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April 30th, 2010, 11:05 AM
#1
Problem with Debugging ISAPI Extension on IIS 6.0 ...
Hello All,
I have written a small & Simple ISAPI extension that simply print "Hello" in the browser. The code that I used is below in the code section.
I wanted to Write to a file from the ISAPI extension. So I tried to set permissions of the folder to specify WRITE in addition to READ permission. This is done using the IIS Manager Snap-in. After calling the extension's DLL from the browser, I can see the Hello world in the browser and 200 status code in IIS W3C log file.
The only thing I can't see is the log file at C:\.
Code:
BOOL WINAPI DllMain(IN HINSTANCE hinstDll, IN DWORD dwReason, IN LPVOID lpvContext)
{
return TRUE;
}
BOOL WINAPI GetExtensionVersion(OUT HSE_VERSION_INFO *pVer)
{
const CHAR szExtensionInfo[] = "SGN: ISAPI Extension" ;
pVer->dwExtensionVersion = MAKELONG(HSE_VERSION_MINOR, HSE_VERSION_MAJOR); // HSE_VERSION;
strncpy_s(pVer->lpszExtensionDesc, HSE_MAX_EXT_DLL_NAME_LEN, szExtensionInfo, strlen(szExtensionInfo));
return TRUE;
}
DWORD WINAPI HttpExtensionProc(IN EXTENSION_CONTROL_BLOCK *pECB)
{
static char szMessage[] = "<HTML><HEAD><TITLE> Hello World </TITLE></HEAD>\r\n"
"<BODY><H2>Hello from Simple ISAPI Extension DLL!</H2>\r\n</BODY></HTML>\r\n\r\n";
HSE_SEND_HEADER_EX_INFO HeaderExInfo;
HeaderExInfo.pszStatus = "200 OK";
HeaderExInfo.pszHeader = "Content-type: text/html\r\n\r\n";
HeaderExInfo.cchStatus = strlen(HeaderExInfo.pszStatus);
HeaderExInfo.cchHeader = strlen(HeaderExInfo.pszHeader);
HeaderExInfo.fKeepConn = FALSE;
pECB->ServerSupportFunction(pECB->ConnID, HSE_REQ_SEND_RESPONSE_HEADER_EX, &HeaderExInfo, NULL, NULL);
HANDLE hLogFile = CreateFile(TEXT("C:\\RequestLog.txt"), GENERIC_WRITE, FILE_SHARE_READ, NULL, OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL) ;
if (hLogFile != NULL && hLogFile != INVALID_HANDLE_VALUE)
{
DWORD dwWritten = 0 ;
SetFilePointer(hLogFile, 0, NULL, FILE_END) ;
if (WriteFile(hLogFile, szMessage, strlen(szMessage), &dwWritten, NULL) == FALSE)
{
// Write to Event Log then ... (if possible)
}
CloseHandle(hLogFile) ;
}
DWORD dwBytesToWrite = strlen( szMessage );
pECB->WriteClient( pECB->ConnID, szMessage, &dwBytesToWrite, 0 );
return HSE_STATUS_SUCCESS;
}
BOOL WINAPI TerminateExtension(IN DWORD dwFlags)
{
return TRUE;
}
I have a few questions in my mind after this:
- Can someone let me know, what can I do to troubleshoot the issue ? The machine with IIS has the MS VC Remote Debugger (MSVCMON.exe) installed there. However, After connecting to IIS, My Visual Studio 2008 freezes until Infinity.
- How do I debug and confirm that which functions are getting failed ?
- How do I log information from inside of my ISAPI extension ?
- Is it possible to log entries into Window Event Log from inside of my ISAPI extension ?
- What else permissions are required for my ISAPI extension to be able to write to file ?
I know, lots of questions but Your Answer would be of great help in clearing the clouds and will be appreciated.
Thanks,
(*Vipul)() ;
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April 30th, 2010, 02:43 PM
#2
Re: Problem with Debugging ISAPI Extension on IIS 6.0 ...
OPEN_ALWAYS implies the file already exists. 
Best regards,
Igor
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April 30th, 2010, 08:44 PM
#3
Re: Problem with Debugging ISAPI Extension on IIS 6.0 ...
Thanks Igor,
However I used OPEN_ALWAYS after seeing the following description from MSDN. I think what you said is OPEN_EXISTING:
OPEN_ALWAYS (4)
Opens a file, always.
If the specified file exists, the function succeeds and the last-error code is set to ERROR_ALREADY_EXISTS (183).
If the specified file does not exist and is a valid path to a writable location, the function creates a file and the last-error code is set to zero.
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May 1st, 2010, 12:31 PM
#4
Re: Problem with Debugging ISAPI Extension on IIS 6.0 ...
Yeah, my bad, sorry. But anyway, did you give a try with already existing file?
Best regards,
Igor
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May 3rd, 2010, 05:03 AM
#5
Re: Problem with Debugging ISAPI Extension on IIS 6.0 ...
Yes Igor, I tried it with an existing file as well, but the result was same :-(
Then Instead of trying on a remote IIS server which doesn't have any debugger installed, I installed IIS 7 on my local development machine and tried to run the ISAPI extension on it.
The VS 2008 (C++) is now able to attach to Process w3wp.exe (IIS7). The process now break in the VC++ debugger.
What I can see now is that -
Code:
HANDLE hLogFile = CreateFile(TEXT("C:\\RequestLog.txt"), . . .
has the problem. it is returning 0xFFFFFFFF in hFile and on calling GetLastError() it returns 5.
I have changed the path C:\\RequestLog.txt to C:\\IsApi\\temp\\RequestLog.txt and given READ+WRITE+EXECUTE+MODIFY permissions to the user LOCAL_SERVICE under which the service World Wide Web Publishing is executing.
Yet it is the same .... No Luck :-(
Any thing that you can see here ...
Regards,
(*Vipul)() ;
(*Vipul)() ;
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May 4th, 2010, 10:00 AM
#6
Re: Problem with Debugging ISAPI Extension on IIS 6.0 ...
on calling GetLastError() it returns 5
Seems like extension is not allowed to write to local path
net helpmsg 5
Access is denied.
Last edited by Igor Vartanov; May 4th, 2010 at 10:04 AM.
Best regards,
Igor
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May 5th, 2010, 12:47 PM
#7
Re: Problem with Debugging ISAPI Extension on IIS 6.0 ...
Yes, Definitely its Access Denied. Though I have already given READ+WRITE+EXECUTE+LIST+MODIFY permission to the user LOCAL_SERVICE. The WWW service executes under user LOCAL_SERVICE.
(*Vipul)() ;
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May 5th, 2010, 12:59 PM
#8
 Re: Problem with Debugging ISAPI Extension on IIS 6.0 ...
I ran SysInternal's ProcMon utility on the machine where the WWW service was running. I enabled file system monitoring while disabling other type of monitoring.
I observed that an attempt to CreateFile() was failed with ACCESS_DENIED error on File RequestLog.txt. The request was Impersonating the UserId IIS_IUSR.
So then, I granted READ+WRITE permissions on the said folder to the impersonated User/Group and BINGO !!
It works! Ever since I saw permission denied, I was trying to figure out why the request is failing despite the fact that I have already granted permission.
Thanks Igor for discussing the problem ...
(*Vipul)() ;
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