One more in the list of technical posts! Yesterday was a day of 17 hrs in the lab (phew 🙂
So we were capturing packets but the packit tool did not randomize the source IPs enough so we were getting decent signatures for TCP traffic but not for ICMP! So looking at the signature generation I found that the checksum was also being used to get the hash value. But, when I stopped using the checksum values for generation of hash the signatures started coming properly. Antoine, somehow, thought that the IP addresses were affecting the has values that we got. But looking deeply into the code we saw that it was not the case. The conclusion (which is really surprising) is that packit was generating similar packets quite a few packets and that too from the same source IP (but they really should have been randomized!)…I don’t know whether this conclusion is correct??? May be some packit developers would be able to help me on this!
So now the challenge becomes to send those ICMP signatures across…but icmp_send() method requires skbuff structure…I looked at the net/ipv4/ipip.c file for the usage of icmp_send() methods but it is still not clear to me how it should be used!

-Rajat
Rajat’s Homepage

An interesting thing happened today …I was trying to redirect some input to /dev/null in cygwin…using something like:
some_exec -p params 2>&/dev/null | grep blah
I kept getting an error : bash: Ambiguous redirect.
I then realized that I should probably doing a simple direct and not a re-direct…seemed to solve my problem. Come to think of it…it makes sense, why should I need to redirect when I’m sending it to /dev/null…should simply be able to direct it using:
some_exec -p paraa 2>/dev/null | grep blah

hey, we need to check that your connection works, torrent this file and md5 it

http://services.2014.shallweplayaga.me/hackertool.torrent_fe3b8b75e9639d35e8ac1d9809726ee2

The torrent file when loaded into Vuze showed that the file name was every_ip_address.txt. So I downloaded some of the file and observed the format. The format of the file was “0.0.0.1\n0.0.0.2\n…. “.

So I wrote a quick python script to calculate the md5:

#!/bin/python
import hashlib
m = hashlib.md5()
fsize = 0
a = ''
for i in xrange(256):
    for j in xrange(256):
        for k in xrange(256):
            for l in xrange(256):
                a = str(i)+'.'+str(j)+'.'+str(k)+'.'+str(l)+'\n'
                fsize += len(a)
                m.update( a )
print m.hexdigest()

The flag was “1a97f624cc74e4944350c04f5ae1fe8d”.

A very typical scenario is that by default the Tomcat Servers tend to have a 404 Error page that displays the name of the file that was requested and not found. It seems to me that though display of such pages might be considered as merely an informational item for the purpose of any security test…this definitely presents a risk.
E.g., take this scenario.
1. The attackers has a SQL injection vulnerability in an application
2. The App server and DB can reach each other
3. The DB cannot directly reach the attacker and his system (on any port outbound)
4. The app server issues 404 error messages with the name of the file being disclosed in the 404 error message (e.g., The requested resource indexblah.html was not found).
5. The attacker can see the responses to the injected SQL queries (i.e., the injection is not blind).

Assuming that the DB accesses have been tightly controlled and you can’t get much access to any tables except the current one. This can be exploited as follows:
Invoke a SQL query (in the injection string) on the DB to request a page from the app server based on the contents of the DB such as send me /blahusername, /blahpassword where /blah is a string the attacker’s put in to make sure that such a resource doesn’t actually exist on the app server and username and password are columns or DB names from the DB. These error messages will be reflected in the response to the SQL query to the attacker. This could create an interesting side-channel attack whereby even though the data from the DB doesn’t actually reach the attacker, it can be inferred from the 404 – error messages.

___________       ______________        __________
| Attacker| <===> | App server | <=====>|  DB    |
___________       ______________        __________
      1  ----------> 2  -----------------> 3
                     5  <----------------  4
                     6  -----------------> 7
      10 <---------- 9 <-----------------  8   
1. Attacker sends sql to make the db query the app server for a non-existent page
2. The app server sends this sql query to the DB
3. The DB receives this SQL query and acts on it
4. The HTTP query for a missing resource is sent to the app server
5. App server looks up the resource and can't find it
6. The App server responds with a 404 /blahusername not found
7. The response recd is put in the SQL query response
8. The SQL query response is sent to the app server
9. The App server received the SQL query response (404 /blahusername not found as a line in there)
10. The attacker receives the 404 response with the data from the username in the 404 error message  

An interesting attack vector to say the least!

I recently purchased a Proxmark3 from GeZhi Electronics. The proxmark3 client wouldn’t work. In fact the `dmesg` output did not even show the /dev/ttyACM0 device as was said all across the forum. i tried flashing the firmware but kept getting this error:

~/proxmark3/client# ./flasher -b ../bootrom/obj/bootrom.elf 
Loading ELF file '../bootrom/obj/bootrom.elf'...
Loading usable ELF segments:
0: V 0x00100000 P 0x00100000 (0x00000200->0x00000200) [R X] @0x94
1: V 0x00200000 P 0x00100200 (0x00000b38->0x00000b38) [RWX] @0x298
Attempted to write bootloader but bootloader writes are not enabled
Error while loading ../bootrom/obj/bootrom.elf

Also this is what showed up in the dmesg:

