Installing a zero-permission Android application on certain Samsung Android devices with KK(4.4), L(5.0/5.1), and M(6.0) software can continually crash the system_server process in the Android OS. The zero-permission app will create an active install session for a separate app that it has embedded within it. The active install session of the embedded app is performed using the android.content.pm.PackageInstaller class and its nested classes in the Android API. The active install session will write the embedded APK file to the /data/app directory, but the app will not be installed since third-party applications cannot programmatically install apps. Samsung has modified AOSP in order to accelerate the parsing of APKs by introducing the com.android.server.pm.PackagePrefetcher class and its nested classes. These classes will parse the APKs present in the /data/app directory and other directories, even if the app is not actually installed. The embedded APK that was written to the /data/app directory via the active install session has a very large but valid AndroidManifest.xml file. Specifically, the AndroidManifest.xml file contains a very large string value for the name of a permission-tree that it declares. When system_server tries to parse the APK file of the embedded app from the active install session, it will crash due to an uncaught error (i.e., java.lang.OutOfMemoryError) or an uncaught exception (i.e., std::bad_alloc) because of memory constraints. The Samsung Android device will encounter a soft reboot due to a system_server crash, and this action will keep repeating since parsing the APKs in the /data/app directory as performed by the system_server process is part of the normal boot process. The Samsung ID is SVE-2016-6917.
The product performs operations on a memory buffer, but it can read from or write to a memory location that is outside of the intended boundary of the buffer.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Samsung_mobile | Samsung | 4.4 (including) | 4.4 (including) |
| Samsung_mobile | Samsung | 5.0 (including) | 5.0 (including) |
| Samsung_mobile | Samsung | 5.1 (including) | 5.1 (including) |
| Samsung_mobile | Samsung | 6.0 (including) | 6.0 (including) |
Certain languages allow direct addressing of memory locations and do not automatically ensure that these locations are valid for the memory buffer that is being referenced. This can cause read or write operations to be performed on memory locations that may be associated with other variables, data structures, or internal program data. As a result, an attacker may be able to execute arbitrary code, alter the intended control flow, read sensitive information, or cause the system to crash.
Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer.
Be wary that a language’s interface to native code may still be subject to overflows, even if the language itself is theoretically safe.
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Examples include the Safe C String Library (SafeStr) by Messier and Viega [REF-57], and the Strsafe.h library from Microsoft [REF-56]. These libraries provide safer versions of overflow-prone string-handling functions.
Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking.
D3-SFCV (Stack Frame Canary Validation) from D3FEND [REF-1334] discusses canary-based detection in detail.
Consider adhering to the following rules when allocating and managing an application’s memory:
Run or compile the software using features or extensions that randomly arrange the positions of a program’s executable and libraries in memory. Because this makes the addresses unpredictable, it can prevent an attacker from reliably jumping to exploitable code.
Examples include Address Space Layout Randomization (ASLR) [REF-58] [REF-60] and Position-Independent Executables (PIE) [REF-64]. Imported modules may be similarly realigned if their default memory addresses conflict with other modules, in a process known as “rebasing” (for Windows) and “prelinking” (for Linux) [REF-1332] using randomly generated addresses. ASLR for libraries cannot be used in conjunction with prelink since it would require relocating the libraries at run-time, defeating the whole purpose of prelinking.
For more information on these techniques see D3-SAOR (Segment Address Offset Randomization) from D3FEND [REF-1335].
Use a CPU and operating system that offers Data Execution Protection (using hardware NX or XD bits) or the equivalent techniques that simulate this feature in software, such as PaX [REF-60] [REF-61]. These techniques ensure that any instruction executed is exclusively at a memory address that is part of the code segment.
For more information on these techniques see D3-PSEP (Process Segment Execution Prevention) from D3FEND [REF-1336].