# VolgaCTF Quals 2015: Russian doll
----------## Challenge details| Contest        | Challenge     | Category  | Points ||:---------------|:--------------|:----------|-------:|| VolgaCTF Quals 2015 | Russian doll | Forensics |    300 |
**Description:**>*Russian doll*
>*We got a strange file, can you find a flag in it image*
----------## Write-up
We are given a 500MB file called "russian_doll.iso" about which file has to say the following:
>```bash> file russian_doll.iso>> russian_doll.iso; x86 boot sector, code offset 0x58, OEM-ID "-FVE-FS-", sectors/cluster 8, reserved sectors 0, Media descriptor 0xf8, heads 255, hidden sectors 46626816, FAT (32 bit), sectors/FAT 8160, reserved3 0x800000, serial number 0x0, unlabeled>```
The "-FVE-FS-" OEM-ID indicates we are probably dealing with a [bitlocker encrypted volume](http://www.forensicswiki.org/wiki/BitLocker_Disk_Encryption). So we fire up [Diskinternals EFS recovery](http://www.diskinternals.com/efs-recovery/) and mount russian_doll.iso as a raw disk image. In the Diskinternals EFS recovery interface we can now see the volume name which contains the pass (WIN-VQ2T0GLLBKC pss : d@7raLzVolg@CTF):
![alt recovery1](recovery1.png)
Next we perform recovery on disk (choosing Fast EFS recovery), enter the password (d@7raLzVolg@CTF) and after being notified no deleted files have been recovered we are presented with an overview of the folders and files in the volume:
![alt recovery2](recovery2.png)
The volume contains only a single file called "flag.gif" which we can preview (but not save in our trial version):
![alt recovery3](recovery3.png)
Taking a look at the file with the built-in hex viewer we can see the flag all the way down at the end of the file:
![alt recovery4](recovery4.png)
Giving us the flag:
>*{fkw2pef460hlcm2vefvblowmfldqaw34volgactf}*