[strongSwan] Strongswan not sending encryption algorithm

[Andreas Steffen]

Hi Lakshmi,

yes, your understanding is correct. Since AES-GCM is an
authenticated encryption algorithm, you don't need an
additional integrity protection function. Thus

Valid IKEv1 combo:
------------------

keyexchange=ikev1
ike=aes256-sha256-modp2048!
esp=aes256gcm128!


Valid IKEv2 combo:
------------------

keyexchange=ikev2
ike=aes256gcm128-prfsha256-modp2048!
esp=aes256gcm128!

Regards

Andreas

On 05.08.2016 10:41, Lakshmi Prasanna wrote:
> Thank you for the reply Andreas.
>
> Can you please validate my understanding?
>
> Valid combo:
> -------------------
>
> keyexchange=ikev1
>
> ike=aes256-sha256-modp2048!
>
> esp=aes256gcm128-sha256!
>
>
> Invalid combo:
> --------------------
>
> keyexchange=ikev1
>
> ike=aes256gcm128-sha256-modp2048!
>
> esp=aes256gcm128-sha256!
>
>
> Thanks,
>
> Lakshmi
>
>
> On Fri, Aug 5, 2016 at 1:49 PM, Andreas Steffen
> <andreas.steffen at strongswan.org <mailto:andreas.steffen at strongswan.org>>
> wrote:
>
>     Hi Lakshmi,
>
>     The old IKEv1 protocol does not support AES-GCM for IKE since
>     IANA hasn't assigned any encryption transform numbers:
>
>     http://www.iana.org/assignments/ipsec-registry/ipsec-registry.xhtml#ipsec-registry-4
>     <http://www.iana.org/assignments/ipsec-registry/ipsec-registry.xhtml#ipsec-registry-4>
>
>     AES-GCM can be used for IKE protection with IKEv2, only:
>
>     http://www.iana.org/assignments/ikev2-parameters/ikev2-parameters.xhtml#ikev2-parameters-5
>     <http://www.iana.org/assignments/ikev2-parameters/ikev2-parameters.xhtml#ikev2-parameters-5>
>
>     Anyway, you profit from the speed advantage of AES-GCM mainly
>     with ESP because many payload packets must be processed.
>     AES-GCM for ESP can be negotiated both via IKEv1 and IKEv2.
>
>     Regards
>
>     Andreas
>
>     On 08/05/2016 08:42 AM, Lakshmi Prasanna wrote:
>      > Hi Team,
>      >
>      > I am trying to use AES-GCM with IKEV1 and see that strongswan
>     does not
>      > send the encryption algorithm.
>      >
>      > Is there any plugin or knob to enable the same?
>      >
>      > Logs:
>      >
>      > --------
>      >
>      > received proposals: IKE:HMAC_SHA2_256_128/PRF_HMAC_SHA2_256/MODP_2048
>      >
>      > configured
>      >
>     proposals:IKE:AES_GCM_16_128/HMAC_SHA2_256_128/PRF_HMAC_SHA2_256/MODP_2048
>      >
>      >
>      > Thanks and Regards,
>      >
>      > Lakshmi
>
>     ======================================================================
>     Andreas Steffen andreas.steffen at strongswan.org
>     <mailto:andreas.steffen at strongswan.org>
>     strongSwan - the Open Source VPN Solution! www.strongswan.org
>     <http://www.strongswan.org>
>     Institute for Internet Technologies and Applications
>     University of Applied Sciences Rapperswil
>     CH-8640 Rapperswil (Switzerland)
>     ===========================================================[ITA-HSR]==
>
>

-- 
======================================================================
Andreas Steffen                         andreas.steffen at strongswan.org
strongSwan - the Open Source VPN Solution!          www.strongswan.org
Institute for Internet Technologies and Applications
University of Applied Sciences Rapperswil
CH-8640 Rapperswil (Switzerland)
===========================================================[ITA-HSR]==

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