[Solved] OVPN Scramble (obfuscated) server/client

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foz111
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Joined: 01 Oct 2017
Posts: 704
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PostPosted: Tue Sep 20, 2022 17:12    Post subject: [Solved] OVPN Scramble (obfuscated) server/client Reply with quote
Below information taken from egc ovpn client doc:

Scramble options
Scramble options can be used to obfuscate the connection this can be useful to escape censoring.
Note: scramble options must be the same on client and server side!
In the Additional config add:
scramble "password"
DDWRT OpenVPN Client Setup guide by egc, last modified: 23-Aug-22 page 13
scramble is the leftmost option name. This can be followed by a string which will be used to perform a simple xor
operation the packet payload.
However if the following are used instead, a different action will occur.
scramble reverse
This simply reverses all the data in the packet. This is enough to get past the regular expression detection in both
China and Iran.
scramble xorptrpos
This performs a xor operation, utilising the current position in the packet payload.
scramble obfuscate "password"
This method is more secure. It utilises the 3 types of scrambling mentioned above. "password" is the string which
you want to use.

Question:
If i add scramble obfuscate "password" to the ovpn additional config section what is added to the client ovpn config to match?
Trying to let a friend use my server/wan out to access his emails while away on a ship but DPI is picking up he's using a vpn. Currently configured with UDP on a high port 48917 not 1194 etc
Also will the scramble obfuscate "password" work with both TCP & UDP?
Would i add scramble obfuscate "password" in both server side (additional config section) and client config & or do i change the "password" to my ovpn password and remove the ""?
i currently dont use user and pass i removed when i added tls key but i can add again pretty sure it #'ed out in config still.
Sorry penny hasn't dropped with this as i am unsure how it works.
Cheers for any input

_________________
Netgear R7800 PPPoE Main Router
Network IPV4 - Isolated Vlan's with IoT Devices. Unifi AC-Pro x 3 AP's, Router Wi-Fi Disabled. OVPN Server With Paid Commercial Wireguard Client's. Gateway Mode, DNSMasq, Static Leases & DHCP, Pi-Hole DNS & Running Unbound.

No one can build you the bridge on which you, and only you, must cross the river of life!


Last edited by foz111 on Fri Sep 30, 2022 13:15; edited 1 time in total
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foz111
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Joined: 01 Oct 2017
Posts: 704
Location: Earth

PostPosted: Wed Sep 21, 2022 10:39    Post subject: Reply with quote
I can't seem to get this to work with an android client
added: scramble obfuscate password into server additional config and rebooted router and added the same into client ovpn file (obviously not used the word password).
Tried openvpn connect & openvpn for android apps but get error, unrecognized option in stdin:128:scramble (2.6_master) so assume this will not work with official ovpn android app or am i doing something wrong?
it's my understanding from what i've read that this should work on any port and with TCP & UDP any idea's why this is not working?
I see this is an unofficial patch is this why it's not working in the android apps but if that's the case will it work with official windows app (cant test this myself)?

_________________
Netgear R7800 PPPoE Main Router
Network IPV4 - Isolated Vlan's with IoT Devices. Unifi AC-Pro x 3 AP's, Router Wi-Fi Disabled. OVPN Server With Paid Commercial Wireguard Client's. Gateway Mode, DNSMasq, Static Leases & DHCP, Pi-Hole DNS & Running Unbound.

No one can build you the bridge on which you, and only you, must cross the river of life!
egc
DD-WRT Guru


Joined: 18 Mar 2014
Posts: 12812
Location: Netherlands

PostPosted: Wed Sep 21, 2022 10:50    Post subject: Reply with quote
It works on DDWRT client and server.

There are also some VPN providers which use it (I think it is Strong VPN) to circumvent the great firewall.

But it is not in official apps, there might be apps available which have it.

_________________
Routers:Netgear R7000, R6400v1, R6400v2, EA6900 (XvortexCFE), E2000, E1200v1, WRT54GS v1.
Install guide R6400v2, R6700v3,XR300:https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=316399
Install guide R7800/XR500: https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=320614
Forum Guide Lines (important read):https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=324087
foz111
DD-WRT Guru


Joined: 01 Oct 2017
Posts: 704
Location: Earth

PostPosted: Wed Sep 21, 2022 11:52    Post subject: Reply with quote
i thought that must be the case egc thanks for confirming this.
i see vpn client pro supports scrambled, this a paid Android app but i will let him know.
Cheers

_________________
Netgear R7800 PPPoE Main Router
Network IPV4 - Isolated Vlan's with IoT Devices. Unifi AC-Pro x 3 AP's, Router Wi-Fi Disabled. OVPN Server With Paid Commercial Wireguard Client's. Gateway Mode, DNSMasq, Static Leases & DHCP, Pi-Hole DNS & Running Unbound.

No one can build you the bridge on which you, and only you, must cross the river of life!
foz111
DD-WRT Guru


Joined: 01 Oct 2017
Posts: 704
Location: Earth

PostPosted: Sat Sep 24, 2022 10:05    Post subject: Reply with quote
For anybody searching for this:-
I've found a free project that has re-coded Android and windows clients with xor scramble patch.
Please check code as this is nothing to do with me!
Github:
https://github.com/lawtancool

Android:
https://github.com/lawtancool/ics-openvpn-xor/releases

Windows:
https://github.com/lawtancool/openvpn-windows-xor/releases

Android confirmed working bypassing DPI not tested windows yet.

_________________
Netgear R7800 PPPoE Main Router
Network IPV4 - Isolated Vlan's with IoT Devices. Unifi AC-Pro x 3 AP's, Router Wi-Fi Disabled. OVPN Server With Paid Commercial Wireguard Client's. Gateway Mode, DNSMasq, Static Leases & DHCP, Pi-Hole DNS & Running Unbound.

No one can build you the bridge on which you, and only you, must cross the river of life!
egc
DD-WRT Guru


Joined: 18 Mar 2014
Posts: 12812
Location: Netherlands

PostPosted: Sat Sep 24, 2022 10:32    Post subject: Reply with quote
Nice find!

I see it is based on Arne Schwabe's app, I use that on my Android phone much better than the "official" app Smile

Will add it to the docs

_________________
Routers:Netgear R7000, R6400v1, R6400v2, EA6900 (XvortexCFE), E2000, E1200v1, WRT54GS v1.
Install guide R6400v2, R6700v3,XR300:https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=316399
Install guide R7800/XR500: https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=320614
Forum Guide Lines (important read):https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=324087
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