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Raidsonic NAS-4220 Crypt Disk Key Leak
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SUMMARY
The
<http://www.raidsonic.de/de/pages/products/details.php?we_objectID=5051>
NAS-4220-B offers disk encryption through it's web interface. The key used
for encrypting the disk(s) is stored on a unencrypted partition. Therefore
one can extract the encryption key by removing the disk from the Raidsonic
NAS-4220 and reading the value from the unencrypted partition. The key
itself is stored in a file in plain (base64 encoded). Therefore the
NAS-4220 crypt disk support can not be considered secure.
DETAILS
The NAS-4220-B can hold two SATA disks. Disk are encrypted through a loop
back device using AES128. The problem came to Collin's attention when he
could access the NAS after reboot without suppling the hard disk key.
The key is stored in /system/.crypt, "/system" is a small configuration
partition on the same disk that holds the encrypted partition. The system
partition is created by the system software running on the NAS-4220. The
configuration partition of the second hard disk is not mounted by default
but also contains the .crypt file holding the key for the encrypted
partition on the same disk.
Accessing the key (key value is the example Collin used):
$ cat /system/.crypt
MTIzNDU2Nzg5MDEyMzQ1Njc4OTA=
key in plain key in base64
12345678901234567890 MTIzNDU2Nzg5MDEyMzQ1Njc4OTA=
Base64 decode:
#!/usr/bin/python
from base64 import *
print b64decode("MTIzNDU2Nzg5MDEyMzQ1Njc4OTA=")
ADDITIONAL INFORMATION
The information has been provided by <mailto:collin@betaversion.net>
Collin Mulliner.
The original article can be found at:
<http://www.mulliner.org/security/advisories/raidsonic_nas4220_crypt_disk_key_leak_09Mar2008.txt>
http://www.mulliner.org/security/advisories/raidsonic_nas4220_crypt_disk_key_leak_09Mar2008.txt
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