The Sony Xperia L1 Android device with a build fingerprint of Sony/G3313/G3313:7.0/43.0.A.6.49/2867558199:user/release-keys contains the android framework (i.e., system_server) with a package name of android (versionCode=24, versionName=7.0) that has been modified by Sony or another entity in the supply chain. The system_server process in the core android package has an exported broadcast receiver that allows any app co-located on the device to programmatically initiate the taking of a screenshot and have the resulting screenshot be written to external storage. The taking of a screenshot is not transparent to the user; the device has a screen animation as the screenshot is taken and there is a notification indicating that a screenshot occurred. If the attacking app also requests the EXPAND_STATUS_BAR permission, it can wake the device up using certain techniques and expand the status bar to take a screenshot of the user’s notifications even if the device has an active screen lock. The notifications may contain sensitive data such as text messages used in two-factor authentication. The system_server process that provides this capability cannot be disabled, as it is part of the Android framework. The notification can be removed by a local Denial of Service (DoS) attack to reboot the device.
The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.
Input validation is a frequently-used technique for checking potentially dangerous inputs in order to ensure that the inputs are safe for processing within the code, or when communicating with other components. When software does not validate input properly, an attacker is able to craft the input in a form that is not expected by the rest of the application. This will lead to parts of the system receiving unintended input, which may result in altered control flow, arbitrary control of a resource, or arbitrary code execution. Input validation is not the only technique for processing input, however. Other techniques attempt to transform potentially-dangerous input into something safe, such as filtering (CWE-790) - which attempts to remove dangerous inputs - or encoding/escaping (CWE-116), which attempts to ensure that the input is not misinterpreted when it is included in output to another component. Other techniques exist as well (see CWE-138 for more examples.) Input validation can be applied to:
Data can be simple or structured. Structured data can be composed of many nested layers, composed of combinations of metadata and raw data, with other simple or structured data. Many properties of raw data or metadata may need to be validated upon entry into the code, such as:
Implied or derived properties of data must often be calculated or inferred by the code itself. Errors in deriving properties may be considered a contributing factor to improper input validation.
Note that “input validation” has very different meanings to different people, or within different classification schemes. Caution must be used when referencing this CWE entry or mapping to it. For example, some weaknesses might involve inadvertently giving control to an attacker over an input when they should not be able to provide an input at all, but sometimes this is referred to as input validation. Finally, it is important to emphasize that the distinctions between input validation and output escaping are often blurred, and developers must be careful to understand the difference, including how input validation is not always sufficient to prevent vulnerabilities, especially when less stringent data types must be supported, such as free-form text. Consider a SQL injection scenario in which a person’s last name is inserted into a query. The name “O’Reilly” would likely pass the validation step since it is a common last name in the English language. However, this valid name cannot be directly inserted into the database because it contains the “'” apostrophe character, which would need to be escaped or otherwise transformed. In this case, removing the apostrophe might reduce the risk of SQL injection, but it would produce incorrect behavior because the wrong name would be recorded.