Question

LogonUser problem

Asked by: phadar

I'm using the LogonUser to interact with the user dektop from within a service.
The call is:
if LogonUser(PChar(User), PChar(Domain), PChar(Password), LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT, Token) then
....

So for example
LogonUser(PChar('MyUser'), PChar('.'), PChar('MyPassword') - works

This works when I have the user logon with a password but I can't make it work when there is no password

LogonUser(PChar('MyUser'), PChar('.'), PChar('') - DOES NOT

Thanks

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Asked On
2009-02-11 at 07:22:08ID24133495
Topic

Delphi Programming

Participating Experts
3
Points
500
Comments
12

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Answers

 

by: JohnjcesPosted on 2009-02-11 at 07:38:35ID: 23612428

Did you try... (I forget sometimes whether it is nil or 0)

LogonUser(PChar('MyUser'), PChar('.'), Nil,  or

LogonUser(PChar('MyUser'), PChar('.'), 0,

John

 

by: phadarPosted on 2009-02-11 at 08:42:31ID: 23613203

It's a PAnsiChar so it cannot be 0.
And I already tried Nil but without success, that is the reason for my post (:

 

by: JohnjcesPosted on 2009-02-11 at 08:45:33ID: 23613240

"And I already tried Nil but without success, that is the reason for my post"

Sorry... I did not see in your post Nil. I just see Pchar('').

John

 

by: phadarPosted on 2009-02-11 at 08:51:07ID: 23613346

John,
PChar('') is equal to Nil   (:

 

by: JohnjcesPosted on 2009-02-11 at 09:02:19ID: 23613474

Well, it should.

However in some of my tinkering with similar functions, when I did a PChar(''), when no password was needed, it would not work. When I enter Nil, it would.

Here is an example, at least i Delphi 5, that if I have a null password or user and passed a null string to my WNEtAddConnection2, as a PChar, I would not connect. So I had to test for it being null and then specifically add  Nil. Then it worked!

if (APassword <> '') or (AUser <> '') then
 i:=WNetAddConnection2(n,PChar(APassword),PChar(AUser),0)
   else
     i:=WNetAddConnection2(n,nil,nil,0);

That is why I threw it out to you.

John

 

by: phadarPosted on 2009-02-11 at 09:31:07ID: 23613735

well, I never had problem with that but anyway, I tried PChar('') and Nil as password, both aren't working.

 

by: JohnjcesPosted on 2009-02-11 at 09:32:44ID: 23613751

Alrighty then... that settles that.

Never had a problem either until that one function above! Thought it might help.

Good luck!

John

 

by: rllibbyPosted on 2009-02-11 at 09:45:48ID: 23613875

Run secpol.msc, then check the setting for

Local Policies | Security Options -> Accounts: Limit local account use of blank passwords to console logon only

Description
Determines whether remote interactive logons by network services such as Terminal Services, Telnet, and FTP are allowed for local accounts that have blank passwords. If this setting is enabled, a local account must have a nonblank password to be used to perform an interactive logon from a remote client.

Default: Enabled


---

If this setting is enabled, then your LogonUser call is going to fail.

Regards,
Russell



 

by: phadarPosted on 2009-02-11 at 10:05:38ID: 23614103

Hi Russell

It's correct, I disabled the entry and it works.
Now...Is there a way change that flag programmatically or through the registry?

Thanks

 

by: rllibbyPosted on 2009-02-11 at 10:42:59ID: 23614526

Have no idea. I was only attempting to answer your original question as to why the call failed with a blank password.

Russell

 

by: phadarPosted on 2009-02-11 at 15:10:42ID: 23617700

Hi Russell,

Well your attempt to answer my original question helped me well (:
I found the registry entry so here it is for anyone who might need it:

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa]
LimitBlankPasswordUse=dword
0 - Disabled
1 - Enabled

Thanks
Philip


 

by: rotem156Posted on 2011-06-11 at 03:12:59ID: 35951242

phadar: thanks for your wonderfull answer !!

20120131-EE-VQP-002

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