picoCTF2018

At this challenge , We have a file asm :

test image

With three paramater for function asm3(0xb3fb1998,0xfe1a474d,0xd5373fd4). we have the stack frame will be like this:

test image

Firstly, instruction mov eax,0x62 -> eax=0x00000062 -> al=0x62, ah=0x00

Next, xor al,al -> al=0 -> eax=0x00000000

Next mov ah,BYTE PTR [ebp+0xa] -> ah = 19 -> ax= 0x1900

Next sal ax,0x10 -> left shifts ax -> ax=0x0000

Next sub al,BYTE PTR [ebp+0xd] -> al = 0x00-0x47 = 0xb9

Next add ah,BYTE PTR [ebp+0xe] -> ah = 0x00+0x1a = 0x1a

Next xor ax,WORD PTR [ebp+0x10] -> ax=0x1ab9 xor 0x3fd4 = 0x256d

The result for this challenge is 0x256d