2024年1月18日 星期四

Stop Using MD-5, Now!

TL;DR: Don't use MD-5 to identify malware samples. Believe me, it is a bad idea. Use SHA-256 or a stronger hash function.

This post is dedicated to all malware researchers, still using MD-5 to identify malware samples.

Before deep-diving into the details, let me explain my view on this topic. Whenever you want to identify a malware, it is only OK to publish the MD-5 hash of the malware if you post at least the SHA-256 hash of the malware as well. Publishing only the MD-5 hash is unprofessional. If you want to understand why, please continue reading. If you know about the problem, but want to help me spread the word, please link to my site www.stopusingmd5now.com.

By writing articles/posts/etc. and publishing the MD-5 hash only, it is the lesser problem that you show people your incompetency about hash functions, but you also teach other people to use MD-5. And it spreads like a disease... Last but not least, if I find a sample on your blog post, and you use MD-5 only, I can't be sure we have the same sample.

Here is a list to name a few bad examples (order is in Google search rank order):


Introduction to (cryptographic) hash functions

A long time ago (according to some sources since 1970) people started designing hash functions, for an awful lot of different reasons. It can be used for file integrity verification, password verification, pseudo-random generation, etc. But one of the most important properties of a cryptographic hash function is that it can "uniquely" identify a block of data with a small, fixed bit string. E.g., malware can be identified by using only the hash itself, so everybody who has the same malware sample will have the same hash; thus they can refer to the malware by the hash itself.

It is easy to conclude that there will always be collisions, where a different block of data has the same result hashes. The domain (block of data) is infinite, while the codomain (possible hash values) is finite. The question is how easy it is to find two different blocks of data, having the same hash. Mathematicians call this property "collision resistance." Proper cryptographic hash functions are collision-resistant, meaning it is impractical or impossible to find two different blocks of data, which have the same hash.

In 1989 Ronald Rivest (the first letter in the abbreviation of the RSA algorithm) designed the MD-2 hashing algorithm. Since 1997 there are publications about that this hashing algorithm is far from perfect.

In 1990 Ronald Rivest designed the MD-4 algorithm, which is considered as broken at least from 1991. But MD-4 is still in use from Windows XP until Windows 8 in the password protocol (NTLM). Unfortunately, there are more significant problems with NTLM besides using MD-4, but this can be the topic of a different blog post.

In 1991 (you might guess who) designed yet another hashing algorithm called MD-5, to replace MD-4  (because of the known weaknesses). But again, in from 1993 it has been shown many times that MD-5 is broken as well. According to Wikipedia, "On 18 March 2006, Klima published an algorithm [17] that can find a collision within one minute on a single notebook computer, using a method he calls tunneling". This means, that with the 8 years old computing power of a single notebook one can create two different files having the same MD-5 hash. But the algorithms to generate collisions have been improved since, and "a 2013 attack by Xie Tao, Fanbao Liu, and Dengguo Feng breaks MD-5 collision resistance in 2^18 time. This attack runs in less than a second on a regular computer." The key takeaway here is that it is pretty damn hard to design a secure cryptographic hash function, which is fast, but still safe. I bet that if I would develop a hash function, Ron would be able to hack it in minutes.

Now, dear malware researcher, consider the following scenario. You as, a malware analyst, find a new binary sample. You calculate the MD-5 hash of the malware, and Google for that hash. You see this hash value on other malware researchers or on a sandbox/vendor's site. This site concludes that this sample does this or that, and is either malicious or not. Either because the site is also relying solely on MD-5 or because you have only checked the MD-5 and the researcher or sandbox has a good reputation, you move on and forget this binary. But in reality, it is possible that your binary is totally different than the one analyzed by others. The results of this mistake can scale from nothing to catastrophic.

If you don't believe me, just check the hello.exe and erase.exe on this site from Peter Sellinger. Same MD-5, different binaries; a harmless and a (fake) malicious one... And you can do the same easily at home. No supercomputers,  no NSA magic needed.

On a side-note, it is important to mention that even today it can be hard to find a block of data (in generic), if only the MD-5 hash is known ("pre image resistance"). I have heard people arguing this when I told them using MD-5 as a password hash function is a bad idea. The main problem with MD-5 as a password hash is not the weaknesses in MD-5 itself, but the lack of salt, lack of iterations, and lack of memory hardness. But still, I don't see any reason why you should use MD-5 as a building block for anything, which has anything to do with security. Would you use a car to drive your children to the school, which car has not been maintained in the last 23 year? If your answer is yes, you should neither have children nor a job in IT SEC.

Conclusion

If you are a malware researcher, and used MD-5 only to identify malware samples in the past, I suggest to write it down 1000 times: "I promise I won't use MD-5 to identify malware in the future."

I even made a website dedicated to this problem, www.stopusingmd5now.com . The next time you see a post/article/whatever where malware is identified by the MD-5 hash only, please link to this blog post or website, and the world will be a better and more professional place.


