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SSH, PubkeyAuthentication and UsePam - security problem or RTFM?



[Matthew, Colin - I suspect you're on debian-security anyway. If so, no 
need to reply off-list; I just wanted to make sure you see this, since 
I considered filing a bug about this.]

Hi,

Package: ssh
Version: 1:3.8p1-3
Tags: bug-not-filed

I have a cople of issues with UsePam in ssh.

First, it seems to always enable PasswordAuthentication. All my systems 
have 'PasswordAuthentication no' and 'PubkeyAuthentication yes', so I 
was very surprised when I was prompted for a password trying to login 
to one of the systems, to an account with an outdated authorized_keys 
file. Investigation showed that 'UsePam yes' is causing this behaviour 
(i.e. 'UsePam no' turns off PasswordAuthentication).

IMHO this is quite a bug, as I rely on the fact that 
'PasswordAuthentication no' disables password authentication.


But of course, having to disable pam has a big drawback: the pam_env 
module is not loaded anymore :-(

I can see how PubkeyAuthentication and pam could conflict, but is there 
no way to work around this? And, for the short term, what is the 
'official' suggested way to read /etc/environment? IIRC it is not 
really recommended to just source it in /etc/profile (all users have 
$SHELL == bash.) Preferably in a way that does not blindly 
read /etc/environment when pam_env *was* loaded.

greetings
-- vbi


-- 
Lieber schlau in die Bluse schau'n, als dumm in die Wäsche gucken!

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