joe
Posts: 29
Joined: Tue Oct 18, 2011 2:40 pm

Re: SSH without the time?

Tue Oct 18, 2011 3:46 pm

I'm thinking of using one of these as a time-lapse camera controller. I've not thought through it entirely, but it might send images to a server across a secure connection. The power may be interrupted, or it may be switched off at night to save power etc. I'm aware that there are no current plans for a battery-backed RTC. There's no problem with time-stamping photos, as the server could take care of all that (fixup deltas etc) so long as photos are sent before the power goes off. In theory the machine could keep living in January 1970, groundhog-day for all I care.

Question is, will it be possible to authenticate against SSH/SCP without having a correct clock? I imagine certificate acceptance would be a problem if the rpi had no way of knowing the time.

Thoughts?

jamesh
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 23059
Joined: Sat Jul 30, 2011 7:41 pm

Re: SSH without the time?

Tue Oct 18, 2011 4:02 pm

Best option is to sync the clock on boot using the net connection and a time server somewhere.
Principal Software Engineer at Raspberry Pi (Trading) Ltd.
Contrary to popular belief, humorous signatures are allowed. Here's an example...
"My grief counseller just died, luckily, he was so good, I didn't care."

nullstring
Posts: 178
Joined: Sun Oct 02, 2011 3:05 pm

Re: SSH without the time?

Tue Oct 18, 2011 5:49 pm

I did not think that SSH worked that way.
Certs for HTTPS are different than keys for SSH. (Or so I thought)

Thus, I don't think SSH keys can "expire" or be valid only within a certain time frame.

NoSuchNick
Posts: 42
Joined: Tue Sep 20, 2011 1:38 pm

Re: SSH without the time?

Wed Oct 19, 2011 12:55 am

I can't say for sure, but i'm pretty sure that i have ssh'ed into machines with an incorrect date set. To my knowledge ssh doesn't have anything that can expire, but since most of my linux machines now just sync during startup, it's kind of hard to tell.

Return to “Other projects”