SYSENTER hook

[niom]

Originally Posted by bilbo

on a theorethical point of view you are right. In the same way one replaces INT 3 handler with a preamble (e.g. for tracing purposes) and then jumps to the old handler, the same guy on Windows XP must replace MSR register 176 (EIP) - which points currently at KiFastCallEntry - with some preamble and then jump to KiFastCallEntry.

k
thx


but i have a new question:

do you think, it is possible to "instrument" all ntoskrnl exports like detours does? (detours inserts a jump at the function entry, that points to a custom trampoline, which calls the old code: http://research.microsoft.com/~galenh/Publications/HuntUsenixNt99.pdf)

or do you know an easier way to intercept ring0->ring0 calls?

just done driver to revert back to INT2E from SYSENTER..

i'm interesting about SP2 NTOSKRNL.EXE..
also code on 7FFE0300h on AMD machines..

at Woodmann.com posted..

to bilbo:

AMD very well has own "SYSENTER-SYSEXIT":
SYSCALL 0F05h
SYSRET 0F07h

exactly about this i'm interesting:
do someone see usage of these on AMD at 7FFE0300h?

[bilbo]

Well done, evaluator!
The trick I told before is just avoiding to copy the INT 2E snippet on top of SYSENTER snippet: in this way you would fuck all the pending system calls!
You are copying it at a displacement of 16 bytes: good.
You have also done a lot of checks... even address FFDF0300 (which is the same physical memory as 7FFE0300), SYSEXIT(at KiSystemService), the code inside KiSystemService (which force you to detect eventually softice) and two times the SYSENTER snippet... but better sure than unsure...

I found also it is not necessary to patch KiSystemCallExitBranch from 7506 (jnz KiSystemCallExit2) to 7505 (jnz KiSystemCallExit).

do someone see usage of these on AMD at 7FFE0300h?

No, my experiments were done on a rather old AMD K6 and there INT 2E was used.

niom: it looks like you are interested to ring0 detouring. This is for you: http://www.rootkit.com/newsread.php?newsid=152
It comes with nice code too

Regards, bilbo


Edited for evaluator...
Regarding ring0 detouring suggestion, it was for niom, as I wrote, not for you...
Regarding 9th post: look where I posted the answer, and look to my previous posts, please...
Regarding SYSEXIT patching... I have posted on WOODMANN a snippet which does not patch anything more than necessary...
Please don't be so aggressive... We are here to learn, not to flame each other
Best regards!

P.S. only 3 addresses for phys 41000? or 4? Do PHYS 41000 and you will know!!!

>>it looks like you are interested to ring0 detouring
nope.

>>I found also it is not necessary to patch KiSystemCallExitBranch
>>from 7506 (jnz KiSystemCallExit2) to 7505 (jnz KiSystemCallExit).

verry nessesary:) remember, why we are replaicing pair SYSENTER-SYSEXIT
by INT-IRET!?

(that will your 9th power post~:)

another Q: there is III virtual address for 41000, wich is!? :)

Hey guys, I've found some info about SYSENTER and int 2e at ElicZs website... here is the txt

http://www.anticracking.sk/elicz/infos/FastNTCALL.txt

Hopefully you guys can use this to gain some knowledge

[JMI]

Wow, and it was only written four years ago. Where has it been hiding? Oh yah. In plain sight.

Regards,