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DJ'SOUTSOURCING

Bypassing Blockchain Authorization via Unsecured Functions

Note: Since the first part of this series I have also uploaded some further videos on remediation of reentrancy and dealing with compiler versions when working with this hacking blockchain series. Head to the console cowboys YouTube account to check those out. Haha as mentioned before I always forget to post blogs when I get excited making videos and just move on to my next project… So make sure to subscribe to the YouTube if you are waiting for any continuation of a video series.. It may show up there way before here.

Note 2: You WILL run into issues when dealing with Ethereum hacking, and you will have to google them as versions and functionality changes often... Be cognizant of versions used hopefully you will not run into to many hard to fix issues.

In the second part of this lab series we are going to take a look at privacy issues on the blockchain which can result in a vulnerably a traditional system may not face. Since typically blockchain projects are open source and also sometimes viewable within blockchain explorers but traditional application business logic is not usually available to us. With traditional applications we might not find these issues due to lack of knowledge of internal functionality or inability to read private values on a remote server side script. After we review some issues we are going to exploit an authorization issues by writing web3.js code to directly bypass vertical authorization restrictions.

Blockchain projects are usually open source projects which allow you to browse their code and see what's going on under the hood. This is fantastic for a lot of reasons but a developer can run into trouble with this if bad business logic decisions are deployed to the immutable blockchain. In the first part of this series I mentioned that all uploaded code on the blockchain is immutable. Meaning that if you find a vulnerability it cannot be patched. So let's think about things that can go wrong..

A few things that can go wrong:

Randomization functions that use values we can predict if we know the algorithm
Hard-coded values such as passwords and private variables you can't change.
Publicly called functions which offer hidden functionality
Race conditions based on how requirements are calculated

Since this will be rather technical, require some setup and a lot of moving parts we will follow this blog via the video series below posting videos for relevant sections with a brief description of each. I posted these a little bit ago but have not gotten a chance to post the blog associated with it. Also note this series is turning into a full lab based blockchain exploitation course so keep a lookout for that.

In this first video you will see how data about your project is readily available on the blockchain in multiple formats for example:

ABI data that allows you to interact with methods.
Actual application code.
Byte code and assembly code.
Contract addresses and other data.

Lab Video Part 1: Blockchain OSINT:

Once you have the data you need to interact with a contract on the blockchain via some OSINT how do you actually interface with it? That's the question we are going to answer in this second video. We will take the ABI contract array and use it to interact with methods on the blockchain via Web3.js and then show how this correlates to its usage in an HTML file

Lab Video Part 2: Connecting to a Smart Contract:

Time to Exploit an Application:

Exploit lab time, I created an vulnerable application you can use to follow along in the next video. Lab files can be downloaded from the same location as the last blog located below. Grab the AuthorizationLab.zip file:

Lab file downloads:

https://github.com/cclabsInc/BlockChainExploitation

Ok so you can see what's running on the blockchain, you can connect to it, now what? Now we need to find a vulnerability and show how to exploit it. Since we are talking about privacy in this blog and using it to bypass issues. Lets take a look at a simple authorization bypass we can exploit by viewing an authorization coding error and taking advantage of it to bypass restrictions set in the Smart Contract. You will also learn how to setup a local blockchain for testing purposes and you can download a hackable application to follow along with the exercises in the video..

Lab Video Part 3: Finding and hacking a Smart Contract Authorization Issue:

Summary:

In this part of the series you learned a lot, you learned how to transfer your OSINT skills to the blockchain. Leverage the information found to connect to that Smart Contract. You also learned how to interact with methods and search for issues that you can exploit. Finally you used your browsers developer console as a means to attack the blockchain application for privilege escalation.

More information

DJ'SOUTSOURCING

This is the second blog post in the "Attacking financial malware botnet panels" series. After playing with Zeus, my attention turned to another old (and dead) botnet, SpyEye. From an ITSEC perspective, SpyEye shares a lot of vulnerabilities with Zeus.

The following report is based on SpyEye 1.3.45, which is old, and if we are lucky, the whole SpyEye branch will be dead soon.

