Download Goldfish 2.6 Kernel _TOP

In this work we present an industry-driven case study of applying static program analysis to the Android kernel. In particular, we investigate the ability of open source tools as represented by Cppcheck and of commercial tools as represented by Goanna to detect security vulnerabilities. In our case study, we explore static security checking along the dimensions of setup effort, run time, quality of results and usability for large code bases. We present the results we obtained from analyzing the Android Goldfish kernel module of around 740 kLoC of C/C++ code. Moreover, we highlight some lessons learned that might serve as a guidance for future applications.

The following table is a list of goldfish device drivers. This is based on kernel version 3.10.0. At the moment, kernel version 3.10.0 is for ranchu and 3.4.67 is for goldfish. The following table lists some goldfish specific devices. In ranchu, Virtio devices are used as block devices to simulate EMMC. Virtio devices are paravirtualized devices in QEMU that have better performance than emulated ...

Download Goldfish 2.6 Kernel

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Recently, I needed to compile a custom Android kernel for a research projectthat required a newer kernel version (as well as a few kernel configs) thanwhat was available from the standard Android emulator images.

There are multiple branches depending on which kernel version you wish tobuild. From my results, the android-* branches do not work properly whilethe android-goldfish-* branches do. If you have issues running your compiledkernel, try using another branch instead.

After the build process is finished, we can run and debug the kernel in the Android emulator. The compressed kernel image can be found at arch/arm/boot/zImage. This image can be used to run the kernel in the emulator. The image file vmlinux is in ELF format; it can be used by gdb to get the debug symbol. We give the following command to start the Android emulator using our own kernel image:

After the emulator is running, we can start the gdb debugger to debug the kernel. We will use the graphical interface ddd to start the gdb debugger; it produces a more user-friendly environment. In the following command line, we tell ddd to use arm-eabi-gdb as the debugger and vmlinux as the binary image:

After gdb starts, it needs to connect to the gdbserver in the emulator using the command target remote localhost:1234. To track the boot-up progress, we can set a breakpoint at the function start_kernel:

After the system boots up, a console like that shown in Figure 10.3 appears. The entire Android system should be ready to use at this point. From here, we boot the kernel in the Android emulator directly. In the next few sections, we will boot this kernel using U-Boot.

Similar to ASAN, KASAN uses a combination of memory-function instrumentation at compile time and shadow memory to track memory accesses at runtime. In KASAN, an eighth of the kernel memory space is dedicated to shadow memory, which determines if a memory access is valid or not.

memcpy is just one trigger point that can trigger kasan check. check_memory_region checks whether the target memory scope is poisoned. Here, memcpy checks whether memory of [src, len] and [dst, len] is poisoned, if poisoned, kasan reports this illegal operation and panic the kernel.

As for memory poison check, it actually checks its shadow memory. All the shadow bytes of the memory is checked:

when the memory is freed, the shadow memory changes to:

Now the shadow bytes all become 0xff(different status has different value), if UAF/double free occurs, memory opertion triggers kasan check, and the shadow bytes are illegal now, kasan gives report and panics the kernel.

In android kernel, the status can be:

Once you have source downloaded you have to breakfast or lunch;so that, the kernel sources for your device are downloaded. Also please check your device specific build guides in case you are using CyanogenMod in order to retrieve pre-builts and proprietary blobs.

As I am building for the emulator, I have selected the option 6, which is the cm_goldfish-eng. Instead of the lunch command, you can also use the breakfast command which takes the device code (these device codes can be found here) name as a parameter. So in our case it would be:

After the lunch or breakfast command (whichever you have used) it take a couple of minutes to download the kernel sources for your device in our example it will download the Goldfish Kernel (3.4.xxx).

b) Once you are in the kernel source folder. We will create a directory for our module in the drivers directory of the kernel source. So technically we are building a driver which will print hello world on kernel message buffer. In order to do so go to the drivers directory and create a directory for your module.

