SPU Isolated Modules Reverse Engineering

anergistic

Using a static analysis (IDA) could give you a good view of what the program does, but sometimes you want to know what a program does in real time and how it reacts to different parameters, this is where anergistics becomes a powerful tool. It simulates the SPU including its communication, and storage.

Current repos

• https://github.com/kraiskil/anergistic.git
• http://foxbrew.org/git/anergistic.git/

usage

anergistic can be launched in two different modes, one that only emulates (runs) the program through the SPU and the the other that lets you debug the process through gdb

only emulate

./anergistic spu_elf_name.elf

this mode runs an elf with all the parameters and actions defined on main.c, channel.c a

debug

terminal 1

./anergistic -g 1234 spu_elf_name.elf //simulate debug server in the local host on port 1234

terminal 2

spu-gdb spu_elf_name.elf 
(gdb)target remote :1234 //connect to the local host on port 1234
(gdb)help //gives you information of the command available

Documentation

• http://publib.boulder.ibm.com/infocenter/ieduasst/stgv1r0/topic/com.ibm.iea.cbe/cbe/1.0/LinuxOnCell/L2T1H1_31_LinuxonCellToolchainGDB.pdf
• SPU specific commands
  • http://sourceware.org/gdb/onlinedocs/gdb/SPU.html

this mode performs the same as above but lets you debug the process through gdb

Customizations

see example below

Running in aim_spu_module anergistic

Problems

Connection proble

when in debugger mode

Waiting for gdb to connect...
Client connected.
recv failed: Success

Solution

use ppu-gdb

aim_spu_module

It is used to retrieve the device type, device id, open psid and the pscode from the EID0 data that is passed in.

Debug messages

Address		Message
? 3.41 ?	355 CEX
0x36f0	0x3570	"(spu)start aim spu module!\n"
0x3710	0x3590	"(spu) PU DMA area start address is not align 16byte\n"
0x3750	0x35d0	"(spu) PU EID area start address is not align 16byte\n"
0x3790	0x3610	"(spu) PU DMA area size is not equall to AIM_DMA_SIZE\n"

This messages are DMAed to the ppu if a debug output address is specified.

Data

Address		Message
? 3.41 ?	355 CEX
0x37e0	-	Reference tool fallback IDPS
0x37f0 - ...	0x3650 - ...	Start of AIM keys Keys#aim_keys
0x3ac0	0x3870	AES sbox (16*16 bytes)
0x3c70	0x3a20	AES inverse sbox (16*16 bytes)

Functions

Address		Name	Parameters	Info
3.41  CEX/DEX	355 CEX
0x9e0		stop_func	unknown	Stops the module execution with various stop codes.
0xa18		main_func	unknown	Main routine.
0xf18		response	unknown	Sends response to ppu over DMA.
0x1158		process_eid	unknown	Decrypts EID0.
0x1438		prepare_print	unknown	Prepares debug output.
0x1440		debug_print	unknown	As the name already states... (this outputs over DMA)
0x17f0		-	-	AES 1 Part of aes implementation.
0x1c48		-	-	AES 2 Part of aes implementation.
0x1df0		-	-	AES 3 Probably part of aes implementation.
0x20f0		-	-	AES 4 Probably part of aes implementation.
0x2300		-	-	AES 5 Probably part of aes implementation.
0x2418		-	-	AES 6 Part of aes implementation.
0x2608		-	-	AES 7 Part of aes implementation.
0x30c0		do_dma	ls_addr:$4, dma_effective_addr:$5, size:$6, tag_id:$7, unk0:$8, unk1:$9	Used to dma data in and out of the isolated module's LS.
0x3168		write_tag_mask_bit	mask_bit:$4	Used to set a specific bit in MFC_WrTagMask.

Disasm

The complete disassembly is available at [1].

Decrypting EID

Dumper Payload

• http://pastie.org/pastes/2101977

Running in aim_spu_module anergistic

//Partial code modified to run aim_spu_module

• http://pastie.org/2000330

isoldr

loads, decrypts, runs isolated modules, and creates through aes the required key in LS 0x0

Debug messages

This module doesnt contain debug messages

Data

Address		Message
? 3.41 ?	355 CEX
0x34C40 - ...		Start of isoldr keys Keys#Modules
0x35130		AES sbox (16*16 bytes)
0x35300		AES inverse sbox (16*16 bytes)

Functions

Address		Name	Parameters	Info
? 3.41 ?	355 CEX
0xa18		main_func	unknown	Main routine.
0x2BF28		-	-	AES 2 Part of aes implementation.
0x2C240		-	-	AES 3 Probably part of aes implementation.
0x2C8D0		-	-	AES 4 Probably part of aes implementation.
0x2CDC8		-	-	AES 5 Probably part of aes implementation.
0x2D7C0		-	-	AES 6 Part of aes implementation.
0x2D9B0		-	-	AES 7 Part of aes implementation.
0x346B0		write_tag_mask_bit	mask_bit:$4	Used to set a specific bit in MFC_WrTagMask.

from isoldr 3.15 iirc -> http://pastie.org/2774207