IBoot

Last updated
iBoot
Developer(s) Apple Inc.
Operating system Darwin, macOS, [1] iPadOS and iOS [2]
Platform x86, ARM
Type Boot loader
License Proprietary software

iBoot is the stage 2 bootloader for all Apple products. [3] It replaces the old bootloader, BootX. Compared with its predecessor, iBoot improves authentication performed in the boot chain. [2]

Contents

For x86-based Macs, the boot process starts by running code stored in secured UEFI Boot ROM (stage 1). Boot ROM has two primary responsibilities: to initialize system hardware and to select an operating system to run (the POST and UEFI component). For ARM-based Macs, the Boot ROM does not include UEFI. [4]

For iOS, iPadOS and ARM macOS, the boot process starts by running the device's Boot ROM. The Boot ROM loads the Low-Level Bootloader (LLB), which is the stage 1 bootloader and loads iBoot. If all goes well, iBoot will then proceed to load the iOS, iPadOS or macOS kernel as well as the rest of the operating system. [5] [6] If the iBoot fails to load or fails to verify iOS, iPadOS or macOS, the bootloader jumps to DFU (Device Firmware Update) [7] mode; otherwise it loads the remaining kernel modules. [2]

On x86 macOS, iBoot is located in /System/Library/CoreServices/boot.efi. [8] Once the kernel and all drivers necessary for booting are loaded, the boot loader starts the kernel’s initialization procedure. At this point, enough drivers are loaded for the kernel to find the root device. [9]

Memory safety

Apple has modified the C compiler toolchain that is used to build iBoot in order to advance memory safety since iOS 14. This advancement is designed to mitigate entire classes of common memory corruption vulnerabilities such as buffer overflows, heap exploitations, type confusion vulnerabilities, and use-after-free attacks. These modifications can potentially prevent attackers from successfully escalating their privileges to run malicious code, such as an attack involving arbitrary code execution. [10]

Source code leak incident

in 2018, a portion of iBoot source code for iOS 9 was leaked on GitHub, [11] Apple then issued a copyright takedown request (DMCA) to GitHub to remove the repository. It was believed an Apple employee was responsible for the leak. However, this was not confirmed by Apple.

Related Research Articles

<span class="mw-page-title-main">BIOS</span> Firmware for hardware initialization and OS runtime services

In computing, BIOS is firmware used to provide runtime services for operating systems and programs and to perform hardware initialization during the booting process. The BIOS firmware comes pre-installed on an IBM PC or IBM PC compatible's system board and exists in some UEFI-based systems to maintain compatibility with operating systems that do not support UEFI native operation. The name originates from the Basic Input/Output System used in the CP/M operating system in 1975. The BIOS originally proprietary to the IBM PC has been reverse engineered by some companies looking to create compatible systems. The interface of that original system serves as a de facto standard.

<span class="mw-page-title-main">Booting</span> Process of starting a computer

In computing, booting is the process of starting a computer as initiated via hardware such as a button or by a software command. After it is switched on, a computer's central processing unit (CPU) has no software in its main memory, so some process must load software into memory before it can be executed. This may be done by hardware or firmware in the CPU, or by a separate processor in the computer system.

<span class="mw-page-title-main">Boot sector</span> Sector of a persistent data storage device

A boot sector is the sector of a persistent data storage device which contains machine code to be loaded into random-access memory (RAM) and then executed by a computer system's built-in firmware.

<span class="mw-page-title-main">GNU GRUB</span> Boot loader package

GNU GRUB is a boot loader package from the GNU Project. GRUB is the reference implementation of the Free Software Foundation's Multiboot Specification, which provides a user the choice to boot one of multiple operating systems installed on a computer or select a specific kernel configuration available on a particular operating system's partitions.

<span class="mw-page-title-main">XNU</span> Computer operating system kernel

XNU is the computer operating system (OS) kernel developed at Apple Inc. since December 1996 for use in the Mac OS X operating system and released as free and open-source software as part of the Darwin OS, which in addition to macOS is also the basis for the Apple TV Software, iOS, iPadOS, watchOS, visionOS, and tvOS OSes.