PS: If you are a forensics investigator, or software developer developing software used in forensics, the same applies to you.
PS 2: If you find this post too provocative and harsh, there is a reason for this ...

Update: I have modified two malware (Citadel, Atrax) with the help of HashClash, and now those have the same MD-5. Many thanks for Marc Stevens for his research, publishing his code, and help given during the collision finding.

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Learning Web Pentesting With DVWA Part 2: SQL Injection

In the last article Learning Web Pentesting With DVWA Part 1: Installation, you were given a glimpse of SQL injection when we installed the DVWA app. In this article we will explain what we did at the end of that article and much more.
Lets start by defining what SQL injection is, OWASP defines it as: "A SQL injection attack consists of insertion or "injection" of a SQL query via the input data from the client to the application. A successful SQL injection exploit can read sensitive data from the database, modify database data (Insert/Update/Delete), execute administration operations on the database (such as shutdown the DBMS), recover the content of a given file present on the DBMS file system and in some cases issue commands to the operating system. SQL injection attacks are a type of injection attack, in which SQL commands are injected into data-plane input in order to effect the execution of predefined SQL commands."
Which basically means that we can use a simple (vulnerable) input field in our web application to get information from the database of the server which hosts the web application. We can command and control (at certain times) the database of the web application or even the server.
In this article we are going to perform SQL injection attack on DVWA, so let's jump in. On the DVWA welcome page click on SQL Injection navigation link. We are presented with a page with an input field for User ID.
Now lets try to input a value like 1 in the input field. We can see a response from server telling us the firstname and surname of the user associated with User ID 1.
If we try to enter a user id which doesn't exist, we get no data back from the server. To determine whether an input field is vulnerable to SQL injection, we first start by sending a single quote (') as input. Which returns an SQL error.
We saw this in the previous article and we also talked about injection point in it. Before diving deeper into how this vulnerability can be exploited lets try to understand how this error might have occurred. Lets try to build the SQL query that the server might be trying to execute. Say the query looks something like this:
SELECT first_name, sur_name FROM users WHERE user_id = '1';
The 1 in this query is the value supplied by the user in the User ID input field. When we input a single quote in the User ID input field, the query looks like this:
SELECT first_name, sur_name FROM users WHERE user_id = ''';
The quotes around the input provided in the User ID input field are from the server side application code. The error is due to the extra single quote present in the query. Now if we specify a comment after the single quote like this:
'-- -
or
'#
we should get no error. Now our crafted query looks like this:
SELECT first_name, sur_name FROM users WHERE user_id = ''-- -';
or
SELECT first_name, sur_name FROM users WHERE user_id = ''#';
since everything after the # or -- - are commented out, the query will ignore the extra single quote added by the server side app and whatever comes after it and will not generate any error. However the query returns nothing because we specified nothing ('') as the user_id.
After knowing how things might be working on the server side, we will start to attack the application.
First of all we will try to determine the number of columns that the query outputs because if we try a query which will output the number of columns greater or smaller than what the original query outputs then our query is going to get an error. So we will first figure out the exact number of columns that the query outputs and we will do that with the help of order by sql statement like this:
' order by 1-- -
This MySQL server might execute the query as:
SELECT first_name, sur_name FROM users WHERE user_id = '' order by 1-- -';
you get the idea now.
if we don't get any error message, we will increase the number to 2 like this:
' order by 2-- -
still no error message, lets add another:
' order by 3-- -
and there we go we have an error message. Which tells us the number of columns that the server query selects is 2 because it erred out at 3.
Now lets use the union select SQL statement to get information about the database itself.
' union select null, version()-- -
You should first understand what a union select statement does and only then can you understand what we are doing here. You can read about it here.
We have used null as one column since we need to match the number of columns from the server query which is two. null will act as a dummy column here which will give no output and the second column which in our case here is the version() command will output the database version. Notice the output from the application, nothing is shown for First name since we specified null for it and the maria db version will be displayed in Surname.
Now lets check who the database user is using the user() function of mariadb:
' union select null, user()-- -
After clicking the submit button you should be able to see the user of the database in surname.

Now lets get some information about the databases in the database.
Lets determine the names of databases from INFORMATION_SCHEMA.SCHEMATA by entering following input in the User ID field:
' union select null, SCHEMA_NAME from INFORMATION_SCHEMA.SCHEMATA-- -
This lists two databases dvwa and information_schema. information_schema is the built in database. Lets look at the dvwa database.
Get table names for dvwa database from INFORMATION_SCHEMA.TABLES
' union select null, TABLE_NAME from INFORMATION_SCHEMA.TABLES-- -
It gives a huge number of tables that are present in dvwa database. But what we are really interested in is the users table as it is most likely to contain user passwords. But first we need to determine columns of that table and we will do that by querying INFORMATION_SCHEMA.COLUMNS like this:
' union select null, COLUMN_NAME from INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME = 'users'-- -

We can see the password column in the output now lets get those passwords:
' union select user, password from users-- -
Of-course those are the hashes and not plain text passwords. You need to crack them.
Hope you learned something about SQL injection in this article. See you next time.

