Android Mobiles Showcase

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  • Bypass ART CFI: A Step-by-Step Guide to Circumventing Control Flow Integrity

    Introduction: ART’s Control Flow Integrity Fortress

    The Android Runtime (ART) is the heart of modern Android’s application execution environment, responsible for compiling and running app code. With each iteration, ART has introduced robust security mechanisms to thwart exploitation attempts. One of the most significant advancements in this regard is Control Flow Integrity (CFI). CFI is a powerful exploit mitigation technique designed to prevent arbitrary code execution by ensuring that the execution flow of a program adheres to a pre-determined, valid graph. For exploit developers, this means that traditional Return-Oriented Programming (ROP) or Jump-Oriented Programming (JOP) attacks are largely ineffective, as any deviation from valid call targets is immediately detected and terminated.

    This article dives deep into the architecture of ART’s CFI and presents a conceptual, step-by-step guide to circumventing its protections. We will focus on exploiting the dynamic nature of JIT (Just-In-Time) compilation, a critical component of ART, to achieve code execution in a CFI-protected environment. Understanding these techniques is crucial for advanced Android security researchers and penetration testers aiming to push the boundaries of ART exploitation.

    How ART Implements CFI

    ART’s CFI implementation primarily focuses on indirect calls and returns. For indirect calls (e.g., virtual method calls, interface method calls, function pointers), CFI ensures that the target address belongs to a valid function and, more importantly, that its type signature matches the expected signature at the call site. This is often achieved through type-based CFI, where metadata associated with each function or method defines its legitimate call sites.

    Key Aspects of ART’s CFI:

    • Virtual Table (VTable) / Interface Table (ITable) Checks: When a virtual or interface method is invoked, CFI ensures that the target method pointer exists within the legitimate VTable or ITable of the object’s actual type.
    • Method Signature Validation: Even if a VTable pointer is valid, CFI further checks if the method’s signature (return type, argument types) matches the expected signature, preventing calls to incompatible methods.
    • JIT-Compiled Code Integration: ART dynamically compiles frequently executed code paths using its JIT compiler. This introduces additional complexities, as CFI checks must be applied consistently to both ahead-of-time (AOT) and JIT-compiled code. JIT stubs and trampolines play a significant role in resolving method calls, and these are also subject to CFI scrutiny.

    The core `libart.so` library, along with various internal ART data structures like `art::ArtMethod` objects, contain the necessary metadata for CFI enforcement. The `ArtMethod` object, for instance, holds pointers to the actual compiled code entry points, its declaring class, and various flags relevant to its execution.

    The Attacker’s Challenge: Beating the Checks

    The primary challenge for an attacker against CFI is to gain arbitrary code execution without triggering a CFI violation. Traditional exploits often involve redirecting control flow to attacker-controlled shellcode or a ROP chain. CFI directly thwarts this by validating every indirect jump or call. If the target address or its type signature doesn’t match what CFI expects, the program aborts.

    This means that even if an attacker achieves an arbitrary read/write primitive (which is often a prerequisite for exploitation), simply overwriting a function pointer to point to shellcode is unlikely to work. CFI will detect the type mismatch or the invalid target address and terminate the process. Therefore, a successful CFI bypass requires a more sophisticated approach: one that either subverts the CFI mechanisms themselves or leverages a vulnerability that allows code execution *before* CFI can fully interdict it, or by making CFI believe the attacker’s code is legitimate.

    Circumventing CFI: A JIT-Assisted Strategy

    One powerful avenue for circumventing ART CFI lies in exploiting the dynamic nature of JIT compilation. The idea is to manipulate data structures that the JIT compiler relies on to generate or resolve code, thereby tricking CFI into validating attacker-controlled code as legitimate. This often involves finding a way to overwrite a code pointer *within* a valid `ArtMethod` object after its initial CFI validation, or to influence the JIT to generate code that ultimately leads to arbitrary execution.

    1. Gaining an Arbitrary Write Primitive

    Before any CFI bypass can be attempted, an attacker typically needs to achieve an arbitrary write primitive. This usually stems from memory corruption vulnerabilities such as heap overflows, use-after-free conditions, or out-of-bounds writes. This primitive allows the attacker to modify arbitrary memory locations within the process’s address space. CFI primarily protects control flow, not data integrity, so a successful memory corruption allows the initial setup for the bypass.

    // Conceptual C/C++ example of an arbitrary write primitive setup (simplified) // Assume 'g_arbitrary_write_address' and 'g_arbitrary_write_value' are controlled by attacker void* target_address = get_controlled_target_address(); long value_to_write = get_attacker_controlled_value(); // The vulnerability allows writing 'value_to_write' to 'target_address' *(long*)target_address = value_to_write; // This is the prerequisite for CFI bypass

    2. Analyzing ART Internals: ArtMethod and JIT Stubs

    To bypass CFI through JIT manipulation, a deep understanding of ART’s internal structures is paramount, especially the `art::ArtMethod` object. Each `ArtMethod` instance represents a Java method and contains critical pointers, including `entry_point_from_quick_compiled_code_`, which points to the actual compiled native code (AOT or JIT-generated) for that method.

    JIT stubs and trampolines are helper functions generated by ART to handle various method invocation types (e.g., `InvokeVirtual`, `InvokeInterface`). These stubs perform initial checks and then dispatch to the actual method implementation. Analyzing `libart.so` using tools like IDA Pro or Ghidra, and runtime introspection with Frida, can reveal the structure of `ArtMethod` and the behavior of these JIT components. The goal is to identify a `ArtMethod` instance whose `entry_point_from_quick_compiled_code_` we can overwrite.

    // Conceptual representation of a simplified ArtMethod structure struct ArtMethod {   // ... other fields ...   void* entry_point_from_quick_compiled_code_; // Pointer to native code   void* entry_point_from_interpreter_;        // Pointer for interpreter   void* declaring_class_;                     // Pointer to the method's class   // ... other fields like access flags, dex_method_index ... };

    3. Manipulating JIT-Compiled Code Entrypoints

    The core of this CFI circumvention strategy involves using the arbitrary write primitive to overwrite the `entry_point_from_quick_compiled_code_` within a legitimate `ArtMethod` object. The key insight is that CFI often performs its extensive type and signature checks when a method is initially resolved or invoked. If we can replace the *target code pointer* of an already validated `ArtMethod` instance, a subsequent call to that method would then execute our attacker-controlled code without triggering a CFI violation, as the call itself is to a

  • Practical ART Heap Spraying: Achieve Code Execution on Android Devices

    Introduction to ART Heap Spraying

    The Android Runtime (ART) is the backbone of modern Android devices, responsible for compiling and executing application code. Unlike its predecessor, Dalvik, ART uses Ahead-of-Time (AOT) compilation and improved garbage collection, which introduces new challenges and opportunities for exploit development. Heap spraying, a classic memory exploitation technique, remains a potent tool even in the face of ART’s sophisticated memory management. This article delves into the practical aspects of ART heap spraying, demonstrating how it can be leveraged to achieve reliable code execution on Android devices.

    Understanding ART’s memory layout and object management is crucial. ART objects are typically allocated on the heap and include metadata like object header and class pointer (which points to the object’s class definition, including its virtual method table). A successful heap spray aims to fill the heap with carefully crafted objects, increasing the probability that a memory corruption vulnerability (e.g., Use-After-Free or Out-of-Bounds write) will corrupt an attacker-controlled structure, ultimately leading to arbitrary code execution.

    Understanding ART’s Memory Model and Object Layout

    ART manages memory using a sophisticated garbage collector. When an Android application runs, ART allocates various types of objects on its heap, including Java objects, byte arrays, and native JNI-allocated memory. For an attacker, the predictability of object placement and layout is key. ART objects, particularly those used for virtual method dispatch, contain pointers to their respective virtual method tables (VMTs or vtables).

    A typical ART object’s memory layout might look something like this:

    +-----------------------+ +-----------------------+ |  Object Header        | |  Class Pointer (VTable) | +-----------------------+ +-----------------------+ |  Instance Data (Fields) | |  ...                  | +-----------------------+ +-----------------------+

    The Class Pointer is particularly interesting. If we can corrupt this pointer to point to attacker-controlled data, subsequent virtual method calls on the corrupted object will jump to a controlled address, leading to arbitrary code execution.

    The Core Concept of Heap Spraying

    Heap spraying involves allocating a large number of objects of a specific type or size, such that they occupy predictable locations on the heap. When combined with a memory corruption primitive (like a Use-After-Free), this allows an attacker to control what data is overwritten. The goal is often to overwrite a critical pointer, such as a virtual method table pointer, or to create a fake object at a specific address.

    In the context of ART, a common strategy is to spray the heap with `byte[]` arrays or custom Java objects whose layout is known. These objects will contain attacker-controlled data, including forged pointers that will be used to redirect program execution.

