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SoLID

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shellcode_i_a32

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SoLID - UNC Charlotte 3

decrement the ecx register and jump to the decode label if the contents of the ecx register is not zero else jump short to the shellcode label

loop decode \n jmp short shellcode

jump short to encodedshellcode if equal

je short encodedshellcode

add 20 to the single byte stored at memory address var

add byte [var], 20

perform xor operation between ebx register and the word __flag_byte and save the result in ebx

xor [ebx], word __flag_byte

compare if edi is equal to 0

cmp edi, 0

move the contents of ebx into the 4 bytes at memory address var

mov [var], ebx

call _continue

call _continue

push the value 10 onto the stack and point eax to the stack register

push 10 \n mov eax, esp

move the value of ax into memory at address 1000h

mov [1000h], ax

add 0x2 to the contents in cl and save the result in cl

add cl, 0x2

push the value 0x61702f2f and the value 0x6374652f onto the stack and point the eax register to the stack register

push 0x61702f2f \n push 0x6374652f \n mov eax, esp

jump to the two label

jmp two

define the numeric label 3

3:

reserve array realarray of 10 real numbers

realarray resq 10

move the address of the character on the stack into ebx

mov ebx, esp

move 0x80 into ah

mov ah, 0x80

jump to the _next label if the doubleword starting at the address [eax-8] is not equal to the contents stored at the egg address

cmp dword [eax-8], egg \n jne _next

move 5 into al

mov al, 5

zero out the eax register and the ebx register

xor ebx, ebx \n mul ebx

define decode function

decode:

move 0x7 into bl

mov bl, 0x7

push the dword 0x6f702f6e onto the stack

push dword 0x6f702f6e

jump to the label l2 if the unsigned contents of the al register is lower than the unsigned contents of the bl register

cmp al, bl \n jb l2

move the address of msg3 into eax

mov eax, msg3

move the contents of x into ebx

mov ebx, x

push '//pa' onto the stack

push '//pa'

close

mov eax, 6

push 0x6e69622f onto the stack

push 0x6e69622f

subtract 0x6374612e from the contents in ecx and save the result in ecx

sub ecx, 0x6374612e

subtract the byte 0x1 from the contents of the esp register

sub esp, byte 0x1

jump to the label l3 if the unsigned contents of the cl register is lower than the unsigned contents of the dl register

cmp cl, dl \n jb l3

move a byte from the address buff+ecx into al

mov al, byte[buff+ecx]

load the effective address of ebp-8 into the ebx register

lea ebx, [ebp-8]

decrement the contents of the cl register and jump to the loop_dup label if the result is not negative

dec cl \n jns loop_dup

declare the format label

format:

test the value of eax

test eax, eax

push 1 onto the stack

push 1

put the byte CHMOD_CALL into the eax register

push byte CHMOD_CALL \n pop eax

move 0x04 into bl

mov bl, 0x04

push the word 0x3905 onto the stack

push word 0x3905

define the callpop label

callpop:

perform the xor operation between the al register and the value 0x41

xor al, 0x41

move 04h into al

mov al, 04h

add 24 to eax

add eax, 24

initialize ecx to zero

xor ecx, ecx

initialize cx to 01

mov cx, 01

move the contents of eax into address defined by ebp+var_a

mov [ebp+var_a], eax

zero out ah register

xor ah, ah

jump to the _start label if the contents of the al register is equal to the value 0xf2 else move the value 0x50905090 into the eax register

cmp al, 0xf2 \n je _start \n mov eax, 0x50905090

point ebp to the esp register

mov ebp, esp

move 4 into eax

mov eax, 4

put syscall value into eax

pop eax

call the prepare function

call prepare

push 0x76766c2d to the stack

push 0x76766c2d

push 0x2f2f2f2f to the stack

push 0x2f2f2f2f

push 0x46 onto the stack

push 0x46

push 0x6f723a30 onto the stack

push 0x6f723a30

invoke subroutine socket

mov ebx, 1

right rotate the contents of the esi register by 1 bit

ror esi, 1

move 0x17 into al

mov al, 0x17

zero out the edx register and jump to the l2 label if the contents of the ecx register is equal to the contents of the edx register

xor edx, edx \n cmp ecx, edx \n je l2

move readbuffer into edx

mov edx, readbuffer

move m_src1 to ebx

mov ebx, m_src1

define the label 2

2:

move the value 5 into the al register then decrement the contents of the al register and jump to the l2 label if the result is not zero

mov al, 5 \n dec al \n jnz l2

push the byte +0x6 onto the stack

push byte +0x6

if the contents of the edx register is equal to the contents of the ebx register then jump to the memory address 0x8

cmp edx, ebx \n je 0x8 \n

define the byte string '/sbin/insmod#/tmp/o.o'

db '/sbin/insmod#/tmp/o.o'

zero out eax and ecx

xor ecx, ecx \n mul ecx

move the value 672274793 into the ecx register

mov ecx, 672274793

copy the address of var into esi

mov esi, var

restore edx from the value we pushed onto the stack at the start

pop edx

push the 0x69622f65 onto the stack

push 0x69622f65

compare the contents of the al register and 0xf2

cmp al, 0xf2

move the contents of the esp register into the ecx register

mov ecx, esp

jump to the connect label if the contents of the eax register is equal to the contents of the ebx register else jump to the exit label if the unsigned contents of the eax register is greater than the unsigned contents of the ebx register

cmp eax, ebx \n je connect \n ja exit

push 0x30313a31 to the stack

push 0x30313a31

push 0x1 onto the stack

push 0x1

compare the word at the address ecx and 0x5951

cmp word [ecx], 0x5951

move the contents of the esi register into the bx register

mov bx, [esi]

define writestring function

writestring:

subtract 88 from the contents of the al register

sub al, 88

define the byte string '/etc/passwd#'

db '/etc/passwd#'

push the byte 0x1 onto the stack and point ecx to the stack register

push byte 0x1 \n mov ecx, esp

subtract the byte 8 from the contents of the ebx register

sub ebx, byte 8

define shellcode as an array of bytes and initialize it to 0x4b,0xf7,0x13,0x59,0xcc,0x8c,0x63,0x5e,0x9f,0x8d,0x99,0x9f,0x1f,0xa4,0x3b,0x6e,0xc6,0x36,0x23

shellcode: db 0x4b,0xf7,0x13,0x59,0xcc,0x8c,0x63,0x5e,0x9f,0x8d,0x99,0x9f,0x1f,0xa4,0x3b,0x6e,0xc6,0x36,0x23

move permissions to read write and execute into ecx

mov ecx, 0777

zero out the eax and ebx register

xor ebx, ebx \n mul ebx

move the contents of memory address ebp+12 into esi

mov esi, [ebp+12]

declare msglength to have the constant value 12

msglength: equ 12

increment the memory variable count

inc count

move 0x2f3e20 into eax

mov eax, 0x2f3e20

perform a logical xor between the dl register and 0xbb and save the result in dl

xor dl, 0xbb

push the dword 0x3a303a3a onto the stack

push dword 0x3a303a3a

push the dword 0x6f726577 onto the stack

push dword 0x6f726577

push the 0x656c6966 onto the stack

push 0x656c6966

push the byte 6 onto the stack

push byte 6

push the value 0x7461632f and the value 0x6e69622f onto the stack and point the esi register to the stack register

push 0x7461632f \n push 0x6e69622f \n mov esi, esp

push the double word 0x303a3a31 onto the stack

push dword 0x303a3a31

push 0x74 to the stack

push 0x74