Nuit Du Hack CTF 2013 : k1986 write-up

I’ve participed to NDH2013 this year and worked on a very interesting binary : k1986. It comes with two files :

aris@kali64:~/ndh2013$ ls -l k1986 license.db 
-rwxr-xr-x 1 aris aris 14984 jun 23 02:07 k1986
-rwx------ 1 aris aris   360 jun 22 22:54 license.db
aris@kali64:~/ndh2013$ file k1986-orig license.db 
k1986-orig: ELF 64-bit LSB executable, x86-64, invalid version (SYSV), for GNU/Linux 2.6.32, 
dynamically linked (uses shared libs), corrupted section header size
license.db: data

It’s starting well, corrupted ELF file. The content of license.db seems encrypted, so my first guess was that it was a DRM server of some kind. It becomes more fun when you try to check what it does:

aris@kali64:~/ndh2013$ objdump -t k1986-orig 
objdump: k1986-orig: File format not recognized
aris@kali64:~/ndh2013$ gdb --quiet ./k1986-orig 
"/home/aris/ndh2013/k1986-orig": not in executable format: Format de fichier non reconnu
(gdb) quit
aris@kali64:~/ndh2013$ nm ./k1986-orig 
nm: ./k1986-orig: File format not recognized
aris@kali64:~/ndh2013$ ldd ./k1986-orig 
	 n'est pas un exécutable dynamique

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Adding physical drives to VMware ESXi

I built a new lab environment at home, using VMWare ESXi 5.0, which is a very nice product, if we expect the windows-only GUI 1GB HDD needed to install bloatware. You can do pretty much anything from there, except something that looks so important that I wonder why it’s not on the windows GUI: mapping local disks to VMs.

I made this little post as a reminder for myself rather than a full tutorial. You can get more info on, on which this post is based.

In a nutshell:

  1. log on vmware ESXi as root.
  2. locate the name of your fs in /vmfs/devices/disks/, i.e. “/vmfs/devices/disks/t10.ATA_____Hitachi_HDT725025VLA380_______________________VFL104R6CNYSZW
  3. go to where you want to copy it. I suggest you create a directory in a datastore for this, like “/vmfs/volumes/datastore1/harddisks/
  4. vmkfstools -z /vmfs/devices/disks/t10.ATA_____Hitachi_HDT725025VLA380_______________________VFL104R6CNYSZW Hitashi250.vmdk
  5. In your VM, use “attach existing virtual disk” and browse the harddisks directory on datastore.
  6. On linux, you will need “rescan-scsi-bus” to have you new hard disk detected.
  7. Profit

Remotemouse considered harmful

The problem

This weekend I found a nice application to control my mac from my iPhone. It’s Remotemouse from

Unfortunately, when testing I found out that there was no pairing request nor any authentication… I just fired up wireshark to see what was happening and as expected, it’s a very dump cleartext protocol that indicates mouse gestures, clicks, and keyboard events.

I took my editor and went with this little script that connects to my mac, put the mouse on the upper right corner (over the search lense), click it and search for the terminal. Opens it and launches a bindshell.

Remotemouse is binding on all interfaces, ipv4 and ipv6, so if you’re using it and allow direct connections from the outside, you are vulnerable.
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Reversing C++ programs with IDA pro and Hex-rays


During my holidays, I had plenty of time to study and reverse a program, which was completely coded in C++. This was the first time I seriously studied a C++ codebase, using IDA as the only source of information, and found it quite hard.

Here’s a sample of what you get with Hex-rays when you start up digging into an interesting function:

v81 = 9;
v63 = *(_DWORD *)(v62 + 88);
if ( v63 )
   v64 = *(int (__cdecl **)(_DWORD, _DWORD, _DWORD,
   _DWORD, _DWORD))(v63 + 24);
   if ( v64 )
     v62 = v64(v62, v1, *(_DWORD *)(v3 + 16), *(_DWORD
     *)(v3 + 40), bstrString);

It’s our job to add symbol names, identify classes and set up all the information to help hex-rays in giving us a reliable and certainly understandable output:

padding = *Dst;
if ( padding < 4 )
  return -1;
buffer_skip_bytes(this2->decrypted_input_buffer, 5u);
buffer_skip_end(this2->decrypted_input_buffer, padding);
if ( this2->encrypt_in != null )
  if ( this2->compression_in != null )
    avail_len = buffer_avail_bytes(this2->compression_buffer_in);
    ptr = buffer_get_data_ptr(this2->compression_buffer_in);
    buffer_add_data_and_alloc(this2->decrypted_input_buffer, ptr, avail_len);
packet_type = buffer_get_u8(this2->decrypted_input_buffer);
*len = buffer_avail_bytes(this2->decrypted_input_buffer);
this2->packet_len = 0;
return packet_type;

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