    Prerequisites for ART Heap Spraying

    Before initiating a heap spray, an attacker requires a memory corruption vulnerability. This could be:

    • Use-After-Free (UAF): An object is freed, but a pointer to it remains. Later, the memory is reallocated with attacker-controlled data, and the stale pointer is dereferenced.
    • Out-of-Bounds (OOB) Write: Writing data beyond the allocated bounds of a buffer, overwriting adjacent memory regions.
    • Type Confusion: Treating an object of one type as another, leading to incorrect interpretation of its data and potential pointer corruption.

    Without such a primitive, heap spraying alone cannot achieve code execution; it merely sets the stage for a subsequent exploit trigger.

    Crafting the Heap Spray Payload for ART

    The choice of objects for spraying depends on the target vulnerability and the desired outcome. Often, byte arrays are preferred due to their simplicity and direct control over their contents. Custom Java objects can also be used if their memory footprint and layout are more suitable for a specific corruption scenario.

    Example: Spraying with Byte Arrays

    Consider a scenario where an attacker wants to replace a freed object’s vtable pointer with a controlled address. The attacker would spray the heap with byte arrays, carefully crafted to include the fake vtable pointer at a specific offset. The size of these byte arrays should match or be slightly larger than the target object to ensure successful reclamation.

    public class ArtHeapSprayer { public static void sprayHeap(int numObjects, int objectSize) { System.out.println("Starting heap spray with " + numObjects + " objects of size " + objectSize + " bytes."); byte[][] sprayObjects = new byte[numObjects][]; for (int i = 0; i < numObjects; i++) { sprayObjects[i] = new byte[objectSize]; // Fill with controlled data. For example, a target address: // byte[] fakeVtable = { 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41 }; // System.arraycopy(fakeVtable, 0, sprayObjects[i], offset_to_vtable, fakeVtable.length); // More complex payloads can be constructed. // For demonstration, let's fill with a pattern to observe later if needed. for (int j = 0; j < objectSize; j++) { sprayObjects[i][j] = (byte)(j % 256); } } System.out.println("Heap spray completed. Objects are kept alive."); // To prevent garbage collection, these objects must be referenced. } public static void main(String[] args) { // Example usage: Spray 10,000 objects, each 256 bytes. sprayHeap(10000, 256); // Keep the main thread alive to ensure objects are not GC'd immediately. try { Thread.sleep(60000); } catch (InterruptedException e) { e.printStackTrace(); } } }

    In a real exploit, the `offset_to_vtable` would be determined through reverse engineering or experimentation on the target device, identifying where the class pointer (or vtable pointer) resides within the target object’s structure.

    Triggering the Vulnerability and Achieving Code Execution

    Once the heap is sprayed, the next step is to trigger the memory corruption vulnerability. If successful, the vulnerability should overwrite a portion of one of the sprayed objects. With carefully constructed spray data, this overwrite will corrupt a vtable pointer, replacing it with an address pointing to a controlled region within the spray. This controlled region would contain a crafted fake vtable.

    When a virtual method is subsequently called on the corrupted object, ART will attempt to dispatch the call using the now-corrupted vtable pointer. Instead of calling the legitimate method, execution will jump to the attacker-controlled address within the fake vtable, thereby achieving arbitrary code execution.

    The arbitrary code execution primitive can then be used to:

    1. Bypass ASLR (Address Space Layout Randomization) by leaking memory addresses.
    2. Disable SELinux for the process, allowing greater freedom for subsequent actions.
    3. Load native libraries (e.g., via `dlopen`) with attacker-controlled shellcode.
    4. Manipulate other critical process structures.

    Post-Exploitation Steps

    After gaining initial code execution (often referred to as a “code cave” or ROP gadget), the attacker typically aims for a more stable and powerful primitive. This might involve:

    • **ROP (Return-Oriented Programming):** Chaining small snippets of existing code (gadgets) to perform complex operations, especially when direct code injection is prevented by NX (No-Execute) bits.
    • **Shellcode Injection:** Injecting and executing custom machine code, typically into a writable and executable memory region, if such a region can be created or found.
    • **Privilege Escalation:** Leveraging the compromised process’s capabilities to gain higher privileges on the system, such as root access.

    Mitigation and Defense Strategies

    Android and ART implement various security features to thwart heap spraying and memory corruption exploits:

    • **ASLR (Address Space Layout Randomization):** Randomizes memory addresses, making it harder to predict the location of sprayed objects or essential libraries.
    • **DEP/NX (Data Execution Prevention/No-Execute):** Prevents execution of code from data segments, making direct shellcode injection more difficult.
    • **Hardened Memory Allocators:** Modern allocators (e.g., jemalloc, scudo) are designed to reduce predictability and prevent common heap-based attacks.
    • **Integer Overflow/Underflow Protections:** Compilers with sanitizers (e.g., AddressSanitizer, UndefinedBehaviorSanitizer) help detect and prevent integer-related bugs that can lead to OOB writes.
    • **Strict JNI Safety Checks:** Reduced opportunities for native code to corrupt the ART heap inadvertently.

    Despite these defenses, sophisticated vulnerabilities coupled with precise heap spraying techniques can still bypass them, underscoring the continuous cat-and-mouse game between exploit developers and security engineers.

    Conclusion

    ART heap spraying remains a relevant and powerful technique for achieving code execution on Android devices when a memory corruption primitive is present. By meticulously understanding ART’s memory model, object layouts, and leveraging controlled heap allocations, attackers can reliably steer program execution to arbitrary locations. While Android’s security landscape continuously evolves, deep understanding of runtime internals and exploitation techniques is essential for both defense and offensive security practitioners. The ability to craft a precise heap spray payload and trigger execution requires expertise in reverse engineering, binary exploitation, and ART’s specific memory management nuances.

  • Android 10+ Dynamic Partitions and Bootloader Unlocking: Advanced Implications for Security Exploits

    Introduction: The Shifting Sands of Android Partitioning

    The Android ecosystem has continuously evolved to enhance security, facilitate seamless updates, and improve device management. A significant architectural shift arrived with Android 10 and its widespread adoption of Dynamic Partitions. This change, building upon the A/B (Seamless Updates) scheme, fundamentally altered how system images are stored and managed, profoundly impacting bootloader unlocking, custom ROM development, and, critically, the landscape of security exploits.

    This article dives deep into Dynamic Partitions, exploring their technical underpinnings and analyzing the advanced implications they present for bootloader unlocking processes and the strategies employed in security exploits on modern Android devices.

    Understanding Dynamic Partitions: A Logical Revolution

    Before Android 10, devices typically had fixed-size physical partitions for system, vendor, product, etc. With Dynamic Partitions, these are replaced by a single, large super partition. Within this super partition, logical partitions like system, vendor, product, system_ext, and odm are dynamically sized and managed. This offers several benefits:

    • **Flexibility:** OEMs can adjust partition sizes without re-partitioning the entire disk.
    • **A/B Updates Enhancement:** It further streamlines A/B updates by allowing logical partitions within the super partition to be updated independently.
    • **Reduced Storage Waste:** No need to reserve fixed space for each partition, only for the overall super partition.

    The `super` partition itself contains metadata that describes the layout of the logical partitions within it, typically managed by a `lpm_metadata` (Logical Partition Manager metadata) structure. The bootloader reads this metadata to locate and load the necessary partitions during boot.

    Traditional fixed partitions are still present for critical components like boot, dtbo (Device Tree Blob Overlay), vbmeta (Verified Boot metadata), and sometimes a dedicated recovery partition if not A/B. However, the core system components reside dynamically.

    Impact on Bootloader Unlocking

    Bootloader unlocking remains the gateway to modifying Android’s core system, allowing for custom recoveries, kernels, and ROMs. However, the methodology of flashing these components changed dramatically with Dynamic Partitions.

    The Legacy vs. Dynamic Flashing Paradigm

    In the pre-dynamic era, flashing a custom system image involved a simple fastboot flash system command. With Dynamic Partitions, this direct approach is often invalid or ineffective for logical partitions. The bootloader or a specific fastboot implementation must understand and manipulate the `lpm_metadata` within the super partition.

    Instead of direct `fastboot flash system`, flashing a new system image often requires:

    1. **Creating a Super Image:** Merging all logical partitions (system, vendor, product, etc.) into a single `.img` file or a set of `.img` files that the fastboot toolchain can handle.
    2. **Using `fastboot update`:** This command is designed to process OTA packages or full factory images that contain the necessary instructions and images to update dynamic partitions correctly.
    3. **Intermediate Reboot to Fastbootd:** Some devices, especially those with Virtual A/B or full A/B and dynamic partitions, require a reboot into a special ‘fastbootd’ mode (also known as userspace fastboot). This mode, running from the userspace, has more capabilities to manipulate the `super` partition than the primary bootloader fastboot mode.
    # Example: Flashing a factory image (contains super_*.img or partitions.zip) fastboot update <factory_image.zip> # Example: Rebooting to fastbootd for advanced partition manipulation fastboot reboot fastboot # Once in fastbootd, you might be able to flash individual logical partitions again fastboot flash system system.img fastboot flash vendor vendor.img # Note: Direct flashing in fastbootd is still OEM/device dependent. # Often, a 'super.img' is constructed and flashed, or the 'update' command is used.

