On Wed, Feb 28, 2001 at 08:00:58AM +1100, Dave Fitch wrote:
> On Tue, Feb 27, 2001 at 11:54:20PM +1100, Ian Tester wrote:
> >
> > from ssh(1):
> > If other authentication methods fail, ssh prompts the user for a pass-
> > word. The password is sent to the remote host for checking; however,
> > since all communications are encrypted, the password cannot be seen by
> > someone listening on the network.
>
> yeah but from my /etc/ssh/sshd_config:
>
> # To disable tunneled clear text passwords, change to no here!
> PasswordAuthentication yes
>
> So I'm confused...
ssh sets up an encrypted tunnel between two hosts. The client uses the
hosts's public RSA key (/etc/ssh/ssh_host_key.pub) to initiate the
tunnel, encrypted with a stream cipher (eg. IDEA).
Once the encrypted tunnel is established, user authentication is
attempted.
This can take one of several forms, eg.:
* it can send your password over the encrypted tunnel for the other
end to authenticate using its system passwords
* it can use your personal ssh RSA keys: the authenticating host
issues a challenge using a public key stored in your ~/.ssh/authorized_keys;
the connecting host meets it using your private key in ~/.ssh/identity.
Your personal keys aren't used for encryption, just authentication.
Remember that ssh uses host keys for encryption, not personal keys. A
host's private key is stored on disk and is available to anyone with
root access.
(cf. personal encryption software, such as GPG, which allows you to store
your private key on a floppy disk in your shirt pocket, and can take steps
to ensure that key data is only ever kept in memory and never paged to
disk).
Conrad.
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