141 lines
2.4 KiB
NASM
141 lines
2.4 KiB
NASM
format binary
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use32
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include 'std.inc'
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; On entrance to each shellcode segment the ebx register will be a vtable of std funcs
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; printf
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; puts
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; scanf
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; sin
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; cos
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; tan
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; asin
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; acos
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; atan
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; malloc
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; free
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; esi contains the base address of the shellcode segment
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; edi contains the address of the part of the flag that this segment fills
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; edx contains the number of the block
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start:
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push edx
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push edi
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push esi
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mov eax, dword [ebx]
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lea ecx, [esi + base_txt]
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push ecx
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call dword [eax]
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add esp, 4
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xor eax, eax
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push eax
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mov eax, esp
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push eax
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lea eax, [ebx + 8]
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mov eax, dword [eax]
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lea ecx, [esi+scanf_txt]
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push ecx
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call dword [eax]
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add esp, 8
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; inputt'd float is now on top of the stack
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pop eax
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mov dword [esi+temp_val], eax
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sub esp, 8
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cvtss2sd xmm0, dword [esi+temp_val]
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movsd qword [esp], xmm0
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; call cos
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lea eax, [ebx + 0x10]
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mov eax, dword [eax]
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call dword [eax]
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fstp qword [esp]
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movsd xmm0, qword [esp]
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add esp, 8
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cvtss2sd xmm1, dword [esi+c_val]
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mulsd xmm0, xmm1
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push ebp
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push ebp
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movsd qword [esp], xmm0
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; call atan
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lea eax, [ebx + 0x20]
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mov eax, dword [eax]
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call dword [eax]
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fstp qword [esp]
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movsd xmm0, qword [esp]
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pop eax
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cvtss2sd xmm1, dword [esi+b_val]
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pop ecx
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mulsd xmm0, xmm1
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push esp
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push ebp
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movsd qword [esp], xmm0
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; call sin
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lea eax, [ebx + 0xc]
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mov eax, dword [eax]
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call dword [eax]
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fstp qword [esp]
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cvtss2sd xmm1, dword [esi+a_val]
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movsd xmm0, qword [esp]
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mulsd xmm0, xmm1
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movsd qword [esp], xmm0
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cvtsd2ss xmm0, qword [esp]
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pop eax
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movss dword [esp], xmm0
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pop eax
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pop esi
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push esi
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cmp eax, dword [esi+final_val]
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jnz trash
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lea ecx, [esi+right_txt]
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jmp past_trash
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trash:
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lea ecx, [esi+wrong_txt]
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; Make this so it crashes badly
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inc esp
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past_trash:
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push ecx
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lea eax, [ebx + 0x4]
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mov eax, dword [eax]
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call dword [eax]
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pop ebp
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pop esi
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pop edi
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pop edx
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mov eax, dword [esi+temp_val]
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; 0x61375a7b = little endian of '{Z7a'
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; 0x61375a7b ^ 0x3fab396d which is the value of the correct input 1.33769
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; is equal to 0x5e9c6316
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xor eax, 0x5e9c6316
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mov dword [edi], eax
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xor eax, eax
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mov dword [esi+temp_val], eax
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retn
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b_val dd 0x4039999a
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base_txt db 'Please enter the best number, round to 6 significant figures.', ENDL, 0
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a_val dd 0x40d00000
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scanf_txt db '%f', 0
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final_val dd 0xc092e6a0
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right_txt db 'You got it!', 0
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c_val dd 0xbf99999a
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wrong_txt db 'You dumb.', 0
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temp_val dd 0
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resv_stuff 512-$
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