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Re: [tlug] bootable linux with sshd



On 03/01/07, Curt Sampson <cjs@example.com> wrote:
On Tue, 2 Jan 2007, Fergal Daly wrote:

> BTW, it stops password logins but allows root logins. I don't really
> see the point of not allowing root logins, I'd only go and create
> another user with sudo permission - it'd require knowing a second
> secret to be able to get root....

That's the whole point. It's especially good if you disallow password
logins, since then you've got to get hold of two different sorts of
secrets (a password and a key file, which also usually has a passphrase
on it), only one of which is subject to guessing. (Nobody's going to
guess an ssh private key.) In fact, it adds even a third level of
difficulty in that the attacker not only has to have a password and an
ssh private key, but also has to know the name of the account that can
sudo.

From an information theory point of view and for many practical purposes

1 long secret == 3 shorter secrets

especially if the 3 shorter secrets tend to be used close together in
time. If someone can get my private key, they're a good chance they
can get my username and password too.

The only benefit I can see is that you might be less vulnerable to ssh
security holes. If root logins are disallowed then the security hole
caused by a bug might not get someone root.

Given that I hope to never use this, I'm happy enough with what I have,

F


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