On Wed, May 01, 2002 at 01:56:41PM -0500, Mike wrote:

> Has anyone done any host based authentication with SSH or OpenSSH. 
> I'm trying to automate a scp (secure copy) cron job.

Yep, I've done it.  It's not as hard as the docs want to make it 
out to be.  Here's how:

In the user's ~/.ssh directory are several relevant files:

   authorized_keys
   identity.pub
   known_hosts
   known_hosts2

So let's assume for a moment that "host1" is the machine from which 
the file is being copied, and "host2" is the target of the copy.  
Let's further assume that user "wrstone" with the home directory 
path "/home/wrstone" is making the copy and that both users exist 
on both machines.

Here's the basic crux of the matter.  To do this seamlessly, the 
file host2:/home/wrstone/.ssh/authorized_keys needs to have the
contents of host1:/home/wrstone/.ssh/identity.pub.

This is actually pretty easy.  Copy 
host1:/home/wrstone/.ssh/identity.pub to 
host2:/home/wrstone/.ssh/identity.host1.

Next, cat identity.host1 >> authorized_keys.

And that's that.  Now host1 should be able to scp files to and from 
host2 without being prompted for a password or other identifying 
characteristics.  For that matter, the user will be able to ssh to 
host2 without being prompted, either.

Now, it goes without saying that this shouldn't be done with user 
root -- if someone were to hack host1, they've automatically hacked 
host2.

In fact, if you want to do it really slickly, you'll invent some 
user on both hosts with really limited access rights -- a user 
whose sole purpose is to scp files for other users.  When the real 
user drops a file in a copy directory on host1, a user level 
cronjob watches that directory and eventually copies it to an 
inbound directory on host2.  And then you have some user cronjob on 
host2 watch for inbound files and distribute them.

It's a little more complicated, but by doing it this way, you avoid 
"trusted" users between systems.

Hope this helps.

Bill Stone
___________________________________________________________________    
  William Stone, III          | Certifications:  CISSP, RHCE, CCNA
  Proprietor                  | Phone:  (605) 232-6771
  William Stone & Associates  | FAX:    (605) 232-6763
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