linux-kernel - Re: [PATCH] xfrm: Added the auth and enc update support in "state update"

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Message-ID: <20170307125613.GL694@gauss.secunet.com>
Date:   Tue, 7 Mar 2017 13:56:13 +0100
From:   Steffen Klassert <steffen.klassert@...unet.com>
To:     <trajaraman@...sta.com>
CC:     <davem@...emloft.net>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] xfrm: Added the auth and enc update support in "state
 update"

On Tue, Mar 07, 2017 at 05:33:13PM +0530, trajaraman@...sta.com wrote:
> From: Thiruvadi rajaraman <trajaraman@...sta.com>
> 
> The "ip xfrm state update" process doesn't update the new authendication
> and encryption keys as well as it doesn't return an error.
> 
> Test logs: (Default)
> ==========
> ~# ip xfrm state list
> ~# ip xfrm state add src fe80::/10 dst ff02::3 proto esp spi 1235 mode transport auth sha1 0xAABBCCDDEEFF0010 enc des 0xAABBCCDDEEFF0010
> ~# ip xfrm state list
> src fe80:: dst ff02::3
>         proto esp spi 0x000004d3 reqid 0 mode transport
>         replay-window 0
>         auth-trunc hmac(sha1) 0xaabbccddeeff0010 96
>         enc cbc(des) 0xaabbccddeeff0010
>         sel src ::/0 dst ::/0
> ~#
> 
> ~# ip xfrm state update src fe80::/10 dst ff02::3 proto esp spi 1235 mode transport auth sha1 0xAABBCCDDEEFF0015 enc des 0xAABBCCDDEEFF0020
> src fe80:: dst ff02::3
>         proto esp spi 0x000004d3 reqid 0 mode transport
>         replay-window 0
>         auth-trunc hmac(sha1) 0xaabbccddeeff0010 96   ----> [ Auth key doesn't changed and remains same ]
>         enc cbc(des) 0xaabbccddeeff0010               ----> [  Enc key doesn't changed and remains same ]

This is intentional, the original state is not XFRM_STATE_ACQ,
so you are not allowed to update keys without requesting for
a new SPI. The original code was written 15 years ago, based
on RFC 2367 (PF_KEY) which says we must return -EINVAL in this
case. So if we change this, we should return an error.