[ 7953.991935] usb 2-1.4: new full-speed USB device number 40 using ehci_hcd
[ 7959.078302] usb 2-1.4: New USB device found, idVendor=9ac4, idProduct=4b8f
[ 7959.078314] usb 2-1.4: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 7959.078321] usb 2-1.4: Product: ProxMark-3 RFID Instrument
[ 7959.078326] usb 2-1.4: Manufacturer: J. Westhues
[ 7959.078331] usb 2-1.4: SerialNumber: ChangeMe
[ 7959.080485] hid-generic 0003:9AC4:4B8F.0014: hiddev0,hidraw0: USB HID v1.00 Device [J. Westhues ProxMark-3 RFID Instrument] on usb-0000:00:1d.0-1.4/input0

Note that in the above the device doesn’t show up as a /dev/ttyACM0 device which is what we need for the proxmark3 client application to work.
So it seemed like there was an issue with the Proxmark3 not being recognized as a CDC device. So I went through the googlecode repository and went to a version of firmware where CDC was not being used. It also seemed that the flasher was the issue. So I used an old flasher to flash with the latest firmware and boom it worked! Remember to keep the button on the Proxmark3 pressed when you plug it in, and keep holding it down until the firmware update has finished.
Here are the commands:

# svn checkout http://proxmark3.googlecode.com/svn/trunk/ proxmark3
# export DEVKITPRO=$HOME/proxmark3/
# export DEVKITARM=$DEVKITPRO/devkitARM
# export PATH=${PATH}:${DEVKITARM}/bin
# cd proxmark3
# make all
# cd ..
# svn checkout -r 629 http://proxmark3.googlecode.com/svn/trunk/ ~/proxmark3-old-3
# cd proxmark3-old-3/
# make all
# cd client
# ./flasher -b ../../proxmark3/bootrom/obj/bootrom.elf ../../proxmark3/armsrc/obj/osimage.elf ../../proxmark3/armsrc/obj/fpgaimage.elf

And boom! There you … all flashed and now the device is recognized as a /dev/ttyACM0 device.

The New Year brings in interesting things (or so we hope). My friend came up to me with an “infected” computer with a fantastic piece of malware installed. The malware was presented the user with a completely different HTML page when something was searched on Google. Browser Helper Objects (BHOs) are Dynamic Link Libraries (DLLs) that are installed in Internet Explorer (IE) and have a complete access to the DOM tree of the browser window. The name of the DLL was xyusx.dll (or something like that). This DLL was packed so that it wouldn’t permit a clean disassembly. The usual tricks seemed to work and I was able to unpack the DLL.

The procedure is simple. Open the DLL in OllyDbg. Search for the PUSHAD instruction (this instruction stores all the registers on the top of the stack) and set a breakpoint (F2 key in OllyDbg) on that instruction.

Press F9 to continue the debugging. Press F8 to execute the instruction, and then set a hardware breakpoint on the top of the stack in the Dump Window as shown in the image. You can do this easily by right clicking on the ESP register and clicking on “Follow in Dump”.
Once you reach the POPAD instruction or the hardware breakpoint is activated, this shows that the registers that were saved on the stack are now going to be restored in the respective registers. This indicates that the program has now finished extracting itself and is ready to execute the instructions.
I used OllyDump to dump out the contents of this DLL and then used LordPE to repair the import table. This process, however, needs more work due to the nature of the automated import address table repairing as some things can be missed.
Once this repairing was finished, I opened the file in IDA Pro to disassemble the unpacked DLL. This did give me a lot of information about this DLL, however, I’m still in the process of completing a good disassembly of this DLL.
As for now, I can say that this DLL installed a bunch of spyware CLSIDs into the system.
Some of the CLSIDs (out of the 45 that it uses) by this malware are listed below:

{CF46BFB3-2ACC-441b-B82B-36B9562C7FF1}
{67C55A8D-E808-4caa-9EA7-F77102DE0BB6}
{1557B435-8242-4686-9AA3-9265BF7525A4}
{55DB983C-BDBF-426f-86F0-187B02DDA39B}
{A24B57F8-505D-4fc5-9960-740E304D1ABA}
{4B646AFB-9341-4330-8FD1-C32485AEE619}
{CD3447D4-CA39-4377-8084-30E86331D74C}
{DEBEB52F-CFA6-4647-971F-3EDB75B63AFA}
{8F2183B9-F4DB-4913-8F82-6F9CC42E4CF8}
{92A444D2-F945-4dd9-89A1-896A6C2D8D22}
{1F6581D5-AA53-4b73-A6F9-41420C6B61F1}
{1126271C-A8C3-438c-B951-7C94B453B16B}
{938A8A03-A938-4019-B764-03FF8D167D79}
{44218730-94E0-4b24-BBF0-C3D8B2BCE2C3}

This DLL also seemed to communicate to :

89.188.16.10
89.188.16.16
65.243.103.56
65.243.103.60
65.243.103.62

Whatever you do to these servers is upto you. Some google searches allude that this is a “Vundo infection”. I’m also not sure what solutions people are posting to this problem but I’d not feel safe if this malware was on my computer and I’d definitely format my Windows install, patch it and change my passwords! I’m not completely dne with the disassembly and reversing of this malware yet, but I’m sure I’ll post more when I delve into this disassembled code deeper.

Interestingly enough, I found last week that the new Nessus 4.2.0 works by default as a web interface. Gone are the days of using the NessusClient and connecting to TCP port 1241 and using it to connect to the nessusd. Connecting to local TCP port 8834 (https://localhost:8834) brings you to a web interface that you can use to connect to the new Nessus daemon. The nesssusd listener does not even listen on port 1241 by default.
I’ll shortly get used to it but I know the transition would be slow for me …. after it takes getting used to when you completely change the architecture after maintaining it for at least a good 7 years or so!