SYSKEY2. Request For Comments

[Luke Kenneth Casson Leighton]

On Tue, 8 Feb 2000, Simon Lodal wrote:

> I am not a security expert, but trying to keep up. I do not understand the
> real point in SYSKEY2, what is the primary purpose? I only see it making
> trouble, no solutions. Excuse me if I'm lame, I know that, but please read
> on. Quoting from luke's recent mails:
> 
> > recently, netect / bindview posted a review of the syskey system and how
> > the RC4 cypher stream was reset each time.  standard RC4 attack analysis
> > shows that XORing two obfuscated passwords together results in the XOR
> > cypher stream dropping out, and you have the two XORed password.  further
> > attack analysis can decrypt the  passwords.
> 
> So the problem is that MS' encryption is again too weak?

no, that was a side-note explaining that microsoft's current algorithm is
useless, indicating that i wish to do better.

 
> > i need to make the sam database read-accessible to all unix users.  just
> > like /etc/passwd.
> 
> So the real problem is that we can't hide these weak password hashes from
> anyone?
> 
> Jeremy suggested something along the lines of /etc/shadow.

that's one specific inplementation option.  it doesn't mean that SYSKEY2
isn't necessary.
 
> > well, the trouble with that is that i will have to maintain (and lock, and
> > maintain), two databases, for users.
> 
> So it could be done, only with a slight more trouble? What's worst;
> implementing a new encryption system (which may itself open
> vulnerabilities), or locking just another file?
> 
> The same mail also said:
> > i won't be -- over-the-wire.  i blank those out.
> 
> But 3 days later:
> > but it's not.  think.  ldap.  sql.  nis+.  we can't trust them, and
> > they're all publicly accessible network protocols.
> 
> So the real problem has now turned out to be that we are using other
> protocols that someone might be able to listen on, over the wire?

YES.  [thank you for noticing.  noone else has].

> 1) If the problem is only local storage, the obvious solution is a shadow
> password system. The argument that you must trust root applies.

correct.

as you noticed [the real problem], it's not JUST locak storage.

> 3) The idea of storing the necessary key on a diskette off the machine only
> makes things much worse. In theory it will add security, but in real life
> there will be a major vulnerability: The human factor. Good old word says
> that the only safe server is one that is shut down and locked in a closet.
> It's the same if you need that disk to boot the machine. People will not
> lock it in a closet, and they will not carry it around all day long, keep it
> under their pillow when they sleep. So where will it be, in real life? Ha,
> probably in the disk drive. How disciplined would you be? So when a

that's their problem, not ours.

thx 4 comments.

luke