Am 10.03.22 um 15:14 schrieb Jakob Curdes:
Hello all,
I think I have found a bug in the OpenVPN Windows client , can you help
me to determine if this is true and how to proceed?
We are trying to implement 2FA for several existing Firebox SSL VPNs
(which essentially uses OpenVPN on server and client side). The remote
users all use the Windows OpenVPN client. This works perfectly without
2FA, and it works also if you do not need to specify the authentication
domain on user logon. But for the migration it is necessary to do that
as I cannot convert all users at once - the domain you enter in the
username field is then "authpoint" instead of something like
"company.private". In the 2FA process, the OpenVPN client then opens a
text window where you can enter a TOTP token or a "p" for a push
request. The Backslash is no problem when not using 2FA, then the user
auth succeeds.
So it seems in the part for the extra control message handling handles
backslashes incorrect.
Be aware that there is a also a newer 2FA method based on auth-pending
that addresses many of the shortcoming of the old AUTH_FAILED based method.
/Typed in Username: authpoint\UserN and corresponding password/
Thu Mar 10 10:35:31 2022 VERIFY OK: depth=0, O=WatchGuard_Technologies,
OU=Fireware, CN=Fireware SSLVPN Server
Thu Mar 10 10:35:31 2022 Control Channel: TLSv1.2, cipher TLSv1.2
ECDHE-RSA-CHACHA20-POLY1305, peer certificate: 2048 bit RSA, signature:
RSA-SHA256
Thu Mar 10 10:35:31 2022 [Fireware SSLVPN Server] Peer Connection
Initiated with [AF_INET]1.2.3.4:443
Thu Mar 10 10:35:32 2022 MANAGEMENT: >STATE:1646904932,GET_CONFIG,,,,,,
Thu Mar 10 10:35:32 2022 SENT CONTROL [Fireware SSLVPN Server]:
'PUSH_REQUEST' (status=1)
Thu Mar 10 10:35:32 2022 AUTH: Received control message:
AUTH_FAILED,CRV1:R,E:1796:Yoirtuqeprtiqrew4==:*Type "p" to receive a
push notification or type your one-time password*
/(Typed in "p")
/
Thu Mar 10 10:35:32 2022 SIGUSR1[soft,auth-failure] received, process
Where are you typing this in? in the normal cmd.exe terminal that runs
OpenVPN? because that looks like the client just gives you the
AUTH_FAILED and then proceeds to connect to the next server.
restarting
Thu Mar 10 10:35:32 2022 MANAGEMENT:
>STATE:1646904932,RECONNECTING,auth-failure,,,,,
Thu Mar 10 10:35:32 2022 Restart pause, 5 second(s)
*Thu Mar 10 10:35:40 2022 Previous command sent to management failed:
ERROR: Options warning: Bad backslash ('\') usage in TCP:0: remember
that backslashes are treated as shell-escapes and if you need to pass
backslash characters as part of a Windows filename, you sho*
Thu Mar 10 10:35:40 2022 MANAGEMENT: CMD 'username "Auth"
"*authpoint\UserN*"'
Thu Mar 10 10:35:40 2022 MANAGEMENT: CMD 'password [...]'
This sounds like I need to escape the backslash, but if I do this the
auth fails completely before the 2FA part comes into the picture.
Other tricks like forward slashes or "@" do not help here as these are
not understood by the auth backend in the firebox.
When using the WatchGuard SSL VPN app this all works (and it has OpenVPN
inside....) but I would like to stick to the OpenVPN clients as all the
users already have it and know how to handle it.
Best regards and thank you for hints,
The new auth-pending method is much easier to implement. With the old
method you need to part the AUTH_FAILED message and wait until the
client asks again for the user password on the next connection and give
the session password/repsonse then.
For the new method, example of implmentating it on Android:
parsing of the info message:
https://github.com/schwabe/ics-openvpn/blob/97546b9f8b51c0dc60d591b96ae835f00f2b6805/main/src/main/java/de/blinkt/openvpn/core/OpenVPNService.java#L1323
and sending the response:
https://github.com/schwabe/ics-openvpn/blob/97546b9f8b51c0dc60d591b96ae835f00f2b6805/main/src/main/java/de/blinkt/openvpn/core/OpenVpnManagementThread.java#L748
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