Google dorks to find SpyEye C&C server panel related stuff:

if the img directory gets indexed, it is rather easy, search for e.g. inurl:b-ftpbackconnect.png
if the install directory gets indexed, again, easy, search for e.g. inurl:spylogo.png
also, if you find a login screen, check the css file (style.css), and you see #frm_viewlogs, #frm_stat, #frm_botsmon_country, #frm_botstat, #frm_gtaskloader and stuff like that, you can be sure you found it
otherwise, it is the best not to Google for it, but get a SpyEye sample and analyze it

And this is how the control panel login looks like, nothing sophisticated:

The best part is that you don't have to guess the admin's username ;)

This is how an average control panel looks like:

Hack the Planet! :)

Boring vulns found (warning, an almost exact copy from the Zeus blog post)

Clear text HTTP login - you can sniff the login password via MiTM, or steal the session cookies
No password policy - admins can set up really weak passwords
No anti brute-force - you can try to guess the admin's password. There is no default username, as there is no username handling!
Password autocomplete enabled - boring
Missing HttpOnly flag on session cookie - interesting when combining with XSS
No CSRF protection - e.g. you can upload new exe, bin files, turn plugins on/off :-( boring. Also the file extension check can be bypassed, but the files are stored in the database, so no PHP shell this time. If you check the following code, you can see that even the file extension and type is checked, and an error is shown, but the upload process continues. And even if the error would stop the upload process, the check can be fooled by setting an invalid $uptype. Well done ...

        if ($_FILES['file']['tmp_name'] && ($_FILES['file']['size'] > 0))         {                 $outstr = "<br>";                 set_time_limit(0);                 $filename = str_replace(" ","_",$_FILES['file']['name']);                 $ext = substr($filename, strrpos($filename, '.')+1);                 if( $ext==='bin' && $uptype!=='config' ) $outstr .= "<font class='error'>Bad CONFIG extension!</font><br>";                 if( $ext==='exe' && $uptype!=='body' && $uptype!=='exe' ) $outstr .= "<font class='error'>Bad extension!</font><br>";                  switch( $uptype )                 {                 case 'body': $ext = 'b'; break;                 case 'config': $ext = 'c'; break;                 case 'exe': $ext = 'e'; break;                 default: $ext = 'e';                 }                 $_SESSION['file_ext'] = $ext;                 if( isset($_POST['bots']) && trim($_POST['bots']) !== '')                 {                         $bots = explode(' ', trim($_POST['bots']));                         //writelog("debug.log", trim($_POST['bots']));                         $filename .= "_".(LastFileId()+1);                 }                 if( FileExist($filename) ) $filename .= LastFileId();                 $tmpName  = $_FILES['file']['tmp_name'];                 $fileSize = $_FILES['file']['size'];                 $fileType = $_FILES['file']['type'];                 ## reading all file for calculating hash                 $fp = fopen($tmpName, 'r');

Clear text password storage - the MySQL passwords are stored in php files, in clear text. Also, the login password to the form panel is stored in clear text.
MD5 password - the passwords stored in MySQL are MD5 passwords. No PBKDF2, bcrypt, scrypt, salt, whatever. MD5. Just look at the pure simplicity of the login check, great work!

$query = "SELECT * FROM users_t WHERE uPswd='".md5($pswd)."'";

ClickJacking - really boring stuff

SQL injection

SpyEye has a fancy history of SQL injections. See details here, here, here, video here and video here.

It is important to highlight the fact that most of the vulnerable functions are reachable without any authentication, because these PHP files lack user authentication at the beginning of the files.

But if a C&C server owner gets pwned through this vuln, it is not a good idea to complain to the developer, because after careful reading of the install guide, one can see:

"For searching info in the collector database there is a PHP interface as formgrabber admin panel. The admin panel is not intended to be found on the server. This is a client application."

And there are plenty of reasons not to install the formgrabber admin panel on any internet reachable server. But this fact leads to another possible vulnerability. The user for this control panel is allowed to remotely login to the MySQL database, and the install guide has pretty good passwords to be reused. I mean it looks pretty secure, there is no reason not to use that.

CREATE USER 'frmcpviewer' IDENTIFIED BY 'SgFGSADGFJSDGKFy2763272qffffHDSJ';

Next time you find a SpyEye panel, and you can connect to the MySQL database, it is worth a shot to try this password.

Unfortunately the default permissions for this user is not enough to write files (select into outfile):

Access denied for user 'frmcpviewer' (using password: YES)

I also made a little experiment with this SQL injection vulnerability. I did set up a live SpyEye botnet panel, created the malware install binaries (droppers), and sent the droppers to the AV companies. And after more and more sandboxes connected to my box, someone started to exploit the SQL injection vulnerability on my server!

63.217.168.90 - - [16/Jun/2014:04:43:00 -0500] "GET /form/frm_boa-grabber_sub.php?bot_guid=&lm=3&dt=%20where%201=2%20union%20select%20@a:=1%20from%20rep1%20where%20@a%20is%20null%20union%20select%20@a:=%20@a%20%2b1%20union%20select%20concat(id,char(1,3,3,7),bot_guid,char(1,3,3,7),process_name,char(1,3,3,7),hooked_func,char(1,3,3,7),url,char(1,3,3,7),func_data)%20from%20rep2_20140610%20where%20@a=3%23 HTTP/1.1" 200 508 "-" "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729; .NET4.0C; .NET4.0E)"

Although the query did not return any meaningful data to the attacker (only data collected from sandboxes), it raises some legal questions.