    Unlocking the bootloader still disables Verified Boot (dm-verity and avb_hash/avb_hashtree checks), allowing unsigned images to boot. However, the complexity of how those unsigned images are installed has increased.

    Advanced Implications for Security Exploits

    Dynamic Partitions introduce both new challenges and new opportunities for security exploit development and mitigation.

    1. Reduced Pre-Unlock Attack Surface for Persistent System Modifications

    For an attacker without bootloader unlock (pre-exploit), achieving persistent modification of system partitions is significantly harder. Since logical partitions exist within the `super` partition, manipulating them requires a sophisticated understanding of `lpm_metadata` or a vulnerability in the bootloader’s partitioning logic. Combined with Verified Boot, which ensures the integrity of partitions (including `super`), it becomes extremely difficult for malware to modify system components and persist across reboots or OTA updates without detection.

    2. Enhanced Importance of Bootloader Exploits

    If a bootloader exploit exists that allows an attacker to bypass bootloader unlock restrictions or gain control during the initial boot sequence, its value increases immensely. Such an exploit could:

    • **Manipulate `lpm_metadata`:** Re-allocate or corrupt logical partitions.
    • **Inject Malicious Images:** Force the bootloader to load an untrusted system or boot image.
    • **Disable Verified Boot:** Even without a traditional `fastboot flashing unlock` command.

    The complexity of Dynamic Partitions means that any vulnerability in the bootloader’s handling of these structures could have far-reaching implications for device security.

    3. New Avenues for Brickage (Post-Unlock)

    For users who have unlocked their bootloaders, improper manipulation of Dynamic Partitions can easily lead to a

  • Bypassing Dynamic Partition Verification: Enabling Unsigned Custom Kernels on Android 10+

    Introduction: The New Frontier of Android Flashing

    Since Android 10, the landscape of device partitioning has undergone a significant transformation with the introduction of Dynamic Partitions. This innovation, while streamlining OTA updates and enhancing system flexibility, simultaneously created new hurdles for enthusiasts and developers aiming to flash custom kernels or modify system images. Traditional methods of flashing individual partitions directly became problematic, primarily due to the integrated verification mechanisms like Android Verified Boot (AVB) 2.0 and dm-verity, which are now deeply intertwined with the dynamic partition structure. This expert-level guide will demystify dynamic partitions and provide a comprehensive methodology to bypass their verification, enabling the use of unsigned custom kernels on Android 10+ devices.

    Understanding Dynamic Partitions and Their Impact

    Dynamic Partitions consolidate multiple physical partitions (like system, vendor, product, odm) into a single logical partition called the super partition. These logical partitions are dynamically sized and managed by a Linux device-mapper layer. This design allows for more flexible allocation of space during OTA updates, enabling A/B seamless updates by resizing partitions as needed.

    Why This Matters for Custom Kernels

    Historically, flashing a custom kernel involved replacing the boot.img. However, with dynamic partitions, the kernel often resides within boot.img, but critical verification information, and sometimes the kernel itself for Generic Kernel Image (GKI) devices, is handled by vendor_boot.img. The bootloader, before handing control to the kernel, verifies the integrity of critical partitions using AVB. Any modification to a verified partition, especially vendor_boot or the logical partitions within super, without proper signing, will trigger a verification failure, preventing the device from booting.

    The Verification Challenge: AVB 2.0 and dm-verity

    Android Verified Boot (AVB) 2.0 ensures that all executed code comes from a trusted source. It cryptographically verifies each stage of the boot process, from the bootloader to the kernel and system partitions. dm-verity, a kernel feature, provides transparent integrity checking of block devices, preventing persistent rootkits and malware from modifying the system partition. When you flash an unsigned custom kernel or modify system components, these mechanisms actively prevent your device from booting.

    To bypass this, we need to:

    • Disable AVB checks at the vbmeta level.
    • Modify the vendor_boot image’s ramdisk to instruct the kernel to ignore dm-verity and AVB checks for logical partitions.

    Prerequisites for Bypassing Verification

    Before proceeding, ensure you have the following:

    • An Android device with an unlocked bootloader. This is non-negotiable, as you cannot flash custom images otherwise.
    • ADB and Fastboot tools installed and configured on your computer. (Android SDK Platform Tools).
    • Device-specific firmware images: Specifically, boot.img, vendor_boot.img, and vbmeta.img from your device’s stock firmware. These are crucial for patching.
    • A custom kernel image (e.g., a modified boot.img or a new kernel binary to be placed in vendor_boot).
    • Magisk (specifically the Magisk app) for patching the boot.img if needed for root access, or if your custom kernel is packaged as a standard boot.img.
    • A boot image unpacking/repacking tool such as ai_boot_image_editor (available on GitHub) or a similar script.

    Methodology: Patching vbmeta and vendor_boot

    The core of this bypass involves two main steps: disabling global AVB verification via vbmeta and instructing the kernel to ignore dm-verity for logical partitions by modifying vendor_boot‘s ramdisk.

    Step 1: Obtain Stock Firmware Images

    Download the full stock firmware package for your specific device model. Extract boot.img, vendor_boot.img, and vbmeta.img. These are essential baselines for our modifications.

    Step 2: Disable Android Verified Boot (AVB)

    This step tells your bootloader to ignore signature verification for future flashes. You must flash a ‘disabled’ vbmeta image.

    fastboot --disable-verity --disable-verification flash vbmeta vbmeta.img

    This command flashes the stock vbmeta.img but crucially modifies its flags in the bootloader to disable AVB and dm-verity checks globally. If your device supports it, `fastboot flash vbmeta_a vbmeta.img` or `fastboot flash vbmeta_b vbmeta.img` might be necessary for A/B devices.

    Step 3: Unpack and Modify vendor_boot.img

    vendor_boot.img contains the vendor ramdisk, which houses critical device-specific initialization scripts, including the fstab file that dictates how partitions are mounted and verified. We need to modify this fstab.

    1. Extract vendor_boot.img:

      Use a tool like ai_boot_image_editor or a manual process:

      python3 ai_boot_image_editor.py --unpack-vendor-boot vendor_boot.img --output_dir vendor_boot_unpacked

      This will extract the contents, including ramdisk-vendor.img, to the vendor_boot_unpacked directory.

    2. Unpack ramdisk-vendor.img:

      The ramdisk-vendor.img is typically a CPIO archive. Create a directory and extract its contents:

      mkdir vendor_ramdisk_contentcd vendor_ramdisk_contentgzip -dc ../vendor_boot_unpacked/ramdisk-vendor.img | cpio -id

    3. Modify the fstab file:

      Navigate to the extracted ramdisk content. Look for files named fstab. or similar (e.g., fstab.qcom, fstab.pixel) usually in the root or an /etc directory within the ramdisk. Open this file with a text editor.

      Identify lines corresponding to /system, /vendor, /product, etc., which are usually mounted from the super partition. These lines will often contain `avb` or `verify` flags. You need to change or remove these flags. Look for something like:

      /dev/block/by-name/system /system ext4 ro,barrier=1,wait,avb=vbmeta_system,verify=vbmeta_system wait/dev/block/by-name/vendor /vendor ext4 ro,barrier=1,wait,avb=vbmeta_vendor,verify=vbmeta_vendor wait

      Modify these lines to effectively disable verification. The common approach is to add forcefdeorfbe=1,disable-verity or replace `avb` and `verify` with `noavb`. A robust modification would look like this:

      /dev/block/by-name/system /system ext4 ro,barrier=1,wait,forcefdeorfbe=1,disable-verity,noavb wait/dev/block/by-name/vendor /vendor ext4 ro,barrier=1,wait,forcefdeorfbe=1,disable-verity,noavb wait

      Save the modified fstab. file.

    4. Repack ramdisk-vendor.img:

      Go back to the vendor_ramdisk_content directory and repack it:

      find . | cpio -o -H newc | gzip > ../vendor_boot_unpacked/ramdisk-vendor_patched.img

    5. Rebuild vendor_boot.img:

      Now use your boot image editor or mkbootimg to rebuild the vendor_boot.img with the patched ramdisk. If using ai_boot_image_editor, it might look like:

      python3 ai_boot_image_editor.py --repack-vendor-boot vendor_boot_unpacked --output vendor_boot_patched.img

      Make sure to specify the kernel and original headers correctly if using mkbootimg directly. The tool typically handles this for you.

