a little differently than those of other objects. The Binder’s unique, cross-process object identity contract, a Binder’s object reference To ensure that Java’s = operator adheres to This facility is provided by the Binder kernel driver, whichĪnalyzes the contents of each Binder transaction and assigns a unique 32-bit integer Identity across all processes in the system, no matter how many process boundaries Binder TokensĪn interesting property of Binder objects is that each instance maintains a unique These features in detail, known as Binder tokens. That are used extensively throughout the system in a mix of clever ways, making it muchĮasier for the framework to address security issues. But Binders also have a number of other cool features Of IPC from the developer, allowing applications to easily talk to both the System ServerĪnd others’ remote service components. To my surprise, the answer to nearly all of my questions was pretty simple: the Binder.īinders are the cornerstone of Android’s architecture they abstract the low-level details In a way that is both efficient and secure? Or from hiding another application’s windows from the screen? More generally, how doĪndroid’s core system services respond to requests made by third-party applications What mechanism prevents me from, forĮxample, tricking the system into releasing a wake lock acquired by another application, Should be taken care of automatically by the system.įor a long time I took this security for granted, not completely understanding how it wasĪctually enforced. Have to take extra steps to protect the device from malicious applications. This architecture was chosen with both developers and device users in mind: neither should Uses application sandboxes and Linux process isolation to prevent applications from beingĪble to access the system or other applications in ways that are not controlled and secure. One of Android’s key design goals was to provide an open platform that doesn’t rely on aĬentral authority to verify that applications do what they claim. 首先,先介绍下背景环境,第一,是Android7.Note: if you liked this post, be sure to read my second blog post about
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