CVE-2018-14997

The Leagoo P1 Android device with a build fingerprint of sp7731c_1h10_32v4_bird:6.0/MRA58K/android.20170629.214736:user/release-keys contains the android framework (i.e., system_server) with a package name of android that has been modified by Leagoo 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 users 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.

Weakness

The product does not perform an authorization check when an actor attempts to access a resource or perform an action.

Affected Software

Extended Description

Assuming a user with a given identity, authorization is the process of determining whether that user can access a given resource, based on the user’s privileges and any permissions or other access-control specifications that apply to the resource. When access control checks are not applied, users are able to access data or perform actions that they should not be allowed to perform. This can lead to a wide range of problems, including information exposures, denial of service, and arbitrary code execution.

Potential Mitigations

• Divide the product into anonymous, normal, privileged, and administrative areas. Reduce the attack surface by carefully mapping roles with data and functionality. Use role-based access control (RBAC) [REF-229] to enforce the roles at the appropriate boundaries.
• Note that this approach may not protect against horizontal authorization, i.e., it will not protect a user from attacking others with the same role.
• Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
• For example, consider using authorization frameworks such as the JAAS Authorization Framework [REF-233] and the OWASP ESAPI Access Control feature [REF-45].
• For web applications, make sure that the access control mechanism is enforced correctly at the server side on every page. Users should not be able to access any unauthorized functionality or information by simply requesting direct access to that page.
• One way to do this is to ensure that all pages containing sensitive information are not cached, and that all such pages restrict access to requests that are accompanied by an active and authenticated session token associated with a user who has the required permissions to access that page.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/665.html

References

• https://www.kryptowire.com
• https://www.kryptowire.com/portal/android-firmware-defcon-2018/
• https://www.kryptowire.com/portal/wp-content/uploads/2018/12/DEFCON-26-Johnson-and-Stavrou-Vulnerable-Out-of-the-Box-An-Eval-of-Android-Carrier-Devices-WP-Updated.pdf
• https://www.kryptowire.com
• https://www.kryptowire.com/portal/android-firmware-defcon-2018/
• https://www.kryptowire.com/portal/wp-content/uploads/2018/12/DEFCON-26-Johnson-and-Stavrou-Vulnerable-Out-of-the-Box-An-Eval-of-Android-Carrier-Devices-WP-Updated.pdf