1. CHAPTER 14 - DEBUGGING WINDOWS SERVICES
Service Basics
Creating Windows Services –
The API
User Accounts
Debugging Windows Services –
Debugging the Core Code
Debugging the Basic Service

2. Service Basics SCM (Service Control Manager)
Maintains a database of installed services.
RPC Server. Can be remotely accessed.
Transmits control requests to running services.
Starting Services at System Startup (or on user-demand).
Maintains Status Info for running services.

3. Service Basics
The Following Programs use the functions provided by the SCM –
Service Program
Executable code for a service.
Service Configuration Program
Install / Delete services.
Modify configurations / Security Settings.
Service Control Program
Starts , Controls services by requesting the SCM.

4. Creating Windows Services – The API
Writing Service Program’s Main()
Can use main() or WinMain().
First call the StartServiceCtrlDispatcher.
Pass a SERVICE_TABLE_ENTRY structure.
This structure indicates the name and main entry point for you service.
StartServiceCtrlDispatcher talks to SCM to start your service. SCM starts Control Dispatcher thread.

5. Creating Windows Services – The API
Writing the ServiceMain()
Control Dispatcher thread calls into your ServiceMain().
This entry point must register a handle SERVICE_STATUS_HANDLE with RegisterServiceCtrlHandlerEx().
It must then call SetServiceStatus() to communicate to the SCM, its status (starting, stopping, pausing).

6. Creating Windows Services – The API
So what ??

7. Creating Windows Services – The API
Your Service Program’s main() must call the StartServiceCtrlDispatcher within 30 seconds of starting.
Your ServiceMain() must call SetServiceStatus within 82 seconds of starting.
Else the SCM will terminate your service.

8. Creating Windows Service – User Account
Every Service has an associated account. (Default = LocalService account).
When a Service starts, the SCM logs on to the account.
The System produces an access tokens and attaches it to the service process.
The system compares the service’s access token to a securable object’s Security Descriptor before granting access.

9. Creating Windows Service – User Account
Alternative for User Accounts –
LocalService
Anonymous Network Access (no password required)
SE_AUDIT_NAME
SE_CHANGE_NOTIFY_NAME
SE_UNDOCK_NAME
NetworkService
Credentials Supplied to Remote Servers

10. Creating Windows Service – User Account
Alternative for User Accounts –
LocalSystem Account
SE_ASSIGNPRIMARYTOKEN_NAME, SE_AUDIT_NAME
SE_BACKUP_NAME, SE_CHANGE_NOTIFY_NAME
SE_CREATE_PAGEFILE_NAME, SE_CREATE_PERMANENT_NAME
SE_DEBUG_NAME, SE_INC_BASE_PRIORITY_NAME
SE_INCREASE_QUOTA_NAME, SE_LOAD_DRIVER_NAME
SE_CREATE_TOKEN_NAME, SE_LOCK_MEMORY_NAME
SE_PROF_SINGLE_PROCESS_NAME, SE_RESTORE_NAME
SE_SECURITY_NAME, SE_SHUTDOWN_NAME
SE_SYSTEM_ENVIRONMENT_NAME, SE_TCB_NAME
SE_SYSTEMTIME_NAME, SE_SYSTEM_PROFILE_NAME,
SE_TAKE_OWNERSHIP_NAME , SE_UNDOCK_NAME

11. Debugging – The Core Code
Ensure that –
Service core code is on the same machine.
Client code is also on the same machine.
Log in using your developer account.
Hence you do not have to worry about nasty security or network issues while debugging your logic.
These pleasures are reserved for later !

12. Debugging – The Service
Step 1 – Allow Service to interact with Desktop

13. Debugging – The Service
Step 2 – Set your Service Identity
Set you service to start under an administrator privilege to avoid security problems.

14. Debugging – The Service
Step 3 – Attach to your Service

15. Debugging – The Service
Step 3 – Attach to your Service

16. Debugging – The Service
Alternative Method – (Attach to your Service)
Key: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\YOUR SERVICE
Value: Full path of the Debugger (REG_SZ)

17. Debugging – The Service
Yet Another Method – (Attach to your Service)
DebugBreakProcess() – Generates breakpoint exception in specified process.
Invokes the debugger for just-in-time debugging.

18. Debugging – The Service
A Reminder………
Your Service Program’s main() must call the StartServiceCtrlDispatcher within 30 seconds of starting.
Your ServiceMain() must call SetServiceStatus within 82 seconds of starting.
Else the SCM will terminate your service

19. Debugging – The Service
Solutions –
Use DebugView.
Change SCM timeout limit
typedef struct _SERVICE_STATUS {
DWORD dwServiceType;
DWORD dwCurrentState;
DWORD dwControlsAccepted;
DWORD dwWin32ExitCode;
DWORD dwServiceSpecificExitCode;
DWORD dwCheckPoint; SET TO ZERO
DWORD dwWaitHint; INCREMENT
} SERVICE_STATUS, *LPSERVICE_STATUS;