Re: [Openvpn-users] migrating from lzo to lz4

[Илья Ш. <chi...@gm...>]

2017-11-16 13:35 GMT+05:00 David Sommerseth <
op...@sf...>:

> On 16/11/17 06:59, Илья Шипицин wrote:
> > hi,
> >
> > I'm running vpn server since 2012, with comp-lzo enabled (on both client
> > and server side)
> >
> > in openvpn-2.4 comp-lzo is deprecated in favor of compress option.
> >
> > also, I'm considering switching to lz4 from lzo.
> >
> > any best practice how to switch lzo --> lz4 without operation
> interruption ?
>
> First of all, I'd recommend you to do some performance testing on the
> typical payload you're pushing through your tunnel.  You might find that
> LZO can perform better than LZ4 in some scenarios with a lower CPU load.
>  But it is hard to come with a generic recommendation; it depends a lot
> on what you push through your tunnel and how compressible that data
> stream is.  A bit more info can be found here: <
> https://github.com/lz4/lz4/>
>
> Another detail is the security aspects related to compressing data
> streams.  The CRIME attack [0] is now an ageing side-channel attack
> vector which is made possible due to compression.  And there are other
> compression oracle attacks [1] too, like BREACH [2].
>
> [0] <https://en.wikipedia.org/wiki/CRIME>
> [1] <https://en.wikipedia.org/wiki/Oracle_attack>
> [2]
> <https://threatpost.com/breach-compression-attack-
> steals-https-secrets-in-under-30-seconds/101579/>
>
> --compress is pushable.  Not sure if you can mix lzo and lz4
>

it is a separate question, why pushing must be enabled (and it is not
enabled by default).


however, I address here another question, are lzo and lz4 mutually
exclusive ?

according to man page, you must explicitely specify either "compression
lzo" or "compression lz4".


> compression, but I'd just add 'compression' in all the config files and
>

just "compression" is somewhat not clearly covered by documentation. is it
"stub" ? or is it "enable both lzo and lz4" ?


> then only push 'compress {lzo,lz4}' to those clients that is reasonable
> to use.  I would not, however, enable compression itself on by default -
> just have the compression framing available.
>
>
> --
> kind regards,
>
> David Sommerseth
>
>