| ctf

note: This challenge is a continuation of for100.

Introduction

This is a write-up for the for200 challenge of the HiTB 2016 CTF.

Some customers complained over the phone over not being able to access the Culinary Tour de Force’s website. They got a strange message and couldn’t make a reservation.

We think the sever might be hacked, but we are not sure, we are chef’s not investigators. You have access to this image and our packet capture .

The attacker deleted some files and database information, are you able to reconstruct the deleted data? Note: !!!!Flagformat is not HITB but HITBCTF!!!!

Could you check if his secrets are safe?

Image file here. Pcap file here

Analysis

The description implies we need to look at the pcap and probably decrypt HTTPs traffic.

Mounting

We mount the first disk label of the image:

# slot 02: 64      * 512 = 32768
# Slot 03: 2477952 * 512 = 1268711424
# Slot 04: 8769408 * 512 = 4489936896

mount -o ro,loop,offset=32768,ufstype=44bsd recipe.img mnt4

And we quickly find etc/ssl/private/server.key

-----BEGIN RSA PRIVATE KEY-----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-----END RSA PRIVATE KEY-----

Wireshark

Wireshark supports SSL decryption through the SSL dissector so in theory all we need to do is load our server.key into the dissector.

Start Wireshark and open FOR200.pcap.

Edit -> Preferences -> Protocols -> SSL

Specify SSL Debug File: /tmp/lulz.debug

Click ‘RSA key list’. Click ‘New’.

Ip Address: 10.0.2.4 (The server using the certificate)
Port: 443 (TCP port at the server side)
Protocol: HTTP (the protocol carried inside the SSL/TLS session)
File: [Pick 'etc/ssl/private/server.key' from the previously mounted disk'

And apply the changes.

If configured correctly, Wireshark has written the decrypted traffic to /tmp/lulz.debug. Lets grep through it:

$ grep "HITBCTF{" /tmp/lulz.debug          
<tr><td>qqzzqHITBCTF{FAKEFAKE}mjasej1mjasej1mjasejwhipped creamqbxqq</td><td></td>
<td></td></tr><tr><td>qqzzqHITBCTF{FAKEFAKE2}mjasej10mjasej2mjasejprime ribqbxqq</td><td></td><td></td></tr>
<tr><td>qqzzqHITBCTF{2d4a2238545194cdcd938f4a223ff203}mjasej1mjasej3mjasejfrikandellenqbxqq</td><td></td><td></td></tr>
<tr><td>qqzzqHITBCTF{FAKEFAKE3}mjasej2mjasej4mjasejappeltaartqbxqq</td><td></td><td></td></tr></table></html>

And there we see the flag.

HITBCTF{2d4a2238545194cdcd938f4a223ff203}