Re: Status update on openvpn work

[ummeegge <ummeegge@ipfire.org>]

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Am Samstag, dem 14.10.2023 um 13:10 +0100 schrieb Michael Tremer:
> Hi Erik,
> 
> Long time no see :)
May it will become in the next time a little more often ;-) (a project
has been canceled)...

> 
> > On 11 Oct 2023, at 15:20, ummeegge <ummeegge(a)ipfire.org> wrote:
> > 
> > Hi Adolf,
> > 
> > Am Montag, dem 09.10.2023 um 19:26 +0200 schrieb Adolf Belka:
> > > Hi All,
> > > 
> > > I thought it was too good to be true.
> > > 
> > > Before creating a client connection with something like BlowFish
> > > I
> > > thought I would just test the server settings with selecting BF
> > > in
> > > the data-ciphers-fallback selection box.
> > Have disabled all the 64 bit block cipher in my previouse patches
> > since
> > the cipher negotiaton managed the whole thing. I think AEAD ciphers
> > are
> > since OpenSSL-1.0.1 available so if AES-GCM is available in --data-
> > ciphers, the clients will use them even BF-CBC is set in
> > client.ovpn .
> > We have had a conversation about this also with some tests which
> > you
> > can find in here -->
> > https://community.ipfire.org/t/openvpn-2-6-development-version/8603/3
> > 
> > > 
> > > Then pressed Start OpenVPN Server and nothing happened. Checked
> > > the
> > > logs and there is the openssl error
> > > 
> > > OpenSSL: error:0308010C:digital envelope routines::unsupported
> > > 
> > > which occurs because Openssl-3.x doesn't support the older
> > > ciphers
> > > like BF unless legacy is selected. In this case I think it is the
> > > OpenVPN server conf file that requires the
> > > 
> > > providers legacy default
> > > 
> > > to be included, rather than the client conf file.
> > > 
> > > Still it does feel like two steps forward and one backwards so
> > > overall still making progress.
> > > 
> > > 
> > > Regards,
> > > 
> > > Adolf.
> > 
> > Best,
> > 
> > Erik
> > > 
> > > 
> > > On 09/10/2023 14:05, Adolf Belka wrote:
> > > > Hi All,
> > > > 
> > > > 
> > > > Over the last week I have been working on the openvpn update
> > > > using
> > > > Erik's previous patches as my starting point.
> > > > 
> > > > My first attempt to try and be able to understand the changes
> > > > from
> > > > each patch to figure out what I needed to do proved difficult
> > > > for
> > > > me to work with.
> > > > 
> > > > What I then did was take the current ovpnmain.cgi and apply all
> > > > of
> > > > Erik's patches to it.
> > > > 
> > > > Then I have gone through that new version of ovpnmain.cgi and
> > > > made
> > > > the changes based on previous discussions with Michael.
> > > > 
> > > > So I have removed the b2sum options that were present for the
> > > > Data
> > > > and Channel Authentication.
> > > > 
> > > > I also moved all the cryptographic options from an additional
> > > > advanced cryptographic options button into the Advanced Server
> > > > options button.
> > > > 
> > > > I was successful in doing all the above and then tested the
> > > > ovpnmain.cgi out with a vm using the existing openvpn-2.5.9
> > > > version
> > > > for openvpn.
> > > > 
> > > > My old profile for my laptop which had a ciphers entry worked
> > > > without any problem. My laptop was working withy openvpn-2.6.6
> > > > 
> > > > I then created a new profile using the new ovpnmain.cgi using
> > > > the
> > > > negotiation option which ended up with a data-ciphers line.
> > > > That
> > > > also worked in making a successful openvpn tunnel with my
> > > > laptop
> > > > without any issues.
> > > > 
> > > > I then downgraded my laptop to openvpn-2.4.8 and had to install
> > > > openvpn-1.1.1 to make that work.
> > > > 
> > > > With that client version on my laptop both the old and new
> > > > profiles
> > > > connected with a tunnel with no problems.
> > > > 
> > > > I then tried downgrading my laptop to openvpn-2.3.14 but to
> > > > make
> > > > this work I would have had to downgrade the laptop to openssl-
> > > > 1.0.0
> > > > which I was not willing to do as that is very old and very
> > > > insecure.
> > > > 
> > > > The oldest openvpn version working with openssl-1.1.1 is 2.4.0
> > > > which is nearly 7 years old.
> > > > 
> > > > That version also worked with both the old and new laptop
> > > > profiles.
> > > > 
> > > > I then tested out the openvpn server on my IPFire vm with a
> > > > 2.6.0
> > > > and 2.6.6 version of openvpn.
> > > > 
> > > > Both these openvpn versions worked with both the old and new
> > > > laptop
> > > > connection profiles with my laptop on version 2.4.0 and on
> > > > 2.6.6
> > > > 
> > > > All the above was using network manager with its openvpn plugin
> > > > option on the laptop for making the openvpn tunnel connections.
> > > > 
> > > > As far as I can tell everything is working fine when
> > > > negotiation is
> > > > specified on the server. Old profiles that just use the cipher
> > > > option also work fine. Therefore my plan is to only use the
> > > > negotiation option and not make it selectable for older
> > > > clients.
> > > > The data-ciphers-fallback option in the server seems to be
> > > > doing
> > > > its job.
> > > > 
> > > > The negotiation option on the server was able to connect to a
> > > > 2.4.0
> > > > client on my laptop.
> > > > 
> > > > According to the OpenVPN wiki on cipher negotiation the data-
> > > > ciphers-fallback option will work with 2.4.x and 2.3.x clients.
> > > > As
> > > > the 2.3.x clients need to be using openssl-1.0.0 then I think
> > > > if
> > > > those clients work then fine but nothing further back.
> > > > 
> > > > Overall, I am very happy with what I have succeeded in doing so
> > > > far. I achieved things much quicker than I had expected.
> > > > 
> > > > I will now try and see about creating a profile on a CU 179
> > > > based
> > > > system that uses one of the old insecure ciphers such as Blow
> > > > Fish
> > > > and restore that into my evaluation vm and see how that works
> > > > with
> > > > my laptop when I have it downgraded to openvpn-2.4.0
> > > > 
> > > > I already know that if the laptop is at openvpn-2.6.6 then it
> > > > will
> > > > not accept a blowfish cipher (or another weak cipher such as
> > > > DES)
> > > > as that is something I tested in the past.
> > > > 
> > > > If that also works then my plan will be to take the updated
> > > > ovpnmain.cgi and split the changes into a new range of patches
> > > > and
> > > > then submit them for consideration.
> > > > 
> > > > That will probably end up later in November as I will be busy
> > > > with
> > > > personal things at the end of October / beginning of November.
> > > > 
> > > > 
> > > > Regards,
> > > > 
> > > > Adolf.
> 
>