On Sat, 2006-01-28 at 11:46 +0100, David Härdeman wrote:
> Not necessarily, if you have your ssh-keys in ssh-agent, a compromise of
> your account (forgot to lock the screen while going to the bathroom?
> did the OOM-condition occur which killed the program which locks the
> screen? remote compromise of the system? local compromise?) means that a large
> array of attacks are possible against the daemon.
>
> In addition, as stated before, the "backup" account, or whatever user the
> daemon which wants to sign stuff with your key is running as, might be
> compromised.
>
> Currently, if you want to give the daemon access to the keys via
> ssh-agent (or something similar), you have to change the permissions on
> the ssh-agent socket to be much less restricted (especially since it's
> unlikely that you have permission to change the uid or gid of the socket
> to that of the daemon). Alternatively you can provide the backup daemon
> with the key directly (via fs, or loaded somehow at startup...etc), but
> then a compromise of the daemon means that the attacker has the private
> key.
>
> Finally, the in-kernel system also provides a mechanism for the daemon
> to request the key when it is needed should it realize that the proper
> key is missing/has changed/whatever.
Then fix ssh, not the kernel. As I said before, this is a problem that
has been solved entirely in userspace by means of proxy certificates:
they allow the user to issue time-limited certificates that are signed
by the original certificate (hence can be authenticated as such), and
that authorise a service to do a specific thing.
Cheers,
Trond
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