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This is the Application Processor shared between the [[M68ap|iPhone]], [[N45ap|iPod touch]], and the [[N82ap|iPhone 3G]]. Not much is known about it through official sources. This processor is not used in any of the newest devices, being replaced by the [[S5L8720]] and [[S5L8920]].
  
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The '''S5L8900''' in the technical name of the [[Application Processor|application processor]] shared between the [[M68AP|iPhone]], [[N45AP|iPod touch]], and the [[N82AP|iPhone 3G]]. Not much is known about it, even through official sources. According to [[saurik]], this is an [http://infocenter.arm.com/help/topic/com.arm.doc.ddi0301h/DDI0301H_arm1176jzfs_r0p7_trm.pdf <code>arm1176jzf-s</code>]. This processor was succeded by the [[S5L8720]] used in the [[N72AP|iPod touch (2nd generation)]] and the [[S5L8920]] in the [[N88AP|iPhone 3GS]]. Those have subsequently been succeded by newer processors.
   
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== [[VROM (S5L8900)|VROM]] Exploits ==
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==[[S5L File Formats|Firmware File Formats]]==
  
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==Exploits==
  
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===[[Firmware|Userland]]===
  
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* [[Restore Mode]] - Firmware v1.0.2 and below
  
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* [[Symlinks]] - Firmware v1.1.1 and below
  
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* [[LibTiff|LibTIFF]] - Firmware v1.1.1 and below
  
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* [[Mknod]] - Firmware v1.1.2 and below
  
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* [[Dual Boot Exploit]] - Firmware 1.1.4 / v2.0b3 and below
  
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===[[iBoot]] / [[Kernel]]===
  
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* [[Ramdisk Hack]] - 1.1.4 / 2.0 beta 3 and below
  
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* [[diags|Diags Exploit]] - 1.1.4 / v2.0 beta 5 and below
  
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* [[iBoot Environment Variable Overflow]] - 3.1 beta 1 and below
  
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* [[usb_control_msg(0x21, 2) Exploit]] - 3.1.2 and below
  
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===[[VROM (S5L8900)|Bootrom]]===
  
 
* [[pwnage|Pwnage 1.0 (Ramdisk + AppleImage2NORAccess)]]
  
* [[pwnage|Pwnage 1.0 (Ramdisk + AppleImage2NORAccess)]]
 
* [[Pwnage 2.0|Pwnage 2.0 (DFU + Malformed Certificate)]]
  
* [[Pwnage 2.0|Pwnage 2.0 (DFU + Malformed Certificate)]]
   
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==Boot Chain==
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== Boot Chain ==
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[[VROM (S5L8900)]]->[[LLB]]->[[iBoot]]->[[Kernel]]->[[Firmware|System Software]]
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* [[VROM (S5L8900)|VROM]] ([[Bootrom Rev.2]])
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* [[LLB]]
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* [[iBoot (Bootloader)|iBoot]]
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* [[Kernel]]
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* [[/|System Software]]
   
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=== [[iDroid]] ===
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One of the many goals of the [[iDroid]] project is to modify the boot chain immediately after the bootrom:
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* VROM ([[Bootrom Rev.2]])
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* [[OpeniBoot]]
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* [http://www.kernel.org Linux Kernel]
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* [http://www.x.org X Server]
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* [[wikipedia:X Window System|X Window System]] (X11)
   
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This is possible thanks to the [[Pwnage]] and [[Pwnage 2.0]] exploits discovered by the [[iPhone Dev Team]]. The exploit in a nutshell exploits the fact that the [[VROM (S5L8900)|VROM]] ([[Bootrom Rev.2]]) doesn't signature check the [[LLB]], and as such, by uploading a maliciously crafted LLB, one can gain control of the entire device.
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One of the [[iPhoneLinux]] goals are to replace that Boot Chain after iBoot:
  
   
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Despite many years of work, it appears that the project will never be finished, much akin to many other big open source projects, such as [[wikipedia:ReactOS|ReactOS]] and the [[wikipedia:GNU Project|GNU]]'s own kernel, the [http://www.gnu.org/software/hurd/hurd.html Hurd].
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[[VROM (S5L8900)]]->OpeniBoot->Linux Kernel->X Server->Window Manager
  
