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

I’ll be attending the Shmoocon in Washington, DC from Feb 6th-8th. Hope to see all you h4X0rs out there!

This is not a post but nostalgia. This post is actually a transcript of the first interview of my life. It was for a top Indian Software Consultancy Company (referred to as “XYZ” from now on). I remember that it was July 9th, 2001 and it was a really rainy day in Bombay. While coming to the college I was totally drenched and was looking rather distraught! I cleared the aptitude test and then came the Big One – The Interview!
I went to the interview thinking that i wanted to completely screw up the interview (coz I was interested in some other company) so i went there casually dressed with a demonic smile on my face >:-) . In hindsight, I think the way I appeared for this interview was really gutsy for me and I probably couldn’t have done that had I been craving to get a job in this company. Here is the transcript of the interview.

XYZ: So Mr Rajat … tell me about urself and ur family in *short*
Me : In the year 1980 i was born in allahabad and spent the initial yrs of mylife in blah blah blah ….and completed my schooling in Shree Ram Welfare Society’s High School, Andheri(W), Mumbai . therafter i went to Sathaye College….(blah blah blah) and i came to this college thinking that this college would be good.
XYZ: & how did u find this college?
Me : (thinkin for a while and then with a heavy heart ) ok !
XYZ: Rajat y did u chose our company (XYZ) instead of other companies.
Me : i did not choose XYZ i’ve just come for this interview ! In fact u guys have come to our college (for on-campus placements) i haven’t come for this interview.
XYZ: but would u like to join our co.?
Me: i’ve come for this interview ! what does this indicate to u?
XYZ: give me one reason why u want to join XYZ?
Me: i don’t want join XYZ… i’ll goto any other co. that comes next…as a matter of fact any other co. will take me!
XYZ: Mr Rajat in this form (these guys had given us a form to fill in whichwe were supposed to write the salary we desired which i forgot to fill… oops faux pas ? well not quite) which we have given to u , uhaven’t mentioned the salary u want…. what r ur expectations?
Me : I want more!
XYZ: MORE !%#$%$#$ y do u want more?
Me: because i know i’m worth it!
XYZ: u say so but it is for us to see whether u r worth it!
Me: put me to test and i’ll prove i’m worth it !
XYZ: but why do u want more ?
Me : everybody wants more so what is wrong if i want more!(the guy seems to be pissed off to my delight)
XYZ: but u must be having some expectations , don’t u?
Me : yes of course , i have . but u r not gonna live up to them. u had made it quite clear the salary u’ll be offering to us … so it doesn’t matter what my expectations are u r gonna give only what *you* want to give us , so there rests the matter.
XYZ: tell me about this person whom u know & works in XYZ.
Me : He is my cousin and he stays at andheri.
XYZ: so what have u heard from him about our co. ?
Me : NOTHING!
XYZ: but u might have heard something at least!!!!!
ME : we meet at social gatherings and the last thing we want to speak about is XYZ!!!
XYZ: ok tell me about ur project … this assembler
Me : blah blah blah
XYZ: ok … so in ur form u write u want “A GOOD NETWORKING PROJECT PREFERABLY BASED ON NETWORK SECURITY” . what do u know about networking?
Me : NOTHING!
XYZ: (a very surprised Mr. Sleepy said) NOTHING !?!? then how can u say u want a project in it?
Me: well , i’ve attended a few seminars @ IIT and it ensured me that that was the only field i’m interested in.
XYZ: then ur interest may change after studying the subject!
Me : No, it won’t change!!!!
XYZ: wat do u know bout networkin?
Me: latest happenings … blah blah blah
XYZ: suppose that we don’t have a project in network securities for you then what will u do?
Me: i have written that it is my ambition to work on a networking project…AMBITIONS ARE NOT ALWAYS FULFILLED.
XYZ: Rajat … there is a rule in ur college that if u get 1 co. u r noteligible for the rest.we offer u 16k .. so if tomorrow infosys comes and offers u 20k wat will u do?
Me : I WILL GO !!!!!
XYZ: u’ll go !?! that means you are after money ?
Me : who said that !? i never said that ! i want more money but more important than that is the work environment & the kind of projects i get. if i getbetter projects there i’ll go money is secondary but still important .
XYZ: (as if trying to juistify a lesser salary) u know rajat that on paper their (Infosys) salary may look large but 20% blah blah blah ….. 12.5 % blahblah blah …6% blah blah blah … (and lots more statistics which lasted foran eternity as far as my viewpoint goes)
XYZ: do u realise that XYZ has a 3yr. service agreement or u r chargedRs.50,000/- . what are your feelings about that?
Me : it is absolutely wrong.
XYZ: why?
Me: The word “bond” itself says that u r “bound” to the co. no matter what.
XYZ: that is why we don’t call it a “bond” we call it a “service agreement”.
Me: ok…that’s just another name for it. i personally think that instead of”binding” people to ur co. u should create such an environment that people like to stay in ur co. with their wishes and so the co. will benefit if peoplework with their wishes.
XYZ: do u havre any questions for us?
Me: yes , sir i do! in ur qns a few minutes back u mentioned infosys and in ur pre-placement talks u said u r no.1 software co. of india. how can u say thatwhen all that we see in the newspapers is infosys and with u comparing urself to infosys?
XYZ: infosys is 12% blah blah blah … 19% blah blah blah …(and lots morestatistics that made me feel as miserable as our indian cricket team witheverything out of control)does that answer ur qn?
Me: ya! sir may i ask another question ?
XYZ: ya sure! (with some uneasiness)
Me: sir, this yr. we have seen our seniors get whole lot of “back out” letters! what r ur feelings about that?
XYZ: OUR FEELINGS !!??!
Me: i mean r u people going to do the same with us?
XYZ: (i think this was it and he lost his complete cool and he pointed to me & said sternly) till this date our company has not given any “back-out” letters to anybody.
Me: Thank u .sir. it was a pleasure!