    Step 4: Flash the Patched vendor_boot.img

    Now, flash your newly created vendor_boot_patched.img to your device:

    fastboot flash vendor_boot vendor_boot_patched.img

    Step 5: Prepare and Flash Your Custom Kernel

    This step depends on how your custom kernel is packaged:

    • If your custom kernel is a standalone boot.img: Patch this boot.img with Magisk. Copy the custom boot.img to your phone, install Magisk, then select “Install” -> “Select and Patch a File” and choose your custom boot.img. Magisk will output a magisk_patched_boot.img. Transfer this back to your PC and flash it:
    fastboot flash boot magisk_patched_boot.img
    • If your custom kernel modifies the kernel within vendor_boot: You would have replaced the kernel binary (e.g., Image or Image.gz-dtb) within the vendor_boot_unpacked directory *before* rebuilding vendor_boot_patched.img in Step 3. In this scenario, the `vendor_boot_patched.img` already contains your custom kernel.

    Once all images are flashed, reboot your device:

    fastboot reboot

    Troubleshooting and Considerations

    • Bootloop: If your device bootloops, ensure your fstab modifications are correct and you haven’t introduced syntax errors. Re-flash your stock boot.img and vendor_boot.img if necessary, then re-attempt the process carefully.
    • Device Specifics: Partition names, fstab locations, and specific mkbootimg arguments can vary slightly between devices and Android versions. Always consult device-specific forums (e.g., XDA Developers) for nuances.
    • Security Implications: Disabling AVB and dm-verity significantly reduces your device’s security posture. Only proceed if you understand and accept these risks. Your device will likely show a warning about unlocked bootloader and disabled verification on startup.
    • OTA Updates: Modifying vendor_boot and disabling verification will break OTA updates. You’ll need to re-flash stock images and re-patch after every major update.

    Conclusion

    Bypassing dynamic partition verification on Android 10+ is a more intricate process than with older Android versions, but it’s entirely achievable with a clear understanding of AVB, dm-verity, and the dynamic partition structure. By carefully modifying the vbmeta and the vendor_boot ramdisk’s fstab, you can successfully enable unsigned custom kernels and reclaim full control over your device’s software. This detailed guide equips you with the knowledge and steps to navigate this advanced customization challenge.

  • The Ultimate Guide to Reverting Stock Firmware on Android 10+ Devices with Dynamic Partitions

    Introduction to Dynamic Partitions on Android 10+

    Android 10 introduced a significant architectural change to device storage management: Dynamic Partitions. Building upon the A/B (seamless update) system, Dynamic Partitions abstract the physical partition layout, allowing OEMs greater flexibility in managing system, vendor, product, and other logical partitions. Instead of fixed-size partitions, these are now logical volumes residing within a single, massive physical partition called the ‘super’ partition.

    This change was primarily driven by the need to optimize over-the-air (OTA) updates, enabling Google and OEMs to resize partitions on the fly without needing to reformat the entire device. While beneficial for updates, it presents new challenges for users attempting to revert to stock firmware, especially when a device has been modified through rooting or custom ROM installation. Understanding this underlying architecture is crucial for a successful firmware reversion.

    Challenges of Reverting Firmware with Dynamic Partitions

    Traditional Android devices had distinct, physically separate partitions for system, vendor, boot, etc. Flashing a new image simply meant overwriting that specific physical block. With dynamic partitions, system, vendor, and product are no longer fixed physical partitions but are ‘logical partitions’ within the super partition. The super partition itself is a physical partition that contains a metadata header describing the layout and sizes of these logical volumes.

    The primary challenge when reverting firmware on a dynamic partition device is ensuring the super partition’s metadata correctly aligns with the stock firmware’s expected layout. If this metadata gets corrupted, mismatched, or resized incorrectly (e.g., by a custom ROM that alters partition sizes), flashing individual images can lead to various issues, including boot loops, device not booting, or errors indicating insufficient space. The Fastboot toolchain has evolved to handle dynamic partitions, but specific flashing sequences or flags might be necessary depending on the device OEM and the state of your device.

    Prerequisites and Essential Tools

    Before attempting to revert your firmware, gather these essential tools and ensure your device meets the following conditions:

    • Unlocked Bootloader: This is non-negotiable. If your bootloader is locked, you cannot flash custom or stock firmware images. Unlocking typically wipes your device, so do it beforehand if not already done.
    • ADB and Fastboot Tools: Ensure you have the latest platform-tools installed on your computer.
    • Device-Specific USB Drivers: Install these to ensure your computer correctly recognizes your device in ADB and Fastboot modes.
    • Official Stock Firmware: Download the exact factory image for your device model, SKU, and region. Using the wrong firmware can lead to a bricked device. Verify the Android version matches or is newer than what was previously on the device.
    • Data Backup: Reverting stock firmware, especially through Fastboot, will typically wipe all user data. Back up everything important.
    • Sufficient Battery: Your device should be charged to at least 80% to prevent power loss during the flashing process.
    • Reliable USB Cable: A faulty cable can cause data corruption during transfers.

    Understanding Your Device’s Firmware Structure

    Official factory images from OEMs (like Google’s Pixel factory images or OnePlus’s full stock ROMs) often contain a collection of .img files and a flashing script (e.g., flash-all.bat for Windows or flash-all.sh for Linux/macOS). For devices with dynamic partitions, these images will typically include boot.img, dtbo.img, vendor_boot.img (for some devices), and individual images for logical partitions like system.img, vendor.img, product.img, and sometimes system_ext.img. You might or might not find a combined super.img, as modern Fastboot tools usually handle writing logical images directly into the `super` partition.

    Step-by-Step Guide to Reverting Stock Firmware

    Step 1: Download the Correct Factory Image

    Navigate to your device manufacturer’s official support page or a trusted community forum (e.g., XDA Developers) to download the factory image. Double-check the model number, region, and Android version to ensure it’s the correct firmware for your device.

    Step 2: Prepare Your Device for Flashing

    1. Enable USB Debugging on your device (Settings > About phone > Tap Build number 7 times > Go back to Settings > System > Developer options > Enable USB debugging).
    2. Connect your device to your computer via USB.
    3. Open a command prompt or terminal on your computer.
    4. Verify ADB connection:adb devices
      You should see your device listed.
    5. Reboot your device into Bootloader/Fastboot mode:adb reboot bootloader
      Alternatively, power off your device and then hold down the appropriate key combination (e.g., Volume Down + Power for many devices) to enter Fastboot mode.
    6. Verify Fastboot connection:fastboot devices
      You should see your device’s serial number listed. If not, reinstall drivers or try a different USB port/cable.

    Step 3: Extract and Identify Key Partition Images

    Extract the contents of the downloaded factory image ZIP file into your ADB and Fastboot tools directory for easy access. Inside, you’ll find various .img files and potentially a flash-all script.

    Step 4: Flashing the Stock Firmware (Fastboot Method)

    Scenario A: Using an OEM-Provided flash-all Script (e.g., Google Pixel)

    Many OEMs, especially for devices like Google Pixels, provide a convenient script. This script typically handles the correct flashing order and any necessary partition resizing or wiping.

    # For Windows: flash-all.bat# For Linux/macOS: ./flash-all.sh

    Important: Review the contents of the flash-all script before running it. Ensure it doesn’t contain any commands that could be detrimental to your specific situation, although official scripts are generally safe.

    Scenario B: Manual Fastboot Flashing for Devices with Dynamic Partitions

    If no flash-all script is provided, or if you prefer manual control, follow these steps. Remember that Fastboot on modern Android versions (10+) intelligently handles writing logical partitions into the super partition.

    1. Flash Bootloader and Radio (if applicable):

      fastboot flash bootloader <bootloader_image_name>.imgfastboot reboot bootloader # Some devices require this

      and if a radio/modem image is present:

      fastboot flash radio <radio_image_name>.imgfastboot reboot bootloader # Some devices require this

    2. Flash Core System Images:

      fastboot flash boot boot.img # Your core boot imagefastboot flash dtbo dtbo.img # Device Tree Blob Overlay (if present)fastboot flash vbmeta vbmeta.img # Verified Boot metadata (if present)

      For A/B slot devices, you might need to specify slots (e.g., boot_a.img or fastboot flash boot_a boot.img). Modern Fastboot often handles this implicitly by flashing to the current active slot.

    3. Provision and Flash Dynamic Partitions:

      This is where the dynamic partition handling occurs. You typically flash each logical partition individually. Fastboot will communicate with the device’s bootloader to write these images into the correct logical volumes within the super partition.

      fastboot flash system system.imgfastboot flash vendor vendor.imgfastboot flash product product.imgfastboot flash system_ext system_ext.img # If present

      You do NOT usually need to directly interact with `super.img` or `fastboot erase super` unless you are recovering from a very specific `super` partition corruption and have an OEM-provided `super.img` to flash. Flashing individual logical partitions via `fastboot flash` is the standard and safest method.