References:

1. SQL Injection: https://owasp.org/www-community/attacks/SQL_Injection
2. MySQL UNION: https://www.mysqltutorial.org/sql-union-mysql.aspx
3. Chapter 25 INFORMATION_SCHEMA Tables: https://dev.mysql.com/doc/refman/8.0/en/information-schema.html
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2024年1月17日 星期三

DSploit

DSploit

After playing with the applications installed on the Pwn Pad, I found that the most important application (at least for me) was missing from the pre-installed apps. Namely, DSploit. Although DSploit has tons of features, I really liked the multiprotocol password sniffing (same as dsniff) and the session hijacking functionality.

The DSploit APK in the Play Store was not working for me, but the latest nightly on http://dsploit.net worked like a charm.

Most features require that you and your target uses the same WiFi network, and that's it. It can be Open, WEP, WPA/WPA2 Personal. On all of these networks, DSploit will sniff the passwords - because of the active attacks. E.g. a lot of email clients still use IMAP with clear text passwords, or some webmails, etc. 

First, DSploit lists the AP and the known devices on the network. In this case, I chose one victim client.


In the following submenu, there are tons of options, but the best features are in the MITM section. 


Stealthiness warning: in some cases, I received the following popup on the victim Windows:


This is what we have under the MITM submenu:


Password sniffing

For example, let's start with the Password Sniffer. It is the same as EvilAP and DSniff in my previous post. With the same results for the popular Hungarian webmail with the default secure login checkbox turned off. Don't forget, this is not an Open WiFi network, but one with WPA2 protection!


Session hijack

Now let's assume that the victim is very security-aware and he checks the secure login checkbox. Another cause can be that the victim already logged in, long before we started to attack. The session hijacking function is similar to the Firesheep tool, but it works with every website where the session cookies are sent in clear text, and there is no need for any additional support.

In a session hijacking attack (also called "sidejacking"), after the victim browser sends the authentication cookies in clear text, DSploit copies these cookies into its own browser, and opens the website with the same cookies, which results in successful login most of the time. Let's see session hijacking in action!

Here, we can see that the session cookies have been sniffed from the air:


Let's select that session, and be amazed that we logged into the user's webmail session.




Redirect traffic

This feature can be used both for fun or profit. For fun, you can redirect all the victim traffic to http://www.kittenwar.com/. For-profit, you can redirect your victim to phishing pages.


Replace images, videos

I think this is just for fun here. Endless Rick Rolling possibilities.


Script injection

This is mostly for profit. client-side injection, drive-by-exploits, endless possibilities.

Custom filter

If you are familiar with ettercap, this has similar functionalities (but dumber), with string or regex replacements. E.g. you can replace the news, stock prices, which pizza the victim ordered, etc. If you know more fun stuff here, please leave a comment (only HTTP scenario - e.g. attacking Facebook won't work).

Additional fun (not in DSploit) - SSLStrip 

From the MITM section of DSploit, I really miss the SSLStrip functionality. Luckily, it is built into the Pwn Pad. With the help of SSLStrip, we can remove the references to HTTPS links in the clear text HTTP traffic, and replace those with HTTP. So even if the user checks the secure login checkbox at freemail.hu, the password will be sent in clear text - thus it can be sniffed with DSniff.

HTML source on the client-side without SSLstrip:


HTML source on the client-side with SSL strip:


With EvilAP, SSLStrip, and DSniff, the password can be stolen. No hacking skillz needed.

Lessons learned here

If you are a website operator where you allow your users to login, always:
  1. Use HTTPS with a trusted certificate, and redirect all unencrypted traffic to HTTPS ASAP
  2. Mark the session cookies with the secure flag
  3. Use HSTS to prevent SSLStrip attacks
If you are a user:
  1. Don't trust sites with your confidential data if the above points are not fixed. Choose a more secure alternative
  2. Use HTTPS everywhere plugin
  3. For improved security, use VPN
Because hacking has never been so easy before.
And last but not least, if you like the DSploit project, don't forget to donate them!

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2023年7月2日 星期日

Dual functionality for commercial and office use

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Name: Mini Industrial PC
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RAM: 2xDDR3 memory slot, up to 16GB available
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Support OS: Windows 7,10 and Linux

It's popular in Europe and America, you can find it from Amazon, would you know some of your clients already using this kind mini pc? And how much you may get if you sold it to them?

Don't hesitate to contact us if you need any information, thank you.

Sincerely

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Sales || Hystou Technology Co., Limited
Email:  Sales19@hystou.com  
Skype: live:jacy_182
Cel & WhatsApp:  +86 17727927495
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