167 lines
2.1 KiB
NASM
167 lines
2.1 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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; 2 - 3,5 - '-'
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; 3 - 5,7 - '_'
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; 5 - 7,11 - 'e'
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; 7 - 11,13 - 'x'
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; 11 - 13,17 - 't'
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; 13 - 17,19 - '}'
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; 17 - 19,23 - '}'
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; 19 - 23,29 - '}'
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; 3 * 7 * 11 * 17 = 3927
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; answer "2 4 6 12"
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; flag _xt}
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start:
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push edi
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lea eax, [ebx + 0x4]
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lea ecx, [esi+startup_txt]
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mov eax, dword [eax]
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push ecx
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call dword [eax]
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pop ebp
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pop edi
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lea ebp, [esi+one]
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.lp:
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call process
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cmp byte [ebp+8], 125
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jnz .lp
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mov eax, dword [esi+super_val]
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cmp eax, 3927
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jnz .bad
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jmp .finish
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.bad:
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lea eax, [ebx + 0x4]
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lea ecx, [esi+wrong_txt]
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mov eax, dword [eax]
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push ecx
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call dword [eax]
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pop ebp
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inc esp
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.finish:
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ret
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two:
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dd three,five
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db '-',2
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startup_txt db 'Numberz?', 0
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three:
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dd five,seven
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db '_',3
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fmt_txt db '%u',0
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five:
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dd seven,eleven
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db 'e',5
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; ebp = current node
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process:
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push ebp
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push ebp
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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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lea ecx, [esi+fmt_txt]
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mov eax, dword [eax]
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push ecx
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call dword [eax]
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pop ebp
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pop eax
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pop ecx
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pop ebp
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movzx eax, byte [ebp+9]
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cmp eax, ecx
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jle above_handler
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jmp below_handler
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seven:
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dd eleven,thirteen
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db 'x',7
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above_handler:
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mov ecx, dword [ebp+4]
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lea ebp, [esi+ecx]
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jmp add_next_char
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eleven:
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dd thirteen,seventeen
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db 't',11
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mul_handler:
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movzx eax, byte [ebp+9]
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mov edx, dword [esi+super_val]
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mul edx
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mov dword [esi+super_val], eax
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ret
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thirteen:
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dd seventeen, nineteen
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db '}',13
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below_handler:
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mov ecx, dword [ebp]
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lea ebp, [esi+ecx]
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jmp add_next_char
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seventeen:
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dd nineteen, twentythree
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db '}',17
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add_next_char:
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movzx eax, byte [ebp+8]
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mov byte [edi], al
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inc edi
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jmp mul_handler
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nineteen:
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dd twentythree, twentynine
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db '}',19
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super_val dd 1
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twentythree:
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dd 0, 0
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db ':',23
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twentynine:
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dd 0, 0
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db ')',29
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wrong_txt db 'Nope!',0
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one:
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dd two, three
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db 0,1
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resv_stuff 512-$
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