Run application from a Windows service
lazarus / 34-Windows

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arodriguezfarfan · 2021-12-01 15:19

I'm trying to create a Windows service that after a certain load time
runs an external application.

The idea is that if it is detected that the necessary configuration
has not been made, a program is loaded with which the necessary
parameters can be configured.

The attachment contains the sample project that I am using with which
I charge notepad.exe, however the problem I have is that at the time
of loading the program it does not show the window although it appears
in the Task Manager. My question is whether I want to do it or what am
I doing wrong?

Any suggestions are welcome

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dseligo · 2021-12-01 16:57

It could be the user under which you run service.

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balazsszekely · 2021-12-01 19:21

@arodriguezfarfan

QuoteI'm trying to create a Windows service that after a certain load
time runs an external application.You have to break session 0
isolation. For security reasons, since windows vista, the services run
in session 0. The first user logs on to session 1, the second one to
session 2 and so on. Session 0 cannot interact with session 1,2...x,
so you cannot show an UI element from your service. You have to start
the external application in user space.  CreateProcessAsUser api for
example will run the application in the security context of the user.

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arodriguezfarfan · 2021-12-02 01:27

Thanks Getmen for the explanation. I researched about
CreateProcessAsUser, but I think what I intend to do is not the right
thing to do, so I'm going to look for another alternative. Thank you.

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balazsszekely · 2021-12-02 06:02

@arodriguezfarfan

QuoteThanks Getmen for the explanation.You're welcome!

QuoteI researched about CreateProcessAsUser, but I think what I intend
to do is not the right thing to doSometimes there are good reasons to
run a process from a service, then exchange message between them via
inter process communication(sockets, pipes, named pipes, memory mapped
files, etc...). If you change your mind, you can try something like
this:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i function
FindWinlogon(ASessionId: DWord): DWord;var  PID, SessionId: DWord; 
hSnap: THANDLE;  procEntry: TProcessEntry32;begin  Result := 0;  hSnap
:= CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);  if (hSnap <>
INVALID_HANDLE_VALUE) then  begin    procEntry.dwSize :=
Sizeof(PROCESSENTRY32);    PID := 0;    SessionId := 0;    if
Process32First(hSnap, procEntry) then    begin      while
Process32Next(hSnap, procEntry) do      begin        if
Pos('winlogon.exe', LowerCase(procEntry.szExeFile)) > 0 then       
begin          if ProcessIdToSessionId(procEntry.th32ProcessID,
SessionId) then          begin            if SessionId = ASessionId
then            begin              PID := procEntry.th32ProcessID;   
         Break;            end;          end        end;      end;   
 Result := PID;    end;  end;end; function RunProcessAsUser(APath:
WideString): DWord;var  pi: PROCESS_INFORMATION;  si: STARTUPINFOW; 
dwSessionId, PID, DesiredAccess, dwCreationFlags: DWord; 
hUserTokenDup, hPToken, hProcess: THANDLE;begin  Result := 0; 
RevertToSelf;  dwSessionId := WtsGetActiveConsoleSessionID;  PID :=
FindWinLogon(dwSessionId);  if PID <> 0 then  begin    hPToken := 0; 
 hProcess := OpenProcess(MAXIMUM_ALLOWED, False, PID);       
DesiredAccess := TOKEN_ADJUST_PRIVILEGES or TOKEN_QUERY or
TOKEN_DUPLICATE or                      TOKEN_ASSIGN_PRIMARY or
TOKEN_ADJUST_SESSIONID or TOKEN_READ or TOKEN_WRITE;    if
OpenProcessToken(hProcess, DesiredAccess, hPToken) then    begin     
hUserTokenDup := 0;      if DuplicateTokenEx(hPToken, MAXIMUM_ALLOWED,
nil, SecurityIdentification, TokenPrimary, hUserTokenDup) then     
begin        ZeroMemory(@si, SizeOf(si));        ZeroMemory(@pi,
SizeOf(pi));        dwCreationFlags := NORMAL_PRIORITY_CLASS or
CREATE_UNICODE_ENVIRONMENT;        if
CreateProcessAsUserW(hUserTokenDup, PWideChar(APath), nil, nil, nil,
False, dwCreationFlags, nil, nil, si, pi) then          Result :=
pi.dwProcessId      end    end  end;end;
Then inside your services, create a  worker thread, wait a few
seconds, then run notepad "as user":
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i procedure
TThreadWorker.Execute;var  WPath: WideString;  PID: DWord;begin  FTick
:= 0;  while not Terminated do  begin    Inc(FTick);    Sleep(1000); 
 if FTick = 5 then    begin      WPath := 'c:\windows\notepad.exe';  
  PID := RunProcessAsUser(WPath);      if PID > 0 then       
//notepad successfully executed      Break;    end;     end;end;

PS: Actually I ran a few test and notepad starts fine, with a nice
visible window.

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PascalDragon · 2021-12-02 07:57

Quote from: arodriguezfarfan on December 02, 2021, 02:27:54 amThanks
Getmen for the explanation. I researched about CreateProcessAsUser,
but I think what I intend to do is not the right thing to do, so I'm
going to look for another alternative.
There is no alternative except for using the functionality provided by
the operating system as it's intended.

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arodriguezfarfan · 2021-12-02 14:15

Thank you Getmen for the solution you sent me, I will run the
published code. I hope to see the notebook start fine, with a nice
window visible         .

Thank you.

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balazsszekely · 2021-12-02 15:10

I forgot to attach my test daemon. After you build the executable, run
_install.bat form the same folder. If the install was successful,
start the service. In order for the notepad window to appear, you have
to wait approximately five seconds. If something went wrong check
log.txt.

PS: Tested with Lazarus Trunk/FPC 3.2.0(32 bit) on a 64 bit Windows

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arodriguezfarfan · 2021-12-03 14:57

Thank you Getmen. The project works perfectly. Now I have to study it
and implement in my project.

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balazsszekely · 2021-12-03 15:32

Quote from: arodriguezfarfan on December 03, 2021, 03:57:26 pmThank
you Getmen. The project works perfectly. Now I have to study it and
implement in my project.
You are welcome, I'm glad it's working.
I made a few improvement, now the worker thread is properly terminated
and freed, no more memory leaks. However I cannot properly "self" shut
down the service. It would be nice to find a method to terminate the
service from inside, without using the service manager. Of course a
Halt always work, but I'm not satisfied with this method.

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balazsszekely · 2021-12-04 09:05

@GetMem
QuoteHowever I cannot properly "self" shut down the service. It would
be nice to find a method to terminate the service from inside, without
using the service manager. Of course a Halt always work, but I'm not
satisfied with this method.
I will answer my own question. The idea is to pass the daemon to the
workerthread constructor(FDaemon), when it's time to shut down the
service:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i var 
Daemon: TCustomDaemon;  DaemonThread: TDaemonThread;begin  Daemon :=
TCustomDaemon(FDaemon);  DaemonThread :=
TDaemonThread(Daemon.DaemonThread);  DaemonThread.ShutDownDaemon;end; 
It works very nicely. The method though is somewhat convoluted. I
would implement a procedure inside TCustomDaemon(daemonapp.pp) class
to achieve the same thing. I wonder if a patch would be accepted.

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PascalDragon · 2021-12-06 12:51

Quote from: GetMem on December 04, 2021, 10:05:48 amIt works very
nicely. The method though is somewhat convoluted. I would implement a
procedure inside TCustomDaemon(daemonapp.pp) class to achieve the same
thing. I wonder if a patch would be accepted.

If you make clear what the use case is and what implications it has
you might at least try...