<span class="mw-page-title-main">Bootloader</span> Software responsible for starting the Computer and Load other software to the CPU memory

A bootloader, also spelled as boot loader or called bootstrap loader, is a computer program that is responsible for booting a computer. If it also provides an interactive menu with multiple boot choices then it's often called a boot manager.

The Macintosh Toolbox implements many of the high-level features of the Classic Mac OS, including a set of application programming interfaces for software development on the platform. The Toolbox consists of a number of "managers," software components such as QuickDraw, responsible for drawing onscreen graphics, and the Menu Manager, which maintain data structures describing the menu bar. As the original Macintosh was designed without virtual memory or memory protection, it was important to classify code according to when it should be loaded into memory or kept on disk, and how it should be accessed. The Toolbox consists of subroutines essential enough to be permanently kept in memory and accessible by a two-byte machine instruction; however it excludes core "kernel" functionality such as memory management and the file system. Note that the Toolbox does not draw the menu onscreen: menus were designed to have a customizable appearance, so the drawing code was stored in a resource, which could be on a disk.

<span class="mw-page-title-main">UEFI</span> Operating system and firmware specification

Unified Extensible Firmware Interface is a specification that defines the architecture of the platform firmware used for booting the computer hardware and its interface for interaction with the operating system. Examples of firmware that implement the specification are AMI Aptio, Phoenix SecureCore, TianoCore EDK II, InsydeH2O. UEFI replaces the BIOS which was present in the boot ROM of all personal computers that are IBM PC compatible, although it can provide backwards compatibility with the BIOS using CSM booting. Intel developed the original Extensible Firmware Interface (EFI) specification. Some of the EFI's practices and data formats mirror those of Microsoft Windows. In 2005, UEFI deprecated EFI 1.10.

coreboot Open-source computer firmware

coreboot, formerly known as LinuxBIOS, is a software project aimed at replacing proprietary firmware found in most computers with a lightweight firmware designed to perform only the minimum number of tasks necessary to load and run a modern 32-bit or 64-bit operating system.

<span class="mw-page-title-main">Hackintosh</span> Non-Apple computer running macOS

A Hackintosh is a computer that runs Apple's Macintosh operating system macOS on computer hardware that is not authorized for the purpose by Apple. This can also include running Macintosh software on hardware it is not originally authorized for. Benefits of "Hackintoshing" can include cost, ease of repair and piecemeal upgrade, and freedom to use customized choices of components that are not available in the branded Apple products. macOS can also be run on several non-Apple virtualization platforms, although such systems are not usually described as Hackintoshes. Hackintosh laptops are sometimes referred to as "Hackbooks".

<span class="mw-page-title-main">GUID Partition Table</span> Computer disk partitioning standard

The GUID Partition Table (GPT) is a standard for the layout of partition tables of a physical computer storage device, such as a hard disk drive or solid-state drive, using universally unique identifiers, which are also known as globally unique identifiers (GUIDs). Forming a part of the Unified Extensible Firmware Interface (UEFI) standard, it is nevertheless also used for some BIOSs, because of the limitations of master boot record (MBR) partition tables, which use 32 bits for logical block addressing (LBA) of traditional 512-byte disk sectors.

The boot ROM is a type of ROM that is used for booting a computer system. There are two types: a mask boot ROM that cannot be changed afterwards and a boot EEPROM, which can contain an UEFI implementation.

quik is a boot loader designed to start Linux on Apple Macintosh PowerPC systems based on the Old World ROM architecture. It was originally written by Paul Mackerras, and portions of its code were reused in all other Linux boot loaders for PowerPC, including the one known as BootX, which is dependent on the Mac OS. Quik's loader boots from Open Firmware and bypasses the Mac OS entirely. New World ROM systems use yaboot.

<span class="mw-page-title-main">Das U-Boot</span> Open-source, primary boot the devices operating system kernel

Das U-Boot is an open-source boot loader used in embedded devices to perform various low-level hardware initialization tasks and boot the device's operating system kernel. It is available for a number of computer architectures, including 68k, ARM, Blackfin, MicroBlaze, MIPS, Nios, SuperH, PPC, RISC-V and x86.

