[VPN] Re: Cisco VPN client .pcf file security hole

[Gene Engelke]

Here is a link to the tool that will decrypt both passwords.
Cisco is aware, but their fix was to upgrade to the new client.
 
 
To: full-disclosure at lists.grok.org.uk 
Cc: bugtraq at securityfocus.com 
 
 
 
Dear List,
 
[1] heise published a news article today.
[2] EvilScientists reverse engineered the algorithm Cisco uses to
_obscufate_ the
    passwords.
[3] PoC
 
Summary :
Cisco uses 3des to encrypt the passwords, however it does so using
a deterministic encryption sheme (no user input) and thus must be
reproducible.
 
The algorithm [2] found was as follows :
 
* GetDate - convert to string
* Generate an SHA Hash from that string h1 (20 Bytes)
* h1 is modified into Hash h2
* h1 is modified into Hash h3
* h2 and the first 4 Bytes from h3 give the 3DES Key
* The clear text password no encrypted in 3DES CBC Mode. The IV is the
first 8 Bytes of h1.
* If the size of the clear text password is not a multiple of the
  Block size, the differece to the next block is calculcated and padded
  with a Digit. -> length of password is known
* A last hash is calculated from the encrypted Password h4
* The value of the Key "enc_UserPassword" is: h1|h4|verschlüsseltes Passwort
 
Credits:
[1] http://www.heise.de/newsticker/meldung/64954 
[2] http://evilscientists.de/blog/?page_id=339 
[3] http://www.evilscientists.de/blog/?dl=CiscoPasswordRevealer.rar 



-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.shmoo.com/pipermail/vpn/attachments/20051108/ddc60f1a/attachment.htm