"premature exit: string too long"

Matt Johnston matt at ucc.asn.au
Sat May 13 12:42:40 WST 2006

On Sat, May 13, 2006 at 12:44:07AM +0200, Sebastian Haag wrote:
> Hi,
> I´m using dropbear 0.48.1 and have a little problem with the public/private 
> keys.
> I generated the public and private keys with dropbearkey and copied the public 
> key to "/etc/dropbear/dropbear_rsa_host_key" (on the SERVER, where 'dropbear' 
> is running/should run). This file is readable and writeable only to user 
> root. 

> When i want to start dropbear (with 'dropbear'), i get the following message: 
> "premature exit: string too long".

The /etc/dropbear/dropbear_rsa_host_key file is the server's
_private_ key, used for all sessions (even password authed)
so that the client knows that it's talking to the same
server each time. This is independent of using public keys for
user auth. If you generate a key using dropbearkey and copy
the private key part to dropbear_rsa_host_key, it should
work fine.

If you then want to use public key authentication, on the
client you have to generate a key, then paste the public
part into ~/.ssh/authorized_keys on the server. If you're
using dbclient then you'd generate it with dropbearkey and
specify it with "dbclient -i ~/.ssh/id_rsa.db", otherwise
you'd use the client-specific key generator - dbclient for
OpenSSH, PuTTYgen for putty, etc.


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