<span class="mw-page-title-main">EFI system partition</span> Partition used by Unified Extensible Firmware Interface

The EFIsystem partition or ESP is a partition on a data storage device that is used by computers that have the Unified Extensible Firmware Interface (UEFI). When a computer is booted, UEFI firmware loads files stored on the ESP to start operating systems and various utilities.

The Linux booting process involves multiple stages and is in many ways similar to the BSD and other Unix-style boot processes, from which it derives. Although the Linux booting process depend very much on the computer architecture, those architectures share similar stages and software components, including system startup, bootloader execution, loading and startup of a Linux kernel image, and execution of various startup scripts and daemons. Those are grouped into 4 steps: system startup, bootloader stage, kernel stage, and init process. When a Linux system is powered up or reset, its processor will execute a specific firmware/program for system initialization, such as Power-on self-test, invoking the reset vector to start a program at a known address in flash/ROM, then load the bootloader into RAM for later execution. In personal computer (PC), not only limited to Linux-distro PC, this firmware/program is called BIOS, which is stored in the mainboard. In embedded Linux system, this firmware/program is called boot ROM. After being loaded into RAM, bootloader will execute to load the second-stage bootloader. The second-stage bootloader will load the kernel image into memory, decompress and initialize it then pass control to this kernel image. Second-stage bootloader also performs several operation on the system such as system hardware check, mounting the root device, loading the necessary kernel modules,... Finally, the very first user-space process starts, and other high-level system initializations are performed.

<span class="mw-page-title-main">BootX (Apple)</span> Boot loader developed by Apple Inc.

BootX is a software-based bootloader designed and developed by Apple Inc. for use on the company's Macintosh computer range. BootX is used to prepare the computer for use, by loading all required device drivers and then starting-up Mac OS X by booting the kernel on all PowerPC Macintoshes running the Mac OS X 10.2 operating system or later versions.

<span class="mw-page-title-main">SeaBIOS</span> Open-source implementation of x86 BIOS

SeaBIOS is an open-source implementation of an x86 BIOS, serving as a freely available firmware for x86 systems. Aiming for compatibility, it supports standard BIOS features and calling interfaces that are implemented by a typical proprietary x86 BIOS. SeaBIOS can either run on bare hardware as a coreboot payload, or can be used directly in emulators such as QEMU and Bochs.

rEFInd Boot manager for UEFI systems

rEFInd is a boot manager for UEFI and EFI-based machines. It can be used to boot multiple operating systems that are installed on a single non-volatile device. It also provides a way to launch UEFI applications.

The booting process of Android devices starts at the power-on of the SoC and ends at the visibility of the home screen, or special modes like recovery and fastboot. The boot process of devices that run Android is influenced by the firmware design of the SoC manufacturers.

References

  1. ↑ "Darwin 9.2 Source Code". Apple Inc. Archived from the original on September 21, 2020. Retrieved January 19, 2020.
  2. 1 2 3 Ryan, Peter Y. A.; Naccache, David; Quisquater, Jean-Jacques (2016-03-17). The New Codebreakers: Essays Dedicated to David Kahn on the Occasion of His 85th Birthday. Springer. ISBN   9783662493014.
  3. ↑ Hayes, Darren R. (2014-12-17). A Practical Guide to Computer Forensics Investigations. Pearson IT Certification. ISBN   9780132756150.
  4. ↑ "boot process for T2, M1, and iOS devices".
  5. ↑ Apple Inc. (May 2016). "iOS Security Guide" (PDF). apple.com. Archived (PDF) from the original on February 27, 2016.
  6. ↑ "Boot process for a Mac with Apple silicon - Apple Support". Jan 2024.
  7. ↑ "iFixit Support: DFU Restore". iFixit . Retrieved 2019-09-29.
  8. ↑ "rEFIt - The Intel Mac boot process". refit.sourceforge.net. Retrieved 2017-08-26.
  9. ↑ "The Early Boot Process". developer.apple.com. Retrieved 2017-08-26.
  10. ↑ "Memory safe iBoot implementation". Apple Platform Security. Apple. Retrieved 25 January 2023.
  11. ↑ "Apple confirms iPhone source code leak". BBC News. 9 February 2018.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.