Windows 7 - "Authentication Failed" issue

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Windows 7 - "Authentication Failed" issue

Postby dmhardy » 2015-06-22 02:09

I have been looking through your forum for help on the "Authentication Failed" issue.

I install VNC on my W7 Pro machine, change my password to my one and test, all works well.
I then proceed to re-boot the PC and then try the VNC from my other PC again, and get the "Authentication Failed" issue.

I read your previous posts from 2010 about removing ORL' from the registry, I have only installed UVNC, nothing else, not Real VNC or the like.
Setup the Administrator account.
Firewall is Completely disabled.
I have an Inbound FW rule for allowing ports 5900 and 5800, only one these rules are listening.
This has happened on all my W7 machines.

It has never appeared on the old XP Machines I am replacing.
I check the UVNC INI file to see the password is changing, which it is, but it still doesnt work.

Is there something simple I am missing with the install ???
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Re: Windows 7 - "Authentication Failed" issue

Postby Rudi De Vos » 2015-06-22 08:20

password exist only at one spot, the ultravnc.ini file. ( reg settings are not longer used)
-reset: remove ultravnc.ini
-copy: You can copy files between systems. A xp ultravnc.ini is the same as the win7 version.
If you have working xp, first test by copying this file to win7

Works after changing but not after reboot "authentication failed"

This indicate that something goes wrong while saving the file, usual this is the case when the desktop user is a domain user.

cause:
Running as service, vnc has the System credentials and try to impersonate the desktop user. This fail if the the local system
can't impersonate him. Fom Vista "program files" is a secure location protected by UAC. THis is great to protect the ini file,
but not so easy the save to it, if uac elevation fail we can't write to the file.

workarounds
+logon as local admin
+use the uvnc_settings.exe ini editor
-stop the service and start winvnc manual ( winvnc now run as desktop user, so we don't need to impersonate)
-copy from another system
-copy winvnc.exe to a "full access" folder and do the changes in this folder, after that copy the file back to the secure
"program files"
Rudi De Vos
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Re: Windows 7 - "Authentication Failed" issue

Postby Johnnnnn » 2015-08-09 09:53

there seems to be a bug in the program, when you change things, for login with secure plugins ore with windows authentication, it does not clear the ultravnc.ini, maybe someone can make the program so that the ultravnc.ini alway's write a new one when you change someting. That would make things more easy.
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Re: Windows 7 - "Authentication Failed" issue

Postby Rudi De Vos » 2015-08-09 21:40

bug: Yes/No
When vnc run as service, and we would simple save the settings, everybody could change them ( A service has local admin permissions).
To avoid this we impersonate the desktop user.
But when the desktop user is protected, like domain admins, even a local service can not impersonate him and you can not save as
the ultravnc.ini

MS does not want that a service taskbar is used to save something as the consider it as unsecure.
To avoid all trouble we can remove the save options from the taskbar and force people to use the
seperate tool uvnc_settings.exe. This always start as desktop user and there is no service dependency...

bug: WHen vnc is running as service and desktop can not be impersonated by a local service, settings can not be saved.

workaround:
+logon as local admin
+start vnc as application
+use uvnc_settings.exe ( restart service is required before some options work)
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