    4. Wipe Userdata (Highly Recommended):

      To prevent conflicts and ensure a clean slate, it’s highly recommended to wipe user data.

      fastboot -w # This command wipes data and cache partitions

      Alternatively, if you have a userdata.img in your factory image:

      fastboot flash userdata userdata.img

    5. Reboot Your Device:

      fastboot reboot

    Step 5: Post-Flashing Steps

    The first boot after flashing stock firmware can take significantly longer than usual (5-15 minutes). This is normal as the device is setting up the Android system for the first time. If your device experiences a boot loop or fails to boot after a prolonged period, proceed to the troubleshooting section.

    Troubleshooting Common Issues

    • Device Stuck in Boot Loop: Re-enter Fastboot mode and carefully re-flash the entire firmware package. Ensure you’ve wiped userdata. Sometimes, flashing to the inactive A/B slot and then switching active slots can resolve issues:fastboot --set-active=b # or a fastboot reboot
    • fastboot: Partition doesn't exist Error: This often means you’re trying to flash an image to a partition name that doesn’t exist on your device, or you’re using an incorrect firmware version. Double-check your firmware and Fastboot commands.
    • Failed to allocate space or Size Mismatch Errors: This indicates an issue with the super partition’s logical volume allocation. In rare cases, you might need to explicitly wipe the super partition. WARNING: This is a highly risky command and should only be used if directed by specific device recovery guides, as it can potentially brick your device if not followed by a full re-flash. If necessary, you might try:fastboot erase super followed by a full re-flash of all logical partitions. This is generally avoided unless absolutely necessary.
    • Device Not Recognized by ADB/Fastboot: Reinstall USB drivers, try a different USB port or cable, and ensure you’re using the latest platform-tools.

    Conclusion

    Reverting to stock firmware on Android 10+ devices with dynamic partitions requires a deeper understanding of the underlying storage architecture. While the process is more involved than with older devices, modern Fastboot tools simplify much of the complexity. By carefully following these steps, ensuring you have the correct firmware, and understanding the implications of dynamic partitions, you can successfully restore your device to its factory state. Always proceed with caution, back up your data, and double-check every command.

  • Demystifying A/B System-as-Root with Dynamic Partitions: What Modders Need to Know for Android 10+

    Introduction: The Evolving Landscape of Android Partitioning

    For years, Android modding revolved around familiar partition structures: /boot, /system, /vendor, /data, and /recovery. Flashing a custom ROM or rooting often meant directly interacting with these block devices. However, with the introduction of A/B (Seamless) System Updates and, more significantly, Dynamic Partitions in Android 10+, the underlying architecture has undergone a profound transformation. This shift presents new challenges and necessitates a deeper understanding for anyone looking to modify their Android device, from flashing custom kernels to installing full-blown custom ROMs. This guide will demystify these modern partitioning schemes, detailing their inner workings and providing essential knowledge for modders.

    Understanding A/B System-as-Root: Seamless Updates

    A/B (also known as Seamless Updates) was introduced to enable software updates to be installed in the background while the device is running, minimizing downtime during reboots. It achieves this by maintaining two identical sets of partitions: Slot A and Slot B.

    How A/B Works

    • Dual Partition Sets: The device has two complete sets of root partitions (e.g., system_a, vendor_a, boot_a and system_b, vendor_b, boot_b). Only one set is active at any given time.
    • Background Updates: When an update is available, the system downloads and applies it to the currently inactive slot. For example, if Slot A is active, the update is installed on Slot B.
    • Seamless Transition: After the update is applied, the user is prompted to reboot. During the reboot, the device simply switches to the newly updated slot (Slot B in our example), making the transition almost instantaneous from the user’s perspective. If there’s an issue, the device can revert to the previous working slot.

    Implications for Modding with A/B

    For modders, A/B means you’re always interacting with an active slot. Tools like fastboot or adb will typically operate on the currently booted slot. When rooting with Magisk, for instance, you’re patching the boot.img of the active slot. If an OTA update comes, it will apply to the inactive slot, and switching to it will mean you lose your root until you re-patch that newly active slot.

    # Check current active slot
adb shell bootctl get-current-slot
# Output example: _a

# Set a different slot as active (use with extreme caution!)
# adb shell bootctl set-active-boot-slot _b

    The Rise of Dynamic Partitions (Android 10+)

    While A/B streamlined updates, Dynamic Partitions, introduced in Android 10, fundamentally altered how storage is managed. Previously, partitions like /system, /vendor, and /product were fixed-size physical partitions on the storage device. Dynamic Partitions consolidate these into a single, large super partition.

    What are Dynamic Partitions?

    Dynamic Partitions are logical partitions allocated within a larger, static super partition. This allows OEMs to dynamically resize these partitions during OTA updates, offering greater flexibility and efficiency in device storage management. For instance, if a future Android version requires a larger system partition, an OEM can resize it without needing to repartition the entire device.

    Why Dynamic Partitions?

    • Flexibility: OEMs can adjust partition sizes without changing the partition table, optimizing space usage.
    • Project Treble Enhancement: Further decouples the Android framework from vendor implementations, making GSI (Generic System Image) development and flashing more adaptable.
    • Reduced Partition Count: Simplifies the overall partitioning scheme.

    Challenges for Modders with Dynamic Partitions

    The primary challenge is that traditional methods of flashing images to fixed-size partitions (e.g., fastboot flash system system.img) no longer work directly. The system partition isn’t a standalone block device anymore; it’s a logical volume inside super.

    # This command will fail on devices with Dynamic Partitions (Android 10+)
# unless fastbootd is running and handling logical partitions.
fastboot flash system system.img

    The ‘super’ Partition and Logical Partition Management

    At the heart of Dynamic Partitions is the super partition. This is a physical partition that acts as a container for all dynamic, logical partitions (e.g., system, vendor, product, system_ext, odm). Inside the super partition, there’s metadata that describes the layout and sizes of these logical partitions.

    Key Concepts:

    • Logical Partitions: These are the partitions you interact with (system_a, vendor_a, etc.), but they exist as volumes within super.
    • Partition Groups: Dynamic partitions can be grouped (e.g., default or qcom_dynamic). This aids in managing different sets of logical partitions.

    To interact with these logical partitions, standard fastboot commands needed an overhaul. This led to the introduction of fastbootd.

    Modding in the Dynamic Partitions Era: fastbootd to the Rescue

    fastbootd is a new userspace fastboot implementation that runs on the Android device itself, not just in the bootloader. It can parse and understand the structure of the super partition and manage logical partitions. When your device is in fastbootd mode (often referred to as ‘userspace fastboot’), you gain the ability to manipulate logical partitions.

    Entering fastbootd

    Typically, you enter the standard bootloader/fastboot mode first, then issue a command to transition to fastbootd:

    # 1. Reboot to standard bootloader/fastboot mode
adb reboot bootloader

# 2. Once in standard fastboot, reboot into fastbootd
fastboot reboot fastboot

    The device may reboot or change screens, often displaying a different fastboot interface or a specific text indicating fastbootd mode.

    Manipulating Logical Partitions with fastbootd

    With fastbootd, you can now interact with logical partitions. Here are some critical commands:

    • List logical partitions:
    fastboot getvar all
# Look for entries like: product-l partition-size: 0x...
# or similar related to dynamic partitions
    • Delete a logical partition: (e.g., to make space for a larger GSI)
    fastboot delete-logical-partition system_a
    • Create a logical partition with a specific size (in bytes):
    fastboot create-logical-partition system_a 1073741824 # Example: 1GB
    • Flash an image to a logical partition: This is the most common use case for GSIs or custom system images. fastboot flash will auto-resize if possible, but fastboot flash:raw is more explicit.
    # This command flashes system_a, but fastbootd handles allocating within super
fastboot flash system_a system.img

# Alternatively, for raw flashing (less common for modders)
# fastboot flash:raw system_a system.img
    • Wipe a logical partition:
    fastboot erase system_a

    Rooting with Magisk on Dynamic Partition Devices

    Magisk largely abstracts away the complexities of dynamic partitions by focusing on patching the boot.img or init_boot.img (for Android 12+). The process remains similar:

    1. Extract the stock boot.img or init_boot.img for your device and current slot.
    2. Patch it using the Magisk app.
    3. Flash the patched image via fastboot (this still works directly as boot.img is not a dynamic partition):
    fastboot flash boot magisk_patched.img
# For Android 12+ on some devices, it might be init_boot
# fastboot flash init_boot magisk_patched.img

    After flashing, reboot, and Magisk should be installed. If an OTA update comes, it will update the inactive slot, and you’ll need to repeat the patching process for that slot once it becomes active.

    Flashing Custom ROMs and GSIs

    Flashing custom ROMs or GSIs on dynamic partition devices often involves using fastbootd. The general steps usually involve:

    1. Booting to fastbootd.
    2. Wiping existing logical partitions (like system_a, vendor_a) or deleting them to recreate them with appropriate sizes for the GSI.
    3. Flashing the new system image to the respective logical partition.
    4. Flashing other necessary components like vendor (if a separate vendor image is required).
    5. Rebooting the device.

