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Difference between revisions of "Research: Pwnage Patches"
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=== Why does this help us? === |
=== Why does this help us? === |
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| + | ROM:18005D72 FF F7 D2 FC BL sub_1800571A ; Branch with Link |
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| − | Damn! Overlooked ONE THING! New, and correct, explanation will be here shortly. |
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| + | That jumps to 0x1800571A. Why does that matter? well, the above "Patched Area" is at the end of this routine, and then we come back with our modified R0. Right after this BL, we get this, which is where our new R0 comes into play: |
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| + | |||
| + | ROM:18005D76 00 28 CMP R0, #0 ; Set cond. codes on Op1 - Op2 |
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| + | ROM:18005D78 00 D0 BEQ loc_18005D7C ; Branch |
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| + | ROM:18005D7A 8A E0 B loc_18005E92 ; Branch |
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| + | |||
| + | If R0 = 0, which is does, it will jump to 0x18005D7C. If not, it will go to 0x18005E92. I don't know the nitty gritty, but basically this is to make it so that we jump to an earlier part in the file that we were supposed to. A further analysis may be in order, I will definitely get to that later. |
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== 2.0 (5A347) [[Lockdownd]] == |
== 2.0 (5A347) [[Lockdownd]] == |
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This may actually confuse some people. You see, there is 'technically' two patches, but in reality, there is only one. The second one is the rehashed signature done with ldid, because you must remember that this is a userland binary, not a lower level one like the [[iBoot]], which resides in the [[NOR]]. These files on the main filesystem must cohere to the demands of the [[kernel]], and according to a [[devteam]] member, the patches to not require this were to complex and it would just be much easier to use ldid to take care of it. So that is what they did here. They took the original file, then one with the one patch that they needed, rehashed the patched one, BsDiff'd them, and then as you can now tell, the .patch tile contains the actual patch + the new sig :) |
This may actually confuse some people. You see, there is 'technically' two patches, but in reality, there is only one. The second one is the rehashed signature done with ldid, because you must remember that this is a userland binary, not a lower level one like the [[iBoot]], which resides in the [[NOR]]. These files on the main filesystem must cohere to the demands of the [[kernel]], and according to a [[devteam]] member, the patches to not require this were to complex and it would just be much easier to use ldid to take care of it. So that is what they did here. They took the original file, then one with the one patch that they needed, rehashed the patched one, BsDiff'd them, and then as you can now tell, the .patch tile contains the actual patch + the new sig :) |
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Revision as of 21:05, 2 August 2008
If you have IDA Pro and you are at least semi-handy with ARM please contribute :)
Thanks to CPICH for helping out!
2.0 (5A347) iBoot
Patched Area
There is only 1 patch made to the iBoot, iBEC, iBSS, and WTF.n82ap. They are all iBoots, pretty much, so I am going to assume that they all have this same patch for the same reason. Please feel free to correct this if this is not true.
Here is a snippet of it from IDA:
ROM:1800587C 01 20 MOVS R0, #1 ; R1 = 1 ROM:1800587E 40 42 NEGS R0, R0 ; PWNAGE PATCH ROM:1800587E ; Change 40 42 > 00 20 ROM:1800587E ; That will make it: ROM:1800587E ; MOVS R0 = #0 ROM:1800587E ; ROM:1800587E ; R0 (unpatched) = -1 ROM:1800587E ; R0 (patched) = 0
Why does this help us?
ROM:18005D72 FF F7 D2 FC BL sub_1800571A ; Branch with Link
That jumps to 0x1800571A. Why does that matter? well, the above "Patched Area" is at the end of this routine, and then we come back with our modified R0. Right after this BL, we get this, which is where our new R0 comes into play:
ROM:18005D76 00 28 CMP R0, #0 ; Set cond. codes on Op1 - Op2 ROM:18005D78 00 D0 BEQ loc_18005D7C ; Branch ROM:18005D7A 8A E0 B loc_18005E92 ; Branch
If R0 = 0, which is does, it will jump to 0x18005D7C. If not, it will go to 0x18005E92. I don't know the nitty gritty, but basically this is to make it so that we jump to an earlier part in the file that we were supposed to. A further analysis may be in order, I will definitely get to that later.
2.0 (5A347) Lockdownd
This may actually confuse some people. You see, there is 'technically' two patches, but in reality, there is only one. The second one is the rehashed signature done with ldid, because you must remember that this is a userland binary, not a lower level one like the iBoot, which resides in the NOR. These files on the main filesystem must cohere to the demands of the kernel, and according to a devteam member, the patches to not require this were to complex and it would just be much easier to use ldid to take care of it. So that is what they did here. They took the original file, then one with the one patch that they needed, rehashed the patched one, BsDiff'd them, and then as you can now tell, the .patch tile contains the actual patch + the new sig :)
(Be back in a little bit with actual snippets from IDA showing the actual patch done, I want to go through the actual low level stuff first)
