C / C++ / MFC

11-Sep-07 1:44

Hi,
I have implemented Client and server applications using Named pipes.
Server is written as a Service. This is working fine in admin user mode, Server (service) and client able to communicate properly.

where as in a guest user mode , Server is able to start( at the startup service starts automatically). But client not able to connect getting access denied error.
Not sure any privilizes have to provide while creating a pipe or creating a file from client.

Can any one help me out in this.

Nagadravid

KarstenK11-Sep-07 1:58

KarstenK

11-Sep-07 1:58

I think your OS is Vista! It is so sure, that you cant do think the easy way.

You got to create accessable objects in your service. This is a sample from the great Micheal Dunn, which should help you: http://www.codeproject.com/vista-security/PMSurvivalGuide.asp

Greetings from Germany

nagadravid11-Sep-07 4:19

11-Sep-07 4:19

Thanks Karstenk.
My OS is XP. One thing m not able to understand is if I run server as a normal console application (rather than as a service), even in guest usermode it is working fine. but in case of service it is failing.

Mark Salsbery11-Sep-07 7:06

Mark Salsbery

11-Sep-07 7:06

What account is your service running in the context of?

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

nagadravid11-Sep-07 8:56

11-Sep-07 8:56

Service is running in Local system account (admin mode). Below are the service creation properties.

CreateService(
shSCManager, // SCM database
m_pServiceName, // name of service
m_pServiceName, // service name to display
SERVICE_ALL_ACCESS, // desired access
SERVICE_WIN32_OWN_PROCESS |SERVICE_INTERACTIVE_PROCESS, // service type
SERVICE_AUTO_START, // start type
SERVICE_ERROR_CRITICAL, // error control type
szServicePath, // path to service's binary
NULL, // no load ordering group
NULL, // no tag identifier
NULL, // no dependencies
NULL, // LocalSystem account
NULL);

There is no dependencies on the service.

carrivick11-Sep-07 10:37

11-Sep-07 10:37

Hey weird just solved this problem ! with the help of the really cool tool Process Explorer

Mine was to do with passing events but the same problems occur. It is todo with Security descriptors.

My guess is that you are using CreateNamedPipe

HANDLE WINAPI CreateNamedPipe(
LPCTSTR lpName,
DWORD dwOpenMode,
DWORD dwPipeMode,
DWORD nMaxInstances,
DWORD nOutBufferSize,
DWORD nInBufferSize,
DWORD nDefaultTimeOut,
LPSECURITY_ATTRIBUTES lpSecurityAttributes
);
Now my other guess is that your are passing NULL as lpSecurityAttributes. Refering to MSDN

"If lpSecurityAttributes is NULL, the pipe gets a default security descriptor"

You will not that is doesn't say THE default security descriptor. This is because it creates the pipe with the security descriptor for the user that creates it.

This explains your "It works in user mode command-line" but not as a service because the service will be running as SYSTEM.

FIRST SOLUTION

Pass an empty (DACL) security descriptor which has the behaviour of allowing any user/system process to access your pipe.

SECURITY_ATTRIBUTES sa;
SECURITY_DESCRIPTOR* psd=(SECURITY_DESCRIPTOR*)new unsigned char[SECURITY_DESCRIPTOR_MIN_LENGTH];
InitializeSecurityDescriptor(psd,SECURITY_DESCRIPTOR_REVISION);
SetSecurityDescriptorDacl(psd, TRUE,(PACL)NULL,FALSE);
sa.nLength = 0;
sa.bInheritHandle = TRUE;
sa.lpSecurityDescriptor = psd;

Now use "sa" in the call to CreateNamedPipe

SECOND MORE SECURE SOLUTION

pass a fully filled out security descriptor, have a look at MSDN for an example.

nagadravid11-Sep-07 19:02

11-Sep-07 19:02

Thanks Carrivick. I hope it will resolve my problem.