    Specific instructions can vary significantly between devices and ROMs, so always consult the device-specific guides. Some advanced ROMs might provide a flashable ZIP that handles these fastbootd operations internally via a custom recovery, but the underlying principle remains the same.

    Conclusion: Adapting to the New Modding Paradigm

    A/B System-as-Root combined with Dynamic Partitions represents a significant evolution in Android’s architecture. While it makes device updates more robust and efficient, it introduces a steeper learning curve for modders. The key takeaway is understanding that most traditional partitions are now logical volumes within a super partition, and interacting with them requires the use of fastbootd. By mastering these concepts and the associated fastboot commands, modders can continue to explore, customize, and push the boundaries of their Android devices in this new, dynamic era. Always proceed with caution, back up your data, and refer to device-specific guides for the most accurate instructions.

  • Troubleshooting ‘Super Partition Corrupt’ Errors: Fixing Flashing Failures on Android 10+ Devices

    Introduction: Navigating ‘Super Partition Corrupt’ on Modern Android

    The advent of Android 10 introduced a significant architectural shift with Dynamic Partitions, fundamentally altering how system updates and flashing operations are managed. While designed for greater flexibility and efficiency, this change also brought new challenges for enthusiasts and developers. One of the most common and perplexing errors encountered during flashing attempts on Android 10+ devices is the dreaded ‘Super Partition Corrupt’ message. This error often halts the flashing process, leaving devices in a seemingly unrecoverable state, primarily due to issues within the `super` partition, which now virtualizes other critical partitions like `system`, `vendor`, and `product`.

    This expert-level guide delves into the intricacies of dynamic partitions, dissects the root causes of ‘Super Partition Corrupt’ errors, and provides a comprehensive, step-by-step methodology to diagnose and rectify these flashing failures. Understanding these concepts is paramount for anyone engaging in custom ROM installation, firmware restoration, or device unbricking on modern Android devices.

    Understanding Dynamic Partitions and the ‘super’ Partition

    Prior to Android 10, partitions like `system`, `vendor`, `product`, etc., were static, fixed-size entities on the device’s storage. Dynamic Partitions, however, introduce a layer of abstraction. All these traditional logical partitions now reside within a single physical partition called `super`. The `super` partition itself contains metadata that defines the layout, size, and location of these logical partitions at runtime. This allows for:

    • Flexible Partition Sizing: Partitions can resize without reformatting the entire device.
    • Seamless Updates (Virtual A/B): Updates can be applied to inactive slots using less space than traditional A/B setups.
    • Generic System Image (GSI) Support: Easier deployment of generic Android builds.

    When the `super` partition’s metadata becomes corrupted, the device’s bootloader or flashing tools can no longer correctly interpret the layout of the logical partitions, leading to errors like ‘Super Partition Corrupt’ or ‘Failed to load/verify partition table’.

    Common Causes of ‘Super Partition Corrupt’ Errors

    1. Incorrect Flashing Procedures

    Using outdated or incompatible `fastboot` tools, flashing images not intended for your specific device model, or attempting to flash partitions individually without properly managing the dynamic partition table can easily lead to corruption.

    2. Mismatched or Corrupted Firmware Images

    Flashing a partial or corrupt firmware package, or a package from a different Android version or security patch level that significantly alters the `super` partition structure, can cause inconsistencies.

    3. Interrupted Flashing Operations

    Any interruption during a critical flashing sequence, such as a disconnected USB cable, power loss, or a computer crash, can leave the `super` partition metadata in an incomplete or corrupted state.

    4. Downgrading Firmware

    Attempting to downgrade Android versions, especially across major releases, often leads to `super` partition mismatches, as older firmware might not understand the newer dynamic partition layout, or vice-versa.

    5. Custom Kernel/Recovery Flashing Issues

    Sometimes, flashing a custom kernel or recovery that incorrectly interacts with the partition table can inadvertently corrupt the `super` partition metadata.

    Prerequisites for Troubleshooting

    Before attempting any fixes, ensure you have the following:

    • ADB and Fastboot Tools: Properly installed and updated on your computer.
    • OEM USB Drivers: Installed for your specific device model.
    • Official Stock Firmware: The full factory image or OTA package for your device and its current (or desired) Android version. This is crucial.
    • Charged Device: At least 80% battery to prevent power-related interruptions.
    • Reliable USB Cable: A high-quality cable directly connected to a stable USB port on your computer.
    • Data Backup: Although often impossible when facing this error, if you can access any data, back it up.

    Troubleshooting Steps: Rectifying ‘Super Partition Corrupt’

    Step 1: Attempt a Standard Full Firmware Flash

    Often, a full, clean flash of the stock firmware can resolve the issue by overwriting all partitions, including the `super` metadata. Ensure your device is in Fastboot Mode.

    fastboot devices fastboot flashall

    If `fastboot flashall` isn’t available or fails, you might need to use `fastboot update` with the full OTA package (usually a `.zip` file from the OEM):

    fastboot update <firmware-file>.zip

    This command typically handles all necessary partitioning and flashing steps automatically. If this still fails, proceed.

    Step 2: Inspecting the ‘super’ Partition State

    Understanding the current state of your `super` partition can provide clues. In Fastboot Mode, use:

    fastboot getvar all

    Carefully examine the output for lines related to `super-partition-size`, `super-partition-name`, or any `is-logical` properties. This helps confirm dynamic partition usage. Some devices also support:

    fastboot --list-logical-partitions

    This command lists the logical partitions within the `super` partition, which can be useful for advanced diagnostics.

    Step 3: Erasing and Recreating ‘super’ Metadata (Use with Extreme Caution)

    This is a more aggressive step and should only be attempted if standard flashing fails. Erasing the `super` partition metadata essentially tells the device to forget its current dynamic partition layout. This is often the key to resolving deep corruption. If your device supports it, this is the command:

    fastboot erase super

    After erasing, you must reboot your device back into Fastboot Mode:

    fastboot reboot fastboot

    Once back in Fastboot, immediately attempt the full firmware flash again using `fastboot update .zip` or `fastboot flashall`. This will force the device to recreate the `super` partition metadata and lay out the logical partitions according to the new firmware.

    Note: Not all devices allow `fastboot erase super`. If it returns an error, this method is not applicable to your device.

    Step 4: Flashing Individual Logical Partitions (Advanced)

    In rare cases, if you have access to individual `img` files (e.g., `system.img`, `vendor.img`) from your stock firmware and know the active slot (A or B), you can try flashing them manually after erasing `super` (if possible). First, determine your active slot:

    fastboot getvar current-slot

    Then, flash the critical logical partitions:

    fastboot flash system_<slot> system.img fastboot flash vendor_<slot> vendor.img fastboot flash product_<slot> product.img fastboot flash boot_<slot> boot.img

    Replace `<slot>` with `a` or `b` based on your `current-slot`. This method is highly dependent on the device and firmware structure and generally less reliable than `fastboot update`.

    Step 5: Seeking Device-Specific Tools or Factory Restore Images

    Some OEMs provide specialized flashing tools (e.g., Xiaomi’s MiFlash, OnePlus’s MSM Download Tool) that can often recover devices from deep brick states by performing a low-level format and flash. These tools typically bypass standard `fastboot` limitations and are highly effective for ‘Super Partition Corrupt’ issues. Always look for these resources on official forums or trusted developer communities.

    Step 6: Factory Reset from Stock Recovery

    If you can somehow boot into your device’s stock recovery (even if fastboot is failing), performing a factory reset and wiping cache might clear residual data that’s causing issues. However, if the `super` partition itself is corrupted, this might not resolve the core problem.

    Prevention is Key

    • Always Use Official Firmware: Stick to manufacturer-provided firmware packages.
    • Verify Image Integrity: If available, check MD5 or SHA256 checksums of downloaded files.
    • Stable Environment: Use a reliable computer and USB connection. Avoid hubs.
    • Follow Guides Precisely: When using custom ROMs or recoveries, meticulously follow the instructions for your specific device model.
    • Keep Tools Updated: Ensure your ADB and Fastboot binaries are always the latest version.

    Conclusion

    The ‘Super Partition Corrupt’ error, while daunting, is a recoverable issue on most Android 10+ devices if approached systematically. The key lies in understanding the dynamic partition architecture and leveraging `fastboot` commands, particularly the `erase super` command and the comprehensive `fastboot update` method, to re-establish a valid partition table. Always proceed with caution, ensure you have the correct firmware, and remember that patience and thoroughness are your best tools in bringing your device back to life.