   
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==Upgrade Process==
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== Upgrade Process ==
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=== [[Restore Mode]] ===
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The restore process of the processor is:
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* [[VROM (S5L8900)|VROM]] ([[Bootrom Rev.2]])
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* [[DFU Mode]]
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* [[WTF]]
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* [[iBoot (Bootloader)|iBoot]]
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* [[Kernel]] (wait for [[Ramdisk|Restore Ramdisk]] upload)
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* Restore Ramdisk
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* [[Restore Mode]]
   
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=== [[Restore Mode]] ===
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=== [[DFU Mode]] ===
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In order to flash an older version of [[iOS|iPhone OS]] onto the device, you need to enter [[DFU Mode]]. The entry into DFU Mode is in the [[iDevice|device]]'s circuitry and the processor itself. This allows a non-responsive device to enter DFU Mode nearly anywhere, essentially making it improbable to [[bricked|brick]] the device.
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The common upgrade process chain is [[VROM]]->[[DFU]]->[[WTF]]->[[iBoot]]->[[Kernel]]->[[Ramdisk]]->[[Restore Mode]].
  
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Once in [[DFU Mode]], [[iTunes]] will notify you of a device in [[Restore Mode]], even though it isn't. This is common across all devices. In iTunes, you just hold the [[wikipedia:Option key|Option key]] ([[wikipedia:File:Third-party option key.JPG|&#x2325;]]) on [[wikipedia:OS X|OS X]] or the [[wikipedia:Shift key|shift key]] on [[wikipedia:Microsoft Windows|Windows]] while clicking the "Restore" button. Just navigate to the [[IPSW File Format|IPSW]] for the specific version you want. As [[SHSH|SHSH blobs]] didn't exist before [[iOS|iPhone OS]] 3.0 with the [[S5L8920]] on the [[N88AP|iPhone 3GS]], you are only limited by your ability to obtain the [[firmware]] IPSW.
   
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The boot chain is a very simple one:
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=== [[DFU|DFU Mode]] ===
  
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* [[VROM (S5L8900)|VROM]] ([[Bootrom Rev.2]])
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To flash an older version of the iPhone software you have to let your phone reside in [[DFU]]. In iTunes you have to press the option key (Mac) or the shift key (Windows) when pressing 'Restore' to be able to manually chose an [[IPSW File Format|IPSW]].
  
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* [[DFU Mode]]
   
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==== Boot Chain ====
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== See Also ==
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[[VROM]]->[[DFU]]
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* [[VROM (S5L8900)]]
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** [[Bootrom Rev.2]]
   
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[[Category:Application Processors]]
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==External Links==
  
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* [http://infocenter.arm.com/help/topic/com.arm.doc.ddi0301h/DDI0301H_arm1176jzfs_r0p7_trm.pdf Technical Reference Manual: ARM1176JZF-S]
  

Latest revision as of 18:22, 22 March 2017

The S5L8900 in the technical name of the application processor shared between the iPhone, iPod touch, and the iPhone 3G. Not much is known about it, even through official sources. According to saurik, this is an arm1176jzf-s. This processor was succeded by the S5L8720 used in the iPod touch (2nd generation) and the S5L8920 in the iPhone 3GS. Those have subsequently been succeded by newer processors.

VROM Exploits

Boot Chain

iDroid

One of the many goals of the iDroid project is to modify the boot chain immediately after the bootrom:

This is possible thanks to the Pwnage and Pwnage 2.0 exploits discovered by the iPhone Dev Team. The exploit in a nutshell exploits the fact that the VROM (Bootrom Rev.2) doesn't signature check the LLB, and as such, by uploading a maliciously crafted LLB, one can gain control of the entire device.

Despite many years of work, it appears that the project will never be finished, much akin to many other big open source projects, such as ReactOS and the GNU's own kernel, the Hurd.

Upgrade Process

Restore Mode

The restore process of the processor is:

DFU Mode

In order to flash an older version of iPhone OS onto the device, you need to enter DFU Mode. The entry into DFU Mode is in the device's circuitry and the processor itself. This allows a non-responsive device to enter DFU Mode nearly anywhere, essentially making it improbable to brick the device.

Once in DFU Mode, iTunes will notify you of a device in Restore Mode, even though it isn't. This is common across all devices. In iTunes, you just hold the Option key (⌥) on OS X or the shift key on Windows while clicking the "Restore" button. Just navigate to the IPSW for the specific version you want. As SHSH blobs didn't exist before iPhone OS 3.0 with the S5L8920 on the iPhone 3GS, you are only limited by your ability to obtain the firmware IPSW.

The boot chain is a very simple one:

See Also

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