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100 lines
4.5 KiB
100 lines
4.5 KiB
# BEDaisy
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reverse engineering of bedaisy.sys (battleyes kernel driver). By registering on image load callbacks and IAT hooking BEDaisy's `MmGetSystemRoutineAddress` we can simply hook any imports
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we want and have control flow over subsequent functions. Write up can be found here: https://back.engineering/post/battleye/
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<img src="https://imgur.com/NFGyGrY.png"/>
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# APCS
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The below function will be executed in each thread that bedaisy registers an APC on.
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```cpp
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__int64 __usercall apc_callback@<rax>(char _CL@<cl>, char _BH@<bh>, __int64 *a3@<r9>)
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{
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__int64 v4; // rbx
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__asm { rcl bh, cl }
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v4 = *a3;
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*(_DWORD *)(v4 + 2160) = RtlWalkFrameChain(*a3 + 0x70, 256i64, 0i64);
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return KeSetEvent(v4 + 88, 0i64, 0i64);
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}
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```
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Registeration of APCS:
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```cpp
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status = PsLookupThreadByThreadId(thread_id, &some_pethread);
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v17 = 0;
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if ( (int)status >= 0 )
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{
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allocated_pool = ExAllocatePool(0x200i64, 0x878i64);
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allocated_pool_1 = allocated_pool;
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allocated_pool_2 = allocated_pool;
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if ( allocated_pool )
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{
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allocated_pool_plus_58 = allocated_pool + 0x58;
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KeInitializeEvent((PRKEVENT)(allocated_pool + 0x58), NotificationEvent, 0);
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__asm { rcl cx, 0C6h }
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LOBYTE(v77) = 0;
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KeInitializeApc(allocated_pool_2, some_pethread, 0i64, j_apc_callback, 0i64, 0i64, v77, 0i64);
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if ( (unsigned __int8)KeInsertQueueApc(allocated_pool_2, allocated_pool_2, 0i64, 2i64) )
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```
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# HWID
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BEDaisy opens a handle to DR0 (disk.sys).
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```
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02646022 190.98799133 [GoodEye]ZwOpenFile called from: 0xFFFFF804DEFDB904
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02646023 190.98799133 [GoodEye] - ZwOpenFile(\Device\Harddisk0\DR0)
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02646024 190.98869324 [GoodEye] - ZwOpenFile handle result: 0xFFFFFFFF80003E28
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```
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BEDaisy then sends a few IOCTL's to disk.sys using `ZwDeviceIoControlFile`
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```
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02646049 190.99142456 [GoodEye]ZwDeviceIoControlFile Called From 0xFFFFF804DEFDB94A
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02646050 190.99143982 [GoodEye] - FileHandle: 0xFFFFFFFF80003E28
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02646051 190.99143982 [GoodEye] - IoControlCode: 0x00000000002D1400
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02646052 190.99143982 [GoodEye] - OutputBufferLength: 0x0000000000000008
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02646053 190.99143982 [GoodEye] - InoutBufferLength: 0x000000000000000C
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02646059 190.99192810 [GoodEye]ZwDeviceIoControlFile Called From 0xFFFFF804DEFDB960
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02646060 190.99192810 [GoodEye] - FileHandle: 0xFFFFFFFF80003E28
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02646061 190.99192810 [GoodEye] - IoControlCode: 0x00000000002D1400
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02646062 190.99192810 [GoodEye] - OutputBufferLength: 0x0000000000000000
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02646063 190.99194336 [GoodEye] - InoutBufferLength: 0x000000000000000C
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02646072 190.99209595 [GoodEye]ZwDeviceIoControlFile Called From 0xFFFFF804DEFDB9B1
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02646073 190.99211121 [GoodEye] - FileHandle: 0xFFFFFFFF80003E28
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02646074 190.99211121 [GoodEye] - IoControlCode: 0x000000000007C088
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02646075 190.99211121 [GoodEye] - OutputBufferLength: 0x0000000000000211
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02646076 190.99211121 [GoodEye] - InoutBufferLength: 0x0000000000000021
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```
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# IRP
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BEDaisy checks the IRP's of every single loaded driver. Below is the checks done on dxgkrnl.sys on windows 10-2004. Base address of dxgkrnl.sys is `0xfffff80498f10000`.
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```
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00042942 92.55983734 [GoodEye]gh_wcsnicmp called from: 0xFFFFF804DEFDD874
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00042943 92.55983734 [GoodEye] - string1: C:\Windows\System32\drivers\dxgkrnl.sys
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00042944 92.55983734 [GoodEye] - string2: C:\Windows\System32\drivers\dxgkrnl.sys
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00042945 92.55983734 [GoodEye] - count: 0x27
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00042946 92.55996704 [GoodEye]MmIsAddressValid Called From: 0xFFFFF804DEFDD8B6
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00042947 92.55996704 [GoodEye] - NonPaged VirtualAddress: 0xFFFFF80498F10000 // base address of dxgkrnl.sys
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00042951 92.56208801 [GoodEye]MmIsAddressValid Called From: 0xFFFFF804DEFE1116
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00042952 92.56209564 [GoodEye] - NonPaged VirtualAddress: 0xFFFFF8049905E400 // address of DxgkCreateClose
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00042953 92.56209564 [GoodEye]MmIsAddressValid Called From: 0xFFFFF804DEFE1116
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00042956 92.56209564 [GoodEye] - NonPaged VirtualAddress: 0xFFFFF8049905E400 // address of DxgkCreateClose
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00042957 92.56209564 [GoodEye]MmIsAddressValid Called From: 0xFFFFF804DEFE1116
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00042980 92.56213379 [GoodEye] - NonPaged VirtualAddress: 0xFFFFF80498F516A0 // address of DxgkDeviceIoctl
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00042981 92.56213379 [GoodEye]MmIsAddressValid Called From: 0xFFFFF804DEFE1116
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00042982 92.56213379 [GoodEye] - NonPaged VirtualAddress: 0xFFFFF80499059670 // address of DxgkInternalDeviceIoctl
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```
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# Imports
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All import addresses are stored in the `.data` section of the driver and can easily be changed to hook imported functions.
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<img src="https://imgur.com/hafZdDd.png"/> |