> > The additional random salt prevents someone from sniffing
> > the communication between client and server and then simply log in by
> > sending the known hash of the password. The challenge-response means that
> > sniffing one login doesn't allow you to fake the next one.
>
> How so? The server sends out one fixed salt (the one stored for that
> user's password in pg_shadow) and one randomly-chosen salt. The client
> sends back two crypted passwords. The server can check one of them.
> What can it do with the other? Nothing that I can see, so where is the
> security gain? A sniffer can still get in by sending back the same
> pair of crypted passwords next time, no matter what random salt is
> presented.
No, you crypt the user-supplied password twice.
'fred' -> crypt with fixed -> crypt with random
Server does:
pg_shadow password -> crypt with random
Then check to see they match.
Does that help?
-- Bruce Momjian | http://www.op.net/~candle pgman@candle.pha.pa.us | (610)
853-3000+ If your life is a hard drive, | 830 Blythe Avenue + Christ can be your backup. | Drexel Hill,
Pennsylvania19026