  • Deep Dive: Reverse Engineering Android 10+ Dynamic Partition Layouts for Custom Recovery Development

    Introduction to Dynamic Partitions in Android 10+

    The Android operating system has undergone significant architectural shifts over the years, aiming to enhance security, improve update mechanisms, and provide greater flexibility for device manufacturers. One of the most impactful changes introduced with Android 10 (and refined in subsequent versions) is the implementation of Dynamic Partitions. This paradigm shift moves away from the traditional, statically sized partitions like system, vendor, and product, consolidating them into a single, large logical partition called super.

    For custom recovery developers, this change presents a formidable challenge. Where previously a recovery could directly mount fixed block devices, it now needs to understand and interact with the Logical Partition Manager (LPM) to correctly map and access these dynamic volumes. This article will provide a deep dive into reverse engineering Android 10+ dynamic partition layouts, offering practical insights and steps for those engaged in custom recovery (e.g., TWRP) development.

    Understanding the super Partition and LPM

    At the heart of dynamic partitions lies the super partition. This is a physical block device that acts as a container for all dynamically allocated partitions. Instead of having dedicated block devices for system, vendor, etc., these are now logical volumes within super. The allocation and management of these logical volumes are handled by the Logical Partition Manager (LPM), which utilizes the Linux device mapper (dm-linear and dm-verity) to create virtual block devices that the system can interact with.

    Key characteristics:

    • Metadata: The super partition contains metadata (metadata_v1 or metadata_v2) that describes the layout of the dynamic partitions, including their names, sizes, and groups.
    • Partition Groups: Dynamic partitions are often organized into groups (e.g., qcom_dynamic_partitions) to facilitate A/B updates and management.
    • A/B Support: Dynamic partitions seamlessly integrate with A/B (seamless) updates, allowing updates to be applied to an inactive slot while the device is running, significantly reducing downtime. Each dynamic partition might have _a and _b suffixes indicating the active slot.

    Identifying Dynamic Partition Layout On-Device

    The first step in reverse engineering is to identify the super partition on your target device. This can typically be found by examining the block device symlinks:

    adb shell ls -l /dev/block/by-name | grep super

    This command will usually yield an output similar to:

    lrwxrwxrwx 1 root root 16 2023-10-27 10:30 super -> /dev/block/sdaX

    Where sdaX (or similar, like mmcblk0pX) is the actual physical block device for the super partition.

    Once identified, you can use the Android build system’s lpm_tool utility (if available on the device or compiled separately) to dump the metadata contained within the super partition. If direct access to lpm_tool on the device is not feasible, you’ll need to pull the super image and analyze it offline.

    Dumping super Partition Metadata (On-Device)

    If you have a rooted device with lpm_tool (often found in /system/bin or /vendor/bin), you can dump the layout directly:

    adb shell lpm_tool dump /dev/block/by-name/super

    An example output might look like this:

    Partition 0: system_a (group: qcom_dynamic_partitions_a, attributes: 0, size: 2147483648 bytes)Partition 1: vendor_a (group: qcom_dynamic_partitions_a, attributes: 0, size: 1073741824 bytes)Partition 2: product_a (group: qcom_dynamic_partitions_a, attributes: 0, size: 536870912 bytes)Partition 3: system_b (group: qcom_dynamic_partitions_b, attributes: 0, size: 0 bytes)Partition 4: vendor_b (group: qcom_dynamic_partitions_b, attributes: 0, size: 0 bytes)

    This output clearly shows the logical partitions, their respective groups (indicating A/B slots), and their current sizes. Note that partitions for the inactive slot (e.g., _b in this example) might show a size of 0 bytes if they are not currently allocated/used.

    Rebuilding for Custom Recovery Development

    The core challenge for custom recoveries is to parse this super metadata and dynamically create the necessary block devices that can then be mounted. A custom recovery needs to perform the following conceptual steps:

    1. Locate the super partition: Identify the physical block device corresponding to super.
    2. Read super metadata: Parse the metadata (either metadata_v1 or metadata_v2) to understand the logical partition layout. The format is defined in `system/core/fs_mgr/liblp/include/liblp/liblp.h` in AOSP.
    3. Determine Active Slot: Identify the currently active A/B slot (usually stored in bootloader variables or `misc` partition).
    4. Create Device Mapper Devices: For each active logical partition (e.g., `system_a`, `vendor_a`), use the Linux `dmsetup` utility to create a corresponding virtual block device.
    5. Mount Partitions: Once the `dm` devices are created, they can be mounted as regular block devices.

    Practical Steps for Offline Reverse Engineering

    Step 1: Obtain a super.img

    The most common way to get a super.img is from an official OTA package’s payload.bin. Tools like `payload-dumper-go` can extract `super.img` from `payload.bin`.

    ./payload-dumper-go -p super payload.bin

    Alternatively, if your device is rooted, you can dump the `super` partition directly:

    adb pull /dev/block/by-name/super super.img

    Step 2: Analyze super.img Metadata

    On your development machine, you can use the `lpm_tool` from the Android source tree (or a pre-compiled binary) to analyze the `super.img`.

    ./lpm_tool dump super.img

    This will provide the same partition layout information as seen on-device, including names, sizes, and offsets within the `super` image. Pay close attention to the `extents` information, which details where each logical partition’s data resides within `super`.

    Step 3: Creating Device Mapper Devices (Recovery Logic)

    In a custom recovery environment (which typically runs a stripped-down Linux kernel), you would translate the parsed `lpm_tool` output into `dmsetup` commands. The `dmsetup` command creates virtual block devices based on linear mappings. For example, to create a device for `system_a`:

    # Example: Assume system_a starts at offset 1024KB with size 2GB (2097152KB)dmsetup create system_a --table '0 2097152 linear /dev/block/by-name/super 2048'

    Explanation of `dmsetup create`:

    • `system_a`: The name of the new device mapper device (e.g., `/dev/mapper/system_a`).
    • `–table ‘0 2097152 linear /dev/block/by-name/super 2048’`: This defines the mapping table.
      • `0`: The starting sector on the `dm` device.
      • `2097152`: The total number of sectors for this `dm` device (2GB / 512 bytes per sector).
      • `linear`: Specifies a linear mapping.
      • `/dev/block/by-name/super`: The underlying physical device.
      • `2048`: The starting sector on the physical device (1024KB / 512 bytes per sector).

    This process needs to be repeated for every dynamic partition that the recovery needs to access (e.g., `vendor`, `product`). The `lpm_tool` output provides the exact starting sectors and lengths in bytes (which you convert to 512-byte sectors) for each extent of a logical partition.

    Addressing A/B Updates in Recovery

    When dealing with A/B devices, the recovery must determine the active slot (_a or _b) to correctly identify which set of dynamic partitions to map. This information is typically retrieved from the boot control block in the `misc` partition or from Android’s `boot_control` HAL. The `lpm_tool` output will clearly show partitions suffixed with `_a` or `_b`, helping the recovery logic choose the correct ones.

    Conclusion

    Reverse engineering Android 10+ dynamic partition layouts is a critical skill for custom recovery developers. By understanding the role of the super partition, utilizing tools like lpm_tool, and mastering the Linux `dmsetup` commands, developers can successfully adapt their recoveries to mount and interact with these modern Android storage configurations. While the initial learning curve is steeper than with static partitions, this dynamic approach offers greater flexibility and efficiency for Android updates, making it an essential component of the ecosystem to understand for any advanced system developer.

  • How to Resize Dynamic Partitions for Custom System Images on Android 10+: A Practical Walkthrough

    Introduction to Dynamic Partitions on Android 10+

    Since Android 10, Google introduced a significant architectural change with Project Treble, moving towards a ‘Dynamic Partitions’ system. This system replaces traditional fixed-size partitions like system, vendor, and product with logical partitions residing within a single ‘super’ partition (super.img). This allows for more flexible allocation of space, enabling features like seamless A/B updates and reducing the barrier for Generic System Images (GSIs).

    However, this flexibility comes with new challenges for custom ROM developers and enthusiasts. When installing custom ROMs or GSIs, especially those with different size requirements than the stock images, the default logical partition sizes within your device’s super.img might be insufficient. For instance, a GSI might require a larger system partition than your stock firmware allocates, leading to ‘not enough space’ errors during flashing. This guide will walk you through the process of rebuilding and resizing your super.img to accommodate custom system images on Android 10+ devices.

    Prerequisites and Tools

    Before embarking on this journey, ensure you have the following prerequisites and tools ready:

    Unlocked Bootloader & ADB/Fastboot

    • Your device’s bootloader must be unlocked. This is a critical first step for any custom firmware modification.
    • You need ADB (Android Debug Bridge) and Fastboot tools installed and properly configured on your computer. These are typically part of the Android SDK Platform Tools.

    Essential Tools for Dynamic Partition Manipulation

    You’ll need specific tools, often compiled from AOSP source, to work with dynamic partitions:

    • lpmake: Used to create a super.img from individual partition images and a configuration file.
    • lpunpack: Used to extract individual partition images from an existing super.img.
    • fastboot: The standard tool for flashing partitions to your device.

