[strongSwan-dev] [RFC] Be lenient about downstream encryption

Martin Willi martin at strongswan.org
Mon Apr 14 14:56:15 CEST 2014

Hi Paul,

> I discovered an interop issue with XAUTH authentication
> with StrongSwan VPNs.  Does anyone have a deep enough
> knowledge of this frame to understand what the remote
> VPN is giving away?

Thanks for your analysis, and the patch.

It seems that Sonicwall sends the ID/Hash payloads unencrypted even in
Main Mode, probably to select different PSK keys based on the peer
Identity. Something like an "Aggressive Mode light"?

If that helps for interoperability, I'm not against upstreaming a
work-around, even if it is not strictly within the specs.

How about the (untested) patch at [1]? It introduces a
charon.sonicwall_quirk strongswan.conf option to enable that behavior.

@Tobias: What do you think about such an option? Don't know if it is
worth it, as remote sends these unencrypted payloads anyway. On the
other side, it can make the implications clear to the
administrator/user, given that an attacker can snoop these identities
sent in clear-text.

Best Regards


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