Hello Martin,

I have the split authentication running. 
I tried it out, if I can authenticate me as server, if I get the psk from the 
client (split authentication (psk-rsa sig). 
So I changed the ipsec.conf of the server. I added "authby=secret" and 
commented out the lines which are for the rsa authentication.
I changed the ipsec.secrets: : PSK "psk_client"

But it doesnt work: Authentication failed.

Are you sure that it is possible in split authentication to masquerade the 
vpn-gateway with the psk from the client ?

Kind Regards


-------- Original-Nachricht --------
> Datum: Wed, 17 Dec 2008 09:02:59 +0100
> Von: Martin Willi <[email protected]>
> An: "\\"Peter" Müller" <[email protected]>
> CC: [email protected]
> Betreff: Re: [strongSwan] ikev2 split authentication - DoS?

> Hi,
> 
> > I use the split authentication of ikev2 (client with psk, gateway with
> > cert)
> 
> Keep in mind to use such a setup only with strong secrets. PSK client
> authentication is subject to dictionary attacks, don't use it with
> simple passwords.
> 
> > in the split modus it is for an attacker also possible to play mitm, if
> > he gets the psk from the client.
> 
> A compromised PSK will not allow a MITM to do valid RSA signatures. But
> when using ipsec.conf, there is currently no way to enforce the
> authentication method the other peer should use. The client will accept
> a forged PSK authentication of the server, as it signs with a valid
> secret.
> Therefore, using the same secret for each client is probably not a good
> idea. A better solution would:
> 1. use a separate secret for each client
> 2. use EAP, e.g. MD5
> 3. use a CA signed certificate for each client
> 4. extend strongSwan to enforce an authentication method
> 
> Regards
> Martin
> 

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