Vulnerabilities: Difference between revisions
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<pre> | <pre> | ||
ROM:BFC00004 lw $v0, 0xBC100000 | ROM:BFC00004 lw $v0, 0xBC100000 # stores 0xBC100000 to $v0 | ||
ROM:BFC0000C bnez $v0, loc_BFC00064 | ROM:BFC0000C bnez $v0, loc_BFC00064 # if $v0 (0xBC100000) is not equal to zero, jump to 0xBFC00064 | ||
</pre> | </pre> | ||
<pre> | <pre> | ||
ROM:BFC00064 cfc0 $v0, $9 | ROM:BFC00064 cfc0 $v0, $9 #store coprocessor $9 to $v0 | ||
ROM:BFC00068 beqz $v0, loc_BFC00078 | ROM:BFC00068 beqz $v0, loc_BFC00078 $ if $v0 (coproc $9) is equal to 0 jump to 0xBFC00078 | ||
ROM:BFC0006C nop | ROM:BFC0006C nop | ||
ROM:BFC00070 jr $v0 | ROM:BFC00070 jr $v0 #jump to register $v0 (value initially set in coproc $9) | ||
</pre> | </pre> | ||
Because both address 0xBC100000 and coprocessor register $9 are controlled by syscon, this backdoor would allow an attacker performing a hardware based attack on syscon (by either replacing syscon or performing a man in the middle data injection) to set those values and gain Lib-PSP iplloader/pre-ipl time code execution (this requires using kernel code execution to fill memory with a payload to jump to beforehand), and thus potentially dump the pre-ipl code on newer targets. | Because both address 0xBC100000 and coprocessor register $9 are controlled by syscon, this backdoor would allow an attacker performing a hardware based attack on syscon (by either replacing syscon or performing a man in the middle data injection) to set those values and gain Lib-PSP iplloader/pre-ipl time code execution (this requires using kernel code execution to fill memory with a payload to jump to beforehand), and thus potentially dump the pre-ipl code on newer targets. | ||
Revision as of 23:52, 13 November 2018
Lib-PSP iplloader (PRE-IPL)
NMI Backdoor
(Found by: Mathieulh, Proxima, C+D/Prometheus, Anyone spending time reverse engineering the pre-ipl) - Earliest discovery: 4/4/2007
Fixed: Never
Vulnerable: Lib-PSP iplloader (all ROM Versions, 0.7.0 and newer Kbooti versions, PS Vita's PSP Bootrom)
The Lib-PSP iplloader rom (present within tachyon's IC package) as well as Lib-PSP iplloader versions 0.7.0 and onward feature a NMI/Interrupt handler backdoor in its loader part at the very first instructions of the bootrom.
This backdoor allows anyone in control of the memory location address 0xBC100000 to perform a jump to an arbitrary location defined in coprocessor register $9
If 0xBC100000 is not equal to 0 and coprocessor register $9 is set, Lib-PSP iplloader will jump to the address set in the register very early in the code (by the 8th instruction). If 0xBC100000 is equal to 0, coprocessor register $9 will be reset back to 0.
Below are the relevant pieces of code:
ROM:BFC00004 lw $v0, 0xBC100000 # stores 0xBC100000 to $v0 ROM:BFC0000C bnez $v0, loc_BFC00064 # if $v0 (0xBC100000) is not equal to zero, jump to 0xBFC00064
ROM:BFC00064 cfc0 $v0, $9 #store coprocessor $9 to $v0 ROM:BFC00068 beqz $v0, loc_BFC00078 $ if $v0 (coproc $9) is equal to 0 jump to 0xBFC00078 ROM:BFC0006C nop ROM:BFC00070 jr $v0 #jump to register $v0 (value initially set in coproc $9)
Because both address 0xBC100000 and coprocessor register $9 are controlled by syscon, this backdoor would allow an attacker performing a hardware based attack on syscon (by either replacing syscon or performing a man in the middle data injection) to set those values and gain Lib-PSP iplloader/pre-ipl time code execution (this requires using kernel code execution to fill memory with a payload to jump to beforehand), and thus potentially dump the pre-ipl code on newer targets.