Hello Matt, Matt Johnston <[email protected]> wrote: > > Hi Roy, > > On Tue 29/6/2021, at 7:18 pm, [email protected] wrote: > > > - Make failure delay more consistent to avoid revealing valid usernames, set > server password > limit of 100 characters. Problem reported by usd responsible disclosure team > > > What is the technical reason of limiting server password length to > such a low value? It is even shorter than Windows PATH_MAX which I > think this doesn't make any sense. > > - Change handling of failed authentication to avoid disclosing valid > usernames, > CVE-2018-15599. > > > The problem with longer passwords is that the time taken to calculate a > password crypt is dependent on the length of the password. Passwords longer > than a certain length will take longer to crypt than the failure delay time - > 100 characters was less than what I tried empirically. > > That itself wouldn't be a problem if we could just crypt all incoming > password attempts before checking a username's existence - the problem is > that the password crypt algorithm can vary per user, so the time will vary > too. We have to guess which algorithm to use for unknown users. So rather > than adding some complicated logic I just limited the password length.
OK I got it. But does the risk become higher if I change DROPBEAR_MAX_PASSWORD_LEN to higher value. for example, 200? > > Cheers, > Matt Regards, Roy
