Ubuntu 10.10->11.04 encrypted LVM fail, rebuilding initramfs, rdinit

One of my workstations was an Ubuntu 10.10 on an encrypted LVM. I decided to upgrade to 11.04 and was unable to boot, falling back to initramfs busybox shell.

If you are not familiar with this kind of setup, it basically works with:

• a non-encrypted /boot with kernel and initramfs
• initramfs contains required modules (aes, lvm, etc.) and a few scripts to mount the filesystem: in this case, a script to ask for the password, decrypt the LVM and mount the root filesystem

pCTF 2011 #18 A small bug

Challenge #18 "A small bug" was a common TOCCTOU bug very interesting to exploit reliably.

@hellman already did a write-up on this challenge. His exploit reads the file name on stderr and hopes to win the race on symlink creation. But actually there is a way to win the race every time! Let's see that.

pCTF 2011 #19 Another small bug

Challenge #19 "Another small bug" was a stack-based buffer overflow.

Djo (@shell_storm) has already published a write-up (english) on Nibbles' blog, as well as @hellman on Leet More's blog, and Agix (@Agixid) on shell-storm. Just like hashcalc1 or hashcalc2, there was no NX. However, ASLR was enabled. Djo and hellman both used a big nopsled + brute-force to circumvent ASLR, Agix used a nice ret2ret, while I chose ROP to mmap rwx. Good thing is that it would also have worked if NX had been effectively enabled.

Not familiar with ROP? Have a look at the references posted on this exploit writing tutorial by @corelanc0d3r.

pCTF 2011 #26 Hashcalc2

Challenge #26 "Hashcalc2" was very similar to Hashcalc1.

Again, a good write-up is already available on sleepya's blog. He made an exploit bypassing any ASLR/NX using ROP.

Again since NX was not enabled, I used a similar exploitation with a few adjustements.

pCTF 2011 #22 Hashcalc1

Challenge #22 "Hashcalc 1" was binary exploitation over the network.

A good write-up is already available on sleepya's blog. He made an exploit bypassing any ASLR/NX using ROP.

However, NX was not enabled on the wargame machine... Organizers thought they did, but it was not effective :( Good for us it means only ASLR, and the binary was not even PIE. One could exploit it quickly by writing a shellcode in the GOT, let's see that.

pCTF 2011 #32 That's no bluetooth

The only networking problem at pCTF 2011 was unusual because it involved ZigBee, based on IEEE 802.15.4.

Context

We captured this network traffic from outside of an AED employee's home.

Decrypt it and find the key.

Update: Our operatives were able to decrypt packet #18 in the capture file.

The decrypted data is 18060a0700421a63343a636f6e74726f6c345f73723235303a43342
d53523235300400420830332e30312e3534050020040600213c00
or (printable text only) Bc4:control4_sr250:C4-SR250B03.01.54 !<

If you aren't getting the correct values, make sure your keys are correct,
and that they are entered correctly. Keep in mind bits sometimes flip when
transmitting signals wirelessly. 

download file

Plaid Parliament of Pwning CTF 2011

As @dinodaizovi nicely put on twitter, CTF team Plaid Parliament of Pwning have gone from winning everyone else's CTFs to hosting their own, namely the plaid CTF or pCTF (@pctf2011). It was 48 hours of intense challenge-based CTF like Defcon quals.

I expected a lot of fun challenges for this CTF because PPPs are highly skilled in areas such as binary exploitation. And I wasn't disappointed! Expect a few write-ups from me in the following posts :)

As you can see on the final scoreboard, more than 400 teams registered and 155 teams scored points. Since I no longer play with Nibbles guys, this time I played with a new team called CoP. We got the 2nd place, 1st place being taken at the last moment by our CTF friends HFS (Hacking for Soju). Good game, it was intense!

Congratulations to everyone for playing, and especially to PPP members who made this CTF possible. Very good challenges, organization, and IRC presence for support. You pwn guys!

If you want to have a look at the challenges, I mirrored them here (except remote/web of course), along with screenshots of problems, scoreboard, etc.

Hackito Ergo Sum 2011

Hackito Ergo Sum (@hackitoergosum) 2011 edition was held in Paris, France from April 7th to 10th. Three days of technical talks, like last year a wargame by Steven from OverTheWire and great people to meet and drink with!

If you did not have the opportunity to come, Gal Diskin (@gal_diskin) took the time to wrap up most of the talks: day 1 (part 1, part 2), day 2 and day 3.

During the time they release papers, slides and videos of the talks, you might want to have a look at Steven's wargame. Good levels and funny story, it starts here...

CRC-32 forging

You may already know that the CRC-32 of any text can be forged if you can add 4 bytes anywhere in the text. See anarchriz's paper on the subject.

A real-world example of such a situation can be seen in JB's ESET CONFidence Crackme Writeup. Good code that I recently used it in another situation, in order to forge a text of a given CRC-32 by inserting 4 bytes at a specific position.

Honeynet Project Public Conference

Last week was held the first-ever Honeynet project public conference in Paris at ESIEA. Great speakers, interesting conferences (slides online, CV+O notes) and nice people to meet at the social event.

During the conferences was also a small capture-the-flag (CTF) competition, which I played. It was composed of 8 challenges by Mark Schloesser and Felix Leder, including a forensic one by Guillaume Arcas. This is how the challenge board looked: