Re: Status update on openvpn work

[Adolf Belka <adolf.belka@ipfire.org>]

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Hi Erik,

On 12/10/2023 08:06, ummeegge wrote:
> Am Donnerstag, dem 12.10.2023 um 07:56 +0200 schrieb ummeegge:
>>> OpenVPN plan to remove those weak ciphers completely in version 2.7
>>> If a user at that time still had a client with say BF-CBC would the
>>> negotiation still work then or would it fail because OpenVPN no
>>> longer
>>> recognises the old weak cipher?
>> This is true according to the OpenVPN 'Deprecated Option' wiki -->
>> https://community.openvpn.net/openvpn/wiki/DeprecatedOptions#Policy:Migrateawayfromdeprecatedciphers.Status:Inprogress
I had seen that overall page before but obviously not read the details 
well enough of that specific entry. The entry makes it clear that from 
openvpn-2.7 onwards the 64 bit ciphers will no longer be accepted even 
as data-fallback ones.
>> that´s causes, beneath the OpenSSL-3.x decision, to leave the
>> deprecated ciphers out of the Roadwarrior list (N2N is another thing
>> since it do no understands cipher negotiation) but pushed at that
>> time
>> an idea to bring on some warnings for the users before the IPFire
>> decision to leave the broken ciphers out of any list since the server
>> can not see what client configuration is in place.
> To correct this statement, mostly users do not see/recognize such
> warnings in the  OpenVPN logs, the server does see it!
I see what you are saying. The users tend not to look at their logs and 
so will miss the message about the 64 bit BF-CBC etc being removed from 
2.7 onwards.

So having the 64 bit ciphers in the data-fallback table but not allowing 
them to be used and instead giving a warning message about the cipher 
being removed in the future is a way to make the changes more visible 
that the user needs to do and the potential timing scenario.

I think I will also need to put together a supporting info blog post on 
the openvpn changes that will come with the IPFire updates being worked 
on and the future ones with openvpn-2.7
>> This patch can be found in here -->
>> https://git.ipfire.org/?p=people/ummeegge/ipfire-2.x.git;a=commit;h=dd11f42776f1b60660f4e862d6e847e746b9411b
Thanks for the clarification.

Regards,
Adolf.
>>> Regards,
>>>
>>> Adolf.
>> Best,
>>
>> Erik
>>
>>>>> 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.
>>>>>>

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