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2001 Dec 30 17:11

The following is an archive of a post made to our 'vox-tech mailing list' by one of its subscribers.

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Re: [vox-tech] Secure Email Access (fetchmail and ssh)
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Re: [vox-tech] Secure Email Access (fetchmail and ssh)



On Fri, 12 Oct 2001, ME wrote:

> On Thu, 11 Oct 2001, Matt Roper wrote:
> > I am trying to find a secure way to have the box that I use as a mail
> > server go download all my @ucdavis email from the UCD mail server.  My
> > plan is to use fetchmail with an ssh preconnect string to accomplish
> > this.  I believe that my .fetchmailrc file should have an entry that
> > looks something like the following:
> > 
> > poll yellow.ucdavis.edu via localhost port 1234 with proto pop3:
> >     user 'mattrope' there with password 'XXXXXXX' is mattrope here
> >     preconnect "ssh -f -q -L 1234:yellow.ucdavis.edu:110
> >     yellow.ucdavis.edu sleep 20 < /dev/null > /dev/null"
> 
> Hmmm...
> 
> > The problem with this is that ssh would have to ask for my password
> > every time it tries to connect to the UCD mailserver, which is
> > unacceptable if fetchmail is running in daemon mode.  I believe that the
> > way most people overcome this is by generating an ssh keypair with no
> > passphrase and sticking the public key in their ~/.ssh/authorized_keys
> > file on the server.  However UCD does not allow students to login to the
> > mail servers directly, so there is no way I can put my public key on the
> > server.  This seems to rule out the use of public key authentication for
> > establishing a secure connection.
> 
> I am not so sure that you can have an ssh client arbitrate a "secure
> session" with a pop3 server (port 110) like that unless you are certain
> the mail server also runs ssh and can allow for redirections with the
> connecting ssh client. If there is really an ssh server on the mail
> server, you may be able to grab your private keys on the server with scp
> and make some guesses on the locations of the keys.

If you don't have shell access, you probably don't have a home
directory.  Without a home directory, where would your key be kept?

[...]

> There are many people on this list more skilled than me who might have
> other ideas.

With respect to unsecured public keys, Bill Broadley has discussed using
ssh-agent to allow passphrase entry at bootup.  But that won't help if you
can't keep a public key on the server.

I would ask your sysadmin for a solution (preferably), or use expect as ME
suggested.

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