Naag

carrivick12-Sep-07 0:49

12-Sep-07 0:49

Were you passing NULL in the Secutity Attributes ?

"Please enter a number" - Dialog

KarstenK11-Sep-07 20:21

KarstenK

11-Sep-07 20:21

As Mark pointed to, it is important to run the service in a spezific account, so an outside program has access rights. Or as in M.Dunn project the objects becomes lower rights so it can accessed.

This is all about accounts and access rights, really boring and bad documented stuff. Unsure | :~

Greetings from Germany

RajiRaghu11-Sep-07 1:43

RajiRaghu

11-Sep-07 1:43

I have a Form where i need to set a string value (NA) and double value.

In DDX_TEXT i use a double variable.

When i set the string value, and updatedata(TRUE), it says "Please enter a number". How to avoid this error message?
Thanks

Thanks
Raji

Hamid_RT11-Sep-07 1:54

Hamid_RT

11-Sep-07 1:54

if you want to enter a string on the editbox(I think you used of editbox) you can use of SetWindowText.

RajiRaghu11-Sep-07 2:21

RajiRaghu

11-Sep-07 2:21

Thanks. It works. But since it is a string, while modifying some other edit filed (number) and updatedata(TRUE), the error message "Please enter a number" is displayed. Please let me know a way to avaoid this error / catch this error message.

Thanks

Thanks
Raji

Nishad S11-Sep-07 2:12

Nishad S

11-Sep-07 2:12

RajiRaghu wrote:
string value (NA) and double value.

I think you need to use SetWindowText and GetWindowText, instead of using control variable as double. Or simply how can string value like "NA" be stored in double?

- NS -

RajiRaghu11-Sep-07 2:23

RajiRaghu

11-Sep-07 2:23

ya. But there are lots of calculations involved.

Thanks
Raji

Nishad S11-Sep-07 2:39

Nishad S

11-Sep-07 2:39

AfxTextFloatFormat is called by DDX_Text where this message is generated.

I can say another option. Add a member function same as UpdateData(BOOL bSaveAndValidate = TRUE). Remove DDX_Text entry in the DoDataExchange. Convert the window text to double in the new UpdateData if the BOOL bSaveAndValidate is TRUE (if it is NA you can check it also) and do vice versa if FALSE. Also call the CDialog::UpdateData(bSaveAndValidate) so that other control variables will not be affected.

Hope it is OK.

- NS -

How to prevent copying a file

David Crow11-Sep-07 3:01

David Crow

11-Sep-07 3:01

RajiRaghu wrote:
When i set the string value, and updatedata(TRUE)...

That could be a source of your problem. Use SetWindowText() instead of UpdateData().

"A good athlete is the result of a good and worthy opponent." - David Crow

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne

nps_ltv11-Sep-07 0:22

nps_ltv

11-Sep-07 0:22

In an Visual C++ 6.0 application, I need to prevent copying the specified file to other directory, but I don't know how to do.
Please help me!!!
Thank you very much!

P.S. If maybe, you can demonstrate an small application about this.
Thank you!

Maximilien11-Sep-07 2:45

Maximilien

11-Sep-07 2:45

Prevent who ?

You could open the file with CFile and use one of the flag to prevent other processed to access it.

Maximilien Lincourt
Your Head A Splode - Strong Bad

David Crow11-Sep-07 3:02

David Crow

11-Sep-07 3:02

You would need to set this restriction at the OS level.

"A good athlete is the result of a good and worthy opponent." - David Crow

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne

carrivick11-Sep-07 10:40

11-Sep-07 10:40

Create a service which opens an exclusive handle to the file. This will prevent copying and deleting.

nps_ltv12-Sep-07 22:45

nps_ltv

12-Sep-07 22:45

If maybe, you can demonstrate how you do it? Because, I don't still understand you. Can you help me!!! Please!!!

Thank you very much!

carrivick13-Sep-07 11:03