    These tools can often be found pre-compiled in various Android modding forums or by compiling them from the Android source tree yourself. Ensure they are added to your system’s PATH or are located in the directory where you’ll be executing commands.

    Understanding Your Device’s Super Partition Layout

    The first step is to understand the current layout of your device’s super partition. You’ll typically obtain this by extracting the super.img from your device’s factory image. If a super.img is not directly available, you might find a super_empty.img along with individual partition images (system.img, vendor.img, etc.) which can be used to reconstruct it.

    1. Obtain Your Device’s Factory Image or Dump

      Download the full factory image for your specific device model and Android version. Inside, look for a super.img or individual partition images. If your device uses A/B slots, you might see super_a.img or super_b.img.

    2. Extract and Inspect the Super Partition

      Use lpunpack to examine the contents and layout of your super.img. Navigate to the directory containing super.img in your terminal and run:

      lpunpack --sparse --output_dir extracted_super super.img

      This command will extract the logical partitions (like system.img, vendor.img, product.img) into the extracted_super directory. Inspecting these files will give you an idea of the default sizes and the partitions present.

    Planning Your New Partition Layout

    Now, you need to decide on the new sizes for your dynamic partitions. This is crucial for installing your custom ROM or GSI. The new sizes should be large enough to accommodate the images you intend to flash. Typically, a GSI requires a system partition of around 3-5 GB, and a vendor partition that matches the stock firmware’s requirements or the GSI’s specific needs.

    • Identify the sizes of the system.img, vendor.img, etc., from your custom ROM or GSI. You can check the file size of these images.
    • Allocate additional space for future updates or expansion, but be mindful of the total available space on your device.
    • Remember that the super.img has a maximum total capacity, which is dictated by your device’s hardware. Exceeding this will cause flashing errors.

    Step-by-Step: Rebuilding Your Super Partition

    Step 1: Obtain Custom Partition Images

    Extract the system.img, vendor.img, product.img, etc., from your custom ROM ZIP file or GSI package. Place these images in a working directory on your computer.

    Step 2: Create a Configuration XML for lpmake

    lpmake requires a configuration XML file that defines the structure and sizes of the dynamic partitions. This XML specifies partition groups, their maximum sizes, and the logical partitions within them. A typical lpmake manifest might look like this:

    <?xml version="1.0" encoding="UTF-8"?> <lpmake> <super_partition_groups> <group name="main" max_size="YOUR_TOTAL_SUPER_SIZE_IN_BYTES" /> </super_partition_groups> <super_partitions> <partition name="system_a" size="SYSTEM_PARTITION_SIZE_IN_BYTES" readonly="true" group="main" /> <partition name="vendor_a" size="VENDOR_PARTITION_SIZE_IN_BYTES" readonly="true" group="main" /> <partition name="product_a" size="PRODUCT_PARTITION_SIZE_IN_BYTES" readonly="true" group="main" /> <!-- Add other partitions like odm_a, system_ext_a as needed --> </super_partitions> </lpmake>

    Replace YOUR_TOTAL_SUPER_SIZE_IN_BYTES with the total maximum size you want for your super.img (e.g., 8GB = 8000000000 bytes). For individual partition sizes, use values appropriate for your custom ROM images. Ensure you account for A/B slots if your device supports them (e.g., system_a and system_b partitions).

    Step 3: Use lpmake to Create the New super.img

    With your custom partition images and the XML configuration file (let’s call it new_super_config.xml), you can now use lpmake. The command structure typically looks like this:

    lpmake --metadata 4 --partition-config new_super_config.xml --image system_a=path/to/your/system.img --image vendor_a=path/to/your/vendor.img --output super_new.img

    Let’s break down the arguments:

    • --metadata 4: Specifies the number of metadata copies (usually 2 or 4, 4 is safer for A/B devices).
    • --partition-config new_super_config.xml: Points to your XML configuration file.
    • --image system_a=path/to/your/system.img: Maps your system.img file to the logical partition system_a defined in the XML. Repeat for all partitions you want to include in the initial super_new.img.
    • --output super_new.img: The name of the new super image file to be created.

    It’s important to note that you don’t necessarily have to include all partition images in the `lpmake` command; often, you just define the partition slots, and then flash the actual `.img` files separately. However, for a complete `super.img` to flash, it’s safer to include the images.

    # Example if you want to include images directly in super.img (less common for custom ROMs, often just flash empty super then system/vendor) lpmake --metadata 4 --group main:8000000000 --partition system_a:readonly:4000000000:main --image system_a=system.img --partition vendor_a:readonly:1000000000:main --image vendor_a=vendor.img --sparse --output super_new.img

    In this example, main:8000000000 defines a group named ‘main’ with a max size of 8GB. The system_a and vendor_a partitions are allocated specific sizes within this group.

    Step 4: Flash the New super.img

    Reboot your device into Fastboot mode. Then, flash your newly created super_new.img:

    fastboot flash super super_new.img

    This step will overwrite your device’s existing super partition with your resized layout. This is a critical step; ensure your super_new.img is correctly built to avoid bricking your device.

    Step 5: Flash Your Custom System Image(s)

    With the new super partition layout in place, you can now flash your custom system images onto the resized logical partitions. These will automatically utilize the new sizes you’ve defined.

    fastboot flash system system.img fastboot flash vendor vendor.img fastboot flash product product.img fastboot reboot

    Flash all necessary dynamic partition images (`system`, `vendor`, `product`, `odm`, `system_ext`) that are part of your custom ROM or GSI. After flashing, reboot your device to experience your custom ROM.

    Troubleshooting Common Issues


  • SAR Partition Forensics: Extracting and Analyzing Data from System-as-Root Layouts for Developers

    Introduction to System-as-Root (SAR)

    The System-as-Root (SAR) partition layout, introduced with Android 9 (Pie), fundamentally changed how the Android operating system is structured on devices. Unlike previous layouts where a dedicated system partition held the read-only OS components and the ramdisk was part of the boot partition (with /system mounted separately), SAR integrates the system.img directly into the ramdisk. This unified approach means the root filesystem is now served from the system_root, which is part of the boot image itself or a logical partition within a `super` partition. This design offers benefits like simplified A/B updates and improved security but introduces new complexities for forensic analysis and low-level development.

    The Forensics Challenge of SAR

    For developers and forensic analysts, SAR presents unique challenges. The traditional separation of boot and system partitions is blurred. The kernel, ramdisk, and system image are all bundled together, or the `system` image is treated as the initial root partition. This means that:

    • There is no longer a distinct /system block device that can be directly mounted and analyzed in isolation.
    • The root filesystem (/) is directly derived from the system.img contents within the `boot` image or a dynamic partition.
    • Tools and techniques designed for older partition layouts often fail or provide incomplete results when confronted with SAR.
    • `dm-verity` and full-disk encryption (FDE) or file-based encryption (FBE) are often tightly integrated, adding layers of protection that must be addressed.

    Understanding how to correctly identify, extract, and analyze data from SAR layouts is crucial for advanced debugging, vulnerability research, and digital forensics.

    Identifying a SAR Layout

    Before proceeding with extraction, it’s essential to confirm if a device utilizes a SAR layout. Several indicators can help determine this:

    1. Checking System Properties via ADB

    The easiest way is to query system properties using ADB (Android Debug Bridge):

    adb shell getprop ro.build.system_root_image

    If the output is true, the device uses a SAR layout. If it’s empty or false, it likely uses a traditional or A/B non-SAR layout.

    2. Analyzing the Filesystem Structure

    Once you have an ADB shell, examine the root directory and the /system mount point:

    adb shell ls -l /adb shell mount | grep ' /system '

    In a SAR setup, /system will typically be a symlink to /system_root/system or similar, and the root directory (/) will contain traditional system directories like /bin, /etc, /sbin, etc., directly from the system image rather than separate partition mounts.

    Methods for Data Extraction

    Extracting data from a SAR device requires careful consideration of its state (live, recovery, or offline) and protection mechanisms.

    1. Live Device Extraction (via ADB)

    For a live, rooted device, you can use adb pull, but direct pulling of entire system trees can be slow or encounter permission issues. A more robust approach involves packaging the data on the device first:

    adb shell "cd /system_root && tar -czvf /sdcard/system_root.tar.gz ."adb pull /sdcard/system_root.tar.gz .adb shell rm /sdcard/system_root.tar.gz

    This command archives the entire /system_root directory (which effectively contains the system image) into a compressed tarball on the device’s internal storage, then pulls it to your host machine, and finally cleans up the temporary file.

    2. Recovery Mode Extraction (via Custom Recovery like TWRP)

    If you have access to a custom recovery, extraction becomes more straightforward as it bypasses the running Android OS’s restrictions.

    1. Boot the device into TWRP recovery.
    2. Connect your device to your computer via USB.
    3. In TWRP, navigate to