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- ; [madmouse@yourmomsb0x ~]$ nasm -f bin -o test test.s&&chmod +x test&&./test;cat test|xxd
- ; 0000000: 7f45 4c46 31c0 31db 40cd 8041 4141 4141 .ELF1.1.@..AAAAA
- ; 0000010: 0200 0300 0100 0000 0480 0408 3400 0000 ............4...
- ; 0000020: 0000 0000 0000 0000 3400 2000 0100 0000 ........4. .....
- ; 0000030: 0000 0000 0100 0000 0000 0000 0080 0408 ................
- ; 0000040: 0080 0408 5400 0000 5400 0000 0700 0000 ....T...T.......
- ; 0000050: 0010 0000 ....
- ; [madmouse@yourmomsb0x ~]$ readelf -e test
- ; ELF Header:
- ; Magic: 7f 45 4c 46 31 c0 31 db 40 cd 80 41 41 41 41 41
- ; Class: <unknown: 31>
- ; Data: <unknown: c0>
- ; Version: 49 <unknown: %lx>
- ; OS/ABI: <unknown: db>
- ; ABI Version: 64
- ; Type: EXEC (Executable file)
- ; Machine: Intel 80386
- ; Version: 0x1
- ; Entry point address: 0x8048004
- ; Start of program headers: 52 (bytes into file)
- ; Start of section headers: 0 (bytes into file)
- ; Flags: 0x0
- ; Size of this header: 52 (bytes)
- ; Size of program headers: 32 (bytes)
- ; Number of program headers: 1
- ; Size of section headers: 0 (bytes)
- ; Number of section headers: 0
- ; Section header string table index: 0
- ;
- ; There are no sections in this file.
- ;
- ; Program Headers:
- ; Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
- ; LOAD 0x000000 0x08048000 0x08048000 0x00054 0x00054 RWE 0x1000
- ; [madmouse@yourmomsb0x ~]$
- [bits 32]
- section .text
- global start
- org 0x08048000
- ehdr: ; Elf32_Ehdr
- db 0x7F,"ELF" ;, 1, 1, 1, 0 ; e_ident
- ; ^ 4 more bytes for code caving
- ; times 8 db 0
- ; We can replace ^ this with the following for a code cave inside the elf header itself
- start:
- xor eax, eax
- xor ebx, ebx
- inc eax
- int 0x80
- end:
- times 12-(end-start) db 'A' ; we need bytes for padding, the code cave here is 12 bytes long
- ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
- dw 2 ; e_type
- dw 3 ; e_machine
- dd 1 ; e_version
- dd start ; e_entry
- dd phdr - $$ ; e_phoff
- dd 0 ; e_shoff
- dd 0 ; e_flags
- dw ehdrsize ; e_ehsize
- dw phdrsize ; e_phentsize
- dw 1 ; e_phnum
- dw 0 ; e_shentsize
- dw 0 ; e_shnum
- dw 0 ; e_shstrndx
- ehdrsize equ $ - ehdr
- phdr: ; Elf32_Phdr
- dd 1 ; p_type
- dd 0 ; p_offset
- dd $$ ; p_vaddr
- dd $$ ; p_paddr
- dd filesize ; p_filesz
- dd filesize ; p_memsz
- dd 7 ; p_flags
- dd 0x1000 ; p_align
- phdrsize equ $ - phdr
- filesize equ $ - $$
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