Which company/organization has the right to attack my server?

police (having a warrant)
military (if we are at war)
spy agencies (always/never, choose your favorite answer)
CERT organisations?

But, does an AV company or security research company has the legal right to attack my server? I don't think so... The most problematic part is when they hack a server (without authorization), and sell the stolen information in the name of "intelligence service". What is it, the wild wild west?

The SQLi clearly targets the content of the stolen login credentials. If this is not an AV company, but an attacker, how did they got the SpyEye dropper? If this is an AV company, why are they stealing the stolen credentials? Will they notify the internet banking owners about the stolen credentials for free? Or will they do this for money?

And don't get me wrong, I don't want to protect the criminals, but this is clearly a grey area in the law. From an ethical point of view, I agree with hacking the criminal's servers. As you can see, the whole post is about disclosing vulns in these botnet panels. But from a legal point of view, this is something tricky ... I'm really interested in the opinion of others, so comments are warmly welcome.

On a side note, I was interested how did the "attackers" found the SpyEye form directory? Easy, they brute-forced it, with a wordlist having ~43.000 entries.

(Useless) Cross site scripting

Although parts of the SpyEye panel are vulnerable to XSS, it is unlikely that you will to find these components on the server, as these codes are part of the install process, and the installer fails to run if a valid install is found. And in this case, you also need the DB password to trigger the vuln...

Session handling

This is a fun part. The logout button invalidates the session only on the server side, but not on the client side. But if you take into consideration that the login process never regenerates the session cookies (a.k.a session fixation), you can see that no matter how many times the admin logs into the application, the session cookie remains the same (until the admin does not close the browser). So if you find a session cookie which was valid in the past, but is not working at the moment, it is possible that this cookie will be valid in the future ...

Binary server

Some parts of the SpyEye server involve running a binary server component on the server, to collect the form data. It would be interesting to fuzz this component (called sec) for vulns.

Log files revealed

If the form panel mentioned in the SQLi part is installed on the server, it is worth visiting the <form_dir>/logs/error.log file, you might see the path of the webroot folder, IP addresses of the admins, etc.

Reading the code

Sometimes reading the code you can find code snippets, which is hard to understand with a clear mind:

$content = fread($fp, filesize($tmpName)); if ( $uptype === 'config' )     $md5 = GetCRC32($content); else $md5 = md5($content); .... <script> if (navigator.userAgent.indexOf("Mozilla/4.0") != -1) {         alert("Your browser is not support yet. Please, use another (FireFox, Opera, Safari)");         document.getElementById("div_main").innerHTML = "<font class=\'error\'>ChAnGE YOuR BRoWsEr! Dont use BUGGED Microsoft products!</font>"; } </script>

Decrypting SpyEye communication

It turned out that the communication between the malware and C&C server is not very sophisticated (Zeus does a better job at it, because the RC4 key stream is generated from the botnet password).

function DeCode($content) {         $res = '';         for($i = 0; $i < strlen($content); $i++)         {                 $num = ord($content[$i]);                 if( $num != 219) $res .= chr($num^219);         }         return $res; }

Fixed XOR key, again, well done ...

This means that it is easy to create a script, which can communicate with the SpyEye server. For example this can be used to fill in the SpyEye database with crap data.

import binascii import requests import httplib, urllib  def xor_str(a, b):     i = 0     xorred = ''     for i in range(len(a)):         xorred += chr(ord(a[i])^b)     return xorred              b64_data= "vK6yv+bt9er17O3r6vqPnoiPjZb2i5j6muvo6+rjmJ/9rb6p5urr6O/j/bK+5uP16/Xs7evq9ers7urv/bSo5u316vXs7evq/a6v5pq/trK1/bi4qbjm453j6uPv7Or9tr/u5um+uuvpve3p7eq/4+vsveLi7Lnqvrjr6ujs7rjt7rns/au3vOa5sre3srW8s7q2tr6p4Lm3tLiw4LmuvKm+q7Spr+C4uPu8qbq5ub6p4Li4vKm6ubm+qeC4qb6/sq+8qbq54LiuqK+0tri0tbW+uK+0qeC/v7So4L+1qLqrsuC+trqyt7ypurm5vqngvb24vqmvvKm6ubm+qeC9/aivuq/mtLW3srW+" payload =xor_str (binascii.a2b_base64(b64_data), 219)  print ("the decrypted payload is: " + payload) params = (binascii.b2a_base64(xor_str(payload,219))) payload = {'data': params} r = requests.post("http://spyeye.localhost/spyeye/_cg/gate.php", data=payload)

Morale of the story?