This was the first interview of my life and I ended up getting selected for this company. It was a great experience working there and I realized that money is not everything! At the end of it I think I was not rude but dangerously honest in giving my answers and this plan could have backfired on me but it didn’t … may be I was lucky or may be this was destiny!

I recently purchased 2x2GB Memory upgrades for my fantastic Dell XPS M1210. To upgrade the memory there were 2 slots one located at the base of the laptop (the black bottom) and the other was located below the keypad. I searched a lot on the Internet but could not find the location of the 2nd slot.
The owner’s manual also did not mention the location of the DIMM B slot (the 2nd memory slot). See the details on the manual about how to remove the keyboard to reach the 2nd memory slot.
The key to reach the 2nd slot is to first remove the hinge cover (the cover that has three button saying Power, “Media Direct”, etc.). The hinge cover is not screwed so you can just lever it up using a thin, flat object and pop-it up, remove the three screws fixing the keyboad, pulling the keyboad out and right in the middle you will see the memory slot.
Hopefully, this post will help someone upgrading memory on their Dell XPS M1210.

I was using the vpnc the other day on my Backtrack 4 R2 system to log in to VPN. I noticed that there was nothing that would give me the status of whether or not the tunnel was up. So I wrote a small one-liner to help me:

while [ `ps aux |grep vpnc|grep -v grep|awk '{print $2}'` ] ; do printf "Connected\r"; done


Yesterday was a fantastic day trying to get the IP data field to be pointed to by in the skbuff structure. The documentation in the files did not help make things clearer.
The situation was where I was supposed to use the
unsigned char* data field in the skbuff structure to point to the IP data starting point.
Tried a lot of pointer math and the following finally worked:
IP Data pointer location:

unsigned char * ptr = sb->data +
sb->nh.iph->ihl*4;
int byte_size = ntohs(sb->nh.iph->tot_len) –
sb->nh.iph->ihl*4;

In fact, Vinay Reddy (vinayvinay@gmail.com) suggested something which I think was even better than the stuff that was working for me. He said the pointer value should be:

unsigned char * ptr = sb->nh.iph->raw + sb->nh.iph->ihl*4;

I think this actually grabs the gist of what I exactly want to do.
I *really* want to point with respect to the IP Header. I do not really care about where sb->data really points to so I guess Vinay’s method is much better. Haven’t implemented it so I really don’t know but sounds the most logical!

– Rajat
http://www-scf.usc.edu/~swarup/

Dell had this program called Dell Vista Express Upgrade as a part of which once you pay for your XP Pro you become eligible for a Vista upgrade. The interesting thing was it was an introductory offer and they would ship the DVDs upon Vista’s release if we activated the upgrade. I did activate the upgrade but I did not receive my DVDs until a few days but when I eventually did it was a “Dell Vista Upgrade Assistant DVD”. What was even more interesting was that this DVD was not even an installation DVD (with no warnings on it that it was not the OS installation itself which I assumed all along). It was just a DVD because Dell likes sending DVDs to users! So I contacted Dell about the OS when I couldn’t boot up the OS and they said that no wonder…this is not the OS. So I asked them where’s the OS and the customer care went “you should have it”! Now if they didn’t ship it and I didn’t receive it (although I paid Dell for it), who should have it! They tell me Microsoft has it. It just seems illogical that the person who I pay for the software would not be the one to ship it out to me. The Dell Resolution specialist called today and said there’s nothing he could do. They have my money, they didn’t ship out the DVD…and so be it! Do what you can! That’s just the worst ever case of customer care I’ve ever seen!