no password ssh not working as it used to
 

I backup stuff on my home machine by rsyncing with my work machine. I have to pull from work because I can't see my work machine externally.

The process is usually as follows:
1) logon to visible machine at work
2) login to my machine
3) switch to root (i have a external HD that only root can see)
4) run rsync script

Since there are several rsync commands I set up no password ssh by copying the root@work public key in to my authorised keys. THen out of the blue this stopped working.

I cannot get it to work again, even by starting all over from scratch. On my home network public keys work.

I allow access via ssh to my home network using a non standar port and my hostname is set via ddclient, although my ISP tends to give me the same IP address at all times anyway.

How can I trouble shoot this?

Many thanks,

Dave

start with manual ssh connection using verbose flag and tail -f logs at remote side at the same time

[/code]

Also, are you watching /var/log/auth.log? I presume since you say "my work machine" that you are in control of that machine? So another sysadmin would not have blocked root logins?

If I were the sysadmin, I would have blocked it. That's a standard security practice. I use a restricted user account for backups and use sudo when needed. The keys are also restricted so that the connections can only do what I originally intended. It works just fine for doing backups, and root is not allowed to login remotely.

By the way, if you aren't familiar with it already, http://sial.org/howto/openssh/publickey-auth/ is a pretty standard reference for setting up keys. It also has some debugging notes.

My WAG is that you have sshd's StrictModes enabled, and that you changed your user's home directory permissions on the server side. e.g. /home/foo can not be group writable or world writable, or pubkey authentication will not work.

A quick -
- will correct that.

While you're reviewing and fixing that, also confirm that /home/foo/.ssh and /home/foo/.ssh/authorized_keys is readable by only foo.

Hi,

@choogendyk So I have full root access to my work machine. I'm an academic and things are a little more relaxed. root logins over ssh are not allowed though. I'm backing up as root for some reason that I can't remember. I think I wanted to mount the drive as read only for my user account.

Here is the verbose output of ssh. I think the lines at the end are telling what is going wrong, but I don't understand it.

Is it trying to access as root on my home machine even though the ssh command is user@homemachine?:

This is the tail of /var/log/auth.log on my home machine


Thanks,

Dave

looks like a key pair mismatch
i say this because


should have been more like

[code]
debug1: Trying private key: /home/root/.ssh/identity
debug1: Trying private key: /home/root/.ssh/id_rsa
debug1: Offering public key: /home/root/.ssh/id_dsa
debug2: we sent a publickey packet, wait for reply
debug1: Server accepts key: pkalg ssh-dss blen 433




you may get some more info from

but i doubt you will need that.
points to keypair mismatch

I don't really understand. I generated a fresh pair in .ssh as root on my work machine:

I then cat id_dsa.pub into .ssh authorized_keys2 on my home machine.

Which keys are mismatched?

Many thanks,

Dave

authorized_keys2? I thought more recent versions of OpenSSH had dropped that distinction. Try authorized_keys, and see if that does something. Also, do look at

the sshd_config file will tell you if ssh looks for authorized_keys or authorized_keys2.


the key isnt being found......according to the verbose output

my bad

looks like authorized_keys is being checked.

so append the key there./....

@robotronic: Have you explored my suggestion yet?

@anomie Yes thanks.

I should point out that I can log in with public keys from two other machines: 1) the a laptop on my home network 2) a work machine visible to the outside world.

This implies to me that I have things set up correctly at this end. The machine I am rsyncing from is not visible externally (which is why I am pulling to it). This is the one that is not working, (Although it used to!!!!).

Now, here is what I don't get:

Why is it looking at /root/ssh/authorized_keys?

Okay so the work user is root, but it is logging on as myname:

Shouldn't it be looking in /home/myname/.ssh/authorized_keys?????

Many thanks for all your help so far!

Dave