Criminals produce the same shitty code as the rest of the world, and thanks to this, some of the malware operators get caught and are behind bars now. And the law is behind the reality, as always.

Read more

DJ'SOUTSOURCING

This file is an 32bits elf binary, compiled from go language (i guess ... coded by @nibble_ds ;)

The binary has some debugging symbols, which is very helpful to locate the functions and api calls.

GO source functions:

- main.main

- main.function.001

If the binary is executed with no params, it prints "Nope!", the bad guy message.

~/ncn$ ./inbincible

Nope!

Decompiling the main.main function I saw two things:

1. The Argument validation: Only one 16 bytes long argument is needed, otherwise the execution is finished.

2. The key IF, the decision to dexor and print byte by byte the "Nope!" string OR dexor and print "Yeah!"

The incoming channel will determine the final message.

Dexor and print each byte of the "Nope!" message.

This IF, checks 16 times if the go channel reception value is 0x01, in this case the app show the "Yeah!" message.

Go channels are a kind of thread-safe queue, a channel_send is like a push, and channel_receive is like a pop.

If we fake this IF the 16 times, we got the "Yeah!" message:

(gdb) b *0x8049118
(gdb) commands
>set {char *}0xf7edeef3 = 0x01
>c
>end

(gdb) r 1234567890123456
tarting program: /home/sha0/ncn/inbincible 1234567890123456
...
Yeah!

Ok, but the problem is not in main.main, is main.function.001 who must sent the 0x01 via channel.

This function xors byte by byte the input "1234567890123456" with a byte array xor key, and is compared with another byte array.

=> 0x8049456: xor %ebp,%ecx

This xor, encode the argument with a key byte by byte

The xor key can be dumped from memory but I prefer to use this macro:

(gdb) b *0x8049456
(gdb) commands
>i r ecx
>c
>end
(gdb) c

Breakpoint 2, 0x08049456 in main.func ()
ecx 0x12 18

Breakpoint 2, 0x08049456 in main.func ()
ecx 0x45 69

Breakpoint 2, 0x08049456 in main.func ()
ecx 0x33 51

Breakpoint 2, 0x08049456 in main.func ()
ecx 0x87 135

Breakpoint 2, 0x08049456 in main.func ()
ecx 0x65 101

Breakpoint 2, 0x08049456 in main.func ()
ecx 0x12 18

Breakpoint 2, 0x08049456 in main.func ()
ecx 0x45 69

Breakpoint 2, 0x08049456 in main.func ()
ecx 0x33 51

Breakpoint 2, 0x08049456 in main.func ()
ecx 0x87 135

Breakpoint 2, 0x08049456 in main.func ()
ecx 0x65 101

Breakpoint 2, 0x08049456 in main.func ()
ecx 0x12 18

Breakpoint 2, 0x08049456 in main.func ()
ecx 0x45 69

Breakpoint 2, 0x08049456 in main.func ()
ecx 0x33 51

Breakpoint 2, 0x08049456 in main.func ()
ecx 0x87 135

Breakpoint 2, 0x08049456 in main.func ()
ecx 0x65 101

Breakpoint 2, 0x08049456 in main.func ()
ecx 0x12 18

The result of the xor will compared with another array byte, each byte matched, a 0x01 will be sent.

The cmp of the xored argument byte,
will determine if the channel send 0 or 1

(gdb) b *0x0804946a
(gdb) commands
>i r al
>c
>end

At this point we have the byte array used to xor the argument, and the byte array to be compared with, if we provide an input that xored with the first byte array gets the second byte array, the code will send 0x01 by the channel the 16 times.

Now web have:

xorKey=[0x12,0x45,0x33,0x87,0x65,0x12,0x45,0x33,0x87,0x65,0x12,0x45,0x33,0x87,0x65,0x12]

mustGive=[0x55,0x75,0x44,0xb6,0x0b,0x33,0x06,0x03,0xe9,0x02,0x60,0x71,0x47,0xb2,0x44,0x33]

Xor is reversible, then we can get the input needed to dexor to the expected values in order to send 0x1 bytes through the go channel.

>>> x=''
>>> for i in range(len(xorKey)):
... x+= chr(xorKey[i] ^ mustGive[i])
...
>>> print x

G0w1n!C0ngr4t5!!

And that's the key :) let's try it:

~/ncn$ ./inbincible 'G0w1n!C0ngr4t5!!'
Yeah!

Got it!! thanx @nibble_ds for this funny crackme, programmed in the great go language. I'm also a golang lover.

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Tuesday, May 30, 2023

Blockchain Exploitation Labs - Part 2 Hacking Blockchain Authorization