In order to check this, goto the kernel source parent directory (in our example case kernel/goldfish) and than navigate to the "arch" directory and than from there navigate to the architecture for which you are building android. As most of the Android based smartphones are ARM based so most of the times you have to go into the arm directory unless you are building Android for some other architectures listed in the arch directory. As for our example we are using the android emulator which is emulating the ARM instruction set so, I have navigated to the "arm" directory and than from here to the "configs" directory.

It would take tens of minutes to do the build if everything is smooth and fine. Once the build finishes now you can flash the zip on your device. As we are using emulator for our example, we need to do one step more because the emulator, normally uses a prebuilt kernel which most of the time is compiled with the CONFIG_MODULES=n. So the prebuilt kernel cannot load our modules and we have to change the prebuilt kernel image with the one which we have just compiled.

Step 7: This step only implies if you are using emulator. To replace the prebulit emulator kernel first backup the prebuilt emulator. The prebuilt emulator kernel file is "prebuilts/qemu-kernel/arm/kernel-qemu-armv7". Backup this "kernel-qemu-armv7" file and than replace the "prebuilts/qemu-kernel/arm/kernel-qemu-armv7" image with the newly compiled kernel image which is found at copy the "out/target/product/generic/kernel" . Now, once kernel is replaced from the Android/CyanogenMod source parent directory write the following command.

Now the module we have built can be found in the device "system/lib/modules" directory it is clear from the screenshot also. Now, we have to insert that module using "insmod" and than have to check the kernel message buffer whether the message is printed or not. you can remove the module using "rmmod". Now from the device shell insert the module using the following command, the output of the module is also listed in the above screenshot:

Note: You won't be able to see this commit history because we did a shallow clone. However, I have a full clone of the q-goldfish-android-goldfish-4.14-dev branch.

This article is about Linux kernel pwn. The kernel that can be studied is just privilege escalation, among which what has been studied most is the Linux system privilege escalation of x86 and arm instruction set. The Linux system privilege escalation of arm instruction set is basically Android root and iOS jailbreak, while there is a few about mips instruction set, which may because there are few application scenes.

It is very troublesome to clone directly and compile under the git directory because the Android kernel source code is goldfish[1]. If you want to study that version, you can download the "tar.gz" for that branch directly.

When I learn the Android kernel pwn at the beginning, I have studied a project on Github [3], which relies on the old kernel. It is estimated that the kernel is below Android 3.4, and there are various problems in 3.10 or above, so I made some modifications myself, and opened a Github source as well.

To add debug symbols to the kernel just needs to add CONFIG_DEBUG_INFO=y in the above configuration file. If it is goldfish, you need to add by yourself. There are already debug symbols in the default configuration of ranchu, so you don't need to modify it.

The compiled kernel is in the /tmp/qemu-kernel directory. There are two files: one is zImage--the kernel boot image; the other one is vmlinux--the kernel binary file, which is either used to analyze the kernel IDA or to provide symbolic information to gdb.

My environment is derived from the AndroidKernelExploitationPlayground project [3], but the actual test found that it may rely on the 3.4 kernel in the project, while the current emulator requires the kernel version to be greater than or equal to 3.10.

There are many changes from kernel 3.4 to 3.10. Firstly, some functions in the kernel were deleted and modified, so the driver code needs to be changed. Secondly, the kernel 3.4 does not turn on the PXN protection. In kernel mode, it can jump to the memory space of user mode to execute the code. Therefore, the exp given in the project is to use shellcode, but in the 3.10 kernel, PXN protection is enabled, and shellcode in user mode memory cannot be executed.

So, if we can get one of the stack addresses where the current process is running in the kernel, we can find thread_info, which will give us the address of cred, and if we can write the kernel arbitrarily, we can modify the information of cred to achieve privilege escalation.

In general, there is only one way to the kernel privilege escalation-- modify the cred information, while commit_creds(prepare_kernel_cred(0)); is just a function provided by the kernel to modify the cred.

Then we find the address of the two functions: commit_creds and prepare_kernel_cred. They are in the kernel without kalsr enabled. We can send vmlinux directly into IDA to find out the address of these two functions.

Having modified the permissions of the current process successfully, we need to switch the current process from the kernel mode back to the user mode, and then execute /bin/sh in the user mode, thus the privilege escalation is successful. e24fc04721